U.S. patent application number 09/441628 was filed with the patent office on 2002-01-31 for park brake cable system including connector clip.
This patent application is currently assigned to DORSEY & WHITNEY LLP. Invention is credited to PETRAK, GREGORY H..
Application Number | 20020011129 09/441628 |
Document ID | / |
Family ID | 26722313 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020011129 |
Kind Code |
A1 |
PETRAK, GREGORY H. |
January 31, 2002 |
PARK BRAKE CABLE SYSTEM INCLUDING CONNECTOR CLIP
Abstract
A park brake cable system including a brake actuation lever, a
connector clip having a first end and a second end, and including a
shear member, having a shear failure force, positioned between the
first and second ends. A brake assembly, a front cable strand
having a first and second ends, the first end attached to the brake
actuation lever, and the second end engaging the shear member on
the connector clip are also included. Further included are a rear
cable strand having a first end and a second end, the first end
attached to the second end of the connector clip and the second end
attached to the rear brake assembly, and tensioner means are
attached in a tension force transmitting relationship with the
front cable strand and the rear cable strand. Applying tension to
the front and rear cable strands by the tensioner means creates at
least the sufficient shear failure force to cause the second end of
the front cable strand to break the shear member and move to the
first end of the connector clip The present invention also includes
a connector clip including a main body having an interior cavity,
and open first and second ends, and a shear member extending across
a portion of the interior cavity.
Inventors: |
PETRAK, GREGORY H.; (GOLDEN,
CO) |
Correspondence
Address: |
DORSEY & WHITNEY, LLP
SUITE 4700
370 SEVENTEENTH STREET
DENVER
CO
80202-5647
US
|
Assignee: |
DORSEY & WHITNEY LLP
|
Family ID: |
26722313 |
Appl. No.: |
09/441628 |
Filed: |
November 16, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09441628 |
Nov 16, 1999 |
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09064402 |
Apr 22, 1998 |
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5983745 |
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60045044 |
Apr 28, 1997 |
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Current U.S.
Class: |
74/502.6 |
Current CPC
Class: |
B60T 11/06 20130101;
F16C 1/22 20130101; Y10T 74/20408 20150115; B60T 7/108 20130101;
B60T 11/046 20130101; Y10T 74/20462 20150115; Y10T 74/2045
20150115; B60T 7/08 20130101; F16C 1/101 20130101 |
Class at
Publication: |
74/502.6 |
International
Class: |
F16C 001/10 |
Claims
I claim:
1. A park brake cable system comprising: a brake actuation lever; a
connector clip having a first end and a second end, and including a
shear member, having a shear failure force, positioned between the
first and second ends; a brake assembly; a front cable strand
having a first and second ends, the first end attached to the brake
actuation lever, and the second end engaging the shear member on
the connector clip, a rear cable strand having a first end and a
second end, the first end attached to the second end of the
connector clip and the second end attached to the rear brake
assembly; and tensioner means attached in a tension force
transmitting relationship with the front cable strand and the rear
cable strand; wherein applying tension to the front and rear cable
strands by the tensioner means creates at least the shear failure
force to cause the second end of the front cable strand to break
the shear member and move to the first end of the connector
clip.
2. The park brake cable system as defined in claim 1 wherein
actuating said tensioner means develops a first tension level prior
to breaking the shear member, and a second residual tension level
after breaking the shear member.
3. The park brake cable system as defined in claim 1 further
comprising: a rear left brake assembly; a rear right brake
assembly; an equalizer structure; a rear left cable strand attached
to and extending between said equalizer and said rear left brake
assembly; and a rear right cable strand attached to and extending
between said equalizer and said rear right brake assembly; wherein
the actuation of said tensioner means tensions said front, rear
right and rear left cable strands.
4. The cable system as defined in claim 3 wherein said tensioner is
positioned on said equalizer.
5. The cable system as defined in claim 3 wherein said tensioner is
positioned on said brake actuation lever.
6. A connector clip for a cable system comprising: a main body
having an interior cavity, and open first and second ends; and a
shear member extending across a portion of the interior cavity
7. A connector clip as defined in claim 6 wherein. said shear
member is a tab extending into said interior cavity.
8. A connector clip as defined in claim 7 wherein: said shear
member defines a stress riser.
9. A connector clip as defined in claim 7 wherein: said shear
member has a front face and a rear face, and defines a stress riser
in said front face.
10. A connector clip as defined in claim 7 wherein: said shear
member has a front face and a rear face, and defines a stress riser
in said rear face.
11. A connector clip as defined in claim 6 wherein: said shear
member has a partial cylindrical main body and defines a tab
extending orthogonally inwardly; said main body defines an outer
surface and an aperture formed through said main body from said
outer surface to said interior cavity; said shear member mounts on
said outer surface and said tab extends through said aperture to
extend across at least a portion of the interior cavity.
12. A connector clip as defined in claim 6 wherein: said main body
is a cylindrical body defining a bore therethrough having interior
side walls; said shear member is a shear disk attached to said
interior side walls and extends across said bore.
13. A connector clip as defined in claim 12 wherein said shear disk
is attached at selected locations along said side wall.
14. A connector clip as defined in claim 12 wherein said shear disk
is attached continuously along said side wall.
15. A connector clip as defined in claim 12 wherein said shear disk
extends radially across said interior cavity.
16. A connector clip as defined in claim 12 wherein said shear
member defines a stress riser therein.
17. A connector clip as defined in claim 12 wherein. said shear
disk has a front face and a rear face; and said front face defines
a stress riser therein.
18. A connector clip as defined in claim 12 wherein: said shear
disk has a front face and a rear face; and said rear face defines a
stress riser therein.
