US 3789220 A
Method and apparatus for controlling energization and deenergization of an electrical load circuit such as a flood-lighting circuit utilizing a control system that is responsive to predetermined conditions of atmospheric light. A timing sequence may be initiated upon the occurrence of a predetermined degree of morning atmospheric light which timing sequence functions to deenergize the load circuit at the end of a predetermined period of time measured from dawn, the load circuit being previously energized responsive to predetermined decrease in the amount of evening atmospheric light. The timing sequence may be variable, responsive to variations in the length of daylight hours, and may function to achieve deenergization of the load circuit at approximately the same time each night, thereby precluding unnecessary operation of the load circuit during certain periods during the year.
Claims available in
Description (OCR text may contain errors)
Waited Etates Patent [1 1 Schacht ,lan. 29, 1974 Primary ExaminerWalter Stolwein Attorney, Agent, or Firm-Paul M. Janicke et al.
[ 5 7] ABSTRACT Method and apparatus for controlling energization and deenergization of an electrical load circuit such as a flood-lighting circuit utilizing a control system that is responsive to predetermined conditions of atmospheric light. A timing sequence may be initiated upon the occurrence of a predetermined degree of morning atmospheric light which timing sequence functions to deenergize the load circuit at the end of a predetermined period of time measured from dawn, the load circuit being previously energized responsive to predetermined decrease in the amount of evening atmospheric light. The timing sequence may be variable, responsive to variations in the length of daylight hours, and may function to achieve deenergization of the load circuit at approximately the same time each night, thereby precluding unnecessary operation of the load circuit during certain periods during the year.
3 Claims, 28 Drawing Figures LlGHT SENSITIVE ELECTRICAL TIMING CIRCUIT  Inventor: Ezra L. Schacht, 1620 W. Main St.,
Houston, Tex. 77006  Filed: Sept. 8, 1972  Appl. No.2 287,369
Related US. Application Data  Continuation-impart of Ser. No. 238,088, March 27,
 US. Cl 250/206, 250/239, 337/102  Int. Cl. HOlj 39/12  Field of Search 337/102, 103, 107, 59; 250/206, 239
 References Cited UNITED STATES PATENTS 3,254,183 5/1966 Quinn 337/102 X 3,056,035 9/1962 Bernheim.... 250/239 3,260,825 7/1966 Owen et a1.. 337/102 X 3,408,606 10/1968 Myers 337/102 X PHO r0 1: 409
V PAIEMED Z 3.789220 PATENTED 3.789.220
SHEET 3 BF 8 Q- LOAD PAIENTEB JANZS I974 FIG. 79
sum 6 or a FlG 22 LIGHT SENSITIVE ELECTRICAL TIMING CIRCUIT This is a continuation-in-part of my application Ser. No. 238,088, filed March 27, 1972.
FIELD OF THE INVENTION This invention is directed generally to a method and apparatus for controlling energization and deenergiz ation of an electrical load circuit, such as a floodlighting circuit and more particularly is directed to controlling such energization and deenergization to achieve interruption of the load circuit at approximately the same time each night by a timing sequence initiated by a predetermined degree of morning light and, if desired, by additionally compensating for the variations in length of days and nights during the year.
BACKGROUND OF THE INVENTION Load circuits such as lighting circuits of the type frequently utilized to flood streets, buildings, parking lots, and the like with light at night, frequently employ devices to energize the lighting circuit at dusk and deenergize the lighting circuit at dawn. In view of the fact that less activity may occur in any given area after a certain time of night, for example midnight, it may be appropriate to terminate flood-lighting after any predetermined hour for the purpose of conserving electrical power. Lighting systems have been developed, therefore, that employ timing mechanisms initiating a timing sequence at dusk, which timing sequence achieves deenergization of a lighting circuit at the end of the timing sequence. Automatically actuated lighting systems having light responsive timing sequence cutoff, it designed for cutoff at a preselected time during the longest evenings of the year, will logically provide lighting several hours past the desired cutoff time during that period of the year when evening hours are relatively short. Lighting systems that are energized several hours past the desired cutoff time are quite inefficient from the standpoint of electrical power costs.
One way to insure cutoff at a predetermined time each evening would be to employ a timing circuit that is synchronized with the time zone in which the circuitry is installed. An installation of this nature would be particularly disadvantageous because of the requirement that actuating mechanism of the timing circuit be synchronized manually with the time of day when operation of the circuitry is initiated. This is, of course, undesirable because of the labor costs that would be involved in manual synchronization of the timing circuits. Another disadvantage of this particular type of timing circuit lies in the fact that temporary interruption of electrical power to the timing circuit would require resynchronization of the timing circuit thereby rendering timing systems of such nature highly impractical.
During the Summer season of the year and especially during periods when daylight saving time is in effect, dusk occurs quite late and lighting systems which, for example, may employ a seven and one-half hour timing sequence appropriate for the long nights of the Winter season, would cause the lighting system to remain energized much longer than is desirable. For example the lighting system might be on until 3:30 to 4:00 A.M. during the shortest nights of Summer, causing the lighting system to be operated three and one-half to four hours longer than the desired cutoff time. Lighting systems of this nature, of course, are quite undesirable.
Accordingly, it is a primary object of the present invention to provide a novel load circuit control mechanism that compensates for variations in daylight and darkness and achieves deenergization of the load circuit at approximately the same time each night.
It is a further object of the present invention to employ novel methods of controlling energization and de energization of a load circuit by employing a timing sequence measured from the occurrence of a predetermined degree of morning atmospheric light such as dawn, for example.
It is an even further object of the present invention to provide a novel circuit control mechanism that is effective to provide for automatic and economical operation of a load circuit timed by atmospheric light conditions.
Among the several objects of the present invention is noted the contemplation of a novel load circuit control mechanism that is actuated by a variable time sequence that is capable of variation responsive to seasonal variations in the length of the period of daylight.
It is also an object of the present invention to provide a novel circuit control mechanism that incorporates a heat actuated mechanism that compensates for differences in ambient temperature without creating variations in the time of switch actuation.
It is another object of the present invention to provide a light responsive novel timing mechanism for a load circuit that may incorporate a temperature sensitive mechanism that may be effective to retard initiation of a timing sequence responsive to ambient temperature.
It is also an object of the present invention to provide a novel timing mechanism for controlling a load circuit that is simple in nature, reliable in use, and low in cost.
Other and further objects, advantages and features of the present invention will become apparent to one skilled in the art upon consideration of the written specification, the attached claims, and the annexed drawings. The form of the invention, which will now be described in detail, illustrates the general principles of the invention, but it is to be understood that this detailed description is not to be taken as limiting the scope of the present invention.
SUMMARY OF THE INVENTION The invention embodies a method for controlling energization and deenergization of a load circuit, such as an electric flood-lighting circuit, for example, in response to atmospheric light conditions and achieves deenergization of the load circuit at approximately the same time each night.
A load circuit may be provided across which a load, such as one or more electrical lamps, is connected. The load circuit may be energized and deenergized by a contact that is opened and closed responsive to predetermined resistance levels of a first photoelectric cell circuit. A shunt circuit may be connected to the photoelectric cell circuit and may include a first switch that is closed to shunt the photoelectric cell circuit and reduce the resistance thereof sufficiently to open the load circuit contact. A timing circuit may be employed which includes an electrically energized clock motor that may provide a predetermined timing sequence at the termination of which the load circuit contact is opened to deenergize the load circuit. The timing circuit may include a switch through which it may be energized.
