US2598604A - Power-operated hydraulic pressure device, including yieldable piston stop - Google Patents

Description

May 27, 1952 E. .1. RINGER 2,598,604

' POWER-OPERATED HYDRAULIC PRESSURE DEVICE, INCLUDING YIELDABLE PISTON STOP Filed Oct. 8. 1945 l I 1 ay v V U l 6? 40 3a z l 82 l :Fl 5.. Z

INVENTOR. fz aidfl/v ffi BY Patented May 27, 1952 POWER- PE AT D YD AU C, B t URE VICE, INCLUDING" YmLnnnnl p sgron Evue J. Ringer, South Bend, Ind., assignor to Bendix Aviation Corporation, South a"cexplorationof Delaware I show 1945, se al ia-fil fioi 8 class. (01.60 516) 1 on relates to a power operincluding yieldable piston fishy to" the device 3533755, h H presentinvention is v a unit o; the type'disclosed in said patent which will be an improvement thereover 1) in reducing the cost of making the unit, and (2) in inciieafsingfthe reliability of operation of. the unit" to pr ovid "A-iiibi-' spefiific object of the present invention is to proyide in proyed means rerretraetmg the "e' p weroperat dnydra ine cylinder, ociated' therewith" for n sage; through said 'piston is co rolled tan times; an is'sumeiently "the unit'i's in released posiflow or fluid therethro'ugh, turing tolerances. jec'tsa n'd adyantaes' of the present pastels: during the course i on} wherein reference'is a ny g'drawinain whit-hr lEigi'rre lis a eftlcal cross sectional View taken tie ioii'vgliitbli iiicoi'poratesmy'invem d'e ice, being the" combination of a 2 is an enlarged cross-sectional view shwifi'g the rear'portitnbi the hydraulic cylinden oi Figure 1.

"Fl a cross section taken through the 'p 1ston treaties 1 and '2 at'iight mas euse s own-n Figures 1 "and 2. U "a' d'ifii'ntial aif pressure V -t'l2'is arranged to V Tplstbn-iiia hydraulic actuator :4, 1y witri'tna'assistah ce"of pressure we: niiefiti'onal manually operated The 'liydra'ulic actuator is disdain-eat or the invention is intended ld'vacuutn" the sourc'of power,

it it is constructed as a vacuumv the? thana n atmosphresuspefided Therefore, thecoostafifipressure chamber h ift 't se ers? w re 2 2 is connected by suitable means (not, shown) to avacuum source, such as the usual intake mani fold of an automotive vehicle; Control chamber is connctewby means. of. conduit 24 with chamber 26' of. a control valve. 28, which regulates operation ofthe-power cylinder, v

Pow'erpiston' [61 is biased to retracted position by. means'of a, relativelyfheavy return spring 3 whichis compressed between the forward end 32 ofthe power cylinder and, the piston I-Ei The released or rtracted'p'osition of the power; piston is determined by contact thereoi with the rear wall t l of the poWercylinder casing, a project'ion 316'preferab1y being provided-at the rear of piston 16. adapted to contactthe rear wall of the;

' power cylinder casing for this-purpose.

Reciproe'abl in hydraulic Y cylinder i4 is a piston 33, whi'ch divides said cylinder into arear chamber 40. and a forward chamber 52. When piston 38 isin released position, as shown, cornmunicati'on between chambers 4 0 and is permitted by a passage 4.4, which extends longitudk nally through the center. of said piston. An inlet opening 46 is intended to permit communication of "chamber 40 "with the conventional manually operable master cylinder, suitable conduitmeans being provided. An outlet'opening 4 8 is arranged to permit communication ofchamber 4 2, through suitable conduit means; with the motor ormotors which are to be operated, such the conventiohalwheel cylinders of a hydllaullo brake system.

