Involute cam actuator with piston drive

• US 4,966,067 A
• Filed: 02/27/1989
• Issued: 10/30/1990
• Est. Priority Date: 02/27/1989
• Status: Expired due to Fees

• Current Assignee: Sundstrand Corporation (Rtx Corporation)
• Original Assignee: Sundstrand Corporation (Rtx Corporation)
• Inventors: Ames, John, Lang, David J., Walsh, Richard E.
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): DENION, THOMAS E
• Application Number:
  US07/315,715
• Time in Patent Office: 610 Days
• Field of Search: 92/72, 92/73, 92/74, 92/129, 92/138, 92/146, 92/150, 92/151, 92/147, 74/55, 74/569
• US Class Current: 92/150
• CPC Class Codes: F01B 1/08 with cylinders arranged oppositely relative to main shaft and of "flat" type
• CPC Class Codes: F01B 2009/063 Mono-lobe cams
• CPC Class Codes: F01B 9/06 the piston motion being transmitted by curved surfaces
• CPC Class Codes: Y10T 74/18296 Cam and slide
• CPC Class Codes: Y10T 74/2107 Follower

Abstract

A mechanism for converting linear displacement of a piston to angular displacement of a shaft by positioning a cam in a recess of a unitary piston which is adapted for positioning by differential fluid forces applied to opposite ends of the piston. To provide a linear displacement drive for a shaft positioned to rotate about an axis perpendicular to the axis of the piston, a cam profile consisting of two symmetrical, opposite and identical involutes is employed.

Claims

1. A mechanism for producing a linear relationship between angular movement of a shaft and axial movement of a piston comprising:

a piston operating along an axis of a cylinder and having first and second fluid pressure faces at opposite ends thereof;

a recess in a central portion of said piston;

a shaft mounted for rotation about an axis that extends transversely to said cylinder axis and having fixed thereto a cam member which is mounted for angular movement about the shaft axis in said recess;

cam engaging surfaces mounted on said piston with an invariant spacing at opposite sides of the recess and in constant engagement with opposed sides of said cam member; and

said cam member having a shape such that linear movement of the piston has a linear relationship with the angular movement of said shaft through a stroke which extends from both sides of a central position of said piston whereby, upon an application of a fluid pressure on one of said first and second fluid pressure faces of said piston, the piston is linearly moved causing an associated cam engaging surface to engage the cam member and rotate said shaft.

2. A mechanism as defined in claim 1 wherein the cam surface has the shape of a pair of involute curves which each extend from a base circle of said involute.

3. A mechanism as defined in claim 2 wherein said involute curves are symmetrical, opposite and identical and the center of a base circle of the involute curves is coincident with the rotational axis of said shaft.

4. A mechanism as defined in claim 1 further including means for applying a differential fluid pressure to the opposite faces of said piston for controlling the linear movement of the piston from a central position in said cylinder to thereby produce the rotation of said shaft.

5. A mechanism as defined in claim 1, wherein the rotational axis of said shaft is perpendicular to the axis of said cylinder and located so that a line extending through points of engagement between the cam engaging surfaces and involute curves of the cam member is substantially tangent to a base circle of the involute curves.

6. A mechanism as defined in claim 1, wherein the cam engaging surfaces on said piston include rollers mounted for rotation about axes that are parallel to each other and to the rotational axis of the shaft, and wherein a plane defined by said roller axis is substantially tangent to a base circle of involute curves forming said cam engaging surfaces.

7. A mechanism for producing a linear relationship between angular movement of a shaft and axial movement of a piston comprising:

a piston operating along an axis of a cylinder and having first and second fluid pressure faces at opposite ends thereof;

a recess in a central portion of said piston;

a shaft mounted for rotation about an axis that extends transversely to said cylinder axis and having fixed thereto a cam member which is mounted for angular movement about the shaft axis in said recess;

cam engaging surfaces mounted on said piston with an invariant spacing at opposite sides of the recess and in constant engagement with opposed sides of said cam member, said cam engaging surfaces have the shape of a pair of involute curves which each extend from a base circle of the involute, said involute curves are symmetrical, opposite and identical and the center of a base circle of the involute curves is coincident with the rotational axis of said shaft;

said cam member having a shape such that linear movement of the piston has a linear relationship with the angular movement of said shaft through a stroke which extends from both sides of a central position of said piston; and

wherein the rotational axis of said shaft is perpendicular to the axis of said cylinder and located so that a line extending through points of engagement between the cam engaging surfaces and the cam is substantially tangent to the base circle of the involute curves.

8. A mechanism for producing a linear relationship between angular movement of a shaft and axial movement of a piston comprising:

a piston operating along an axis of a cylinder and having first and second fluid pressure faces at opposite ends thereof;

a recess in a central portion of said piston;

a shaft mounted for rotation about an axis that extends transversely to said cylinder axis and having fixed thereto a cam member which is mounted for angular movement about the shaft axis in said recess;

cam engaging surfaces mounted on said piston with an invariant spacing at opposite sides of the recess and in constant engagement with opposed sides of said cam member, said cam engaging surfaces have the shape of a pair of involute curves which each extend from a base circle of the involute, said involute curves are symmetrical, opposite and identical and the center of a base circle of the involute curves is coincident with the rotational axis of said shaft;

said cam member having a shape such that linear movement of the piston has a linear relationship with the angular movement of said shaft through a stroke which extends from both sides of a central position of said piston; and

wherein the cam engaging surfaces on said piston are rollers that are mounted for rotation about axes that are parallel to each other and to the rotational axis of said shaft, and a plane defined by said roller axis is substantially tangent to the base circle of said involute curves.

9. A mechanism for producing a linear relationship between angular movement of a shaft and axial movement of a piston comprising:

a piston operating along an axis of a cylinder and having first and second fluid pressure faces at opposite ends thereof;

a recess in a central portion of said piston;

a shaft mounted for rotation about an axis that extends transversely to said cylinder axis and having fixed thereto a cam member which is mounted for angular movement about the shaft axis in said recess;

cam engaging surfaces mounted on said piston with an invariant spacing at opposite sides of the recess and in constant engagement with opposed sides of said cam member, said cam engaging surfaces have the shape of a pair of involute curves which each extend from a base circle of the involute, said involute curves are symmetrical, opposite and identical and the center of a base circle of the involute curves is coincident with the rotational axis of said shaft;

said cam member having a shape such that linear movement of the piston has a linear relationship with the angular movement of said shaft through a stroke which extends from both sides of a central position of said piston; and

means for applying a differential fluid pressure to the opposite faces of said piston for controlling the displacement of the piston form a central position in said cylinder to thereby produce a predetermined angular movement of said shaft.