US3386065A

US3386065A - Snap acting thermal element

Info

Publication number: US3386065A
Application number: US623440A
Authority: US
Inventors: Joseph M Algino
Original assignee: Dole Valve Co
Current assignee: Dole Valve Co
Priority date: 1967-03-15
Filing date: 1967-03-15
Publication date: 1968-05-28
Anticipated expiration: 1985-05-28

Description

y 28, 1968 J. M. ALGINO 3,386,065

SNAP AC'I ING THERMAL ELEMENT Filed March 15, 1967 2 Sheets-Sheet 2 F 4 9 6 0 xv I v J-Lz 7 mi W" ii /l "WW @5 72 7/ INVENTOR. JOSEPH M '44 G/A/O C Q I a ATTORNEYS United States Patent 3,386,065 SNAP ACTING THERMAL ELEMENT Joseph M. Algino, Niles, Ill., assignor to The Dole Valve Company, Morton Grove, 11]., a corporation of Illinois Filed Mar. 15, 1967, Ser. No. 623,440 12 Claims. (Cl. 337-315) ABSTRACT OF THE DISCLOSURE A thermal power unit having a base cup and a guide member secured to the base cup to form a cavity therebetween and having a thermally expansible substance within the cavity and a resilient squeeze type boot displaced between the thermally expansible substance and the guide portion. The boot has an opening for receiving a power piston and the expansion of the thermally expansible substance compresses the boot to cause the power piston to extend therefrom. A detent groove 1s formed about the power member piston in the vicinity of the guide member and a resilient catch means is biased into engagement with the detent groove to convert the otherwise smooth extension of the piston into a snap action motion.

BACKGROUND OF THE INVENTION Field of the invention An important feature of this invention is the provision of a thermal power unit having a cup member and a resilient squeeze type boot operably disposed within the cup member for moving a piston relatively therefrom wherein the piston has an irregular surface portion engageable with a resilient catch means to convert the otherwise smooth motion of the piston into a snap action motion.

Another feature of the invention is the provision of a snap acting power member wherein the snap acting motion of the member is confined to a specific temperature differential and to a specific piston travel distance and wherein the motion of the piston outside of the specified travel distance and temperature is a smooth steady motion.

An object of the invention is the provision of a thermal power unit having a cup member and a guide member secured at out-turned flanges for maintaining a resilient squeeze type boot in position within the cup member and wherein a detent groove is formed about the circumference of the power member piston in the vicinity of the guide member and wherein a detent ball is spring biased into engagement with the detent groove to limit the travel of the piston until a specific temperature level and, hence, a specific compression of the squeeze boot is reached.

Another object of this invention is to provide a thermally operated power member piston wherein the motion of the piston is abrupt over a relatively low temperature range and is steady as the temperature increases to points above the relatively low temperature range.

A still further object of this invention is to provide an improved means for temporarily loading a power piston of a thermal power unit during the extension of the piston from a resilient squeeze type boot as the temperature ambient rises from a low level to a high level.

ice

Another object of this invention is to provide a leaf spring type switch having two blades mounted in a housing and having a thermal power unit also mounted in the housing to move one of the blades out of contact with the other blade and wherein a thermal power unit has a detent groove formed about the power member piston thereof and wherein a detent ball bearing is biased into engagement with the power piston to inhibit the motion of the piston until a specified temperature is reached and then to release the piston into a snap action travel for breaking the contact between the switch blades.

A still further object of the invention is to provide a fluid control valve having an inlet and an outlet and a valve means disposed between the inlet and the outlet and having a thermal power unit of the type described above disposed in the valve housing so as to move the valve means into an open position by a snap acting motion and to close the valve means by an initial snap motion and a subsequent slow close motion.

Other and further objects of this invention will be apparent to those skilled in this art from the following detailed description and the annexed sheets of drawings which show several embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a sectional view through a thermal power unit having the features of this invention and specifically showing the positioning of the detent groove and the detent ball bearing which is biased into engagement with the groove;

FIGURE 2 is a temperature versus travel graph showing the motion of a conventional power member piston;

FIGURE 3 is a graph similar in nature to the graph of FIGURE 2 and showing the travel of a power member piston in response to changes in temperature ambient the thermally expansible wax and showing in particular the presence of the snap action and its confinement to a specific region of the piston travel;

FIGURE 4 is a sectional view of a leaf spring type switch having switch contacts which are engaged and moved out of engagement by a power member piston similar to the piston shown in FIGURE 1; and

FIGURE 5 is a sectional view through a fluid control valve having a valve member which is opened and closed by a thermal power unit according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The thermal power unit of this invention has a cup member 10 and a guide member 11. The cup member 10 has a cylindrical side wall 11, a base Wall 12 and an out-turned annular flange 13. The side wall 11 and the base wall 12 form a cavity 14 which contains a thermally expansible pellet 15.

