Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
BP File No. 6052-0~
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Title: S~INRABL~ AUTOMOTIVE CT.AMP AND PROTECTIVE COATING
FIELD OF THE INV~NTION
This invention relates to automoti~e
applications of shrink-wrap polymers. In one preferred
embodiment the invention relates to a clamp made of a
shrink-wrap polymer for attaching two automotive parts
together in a fluid-tight manner. In another embodiment
the invention relates to coatings made of a shrink-wrap
polymer for protecting automotive parts.
10 BACKGROUND OF 1~ INVENTION :
Front wheel drive automobiles have drive axles
~ connected to the transmission by constant velocity ~oints. ;~
¦ ("CVJ"). The CVJs are highly vulnerable to dirt and water
and are therefore protected by bellows type drive axle
covers or seals. Each drive axle seal is usually attached
to a drive axle by metal screw-type clamps normally
referred to as "hose clamps~.
Typically a lip of the drive axle seal is fitted
over the drive axle; the hose clamp is placed over the
lip, and the clamp is tightened to exert a radially
inwardly directed force on the lip, thus clamping the lip
to the drive axle.
To achieve the required clamping force to engage
the seal with the axle 60 that it will not leak, and to
prevent the seal from slipping on the axle, special
"heavy-duty" hose clamps are used. Such clamps must
provide a sealing force of about 140 Newton-meters (Nm).
These clamps are heavy and costly and it is awkward,
cumbersome, and time consuming to insert them on the lip
of the seal.
In other automotive applications, e.g. in rack
and pinion steering mechanisms, cover type seals are also
used, but the clamping forces can be lower since thç
~ bending forces involved are smaller. However even here,
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the expense of providing and installing clamps is
substantial.
Automobiles also deteriorate over time as a
result of road conditions, driving habits, improper and
untimely maintenance, and the like. Automotive member6 or
parts must be replaced on a regular basis due to ~normal
wear and tear", and some parts are replaced much sooner
than anticipated due to premature deterioration or
breaXage. Repairing or replacing parts is often costly
and time consuming, and so it is desirable to extend the
life of automotive parts. One way of achieving this
object is to provide an effective barrier between an
automotive part and that which causes it to deteriorate.
Plastic automotive covers are frequently used
because they provide a flexible cover for moving
automotive parts. One such plastic cover, mentioned
earlier, is the seal which covers a CVJ and houses a
lubricant for the CVJ (sometimes termed a "CVJ boot~
The CVJ boot also protects the CVJ from elevated
temperatures from external heat sources, including heat
from the automobile's brakes and the road surface. This
external heat is usually greater than the heat generated
from the drive axle and CVJ within the CVJ boot.
Unfortunately, CVJ boots deteriorate rather quickly
because they are exposed to particularly harsh conditions.
At high speeds, the CVJ boot is subject to impacts by
extraneous matter ranging in size from sand particles to
laxge stones. If the CVJ boot is cracked, then water and
salt may enter the boot and the lubricant within may
escape, resulting in damage to the CVJ.
It is therefore an object of the invention in
one aspect to provide a clamp to fluidly seal a drive axle
seal with an axlet which clamp weighs less and is less
expensive than the prior art "heavy-duty" hose clamps. In
135 another aspect it is an object of the invention to
Idispense, in some applications, with the need for separate
mechanical clamps.
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It is a further object of the present invention
in another aspect to provide a protective coating for
automotive parts such as CVJ boots, rack and pinion
steering covers, and the like.
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SUMMARY OF THE INVENTION
) In one aspect, the invention provides a method
of clamping an automotive seal to an automotive shaft, -~
comprising: providing a said seal with a lip shaped to
fit snugly over said shaft, inserting said lip over said
shaft, inserting a band of heat-shrinkable polymer
material over said lip, and heating said band for a time
sufficient to clamp said lip to said shaft.
~iIn a second aspect, the invention provides a :
method of clamping an automotive seal to an automotive
lS shaft, comprising: providing said seal with a lip shaped
to fit snugly over said shaft, said seal being of heat~
shrinkable material, inserting said lip over said shaft, ~iand heating said lip for a time sufficient to clamp said ~
lip to said shaft. ; ~;
20In a third aspect, the invention provides in
combination, an automotive shaft, a seal having an annular
lip extending over and snugly engaging said shaft, and a
band of heat-shrinkable polymer material encircling said
lip, said band being heat-shrunk to clamp said lip to said
shaft.
