Note: Descriptions are shown in the official language in which they were submitted.
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S P E C I F I C A T I O N
l'~OLERAMCE RING AND SHIM ANI:) METHOD OF USE"
The present invention relates to tolerance rings and
more particularly to improvements in the use of tolerance rings
to provide their use for mounting in relatively soft materials.
Tolerance rings are generally formed as split ring
members having a corrugated or wavy surface and are sandwiched
batween two cylindrical surfaces, that is, an outer cylindrical
surface and an inner cylindrical surface, to provide frictional
engagement between two members having the respective cylindrical
surfaces. The corrugations or waves on the ring may protrude
inwardly from an outer surface thereof, outwardly from an inner
surfase thereof or alternatively inwardly and outwardly. Such
tolerance rings are illustrated in U.S. Patent Nos. 3,142,887 and
3,145,547. The corrugations on the tolerance rings may be of
varying heights or may be arranged in more than one row around
the circumference of the ring as illustrated in U.S. Patent Nos.
3,700,271; 3,838,928 and 4,286,894.
In some applications it is desirable to mount a
cylindrical member within a hole in a relatively soft material
such as plastic or metal powder parts. Tolerance rings may be
used to provide an increased frictional engagement between the
cylindrical member and the hole in the soft material due to a
compression of the corrugations of the rlng, however, if there
is a significant amount of vlbration or radial load present, the
tolerance ring may tend to deform the soft material or to set in
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the material such that the corrugations will no longer be
compressed, thereby resulting in a loss of frictional engagement
between the cylindrical member and the hole.
In other applications the tolerance ring may surround
a ~ylindrical object formed of a relatively soft material and
that assembly inserted into a hole whereby compression of the
corrugations on the ring will provide a desired frictional
engagement between the cylindrical object and the hola. Again
if the two objects, the cylindrical member and the object in
which the hole is located, are subject to vibration or radial
loads, the tolerance ring may set into the soft cylindrical
object thereby resulting in a loss of frictional engagement.
Thus, it would be desirable to have a means for preventiny such
setting or deformation of the relatively soft material by the
tolerance ring. Also, the force of the corrugations under their
normal compression will sometimes deform the adjoining surfaca
if it is a soft material, without requiring additional forces
such as vibration or radial loading.
The present invention provides means for overcoming
each of the problems described above. Specifically, a standard
tolerance ring is to be used in conjunction with a shim which is
in- the form of a split cylindrical ring, generally having an
axial height at least as great as the axial length of the
corrugations. When the tolerance ring is pressed into an opening
in a relatively soft material, the shim is to surround tha ring
and will thereby spread the focused load of the corrugations
evenly around the entire circumference of the hole to prevent
deformation of the opening in the soft material. Similarly, when
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the tolerance ring is to surround a soft material, the
cylindrical shim will be placed on the interior of the tolerance
ring to spread the force of the corrugations evenly over the
circumference of the soft cylindrical object. Therefore,
deformation of the soft material will be preventsd and the
desired fricticnal engagement will be maintained.
Fig. 1 is a plan view of a tolerance ring and shim
embodying the principles of the present invention when the ring
is to be placed in a hole in a relatively soft material.
Fig. 2 is a sectional view of the tolerance ring and
shim taken generally along the lines II-II of Fig. 1.
Fig. 3 is a plan view of a tolerance ring and shim
embodying the principles of the present invention when the ring
is to be placed around a cylindrical object of a relatively soft
material. Fig. 4 is a sectional view of the tolerance ring and
shim taken generally along the line IV-IV of Fig. 3.
FigO 5 is a plan view of a tolerance ring and two shims
embodying the principles of the present invention where the ring
is to be placed around a cylindrical object of a relatively soft
material and within a hole in a relatively soft material.
Fig. 6 is a side sectional view of the tolerance ring
and shims taken generally along the line VI-VI of Fig. 5.
Figs. 1-6 illustrate a tolerance ring lO and a
cylindrical shim 12 embodying the principles of the present
invention. The tolerance ring has a cylindrical inner surface
14 and a plurality of radially outwardly projecting corrugations
16. Tolerance rings generally are formed from spring steel and,
when sandwiched between an inner cylindrical member 18 and a
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cylindrical opening or hole 20 in an outer member 22 assure a
snug fit between the inner member 1~ and the outer member 22 and,
in varying degrees, provides a means for the transfer of torque
and axial resistance between the two members. A radial force is
transferrPd from the tolerance ring to the surface of the opening
due to compression of the corrugations, this force being foc~lsed
or concentrated in axial lines corresponding to the outward and
inward peaks of the corrugations. When the outer member is
fabricated of a soft material relative to the sprin~ steel of the
tolerane ring, such as plastic, metal powder parts or metals
softer than spring steel, the hole in the outer member may be
deformed causing the ring to set into the material thereby
reducing the radial force between the members to a point which
may result in undesired slippage between the two members.
To prevent such setting, the shim 12 is placed around
the exterior of the ring to spread the radial force of the
tolerance ring over the entire circumferential surface of the
opening. The shim 12 has an axial length L at least as long as
an axial length 1 of the corrugations and pre~erably as long as
an axial length 1' of the entire tolerance ring. The shim is to
be fabricated of a spring carbon or stainless steel similar to
or the same as that used for the tolerance ring so that it will
be able to absorb and redistribute the localized radial forces
of the tolerance ring.
Figs. 3 and 4 show a tolerance ring 30 and shim 32
which are merely in a reversed position from those shown in Figs.
1 and 2, in that a surrounded cylindrical member 34 is formed of
a relatively soft material as compared to the tolerance ring.
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The shim is therefore placed between the tolerance ring and the
interior cylindrical member 34. Again the radial force from the
ring will be spread by the shim evenly over tha entire outer
cylindrical surface of the inner cylindrical member.
Figs. 5 and 6 show a tolerance ring 40, an outer shim
42 and an inner shim ~4 all in concentric engagement which
surround a cylindrical member 46 which is formed of a relatively
soft material as compared to the tolerance ring. An outer member
48 is also formed of a relatively soft material and therefore the
shims are used both on the inside and outside circumference of
the tolerance ring to spread the radially inwardly directed
forces as well as the radially outwardly directed forces to
prevent de~ormation of either the inner member 46 or outer member
48.
Thus, it is seen that our present invention provides
for improvements in ~he use of tolerance rings and shims
permitting them to be utilized in holding cylindrical members
within cylindrical openings in relatively soft materials or
holding cylindrical members formed of relatively soft materials
in an outer member while preventing the tolerance ring from a
setting in the relatively soft material, thereby ensuring
continued frictional engagement, torque transfer and axial
retention between the inner and outer members~
As is apparent from the foregoing specification, the
invention is susceptible of being embodied with various
alterations and modifications which may differ particularly from
those that have been described in the preceding speoification and
description. It should be understood that we wish to embody
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within the scope of the patent warranted hereon all such
modifications as reasonably and properly come within the scope
of our contribution to tha art.
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