Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to rubber cushioned Pads,
and more particularly to pads of the type used in railway
and mine vehicles or in suspension devices for trucks for
cushioning impact and shock.
This is a division of copending Canadian Patent
Application Serial No. 288,830, filed on October 17, 1977.
Rubber cushioned pads have been in use for years
on railway and mine vehicles for cushioning impacts and
shocks. Such pads also have been used in suspension systems
on trucks and off-highway vehicles. A typical cushioning
pad which has given excellent performance is disclosed in
D. Willison United States Patent 2,686,667, in which the
rubber cushion thereof has a corrugated surface. In that
patent the ridges in the corrugations are linear and of
constant cross-sectional area throughout their length.
When a pad o such configuration is compressed, the
opposing side faces of the ridges will bulge toward each
other and will come into contact first at the midpoint o~
the ridges and such contact will progressively increase
toward the ends of the ridges until the faces are engaged
substantially the entire length of the ridges. Once the
faces of the ridges are in contact, the valleys are, of
course, completely filled and under ~urther loading the
cushion will compress as though it were a block of solid
body. The load-deflection characteristics of that pad will
be such as to produce a stiffer action at light loads than
may be desirable for a given type of service.
The present invention is directed to a pad having
a resilient cushion oE corrugated configuration having
alternate ridges and valleys. In the preferred embodiment
the sides o~ the rid~es are so contoured that as the cushion
is compressed, they will flow inwardly toward each other in
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such a manner as to come into contact approximately
simultaneously over their entire length. In this manner,
full-length contact between the opposing sides o~ the
ridges is delayed as compared with the pad in the afore-
mentioned patent. Hence, at light loads this pad will
provide a larger deflection and, therefore, softer action
than the prior art pad. In another form of pad the sides
of the ridges may be so contoured as to cause the opposing
sides of the ridges to engage at their midpoint shortly
after the pad is subjected to a compressive loading. This
form of pad results in a stiffer action than the pad having
its ridges of constant cross-sectional area and also provides
greater deElection at higher load levels.
An object is to provide a cushioning pad of the
afoxementioned type whereby a modiied force-travel ~
characteristic is obtained, particularly in the early stages
of compression of the pad. ``
A further object is to provide a cushioning pad
having an elastomeric cushion bonded to a metallic plate,
the cushion having a corrugated surface configuration wherein
the ridges of the corrugations are so contoured as to
provide a load rate for suspension devices for trucks and
other ~ehicles that is particularl~ suitable or empty
or light load conditions.
A more specific object is to provide a cushioning
pad having an elastomeric cushion formed with a corrugated
surface configuration, the cross-sectional area of the ridges
oE the cushion var~ing at a predetermined rate from mid- ;
point o~ a ridge to its ends~
Accordin~ to the present invention there is
pro~ided a compression type cushioning pad, the pad
including a rigid planar plate having a palr of parallel
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surfaces and a single elastomeric cushion bonded to and
covering each of the surfaces, the cushions extending
from the plate in opposite directions. Each of the
cushions has alternate ridges and valleys formed therein
and extending across the pad, the valleys in a direction
crosswise thereof being generally concavely shaped relative
to the plane o~ the plate and extending to at least
adjacent the top of the ridges. Each ridge between
adjacent valleys has a flat top and a maximum cross-
sectional area at its longitudinal midpoint and a pair oopposing longitudinally extending sides which are generally
convexly shaped in a lengthwise direction relative to the `
longitudinal axis of the ridge. The flat tops of the
ridges o each cushion is in substantiall~ the same plane
parallel to the plane o the plat~. The ridges and valleys
are so contoured that upon compression of the cushions
of the pad the opposing sides of adjacent ridges will flow
towards each other in such a manner as to cause the valleys
therebetween to fill commencing at the bottom thereof and
progressing in the direction away rom the plate member.
The eatures and advantages of the invention will
become apparen~ rom the detailed description taken in
conjunction with the accompanying drawings.
Brief Description of the Drawings
Fig. 1 is a plan view of a cushioning pad.
Fig. la is a vertical section taken along line
la-la o Flg. 1.
Fig. lb is a vertical section taken along line
lb-lb of Fig. 1.
Fig. 2 is a s;de elevational view of the pad shown
in Fig. 1.
Fig. 3 is an end view of the pad o~ Fig. 1.
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Fig. 4 is a side elevational view of pads of
the type shown in Fig. 1 compressed a predetermined amount.