19. A method of adjusting the tension in a park cable brake system
comprising the steps of: providing a brake actuation lever, a
connector clip having a first end and a second end, and including a
shear member, having a shear failure force, positioned between the
first and second ends, a brake assembly, a front cable strand
having a first and second ends, the first end attached to the brake
actuation lever, and the second end engaging the shear member on
the connector clip, a rear cable strand having a first end and a
second end, the first end attached to the second end of the
connector clip and the second end attached to the rear brake
assembly, and tensioner means attached in a tension force
transmitting relationship with the front cable strand and the rear
cable strand; tensioning said first and second cable strands with
said tensioner means; and breaking said shear member.
20. The method as defined in claim 19, further comprising the steps
of: actuating said brake lever to break said shear member.
21. A method of adjusting the tension in a park cable brake system
comprising the steps of: tensioning a first and second cable
strands with a tensioner means; and breaking a shear member engaged
by one end of said first cable strand.
Description
FIELD OF THE INVENTION
[0001] This invention relates to cable connector clips and
particularly to connector clips of the type used to adjust the
tension of park brake cable systems used in motor vehicles.
BACKGROUND OF THE INVENTION
[0002] Most motor vehicles utilize some type of cable system to
engage and release the rear brakes to act as a parking brake. The
parking brake system basically includes a pedal or lever actuator,
a front cable strand, a left rear cable strand, a right rear cable
strand, a front cable conduit, a left rear cable conduit, and a
right rear cable conduit through which the front and rear cable
strands extend, respectively, an equalizer assembly positioned
between the front and rear cable strands, tensioning rod and nut,
cable connector and left and right rear brake assemblies. The left
and right rear cable strands are attached to the left and right
rear brake assemblies, respectively.
[0003] The following, is a description of the general operation of
a park brake system to assist in understanding the invention. A
brake pedal or lever is actuated to apply tension to the front
cable strand. The front cable strand is connected to the left and
right rear cable strands through an equalizer. The function of the
equalizer is to equally distribute tension in the front cable to
the right and left rear cables so that the tension is balanced
between the cables extending to the left and right rear brake
assemblies when the lever is actuated. The added tension applied to
the rear cable strands overcome the spring in each rear brake
assembly to cause the brakes to engage and act as a parking brake.
The spring normally holds the rear brake shoes or calipers open and
thus disengaged.
[0004] In operation, it is desirable that high tension exists in
the cables even when the pedal or lever is in the non-actuated
position (residual tension). Adequate residual tension in the cable
system means that the pedal or lever does not have to be extended a
great distance to achieve a strong force at the brake assemblies to
provide for secure engagement. Furthermore, the high tension helps
eliminate the slack and voids in the cables and conduits, which
reduces creep or lengthening of the cable thus making consistent
the range of motion of the lever. This same high level of
consistency in actuator travel will also exist from vehicle to
vehicle.
[0005] The objective at the time of installation of the park brake
cable system is, therefore, to introduce enough high tension to the
cables so that "voids" in the conduit system and cable stretch are
effectively removed In this way the system will not continue to
loosen-up over repeated actuation and there will be continued
consistency in pedal or lever travel over the life of the vehicle
and from vehicle to vehicle This objective is difficult to achieve
in a rapid and inexpensive manner such as required in a high volume
automotive assembly line environment.
[0006] Various methods of tensioning the cable system are used, all
with the goal of introducing enough tension to the cable system
during installation to remove voids minimize variation in actuator
travel from vehicle to vehicle. One method of tensioning the cable
system is to tension the cables during installation to a level
where the brakes are almost starting to drag and no further. In
this method a predefined level of tension is determined and the
park brake cable system of all the vehicles on the assembly line
are tensioned to this level. This method typically results in wide
variation in lever travel from vehicle to vehicle and also results
in a system that loosens-up over time since the voids in the cable
and conduit are not sufficiently removed. Merely tensioning to a
level just below brake drag does not introduce enough initial
tension to completely remove system voids and eliminate cable
stretch.
[0007] Another method is to tension the cable system during
installation to a level far beyond what is required to merely
engage the brakes. In doing so, many of the voids in the cable and
conduit system are removed and the cable stretch accomplished. The
tension in the cable system is then reduced just enough until the
brake assemblies are no longer engaged. This method results in an
optimally tensioned park brake cable system, however, it is time
consuming because the cables must be initially tensioned to a very
high level and then de-tensioned to a desired residual tension
level. Expensive instruments are required to measure the tension in
the cable system at both the tensioning and de-tensioning steps to
insure the final or residual tension in the cable system is
adequate. This method takes a relatively long time to perform
during production of the vehicle.
[0008] There is a continuing need in the art for an improved park
brake cable system and method for adjusting, including a cable
connector clip, that provides the proper amount of tensioning and
tension relief for consistent park brake performance for a vehicle,
and minimal variation of park brake performance from vehicle to
vehicle. It is with the shortcomings of the prior art in mind that
the instant invention was developed
SUMMARY OF THE INVENTION
[0009] The invention described herein provides a simple mechanism
that simulates the second optimal method without requiring the time
necessary to both tension and de-tension the cable system, and
without requiring the expensive tooling and instrumentation
necessary to perform this method of brake adjustment.
[0010] The benefit of the shear tab cable connector is two fold: 1)
to reduce variation in cable and actuator travel from vehicle to
vehicle and 2) to allow the cable system to be over-tensioned to
remove voids and then to release sufficient tension to unlock the
brakes and allow adequate residual tension to remain in the cable
system. In this way the cable system does not loosen appreciably
over time. An additional objective of the shear tab cable connector
is to provide for an optimal cable system tensioning method that
does not consume a great deal of time and is therefore suitable for
rapid automotive assembly operations.
[0011] These objectives are accomplished with the shear tab cable
connector as described herein, where during the vehicle assembly
process the cable is highly tensioned to a point beyond what is
required to lock-up the rear brake assemblies. The shear member is
then broken to allow the cable system to slightly de-tension to a
desired residual tension level. The amount of residual tension in
the cable system is enough so that when the pedal or lever is
released the rear brakes disengage only enough to disengage the
rear brake assemblies so they are no longer dragging. The shear tab
member can be broken by activation of the brake lever, or by
continued adjustment of the tensioning means.
