US1592918A - Power actuator - Google Patents

Description

/ July 2O 1926. `l.592,918

c. s. BRAGG ET AL Filed June 26. 1924 ATTORNEY 7 July 20 s. BRAGG ET AL POWER ACTUATOR Fjnd June 26, 1924 '3. sheets-sheet 2 gfo INVENTORS xm ATroRNEw Patented July 20, 1926.

UNITEDV STATES PATE-Nr carica CALEB S. BBAGG, 0F PALM BEACH, FLORIDA, AND VICTOR W. KLISRATH, 0F PORT WASHINGTON, NEW YORK, ASSIGNORS T0 BRAGG-KLIESRATH CORPORATION, @E l LONG ISLAND CITY, NEW YORK, A CORPORATION OF NEW YORK.

rowna acTUAToR.

v v ,Y

Application lled June 26, 1924.- Serial No. 722,487.

the actuator being provided with two pistonsV working in the/same cylinder, each of which kpistons is operatively connected with the brake mechanism for two wheels, preferably arranged opposite to each other at the same end of the chassis. The pistons are caused to move in thecylinder toward and from each other by establishing differential pressures between that portion of the cylinderv between the pistons and the portions at each end of the cylinder 'on the opposite sides of the piston, and we provide reveising' valve mechanism connected with an operator operated device for controlling the movements of said pistons, the valve mechanism being" constructed to maintain the istons in balanced condition at any inter]ace`nt position of the valve mechanism between its limits of `movement, so that the movements of the pistons and their connected brake mechanisms can be controlled with the utmost delicacy, while the operator is relieved from the exertion of actually operating the brake mechanism. The valve mechanismis also connected to one of the pistons by means ermitting lost motion, sothat in case of ailure of the power, the said piston and its connected brake mechanism may nevertheless be operated directly by the operator; In the application of our improved mechanism to automobiles Vin which an internal combustion engine furnishes the propelling power, the internal combustionengine affords a convenient means of obtaining the differential pressures required. Thus, in the operation of an internal combustion engine, there isV suction roduced by the cylinders in drawing in the c arges of explosive mixture between the cylinders and the throttle valve which is at its maximum when the engine is throttled down, and decreases as the throttle is for locking an opened. There is also high compression in the cylinders of the engine which is greatest when the throttle is wide open, and decreases as the throttle is closed. Our improved power actuator, can, therefore, be readily .pressure acting on one ace of each piston and atmospheric air as the low pressure actmg on the other face of each piston, or compressed gases from a cylinder of the en .gine maybe employed as the high pressure and suction from the intake manifold may be employed as the low pressure. In practice, however, we lind it most convenient and advantageous to employ the suction from the intake manifold for the low pressure and atmospheric air for the high pressure, as speciiically shown in the accompanying drawings. Our present invention also contemplates means for preventing one of the pistons from movement in the cylinder and thereby holdingout of operation the brake mechanism' connected therewith, leaving the other piston to operate the brake mechanism connected to it sothat in a four wheel brake mechanism for example, the operator operated part, as the foot lever, may be operated under normal conditions so as to apply only two of the brakes, as those for the rear wheels, while in an emergency, or when heavy braking action is required, the locked piston may be released s0 that both pistons will operate, and simultaneously apply the brakes of all four of the wheels, when required, and under the entire-control of the y operator. In some instances this may be accomplishedby providing mechanical means unlocking the free piston not underthe mechanical control of an o erator operated part, and this result may accomplished in other ways, as by providing anauxiliary valve for closing the communication between the opposite ends of the cylinder at times when only one piston and the brake mechanism connected therewith are to be employed, and by providing means, under the control of the operator, hereinafter described, for effecting the opening of said auxiliary valve when the operation-of both pistons and the brakemechanism connected therewith, is required. Referring to the accompanying drawm j sig. 1 is a diagrammatic view representing an automobile provided with four brakes, one for each of the wheels thereof, and having our improved double piston power actuator operatively connected therewith, and with t e intake manifold of the engine for supplying the lower pressure for operating the power actuator.

F1 2 is an enlarged sectional view of the doub e piston power actuator.

Fig. 2a is a detail drawn ,to an enlarged scale showing the parts at the left of Fig. 2. F Fig. 2b is a section on the line 2"--2b of rigs. 3 and 4 are enlarged sectional views` ofl a form of valve mechanism which may be conveniently employed in connection with the power actuator, showing the valve mechanism in reversed positions.