Fig. 4a is a side elevational view of the pads of
Fig. 4 compressed an additional amount.
Fig. 5 is a plan view of the pad shown in Fig. 1
but illustrating the flow of the ridges into the valleys
during the compression of the pad.
Fig. 6 is a graph showing typical load-travel
curves for various cushioning pads.
Fig. 7 is a plan view of a cushioning pad of
the prior art type. `
Fig. 7a is a side elevational view of the pad
shown in Fig. 7.
Fi~. 8 is a plan view of a cushioning pad
according to the present invention.
E'ig. 9 is a plan view of a group of pads embodying
the invention applied to a railway vehicle.
Description of the Preferred Embodiments
:
Cushioning pad 10 comprises a flat metallic
plate 12 having a resilient cushion 1~ of an elastomer
such as rubber or similar material bonded to each side
thereof. Cushion 14 in its free or uncompressed condition
has a corrugated surface configuration comprising alternate
ridges 16 and valleys 18 extending across the pad. In
Fig. 1 three ridges and two valleys are shown for purposes
of illustration, it being understood, however, that a
greater number of ridges and valleys may be provided
depending on the pad size and capacity required. It will `
be apparent that two ridses with a valley therebetween
are the minimum number that is practicable. Cushion 14 at
its peripheral edges slopes gradually upwardly from the
surface of the plate, as at 20, to the edge of flat tops
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16a of rid~es 16. The thickness of the elastomer at
each ridge 16 is preferably of the same dimension, each
flat top surface 16a lying in a plane parallel to the
plane o~ plate 12. The thickness of the elastomer at
bottom of valley 18 may vary depending on the load-
deflection characteristics required but, for manufacturing
purposes and pad durability, should not be less than a~out
10~ of the thickness of the ridges. In order to accurately
align a group of pads in face-to-face engagement the pad is
provided with a dowel 21 and a complementary recess 22.
Dowel 21 is preferably in the shape of the frustum of a
cone. The fit between the dowel and a dowel recess in an
adjacent pad is precise so that accurate alignment of a
group of pads is obtained. --
The opposing sides oE ridges 16 are concavely
contoured in a lengthwise direction as at 16b (see Fig. 1).
This configuration results in the cross-sectional area of
each ridge being a minimum midway between its ends and a
maximum at each end, as seen in Figs. la and lb. It will
be noted in Figs. la and lb that valleys 18 in transverse
section are also concavely shaped, and ~or purposes o~
illustration are o~ approximately the same area as ridges
16~ The outer sides o~ end ridges 16 are shown as being
linear.
As the pad is subjected to a compressive load,
the opposing sides 16b Qf the ridges will bulge or flow
toward each other, thereby decreasing the size of valley
18. As the compression of the pad continues, sides 16b
attain the position shown in Fig. 4 in which the valleys
18 have become filled to a considerable extent. In Fig.
5, dot-dash line "x" represents the leading edge of the
side surface 16b when the pad is compressed about the same
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amount as in Fig. 4. It will be observed that line x is
less concave than the edge "e" of the ridge in its unloaded
condition. As the pad is compressed further, the opposing
sides of the ridges move closer together and come into
contact substantially simultaneously along a straight line.
This filling of the valley is illustrated in Fig. 4a and
also in Fig. 5 in which line "f" represents the common
line of engagement between the sides of the ridges. Once
the valleys have been filled the cushion becomes in effect ~````
a solid block and upon further compressive loading the
elastomer expands only along its outer peripheral surfaces.
Prior to explaining the load-travel characteristics ;
of the pad, reference is made to the prior art pad 29
shown in Figs. 7 and 7a, in which the ridges 30 are straight
and oE constant cross-sectional area. As this pad is
compressed,-contact between the opposing sides 32 of the
ridges will occur first at the midpoint of the ridges.
As compression of the pad continue~, the engagement between
the sides of ~he ridges will progre!ss from the initial
contact at midpoint toward the ends of the ridges until
tha valleys are ~illed and complete engagement exists.
Re~erring now to Fig. 6, in which loaa in
thousands of pounds is plotted against the travel or com-
pression in inches, curve A represents the approxi~ate
load-travel characteristics of a block-type pad, such as
one in which the cushion corresponds approximately in size
and shape to that shown in Figs. 1 or 7 but without the
corr~lga~ions. This curve indicates that even for small
initial deflection or travel the load increases rapidly.