[0012] The instant invention allows a cable tension adjusting
process where the cables are over-tensioned to remove system voids
and then loosened only enough to just disengage the brake
assemblies. Significant residual tension is therefore left in the
cable system even when the brake actuator lever is in the released
position, the result being a tight, responsive cable system with
little variation in brake actuator lever travel from vehicle to
vehicle and a cable system that will not loosen significantly over
the life of the vehicle.
[0013] The present invention encompasses a park brake cable system
including a brake actuation lever, a connector clip having a first
end and a second end, and including a shear member, having a shear
failure force, positioned between the first and second ends. A
brake assembly, a front cable strand having a first and second
ends, the first end attached to the brake actuation lever, and the
second end engaging the shear member on the connector clip are also
included. Further included are a rear cable strand having a first
end and a second end, the first end attached to the second end of
the connector clip and the second end attached to the rear brake
assembly, and tensioner means are attached in a tension force
transmitting relationship with the front cable strand and the rear
cable strand. Applying tension to the front and rear cable strands
by the tensioner means creates at least the sufficient shear
failure force to cause the second end of the front cable strand to
break the shear member and move to the first end of the connector
clip.
[0014] In further detail, the instant invention also includes a
rear left brake assembly, a rear right brake assembly, an equalizer
structure, a rear left cable strand attached to and extending
between the equalizer and the rear left brake assembly, and a rear
right cable strand attached to and extending between the equalizer
and the rear right brake assembly. The actuation of the tensioner
means tensions the front, rear right and rear left cable
strands.
[0015] The tensioner means can be positioned either on the
equalizer or on the brake actuation lever.
[0016] The present invention also includes a connector clip
including a main body having an interior cavity, and open first and
second ends, and a shear member extending across a portion of the
interior cavity.
[0017] In further detail, the present invention also includes a
connector clip for park brake cable systems where the shear member
has a partial cylindrical main body and defines a tab extending
orthogonally inwardly, the main body defining an outer surface and
an aperture formed through the main body from the outer surface to
the interior cavity, the shear member mounting on the outer surface
and the tab extending through the aperture to extend across at
least a portion of the interior cavity.
[0018] Alternatively, the connector clip also includes the main
body having a cylindrical body defining a bore therethrough having
interior side walls, the shear member is a shear disk attached to
the interior side walls and extends across the bore.
[0019] The present invention encompasses a method of adjusting the
tension in a park cable brake system comprising the steps of
providing a brake actuation lever, a connector clip having a first
end and a second end, and including a shear member, having a shear
failure force, positioned between the first and second ends, a
brake assembly, a front cable strand having a first and second
ends, the first end attached to the brake actuation lever, and the
second end engaging the shear member on the connector clip, a rear
cable strand having a first end and a second end, the first end
attached to the second end of the connector clip and the second end
attached to the rear brake assembly, and tensioner means attached
in a tension force transmitting relationship with the front cable
strand and the rear cable strand; tensioning the first and second
cable strands with the tensioner means; and breaking the shear
member.
[0020] In more detail, the present invention also encompasses a
method having the additional steps of actuating the brake lever to
break the shear member.
[0021] Alternatively, the present invention also encompasses a
method having the additional steps of tensioning a first and second
cable strands with a tensioner means; and breaking a shear member
engaged by one end of the first cable strand.
[0022] Accordingly, it is the primary object of the present
invention to provide a park brake cable system that is easily
adjusted and set at the appropriate tension during assembly.
[0023] It is another object of the present invention to provide a
connector clip for park brake cable systems that includes a shear
member that allows sufficient high tension application, and once
broken, establishes the proper residual stress in the cable
system.
[0024] Other aspects, features and details of the present invention
can be more completely understood by reference to the following
detailed description of a preferred embodiment, in conjunction with
the drawings, and from the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a schematic diagram of a reaction conduit side
pull park brake cable system of the present invention, including
the connector clip having a shear tab, the system being in a
relatively low tension state.
[0026] FIG. 2 is a schematic diagram of a reaction conduit side
pull park brake cable system of the present invention, including
the connector clip having a shear tab, the system being in a
relatively high tension state.
[0027] FIG. 3 is a schematic diagram of a reaction conduit side
pull park brake cable system of the present invention, including
the connector clip having a shear tab, the system being in a lower
tension state after the shear tab has broken.
[0028] FIG. 4 is a schematic diagram of a reaction conduit side
pull park brake cable system of the present invention, including
the connector clip having a shear tab, the system being in a
residual tension state.
[0029] FIG. 5 shows a view of the cable ends.
[0030] FIG. 6 is a bottom view of the first embodiment of the
connector clip used with the side-pull park brake cable system.
[0031] FIG. 7 is a top perspective view of the connector clip of
FIG. 6.
[0032] FIG. 8 is a bottom perspective view of the connector clip of
FIG. 7.
[0033] FIG. 9 is a bottom perspective view of the shear member used
with the connector clip of FIG. 6.
[0034] FIG. 10 is an end view of the shear member of FIG. 9.
[0035] FIG. 11 is a bottom view of the shear member of FIG. 10.
[0036] FIG. 12 is a perspective view of the first embodiment of the
connector clip of FIG. 6, with the shear member of FIG. 9 applied
thereto, and the cable ends of FIG. 5 positioned therein.
[0037] FIG. 13 is a section taken along line 13-13 of FIG. 12,
showing one cable end in the intermediate position resting on the
shear tab.
[0038] FIG. 14 is a section taken along line 14-14 of FIG. 12 FIG.
15 is a section similar to that of FIG. 14, with the shear tab
broken and one cable end repositioned to the terminal position.
[0039] FIG. 16 is top perspective view of an alternative embodiment
of the connector clip of FIG. 6.
[0040] FIG. 17 is a section view taken along line 17-17 of FIG.
16
[0041] FIG. 18 is a representative section view of the connector
clip of FIG. 16.
