U.S. patent application number 09/739599 was filed with the patent office on 2001-06-21 for chain with improved rocker pin joint structure.
Invention is credited to Fukuda, Shigekazu, Funamoto, Takayuki, Horie, Hiroshi, Iwasaki, Yoshinori, Matsuno, Kazumasa.
Application Number | 20010004615 09/739599 |
Document ID | / |
Family ID | 18454694 |
Filed Date | 2001-06-21 |
United States Patent
Application |
20010004615 |
Kind Code |
A1 |
Horie, Hiroshi ; et
al. |
June 21, 2001 |
Chain with improved rocker pin joint structure
Abstract
A chain includes a pair of rocker joint pins inserted through
laterally aligned pin holes of two adjacent link plates. The pin
holes have a pair of upper and lower pin-position constraining
surfaces arranged to face upper and lower flat surfaces,
respectively, of each rocker joint pin with a very small clearance
defined therebetween so that the rocker joint pin is always kept in
position against displacement in a vertical direction relative to
the link plates. When the chain is urged to warp or bend into a V
shape, each of the rocker joint pins is gripped by the upper
pin-position constraining surface of one of the two adjacent link
plates and a warp blocking surface of the other of the two adjacent
link plate. Thus, such warping of the chain does not take
place.
Inventors: |
Horie, Hiroshi; (Osaka,
JP) ; Matsuno, Kazumasa; (Osaka, JP) ; Fukuda,
Shigekazu; (Osaka, JP) ; Funamoto, Takayuki;
(Osaka, JP) ; Iwasaki, Yoshinori; (Osaka,
JP) |
Correspondence
Address: |
HOWSON AND HOWSON
Spring House Corporate Center
P.O. Box 457
Spring House
PA
19477
US
|
Family ID: |
18454694 |
Appl. No.: |
09/739599 |
Filed: |
December 18, 2000 |
Current U.S.
Class: |
474/214 ;
474/229 |
Current CPC
Class: |
B21L 15/005 20130101;
F16G 13/04 20130101 |
Class at
Publication: |
474/214 ;
474/229 |
International
Class: |
F16G 013/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 16, 1999 |
JP |
357547/99 |
Claims
What is claimed is:
1. A chain comprising: a plurality of interleaved rows of link
plates articulately connected together in an endless fashion by
means of rocker joint pins, each of said link plates having a pair
of pin holes, each of said rocker joint pins being composed of a
pair of rocker joint pins inserted through each of said pair of pin
holes in one link plate and each of said pair of pin holes in an
adjacent link plate; said pair of rocker joint pins having a
convexly arcuate rolling surface, a back surface opposite to said
rolling surface, and a pair of upper and lower flat surfaces formed
between said rolling surface and said back surface and extending in
a longitudinal direction of the chain; and each of said pin holes
having a seat surface engaged with said back surface and formed on
a side located closer to an outer end of each link plate than to a
center of the link plate, and a pair of upper and lower
pin-position constraining surfaces facing said upper and lower flat
surfaces, respectively, of one of said pair of rocker joint pins
seated on said seat surface with a very small clearance defined
between each of said flat surfaces and a corresponding one of said
pin-position constraining surfaces, a bend permitting surface
contiguous to said upper pin-position constraining surface and
spaced from said upper flat surface of the other rocker joint pin
seated on said seat surface of said pin hole in said adjacent link
plate, a warp blocking surface contiguous to said lower
pin-position constraining surface and facing said lower flat
surface of said other rocker joint pin seated on said seat surface
of said pin hole in said adjacent link plate with a very small
clearance defined therebetween, and a concavely arcuate surface
contiguous to said bend permitting surface and said warp blocking
surface and spaced from said back surface of said other rocker
joint pin seated on said seat surface of said pin hole in said
adjacent link plate.
