US 3815816 A
A condition responsive switch device comprising a member with a liquid passageway therein, a reservoir of conductive liquid, such as mercury, at one end of the passageway defining a movable contact, a stationary contact at the opposite end of the passageway normally spaced from the conductive liquid but contacted thereby under predetermined conditions. Preferably, an expansion chamber is provided above the passageway permitting uninhibited movement of the conductive liquid toward the stationary contact. In addition, a solid conductor may be provided in the passageway to reduce the volume of the conductive liquid and increase the current carrying capacity of the device.
Claims available in
Description (OCR text may contain errors)
United States Patent [1 Scarelli 1 June 11, 1974  gg jgg RESPONSWE SWITCH FOREIGN PATENTS OR APPLICATIONS 957,227 9/]927 Australia 337/331  Inventor: David F. Scarelli, 214% E. Spruce 1,233,461 2/1967 Germany 337/331 St., East Rochester, N.Y. 14445  Filed, Jam 3, 1973 Prirnary EXamir IeF-Bernard Gilheany Asszstant Examiner-A. T. Grlmley PP 320,814 Attorney, Agent, or Firm-Clarence A. OBrien; Harvey B. Jacobson  [1.5. CI 337/331, ZOO/84 R, 2OO/l9l,
337/21, 337/119, 337/122, 337/332 ABSTRACT  111i. Cl. 01h 37/36 A ondition responsive switch device comprising a Fleld of Search member a passageway therein, a reservoir 337/222, 298, 320, 321, 324, 331, of conductive liquid, such as mercury, at one end of 416; 340/329; 200/84 R, 84 A, 84 B, 191, the passageway defining a movable contact, a station- 192, 213; 335/52, 56 ary contact at the opposite end of the passageway normally spaced from the conductive liquid but contacted References Cited thereby under predetermined conditions. Preferably,
UNITED STATES PATENTS an expansion chamber is provided above the passage- 1,945,434 1/1934 Greer 337 331 x y Permitting uninhibited movement of the conduc- |979,441 1 H1934 Benya I I i D I goo/g4 B X tive liquid toward the stationary contact. In addition, a 1,992,066 2/1955 Greer 337/331 X solid conductor may be provided in the passageway to 2,709,738 5/1955 Walter 336/52 X reduce the volume of the conductive liquid and in- 3,028,464 4/1962 ZCHFfO-SS, Jr, 337/33l X crease the current carrying capacity of the device. 3,l42,736 7/1964 Mitchell 335/52 3,361,995 1/1968 Marcum 335/56 16 Claims, 8 Drawing Figures PAIENTEB N Y 1 I97 3.815.816 sum 1 or 2 1 CONDITION RESPONSIVE SWITCH DEVICE The present invention is generally related to switch devices and, more particularly, to an improved, relatively simple switch device for sensing predetermined high temperatures, or pressure conditions.
In the past, various switches have been provided for sensing temperatures and pressure conditions. Several conventional switches utilized mercury, or other conductive liquid, which was displaced in response to predetermined temperature conditions, or the like, to effect switching. For the most part, these switch devices were comprised of extremely delicate components which were subject to easy damage, particularly during shipment. Furthermore, such switches often required assembly after they were shipped from the factory, whereby the purchaser was required to supply mercury and calibrate the switch. This was a source of considerable aggravation and often led to errors. Also, such conventional switches were either very limited in their current carrying capacities, making them unsatisfactory for many applications, or required a considerable volume of costly mercury which significantly increased the price of the device.
It is an object of the present invention to provide an improved condition responsive switch device of compact construction including a minimum number of parts and which may be calibrated or preset at the factory to respond to predetermined conditions in the field.
Another object of the present invention is to provide a novel temperature responsive device which is of heavy duty construction and which is calibrated and sealed at the factory prior to shipment.
A further object of the present invention is to provide a versatile temperature responsive switch device including a thermally expandable conductive liquid, part of which is displaced through a passageway into an overflow reservoir to calibrate or preset the device for a desired response temperature.
Still another object of the present invention is to provide a compact, highly reliable temperature responsive switch which is readily adaptable for use with building structure fire alarm systems, with several of the switches being placed at various locations throughout the building structure.
It is another object of the present invention to provide a unique switch device with both a solid conductor and conductive liquid disposed in a capillary-like passageway to increase the current carrying capacity of the switch without significantly increasing the total volume of conductive liquid required.