[0042] FIG. 19 is a schematic view of a second embodiment of the
side pull park brake cable system, including a second embodiment of
the connector clip, having a shear member, used therein.
[0043] FIG. 19a is an enlarged section of the second embodiment of
the connector clip.
[0044] FIG. 20 is a schematic view of the second embodiment of the
side pull park brake cable system in a higher tension state.
[0045] FIG. 21 is an enlarged section of the second embodiment of
the connector clip after the shear member is broken.
[0046] FIG. 22 is a schematic view of the second embodiment of the
side pull park brake cable system in a residual tension state after
the shear member is broken.
[0047] FIG. 23 is an enlarged section of the second embodiment of
the connector clip.
[0048] FIG. 24 is an enlarged section of an alternative embodiment
of the second embodiment of the connector clip.
[0049] FIG. 25 is a section taken along line 25-25 of FIG. 24.
[0050] FIG. 26 is a schematic view of the center pull park brake
cable system of the present invention, including the second
embodiment of the connector clip.
[0051] FIG. 27 is an enlarged view of the brake lever and connector
clip of FIG. 26.
[0052] FIG. 28 is a schematic view similar to that of FIG. 26,
wherein the cable system is under relatively high tension and the
brake pads engage the brake drums.
[0053] FIG. 29 is an enlarged view of the brake lever and connector
clip of FIG. 28.
[0054] FIG. 30 is a schematic view similar to that of FIG. 28,
wherein the shear plate has broken and the cable system is at the
state of residual tension.
[0055] FIG. 31 is an enlarged view of the brake lever and connector
clip of FIG. 30.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0056] As a general description with reference to FIG. 1, the
present invention concerns the use of a connector clip 40 having a
shear member 42 in a park brake cable system. The shear member 42
allows the application of a very high tension to the cable system
44 to eliminate voids in the system and accelerate the cable
stretch that would otherwise occur during use. The shear member 42
also allows a calculated de-tensioning of the cable system 44 to a
residual tension level desired for consistent performance.
[0057] The cable systems described below fall into one of two
categories: a side-pull park brake cable system, also referred to
as a reaction-conduit system, and a center-pull park brake cable
system. Each of these two types of cable systems includes a brake
activation lever movably attached to the vehicle, a front cable
strand, an equalizer structure, left and right rear cable strands,
conduits through which the cables extend, left and right rear brake
assemblies, and a connector clip having a shear member.
[0058] The park brake cable system of the present invention is
described below with respect to brake assemblies having brake pads
and brake drums. It is contemplated that the park brake cable
system of the present invention would work equally well with disk
brake systems having calipers and rotors.
[0059] The connecting clip on which the inventive park brake system
is based includes a body structure having either a shear tab or a
shear disk attached thereto. The shear member can be integrally
formed with the connector clip, or can be a separate member
attached to the connector clip. The shear tab or disk is designed
to require a calculated shear force to break the tab or disk from
the body member, which allows the tension in the cable system to
change from a desired high tension (for removing voids and
stretching the cable) to a desired residual tension.
[0060] The park brake cable system, the connector clip and shear
member, and associated method, are described below in detail.
[0061] Referring to FIGS. 1 through 4, the operation of a side-pull
parking brake cable system is shown in schematic form. A side-pull
parking brake cable system 46 utilizes a known or available
reaction-conduit type structure. The reaction-conduit structure
includes a brake actuating lever 48 movably attached to the
structure 50 of the vehicle, a front cable strand 52 attached at
one end to the lever 48 and defining at the other end a cable bead
54. The front cable strand 52 extends through a flexible conduit
56. The conduit 56 is flexible along its length, but is relatively
rigid in the axial orientation, and can be made of wound metal as
is known in the art. The first end of the conduit 56 is attached to
the vehicle frame 50 and the second end 58 of the conduit is
attached to an equalizer structure 60 The front conduit 56 extends
through an aperture in the side of the equalizer structure 60 with
its second end 58 abutting the inside of the first end 62 of the
equalizer structure 60 The front cable strand 52 extends out of the
first end 62 of the equalizer structure 60 and is seated in an
intermediate position in the connector clip 64 of the present
invention. The front cable strand 52 is functionally attached to
two rear cable sections, left 66 and right 68 as shown in FIG. 1.
The front cable strand 52 is attached to the right rear cable
strand 68 by the connector clip 64, and is attached to the left
rear cable strand 66 through the second end 70 of the equalizer
structure 60.
[0062] The right rear cable strand 68 extends through a conduit 72,
similar to the conduit 56 described above, and attaches to a right
rear brake assembly 74. The assembly shown in FIG. 1 is a
representation of a drum brake assembly as is known in the art with
brake pads 76, a drum 78, and associated internal mechanisms 80.
Drum brake assemblies 74 are well-known. The right rear cable
strand 68 is attached to a lever arm 82 which actuates the brake
pads 76 to engage the brake drum 78 to effect a stopping force on
the turning drum (and acts as a brake), as is well-known in the
art. The rear left cable strand 66 extends from the second end 70
of the equalizer 60 to a left drum brake assembly 84, in an
analogous manner to that of the right drum brake assembly 74. The
left rear cable strand 66 also extends through a conduit 86 similar
to that described above. At least the first ends 83, 90 of the rear
right conduit 72 and rear left 86 conduit are structurally fixed to
the vehicle frame 50.
[0063] The rear right cable strand 68 at its first end includes a
crimp-on-end bead 90 which is inserted into the connector clip 64
of the present invention, which is seated in the second end 92 of
the connector clip 64 of the present invention. The first end 94 of
the rear left cable strand 66 is attached to a threaded rod 96,
such as the shank of a bolt or screw. The threaded rod 96 is
received in a tension adjusting nut 98, which is in turn rotatably
engaged in the second end 70 of the equalizer structure 60. The
tension adjusting nut 98 is fixed in axial position with respect to
the equalizer 60, but is allowed to rotate. The rotation of the
tension adjusting nut 98 either draws the threaded rod 96 into the
nut 98 and tightens the left rear cable strand 66 (and the whole
cable system), or moves the threaded rod 96 away from the tension
adjusting nut 98 and loosens the left rear cable strand 66 (and the
whole cable system).
