Note: Descriptions are shown in the official language in which they were submitted.
1 BACKGROUND OF THE INVENTION
This invention relates to chains, and, more
particularly to pintle type conveyor chains made of a polymeric
material.
Several problems have been encountered in -the polymeric
chains of the prior art. For example, it has been difficult to
find a pin which will be retained in the link when there ar~
forces present which tend to flex the sidebars relative to each
other. There is a tendency in the chains of the prior art for
the pins to work their way out of the link if the sidebars move
relative to each other. Knurls have been used on one end of a
chain pin in an attempt to retain the pin in the link. However,
if the knurled end of the pin ever begins to turn relative to
the sidebar, the knurls in the pin tend to cut into the aperture
in the sidebar until the pin becomes loose.
Pins with a D-shaped cross-section have been used, but
they present a problem because they reduce the cross-section of
the pin throughout its length and because either the sidebars of
one link or the barrel of the next adjacent link will be bearing
against the flat surface portion of the pin rather than on the
semicylindrical surface, thereby resulting in stress
concentration at the corners of the sidebar holes, which weakens
the link, or resulting in contact between the barrel and the
flat surface portion of the pin, which reduces wear life.
Some of the pins of the prior art are formed by
pressing a cylindrical piece of metal between dies to form it
into the desired shape. This becomes more difficult as the pin
becomes larger in diameter and more material has to be moved in
the forming process.
1 Another problem encountered in pintle type links which
are molded of a polymeric material is that flexing of the
sidebars relative to each other tends to cause fatiyue crackiny
in the link.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a chain in whi.ch the
links are held together by pins which not only retain themselves
in the links but also tend to maintain rigidity of the link
sidebars relative to each other.
The present invention provides a rigid link which
reduces the flexing of the sidebars, thereby reducing the
opportunity for fatigue failure.
The present invention also provides a pin which can be
relatively easily manufactured, even in large-diameter sizes.
The present invention also provides a pin which has no
head and therefore will not protrude beyond the links even
though the sidebars of the link are not recessed.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a chain link and pin
made in accordance w~th the present invention.
Figure 2 is a perspective view showing the other side
of the link of Figure 1.
Figure 3 is a top view partially in section of a chain
made up of links and a pin as shown in Figure 1.
Figure 4 is a side view of the chain shown in Figure 3.
Figure 5 is a pin made in accordance with the present
invention.
Figure 6 is a top view of a chain made up of links as
shown in Figure l; the chain is shown when going around a
corner.
1 Fi~ure 7 is an enlarged, broken-away view of the chain
shown in Figure 6.
DESCRIPTION OF THE ~REFERRED EMBODIMEMTS
Figures 1 through 4, 6 and 7 ilLustrate a chain 10
which is made up of pintle links 12 and pins 14. Each link 12
has a first sidebar 16 and a second sidebar 18. A barrel
portion 20 connects the first and second sidebars 16, 18 at a
first end 22. The barrel portion 20 has a bore 24 for receiving
a pin 14. It will be noted in Figure 3 that the bore 24 has a
small diameter at the center which tapers to a larger diameter
at the ends so as to permit the chain 10 to flex laterally. The
second ends 26 of the first and second sidebars 16, 18 are
spaced wide enough apart to receive the barrel portion 20 of the
adjacent link 12. Each sidebar 16, 18 has an aperture 28, 30
near its second end 26. As shown in Figure 3, a pin 14 is
received by the apertures 28, 30 of one link 10 and by the bore
24 of the barrel 20 of the adjacent link 10. The links which
are shown herein are links which are molded from a polymeric
material.
The pin 12 is substantially cylindrical in shape. The
first end 32 of the pin 14 is a noncylindrical, necked-down
portion having a D-shaped cross-section. This necked-down end
may be formed by milling or by other methods known in the art.
The second end 34 of the pin 14 is substantially cylindrically
shaped and has a diamond-shaped knurl on its outer surface. The
apertures 28, 30 in the first and second sidebars 16, 18 are
shaped so as to receive the pin 14. The necked-down end 32 of
the pin 14 is small enough to pass through the aperture 30 in
the second sidebar 18, and the aperture 28 has a D-shaped
6t3~9
1 cross-section corresponding with the cross-section of the
necked-down end 32 so as to receive the end 32 with an
interference fit. The aperture 30 in the second sidebar 18 is
substantially cylindrical and corresponds in size to the end 34
of the pin 14 so as to receive the end 34 with an interference
fit. It can be seen that the flat surface 33 of the end 32 is
oriented so that the semicylindrical surface 31 bears against
the first sidebar 16 during operation of the chain. The
provision of cylindrically-shaped bearing surfaces is preferred,
as it means that the force is spread over a larger bearing area,
thereby reducing wear. The pin 14 shown here is made of metal.
