GB2355291A

GB2355291A - Brake wear sensor system with mounting clip

Info

Publication number: GB2355291A
Application number: GB0100174A
Authority: GB
Inventors: David Michael Preston; G Clark Fortune
Original assignee: Sanford Acquisition Co
Current assignee: Sanford Acquisition Co
Priority date: 1997-05-27
Filing date: 1998-05-27
Publication date: 2001-04-18
Anticipated expiration: 2018-05-27
Also published as: GB2355291B; GB0100174D0

Abstract

A brake wear sensor comprises a sensor housing 12 and a housing cap 17 with an abradable conductor 11 disposed therein, and a spring clip 6 for holding the cap and housing together and for retaining the sensor in an opening slot 9 formed in a brake table 14 between two brake pads 5A, 5B. The spring clip 6 engages the opening slot 9 with clip arms 6A, 6B which compress preload springs 7A, 7B against the sensor housing 12 thereby forcing the sensor housing 12 and housing cap 17 against the underside of the brake table 14.

Description

1 2355291 BRAKE WEAR SENSOR WITH MOUNTING CLIP

BACKGROUND OF THE INVENTION

1 Field of the Invention

The present invention relates to a brake shoe wear sensor and more specifically to a brake shoe wear sensor comprising a housing cap adapted to form a channel allowing a conducting wire to be passed t.herethrough.

2. Description of the PriorArt

There are several brake wear sensors in the prior art which are typicaffy shown mounted an the underside of the brake shoe table and extend into the brake shoe material. It is known to embed in the f7ictiori material of the brake shoes an electrical sensor to signal to the operator when brake servicing is required. One such type af sensoris a single length of wire which is eventually wom through by the fliction of the brae drum when the brake shoe reaches its service limit. Several prior art methods of securing the wire in place within the.brake shoe friction material have been disclosed. The mourtrig technologies most commonly shown involve a threade&- fastener enclosing or formed in the brake wear sensor for positioning within a cavity found in the brake shoe friction material. Examples of such mounting systems are disclosed in U.S. Patent Nos. 3,800,278; 2,814,684; 2,7331,519; 4,188 613 and 3,297,985. The majority of these retaining systems make use of threaded elements to provide a crush force on the brake table to retain the sensor in pla.ce.. Other prior art methods of retaining a brake wear sensor include fitfing's that are later deformed to provide retention in the brake shoe or brake table. Examples of such systems are shown in US Patent Nos. 3,440,604 and 3,689,880.

Another known method to retain a brake wear sensor' in the brake table is to incarporaW a clip mechanism in the sensor housing which elbninates the need to provide threads on at least two elements. Examples of 2 such prior art clip design are shown in U.S. Patent Nos. 4,298,857; 4,869, 350;

4,318,457; 4,274,511; 4,344,509 and 5,133,431. The disclosures of which are hereby incorporated by reference. A spring clip formed in the sensor housing supports the wear sensor in the brake table using an interference fit established by the deformation of the spring clip upon insertion.

The problem with these clip systems is primarily a packaging limitation where it is desirable to firmly fix a wire loop between two brake shoes mounted on a common brake table. It would be desirable to use a clip that would fit between the two shoes using a stamped opening in the brake table that does not extend beyond the areas occupied by the brake shoe. It is also desirable to use one clip to provide retention and an axial preload on the system.

According to the present invention, there is provided a brake is assembly comprising a brake wear sensor for first and second brake pads mounted to a brake table of a vehicle brake assembly, the wear sensor designed to be mounted through an opening slot formed in the brake table between the first and second brake pads so that an electrical conductor forming a part of the wear sensor is rubbed against by a rotating brake drum when the first and second brake pads reach a thickness less than a predetermined limit, the wear sensor comprising:

a sensor housing; a housing cap adapted to fit over a portion of said sensor housing thereby forming a channel for allowing the conductor to be passed therethrough; a spring clip adapted to retain said sensor housing and said housing cap in proper position relative to said brake table.

