FR2473440A1 - BRAKE ACTUATING DEVICES - Google Patents

Abstract

Brake actuation device allowing release comprising a brake actuating member connected by a disengageable coupling to the assembly actuated by fluid pressure, and disengaging means for disengaging the coupling and allowing movement of the member actuation. The disengaging means comprise a movable plunger 15 located in the actuating member 8A comprising a part of large diameter 26 and a hollowed out pulley 27. Balls 11 are placed around the part hollowed out by positioning members. 12 elastically stressed and a sleeve 28 which surrounds the positioning members 12. (CF DRAWING IN BOPI)

Description

The invention relates to actuating devices

  for vehicle wheel brakes.

  Brake actuating devices are known comprising a piston connected to a brake actuating push rod and biased towards a brake clamping position, the piston being normally held apart against the biasing of the spring by a fluid pressure. Loosening means, which can be actuated to allow the axial movement of

  the push rod relative to the piston, are usually

  provided that if there is a fluid pressure failure, the brake can be released to bring the vehicle to a service station for

repair.

  In British Patent 1,572,812, an actuating device of this type is described and shown.

  wherein the piston is mounted on the push rod.

  A series of circumferentially spaced balls are retained in a cage and placed in the wall of a hollow portion of the push rod, the spring force being transmitted via the piston and balls to the push rod in case of failure of

  pressure. inside the hollow part of the

  of the thrust is placed a release member under the

  the shape of a step diver axially movable to the

  inside the push rod against a spring bias, between a normal operating position 1 the balls apply to a cylindrical surface of large diameter of the plunger and are thus maintained

  in a radially outward position and a posi-

  loosening action where the balls are adjacent to a cylindrical surface of small diameter of the plunger,

  the position of loosening, the balls move radially

  inwardly by ceasing to cooperate with the piston to allow the push rod to move

  relative to the piston and to release the brake.

  To assemble the loosening device, the small diameter surface of the plunger is aligned on circumferentially spaced holes provided in the cage & balls and the balls are pushed into the respective holes. The holes in the cage have a diameter slightly smaller than the balls and it is expected that the

  edges of the holes deform elastically to allow

  put the balls to go through the holes, after

  what they are kept in place by the cage. The book

  The effect of the diver's beration is that the balls rise to the larger diameter surface and adopt

  their normal operating position.

  There are disadvantages with the assembly mode above, in that there can be a plastic deformation of the cage, so that the balls are not held securely. This results in a difficulty when inserting the push rod into the actuating assembly and when the actuating device is in the unclamping state, it is

  may be that the balls escape radially out

  laughing through the holes in the cage. In such a case, when the piston chamber is again pressurized, the components do not automatically return to their normal operating state and the actuating device has no effect. Of course, such a state of affairs could be extremely dangerous and

possibly go unnoticed.

  The invention aims to avoid the need

  to deform the cage to assemble the balls in that

  here and therefore the possibility to see the marbles out

  radially through the holes in the cage.

  According to the invention, a device for

  vehicle wheel brake assembly comprising an assembly operable by fluid pressure urged resiliently toward a brake clamping position and normally held apart by a fluid pressure applied to the assembly and opposing the resilient bias, a brake actuating member connected by a disengageable coupling to the assembly which can be actuated by fluid pressure and being able to move with this assembly in the direction of clamping of the brake, and disengaging means which can be actuated to release the mating and allow movement

  of the brake actuator relative to the en-

  it can be actuated by fluid pressure and its passage to the loosened state, the disengaging means comprising a movable plunger axially located in a hollow portion of the brake actuating member and having a portion of larger diameter and a recessed part, the coupling comprising balls arranged around the hollow part of the organ

  brake actuation, the balls applying normally

  to the portion of larger diameter of the plunger and being applied to the assembly that can be actuated by fluid pressure, the axial movement of the plunger allowing the balls to penetrate into the recessed portion so as to disengage the coupling, characterized by the fact that the balls are

  respectively set up axially by multi-

  ples elastically biased positioning members, surrounding the plunger and that a sleeve surrounds the establishment members and is designed to implement

  place the balls radially in the disengaged state.

