GB2296299A

GB2296299A - Caliper assembly for a disc brake

Info

Publication number: GB2296299A
Application number: GB9525837A
Authority: GB
Inventors: Gyou Ryeon Chung
Original assignee: Daewoo Heavy Industries Ltd
Current assignee: Hyundai Doosan Infracore Co Ltd
Priority date: 1994-12-21
Filing date: 1995-12-18
Publication date: 1996-06-26
Anticipated expiration: 2015-12-18
Also published as: GB2296299B; DE29520235U1; KR960022051U; KR970003893Y1; GB9525837D0; SG34343A1; HK1013677A1

Abstract

A caliper assembly for a disc brake of a forklift truck comprises a caliper base 104, a pair of caliper arms 106, 108 attached to the base for pivotal movement between the illustrated braking position and a release position, first and second pad holders 112, 114 pivotally mounted on the caliper arms, and first and second friction pads 120, 122 secured to the first and second pad holders for making contact with the disc when the caliper arms are biased by springs 126, 128 into the braking position. When an operator, in use, depresses the brake pedal, the cam 134 will rotate to engage adjustable screws 130, 132 and release the brake. The pivots of the pad holders may be offset from their centres of gravity (figure 5), and lugs (140, 142 figures 5 and 6) and resilient supports (148, 150 figure 6) limit movement of the pad holders. <IMAGE>

Description

CALIPER ASSEMBLY FOR A DISC BRAKE FIELD OF THE INVENTION 'l'he present invention is generally directed to a disc brake device and, more specifically, to a caliper assembly for a disc brake whereby a braking force can be releasably applied lo the opposite sicles of a rotating that are fixedly mounted on the driving shaft of an electrically operated travel motor in a forklift tuck DESCRIPTION OF THE PRIOR ART As ordinary artisans are aware, the forklift truck has been extensibly employed for the load shipping purpose or for the transportation of heavyweight articles from one place to another, usually within a limited working area.

Characterized by dual forks capable of up-and-down movement along a mast, the forklift truck has a turning ability and maneuverability excellent enough to carry out the assigned tasks in a highly efficient manner. Similar to other kind of industrial vehicles, the forklift Trick should rely upon the torque of a travel motor in moving forward or rearward and therefore is less suitable for long-distance and high-speed travel. Partly clue to such nature of the forklift truck, the driver will usually keep standing on the forklift truck to operate a steering wheel, joy sticks, an accelerator pedal, a brake pedal and the like, rather than take a seat as ordinarily done in other industrial vehicles.

For the reason noted above, most of the state-of-the-art forklift trucks make use of what is referrecl lo as "deadman" type disc brake device that, in a diamelrically opposite manner to the disc brake of a passenger car, can remove a braking force out of a rotating disc upon depression of the brake pedal but will exert the braking force on the disc in the event of releasing the brake pedal. As illustrated in Fig. 1, the deadman type brake device typically consists of a rotating disc 12 fixedly mounted on the driving shaft of an electric travel motor 10 for rotation therewith and a' caliper assembly 14 adapted to apply a brains force to the disc 12 in response to the release of a brake pedal.

The caliper assembly 14 is IDlovicled wilh a bracket 1(3 affixed zooto the framework of a forklift truck not shown in the drawings for simplicity. A pair of caliper arms 18, 20 are pivotally attached to one end of the bracket 16 by means of a pivot pin 22, with an actuator cam 24 carried on the other end of the bracket 16 for rotation about a cam shaft 26, to spread out the caliper arms 18, 20 inlo an out-of-braking position. The actuacor cam 24 is operatively associated with the afore-mentioned brake pedal through the use of a suitable linkage means.

The caliper arms 18, 20 extend generally parallel to each other and remain spaced apart from the flank sides of the disc 12. A pair of gap adjustment bolts 28, 30 are threadedly coupled to the free ends of the caliper arms 18, 20 in a confronting relationship with respect to each other, to allow adjustment of the gap between the respective caliper arm 18 or 20 and the disc 12. Unwanted loosening and tightening of the gap adjustment bolts 28, 30 may be avoided by detachably securing stopper hooks '32, 34 to the caliper anns 18, 20 to respectively engage With the gap adjustment bolts 28, 30.Provided on the caliper arms 18, 20 in the vicinity of the gap adjustment bolts 29, 30 are through-holes 18a, 20a through which a tie rod 36 is inserted to project past the caliper arm 20 at one encl thereof, thus forming a partially threaded protrusion 36a. A great diameter comlrression spring 38 and a small diameter compression spring 40 are coaxially retained on the protrusion 36a to have the caliper arms 18, 20 resiliently urged toward each other into a braking position.