¦ In a fourth aspect the invention provides in
combination, an automotive shaft, a seal having a body and
an integral annular lip extending from said body and
fitted snugly over said shaft, said seal being of heat-
shrinkable material, said lip being heat-shrunk over said
shaft and clamping said seal to said shaft.
In a fifth aspect the invention provides a
method of protecting an automotive member from damage
caused by heat or extraneous matter comprising:
35(1) providing an automotive member;
(2) surrounding the automotive member with a
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layex of heat-shrinkable polymer material
having a minimum thickness of 0.1 mm, and
being capable of withstanding impacts by
the extraneous matter; and
. 5 (3) heating the polymer material for a time
and at an elevated temperature sufficient
to shrink said layer to interlock the
polymer material with the automotive
member.
In a sixth aspect the invention provides a
coating for protecting an automobile member from damage
caused by heat or extraneous matter, the coating
comprising a layer of heat-shrinkable polymer material
having a minimum thickness of 0.1 mm, and being capable of
withstanding impacts by the extraneous matter, said
polymer material being adapted to surround the automobile
member and to interlock therewith upon heating the polymer
material.
DES(:RIPTION QF 1~ DRAWINGS
Preferred embodiments of the present invention
are described below with reference to the accompanying
drawings in which~
Figure l is a perspective view of a drive axle,
a drive axle seal and a shrinkable automotive clamp
according to a first embodiment of the present invention;
Figure lA is an enlarged cross sectional view of
the encircled area of Figure l;
Figure 2 is a side view of two automotive
members and a shrinkable automotive clamp.according to a
second embodiment of the present invention;
Figures 3a and 3b are perspective views of
shrinkable automotive clamps according to a third
embodiment of the invention;
Figure 4 i8 a cross sectional view through the
drive axle seal of Figure 1 and a coating for protecting
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the drive axle seal according to another embodiment of the
present invention in an unshrunk configuration;
Figure 5 is a cross sectional view of the
invention shown in Figure 4 after shrinking the coating;
and
Figure 6 is a sectional view of a mold showing
a blow molding process to produce a coated automotive ~-
mfember according to the present invention.
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DESCRIPTIQN OF PRE:FERRE:D EMBODIME:N~S
10Reference is first made to Figures 1 and lA
which show an automobile drive axle 2 connected to a drive
axle seal 4. The drive axle 2 is of conventional form,
having a cylindrical center shaft 6, a first end 8 which
connects, for e.g., to an automobile transmission, and an
enlarged or cup-shaped second end 10. The second end lO
has a flat end face 12 and a generally cylindrical outer
surface 14. A groove 16 encircles the outer surface 14.
The drive axle seal 4 has the form of a tapered
bellows, having corrugations 20 and terminating at its
enlarged end in a cylindrical lip 22. Lip 22 is
dimensioned to fit snugly over the outer surface 14 at end
10 of the drive axle.
The seal 4 terminates at its smaller end in
another cylindrical lip 24 adapted to be placed over
another drive axle section (not shown).
As is well known, the seal 4 is formed (normally
by a blow molding process) from a plastic material able to
withstand flexing, impacts from stones and the like, and
relatively high temperatures produced during operation of
the automobile.
In the past, lip 22 of seal 4 was clamped over
outer surface 14 by a very strong hose clamp, as
previously mentioned. Because of the stresses i~volved,
high clamping forces, typically 140 Nm, have been required
for such clamps.
According to the invention, the seal 4 is held
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in place by a combination of means. Firstly, pressure or
heat sensitive adhesive 26 is provided, in a quantity
sufficient to fill the groove 16 and to flow onto the
i outer surface 14 to form a T-shape in cross section.
Adhesive 26 bonds the lip 22 of seal 4 to the outer
surface 14 in a sealing manner. Suitable adhesives for
$ example are provided by Raychem or Shaw Industries under
the trade mark "RAYCHEM".
