US2803494A - Thermo-actuator - Google Patents

Description

All-g 1 7 Y J. F. SCHERER 2,803,494

THERMO-AGTUATOR Filed March 16, 1955 INVENTOR.

JAMES E SCHERER Unite States Patent THERMO-ACTUATBR James F. Scherer, Terrace Park, G'hio Application March 16, 1955, Serial No. 494,751

15 Claims. (Cl. 297-6) This invention relates to temperature responsive devices and, more particularly, to that class of devices known as thermostatic actuators which are characterized by their ability to produce a powerful thrust within a narrow temperature range and thereby provide an accurate and positive type of thermostatic control.

Prior art devices of this nature have, in general, been comprised of a metal cup covered by a resilient diaphragm for retaining the heat responsive material within the cup. It has been found quite ditficult, however, to effect a tight seal between the cup and the diaphragm which is capable of resisting the extremely high pressure developed inside the cup. To overcome this source of trouble, I have developed a new type of thermostatic actuator in which the. material is completely enclosed within a capsule formed of resilient material. This capsule is received within a housing in which a piston is guided for reciprocatory movement in response to expansion and contraction of the heat expansible material contained inside the capsule. External heat is conducted to the material within the capsule by a heat transfer pin which passes through the Wall of the capsule and extends into the cavity where it is surrounded by the material. The point of entrance of the pin into the capsule is sealed by an inwardly directed lip formed integrally with the wall of the capsule which surrounds a portion of the pin and provides an effective seal against the escape of heat expansible material from the capsule even at the extreme pressures encountered in this sort of application. The exterior end of the pin is so arranged as to be in heat conducting relationship with the heat conductive material of the housmg.

Accordingly it is an object of my invention to provide a novel and improved form of thermoactuator.

Another object of my invention is to provide a thermoactuator in which the heat expansible material is enclosed within a capsule containing a heat transfer pin which is sealed into the wall of the capsule by means of a lip seal.

Another object of my invention is to provide a novel type of housing for a thermo-actuator in which a capsule containing heat expansible material and a piston adapted for operation thereby are enclosed and held in operative relation with respect to one another.

Another object of my invention is to provide a housing for a capsule type thermo-actuator in which a recess is provided within the housing for receiving and journaling the outer end of a heat transfer pin sealed into the wall of the capsule.

Another object of my invention is to provide a novel housing for a thermo-actuator which is formed of two stampings made of heat conductible material and having the heat transfer pin formed integrally with one of them.

With these and other objects in view which will become apparent from the following description, the invention includes certain novel features of construction and combinations of parts the essential elements of which areset forth in the appended claims and a preferred form or ice embodiment of which will hereinafter be described with reference to the drawings which accompany and form a part of this specification.

In the drawings:

Fig. 1 is a perspective view of a cross-sectional elevation of a preferred embodiment of my device.

Fig. 2 is a top plan view of the thermo-actuator shown in Fig. 1.

Fig. 3 is a cross-sectional view taken along the line 3-3 of Fig. 2.

Fig. 4 is a side view of the thermo-actuator shown in the preceding views.

Fig. 5 is a horizontal section taken along the line 5-5 in Fig. 4.

Fig. 6 is a cross-sectional view showing a modified form of the device.

In the form of my invention shown in the accompanying drawings, the thermo-actuator housing consists of an upper, body portion 10 (Fig. 1) and a lower, cover portion 11. The body portion 10 is recessed in the manner required to accommodate therein a capsule 12 and a piston 13 having a curved face 14 adapted to bear against the correspondingly curved wall of the capsule 12. The piston 13 is generally rectangular in shape and is adapted to be guided for sliding movement within a rectangular recess 15 provided therefor in the body portion 10. The piston is further guided by a piston rod 16 formed integrally therewith and received for sliding movement within an aperture provided in the end wall 17 of the portion 10. The piston 13 may be loaded by an external spring-biased member pressing against the end of piston rod 16 so as to maintain the curved face 14 of the piston in contact at all times with the side wall of the capsule 12.

The capsule 12 may be molded or otherwise formed from any suitable resilient material such as rubber etc., and is provided with an internal cavity which may be filled with any desired type of heat expansible material 20. The heat expansible substance may be any of those heretofore used for this purpose, or any other compound suited to this type of application and characterized by a rapid volume change over a narrow temperature range so as to cause positive actuation of the piston 13 when the critical temperature is reached at which the material within the capsule undergoes rapid expansion.