Somewhere between the pivot ends and the free ends of the caliper arms 18, 20, pad units 42, 44 are replaceably attached by virtue of fixture bolts 54, 56.

Each of the pad units 42, 44 is composed of a support block 46 or 48 and a friction pad 50 or 52 remaining fixedly secured to the support block 46 or 48.

Since the friction yads 50, 52 ate arranged lo face the disc 12, they xvill normally come into contact with and press against the flank surfaces of the disc 12 under the action of the compression springs 38, 40 to thereby apply a braking force thereto. Updn the caliper arms 18, 20 being spread apart by the actuator cam 24, the friction pads 50, 52 will be brought out of contact with the disc 12 to pennil free rotation of the taller.

By use of the conventional disc brake device referred to above, a need arises often to replace the friction pads with new ones of uniform thickness depending on the severity of wear. The fresh friction pads, however, has a strong tendency to make a partial contact with the disc, which in turn leads to a reduced braking force. In other words, although the surface region of the new pads nearer to the pivot end of the caliper arm may positively contact with the disc, the remainder region would be prohibited from any contact with the disc unless and until the just replaced friction pads are subjected to a considerable wear. This is mainly because the caliper arms 18, 20 are designed for pivotal movement about the pivot pin 22 rather than for parallel movement.Such a "partial contact" will continue to occur for a while after the friction pads are freshly replaced, rendering the braking action unstable. What makes the matter worse, the partial contact will almost certainly result in an irregular wear of the friction pads which would shorten the service life of the pad units to an unacceptable degree.

SUMMARY OF THE INVENTION Accordingly, it is an object of the invention to provide a caliper assembly for a disc brake which can substantially eliminate the drawbacks posed in the prior art brake device and which assures a uniform contact of friction pads with a disc throughout the entire service el-ii)d thereof, While avoiding irregular wear of the friction pads and eventually prolonging its service life significantly.

With this object in view, the present invention provides a caliper assembly for a forklift disc brake adapted to apply a braking force to flank sides of arotating disc, comprising: a caliper base; a pair of caliper arms pivotally attached to the caliper base for l)ivolal movement l-elaLive lo the disc between a braking position and a release position, each of the caliper arms extending from a proximal end to a distal end; first and second pad holders each hingedly carried on the caliper arms for swinging movement relative to the caliper arms within a limited angular extent; first and second friction pads fixedly secured to the first and second pad holders for making contact with the disc when the caliper arms are in the braking position; arm closing means for normally causing the caliper arms to pivot toward each other into the braking position; and arm spreading means for causing the caliper arms to pivot away from each other into the release position.

BRIEF DESCRIPTION OF THE DRAWINGS The above ancl other objects, features, advantages of the invention will become apparent from a review of the following detailed description of the preferred embodiment taken in conjunction with the accompanying drawings, in which: Fig. 1 is a front elevational view showing the prior art disc brake device designed for use in a forklift truck; Fig. 2 is a partially cut away, front elevational view of the caliper assembly for a disc brake in accordance with the first embodiment of the invention, with caliper arms remaining in a braking position; l::ig 3 is a sectional view laheil along line m-m in Fig. 2; Fig. 4 is a sectional view taken along line IV-IV in Fig. 2; Fig. 5 is a view similar to Fig. 2 but showing the caliper assembly in accordance with the second embodiment of the invention, with caliper arms lying in a braking position; and Fig. 6 illustrates the caliper assembly in accordance with the third embodiment of the invention, with caliper arms kept in a braking position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to Figs. 2 through 4, there is shown a caliper assembly for a disc brake in accordance with the first embodiment of the invention. The caliper assembly is operatively connected to a brake pedal (not shown) of, e.g., a forklift truck and adapted to apply a braking force to a rotating disc 102 which is mounted to the driving shaft of, e.g., an electrically operated travel motor 100.