[0064] The parking brake lever 48 is movable from a released
position where no increased tension is applied to the cable system
46, and can move to subsequent positions of ever increasing tension
applied to the cable system, which occurs when the lever is moved
upwardly with respect to the position shown in FIG. 1.
[0065] In assembling the park brake cable system 46, the tension of
the rear left 66 and right 68 cable strands and the front cable
strand 52 are very important. It is important to note in FIG. 1
that the brake pads in the left and right rear brake assemblies are
not in engagement with the brake drums at the initial level of
tension in the brake cable system 46 when assembled. The cable bead
54 at the second end of the front cable strand 52 is seated in the
intermediate position of the connector clip 64 with one end of the
bead 54 engaging a shear member 100, in this case a shear tab,
extending through the wall of the connector clip 64, which inhibits
the axial movement of the bead 54 from this position toward the
first end 102 of the connector clip 64. The particular structure of
the connector clip 64 and the shear tab 100 are described in
greater detail below with respect to FIGS. 6-18.
[0066] After the cable system 46 is initially assembled into the
structure shown in FIG. 1, the cable system must be tensioned to a
high level to remove voids from the cables themselves, as well as
those formed by the interactions of the cables and the conduits,
and to accelerate the creep, or lengthening, of the cables when
initially put under tension. A sufficient level of tension for the
side pull system 46 depends on the particular components, but
generally is in the range of 160 to 250 pounds of force.
[0067] Tension can be applied to the cable system 46 shown in FIG.
1 by either moving the lever upwardly to pull the front cable
strand 52, which tightens the right 68 and left 66 rear cable
strands, or by actuating the tension adjusting nut 98 to draw the
threaded rod 96 into the equalizer structure 60. Due to the forced
balancing of the front 52 and rear left 66 and right 68 cable
conduits, either of the above methods increases the tension in the
cable system 46.
[0068] In FIG. 2, tension is increased in the cable system 46 by
actuation of the tension adjusting nut 98 which draws the threaded
rod 96 towards or into the equalizer 60, as mentioned briefly
above. The length of the left rear cable strand 66 is thus
effectively shortened and actuates the left rear brake assembly 84
and right rear brake assembly 74 to cause the brake pads to engage
the brake drum, respectively The brake lever 48 is still in its
initial position, and the shear tab 100 holds the end bead 54 at
the intermediate position in the clip connector 64. At this point
the entire cable system 46, including the left rear strand 66,
right rear strand 68, and front cable strand 52 are all under a
relatively high tension force due to the actuation of the adjusting
nut 98 to draw the threaded rod 96 towards the equalizer 60. The
tension in the cable system 46 increases slightly as the adjusting
nut 98 is actuated while the brake pads move towards the drums and
the tension overcomes the springs in the brake assembly. However,
once the brake pads engage the drums, the tension increases more
quickly because the terminal ends of each of the cables are
substantially fixed (at the brake assemblies and at the brake
lever). At this point the cable strands themselves are lengthening
under the increased tension, and the voids are being removed in the
engagement of the various cables with the various conduits. This
initial tensioning step is preferably performed at the beginning of
the vehicle assembly line, just after the park brake cable system
is installed.
[0069] This increased tension level is maintained until, as shown
in FIG. 3, the brake lever 48 is actuated to further increase the
tension in the system 46 through the pulling motion applied to the
front cable strand 52 by the movement of the brake lever 48
(upwardly as in FIG. 3). As the brake lever 48 is applied, the
shear strength of the shear tab 100 is overcome by the force of the
front cable strand 52 on the end bead 54 and the end bead 54 thus
moves from the intermediate position in the clip connector 64 to
the terminal position in the first end 102 of the clip connector
64. The tab shear strength is approximately 160 to 250 pounds but
can be modified as desired. The amount of axial movement of the end
bead 54 from the initial position to the terminal position in the
first end 102 of the clip connector 64 is a calculated distance,
called the relief distance, which de-tensions the cable system 46 a
calculated amount. The relief distance is approximately 13-25
millimeters, which de-tensions the cables. While the cable system
46 is de-tensioned somewhat by the failure of the shear tab 100 and
the movement of the end bead 54 through the relief distance, the
brake pads are all still engaged with the brake drums to keep the
left and right rear brakes in an engaged condition.
[0070] As shown in FIG. 4, the brake lever 48 is then moved back to
its initial position. which further de-tensions the cable system
46. This level of tension is called the residual tension, and is
approximately 90 to 130 pounds. When the brake lever 48 is moved
back to its initial position (downwardly in FIG. 4), the tension is
decreased sufficiently to allow the brake pads to disengage from
the drums. The combination of the relief distance and the movement
of the brake lever 48 actuated to its initial position is
calculated to disengage the brake pads from the brake drum to allow
the wheels to turn uninhibited by the park brake cable system. The
brake lever 48 can now be activated to engage the brake assemblies
without appreciable loosening over time, since the voids in the
cable system 46 have been significantly reduced, and the cable
stretch has been accounted for.
[0071] In summary, FIGS. 1 through 4 show the steps of assembling
the park brake cable system with its various components, tensioning
the park brake cable system by the tension adjusting nut 98 to
cause the brake pads to engage the brake drums and allow a high
tension to be applied, actuating the brake lever 48 to cause the
shear tab 100 to fail and allow the front cable strand bead 54 to
move through the relief distance from the intermediate position to
the terminal seated position in the connector clip 64 (which
relieves some tension in the cable system yet maintains engagement
of the brake shoes with the brake drums), and finally moving the
brake lever 48 from the actuated position to its initial position
to further relieve tension (only residual tension remains) in the
cable brake system and allow the brake pads to disengage from the
brake drums. The cable system is still under a residual tension at
this point, which is not sufficient to overcome the spring force in
the break assemblies and cause the brake pads to engage the brake
drums. This residual tension is controlled by the force of the
springs in the brake assemblies.