A reset circuit may also be connected across the load circuit and may function in response to resistance of a second photoelectric cell functioning in response to predetermined morning light conditions to reset the timing circuit mechanism. The reset circuit may trip a switch mechanism including switches for the shunt circuit, the timing reset circuit and the timing circuit in such manner that the switches are actuated sequentially to allow the circuit control mechanism to reset itself in readiness for a subsequent actuation cycle.
If desired, the timing mechanism may be responsive to the length of the daylight period of any given day to vary the length of the timing cycle. Such variation may be accomplished by a shield mechanism for shielding atmospheric light from a photoelectric cell and being movable responsive to temperature conditions for exposing the photoelectric cell and thereby accomplishing variations in the starting time of the timing sequence.
The timing mechanism may also incorporate a mechanism responsive to the length of daylight hours of any given day for varying termination of the timing sequence.
BRIEF DESCRIPTION OF THE DRAWINGS So that the manner in which the above recited features, advantages and objects of the present invention as well as others which will become apparent are attained and can be understood in detail, more particular description of the invention, briefly summarized above, may be had by reference to the embodiments hereof which are illustrated in the appended drawings, which drawings form a part of this specification.
It is to be noted, however, that the appended drawings illustrate only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope for the invention may admit to other equally effective embodiments.
IN THE DRAWINGS FIG. 1 is an elevational view of a load circuit timing mechanism constructed in accordance with the present invention.
FIG. 2 is a side elevational view of the load circuit timing mechanism illustrated in FIG. 1.
FIG. 3 is a fragmentary sectional view of the timing mechanism of FIG. 1, illustrating the timing gear mechanism in the operative positions thereof.
FIG. 4 is a plan view of a load circuit timing mechanism representing one embodiment of the present invention.
FIG. 5 is a simple electrical schematic diagram illustrating the basic electrical circuitry of the load circuit timing mechanism of FIGS. 1-3.
FIG. 6 is a partial sectional view of the load circuit timing mechanism of FIGS. 1-3 illustrating a light responsive switch actuating mechanism constructed in accordance with the present invention.
FIG. 7 is a fragmentary sectional view of the light responsive switch actuating mechanism of FIG. 6, illustrating portions of the light responsive elements of the switch actuating mechanism in detail.
FIG. 8 is a sectional view of an alternative light responsive switch actuating mechanism for the load circuit timing mechanism of FIGS. 1-3.
.FIG. 9 is an elevational view of a further embodiment of the light responsive switch actuating mechanism of this invention illustrating electrical circuitry thereof in schematic form.
FIG. 10 is a plan view of the heat responsive bimetal element utilized in the switch actuating structure of FIG. 9.
FIG. 11 is an elevational view illustrating a further modified embodiment of the light responsive switch actuating mechanism with which the timing mechanism of FIGS. 1-3 may be provided.
FIG. 12 is a fragmentary sectional view of the switch actuating mechanism in FIG. 11 illustrating the position of the operating parts thereof upon opening of the switch contacts.
FIG. 13 is a sectional view of an even further modified embodiment of the light responsive switch actuating mechanism for which the timing mechanism of FIGS. 1-3 may be provided.
FIGS. 14-18 are plan views in schematic form illustrating a light responsive switch control mechanism and electrical circuitry therefore having the capability of compensating for differences in length of daylight and darkness to achieve deenergization of the load circuit at approximately the same time each night.
FIG. 19 is a schematic illustration of a part of a time delay circuit for achieving delay in cutoff time of a load circuit by compensating for differences in the length of daylight hours.
FIG. 20 is a schematic illustration of the remaining part of the time delay mechanism illustrated in FIG. 19.
FIG. 21 is an electrical schematic diagram illustrating the electrical circuitry of a multiple voltage module adapting the load circuit control mechanism of the present invention for service under various voltage conditions.
FIG. 22 is an exploded isometric view illustrating the multiple voltage module in mechanical form.
FIG. 23 is a plan view illustrating a bimetallic temperature responsive contact actuating mechanism that may be provided for controlling energization of the timing control mechanism of the present invention under high voltage conditions.
FIG. 24 is a side elevational view illustrating the bimetallic temperature responsive contact actuating mechanism of FIG. 23.
FIG. 25 is a bottom view of the bimetallic element of FIG. 23 illustrating the relationship of the flexible braid to the switch actuating arm of the bimetallic element.
FIG. 26 is a side view illustrating yet another embodiment of the light-responsive switch actuating mechanism of this invention, wherein the resistor is springbiased in position.
FIG. 27 is a top view illustrating the spring element employed in the structure of FIG. 26.
FIG. 28 is an enlarged view of the stabilizing button 403 of FIG. 26.
DESCRIPTION OF PREFERRED EMBODIMENTS Now referring to the drawings and first to FIG. I there is illustrated a load circuit timing mechanism generally at 10 including a base support wall 12 to which an electrical connector 14 may be fixed in any suitable manner with connector element 16 thereof depending through an opening 18 that may be formed centerly of the base support wall.
A pair of clock motor support elements 20 may also be fixed to the base support wall 12 and may be operative to support an electric clock motor 22 and an upper support wall 24 by means of screws 26 extending through the support wall and through an upper support element of the clock motor 22.
It may be desirable to utilize rotary motion of the clock motor 22 for actuation of one or more switching elements capable of switching various control components of the timing mechanism as desired. For such purpose the clock motor may include a drive shaft 28 driving a pinion gear 30 that may be disposed in engagement with a large pinion gear 32 having a cam element 34 suitably connected thereto. As illustrated in FIG. 3 the cam element 34 may be provided with an internal cavity 36 within which a compression spring 38 may be disposed. A retainer element 40 may be pressfitted within an enlarged portion of the cavity 36 and may be operative to retain the compression spring 38 within the cavity. The rotatable cam element 34 may be movable from the full line position thereof, illustrated in FIG. 3, to the broken line position thereof upon compression of the spring 38 thereby causing gear teeth on the large gear 32 to become disengaged from the gear teeth of the pinion gear 30. Upon such disengagement the cam element 34 may then be rotated in its depressed condition to any suitable position and, upon release, the compression spring 38 will again move the cam elements upwardly to the full line position thereof causing reengagement of teeth of gears 30 and 32.
As illustrated in FIG. 3, the cam 34 may be provided with a cam depression 42 of any desirable configuration within which may be received the free extremity of the switch actuating arm 44 of one or more switching elements 46. The switching elements 46 may be provided for energizing and deenergizing a load circuit such as a flood-lighting circuit for streets, parking lots or the like or, in the alternative, the switches 46 may be provided to actuate appropriate electrical circuitry that may in turn program the load circuit switch mechanism for appropriate actuation. For example, the switches 46 may be employed to energize a relay shown in broken line at 48 in FIG. 5 that may actuate the switching mechanism of the electrical circuitry disclosed therein.