In stark contrast to ordinary passenger cars, the caliper assembly in the forklift truck can produce the braking force when the brake pedal is released rather than depressed by the driver's foot.

The caliper assembly includes, among other components, a caliper base 104 mounted on a framework (nol shown) of the forklift truck. The caliper base 104 is provided with first and second projections 104a, 104b, both of which extend up to the circumferential surface of the disc 102, with an appropriate gap left between the projections 104a, 104b and the disc 102. Pivotally attached to the first projection 104a of the caliper base 104 are a pair of caliper anns 106, 108 that has the capability to turn about a pivot pin 110 into a braking position as shown in Fig. 2 and a release position not shown in the drawings.While the caliper arms 106, 108 remain closed up generally in parallel to the flank surfaces of the disc 102 in the br-akikg )silion, ihkk\kill be spread apart to form an acute angle relative to the flank surfaces of the disc 102 in the release position.

Each of the caliper arms 106. 108 has a cutout 106a or 108a provided somewhere between the proximal and distal ends thereof and a hinge hole 106b or 108b whose axis extends through the center of the cutout 106a or 108a. Also formed side by side through the respeclive caliper ann 106 or 108 are a thread hole 106c or 1OSe of relatively large diameter and a through-hole 106d or 108d having a far smaller diameter than the thread hole 106c or 10 &

First and second pad holders 112, 114 are hingedly attached to the cutouts 106a, 108a of the caliper arms 106, 108 in a confronting relationship with each other such that they can be subjected to a swinging movement relative to the caliper arms 106, 108 within a limited angular extent. Each of the pad holders 112, 114 consists of a pad support portion 112a or 114a extending a short distance along the corresponding caliper arm 106 or 108 and a rear protuberance 112b or 114b of semi-circular configuration protruding backwardly from the pad support portion 112a or 114a.As most clearly indicated in Fig. 4, a pin hole 112c or 114c is formed through the rear protuberance 112b or 114b in an exact alignment with the hinge hole 106b or 10sub of the caliper arms 106, 108; and a hinge pin 116 or 118 is fitted through the hinge hole 106b or 108b and the pin hole 112c or 114c to allow the respective pad holder 112 or 114 to swing with respect to the corresponding caliper arm 106 or 108.

Affixed to each of the pad holders 112, 114 is a friction pad 120 or ln that can make a frictional contact wilh the disc 102 in response to the pivotal movement into the braking position of the caliper arms 106, 108 but will be kept out of contact with the disc 102 at the time when the caliper arms 106, 108 are in the release position. Inasmuch as the pad holders 112, 114 remain hingedly attached to the caliper anns Iota, 10S as set forth hereinabove, the friction pads 120, 122 will be automatically self-aligned in parallel to the flank surfaces of the disc 102 as the former comes into contact with the latter in the braking process, assuring a uniform and partial-wear-free contact between the friction pads 120,122 and the disc 102.

It can be seen in Figs. 2 and 3 that an elongated tie rod 124 is loosely fitted through the through-holes 106d, 108d of the caliper arms 106, 108 to inerlink the latter. The tie rod 124 has an enlarged head 124a kept in an engagement with the caliper arm 108 and a partially threaded outer extension 124b projecting far away fi-om the caliper arm 106. A large diameter compression spring 126 and a small diameter compression spring 128 are coaxially retained on the outer extension 124b of the tie rod 124 to urge the caliper arms 106, 108 into the braking position at all times. Specifically, the combination of tie rocl 124 and compression springs 126, 128 is designed to apply a biasing force to the caliper anns 106, 108 so that they can be closed up into the braking position to have the friction pads make a contact with the disc 102. To reduce or avoid any undesirable slippage which might occur between the friction pads 120, 122 and the disc 102. the compression springs 126, 128 should have as great a spring constant as possible.

