US3568120A - Heatmotor operator - Google Patents

Abstract

A heatmotor operator including a bimetal assembly having a bimetal motor arm and a bimetal compensating arm superposed above the motor arm, a lever having an operating end and a pivot end secured to one end of the compensating arm, the other end of the compensating arm being coupled with a movable end of the motor arm such that ambient temperature compensation is provided by the deflection of the motor arm and the compensating arm in the same direction, and actuating means for the bimetal assembly to control the position of the operating end of the lever.

Description

United States Patent 1 1 3,568,120

[72] Inventor Lauren D. Haskins I [56] References Cited Long Beach, Calif. UNITED STATES PATENTS pp 857,839 2,574,869 11/1951 Green 337/99 1 Had Sept-15,1969 2,748,223 5/1956 Frank 337/100 1 Patented Mar-2,1971 2,605,372 7/1952 Spooner 337/96 1 Assignee Robemhawcontmlscmlany 3,108,167 10/1963 Prouty 337/101 Richmond, Va.

Primary Examiner-Harold Broome Attorney-Anthony A. OBrien ABSTRACT: A heatmotor operator including a bimetal assembly having a bimetal motor arm and a bimetal compensating arm superposed above the motor arm, a lever having an operating end and a pivot end secured to one end of the com- [54] HEATMOTOR OPERATOR pensating arm, the other end of the compensating arm being l4 Clams 4 Drawmg coupled with a movable end of the motor arm such that am- [52] U.S. Cl 337/100 bient temperature compensation is provided by the deflection [51] Int.Cl.... ....H01h 71/16 of the motor arm and the compensating arm in the same [50] Field of Search 337/100, direction, and actuating means for the bimetal assembly to 101, 99, 90, 366, 370, 371, 378, 111, 112, 342, 96 control the position of the operating end of the lever.

54 64 24 66 28 72 58 7o 38w 56 f l P -e2 46 36 E- 68 74 34 4O 47 44 42 2g E L b 30 20/ 76 so PATENTED MAR 2L9?! IIIIIIIIIIII'III'IIIII,

FIG. 2

FIG 3 FIG. 4

INVENTOR, Lauren D. Hoskins BY94 M 5 ATTORNEY HEATMOTOR OPERATOR BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention pertains to heatmotor operators in general and more particularly to heatmotor operators for con trolling valves.

2. Description of the Prior Art Heatmotor operators for valves, electric switches, and the like are known; however, known conventional heatmotor operators suffer from the disadvantages of not providing proper response with variations in applied voltage, energization time and ambient temperature.

It is desirable to construct heatmotor operators so that they are snap acting to avoid gradual or steplike operation which is not acceptable in electric switch and valve controls for obvious reasons. While manyconventional heatmotor operators are designed to'be snap acting, the conditions under which they will properly operate are so limited as to render'them infeasible and in some cases dangerous when utilized with equipment or in systems where accurate control is required.

The ineffectiveness of conventional heatmotor operators in controlling valves is .particularly acute, because failure of a valve to operate or gradual opening or closing of a valve can precipitate potentially dangerous situations, especially with respect to valves used to control the flow of fuel to a burner. Moreover, inaccurate operation of valves is uneconomical and can cause the failure of entire systems.

One prior art heatmotor operator utilized to control a valve has a bimetal assembly which is intended to be directly coupled with a valve member or'a valve stem. Accordingly, at high and low ambient temperatures, the valve member has a tendency to tip and the valve stem has a tendency to be cocked in its bushing both of which cause gradual opening and closing of the valve. Other prior art heatmotor operators utilize a compensating bimetal along with a motor bimetal to compensate for ambient temperature; however, the compensating bimetal is conventionally coupled directly with a valve member or valve stem thereby failing to solve the problem of gradual opening and closing of the valve.