Fig. 5 is a detail sectional view of a part of a'modified form of power actuator, in which an auxiliary valve and operator controlled cam for the same are employed for connecting and disconnecting the opposite ends of the cylinders, to enable the operator to employ one piston and the brake mechamsm connected therewith or both pistons and their respective brake mechanisms as re uired. f c

i 6 is a detail view showing another modi cation of our improved actuator for enabling theoperator to operate one or both pistons of the actuator as required.

Referring to the drawings, 1, represents the power cylinder of our vimproved power actuator, both ends being closed by suitable heads, vindicated' at 2 3, respectively, secured to the cylinder by any suitable means, as b connecting bolts and nuts, 4 see Fig. 1. Wit ln the cylinder, l, is a main double actin piston, indicated at l0, provided with ann ar gaskets, 11, extending in opposite directions and engagin the inner surface of the cylinder wall. T e piston, 10, is rovided with a hollow piston rod, 12,w ich extends through a guiding sleeve, 13,' 'bushing, 14, and stufiingbcx, 15, with which the head, 3, of the cylinder isprovided. The cylinder is also'provided with asecond pist0n, 10, which we term/the auxiliary or floating piston, having similar gaskets, 11, extending in opposite directions, and engaging the inner -surface of the cylinder. The piston, 10a, is provided with a hollow piston rod, 12, extending through a guiding sleeve, 13, bushing, 14, and stuffing box, 152, with which the head, 2, ofthe cylinder is provided. The opposite ends of the cylinder are connected y means of a; pipe, or passage, 70,' so that one or both of said pistons may be actuated by creating different pressures in the space, A, between said pistons and the connected spaces, B-B, at the opposite ends of the cylinder. 16, 16 represents a longitudinally movable valve sleeve extending in opposite directions from the reversing valve mechanism, which in this instance is located in the hub `of the main piston, 10. The piston, l0, is provided with two chambers, indicated respectively at- 28 and `30. The chamber, 28, is connected by passages, 39--40, with the central portion, A, of the cylinder between the pistons, while the chamber, 30, is connected by passage, 36, with the portion B, in the end of the cylinder beyond the piston, 10, which, through the pipe or passage, 70, is connected to the portion, B. Within the chamber, 28, is a valve collar, 27, secured to the valve sleeve, which is ground to fit the interior of the chamber, 2S, and is movable therein between end washers, 27@L and 27h, of leather or other suitable material, thus establishing a limit of lost motion amounting to substantially ff@ of an inch in this particular instance between theo valve sleeve and the piston, 10. The portion, 16, of the'valve sleeve, also communicates lwith a plurality of air inlet ports, 25, which can be brought into communication with the chamber, 28, whenthe valve, 27, is in one extreme position, and can be brought into communication with the chamber, 30, when the valve is in its other extreme position, the said ports, 25, being maintained closed when in an interjacent position between the limits of movement of leo the valve mechanism. Within the chamber,

the portion, 16a ofthe valve sleeve is provided with a plurality of suction ports, indicated at 24, which are capable of being brought into communication with the chamber, 30, in one extreme movement of the valve mechanism and into communication with the central space, A, of the cylindery when in thel other extreme position of the valve mechanism, said ports being normally closed when t-he valve mechanism is in an interjacent position.r reference we term the ports, 24, the low pressure ports, and the ports, 25, the high pressure ports.

Ilfn this instance, as shown in Figs. 1 and 2, the low pressure is supplied by suction from the intake manifold, 121, of the internal combustion engine, 22, of the automobile, which is conneetedto an inlet port, 20, in the exterior portion of the piston rod, 12, by a iexible connection permitting the necessary movement of the piston rod. In order to insure the instantaneous operation For convenience ot lso adjacent to the tank. AA iexible pipe, 23,

which may be of considerable diameter, eX- tends from the tank, 23a, to the port, 20. Communication between the port, 20, and the low pressure ports, 24, is established through the hollow piston rod, 12a, and the movable valve sleeve section, 16a. In order to further provide forcutting oli the sucl tion when the pistons are in retracted positions, which is the normal or oit position of the pistons, as indicated in Fig. 2, we prefer to provide the hollow piston rod, 12a, with a plug or partition, 18a, permanently secured therein adjacent to the port, 20, and provided with an axial aperture, 18", and a valve seat, 18, as best shown in'Fig. 2'. We also provide a valve, 18, for engag- .ing the valve seat, 18, when the parts are in normal or off position, said valve being secured to a rod, 9, extending through the hollow rod and being connected to the sleeve section, 16, by means providing lost motion, in this instance a wrist pin, 19, on

