FR2775743A1 - Brake drum with automatic play take up compensator - Google Patents

Abstract

The brake drum has a play take up cylinder (100) mounted between the two brake segments. It is formed by a helicoidal spring (108,109) which is mounted between two telescopic pistons (101,102) each acting on a brake segment. One of the ends (108A,109A) of the spring is supported on one of the telescopic pistons and the other end (108B,109B) is buttressed against the other piston at the end of the telescopic movement of the two pistons.

Description

The drum brake with automatic play adjustment The present invention

  relates to a drum brake with automatic play compensation comprising a play catching member mounted between the two brake shoes to keep them apart with a substantially constant clearance

despite the wear of the fittings.

  Game take-up systems are well

  naked in the prior art as illustrated for example by

  documents GB - 472 103, DE - 690 659, or WO 89/00254.

  According to an example of the prior art (FIG. 1), a drum brake consists of two segments 202, 203 of arcuate shape, placed inside the drum 201 of the brake for

  cooperate by their lining 204, 205 with the track of the drum

  bour; the segments consist of parts of curved shape each comprising a core of cut sheet metal, carrying a sole plate itself provided with the brake lining 204, 205. The cores 206, 207 of the segments come flat against the plate 208 of the drum brake . The lower end of

  each soul rests by its nose against a fixed stop 209 ap-

  peeled fixed point secured to the tray. At their other extremi-

  tee, the segments are actuated by a double actuator 210 or double cylinder which spreads the ends to press the

  linings of the two segments against the track and brake.

  The recall of the segments 202, 203 to release the linings relative to the track is provided by one or two springs 211, 212 each hung by its two ends

  in an opening of each of the segments.

  Generally, a spring is provided in the vicinity

  swings the fixed point and a spring in the vicinity of the actuator. Finally, near the actuator, it is generally

  provided a wear compensator 213. This is a ri-

  guide connected to the two segments to limit the return stroke to a fixed guard despite the wear of the linings. This wear compensator prevents the segments from being returned to their initial position before the linings wear out. In fact, as the linings wear out, the travel along which the two segments must be moved aside to brake, increases. Although in general this increase in travel is relatively small since at most for each segment it can correspond to the thickness of the lining (at the end of wear of the lining), this uncompensated approach movement of the linings against the drum track is perceived by the driver who applies the brake as an idle movement, which does not allow him to control

  fully and to dose the brake control.

  The compensator known under multiple variants and in particular that represented in FIG. 1, prevents the springs from completely recalling the brake segments, always in the initial position (by pushing the pistons of the actuator to their end of travel position (position

  initial)). These wear compensators are generally relati-

vely complicated to carry out.

  The object of the present invention is to develop a drum brake with wear compensator, the compensator of which

  is particularly simple and effective.

  To this end, the invention relates to a drum brake.

  Bour with wear compensator of the type defined above, characteristic

terrified in that:

  - the play take-up member is formed of at least one res-

  helical type spell, mounted between two telescopic parts

  ques each acting on a brake segment, - these two parts performing between them a telescopic extension movement during braking, - one of the ends of the spring bearing on one of the parts, - the other end of the spring bracing against the other

  piece at the end of the telescopic movement of the two pieces.

  The wear compensator according to the invention provides regular, continuous compensation, so that the user who actuates the brake always has the feeling of controlling a brake that responds exactly. This compensator is particularly simple to manufacture and assemble, which allows a significant reduction in the cost of the entire

  drum brake. According to a particularly interesting solution-

  health: - one of the parts is the brake cylinder and the other is a piston housed in the brake cylinder, - the spring being mounted at one end on a stud of the

  piston and its other end slides against the surface

  of the cylinder when the piston pulls the spring during a braking operation and bends against this interior surface of the cylinder at the end of the movement

  relative extension between the piston and the cylinder,

  that the piston is pushed back into the cylinder after an

  braking, and in particular - one of the parts is the brake cylinder and the other part consists of each of the two pistons housed in the cylinder, - a helical type spring being associated with each of the pistons and s' flying buttress against the inner surface of the cylinder. Thus, the wear compensator is integrated into the brake cylinder without constituting any additional part,