Furthermore, the use of an ambient temperature compensating bimetal creates a problem in that heat from the motor bimetal adversely affects the ambient temperature compensating bimetal. This problem is remedied in some prior art heatmotor operators by attempting to overpower the heat leaking from the motor bimetal to the ambient temperature compensating bimetal with large temperature differences. The result is that proper ambient temperature compensation is obtained only within limited ambient temperature ranges and limited energization and deenergization times; and, for longer energization and deenergization times, actuation and deactuation times of the heatmotor operator will vary greatly.

Another problem that exists with conventional heatmotor operators is that the heat obtained when the operating voltage is much greater than the nominal operating voltage causes gradual opening and closing and adversely affects operation in the same manner as high and low'ambient temperature and long energization times. Similarly, the reduction in heat when the applied voltage is at a value much lower than the nominal operating voltage creates longer actuating and deactuating times than are desirable.

Accordingly, it can be seen that problems exist with respect to the utilization of heatmotor operators with valves, particularly in providing the ability to operate safely and to close and remain closed under abnormal operating conditions. These problems are particularly acute in solid state systems since less power is available for normal operation, yet the same range of abnormalities exists.

SUMMARY OF THE INVENTION Accordingly it is an object of the present invention to construct a heatmotor operator that operates accurately under variable conditions such as applied voltage, energization time and ambient temperature.

Another object of the present invention is to maintain snap acting operation of a heatmotor operator'under adverse conditions.

The present invention has another object in that a snap acting heatmotor operator requires less than full ambient temperature compensation by utilizing magnetic means to provide snap action.

A further object of the present invention is to control the opening and closing of a valve with a lever which in turn is controlled by a bimetal assembly to thereby prevent gradual opening and closing of the valve.

Another object of the present invention is to superpose a compensating bimetal arm above a motor bimetal arm such that the movable end of the motor bimetal arm is coupled with the compensating bimetal arm to provide ambient temperature compensation by deflection of both the compensating bimetal arm and the motor bimetal arm in the same direction.

l-leatmotor operators constructed in accordance with the present invention are advantageous over conventional heatmotor operators in that snap action is provided under adverse operating conditions such as long energization times, high and low ambient temperatures, and varying applied voltages. Actuating and deactuating times are maintained within predetermined limits regardless of adverse conditions since by utilizing a magnet for snap action complete ambient temperature compensation is not required thereby permitting bimetal deflection to be utilized for preconditioning. Heatmotor operators constructed in accordance with the. present invention are further advantageous in that long bimetal arms are utilized to provide more effective action with less cross bending and the motor bimetal may be thermally insulatedfrom both the support housing and the compensating bimetal.

The present invention is generally characterized in a heatmotor operator including a support, a temperature responsive assembly including a first temperature responsive element having a stationary end secured to the support and a movable end, and a second temperature responsive element superposed above the first temperature responsive element and having a first end coupled with the movable end of the first temperature responsive element and a second end, a lever having an operating endadapted to operate a control device and a pivot end coupled with the support and the second end of the second temperature responsive element, and actuating means for the temperature responsive assembly, the first and second temperature responsive elements deflecting in the same direction in response to heat to provide ambient temperature compensation.

Further objects and advantages of the present invention will become apparent from the following description of a preferred embodiment taken in conjunction with the accompanying drawings.

FIG. 1 is a top plan view of a heatmotor operator in accordance with the present invention.

FIG. 2 is an elevational sectional view of the heatmotor operator of FIG. 1 taken along line 2-2.

FIGS. 3 and 4 are simplified elevational views of the heatoperation.

DESCRIPTION OF THE PREFERRED EMBODIMENT The heatmotor operator of the present invention is described hereinafter as utilized to control a valve; however, it is clear that the present invention is not limited to valve actuators and may be used with any control device requiring precise actuation, such as an electrical switch.

A heatmotor operator according to the present invention is illustrated in FIGS. 1 and 2 and is set in a support housing 10 having upstanding sidewalls l2 and 14, end walls 16 and 18 and a bottom surface 20. End wall 16 has an annular supporting step 22 to support the heatmotor operator, and a screw 24 threadedly engages a threaded bore in step 22.