the rod,-9,`engaging a slot, 19, in the sleeve section. When the pistons move away from each other and return to normal or retracted positions, as shown in Fig. 2, the wrist pin, 19, will be engaged by the end of the slot, 19, in the` sleeve, 16, and this will draw the valve, 18, firmly upon its seat and form an additional seating means, when the parts are not in operation. When the valve sleeve, 16a is moved in the direction of the arrow in Fig. 2, the end of slot, 19, relieves thewrist in, 19, and permits the valve, 18, to openy suction, and it will be assisted in opening by the frictional engagement between the valve sleeve, 16, and the wrist pin. The valve, 18, will remain open until it is closed by the return of the pistons and valve sleeve, 16, to normal or retracted positions. The slot, 19, permits the lvalve sleeve to move in the direction of the arrow in Fi 2, to a greater or less extent as requre without interference from the valve ro 9.

The hi lher pressure Huid' in this instance is atmosp eric air, which is admitted to the interior of the valve -sleeve section, 16, through a port or opening, 43, at the outer end of the valve sleeve section, and preferably 'provided in a plug, 41, screwed into the outer end'of the hollow piston rod, 12, and rovided with perforated ears, 42, by whic it is -connected to one pair of brake mechanisms, as the brakes for the rearI The outer end of the wheels of the automobile.y

slide rods,

the other piston rod, 12, is provided with instance as shown in Fig. 1, the piston rod,

12, is connected by a link., 63, withan arm, l

64, on a rock shaft, 59, provided with arms, 58, each of which is connected by alinlr, 57, to an arm, 56, for rotating forwardly a cam, 55, of one of the rear wheel brake mechanisms, .which in this instance, is shown as comprising brake drums, 52, and separable braking shoes, 53, pivoted at 54, and provided with the usual retracting springs, 61. It is to be understood, further, that the particular form of brake mechanism and its connections with the actuator form no part of our present invention. The piston rod, 12a, is connected in a similar manner with the brake mechanisms for the forward wheels and the various parts of the brakes and connecting mechanisms are indicated by similar numerals.

50 represents the operator operated part which in this instance is the usual foot lever pivoted to the chassis and provided with a retracting spring, 51. This lever is connected to the longitudinally movable valve sleeve, 16-16, and reversing valve mechanism by any usual or desired means.. In the present instance we have shown the lever, 50, connected by a link rod, 62, with a rectangular frame comprising longitudinally movable 71, engaging guiding apertures, 72, in parts secured to the cylinder heads and projecting therefrom, said rods being lso connected at their forward ends by cross rod, 73, extending aroundthe piston rod, 12a,

and being provided at their' rear ends with` a cross i'sod, 74, which extends through a slot, 75, in the piston rod 12, and engages suitable apertures in the sleeve, 16, so that the sleeve and valve mechanism, including the collar valves, 27 and 29, maybe shifted lon itudinally with respect to the piston, 10, y the operation of the foot lever, and in the .reverse direction by the retracting spring, 51.

In the operation of the apparatus, as shown in Figs. 1, 2, -3 and 4 of the drawings, when it is desired to apply the brakes, theoperator will depress the foot lever, 50, thereby shifting the sleeve, 16, and the re.- versing valve mechanism in the direction vof the arrow in Fig. 2. This releases the valve, 18, from the retaining. action of the rod 9,