A pressure transmitting rod 50 is secured to power piston IS and extends through an opening 52 in the forward end'of the power cylinder into the bore'of hydraulic cylinder [4; The forward end or rod 55 is secured'to hydraulic piston 38 by ns of a p itive c nn c ion, such as h .105 pin as. "There should be a sli ht l arance etween the pin'and the pin slot inorder that the end of the rod can act directly; against the hardened thrust plate 57., which is pressed into piston 38. With this' arrangement," the power piston it controls both-the pressure stroke' and the retraction strolseoi hydraulic piston'38 and the single return spring 3,lI-ser ves the dual function of retracting both the power piston and the d aulic biston; Here Qfore it h sbeen 9 nsider ed necessary to provide separate return springs for the power andhydraulic pistons", but

' the pfesentinvention makes it possible to utilize a single-51 111181 9 return be h fstons. 7

"When th ombina ion p w r, and dr u ic one another, in order that chamber 42 and the wheel cylinders may compensate for variations in the volume of the fluid by communication with the manually operated master cylinder, which in turn is adapted to compensate for volume variations in the fluid because of its direct connection with the usual integral reservoir. On the other hand, during the pressure stroke of hydraulic piston 38 it is necessary that communication between chambers 40 and 42 be prevented, otherwise the entire force developed by the power cylinder will react against the manually operated master cylinder, and the full brake applying pressure will have to be developed by the operator.

In order to control the flow of fluid through passage 44, a valve element 56 is provided. When the valve element 56 seats at 58, flow of fluid from chamber 42 to chamber 40 is prevented, although flow in the reverse direction can still occur. A light spring 60, mounted in'a retaining case or cage member, 62, urges the valve element 56 to ward seated position.

Means must be provided to hold valve element '56 away from its seat when piston 38 is in released position. This means may take the form of the valve unseating element 64 which has a forward projection 66 extending through passage 44 to contact valve element 56, and which has offset rearwardly extending projections 68 which are located in slot 16 provided in piston 38 and which are adapted to contact a stop member slightly before piston 38 has returned to released position, in order that said stop member will cause relative movement between member 64 and piston 38 to force valve element 56 from its seat. Member 64 is loosely assembled in piston 38 by means of a snap ring 12 which is fixed in place on the piston, and which extends into an elongated groove 14 in each rear extension 68 of member 64. Snap ring 12 also serves to retain the loose cross pin 54 in position.

Because of the accumulated tolerances in the power cylinder and hydraulic cylinder, it is impossible to have more than one definite stop for the power and hydraulic piston combination to determine the released position of said pistons. In arrangements of the type heretofore provided, in which the power piston and hydraulic piston were not positively connected, it was possible to provide a separate stop for each of them, and it was of course necessary to provide a separate spring urging each piston toward the respective stop.

When the power and hydraulic pistons are positively connected, as in the present case, if separate fixed stops are provided for each of said pistons, then the presence of tolerances in the combination unit means that it is almost certain that one of the pistons will reach its released position ahead of the other, and that the latter will therefore be held away from fully retracted position. Such a situation has certain very troublesome disadvantages. For example, if the hydraulic piston reaches its retracted position ahead of the power piston, then the entire force of the large return spring 30 will have to be taken as a'shear load'on the small connecting pin 54. On the other hand, if the power piston returns to its released position ahead of the hydraulic piston, there is no guarantee that said hydraulic piston will have moved sufliciently far toward its released position to insure unseating of ball valve 56 by member 64. If the ball valve is not held away from its seat when the parts are in released position, there is the danger that a varia tion in volume of fluid in chamber 42 of the wheel cylinder will cause the brakes to lock.

To obtain the advantages of a direct connection between the power piston and the hydraulic piston, and at thesame time entirely overcome the difliculty heretofore discussed, I have provided novel means for causing member 64 to unseat valve element 56, regardless of the exact position which piston 38 assumes when fully retracted. This means is a yieldable stop member arranged to contact valve unseating element 64 to cause a predetermined amount of relative movement between said member 64 and piston 38, while yet limiting the shear load on pin 54 to a relatively low amount. For this purpose, I provide a compression spring 16 located in the rear of chamber 40 and'compressed between the closure member 78 and a washer or stop element 50. The washer '60 is prevented from moving toward the right by means of a movement limiting member 82 which snapped into a groove 84 provided in the inner wall of the hydraulic cylinder. I prefer to use a non-circular resilient member for this purpose, such as a member having a hexagonal or octagonal shape, in order to avoid any danger that the washer 80 might slip through the limiting member 82.

The spring I6 must be sufiiciently strong to overcome the force of spring 60 plus any pressure differential in the hydraulic system tending to hold valve 56 seated.

