US3447423A

US3447423A - Rotary fluid pressure actuators

Info

Publication number: US3447423A
Application number: US571550A
Authority: US
Inventors: Howarth Padgett Henry
Original assignee: MATHEWS ENG CO Ltd E
Current assignee: E MATHEWS ENG Co Ltd; MATHEWS ENG CO Ltd E
Priority date: 1966-08-10
Filing date: 1966-08-10
Publication date: 1969-06-03
Anticipated expiration: 1986-06-03

Description

June 3, 1969 H. P. HENRY ROTARY FLUID PRESSURE ATUATORS Sheet of 4 Filed Aug. 10, 1966 a a %E June 3, 1969 H P HENRY 3,447,423

ROTARY FLUID PRESSURE ACTUATORS Filed Aug. o, 1966 Sheet Z of 4 June 3, 1969 H. P. HENRY ROTARY FLUID PRESSURE ACTUATORS Sheet Filed Aug. 10, 1966.

United States Parent Ofiice 3,447,423 Patented June 3, 1969 U.S. CI. 91-395 2 Clams ABSTRACT OF THE DISCLOSURE A rotary fluid pressure actuator comprises at least one double acting piston mounted in a cylinder having end closures, an output shaft mounted intermediate the ends of the cylinder with its axis normal to and ofiset from that of the cylinder, bearings for the output shaft, *a rack on the piston, a gear pinion on the output shaft engaging the rack of the piston, ports in the end closures of the cylinder for the admission of fluid under pressure to move the piston and rotate the output shaft and for the escape of fluid, the ports in the end closures comprsing passages parallel to the aXis of the cylinder, and means carried by the piston to obstruct the passages comprising pins arranged to enter and restrict flow of fluid through the passages as the piston approaches the end of its stroke. The pins having a maximum diameter less than the diameter of the passages providing a clearance constituting an escape path for liquid which is increasingly restricted as the pins move into the passages.

This application is a continuation-in-part application of -my copending application Ser. No. 519,@33, filed Jan. 6, 1966, now abandoned.

This invention relates to rotary fluid pressure actuators of the kind in which a double acting piston mounted in a cylinder, or a pair of double acting pistons mounted in juxtaposed and mutually parallel cylinders is or are provided with a rack or racks engaging a gear pinion on an output shaft mounted in bearings so as to extend normal to the axis of the cylinder or to the axes of both cylinders and to be oflset from the said aXis or axes. By supplying fluid under pressure to the cylinder or cylinders the output shaft is caused to rotate, the angle through which it rotates depending on the stroke of the piston or pistons and the pitch circle diameter of the pinion.

It is one object of the invention to provide improved cushioning means for clamping the move-ment of the piston or pistons at the end of their strokes.

A fluid pressure actuator according to the invention comprises at least one double acting piston mounted in a cylinder having end closures, an output shaft mounted intermediate the ends of said cylinder with its axis normal to and oflset from the aXis of the said cylinder, bearings for said output shaft, a rack on said piston, a gear pinion on said output shaft engaging the rack on said piston, ports in the end closures of said cylinder for the admission of fluid under pressure thereto to move the piston and thereby rotate the output shaft and for the escape of said fluid therefrom, said ports in the end closures comprising passages parallel to the aXis of the cylinder, and means carried by the piston to obstruct the said passages comprising pins arranged to enter, and restrict the flow of fluid through the said passages as the piston approaches the ends of its stroke.

The invention is hereinafter described with reference to the accompanying drawings, which show examples of rotary fluid pressure actuators according to the invention and in which:

FIGURE 1 is a side elevation, partly in section, of one form of fluid pressure actuator according to the invention having two pistons acting in parallel juxtaposed cylinders;

FIGURE 2 is a section through one of the head mem- `bers of the cylinders, on the line 2-2 of FIGURE 1;

FIGURE 3 is a section through the other head member, on the line 3-3 of FIGURE 1;

FIGURE 4 is a section on the line 4-4 of FIGURE 1;

'FIGURE 5 is a longitudinal section through another form of fluid pressure actuator according to the invention having a single piston acting in a single cylinder; and

FIGURE 6 is a transverse section on the line 6-6 of FIGURE 5.

Referrng to FIGURES 1 to 4 of the drawings, the actuator comprises a central housing 10 which supports a shaft 11 carrying a pinion 12, two

tubes

13 and 14 mounted side-by-side and passing through the housing 10, and a pair of

head members

15 and 16 each closing the two

tubes

13 and 14 at one end. The

head members

15 and 16 are formed with spigots 17 which enter the ends of the

tubes

13 and 14 and are grooved circumferentially to receive packng rings 18 engaging the walls of the tubes. The central portions of the

tubes

13 and 14 are cut away inside the housing 10 to accommodate the pinion 12, and packing rings 19 mounted in grooves in the housing engage the tube walls to maintain fluidtight joints.

