US2322010A - Piston - Google Patents

Description

Patented June 15, i943 STT E PESTON Original application March 7, 1940, Serial No.- 322,790. Divided and this application January 10, 1941, Serial No. 374,005

17 Claims.

This invention relates to improvements in pistons for liuid pressure producing devices.

This application is a division of my pending application, SeriallNo.' 322,790, viiled March '7,

1940, and is made in accordance with the United States Patent Oice Rule No. 42. n

The invention is shown as embodied in a high pressure piston in a i'luld pressure producing device of the two phase type, as, for example, the master cylinder in hydraulic brake mechanism. The piston embodying the invention is constructed lto produce an effective seal within the high pressure chamber, and, further,it separates the high pressure chamber within the cylinder from the low pressure chamber therein and also permits iiow of liquid under pressure from the low pressure chamber into the high pressure chamber.

An object of the invention is to provide a piston constructed to withstand high pressures and to effectively seal in a chamber complementary thereto. l

One object of the invention is the provision of a piston having improved means on its head yieldable under high pressure to eiectively inhibit the passage of iiuid past the piston.

Another object of the invention is to provide a piston having a yieldable washer on its head, a pressure block thereon, and a sealing cup on the block effective under high pressure to cooperate and form an effective seal.

Another object of the invention is to provide a piston, including a head having thereon' a rubber washer of high durometer reading, a pressure block having a convex face seated upon a complementary face on the washer, and a flexible sealing cup on the pressure block operative to function as a unit to establish an effective high pressure seal.

Other objects and advantages of the invention lwill appear from the following description taken in connection with the accompanying drawing Fig. 6 is an enlarged sectional view of the high pressure piston illustrated in Figs. 1 and 2.

Referring to the drawing for more specific details of the construction in which the invention is embodied, there is a single casting including a reservoir i0 having a filling opening i2 normally closed-as by a head i4 having openingsi therethrough for venting the reservoir to the atmosphere, and a cylinder i3 at the base of the reservoir having one of its ends closed as by a head 20 provided with a discharge port, 22 and its other end open. 1n the open end of the cylinder is a chamber 24 of standard gauge, bearingized, and provided with spa-ced ports 2t and 28 affording communications between the chamber 24 and the reservoir iii. The cylinder i3 also has a bore 30, preferably of slightly less diameter than the chamber 24 arranged forward of, concentric to, and in direct communication with the chamber 24 and also with the discharge port 22.

A cylinder section 32 fitted tightly and sealed in the bore 30 has a. bearingized chamber and a circumierentially reduced portion providing in conjunction with the wall deiningfthe bore 30 an annular passage 36 communicating with the chamber 24, and a port 38 arranged in the wall of the cylinder 32 provides a communication between the chamber 34 and the annular passage 36.

A piston 40 reciprocable in the chamber 24 is retained against displacement by a washer 42 seated on the annular shoulder in the open end of the cylinder I8 and held in place by a retaining "ing 44 seated in a groove in the wall of the cylinder. The piston 40 includes a head 46, a body' 48 having a reduced diameter providing in conjunction with the wall of the cylinder I8 an annular chamber 50 communicating with the reservoir ill as by way of the port 26, and a skirt 52 supporting a sealing cup 54 for inhibiting seepage of uid from the annular chamber 50 past the piston. The head 46 has a plurality of spaced passages 56 therethrough providing communications between the annular chamber 50 and that portion of the chamber 24 forward of the piston, and a sealing cup 58 seated on the head 46 of the piston controls the passages 56.

A washer 60 seated on the end of the cylinder 32 opposite the piston 40 has in its periphery a plurality of spaced notches 62 for the passage of fluid between the chamber 24 and the annular of the washer, and a spring 66 interposed be- .y

tween the sealing cup 58 and the washer 60 serves to retain the cup and washer against displacement and also to assist in return of the piston 40 to its retracted position.

The piston 40 has disposed concentrically in its body 48 a valve chamber 68 opening through the head of the piston. This valve chamber has a port 10 providing a communication between the valve chamber and the annular chamber 50, and also a vent 12 opening from adjacent the bottom of the valve chamber into the annular chamber 50 for inhibiting fluid lock. A valve 14 slidable in the valve chamber abuts a compression spring 16 of high elasticity seated on the bottom of the valve chamber.

.The valve includes a cylindrical body 18 fitted snugly for reciprocation in the valve chamber. 'Ihis cylindrical body has a peripheral groove or slot 80 adapted to register with the port 10 in the valve chamber so as to provide for passage of fluid from the chamber 24 through the valve and into the annular chamber 50. The groove or slot 80 is preferably tapered or calibrated so that uid may be metered gradually from the'chamber 24 through the valve into the annular passage 50.

