Note: Descriptions are shown in the official language in which they were submitted.
RELEASABLE SELF-LOCKING DEVICE AND METHOD FOR USING SAME TO
REPLACE BUSHINGS
Field of the Invention
[001] The present invention relates to the field of automotive and industrial
tools, more
specifically to tools for removing and installing bushings in a variety of
applications.
Background / Description of the Related Art
[002] Generally, a mechanical bushing (also sometimes referred to as a plain
bearing) is a
cylindrical lining, sleeve or spacer that is configured to be housed within a
cylindrical cavity, and
used to reduce friction and wear inside such cylindrical cavity, or to
constrict and restrain motion
of mechanical parts. For example, bushings are often found in vehicle
suspension systems,
excavators, aggregate equipment, and pump housings. Typically, bushings are
designed to fit
very tightly within such cylindrical cavities. Bushings can be made from
materials such as
various metals, plastics, and numerous other materials.
10031 Due to the nature of their use, bushings wear out over time and cease to
sufficiently hold
the components that pass through them in place. The damaged or worn-out
bushings must then
be removed from the cylindrical cavities within which they are tightly housed,
and replaced with
new bushings. Bushings can be removed and installed by various mechanical
means. In many
applications, a hollow hydraulic cylinder is utilized along with a threaded
shaft assembly to
remove and install bushings. Depending on the type of system involved, it is
not uncommon for
a large number of bushings to all have to be replaced in succession.
[004] Hydraulically removing bushings requires the use of various components.
One
conventional method (sometimes referred to herein as the "threaded shaft
method") comprises a
hollow hydraulic cylinder, a hydraulic power pack to actuate the hydraulic
cylinder, a
sufficiently sized hollow cylindrical sleeve which has an inner diameter that
is larger than the
outer diameter of the bushing to receive the bushing when removing it, a
length of threaded
shaft, a thick washer which has an outer diameter slightly smaller than the
outer diameter of the
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bushing, and one or more nuts on each end of the threaded shaft to keep the
assembly captive
while operating on the bushing. To remove the bushing, the threaded shaft is
passed through the
bushing and the thick washer is placed onto the threaded shaft and pushed up
against the
bushing. Next, a washer and a nut are installed on the same end to press up
against the thick
washer. A hollow cylindrical sleeve is then slid over the threaded rod from
the opposite side of
the thick washer. A hollow hydraulic cylinder is then slid onto the threaded
shaft and pressed up
against the hollow cylindrical sleeve. The hollow hydraulic cylinder is
followed by a washer and
a nut. The nut is spun on the threaded shaft until the assembly is held
tightly together. Finally,
hydraulic force is applied to pull the bushing from its housing and into the
receiving cylinder.
Some bushings are longer than the stroke of the hydraulic cylinder, so the
bushing must be
pulled out in multiple steps, tightening the nuts on either end of the
threaded shaft after each
step.
[005] Hydraulically installing bushings requires the use of similar components
as for
hydraulically removing bushings. When installing the bushing, it is often not
necessary to use
the cylindrical receiving sleeve since the thick washer pushes directly on the
bushing as it is
installed. Some applications may require the receiving sleeve, for example, if
the bushing sticks
out past the end of the housing on each side.
[006] Through repeated use, or because of improper storage, the threaded shaft
can become
more difficult to use. It may become dirty due to the environment that it is
used in. It may also
get damaged through use and improper storage. In particular, once the threaded
shaft becomes
dirty or damaged, hand tools may be required to hold the threaded shaft to
prevent it from
rotating while the nuts are spun into place with a wrench. This slows the
mechanic's progress
and adds significant time and frustration to the process. The time required to
complete a removal
or installation is amplified when a bushing must be pulled out or installed in
multiple steps.
Each time the cylinder reaches the end of its stroke and is collapsed back in,
the nut must be spun
further up the threaded shaft to continue the operation. After the operation
is complete, the nut
must be spun further off the threaded shaft to remove it.