Referring now again to FIG. 1, support element 50 may be provided with a flange 52 at the lower extremity thereof that may be fixed in any suitable manner to the support base wall 12. The vertical support 50 may be provided with upper and lower apertures respectively receiving upper and lower photoelectric cells 54 and 56 in fixed relation therein. The upper photoelectric cell 54 may be primarily supported by a photoelectric control housing 58 and may merely extend through an aperture provided in the vertical support 50 to expose the photoelectric cell in position to receive atmospheric light. The photoelectric control housing 58 may be composed of any suitable insulating material and may include a switch actuating mechanism responsive to relative flow of electrical current transmitted by appropriate electrical circuitry under control of the photoelectric cell 54 in response to light being received by the photoelectric cell. Typically, the switch actuating mechanism may incorporate a bimetal device that may be actuated by heat developed by a resistance element maintained in contact with the bimetal device. The bimetal device, upon being suitably heated, will cause physical movement of the contacts to the open position thereby deenergizing the load circuit to which the contacts may be connected. Specific examples of thermal responsive deenergization of a load circuit will be discussed hereinbelow in connection with FIGS. 6-14.
Referring now to FIG. 5, there is disclosed a basic schematic electrical circuit for actuation of a timing mechanism constructed in accordance with the present invention. A pair of conductors 60 and 62 may be provided across which a load 64 may be connected, which load may be any electrical structure powered by current from the conductors 60 and 62. To promote understanding of the present invention, however, the load will be described as an electrically energized floodlighting system that is desired to be energized at any suitable reduced atmospheric light condition and is adapted to be deenergized after the passage of a predetermined period of time that may be initiated by a suitable degree of morning atmospheric light. For purposes of simplicity, the predetermined condition of morning atmospheric light shall be referred to herein as dawn while the predetermined condition of evening atmospheric light shall be referred to herein as dusk. It is considered obvious that the apparatus of the present invention may be readily adjusted for any suitable as tronomical lighting condition such as twilight, dawn, sunrise or daylight, for example, without departing from the spirit or scope of the present invention.
Conductor 60 may be provided with a contact 66 that may be actuated between opened and closed positions by the photoelectric cell 54 that may also be connected across the conductors 60 and 62 and placed in series with a resistance 68. The photoelectric cell 54, the resistance 68 and the contact 66 are enclosed in broken line to illustrate such circuitry as the equivalent of a conventional dusk-dawn actuated photoelectric control system for a load such as a flood-lighting circuit.
The present circuitry incorporates a shunt circuit 70 having a shunt switch 72 that may be closed to shunt the photoelectric cell 54 thereby decreasing the resistance of the photoelectric circuit and causing the contacts 66 to open and thereby deenergizing the load circuit. A photoelectric cell, such as employed herewith, may have a resistance of 1,000 ohms in full daylight which resistance may increase to one megohm upon the occurrence of full darkness. The photoelectric cell 54 therefore controls the amount of current flowing across the resistance 68.
The resistance is typically the heater winding of a bimetal control mechanism for actuation of the contact 66 between its open and closed positions. It is obvious, therefore, that under conditions of darkness, the resistance of the photoelectric cell 54 will be sufficiently high to retard the flow of current across the resistance 68 sufficiently to cause the bimetal mechanism to maintain the contacts 66 in the closed position thereof energizing the load circuit. As dawn approaches, the light received by the photoelectric cell will cause its resistance to drop thereby increasing the flow of current across resistor 68 and heating the bimetal mechanism which in turn actuates the contact to its open position and deenergizes the load circuit when sufficient heat is developed in the resistance 68.
Assuming that the photoelectric cell 54 is in a condition of darkness and its resistance is increased sufficiently to retard the flow of current in resistance 68, the heat generated by the resistance will be insufficient to cause the bimetal element to retain the contact 66 in the open position thereof, which maintains the load circuit in energized condition through the closed contact. Under this condition the flood-lighting circuit would be operating. Upon closure of the shunt switch 72, current across the photoelectric cell 54 will be diverted eliminating the resistance of the photoelectric cell and suddenly increasing the flow of current across the resistance 68 and rapidly heating the bimetal element sufficiently to move the contact 66 to its open position resulting in deenergization of the load circuit, causing the lighting system to turn off.
The control circuitry may incorporate a clock motor circuit 74 having a clock motor switch 76 that may be actuated between open and closed positions to control energization of the clock motor circuit. The circuitry may also include a clock reset circuit 78 having the photoelectric cell 56 connected therein in series with a resistance element 80 and a reset switch 82. The resistance element 80 may be a resistance winding adapted for heating a bimetal element 81 that is operative to control actuation of a reset mechanism that resets the clock motor at its starting position upon thermal actuation of the bimetal element. The photoelectric cell 56, like the cell 54, is of low resistance in full light and increases substantially in resistance in darkness. Assuming the switch 82 to be closed, substantially retarded current will flow through the resistance winding 80 with the photoelectric cell 56 in darkness thereby maintaining temperature of the winding sufficiently low to prevent actuation of the bimetal element 81 to the reset position thereof. As dawn approaches, the resistance of the photoelectric cell 56 will decrease, thereby increasing the flow of the current in the resistance element 80 causing heating of the bimetal element 81. After the bimetal element has become sufficiently heated, it will actuate an electric circuit or move a mechanical mechanism identified by broken line, thereby causing the clock motor 22 to become reset to the starting position thereof.
It may be desirable to provide a temperature responsive mechanism for the timing sequence control mechanism of the present invention, which, according to the present invention may conveniently take the form illustrated in FIG. 2 where a light shield 51 may be disposed adjacent the lower photoelectric cell 56. The light shield may be capable of being moved from the full line position to the position illustrated in broken line at 56, responsive to a certain predetermined range of ambient temperature, to partially shield the photoelectric cell and thereby retard the light responsive initiation of the timing sequence. A bimetallic support element 53 may be fixed in any suitable manner to the vertical support 50 and may be adapted to support the light shield 51 in movable relation with the vertical support.
During the Winter season, when the ambient temperature is relatively low, the bimetallic support element 53 will be operative to move the light shield 51 to or near the full line position thereby allowing the photoelectric cell to be fully responsive to all available atmospheric light. Initiation of the timing sequence is not delayed and deenergization of the load circuit is achieved at or near the preselected cutoff time.
Conversely, during the Summer season when the ambient temperature is quite high in most parts of the Northern hemisphere, the bimetallic support element, responding to the high ambient temperature condition, will be operative to move the light shield from the full line position to or near the broken line position. The photoelectric cell is thereby partially shielded from the available atmospheric light and the internal resistance of the photoelectric cell will remain high preventing actuation of the timing sequence until light conditions become sufficiently bright to reduce the resistance of the shielded photoelectric cell.
To achieve proper contact actuation to open and close the contacts of the load circuit only in response to thermal conditions generated by the resistance level of a photoelectric cell, it is necessary that the contact actuating mechanism compensate for changes in ambient temperature and yet remain quite sensitive to heat induced by electrical resistance. It is also necessary that contact alignment be accurately maintained in order to insure full surface contact engagement to prevent burning that might otherwise occur by arcing across the contact elements. Where a single bimetal arm is employed to control contact movement, the controlling contact movement is typically of arcuant nature which tends to complicate a problem of maintaining positive alignment of the contacts. The contacts should be moved as nearly linearly as possible into full engagement to prevent arcing that might otherwise occur if the contacts should engage in misaligned condition. It is also appropriate that the contacts snap or move quickly to the open and closed positions without vibrating or chattering before positive opening or closing movements are achieved. A chattering or vibrating condition may tend to cause arcing and burning of the contacts.
