FR2548120A1 - INERTIAL HYDRAULIC BRAKE DEVICE EQUIPPING TRAILERS WITH ONE OR MORE AXLES - Google Patents

Abstract

THE INVENTION CONCERNS A HYDRAULIC BRAKING DEVICE BY INERTIA EQUIPPING TRAILERS WITH ONE OR MORE AXLES. IN THIS DEVICE, A MASTER CYLINDER 20 IS CONNECTED TO A DRAWBAR 7. A TRACTION PISTON 26 AND A PUSH PISTON 28, BETWEEN A COMPRESSION SPRING 30, ARE LOCATED IN AN ANNULAR CHAMBER 27 BETWEEN THE MASTER -CYLINDER 20 AND A WORKING PISTON 21 CONTAINED BY THE LATTER. THROUGH THE RESPECTIVE PRESSURE 15 AND DISCHARGE 16 DUCTS, A CONTROL DRAWER SELECTIVELY CONNECTS THE MASTER CYLINDER 20 OR THE ANNULAR CHAMBER 27 TO BRAKING CYLINDERS. APPLICATION TO INERTIA BRAKES FOR TRAILERS.

Description

1. The present invention relates to a braking device

  inertia hydraulic system fitted to trailers with one or more axles, comprising a drawbar mounted movably in a drawbar, a master cylinder with a working piston, and respective pressure and discharge ducts gaining a cylinder incorporated in each wheel brake and provided with

  brake pistons for operating the brake shoes of a wheel brake.

  Such a hydraulic device for braking by inertia is known, for example, from patent DE-876 216 This known device is however affected by the disadvantage of requiring, for the movement in reverse, a particular locking mechanism of the reversing 15 to put the inertia brake off so that no braking torque is generated In addition, with this known hydraulic device, it is not possible to

  braking the trailer after a downtime on a gradient when the towing vehicle is pulled back under the action of the towed load.

  DE-AS-2 161 559 discloses a mechanical inertia braking device fitted to a brake with internal jaws and in which the support system incorporated in each wheel brake is produced in such a way that the integral braking torque can be reached when moving forward, and that there is practically no braking in the case of a reverse movement without any reversing locking mechanism For this purpose , the two brake shoes of each wheel brake are supported on a pivoting cam which is mounted eccentrically on a guide element and to which, in the case of braking in reverse, pivoting can be printed by force more of the secondary jaw, so that it allows a decrease in the spacing between the

  support ends of the primary and secondary jaws.

  Admittedly, this mechanical device for inertial braking is already equipped with an automatic operating system in reverse, but it continues to have the disadvantage that a braking of the trailer is not possible when rolling. at the rear, after stopping on a slope, because the automatic system of operation in reverse prohibiting braking then comes into action in order to counterbalance at least partially this disadvantage for the parking brake and the breaking brake of coupling, it is necessary to provide in this known braking device, in the actuating path of the main brake and the parking brake, a special accumulator of elastic force 15 which again allows compensation of the deflection stroke of the two jaws when the automatic reverse system

his action.

  Based on this known prior art for hydraulic and mechanical inertia braking devices, the object of the invention is to provide an inertia hydraulic braking device of simple construction, whereby the integral braking torque can be obtained in forward motion and with which no braking occurs in reverse, even without any particular mechanism for locking the reverse gear A further object of the invention is to design this hydraulic braking device so that even when from immobilization on a slope, automatic braking of the trailer is possible when the towing vehicle is descending the slope under the action of the towed load. To achieve this object, there is provided an inertial hydraulic braking device of the aforementioned type, in which the master cylinder is connected to the drawbar and the movable working piston in this master cylinder is supported in the direction of pulling through a compression spring and bears on the trailer in the direction of inertia; a pulling piston and a pushing piston, between which is inserted a compression spring, are housed as a second working piston group in an annular chamber between the master cylinder and the working piston; and the brake cylinders are associated with at least one control spool which, depending on the direction of rotation of the wheel, communicates with said brake cylinders via respective separate pressure and discharge conduits. one of the other, either said master cylinder of the working piston, or the annular chamber

  interposed between the two pistons of the second group of working pistons.