  which would be mounted between the brake shoes. This facilitates

  lite not only the manufacture of the backlash device itself but also the mounting of the brake. Finally,

  this simplifies the structure of the brake and facilitates its accessi-

  flexibility for maintenance work or changing the seg-

  is lying. Moreover, to change the brake lining, it suffices, to compress the cylinder, to act on the pistons by screwing them in the winding direction of the springs of the

  backlash device. This screwing reduces the diameter

  be external turns and thus facilitates the sliding of each assembly formed by a piston, a cup and a spring, without the spring tending to brace

  against the inner surface of the cylinder.

  This device also facilitates the installation of a device preventing the taking up of excessive play in

  if the brake temperature rises sharply. This device is simply constituted by a locking ring, placed5 behind the large turns of the helical spring; this ba-

  gue bends under the effect of its expansion against the over-

  inner side of the cylinder to prohibit, from this

  moment, the advancement of the spring and consequently, at the time of the re-

  this prevents the end of the spring from bending

  push against the cylinder in a position further away than

  that corresponding to the catching up of the actual wear of the gar-

brake nitrides.

  This means is a particularly simple solution since it consists of a ring; it does not require any precise or sensitive adjustment which would have to be made each time

  disassembly of the brake to replace worn linings.

  Finally, this device is automatically installed without

  that there is no need for adjustment or positioning by-

  individuals. According to another advantageous characteristic, the play take-up member is formed of two parts and - one of the parts is a rod and the other a sleeve, these two parts being engaged telescopically, one in

  the other by one of their ends, each of the other ex-

  hoppers being connected to a brake segment,

  - the rod externally carrying the helical type spring-

  dal one end of which rests on the rod and the other con-

  be the end of the sleeve receiving the rod,

  - the guide end of the sleeve being flared to overlap

  expensive at least the spring end turn and block the

  retraction movement of the rod and the sleeve by an ef-

  corner wedge, this blocking is released automatically when the two telescopic elements are subjected to a force

  acting in the opposite direction.

  Depending on the case, the rod and the sleeve are

  formed by rectilinear pieces or by pieces of curved shape. According to another advantageous characteristic, the end of the rod and that of the sleeve intended to be fixed to a respective segment consist of a loop and the orifice of the segments each receiving one end of the compensating member is an oblong hole. According to another characteristic, the helical type spring is a helical compression spring or

  extension, cylindrical or conical envelope.

  According to another advantageous characteristic, the end of the rod and that of the sleeve intended to be fixed to the respective segment consist of a loop and the orifice of the segments each receiving one end of

  the compensating member is an oblong hole.

  The choice of compensator in straight form or

  curve depends on the space available in the drum brake.

  The curved shape allows you to add a bracing effect

  be the two telescopic elements, in addition to the arch-

  pushing the opening of the sleeve against the first turn

spring.

  Finally, the compensator is set up in an extremely simple manner by snap-on without requiring any other

  fixing means since the brake is closed by a cover

  key, so that the compensator cannot escape from the ori-

mounting fices.

  The present invention will be described below from

  in more detail using the accompanying drawings in the-

which:

  - Figure 1 shows an example of a drum brake

  bour according to the prior art, - Figure 2 is an axial sectional view of a first embodiment of a wear compensator for drum brake integrated in the drum brake control cylinder, - Figure 2A is a side view cut according to

  IIA, IIA of Figure 2 showing the shape of the blocking ring

  thermal cage, - Figure 3 shows schematically and in sectional view a first embodiment of a wear compensator for drum brake according to the invention, - Figure 4 shows in section a second embodiment of a wear compensator, - Figure 5 shows in plan view and in section the attachment of the end of a wear compensator in the segment orifice, - Figure 6 is a detail view of

  the end of a brake shoe with the hole for receiving

  see the end of the wear compensator.

  The brake control cylinder or actuator

  with drum according to the invention consists of a 100 lo cylinder

  giant two pistons 101, 102 opposite to each other and movable along the axis XX of the cylinder. These pistons 101, 102 bear by means of their notches 103, 104 against the nose of the brake segments such as the segments 202, 203 of the

figure 1.

