US3298606A

US3298606A - Thermostatic control device

Info

Publication number: US3298606A
Application number: US399757A
Authority: US
Inventors: Harold W Rice
Original assignee: Robertshaw Controls Co
Current assignee: Robertshaw Controls Co
Priority date: 1964-09-28
Filing date: 1964-09-28
Publication date: 1967-01-17
Anticipated expiration: 1984-01-17

Description

moi

INVENTOR ATTORNEY Jan. 17, 1967 H. w. RICE THERMOSTATIC CONTROL DEVICE Filed Sept. 28, 1964 HAROLD W. RICE /L p/ fl United States Patent Ofiice Patented Jan. 17, 1967 3,298,606 THERMOSTATIC CONTROL DEVICE Harold W. Rice, Fullerton, Calif, assignor to Robertshaw Controls Company, Richmond, Va., a corporation of Delaware Filed Sept. 28, 1964, Ser. No. 399,757 9 Claims. (Cl. 236-21) This invention relates to fuel flow control devices and more particularly to a thermoelectric safety device utilized in a thermostatic control for regulating the flow of fuel to a heating appliance such as a hot water heater and the like.

In heating appliances such as hot water heaters, it is common practice to supply fuel to a main burner and to a pilot burner, with the main burner flow being thermostatically controlled and the pilot burner flow being controlled by a thermoelectric safety device that shuts off flow to both burners. The thermoelectric safety means conventionally includes a valve member connected to an armature biased to a valve closing position but retained in a valve opening position when an electromagnet is energized by a thermocouple responding to the flame at the pilot burner; the voltage generated by the thermocouple is great enough to hold the armature but is not great enough to move the armature, so a reset button is utilized to move the armature against the electromagnet. While such safety devices are adequate for their designed function of shutting down the burner apparatus in the event of flame extinguishrnent, there is no provision for shut down when over temperature conditions occur.

a preferred embodiment taken in connection with the accompanying drawing wherein:

FIG. 1 is a longitudinal section through a control de= vice embodying this invention;

FIG. 2 is a section similar to FIG. 1 showing the elements thereof in another controlling position; and

FIG. 3 is a schematic diagram of a heating control system embodying the control device of FIGS. 1 and 2.

Referring first to FIG. 3, the heating control system for a water heater includes a. control device, indicated generally at 10, receiving a flow of fuel from a gas supply conduit 12, and delivering a. main flow of gas to the main burner conduit 14 leading to the main burner 16 and a pilot flow of gas to the pilot burner conduit 18 leading to the pilot burner 20; a thermocouple 22 is disposed adjacent the pilot burner so as to be responsive to the It is, therefore, an object of the present invention to close the electromagnetic valve controlling fuel flow to burner apparatus upon abnormal conditions resulting from operation of the burner apparatus.

Another object of this inventionis to control the actuation of an electromagnetic valve in response to abnormal conditions and independent of the energization of the electromagnet acting on the valve.

The present invention has another object in that the valve means and electromagnetic means in a safety con trol device are connected by releasible latching means.

The present invention has another object in that the flame thereat and includes the usual electrical leads cable 24 for connection to the control device.

The interior of the control device 10 includes a main flow passageway 26 having a thermostatic valve 28 therein for regulating the main flow of gas to the main burner 16, and a pilot flow passageway 30 having a flow restriction valve 32 therein for adjusting the flow of gas to the pilot burner 20. The

passageways

26 and 30 are supplied from a common passageway 34 which has an inlet passageway 36 communicating with the gas supply conduit 12 and which is controlled by the safety valve means, indicated generally at 38.