  In an inertial hydraulic braking device made according to this technical design, the general idea of the present invention is to relax depending on the direction of rotation of the wheel, via an additional discharge duct and by example, in a pressure equalization vessel of a pressurized fluid, the braking pressure developed by the working piston in the master cylinder in the inertia phase of the trailer and transmitted to the braking cylinders via a pressure duct, in order to completely suppress this braking pressure For this purpose, at least one control spool is associated with the braking cylinders and the two respective pressure and discharge ducts, connected to this spool, are put into communication with said brake cylinders depending on the direction of rotation of the wheel When, for example, the direction of rotation of this wheel is reversed by about 2 in In the forward / reverse direction, the control spool breaks the connection of the pressure line and establishes the communication of the discharge duct with the brake cylinders. The braking pressure resulting from the inertia in reverse is thus completely eliminated. In this way, this hydraulic braking device is also simultaneously provided with an automatic operating system

backwards.

  According to another embodiment of the invention, it is furthermore proposed to install, downstream of the first group comprising the working cylinder and the piston, a second cylinder and piston group comprising the annular chamber and the pistons. of traction and thrust, so as to be able to brake the trailer even in the event of immobilization on a gradient, when the tractor 10 is driving down the slope under the action of the towed load In this case, that is, say when the drawbar is deployed, each brake cylinder is connected to the discharge duct by the control spool when the direction of rotation is reversed However, this discharge duct is not in communication with the balancing vessel fluid pressure through the annular chamber of the second piston unit, because this communication is interrupted by the first working piston when a load is towed or the 0 drawbar is deployed (when no inertia braking occurs), so that the brake pressure, generated in said second piston group by the tractive force or the towed load, can be transmitted to the braking cylinders from the annular chamber 25 as soon as the control spool makes the discharge duct communicate with this annular chamber during a reversal of the direction of rotation In this hydraulic connection, the discharge duct coming into action during the automatic operation in operation The advanced pressure-flow device acts as a discharge duct. An improved hydraulic inertia braking system according to this technical design is not only provided with a fully efficient system of automatic operation. in reverse, but it also allows to brake the trailer as soon as it descends the slope after the immobili on a gradient, the braking torque then being

  proportional to the towed load.

  In a practical embodiment, the master cylinder can be incorporated in the pulling bar itself and have a stepped enlarged portion, a working cylinder associated with the working piston being respectively contiguous to a throttling channel ensuring the junction with the vase fluid pressure balancing, a stop cooperating with the traction piston and finally to the annular chamber of the second piston group. In this case, there is provided a pumping channel between the abutment and the junction with the pressure balancing vessel, and the working piston has a head in which a balancing channel is disposed between said throttling channel. and a seat of said traction piston, as well as, behind this head, a narrowed region on which are located the traction piston and the thrust piston of the

second piston group.

  At its end, the working piston has an enlarged tail stepped on the steps of which respectively support the thrust piston of the second piston group and the compression spring of the first working piston group. In addition, an annular channel of control connecting the seat to the annular chamber is formed in the traction piston and, when the automatic operating system in reverse goes into action, this channel allows a relaxation of the brake pressure into

the pressure balancing vessel.

  Judiciously, the pressure balancing vessel

  The fluid may be an uninterrupted U-shaped ring attached to the drawbar.

  To allow a detection of the direction of rotation of the wheel and a movement of the control spool, it is proposed to apply against the hub of said wheel, a pad which is in effective connection with said control spool via a selector lever with two arms and a

bending spring.

  According to another embodiment of the invention, it is proposed to insert between the outer end of the working piston and the drawbar, a compression spring which determines the pressure in the working cylinder when the drawbar is retracted up to the stop This extra compression spring

  can be housed in an annular chamber between the outer end of the working piston and a guide tulip bearing against the drawbar.