[0072] FIG. 5 shows the end beads 54, 90, representative of those
formed at the end of each cable. The beads are typically
cylindrical pieces of metal fixed to the end of the cable strands
such as by crimping. The end beads are attached to the cable
strands to withstand tension forces, and allow the cable strands to
be attached at their ends to various fixtures, such as the clip
connector.
[0073] FIGS. 6 through 18 show two embodiments of the clip
connector 64 of the present invention. FIG. 6 is a bottom view of
the first embodiment 104 clip connector. The clip connector 104 is
generally a cylindrical tube having an axial cavity 106 and a
continuous slot 108 formed along one side, denoted the bottom side,
and having various other crimpings and stampings formed along the
length of the cylindrical tube. A central portion 110 of the bottom
slot 108 is widened to allow the insertion of an end bead 54 (not
shown) through the widened portion into the axial cavity 106. The
end bead 54 cannot pass through the slot 108 other than at the
widened portion.
[0074] Opposing cantilever springs 12 are formed in the top surface
of the clip connector 104. The cantilever springs 112 extend
longitudinally along the length of the clip connector. Each of the
springs is a cantilever, with the free end 114 of each of the
springs 112 being bent to extend slightly into the cavity 106 of
the clip connector 104 for purposes described below. Each of the
ends 114 of the clip connector 64 are crimped inwardly to form an
abutment surface 116 against which the end bead of a cable strand
engages. The abutment surface 116 keeps the end bead from exiting
the clip connector 104 through either end.
[0075] A radial slot 118 is formed through the clip connector 104
near its first end 102 and adjacent to the free end 114 of the
cantilever spring member 112. See FIGS. 6 through 8. Apertures 120
are formed at both the first and second ends of the clip connector
adjacent to the crimped region. The apertures 120 allow the crimped
ends to form the abutment surface 116, and allow another exit port
for the broken portion of the shear tab 100.
[0076] The shear member 100 is shown in FIGS. 9, 10 and 11. The
shear member 100 has a main body 122 defining an elongated C-shaped
partially cylindrical clamp which defines a shear tab 124 extending
radially inwardly. The C-shaped clamp fits over the outside of the
clip connector 104, and because of its concentric shape, is not
readily removed therefrom. The shear tab 124 extends through the
radial slot 118 formed in the outside of the clip connector 104 and
extends radially inside the cavity 106 of the clip connector. The
shear tab 124 defines an annular depression 126 near the connection
of the shear tab 124 with the C-shaped clamp portion. This annular
depression 126 is a stress riser. The inside edge 128 of the shear
tab 124 also defines a radial curve. The curved shape of the tab
124 helps maximize contact with the end bead for consistent and
evenly applied force between the end bead and the shear tab
124.
[0077] The stress riser 126 is on the front surface of the shear
tab 124 and is designed to create a calculated shear force
necessary to shear the shear tab 124 from the clamp when it is
positioned through the wall of the clip connector. The sheer force
is applied by the cable end in step three of the method described
above. The necessary shear force is related to the dimensions of
the stress riser 126, the material used in the shear member 100,
and the length of connection of the shear tab 124 to the main body
122. A desired shear strength is 160 to 250 pounds. The shear
member 100 is made of a rigid glass-filled plastic with a high
flexural strength or a high modulus of elasticity, and the shear
tab 124 is typically the same material.
[0078] As shown in FIGS. 12, 13 and 14, the second end bead 54 of
the front cable strand 52 is inserted into the clip connector 104
through the wide portion 110 in the bottom slot 108 and is held
relatively tightly in the cavity 106 of the clip connector 104 by
the cantilever spring 112, which pushes the end bead 54 against the
opposing side of the clip connector 104. The end bead 54 engages
the front surface of the shear tab 124 when the cable system is put
under virtually any amount of tension, such as in FIGS. 1 and 2
above. The distance between the rear surface of the shear tab 124
and the front end of the crimping 116 to which the bead abuts once
the shear tab 124 is broken defines the relief distance. When the
brake lever 48 is actuated, as described above, the end bead 54 is
pulled by the front cable strand 52 with sufficient force to
overcome the shear strength of the shear tab 124. The shear tab 124
thus breaks and allows the end bead 54 to move through the relief
distance to the crimping 116, against which it abuts and is firmly
held under tension. See FIG. 15. The initial, or intermediate
position of the end bead 54 is defined by the front surface of the
shear tab 124, and after Step 3 above, the terminal position of the
end bead 54 is defined by the abutting surface 116 of the crimp in
the first end 102 of the clip connector 104.
[0079] The bead 90 on the first end of the right rear cable strand
68 is inserted into the clip connector 104 through the wide portion
110 in the bottom slot 108 and pulled against the crimping 116 at
the second end of the clip connector, and is held in place at that
position by the cantilever spring 112 to minimize or prohibit axial
movement of the end bead 90 within the cavity 106 of the clip
connector 104.
[0080] FIGS. 16 and 17 show a second embodiment of the clip
connector 130. The cantilever spring adjacent the second end 112 of
the clip connector 130, in this embodiment, is replaced with a much
smaller spring detent 134 which forces the end bead 90 against the
opposing side wall when in contact with the side of the end bead,
and when the end bead 90 is slid past the detent 134 the end of the
end bead engages the free end of the detent, thus fixing the end
bead against axial movement within the cavity 136 at the second end
132 of the clip connector 130. See FIG. 18. The rest of the
connector clip 130 is identical to the clip connector 104 described
above.
[0081] FIGS. 19 through 26 show a third embodiment of the connector
clip 140 as used in a side-pull park brake system. The steps of
adjusting the tension in the cable system of a park brake system
using this third embodiment of the clip connector 140 are shown in
FIGS. 19, 20, and 22.