In addition to the adhesive 26, a heat
shrinkable clamp 30 is provided. Camp 30 is a continuous
circular band of heat-shrinkable plastic, such as
polyester plastic or other suitable material adapted to
shrink when heat is applied thereto, and to retain the
shrunken state when the heat is removed. Preferably the
material used for clamp 30 can shrink up to 40% from its
original expanded size when heated. In thè embodiment
shown in Fiq. 1, the width of clamp 30 is less than that
of lip 22, so that the entire clamp 30 overlies lip 22 and
does not extend beyond the free edge 32 of the lip 22.
In use, after the adhesive 26 is placed in the
groove 16 of the drive axle 2, the lip 22 of the drive
axle seal 4 is inserted over both the outer surface 14 and
the adhesive 26 as shown in Figs. 1 and lA. Next, the
clamp 30 is placed over lip 22 (although this may also be
effected before the lip 22 is inserted onto the drive axle
2). The clamp 30 is then heated to contract it around the
lip 22. The pressure of the clamp 30 on the lip 22 clamps
the drive axle seal 4 to the drive axle in a sealing
manner. The pressure also causes the adhesive 26 to bond
the interior surface of the lip 22 to the outer surface 14
of the drive axle. 2.
Typically the level of heat applied to provide
the required shrinkage is in the range 70 to 150C and
for enough time to allow the thermo-plastic to shrink,
typically for between 2 and 5 seconds. The temperature
and time of heat application depends on several factors,
including the type of plastic used and the thickn~ss of
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the clamp 30. It will be appreciated that gamma radiation
could be applied to produce the required high heat for
shrinkage It is also understood that the applied heat
should be k~pt below the melting point of the plastic.
A typical material for the clamp 30 may be the
polyester material commonly sold by DuPont under its trade
mark "Hytrel".
Another type of material for clamp 30 is a line
of heat shrinkable tubing sold by Raychem under the trade
mark "Thermofit~. The Thermofit tubing is manufactured by
first subjecting the tubing material to high-energy
radiation to crosslink its molecules. Next, the tubing is
heated and pressure is applied to stretch the tubing from
its original form into an expanded form. The tubing is
then cooled to adopt this expanded form. When the
expanded form of Thermofit tubing is subsequently heated
to an elevated temperature, the tubing shrinks, or
"recovers"l back to or near its original shape (if
unrestrained). Upon reheating of the ~'recovered" tubing,
the tubing will not change shape (unless mechanical force
is used).
Good results have been achieved using a version
of Thermofit tubing sold under the trade mark "CRM". Upon
heating the expanded form of the CRM tubing at about a
temperature of 135C, its diameter shrinks or recovers up
to 50% of the expanded diameter. Recovered CRM tubing can
operate in temperatures ranging from -55C to +135C, and
up to a temperature of +300C for short periods of time.
In some applications, particularly for seals
used for automotive constant velocity joint drive axle
applications, the lateral forces imposed on the clamp are
80 high (typically up to 140 Nm) that the clamp 30 and
adhesive 26 will not themselves be sufficient. In that
case, a metal hose clamp may be used. However since the
heat-shrinkable clamp 30 will typically supply up to
between 60 and 70 Nm of clamping force, the remaining 70
Nm clamping force needed can be supplied by small and
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inexpensive hose clamps, typically costing far less than
those which would otherwise be needed.
For applications where there is less bending
force, e.g. seals used for rack and pinion steering in
automobiles, additional metal clamps are not normally
needed; the heat-shrinkable clamp 30 will in many cases be
sufficient. In fact, in some cases it may be possible to
omit the adhesive 26 since the clamping force of the clamp
30 alone may be sufficient to provide the required seal.
Reference is next made to Fig. 2, in which
primed reference numerals indicate parts corresponding to
those of Fig. 1. In Fig. 2 the drive axle 2' is not
enlarged, and the clamp 30' is shown as being sufficiently
wide to extend beyond the periphery of lip 22l and over
the circumferential outer surface 14~ of the drive axle
2', as indicated at 32. This arrangement provides
additional clamping of the seal 4' to the drive axle 2'
and also helps to prevent dirt and other materials from
entering under the edge 34 of the lip 22~.
Figs. 3A and 3B show a third embodiment of the
invention. Double primed reference numerals in Figs. 3A
and 3B indicate parts corresponding to those of Figs. 1
and 2.