The

tubes

13 and 14 constitute cylinders in which are reciprocable pistons 21 and 22 each having a packing 23 at each end to engage the cylinder wall, the central parts of the pistons being formed as racks 24 meshing with the pinion 12.

Each of the

head members

15 and 16 is formed with two bores 2'5 and 26 coaxial respectively with the

tubes

13 and 14, the said bores opening into the cylinders and being closed at their open ends. The

bores

25 and 26 in the head member 15 communicate respectively with

transverse bores

27 and 28 in that head member, and the

bores

25 and 26 in the head member 16 communicate with

transverse bores

29 and 31 in that head member, the

bores

27 and 28, and the

bores

29 and 31 being interconnected respectively by further pairs of

bores

32, 33 and 34, 35, each of the

bores

32, 33, 34 and 35 containing a relief valve 36 and the relief valves in the

bores

32, 34 opening in the opposite direction to the relief valves in the

bores

33 and 35.

The

bores

27 and 28 in the head 'member 15 have external connections at 37 and 38, respectively, and are connected by tubes extending between the head members, which tubes are shown at 39 and 40 in FIGURE 4, and by passages 41, 42 in the head member 16, to the

bores

31 and 29 respectively in the said head member 16, the remaining bores being all stopped at their outer ends as shown.

Thus, if the external connections at 37 and 38 are coupled through a selector valve to a source of fluid pressure and to a low pressure reservoir or exhaust, one end of one cylinder and the opposite end of the other cylinder can be simultaneously connected to the source of pressure to move the pistons so as to rotate the pinion in one direction, the other ends of the two cylinders being connected to low pressure or exhaust, and the connections can be reversed to reverse the direction of rotation of the pinion.

Each of the pistons 21 and 22 is formed at each end with a coaxial recess 43 havng a flat inner end. In each recess 43 is mounted the disc-shaped head 44 of a pin 45 which projects from the end of the piston, the head 44 being retained in the recess by a bush 46 which surrounds the pin 45 and is held in position in the recess by a clip ring 47. The head 44 on the pin 45 is of smaller diameter than the recess, and the pin 45 itself is of smaller diameter than the bore of the bush 46, so that the pin 45 is free to move in a direction normal to the axis of the piston. A ring 48 of elastomeric material, or some other resiliently deformable member such as a spring Washer, is interposed between the bush 46 and the head 44 of the pin to provide frictional restraint of transverse movement of the pin.

Each pin 45 is tapered at its free end, as indicated at 49, and has a maximum diameter such that it has only a very small clearance in the

bore

25 or 26 in the cylinder head member. A bypass passage 51, controlled by a nonreturn valve 52, provides a flow path between each of the

bores

27, 28, 29 and 31 and the respective cylinder ends to which they are connected by the

bores

25 and 26, to provide free flow of fluid into the cylinder ends when the

said bores

25 and 26 are obstructed by the pins 45.

As the pistons 21 and 22 move to-and-fro in the

cylinders

13 and 14, each piston, as it approaches either end of its stroke causes the pin 45 on the approaching end thereof to enter the

coaxial bore

25 or 26 in the

head member

15 or 16. Fluid at this time is flowing outwardly through the said

bore

25 or 26, so that its outward flow is restricted and the final movement of the piston is damped or cnshioned.

The ability of the pins 45 to move in a direction normal to the axes of the pistons enables them to align themselves with the said

bores

25 and 26, the pins, once they have aligned themselves, being retained in their aligned positions by the frictional restraining means 48. During initial movement of the pistons away from the ends of the cylinders, fluid enters the latter through the bypass passages 51, thus avoiding restriction of inward flow during this movement.

The relief valves 36 in the

head members

15 and 16 enable fluid to pass directly from those of the

passages

27, 28, 29 or 31 which are serving at any time as inlets to the remaining passages of that group which are serving as outlets, thus reducing the risk of damage to the actuator as the result of external overloads applied to the output shaft.

Referring now to FIGURES and 6 of the drawngs, the rotary fluid pressure actuator comprises a cylinder 55 in the form of a tube 56 closed at its ends by

closure plates

57 and 58 Secured to the said tube by screws 59 entering holes in lugs (not shown) at the ends of the tubes. The

closure plates

57 and 58 are formed with spigots 61 which enter the ends of the tube. A central body member 62 having a through bore is press fitted on to the cylinder 55, the central part of the cylinder, which lies in the bore of the body member 62, having an external diameter less than that of one end portion of the cylinder and greater than that of the other end portion of the said cylinder. The central body member 62 has a partcylindrical projection 63 on one side thereof, in which is formed a transverse bore 64 normal to the axis of the cylinder 55 and having its axis oflset from the axis of the said cylinder, the two bores in the body member 62 breaking into each other as shown in FIGURE 5, and the cylinder 55 being cut aaway at 65 to connect the bore 64 with its interier.

