Endless belt power transmission systems or components – Positive drive belt – Belt formed of rigid links
Reexamination Certificate
2001-02-02
2003-06-03
Charles, Marcus (Department: 3682)
Endless belt power transmission systems or components
Positive drive belt
Belt formed of rigid links
C474S215000
Reexamination Certificate
active
06572504
ABSTRACT:
This invention relates to a silent chain and, in particular, to the structure of a guide link washer for a silent chain.
BACKGROUND OF THE INVENTION
Conventionally, a silent chain is used as a power transmission chain.
FIGS. 6 and 7
show an example of a typical silent chain.
As shown in the figures, silent chain
100
has a multiple link plate
102
having a pair of teeth
121
. The links are interleaved in the transverse and longitudinal directions. The link plate
102
is pivotably connected by connection pin
103
, composed of a pair of long and short joint pins
131
and rocker pins
132
, which are inserted into pinhole
122
of link plate
102
. Guide link
104
is placed on the outside of outermost link plate
102
. Both ends of joint pin
131
are fixed to pinholes formed in guide link
104
.
When the chain runs on a sprocket during its operation, the link plates bend and, at such time, joint pin
131
makes rolling contact with the sliding surface of
132
.
Recently, silent chain power transmission has been used under high load conditions and, for this, a silent chain of high wear resistance is required. However, when a conventional silent chain is used under high load, very high contact surface pressure is generated in the contact surfaces of the joint pin and rocker pin due to their convex—convex contact and, as a result, pitting wear occurs in those pins. Therefore, the requirement for high wear resistance cannot be adequately satisfied by the conventional silent chain.
The increased radius of curvature of the rolling surface of each pin can decrease contact surface pressure between joint pin and rocker pin, but a larger radius of curvature reduces the bendability of the link plates and that of the entire chain. As a result, it becomes difficult for the chain to be wrapped or wound around a small diameter sprocket. Therefore, increase of radius of curvature of the rolling surface is limited to ensure bendability of the entire chain.
In a conventional silent chain, both ends of the joint pin are fixed to a guide link of higher rigidity than link plates in general, so that, when excessive tensile load, such as a prestressing load, is applied to a chain, the shear load from the link plate acts on the center part of the joint pin while stretching of the pitch of the holes in the guide row is suppressed and, as a result, the bending load acts on the joint pin and the center of the joint pin and rocker pin can warp.
This invention addresses such a conventional problem and it offers a silent chain that retains the bendability of the entire chain, reduces the surface pressure acting on the connection pin and prevents or minimizes bending of the connection pin.
SUMMARY OF THE INVENTION
In one embodiment, the connection pin of the chain of the present invention is shown in FIG.
3
. In the figure, link plates
2
a
,
2
b
are mutually bent. Incidentally, the bending angle here is given as &agr;. Connection pin
3
that pivotably supports the said link plates
2
a
,
2
b
is inserted in aperture
22
formed in each of link plates
2
a
,
2
b.
Connection pin
3
is composed of center pin
31
placed in the center of pinhole
22
and the opposing pair of rocker pins
32
on both sides of said center pin. Both side faces of center pin
31
are curved convex, and convex curved face
32
a
, corresponding to side face
31
a
of the center pin, is formed in rocker pin
32
.
For a conventional rocker joint-type silent chain (FIGS.
6
and
7
), rolling contact with angle &agr; is necessary at the contact between rocker pin
132
and joint pin
131
to produce bending angle &agr;.
Whereas in the present invention, rocker pins
32
are placed on both sides of center pin
31
, as shown in FIG.
3
. Therefore, if rolling contact with angle &agr;/2 for each rocker pin
32
is realized, then bending angle &agr; can be realized between adjacent link plates
2
a
,
2
b.
Therefore, in the present invention, rolling contact of the rocker pin with one half of the necessary rolling contact angle suffices, so that the radius of curvature of each pin can be increased by that much; thereby, the surface pressure of the contact surface of the pin can be reduced while bendability of the entire chain is kept and wear resistance is improved.
Guide washers corresponding to each connection pin are provided to the chain of the invention and the end of the center pin is fixed to the pinhole of the guide washer. Therefore, stretching of the hole pitch of the guide row is not restricted, even if excessive tensile load, such as a prestressing load is added to a chain and the shear load from the link plate acts on the joint pin and no bending load acts on the joint pin, so that bending of the joint pin and rocker pin is prevented.
The preferred cross-section of the center pin is shaped like a Japanese drum or general ellipse. That is, a shape with the center of both side faces curved convex outward.
Convex opposing faces of the rocker pin are curved concave or convex. The entire length of the rocker pin is equal to or slightly longer than the total width of the laminated link plates and shorter than the distance between opposing guide washers in the chain width direction.
That is, in this case, guide washers are placed independently to each connection pin so that even if the entire length of the rocker pin is somewhat longer than the total width of the laminated link plates, it does not interfere with the attachment of the guide washer. In this manner, the length of the rocker pin has a large tolerance for ease of dimension control.
Whereas in a conventional silent chain, the guide link has a pair of pinholes on both of its ends (see
FIGS. 6 and 7
) so that it is preferable to have the entire length of the rocker pin shorter than the total width of the interleaved link plates. In such case, both ends of the rocker pin need not be too deep inside the pinholes of the outermost link plate, so that the entire length of the rocker pin needs to be close to the total width of the link plates. Because of this reason, tolerance on the rocker pin length of a conventional silent chain is tight and its dimensional control is not easy.
In the present invention, the entire length of the rocker pin is longer than the total width of the link plates, so that an effective cross-sectional area of the connection pin can be uniform across the total width of the link plates.
The guide washer can also have a blade spring portion. In such case, the elastic force of the blade spring acts in the chain width direction and a frictional force is generated between adjacent link plates in the chain width direction for high bending resistance of the chain and reduced chordal vibration of the chain.
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patent: 1598906 (1926-09-01), Dull
patent: 2525561 (1950-10-01), Pierce
patent: 2602344 (1952-07-01), Bremer
patent: 2775156 (1956-12-01), Imse et al.
patent: 3877688 (1975-04-01), McCarty
patent: 4041790 (1977-08-01), Paul
patent: 4186617 (1980-02-01), Avramidis et al.
patent: 5176584 (1993-01-01), Ishida et al.
patent: 5345753 (1994-09-01), Okuda et al.
patent: 5372554 (1994-12-01), Okuda
patent: 5445570 (1995-08-01), White
patent: 5464374 (1995-11-01), Mott
patent: 6142903 (2000-11-01), Heinrich
patent: 260510 (1926-11-01), None
patent: 305167 (1929-08-01), None
patent: 317467 (1930-06-01), None
European Search Report, Appln. No. 01301527.6, Applicant: Borg-Warner Automotive K.K., 4 pages.
Abrams Hugh A.
Borg-Warner Automotive K.K.
Charles Marcus
Dziegielewski Greg
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