These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.
FIG. 1 is a perspective view of a first embodiment switch device of the present invention together with a schematic diagram of a typical alarm circuit.
FIG. 2 is a longitudinal sectional view of the device shown in FIG. 1.
FIG. 3 is a cross-sectional view taken along section 3-3 of FIG. 2.
FIG. 4 is a cross-sectional view taken along section 4-4 of FIG. 2.
FIG. 5 is an exploded perspective view of the device shown in FIG. 1.
FIG. 6 is a partial sectional view of the device shown in FIG. 2 with the conductive liquid flowing into the overflow reservoir during calibration.
FIG. 7 is a longitudinal sectional view of a second embodiment of the present invention.
FIG. 8 is a cross-sectional view taken along section 88 of FIG. 7.
Referring now, more particularly, to FIG. 1 of the drawings, the condition responsive switch device of the present invention is generally indicated by the numeral 10 and includes upper and lower end caps 12 and 14, preferably of conductive material and of cylindrical configuration. The end caps are spaced from each other by a center member 16, preferably of glass or other non-conductive material. Center member 16 is provided with an elongated liquid passageway which permits the flow of mercury, or other conductive liquid between upper and lower caps 12 and 14, under predetermined temperature conditions, as hereinafter explained.
The switch device is of relatively compact construction and is adapted to detect high temperatures, such as those normally associated with hazardous fire conditions. Caps 12 and 14 may be appropriately connected to a conventional alarm circuit, such as that indicated at 17 including a battery or other voltage source 18 and an audio alarm or other indicator 20. When the switch device senses a predetermined temperature condition, it effects closure of the circuit to energize the alarm. It will be appreciated that several of the switch devices may be placed at various locations in a building structure and connected in parallel to the alarm circuit, such that high temperatures sensed by any one of the devices will effect closure of the circuit. Of course, it is not intended that the device be limited to use with the circuit illustrated, as any appropriate alarm circuit may be utilized dependent upon the particular application.
Referring now, more particularly, to FIGS. 2-5, the structure of the switch device of the present invention may be seen in more detail. It will be observed that center member or body 16 is of generally cylindrical configuration with upper and lower portions 22 and 24 of lesser diameter than a medial spacer portion 26. The medial portion defines a pair of circular shoulders 28 and 30 which are abutted by the end surfaces of the upper and lower caps 12 and 14. Lower cap 14 is retentatively mounted to center member 16 and defines in part a reservoir which is filled with mercury, or other conductive liquid 32 which expands with an increase in temperature. An elongated, relatively narrow passageway 30 extends between the upper and lower ends of center member 16. Upon heating, the mercury expands and is forced up into passageway 30 through a lower opening 34. Preferably, the lower end of body 16 is provided with surfaces 36 which slope slightly upwardly and inwardly toward the lower opening. This prevents the entrapment of air or other gases in the reservoir when the conductive liquid is expanded up into passageway 30.
A stationary contact 38 is disposed immediately adjacent the upper opening of passageway 30 and is provided with a relatively small aperture 40 which is in general alignment with the upper opening of the passageway. Preferably, the stationary contact is of generally conical configuration with peripheral edge portions which are retentatively engaged by upper cap member 12. The stationary contact is made of relatively thin, deformable material, such as copper, with the peripheral edge portions being bent down by the upper cap member during assembly. This sandwiches the peripheral edge portion of the stationary contact between the center member 26 and upper cap 12, as indicated at 42.
It will be appreciated that the conductive liquid expands upon heating, such that when it is heated to a predetermined temperature, it is forced up passageway 30 and makes contact with stationary contact 38. This is effective to energize an alarm or cause closure of another appropriate circuit. The temperature at which the conductive liquid comes in contact with stationary contact 38 is dependent upon the coefficient of thermal expansion of the conductive'liquid and the volume of conductive liquid which must be displaced in order that the conductive liquid reach the stationary contact. Once the reservoir has been sealed, for each temperature, there is a corresponding position for the height of the liquid column in passageway 30. This makes it possible to calibrate the device for circuit closure at a predetermined temperature. With a considerable volume of conductive liquid in the reservoir, sufficient heating will cause the liquid to be displaced through aperture 40 of the stationary contact 38. This is best illustrated in FIG. 6. As the liquid is forced through the aperture, it tends to roll down the inclined surfaces of the stationary contact which is conical in shape. Thus, the inclined surfaces in effect define an overflow reservoir. The overflow mercury or other conductive liquid accumulates in the form of globules, such as indicated at 46. When the temprature is subsequently decreased, the column of mercury recedes down passageway 30, leaving globules 46 in the overflow reservoir. This calibrates the device for switch closure at the calibration temperature. Thus, when the conductive liquid is again heated to the calibration temperature, the top of the liquid column will just come in contact with stationary contact 38 to effect circuit closure. 1
It will be appreciated that aperture 40 is of relatively small dimension, preferably 5 mils in diameter. Since the surfaces of the stationary contact slope away from aperture 40, once the switch has been calibrated, it is impossible for the conductive liquid to return to passageway 30 under the influence of gravity or even mild shaking of the device. This is due in part to the surface tension of each globule of mercury which prevents the globule from breaking up to fit through the aperture.