2. The chain according to claim 1, wherein said upper and lower
pin-position constraining surfaces of each of said pin holes are
formed on one side of a vertical centerline of said each pin hole
which is located closer to said outer end of each link plate than
to the center of the link plate, and said bend permitting surface
and said warp blocking surface are formed on the other side of the
vertical centerline which is located closer to the center of the
link plate than to the outer end of the link plate.
3. The chain according to claim 2, wherein said upper and lower
flat surfaces of each said rocker joint pin are straight and
parallel with each other, and said upper and lower pin-position
constraining surfaces of each said pin hole are straight and
parallel with each other.
4. The chain according to claim 3, wherein said bent blocking
surface is straight and symmetrical with said straight lower
pin-position constraining surface about said vertical centerline of
said pin hole
5. The chain according to claim 4, wherein said upper and lower
pin-position constraining surfaces are sloping down toward said
outer end of the link plate.
6. The chain according to claim 5, wherein said bent permitting
surface is straight and extends at an angle to said upper
pin-position constraining surface in such a manner that the bent
permitting surface gradually retreats from said upper pin-position
constraining surface in a radial outward direction of the pin hole.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to a chain having a
number of interleaved rows of link plates articulately connected
together in an endless fashion by means of rocker joint pins, and
more particularly to a chain having an improved rocker pin joint
structure.
[0003] 2. Description of the Related Art
[0004] A chain having a number of interleaved rows of link plates
articulately connected together in an endless fashion by means of
rocker joint pins is used as a silent chain or a CVT (Continuously
Variable Transmission) chain. The silent chain is used as a driving
chain for an engine camshaft, or a power-transmitting chain for a
transmission. The CVT chain is used as a power-transmitting chain
for a CVT unit.
[0005] These chains are essentially comprised of a plurality of
interleaved rows of link plates connected together in an endless
fashion by rocker joints each composed of a pair of rocker joint
pins of different lengths. The link plates each have a pair of pin
holes. A longer pin and a shorter pin jointly forming one rocker
joint are inserted through the respective pin holes in the link
plate of one row and the respective pin holes in the link plate of
an adjacent row so as to join the two adjacent link plate rows.
[0006] The pin holes of the conventional chain have a generally
circular shape. The inner peripheral surface of the generally
circular pin hole includes a chord-like seat surface located closer
to an outer end of the link plate than to the center of the link
plate. The longer pin and the shorter pin have the same
cross-sectional shape and each include a convexly arcuate rolling
surface. These pins are inserted through laterally aligned pin
holes of the overlapping link plates in such a manner that the
respective rolling surfaces of the longer and shorter pins are in
confrontation with each other with the longer pin bing seated on
the seat surface of the pin hole in one link plate, and the shorter
pin being seated on the seat surface of the pin hole in an adjacent
link plate.
[0007] The chain of the foregoing construction, when used as a
silent chain for an automobile, is required to have high wear
resistance, great noise reduction and high lubricating property in
addition to easy assembly, inexpensiveness, and producibility.
[0008] In order to improve the wear resistance, an attempt has been
made to provide a large space between upper and lower portions of
the outer peripheral surface of each pin and corresponding upper
and lower portions of the inner peripheral surface of the pin hole
for holding therein a lubricating oil. The prior attempt is not
satisfactory because the rocker joint pins are liable to displace
within the pin holes when they are designed to have a relatively
small thickness for enabling adjustment of the chain pitch during
the assembly, or when they becomes thin due to the progress of
wear.
[0009] Once the rocker joint pins are displaced from the correct
position within the pin holes, it becomes no longer possible for
the respective rolling surfaces to contact with each other on a
pitch line of the chain. Even though a large lubricating oil
holding space is provided for improving the wear resistance, wear
has occurred with rocker joint pins and the link plates due to
interference between the displaced rocker joint pins and the inner
peripheral surfaces of the pin holes.
[0010] In addition, since the respective rolling surfaces of the
longer and shorter pins contact with each other at an incorrect
position, wear on the rolling surfaces is locally intensified,
deteriorating the durability of the chain. The rolling surfaces
contacting at the incorrect position give rise to an additional
problem that the link plates are displaced or offset from the pitch
line and hence unable to start meshing with a sprocket at a correct
position. This will result in a remarkable increase in operation
noise.