  In fact, the sectional view of Figure 2 is a view perpendicular to the mounting plane of the cylinder 210 of Figure 1 since the notches 103, 104 are not parallel

  in the plane of the figure but perpendicular.

  The noses of the souls of the segments are placed free

ment in these notches 103, 104.

  The pistons 101, 102 are provided, on the inner side

  of sealing cups 105, 106 carried by a head

  ton 10lA, 102A of each piston 101, 102. These sealing cups 105, 106 delimit and ensure the sealing of

chamber 107 of the jack.

  This cylinder is provided with a play take-up member constituted by two helical springs 108, 109, one of which

  end 108A, 109A is helical on a cylindrical surface

  drique and the other end 108B, 109B is of truncated form

  that flared so that the large base of this frustoconical shape slides or rests against the interior surface of the cylinder 1

of the cylinder.

  The end 108A, 109A is fixed by screwing on

  the pin 0llA, 102A of each piston.

  As indicated, the turns of the large base of

  two springs 108, 109 bear against the internal surface

  cylinder and slide on it when the pis-

  tones 101, 102 are separated by the pressurized fluid introduced into the chamber 107 by an orifice not shown. This spreading movement in the direction of the double arrow D causes the nose pieces of the brake shoes to spread and consequently the braking. During the spacing movement of the pistons 101, 102 the springs 108, 109 are pulled by the pistons and

  they follow the movement, all the more easily as the

  ger elongation suffered by the pistons due to the friction

  ment of the external turns of the part 108B, 109B against the internal surface of the cylinder 100 creates an elongation of the springs and consequently a reduction in the external diameter

  therefore also from part 108B, 109B of larger diameter

  be. The spring can therefore follow the movement of the pistons

101, 102 without disturbing them.

  When braking stops, that is to say when

  that the fluid no longer arrives in the chamber 107, the springs 211, 212 (see FIG. 1) bring the two segments of

  brake and push the pistons 101, 102 inside the cy-

  lindre 100. This movement of repulsion compresses the liquid

  under pressure in chamber 107 and discharges it.

  During the first phase of this recoil movement of the pistons 101, 102, the springs 108, 109 follow the movement and the outer turns of the parts 108B, 109B do not

  are not yet seized against the surface of cylinder 100.

  It is only after a certain retreat that the outer turns of the parts 108B, 109B are sufficiently compressed to be

  expand and grip against the inner surface of the cylinder

  dre 101 and hang. The turns thus retain the pis-

  tones 101, 102 in a certain position. This delay of

  seizure when backing up creates the brake guard.

  In fact, each time the brake is applied, wear and tear

  is weak enough that the springs 108, 109 follow

  wind the movement of the associated piston 101, 102 and return to their initial position since the recoil is not sufficient to expand the turns 108B, 109B and block them in the cylinder 100. It is only if the stroke of the pistons 101, 102 exceeds a certain amplitude that the associated springs 108, 109 have the possibility by the external turns 108B, 109B of 5 bracing against the interior surface of the cylinder 101, thus preventing the piston 101, 102 from moving back further inside the cylinder 100. The pistons are thus

  in a corrected wear take-up position of the seals

brake res.

  These progression operations are repeated as soon as

  wear reaches a certain threshold, the large turns of the res-

  spells 108, 109 going from the sliding phase to the phase

  bracing inside cylinder 100.

  To avoid excessive take-up of the play which could be caused by the increase in the temperature of the brakes, there is provided, at each spring 108, 109, a ring 110, 111 preventing excessive take-up of wear in the event of overload. This ring 110, 111, placed on each spring 108, 109, behind the outer turns of the

  parts 108B, 109B, slides smoothly against the surface

  of the cylinder 100. However, when the brake temperature exceeds a certain threshold, the rings 110, 111 are sufficiently expanded to firmly brace

  inside the cylinder 100 and then prohibit any pro-

  gression of the parts 108B, 109B towards the outside of the cylinder 100.