[0082] In FIG. 19 a Z-shaped equalizer structure 142 is shown used
with the third embodiment of the clip connector 140. The Z-shaped
equalizer 142 is currently used by Dominion Controls Company of
Wixom, Mich., which is part of FKI Automotive Group. The Z-shaped
equalizer 142 is one example of an equalizer structure used with
this third embodiment of the clip connector 140, but is not the
only type of equalizer structure with which this clip connector 140
can be used.
[0083] In this third embodiment, the clip connector 140 is used in
conjunction with the rear left cable strand 66 and the Z-shaped
equalizer structure 142. The Z-shaped equalizer 142 has an
elongated body with a first end 144 forming an upwardly extending
L-shape, and a second end 146 forming a downwardly extending
L-shape. The first end of the front conduit 56 is fixed to the
frame 50 of the vehicle, and the second end of the front conduit 56
abuts against the upwardly extending L-shaped leg at the first end
144 of the equalizer 142. A normal cable end connector 148 is used
to connect the end bead 54 of the front cable strand 52 with the
end bead 90 of the rear right cable strand 68. The rear left cable
strand 66 is attached to the downwardly extending portion of the
second end 146 Z-shaped equalizer structure 142 by the clip
connector 140. The threaded rod 96 is positioned through an
aperture 150 formed in the second end 146 of the equalizer
structure 142, through the interior cavity of the clip connector
140, and through an aperture 152 (FIG. 19A) in the shear member 154
(shear plate) of the clip connector 140 The threaded rod 96 is held
in position by a threaded fastener 156, such as a hex nut
threadedly received on the end of the threaded rod 96 and tightened
to engage the outside surface of the shear plate 154.
[0084] In more detail, as shown in FIG. 19a, the connector clip 140
includes a short cylindrical collar 158 defining an axial bore 160
therethrough. At one end of the axial bore, the shear member 154
(shear plate) extends radially inwardly from the walls of the axial
bore 160 and defines an interior aperture 152 at the center of the
shear disk. The shear disk 154 is formed integrally with the collar
158 and is attached to the inner wall of the axial bore 160 either
continuously or at discrete locations by attachment sections 162.
The discrete locations of the attachment sections are centered at
about 120 degree increments and extend in an arc in a range of
approximately 20-60 degrees, and preferably 40 degrees, at a radius
of approximately 4 millimeters. The size of the attachment sections
can be changed based on the desired maximum shear load that the
shear plate must sustain prior to failure. The attachment sections
162 are thinner than the shear plate 154 itself in order to form a
stress riser 166 on the rear face 164 of the shear plate 154. The
thickness dimension of the stress riser of the attachment section
can be approximately 0.7 millimeters. The rest of the shear plate
has a thickness of approximately 1.0 to 1.2 millimeters. Again,
these dimensions can be modified depending on the desired maximum
shear load of the shear plate. The attachment sections 162 are
flush with the front side 168 of the shear plate 154 and offset
from the rear face 164 of the shear plate as shown in FIGS. 19a to
form the stress riser 166. The stress riser 166 could also be on
the front face 168 of the shear plate 154. A washer 170 is
positioned between the threaded fastener 156 and the shear plate
154. The length and thickness of the attachment sections 162 are
determinative of the shear force required to break the shear plate
154 free of the collar 158. A desired shear strength for this
embodiment is between approximately 160 and 250 pounds.
[0085] As with the first embodiment, the park brake cable system
allows the proper tensioning of the cable system to minimize voids
and accelerate the creep lengthening of the cable, which helps
enhance performance of the park brake cable system in the vehicle,
as described above with respect to the first embodiment.
[0086] After the park brake cable system has been assembled in the
vehicle, the cable system is initially tensioned from having no
brake engagement to having brake engagement by actuating the
threaded fastener 156 on the end of the threaded rod 96. This can
be done with a socket wrench 172, or other type of wrench, as shown
in FIG. 20. The threaded fastener 156 is tightened to draw the
threaded rod 96 towards the equalizer structure 142, which in turn
moves the brake pad towards the brake drum in the left 84 and right
74 brake assemblies. When the left and right brake pads engage the
respective brake drums in the left 84 and right 74 brake
assemblies, the brake assemblies are engaged. The threaded fastener
156 continues to be tightened to apply more tension load on the
park brake cable system.
[0087] At the calculated tension load, sufficient shear force has
been developed by the threaded fastener 156 on the shear plate 154
to break the shear plate at the attachment sections 162 from the
wall of the axial bore of the collar 158. This allows the fastener
156 to exit the tool 172 and pass through the collar 158 to engage
the second end 146 of the equalizer structure 142 on top of the
washer 170 and the shear plate 154. See FIG. 21. The washer 170
helps evenly distribute the tension load on the shear plate 154.
The distance that the disk moves is the relief distance which
de-tensions the cable system sufficiently to disengage the brake
pads from the hubs the right amount, with the desired residual
tension remaining in the cable system. FIG. 22 shows the cable
system after the shear plate has broken. The residual tension for
the embodiment of the clip connector in the side pull cable system
is also between approximately 90 and 130 pounds.
[0088] This method requires only three steps in assembling and
setting the park brake cable system. The first is tightening the
threaded fastener to tension the cable system sufficiently to
eliminate or reduce voids and accelerate the creep of the cable.
The second step is increasing the tension by further actuating the
threaded fastener 156 until the shear plate 154 severs. The shear
force required to brake the shear plate 154 is calculated so as to
allow the user to generate sufficiently high tension during
tightening of the threaded fastener 156 to adequately minimize
voids and accelerate the creep of the cable system. The third step
in the first embodiment of actuating the brake lever is thus not
required in this embodiment This embodiment automatically sets the
proper tension and cannot be over-adjusted because the fastening
member is pulled inside the connector clip 140.
[0089] An alternative to the third embodiment is shown in FIG. 24.
