Hydraulic apparatus with return to neutral mechanism

• US 6,782,797 B1
• Filed: 11/26/2002
• Issued: 08/31/2004
• Est. Priority Date: 02/20/2001
• Status: Expired due to Term

• Current Assignee: Hydro-Gear Limited Partnership
• Original Assignee: Hydro-Gear Limited Partnership
• Inventors: Wilson, Jeffrey A., Brandenburg, Neil, Poplawski, Herb
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): Kershteyn, Igor
• Application Number:
  US10/305,213
• Time in Patent Office: 644 Days
• Field of Search: 92/122, 915/05, 748/39, 604/87
• US Class Current: 92/12.2
• CPC Class Codes: F01B 13/04 with more than one cylinder F01B3/0032 takes precedence
• CPC Class Codes: F16H 61/42 involving adjustment of a pump or motor with adjustable output or capacity F16H61/46 takes precedence
• CPC Class Codes: F16H 61/439 Control of the neutral position, e.g. by zero tilt rotation holding means

Abstract

A control mechanism for a hydraulic drive apparatus such as a transaxle having a hydraulic pump and moveable swash plate mounted in a housing including a control arm for moving the swash plate between forward and reverse positions and a unidirectional return to neutral mechanism for biasing and returning the swash plate to a neutral position when the control arm is in one of the reverse or forward positions but not from the other position.

Claims

1. A hydraulic drive apparatus, comprising

a casing having a hydraulic pump mounted therein;

a moveable swash plate cooperable with the hydraulic pump for controlling the output thereof;

a rotatable shaft coupled to the moveable swash plate and extending from the casing; and

a speed adjusting mechanism mounted to the casing and drivingly coupled to the rotatable shaft, the speed adjusting mechanism comprising;

a control arm engaged to the rotatable shaft to move the swash plate between forward and reverse positions; and

a unidirectional return to neutral mechanism for biasing and returning the rotatable shaft to a neutral position when the shaft is in one of the reverse or forward positions but not from the other position.

2. A transaxle having a casing and comprising:

a hydraulic transmission mounted within the casing and comprising a rotatable hydraulic pump and a moveable swash plate cooperable with the rotatable hydraulic pump for controlling the output thereof;

a rotatable trunnion arm coupled to the moveable swash plate and extending from the casing; and

a speed adjusting mechanism mounted to the casing and drivingly coupled to the rotatable trunnion arm, the speed adjusting mechanism being used to rotate the rotatable trunnion arm to change the orientation of the swash plate, the speed adjusting mechanism including a unidirectional return to neutral mechanism for biasing and moving the rotatable trunnion arm from one of a forward driving or reverse driving position to a neutral position.

3. The transaxle as set forth in claim 2, wherein the speed adjusting mechanism is further comprised of a return arm that is mounted to the casing in a fixed position indicative of the neutral position, a control arm that is mounted to the rotatable trunnion arm, and a pair of scissor return arms only one of which is adapted to move the control arm in cooperation with the return arm for the purpose of moving the rotatable trunnion arm to the neutral position.

4. The transaxle as set forth in claim 3, wherein the return arm has a plurality of openings for accepting a bolt used to mount the return arm to the casing and the control arm has a plurality of openings adapted to engage the bolt to limit the degree of control arm movement.

5. The transaxle as recited in claim 3, further comprising a spring linking the pair of scissor return arms that places a bias on the scissor return arms that acts to move the control arm and the rotatable trunnion arm toward the neutral position.

6. The transaxle as set forth in claim 2, where the transaxle is a zero turn transaxle.

7. The transaxle as recited in claim 4, wherein the plurality of openings in the return arm are spaced by approximately 180 degrees.

8. The transaxle as recited in claim 4, wherein the plurality of openings in the return arm are spaced by approximately 90 degrees.

9. The transaxle as recited in claim 4, wherein the plurality of openings in the control arm are spaced by approximately 180 degrees.