  Preferably, each placing member is disposed inside a corresponding slot

  directed axially, practiced in the organ of action-

  ment. Preferably, the assembly being capable of being

  born by fluid pressure comprises a piston provided with

  of a hollow extension which receives the organ of action-

  the sleeve is constantly being subjected to

  position of cooperation with the extension of the piston.

  Thus, the balls are constantly retained either by extension during normal operation or

  by the sleeve during assembly or loosening.

  An example will now be an arrangement

  A vehicle wheel brake operating system according to the invention and a variant thereof, with reference to the accompanying drawings in which Figure 1 is a sectional view. axial axis of the actuating device comprising a disengaging mechanism;

  FIG. 2 is a detail in axial section of the mechanism

  disengage me of Figure 1; Figure 3 an axial section of a portion of an actuating rod of the actuating device; FIG. 4 is a view similar to FIG. 2, showing a variant of the disengaging mechanism and

  FIG. 5 is a detailed view of an equalizer

  loader of the mechanism of Figure 4.

  The actuating device described is a

  variant of that described in the above-mentioned patent.

cited above.

  We will consider Figure 1; the part of the actuating device which is shown in phantom is well known and comprises, in short, a service brake chamber 1 inside which acts a diaphragm 2 carrying a brake push rod 3 and a chamber of emergency or parking brake 4 inside which operates a piston 5 having a hollow extension 6. The piston 5 is biased by a spring 7 towards a brake actuating piston and is normally held apart, in the position shown , by one

  fluid pressure prevailing in the chamber 4.

  As can be seen mainly in Figures 2 and 3,

  the actuating device comprises the action rod

  8A is hollow and the portion 8A has a blind bore 9. The right portion 8A has slots 10, four in the case shown, to the inside which are placed balls

  respective 11 and elongated positioning members 12.

  Each positioning member 12 has a projection 13 which forms a seat for one end of a spring 14 whose other end rests on the end of

  the actuating rod portion 8B.

  Inside the blind bore 9 of the actuating rod portion 8A is a plunger 15 formed of two parts 15, 15B screwed together, the

  plunger 15 being urged towards its position

  The plunger 15 is forked at its rear end and has a recess 17 for receiving the end of the target 18 of a Bowden transmission 19 (FIG. 1), the target 18 and the plunger. 15 being prevented from moving backward by a perforated retaining plate 21 held in position by a rod 22 attached to the actuating rod portion 8B. The fork legs 23 of the plunger 15 have shoulders 24 against which can be applied the sheath 25 of the Bowden transmission. At its other end, the Bowden transmission is connected to a handle conveniently located in the passenger compartment of the vehicle, the movement of the handle having the effect of moving the cable 18 to the left and the sheath 25 (and thus the plunger 15) towards the right

  against the bias of the spring 16.

  The anterior part 15A of the plunger has a cylindrical section of larger diameter 26 and

  a recessed section of smaller diameter 27.

  Between the end of the piston extension 6 and the rod portion 8B is placed, around the positioning members 12, a sleeve 28 urged by a coil compression spring 29 to cooperate with

  the end of the piston extension 6.

  The end of the extension 6 has a flange which forms a seat for a conical ring 31 which can

  cooperate with the balls 11 as will be explained.

  In order to assemble the arrangement of FIG. 2, the actuating rod portions 8A, 8B are fixed together, the plunger 15 is inserted into the blind bore 9 of the actuating rod and the Bowden transmission and the transmission are put in place. retaining plate 21. With the plunger depressed, the balls 11 and the positioning members 12 are positioned so that the balls are located in the recessed portion 27 of the plunger. The biasing of the spring 14 is sufficient to maintain the balls 11 in position at this stage of the assembly. We position

  then the spring 29 around the rod 8, an end

  abutting against the plate 21 and the sleeve 28 is inserted into the other end of the spring 29.

  the disengagement mechanism towards the end of the extension

  6 until the sleeve 28 stops

  longement. When further movement of the mechanism, the rod portion 8A enters the extension and the balls 11 pass through the sleeve 28 and the rim 30 of the extension. Au. beyond the rim 50, the

  11 balls can move radially outward

  which allows the diver 15 to take the posi-

  represented. The return of the plunger 15 is assisted by the spring 16 but instead of the spring 16, a compression spring (not shown) can be placed in

  the blind bore 9 to assist the return of the plunger 15.