Upper cap 12 defines an expansion chamber 48 which is filled with air or other gas. This allows the device to be sealed from the atmosphere, but at the same time permits the conductive liquid to move up through the passageway substantially unhindered by any pressure. The gas within the expansion chamber, however,
is slightly compressed during high temperature conditions and applies mild pressure against the liquid column which aids in returning the conductive liquid down through the passageway upon cool down after calibration. Preferably, a pressure of approximately 1.5 atm. at room temperature is provided within the expansion chamber. This is achieved during assembly as the upper cap is forced over the upper portion of center member 16 until it abuts shoulder 28. It will be appreciated that by providing the expansion chamber in the upper cap, the switch device will not explode when exposed to high temperatures, as is the case with many conventional fire detecting devices.
Referring now, to FIGS. 7 and 8, a second embodiment of the present invention is generally indicated by the numeral 50 and is similar to the first embodiment, but is provided with a liquid passageway 52 of larger diameter or cross-sectional area. This increases the current carrying capacity of the device, such that it may be utilized with alarm circuits drawing considerably more current than those which would be utilized with the first embodiment. Since the cross-sectional area of the liquid passageway is greater, the resistance to electrical current flow is significantly decreased. However, it has been found thatsuch an increase in cross section requires a considerable increase in the volume of mercury or other conductive liquid being utilized. This is undesirable, since the cost of mercury is considerably high. In addition, there are many solid metals of better electrical conductivity than mercury. In order to increase the current carrying capacity without significantly increasing the cost of the device, an elongated, solid conductor 54, preferably of copper, is inserted into the device during assembly. The solid conductor extends at least partially into passageway 52 and is of a diameter or transverse dimension less than that of the passageway, such that it is substantially surrounded by a layer of mercury and is free to move within the confines of the passageway. When circuit closure is effected, current is caused to flow through both the conductive liquid and the solid conductor. Since the cross-sectional area is greater and the resistivity of the copper conductor is significantly less than mercury, the second embodiment provides much greater current carrying capacity. Preferably, the solid conductor is of a lesser specific gravity than the conductive liquid, such that it tends to float in the liquid and move up the passageway as the temperature is increased. It will be appreciated that this provides a unique means of increasing the current carrying capacity of the switch device, without increasing the total volume of mercury required. In some cases the volume of mercury may be less than that of the first embodiment, depending upon the relative dimensions of the solid conductor and the passageway.
From the foregoing descriptions, it will be appreciated that the condition responsive switch device of the present invention provides a compact, relatively simple, yet highly versatile means of sensing predetermined temperature conditions. The manner in which the upper end of the center member is contoured pro vides an overflow reservoir for easy calibration of the device. By merely heating the device to the desired temperature, it is automatically calibrated. The switches may be accuratelycalibrated in large numbers by merely placing in a temperature controlled oven, or otherwise exposing them to the desired temperature. Preferably, the device is only 1.025 inches in length and 0.375 inch in diameter, providing an extremely compact structure which may be mounted in almost any location in a building for connection to a fire detection alarm system. Of course, it is not intended that the invention be limited to the embodiments illustrated. The center member need not be made of glass or other insulating material, so long as it is insulated from the stationary contact and upper cap. Furthermore, the upper and lower caps need not necessarily be conductive, as other appropriate means of completing the circuit through the liquid reservoir and stationary contact may be provided. Also, the stationary contact need not be conical in configuration, so long as it is disposed adjacent the upper opening of the liquid passageway, and the upper end of the center member is of appropriate configuration to define an overflow reservoir for calibration purposes. It should also be noted that the present invention is not limited to use solely as a tempera- .ture responsive device. It is possible to connect the mercury reservoir in communication with conventional pressure bellows, diaphragms or the like to effect displacement of the mercury in response to predetermined pressure conditions.