[0011] Japanese Utility Model Laid-open Publication No. 62-196950
and Japanese Patent No. 2924915 disclose a chain wherein a
projection is provided at an upper portion or a lower portion of
the inner peripheral surface of each pin hole so as to prevent
displacement including rotation of rocker joint pins within the pin
hole and also prevent adjacent link plates from becoming bent into
a V shape. By the projection thus provided, the rocker joint pins
are held in position against displacement relative to the link
plates.
[0012] However, the projection gives rise to another problem that
the effective contact area between respective rolling surfaces of
the longer and shorter pins is reduced by the projection, and the
wear resistance of the chain deteriorates with a reduction of the
effective contact area. In addition, since the projection partly
surrounds the contour of each rocker joint pin, a space defined
between the opposed rolling surfaces for holding therein a
lubricating oil is reduced. This may accelerate wear of the rolling
surfaces due to insufficient lubrication. Furthermore, due to the
presence of the projection, placement of the rocker joint pins into
the pin holes is uneasy to achieve, thereby lowering the assembling
efficiency and increasing the assembling cost. In addition, the
presence of the projection makes it difficult to produce the link
plates by punching due to a shortened service life of punching
dies. This may add to the cost of the chain.
SUMMARY OF THE INVENTION
[0013] It is accordingly an object of the present invention to
provide a chain having an improved rocker pin joint structure which
is capable of holding rocker joint pins in a correct position
against displacement relative to link plates.
[0014] Another object of the present invention is to provide a
rocker pin joint structure of a chain, having a combination of a
unique profile of pin holes and a unique cross-sectional shape of
rocker joint pins, which is capable of preventing warping or
reverse bend of the chain.
[0015] A further object of the present invention is to provide a
chain having an improved rocker pin joint structure capable of
withstanding a great load.
[0016] According to the present invention, there is provided a
chain comprising a plurality of interleaved rows of link plates
articulately connected together in an endless fashion by means of
rocker joint pins. Each of the link plates has a pair of pin holes.
Each of the rocker joint pins is composed of a pair of rocker joint
pins inserted through each of the pair of pin holes in one link
plate and each of the pair of pin holes in an adjacent link plate.
The pair of rocker joint pins has a convexly arcuate rolling
surface, a back surface opposite to the rolling surface, and a pair
of upper and lower flat surfaces formed between the rolling surface
and the back surface and extending in a longitudinal direction of
the chain. Each of the pin holes has a seat surface engaged with
the back surface and formed on a side located closer to an outer
end of each link plate than to a center of the link plate, a pair
of upper and lower pin-position constraining surfaces facing the
upper and lower flat surfaces, respectively, of one of the pair of
rocker joint pins seated on the seat surface with a very small
clearance defined between each of the flat surfaces and a
corresponding one of the pin-position constraining surfaces, a bend
permitting surface contiguous to the upper pin-position
constraining surface and spaced from the upper flat surface of the
other rocker joint pin seated on the seat surface of the pin hole
in the adjacent link plate, a warp blocking surface contiguous to
the lower pin-position constraining surface and facing the lower
flat surface of the other rocker joint pin seated on the seat
surface of the pin hole in the adjacent link plate with a very
small clearance defined therebetween, and a concavely arcuate
surface contiguous to the bend permitting surface and the warp
blocking surface and spaced from the back surface of the other
rocker joint pin seated on the seat surface of the pin hole in the
adjacent link plate.
[0017] When the chain is stretched substantially straight, the
rocker joint pins are in contact with each other at their rolling
surfaces within the pin holes of the two adjacent link plates.