  The invention will now be described in more detail by way of non-limiting examples, with reference to the accompanying diagrammatic drawings in which: FIG. 1 is a plan view of a single-axle trailer equipped with a device hydraulic braking by inertia occupying its initial position; Figure 2 is a fragmentary section on an enlarged scale corresponding to Figure 1 and illustrating said braking device in its initial position; Fig. 3 is a cross-section of an internal jaw brake viewed from the inside out and having a brake cylinder in the initial position; Figure 4 is a fragmentary longitudinal section of the braking device in the service position which it occupies in the case of a forward motion or braking on a declivity; Figure 5 is a section corresponding to Figure 4 and illustrating said braking device in the position it occupies in case of braking by inertia in forward or reverse; Figure 6 is a longitudinal section of the brake with internal jaws in the position it occupies in the case of inertia braking in the forward direction; Figure 7 is a section corresponding to Figure 6 and showing said brake with internal jaws in the position it occupies when the automatic operating system in reverse enters into action, or when braking on a declivity; and FIG. 8 is a section corresponding to FIG. 2 and illustrating another embodiment of the inertia hydraulic braking device in its position of

fully retracted service.

  A drawbar 7 provided with a pull eyelet

  8 is movably mounted in a bearing 6, on a drawbar 1 comprising longitudinal longitudinal members 2, a support spacer 3, a crossbar 4 and a central spar 5.

  A traction stop 9 is fixed on this bar 7, while the rear end of the eyelet 8 forms a

braking stop 10.

  A fluid pressure balancing vessel 11 is attached to the drawbar 7 in the central spar 5. In the case of the single-axle trailer shown, the rear ends of the longitudinal spars 2 are rigidly connected to an axle body 12 (dashed in FIG. 1), but, in the case of a multi-axle trailer, they can also be connected, by means of articulations 13, to the front axle body 12 which is then braquable Hydraulic brakes 14 with internal jaws, installed on the axle body 12, are actuated by the intermediary of a pressure conduit 15

and a discharge duct 16.

  In addition, a mechanical parking brake is connected to the two brakes 14 with internal jaws and this brake, provided with a manual brake lever and a cable 18 of coupling failure, acts via a mechanism 19 traction cable, on a mechanical device (no

  shown) incorporated in said brakes 14.

  A maler cylinder 20 associated with a working piston 21 is housed in the drawbar 7 This master cylinder 20 is enlarged in a stepped configuration and defines a working cylinder 22, a throttling channel 23 in communication with the vase 11 35 of pressure equalization through a junction channel 24, a stop 25 cooperating with a traction piston 26, and

  an annular chamber 27 housing a thrust piston 28.

  A pumping channel 29 extends between the abutment 25 and the connecting channel 24. The traction piston 26 and the thrust piston 28 are pushed into their respective initial positions by a compression spring 30. The traction piston 26 has a channel annular order 31 which

  connects the abutment 25 to the annular chamber 27.

  The working piston 21 comprises a head 32 which acts in the working cylinder 22, as well as a balancing channel 33 which connects the throttle channel 23 to the abutment 25. Behind its head 32, this working piston 21 has a control bulge 34 which closes the throttle channel 23 and, behind this bulge, a seat which cooperates with the traction piston 26 Behind said seat, the working piston 21 has a narrowed region 36 on which the piston is located Traction 26 and the thrust piston 28 At its outer end, this working piston 21 is provided with a stepped enlarged tail 37 on steps 38 and 39 from which the pushing piston 28 and, on the one hand, on the other hand, a compression spring 40 whose other end is applied against the central spar 5 This compression spring 40 determines the value of the pressure that prevails

in the annular chamber 27.

  In the outer end of the working piston 21 is formed a bore 41 which communicates internally and externally with the annular chamber 27 and with the discharge conduit 16, respectively The pressure conduit 15 communicates with the master cylinder 20 by the intermediate

a hole 42.

  Each brake 14 with internal jaws consists of a brake drum 43 in which braking jaws 44 are located which bear against a support bearing 46 which is secured to a brake plate 45, and which

  may be spaced apart by a brake cylinder 47 also secured to said brake plate 45.

  Each brake cylinder 47 houses two brake pistons 48 for actuating the brake jaws 44 A control spool 49, located upstream of the cylinder 47, has two annular control grooves 50 and 51 which connect the respective pressure conduits 15 and discharge device 16 to said cylinder 47, via a junction channel 52. A shoe 54, applied against a wheel hub 53, detects the direction of rotation of the hub 53 and is in effective connection with the control 49 via a bending spring 55 rotatably mounted, and a selector lever 56 with two arms pivotally mounted by one of its branches, the bending spring 55 is hooked in the shoe 54 and at its other end, it bears against the braking jaw 44 which is contiguous thereto. The selector lever 56, to which the spring 55 is secured, engages in the control spool 49 by a

nipple 57.

