US 3776200 A
A system for preventing "dry-boiler" failures which includes a float mechanism for detecting the water level in a heated reservoir and a device for testing the float mechanism to determine if it is operating properly and for preventing activation of the burner if improper operation is detected.
Description (OCR text may contain errors)
United States Patent 1 Tine et al.
I Dec. 4, 1973 AUTOMATIC SELF-TESTING LOW-WATER CUT-OFF  Inventors: Sebastian David Tine, Lawrence,
Calvin Ru'shforth, Andover, both of Mass.
[7 3] Assignee: Watts Regulator Compan Lawrence, Mass.
22 Filed: Sept, 1, 1972 21 Appl. No.: 285,638
 U.S. Cl. 122/504, 122/504.2  Int. Cl. F22b 37/42  Field of Search 122/504, 504.2
 I I References Cited UNITED STATES PATENTS 1,854,519 4/1932 McDonnell et al. 122/504 X 2/1934 Dillman 122/504 X 1,949,371 2,846,985 8/1958 Blanchard.... 122/504.2
3,614,278 10/1971 DiNoto, Jr. ...122/504.2
Primary Examiner-Kenneth W. Sprague Attorney -Norman Lettvin I  ABSTRACT A system for preventing dry-boiler" failures which includes a float mechanism for detecting the water level in a heated reservoir and a device for testing the float mechanism to determine if it is operating properly and for preventing activation of the burner if improper operation is detected.
If the float mechanism is operating properly but the vvater level is below a pre-determined safety level, then activation of the burner can be prevented andvarious alarms actuated to notify the operator.
12 Claims, 12 Drawing Figures 7 3.776200 SHEET 10F 3 PATENTED DEC 4 1975 AUTOMATIC SELF-TESTING LOW-WATER CUT-OFF BACKGROUND OF THE INVENTION This invention relates to a control system for use in water-boiling furnaces .to detect the waterlevel therein and prevent activation of the water heater in unsafe conditions.
Most water-boiling furnaces, such as steam furnaces,
include a reservoir in which the water is heated by the burner and a safety control system having afloat mechanism for de-activating or preventing activation of the burner in the event the water level dropszbelow a .predetermined danger or cut-off point. The float'is nor,- mally connected to the control system by-apivotable linkage surrounded by an accordion-type protective sleeve or bellows. Over extended periods of operation mu and other products accumulate in the float chamber and can pre-. vent movement of the float in response to changes in the water level. This mud can also accumulateon the bellows and prevent movement of the linkage. F urthermore, although the linkage itself is protected from the mud, it may become frozen by corrosion at the pivot points which would prevent the float from moving, in. response to changes in the water level. In anyof these situations the float may become stuck in an upper position, above the water level, and thus provide noindication when the. water level reaches .the'predetermined cut-off level and, therefore, not'deactivate or'prevent activation of the burner which could result'in all the water being boiled off and failure of the furnace.-.
It has been established that the control systemsare:
infrequently servicedand thus dry boiler failures are not uncommon, and in an attempt to remedythe problem two central systems connected in series have been used. This arrangement assumes that both "systems will. not fail simultaneously. 1
BRIEF DESCRIPTION on THE DRAWINGS FIG. 1 is a diagrammatic presentation of the mechanical and electrical means employed in the control system -ofthis invention;
FIG. 2 is a vertical sectional view of one side of the control assembly with the float in an upper position;
FIG. 3 is a vertical sectional view of the other side of the control assembly with the float in a lowered position; I
FIG. 4 is: a sectional view taken substantially along line. 4 4 of FIG. 3;
FIGS. 5, .6, 7 and 8 are various views of a cam member employedin this control system, with FIG. 8 showing an expanded view of one lobe of said cam member,
taken substantially along line 88 of FIG. 5;
FIGS. 9, l0 and 11 are side elevational, bottom plan and top plan views respectively, of a pair of switches associated with said cam; and
FIG. l2fis a'diagrammatic presentation of the open and closed phases of various switches as related to cam rotation;
DESCRIPT ION OF THE PREFERRED EMBODIMENT reservoir l0. If the water-level is too low or the control I unit is operating improperly, activation of the bume'r is prevented and an alarm or the like may be provided to notify the operator of this condition-Such devices for" this purpose may be provided at 18.
Therefore, it is an object of this invention to provide a fail-safe low-water cut-off system.
It is another object to provide a systemzwherein the float, bellows and linkage are checked automatically .to I determine if they are operating properly.
Yet another object is to provide a system wherein the burner is activated only after the float, bellows and linkage have been found to be operating properly andthe water level is above the predetermined danger-- level.
These and other objects will become apparent from the following description. and appended claims.
SUMMARY OF THE INVENTION- There is provided by virtue of this invention awater level detection system for use on water boilers in which the float, bellows and linkage mechanismis tested autoerly and the water level is below thedanger level, the 65,
properly and the water level is above the cut-off level.