, The heatrnotoroperator includesa temperature responsive bimetal assembly having a motor arm 26 and an ambient temperature compensating arm 28, each of which is constructed as a bimetallic strip. Motor arm 26 has a stationary end 30 securedto a support member32 through a thermal insulator 34 by means of a rivet Support member 32 has an upper offset end 38 which is secured to a step 22 by screw 24. A heating element 40 is wound around motor arm 26 and is adapted to beconnected to any conventional source of electrical power through a pair of terminals, not shown, extending from housing 10,. A free end 42 of motor arm 26 extends through a slot 44 in a transverse end 46 of compensating arm 28. A thermal insulator 47 may be inserted in slot 44 is so desired. Compensating arm 28 has a movable end 48 secured by means or rivets 50 to a lever 52, which may be made of aluminum, and a planar flex spring 54, which is secured to step 22 through screw 24 and may be made of a material such as an alloy of beryllium and copper. I

Compensating arm 28 is superposed over motor arm 26 such that end 48 of compensating arm 28 overlies stationary end 30 of motor arm 26. The bimetal structures of both motor arm 26 and compensating arm 28 are such that, looking at FIG. 2, the metal havingthe higher coefficient of thermal expansion is disposed below the metal having the lower coefficient of thermal expansion.- Thus, both motor arm 26 and compensating arm 28 will deflect or 'move in the same direction with temperature increase or decrease.

Lever 52 has a pivot end 56 secured to flex spring 54 and an operating end 58 having a narrowed offset portion 60 extending therefrom through a large slot 62 in a generally U-shaped armature piece 64. A rectangular window 66 is provided in lever 52 between pivot end 56 and operating end 58 and is longer than compensating arm 28 and positioned adjacent thereto. Armature piece 64 defines a primary armature 68 and a secondary armature 70. An annular permanent magnet 72 is secured to the underside of operating end 58 of lever 52, and an operator 74 is mounted in the center of magnet 72 by use of an adhesive such as Glyptal. Primary armature 68 underlies the entire area of the magnet 72 whereas secondary armature 70 overlies only part of the area of magnet 72. Operator 74 abuts a member 76 extending from a control device 78 which may be a valve, an electrical switch or any other control device. Control device 78 is supported by bottom surface 20 of housing inside a wall 80 extending from bottom surface 20 and supporting armature piece 64. I

The heatmotor operator is illustrated in the deactuated state in FIG. 2 with operator 74 depressing member 76 to place control device 78 in a first state. For instance, assuming control device 78 to be a valve and member 76 to be a valve stem, the valve may be closed when the valve stem is depressed by operator 74. In the deactuated state there is no electricity supplied to winding 40; and, thus, motor arm 26 is substantially linear to permit the magnetic attraction between magnet 72 and primary armature 68 to maintain operator 74 in the position illustrated.

The response of the heatmotor operator to high ambient temperature conditions when no electricity is supplied'to heating element 40 is illustrated in FIG. 3,. The rise in ambient temperature causes both motor arm 26 and compensating arm 28 to deflect upwards; however, the force on the pivot end 56 of lever 52 remains the same due to the deflection of both arms in the same direction. That is, flex spring 54 supports lever 52 in a pivotable or movable manner such that forces applied to the pivot end 56 of lever 52 can pivotally move the lever; however, since both motor arm 26 and compensating arm 28 deflect upward at overlying ends 46 and 42, respectively, there is no force or movement at pivot end 56 of lever 52. To this end, the superposed relation of the motor and compensat ing arms permits the length of the motor and compensating arms to be substantiallythe same to provide complete ambient temperature compensation. The window 66 in lever 52 permits compensating arm 28 to deflect without restriction by lever 52 as well as exposing compensating arm 28 to ambient temperatures. In a similar manner under low ambient temperature conditions both motor arm 26 and compensating arm 28 will deflect downward and of course will not act to actuate the heatmotor operator. The ambient temperature compensation provided by the superposed position of the compensating arm over the motor arm permits the heatmotor operator to be actuated within prescribed time limits over a great range of ambient temperatures.