A resilient boot 16 which is disposed within the cavity 14 has a tapered wall portion 17 and a web portion 18. A bead 19 is formed at the outer periphery of the web 18 as shown in FIGURE 1.

The boot 16 is held in position within the cavity 14 by the presence of the guide member 11 against the out turned flange 13 of the cup member 10. In particular, the guide member 11 also has an out-turned flange 20 which has a groove 21 formed at the outer perimeter thereof. The web 18 is disposed between the flanges 13 and 20, and the flange 13 is spun over the flange 20 to securely grip the flanges in position and to compress the web 18 between the flanges as shown.

The boot 16 has a further tapered wall portion 22 extending upwardly from the web 18, and the guide member 11 has a surface 23 substantially conforming to the upper surface of the boot and preventing the movement of the boot upwardly from the cavity 14.

The resilient boot 16 has a central opening 24 formed therethrough, and likewise the guide member 11 has a central opening 25 formed in substantial alignment with the opening 24 of the boot. Therefore, a power member piston 26 may be disposed centrally through the opening 25 and the opening 24 to seat at the lower surface 27 of the boot opening 24.

Considering only the features of the thermal power unit of FIGURE 1 which have been described to this point, it is apparent to those skilled in the art that the elevating of temperature about the cup member 11 will heat the thermally expansible wax and compress the walls of the boot to sequeeze the piston 28 outwardly therefrom and upwardly through the Opening of the guide member 11. This motion would be substantially uniform and, due to the specific design of the boot 16 and the cup member 11, the movement of the piston 26 will not be characterized by sharp abrupt motions but will be steady in response to temperature rise.

For instance, in FIGURE 2 the travel of the piston 26, as would be expected from a conventional thermal power unit, is shown. In particular, the line 28 illustrates the amount of travel experienced by the piston 26 in response to a given temperature rise measured along the horizontal axis. Only when the point 29 is reached, at which the piston is physically halted due to a stop member on the piston or the like, does the travel of the piston cease to be steady for increasing temperature. The line 29, which corresponds to the travel of the piston measured during a temperature decline, is also steady and is not characterized by abrupt piston motions.

However, in certain devices in which thermal power units are utilized, it is desirable to have the piston move abruptly during a specific time or temperature interval and to move slowly at other time or temperature intervals. Accordingly, the thermal power unit of this invention as shown in FIGURE 1 incorporates a means for conforming the travel of the piston to an irregular desired motion temperature response.

The means to control the motion of the piston 26 in FIGURE 1 includes a detent groove 31 which is formed circumferentially about the piston in the vicinity of the guide member 11 and a catch bore 32 which is formed substantially perpendicular to the guide bore 25 and which intersects the guide bore 25. The catch bore 32 has a detent ball bearing 33 slideably mounted therein and has a coiled spring 34 disposed between the ball 33 and a plug 35. The plug 35 is threadedly mounted within the catch bore 32 such that by the use of a screwdriver or other suitable tool within the groove 36, the plug 35 may be advanced or retarded to increase or decrease the compression of the coil spring 34. Essentially, the ball 33, together with the coil spring 34, places an axial loading on the piston 26 so long as the groove 31 is aligned with the ball 33. After, however, the groove 31 is moved out of contact with the ball 33, the smooth surface of the piston 2-6 maintains the ball in a recessed position within the catch bore 32, and the presence of the ball has substantially no effect on the subsequent motion of the piston.-

The axial loading of the piston 26 is accomplished either at the edge 37 of the detent groove 31 or at the edge 38 thereof. During the upward travel of the piston 26, the ball 33 acts against the edge 37 to retard the motion of the piston, and during the retraction motion of the piston 26, the ball 33 acts against the edge 38 to retard the motion. Of course, as soon as either of the

edges

37 or 38 are moved past the center of the ball 33, the motion of the piston is then unaffected by the presence of the ball 33.

Movement of a piston in a thermal power unit similar to the unit shown in FIGURE 1 is illustrated graphically in FIGURE 3. In particular, a first line segment 39 illustrates the motion of the piston when the groove 31 is closer to the boot 16 than the ball 33. At this time, the presence of the ball does not affect the axial motion of the piston in response to temperature and accordingly the movement of the piston is substantially uniform. However, at a point 40, the groove 31 engages the ball 33 and a further axial movement of the piston is prohibited until the temperature rises to T2 at which time the travel of the piston suddenly snaps from the point 41 to the point 42. This snap action is generated due to the fact that while the piston is locked into engagement with the ball 33, the wax is building up compression within the cavity 14 and the boot 16 is being compressed due to the extra loading on the piston 26 by the ball 33. When the ball 33 is released from engagement with the groove 31, the sudden decrease in loading causes the wax and boot to bounce upwardly to release the compression thereof. This bounce is then responsible for the snap action of the piston in moving from 41 to 42 in the graph of FIGURE 3. After the motion of the piston has been released from the engagement of the groove 31 with the ball 33, the piston travels uniformly in the region 43. At the point 44, a stop means or the like engages the piston and prevents the piston from further motion in response to temperature rise.