3 BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of the brake wear sensor of the present invention; FIG. 2 is a top elevational view of the brake wear sensor of the present invention; FIG. 3 is a cross-sectional view of the brake wear sensor of the present invention; FIG. 4 is a partial cross-sectional view of the brake wear sensor of the present invention mounted to a brake table; FIG. 5 is a partial cross-sectional view of the brake wear sensor of FIG. 4 taken along line V-V; FIG. 6 is a cross-sectional view of the sensor housing of the brake wear sensor of the present invention; FIG. 7 is a side elevational view of the sensor housing of the brake wear sensor of the present invention; I 4 FIG. 8 is an end elevational view of the senoor'h,Dusing ct the brake wear sensor of the present invention; FIG. 9 is a cross-secticnal view of, the housing cap of the brake wear sensor of the present invention; and FIG. 10 is a side elevation view of the housing cap of the br-ake wear sensor of the present invention; FIG. 11 is an end elevatonaf view of the housing gap of the brake wearsensor of the present invention; FIG. 12 is a front elevational view of the spring clip of the present invention; and Fig. 13 is a bottom elevationa.1 view o f the spfin clip of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodbnent illust-ated in the drawings and specific language will be usedto describe the same. It will nevertheless be understood ftt no limitation of the s6we of the invention is thereby intended, such alterations and future mcclificaticns in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

Now referTing to FIG. 1, a front elevational view of the sensor housing 12 of the brake wear sensor 2 of the present invention is shown. The sensor housing 12 is molded using a high temperature material suitable for use in a vehicle brake. environment Many suitable materials are known to those skilled in the at A channel 10 (see FIG. 3) is formed in the interior of the'sensor housing 12 to allow a wire conductor 11 to pass there through.

The, housing cap 17 (see FIG. 2) is secured #10 the sensor housinq 12 after :30 instOllation oil the wire conductcr 11 in channel 10. The sensor housing 12 t and the housing cap 17 could be made as one piec:-t forming a szrsor assembly 3 having the channel 10 fbmried therein. The housing car) 17 secures the wire conductor 11 in position and environmentally protects the wire conductor 11. Mounting ears 17A and 17B extend from the housing cap 17 to facilitate positonin'g against a brake table.

The spring clip 6 includes a first front clip arm 6A and an opposing first rear clip arm 6C and a- second front clip arm 66 and an opposing second rear clip arm 6D (see FIG. 2)which contain the sensor housing 12 and housing cap 17 for engagement with a brake table 14 through an opening slat 9 (see FIGs. 4 and -9). The first front clip arm 6A and the first rear clip arm 6C could be combined into one first clip arm that engages the brake table 14 (see FIGS. 2 & 4). in a similar manner, the second front clip arm 6B and the second rear clip arm 6D could be combined into,pne second clip arm that engages the brake table 14 (see FIG. 4).

A'first preload spring 7A and second preload spring 73 extend from the spring clip 6 and engage the sensor housing 12 in a manner to apply a compressive force on the sensor housing 12 and housing cap 17, when the wear sensor 2 is mounted into ft opening slot 9 in the brake ta.6 t i 14 (see F1 G. 5).

FIG. 2 is a top e)evation2l View of the brake wear sensor 2 of the present invention showing its rectangular shape that Js designed to occupy the runited space behmeen brake shoes 5A and 5B. A rectangular opening slot 9 just larger than the rectangular cross section of the sensor housing 12 is formed in t he brake table 14 onfentated to lie between the brake shoes 5A and 5B (see FIG. 4). The brake wear sensor 2 is inserted into this rectangular slot so that the spring clip arms 6A and 68 compress and then expand to engage the edge of the rectangular slot. At this point, the fl'St and second preload spr.ngs 7A and 7B are compressed which thereby finally hold the brake wear sensor 2 in position. Preferably, the brake wear sensor 2 is located toward the inboard side of the brake table 14 (see FIG. 4) to facilitate 6 electric2i connection.

