US2915900A

US2915900A - Squeeze type power element

Info

Publication number: US2915900A
Application number: US577769A
Authority: US
Inventors: Vernet Sergius
Original assignee: Antioch College
Current assignee: Antioch College
Priority date: 1956-04-12
Filing date: 1956-04-12
Publication date: 1959-12-08
Anticipated expiration: 1976-12-08

Description

Dec. 8, 1959 s. VERNE-r sQuEEzE TYPE POWER ELEMENT Filed April 12, 1956 INLET ,.,1 8 M 8 f f 2 o .MJ/f/.f//V/.Y/NJ/,w//VJ/ a# l E. 1 U. E,... ,u .E n, 4 //V/ J///// E M ../o m H nited States Patent Q 2,915,900 SQUEEZE TYPE POWER ELEMENT Sergius Vernet, Yellow Springs, Ohio, assignor to Antioch College, Yellow Springs, Ohio, a corporation of h10 Application April 12, 1956, Serial No. 577,769 2 Claims. (Cl. 73-368.3)

This invention relates to a power element operable by pressure change in a pressuredproducing material. The pressure-producing material may be a contained thermally expansible material as, for example, disclosed in U.S. Patent No. 2,259,846, or the pressure-producing material may be a uid introduced from a remote source as illustrated in Fig. 3 of U.S. Patent No. 2,534,497.

Power elements of the instant type include a casing for the pressure-producing material, and a piston slidably mounted in the casing. Pressure change in the pressureproducing material causes the piston to move into and out of the casing. A resilient diaphragm, or liner element is provided between the piston and pressure-producing material to prevent iiuid fiow into or out of the power element interior.

Objects of the present invention are to provide a power element wherein:

(l) A relatively great piston movement distance is obtained per given size power element.

(2) The piston movement distance per given pressure change in the pressure-producing material is the same over successive power element cycles.

' (3) The liner is prevented from wrinkling, working irregularly, or binding in the power element, as by being pinched or extruded in the joint between the liner and power element casing.

(4) The liner is readily formed to such precision limits as are required to secure the desired piston travel without wrinkling or binding of the liner material.

(5) The piston is accurately guided for straightline movement so as not to be thrown oii its predetermined course and cause binding of the liner.

(6) The piston extends through the element to permit attachment of an operated device on either end of the piston in accordance with clearance considerations, and desirability of actuating the device in a given direction by power element pressure increase or decrease.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

In the drawings:

Fig. 1 is a sectional view through one embodiment of the invention.

Fig. 2 is a sectional view through a liner element e'mployed in the Fig. 1 embodiment prior to its assembly on the Fig. l power element shaft.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

In the drawings there is shown a power element 1 li11- 2 cluding a casing 2. Casing 2 includes a tubular wall 3 and end walls 4 and 5. Se'curemen't of walls 4 and 5 on wall 3 is effected by rolling each of wall portions 26 from its dotted line position 27 into its full line position overlying the adjacent end wall; l l

Walls 4 and 5 are provided with aligned openings 6 and 7 which slidably receive a piston `8. Piston 8 includes a first section 9 of uniform diameter, and a second section 10 of a lesser uniform diameter. A shoulderforming section 11 is provided between

sections

9 and 10. The angle between shoulder 11 and

sections

9 and 10 is preferably about twelve degrees.

The upper end 2d of piston 8 is enlarged to form a shoulder 21 for limiting downward movement of the piston to its illustrated position. Downward movement of the piston is obtained by means of a compression coil spring 22 retained between two washers 23 and 24. Each of the washers is provided with an annular groove or recess 25 adjacent its outer peripheral edge for correctly seating spring 22 between the washers. Washer 24 is immovably attached on piston `8, and washer 23 is loosely received on piston y8.

Within power element 1 and surrounding piston 8 is a liner 12, preferably formed of rubber or rubber-like elastic material. Liner 12 includes a tubular portion 13 and annular wall portions 1-4 radiating right angularly from opposite ends of portion 13. Each of wall portions 14 includes an annular projection 15 fitting in an annular groove 16 in the adjacent casing end wall, and a flash edge portion 17 clampingly positioned between the casing end wall and tubular wall 3. The construction of

portions

15, 17 is the same as that of in U.S. Patent No. 2,636,776.