[0018] Assuming that the one rocker joint pin is a longer pin and
the other rocker joint pin is a shorter pin, the back surface of
the longer pin is seated on the seat surface of a first link plate
of the two adjacent link plates, and the back surface of the
shorter pin is seated on the seat surface of a second link plate of
the two adjacent link plates. The upper and lower flat surfaces of
the longer pin face the upper and lower pin-position constraining
surfaces, respectively, of the first link plate with a very small
clearance being defined between each of the flat surfaces and a
corresponding one of the pin-position constraining surfaces, so
that the longer pin is prevented from moving in a vertical
direction relative to the first link plate. The upper and lower
flat surfaces of the shorter pin face the upper and lower
pin-position constraining surfaces, respectively, of the second
link plate with a very small clearance being defined between each
of the flat surfaces and a corresponding one of the pin-position
constraining surfaces, so that the shorter pin is prevented from
moving in a vertical direction relative to the second link plate.
Accordingly, when the chain in stretched substantially straight,
both the longer pin and the shorter pin are held in position
against vertical displacement relative to the first and second link
plates. The respective rolling surfaces of the longer and shorter
pins are, therefore, able to contact with each other at a correct
position, so that they are free from local wear. In addition, the
chain while in a stretched condition does not cause whipping or
waving, thus reducing noises produced when the chain comes into
meshing engagement with the sprocket.
[0019] The very small clearance provided between the upper flat
surface of each rocker joint pin and the upper pin-position
constraining surface of each link plate is indispensable for
enabling placement of the rocker joint pins into the pin holes to
thereby articulately join two adjacent link plates. The clearance
is determined in view of manufacturing tolerances of the link
plates and the rocker joint pins and should preferably be as small
as possible.
[0020] When the chain is about to travel around the sprocket, the
first link plate, for example, comes into meshing engagement with
the sprocket before the second link plate. This movement causes the
first link plate to turn or pivot about a common center of the pin
holes of the first and second link plates. In this instance, the
longer pin seated on the seat surface of the first link plate rolls
on the rolling surface of the shorter pin which is seated on the
seat surface of the second link plate. The upper pin-position
constraining surface of the first link plate and the upper flat
surface of the longer pin angularly move in phase with each other.
During that time, the angular movement of the upper flat surface of
the longer pin caused due to pivotal movement of the first link is
permitted or accommodated by the bent permitting surface of the
second link plate because the bent permitting surface is spaced
from the upper flat surface of the longer pin when the chain is
stretched substantially straight.
[0021] In addition, since the back surface of the longer pin is
spaced or separated from the concavely arcuate surface of the
second link plate, angular movement of the back surface occurring
when the first link plate is caused to turn relative to the second
link plate is permitted.
[0022] The chain as it is in the stretched straight state is
sometimes forced to warp or bend about a rocker pin joint into a V
shape. Such warping of the chain is prevented from occurring by
means of the warp blocking surface of the present invention. For
instance, when the first link plate is urged to turn or pivot in
the reverse direction about the common center of the pin holes of
the first and second link plates, the longer pin is gripped between
the upper pin-position constraining surface of the first link plate
and the warp blocking surface of the second link plate because the
upper and second flat surfaces of the longer pin face the upper
pin-position constraining surface of the first link plate and the
warp blocking surface of the second link plate, respectively. At
the same time, the short pin is gripped between the upper
pin-position constraining surface of the second link plate and the
warp blocking surface of the first link plate because the upper and
second flat surfaces of the shorter pin face the upper pin-position
constraining surface of the second link plate and the warp blocking
surface of the first link plate, respectively.
[0023] In one preferred form of the present invention, the upper
and lower pin-position constraining surfaces of each of the pin
holes are formed on one side of a vertical centerline of the pin
hole which is located closer to the outer end of each link plate
than to the center of the link plate, and the bend permitting
surface and the warp blocking surface are formed on the other side
of the vertical centerline which is located closer to the center of
the link plate than to the outer end of the link plate.