If control device 78 is a normally closed valve, when it is desired to open the valve electrical power is supplied to heating element 40 to actuate the heatmotor operator, as illustrated in FIG. 4. The heat emitted from heating element 40 causes movable end 42 of motor am 26 to deflect upward as illustrated in FIG. 4, and the deflection of motor arm 26 is transmitted to the pivot end 56 of lever 52 by compensating arm 28 which does not deflect. When the deflection force from motor arm 26, as transmitted to lever 52 by compensating arm 28, overcomes the magnetic attraction between primary armature 68 and magnet 72, the operating end 58 of lever 52 will snap into an actuated position with magnet 72 adjacent secondary armature 70. Since the magnetic force between magnet 72 and primary armature 68 is a function of the square of the distance therebetween, the movement of operating end 58 is accelerated with movement away from the deactuated position; and, as magnet 72 approaches secondary armature 70, the magnetic attraction therebetween will further accelerate movement. Thus, the transition between the deactuated state and the actuated'state of the heatmotor operator is accomplished with snap action, and gradual opening, or tipping of the valve is prevented since the valve is operated by lever 52 rather than directly by the bimetal assembly. v

The upward movement of lever 52 and operator 74 permits member 76 to move upward and open the valve of control device 78. Control device 78 will normally contain bias means forcing member 76 upward against operator 74 such that member 76 will follow the movement of operator 74 to change the state of control device 78.

The use of thermal insulator 32 restricts any drain of heat from motor arm 26 to housing 10 once heating element 40 has been energized; and, accordingly, the heatmotor operator is quickly moved from the deactuated state to the actuated state. Once the heatmotor operator is actuated some heat from motor arm 26 does leak to compensating arm 28; however, while the leaked heat causes compensating arm 28 to deflect slightly upward which has a tendency to pull lever 52 down, the leaked heat is not sufficient to cause the heatmotor operator to change states. The heating of compensating arm 28 from motor arm 26 is limited due to the heat losses to the housing 10 through flex spring 54 and through window 66. The deflection of compensating arm 28 acts to precondition the bimetal assembly for quick transition to the deactuated state once the electrical power supplied to heating element 40 is terminated. If desired, the thermal insulator 47 may be positioned in slot 44 between the movable end 42 of motor arm 26 and the transverse end 46 of compensating arm 28 to increase the temperature differential between motor arm 26 and compensating arm 28 to provide additional movement and power.

When it is desired to return the valve to its closed state, the heatmotor operator is deactuated by removing the electrical power supplied to heating element 40 such that motor arm 26 cools and returns to its linear state to apply a force on pivot end 56 of lever 52 through compensating arm 28 to break'the magnetic attraction between magnet 72 and secondary armature such that operator 74 returns to its deactuated position with snap action, in the same manner as previously described with respect to actuation of the heatmotor operator. The preconditioning of compensating arm 28 decreases deactuation time and compensates for the slow cooling of motor arm 26 due to its thermal isolation.

It is desirable to provide a gap of a few thousands of an inch between magnet 72 and armatures 68 and 70 in order to prevent magnetic sticking due to the extremely high rate of change of field intensity at magnetic contact. To this end, it is noted that lever 52 acts as a spacer between magnet 72 and secondary armature 70. Assuming control device 78 to be a normally closed valve, member 76 will be stepped on the valve seat and the abutting of operator 74 with member 76 spaces magnet 72 from primary armature 68. Similarly, if control device 78 is normally opened, member 76 will be stopped in an open position to space magnet 72 from primary armature 68. The spacing between magnet 72 and primary armature 68 may "be adjusted by adjusting the position of operator 74 in magnet 72.