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Brief Summary of the Invention
[007] Disclosed herein is a releasable self-locking device for use with a
shaft. More
specifically, the releasable self-locking device and shaft may be utilised as
a tool for removing
and installing bushings. A preferred embodiment of the bushing removal tool
comprises a
hexagonal shaft and a releasable self-locking device. The hexagonal shaft has
two opposing
ends, one of which is threaded. The releasable self-locking device utilizes a
plurality of jaws,
each with an internal angled slot and external teeth. The jaws are supported
by guide pins which
sit inside the slot in the jaws and are held in place in the main body of the
releasable self-locking
device. Once the device is slid onto the hexagonal shaft, springs are used to
hold the jaws
against the hexagonal shaft. When axial force is applied on the self-locking
device in a direction
opposite to the direction in which the self-locking device was installed, the
teeth on the jaws start
to frictionally engage and bite into the hexagonal shaft. As the teeth on the
jaws bite, the jaws
travel on the supporting guide pins and are pulled inwards toward the centre
of the shaft. As
more force is applied on the releasable self-locking device axially in the
direction opposite to the
direction of installation, the jaws push harder toward the centre of the shaft
and bite harder. In
this configuration, the releasable self-locking device functions as a one-
directional lock, i.e. it is
allowed to slide/move along the shaft in one direction (the direction from
which it was installed
onto the hexagonal shaft, sometimes referred to herein as the non-locking
direction), but it locks
against movement in the opposite direction (the direction opposite to which it
was installed,
sometimes referred to herein as the locking direction). As mentioned above,
once the jaws of the
releasable self-locking device are engaged on the hexagonal shaft, if
additional force is applied
to the self-locking device axially in the locking direction (or put another
way, if the hexagonal
shaft is pulled axially from the self-locking device in a non-locking
direction), this operates to
pull the jaws closer towards the axis of the hexagonal shaft and thus bite
harder.
[008] The releasable self-locking device is configured with a release ring,
which when
squeezed by the operator, acts against the spring force and lifts the jaws
from the surface of the
hexagonal shaft, thereby releasing the releasable self-locking device. Once
the releasable self-
locking device is released from the hexagonal shaft, it can be pushed back
along the hexagonal
shaft in the locked direction, and removed if desired. Some of the advantages
of the tool include
the following:
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= The releasable self-locking device is simply pushed onto the shaft and
may be quickly
slid into the desired location along the shaft and locked, without requiring
the user to
make many turns of a locking nut.
= The releasable self-locking device requires no additional tools to
install or remove it on a
hexagonal shaft.
= The jaws inside the releasable self-locking device allow it to lock onto
the shaft in any
location.
= When removing or installing a bushing in multiple stages due to limited
hydraulic
cylinder stroke, the releasable self-locking device is simply slid further
onto the
hexagonal shaft.
= In contrast to the conventional threaded shaft and nut method, damage to
the shaft can
help the jaws bite quicker and easier.
= The jaws are designed to self-locate in that they can rotate around their
support pin. This
allows them to bite onto the shaft more easily. This also allows them to bite
onto the
shaft even after the shaft has become bent.
= The release ring allows the operator to quickly and easily remove the
releasable self-
locking device.
[009] The present invention addresses some of the disadvantages related to the
use of the
threaded shaft when removing or installing bushings hydraulically. A hexagonal
shaft replaces
the threaded shaft. The hexagonal shaft is placed through the bushing just as
the threaded shaft
would be. One end of the hexagonal shaft will receive the thick washer and
will be held in place
with a flanged nut or securing nut; the securing nut does not need to be
removed during the
removal or installation of the bushing. The other end of the hexagonal shaft
will receive the
hollow hydraulic cylinder and the releasable self-locking device. The
releasable self-locking
device is simply pushed along the shaft toward the hydraulic cylinder until
the assembly is tight.
Hydraulic force is then applied by use of the hydraulic cylinder to remove the
bushing. Once
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completed, the releasable self-locking device is quickly released and slid
back off the hexagonal
shaft.
100101 Similar to a threaded shaft in the threaded shaft method, the
hexagonal shaft will
become dirty and damaged through use. However, the releasable self-locking
device will
continue to work as though the hexagonal shaft was new. The self-locking
device does not rely
on a specifically formed shaft to hold it in place. Rather, it will hold onto
the hexagonal shaft at
any location and it self-locates on rough surfaces because the jaws can be
configured to pivot to
follow the contours of the central shaft.