When the rearwardly extending forks of member 64 contact washer 80, further rearward movement of member 64 is prevented, and subsequent movement of piston 38 towards the left will cause the valve seat 5 8 to move away from valve element 56, thereby opening communication between chambers 40 and 42. However, if the rear surface, of piston 36 contacts washer before projection 36 of power piston l6 has engaged the rear wall of the power cylinder casing, spring 16, which is much lighter than spring 30, will compress, permitting the hydraulic piston assembly to continue moving toward the left until the power piston has come to its resting position. The full shearing load on pin 54 is therefore the force exerted by spring 16, rather than that exerted by spring 30. Also, loads on the other ports of the hydraulic piston are limited to the force of spring 16.

In making the combined power unit and hydraulic actuator, the tolerances should be so arranged that hydraulic piston 38 will never remain too far to the right when the power piston has reached fully retracted position. In other words, any tolerances allowed should be in the direction of causing compression of spring 16, thereby insuring that the return movement of piston 38 will always be suflicient to cause valve element 56 to be moved away from its seat.

The general operation of the device is as follows. When the operator wishes to apply the brakes, he develops pressure in the manually operated master cylinder by means of the usual pedal. The fluid under pressure moves from the manually operated master cylinder through the connecting conduits and through opening 46 into chamber 40. Because, in the released position of the unit, valve element 56 is away from its seat, a certain amount of the fluid may flow through passage 44 into chamber 42 and thence to the wheel cylinders to initiate application of the brakes. At the same time fluid under pressure from the manually operated master cylinder moves from chamber '40 through passage 86 into chamber 88; to, act on piston x9 9, driving the, same,

cation. between chamber. 26 and chamber 9 6,

which, is. connected. to. vacuum. Further move.- ment of. pistonell. and valveseat 9.2 pushes thrust connection 58 tO.-mV.e. valve element lflil away from valve. seat [02,. thereby admitting air atatmosphericpressure from chamber N34 to chamber 25, whence. the air. is. conducted to control chamber. 23}. of. the power cylinder, developing a pressure. differential. over power piston 16 which moves. thesame, towards the right against the resistance of return spring 33'. The force developed by thepower piston acts through rod 50 to driveipiston- 38' toward the right, the force being. exerted: directly against thrustplate '51. Sincemember 64 is only loosely assembled in piston 38., a slight movement of said piston toward. the right. will. permit spring 60 to move ball valve element 56 to seated position, after: which fluid. in high pressure chamber 42 can no longer. flow into. chamber 40, although it isstill possible for fluid. to flow in the reverse direction in. case. of power. failureor power run-out. The manually developed pressurewhich,is transmitted from the operator operated master cylinder to chamber 40 continues to assist in applying the brakes by exerting. a pressure against the rear of piston 38.. Therefore, the work output at the brake. is a total. of. the. work done by the power cylinder and. the. work done by the operator.

When the operator wishes to release the brakes, he releases. pressure in the manually operated master cylinder. This reduces the pressure in chamber 49, and, also in chamber 88, permitting valve return spring. [B6 to move member 92 toward the left, first causing valve element I00 to seat under the influence of spring I08, and subsequently causing valve seat 92 to move away from valve. element 94., again evacuating control chamber 2001 the. power cylinder, and destroying the differential. over power piston l6. This permits return spring 30. to force power piston I6 toward the left, drawing with it hydraulic piston 33'. Just before the power and hydraulic pistons have reached released position, member 64 contacts washer 80 and forces ball valve element 56 away from its seat. As explained above, should it be necessary for piston 38 to move farther to the left, after it has contacted washer 80, this is permitted by spring 16.

With the present arrangement, no initial adjustment is necessary to compensate for manufacturing tolerances, because the proper control of the passage through the hydraulic piston is insured. Furthermore, large parts of the unit, such as the power cylinder parts, can be bottomed or rested against a rugged structural element, i. e., the power cylinder casing.

Although a particular embodiment-of my invention has been described, it will be understood by those skilled in the art that the object of the invention may be attained by the use of constructions different in certain respects from that disclosed without departing from the underlying principles of the invention. I therefore desire by the following claims to include within the. scope of my invention all such variations and modifications by which substantially the results of my invention may be obtained through the use of substantially the same or equivalent means.