As is illustrated in FIG. 2, the safety valve means 38 includes a valve seat 40 formed in an interior wall of the control device housing 10 and disposed between the passageways 36 and 34 to control the fuel flow therebetween. The downstream side of valve seat 40 leads to a bore 42 which houses the reset means. The bore 42 is sealed by a retaining .washer 44 fixed by any suitable means to the bore wall above the opening for passageway 34. A reset plunger has a reduced portion 46 slidably extending through a central aperture in the retaining washer 44, a lower end portion 48 disposed for reciprocation through the valve seat 40, and an upper portion 50 slidably eX- tending through the control housing wall 10. The plunger portion 50v defines a reset button and slidably extends through upper sealing means for the bore 42 such as a sealing nut 52. The reset plunger is biased upwardly by means of a coil spring 54 encircling the reduced portion 46 and mounted in compression between the upper surface of retainer 44 and the annular shoulder between the the valve means of an electromagnetic safety device for burner apparatus to move as a unit with its electromagnetic means in response to operating conditions at the burner apparatus and to permit such valve means to move independently of the electromagnetic means in response to a predetermined condition resulting from operation of the burner apparatus. 1

In practicing the present invention, a preferred embodiment of a safety control device for controlling fuel to burner apparatus includes a valve means movable between open and closed positions, electromagnetic means adapted for movement between attracted and released positions corresponding to respective operative and inoperative conditions of the burner apparatus, an operative connection between the valve means and the electromagnetic means permitting unitary movement thereof, and means to deactivate the operative connection whereby the valve means may move independently of the electromagnetic means.

Other objects and advantages of the present invention will become apparent from the following description of reduced portion 46 and the upper portion 50.

The upstream side of valve seat 40 defines a valve chamber which houses a valve member 56 movably disposed for cooperation with the valve seat 40. The valve member 56 is generally disc shaped with its upper portion including an annular element made of any suitable sealing material and with its lower portion including a central annular shoulder defining a fulcrum 58 and a hollow cylindrical valve stem 60 integral with the valve disc 56 for movement therewith.

An armature stem 62 has an upper end portion slidably disposed in the hollow valve stem; such upper end portion has an end disc 64 adapted to abut the undersurface of valve element 56, shaft portion 66 of reduced diameter, and a frusto-conical collar 68 defining a portion of increasing diameter from the shaft 66 to an annular collar 70 having the same diameter as that of end disc 64. The collar 70, shaft 66 and end disc 64 are telescopingly slidable in the hollow stem 60. Adjacent the collar 70, the armature stem 62 has a portion of reduced diameter defining a latching recess 72. A lower end portion of the armature stem 62 slidably extends through a flanged collar 74 of a magnet housing 76 which seals the lower end of the housing chamber and which is fixed to lower end of the control housing 10.

An armature 78 secured to the lower end of the armature stem 62 reciprocates between released and attracted positions relative to electromagnetic means in the form of a generally U-shaped magnet core 80 and an electric coil 82 wound thereon. The magnet core 80 is secured to the magnet housing 76 by any suitable means and the electric coil 82 is connected to the thermocouple cable 24 as by a conventional thermocouple cable connector which is not shown because such connectors are wellknown in the art.

The valve stem 60 and the armature stem 62 are operattively connected for unitary movement by latching means including a base plate 84, the upper surface of which normally abuts the annular shoulder defining the fulcrum 58. The base plate 84 is centrally apertured to loosely fit around the valve stem 60 and is provided with an arcuately shaped actuator tang 86 extending downwardly from the periphery of the base plate 84. Adjacent its central aperture, the base plate 84 has a perpendicularly bent short tab 88 and a perpendicularly bent long tab 90; the length of the long tab 90 corresponds to the length of the valve stem 60 whereby a latching lug 92 extends horizontally from the lower end of tab 90 to be underneath the valve stem 60 and to be adapted to extend in the latching recess 72. A coil spring 94 encircles the armature stem 62 and valve stem 60 with its valve stem end surrounding the retaining tabs 88 and 90, and is mounted in compression between the undersurface of the base plate 84 and the end wall of magnet housing 76.

