US2709422A

US2709422A - Hydraulic motors

Info

Publication number: US2709422A
Application number: US219187A
Authority: US
Inventors: Bray Peter Eric
Original assignee: Integral Ltd
Current assignee: Lucas Support Services Ltd
Priority date: 1950-04-26
Filing date: 1951-04-04
Publication date: 1955-05-31
Anticipated expiration: 1972-05-31

Description

May 31, 1955 REBRAY 2,709,422

HYDRAULIC MOTORS Filed April 4, 1951 3 Sheets-Sheet l 112 1 ya i 111 125 106 l fi 102 I 179' F l: w I: Z7

-l 0 a0 52? I00 m May 31, 1955 P. E. BRAY 2,709,422

HYDRAULIC MOTORS Filed April 4, 1951 s Shets-$heet 2 May 31, 1955 P. E. BRAY 2,709,422

' HYDRAULIC MOTORS I iled April 51, 1951 s Sheets-Sheet s HYDRAULIC MOTORS Peter Eric Bray, Compton, England, assignor to Integral Limited, Wolverhampton, England, a company of Great Britain Application April 4, 1951, Serial No. 219,187

Claims priority, application Great Britain April 26, 1950 3 Claims. (Cl. 121-120) This invention provides a hydraulic motor comprising a shaft, two sets of cylinders disposed radially in relation to the shaft, each cylinder of the one set being paired with a cylinder of the other set, two cams on the shaft, one coacting with and driven by the pistons in the cylinders of one set and the other coacting with and driven by the pistons in the cylinders of the other set, the two cams being of the same shape but being disposed in antiphase on the shaft, a set of reciprocating control valves, each coacting with a cylinder of the one set and its paired cylinder of the other set and arranged, as it is reciprocated, alternately to connect said cylinders one to a pressure inlet and the other to an exhaust outlet, mechanism driven by the shaft for imparting forward strokes to the valves in succession and springs for imparting return strokes to the valves, the valves cooperating with the cylinders so that at all times they connect to pressure those cylinders in which the pistons are moving inwards and to exhaust those cylinders in which the pistons are moving outwards.

An advantage of this arrangement is that seizure of any sliding part will not interfere with rotation of the shaft. Thus, if a piston seizes it is almost certain to seize at the end of the discharge stroke, i. e. at its outermost position in which it cannot obstruct rotation of its associated cam. Again, if one of the valves seizes, its spring Will be unable to return it and the associated pair of cylinders will be rendered ineffective. Furthermore, if the power is cut ofi, the motor can free-wheel indefinitely, since the pistons will be pushed outwards by the cams and there Will be nothing to return them.

These features are of value in the case of duplicated hydraulic systems, particularly for aircraft, since the motors may be mounted on a common shaft without seizure of one, or failure of the pressure supply to one, preventing the other motor from continuing to operate.

In the preferred form of hydraulic motor according to the invention, the spaces occupied by the return springs of the valves are connected to a discharge outlet through a spring-loaded non-return valve, so that liquid leaking into those spaces past the valves is maintained at a substantial pressure, e. g. 40 lbs/sq. in. If therefore any of the valves should tend to become sticky, the pressure of the liquid will assist the spring in maintaining it in contact with the swash plate or other valve-actuating member.

Two embodiments of hydraulic motor according to the invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a sectional view of the first form of motor, taken on the line II in Fig. 2,

Fig. 2 is a right hand end elevation of the motor, partly in section on the line lIlI in Fig. 1,

Fig. 3 is a right hand end elevation of the motor, with the end cover plate, pistons, cams and valves removed, partly in section on the line III-III in Fig. 1,

Fig. 4 is a plan view of the cylinder block,

tes Patent 2,709,422 Patented May 31, 1955 Figs. 5 and 6 are sections respectively on the lines V-V and VIVI in Fig. 4,

Fig. 7 is an enlarged longitudinal section through one of the valve sleeves,

Figs. 811 are sections taken respectively on the lines VIII-VIII, IXIX, XX and XI-XI in Fig. 7,

Fig. 12 is a diagrammatic vertical section through the second form of motor, and

Fig. 13 is a section on the line XIIIXIII in Fig. 12.