While ambient temperature compensation is provided by the deflection in the same direction of motor arm 26 and compensating arm 28 in response to temperature, one of the advantages of the heatmotor operator 'is that the bimetal assembly need not be fully ambient temperature compensated due to the control of the operating end 58 of lever 52 by magnetic interaction. That is, high and low ambient temperature compensation is made much less critical by the magnetic characteristics of the heatmotor operator.

The thermal isolation of motor arm 26 permits accurate operation when the operating voltage applied to heating element 40 is below the nominal operating voltage or when the heatmotor operator is used with solid state control circuitry since heat losses from motor arm 26 are reduced to a minimum. If the voltage applied to heating element 40 is higher than the nominal operating voltage, deactuation time will not be adversely affected .due to the preconditioning of compensating arm 28; and, for the same reason, long energization times do not adversely affect deactuation time of the heatmotor operator.

In as much as the present invention is subject to many variations, modifications and changes in detail, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Iclaim:

l. A heatmotor operator comprising:

support means;

a temperature responsive assembly including first temperature responsive means having a stationary end secured to said support meansand a movable end, and second temperature responsive means superposed above said first temperature responsive means and having a first end coupled with said movable end of said first temperature responsive means and a second end;

lever means having operating means adapted to operate a control device and a pivot end coupled with said support means and said second end of said second temperature responsive means; and

actuating means coupled with said temperature responsive assembly and adapted to be connected to a source of electricity;

said first and second temperature responsive means deflecting in the same direction in response to heat whereby said heatmotor operator is ambient temperature compensated.

2. The invention as recited in claim 1 wherein said first temperature responsive means isa first bimetal arm, and said second temperature responsive means is a second bimetal arm.

3. The invention as recited in claim 2 wherein said lever means has a window therein and said second bimetal arm is disposed adjacent said window whereby said secondbimetal arm is exposed to ambient temperatures and said window permits said second bimetal arm to deflect therethrough.

4. The invention as recited in claim 2 wherein said actuating means includes a heating element wound around said first bimetal arm.

5. The invention as recited in claim 4 wherein said stationary end of said first bimetal arm is secured to said support means through thermal insulating means.

6. The invention as recited in claim 5 wherein said first end of said second bimetal arm is coupled with said movable end of said first bimetal arm through thermal insulatingmeans.

7. The invention as recited in claim 5 wherein said pivot end of said lever means is coupled with said support means through a planar flex spring.

8. The invention as recited in claim 5 wherein said operating means includes a permanent magnet and an armature piece disposed around said permanent magnet and defining a primary armature and a secondary armature, said permanent magnet being adjacent said primary armature when said heatmotor operator is deactuated and said permanent magnet being adjacent said secondary armature when said heatmotor operator is actuated.

9. A heatmotor operator for controlling the position of a valve member comprising:

a housing;

a motor bimetal arm having a stationary end and a movable end;

thermal insulating means mounting said stationary end of said motor bimetal arm on said housing;

a compensating bimetal arm superposed above said motor bimetal arm and having a first end coupled with said movable end of said motor bimetal arm and a second end;

a lever having a pivot end coupled with said second end of said compensating bimetal arm and an operating end adapted to control the position of the valve member;

pivot means supporting said pivot end of said lever on said housing; and

a heating element disposed adjacent said motor bimetal arm and adapted to be connected with a source of electricity to actuate said heatmotor operator;

said motor bimetal arm and said compensating bimetal arm being arranged such that both said motor bimetal arm and said compensating bimetal arm deflect in the same direction whereby said heatmotor operator is ambient temperature compensated.

10. The invention as recited in claim 9 wherein said lever has a window therein between said pivot end and said operating end, said window being disposed adjacent and over said compensating bimetal arm whereby said window exposes said compensating bimetal arm to ambient temperatures and permits deflection of said compensating bimetal arm therethrough.

11. The invention as recited in claim 10 wherein said hous ing supports a primary armature and a secondary armature, and said operating end of said lever carries a permanent magnet disposed between said primary armature and said seconda ry armature.

