Note: Descriptions are shown in the official language in which they were submitted.
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ELECTRICAL B~AKE LI~ING WEAR INDICATOR
Back~round o the Invention
This invention relates generally to an indicator means to remotely
indicate the degrees of ~ear of the vehicle brake lining. More particularily,
the present invention relates to an indicator for indicating the predetermined
amount of wear of the brake lining. The predetermined amount of wear being
that amount characterized as "end-of-life" wear.
A continuing problem that plagues the trucking and automobile
industry is the unexpected depletion of the brake linings. This occurs due
to nonuniform driving and maintenance practices and procedures on the vehicle.
Should the brake linings wear to a point where the shoes or the like are
exposed to the brake system they become gene~ally inoperati~e and, in fact,
may cause erratic and unpredictable braking responses. This latter hazard,
i.e., erratic and unpredictable brake responses, can result in placing the
vehicle in an accident situatiQn- Additionally, undetected worn brake lin-
ings can result in considerable damage to the various operational parts of the
braking system including ~he brake drum which, in turn, may result in high
repair and replacement cost~. Accortingly, from both an economic and
saety point o view, it becomes imperative that a predetermined amount of
wear on the brake lining may be remotely indicated or timely maintenance and
repair.
Summary o the Invention
According to the present invention there is provided an indicator
or indicating a predetermined amount of wear of a brake lining comprising:
a brake lining support member adapted for assembly in a brake mechanism to be
supported thereby, a brake lining fixedly bolted to said brake lining support
member, said brake lining adapted to frictionally engage a rotating m0mber
associated with said brake mechanism, an eleGtrical switch resiliently dis-
posed on said brake lining support member and insulated therefr~m by a resil-
3Q ient insulated bushing, said electrical switch comprising a threaded bolt
attached to said brake lining support member and held thereon by a threaded
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nut, said insulating bushing completely surrounding said threaded bolt and
extending ~hrough said support member to insulate said threaded bolt from said
brake lining support member, a resilient annular insulating washer surrounding
said bolt and disposed between said brake lining support member and said nut
to urther insulate said nut and bolt combination from said brake lining
support member, said nut capturing an electrical connector on said bolt to
electrically connect it thereto, said electricaL connector electrically con-
nected to an insulated wire memberl said brake lining support member being a
brake shoe comprising a brake shoe table supported by and attached to a brake
shoe web and said rotating member being a brake drum, said brake lining being
provided in two longitudinal segments on said brake shoe table and said
threaded bolt having a head di~posed within a groove formed in a longitudinal
end of each of said lining segments and within an opening separating said two
segments of said lining midway from the end of said table, the threaded shank
of said bolt being disposed in an aperture in said brake shoe table offset on
said table from an intersection of said brake shoe table and said brake;shoe
web, said head of said threaded bolt having a cylindrical head portion which
engages the grooves and acts as an electrical contact, said threated bolt
being of brass and which material is a soter material than said drum and of
a greater height than the bolt heads of the bolts that mechanically fasten
said brake l~nings to said brake shoe table and said insulating bushing being
provided with an annular shoulder disposed adjacent to said head pDrtion to
insulate said portion rom said brake shoe table, said insul~ting washer dis-
posed on the side of said brake shoe table opposite said annular shoulder~
It i`~ an object o the present invention to provide an indicator
for indi`cating the predetermined amount of wear of a brake lining which is
itself easy to maintain, reliable in service and generally immune to the
hostile environment to which it is exposed.
Another obiect of the present invention is that the indicator is
simple in deslgn and inexpensive to manufacture.
As a further important object of the present invention, the indic~
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tor can be manufactured using automatic high volume manufacturing techni~ues.
Oth~r objects of ~h~ present inve~tion and detalls of the struct-
ure of the indicator assembly will appear more ully from the following
~, ,
description and accompanying drawings.
Description of the Drawings
Figure I is a side elevational view partially in phantom form
showing a brake shoe including a brake shoe web, a brake shoe table and a brake
lining, the brake shoe embodying the preferred embodiment of the present
invention;
Figure 2 is a partial sectional view in elevation taken along the
line 2-2 of Figure 1.
Description of the preferred Embodiment
lû Referring now to the drawings, including Figures I and 2, there
is shown a brake shoe lû embodying the concept of the present invention. The
brake shoe lû is adapted to be operably connected to and supported by various
forms of brake mechanisms known in the prior art as, for example, the brake
shoe lû is adapted to be assembled in a brake apparatus as manufactured by
Rockwell International Corporation and referred to as their "STOP MASTER"
brakes. Typically, such a brake mechanism or assembly would include a brake
spider (not shown) which is adapted to be bolted to an axle assembly (also not
shown). The brake spider may typically form various parts of a brake actuating
mechanism such as the housing for the wedge assembly and its associated
2û plungers which interact with the brake shoe 10. Typically, the wedge assembly is
driven by an air chamber which is connected to the service air of the vehicle
with which the brake mechanism is associated. The brake plunger, which may
include a self-adjusting mechanism, typically is actuated by the wedge assembly
and is in driving engagement with the ends of the brake show web 12. The brake
shoe web 12 is typically formed with or fixedly attached to a brake shoe table 14.