Circuit Description The thermostat 14 includes a relay 20 which operates to open and :close the circuit for the incoming power lines which are connected to a terminal block 22 at terminals 28 and 30, via lines 29 and 31. The burner unit 12 'is connected to the terminal block 22 at terminals 24 and 26 via lines 25 and 27, and the alarm or similar device l8 is.connected to the terminal block at terminals 32 and 34 through lines 33 and 35. Internal connectionsare provided in the terminal block for conto 40; 30 to 42 32 to 44; and 34 to 46.
The power circuit'extends from terminal 42 via line I 48 to a motor control relay 50, generally, and connects to the terminal 50b. Line 52 connects to terminal 50b I to anormally open motor relay cam switch 54 at termi nal 54a. The switcharm 54c connects the terminal 54a I with the terminal 54b and line 56 connects switch ter- :minal 54b to relay terminal 50h. Terminals 50h and-50g t I are connected across the coil 50m for the relay 5 0.
Line58 from the relay terminal 50g connects to terminal 36 on the terminal block 22 and thus to one side of the burner l2.-
A line 60 extends fromrelay terminal 50h to relay terminal 50c and relay arm 50k normally contacts the terminals 50e and 50a. The line-'64 extends from the terminal 50e to the terminal 66a on the normally open Referring now to the drawings, there is shown a water reservoir 10 which is associated with a water boiler, a burner unit 12 forheating water in the reservoir 10, a
float controlled switch 66. The switch arm 66b normally contacts with the terminal 660 which, in turn, through line 68 connects to terminal 70a of the normally closed motor test cam switch 70. In the normally closed position the switch arm 70b contacts terminal 70c. The normally open terminal 70d connects to the terminal 38 on the terminal block 22 via line 72 and from terminal 38 the connection is made to the burner 12.
Following the power circuit: the burner 12 is connected through line 25, terminal 24, terminal block 22 and terminal 36 to line 74 that connects with motor terminal 76a on the motor 76 generally. The other terminal of the motor of the terminal 76b connects via line 78 to terminal 80a on the motor relay switch 80, generally. The terminal 80b on the motor relay switch connects with the terminal 50d via line 82, and terminal 80e connects with the relay terminal 500. A pair of diametrically-opposed, non-conducting cut-out notches 80c and 80d are provided in a conductive disk, and at the beginning of a cycle the terminal 80e is in registry with the notch 80d. The relay arm 50 connects the terminals 50d with the terminal 50f, so that a path is provided between terminal 80a and terminal 50f. The terminal 50f is connected to a normally closed linkage test switch 86 via line 88 at terminal 86a. The'switch arm 86b is pivoted at the terminal 860 which is connected to line 90 that connects to terminal 40 of terminal block 22. The linkage switch arm 86b connects to the float cam follower at the arm 92a and the switch body is connected to float arm 110a. The motor test cam switch arm 70b connects to the motor test cam follower 94 and the motor relay cam switch arm 54c connects to the motor relay cam follower 96.
The linkage test switch 86 includes a normally open terminal 86d which connects to the lamp 98 via line 100 and to the block terminal 36 via line 102. The alarm or pump starter 18 is connected through the appropriate lines and terminals to the terminals 44 and 46 on the block 22. A normally openalarm float control switch 104 is connected at terminal 104a to the terminal 46 via line 106. The switch arm 104b normally contacts to terminal 104a and the arm 104b is linked to the float link arm 110a associated with the float 110. In the closed position the switch arm 104b contacts the terminal 104d and via line 108 connects to the terminal 112a of an alarm motor relay switch 112.'The switch 112 is a conductive disk which includes a pair of large opposed notches l12b and 1120 with which the terminal 112a may register. These notches extend for approximately 45 about the circumference of the disk. If the arm 104b closes at the beginning of a cycle, a path is established between 112a and terminal 112d which is, in turn, connected via line 114 to the terminal 44 on the terminal block 22 and thus to alarm 18.
Cam Member A single cam 116 having three camming surfaces sequentially activates the float-controlled switches and motor switches (shown in FIG. The top surface 116a provides lobes which define a float cam 1 16b. The same surface provides a motor test cam 116C and the peripheral circumferential edge provides a cam 116d. The cam 116 is mounted to the motor 76 which drives the cam 1 16 in unison with the motor relay switches 80 and 112.
The cam follower 96 which is connected to switch arm 54c cooperates with the motor relay cam 1 16d; the cam follower 94 which is connected to switch arm b cooperates with the motor test cam l 160; and the cam follower 92 which is 'connected to switch .arm 86b cooperates with the float cam 1l6b.'