A similar effect occurs on a temperature decline, and the motion of the piston is substantially uniform in the vicinity of the graph indicated by the reference numeral 45. However, when the groove 31 engages the ball 33 at the point 46, further retraction of the piston is prohibited until the temperature declines to T1 at the point 47. At this point, the groove 31 snaps out of engagement with the ball 33, and the piston travels suddenly into a retracted position to the point 48. After such retraction, the movement of the piston may be uniform as in the region of the graph indicated by the reference numeral 49.

The means for biasing the piston 26 into the opening 24 formed within the boot consists of a coil spring 50 which is disposed between an upper surface 51 of the guide member 11 and a collar 52 of the power member piston 26. The collar 52 and the coil spring 50 are disposed within a cavity 53 which is formed centrally of the guide member 11. Also, the guide member is threaded at the outside surface 54 thereof to permit the thermal power unit to be mounted within a switch or a valve housing and as shown in FIGURES 4 and 5, respectively.

In FIGURE 1, the collar 52 of the piston 26 is resting at a landing 55 of the bore 53 such that further retractible motion of the piston is prohibited. This means that the first motion of the piston will be the snap motion, and the piston will not move through the

segments

39 and 49 as shown in FIGURE 3. However, the collar 52 is not necessarily positioned as shown and the piston could be allowed to travel smoothly on both sides of the snap action.

In FIGURE 4, a use for the thermal power unit of this invention is illustrated. In particular, a leaf spring type switch is shown to include a housing 56 which has side walls 57 and a base wall 58 and a cover plate 59 which is secured to the side wall 57 by a number of connectors 60. First and

second blades

61 and 62 are originally mounted within

slots

63 and 64 formed respectively within the side wall 57.

The

blade members

61 and 62 have

contacts

65 and 66 formed as shown and normally contacting each other to complete an electrical circuit between the

blades

61 and 62.

A thermal power unit 67 having a cup member 68 and a guide member 69 is disposed within an opening 70 formed within the base wall 58 of the housing 56 and is held in position by a nut 71 which is threaded about the threaded surface 72 of the guide member 69.

The thermal power unit 67 has a power member piston 73 which contacts the lower surface 74 of the blade 62 and which serves to break the

electrical contacts

65 and 66 upon the extension thereof as described in connection with FIGURE 1. It is apparent to those skilled in the art that the snap action motion of the

contacts

65 and 66 is desirable to prevent burning of the contacts due to arcing and the like.

A further use for the thermal power unit of this invention is shown in FIGURE 5 wherein a fluid valve housing 75 is shown to have an inlet 76 and an outlet 77 and a valve member 78 which includes a valve head 79 engageable with a valve seat 80 formed between the inlet and the outlet. A cap member 81 is threadedly secured to the housing by a plurality of connectors 82 and a coil spring 83 is disposed between the cap member 81 and the valve head 79 to bias the head into a closed position.

A thermal power unit 84 similar to the unit 67 is mounted within the lower wall 85 of the inlet portion 76 similar to the mounting of the unit 67 in the wall 58 of FIGURE 4. The thermal power unit 84 has a power member piston 86 which contacts the lower surface 87 of the valve head 79 to actuate the valve head in response to the temperature travel characteristics shown in FIG- URE 3. It has also been found that water hammer in a valve of this type can be eliminated by the slow return feature which is described in connection with FIGURE 3.

It will, of course, be understood that other variations and modifications may be made without departing from the spirit and scope of the basic principles which are set forth herein and which are covered in the appended claims.

I claim as my invention:

1. A controlled snap acting thermal power unit comprising:

a base cup having a cavity formed therein, a thermally expansible substance disposed within the cavity and a resilient diaphragm extended across the base cup to confine the thermally expansible substance between the walls of the cavity and the diaphragm,

a guide member rigidly positioned against the base cup oppositely of the diaphragm with regard to the position of the thermally expansible substance,

said guide member having a guide bore formed therein, a power piston operably disposed within the guide bore and contacting the diaphragm,

an irregular surface portion formed in a confined region of the power piston,

a resilient catch means mounted at a fixed point relative to the guide member and engaging said irregular surface portion so as to resist extensible motion of the piston, and

means biasing the piston into the guide bore and against the resilient diaphragm.