Like reference numerals designate like parts throughout the figures.

Considering first of all the hydraulic motor shown in Figs. 1-11, the motor casing consists (Fig. 1) of three parts, viz. a cylinder block 99 and two end cover plates 100, 101. To the cover plate 100 are fitted two

unions

102 and 103. The union 102 communicates, via a pas sage 104, with an annular groove 105, and the other union 103 communicates, via a similar passage, not shown, with an annular groove 106.

The motor comprises a shaft carrying a pair of cams 7'7, 76 spaced at 180 (i. e. in antiphase) on the shaft. Associated with the cam 76 is a set of six cylinders, each containing a piston 78, these cylinders being located radially in relation to the shaft 75. A similar set of six cylinders each containing a piston 79, is associated with the cam 77. Associated with each aligned pair of cylinders is one of six distributing valves 80, each of which is held by a spring 81 in contact with a swashplate 182 on the shaft 75.

Each of the distributing valves is reciprocably mounted in a valve sleeve 107 alongside which run four longitudinal grooves in the cylinder body. Two of these grooves 108, which communicate with the annular groove 106 (see Fig. 3) extend for nearly the whole length of the valve sleeve 107 (see Fig. 4) while the other two grooves 109, which are shorter, communicate with the annular groove 105.

As will be apparent from Figs. 4-6 the bore 110 containing each valve sleeve 107 is adjacent to the pair of aligned

cylinders

111, 112 which the associated distributing valve 80 is to control, the cylinders 111 being those containing the pistons '79 and the cylinders 112 those containing the pistons 78. The cylinder 111 communicates (Fig. 5) by a passage 113 with a port 114 in the bore 110, and the cylinder 112 communicates (Fig. 6) by a passage 115 with a port 116 in the bore 110.

As indicated in Figs. 7-11, the valve sleeve 107 has a pair of ports 117 which communicate with the grooves 108, a pair of ports 118 which communicate with the grooves 109, a port 119 which communicates with the port 116 and the cylinder 112 and a port 120 which communicates with the port 114 and the cylinder 111.

Turning now to Fig. 1, the distributing valve 80 has an annular groove 121,- communicating by a passage 122 with an annular groove 123, and an annular groove 124, communicating by a passage 125 with an annular groove 126. The valve 30 shown in Fig. l is in its extreme left hand position. The right hand end of the groove 121 then communicates with the ports 117 in the valve sleeve, and therefore with the grooves 108, annulus 106 and union 103, while the groove 123 communicates with the

ports

119, 116 and therefore with the cylinder 112; The right hand end of the groove 126 communicates with the ports 118, and therefore with the grooves 109, annulus 105 and union 102, While its left hand end communicates with the

ports

120, 114 and therefore with the cylinder 111. Therefore, assuming the union 102 to be connected to pressure and the union 103 to be connected to exhaust, pressure liquid will be admitted to the cylinder 111 to urge its piston 79 inwards to drive the shaft 75, while the piston 78 will be expelling liquid from its cylinder 112 to exhaust.

When the swashplate 182 has moved the valve 80 to its extreme right hand end position these connections to the associated cylinders will be reversed. The groove 121 remains in register with the ports 117, and therefore with the union 103, but the groove 123 is now brought into register with the ports 12% 114 and therefore with the cylinder 111, which is now connected to exhaust. The groove 126 remains in register with the ports 118, and therefore with the union 132, but is brought out of register with the ports 129, 114-. The groove 124, however, is brought into register with the

ports

119, 116 so connecting the cylinder 112 to pressure.

. The valve 86) is thus reciprocated so as periodically to reverse the pressure and exhaust connections to the aligned pair of cylinders 111, 12 with which it is associated. It will readily be understood that, if the pressure and exhaust connections to the unions 1E2, 103 are reversed, the motor will be driven in the reverse direction.

As the valves 89 are reciprocated by the swashplate, therefore, the aligned

cylinders

111, 112, one in each set, associated with each valve are alternately connected to pressure and exhaust.