  In the embodiment illustrated in FIG. 8, an additional compression spring 58 is interposed between the outer end of the working piston 21 and the support spacer 3, with a view to maintaining and limiting the braking pressure that prevails. in the master cylinder 20, even when the drawbar 7 is fully retracted. For this purpose, a guide tulip 59, which receives the outer end of the working piston 21 and against which the compression spring 40 also bears is mounted movably on the support spacer 3 Inside this tulip 59, the piston 21 comprises a collar 60 against

  which carries the compression spring 58.

  The device illustrated in the drawings and described above operates, when it occupies its different positions

  service, as explained below.

  When this device serves as the main brake in forward and the drawbar 7 is deployed in accordance with Figure 4 during this movement forward, the communication remains established between the maitrecylinder 20 and the vase 11 balancing of pressure through the working cylinder 22, the throttle channel 23 and the connecting channel 24, because no relative movement of the drawbar 7 and the working piston 21 has occurred. a braking pressure for actuating the braking pistons 48 in the braking cylinders 47 can not develop. Compared to the starting position shown in FIG. 2, only the compression spring is subjected to a preload up to 'the stop of

  Pull 9 comes against the bearing 6 of the drawbar.

  When the trailer undergoes inertia in the case of braking in the forward direction, the drawbar 7 takes the

  5 In this case, the working piston 21 moves in the working cylinder 22 and closes the return passage to the balancing vessel 11.

  Thus, in the master cylinder 20, it is possible to develop a braking pressure which is transmitted to the brake cylinder 47 via the pressure conduit 15 and the control spool 49 occupying its starting position 20 shown in FIG. 3 in the case of a forward movement The two braking pistons 48 are then

  pushed to the braking position illustrated in Figure 6.

  As soon as the inertia braking is completed, the drawbar 7 returns to its pulling position of FIG. 4, so that, via the pressure conduit, the pressurized fluid can be discharged from the braking cylinders 47. and enter the master cylinder 20 or

  in the balancing vessel 11, respectively.

  When the braking device serves as a system for automatic operation in reverse and when the trailer is pushed or parked in reverse, the drawbar 7 moves from its starting position in Figure 2 or its 4, to its position shown in FIG. 5 in the case of inertia braking, so that a braking pressure develops again strictly speaking in the braking cylinders 47, by However, due to the rotation of the wheel hub 53 rearward in the direction of an arrow R, the control spool 49 is moved to the position illustrated in FIG. that the braking pressure prevailing in the cylinders 47 is relaxed through the junction channel 52, the annular groove of

  control 51 and the discharge duct 16.

  In this case, the inverse control of the drawer 49 is

  provided by means of the shoe 54, the flexion spring 55, the selector lever 56 and the stud 57.

  The purge of the braking cylinders 47 provided by the discharge duct 16 takes place via the bore 41 located in the working piston 21, the annular chamber 27, the annular control channel 31 and the connecting channel 24, the fluid entering the vase 11

balancing its pressure.

  As soon as the trailer is again moved forward, an inverse control of the spool 49 is again triggered by the movement of the wheel hub 53 in the direction of an arrow V (FIG. 6). Then, the position

  starting point illustrated in Figures 2 to 4 is restored.

  When the trailer has been braked on a slope, the drawbar 7 is in the traction position shown in Figure 4, under the action exerted by the towed load fluid contained by the annular chamber 27 is subjected to pressure beforehand, because the traction piston 26 and the thrust piston 28 are jointly displaced, against the action of the compression spring 40, in proportion to the importance of said towed load As soon as the trailer moves towards the rearwardly, the spool 49 is controlled in the opposite direction to its position in FIG. 7, so that the accumulated pressure can be transferred into the braking rollers 47 from said annular chamber 27, through the intermediary of FIG. The trailer is then braked in proportion to the load transported. As soon as this trailer is towed forwards, there is again a reversal of the load. control of the drawer 49 to its position shown in Figure 6, so that, through the pressure conduit 15, the braking cylinders 47 can be purged of the fluid they contain and which enters the master- cylinder 20. The inertial hydraulic braking device made in accordance with the invention has been shown and described with reference to the example of a jaw brake.