Brief Description of the Drawings
[0011] Embodiments of the present invention are described below with
reference to the
accompanying drawings in which:
[0012] Fig. 1 is an isometric view of an embodiment of the releasable self-
locking
device.
[0013] Fig. 2 is an isometric exploded view of the bushing removal tool.
[0014] Fig. 3 is a front view of the bushing removal tool, with the spring
cap of the
releasable self-locking device removed and the teeth of the jaws engaged on
the hexagonal shaft.
[0015] Fig. 4 is a sectional view of the bushing removal tool showing the
jaws of the
releasable self-locking device engaged on the hexagonal shaft.
[0016] Fig. 5 is a sectional view of the bushing removal tool showing the
jaws of the
releasable self-locking device disengaged from the hexagonal shaft.
[0017] Fig. 6 is an isometric sectional view of the bushing removal tool,
showing the
release ring holding the jaws disengaged from the hexagonal shaft and showing
the springs
pushing on the jaws opposite the release ring.
[0018] Fig. 7 is a sectional view showing the setup, including the bushing
removal tool,
used to remove a bushing from its bushing housing.
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[0019] Fig. 8 is a sectional view of the bushing removal tool in
operation, wherein a
bushing is shown partially removed.
[0020] Fig. 9 is a sectional view showing the setup used to install a
bushing into a
bushing housing.
[0021] Fig. 10 is a sectional view of the bushing removal tool in
operation, wherein the
bushing is shown partially installed.
[0022] Fig. 11 is a sectional view of the releasable self-locking device,
shown installed
upon a hexagonal shaft that has been deformed, and showing the jaws engaged
with the
hexagonal rod.
[0023] Fig. 12 is a sectional view of another embodiment of the releasable
self-locking
device, installed upon a hexagonal shaft.
[0024] Fig. 13 is an isometric view of the embodiment of the releasable
self-locking
device of Fig. 12, installed upon a hexagonal shaft.
Detailed Description of the Invention
[0025] The present invention now will be described more fully hereinafter
with reference
to the accompanying drawings, which form a part hereof, and which show, by way
of
illustration, exemplary embodiments by which the invention may be practiced.
The invention
may, however, be embodied in many different forms and should not be construed
as limited to
the embodiments set forth herein; rather, these embodiments are provided so
that this disclosure
will be thorough and complete, and will fully convey the scope of the
invention to those skilled
in the art. The following detailed description is, therefore, not to be taken
in a limiting sense.
[0026] An isometric view is shown of a releasable self-locking device 1 in
Fig. 1. The
component parts of the releasable self-locking device 1 can be more clearly
seen in Fig. 2, and
are discussed in greater detail below. In terms of what is visible from the
view in Fig. 1, the
releasable self-locking device 1 is shown as having a main body 11, a locking
assembly 13
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(having a plurality of jaws 6 and a plurality of guide pins 2), a spring cap
3, a plurality of cap
screws 5, and a release ring 7.
[0027] Referring to Fig. 2, an exploded isometric view of a bushing
removal tool 12 is
shown, which comprises the releasable self-locking device 1, a hexagonal shaft
4 and a securing
nut 10. As can be seen, the hexagonal shaft 4 is threaded at one end. The
securing nut 10 can be
screwed onto the threaded end of the hexagonal shaft 4 and operates to secure
a workpiece (such
as a bushing that has been installed into a bushing housing) and prevent it
from slipping off the
hexagonal shaft 4. The releasable self-locking device 1 comprises: shaft 4, a
main body 11; a
release ring 7; a locking assembly 13 (comprising a plurality of jaws 6 and
guide pins 2); a set of
springs 9; a spring cap 3 and one or more cap screws 5. Jaws 6 are held in
place inside the main
body 11 by guide pins 2. The set of springs 9 is secured inside spring cap 3.