It is the table 14 that provides the seating surface for the brake lining 16 and the
brake lining 16 may be attached to the table in various ways as, for example, by a
nut and bolt assembly 18. The brake lining 16 may be formed in a single piece and
attached to the brake ~hoe table 14 or may be in the form of segments as shown
in Figures I and 2.
- The aforementioned parts and the descriptions thereof are
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consistent with what is known in the prior art and the present invention is to be
found in the provision of an indicator for indicating a predetermined amount of
wear of the brake lining 16. The basic concept of the present invention is to
provide a contact means on the brake shoe lû which, when in contact with the
brake drum (not shown), is contacted by the brake lining 16 and completes the
circuit to indicate that a predetermined amount of brake lining has been used orconsumed.
To accomplish this object a threaded bolt 20 is disposed within
aperture 22 in the brake shoe table 14. The threaded bolt 20 is provided with a
lûcircular head portion 24. The threaded bolt 20 and its head portion 24 may be
manufactured from cartridge brass (SAE-CA-260 wire), 1/8 hard.
It may be added at this juncture that such brass material would
be softer than the material typically found on the inner surface of the brake
drum. Surrounding the threaded bolt 20 is a shouldered insulator 26 whose
cylindrical portion 28 surrounds a portion of the threaded shank of the bolt 20
while the shoulder 30 provides an insulating gap between the head portion 24 andthe brake shoe table 14, that is to say the shoulder 30 is provided on the same
side of the brake shoe table as the head portion 24. The shouldered insulator 26may be manufactured from a wide range of insulating material, for example,
20NEMA Grade 7 material. An annular washer 32 also surrounds the insulating bolt
2û on the side of the table 14 opposite the shoulder 30 of the shouldered insulator
26. An additional insulating washer 34 may also be provided adjacent the
aforementioned washer 32. Both of the washers 32 and 34 may be manufactured
from the same material as the shouldered insulator 26, namely NEMA Grade 7.
A terminal 36 of the eyelet type is also disposed on the bolt 20 and to
electrically connect the bolt 20 to an electrical lead 38. The function of the
electrical lead 38 will be further described below. The above-noted assemblage
of washers, terminals and the like are all mechanically captured on the bolt 20 by
a threaded torque nut 40. In a typical arrangement, the shouldered insulator 26
3ûmay be placed in the aperture 22 in the brake shoe table 14. After assembling
the insulating washers 32 and 34 and the terminal 36 on the bolt 20. The nut 40
may be torqued on the bolt 20 to approximately 30 - 40 inch pounds.
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The electricql lead 38, as before mentioned, electrically
connects the bolt 20 to an electrical system of the vehicle in which the brake
shoe 10 is installed. The electrical system may include an indicating light or the
like in the driver's compartment to indicate that the brake lining 16 is worn to a
predetermined point. The completion of the circuit will occur when the brass
bolt 20 contacts the rotating drum against which the brake lining 16 acts. For
example, it can be seen from Figure I that the bolt 20 and, more particularly, the
head portion 24 thereof will contact the brake drum when the lining 16 wears to a
point where its thickness is substantially equal to the height of the head portion
24 and the shoulder 30 of the shouldered insulator 26. At this point the drum will
act as a ground for the electrical circuit; thus electricity will flow through the
lead 38 through the terminal 36 and bolt 20 and will be grounded on and through
the drum. As before noted, the brake lining 16 may be provided in segments and
the bolt 20 may be provided within a bore 42 machined or drilled in the lining 16.
A suitable place for such a bore 42 would be at the opening separating the two
segments of the lining 16. Further, the aperture 22 may offset on the table 14 so
as not to interfere with the brake shoe web 12. The indicator, as above
described, may be provided on one brake shoe per axle or may be provided for
each brake shoe assemblage on the vehicle, depending upon the degree of
selectivity desired. Furthermore, the shouldered insulator 26 and the insulatingwashers 32 and 34 can be of suitably resilient material such that the bolt 20
floats with respect to the brake shoe table 14.
It is, therefore, obvious that the present invention is not to be
limited to the specific details of the indicator above described; but is capable of
other modifications and changes without departing from the spirit and scope of
the appended claims.
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