and permits the valve to be opened by the suction, and simultaneously movesv the low pressure ports, 24, into communication lwith the central space, A, of the actuator cylinder, and the high pressure ports, 25, into exhausted from the central space, A, ofthe cylinder, while atmospheric air will be admitted through the high pressure ports, 25, the passage, 36, and connecting pipe or passage, 70, to bothends of the cylinder, so that the pistons. 10 and 10a, will move simultaneously toward each other and thereby simultaneously apply all four of the brake mechanisms connected therewith. It will be understood that if the pedal, 50, is moved forward and held, the movement above indicated of the pistons will instantly follow until the movement of the piston, 10, has covered the low pressure ports 24;, when the pistons will be maintained in a balanced condition until a further movement of the valve mechanism under the action of the pedal takes place. A further forward movement of the pedal is instantly followed by a further movement of the pistons toward each other so that the brake mechanism can be applied with the same accuracy and delicacy of adjustment that is obtained with the usual foot operated brake mechanism, except that the operator isU relieved from the exertion necessary to actually apply the brakes. When the operator releases the pedal, 50, it will be moved in the opposite direction, by spring,.51, thereby shifting the wrist valve sleeve and reversing valve mechanism so as tov place the low pressure ports, 24, 1n

communication with the chamber, 30, andthe high pressure ports, 25, in communication with the passages 39-40, leading to the space, A, lbetween the pistons. The result of this will be to exhaust the air rapidly from the portions B-B of the cylinder and admit air to the central portion between the pistons which move away from each other and simultaneously release both sets of brakes. The movement of the piston, 10, is limited by the venga'gemert of the ,hub which is providedwitha packing ring, 76 surrounding the piston rod, 12) with the head, 3, of the cylinder and the return movement of the piston10, is likewise limited by a projectingfsleeve, 77, surrounding the piston rod, 12, and adapted to engage the other head, 2,- of the cylinder, the said pistons being limited in order to prevent injury to their gaskets. As the pistons return to their normal positions the end of the slot,-

19, in the valve sleeve, 16, will engage the pin, 19, and vexert a draw on the' rod, 9, thereby drawing the'valve, 18, firmly upon its seat-.and-retaining itiin closed position to assist in sealing the cylinder until the foot lever is again operated. The movement of the pistons toward'each other will-normally be "limited by the application of the.

brakes. Should the brakes wear out the pistons will be prevented from coming into contact so as to injure their gaskets, by the engav'ement of their metallic hubs.

t will also be noted that by reason of the lor when it is desired to .hereinafter indicated.-

lost motion between the piston, 10, 'and the reversing valve mechanism, that if the brake pedal, 50, is actuated and for any reason the pressure fails, further pressure on the pedal will bring the collar valves, 27 and 29, against the ends of the chambers, 28 and 30, automatically venting the cylinder, and the operator can then apply physical pressure to the brake pedal to directly move the piston, 10, thus applying the brakes connected therewith by direct physical force o the operator, and thereby preventing what otherwise might result in an accident. It is also to be noted that in the operation of our improved brake mechanism by means of the herein described power actuator, the operator operates the brake pedal in exactly the same manner as to direction of movement and extent of movement as is usual in installations where ,the power is applied wholly by the operator so that it is unnecessary for the operator to learn a new mode of operation while at the same time the brakes may be applied and released by the power actuator without any further exertion on the part of the operator than is required to move the brake pedal and connected valve mechanism against the pressure of the retracting spring.

Our invention valso contemplates, as before stated the employment of means whereby one of the pistdnsas the auxiliary or floating piston, 10, may be permitted to remain stationar while the main piston is operated, there y effecting the operation of m0 one set of brakes, only, and for releasing the said auxiliary or iioating piston, to secure the simultaneous operation of the brake mechanisms connected with both pistons when required under the control of the op- 105 erator. This fs particularly advantageous in connection .with an automobile having four Wheel brakes, as it enables the operator to apply the brakes of two wheels,-as the rear wheels, under ordinary working con- 110 ditions, and also to bring into action the brakes of all four wheels 1n any emergency,

y make a sudden stop, or when additional braking power is re-4 quired, as' on very steep hills. In Fig. 5, 115 have shown a portion of the cylinder of the actuator, at 101, and the pistons are indicated at `110110a respectively, it being understood that the parts of the actuator which are given the same reference numerals, with 100 added, are constructed in the' same manner as is illustrated in Fig.

