US 3821684 A
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United States Patent [191 Keating I  3,821,684 June 28, 1974  REMOTE SETTING THERMOSWITCH  Inventor: Richard T. Keating, 144 N. Cuyler Ave., Oak Park, 111. 60300  Filed: Sept. 10, 1973 21 Appl. No.: 396,085
 US. Cl 337/392, 73/3626, 236/51, 337/323  Int. Cl. HOIh 37/28  Field of Search 337/312, 316, 320, 321, 337/323, 382, 384, 386, 392, 307; 73/3626; 236/51, 98
 References Cited UNITED STATES PATENTS 2,724,030 11/1955 Hilgert 73/3626 4/ 88 f 32 86 36 E: J /4 a4 'l: l I 38 22 2,822,985 2/1958 Johnson et al 73/3626 X Primary Examiner-Roy N. Envall, Jr. Attorney, Agent, or Firm-Rummler & Snow 6 Claims, 2 Drawing Figures 1 REMOTE SETTING THERMOSWITCH BACKGROUND OF THE INVENTION In the control of temperature of a heated zone from remotely positioned control panels using low-cost thermoswitches, push-pull and torsion cables are generally used to transmit the manual input to the dial indicator at a remote location to the desired change of setting of the thermostatic switch at the heated zone.
Push-pull and torsion cable remote control devices suffer from the common problem that in the transmis sion of control signals, lost motion reduces the sensitivity of the control and wear which affects the calibration. Then, too, such mechanically coupled remotely sensing devices also suffer from changes in calibration from ambient temperature fluctuations especially where cost considerations dictate against the use of much expensive invar in construction. Changing calibrations from loosened mechanical connections which have an ever-present tendency to slip are also a prob- -lem with the installation of such devices, requiring periodic checks and recalibrations to insure that at all times there is accurate temperature control of the many processes of industry and home. Recalibration is diff cult and time-consuming. In many cases, time, opportu' nity or inclination are not available for such periodic checks so that the appliance or industrial apparatus continues to be used when it is giving inferior performance. The result is a degradation of processes which can affect economic results which extend far beyond the immediate bounds of concern.
SUMMARY OF THE INVENTION The gist of the remote control that is the subject of this invention lies in a sealed hydraulic system which is charged with a hydraulic fluid which has a zero coefficient of thermal expansion. A closed hydraulic tube of rigid wall construction is in fluid communication at its input end with a cylindrical input metal bellows of a given hydraulic diameter which is extendable or compressible as a spring capsule in the axial direction. The
input bellows comprises a circular back plate having a central aperture which is fixed to and in fluid communication with the hydraulic tube. A cylindrical corrugated input diaphragm is pressure sealed along its circumference to the circumference of the back plate, and to a solid circular face plate which is movable in the extendable and compressible direction. A flat head right handed screw engages a threaded boss which is mounted on the control panel of the heating apparatus bearing on the outer side of the movable face plate of the input bellows. A dial indicator with an adjusting knob is fastened to the head of the screw with graduations thereon which bear a fixed relation to the lead of the thread on the screw. A given number of turns of the dial indicator in a clockwise direction then advances the screw into the threaded boss on the control panel and moves the input face plate a fixed distance therein. Turning the dial indicator in the counterclockwise di rection extends the face plate of the bellows in reverse action under the restoring force of the bellows as a compression spring capsule.
A cylindrical output meta] bellows which is extend able or compressible as a spring capsule in the axial direction also connects to the output of the hydraulic tube in a similar manner to the connection of the input bellows to the input end. The hydraulic diameter of the output bellows may be equal to, greater than or less than that of the input bellows depending on whether the control sensitivity of the remote setting device desired is to be 1.0, greater than 1.0 or less than 1.0. In fact, by using two different size diaphragms, a multiplication ratio can be effected so that the dial control can be turned greater or less for each degree of temperature setting. The output face plate of the output bellows then moves in consonance with the extendable and compressible input movements of the input face plate of the input bellows. A threaded screw closure is inserted in the leg of a tee connector in the hydraulic tube for the filling of the system with hydraulic fluid and the deaerating thereof.