In providing for effective position movement of the contacts of the load circuit between open and closed condition, it may be necessary for the contact actuating mechanism to compensate for changes in ambient temperature and yet achieve positive aligned relation between the contacts to prevent arcing and burning of the contacts that might otherwise occur. It may be also appropriate to cause the contact to move substantially linearly in a snap or rapid opening and closing movement to prevent chattering or burning of the contacts. Accordingly, a temperature responsive contact actuating mechanism according to the present invention, may conveniently take the form illustrated in FIG. 6 where movement of the contacts is achieved substantially linearly and by snap action responsive to ambient temperature compensated helical bimetal elements 82 and 84 that may be secured in spaced relation with the inner wall 86 of a generally circular housing 88 by an insulating material 90 that may be composed of any one of a number of both thermally and electrically insulative materials including the capability of adhering to both metal and plastic. The bimetal elements 82 and 84 may be maintained in spaced relation at the secured extremities thereof by a body 92 of similar insulating and bonding material. It may be appropriate to form a singular body of insulating material to secure the bimetal elements in fixed relation with the wall structure of the housing 88 and to maintain them in spaced and electrically insulated relation.
As illustrated in detail in FIG. 7, which shows portions of the bimetal elements in section, each of the bimetal elements is composed of laminated metal strips 94 and 96 that are capable of controlled movement when heated and cooled. Both of the bimetal elements therefore respond in similar manner to changes in ambient temperature thereby causing contact elements 98 and 100 to be maintained in aligned properly oriented relation at all times regardless of the particular ambient temperature to which the bimetal elements might be subjected. Bimetal 84 may be provided with a covering 102 of insulating material that serves to retard transfer of heat from the atmosphere surrounding the bimetal element to the laminated metallic strip 96. This feature causes the bimetal element 84 to be slowly responsive to changes in ambient temperature and prevents it from being excessively sensitive to changes that occur when the opposite bimetal element 82 is heated electrically.
Bimetal element 82 may include a similar covering 104 of thermal insulating material that also has a capability of providing electric insulation about which a resistance winding 106 may be wound.
As illustrated schematically in FIG. 6, the photoelectric cell 54 may have its circuit connected in series with the resistance winding 106 thereby providing for energization of the resistance winding in direct response to the internal resistance of the photoelectric cell. Conductors 108 and 110 represent a load circuit connected respectively to the bimetal elements 82 and 84 which causes the load circuit to be completed by closing of the contact elements 98 and 100. Contact 100 may be supported by a permanent magnet 112 serving to urge the contacts 98 and 100 into engagement. Magnet 112 insures that the contacts 98 and 100 are snapped closed by the flux of the magnet or open against the force exerted by the magnetic field of the magnet to energize and deenergize the load circuit without allowing a condition of chattering to occur that might otherwise allow arcing to damage the contacts.
As the resistance of the photoelectric cell 54 increases in response to a subdued atmospheric light condition, the flow of current through the resistance winding 106 will be decreased, thereby causing cooling of the bimetal strip 94 of the bimetal element 82 which causes the bimetal element to shorten and cause movement of the contact element 100 and magnet 112 upwardly thereby urging the contact element 100 toward contact element 98. As the contact elements are moved intojuxtaposition by the bimetal element, upon cooling thereof, the magnetic field of the magnet 112 will snap the contacts together thereby completing the load circuit.
Conversely, in response to a condition of increased atmospheric light, the resistance of the photoelectric cell 54 will decrease thereby allowing increased current flow in the resistance winding resulting in heating of the bimetallic strip 94 of bimetal element 82. The bimetal element 82, upon being heated, will elongate and cause movement of the contact element 100 and magnet 112 downwardly tending to separate the contact elements 98 and 100 against the force created by the flux of the magnet. Upon the occurrence of a sufficient separating force, the force created by the magnetic field of the magnet will be overcome and the contact elements will snap apart opening the load circuit.
As an alternative it may be desirable to provide structural elements fixing the inner extremities of the bimetallic arms 82 and 84 relative to the housing 88 and to allow the opposite extremities thereof to be free for movement for the purpose of opening and closing contacts that might be provided adjacent the inner wall 86 of the housing. It is only necessary that the bimetallic arms be capable of movement responsive to changes in temperature thereof and that such movement be compensated for ambient temperature in the manner discussed hereinabove.
With reference now to FIG. 8, there is illustrated a modified embodiment of the thermally compensated bimetal contact actuating mechanism that includes a support element 114 that may be secured in any suitable manner to the inner peripheral wall 116 of a hous ing 118 constructed similar to the housing 88 described above in connection with FIG. 6. A bimetal element 120 may be secured to the support element 114 and may be provided with an insulating covering 122 about which may be wrapped a resistance winding 124. A fixed contact 126 may be secured to the bimetal element 120 adjacent the inturned portion of the support element 114 thereby securing contact 126 in substantially immovable relation with respect to the housing structure. A structural bridge element 128 may be provided with angulated extremities 130 and 132 to which may be fixed corresponding extremities 134 and 136 respectively of the bimetal element 120 and a corresponding bimetal element 138. A permanent magnet element may be provided at the free extremity of bimetal element 138 and may support a contact clement 142 disposed in alignment with contact element 126. As the bimetal element 120 is heated by resistance winding 124, in response to change in the internal resistance of a photoelectric cell 54, the bimetal element 120 will become flexed and through its bridged connection with bimetal element 138 will cause substantially linear movement of the free extremity of bimetal element 138 thereby moving the magnet 140 and contact element 142 in substantially linear manner. The magnet or spring element 140 is provided to cause snap actuation during both opening and closing movements to prevent burning of the contact elements 126 and 142, as discussed above. Opening and closing movements of the contact elements 126 and 142 will be achieved in similar manner as discussed above in connection with FIG. 6.
As shown schematically in FIG. 8 the circuit of the photoelectric cell 54 may be connected in series with the resistance winding 124 to one conductor of the load circuit. The load circuit is shown to be completed through the contact elements 126 and 142 in the closed position thereof.
Referring now to FIGS. 9 and 10 a modified bimetal actuated switch actuating mechanism is illustrated utilizing a snap action blade mechanism for opening and closing the contacts of a load circuit. The bimetal element 144, illustrated in plan view in FIG. 10, is cut away in such manner as to define a blade 146 to which an upper contact element 148 may be fixed in any suitable manner. The blade 146, upon heating of the bimetallic element 144, will snap between positions opening and closing the load circuit in the manner discussed hereinbelow. A base member 150, that may be the bottom wall of a generally cylindrical housing, may be provided to which one extremity of the bimetallic element 144 is secured by means of a screw 152 or any other suitable means of connection. An electrical connector element 154 may be secured between the screw 152 and the bimetal element 144 to establish electrical contact between one conductor 156 of the load circuit. The remaining conductor 158 of the load circuit may be connected to a contact element 160 carried by the base member 150.
Heating of the bimetal element 144 may be accomplished by means of a resistor 162 composed of material having positive temperature coefficient of resistance and which may be of generally circular configuration having one side thereof connected in a series with the circuit of a photoelectric cell 164 and with the opposite extremities thereof connected to leg 156 of the load circuit. A thermally conductive plate 166 that may be composed of copper, for example, may be secured in any suitable manner to the carbon resistor 162 and may be maintained in intimate engagement with the bimetal element 144 in any suitable manner. Alternatively, the resistance element may have metallized upper and lower surface that may be disposed for direct contact with the bimetal element 144. The heat transfer element 166 merely serves to transmit heat generated by the carbon resistance element 162 to the snap action bimetal element 144. The photoelectric cell 164 may be fixed to a wall structure of the housing in such manner that the photoelectric cell is exposed to receive atmospheric light.