The spring cap is
affixed to the main body 11. Preferably, the spring cap is detachably affixed
to the main body
11, so as to allow the inside of the releasable self-locking device 11 and its
internal components
to be more easily accessed, (e.g. for purposes of repair/maintenance, etc.).
In the preferred
embodiment, the spring cap is affixed to the main body 11 using a plurality of
cap screws 5.
[0028] A locking assembly 13 is housed within the main body 11, and is
configured with
one or more jaws 6 and one or more guide pins 2. Each guide pin 2 matingly
engages with a
corresponding angled slot 15 within each jaw 6 and functions to guide the
movement of each jaw
6 relative to the main body 11. (The operation of the locking assembly 13 can
be better seen in
Figs. 4 and 5 below, and is further described below). Each angled slot 15,
which may be
machined directly into the jaws 6, defines a channel bounded by sliding
surfaces within the
locking assembly 13, within which the corresponding guide pin 2 can move. A
set of springs 9 is
configured such that each spring pushes axially on a corresponding jaw 6, the
springs 9 being
mounted between the jaws 6 and spring cap 3. The springs 9 operate to bias
each corresponding
jaw 6 towards an engaged position, which is the position that the jaws are in
when "at rest". The
springs 9 are configured so that when the releasable self-locking device 1 is
installed on the
hexagonal shaft 4, the teeth 16 of the jaws 6 will sit on or proximate to the
surface of the
hexagonal shaft 4. However, it should be understood that it is not the springs
9 that cause the
jaws 6 to lock the releasable self-locking device 1. The springs 9 simply bias
the jaws 6 against
the surface of the hexagonal shaft 4, sufficiently firmly such that, when the
releasable self-
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locking device 1 is pulled from the hexagonal shaft 4 in the locking direction
(upon application
of a force), the interaction of each guide pin 2 and its corresponding angled
slot 15 causes the
teeth 16 of the jaws 6 to lock on the hexagonal shaft 4. Upon such application
of a force on the
releasable self-locking device 1 in the locking direction, the hexagonal shaft
is pulled back in the
opposite direction, each guide pin 2 cooperates with the corresponding angled
slot to cause the
jaws 6 to move towards the centre of the hexagonal shaft 4, thus causing the
teeth 16 of the jaws
6 to bite into the hexagonal shaft 4 and lock thereon. That is, the sliding
surfaces defining the
channels that the pins 2 are seated in, being angled with respect to the
central shaft, confine the
jaws 6 to move along a trajectory that moves the jaws 6 towards the central
shaft 4 when the
locking device 1 moves along the shaft in the locking direction, causing the
jaws 6 to move
oppositely to the locking direction relative to the locking device 1.
[0029] Thus, when the bushing removal tool 12 is to be used, the
releasable self-locking
device 1 has to be installed onto the hexagonal shaft 4 via the opening 14 in
the releasable self-
locking device 1 and positioned in the desired position along the hexagonal
shaft 4. The
releasable self-locking device 1 functions as one-direction lock in that it is
free to slide onto the
hexagonal shaft 4 (i.e. in the non-locking direction), but is constrained from
being able to slide
backwards along the hexagonal shaft 4 (i.e. in the locking direction). Indeed,
once the releasable
self-locking device 1 is installed upon the hexagonal shaft 4, it can readily
be pushed further
along the hexagonal shaft 4 in the non-locking direction, including, for
example, until it abuts or
is proximate to an adjacent workpiece. When a force is applied to the self-
locking device 1 in
the non-locking direction, any friction against the hexagonal shaft 4 will
cause the jaws 6 to push
back on the springs 9 and move out of the way. In order to slide the
releasable self-locking
device 1 backwards along hexagonal shaft 4 (i.e. in the locking
direction)(e.g. when
repositioning or removing the releasable self-locking device 1), the jaws 6
generally must first be
released into a disengaged position e.g. via actuation of the release ring 7
(discussed in more
detail below), before the releasable self-locking device 1 is free to slide
backwards along the
hexagonal shaft 4.