2 ard ,hereinb ore described, except as 170 represents the pipeor passage, connecting the end portions, B2- 3, of the" cylinder, the central vportion between the pistons being indicated at A. The pi e or passage, 170, is pro- ,vided with a va ve casing, indicated at 180,

containing a spring actuated valve, 181, for

closing the pipe or passage, 170, the said l valve being normally held in closed posiwithout the auxiliary or floating piston,

tion by a spring, 182, and being provided with a stem, 183, projecting from the valve casing into position-to be engaged by a cam, 184, carried by one of the lslide rods, 171, for actuating the valve sleeve, in the manner indicated in Fig. 2. The valve casing, 180, is provided with a partition, 185, inter'- posed between the sections of the pipe, or passage, 170, leading from said valve to the opposite ends of the cylinder, 101, respectively, and is provided with a valve seat for the valve, 181. This valve is so located with respect to said seat that it will open against the tension of the spring, 182, when the portion, B2, of the cylinder to the right ofV piston, 110, is connected with the source of lower pressure, of the engine the actuator), while the light spring will maintain the valve normally in closed position at other times except when the valve is positively opened by the cam, 18,4. The cam, 184, is preferably of substantially the same length as the stroke of the pistons, and is preferably adjustable on the rod, 171, as by means of a set screw, 186. When the pistons are in retracted position, the cam 184, is adjusted on the rod, 171, so as to permit a certain amount of movement of said rod, sufficient to shift the valve mechanism of the actuator and secure effective operation of the main piston, 110, without engaging the stem, 183, of the valve, 181, with the cam, 184. The operator can therefore actuate the brake lever so as to secure the operation ofV the main piston, 110, and the brake mechanism (as the rear wheel brakes) 'operatively `connected therewith, producing effective movementn of 110, as the valve, 181, being in closed position, cuts od the space, B2, of the cylinder from the space, B2, and therefore atmospheric air cannot pass from the space, B2, to the space, B2, and the piston, 110a, will, accordingly be held'from movement in the cylinder to permit the voperation of the other piston and the brake mechanism connected therewith without operating the brake mechanism connected with piston, 1102, so held from movement. If it isrequired to operate all of the brakes, the operator can depress the brake lever to a furtherl extent, thus moving the slide rods far enou h to bring the cam, 184, into contact with te stem, 183, of the valve, 181, and opening said valve. This establishes communication for atmospheric airvv between the end spaces, B2, B2, of the actuator cylinder, and permits piston, 110, to move inwardly toward the other piston, 110, and applies the brake mechanismsconnected therewith, thus applying all the brakes, as the front wheel brakes and rear (as the intake manifold by the valve mechanism of` wheel brakes. If the brake pedal is so actuated as to operate both pistons and set the brakes connected therewith, on the release of the brake pedal, the reversing valve will be shifted with respect to the ports of the main piston, 110, thus connecting the suction tank with the end portion, B2, of the cylinder, while the central portion, A', is connected with the atmosphere. The air will be exhausted from the end portions, B2, B2, of the cylinder and both istons will be returned to their normal) positions, as the valve, 181, will be held openas long as the cam, 184:, remains in engagement with its stem, and after the cam releases the valve stem, the valve, 181, will be kept open by the suction, against the action of its spring until the auxiliary or oating piston is fully returned to its normal position. rlfhe operator can, therefore, operate the brake pedal under ordinary conditions without bringing the cam, 184, into engagement lwith the valve. 181, to apply and release only the rear wheel brakes, but can instant- `ly secure the operation of all the brake mechanisms controlled by both istons by depressing the brake pedal su ciently to bring the cam, 184, into operative engagement with the stem of the valve, 181, and opening said valve.

In Fig. 6 we have shown another modi- {ication of our improved actuator by means of which either one or both of the pistons may be operated as desired, under the control of the operator. ln this gure, the parts are also constructed as shown 1n Fig. 2, except as hereinafter noted, and are -ven the same reference numerals with 200 added. In this gure, the piston rod, 212, connected with the floating piston, 1s provided with a groove or recess, 280, adapted to be engaged by a rounded spring detent, 281, mounted in a recess, 282, in the sleeve, 213, of the actuator cylinder, 202, and provided with a spring, 283, held in position by a screw plug, 284, screwed into the recess, 282, by means of which the tension of the' spring may beadjusted. The engagement of` the detent, 281, with the recess, 280, in the. piston rod, 212,` is such that the auxiliary or oating piston, 210",

will be normally held against movement when the valve mechanism of the actuator is moved into position to connect the central portion of the actuator cylinder with the suction, thuspermitting the main piston, connected with the valve sleeve, here indicated .at 216, to be actuated in either direction to apply and release the brakes connected therewith. Y

In case more than normal braking is required, a further depression of the brake pedal suiiicient to actuate the valve sleeve, 216a to itsl full extent (plston 210 being arrested by the resistance of the applied brake iep YA2, in the cylinder between the pistons.