An actuating pin 96 slidably extends through a bored wall of the control housing so that its inner rounded end engages the arcuate tab 86. The outer end of pin 96 engages one end of a lever 98 the other end of which engages a fixed fulcrum 100. Inter-mediate such end en gaging surfaces and on its surface opposite thereto, the lever 98 is engaged by the movable end of a temperature responsive sensor 102 which is carried by a mounting shank 104. As is well known in the art, the mounting shank 104 is threaded for attachment to the casing of a hot water tank (not shown), in such a manner that the free end of temperature sensor 102 is disposed in the water inside of such tank. The mounting shank 104 also carries another temperature sensor 106 with its free end similarly disposed in the hot Water tank and with its opposite end extending through a bored wall of the control housing 10 to actuate the thermostatic valve 28. With such an arrangement, the sensor 102 is adapted to respond to an abnormal temperature condition and the sensor 106 is adapted to respond to normal operating temperature condition. The temperature setting mechanism and the operative connection between the normal temperature sensor 106 and the valve 28 have not been shown since they may take many forms, as for example, that disclosed in US. Patent No. 2,658,686 which is assigned to the same assignee of the present invention. While the two temperature sensors 102 and 106 have been shown as conventional rod and tube type thermostats, it is to be understood that other types of temperature sensing constructions may be utilized as will become apparent from the following description of the sequence of operation.

In order to initiate operation of the main burner 16, the push button 50 is depressed and held against the bias of coil spring 54 causing the plunger end 48 to move the valve member 56 away from the valve seat 40. The flow of gas to the pilot burner is now ignited, as by a match, and as soon as the thermocouple 22 is heated, the push button 50 may be released and the electromagnet 80-82 holds the armature 78 in its attracted position as shown in FIG. 1. While it has not been disclosed in the above description, it is contemplated that the resetting operation includes a safe lighting feature, i.e., the flow to the main burner 16 is cut off while the push button 50 is depressed; such a feature is so well known in the art that a detailed description thereof is omitted for the sake of brevity.

Upon release of the push button 50, the main burner 16 will be ignited by the flame at the pilot burner 20. As soon as the water in the tank reaches the set temperature, the corresponding expansion of the thermal sensor 106 causes the valve 28 to close and thsu shut 01f the flow to main burner 16. The valve 28 includes a snap acting device, and as disclosed in the above mentioned US. Patent No. 2,658,686, whereby the valve 28 is opened and closed with a snap action. When the hot water in the water tank is drawn off and replenished with cold water, the thermal sensor 106 is contracted causing the valve 28 to open whereupon the flow to the main burner 16 is again ignited by the flame of the pilot burner 20.

Should the flame at the pilot burner 20 be extinguished for any reason, the thermocouple 22 will cool and cease or diminish the thermoelectric current to the electromagnetic coil 82; thereupon the armature 78 will be released from the electromagnetic core 80 under the bias of coil spring 94. The released position of the armature 78 as well as the closed position of the valve disc 56 are shown in dashed lines in FIG. 1. However, the latched position of the valve stem 60 and armature stem 62 remains the same as shown in FIG. 1 as long as the water tem perature does not exceed the maximum setting of the normal operating temperature.

With the latching lug 92 disposed in the latching recess 72 to engage the end of valve stem 60, the valve stem 60 and armature stem 62 will move as unit. Accordingly, the valve member 56 and armature 78 move as a unit to a valve closing position whenever the flame at the pilot burner 20 is extinguished.

Due to some malfunction, it may happen that the main burner 16 remains ignited after the water temperature reaches its predetermined maximum temperature. In such eventuality, the thermal sensor 102 will expand causing the lever 98 to pivot clockwise about the fulcrum 100, which in turn causes the inward movement (to the right as reviewed in FIG. 1) of the pin 96. The actuating tang 86 is then displaced by the pin 96 and the latching base plate is cocked or pivoted on the fulcrum 58 to the tilted position of FIG. 2. As soon as the latching lug 92 is displaced from the latching recess 72, the coil spring 94 biases the base plate 84 and the valve disc 56 upward to a valve closed position; thus, the flow of gas to the main burner and to the pilot burner is cut off.