10. A speed adjusting mechanism for use in connection with a hydrostatic drive apparatus comprising a casing in which is mounted a rotating hydraulic pump, a moveable swash plate cooperable with the rotating pump for controlling the output thereof, and a trunnion arm linked to the moveable swash plate for adjusting the orientation of the swash plate, the speed adjusting mechanism comprising:

a return arm having a plurality of openings for accepting a bolt to mount the return arm in one of a plurality of fixed positions indicative of a neutral position of the trunnion arm in which the swash plate does not influence the output of the hydraulic pump;

a control arm adapted to be mounted to and move the trunnion arm; and

a pair of scissor return arms only one of which is adapted to move the control arm in cooperation with the return arm for the purpose of moving the trunnion arm to the neutral position;

wherein the control arm is adapted to be mounted to the trunnion arm in one of a plurality of different positions and the mounted position of the return arm corresponds to the mounted position of the control arm such that the return arm is aligned with the control arm to establish the neutral position.

11. A speed adjusting mechanism for use in connection with a hydrostatic transaxle comprising a casing in which is mounted a rotating hydraulic pump in fluid communication with a rotating hydraulic motor, a moveable swash plate cooperable with the rotating pump for controlling the speed and direction of rotation of the hydraulic motor, and a trunnion arm linked to the moveable swash plate for adjusting the orientation of the swash plate, the speed adjusting mechanism comprising:

a return arm having a plurality of openings for accepting an attachment device to mount the return arm to the casing;

a control arm adapted to be mounted to and move the trunnion arm; and

a pair of scissor return arms only one of which is adapted to move the control arm in cooperation with the return arm for the purpose of moving the trunnion arm to a neutral position established by the position of the return arm, the neutral position corresponding to a trunnion arm position in which the swash plate does not influence the speed and direction of rotation of the hydraulic motor;

wherein the control arm has a plurality of openings adapted to engage the attachment device to limit the degree of control arm movement.

12. The speed adjusting mechanism as recited in claim 11, wherein the plurality of openings in the return arm are spaced by approximately 90 degrees.

13. The speed adjusting mechanism as recited in claim 11, wherein the plurality of openings in the control arm are spaced by approximately 180 degrees.

14. The speed adjusting mechanism as recited in claim 11, wherein the plurality of openings in the control arm are spaced by approximately 180 degrees.

15. An axle driving apparatus, comprising:

a casing having an opening for accepting an attachment device;

a hydraulic transmission mounted within the casing comprising a rotatable hydraulic pump in fluid communication with a rotatable hydraulic motor, a moveable swash plate cooperable with the rotatable hydraulic pump for controlling the speed and direction of rotation of the rotatable hydraulic motor, and a rotatable trunnion arm coupled to the swash plate having a trunnion arm extending from the casing;

an axle shaft carried by the casing and driven by the hydraulic motor;

a speed adjusting mechanism mounted to the casing and drivingly coupled to the rotatable trunnion arm to rotate the trunnion arm to change the orientation of the swash plate, the speed adjusting mechanism having a return to neutral mechanism comprising a return arm having a plurality of openings for accepting the attachment device which is used to mount the return arm to the casing in one of a plurality of fixed positions indicative of a neutral position of the truing trunnion arm in which swash plate does not influence the speed and direction of the rotation of the hydraulic motor, a control arm mounted to the trunnion arm, and a pair of scissor return arms only one of which is adapted to move the control arm in cooperation with the return arm for the purpose of moving the trunnion arm to the neutral position;

wherein the control arm is adapted to be mounted to the trunnion arm in one of a plurality of different positions and the mounted position of the return arm corresponds to the mounted position of the control arm such that the return arm is aligned with the control arm to establish the neutral position.