When the suction has increased` ciently to enable the piston, 210, to overcome the retardin influence of the detenta, the latter will yiel and be forced downward against its retracting spring, thuspermitting the floating piston, 210, to move inwardly and apply the brake mechanism Yconnected therewith, as the front wheel brakes.. When .the reversing valve mechanism is shifted in thev opposite direction by the brake pedal under the action of its retracting spring, both pistons will return to their normal positions, and as soon as the auxiliary or oating piston, 210, is moved far enough to bring the roove or recess 280, into enga ment wit the detent, 281, the latter wil spring into place and again lock the auxiliary piston. This construction will, therefore, enable the operator to actuate one of said istons, and the brake mechanism connecte therewith, as the brakes for the rear wheels, or both pistons, and the brakes for all four wheels, as may be required.

The form of our invention illustrated in F ig. 6 is not specifically claimed herein, Ythis embodiment being specifically claimed in another application for Letters YPatent of the United States filed by us January 31, 1925, and given Serial No. 5498, the said application being a division ofV this ap'- plication.

What we claim and desire to secure by Letters Patent is 1. The combination of apower actuator comprising a cylinder closed at each end, a main piston, and an auxiliary piston both movable in both directions in said cylinder, the said cylinder being provided with a communicating passage connecting the opposite end portions of. the cylinder on the outer facesV of the pistons, means for-l establishingvdiferential pressures within the central portion of the cylinder between said pistons and the connected end portions thereof, including reversing valve mechanism constructed to maintain said pistons in a balanced condition when the reversing valve mechanism isfin 'an interjacent 'position between its limits of movement, and brake mechanism operatively connected with said pistons. i

2. The combination of a ower' 'actuator comprising a cylinder close at each end, a. main piston, and an auxiliary piston movable in both directions in said cylinder,; the said cylinder being provided with a communicating passage connecting the opposite end portions of the cylinder on the Y outer faces of the pistons, means for es- `tablishing differentialV pressures within the central portion of the cylinder between said plstons and the connected end portions tions, one of said thereof, including reversing valve mechanism constructed to maintain said pistons Ain Ya balanced condition `when the reversing valve mechanism is in aninterjacent position between itslimits of movement, brake mechanism operatively connected with one ci said pistons, and independent brake mechanism independently connected with the other piston. Y

3. In a four wheel brake mechanism for automobiles, the combination with a power actuator, comprising a cylinder, a pair of double acting pistons located therein, a communicating passage connecting the end portions of the cylinder on the outer faces of the pistons, means for establishing differential pressures in the central portion of the cylinder between said pistons and said connected end spaces, including" a reversingvalve mechanism constructed to maintain said pistons 1n a balanced condition when in interjacent position between the limits' anism for the front wheels connected with the other piston, and an operator operated device connected with said valve mechanisms.

4. `The combination with a power actuator comprising a cylinder, a pair of double acting pistons working therein, said cylinder having a communicating passage connecting the end portions of the cylinder on the outer faces of said pistons,'means for establishing differential pressures-in the central portion of the cylinder between said pistons and said connected end portions, includin'g reversing valve mechanism YYconstructed to maintain said pistons in balanced conditions whenthe valve mechanism is in an interjacent position between the limits of lits movement, said val-ve Imechanism being provided with a movable part connected with one of said pistons by means providing lost motion, brake mechanism connected with each of said pistons, and an operator operated part connected to said reversing valve mechanism whereby on the failure of power, said pistons may be directly actuated by said operator operated part.

5. The combination of an actuator comprising a cylinder closed at its ends, of double acting pistons in said cylinder, said cylinder being provided with a communciating passage connecting the end portions on the outer faces ofV said pistons, means-for establishing differential pressures in the central portion of the cylinder between said pistons and the said connected end porpistons beingprovided withreversing valve mechanism including a part connected with the said piston by means permitting lost motion, a hollow piston rod connected with said main piston and extendl a pair i ing through the adjacent end of the cylinder, an independent piston rod connected to the other piston and extending through the adjacent end of the cylinder, a longitudinally movable valve sleeve connected with the movable part of said reversin'g valve and having portions extending longitudinally through both of said hollow piston rods, brake mechanism connected with each of said piston rods, an operator operated part, and connections therefrom to said sleeves, and a retracting spring for said operator operated part. p