  Naturally, this device according to the invention 10 can also be applied to a hydraulic disk brake.

  All the new features mentioned

  in the description and shown in the drawings constitute essential features of the invention, and

  It goes without saying that many modifications can be made to the device to which they relate, without

depart from the scope of the invention.

Claims (10)

  1 Inertia hydraulic braking device fitted to trailers with one or more axles, comprising a drawbar mounted movably in a drawbar, a master cylinder housing a working piston, as well as a pressure pipe and a duct discharge device gaining a brake cylinder which is incorporated in each wheel brake and comprises brake pistons for actuating the brake shoes of a wheel brake, characterized in that said master cylinder (20) communicates with said brake bar traction device (7), the working piston (21) movable in this cylinder being supported in the traction direction by means of a compressive bearing (40), and bearing on the trailer in the direction of the inertia; in that a traction piston (26) and a thrust piston (28), between which is inserted a compression spring (30), are housed in an annular chamber (27) between said master cylinder (20). ) and said working piston (21); and in that the braking rollers (47) are associated with at least one control spool (49) which, depending on the direction of rotation of the wheel and via respective pressure and pressure conduits,   discharge (15, 16) separated from each other, connected to said brake cylinders (47) either said master cylinder (20), 25 or said annular chamber (27).   Braking device according to Claim 1, characterized in that the mattress cylinder (20) is arranged in the drawbar (7) and has a stepped enlarged region, a working cylinder (22) associated with the piston of working (21) being contiguous with a throttling channel (23) connecting with a fluid pressure equalizing vessel (11), a stop (25) cooperating with the traction piston (26) and, finally, at the annular chamber (27).   Braking device according to claims 1   and 2, characterized in that a pumping channel (29) is interposed between the abutment (25) and the junction established with the fluid pressure equalizing vessel (11).   4 Braking device according to any one of   Claims 1 to 3, characterized in that the working piston (21) has a head (32) in which a   balancing channel (33) is located between the throttle channel (23) and a seat (35) of the traction piston (26) and, behind this head (32), a narrowed region (36) on which located the respective pistons of traction and thrust (26, 28).   Braking device according to any one of   Claims 1 to 4, characterized in that the piston   work shaft (21) has a stepped enlarged tail (37), on the steps (38, 39) of which the thrust piston (28) and the compression spring (40) respectively bear. 6 Braking device according to any one of   Claims 1 to 5, characterized in that an annular control channel (31) connecting the seat (35) and the   annular chamber (27) is arranged in the piston of traction (26).   7 Braking device according to any one of   Claims 1 to 6, characterized by the fact that the vase   (11) fluid pressure balance consists of an unbroken U-section ring, attached to the bar of traction (7).   8 brake device according to claim 1, characterized in that each control spool (49) cooperates with a pad (54) applied against the hub of wheel (53).   Braking device according to claims 1 35 and 8, characterized in that between the slide of   control (49) and the shoe (54) is interposed a two-arm selector lever (56) which engages on the one hand by a pin (57) in a hole of said control spool (49), and on which is further disposed a bending spring (55) bearing in said shoe (54) and against a jaw braking (44).   Braking device according to claim 1, characterized in that the drawbar (7) is mounted in a bearing (6) which is fixed to the drawbar (1), cooperating in the direction of traction, with a traction stop (9) secured to said bar (7) and,   in the direction of inertia, with a braking stop (10) provided on a pulling eyelet (8).   Braking device according to claim 1, characterized in that a compression spring (58)? interposed between the outer end of the working piston (21) 15 and the drawbar (1), maintains and limits the pressure in the working cylinder (22) when the drawbar (7) is retracted until at the braking stop (10).   Braking device according to claim 11, characterized in that the compression spring (58) is in an annular chamber located between the end of the working piston (21) and a guide rod (59).   bearing against the drawbar (1).