The upward movement of the base plate 84 and valve disc 56 is relative to the armature stem 62 which remains in its attracted position as long as the electromagnet 80-82 is energized. Of course shut down of the pilot burner 20 will result in subsequent deenergization of the electromagnet 8082, however, the armature 78 is not subject to the bias of coil spring 94 because the latching means is released from the armature stem. The armature 78 will now move only in response to gravity according to its mounting position; thus, the armature 78 remains against the pole faces of magnet core 80.

The above arrangement presents the additional safety feature that even though a resetting operation is performed, the valve disc 56 will move to a closed position upon release of the reset button 50 as long as the over temperature condition of the Water exists. This is apparent from FIG. 2 which shows that the latching means remains tilted as long as the pin 96 is actuated by the abnormal thermal sensor 102. Since the latching lug 92 is displaced from the recess 72 of the armature stem 62. While it is possible to depress the reset button 50 together with the valve disc 56 and latching plate 84 against the bias coil spring 94,'the actuating pin 96 will engage the upper portion of tang 86 (similar to FIG. 1) and further tilt the base plate 84 to its maximum released position. Depression of the reset button 50 permits the pilot burner 20 to be ignited but upon subsequent release of the button, the valve disc 56 will close because the latching lug 92 is still displaced from the latching means 72.

Once the over temperature condition of the water has been reduced to normal operating temperatures, the abnormal thermal sensor 102 contracts and the forces acting on lever 98 cause the lever 98 to follow the movement of the sensor; i.e., the latching tang 86, which is biased by the coil spring 94 acting on the undersurface of the base plate 84, forces the pin 96 to the left whereby the lever 98 is pivoted counterclockwise about the fulcrum 100. The latching lug 92 is thus biased toward the latching recess 72.

Correction of the over temperature condition when the elements are in the relative positions sown in FIG. 2 places the latching lug 92 against the reduced shaft 66. Depression of the reset button 50 causes the latching lug 92 to be displaced outwardly by the camming surface 68 during such downward movement and then to be returned to the latching recess 72 wherein the lug 92 engages the keeper surface of collar 70 to latch the armature stem 62 and valve stem 60 for unitary movement. As soon as the pilot burner 20 is ignited and the thermocouple 22 is heated thereby, the push button 50 is released and the valve disc 56 is retained open by being latched to the armature 78 which is retained in its attracted position by energization of the electromagnet 80-82. The heating control system will again return to normal thermostatic cycling by the valve 28 being controlled by the normal thermal sensor 106.

With the above arrangement, there is no need for a substantial amount of force to separate the armature 78 and magnet core 80 when over temperature conditions occur. To the contrary, the releasible latching means according to the present invention effects an unlatching operation by the application of a relatively small force through a relatively small distance; accordingly, a small thermal sensor may be utilized. While the present invention has been described in connection with two thermal sensors 102 and 106, it is to be understood that other thermal sensing constructions may be utilized, e.g., a single thermal sensor having normal expansion to actuate the valve 28 and abnormal expansion to release the latching means.

Inasmuch as the present invention is subject to many variations and changes in details and the preferred embodiment is susceptible to modification for different requirements, it is intended that all matter contained in the foregoing description or shown on the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a safety control device for controlling fuel flow to burner apparatus, the combination comprising valve means movable between open and closed positions, electromagnetic means including armature means adapted for movement between attracted and released positions corresponding to respective operative and inoperative conditions of the burner apparatus, latching means including I a base plate biased into engagement with said valve means for movement therewith, lug means carried by said base plate, keeper means on said armature means engaged by said lug means to unite said valve means and said armature means for unitary movement, and means to release said latching means whereby said keeper means is released from said lug means and said valve means is movable independently of said armature means.

2. The combination as recited in claim 1 wherein said valve means includes a hollow stern and said armature means includes an armature stem end portion slidable in said hollow stem.

3. The combination as recited in claim 2 wherein said keeper means includes a keeper collar adjacent said armature stem end portion.