12. The invention as recited in claim 11 wherein said pivot means includes a planar flex spring secured to said housing and said pivot end of said lever.

13. The invention as recited in claim 12 wherein said first end of said compensating bimetal arm has a slot therein and said movable end of said motor bimetal arm extends through said slot.

14. The invention as recited in claim 12 wherein said first end of said compensating bimetal arm is coupled with said movable end of said movable bimetal arm through thermal insulating means.

Claims (14)

1. A heatmotor operator comprising: support means; a temperature responsive assembly including first temperature responsive means having a stationary end secured to said support means and a movable end, and second temperature responsive means superposed above said first temperature responsive means and having a first end coupled with said movable end of said first temperature responsive means and a second end; lever means having operating means adapted to operate a control device and a pivot end coupled with said support means and said second end of said second temperature responsive means; and actuating means coupled with said temperature rEsponsive assembly and adapted to be connected to a source of electricity; said first and second temperature responsive means deflecting in the same direction in response to heat whereby said heatmotor operator is ambient temperature compensated.

2. The invention as recited in claim 1 wherein said first temperature responsive means is a first bimetal arm, and said second temperature responsive means is a second bimetal arm.

3. The invention as recited in claim 2 wherein said lever means has a window therein and said second bimetal arm is disposed adjacent said window whereby said second bimetal arm is exposed to ambient temperatures and said window permits said second bimetal arm to deflect therethrough.

4. The invention as recited in claim 2 wherein said actuating means includes a heating element wound around said first bimetal arm.

5. The invention as recited in claim 4 wherein said stationary end of said first bimetal arm is secured to said support means through thermal insulating means.

6. The invention as recited in claim 5 wherein said first end of said second bimetal arm is coupled with said movable end of said first bimetal arm through thermal insulating means.

7. The invention as recited in claim 5 wherein said pivot end of said lever means is coupled with said support means through a planar flex spring.

8. The invention as recited in claim 5 wherein said operating means includes a permanent magnet and an armature piece disposed around said permanent magnet and defining a primary armature and a secondary armature, said permanent magnet being adjacent said primary armature when said heatmotor operator is deactuated and said permanent magnet being adjacent said secondary armature when said heatmotor operator is actuated.

9. A heatmotor operator for controlling the position of a valve member comprising: a housing; a motor bimetal arm having a stationary end and a movable end; thermal insulating means mounting said stationary end of said motor bimetal arm on said housing; a compensating bimetal arm superposed above said motor bimetal arm and having a first end coupled with said movable end of said motor bimetal arm and a second end; a lever having a pivot end coupled with said second end of said compensating bimetal arm and an operating end adapted to control the position of the valve member; pivot means supporting said pivot end of said lever on said housing; and a heating element disposed adjacent said motor bimetal arm and adapted to be connected with a source of electricity to actuate said heatmotor operator; said motor bimetal arm and said compensating bimetal arm being arranged such that both said motor bimetal arm and said compensating bimetal arm deflect in the same direction whereby said heatmotor operator is ambient temperature compensated.

10. The invention as recited in claim 9 wherein said lever has a window therein between said pivot end and said operating end, said window being disposed adjacent and over said compensating bimetal arm whereby said window exposes said compensating bimetal arm to ambient temperatures and permits deflection of said compensating bimetal arm therethrough.

11. The invention as recited in claim 10 wherein said housing supports a primary armature and a secondary armature, and said operating end of said lever carries a permanent magnet disposed between said primary armature and said secondary armature.

12. The invention as recited in claim 11 wherein said pivot means includes a planar flex spring secured to said housing and said pivot end of said lever.

13. The invention as recited in claim 12 wherein said first end of said compensating bimetal arm has a slot therein and said movable end of said motor bimetal arm extends through said slot.

14. The invention as recited in claim 12 wherein said first end of said compensating bimetal arm is coupled with said movable end of said movable bimetal arm through thermal insulating means.

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