US 3719085 A
A thermal power element is constructed of a pair of generally hollow casing members with a thermally responsive charge in one casing member and with a sealed plunger protruding from the other casing member. The two casing members are joined together to form a unitary structure by means of interengaging flange elements securely locked together to prevent relative movement between the casing members.
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Description (OCR text may contain errors)
United States Patent Sliger THERMAL POWER ELEMENT  Inventor: Boyd P. Sliger, Concord, Tenn.
 Assignee: Robertshaw Controls Company,
 Filed: Nov. 23, 1970  Appl. No.: 91,647
 US. Cl. ..73/368.3  Int. Cl. ..G01k 5/34  Field of Search ..73/368.3; 60/23; 92/101;
 References Cited UNITED STATES PATENTS 2,942,095 6/1960 Robertson ..73/368.3 UX
[- 51 Mar. s. @973 Bernett ..73/368.3 Wagner ..73/368.3
Primary ExaminerLouis R. Prince Assistant Examiner--William A. Henry, 11 Attorney-Brenner, OBrien & Guay 5 7] ABSTRACT A thermal power element is constructed of a pair of generally hollow casing members with a thermally responsive charge in one casing member and with a sealed plunger protruding from the other casing member. The two casing members are joined together to form a unitary structure by means of interengaging flange elements securely locked together to prevent relative movement between the casing members.
4 Claims, 1 Drawing Figure THERMAL POWER ELEMENT BACKGROUND OF THE INVENTION 1. Field of the invention The present invention relates to thermal power elements functioning as thermostatic devices, and in particular, to such thermal power elements utilizing a fusion type charge which expands and contracts in response to temperature changes to cause actuation of 1 a related control device.
2. Description of the Prior Art Conventional thermal power elements utilizing a variety of charge materials are well known in the prior art as exemplified by U.S. Pat. Nos. 2,917,925, 3,046,787, 3,l53,933, 3,308,668 and 3,407,663. While such prior art devices are satisfactory for their particular purposes, difficulty has been encountered in the design of such devices to prevent both leakage of the pressure producing material (wax and copper powder) at elevated temperatures and introduction of the heat producing material (water, ethylene glycol, etc.) into the thermal power element at temperatures substantially below the operating range of the expansive material during operation. The primary seal in the thermal power element is the flexible diaphragm compressed between the cup and guide member. In order that the seal be preserved, it is essential that the assembled relative positions of the cup and guide are not disturbed. A particular problem has been found in that retention of sealing ability of conventional thermal power elements has decreased after such an element has been operated between extreme temperatures and the cup material has expanded and contracted, due in part to the thermal expansive properties of the cup material and in part to flexing of the cup during operation as the pressure internal to the cup increases and decreases. Additionally, since these thermal power elements are normally assembled into other devices such as valves, switches, etc., the subsequent assembly operations often require the application of compressive forces which tend to cause relative movement between the cup and guide members that disturb the desired relationship of the diaphragm, cup and guide.
SUMMARY OF THE INVENTION The present invention is summarized in that a thermal power element is defined by a cup member and a guide member, an actuator carried by the guide member, a thermally expansible-contractible charge in the cup member, a diaphragm sealing the charge in the cup member and being adapted to control movement of the actuator in accordance with expansion and contraction of the charge, flange means between the cup and the guide connecting them in assembled relation, and interlocking means on the flange means securely fixing the cup and the guide member in assembled relation.
An object of the present invention is to improve a conventional thermal power element by providing an interlock between the assembled members to prevent relative movement therebetween and protect the integrity of the seal between the diaphragm, cup and guide of such a thermal power element.
The present invention has another object in that an interlocking seal permanently and securely fixes the cup and guide members of a thermal power element in assembled relationship.
It is a further object of this invention to construct a thermal power element in a simple and economical manner with interlocking beads and grooves formed in the contiguous faces of the flange means connecting the cup and guide members of such a thermal power element.
Other objects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompany- 0 ing drawing.
BRIEF DESCRIPTION OF THE DRAWING The single FIGURE of the drawing is a longitudinal cross section of a thermal power element embodying the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention constitutes an improvement in the thermal power element shown in U.S. Pat. No. 3,046,787, which is incorporated herein by reference. The present invention is embodied in a fusion type thermal element, commonly known as a thermal power element, which is shown on the drawing as including a pair of hollow casing members defining a lower cup 14 and an upper guide 16. The guide 16 is formed with an annular peripheral flange 18 at one end thereof with a peripheral V-shaped recess 19 extending around its outer circumference; an annular groove 20 is formed in the outer end face of the flange l8 and extends to the peripheral circumference thereof. A cylindrical bore 22 extends from the flange end 18 longitudinally through the casing member 16 for a portion of the length thereof and terminates in a reduced axial bore 24 at the opposite end.
The lower cup 14 is generally cup-shaped with an inner cylindrical side wall 26 which extends between a bottom wall 28 at one end thereof and a recess or counterbore 30 at the opposite end; an annular shoulder 32 defines a connecting wall between the cylindrical side wall 26 and the counterbore 30. An annular sealing ring 34 .formed with a central orifice 36 is seated upon the shoulder 32 and underlies a flexible diaphragm 38 made of rubber or any other suitable resilient sealing material. The diaphragm 38 is formed with an annular collar 40 about its outer periphery which extends into the groove 20 on the flange 18 of the upper guide 16. An end wall 42 of counterbore 30 of the cup 14 extends beyond the flange 18 of the guide 16 and is crimped or otherwise deformed so as to overlie the flange 18. The inner wall of counterbore 30 is provided with an annular projection 41 which is V-shaped in cross section so as to conform and fit in the V-shaped groove 19 in the end face of flange 18.