[0024] It is preferable that the upper and lower flat surfaces of
each rocker joint pin are straight and parallel with each other,
and the upper and lower pin-position constraining surfaces of each
pin hole are straight and parallel with each other. The bent
blocking surface may be straight and symmetrical with the straight
lower pin-position constraining surface about the vertical
centerline of the pin hole. The upper and lower pin-position
constraining surfaces may be sloping down toward the outer end of
the link plate. Further, the bent permitting surface may be
straight and extend at an angle to the upper pin-position
constraining surface in such a manner that the bent permitting
surface gradually retreats from the upper pin-position constraining
surface in a radial outward direction of the pin hole.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] A preferred embodiment of the present invention will now be
described in detail, by way of example only, with reference to the
accompanying drawings, in which:
[0026] FIG. 1 is a fragmentary plan view, partly in cross section,
of a silent chain having rocker joint pins according to an
embodiment of the present invention;
[0027] FIG. 2 is a front elevational view showing the relationship
between two adjacent link plates of the silent chain articulately
connected together by a rocker pin joint composed of a pair of
rocker joint pin;
[0028] FIG. 3 is a front elevational view of the link plate;
[0029] FIG. 4 is a view illustrative of the manner in which a
rocker joint pin is inserted through one pin hole in the link
plate;
[0030] FIG. 5 is a front elevational view showing the relationship
between the pair of rocker joint pins and laterally aligned pin
holes in the two adjacent link plates; and
[0031] FIGS. 6A-6C are views illustrative of the manner in which a
first link plate is caused to turn or pivot about a common axis
relative to a second link plate when the chain starts to mesh with
the sprocket.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0032] The following description is merely exemplary in nature and
is in no way intended to limit the invention or its application or
uses.
[0033] Referring now to the drawings and FIGS. 1 and 2 in
particular, there is shown a silent chain 10 having a rocker pin
joint structure according to the present invention. The rocker pin
joint structure is also useful when embodied in a CVT chain (not
shown).
[0034] The silent chain 10 includes guide link rows 12 and
intermediate link rows 14 arranged alternately in the longitudinal
direction of the chain 10. The guide link rows 12 and the
intermediate link rows 14 are articulately connected in an endless
fashion by means of rocker joint pins 16. The guide link rows 12
each have a pair of guide plates 18 and at least one link plate 20.
The intermediate link rows 14 each have link plates 22 numbering
one more than the number of the link plates 20 in each of the guide
link rows 12. The link plates 20 of the guide link rows 12 are
interleaved with the link plates 22 of the intermediate link rows
14. In the illustrated embodiment, the guide link rows 12 each have
five link plates 20, and the intermediate link rows 14 each have
six link plates 22.
[0035] The link plates 20 of the guide link rows 12 and the link
plates 22 of the intermediate link rows 14 are identical in shape
and configuration. The thickness of the link plates 20 may be
different from the thickness of the link plates 22.
[0036] The rocker joint pins 16 are each composed of a pair of pins
16a, 16b of different lengths The longer pin 16a is inserted
transversely through the link plates 20 in each guide link row 12
and the link plates 22 in the adjacent intermediate link row 14.
The longer pin 16a has opposite end portions firmly fitted with the
pair of guide plates 18 in the same guide link row 12. The shorter
pin 16b is inserted transversely through the link plates 20 in the
guide link row 12 and the link plates 22 in the adjacent
intermediate link row 14. The longer pin 16a and the shorter pin
16b have the same cross-sectional shape and they extend
substantially straight in the widthwise or transverse direction of
the chain.
[0037] As shown in FIG. 3, each of the link plates 20 (22) has a
pair of pin holes 24, 24 (26, 26) formed therethrough in
symmetrical relationship with respect to a center of the link plate
20 (22), and a pair of teeth 28, 28 formed on one side of the link
plate 20 (22) for meshing engagement with teeth on a sprocket (not
shown).
[0038] FIG. 4 shows, in front elevation, the positional
relationship between the pin hole 24 in the link plate 20 and the
longer pin 16a. The positional relationship between the pin hole 26
in the link plate 22 and the shorter pin 16b is the same as the
relationship shown in FIG. 4, and no further description thereof is
needed.