4. In a safety control system for main and pilot burners, the combination comprising thermostatically operated valve means for regulating fuel flow to the main burner, a

safety valve device movable between open and closed positions for shutting off fuel flow to both the main and pilot burners, electromagnetic means energized in response to a flame at the pilot burner, latching means uniting said safety valve device and said electromagnetic means for unitary movement thereof between open and closed positions, and thermal sensor means having normal and abnormal operating ranges and being operatively connected to said valve means and said latching means whereby said valve means is cycled thermostatically in the normal operating range of said thermal sensor means and said latching means releases said safety valve device to its closed position independent of said electromagnetic means in the ab normal operating range of said thermal sensor means.

5. The combination as recited in claim 4 wherein said valve means includes a valve stem, said electromagnetic means includes .an armature stem, a telescoping connection between said valve and armature stems, and said latching means includes means to retain said valve stem and said armature stem in fixed relation.

6. The combination as recited in claim 5 wherein said last mentioned means comprises a keeper collar on said armature stern and lug means carried by said latching means for engaging said keeper collar.

7. In a safety control device for controlling fuel fiow to burner apparatus, the combination comprising a control device housing having passage means for fuel flow therethrough, a valve seat in said passage means, a valve disc movable relative to said valve seat for controlling the fuel flow therethrough, said valve disc having a sealing surface on one side and a hollow valve stem extending from an opposite side, fulcrum means on the said opposite side of said valve disc, electromagnetic means including an armature movable between attracted and released positions and adapted to be energized in response to a flame at the burner apparatus, an armature stem extending from said armature and having an end portion telescoping into said hollow valve stem, a keeper collar on said armature stem adajacent said end portion, a latching base plate surrounding said hollow valve stem and engaging said fulcrum means, a plurality of depending tabs extending from said base plate away from said fulcrum means, lug means carried by one of said tabs for engagement with said keeper collar, spring means biasing said latching base plate to retain said lug means into engagement with said keeper collar to effect unitary movement of said valve stem and said armature whereby said valve disc closes on said valve seat when said armtaure moves to its released position upon deenergization of said electromagnetic means, an actuating tang depending from said latching base plate, and condition responsive means displacing said actuating tang and tilting said latching base plate on said fulcrum means to displace said lug means from said keeper collar whereby said valve stem slides relative to said armature stem under the bias of said spring means and said valve disc closes on said valve seat independently of said electromagnetic means.

References Cited by the Examiner UNITED STATES PATENTS Re. 24,515 8/1958 Eskin 236-21 X 2,303,702 12/1942 Mantz 236-218 2,383,401 8/1945 Mantz 23621 2,781,977 2/1957 Stanley 23621 EDWARD J. MICHAEL, Primary Examiner.

Claims

1. IN A SAFETY CONTROL DEVICE FOR CONTROLLING FUEL FLOW TO BURNER APPARATUS, THE COMBINATION COMPRISING VALVE MEANS MOVABLE BETWEEN OPEN AND CLOSED POSITIONS, ELECTROMAGNETIC MEANS INCLUDING ARMATURE MEANS ADAPTED FOR MOVEMENT BETWEEN ATTRACTED AND RELEASED POSITIONS CORRESPONDING TO RESPECTIVE OPERATIVE AND INOPERATIVE CONDITIONS OF THE BURNER APPARATUS, LATCHING MEANS INCLUDING A BASE PLATE BIASED INTO ENGAGEMENT WITH SAID VALVE MEANS FOR MOVEMENT THEREWITH, LUG MEANS CARRIED BY SAID BASE PLATE, KEEPER MEANS ON SAID ARMATURE MEANS ENGAGED BY SAID LUG MEANS ON SAID ATMATURE MEANS ENGAGED BY MEANS FOR UNITARY MOVEMENT, AND MEANS TO RELEASE SAID LATCHING MEANS WHEREBY SAID KEEPER MEANS IS RELEASED FROM SAID LUG MEANS AND SAID VALVE MEANS IS MOVABLE INDEPENDENTLY OF SAID ARMATURE MEANS.