Gap adjustment bolts l 130. 132 are threadedly engaged with each of the thread holes 106c, 108e of the caliper arms 106, 108 in a confronting relationship with each other. The gap adjustment bolts 130, 132 are respectively provided with a toothed head and a tip bearing surface. The spacing between the tip bearing surfaces of the gap adjustment bolts 130, 132 may be adjusted by way of either tightening or loosening the gap adjustment bolts 130, 132.Just after the spacing adjustment has been done, it will be preferred that locking hooks 133, 135 be delachably fixed lo the end stlrf.lces of lhe calil)el- aa s ]0d, 108 in such a manner as to come into engagement with the toothed head of the gap adjustment bolts 130, 132. This will prevent the gap adjustment bolts 130, 132 from any inadvertent tightening and loosening in the process of using the brake device.

An actuator cam 134 is mounted on the second projection 104b of the caliper base 104 for rotation about a cam shaft 136 between an operating position and a non-operating position. Fixedly secured to the actuator cam 134 is a swing lever 138 which in turn is operatively associated with the brake pedal not shown in the drawings. The actuator cam 134 is normally kept in the non-operating position to permit the caliper arms 106, 108 to pivot toward each other. Responsive to the depression of the brake pedal, the actuator cam 134 gets rotated into the operating position, thus pushing the tip bearing surfaces of the gap adjustment bolts 130, 1.32 to spread the caliper arms 106, 108 apart.

The caliper assembly set forth above will be operated in the following manner. In the event that the forklift: truck is running forward or rearward, the driver should keep standing in the cabin of the forklift truck with the brake pedal depressed by the foot. As a consequence, the swing lever 138 will be rotated to the angular position as indicated in a phantom line in Fig. 2, at which time the actuator cam 134 is also turned a larecletennined angle into the operating position to push against the gap adjustment bolts 130. 132.This will cause the caliper arms 106, 108 to be spread apart into the release position against the biasing force of the compression springs 126, 128, with a result that the friction pads 120, 122 become detached from the disc 102 and, therefore, no longer apply a braking force thereto.

To the contrary, should the driver remove his or her foot from the brake pedal, the swing lever 138 will be returned back to the initial position as indict'LLed in LI solid line ; lig. 2 and, al Lhe Slilld Lisle, tile cal l arms 106, 10S will be closed up into the braking position by dint of the biasing force of the compression springs 126, 128, bringing the friction pads 120, 122 into contact with the disc 102 so as to produce a braking force.Thanks to the fact that the padholders 112, 114 remain hingedly attached to the caliper arms 106, 108, the friction pads 120, 122 will be able to make a uniform contact with flank surfaces of the disc 102, regardless of the angle which the caliper arms 106, 108 would form with respect to the disc 102.

Turning to Fig. 5, there is illustrated a modified caliper assembly in accordance with the second embodiment of the invention wherein the sarne reference numerals as in Figs. 2 through 4 are used to designate like parts with no description given thereto. Among tie important features of the second embodiment caliper assembly is that the rear protuberances 112b, 114b and the pin holes 112c, 114c are shifted or offset from the gravitational centers W1, W2 of the pad support portions 112a, 114a by distances S1, S2. Another feature is that detent lugs 140. 14'2 protrude toward the disc 102 from the caliper arms 106, 108 to bear against one lateral side of the respective pad holder 112 or 114 to thereby restrain the extent of swinging movement of the latter in one direction.

As apparent in Fig. 5, since the pin hole 112c of the pad holder 112 is offset rightwise fiom Ihe gravitational center W1, the pad holder 112 has a tendency or moment to rotate counterclockwise about the hinge pin 116. In contrast, the pad holder 114 will be given a tendency or moment to swing clockwise about the hinge pin 118. because the pin hole 114c of the pad holder 114 is shifted leftwise from the gravitational center W2. The rotational moments exerting on the pad holders 112, 114 are respectively supported by the detent lugs 140, 142 whereby the pad holders 112, 114 can be maintained substantially in p.ll-allel lo llle arms 106, 108 even when the caliper arms 106, 108 are in the release position.For the very reason, it becomes possible to deter any random swinging movement of the pad holders 112, 114 which might otherwise result in an unwanted contact of the friction pads 120, 122 with the disc 102.