[0030] Further, as an optional feature, each of the jaws 6 are preferably
configured, as
shown, to be pivotable about the axis of a corresponding guide pin 2 to follow
the contours of the
surface of the central hexagonal shaft 4 (e.g. in the event the surfaces of
the hexagonal shaft 4 are
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slightly irregular or become rough), such that they self-locate for better
frictional engagement
with the hexagonal shaft 4. Although the guide pins 2 preferably have a
circular cross section, as
shown, since this naturally allows the jaw to pivot about the axis of the
guide pin, it is
contemplated that the guide pins could have other shapes and still function.
By way of example,
the guide pins 2 could have a generally square-shaped cross section, although
in this case, the
jaws 6 would not be pivotable. The releasable self-locking device I can
accordingly be used as a
lock that, when the jaws 6 are in an engaged position, functions to constrain
the axial movement
along a central shaft in one direction; the self-locking device 1 can be
configured to quickly
disengage from and release such central shaft when desired, via use of a
release ring 7 to
simultaneous disengage the jaws 6.
100311 Fig. 3 presents a front view of the bushing removal tool 12, with
the spring cap 3
of the releasable self-locking device 1 removed and the teeth of the jaws 6
engaged on the
hexagonal shaft 4.
[0032] Fig. 4 is a sectional view of the bushing removal tool 12, showing
the jaws 6 of
the releasable self-locking device 1 in an "engaged" position; in this engaged
position, the teeth
16 of the jaws 6 are biased upon the hexagonal shaft 4. As previously
described, after a force is
applied on the self-locking device 1 in the locking direction, this causes the
guide pin 2 and the
angled slot to cooperate such that the jaws 6 move towards the centre of the
hexagonal shaft 4,
causing the teeth 16 on the jaws 6 to "bite" on the surface of the hexagonal
shaft 4, thereby
locking the releasable self-locking device's position on the hexagonal shaft 4
against movement
in the general direction of the spring cap 3 (or locking direction).
100331 In order to disengage the jaws 6 of the releasable self-locking
device 1 from this
engaged/locked position and place them into a disengaged position, the release
ring 7 may be
actuated by the user pulling the release ring in the general direction of the
spring cap 3. This in
turn forces the jaws 6 towards the spring cap 3. Once the force exerted on the
release ring is
greater than the combined spring force from the springs 9, the jaws 6 move in
the general
direction of the spring cap 3. Due to the interaction between the guide pins 2
and the angled
slots 15, as the jaws 6 move axially toward the spring cap 3 (i.e. in the
locking direction), the
guide pins 2 guide the jaws 6 to move radially away from the centre of the
hexagonal shaft 4,
thus releasing the self-locking device 1 from the hexagonal shaft 4. When the
self-locking
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device 1 is in such disengaged position, it can readily and freely slide on
and along the hexagonal
shaft 4, including in the locking direction. Once the release ring 7 is
released, the springs 9 push
axially on the jaws 6 and the release ring 7, thereby returning the jaws 6 to
their tightest radial
position. Fig. 5 is a sectional view of the bushing removal tool 12, showing
the jaws 6 in such
"disengaged" position.
[0034] Referring to Fig. 6, this is an isometric sectional view of the
bushing removal
tool, showing the release ring 7 holding the jaws 6 in a disengaged position,
disengaged from the
hexagonal shaft 4. In this position, the springs 9 are pushing back on the
jaws 6 in opposition to
the direction of the release ring 7.
[0035] Although the shaft (i.e. the hexagonal shaft 4) that the releasable
self-locking
device 1 engages with is illustrated herein as having a cross-section that is
hexagonally shaped, it
will be apparent to one skilled in the art that differently shaped shafts may
also be used, e.g.
round, square, octagonal, etc. Accordingly, the releasable self-locking device
1 would then
preferably be adapted to work with such a shaft. By way of example, if an
octagonal shaft was
used, the releasable self-locking device may be configured to have four jaws 6
(along with
corresponding guide pins and springs therefor) that function to engage the
surfaces of the shaft.
It is contemplated that different shafts and configurations for the releasable
self-locking device
may be used, provided there is enough friction when the jaws engage with the
shaft such that the
releasable self-locking device 1 maintains its position on the shaft 4.