FIG. 3 is a partial cross-sectional view of the brake wear se"or 2 of FIG. 4 of the present invention. FIG. 3 more clearly illustrates the ccnduct,or cavity 10 formed in the sensor housing 12 and by the housing cap 17 when frtted on the sensor housing 12. The spring clip 6 fits over the sensor housing 12 and has firstj and second preload springs 7A and 7E3 which contact the underside of the brake table 14 to apply a Icad to the brake wear sensor 2 for irnproved retention an d proper positioning relative to the brake Oiction pads 5A and 56 (see FIGI 4). The conductor 11 is frtted hnto'the' conductor cavity 10 and consists of a wire 18 covered by an insulating layer 19. The insulating layer 19 functions to protect the wire 18 from premature wear due to- environmental conditions inside - the vehicle brake. The conductor 11 eventually wears to the point that the wire 18 breaks and is no longer electrically conductive.

Now referring to FIG. 4, a partial cross-sectioned view of the brake wear sensor 2 of the present invention mounted to a brake table 14 of brake shoe 13 is shown; A spring clip 6 has a frst front clip ann -6A and a second frant clip arm 68 and correspondingly a first rear clip arm 6C and a second rear clip arm 6D which engage the brake table 14 at opening slot 9 positioned an an inboard side of the brake table 14 and is retained in position so as to compress the first and second preload springs 7A and 7B which are formed as part of the spring clip 6. A sensor housing 12 is formed to provide a channel 10 for wire conductor I I which is to be wom away when the brake friction pads 5A and wear to a service limit condition. The spring clip 6 sits over and caoture the sensor housing 12 and functions to retain it in the brake table 14 at the proper depth relative to the brake friction pads 5A and 5B which are secured to the brake t2ble 14 and ffidonaly interact with the brake daj,M 8. The brake friction pads 5A and 5B couM be cornprised of on-e. single continuous brake friction pad having an opening formed therein over the opening slot 9, k 7 A. housing cap 17 is adapted to cover the end of the sensor housing 12 and the severance sectlan 18 of the conductor 11. The housing cap 17 protects the conductor 11 from elernents that rright compromise the integrity Of the conductor 11 especially of the severance section IS. As the brake friction pads SA and 5B wear to a suffident degree, t)e housing cal) 17 is also Worn. First the housing cap 17 is wom and subsequently the severance section 13 of the conductor 11 wears to the point that electrical continuity is lost which signals -the need for brake service.

FIG. 5 is a partial crass-sectional view of the brake wear sensor 2 shown in FIG. 4 taken along line V-V. Tbe-first, and second preload springs 7A and 78 have been compressed against the sensor housing 12 thereby providing'a compressive load on the sensor housing 12 and a portion ofthe housing cap 17 which Is imporlant for the durability of mclded high temperature plastics. The first preload spring 7A reacts against the first front clip arm 6A and the first rear dip arm 6C while in an identical fashion the preload spring 7B reacts against the second front clip arm 613 and the second rear clip arTn 6D. The clip arms 6A,6B,6C and 6D contact the Odge of the opening slot 9 formed in the brake table 14 and hold the brake wear sensor 2 securely in position relative to the brake friction pads 5A and 5B. As the brake friction pads 5A and 58 wear, the housing cap 17 begins to wear and eventually the conductor I I wears through signaling that the service limit of the brake friction pads 5A and 58 has been reached.

Now referring to FIG, 6, a I ap cross-secticnai view-of the sensor housing 12.of the brake wear sensor 2 of the present invention is shown- The sensor housing 12 has a rectangular cross-sectional shape to lit between the brake friction pads 5A and 58 in the rectangular opening 9 formed in the brake table 14. This- design provides for adequate support of the wire conductor I I while minimizing the required modification to the brake shoe 13.

The,prelcad spring end 6C and 6D press against the underside of the brake tablp 14 to provide a preload on the first and second clip arms 6A and CB for 8 improved retention and axial lacstficning relative to the brake fh&jcjj pa,3s 5A and 5B.

Now referring to FIG- 7, a side elevational view of the sensor housing 12 is shown where the curved sections 12A and 12B areformed in the sensor housing 12 to accommodate the conductor 11. Conductor 11 (not shown) is a section of electrical wire IS which has an insuWjng layer 19. The housing cap 17 and the insulation of conductor 11 provide protection to the wire to improve its (r7tegrity by preventing premature wear through (from action of the drum 8) In the harsh environment of a vehicle brake wherein corrosive chemicals could cause premature- wear-through of the conductor 11. Both the housing cap 17 and the insula-don are required because the conductor -11 is not embedded in the brake pad material and is unprotected once the housing cap 17 is wcm through by the brake drum 8.