Fig. 6 illustrates another modified caliper assembly in accordance with the third embodiment of the invention wherein the same reference numerals as in Figs. 2 through 4 are utilized to designate like parts with no description offered thereto. Similar to the second embodiment set out just above, the caliper anns 106, 108 are provided with detent lugs 144, 146 protruding toward the disc 102, each of which serves as a rigid support for one lateral extension of the corresponding pad support portions 112a, 114a of the pad holders 112, 114. At the opposite locations of the hinge pins 116, 118 from the detnet lugs 144, 146, there are provided elaslically deformable supports 148, 150 to rotatingly urge the pad holders 112, 114 about the hinge pins 116, 118 against the corresponding detent lugs 144, 146. 'I'he elaslically deformable supports 148, 150 may include a rubber block, a compression spring and other suitable resilient material.

While the invention has been shown and described with reference to a preferred embodiment, it should be apparent to one of ordinary skill that many changes and modificalions may be made without departing from the spirit and scope of the invention as defined in the claims.

Claims

WHAT IS CLAIMED IS:

1. A caliper assembly for a disc brake adapted to apply a braking force to flank sides of a rotating disc, comprising: a caliper base; a pair of caliper arms pivotally attached to the caliper base for pivotal movement relative to the disc between a braking position and a release position, each of the caliper arms extending from a proximal end to a distal end; first and second pad holders each hingedly carried on the caliper arms for swinging movement relative to the caliper arms within a limited angular extent; first and second friction pads fixedly secured to the first and second pad holders for making contact with the disc when the caliper arms are in the braking position; arm closing means for normally causing the caliper arms to pivot toward each other into the braking position; and arm spreading means for causing the caliper arms to pivot away from each other into the release position.

2. The caliper assembly for a disc brake as recited in claim 1, wherein each of the caliper anns has a cutout provided at a location between the proximal end and the distal end thereof and wherein each of the pad holders is provided with a pad support portion extending along the respective caliper arm and a rear protuberance protrucling backwardly from the pad support portion into the cutout.

3. The caliper assembly for a disc brake as recited in claim 2, wherein each of the pad holders has a pin hole formed through the rear protuberance thereof, each of the caliper anns having a hinge hole in an alignment with the pin hole of the respective pad holder, and wherein a hinge pin is fitted through the pin hole and the hinge hole to permit the swinging movement of the respective pad holder with respect to the colTeslx)nding caliper ann.

4. The caliper assembly for a disc brake as recited in claim 3, wherein the pin hole of the respective pad holder is offset from the weight center of the pad support portion in a lellglhxvise direction lht,-eof to gi e each of the pad holders a moment to rotate about the hinge pin under the influence of gravity and wherein the respective caliper arm is provided with a detent lug protruding toward the disc to support the respective pad holder against the rotationalmoment to restrain the extent of swinging movement of the pad holder.

5. The caliper assembly for a disc brake as recited in claim 3, wherein each of the caliper arm is provided with a detent lug protruding toward the disc to bear against one lateral extension of the repective pad holder to restrain the extent of swinging movement of the pad holder in one direction, and further comprising an elastically deformable support means provided between the other lateral extension of the respective pad holder and the corresponding caliper ann to rotatingly urge the respective lxld holder against the corresponding detent lug of the caliper arms.

6. The caliper assembly for a disc brake as recited in claim 3, wherein the arm closing means comprises a tie rod interlinking the caliper arms at a location adjacent to the distal ends of lhe arms and a compression spring coaxially retained on the tie rod to have the caliper arms biased toward each other into the braking position.

7. 'Ilie caliper assembly for a disc brake as recited in claim 6, further comprising gap adjustment bolts threadedly attached to the distal ends of the caliper arms in a confronting relationship with each other for changeably setting the extent of pivotal movement of the caliper arms.

& The caliper assembly for a disc brake as recited in claim 7, wherein the arm spreading means comprises an actuator cam rotatably mounted on the caliper base for rotation between an operating position in which the caliper arms are caused to spread apart into the release position and a non-operation position in which the caliper arms are permitted to close up into the braking position by dint of the compression spring.

9. The caliper assembly for a disc brake as recited in claim 7, further comprising locking hooks detachably affixed to the distal ends of the caliper anns for locking the gap adjustment bolts against rotation to avoid unwanted tightening and loosening of the gap adjustment bolts.

10. A caliper assembly for a disc brake adapted to apply a braking force to flank sides of a rotating disk, the assembly substantially as herein described with reference to the accompanying drawings.