Fig. 3A shows a drive axle 2" similar to that of
1 25 Fig. 2, with a telescopic joint (not shown) covered by the
¦ seal 4~. The seal 4" is elongated, having a cylindrical
central section 40 and two bellows sections 42, 44 one at
each end. Each bellows section 42, 44 has at its free end
a lip 22" which seals to the drive axle 2
1 30 In the Fig. 3A embodiment, the entire seal 4" is
¦ formed of heat-shrinkable plastic, such as the CRM tubing
described above. The seal 4" is provided in an expanded
~ form prior to heating the lips 22~.
¦ In use, after the seal 4" is installed on the
3 35 drive axle 2", the lips 22" are heated to shrink them onto
the drive axle. The heating is preferably localized to
the area of lips 22", to avoid affecting (ie. shrinking)
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the remainder of the seal 4l~. Suitable apparatus for
providing a localized band of heat (or gamma radiation, as
mentioned earlier) iB provided for example by Raychem.
Shrinkage of the rest of the seal 4ll should also
be avoided during the operating life of ~he automobile.
Hence, the temperatures to which the seal 4~ will be
exposed during the automobile's life should be below the
shrinking temperature of the seal's material. For
example, the CRM tubing discussed above will be suitable
for seals sub~ected to automobile operating temperatures
below 135C. If an operating temperature of 135C is
reached, or surpassed, then overall shrinkage of the tube
4" will take place. Therefore, for extremely hot
climates, a seal material with a higher shrinkage
temperature may be desirable. An alternative would be to
~; provide an oversize seal and to shrink the entire seal
simultaneously with the lips.
~ The clamping force provided by heat-shrinkable
¦ lips 22 can, as mentioned, be substantial (60 to 70 Nm)
20 and may in some cases be sufficient without using
additional clamps. However if additional clamps are
needed, they can be of much lighter and less costly
construction than was previously required.
In the Fig. 3A embodiment, adhesive as shown in
25 Figs. 1 and 2 may also be used if desired.
Fig. 3B shows two seals 4a", 4b" used with a
rack and pinion steering mechanism 50 having steering
shafts 2a", 2b". Each seal 4a", 4b" has a pair of end
lips 22a", 24a", 22b", 24b" and is formed of heat-
30 shrinkable material as described in connection with Fig.
3A. The lips 22a", 22b" are subjected to heat to shrink
them onto the rack and pinion steering mechanism 50 and
onto shafts 2a", 2b", to provide appropriate seals. Since
~; the bending forces exerted on the seals 4a", 4b" will be
35 very low, additional metal clamps will not normally be
required in the Fig. 3B arrangement.
;~ The seals 4, 4~, 4l~, and 4a~, 4b~ will normally
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be blow-molded in conventional fashion prior to being made
heat-shrinkable as discussed earlier.
Referring now to Figs. 4 and 5, another
embodiment of the present invention is illustrated.
Reference numerals having a prefix ~ are generally used
to identify like elements from previously described
embodiments. Fig. 4 shows a drive axle seal 104 of a like
configuration to seal 4 and having corrugations 120, and
lips 122, 124.
A generally tubular layer 130 is provided around
the seal 104 as shown in Figure 4. The layer 130 is
formed of a heat-shrinkable polymer material which can be
similar or identical to that used for clamp 30 to retain
a shrunken form when heat is removed as shown in Figure 5.
Preferably~ the polymer material of layer 130 is also soft
and very flexible (such as a low modulus polyester) since
it must flex during use. Regarding the seal 104, it may be
formed of a plastic as described above for Figure 1 or of
a rubber modified polypropylene, such as ~PO ~thermo-
plastic olefin).
The overall shape of the layer 130 in itsexpanded form approximates that of the seal 104. The
layer 130 should be adapted to fit over and surround the
seal 104. In the embodiment shown in Figure 4, the
circumference of the layer 130 in its expanded form is
slightly larger than that of the seal 104. The layer 130
covers the length of the seal 104 between the lips 122,
124 as shown. It will be appreciated that the length of
the layer 130 may be slightly more than the length of the
seal 104 to ensure that the lips of the seal 104 are
completely covered after the layer 130 is shrunk. Any
excess shrunk material 130 protruding beyond the ends of
the seal 104 may be removed if necessary. Alternately, if
desired, the layer 130 may be shorter than the seal 104 to
leave the lips 122, 124 exposed for mounting clamps 30
thereon to clamp the seal 104 to drive axles as presented
earlier.