In one version of the invention, the temperature adjusting means of the thermostatic control element is mounted directly on the movable outer face plate of the output bellows. The moving electrical contact of the thermostat is mounted on a standard invar rod and copper tube type temperature sensing element in the standard manner for the temperature sensing thereof.
In another version of the invention, a standard strutand-tube type thermostat comprising an outer shell of high expanding metal and a strut of low expanding metal has its temperature adjusting means mounted on the movable outer face plate of the output bellows. The moving electrical contacts of the thermostat are mounted on the strut elements for the temperature sensing thereof in a standard way.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a fragmentary cross-section of the invar rod-tinned copper tube type remote setting thermoswitch apparatus of this invention; and
FIG. 2 shows a fragmentary cross-section of the strutand-tube type remote setting thermoswitch apparatus of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. l and 2, a sealed hydraulic system 10 is charged with a hydraulic fluid which has a low coefficient of thermal expansion and comprises a hydraulic tube 112 of rigid wall construction having an input end 114 and output end 116. An input metal bellows 13 having a given hydraulic diameter which is extendable or compressible as a compression spring capsule in one direction and rigidly constructed against deflection at right angles thereto is attached to and in fluid communication with the input end M of the tube 12. A control panel 24 mounts to the appliance or industrial apparatus (not shown) adjacent to the input bellows 18 for the control thereof. A circular back plate 20 having a central aperture 22 in fluid communication and in concentric relation with the input end 14 of the tube 12 mounts to the back side of the panel 24. A cylindrical corrugated diaphragm 26 having moving and stationary ends 28 and 29 mounts to and is pressure sealed and in concentric relation with the circumference of the circular back plate 20 at the stationary end thereof. The movable circular face plate 28 mounts to and is pressure sealed and in concentric relation with the moving end of the cylindricalcorrugated diaphragm 26.
A threaded boss 30 mounts on the control panel 24 adjacent to and in concentric relation with the movable face plate 28 of the input bellows 18. A right-hand screw 32 mounts in threaded boss 30 having a flat end 34 bearing against and in concentric relation with the outside of the movable face plate 28. A cylindrical screw extension 36 extends from the screw 32 out of flush relationship with respect to the control panel 24. A dial indicator 38 is fixedly mounted to and in concentric relation with the cylindrical screw extension 36 of the screw 32. A hand, knob 45 mounts to the dial indicator 38. A pointer 41 reads out the index of the indicator 38.
An output metal bellows 42 having a hydraulic diameter which is less than that of the input bellows 18 which is extendable or compressible as a compression spring capsule in one direction only and rigidly constructed against deflection at right angles thereto is attached to and in fluid communication with the output end 16 of the tube 12. A pipe threaded adapter 44 mounts to the heating zone of the appliance or industrial apparatus (not shown) adjacent to the output bellows 42 for the sensing of the temperature therein. A
circular back plate 46 having a central aperture 48 which is in fluid communication and in concentric relation with the output end 16 of the tube 12 mounts to the front side of the adapter 44. A cylindrical corrugated diaphragm 49 having moving and stationary ends 47 and 51 is pressure sealed to and in concentric relation with the circumference of the circular back plate 46 at the stationary end thereof. A movable circular face plate 50 is pressure sealed and in concentric relation with the moving end 47 of the cylindrical corrugated diaphragm 42.
ln FIG. 1, a thermostatic control element 52 mounts to the moving face plate 50 comprising a temperatureadjusting electrical contact 54 which is mounted to the moving face plate 50 of the output bellows 42. A temperature sensing element 56 mounts to and is in concentric relation with the pipe-threaded adapter 44 and adjacent to the moving face plate 50. A tinned copper tube 58 having its innermost end sealed closed mounts to and is in concentric relation with the adapter 44. An invar rod assembly 60 having closed and free and open ends 61' and 63 is mounted to the closed end of tube 58 inside of and in coaxial relation therewith. A threaded bore 64 extends coaxially within the rod 60 from the free and open end 63 thereof. A threaded stud 66 engages the bore 64 having end 68 extending outside the free end 63 of rod 60. A jamb nut 70 mounts on the stud 66 for the final calibrated adjustment of the temperature sensing element 52. A movable temperaturesensing electrical contact 62 is mounted to the extending end 68 of the stud 66 on the invar rod assembly 60 spaced from and adjacent to the fixed electrode 54 for electrical contact with the temperature-adjusting contact 54 in the make or break of the spaced electrical contacts 55 of the thermostatic control.