Prior to its insertion on piston 8 liner 12 takes the Fig. 2 conguration wherein internal dimension (a) is the same as the diameter of piston section 10. As a result the tubular portion 13 of the liner must undergo a stretching action in order to be iitted onto piston section 9. The stretched condition of tubular portion 13 causes it to tightly hug the piston so as to prevent the occurrence of any wrinkling action during movement of piston 8.

Liner 12 effectively isolates and seals piston 8 (and its joint with end walls material 18. Material 18 is in the illustrated embodiment a thermally expansible material, as for example that illustrated in U.S. Patent No. 2,259,846. Material 18 may however be a pressure fluid introduced from a remote source as illustrated in Fig. 3 of U.S. Patent No. 2,534,497. The presence of liner 12 insures that no uid will enter or leave the power element interior from or to ambient atmosphere 19 during pressure change in mal terial 18.

During pressure increase in material 18, as during temperature increase in ambient atmosphere 19, the pressure material acts against shoulder 11 to force piston 8 upwardly against the action of spring 22. During pressure decrease in material 18 (occurring during temperature decrease in atmosphere 19) spring 22 returns piston 8 downwardly to its illustrated position.

Due to the fact that piston 8 extends completely through the power element casing, liner 12 always hugs the piston. This hugging action is enhanced by the fact that liner 12 initially has an internal diameter (a) less than the diameter of section 9. Since the liner is at all times hugging the piston it can never wrinkle during piston movement.

Certain prior art power elements include a piston having a rounded end portion extended into a cup-shaped liner or diaphragm within the power element interior. This type of power element gives comparatively large piston travel distances per power element size but the pisportions 72, 73

ton speed and movement distance tends to be variable or 4 and 5) from pressure-producingv result the liner must wrinkle.

erratic for successive power element cycles. Thiserratic operation is believed to be due to a wrinkling of the liner during piston movement. This wrinkling is believed to `result from the fact that the cup type liner is difficult to mold to the precision limits necessary to maintain all portions of the liner against the piston throughout the entire piston movement. It is also believed that the wrinlcling may be in part due to the fact that the lower r portion of the liner (adjacent the rounded end of the piston) has too much internal surface area to collapse downv tion wherein shoulder 11 is just below the level of washer 28. Due to the guiding action of opening 7 the piston is at all times guided for straightline movement into and out of the power element casing.

During pressure increase in material 18 piston section 10 is pulled toward the power element and piston section Z0 is pushed away from the power element. VAs a result a valve element (or otherdevice to be actuated)` may be secured to either of piston sections lil or 20 accordingly as it may be desired to give a .pull or push -to the actuated ldevice during pressure increase in material `18.

Conventional power elements (wherein the pistol-in does not extend entirely through the power element) have not element the piston is accuratelyguided for straightline f movement throughout the entire range `of piston movement. Prior art power elements (wherein the piston extends only partially through the power element) d o not accurately guide the piston as it nears its outermost position. This is dueto the fact that the length of the available guide surface is reduced as the piston nears its outermost position. The guide surface is usually provided by an elongated sleeve extending from the power element casing, and the guide surface can of course be lengthened by lengthening the sleeve. overall length of the power element, and for many applications the resultant power element would be too long to be accommodated in the available space.

It will be noted-that the guide surfaces provided by openings 6 and 7 are spaced apartv and operable in all positionsof piston 8. In conventional constructions the piston guide is one continuous surface. of any point along the continuous surface or any uneven pressure distributionon the piston may alter the path of the piston. Any alteration of o r change in the piston' movement path may cause localized portions of the liner to be squeezed or extruded into the joint between the liner and guide surface soas to be wrinkled and cut away from the liner body.` VSuch action may intime result in failure of the liner and loss of power element calibration.'