If it is desired to reverse the direction of rotation of the motor shaft 75, the external pressure and exhaust connections to the unions r02, Hi3 are reversed, e. g. by means of an external change-over valve. One end 175 (Fig. 1) of the motor shaft 75 projects from the cover plate 101 and is splined for connection to a member to be driven by the motor.

Liquid escaping past the valves 89 collects in the spaces 127 (Fig. 1) housing the valve springs 81 and thence passes into an annulus 125. This liquid can fiow from the annulus 128, through a non-return valve 129, loaded by a spring 139, to a space 131 communicating with a discharge outlet 132 (Fig. 2).

If a piston seizes it is almost certain to seize at the end of its discharge stroke, in which position it cannot obstruct the movement of the associated cam. The valves 80 are urged into contact with the swashplate 182 not only by their return springs 31, but also by the back pressure of leakage liquid which is maintained in the spaces 127 by the spring loaded valve 129, which may be 40 lbs./ sq. in. The valves 89 are therefore not likely to stick, but, if a valve 86 does stick, its spring 33. will be unable to return it and the associated pair of aligned

cylinders

111, 112 will be rendered ineffective.

As an alternative to the use of an external change-over valve for reversing the direction of rotation of the motor, this may be achieved by alterin the position of the swashplate 132 in relation to the shaft 75', the swashplate being moved through zero position so that the phase relationship between the valves 8% and their respective pistons 78, '79 is appropriately changed.

Thus, in one such arrangement shown in Figs. 12 and 13, the motor shaft is divided, the swasnplate 132 being pivoted at 20 on the portion 2."? of the shaft which carries the cams 76, 7'7 and having an extension 21 fitted with inwardly projecting pins 22 engaging inclined slots 23 in a sleeve 24 keyed to, and mounted to slide on, another portion 375 of the shaft which proiects from the motor and serves to transmit the drive from the motor. The sleeve 24 has a circular groove 25 in it engaged by inwardly projecting pins 26 on a pair of pivoted levers 27 which can be rocked, by a valve stroke control lever 23 external to the motor, to effect axial movement of the sleeve 24 on the shaft and so to vary the inclination of the swashplate 132 to the shaft.

The valves 3% are shown in Fig. 12 as reciprocating in fixed sleeves 33 having ports 34 communicating with a pressure supply line 35 and other ports 36 communicating with a return line .37. As will be readily seen lands on the valves coact with the ports 3 36 so that, as each valve 39 reciprocates, its associated

cylinders

111, 112 will be alternately connected to pressure and exhaust.

The ends of the valve sleeves 33 which contain the valve springs 81 communicate with an annulus 128 which, in turn, communicates, via a spring-loaded ball valve 129, with a discharge outlet 38. The ball valve 129, as above described, maintains a liquid pressure of some lbs./ sq. in. on the ends of the valves 39 loaded by the springs 81.

If desired, the valves 86 can be disposed radially instead of parallel to the motor shaft and operated by a cam instead of by a swashplate.

What I claim as my invention and desire to secure by Letters Patent is:

l. A hydraulic motor, comprising a casing, a pressure inlet to said casing, an exhaust outlet from said casing, a shaft mounted to rotate in said casing, two sets of cylinders in said casing disposed radially in relation to the shaft, each cylinder of the one set being paired with a cylinder of the other set, pistons mounted to reciprocate in the cylinders, two cams on the shaft, one c0- acting with and driven by the pistons in the cylinders of one set, and the other coacting with and driven by the pistons in the cylinders of the other set, the two cams being of the same shape but being disposed in antiphase on the shaft, conduits in the casing for affording passage for liquid between the cylinders and the pressure inlet and exhaust outlet, a set of control valves mounted to reciprocate in said casing, each control valve coacting with a cylinder of the one set and its paired cylinder of the other set and arranged, as it is reciprocated, to control said conduits so as alternately to connect said cylinders one to the pressure inlet and the other to the exhaust outlet, mechanism driven by the shaft for imparting forward strokes to the valves in succession, cavities in said casing, springs in said cavities for imparting return strokes to said valves, a discharge outlet from the casing, a discharge conduit connecting all of said cavities to said discharge outlet, a non-return valve in said discharge conduit, and a spring loading said non-return valve to maintain under substantial pressure liquid leaking past said valves into said cavities, said control valves cooperating with said conduits so that at all times they connect to pressure those cylinders in which the pistons are moving inwards and to exhaust those cylinders in which the pistons are movingoutwards.