A piston 66 slidable in the cylinder 55 is cut away on one side to form a flat surface on which is formed a rack 67, the ends of the piston being grooved circumferentially to receive packing rings 68 making a fluid-tght joint with the cylinder wall. A shaft 69, rotatable in

bearing bushes

71 and 72 in the transverse bore 64, has formed integral with it a pinion 73 meshing with the rack 67. The hearing bush 72 is located in the transverse bore 64 against a shoulder 74, and the hearing bush 71 is held in position by a plate 75 secured to a sideface of the projection 63 by screws 76.

Packng rings

77, 78 and 79 ensure scaling of the transverse bore 64 against the escape of lubricant which is placed in the said bore and in the central portion of the cylinder 55. A lightly loaded relief valve 81,

.4 in a passage leading from the transverse bore 64, prevents pressure from being built up in the cylinder, between the piston packings, due to leakage of working fluid past the packing rings 68.

In each end of the piston 66 there is formed a cylindrical recess 82, coaxial with a port 83 in the

adjacent closure plate

57 or 58, the recesses 82 being of greater diameter than the ports 83. In each of the recesses 82 there is mounted a plunger 84 having a head 85 which lies in the inner end of the recess, and a stem 86 which projects beyond the end of the piston, the stem portion of the plunger being of a diameter such that it fits with a very small clearance in the port 83 and the outer end of the said stern being tapered as shown at 87. The plungers 84 are retained in the recesses 82 by bushes 88 surrounding the stems 86 and held in position in the recesses 82 by clip rings 89, rings 91 of rubber or other elastomeric material, or spring washers, being positioned between the heads 85 of the plungers and the bushes 88 to urge them apart. Both the heads 85 and the bushes 88 have slight radial clearance in the recesses 82, so that the plungers 84 can move laterally to algn themselves with the ports 83, the said plungers being held frictionally in the positions which they take up due to the action of the resilient rings 91 urging their heads against the ends of the recesses.

The ports 83 are connected, through a control valve of conventional type, to a source of fluid pressure and an exhaust or drain, so that fluid under pressure can be supplied to either end of the cylinder 55 to move the piston towards the other end, the said other end then being connected to exhaust or drain. As the piston approaches the end of its stroke, the stem 86 of the appropriate plunger 84 enters the port 83 and restricts the escape of fluid from the cylinder, thus building up a back-pressure which cushions the final movement of the piston and substantially eliminates impact When it engages the end of the cylinder.

A bypass passage 9 2, controlled by a nonreturn valve 93, provides a flow path between the outer end of each port 83 and the adjacent end of the cylinder, which is not obstructed by the plunger 84, so that fluid under pressure can enter the cylinder freely at the commencement of a working stroke.

I claim:

1. In a rotary fluid pressure actuator comprising at least one double acting piston assembly mounted in a cylinder having end closures, an output shaft mounted intermediate the ends of said cylinder with its aXis normal to and offset from the axis of said cylinder, bearings for said output shaft, a rack on said piston, a gear pinion on the out-put shaft engaging the rack of the piston, ports in the end closures of said cylinder for the admission of fluid under pressure thereto to move the piston and thereby rotate the output shaft and for the escape of said fluid therefrom, said ports in the end closures comprising passages parallel to the axis of the cylinder, said piston assembly including means carried by the piston to obstruct said passages comprising pins arranged to enter and restrict the flow of fluid through said passages as the piston approaches the ends of its stroke, and said pins having a maximum diameter less than the diameter of the passages providing a clearance constituting an escape path for liquid which is increasingly restricted as the pins move into said passages, the improvement which comprises: said means carried by the piston assembly to obstruct said passages comprising an axial recess in said piston, a bush mounted in said recess, said pins having an enlarged head and a solid pin portion extending through the bore of said bush, the head of the pin having a smaller diameter than said recess and the pin having a smaller diameter than the bore of the bush so that the pin is free to move in a direction normal to the axis of the piston, and a ring composed of resilient deformable material interposed between the bush and the head of the pin to provide frictional restraint of transverse movement of the pin.

2. A rotary fluid pressure actuator according to claim 1 comprsing a pair of said double acting piston assemblies.

References Cited UNITED STATES PATENTS Sterrett 91-396 Ottestad 91--396 Becker 91-394 Stoltman et al 91--396 X Henkel 92-85 X Griffin 91-395 Huhtala 92-164 Steiner 92-68 6 3,125,120 3/1964 Hasbany 137 596.12 3,213,760 10/1965 Carr 91 395 3,247,767 4/1966 Aslam 91 396x FOREIGN PATENTS 5 631,332 11/1949 Great Britain.

%3,424 8/1963 Great Britain.

MARTIN P. SCHWADRON, Pr'mary Exam'ner.

10 IRVIN c. COHEN, Assistant Exam'ner.

U.S. c. X.R.