In theFig. l construction the spaced guide surfaces provided by openings o and 7 insure straightline piston movement throughout the entire piston travel, and considerably reduce the possibility of any of the liner material being. extruded into the joint between the piston and guide surfaces. This anti-extrusion feature maybe enhanced by a `washer 28 formed of polytetrailuorethylene or other low friction, resilient plastic material. The jointbetweenrend wall 5 and piston section 10 may also be provided with an anti-extmsion washer if .foundnecessary As shown in Fig. l anti-extrusion protection is offered by the configuration of casing Tend wall 5, said end wall'being vformed with an internal annular extension 34) projecting inwardly to define a linercngaging surface which is rounded adjacent its juncture with opening 7 and which slopes at an acute angle-away from the` surface of piston section dt'whereby to cooperate with the cohesiveness of the liner material in deflecting the liner away from the joint between 'thepistonand wall opening 7.

l t will be noted that the entire central portion of'casing 2 is occupied by piston 8 (because the' piston extends completely through the casing). Asa' result all of thermally cxpansibie material 16 is displaced outwardly away from the casing central portion.' Bydisplacing allV of material llt;v toward the casing outer wall the material willl expand and contractmore quickly in response 'to-temperaturechange in; atmosphere 1 9. The power element is thereby enabled to more quickly follow the' condition' of atmosphere 19. Casing 2 can be `made large enough towh'oldV a quantity of material 18 suiiicient for pushing piston 8 upwardly from its illustrated position to a posi- This however increasesv the A n irregularity enabled the user-.to secure Vay push or pull piston action. Considerations such as power element size and placement in confined locations sometimes make it desirable to be able to choose betweeny a push or pull piston action. v n In the illustrated construction the spring pushes the piston into the power element during pressure decrease in; material l8. Itis contemplated however that the springj could pull the piston into the power element, in which; case section 20 could be provided with an extension and encircling spring mechanism.

Ivclaim: f 1. A powerk element comprising a casing including av tubular wall and two opposed walls closing the ends of.` the tubular wall; said end walls having aligned openingsl therethrough; pressure-producing material within the casing; a'pistonV extending throughY the alinged openings; saidland joined to said first section, said second section having a different diameter than'the first section, la shoulder. being formedA at their juncture; an elastic tubular liner of material subject to extrusion engageably surrounding the piston; said liner having annular wall portions extending angularly from itsV ends and lying against interior surfaces ofthe end walls so as to isolate the pressure-producing material from the joints between the piston and 'end walls; said liner being formed throughout the major portion of its length with'an internal diameter substantially the same as that of the smallest diameter pistonsection, whereby to be put in a non-wrinkable condition when engaged with the largestv diameter piston section and smallest diameterV piston section, one of said end walls having an annular recess formed inthe inner surface` thereof and around the openings therethrough; a` washer of low friction, resilient, plastic material seated in said recess, whereby to prevent extrusion of the liner material into the joint between the piston and opening;` the other end wall having an internal annular extension projecting inwardly adjacent the end wall opening to dene a linerengaging surface which is rounded at the juncture with the opening and which slopes therefrom at an acute anglev awayfrom the piston surface, whereby to cooperate with the cohesiveness of the liner material in deflecting the liner away from the joint between thepiston and other end wall opening. i

2. A power element comprising a casing including a tubular wall and two opposed walls closing the endsof the tubular walls; said end walls havingj'aligned openings therethrough; pressure. producing material within, the casingfa pistonV extending through the alignedopenin'gs; said 'pistonincluding a first luniform' diameterV sectionY extending through one of the openings, and a`second uniform' diameter section extending through the .othery opening andrjoined to said rst section, said secondsection having adilferent'diarneter than the first section,`

having annular wall portions extending angularlyfroml itsV lends andlying against interior surfacesV of the `end walls so as to isolate the pressure producing material from the joints between the pistons and end walls; said liner being formed throughout the major portion of its length with an internal diameter substantially the same as that of its smallest diameter piston section, whereby to be put in a non-wrinkable condition when engaged with the largest diameter piston section and smallest diameter piston section; one of said end walls having an internal annular extension projecting inwardly adjacent the end wall opening to define a liner-engaging surface which is rounded at the juncture with the opening and which slopes therefrom at an acute angle away from the piston surface, whereby to cooperate with the cohesiveness of the liner material in deliecting the liner away from the joint between the piston and one end wall opening.

References Cited in the le of this patent UNITED STATES PATENTS 2,208,149 Vernet July 16, 1940 2,494,598 Waring Ian. 17, 1950 2,806,375 Wood Sept. 17, 1957 FOREIGN PATENTS 1,100,683 France Apr. 6, 1955 1,125,435 France July 16, 1956 OTHER REFERENCES Bulletin OB-1152, published by the United States Gasket Company of Camden, New Jersey, 8 pages, only pages 1-4 needed. Received in the Patent Oce February 3, 1956.