Referring now to FIGS. 11 and 12, there is disclosed a further modified embodiment of the thermally responsive load switch actuating mechanism. It may be appropriate to utilize a snap action blade as a simple and effective photocontrol system for actuating the contacts of a load circuit. A contact actuating mechanism of this nature may conveniently take the form illustrated in FIGS. 11 and 12 where a body element 168 of electrically and thermally non-conductive material may be utilized to which may be fixed a pair of bimetal blade elements 170 and 172. The lower bimetal element 172, illustrated in greater detail in FIG. 12, may include a bimetal strip 174 having a covering of electrically and thermally non-conductive material 176 about which may be wrapped a pair of spaced resistance windings 178 and 180. Each of the resistance windings may be connected in series with the circuit of a photoelectric cell 182 which series connection may be modified by a biased contact element 184 fixed to the bimetallic element 172.
A conductive strip 186 may be secured about the bimetallic element 172 and may serve to connect the resistance winding 180 in series with the photoelectric cell depending upon the position of the bimetallic arms 170 and 172. The contact element 184 may be adjusted by means of an electrically non-conductive screw 188, extending through a threaded aperture formed within the upper bimetallic arm or strip 170. In the closed position of the contacts, as illustrated in FIG. 11, the screw 188 will cause the contact element 184 to be urged into contact with the conductive strip 186, thereby connecting winding 180 into series with winding 178 and into series with the circuitry of photoelectric cell 182. As soon as the contacts are moved apart by flexing of the bimetallic strip 174 in response to heating thereof, the contact element 814 will be moved out of engagement with the conductive strip 186, as illustrated in FIG. 12 thereby disconnecting winding 180 and thereby substantially reducing the degree of heat windings 178 and 180, if a series circuit is employed. Opening and closing movement of the upper and lower contacts 190 and 192 is controlled in part by the bimetallic strip 174 and in part by a permanent magnet 194 to achieve snap action in both opening and closing movements of the contacts. The contact actuating structure illustrated in FIGS. 11 and 12, therefore, provides a mechanism for heating the bimetallic strip element that is of variable nature to control the amount of heat being transmitted to the bimetallic strip to opening the contacts and to maintain the contacts in the open position.
An alternative embodiment of the contact actuating mechanism of the present invention may incorporate a body structure 196, as illustrated in FIG. 13, that may support bimetallic arms 198 and 200 supporting contacts 202 and 204 respectively. A permanent magnet 206 may be employed to achieve snap actuation during opening and closing movements in the manner discussed hereinabove. The bimetallic arm 198 may be provided with an insulated covering 208 having a resistance winding 210 wound thereabout and connected in series with the circuit of a photoelectric cell 212. The resistance winding 210 may in turn be connected to one conductor 214 of a load circuit that is completed by closing of contacts 202 and 204 to energize the load circuit.
The contact actuating mechanism illustrated in FIG. 13 functions in similar manner as discussed above with the bimetallic element 198 being heated by the resistance winding 210 and flexing under the influence of heat to move the upper contact element 202 out of engagement with the lower contact element 204.
Although the operational sequence of the circuitry illustrated in FIGS. 4 and 5 may vary depending upon circumstances involved, the following is an example of an operational sequence concerning a lighting system that is desired to become energized at dusk and to become deenergized at some predetermined time thereafter under dark conditions, such as midnight, for example. It is not intended that the lighting system remain energized until dawn as is typically the case. It is desirable however that the lighting system be deenergized as nearly as possible to the preselected time but it is not generally convenient to employ a synchronized timing mechanism to achieve cutoff at the precise preselected time because of the various costs discussed above.
Assuming the relay 48 has been actuated to move the switches 72, 76, and 82 to the positions illustrated in FIG. 5, it is apparent that the clock motor circuit 74 will be energized and the clock motor will thereby be engaged in a timing sequence. Under this condition the reset circuit 78 will be deenergized by virtue of the open switch 82 while the contact actuation circuit 76 will be responsive to the internal resistance of the photoelectric cell 54 to either activate or de-activate the load circuit depending upon conditions of light and darkness to which the photoelectric cell may be subjected.
Assuming that a condition of daylight exists, the resistance of the photoelectric cell 54 will be low and therefore the flow of current through the photoelectric cell 54 and the resistance winding 68 will be sufficient to heat the resistance winding to the point causing bimetal element 69 to maintain the contact 66 in the open position thereof deenergizing the load circuit 64.
Upon the occurrence of dusk the resistance of the photoelectric cell 54 will increase thereby restricting the flow of current through the resistance windings 68 and reducing the temperature of the bimetal elements 69 sufficiently to allow the bimetal element to move the contact 66 to its closed position thereby energizing the load circuit and causing the lighting system to flood the desired area with light. After the clock motor 22 has completed its timing sequence, the relay 48 will be activated thereby moving the switches 72, 76, and 82 to the FIG. position thereof causing the following functions to occur. The shunt switch 72 upon moving to its closed position, shunts the photoelectric cell 54 thereby substantially increasing the flow of current through the resistance winding 68 and heating the bimetal element 69 which causes the contact 66 to be opened to deenergize the load circuit and turn the lighting system off. The switch 82, upon being closed, energizes the reset circuit 78 thereby causing current to flow through the resistance winding 80 and the photoelectric cell 56. Because of the condition of darkness however the resistance of the photoelectric cell will be quite high thereby retarding the flow of electrical current through the resistance winding sufficiently to maintain the bimetal element 81 in inoperative position. The clock motor 22 will be stopped under this condition because the switch 76 will be maintained in its open position by the relay 48.
As dawn approaches, the light received by the photoelectric cell 56 will reduce the resistance thereof sufficiently to increase the flow of current through the resistance winding 80 thereby heating the resistance winding and the bimetal 81 sufficiently to cause the reset bimetal to actuate the clock motor back to its reset position. Simultaneously, the bimetal element will induce actuation of the relay 48 causing the switch elements to move back to the opposite positions thereof.
It may be desirable that switches 72, 76 and 82 be sequentially actuated to allow the circuitry to shut itself down in condition to be reactivated by the reset circuit at dawn. For example, at the termination of a timing sequence of the clock motor it will be necessary that the lighting provided by the load circuit be extinguished prior to energization of the reset circuit to prevent the reset circuit from initiating a timing sequence in response to light produced by the load circuit. This feature may be accomplished by first closing the shunt switch 72 causing opening of the contact 66 in the manner indicated above and thereby extinguishing the lighting system. After this has been accomplished the reset switch 82 may be closed thereby readying the reset circuit for actuation of the reset mechanism at dawn. As soon as the reset switch 82 has been closed, the clock motor switch 76 will be opened thereby deenergizing the clock circuit and eliminating unnecessary actuation of the clock motor. The relay 48 therefore must be effective to cause sequential movement of the switches to their respective positions.