In uses, the thermo-actuator is immersed in or surrounded by the medium whose temperature is to be controlled or used as the basis for control and it is therefore necessary that a rapid transfer of heat be effected from the exterior surface of the thermo-actuator to the heat expansible material 20 contained within the capsule12. For this purpose, the portions 10 and 11 are formed of material having good heat conductive properties such as brass, copper, aluminum, etc., and the capsule is fitted with a heat transfer pin 22 likewise formed of a substance which is a good conductor of heat. As shown, the pin 22 is provided with a head 23 which is adapted to be received within a socket of corresponding shape and size provided in the body portion 10 so as to afford intimate contact between the head and the housing over the entire area of the head.

The shank of the pin 22 is preferably formed with a taper whereby the pin increases in diameter as the bottom end of the pin remote from the head is approached. This assists-in the sealing of the pin within the capsule which is efiected by a lip 24 formed integrally with the wall of the capsule and projecting inwardly toward the center thereof. As shown in the drawings, the lip 24 is tubular in form and, when relaxed, is somewhat smaller in diameter than the pin 22 so that it will be stretched when the pin is pushed, into place with the bottom end thereof situated within the cavity formed within the capsule which is filled with the heat expansible material 20. The lip 24 will, upon expansion of the material 20 be pressed tightly against the shank of the heat transfer pin and provide a seal which becomes more perfect asthe. internal pressure is increased so that the material 20 willbe effectively prevented from escaping, from the capsule despite the extremely high pressures developed Within the cavity.

It will be noted that the capsule 12 is substantially cylindrical in form with protruding, rounded, end portions 27 and 28 which are received in cup-like recesses of corresponding size and shape formed in the body, and cover portions and 11, respectively. The portions 27 and 28.0f the capsule, toegther with thehead 23 of the heat transfer pin, act as trunnions on which the capsule may rotate about its longitudinal axis during repeated operations of the thermo-actuator. For this purpose, the exterior. surface ofthe capsule may be coated with a suitable lubricant before the device is assembled so as to facilitate rotation of the capsule therewithin.

Rotation of the capsule is effected by the off center disposition of the piston 13 with respect to the longitudinal axis of the capsule as shown in Fig. 5. It will be observed from this cross sectional view taken horizontally through the thermo-actuator that the head of the piston extends further to one side of the center of the capsule than the other so that an unbalanced force will be exerted on the capsule during the expansion and contraction thereof so as to cause a creep of the capsule in a clockwise direction as viewd in Fig. 5. This creep, for any given cycle, is small so that a large number of cycles of operation are required to produce a complete rotation of the capsule within the housing. The creep, however, is sufficient to prevent a localized strain from occurring on the cylindrical wall of the capsule at any one particular location, and so that working of the entire wall of the capsule will result with consequent'longer life thereof and less likelihood of failure of the capsule wall due to fatigue.

The assembly of the thermo-actuator is extremely simple, the piston being first put into place with its rod 16 extending through the aperture provided therefor in the end wall 17 of the body portion 10. Thereafter, the capsule 12 is inserted into the recess provided therefor, the head of the heat transfer pin being pressed into the socket formed, to accommodate the same in the bottom of the recess formed in the body portion 10. The cover portion 11 is then pressed down over the trunnion portion 28 of the capsule after which a lip 30 extending around the lower edge of the body portion 10 .is bent over, as herein shown, to clamp and hold the cover portion 11 firmly in place. The device is now ready for installation in the apparatus which is to be controlled thereby. In order to secure the thermo-actuator in place in such apparatus, the housing may be provided with a mounting stud 31 formed on the body portion 10 as shown.

In Fig. 6 is shown a modified form of thermo-actuator in which the heat pin 40 is formed as an integral part of the cover 41 so as to improve the flow of heat from the exterior surface of the device into the heat pin. The construction is otherwise essentially the same except that in the modified form of actuator, the heat pin itself forms a trunnion about which the capsule 42 creeps as the heat expansible material 43 therein expands and contracts during operation of the device. Also, in this case, the body 44 is provided with a recess 45 for receiving the rounded end of the capsule and providing a bearing therefor as the capsulecreepsabout its longitudinal axis.

While I have describedmy invention in connection 7 with one possible form or embodiment thereof and, have used, therefor, certain specific terms and language herein, it is to be understood that the present disclosure is illustrative rather than restrictive and that changes and 4 modifications may be resorted to without departing from the spirit or scope of the claims which follow.