The float cam follower 92 is interconnected with the float by a coiled compression spring 118. If the float 110 and associated linkages are operating prop- The physical embodiment of the control unit includes a housing having a vertical plate 120 with an aperture 120a at the upper end thereof. A pivot support plate 122 is mounted adjacent the aperture 120a and a sealing grommet is mounted within the aperture 120a so as to sealingly engage the float link arm 1 10a whichpasses through the grommet 124. The arm 110a is pivotally connected to the plate 122 by the pin 126. The float 110 includes an intemally-threaded boss 1l0b which threadably engages the extemally-threaded stub 1100 on the arm 1 10a so as to secure the float l 10 to the arm 110a. I
A corrugated accordion-type sleeve 128 covers and shields the pivot connections 122 and 126. In the event corrugations become clogged with mud and the like, free movement of the float 110 is prevented. The float controlled switch 66 is mounted to the housing in the control system so that the switch arm 66b is positioned adjacent and slightly rearwardly of the end of the arm 110a which carries a switch activator link 110d.
The float cam follower 92, generally, is positioned below the link 110d and is guided by a bracket 130 mounted to the plate 120. The bracket 130 includes a longitudinally-extending bore 130a and a pair of diametrically-opposed pin-receiving slots such as l30b. The cam follower 92 includes a roller 92b mounted in molded housing 92c having an axially-extending'bore 92d. A pair. of transversely-extending diametrallyopposed slots such as 92c are provided in the housing and intersect bore 92d. The link test switch 86 is mounted to the housing 92 with the contact 86e extending toward the arm 1100.
An elongated shaft 132 slidably engages the aperture 130a at the bracket 130 and carries a cross pin 1320 which limits the axial movement of the shaft 132 by engagement with the upper and lower ends of the slots l30b. The lower end of the shaft 132 slidably engages the housing bore 92d and its movement therein is limited by the lower cross pin 132b which is disposed with the slots 92e. The intermediate switch activator plate 134 which is equivalent to the arm 92a is fixedly positioned on the shaft 132 by a cross pin 134a. A biasing coiled compression spring 136 (equivalent to spring 118) is positioned between the plate 134 and the housing 92c so as to urge the housing away from the plate 134. The roller 92b is arranged to roll on the cam 116 and move axially toward the link arm 1 10a as it engages the ramp and lobes of the cam surface 116a.;When the roller 92b engages the lobe, it begins to move upwardly which exerts an upward force on the plate 134. If the float 110, the linkage 126 and the bellows 128 are operating freely, the upward force exerted on the plate 134 moves the shaft 132 upwardly into engagement with the inner end of the arm 110a, and pushes. the inner end upwardly, thereby causing the float 1 to bedepressed, thus exercising the bellows and the pivotal connection.
If, however, the float linkage or bellows are stuck, the cam urges the housing upwardly but, the plate-134cm not move upwardly sincetherod 132 is. forced against the immovable inner endofithe linkage l -ltl a, Thus, the roller 92b and housing 92c continue tomove-upwardly and compress the spring 136. The housing continues to move upwardly until the contactarm86e Qf-the switch 86 engages the plate 134, thereby movingtheswitch arm 86b into engagement with thecontact 8611, thus opening the power circuit.
The cam 1 16, its cam followers 92, 94.and,9 6 and the switches 80 and 112 are mounted in circular. relation so that events occur sequentially, dependinguponthe position of rotation of the cam. The motor test.carn follower 94 and thefloat camf0ll0wer92 operate off of the surface 116a of the cam 116. In order to obtain the proper sequencing, the followers are positionedabove the surface 116, approximately 135 apart, As the cam.
is symmetric aboutitscenter line, this means :thatthe operation of the roller 94 is approximately 45. behind the operation of the cam 92. The cam follower 964s mounted to the housing so as tomove laterally with re spect thereto as it engages the circumferentialgedge of the cam.
ing plate 138 and are positioned in spaced parallel relation therewith. An insulation spacer member-140; is secured to both of the switches 80and "112. The terminals 80a, 80b and 80e are secured to the insulating plate 1 38.-v
and arranged for engagement with the switch 80. The terminals 112a and 112d are also mounted; to the plate- 138. It will be appreciated that these switches are driven by the motor shaft 760 which also drives the cam Operation in their home or zero degree positionin FIG. land the switching sequence can be followed from FIG. 12.1% tation of the cam face causes the motor relay cam fol-.
lower 96 to move off the lobe of the camsurface 116d,
thereby moving the motor relay switch arm 54c from its normal position in contact with terminal 54b..into contact with the tenninal 54d. The motor control circuitis now energized only through the relay arm,50j..As the cam rotates to the 45 position, the float cam 116burges the cam follower 92 in a directionso as to exercise the linkage and float 110. At this; timetheswitch;
66 =is open and the switch 104 is. closed. However, the
istry with the notch, 112e, thereby temporarily disconnecting the alarm or pump 18.