  Thus, in case of excessive temperature rise-

  ture whose threshold is fixed by the characteristics of the ba-

  elastic bands 110, 111, the turns 108B, 109B can no longer advance in the direction of the arrows D1, D2. Only the pistons 101, 102 can move apart under the effect of the pressurized fluid introduced into the chamber 107. On brake release, the pistons 101, 102 can thus return to their original position, the turns of the parts 108B, 109B n 'not having

  advanced inside cylinder 100.

  According to Figures 2 and 2A, the rings 110, 111 are preferably copper washers. The rings 110,

111 are generally identical.

  According to FIG. 2A, the ring 110 includes a

  section 1101 at its periphery for the passage of the spring 108;

  this cut is elongated because of the pitch of the turns of the res-

  comes out. The central hole 1102 prevents the ring 110 from

works like a piston.

  According to Figure 3, a second embodiment of a wear compensator or backlash member of a drum brake is a device external to the brake actuator. This game take-up device consists of a

  rod 1 telescopically housed in a sleeve 2.

  One end 11 of the rod 1 carries a means 12 for fixing this end to one of the segments of the drum brake and the other end 21 of the sleeve 2 carries a member 22 to similarly fix this end of the sleeve on the other drum brake segment. The attachment means 12, 22 of

  the rod 1 and the sleeve 2 are for example ends

  folded and shaped into a hook as will be seen later on.

laughing (fig. 5).

  The other end 13 of the rod 1 slides in

the sleeve 2.

  In this first embodiment, the rod 1 and

  the sleeve 2 are straight and the rod 1 is preferably

hollow rence.

  Rod 1 externally carries a helical spring

  coïdal 3, one end 31 of which is fixed relative to the rod 1. It is retained there by a stop or the like not shown in detail. The other end 32 of the spring 3 is formed by one or a few free turns. Spring 3 can

  deploy freely on the rod 1. In the position shown

  felt in Figure 3, the spring 3 is compressed like this

will be described below.

  The sleeve 2 comprises, at its overlapping end

  edge of the rod 1, a flared part 23 in the form of a funnel,

  coming to overlap the first turn or turns 32 of the spring 3.

  These turns, and in particular the first, are then blocked

  quer cooperating with the opening in funnel 23 by ef-

  wedge fet against rod 1 which is thus blocked with respect

port to sleeve 2.

  This blocking is done when the wear compensator 1, 2 is subjected to two compression forces A, B applied to the ends 12, 22 by the segment return spring or springs after a braking action, when the brake pedal is released, releasing the fluid return from the

brake system.

  The blocking of the first turns 32 in the funnel part 23 of the sleeve 2 is not instantaneous. First there is a slight sliding movement until

blocking is done.

  Although this blocking is relatively quick, it has a certain response time. This response time creates the brake guard, i.e. allows the segment and

  pads to move away from the track. Like this time of re-

  response is relatively constant and that the return springs also act with a substantially constant force, the brake shoe returns in a constant manner

  in time; this return does not vary significantly

  ble from one braking to another, also the guard created by this

  response time is it constant.

  Conversely, this response time prevents the

  guard is canceled, i.e. the segments remain applied

  permanently against the drum track.

  When one or a few turns are blocked between the two parts of the telescopic assembly (rod and sleeve) under compression, this blocking is in no way final and the

  spring can always advance on the rod.

  To disassemble the brake, it is generally necessary to

  expensive segments and compress the compensator which is done without difficulty if the compression is slow and not abrupt

like after a brake application.

  Figure 4 is a simplified sectional view of another embodiment of a drum brake wear compensator according to the invention. This compensator consists of a rod 1A, a sleeve 2A curved in a circular arc, engaged telescopically. The end 11A of the rod 1 is straight with an eyelet or folded back to the square with a hairpin shape like that shown in FIG. 6.

  is the same with the end 21A of the tubular sleeve 2A.

  This Figure 4 shows the funnel opening 23A of the sleeve 2A and the coil (s) 32A of the spring 3A. The latter is also fixed by its end 31A to

the end of the rod 1A.

  The end 13A of the rod 1A slides telescopically

only in the sleeve 2A.