The valve 14 has a stem 82 formed integral with a piston 84 reciprocable in the chamber 34. The piston normally seats on the lands 64- of the washer 60, It is essential that this piston be of such structure as to withstand high pressures without seepage of fluid past the piston and also without injury to the component parts of the piston. The invention herein claimed relates to this particular piston and the structure heretofore described constitutes in part the environment within which this piston functions.

As shown, this piston 84 includes a head 86 having a plurality of passages 88 therethrough providing communications between the chambers 24 and 34, and a concentrically disposed shallow bore 90, A rubber washer 92 seated on the head 86 of the piston has a concentric opening therethrough registering with theshallow bore 90. 'I'his washer is preferably constructed from rubber having a high durometer reading. The diameter of the washer is slightly less than the gauge of the chamber 34, so that uid may by-pass the washer when it is not under pressure. The washer 92 has a concaved face 94, and this concaved face in conjunction with the perimeter of the washer provided a pronounced lip 96. A spacer or pressure block 08 seated .on

the concaved face of the washer has a convex face complementary to the concaved face of the washer. The pressure block 98 has an extension |02 concentrically disposed on its convexed face, and this extension is received by the opening in the Washer and also by the bore 90 in the head of the piston with small clearance between lthe bottom of the bore and the free end of the extension |02, so as to limit the compressibility of the washer and thus avoid binding of the washer in the chamber 34.

The pressure block 88 has a plurality of spaced passages |04 therethrough controlled as by a sealing cup |06 seated on the pressure block. High pressure imposed on the sealing cup |00 is transmitted through the pressure block 98 to the washer 82.' This results in radial expansion of the rubber washer 82, and, because of the particular contour thereof, the lip 98, when the washer is 'deformed under pressure, engages the wall of the chamber with substantial bearing surface.

'111e iuid pressure device within which the piston. 84 functions includes a two-way valve |88 seated within the head oi' the cylinder I8 within the chamber 34 and controlling the discharge port 22. A spring ||0 interposed between the sealing cup |06 and the two-way valve |08 serves to retain the cup and valve against displacement and also to return the pistons 40 and 84 to their retracted positions. The spring ||0 is of high elasticity, and is preferably balanced with the spring 16 in the valve chamber 68.

A iiuid pressure delivery pipe or conduit ||2 has branches connected respectively to iluid pressure actuated motors ||4, preferably arranged in pairs, one pair for actuating the brakes associated with the front wheels of a vehicle, and another pair associated with the rear wheels of the vehicle.

The brakes may be of any preferred type. As shown, each of the brakes includes a xed support or backing plate |l6, a rotatable drum H8 associated therewith, a pair of friction elements or shoes |20 pivoted on the backing plate for cooperation with the drum, a retractile spring |22 connecting the shoes, anda motor corresponding to the fluid pressure motors 4 mounted on the backing plate ||6 between the shoes and connected thereto for actuating the shoes into engagement with the drum against the resistance of the retractile spring.

A thrust pin |24 has one of its ends seated in a socket in the back of the piston 40, and on the other end of the thrust pin is a coupling |26 connected by a flexible boot |28 to the open end of the cylinder I8 for the exclusion of dust and other foreign substances, A rod |30 has one oi' its ends connected to the coupling |26 and its other end pivotally connected to a foot pedal lever |32 rockable on a stub shaft |34 and connected by a retractile spring |36 to a xed support |38.

In a normal operation of the fluid pressure lbraking system, upon depressing the foot pedal lever |32 force is transmitted therefrom through the rod |30 and thrust pin |24 to the piston 48. resulting in movement of the piston'40 on its compression stroke, and also advancing the piston 84.

During the initial movement of the pistons 40 and 84 on the compression stroke, the sealing cup 58 on the piston 40 closes the port 28, and the sealing cup |06 on the piston 84 closes the port 38; and, thereafter, as the pistons advance, iluid in the chamber 24 is displaced therefrom through the passages 88 in the piston 84, past the the discharge port 22 and fluid pressure delivery pipes ||2, into the iiuid pressure actuated motors H4, causing energization of the motors with the resultant actuation of the friction elements |20, into engagement with the drums ||0 against the resistance of the retractile springs |22 to effectively retard rotation of the drums. During this operation, a large volume of fluid is displaced from the chamber 24 at a comparatively low pressure to accomplish a quick vmovement of the friction elements into engagement with the drums, and, thereafter, as the pistons advance, the reaction force on the uid in the system forward of the pistons increases the pressure on the fluid in the chambers 24 and 34 until a predetermined equalized pressure on the fluid in the chambersis attained. From this period of operation, further advance of the pistons opposed by the reaction forces produces a, differential vof pressure in the chambers 24 and 34, imposing a slightly greater pressure on the piston 84, tending to hold the piston 84 against movement; and, thereafter, relative movement of the pistons 40 and 84 gradually compresses thespring 16, resulting in cracking the valve and the metering of fluid by the valve from the chamber 24, through the calibrated passage 80 and the port 70 into the annular chamber 50, thence through the port 26 into the reservoir. vThe passage 80 is so calibrated that the relief of iluid in the chamber 24 is elected gradually so as to smooth out the operation.

