Expansible chamber devices – Piston – With separable means for pivotally mounting connecting rod...
Reexamination Certificate
2000-01-10
2002-07-02
Lopez, F. Daniel (Department: 3745)
Expansible chamber devices
Piston
With separable means for pivotally mounting connecting rod...
C403S155000, C411S517000, C384S903000
Reexamination Certificate
active
06412393
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates generally to piston assemblies and, in particular, to an improved piston pin retainer for securing a piston pin within a piston bore.
A piston pin maintains alignment of a piston in a cylinder bore while permitting some angular displacement of the piston rod. The piston pin floats freely in the bore of the piston, promoting even and uniform wear during operation. Conventionally, piston pins are retained within the piston bore by rings placed in grooves near the piston bore opening. Such rings are subject to failure, and upon such failure, the piston pin escapes the piston bore and scores the cylinder wall. Furthermore, the insertion of the retainer rings into the grooves of the piston bore is manual labor intensive and time consuming, resulting in considerable increase in the cost of piston assembly.
Others have attempted to improve piston assembly and piston pin retainers, but without much success. U.S. Pat. No. 2,255,217, discloses two different types of piston pin retaining mechanisms, each having substantial problems and disadvantages. The first mechanism disclosed is a generally straight, helical spring having two ends fastened together to form an annular ring. This type of spring does not exert sufficient force against the inner walls of the piston bore to sufficiently retain the piston pin in place. Furthermore, it is difficult to manually fasten the ends of the generally straight, helical springs together so as to form the ring. When presented in bulk, the springs intertwine and the assembler must untangle and disengage each of the springs before placement, into the bore groove. Increased assembly time increases production costs. This second helical spring is, likewise, unsatisfactory; its design configuration unduly increases material cost and hinders piston assembly.
U.S. Pat. No. 1,637,247 discloses a disc/split ring combination retainer. An annular disc is placed within the groove of the piston bore and a split ring abuts the annular disc to hold the piston pin in place. This device also requires an undue amount of labor because two separate retaining mechanisms are manually installed as part of the manufacture and assembly. Additionally, the shape of the split ring causes the rings to intertwine over the course of shipping and during bulk storage. The time required to untangle the rings prevents efficient and cost effective manufacture and assembly.
In recent years, most piston manufacturers have used a bent wire clip, commonly referred to as a “G-clip” because of its alphabetic resemblance. The “G” clip has an open periphery and, like other piston pins, intertwines when shipped in bulk, preventing automated dispensation during piston assembly. For the same reason, the “G” clip does not fully engage (less than 75% of) the piston pin when positioned within the piston bore groove. Less than complete engagement, increases the risk of failure and may result in the piston pin scoring the cylinder bore wall.
OBJECTS OF THE INVENTION
It is an object of the present invention, to overcome various problems and disadvantages associated with the prior art, including those discussed above. Accordingly, it is an, objective of the present invention to effectively retain a piston pin within a piston bore to prevent scoring of the cylinder wall. This and other objectives can be accomplished with an apparatus and/or through a method of the type described herein.
It will be understood by those skilled in the art that one or more aspects of this invention can meet certain objectives, while one or more aspects can meet certain other objectives. Each objective may not apply equally, in all instances, to every aspect of the present invention. As such, the objects provided herein can be viewed in the alternative with respect to any one aspect of the present invention.
Accordingly, it can also be an objective of the present invention to provide an apparatus for retaining a piston pin having a configuration which prevents entanglement during shipping or storage.
It can be a further objective of the present invention to provide a piston pin retainer that can be used with automatic feed mechanisms to facilitate efficient, cost-effective piston assembly.
Yet another objective of the present invention is to provide an apparatus and/or method to increase contact of a retainer mechanism with a piston pin, so as to better prevent a piston pin from releasing and scoring a cylinder wall.
Other objects, features, benefits and advantages of the present invention will be apparent from the following summary and descriptions of preferred embodiments, and will be readily apparent to those skilled in the art having knowledge of various piston components, mechanisms and assembly procedures. Such objects, features benefits, and advantages will be apparent from the above as taken in conjunction with the following summary, descriptions, figures and all reasonable inferences to be drawn therefrom.
SUMMARY OF THE INVENTION
The disadvantages and limitations of the background art discussed above are overcome by the apparatus, assemblies and/or methods of present invention.
In part, the present invention provides a piston-retaining coil including a base coil and a coil portion post-base and/or subsequent thereto. The post-base/subsequent coil portion can be one or more loops or turns continuous with the base coil. Although the subsequent coil portion can be described as wound about a core, it would be well-known to one skilled in the art that a subsequent coil can be configured to provide a square, rectangle, oval or other such non-loop structure, or series of such non-loop structures. The base coil can be annular with a circumference about equal to or somewhat greater than the circumference of a piston bore groove within which it can be inserted.
Regardless, a subsequent coil portion can be offset from the base coil and have an axis parallel to that of the base coil. The base coil can lie on a plane substantially perpendicular to the axis of the base coil and subsequent coil portions, and can continue at an angle to provide for the subsequent coil portion and/or an apex coil or portion thereof. A coil arranged in this manner takes the shape of a non-helical spring. A piston-retaining coil can be configured, however, with no angle of departure, the subsequent coil portion coplanar with the base coil on a plane perpendicular to the respective axes of the coils.
The coil of the present invention has two end portions and a cross-sectional configuration that can be circular, square, oval, or any other configuration as would be known by those skilled in the art. The base coil has an end-terminus positioned proximate the subsequent coil portion. The distance between the end-terminus of the base coil and a subsequent coil portion is less than the cross-sectional diameter of the coil. Such an arrangement and configuration prevents coils from intertwining, and permits use thereof in assembly lines with an automated feed mechanism.
The subsequent coil end-terminus can be positioned near the subsequent coil portion at a distance less than the cross-sectional diameter of the coil. As discussed above, this structure prevents entanglement with other coils.
The coil and related apparatus of this invention can be made from tempered or heat-treated steel, phosmusic wire, or other similar material known by those skilled in the art. Such a coil or retainer can be obtained from Exacto Spring Corporation of Grafton, Wis.
In part, the present invention also provides a piston-retaining spring having a base coil and a subsequent coil portion continuous with the base coil. The base coil can be in the shape of an annular ring to fit within a circumferential piston bore. The subsequent coil portion may also be annular with at least one loop, turn or part thereof. However, as discussed above, a subsequent coil portion can also have a non-loop configuration. The subsequent coil portion can have an axis substantially parallel with an axis of the base coil, howeve
Heitz William J.
Langer Richard J.
Exacto Spring Corporation
Langer Richard J.
Lopez F. Daniel
Reinhart Boerner Van Deuren s.c.
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