I claim:

1. A combined differential air pressure powerunit and hydraulic actuator operated thereby 6 compri'sing a casing for the power unit; ap ower pistons reciprocable. therein, a hydraulic cylinder secured to the power cylinder casing and having.

a bore concentric with the. power; cylinder piston,

' a hydraulic piston reciprocable in said. bore, said hydraulic cylinder. having an inlet opening behind; Said; piston and; an outlet opening ahead of said piston, said piston having a passage extending, longitudinally. through the center thereof constituting the, only means of direct communication between the inlet and outlet openings, a valve element at the forward end of said. passage which. when seated permits now of fluid only fromrthe inlet side toward the outlet side and not in, the reverse direction, a spring urging said. valve; element toward seated position, a rod secured, tothe. power cylinder piston and extending, into. the hydraulic bore to contact the hydraul'icpistom across-pinproviding a lost motion return connection between the forward endof the rod and; the hydraulic, piston, a relatively heavy spring inthepowerunit acting against the power piston to. retract, both the power piston and the hydraulic pistomsai'dpower piston having a rearwardly extendin projection which contacts the powerunit casing when the piston is in retracted position,a, washer in thehydraulic cylinder which is; contacted by the rear oi the. hydraulic piston when. the. latter is in retracted position, a spring compressed, between the forward end of the power unit; casing and said washer to. oppose yieldably further return; movement. of the hydraulic piston after said piston has come into contact with the washer, said spring. being sufficiently strong to overcome the, spring which urges the valve element to seated. position plus any hydraulic pressure. acting on said valve element, but being relativelyweak in comparisonv to the spring which returns the power piston. to released position, a movement. limiting member secured in a groove in the hydraulic cylinder and arranged to limit forward movement of the washer under the influenceof the spring acting thereon, and a valve unseating member carried by said piston but capable of movement relative thereto and arranged to contact the washer on the return stroke before the piston contacts said washer, thereby forcing the valve element from its seat to permit compensation for changes in the volume of the liquidv on the. forward side of thehydraulic piston.

2,. A combined differential air pressure power unit and hydraulic actuator operated thereby comprising a casing for the power unit, a pressure responsive movable wall reciprocable therein, a hydraulic cylinder supported on the power cylinder casingand having a bore concentric with the power cylinder movable wall, a hydraulic piston reciprocable in said bore, said hydraulic cylinder having an inlet opening behind said piston and an outlet. opening ahead of said piston, said piston having a passage extending longitudinally through the center thereof constituting the only means of direct communication between the inlet and outlet openings, a valve element associated with said passage which when seated permits flow of fluid only from the inlet side toward the outlet side and not in the reverse direetion, a spring urging said valve element toward seated position, a rod secured to the power cylinder movable wall and extending into the hyd eulic bore to est en t h a lic i i qn 16stme ee e u n. conn c i n. b wee h -f end. of th r d. an th h drauli is n; a atively heavy spring in the power unit acting member in the hydraulic cylinder which is contacted by the rear of the hydraulic piston when the latter is in retracted position, a spring compressed between the forward end of the power unit casing and said stop member to oppose yieldably further return movement of the hydraulic piston after said piston has come into contact with the stop member, said spring being sufficiently strong to overcome the'spring which urges the valve element to seated position plus any hydraulic pressure acting on said valve element, but being relatively weak in comparison to the spring which returns the movable wall to released position, a movement limiting member secured inside the hydraulic cylinder and arranged to limit forward movement of the stop member under the influence of the spring acting thereon, and a valve unseating member carried by said piston but capable of movement relative thereto and arranged to contact the stop member on the return stroke before the piston contacts said stop member, thereby forcing the valve element from its seat.