[0039] The outer peripheral surface of each rocker joint pin 16
(the longer pin 16a being shown in FIG. 4) includes a convexly
arcuate rolling surface 30, a concavely arcuate back surface 32
opposite to the rolling surface, and a pair of upper and lower flat
surfaces 34, 36 formed between the rolling surface 30 and the back
surface 32 and extending in the longitudinal direction of the
chain. Circumferentially opposite ends of the convexly arcuate
rolling surface 30 and the flat surfaces 34, 36 are connected
together by a pair of rounded or arcuate surfaces 31 of a
relatively small radius of curvature Circumferentially opposite
ends of the concavely arcuate back surface 32 and the flat surfaces
34, 36 are connected together by a pair of convexly arcuate
surfaces 35. The upper and lower flat surfaces 34 and 36 are
parallel with each other.
[0040] Referring back to FIG. 3, the pin holes 24 formed in the
link plate 20 each have an inner peripheral surface including a
convexly arcuate seat surface 38. The seat surface 38 is
complemental in contour to the concavely arcuate back surface 32 of
the longer pin 16a so that when the chain 10 (FIG. 1) is stretched
substantially straight, the seat surface 38 is in close fit with
the back surface 32 of the longer pin 16a without forming a
clearance therebetween.
[0041] As detailed in FIG. 4, the inner peripheral surface of the
pin hole 24 further has a pair of upper and lower pin-position
constraining surfaces 40, 42. When the longer pin 16a is seated on
the seat surface 38 of the pin hole 24, the upper and lower
pin-position constraining surfaces 40, 42 of the pin hole 24 face
the upper and lower flat surfaces 34, 36, respectively, of the
longer pin 16a. The pin-position constraining surfaces 40, 42 have
a rectilinear profile when viewed from the direction of the axis of
the pin hole 24. These surfaces 40, 42 are formed on one side of a
vertical centerline c of the pin hole 24 which is located closer to
an outer end of the link plate 20 (FIG. 1) than to the center of
the link plate 20. In the illustrated embodiment, the pin-position
constraining surfaces 40, 42 are sloping down toward the outer end
of the link plate 20. The pin-position constraining surfaces 40, 42
are engageable with the flat surfaces 34, 36 of the longer pin 16a
to prevent movement of the longer pin 16a in a vertical direction.
The pin-position constraining surfaces 40, 42 are parallel to the
flat surfaces 34, 36 of the longer pin 16a. the flat surfaces 34,
36 are parallel with each other, the pin-position constraining
surfaces 40, 42 are also parallel with each other. The distance
between the upper and lower flat surfaces 34, 36 is slightly
greater than the distance between the upper and lower pin-position
constraining surfaces 40, 42 so that a very small gap or clearance
G is defined between each of the flat surfaces 34, 36 and a
corresponding one of the pin-position constraining surfaces 40, 42.
The clearance G is indispensable because it is necessary for
enabling placement or insertion of the rocker joint pins 16 through
the link plates 20, 22 during the assembly of the chain. The
clearance G is determined in view of manufacturing tolerances of
the link plates 20, 22 and pins 16a, 16b and should preferably be
as small as possible.
[0042] By the pin-position constraining surfaces 40, 42 thus
provided, the longer pin 16 is held in position against vertical
displacement relative to the link plate 20. However, since the flat
surfaces 34, 36 and the pin-position constraining surfaces 40, 42
are parallel with each other, the longer pin 16a is allowed to move
in the longitudinal direction of the chain 10 relative to the link
plate 20. Even when the longer pin 16a is displaced in the
longitudinal direction of the chain 10 relative to the link plate
20, the longer pin 16a is kept immovable in the vertical direction
by way of abutting engagement between the flat surfaces 34, 36 and
the mating pin-positioning surfaces 40, 42.
[0043] The seat surface 38 and each of the pin-position
constraining surfaces 40, 42 are connected by a concavely arcuate
surface 44. The arcuate surface 44 is substantially complemental in
contour to the convexly arcuate surfaces 35 of the longer pin 16a.