In other words, this pad will provide sti~f cushioning
action under light loads. It will also offer maximum
resistance to compression at increasing loads, as seen from
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the steepness o~ the curve at the higher load levels.
Curve B represents the load-travel characteristics
of the prior art pad of Fig. 7. Curve B indicates that
the Fig. 7 pad has a softer overall cushioning action
than the bloc~ pad. On curve B point "p" indicates the load
and travel at which the opposing sides 32 of pad 29 initially
engage midway between the ends of the ridges, and point
"r" the load and travel at which sides 32 are fully
engaged. It will be noted that the slope of the curve
increases rapidly between points p and r, signifyin~ an
accelerating load rate or resistance of the pad to com-
pression.
Curve C represents the load-travel characteristics
for the improved pad of Figs 1, 2 ~nd 3. An irlspection
oE thiq curve reveals that it has a lesser slope than
curve B from zero to about .45 inches displacement. This
indicates a softer action for light to moderate loads than
the prior art pad and shows that fclr a given load applied
to the pad a greater deflection or compression thereof will
occur. At point "s" on curve C, the sides of the ridges
are not yet engaged but at "t" the engagement o~ the ridges
and consequent filling of the valleys has been completed.
~t point t the pad acts virtually as a solid block and
the curve from that point on progresses steeply upwards.
The load-travel characteristics as shown by curve C are
particularly desirable for use in a suspension mechanism for
vehicles such as trucks and off-highway equipment in which
sot action is desirable for empty or light loads. Thus,
the pad provides the advantage of soft light load cushioning
along with reserve capacity for handling heavy loads. It
will be understood that while the configuration of curve C
is typical for the improved pad, the load-travel character-
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~ OE~8~L3istics of a prescribed size of pad to meet specified
service requirements are dependent on various factors such
as, for example, the thickness and hardness o~ the
elastomer cushion, and the number and spacing of the
ridges. One or more of these factors may be varied to
obtain the desired pad performance. A pad having its
resilient cushion contoured in accordance with the invention
so that the sides of the ridges will engage approximately
simultaneously at a predetermined load will provide softer
cushioning action at light loads than the prior art pad
of Fig. 7 of comparable size.
The above-described pad wherein the ridges have
a minimum cross-sectional area at its longitudinal midpoint
is also described and is claimed in above-identiied
parent application Serial No. 288,830. ~
In Fig. 8 , according to the present invention, -
there i~ shown a pad in which the elastomeric cushion 40
has a ridge and valley configuration that is in a sense
the reverse o the previous embodiments. The opposing
sides of ridges 42 diverge outward:Ly from the midpoint
of the ridges to the ends thereof. The load-travel
characteristics Qf this pad are represented by curve D in
Fig. 6. It will be seen that the most of curve D falls
between that of curves A and B. ~hus, the modified pad
provides softer action than a cushion of the solid block
type but is stiffer than the prior art cushion for light
and intèrmediate loads. This results from the engagement
at the midpoint o~ the opposing sides of the ridges, which
occurs earlier than the prior art pad or the pad of Fig. 1,
during compression of the pad. As the load on this pad is
increased, the engac3ement between the opposing sides of
the ridges progressively increases toward the ends of the
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ridges but at a slower rate than for the pads having Fig.
1, Fig. 7 or Fig. 8 configurations. Curve D, therefore,
in its upper portions crosses curves B and C, which results
from the fact that higher loading is required to close the
valleys near the end of the ridges. This pad, therefore,
offers load-travel characteristics that are suitable for
use in cushioning arrangements requiring softer action than
the solid block-type cushioning pad provides.
Fig. 9 illustrates the application of a group
of pads 10 em~odying the invention to a railway vehicle.
The pads are disposed in the usual draft gear pocket
formed by the car frame 50. Front and rear followers 52
and 54, respectively, are in engagement with stops 56 and
58 on the car frame. A yoke 60 surrounds the pads and
followers ancl transmits draft and buffing loads to the
pads. A car coupler (not shown) is connected to the forward
end 62 of the yoke. It will be observed that end pads ~
of the group have a resilient cushion 14 only on one side
of plate 12. This avoids ab~asion of the cushion by the
followers, as would occur if the end pad were to have
cushion 14 on both sides of the plate.
A group of pads such as shown in Fig. 9 may, of
course, be vertically arranged ~or use in suspension
systems for trucks and off-highway vehicles.
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