3. A combined difierential air pressure power unit and hydraulic actuator operated thereby comprising a casing for the power unit, a pressure responsive movable wall reciprocable therein, a hydraulic cylinder having a bore concentric with the power cylinder movable wall, a hydraulic piston reciprocable in said bore, said hydraulic cylinder having an inlet opening behind said piston and an outlet opening ahead of said piston, said piston having a passage therethrough constituting the only means of direct communication between the inlet and outlet openings, a valve element associated with said passage which when seated permits flow of fluid only from the inlet side toward the outlet side and not in the reverse direction, aspring urging said valve element toward seated position, a, thrust transmitting member secured to the power cylinder movable wall and extending into the hydraulic bore to act on the hydraulic piston, a lost-motion return connection between the thrust transmitting member and the hydraulic piston, a relatively heavy spring in the power unit acting against the movable wall to retract both said movable wall and the hydraulic piston, the released position of said movable wall being determined by the power unit casing, a floating stop member in the hydraulic cylinder which is contacted by the rear of the hydraulic piston when the latter is in retracted position, a spring compressed between the rear .wall of the hydraulic bore'and said stop member to oppose yieldably further return movement of the hydraulic piston after said piston has come into cotnact with the stop member, said spring being sufliciently strong to overcome the spring which urges the valve element to seated position plus any hydraulic pressure acting on said valve element, but being relatively weak in comparison to the spring which returns the movable wall to released position, a movement limiting member secured inside the hydraulic cylinder and arranged to limit forward movement of the stop member under the influence of the spring acting thereon, and a valve unseating member carried by said piston but capable of movement relative thereto and arranged to contact the stop member on the return stroke before 8 the piston contacts said .stop member, thereby forcing the valve element from its seat.

4. In a power-operated hydraulic cylinder, a piston in the cylinder dividing it into two chambers, a conduit adapted to connect said chambers, a valve controlling said conduit, a

resilient member urging said valve to close said conduit, a floating member associated with said valve capable of displacing the same to open the conduit, a stop member which is engaged first by the floating member and then by the piston when the latter approaches retracted position, and a spring which acts on said stop member to urge it toward the piston and which is yieldable to permit movement of the piston and stop member as a unit to reach fully retracted position.

5. In a power-operated hydraulic cylinder, a piston in the cylinder dividing it into two chambers, a conduit adapted to connect said chambers, a valve controlling said conduit, a floating member associated with said valve capable of displacing the same to open the conduit, a stop member which is engaged first by the floating member and then by the piston when the latter approaches retracted position, and a spring which acts on said stop member .to urge it toward the piston and which is yieldable to permit movement of the piston and stop member as a .unit to reach fully retracted position.

6. A combined power unit and hydraulic actuator operated thereby comprising a casing for the power unit, a pressure responsive movable wall reciprocable therein, a hydraulic cylinder associated with the power unit, a piston in the cylinder dividing it into two chambers, a mechanical connection between the movable wall and the piston, a return spring acting on the movable wall to return it and the piston to retracted position, a conduit adapted to connect the two chambers of the cylinder, a valve arranged to control said conduit, a member associated with said valve capable of. displacing the same to open the conduit, and a, yieldable stop which first causes the aforesaid member to move the valve away from closed position as the piston returns to retracted position and thereafter yields to permit further retractile movement of said piston. I

7. A combined power unit and hydraulic actuator operated thereby comprising a casing for the power unit, a pressure responsive movable wall reciprocable therein, a hydraulic cylinder associated with the power unit, a piston in the cylinder dividing it into two chambers, a mechanical connection between the movable wall and the piston, a return spring acting on the movable wall to return it and the piston to retracted position, a conduit adapted to connect the two chambers of the cylinder, a valve arranged'to control said conduit, a member associated with said valve capable of displacing the same to open the conduit, and a yieldable stop which causes the aforesaid member to move the valve away from closed position as the piston returns to retracted position. 7

8. A combined power unit and hydraulic actuator operated thereby comprising a casin for the power unit, a pressure responsive'movable wall reciprocable therein, a hydraulic cylinder associated with the power unit, a piston in the cylinder dividing it into two chambers, a mechanical connection between the movable wall and the piston, a return spring acting on the movable wall to return it and the piston to retracted position, a rigid stop which determines 9 10 the retracted position of the movable wall, a REFERENCES CITED conduit adapted to connect the two chambers of The following references are of record in the the cylinder, a valve arranged to control said me of thi I atent. conduit, a member associated with said valve S p capable of displacing the same to open the con- 5 duit, a stop member which is engaged by the UNITED STATES PATENTS piston when the latter approaches retracted po- Number Name Date sition, and a spring which acts on said step mem- 2,246,140 Main June 17, 1941 her to urge it toward the piston and which is ,2 0, 90 Stelzer Oct. 28, 1941 yieldable to permit movement of the piston and 10 85 Elliott Dec. 14, 1948 stop member as a unit to reach fully retracted position.

EVUE J. RINIGER.

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