The pin may be made of many materials, including stainless steel
or nonmetallic materials in cases in which corrosion resistance
is important.
For assembly of the chain, the knuckle portion of the
barrel portion 20 of one link 12 is placed between the first and
second sidebars 16, 18 of the adjacent link 12 such that the
bore 24 is aligned with the apertures 28, 30. The pin 14 is
then inserted through the aperture 30, the bore 24, and the
aperture 28, until the necked-down portion 32 of the pin 14
bottoms out on the sidebar 16. The two links 12 may then
articulate relative to each other about the pin 14 and may
articulate laterally relative to each other due to the shape of
the bore 24. The noncylindrical shape of the necked-down
portion of the pin 14 and the corresponding noncylindrical shape
of the aperture 28 act together to prevent the pin 14 from
rotating relative to the link 12. If the pin 14 does not rotate
relative to the link 12, there is no opportunity for the knurled
end 34 to cut into the sidebar 18 and become loose. The fact
1 that the pin 14 has bottomed out on the sidebar 16 also iY~es
the pin 14 so that it cannot move outward through the aperture
28. The knurled end 34 of the pin 1~ serves two functions.
First, and most importantly, the knurl resists movement of the
pin outward through the aperture 30. Secondly, the knurl
resists rotation of the pin 14 relative to the sidebar 1~.
The benefits of this assembly of the pin 14 in the
links 12 are, first, that the pin 14 is retained in the links 12
and, second, that the pin 14 resists flexing of the sidebars 16,
18 relative to each other. The pin is retained, because the
necked-down portion 32 bottoms out on the first sidebar 16 and
cannot move further outward through the aperture 28 and because
the knurled end 34 resists movement of the pin 14 outward
through the aperture 30. The fact that the pin 14 cannot move
axially relative to the sidebars 16, 18 and that the pin 14 is
fixed to the sidebars 16, 18 also means that the sidebars 16, 18
cannot flex relative to each other.
It will be noted that a substantially flat roof 36 is
integral with the first and second sidebars 16, 18. The top of
the roof 36 is flush with the top surfaces of the sidebars. The
roof 36 is longitudinally spaced from the apertures 28, 30 to
permit coupling with an adjacent link, as shown in Figure 3.
The roof 36 is also spaced a distance away from the barrel 20 so
as to provide an opening 3~3 in the top surface of the link 12.
The opening 38 provides a place for dirt to pass through the
link so that the chain is self-cleaning as it operates. The
flat roof 36 serves two primary functions. First, it improves
the strength and rigidity of the link 12. Second, it provides a
smooth, flat, broad surface area for supporting articles which
1 are carried by the chain 10, thereby providing a more continuous
surface for more uniform support, and reducing wear.
In Figure 5 is shown a second type of pin 14' which can
be used in place of the pin 14 which was described earlier. It
can be seen that the first end 32' of the pin 14' is necked-down
and has a D-shaped cross-section identical to the first end 32
of the pin 14, and the second end 34' of the pin 14' has an
annular shaped knurl in its outer surface instead of the diamond
shaped knurl of the pin 14. The annular shaped knurl at the end
34' does not prevent the rotation of the pin 14' relative to the
sidebar 18; however, that rotation is already prevented by the
necked-down portion at the other end 32'. The annular knurl
simply serves to prevent movement of the pin 14' along its axis
- relative to the sidebar 18.
Figures 6 and 7 show the chain 10 articulating around a
bend in which there is an inner guide strip 40. The chain is
supported on a wear strip 42. It should be noted that the outer
edges of the sidebars 16, 18 of each link 12 are shaped such
that, when the chain 10 flexes around the bend, the inner
sidebar 16 of each link will contact the guide strip 40 at a
point on the sidebar which is within the bounds of the roof 36.
Because the point of contact with the sidebar is within the
bounds of the roof 36, the link is rigid at the point where it
contacts the guide strip 40, and thereby the tendency for the
sidebars 16, 18 to flex relative to each other is minimized. In
the embodiment shown, the point of contact with the inner guide
strip is designed to be within the bounds of the roof 36 by
making the outer edges of the sidebars 16, 18 straight and
parallel to each other from the apertured ends of the sidebars
to the end of the roof 36 nearest the barrel 20.
1 While the aforedescribed embodiments are those which
are preferred, other embodiments of the present invention will
be obvious to those skilled in the art.