6. The combination with a oWer actuator, comprising among its mem ers, a' power cylinder closed at both ends, a pair of double acting pistons in said cylinder, said cylinder being provided with a communicating passage for connecting the en d portions of the cylinder on the outer `faces of said pistons, la hollow piston rod extending throu h one end of the cylinder and connecte to one of said pistons, and provided with an inlet aperture, a longitudinally lmovable reversing valve sleeve extending through said piston and the hollow piston rod thereof, and provided with separated ports, certain of said ports being connected to said inlet aperture, and other ports separated therefrom being adapted to be connected to an outlet passage from said cylinder, said piston being provided with ports and passages for `connecting either of said separated portswith the portion of the cylin- ,der between the pistons and the connected portions of the cylinder at the opposite ends thereof, valves carried by said sleeve for controlling said piston ports and sleeve ports, and adapted when in an interjacent position between the limits of movement of said sleeve with respect to said piston to maintain the pistons in balancedconditiom a piston rod connected with the other of said pistons, brake mechanisms connected with said piston rods, an operator operated part, andconnections between the same and.

said sleeve.

7. The combination with a power actuator, comprising among its members, a power cylinder closed at both ends, a pair of double acting pistons in said cylinder, said cylinder being provided with a comunicating passage for connecting the end portions of the cylinder on the outerl faces of said pistons, a hollow piston rod extending through one end of the cylinder and connected to one of said pistons, and provided with yan inlet aperture, a longitudinally movable reversing valve sleeve extending through said piston and the hollow piston rod thereof, and provided with separated ports, certain of said ports being connected to saidinlet aperture,

and other ports separated therefrom being adapted to be connectedato an outlet passage from said cylinder, said pistonrbeing provided with ports and passages for connecting either of said separated ports with the portion of the cylinder between the pistons and the connected portions of the cylinder atthe opposite ends thereof, valves carried by said sleeve for controlling said piston ports and sleeve ports, and adapted when in an interjacent position between the limits of movement of said sleeve with respect to said piston to maintain the pistons in balanced condition, a hollow piston rod connected with the other-of said pistons, brakemechanisms connected with said piston rods, said sleeve extending longitudinally through the hollow piston rod of the other piston, and said latter piston rod being provided with an outlet aperture adapted to communicate with said sleeve, an operator operated part` and connections therefrom to said sleeve fr actuating the valve mechamsm.

8. The combination with a power actuator, comprisingr among its members', a power cylinder closed at both ends, a pair. of double acting pistons in said cylinder, said cylinder being provided with a communieating passage for connecting the end portions of the cylinder on the outer faces of said pistons, a hollow piston rod extending through. one end of the cylinder and connected to one of said pistons, and provided with an inlet aperture, a longitudinally movable reversing valve sleeve extending through said piston and the hollow piston rod thereof, and provided with separated ports, certain of said ports being connected to said'inlet aperture, and other ports separated therefrom being adapted to be connected to an outlet passage from said cylinder, said pistons being provided with ports and passages for connecting either of saidv separated poi-ts with the portion of the cylinder between the pistons and the connected portions of the cylinder at the opposite ends thereof, valves carried by said sleeve for controlling said piston port and sleeve port, and adapted when in an interjacent position between the limits of move ment of said sleeve with respect to the piston to maintain the said pistons-in balanced condition, a pistonk rod connected to the other of said pistons, brake mechanisms connected with said piston rods, an operator operated part, connections therefrom to said sleeve including a part passing through one of said hollow piston rods, said piston rod being longitudinally slotted tdpermit of the movement of said connecting part with respectthereto.

9, The combination with a power actuator comprising a cylinder, a pair of double acting pistons movable therein, said cylinder being provided with a communicating pasmeans for establishing differential pressures in the central portion of the cylinder between said pistons and said connected end portions, including reversing valve mechanism constructed to maintain said pistons in balanced condition when in an interjacent position between the limits of movement of the valve mechanism, brake mechanism operatively connected with 4one of said pistons, independent brake mechanism connected with the other piston, an operator Operated device connected with said reversing valve mechanism, and means for holding one of said pistons from movement in the cylinder to permit 4the operation of the other piston and the brake mechanism connected therewith without operating the brake mechanism connected with the piston so held from movement.