Having thus described my invention, what I claim as new and useful, and desire to secure'by United States Letters Patent, is:

1. A temperature responsive actuator of the type having. a substantially cylindrical capsule filled with a heat expansible material and a piston adapted to be actuated by said capsule upon expansion of the material contained therein, said actuator comprising a two-piece housing for receiving the capsule and'said piston with said piston guided for reciprocatory movement therein in a direction transverse to the axis of said capsule, one of said pieces having a recess therein to form the top, sides and ends of said housing, and the other of said pieces comprising a plate for covering the bottom of said housing.

2. The actuator of claim 1 including a deformable means on said one piece for attaching said other piece thereto. a

3. The actuator of claim 2 wherein said means includes a lip extending around the bottom edge of said one piece.

4. The actuator of claim 1 wherein said piston is provided with a guide stem, and said one piece is provided on one of its ends with an aperture for receiving and guiding said stem.

5. The actuator of claim 1 wherein the piston is rectangular, and said recess in said one piece has a rectangular portion for receiving and guiding the piston, and a cylindrical portion for receiving said capsule.

6. The actuator of claim 4 in which the axis of the cylindrical portion of said recess is offset with respectto the line of travel of the center of the piston.

7. A temperature responsive actuator comprising a capsule having walls made of resilient material and containing a heat expansible material, a heat transfer pin extending through the walls of said capsule and into the 7 interior thereof, and an internally extending sleeve formed integrally with said capsule and extending into the interior thereof for surrounding said heat transfer pin within said capsule and forming a lip seal therewith, said sleeve being formed with multifaced, tapered surfaces to cause movement of the sleeve in an outwarddirection along the heat pin under the influence of internal pressure developed within the capsule by the heat expansible material.

8. The actuator of claim 7 wherein said capsule is substantially cylindrical in shape and said inwardly extending sleeve is located at one end of said capsule and directed inwardly along the longitudinal axis of the capsule.

9. The actuator of claim 7 wherein said heat transfer pin is tapered so as to be larger at its inner end than at its outer end.

10. A temperature responsive actuator comprising a substantially cylindrical capsule having walls formed of resilient material and having a portion of reduced diameter at each end thereof to provide trunnions thereon-for supporting said capsule for rotation about its longitudinal axis, a heat expansible material sealed within said capsule, a metal housing having a recess therein for receiving the capsule, said recess being shaped to conform to the configuration of the capsule, a piston supported in said housing for reciprocatory movement in a direction transverse to the axis of said capsule and adapted to be actuated by the side wall of said capsule as it is expanded by the heat expansible material contained therein, said piston having the center of its end face ofiset to one side of the axis of the capsule whereby said capsule will turn about its axis on the trunnions formed thereon upon repeated cycling of the actuator. V

11. The temperature responsive actuator'of claim 10 wherein said capsule includes a heat transfer pin extending from the exterior of said capsule into the interior thereof, and wherein the outer end of said pin forms one of said trunnions on the end of the capsule.

12. A temperature responsive actuator comprising a capsule which is substantially cylindrical in shape, a heat expansible material sealed in said capsule, a piston adapted to be actuated upon expansion of said material, and a housing for receiving the capsule and piston and maintaining them in operative relation with the end face of the piston bearing against the cylindrical Wall of the capsule and having the center of its end face ofiset from the axis of the capsule, said housing including a part recessed to receive said piston for longitudinal sliding movement therein and said capsule for rotation therein with its axis transverse to the direction of movement of said piston, and another part for covering the piston and capsule to retain them in place in said one part.

13. The actuator of claim 12 in which said capsule is provided at each end with a portion of reduced diameter, and corresponding recesses formed in both of said parts for receiving said end portions to thereby support said capsule for rotation within the housing.

14. The actuator of claim 1 wherein said plate is provided with a heat transfer pin formed integrally therewith.

15. The temperature responsive actuator of claim 11 including a head on the outer end of said heat transfer pin shaped to conform to the interior surface of said housing so as to have intimate surface contact therewith and thereby facilitate the transfer of heat from the housing to the material contained Within the capsule.

References Cited in the file of this patent .UNITED STATES PATENTS 1,521,985 Bastian Jan. 6, 1925 2,593,238 Albright Apr. 15, 1952 FOREIGN PATENTS 21,287 Great Britain 1900 345,050 France Sept. 28, 1904 531,280 Great Britain .Tan. 1, 1941

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