Possible options not
specifically illustrated herein, include knurling the shaft, machining a
specific profile into the
shaft, or other similar methods that achieve a "linear ratchet" effect.
Further, the main function
of the teeth 16 of the jaws 6 is that they enable frictional engagement with
the shaft in one
direction; as such, it should be appreciated that they can take various forms,
including various
known friction modifiers. In addition, the teeth 16 can be configured to take
into account the
nature/shape of the shaft used (e.g. the teeth and jaws, rather than being
generally flat as
illustrated herein, may be configured to be in a curved orientation to better
engage with a
cylindrically-shaped shaft or a threaded rod).
[0036] Figs. 7-10 illustrate the bushing removal tool in operation, where
it is used in
combination with various components in order to remove / install a bushing 20.
Figs. 7 and 8
show an exemplary embodiment of the method by which the bushing removal tool
12 can be
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utilised to remove an installed bushing 20 from a bushing housing 23.
Referring to Fig 7, the
hexagonal shaft 4 is placed through the inner diameter of bushing 20 from the
right. It is slid
through bushing 20 until a pulling washer 22 is sandwiched between securing
nut 10 and the
bushing 20. The pulling washer 22 generally has an outer radius that is
greater than the inner
radius of the bushing 20 but less than the outer radius of the bushing 20,
such that there is
sufficient overlap to enable the pulling washer 22 to apply a force and act on
the edges of the
bushing 20. A pulling sleeve 21 is slid over the hexagonal shaft 4 from the
left side and pushed
up to the bushing housing 23. The pulling sleeve 21 serves to receive the
bushing 20 as the
bushing 20 is removed from the bushing housing 23; as such the pulling sleeve
21 generally has
an inside radius that is greater (preferably slightly greater) than the
outside radius of the bushing
20. A hollow hydraulic cylinder 24 is then slid over the hexagonal shaft 4
from the left and
placed such that it abuts the pulling sleeve 21. The releasable self-locking
device 1 is then slid
onto hexagonal shaft 4 from the left until the main body 11 abuts the
hydraulic cylinder ram 25.
Once the assembly is secure, hydraulic pressure is axially applied through use
of the hollow
hydraulic cylinder 24. As the hydraulic ram 25 is forced axially to the left
(in the locking
direction) by hydraulic pressure in the hollow hydraulic cylinder 24, the jaws
6 grasp onto the
hexagonal shaft 4 and pull the hexagonal shaft 4 axially to the left. As
hexagonal shaft 4 moves
to the left, it pulls the securing nut 10, the pulling washer 22, and the
bushing 20 with it.
[0037]
Referring to Fig 8, bushing 20 is shown part-way inside the pulling sleeve 21.
If
the bushing 20 is longer than the stroke of the hydraulic cylinder ram 25,
then further cycles of
pulling will be required to be applied in order to completely remove the
bushing 20 from the
bushing housing 23. To do so, the hydraulic pressure is first released, the
hydraulic ram 25 is
pulled back into the body of the hollow hydraulic cylinder 24 and the
releasable self-locking
device 1 is pushed further along the hexagonal shaft 4 (so that it abuts the
hydraulic cylinder ram
25); then the hydraulic pressure is reapplied, which has the effect of pulling
the bushing 20
further out from the bushing housing 23. Once the bushing 20 is completely
removed from the
bushing housing 23 and sitting inside the pulling sleeve 21, the releasable
self-locking device 1
can be removed from hexagonal shaft 4. Release ring 7 is pulled toward spring
cap 3 to pull the
jaws 6 into a disengaged position away from hexagonal shaft 4. The releasable
self-locking
device 1 is then slid off the hexagonal shaft 4 to the left, freeing the
remainder of the components
for easy disassembly without the need for any tools.