2. A controlled snap acting thermal power unit in accordance with claim 1 wherein said resilient diaphragm comprises a squeeze type boot disposed within the cup cavity and having an opening formed centrally thereof and wherein said power piston extends through the bore and into the boot opening for being actuated by the compression of the boot due to confinement of the thermally expansible substance as said substance expands on the application of heat thereto.

3. A controlled snap acting thermal power unit in accordance with claim 2 wherein said base cup and guide member each have an out-turned annular flange and wherein said resilient boot has a circumferential web and means are provided to sandwich the web between the flanges of the base cup and guide member and wherein the guide member has a boot facing inner surface for confining the extensible movement of the upper surface of the boot when the thermally expansible substance expands due to the application of heat thereto.

4. A controlled snap acting thermal power unit in accordance with claim 1 wherein said thermally expansible substance comprises a wax pellet having a substantial thermal wax bounce.

5. A controlled snap acting thermal power unit in accordance with claim 1 wherein said irregular surface comprises a detent groove formed circumferentially about the piston and wherein said resilient catch means comprises a catch mounted within the guide member and biased into engagement with the piston groove in said bore and being retractible from said guide bore upon movement of said piston so as to displace said groove beyond the point of mounting of said catch means.

6. A controlled snap acting thermal power unit in accordance with claim 5 wherein said catch means includes a second bore formed perpendicular to and intersecting said guide bore, a detent ball bearing fitted within said second bore and spring means urging the ball into said detent groove.

7. A controlled snap acting thermal power unit in accordance with claim 6 wherein the diameter of said detent ball is in substantial excess to the diameter of the crosssection of said detent groove.

8. A controlled snap acting thermal power unit in accordance with claim 7 wherein said second bore is extended from the guide bore through a wall of the guide member to the outside thereof and wherein an adjustment screw is threaded within the bore to adjust the compression of the spring means.

9. A controlled snap acting thermal power unit comprising:

a base cup having a cavity formed therein containing a thermally expansible substance and having an outturned flange,

a guide member having an out-turned flange,

a squeeze type boot fitted within the cavity and having a web disposed between the out-turned flanges ofthe cup and guide member and means securing the flanges together to compress the web therebetween, said boot and said guide member each having a piston guide opening formed centrally therethrou-gh,

a power piston operably disposed within the guide openings of the guide member and the boot and being extensible therefrom due to the expansion of the thermally expansible substance and the squeeze action of the boot generated thereby,

a catch bore formed at right angles to and intersecting the guide opening of the guide member,

a detent groove formed circum'ferentially about the piston,

a detent ball bearing disposed in the catch bore and a spring means biasing the ball into catch engagement with the detent groove, and

means biasing the piston into the guide openings of the guide member and the resilient boot.

10. A controlled snap acting thermal power unit in accordance with claim 9 wherein said ball is slideably fitted within said catch bore and wherein said detent groove has an axial dimension which is less than the diameter of said catch bore.

11. In combination, a leaf spring type switch having first and second contact blades and a housing normally supporting the blades in electrical engagement with one another, and a snap acting thermal power unit mounted to the housing and including:

I a base cup having a cavity formed therein containing a thermally expansible substance and having an outturned flange,

a guide member having an out-turned flange,

a squeeze type boot fitted within the cavity and having a web disposed between the out-turned flanges of the cup and guide member and means securing the flanges together to compress the web therebetween, said boot and said guide member each having a piston guide opening formed centrally therethrough,

said power piston extending outwardly of the guide member and contacting one of said first and second electrical blades so as to break the contact between the blades upon the extension of the piston from the boot,

a detent groove formed circumferentially about the piston,

12. In combination, a fluid control valve including a ings of the guide member and the boot and being extensible therefrom due to the expansion of the thermally expansible substance and the squeeze action of the boot generated thereby,

said power piston extending outwardly of the guide member and contacting said valve member so as to open the valve member upon the extension of the piston from the foot,

a detent groove formed circu rniferentially about the piston,

housing having an inlet and an outlet and a valve member operably disposed between the inlet and the outlet 15 so as to control the flow of fluid therethrough and means biasing the valve member into a closed position, and a snap acting thermal power unit mounted to the housing References Cited UNITED STATES PATENTS and including:

a base cup having a cavity formed therein containing a thermally expansible substance and having an outtumed flange, 2,938,384 5/1960 Soreng et a1 60-230 XR a guide member having an out-turned flange, 299O716 7/1961 Butt s 60' 23 X a squeeze type boo-t fitted within the cavity and having 633; et a1 60 23 a Web disposed between the out-turned flanges of 25 3:336:745 8/1967 Schwartz 6O 23 the cup and guide member and means securing the flanges together to compress the web therebetween, said boot and said guide member each having a piston guide opening formed centrally therethrough,

a power piston operably disposed within the guide open- MARTI-N P. SCHWADRON, Primary Examiner.

C. B. DORITY, Assistant Examiner.