The shear plate 176 in the fourth embodiment 175 shown in FIG. 24
defines the stress riser 178 on the front surface 180 of the sheer
plate 176 along the attachment location 182 and adjacent the walls
of the collar 184. In addition, the washer is replaced by a
threaded fastener 186 having a wider annular base 188 than a
standard threaded fastener, such as a flange nut. The wider base
188 allows a more evenly distributed force to be applied to the
shear plate 176. The shear force required to break the shear plate
176 depends on the stress riser 178, the size of the shear plate
176, and the structure of the attachment location 182 between the
shear plate 176 and the collar 184 (length, thickness, material).
The diameter of the axial bore 160 in both the third and fourth
embodiment is greater in the end of the collar adjacent the rear
face of the shear plate than the diameter of the axial bore 160 in
the end adjacent the front face of the shear plate (where the
threaded fastener engages the shear plate). The larger diameter
allows the threaded fastener to pass through the bore 160 unimpeded
after the shear plate is fractured from the collar. The difference
in diameters between the larger and smaller diameters is
approximately 0.5 millimeter.
[0090] The third and fourth embodiments of the present invention
have the additional advantage over the first and second embodiments
in that they do not require a worker to first apply tension to the
system by turning the tension adjustment nut and then separately
break the shear tab by activating the brake lever. Instead, the
third and fourth embodiments simply require a worker to tighten the
tension adjusting nut sufficiently to brake the shear plate, which
is done all in one operation and saves time and thus manpower. FIG.
25 shows how the shear plate 154 or 176 can be attached only along
discrete sections 162 or 182 to the collar. This can be done for
the previous collar embodiment also.
[0091] An application of the fourth embodiment of the present
invention is shown in FIGS. 26 through 31 FIGS. 26, 28 and 30 show
a center pull park brake cable system 190. Center pull cable
systems are generally known. The center pull system includes a
brake actuation lever 192 movably connected at one end to the
vehicle 194, a front cable strand 196 attached at its first end to
a threaded rod 198 and at the second end to an equalizer assembly
200. The threaded rod 198 extends through the brake actuation lever
192 and through the connector clip 175 described above. A threaded
tension adjusting nut 186 is received on the threaded rod 198 and
engages the shear plate 176 defined in the internal cavity of the
collar 184. The second end of the front cable strand 196 is
attached to the equalizer structure 200, which effectively
transmits equal tension to the left rear cable strand 202 and the
right rear cable strand 204.
[0092] Schematically, the left rear cable strand 202 is attached to
one end 206 of the equalizer structure and the right rear cable
strand 204 is attached to the opposite end 208 of the equalizer
structure, with the front cable strand 196 attached to the
equalizer 200 assembly mid-way between the two. The second ends of
the left rear 202 and right rear 204 cable strands are attached to
the left rear 210 and right rear 212 brake assemblies,
respectively, as shown. The right rear 212 and left rear 210 brake
assemblies work as described above. The equalizer 200 can be a
rigid bar. The front cable strand 196 and the left 202 and right
rear 204 cable strands pass through conduits 214 as in the previous
embodiments. The center pull system 190 does not rely on reaction
conduit force balancing, however.
[0093] The method of properly tensioning the park brake cable
system 190 of this embodiment includes the steps of assembling the
park brake cable system as described above such that the brake
actuation lever 192 is in its release position (FIG. 26) and the
cable system is not yet effectively tensioned. The next step is to
actuate the tension adjusting member 186 to draw the threaded rod
198 upwardly with respect to FIG. 26 and thus apply tension to the
front cable strand 196. The tension adjusting nut 186 can be
actuated by any typical wrench 189 or suitable hand or power tool.
As the front cable strand 196 is put under tension, the left 202
and right rear 204 cable strands are also put under tension through
the equalizer structure 200 The left and right rear cable strands
act to move the brake pads towards the brake drums as the tension
overcomes the springs in the brake assemblies 210 and 212 The
tension adjusting member 186 is continued to be actuated to
increase the tension even after the brake shoes engage the brake
drums. The increased tension in the cable system removes voids from
the system, including from the cable as well as from where the
cable runs through the conduits. The shear plate 176 within the
collar 184 holds the tensioning nut 186 in the initial position at
this heightened tension level. For a center-pull cable system, an
acceptable tension level at this point is between 300-600
pounds.
[0094] Step 3 requires the tension adjusting member 186 to continue
to be actuated until the tension force in the cables overcome the
force required to cause a shear plate 176 to fracture and separate
from the collar 184. This tension load is approximately 300 to 600
pounds, which is sufficient to overcome the shear strength of the
shear plate 176. The cable tension, once the shear plate 176
disconnects, pulls the tensioning member 186 into the collar 184
and out of engagement with the tool used to tighten the adjusting
member 186. The tension member 186 moves a specific distance to the
end of the collar 184 and rests against the brake actuation lever
192. See FIGS. 30 and 31. The tension is relieved just enough to
release the brake shoes from engaging the brake drums, and a
residual tension of approximately 150 to 250 pounds remains in the
cable system 190. As shown in FIG. 31, the distance traveled, or
relief distance, is the distance between the bottom surface of the
shear plate 176 and the brake actuation lever 196 where the bottom
surface of the shear plate 176 rests. The relief distance can
preferably range from 25-50 millimeters. At this point the tension
in the brake cable system 190 is set at the adequate level. As
shown in this example of the use of the fourth embodiment, the
third and fourth embodiments of the cable connector clip can be
used on an equalizer, or elsewhere in the cable system, such as on
the brake lever.
[0095] The connector clip of the present invention works in the
described cable systems to effectively apply sufficient tension to
remove voids and activate cable stretching. In addition, the shear
member acts as a "fuse" to allow the proper offset of tension when
a critical high tension level has been reached. The residual
tension in the system is sufficient to provide consistent park
brake performance.
[0096] Presently preferred embodiments of the present invention and
many of its improvements have been described with a degree of
particularity. The previous description is of a preferred example
for implementing the invention, and the scope of the invention
should not necessarily be limited by this description. The scope of
the present invention is defined by the scope of the following,
claims.
* * * * *