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Preferably the circumference of the layer 130
~, adjacent the lip 124 is smaller than that adjacent the lip
122 (as shown in Figure 4) to reduce the amount of
?, material 130 which is used and to produce a better fit
'~ 5 after the layer 130 is shrunk tas shown in Figure 5). If
1 too much material 130 is provided, then the shrunken
~ material 130 may not conform to the desired shape and an
j excessive number of air pockets or the like will occur
between the layer 130 and seal 104, especially at the
~ 10 narrower lip 124.
i, In use, the layer 130 is placed over the seal
104 to surround the seal 104 as required, and the layer
130 is heated (as discussed previously) to shrink the
layer 130 around the seal 104 as shown in Figure 5.
Preferably, the layer 130 engages every part of the outer
surface of the seal 104 and conforms completely to the
corrugations 120. Some air might be trapped between the
shrunken layer 130 and the seal 104, but this should be
minimized or eliminated for optimum performance of the
layer 130.
There is no need for an adhesive between the
layer 130 and the seal 104 to prevent the layer 130 from
slipping off since a mechanical interlock is achieved due
to the irregular circumference of the seal 104.
Furthermore, the clamping force exerted by the shrunken
layer 130 on the seal 104 also frictionally engages or
interlocks the layer to the seal. It is understood that
the clamping force should not be so great so as to deform
or greatly distort the seal or automotive member being
coated. Although the layer 130 may be used and retained
on an automotive member with a constant circumference and
smooth outer surface due to such frictional engagement (or
by adding an adhesive to said outer surface), it is
preferable to achieve a mechanical interlock to minimize
or eliminate the chances of the layer dislodging and
slipping off the member. Hence, the present invention is
best suited for, but is not limited to, use with
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automotive members having irregular circumferences (for
example, a CVJ boot).
The layer 130 can take the form of a flexible
plastic mesh rather than a continuous tube. The mesh
should be used in combination with an automotive part
which experiences relatively little flex to avoid
separation of the mesh from the part. A suitable part
would be a rack and pinion steering boot as shown in Fig.
3, for instance. The mesh could be applied to the boot to
give it additional structural reinforcement, or
dimensional stability, and to delay or prevent collapse of
the boot should it crack or begin to disintegrate.
Since the seal 104 is normally blow-molded as
mentioned earlier, a blow-molding process for coating an
automotive member with a mesh or layer 130 is briefly
described with reference to Figures 6(a) and (b). Figure
6(a) shows an open blow mold, generally indicated by the
reference numeral 200, of usual construction having a left
portion 203 and a right portion 205 with left and right
inside surfaces 207, 209, respectively. The inside
surfaces 207, 209 provide the external shape of the
automotive member to be produced, such as the seal 104.
The inside surfaces 207, 209 are first lined
with the mesh or layer 130 either loosely (as shown
ad~acent the right inside surface 209), or the layer can
be held in place by suitable means. For example, suction
may be applied through passages 211 to have the layer 130
roughly conform to the shape of the automotive member.
After a parison 213 of thermoplastic polymer material is
introduced into the mold 200, the mold is closed to pinch
the parison 213 as shown in Figure 6(b~. The parison 213
is then blown to expand the thermoplastic material toward
the inside surfaces 207, 209 to form the automotive
member. The expanding parison 213 engages the layer 130
and causes the layer 130 to mechanically interlock with
the automotive member being formed and conform to the
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shape of the member (similar to that shown in Fi~ure 5 for
the seal 104 and layer 130).
If desired, the mesh or layer 130 can then be
heated to its shrinking temperature to further tighten the
mechanical interlock between the seal 104 and mesh 130.
If the parison 213 is hot enough, then the mesh will
already have shrunk during the molding process, and no
further heat shrinking of the mesh is required. An
advantage of molding the mesh and seal together is the
resultant space saving to ship or store the coated
automotive members.
While an important application of the invention ;~
is in automotive applications, it will be realized ~hat
the invention may also be used in other applications where ~-
clamped seals or protective coatings are needed.
The above description is intended in an
illustrative rather than a restrictive sense and
variations to the specific configuration and materials
described may be apparent to skilled persons in adapting
120 the present invention to specific applications. Such
variations are intended to form part of the present
invention insofar as they are within the spirit and scope ~ ~;
of the claims below. -~
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