Depending upon the latitude at which a lighting system or other load circuit may be disposed, it may be desirable to provide a timing sequence control mechanism that compensates for the differences in relative length of night and day during the year in order to achieve cutoff of the lighting system or deenergization of a load circuit as near as is practical to the selected cutoff time. Accordingly, a mechanism for compensating for differences in length of day and night and achieving cutoff of a lighting circuit or other load circuit may conveniently take the form schematically illustrated in FIGS. 14 through 18 where a timing mechanism is illustrated generally at 220 with the various parts thereof illustrated in the neutral position at the start of a timing sequence. A selector plate 222 may be disposed in substantially immovable relation with a permanent stop 224 during any particular timing sequence although the stop 224 may be adjusted relative to the selector plate 222 in order to achieve variation in selected cutoff time. A first rotor 226 may be pivoted about a pivot point 228. A first advance lever 230 may be disposed in fixed relation with rotary plate 226 and may be operative to impart movement to a first switch arm 232 also pivoted at point 228 and being provided with a switch mechanism 234 that is normally closed and is opened upon engagement by the first advance lever 230. A resilient element 236 such as a leaf spring may be provided for the first switch arm 232 and may be disposed for engagement by a timing variation device 238 that may, if desired, conveniently take the form of a pin that is carried by rotary plate 226 and may be disposed in substantially fixed relation with the first advance lever 230.
A second advance lever 240 may be pivoted about the pivot point 228 and may be disposed for engagement with a second switch mechanism 242 conveniently carried by a second switch arm 244. The switch 242 may be normally open and may be closed by slight pressure exerted between the advance lever 240 and the switch mechanism 242. The switch mechanism 242, for example, may include an internal spring mechanism that must be overcome by pressure exerted by the advance lever 240 to cause the normally open switch mechanism to close andactuate the load circuit to which the switch mechanism may be connected.
The timing variation 238 may be a pin, as indicated above, that may be caused to move downwardly upon energization of the load circuit at dusk when not supported by the selector plate 222. It should be noted that the selector plate has an arcuate cutaway portion defining shoulders 246 and 248 and defining an are that represents a predetermined period of time which period may be employed for seasonal control purposes. For example, the period of time represented by the arc between shoulders 246 and 248 may, if desired, represent a sixteen hour period measured from dawn. If seasonal lighting conditions cause dusk to occur before termination of the sixteen hour period, the mechanism is adapted to deenergize the load circuit after passage of a predetermined period of time measured after the occurrence of dawn. If seasonal atmospheric lighting conditions cause dusk to occur after passage of a 16 hour period of time then the mechanism is adapted to deenergize the load circuit after passage of a second selected period of time also measured from the occurrence of dawn. It is therefore seen that the present invention contemplates deenergization of the load circuit after passage of periods of time measured from the occurrence of dawn which periods may be variable depending upon the length of daylight hours determined by seasonal atmospheric lighting conditions.
A second actuating device 250 may be fixed relative to the rotary plate 226 and may be employed to create mechanical pressure locking the first and second ad vance levers in substantially immovable relation during the remainder of any particular timing sequence. The
locking pin or locking mechanism 250 may, for example, be actuated by a bimetal element in response to heat created by a resistance winding that is energized simultaneously with energization of the load circuit. Any other suitable mechanism such as a solenoid actuated locking device, for example, may be employed for temporarily securing the advance levers 230 and 240 in immovable relation.
After any timing sequence has been completed and the load circuit has been deenergized, the various movable parts of the timing mechanism may be returned to the neutral position illustrated in FIG. 14. Spring devices, or any other suitable mechanism, may be employed to return the movable parts of the timing mechanism to the neutral position without departing from the spirit and scope of the present invention.
Assuming the timing sequence to be started by a morning atmospheric lighting condition, referred to as dawn, and as described above in regard to FIGS. 1 and 2, the switch mechanism 242 will be disposed in its normally open position thereby maintaining the load circuit in a deenergized condition. Assuming the load circuit to be an electrical lighting system for streets, parking lots or the like, the lighting system will be off during the daylight hours.
With reference now to FIG. 15, the timing mechanism is illustrated in a position that it may take at the occurrence of dusk. The rotary plate 226 will have rotated the advance lever 230 from the FIG. 14 position to the FIG. '15 position thereof. At the occurrence of dusk, the timing mechanism will actuate the locking mechanism 250 thereby causing the advance levers 230 and 240 to become secured in relatively immovable relation. After the advance lever 240 has become temporarily locked in assembly with the rotary plate 226, continued rotation of the rotary plate by the drive motor of the timing mechanism will cause rotation of the advance lever 240, thereby applying sufficient pressure on the switch mechanism 242 to move it from its normally open position to the closed position, thereby energizing the load circuit. The lighting circuit is therefore energized or turned on at dusk and the timing sequence continues from its initiation at dawn. If desired, the lighting sequence may be initiated at dusk but the timing mechanism may delay energization of the lighting circuit until a condition of substantial darkness exists thereby conserving electrical power.
As shown in FIGS. 15 and 16, dusk occurs before expiration of the sixteen hour period prescribed by the arcuate cutaway portion defined between shoulders 246 and 248 on the selector plate 222. The same mechanism which achieves movement of locking mechanism 250 may also preset the timing variation mechanism 238 to a position controlling the total length of the timing cycle. Described in its simplest terms for purposes of understanding, the timing variation mechanism may move downwardly since no support is provided by the selector plate 222, thereby causing the timing variation device to pass underneath the selector plate 222 to prevent engagement between the timing variation device and the spring 236 of the switch arm 232. Since the spring 236 is not contacted by the timing variation mechanism, the switch arm 232 will remain in the position illustrated in FIG. 16 until it is contacted by the advance lever 230, which causes opening of the normally closed switch mechanism 234 and thereby deenergizes the load circuit or turns the lighting system off.
It is therefore apparent that during Winter lighting conditions, when days are relatively short and dusk occurs quite early, the shutoff period for the lighting system or control circuit will occur at or near a preselected cutoff time such as midnight, for example.
Referring now to FIGS. 17 and 18, it may be observed that dusk occurs after expiration of the sixteen hour period initiated by the occurrence of dawn. The timing sequence will again be initiated with all movable parts thereof in the position illustrated in FIG. 14, with the timing sequence being again initiated by the occurrence of dawn. As illustrated in FIG. 17, the timing sequence has continued rotation of the rotary plate 226 sufficiently to move the advance lever 230, the timing variation mechanism 238 and the position locking mechanism 250 past the shoulder 248 of the selector plate 222. At dusk, the load circuit is energized, turning the lighting system on and actuating the position locking mechanism 250 and the timing variation mechanism 238. The position locking mechanism will function to lock advance arm 240 in fixed relation with the rotary plate 226, thereby causing the advance lever 240 to be moved into actuating engagement with switch mechanism 242 and thereby closing the normally open switch which energizes the load circuit.
The timing variation mechanism will be positioned above the selector plate 222 upon energization of the load circuit, thereby preventing the timing variation mechanism from moving away from a position causing engagement with the spring 236 of switch arm 232. As the timing sequence continues, the timing variation mechanism 238 will move into engagement with the spring 236 and will urge the switch arm 232 to move clockwise about its pivot point 228 toward the positive stop 224. The spring 236 will prevent the advance lever 230 from contacting the switch mechanism 234 until the switch arm 232 has been rotated to a position contacting the permanent stop 224, as shown in FIG. 18. After the switch arm 232 has contacted stop 224, continued rotation of the rotary plate 226 by the timing mechanism, will cause the force of spring 236 to be overcome, thereby allowing advance lever 230 to engage the switch mechanism 234 causing opening of the normally closed switch which deenergizes the load circuit and simultaneously resets the circuit mechanism in condition for energization at dawn. Upon the occurrence of dawn, the photoelectric cell 56 illustrated in FIG. 5 will cause resetting of the mechanical parts of the timing mechanism to the start position and simultaneously will initiate operation of a timing sequence by starting the clock motor 22.