A charge of any suitable thermally expansible-contractible fusion type substance 44 is disposed within the hollow area bounded by the walls 26, 28 of the cup 14 and by the sealing ring 36 and diaphragm 38. The charge 44 is selected in accordance with the desired operating range of temperatures to which the thermal power element is to be applied.
A cylindrical member 46 made of rubber or other resilient material fits closely within the cylindrical bore 22 of the guide 16 and extends from flange end 18 to tenninate in an end wall adjacent the opposite end of cup 16. The cylindrical member 46 is provided with an axial bore 48 intermediate the ends thereof which terminates at one end in a hemispherical section 50. An annular scraper ring 52, preferably formed of a plastic material such as Teflon, is disposed between the end wall of cylindrical member 46 and the interior of the end wall of the bore 22.
A plunger or actuating stem 54 in the form of a generally cylindrical rod is adapted to fit closely within the bore 48 and has a hemispherical end to conform to the same configuration of the hemispherical section 50 of the bore 48. The actuating stem 54 slidably protrudes through the axial bore 24 for engagement with a control mechanism (not shown) that is to be actuated in response to temperature changes as sensed by the thermal power element.
The operation of the above described thermal power element and the various types of thermally responsive materials used in the charge 44 are so well known in the art that specific details are being omitted for the sake of brevity. For a more complete description of such details reference is made to US. Pat. Nos. 3,l53,933 and 3,407,663. As far as the present invention is concerned, it need only be noted that the plunger 54 reciprocates relative to the upper casing bore 24 in response to temperature expansion and contraction of the charge 44 and with the aid of a return spring (not shown).
in order to assemble the thermal power element, the flange end 18 of the guide 16 is placed in the counterbore 30 of the cup 147 The diaphragm 38 is sandwiched between the underside of the flange end 18 and the sealing ring 34. A spring loaded member of an assembly device (not shown) bears on the top surface of the guide 16 and moves the entire guide 16 downwardly compressing the diaphragm 38 with its periphery 40 being moved into the groove 20. With such members in the desired relationship, a conically shaped crimping die (not shown) slightly larger in diameter at the opened end than the outside diameter of the cup 14 is forced down the outside wall of the cup 14. As the crimping die moves downward, a portion of the material from the inner surface of the counterbore 30 is extruded forming the sealing bead 41 into the peripheral recess or groove 19 of the flange end 18. At the same time, the top of the casing 14 is crimped or otherwise deformed so that the end wall 42 overlies the flange end 18 and is spaced in parallel relation to the V- shaped bead 41. It is to be recognized that other methods of assembly may be utilized and that the particular shape of the sealing bead 41 and its cooperating groove 19 may be extruded into other cross sectional shapes such as seimcircular, rectangular, etc., the main factor for forming the sealing bead 41 is to provide it with sufficient material in the similarly shaped groove 19 to be confined therein and to fonn a strong pressure-type seal whereby relative motion between the cup 14 and the guide 16 is prevented and the seal is not disturbed during assembly and/or during subsequent operation of the thermal power element.
The above described invention has a particular advantage in that not only is an effective seal provided for the thermal contracting and expanding charge 44, but
also an effective seal is provided for preventing any fluid flow into the casing elements.
Inasmuch as the present invention 18 sub ect to many variations, modifications and changes in detail, it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.
What is claimed is:
1. A thermal power element comprising a generally hollow cup and a generally hollow guide disposed on a common longitudinal axis,
actuating means in said guide and having a stem protruding therefrom and being movable along said longitudinal axis,
a charge of thermally expansible-contractible material in said cup,
diaphragm means separating interior portions of said cup and guide and defining a movable wall for transmitting movement between said charge and said actuating means,
said cup having a bottom wall and a side wall extending therefrom, an annular recessed wall and an annular shoulder defining a connecting wall between said side wall and said recessed wall, said recessed wall being generally parallel to said longitudinal axis and said annular shoulder being generally transverse to said longitudinal axis,
said diaphragm means having an annular periphery extending against said recessed wall in overlying relation to said annular shoulder,
an annular flange on said guide being disposed in said cup,
a bottom surface of said annular flange extending generally transverse to said longitudinal axis in overlying relation to the annular periphery of said diaphragm means,
a peripheral surface on said annular flange extending generally parallel to said longitudinal axis to engage a contiguous face on said recessed wall,
a radially inwardly directed end wall on said cup overlying said annular flange to retain said cup and guide in assembled relationship,
locking means interconnecting the peripheral surface on said annular flange and the contiguous face on said annular recess,
said locking means extending generally transverse to said longitudinal axis and preventing relative movement between said cup and guide during movement between said actuating means and said charge.
2. The invention as recited in claim 1 wherein said locking means includes a groove in said peripheral surface and a projection extending from said contiguous face into said groove.
3. The invention as recited in claim 2 wherein said groove and said projection have similarly shaped cross sections.