FIG. 8 is a bottom efevational view of the sensor- housing 12 of the present invention more cleady showing the channels 10 through which the conductor I I passes.

FIG. 9 is a cross-sectional view of the housing cap.- 7 of 'the present invention where its interim shape forms to the sensor housing to form the channel 10. The housing cap 17 snaps over the sensor housing 12 after installation of the conductor 11.

FIG. 10 is a side elevaticnaf view of the housing cap 17 of FIG.

9 showing the relatively narrow profile of housing cap 17 for mounting in the narrow opening slot 9 formed in the brake table 14 between the brake iriction pads 5A and 5B (see FIG. 4).

FIG. I I is a bottom elevatJonal view of the housing cap 17 cf FIG. 9 again showing the narTow proffle of the housing cap 17 and the mounting ears 17A and 17aWh[ch cortact the undetticle of the brake table 14 to restrain the brake wear sensor 2 in the opening slot 9 formed in the brake table 14 using the spring clip 6.

I 9 Now referTing to FIG, 12, a front elevational viev., of tie scrino clip 6 of the brake wear sensor 2 of the present invention is shown. The spring clip 6 is made of a resilient material such as steel or plastic, either of which must be selected to withstand the environmeni experienced by a brake shoe without losing holding force. Four preload cFip arms are clearty shown as the first front clip arm 6A and the second front clip arm 68 'and the first rear clip arm 6C and the second rear clip arrn 6D. All of the clip arms 6A, 68, 6C and 6D flex to allow the brake sensor to be inserted into and engage the brake table 14. The first and. second preload springs 7A and 7S are compressed as the brake sensor 2 is pressed into the brake table 14 and provide a retention force on the clip arms 6A, 6B, 6C and 6D acainst the brake table 14.

.Now referring to FIG. 13, a bottom elevational view of the spring clip 6 of the brake wear sensor 2 of the present invention is shown.

The description above refers to particular embodiments of the present invention -and it is understood that many modifications rnay be made without departing from the spirit thereof. The embodiments of the invention disclosed and descnbed in the above specification and draAfings are presented merely as examples of the invention. Other embodiments, materials, form, s and modific-atons thereof are conternplated as failing within the scope of. the present invention only limited by the claims as follows.

L

Claims

1 A brake assembly comprising a brake wear sensor for first and second brake pads mounted to a brake table of a vehicle brake assembly, the wear sensor designed to be mounted through an opening slot formed in the brake table between the first and second brake pads so that an electrical conductor forming a part of the wear sensor is rubbed against by a rotating brake drum when the first and second brake pads reach a thickness less than a predetermined limit, the wear sensor comprising:

a sensor housing; a housing cap adapted to fit over a portion of said sensor housing thereby forming a channel for allowing the conductor to be passed therethrough; a spring clip adapted to retain said sensor housing and said is housing cap in proper position relative to said brake table.

2. The brake assembly as claimed in claim 1, wherein said spring clip is comprised of a first clip arm and a second clip arm which engage said opening slot.

3. The brake assembly as claimed in claim 2, further comprising a first preload spring extending from said first clip arm and a second preload spring extending from said second clip arm, said first and second preload springs engage said brake table at said open slot to capture a portion of said housing cap and said sensor housing between said preload spring and brake table.

11

4. The brake assembly as claimed in claim 2, wherein said first clip arm is comprised of a first front clip arm and a first rear clip arm, and said second clip arm is comprised of a second front clip arm and a second rear clip arm.

5. The brake assembly as cl'airned in claim 1, wherein said opening slot is located on an inboard side of said brake table.

6. The brake assembly as claimed in claim 1, wherein said electrical conductor is comprised of a conducting wire coated with an insulating material.

7. A brake assembly substantially as described herein with reference to, and as shown in the accompanying drawings.

is

8. A brake wear sensor for use in a brake assembly as claimed in any one of the preceding claims.