When the back surface 32 of the longer pin 16a is seated on the
seat surface 38 of the pin hole 24, each of the arcuate surface 35,
35 and a mating one of the arcuate surfaces 44 define therebetween
a slight clearance or gap G1.
[0044] The inner peripheral surface of the pin hole 24 further
includes a straight, bend permitting surface 46 contiguous to the
upper pin-position constraining surface 40, and a straight, warp
blocking surface 48 contiguous to the lower pin-position
constraining surface 42. The bend permitting surface 46 and the
warp blocking surface 48 are formed on the other side of the
vertical centerline c which is located closer to the center of the
link plate 20 than to the outer end of the link plate 20. The bend
permitting surface 46 and the warp blocking surface 48 are
connected together by a concavely arcuate surface 50. The bend
permitting surface 46 extends at an angle to the upper pin-position
constraining surface 40 in such a manner as to retreat gradually
from the pin-position constraining surface 40 in a radial outward
direction of the pin hole 24. The warp blocking surface 48 and the
lower pin-position constraining surface 42 are symmetrical with
each other about the vertical centerline c of the pin hole 24.
[0045] Thus, the inner peripheral surface of the pin hole 24 as a
whole is formed jointly by the seat surface 38, pin-position
constraining surfaces 40, 42, arcuate surfaces 44, 44, bend
permitting surface 46, warp blocking surface 48 and arcuate surface
50.
[0046] FIG. 5 shows two adjacent link plates 20 and 22 connected
together by a pair of rocker joint pins 16a and 16b inserted
through respective pin holes 26, 26 of the link plates 20, 22. For
purposes of illustration, the link plate 22 is indicated by
hatching. The relationship between the pin hole 24 in the link
plate 20 and the longer pin 16a and the relationship between the
pin hole 26 in the link plate 22 and the shorter pin 16b are the
same as those previously described with reference to FIG. 4.
[0047] When the chain 10 (FIG. 1) is stretched substantially
straight, the longer pin 16a and the shorter pin 16b are seated on
the seat surface 33 of the pin hole 24 of the link plate 20 and the
seat surface 38 of the pin hole 26 of the link plate 22,
respectively, with their rolling surfaces 30 being in contact with
each other. In this condition, the upper flat surface 34 of the
longer pin 16a is separated from the bend permitting surface 46 of
the pin hole 26 of the link plate 22. On the other hand, the lower
flat surface 36 of the longer pin 16a is parallel spaced from the
warp blocking surface 48 of the pin hole 26 of the link plate 22 by
the very small gap or clearance G (see FIG. 4) defined
therebetween. The arcuate surfaces 35 of the longer pin 16a are
separated from the arcuate surface 50 of the pin hole 26 of the
link plate 22.
[0048] FIGS. 6A-6C illustrate the operation of the rocker pin joint
structure of the present invention achieved when the silent chain
10 (FIG. 1) is bent. For purposes of clarity, FIG. 6A shows the
relation between the pin hole 26 of one link plate 22 and the
shorter pin 16b, and FIG. 6B shows the relation between the in hole
24 of an adjacent link plate 20 and the longer pin 16a. FIG. 6C
shows the relation of FIG. 6A and the relation of FIG. 6B in
combination. In FIGS. 6A-6B, the link plate 20 is precedent to the
link plate 22 when viewed from the direction of travel of the
chain.
[0049] When the chain is about to travel around a sprocket (not
shown), the link plate 20 begins to turn or pivot counterclockwise
about the common center or axis of the pin holes 24, 26 relative to
the link plate 22. With this pivotal movement of the link plate 20,
the longer pin 16a rolls on the rolling surface 30 of the shorter
pin 16b until it assumes the position indicated by the phantom line
shown in FIG. 6B. During that time, the upper flat surface 34 of
the longer pin 16a does not interfere with the bend permitting
surface 46 of the pin hole 26 of the link plate 22, and the upper
flat surface 34 of the shorter pin 16b does not interfere with the
bend permitting surface 46 of the pin hole 24 of the link plate
20.