16. A zero-turn transaxle, comprising:

a casing adapted to carry a single axle in one of a left-handed or a right-handed drive position;

a hydraulic transmission mounted within the casing comprising a rotatable hydraulic pump in fluid communication with a rotatable hydraulic motor and a moveable swash plate cooperable with the rotatable hydraulic pump for controlling the speed and direction of rotation of the rotatable hydraulic motor, the rotatable hydraulic motor being used to drive the axle;

a rotatable trunnion arm coupled to the moveable swash plate, the rotatable trunnion arm extending from the casing; and

a speed adjusting mechanism mounted to the casing and drivingly coupled to the rotatable trunnion arm, the speed adjusting mechanism being used to rotate the rotatable trunnion arm to change the orientation of the swash plate to change the speed and direction of rotation of the rotatable hydraulic motor;

wherein the speed adjusting mechanism further comprises a unidirectional return to neutral mechanism mounted to the rotatable trunnion arm in one of a plurality of rotational orientations with respect to the rotatable trunnion arm, the speed adjusting mechanism being adapted to bias and move the rotatable trunnion arm from one of a forward or reverse driving position to a neutral position where the swash plate does not influence the speed and direction of rotation of the rotatable hydraulic motor.

17. The zero-turn transaxle as recited in claim 16, wherein the return to neutral mechanism comprises a return arm that is mounted to the casing, a control arm that is mounted to the rotatable trunnion arm, and a pair of scissor return arms only one of which is adapted to move the control arm in cooperation with the return arm for the purpose of moving the rotatable trunnion arm to the neutral position.

18. The zero-turn transaxle as recited in claim 17, further comprising a spring linking the pair of scissor return arms that places a bias on the scissor return arms that acts to move the control arm and the rotatable trunnion arm toward the neutral position.

19. The zero-turn transaxle as recited in claim 17, further comprising a bolt adapted to mate with the casing and wherein the return arm has a plurality of openings each adapted to accept the bolt, the plurality of openings provided for use in establishing the rotational orientation of the speed adjusting mechanism with respect to the rotatable trunnion arm.

20. The zero-turn transaxle as recited in claim 19, wherein the control arm has a plurality of openings adapted to engage the bolt to provide a limit to the degree of movement afforded to the control arm.

21. A speed adjusting mechanism for use in connection with a hydraulic pump carried in a casing and a trunnion arm linked to a swash plate to move the swash plate to affect fluid displacement of the hydraulic pump, the speed adjusting mechanism comprising:

a return arm adapted to be mounted to the casing in a position indicative of a neutral position of the trunnion arm in which the swash plate does not influence the speed and direction of rotation of the hydraulic motor;

a control arm adapted to move the trunnion arm, the control arm being mated with the trunnion arm such that the return arm and the control arm are alignable to establish the neutral position of the trunnion arm; and

a pair of scissor return arms wherein only one of the pair of scissor return arms is adapted to move the control arm in cooperation with the return arm for the purpose of moving the trunnion arm to the neutral position.

22. The speed adjusting mechanism as recited in claim 21, wherein the return arm has a plurality of openings through which an attachment device is adapted to pass to mount the return arm to the casing.

23. The speed adjusting mechanism as recited in claim 22, wherein the plurality of openings are spaced by approximately 90 degrees.

24. The speed adjusting mechanism as recited in claim 22, wherein the plurality of openings are spaced by approximately 180 degrees.

25. The speed adjusting mechanism as recited in claim 22, wherein the attachment device comprises a bolt adapted to mate with the casing.

26. The speed adjusting mechanism as recited in claim 22, wherein the control arm has a plurality of openings adapted to engage the bolt to limit the degree of control arm movement.

27. The speed adjusting mechanism as recited in claim 26, wherein the plurality of openings in the control arm are spaced by approximately 90 degrees.

28. The speed adjusting mechanism as recited in claim 26, wherein the plurality of openings in the control arm are spaced by approximately 180 degrees.

29. The speed adjusting mechanism as recited in claim 25, wherein a first one of the pair of scissor return arms is shorter than a second one of the pair of scissor return arms so as to allow the first one of the pair of scissor return arms to avoid cooperation with the return arm for moving the control arm.

30. The speed adjusting mechanism as recited in claim 21, wherein the control arm comprises a projection that is sized and arranged so as to allow engagement with only one of the pair of scissor return arms so as to avoid cooperation between the return arm and the other of the scissor return arms for moving the control arm.