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[0038] Figs. 9 and 10 show an exemplary embodiment of the method by which
the
bushing removal tool 12 can be utilised to install a new or replacement
bushing 20 into a bushing
housing 23. Referring to Fig 9, the hexagonal shaft 4 is slid through the
hollow hydraulic
cylinder 24 from the right until the securing nut 10 abuts the hydraulic ram
25. The hexagonal
Shaft 4 is then placed through the bore of the bushing housing 23 until the
hollow hydraulic
cylinder 24 abuts the bushing housing 23. The bushing 20 is placed over the
hexagonal shaft 4
from the left and slid up to the bushing housing 23. Lastly, the releasable
self-locking device 1 is
slid onto hexagonal shaft 4 and pushed up to abut with the bushing 20. As the
hydraulic ram 25
is forced axially to the right by the application of hydraulic pressure in the
hollow hydraulic
cylinder 24, the hexagonal shaft 4 is pulled to the right. The jaws 6 grasp
the hexagonal shaft 4
and consequently pull the main body 11 to the right. As the main body 11 moves
to the right, it
presses the bushing 20 into the bushing housing 23.
[0039] Referring to Fig 10, the bushing 20 is shown partially installed in
the bushing
housing 23. If the bushing 20 is longer than the stroke of the hydraulic
cylinder ram 25, then
further cycles of pulling will be required to be applied in order to
completely install the bushing
20 into the bushing housing 23. To do so, the hydraulic pressure is released,
the hydraulic ram
25 is pulled back into the body of the hollow hydraulic cylinder 24, the
hexagonal shaft 4,
hollow hydraulic cylinder 24 and securing nut 10 are pushed to the left until
the hollow hydraulic
cylinder 24 abuts bushing housing 23 and the releasable self-locking device 1,
is pushed further
along the hexagonal shaft 4 to the right (non-locking direction) until
releasable self-locking
device 1 abuts the bushing 20; then the hydraulic pressure is reapplied, which
has the effect of
pushing the bushing 20 further into the bushing housing 23. Once the bushing
20 is completely
installed in the bushing housing 23, the releasable self-locking device 1 can
be easily removed
from hexagonal shaft 4. The release ring 7 is pulled in the general direction
of the spring cap 3
to pull the jaws 6 away from the hexagonal shaft 4. The releasable self-
locking device 1 is then
slid off the hexagonal shaft 4 to the left, freeing the remainder of the
components for easy
disassembly without the need for any tools.
[0040] Fig. 11 is a sectional view of the releasable self-locking device
1, shown installed
upon a hexagonal shaft that has been bent/deformed. This illustrates how the
releasable self-
locking device 1 can operate even in instances where the central shaft has
been damaged or
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undergone wear-and-tear, in contrast to the conventional "threaded shaft"
method. (This could
also be the case if the hexagonal shaft 4 was not bent, but was not passed
straight through the
releasable self-locking device 1). In this example, the jaws 6 can slightly
pivot about the guide
pin 2. This results in better frictional engagement with the deformed central
shaft (than if the
jaws 6 remained horizontal). Thus, although the central shaft 4 is bent, the
teeth 16 of the jaws 6
can nevertheless "bite" on and frictionally engage the central shaft.
100411 Figs. 12 and 13 are respectively, a sectional view and an isometric
view, of an
exemplary alternative embodiment of the releasable self-locking device 1,
installed upon a
hexagonal shaft 4. In this particular embodiment, the jaws are in the form of
cam-shaped jaws
6B, which pivot about a guide pin 2B. The surfaces of the guide pin 2B and the
openings in
which the guide pin 2B are received in the main body of the alternative
embodiment of device 1
define surfaces that confine the jaws 6B to rotate around the center of the
guide pins 2B and
move towards the central shaft 4 when the device 1 is moved in a locking
direction. A spring 9B
functions to bias the cam-shaped jaw 6B against the central shaft 4. The cam-
shaped jaws 6B are
configured and positioned such that when the releasable self-locking device 1
is installed upon a
central shaft, it can freely slide in one direction (non-locking direction,
but if it is pulled in a
locking direction, the cam-shaped jaws operate to provide increasing
frictional force against the
central shaft 4. The teeth of the jaws 6B may also be angled accordingly to
facilitate the locking
in one direction.