[0050] When the link plates 20 and 22 are caused to warp or bent
into a V shape (or when the link plate 20 is caused to turn or
pivot clockwise about the rocker joint pins 16a, 16b), the upper
flat surface 34 of the longer pin 16a is gripped between the upper
pin-position constraining surface 40 of the pin hole 24 in the link
plate 20 and the bent blocking surface 48 of the pin hole 26 of the
link plate 22. Similarly, the upper flat surface 34 of the shorter
pin 16b is gripped between the upper pin-position constraining
surface 40 of the pin hole 26 in the link plate 22 and the bent
blocking surface 48 of the pin hole 24 of the link plate 20. The
relative pivotal movement of the link plates 20 and 22 in the
reverse direction to assume a V shape can thus be prevented. It is
to be noted, however, that due to the presence of the small
clearance G (FIG. 4) between each of the flat surfaces 34, 36 of
each rocker joint pin 16a, 16b and a corresponding one of the
pin-position constraining surfaces 40, 42 of each link plate 20 or
22, the link plates 20, 22 are permitted to slightly turn or pivot
relative to each other until the clearance G becomes zero or
disappears.
[0051] Thus, the rocker joint pins 16a, 16b are held in an
appropriate position relative to the link plates 20, 22 without
causing vertical displacement relative to the link plates. Thus,
wobbling of the rocker joint pins 16a, 16b can be reduced with the
result that wear of the link plates 20, 22 and the rocker joint
pins 16a, 16b is suppressed. In addition, since the vertical
displacement of the rocker joint pins is prevented, the respective
rolling surfaces 30, 30 of the longer and shorter pins 16a, 16b can
always contact with each other at a correct position. The rolling
surfaces 30 are therefore substantially free from local wear.
[0052] As described above, when the chain of the present invention
is in a stretched straight state, a longer pin and a shorter pin
jointly forming a single rocker pin joint are constrained in
position relative to two adjacent link plates. The respective
rolling surfaces of the longer and shorter pins are, therefore,
able to contact with each other at a correct position. As a result,
wobbling of the rocker joint pins is considerably reduced, and the
rocker joint pins do not slide on the inner peripheral surface of
the pin hole of each link plate. The rocker joint pins and the link
plates are thus protected against abrasive wear, and the rolling
surfaces of the rocker joint pins are free from local wear.
[0053] When the chain is forced to warp or bend into a V shape,
each rocker joint pin is gripped between an upper pin-position
constraining surface of a first link plate of the two adjacent link
plates a warp block surface of a second link plate of the two
adjacent link plates. Thus, warping of the chain does not take
place.
[0054] The pin hole of the present invention, as against the pin
hole of the prior art, is free of a projection. Accordingly, by
merely placing the rocker joint pins into the pin holes of the link
plates, the chain of the present invention can be assembled with
high efficiency comparable to the efficiency attained when a
conventional chain with round connector pins. Owing to the absence
of the projection, the link plates can be easily produced at a
relatively low cost, and a die assembly used for producing the link
plates has a relatively long service life.
[0055] Furthermore, due to the absence of the projection, the
rocker joint pins are allowed to have a rolling surface with a
relatively large effective contact area. The rolling surface has a
relatively large radius of curvature which is effective to lower
the contact pressure. This arrangement improves the wear resistance
of the rocker joint pins. In addition, due to the absence of the
projection, the pin hole and the rocker joint pins received therein
jointly form a relatively large space for holding therein a
lubricating oil which is enough to lubricate the rolling surfaces
of the rocker joint pins. The wear resistance of the rocker joint
pins and the link plates is further improved.
[0056] Obviously, various minor changes and modifications of the
present invention are possible in the light of the above teaching.
It is therefore to be understood that within the scope of the
appended claims, the present invention may be practiced otherwise
than as specifically described.
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