2. A hydraulic motor, comprising a casing, a pressure inlet to said casing, an exhaust outlet from said casing, a shaft mounted to rotate in said casing and comprising a first portion disposed wholly within the casing and a second portion projecting from the casing, two sets of cylinders in said casing disposed radially in relation to the shaft, all of said cylinders occupying fixed positions in said casing and each cylinder of the one set being paired with a cylinder of the other set, pistons mounted to reciprocate in the cylinders, two cams on said first portion of the shaft, one coacting with and driven by the pistons in the cylinders of one set, and the other coacting with and driven by the pistons in the cylinders of the other set, the two cams being of the same shape but being disposed in antiphase on the shaft, conduits in the casing for affording passage for liquid between the cylinders and the pressure inlet and exhaust outlet, at set of control valves mounted to reciprocate in said casing in a direction parallel to said shaft, each control valve coacting with a cylinder of the one set and its paired cylinder of the other set and arranged, as it is reciprocated, to control said conduits so as alternately to connect said cylinders one to the pressure inlet and the other to the exhaust outlet, a swashplate, pivotally mounted on said first portion of the shaft, for imparting forward strokes to the valves in succession, springs for imparting return strokes to the valves, a member projecting from the swashplate, a sleeve keyed to and mounted to slide on said second portion of the shaft, a pin on said member engaging an inclined slot in said sleeve and manually operable means external to the casing for imparting axial movement of the sleeve in relation to the shaft and thereby effecting angular adjustment of the swashplate in relation to said shaft from one side to the other of a zero position in which said swashplate is perpendicular to said shaft, said valves cooperating with said conduits so that at all times they connect to pressure those cylinders in which the pistons are moving inwards and to exhaust those cylinders in which the pistons are moving outwards.

3. A hydraulic motor, comprising a casing, a pressure inlet to said casing, an exhaust outlet from said casing, a shaft mounted to rotate in said casing, two sets of cylinders in said casing disposed radially in relation to the shaft, all of said cylinders occupying fixed positions in said casing and each cylinder of the one set being paired with a cylinder of the other set, pistons mounted to reciprocate in the cylinders, two cams on the shaft, one coacting with and driven by the pistons in the cylinders of one set, and the other coacting with and driven by the pistons in the cylinders of the other set, the two cams being of the same shape but being disposed in antiphase on the shaft, conduits in the casing for affording passage for liquid between the cylinders and the pressure inlet and exhaust outlet, a set of control valves mounted to reciprocate in said casing in a direction parallel to said shaft, mechanism on said shaft for imparting forward strokes to the valves in succession, springs for imparting return strokes to the valves, each valve coacting with a cylinder of the one set and its paired cylinder of the other set and said conduits including an annular passage communicating with the pressure inlet, an annular passage communicating with the exhaust outlet,

grooves leading from each of said annular passages to the vicinity of each valve, and a passage leading from each cylinder of each pair to the vicinity of the associated valve, and sleeves surrounding the valves, each sleeve having therein ports, communicating respectively with the grooves leading to the two annular passages and with the passages leading from the associated pair of cylinders, and each valve having therein ports and passages arranged, as the associated valve reciprocates, to cooperate with the ports in the sleeve alternately to connect to the groove leading to the annular passage communicating witht he pressure inlet the cylinder in which the piston is moving inwards and to the groove leading to the annular passage communicating With the exhaust outlet the cylinder in which the piston is moving outwards.

References Cited in the file of this patent UNITED STATES PATENTS 701,300 Crain June 3, 1902 1,151,602 Minue Aug. 31, 1915 1,466,276 Egersdorfer Aug. 28, 1923 1,582,076 Page Apr. 27, 1926 2,326,464 Jones Aug. 10, 1943 2,454,578 Smith Nov. 23, 1948 2,597,420 Westbury May 20, 1952 FOREIGN PATENTS 15,221 Great Britain Aug. 13, 1895