10. The combination with a power actuator comprising a cylinder, a pair of double acting pistons movable therein, said cylinder being provided with a communicating lpassage connecting the end portions of the cylinder on the outer faces of said pistons, means for establishing differential pressures in the central portions of the cylinder between said pistonsand said connected end portions, including reversing valve mechanism constructed to maintain said pistons in balanced condition when in an interjacent position between the limits of movement of the valve mechanism, brake mechanism operatively connected with one of said pistons, independent brake mechanism connected with the other piston, and an operator operated part for effecting the operation of one of said pistons and the brake mechanism connected therewith or both of said pistons and their connected brake mechanisms simultaneously, as required.

11. The combination with a power actuator comprising a cylinder, a pair of double acting pistons movable therein, said cylinder being provided with a communicating passage connecting the end portionsof the cylinder on the outer faces of said pistons, means for establishing differential pressures in the central portion of the cylinder between said pistons and said connected end portions, including reversing valve mechanism constructed to maintain said pistons in balanced condition when in an interj'acent position between the limits of movement of the valve mechanism, brake 'mechanism op-- eratlvely connected with one of said pistons', independent brake mechanism connected with thel other piston, a normally closed auxiliary valve -in said communicating passage for enabling one of said pistons and its connected brake mechanisms to be operated without the other when desired, an operator operated part connected with the reversing valve mechanism, and means operatively I connected with said operator operated part vnected with the other for holding said auxiliary valve in open position to effect the simultaneous actuatlon of both pistons and their connected brake mechanisms. 12. The combination withapower'l actuator comprising a cylinder, a pair of doubleacting pistons movable therein, said cylinder being provided with a communicating passage connecting the end portions of the cyllnder on the louter faces of said pistons, means for establishing differential pressures in the central portion of the cylinder between said pistons and said connected end portions, including reversing valve mechanism constructed to maintain said pistons in balanced condition when in, an interjacent position between`the limits of movement 'of the valve mechanism, brake mechanism operatively connected with one of said pistons, independent brakemechanism connected with the other piston, Closed spring actuated auxiliary valve located in the communicating passage between the ends of the cylinders and adapted to be opened automatically against the action of its spring whenV the reversing valve is in one position, a movable cam. for opening said auxiliary valve and holding it in open 4position, an operator operated device, and connections therefrom to said reversing valve and to said cam.

13. The combination with a power actuator comprising a cylinder, a pair of double acting pistons movable therein, said cylinder being provided with a communicating passage connecting the end portions of the cylinder on the outer faces of said pistons, means for establishing differential pressures in the central portion of the cylinder between said pistons and said connected end portions, including reversing valve mechanism constructed to maintain said pistons in balanced condition when in an intercent position between the limits of movement of the valve mechanism, brake mechanism operatively connected with one of said pistons, independent brake mechanism -conpiston, a normally closed spring actuated auxiliary valve located in the communicating passage between the ends of the cylinders and adapted to be opened automatically against action of its spring when the reversing valvel is in one position, an operator operated device, connections therefrom to said reversing valve, and an adjustable cam connected with said operator operated devicefor actuating said auxiliary valve to open the same said cam being normally out of operative relation withK said auxiliary valve and permitting the operation of said reversing. valve without bringing the cam into operative relation with the said auxiliary valve. 14. The combination with a power actuator comprising a cylinder, a pair of double acting pistons movable therein, said cylinder being provided with acommunicating passa e connecting the end .portions lof the cylin er on the outer faces of said pistons, means for establishing diierentialpres'sures in theeentral portion of (flle cylinder between said pistonsand sai connected end portions, including reversing lvalve mecha.- nism constructed to maintain said pistons in balanced condition -when in an inter'- jacent position .between the limits of movef ment of the valye mechanism, brake mechanism operatively connected with one of said pistons, independent brake mechanism connected with 'the other piston, a normally closed spring actuated auxiliary valve located in the passage between the ends ofthe cylinders and adapted to be opened automatically against the action of vits sprin when 'the reversxngvalve is in lnally movable rod, and a cam'for actuating said auxiliary valve to open the same, adjustably secured to said-rod and normally out of operative relation with said auxiliary valve.

' `emana sBR'AGG.

VICTOR w, KLIESRATH.

In testimony4 whereof we ailix our signatures. i

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