Chain – staple – and horseshoe making – Chain making – Roller chain
Reexamination Certificate
2001-04-19
2002-05-28
Jones, David (Department: 3725)
Chain, staple, and horseshoe making
Chain making
Roller chain
C059S035100, C029S898100, C384S283000, C384S291000
Reexamination Certificate
active
06393818
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a rolled product suitable for use in a chain as a hollow cylindrical component, such as a bushing which is press-fit at opposite ends into [an] the inner plates of the chain, a roller fit on the bushing, or a bushing fitted in the roller. This invention also relates to a method for producing such rolled product.
BACKGROUND OF THE INVENTION
FIG. 14
hereof shows in exploded perspective view a typical chain of the type concerned. The chain comprises inner plates L
1
, outer plates L
2
, bushings B press-fit into the inner plates L
1
, connector pins P press-fit into the outer plates L
2
and extending through the bushings B, and rollers R which are fitted on the bushings B between opposed inner plates L
1
. A lubricant is present between each connector pin P and each bushing B or between each bushing B and each roller R to facilitate sliding.
The cylindrical bushings B and rollers R are each in many cases produced by rolling a rectangular workpiece by means of a forming machine or the like, the rectangular workpiece being obtained by cutting a steel strip. In Japanese Patent No. 2963652 there is disclosed a method of producing the bushing B by rolling. According to the disclosed method, a rectangular workpiece is rolled into a cylindrical shape and the cylindrically rolled product is then forced through the circular orifice or opening of a die for improving the accuracy of its various dimensional properties, including circularity.
More particularly, a rolled product is produced in the following manner. As shown in
FIG. 10
, a plurality of elongated grooves
33
extending in the transverse direction of a steel strip
32
are formed in the surface of the steel strip. Since the grooves
33
are closed at opposite ends and do not extend through the thickness of the steel strip
33
, they are hereinafter referred to as “blind” grooves. The steel strip
32
is then subjected to drawing and subsequently cut into a rectangular workpiece
34
. The workpiece
34
is then rolled so that the cut faces become opposed to each other, to afford a cylindrical product
35
, as shown in FIG.
11
. Then, a core or mandrel
36
is inserted into the cylindrical product
35
, and while keeping this condition, the cylindrical product
35
is forced through the circular orifice or opening of a die
37
, as shown in FIG.
12
. The steel strip
32
is drawn before being cut into rectangular workpieces
34
to obtain a predetermined target plate thickness and width and sectional shape defining the blind grooves.
In the case where the blind grooves are arranged differently from the arrangement shown in
FIG. 10
hereof, for example, in a zigzag pattern, transversely interrupted pattern or diagonal pattern, such as shown in
FIGS. 10
,
11
and
12
, respectively, of Japanese Patent No. 2963652, the distribution density of the blind grooves becomes uneven in the longitudinal and transverse directions of the steel strip. For the unevenly arranged blind grooves, if the depth of the bind grooves is made large, there arises the problem that the steel strip may be broken or raptured when subjected to drawing through a die.
In producing the rolled product
31
in the above manner, when the cylindrical product
35
is forced through the circular orifice of the die
37
for obtaining circularity, plastic flow occurs in the material of the cylindrical product
35
. Since this plastic flow is concentrated at the blind grooves, it has so far not been considered that any large axial dimensional change would occur in the rolled product
31
. However, when the cylindrical product
35
is forced through the circular orifice of the die
37
, there sometimes occurs a case where the plastic flow of the material cannot be sufficiently absorbed by the blind grooves
33
even though no large change occurs in the axial dimension of the rolled product
31
. In this case, as shown in
FIG. 13
, which is a developed plan view of the rolled product
31
, a slight plastic deformation occurs axially and a portion
31
A of the end face along imaginary straight line Y
1
—Y
1
, where there is a blind groove
33
, and a portion
31
B of the end face along imaginary straight line Y
2
—Y
2
, where there is no blind groove
33
, are slightly concave and convex, respectively. As a result, a wave-like phenomenon is seen in the end faces of the rolled product when viewed as a whole. For example, when the rolled product
31
is used as a bushing B and both of its ends are press-fit into inner plates L
1
of the chain, variations occur in the degree of fit when the chain is checked as a whole, and there is a deterioration in the dimensional accuracy between inner plates L
1
. Also in the case in which the rolled product
31
is used as a roller, its end faces undergo a deterioration of dimensional accuracy due to the waving phenomenon.
Moreover, when the rolled product
31
is used as the bushing B or the roller R in the chain, a lubricant such as lubricating oil is retained in the blind grooves
33
in the rotating and sliding portion between the connector pin P and the bushing B or between the bushing B and the roller R to prevent sliding friction. However, since the blind grooves
33
extend axially of the rolled product, once the lubricant leaks from terminal ends
33
A, it leaks to the exterior from end faces of the rolled product
31
, thus giving rise to the problem that satisfactory lubricating performance cannot be ensured over a long period of time.
Further, since the blind grooves are not uniformly formed axially and circumferentially of an inner peripheral surface of the rolled product, there has been the problem that the compressive strength in the axial or circumferential direction of the rolled product varies, being different at different positions on the circumference.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to solve the above-mentioned problems of the prior art and provide a rolled product for a chain capable of preventing a steel strip used as a blank material from being broken or ruptured during drawing thereof, preventing the material of the cylindrical product from undergoing plastic flow partially in its axial direction when the cylindrical product is forced through the circular orifice of a die, and preventing the occurrence of a waving phenomenon at the end faces of the rolled product, and further capable of minimizing the leakage of lubricant in the axial direction of the rolled product and improving the lubricant retaining performance in the rotating and sliding portion. These problems are addressed by arranging depressions or dimples in a zigzag fashion on the steel strip.
Another object of the invention is to provide a method for producing the rolled product.
For achieving the above-mentioned objects, in the first aspect of the invention, a rolled product for a chain is formed by rolling a rectangular workpiece into a cylindrical product and forcing the cylindrical product through a circular orifice of a die, wherein a plurality of dimples are formed zigzag in at least one of inner and outer peripheral surfaces of the rolled product, the dimples being formed for absorbing plastic deformation of the cylindrical product when forced through the circular orifice of the die, and a plurality of recessed portions are defined by the dimples on any imaginary straight line on the dimpled peripheral surface, in the axial direction of the rolled product.
The rolled product may be a bushing adapted to be press-fit at its opposite ends into inner plates of the chain, wherein the dimples are formed in an inner peripheral surface of the bushing. Alternatively, the rolled product may be a roller adapted to be slidably mounted on a bushing of the chain, the bushing being press-fit at its opposite ends into inner plates of the chain, wherein the dimples are formed in an inner peripheral surface of the roller. As a further alternative, the rolled product may comprise a bushing adapted to be press-fit at its opposite ends into inner plates of
Kimura Takeshi
Kondo Takeshi
Maeda Sachihiko
Nakagawa Takerou
Tamiya Atsuhiro
Howson & Howson
Jones David
Tsubakimoto Chain Co.
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