The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
What is claimed as new is as follows:
1. A temperature responsive switch device, said device comprising a center member of non-conductive material with an upper end and a lower end, a fluid passageway extending through said center member between said upper and lower ends and terminating at upper and lower openings, respectively, a reservoir of conductive liquid beneath said non-conductive member and expandable into said fluid passageway through said lower opening under predetermined temperature conditions, a lower conductive terminal electrically connected to said reservoir of conductive liquid, a stationary contact adjacent said upper opening and normally spaced from said conductive liquid, said stationary contact being contacted by said conductive liquid when the liquid is at a temperature greater than a predetermined limit, and overflow reservoir means surrounding said upper opening for draining said liquid away from said upper opening when said liquid is passed through said upper opening, whereby said device may be calibrated to complete a circuit at said predetermined temperature limit, said reservoir means being defined by surfaces adjacent said upper opening and sloping downwardly therefrom, said stationary contact being generally conical in configuration and overlies said upper end of said center member to define said sloped surfaces, said conical stationary contact including an aperture therein in general alignment with said upper opening to allow the passage of liquid therethrough.
2. The device set forth in claim 1 together with an upper conductive cap mounted to said center member at its upper end and retentatively engaging the peripheral edge portions of said conical stationary contact to hold it in place.
3. The device set forth in claim 2 wherein said upper conductive cap defines. a sealed expansion chamber overlying said upper opening to permit the uninhibited flow of said liquid through said passageway.
4. A condition responsive switch device. comprising a non-conductive body having a fluid passageway extending therethrough between opposite longitudinal ends, conductive reservoir means extending from one of the ends of the body for enclosing a conductive fluid expansible into the fluid passageway, a conductive housing non-conductively spaced from the reservoir means enclosing a fluid overflow space adjacent the other end of the non-conductive body, contact means mounted directly on said other end of the body in en gagement with the conductive housing for contact by the conductive fluid in the fluid passageway and oneway passage means in the contact means for conducting fluid in one direction only from the passageway to the overflow space, to enable calibration of the switch device.
5. The combination of claim 4 wherein said body includes an intermediate spacer portion nonconductively spacing the reservoir means and the housing from each other.
6. The combination of claim 4 wherein said contact means comprises a conical element having an apex at which said one-way passage means is located.
7. The combination of claim 6 wherein said body includes an intermediate spacer portion nonconductively spacing the reservoir means and the housing from each other.
8. A condition responsive switch device comprising a center member with upper and lower ends, a passageway extending through said center member between upper and lower openings at said upper and lower ends respectively, a stationary contact adjacent said upper opening, a reservoir of conductive liquid at the lower end of said center member, said conductive liquid defining a movable contact which is displaceable through said passageway for contact with said stationary contact under predetermined conditions, and solid conductor means in said conductive liquid and extending longitudinally into said passageway along a substantial length thereof to provide a relatively low electrical resistance path through said passageway.
9. The combination of claim 10 including a lower conductive terminal electrically connected to said reservoir of conductive liquid, and overflow reservoir means surrounding said upper opening for draining said liquid away from said upper opening when said liquid is passed through said upper opening. I
10. The device set forth in claim 9 wherein said solid conductor means is of a specific gravity less than that of said conductive liquid, such that said solid conductor means floats in said conductive liquid.
11. The structure set forth in claim 8 wherein said solid conductor means is movable relative to said passageway.
12. The structure set forth in claim 11 wherein said solid conductor means is of a specific gravity less than that of said conductive liquid.
13. The structure set forth in claim 8 wherein said device includes a lower cap mounted to the lower end of said center member which together with said lower end defines said reservoir.
14. The structure set forth in claim 13 wherein said device includes an upper cap mounted to the upper end of said center member and in sealing engagement therewith, said upper cap together with the upper end of said center member defining chamber means for permitting the uninhibited movement of said conductive liquid up said passageway.
15. The structure set forth in claim 14 wherein said solid conductor means is movable relative to said passageway.
16. The structure set forth in claim 15 wherein said solid conductor means is of a specific gravity less than that of said conductive liquid.