In FIG. 2, a temperature-sensing element 72 mounts to the moving face plate 50 comprising an outer shell 74 having a closed end 61 and made of metal having a high coefficient of expansion and a strut assembly 76 having one end fastened thereto which is made of metal having a low coefficient of expansion. A pair of electrical contacts 78 mounts one on each of the two struts of assembly 76 and is installed in the shell 74 under a state of residual tension or compression. A threaded sleeve 80 is connected to the other end of the strut 76 in concentric relation to the outer shell 74. A threaded stud 82 engages the threaded sleeve 80. A jamb nut 84 mounts on the stud 82 for fixing the final calibration of the makebreak" position of the electrical contacts 78 of the temperature-sensing element 72. The threaded stud 82 connects to the moving face plate 50 whereby a net change in length of the high-expanding shell 74 as it expands or contracts with changing temperature relative to the low-expansion strut assembly 76 appears as the make or break of the spaced electrical contacts 78 of the thermostatic control.
A tee tubing connector 84 is mounted in hydraulic tube 14 intermediate between the input end 14 and output end 16 thereof for the deaeration and filling of the hydraulic system 10 with hydraulic fluid. Pipe plug 86 is screwed into the open leg 88 of the tee" for the final closure and sealing off of the hydraulic system.
Although but two specific embodiments of this invention are herein shown and described, it will be understood that details of the construction shown may be altered or omitted without departing from the spirit of the invention as defined by the following claims.
1. A remote-sensing, hydraulically-actuated thermostat having a dial index comprising:
a. A sealed system of rigid wall construction completely filled with a hydraulic fluid having a low temperature coefficient of expansion;
b. An input displacement means mounted on the wall of said system and connected to the dial index;
c. An input displacement sensing means filled with said fluid mounted in the wall of and in fluid communication with said system and operationally connected to the input displacement means; and
d. An output displacement responsive means filled with said fluid mounted in the wall of and in fluid communication with said system and operationally connected to the make-break electrical contacts of the thermostatic element.
2. A remote-sensing thermostat as set forth in claim 1 wherein said sealed system comprises a tube.
3. A remote-sensing thermostat as set forth in claim 1 wherein said input displacement means comprises a threaded stud engaging a boss.
4. A remote-sensing thermostat as set forth in claim 1 wherein said input displacement sensing means comprises a bellows.
5. A remote-sensing thermostat as set forth in claim 1 wherein said output displacement responsive means comprises a bellows.
6. A remote-sensing, hydraulically actuated thermostat with a control sensitivity greater than a value of 1.0 having a make-break electrical temperature-sensing element mounted in the wall of a heated zone and a dial index mounted to a control panel in which it takes a greater number of turns of the dial index to reset the thermostat for each degree of change in the thermostat temperature setting comprising:
a. A tube of rigid wall construction filled with hydraulic fluid of low temperature coefficient of expansion having an input end mounted on the panel and an output end mounted on the wall;
b. An input bellows filled with said hydraulic fluid having a given hydraulic diameter and a moving face and a back face mounted on the input end of the tube in fluid communication with the input end of the tube;
c. A threaded boss mounted on the control panel adjacent to and spaced from the moving face of the input bellows;
d. A screw mounted to the dial index and engaged in the boss and having its extending end bearing against the moving face of the input bellows; and
e. An input bellows filled with said hydraulic fluid having a hydraulic diameter less than that of said of the input bellows to the output bellows.