  The curved shape of the rod 1A and of the sleeve 2A promotes an arcboutement effect in addition to the blocking of the turn or turns 32A between the funnel opening 23A of the sleeve 2A and the rod lA; the latter is advantageously

hollow for the sake of lightness.

  The ends 11, 21 of the compensator of the fi-

  gure 3 both have a hairpin shape like the end 300 shown in FIG. 5. The top view shows that this end is flat. The sectional view shows the hairpin shape and its introduction into

  the orifice 301 of one of the segments 302.

  FIG. 6 shows an elongated shape for the orifice 303 of the segment 304 and the positioning of the curved end 300 of the compensator not shown. The

  figure also indicates by the double arrow A the possibility

  end or transverse movement tee of the end 300 in

orifice 303.

Claims (5)

R E V E N D I C A T IONS   1) Drum brake with automatic backlash compensation   nant a play take-up member mounted between the two segments   brake elements to keep them apart with a substantially constant guard despite the wear of the linings, characterized in that - the take-up member (100, 1, 1A) is formed of at least one helical type spring ( 108, 109, 3, 3A) mounted between two telescopic parts (100, 101; 100, 102; 1, 2; 1A, 2A) each acting on a brake segment, these two parts carrying out a telescopic extension movement between them during braking,   - one of the ends (108A, 109A, 31; 31A) of the pre-   bearing on one of the parts (101, 102, 1, 1A)   - the other end (108B, 109B, 32, 32A) of the spring arcs-   flying against the other part (100, 2, 2A) at the end of movement   telescopic of the two parts.   ) Drum brake according to claim 1, characterized in that - one of the parts is the brake cylinder (100) and the other is a piston (101, 102) housed in the brake cylinder, - the spring ( 108, 109) being mounted at one end on a stud of the piston and its other end slides against the interior surface of the cylinder when the piston pulls the spring during a braking operation and arises against this interior surface of the cylinder at the end of   relative extension movement between the piston and the cylinder   dre, when the piston is pushed back into the cylinder after braking action.   3) Drum brake according to claim 1, characterized in that one of the parts is the brake cylinder (100) and the other part is constituted by each of the two pistons (101, 102) housed in the cylinder, - a helical type spring being associated with each of the pistons and bracing against the interior surface of the cylinder. 4) Drum brake according to claim 2, characterized in that the spring (108, 109) has a frustoconical shape whose small base (108A, 109A) is screwed onto the stud (0llA, 102A) of the piston (101, 102 ) and the large base (108B, 109B) slides and bears against the surface of the cylinder (100), a locking ring (110, 111) being mounted behind the large base, on the side of the piston (101, 102) to expand and hang in   the cylinder (100) in the event of an excessive rise in temperature   brake to prevent the large base (108B, 109B) from   spring (108, 109) to follow the movement of extension of the tone (101, 102).    ) Drum brake according to claim 1, characterized in that - one of the parts is a rod (1) and the other a sleeve (2), these two parts being engaged telescopically one   in the other by one of their ends, each of the au-   very ends (12, 22) being connected to a segment of the brake,   - the rod externally carrying the helical type spring-   dal (3), one end (31) of which rests on the rod (1) and   the other (32) against the end (23) of the sleeve (2) receives   before the rod (1), - the guide end (23) of the sleeve (2) being flared   to overlap at least the end turn (32) of the res-   exit (3) and block the retraction movement of the rod (1) and the sleeve (2) by a wedge effect, this blocking   automatically releasing when the two telesco-   spikes (1, 2) are subjected to a force acting in the di- opposite rection.   6) Drum brake according to claim 5, characterized in that the rod (1) and the sleeve (2) are constituted by straight pieces. 7) Drum brake according to claim 5, characterized in that   the rod (1A) and the sleeve (2A) have a curved shape.   8) Drum brake according to claim 5, characterized in that the end of the rod and that of the sleeve intended to be fixed to a respective segment consist of a loop (300)   and the orifice (303) of the segments (302) each receiving an ex-   end of the compensating member is an oblong hole.   9) Drum brake according to claims 1 and 5,   characterized in that the coil type spring is a coil spring of   compression or extension of cylindrical or conical envelope than.