The timing sequence is therefore initiated at dawn each day and continues until expiration of a predetermined period that might be varied by the length of daylight hours occurring in relation to a predetermined portion of the timing sequence such as the 16 hour timing variation control period. The load circuit will be energized at dusk responsive to photoelectric cell circuit and is deenergized after expiration of a predetermined period of time measured from initiation of a timing sequence at dawn. The timing mechanism is reset at the termination of the timing sequence. Although a single variation of the timing sequence is identified by the relationships between a predetermined portion of the timing sequence, i.e., the 16 hour variation control peallowing deenergization of the load circuit to occur at or quite near a preselected time each night without necessitating the provision of a clock actuating device that must be synchronized with the time of day.
As indicated above it may be desirable that the circuit timing mechanism be capable of compensating for difference in the length of periods of daylight and darkness during the year in order to achieve cutoff of the electrical load circuit at approximately the same preselected time during each night. An alternative mechanism for achieving compensated timing may conveniently take the form illustrated in FIGS. 19 and 20 where in FIG. 19 there is diagrammatically illustrated a plan view of a base plate 260 that may be rotated about an axis 262 along with a rotatable cam element 276. The plate 260 may be provided with an arcuate rack element 264 having a plurality of teeth or retention that are disposed for engagement by a bimetallic arm 266 that may be connected to the plate 260 at the pivot 262. The arm 266 is provided with a variable curved portion 261 that causes movement of the arm 266 through an arc defined by rack 264 upon being heated by a resistance winding in response to positioning of a second bimetallic arm carried by the cam element and being disposed in contact with an arcuate resistance element 270. The bi-metallic arm 266 may carry a switch element 272 at the free extremity thereof which may be disposed for engagement with the switch actuating arm 274 carried by a cam element 276 shown in FIG. 20.
In FIG. 20 there is shown the bottom view of a cam element 276 that may be superposed above the base plate 260 and may be retained in assembly therewith. The cam element 276 may include a low temperature clutch 278 composed of an alloy having a relatively low melting point. A bimetallic contact arm 280 may be provided with a resistance winding 282 serving to heat the bimetallic arm and to position the contact 28] thereof relative to the arcuate resistance element of the control mechanism. Heating of the resistance winding 282 may be controlled by energization of a photoelectric cell circuit such as the reset circuit illustrated in FIG. 5. It is evident that the fixed resistance of the resistance winding 268 will be connected in series with a variable resistance determined by engagement between the resistance strip 270 and the contact 281 as the arm 280 is heated by the resistance winding 282. Heating of the bimetallic switch arm 266 is therefore variable in response to positioning of the bimetallic arm relative to the variable resistance 270.
The rotatable cam 276 and the base plate 260 are adapted to be disposed and superposed relation with cam plate 276 being located above the plate 260. The clutch 278 serves to position the plates 260 and 276 one relative to the other for the purpose of controlling cutoff time of a load circuit to which the time delay mechanism may be connected. The two plates are so related that the bimetallic contact arm 280 is disposed with its contact 281 located engagement with the conductive arc of resistance material 270 upon heating of the arm 280 by the resistance winding 282. When the circuitry of the timing mechanism is energized by the photoelectric cell 54 in response to the occurrence of dusk the resistance winding 268 will heat the bimetallic strip 266 for a limited period of time required to cause the bimetallic strip to rotate the switch to some particular step on the arcuate rack 264. The position the arm 266 will take relative to the arcuate rack 264 will be determined by the variable resistance that will be determined by the series connection between the fixed and variable resistance elements 268 and 270, respectively.
After limited heating of the bimetallic switch arm 280 the heating circuit will be automatically deenergized and the rack 264 will retain the switch actauting arm 266 in the particular position it assumed upon being heated. A switch actuating arm, such as illustrated in 230 in FIGS. 14-18, may then be rotated by the timing mechanism sufficiently to contact the switch 272 thereby de-energizing the load circuit.
The operative parts of the time delay mechanism may be allowed to remain in the position assumed during a previous timing sequence until the following morning when the reset mechanism functions in response to the photoelectric circuit 56 at which time the switch arm 266 will be returned to a starting position and will then remain in the starting position until the occurrence of dusk, at which time it will be again set to some predetermined position relative to the arcuate rack to cause a predetermined delay in the cutoff time of the timing mechanism. It can therefore be readily understood that the length of movement of the bimetallic arm 266 bearing the switch 272 will be relatively small when the time period from dawn to dusk is at a minimum, for example 15 hours of daylight, because the full length of the arc of the printed resistance 270 will be disposed in series with the actuating resistance 268. On the other hand should dusk occur after a longer period of time, for example 17 or 18 hours of daylight, there will be less of the arcuate resistance in series with the fixed resistor provided for actuation of the switch arm and therefore the bimetallic arm will be heated in such manner as to move it a greater degree relative to the rack 264. Longer periods of daylight therefore automatically delay cut-off of the load circuit in order to provide cutoff at approximately the same time each night.
Although the structure in FIGS. 19 and 20 generally teach the use of a rheostat or varying resistor in series with a fixed resistor to heat a bimetal element and thereby achieve controlled movement of the bimetal element for time delay purposes, it is not intended that the present invention be limited to thermally controlled time delay circuits of the nature illustrated in FIGS. 19 and 20. Magnetically actuated switches may be employed, for example, to cause selective time delay in such manner to achieve cutoff of a load circuit a predetermined time each night.
It would be desirable to provide a load circuit timing control system that would be adapted to various voltage conditions that might be found where the load circuit is being installed. As illustrated in FIG. 21, one acceptable multiple voltage circuit is illustrated schematically, which may include a varistor 290 that may be connected in parallel with a typical photocell actuated light responsive circuit illustrated generally at 292. Fuses 294 and 296 may be connected in parallel with fixed resistors 298 and 300 respectively to establish operative resistance of the controlled circuitry. Current utilized by the control circuit will flow through the varistor 290 in parallel with 292, and will bypass the resistance elements 298 and 300 by flowing through the fuses 294 and 296. In the event the voltage current across fuses 294 and 296 is excessive, one or both of the fuses will rupture thereby automatically placing one or both of the resistances 298 and 300 in series connection with the varistor and light responsive circuit in parallel. It is evident, therefore, that a low voltage condition will not rupture either of the fuses 294 and 296 and the resistances 298 and 300 will be bypassed. If the circuitry should be installed under conditions where the voltage might be excessive one or both of the fuses will rupture and the total resistive value of the circuitry will be modified automatically to withstand the voltage to which the load circuit might be subjected.
Referring now to FIG. 22, the circuitry of FIG. 1 may conveniently take the form of a multiple voltage module having wafer-like resistors that may be disposed in stacked relation with a varistor and with fuses functioning essentially as illustrated in FIG. 21. A plurality of metal plates 302 may be interposed between the resistors and the varistor of the multiple voltage module and may be provided with connecting tabs 303 to which the various fuses 294 and 296 may be connected. Each of the resistors and the varistor may be provided with metalized surfaces 305 that are disposed for engagement by the plates 302. A header element 304 may be provided with a plurality of connectors 306 to which'the various conductors of the multiple voltage module may be connected. I have therefore provided a multiple voltage module constructed in accordance with the schematic circuit illustrated in FIG. 21 that is readily adapted for typical voltage conditions that might be found at any particular load circuit installation. It will not be necessary, therefore, to provide timing sequence control circuits that are specifically designed for particular voltages that might be encountered because the multiple voltage module effectively adapts the circuitry for effective performance under different voltage conditions.