In instances where the foot pedal lever |32 is actuated impulsively, resulting in an extremely rapid advance of the piston 40, pressure created on the fluid in the chamber 24 causes a rapid forward surge of fluid in the chamber 24 against the back of the piston 34, tending to advance the piston 84. This advance movement of the piston 84 is yieldingly resisted by the column of fluid in the system forward of the piston 84 under the load of the friction elements of the respective brake structures.

The spring also yieldingly resists this movement of the piston 84. This spring is of high elasticity, hence the combined :reaction forces inhibit material movement of the piston 84, and this results in flow of fluid from the chamber 24 through the passages 88 in the piston 84, past the washer 92, through the passages |04 in the pressure block 98, and past the sealing c up |06 into the chamber 34, until the pressures on the fluid in the chambers 24 and 34 are equalized at a predetermined pressure adequate to move the friction elements into engagement with the drums, and, thereafter, as the pressure on the fluid increases, the reaction forces on the piston 84 open the valve 14 against the resistance of the spring 16, as in a normal operation.

Upon conclusion of a braking operation, the foot pedal lever |32 is released, and returns to its retracted position under the influence of the retractile spring |36. This results in retraction of the rod |30 and thrust pin |24, and release of the piston 40 and return of the pistons 40 and 04 under the influence of the springs 66 and H0. During this operation, the spring 16 moves the valve 14 to its closed position.

As the pistons 40 and 84 return to their re- -traeted positions, a partial vacuum is created in the chamber 34, and this results in drawing uid from the reservoir I0 through the supply port 25, into the annular passage 50, thence through the passages 56 in the head of the piston 40, past the sealing cup 58 thereon, into the chamber 24, thence through the passages 88 in the pistonl 84, past the washer 82, through the lpassages |04 in the pressure block 98, and past the sealing cup |06 thereon into the champer 34, completely filling the chambers 24 and 34.

During this operation, fluid is returning to the chamber 34 from the fluid pressure actuated motors ||4, and the fluid pressure delivery pipes connecting the motors to the `cylinder I8 under the influence of the retractile springs |22 connecting the friction elements of the respective brake structures. This may result in the chamber 34 receiving a quantity of fluid in excess of its-capacity, and under this condition, the ex- 38 and passage 36 into the chamber 24, thence through the port 28 into the reservoir.

A modification of the invention is illustrated in Fig. 4. In this modification the piston |40 has a head |42 provided with spaced passages |44' therethrough aiording communications between chambers |46 and |48. The head also has a concentric bore |50, and seated in the bore is a spring |52?,` A resilient washer |54 seated on the head has a marginal lip |56 and a concentric opening |58 registering with the bore |50. This washer is preferably made of rubber, having a high durometer reading, and the diameter of the Washer is slightly less than the gauge of the complementary chamber, so that fluid may normally by-pass the washer.

A spacer or pressure block |60 seated on the washer |54 has a face complementary to the face of the washer and a concentric extension |62 received by the opening |58 in the Washer and the bore |50 in the head of the piston, and seated on the spring |52 so as to limit the compressibility of the Washer to avoid binding thereof in the complementary chamber. The compression block has spaced passages |64 therethrough for the passage of fluid, and seated on the pressure block is a sealing cup |66 for control of the passages through the piston and the pressure block.

As in the preferred embodiment of the invention, high pressure imposed on the sealing cup |66 is transmitted by the pressure block, |60 to the washer |54, resulting in radial expansion of the Washer. Due to the corresponding abutting faces of the washer and the pressure block, the marginal flange or lip |56 of the Washer is deformed under pressure and forced into engagement with the wall of the chamber over a subcessive quantity of fluid received by the chamber 34 `is displaced therefrom through the port LTA device of the class described comprising a piston, an elastic member' thereon expansible radially, means cooperating with the piston and responsive to fluid pressure to move relative to the piston for compressing the elastic member and providing for the radial expansion thereof, and sealing means supported on the elastic member.

2. A device of the class described comprising a piston, a compressible member thereon having a high durometer reading, a lfluid pressure responsive block on the resilient member,and a sealing cup on the pressure block having a relatively low durometer reading and means in the'plston resisting and limiting the movement of the pressure block.

3. A device of the class described comprising a piston, a compressible member thereon, a pres sure block on the compressible member, 'means for limiting movement of the pressure block, and a sealing cup on the pressure block.

