Expansible chamber devices – With releasable stop or latch means to prevent movement of... – Includes interfitting parts engageable at plural positions...
Reexamination Certificate
2000-06-07
2001-11-13
Ryznic, John E. (Department: 3745)
Expansible chamber devices
With releasable stop or latch means to prevent movement of...
Includes interfitting parts engageable at plural positions...
C092S023000
Reexamination Certificate
active
06314860
ABSTRACT:
TECHNICAL FIELD
The present invention relates to limiting the stroke of a ram cylinder, and more particularly to devices for releasable attachment to cylinder pistons for limiting the piston stroke.
BACKGROUND OF THE INVENTION
Ram cylinders are frequently used in applications where the stroke of the ram is used to raise, lower, or hold an implement in a selected position. In an agricultural example, a ram cylinder may be extended to lower a plow to a selected working depth. If the cylinder alone is used to maintain the working depth, continued stress on the plow during operation can stress the hydraulic circuit and can cause damage, or the hydraulics can leak and allow the plow to shift to a different working depth.
Various stroke limiting devices have been developed in the past that can be attached to the cylinder piston shaft for the purpose of limiting the return stroke of the piston. Upon retraction, the head of the piston will come into contact with the limiting device, which in turn will come into abutment with the cylinder body. The return stroke is thus limited by the axial thickness dimension of the stroke limiting device.
Known forms of stroke limiting devices include two clam shell clamp members that have a prescribed thickness dimension. The clamp members are typically held together by a wire or strap spring that yieldably holds the members closed on the piston shaft. The spring is typically attached to the clam clamp members within semi-annular grooves that are machined in the clamp members. Wire and strap springs have been used for this purpose.
A problem with the above forms of existing stroke limiting devices is that they are expensive to produce since machining is required to form the semi-annular grooves for receiving the spring ends. Even if no grooves are formed, there must be some provision made for connecting to the spring ends such as bolts, rivets or the like. Such fasteners add to the cost of the stroke limiting devices.
Prior stops also require special tooling to allow for use of the same spring configurations for cylinder stops of varying thicknesses. Additionally, because cylinder stops are available in both a variety of thickness and in different sizes to accommodate cylinders with piston shafts from, say one inch in diameter to two inches in diameter, different size springs have been required to secure the different size stops.
An object of the present invention is to provide a cylinder stop that is inexpensive to produce without requiring the use of special tooling to enable attachment of springs.
Another object is to provide such a cylinder stop that may be produced in various axial thicknesses dimensions but that make use of the same spring configuration, so a common spring shape needs to be used for different thickness stops for a prescribed piston size.
A further object is to provide a cylinder stop which may be produced in varied sizes to accommodate various size piston shafts, yet still having common spring end receiving sockets so the same spring may be also used with a variety of differently sized piston shafts.
A still further objective is to provide piston shaft gripping members that are extruded with spring end receiving sockets formed in the extrusion, to enable various thickness stop members to be cut from the extrusion with the spring receiving sockets formed integrally therewith.
The above and other objects and advantages may be understood from the following description.
REFERENCES:
patent: 2397516 (1946-04-01), Stewart
patent: 3008772 (1961-11-01), Helsel, Sr.
patent: 3682327 (1972-08-01), Winne
patent: 3818804 (1974-06-01), Miller
patent: 4155433 (1979-05-01), Porter
Photograph of a piston stroke stop that has been in public use or on sale prior to Jun. 7, 1999.
Photograph of piston stroke stops with riveted springs, on sale prior to Jun. 7, 1999.
Ryznic John E.
Wells, St. John, Roberts Gregory & Matkin P.S.
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