Assuming that'the float, the link, or the bellows are improperly operating, the switch 86 will be activated, thereby preventing closing of the power circuit, stopping rotationof the motor and illuminating lamp 98. Activation of the switch 70 is thus prevented.
On the other hand, if the linkage and bellows and float are operating properly, the float cam follower 92 moves off the lobe and the switch 86 stays in its normally closed position. However, if the water level in the reservoir 10 is low, the float 110 will remain in a downwardposition, thereby-keeping the switches 66 and 104 in their normal positions where ,switch 66 is open and switch 104 is closed; As the motor rotates and the cam moves between 45 and 90, the motor relay switch 1 12 moves into. a. position where the contact arm ll2a' moves out of registry with the notch 1 120, therebyactivating the alarm and pump. The float cam switch 66 remains inits open position, thereby preventing arming of the burner 12.
"Assuming the water level to be proper and the float switehes66 and 104 to be returned to their activated The switches 80 and 112 are mounted to an'insulat-v positions, when the motor reaches 90 of rotation, the
motor test cam 116C moves the camfollower 94 and the normally open cam follower switch arm 70b'into the'activating'position. This activates and arms the burner and stops the motor since notch 800 is positioned in alignment with the terminal 80b thereby opening the motor circuit.
Whenthe thermostat relay 20 opens, the relay then opens, thereby moving the arms 50k and 50j to theirnormal positions. By establishing contact between the terminals 50f and 500, the motor is re-energized through terminals 80a and 80e and rotates another 90- until the notch 800 is positioned in registry with the terminal 80e (connected with terminal 50c), thereby; brack-ing the motor circuit and stopping the motor after an additional 90 of rotation. If for some reason or relay switches are not operating properly, the motor would not rotate its additional 90 and the burner relay would remain de-energized until the problem was noted by failure of the. burner to be activated at the next cycle.
Switching Diagram In order'for the burner to be armed, several conditions must exist simultaneously at 90 rotation. These 0 are:
1. The switch 66 must be in its activated position; 2. The switch 86 must be in its normally closed position; 3. The thermostat relay 20 must be closed; 4. The relay 50 must be closed; and
5. Normally open switch must be in its activated" position. If any of these conditions are not present, the burner will not be armed.
In order for the burner to be restarted, cam 116d must have rotated from the armed position to the home or. zero position after the previous shutdown, thereby switch 1 12 is in a position so that the arm 1 12a is in regthis invention.
What is claimed and desired to be secured by Letters Patent of the United States is:
1. In a low-water cut-off control apparatus, for use in systems having a water reservoir and a water heater, said apparatus including float means mounted on a linkage surrounded by a protective bellows for detecting the water level in said reservoir and means operatively associated with said float for preventing activation of the water heater when the water level in the reservoir is below a predetermined safety level, the improvement which comprises said control apparatus having test means associated with said float means, linkage, bellows and heater for urging said float means downwardly and for preventing activation of said heater if said linkage or said bellows is inoperative, thereby preventing free movement of said float means.
2. An apparatus as in claim 1 wherein said test means include means for applying a force to said linkage and means for preventing activation of said burner of a predetermined force is exceeded.
3. An apparatus as in claim 2 wherein said force applying means include cam means; and spring-biased exerciser means operatively associated with said cam means and said float linkage means, said exerciser means including cam follower means, linkage-engaging means and spring means disposed therebetween which permit relative movement of said cam follower means and linkage-engaging means if said predetermined force is exceeded, said exerciser meansalso including means for detecting relative movement of cam follower means and linkage-engaging means toward each other and for preventing activation of said heater when said relative movement exceeds a predetermined distance which is related to said predetennined force.
4. An apparatus as in claim 3 wherein micro-switch means are mounted to said cam follower and stop plate means are mounted to said linkage-engaging means in spaced and aligned relation to said micro-switch means, said switch means and said plate means being engageable after said linkage-engaging means and said float for alertinganoperator when said float is below' the danger position.
7. An apparatus as in claim 5 including bumeractivating means associated with said test means and float level means for activating said burner if said test means and said float means are operating properly.
8. An apparatus as in claim 7 wherein said test means include cam means having lobes thereon for exercising said float linkage and said burner activator means include cam means having lobe means arranged to permit activation of said burner after test means have been exercised.
9. An apparatus as in claim 6 wherein there is provided means for preventing activation of said alarm means during testing of said linkage means.
10. An apparatus as in claim 8 wherein there is further provided motor means for driving said cam means and means for deactivating said motor after said burner is activated.
11. An apparatus as in claim 10 wherein means are provided for reactivating said motor after said burner is deactivated if said motor is operating properly.
12. An apparatus as in claim 11 wherein means associated with said burner activator cam means, other than said activating lobe means, are positioned to reactivate said burner after deactivation thereof and prior to the activation of said test means.