100421 A method of removing a bushing may be described more generally as
follows. A
shaft is inserted through each item of a set of items including a bushing
housing and bushing
assembly, a bushing engagement element for engaging the bushing and sized to
fit within the
bushing housing, a bushing housing engagement element for engaging the bushing
housing and
sized to contain the bushing, and a variable length element for providing a
force. The bushing
engagement element and the bushing housing engagement element are arranged
abutting
opposite ends of the bushing housing and bushing assembly. Pulling washer 22
is an example of
a bushing engagement element and pulling sleeve 21 is an example of a bushing
housing
engagement element. Hydraulic ram 25 and hydraulic cylinder 24 together
comprise an example
of a variable length element for providing a force. A first securing element
and a second securing
element are provided on the shaft for securing the set of items between the
first securing element
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and the second securing element. By making at least one of the first securing
element and second
securing element a directional locking device, the directional locking device
can be conveniently
slid on the shaft to reduce a distance between the directional self-locking
device and the other of
the first and second securing elements, while locking against an increase of
that distance. A
directional locking device defines a locking direction and a non-locking
direction opposite to the
locking direction, such that the directional self-locking device locks against
motion of the device
in the locking direction and allows motion of the device in the non-locking
direction. The
directional self-locking device is arranged on the shaft with the locking
direction oriented away
from the other of the first and second securing elements to lock against
motion of the directional
self-locking device on the shaft away from the other of the first and second
securing elements. In
the embodiment described above, the securing nut 10 is the first securing
element and is threaded
onto a threaded end of the shaft, and the releasable locking device is the
second securing
element. A non-releasable directional locking device could also in principle
be used, as the nut
and set of items could be removed from the shaft first and the directional
locking device slid off
the shaft in the non-locking direction. A releasable locking device is however
more conveniently
removable. It is not necessary for both securing elements to be removable. For
example, a built
in head of the shaft could be used as the first securing element instead of
the nut in the
embodiment above. It is not necessary for the items to be arranged on the
shaft in the order
described in the embodiment above. In order to remove the bushing, the
variable length element
is operated to increase a length of the variable length element. The first and
second securing
element constraining an overall length of the set of items on the shaft to the
distance between the
directional self-locking device and the other of the first and second securing
elements, thereby
forcing the bushing engagement element to move towards the bushing housing
engagement
element and move the bushing relative to the bushing housing. For clarity, the
overall length of
the set of items refers to a distance between portions of the items that
contact the securing
elements in operation and the distance between the securing elements refers to
a distance
between portions of the securing elements that contact the items in operation.
It should be noted
that the engagement elements need not be separate elements. The variable
length element could
be shaped to act as one of the engagement elements and either of the securing
elements could be
shaped to act as an engagement element. In the case that a securing element is
shaped to act as an
engagement element, then the overall length of the set of items refers to an
overall length
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including an engagement portion of the securing element, and the distance
between the securing
elements refers to a distance extending to a boundary between the engagement
portion of the
securing element and a remainder of the securing element. If the above steps
do not sufficiently
move the bushing relative to the bushing housing to remove the bushing froni
the bushing and
bushing housing assembly, then the variable length element may be allowed to
reduce in length
and the directional locking device again slid along the shaft to reduce the
distance between the
directional self-locking device and the other of the first and second securing
elements. The
variable length element can then be operated again to again force the bushing
engagement
element to move towards the bushing housing engagement element and move the
bushing
relative to the bushing housing. These steps can be repeated until the bushing
is removed from
the bushing housing assembly.
[0043] The same method may be used mutatis mutandis to install a bushing
in a bushing
housing. For installation of a bushing in a bushing housing, as the bushing
and bushing housing
are to be moved together and not apart from one another, it is not necessary
to use a bushing
housing engagement element and a bushing engagement element. These elements
may of course
still be used. The set of items will include a bushing housing and a bushing
arranged adjacent to
the bushing housing.
[0044] It will be apparent to one skilled in the art from the above
examples that the
disclosed invention offers advantages over the conventional "threaded shaft
method". Unlike
that method, there is no requirement in the disclosed method (other than to
secure the securing
nut 10) to turn various nuts on a threaded shaft; any savings in terms of
time, effort and
frustration, are amplified further where a bushing must be pulled out or
installed in several
cycles, and where numerous bushings are required to be removed together.
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