Single piece yoke stroking device for bent axis type...

Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage

Reexamination Certificate

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Details

C417S218000, C091S504000

Reexamination Certificate

active

06203283

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to the field of variable displacement bent axis hydraulic units. More particularly, this invention relates to a swingable yoke for a bent axis unit.
Bent axis hydraulic units have been known for many years. However, one of the most persistent challenges facing bent axis designers is the provision of a cost-effective and reliable yoke for carrying the cylinder block kit and varying the displacement of the bent axis unit.
One known transmission utilizes a two-piece yoke design. This design combines an upper trunnion piece with a separate bolt-on endcap. This design relies on dowel pins to locate the endcap to the upper body. Seals are required for high-pressure transition passages and joints between the two parts. Furthermore, several bolts are required to hold the two parts together. The endcap must usually be made utilizing a slow and costly lapping process.
Therefore, a primary objective of the present invention is the provision of a one-piece yoke for a swinging bent axis hydraulic unit.
Another objective of this invention is the provision of a yoke that has a surface for supporting a cylinder block kit in the bottom of its bucket portion.
Another objective of the present invention is the provision of a yoke that has a pair of integrally formed fluid passages connecting the supporting surface to the control trunnion without leaving the wall of the yoke.
Another objective of the present invention is the provision of a yoke which has all of the system pressure and gauge ports located on a single trunnion.
Another objective of the present invention is the provision of an integral shoulder on the yoke for stopping its pivotal movement.
Another objective of the present invention is the provision of a yoke which is economical to manufacture, minimizes the number of parts required, and is reliable in use.
These and other objectives will be apparent from the drawings, as well as from the description and claims which follow.
SUMMARY OF THE INVENTION
This invention relates to a swinging yoke for a bent axis hydraulic unit. More particularly, the invention is a single piece yoke having a variety of other integral features.
Normally a multi-piece yoke assembly is used to vary the displacement in a variable displacement bent axis unit. However, the present invention utilizes a one-piece yoke having a bucket portion adapted to carry the cylinder block kit of the bent axis unit. A trunnion bearing portion for swing control resides on one side of the bucket portion, and a trunnion for fluid porting resides on the other side of the bucket portion.
The bucket portion includes a bottom wall, a continuous side wall, and an open top. The inside of the bucket is generally cylindrical, and the bottom wall of the inside of the bucket portion has an area thereon sufficiently large and strong enough to support the cylinder block kit when the unit is fully pressurized.
The yoke further includes a pair of fluid passages intersecting the support surface and extending separately and entirely within the bottom wall, the side wall and the trunnion for fluid porting. The fluid passages normally carry system pressure. Gauge ports are provided near the top of the yoke, and high pressure system ports are provided in the trunnion for fluid porting.


REFERENCES:
patent: 2931250 (1960-04-01), Ebert
patent: 3142963 (1964-08-01), Thoma
patent: 3148628 (1964-09-01), Boydell
patent: 3958496 (1976-05-01), Wallin
patent: 4129063 (1978-12-01), Ifield
patent: 4893549 (1990-01-01), Forster
patent: 4945817 (1990-08-01), Scholl
patent: 5073091 (1991-12-01), Burgess et al.
patent: 5231912 (1993-08-01), Akasaka et al.
“Data Sheet for Variable Pump/Motor V20,” Volvo Hydraulics, pp. 1-4, published prior to 1980.
“Hydrostatics for power split transmissions,” E. Skirde & M. Gigling, Industrial Vehicle Technology '98, pp. 30-33, published Dec. 1998.

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