  Thus, during assembly, the balls 11 are retained by the sleeve 28 before being put in place & inside the piston extension 6, the spacing

  between the balls 11 and the inner surface of the prolon-

  6 and the inner surface of the sleeve 28 being too small to allow the balls to come out of

slots 10 of the rod portion 8A ,.

  In the operation of the whole, the relay

  The fluid pressure allows the piston 5 to move forward under the action of its spring 7, the spring force being transmitted by the flange 30 of the piston, the conical ring 51 and the balls 11 to the rod. actuator 8 which is thus moved forward so as to apply the brake. In the event of a pressure failure, the brake can be released by pushing the plunger 15 forward to allow the balls 11 to penetrate radially inwards into the

  small part 27 of the plunger 15, thereby disengaging

  coupling between the conical ring 31 and the rod of ac-

  8. Thus, the rod 8 can move back relative to the piston 5 to loosen the

  brake. The sleeve 28 remains applied against the prolon-

  6, holding the balls II and preventing them from leaving the slots 10 by a radial movement towards

outside.

  After the repair, when put back under

  the piston chamber 4, the piston 5 moves

  backwards against the stress of the spring.

  When the posterior end of the flange 30 is applied to the anterior side of the balls 11, the balls are pushed backwards against the solicitation

  14 until the balls are

  The balls are then pushed radially inwardly of the recess 27 and the rim 30 passes backwards over the balls which then reach their position.

represented by Figure 2.

  Figures 4 and 5 illustrate a variant of the actuating device described above. The only difference between the mechanism of Figure 2 and that of Figure 4 is that in the latter, at the end of the blind bore 9 is placed a load equalizing member 33 having a spherical cap base 34 applying at the rod portion 8A and four branches 35 located in the respective slots 10 and applying to respective balls 11. The member 33 serves to equalize the load on the balls 11 and thus on the conical ring 31. Moreover, the structure and

  the mechanism of Figure 4 are

  to those of the mechanism of Figure 2 and do not have

  need to be described further here.

Claims (3)

  1. A vehicle wheel brake actuating device comprising an assembly that can be actuated by pressure of fluid elastically biased towards a brake clamping position and normally main-   held-apart by a pressure of fluid applied to the   seems and opposes the elastic solicitation, a   brake actuator connected by a coupler   disengageable to the assembly that can be actuated by fluid pressure and can move with this assembly in the direction of clamping the brake, and means   which can be operated to release the   coupling and allow the movement of the   brake means relative to the assembly that can be actuated by fluid pressure and its passage to the loosened state, the disengaging means comprising a movable plunger axially located in a hollow portion of the brake actuating member and comprising a   part of larger diameter and a recessed part, the   coupling comprising balls arranged around the hollow portion of the brake actuating member, the balls normally applying to the portion of   larger diameter of the diver and can be applied   to the assembly that can be actuated by fluid pressure, the axial movement of the plunger allowing the balls to enter the recessed portion so as to disengage the coupling, characterized in that the balls (11) are respectively in place axially by a plurality of elastically biased positioning members (12), around the plunger (15) and a sleeve (28) surrounding the positioning members and is designed to set up the   balls radially in the disengaged state.   2. Device according to claim 1, characterized   due to the fact that the positioning members (12) are arranged in respective slots (10) formed in the actuating member (8) and that the positioning members urge respective balls (11) towards   the end of the respective slots (10).   5. Device according to claim 1 or 2,   characterized by the fact that the organ that can be ac-   fluid pressure (5) comprises a piston having a hollow extension (6) into which the actuating member (8) penetrates, the balls (11) being normally placed inside the extension and the sleeve ( 28) is biased towards the position   of cooperation with the end of the extension.