4. A device of the class described comprising a piston, a yieldable member thereon having a concaved face, a pressure block seated in the concaved face, said block responsive to fluidpresl-V sure means for limiting movement of the pressure block, and a free oating sealing cup on the pressure block. A

5. A device of the class described comprising a piston, a radially expansible Washer on the piston having a concaved face, a iiuid pressure responsive block seated in the Washer having a convexface complementary to the concave face of the washer, means for limiting movement of the pressure block, and a exibie sealing cup on the pressure block.

6. A device of the class described comprising a cylinder element, a piston reciprocable Within the cylinder having spaced passages therethrough, a radially expansible washer seated on the piston of less diameter than the cylinder bore, said washer having a concaved face, a pressure block seated on the concave face of the washer having a convexed face complementary to the concaved face of the Washer responsive to fluid pressure, means for limiting movementl of the pressure block, and a exible sealing cup seated on the pressure block.

'7. A device of the class described comprising a cylinder, a piston reciprocable Within the yiinder, said piston having spaced passages therethrough and a concentric recess, an elastic washer on the piston having less diameter than the piston, said washer having a concaved face and a concentric opening registering with the recess, a pressure block having a convexed face complementary to and received by the -concaved face on the washer, an extension on thel convexed face of the pressure block received through the opening in the washer and within the recess in the piston for limited relative movement between the piston and the block, and a sealing cup on the pressure block.

8. A .device of the class described comprising a piston having spaced passages therethrough and a concentric recess, an elastic Washer on the piston having an opening therethrough registering with the recess, a pressure block on the washer havingan extension received by the opening in the washer and the recess in the piston, a compression element between the extension and the bottom of the recess, and a sealing cup on the pressure block.

9. A device of the class described comprising a cylinder, a piston reciprocable Within thecylinder and providing by-pass clearance with the cylinder wall, a radially expansible Washer seated against the head of the piston and normally providing by-pass clearance with the cylinder wall, a fluid pressure responsive member seated against the washer adapted to expand the washer radially when urged axially thereagainst, and a sealing member seated against the pressure member.

10. A device of the class described comprising a cylinder, a piston reciprocable Within the cylinder and providing by-pass clearance with the cylinder wall, a radially expansible washer seated against the head of the piston and normally clearing the cylindrical Wall throughout its circumference and having a dished outer face, a pressure member seated against the dished face of the washer and having by-pass clearance with the cylinder wall and adapted to expand the Washer radially when urged axially thereagainst,

means limiting the compression of the washer by the pressure member, and a sealing member seated against the pressure member.

11. A device of the class described comprising a cylinder, a piston reciprocable therein and having a by-pass clearance with the cylinder wall, a washer seating against the head of the piston and having a normal diameter spaced from the cylinder wall, said washer being radially expansible under axial pressure to seal against the cylinder Wall, and pressure sealing means seating against said washer having a portion normally sealing against the cylinder Wall, said sealing means adapted to exert axial pressure on the washer to expand the same radially into sealing engagement with the cylinder wall.

12. A device of the class described comprising a cylinder, a piston reciprocable therein and having a by-pass clearance with the cylinder Wall, a washer seating against the head of the piston and having a normal diameter spaced from the cylinder wall, said washer being radially expansible-under axial pressure to seal against the cylinder wall, a pressure member seated against said Washer having a part extending therethrough toward the piston adapted to limit the compressibility of the washer, and a sealing cup seated against said pressure member normally sealing against the cylinder wall, and means yieldingly urging said sealing cup pressure member and Washer toward the head of the piston.

13. A device ofthe class described comprising a piston, an elastic member thereon expansible radially, a pressure member'on the elastic member and a sealing member on the pressure member, said members being free floating with respect to the piston and to one another.

14. A device of the class described, comprising a piston, a yieldable member thereon, means limiting the yieldability of the member and a sealing member supported on the means, said means and members being free oating.

15. A device of the class described comprising a piston, a compressible member thereon expansible radially, a pressure block on the member solely axially movable' relative n to the piston having a sealing means associated'J therewith, said sealing means responsive to fluid pressure to actuate the pressure block and thereby compress and provide for radial expansion of. the member, and means in the piston affording resistance to movement of the block.

16. A device of the class described comprising a piston, an elastic` member thereon expansible radially thereto, a fluid pressure responsive block juxtaposed on the member and supported by the piston for axial movement relative thereto, and a sealing cup on the pressure block movable axially relative to the piston and expansible radially relative thereto, the block effective upon movement relative to the piston to compress the central portion of the elastic member and provide for uniform radial expansion thereof.

17. A device of the class described comprising a piston, an elastic member on the head thereof a fluid pressure responsive block juxtaposed on the member and supported by the piston for axial movement relative thereto, the block effective upon movement toward the piston to compress the elastic member therebetween and provide for peripheral expansion of the elastic member, and a sealing means on the block.

OWEN H. FOWLER.

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