As indicated above, when high voltage conditions are encountered, typical resistance windings may not be capable of functioning because the windings are generally of delicate construction. Moreover, it may be necessary or desirable to provide multiple contacts for simultaneous circuit actuation. Accordingly, a temperature responsive mechanism for opening and closing multiple contacts of a load circuit may conveniently take the form illustrated in FIGS. 23, 24 and 25 where a bimetal element 320 is shown to be provided with a heat responsive movable arm 322 carrying a pair of contacts 324 that are electrically insulated from the arm by an insulator 326. The contacts 324 and 326 may be energized by flexible conductive braid 328 and 330 that is looped as best illustrated in FIG. 25 to prevent the weight of the braid from interfering with free movement of the switch actuating arm 322.
The bimetallic element 320 may be provided with a connector portion 332 provided with an aperture 334 through which may be received a screw or other connector device that may function essentially as disclosed in FIGS. 9 and to fix the bimetallic element relative to other structure. Likewise as illustrated in FIGS. 9 and 10, the bimetallic element may be heated by a resistance element that may take the form of a circular resistor such as shown at 162.
As mentioned above, the structure shown in FIGS. 9 and 10 may be modified to eliminate the heatconductive plate 166. A preferred embodiment of the invention without such plate is shown in FIGS. 26 and 27.
In FIG. 26 the bimetallic element 144 is of the same configuration shown in FIG. 10. The resistor 162 may be of the positive temperature coefficient (PTC) type, so as to provide a current-limiting function as the temperature of the resistor 162 and of the bimetallic element 144 increases. The resistor 162 is coated or sprayed on its upper and lower surfaces with an electrically conductive material, such as silver, to assure good contact between the resistor 162, the bimetallic element 144, and a spring element 401, described below.
In the lembodment of FIG. 26, the bimetallic element 144 is fastened to the plastic housing by means of conductive screw 152 and hex nut 404, to which lead 156 is electrically connected by means of any suitable lead connector (not shown). It should be understood that the lead connector and hex nut 404 may be recessed in the bottom wall of the housing 150.
Contacts 148 and 160 may have flat contacting surfaces as shown in FIG. 26, but I have found that it is advantageous in such a structure to round the contacting surfaces, making each such surface somewhat convex. This helps to assure reliable functioning in the assembly here being described. Contact 160 is connected to a conductive rivet shank 405 for fastening in the housing 150 as shown in FIG. 26. Here too it should be understood that the rivet end may be recessed in the housing 150, and that lead 158 is electrically connected to the rivet 405 by means of any suitable lead connector (not shown).
In slidable relationship with the top surface of the re sistor 162 is an electrically conductive spring element 401, having the shape shown in FIGS. 26 and 27. The bifurcated end of spring element 401 permits easy, sliding assembly of the entire structure, in the following manner. A tapered Teflon button 403 is initially seated in the resistor 162, before assembly. The button 403 serves to restrain the resistor against moving off the bimetallic element 144, and it also assures good contact between the bifurcated ends of spring element 401 and the silvered top surface of the resistor 162. From FIG. 28 it will be seen that the Teflon button 403 has a tapered portion 413, and a body portion 414 with rounded corners 415. The body 414 thus sits loosely in resistor 162 (FIG. 26), and the rounded surfaces provide a ball-joint-like action as the switch opens and closes.
As seen in FIGS. 26 and 27, the conductive spring element 401 has a curved portion 407 providing the spring action, biasing the resistor 162 downward, and a straight portion 408. The straight portion 408 contains a hole 406, through which a conductive rivet 402 is passed, to secure the spring element 401 to the housing 150 and to provide an electrical connection for lead 409 to the photocell circuit 410, which operates as described above with regard to FIGS. 9 and 10.
For higher-load applications, the braid and contact arrangement shown in FIGS. 23-25 and described above, may be similarly employed in the structure of FIG. 26.
In view of the foregoing, it is apparent that I have provided a novel timing sequence control mechanism for load circuits, such as electric flood-lighting circuits and the like that utilizes a timing sequence initiated by a predetermined condition of morning atmospheric light such as dawn, for example, that effectively compensates for seasonal differences in the length of daylight and achieves deenergization of the load circuit at approximately the same time each night. The timing sequence control mechanism of my invention effectively utilizes simple photoelectric control circuits to achieve initiation of the timing sequence and to achieve energization of the load circuit in response to predetermined decrease in evening atmospheric light.
I have also provided a novel timing sequence control mechanism capable of providing a timing sequence initiated by a predetermined degree of morning atmospheric light, which sequence may be varied by the relative length of daylight hours during particular seasons of the year or which may conveniently be varied by variations in ambient temperature occurring due to seasonal changes.
In response to changes in internal resistance of a photoelectric cell a resistance is heated by current flowing through the circuit of a photoelectric cell and through a resistance winding connected in series therewith which heats a bimetallic element and causes opening and closing movement of contacts through which the load circuit is completed. My invention effectively provided novel bimetallic elements that compensate for changes in ambient temperature and achieve actuation of the load circuit that is unaffected by changes in ambient temperature. Moreover, the novel construction of the bimetallic contact actuation elements of my invention is such that substantially linear contact movement caused during heating and cooling of the bimetallic elements results in substantially linear movement of the contacts and maintains accurate alignment of the contacts in the closed position to prevent arcing that might otherwise cause burning of the contacts. My invention is also effective to cause snap actuation of the contacts both to the open and closed positions, thereby preventing chattering of the contacts which otherwise might occur and might cause burning of the contacts by arcing.
For applications of the apparatus of FIGS. 26-28 wherein it is desired that the contacts be normally open rather than normally closed, it will be appreciated that, by rearranging the components such that the contacts 148 and 160 are on the opposite side of the bimetal arm 146, normally open operation may be attained.
It is therefore seen that this invention is one well adapted to attain all of the objects and advantages hereinabove set forth together with other advantages which will become obvious and inherent from a description of the apparatus itself. It will be understood that certain combinations and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the present invention.
As many possible embodiments may be made of this invention without departing from the spirit or scope thereof, it is to be understood that all matters, hereinabove set forth or shown in the accompanying drawings, are to be interpreted as illustrative and not in any limiting sense.
1. A light responsive electrical contact actuating device, comprising:
a. A supporting housing;
b. a heat-responsive plate-like bimetallic element carried by the housing, said element including a temperature-movable cutaway blade portion and a first electrical contact carried by the blade portion;
c. a resistor, having flat top and bottom surfaces, mounted on said bimetallic element and movable with the blade portion thereof;
d. an electrically conductive spring fastened to the supporting housing and in spring-biasing, slidable electrical contact with said resistor;
e. a second electrical contact, fixedly connected to the housing; and
f. a photoelectric cell connected in series with said resistor and controlling current therethrough in response to conditions of light and darkness.
2. The device of claim 1:
a. Wherein said contact means comprises a plurality of electrical contacts insulated from and carried by said arm and adapted for contacting engagement with a plurality of associated contact elements; and
b. further comprising flexible insulated electrical braid connected to said electrical contacts and supplying current thereto, said electrical braid being looped to allow unrestricted movement of said arm of said bimetallic element.
3. The device of claim 1:
a. Wherein said spring has a bifurcated end; and
b. further comprising a tapered low-friction button, a portion of the button being seated in the resistor and a portion thereof being engaged between the bifurcations of the bifurcated end of the spring.