FR2645481A1 - Hydraulic braking device for agricultural trailers - Google Patents

Abstract

The invention relates to a hydraulic braking device allowing mechanical braking in the event of the hitch breaking, for parking, or in the event of failure in the braking circuit of the tractor. It consists of a hydraulic circuit 1 connected to two circuits 17 and 14 which each supply one of the chambers of the brake cylinders (expanders) 8, 9, 10 and 11. The control levers for the brakes 13 are kept braked in the rest position by springs 12. An accumulator 5, mounted on the line 17, makes it possible, under normal operation, to balance the force of the springs, and thus unclamp the brakes. A non-return valve 3, held by a spring 4, determines the pumped-up pressure of the accumulator 5. A valve (tap) 16 makes it possible to discharge the accumulator 5 and thus to release the action of the springs 12. This device applies particularly to agricultural trailers with several braked axles.

Description

DESCRIPTION
The present invention relates to a hydraulic braking device for an agricultural trailer with several axles allowing mechanical braking of the axles in the event of coupling breakage, parking and failure of the tractor's hydraulic circuit.

 The hydraulic braking devices of known agricultural trailers provide braking in the event of a coupling breakage and parking by the hydraulic pressure stored in a hydropneumatic accumulator and restored on the brake cylinders by the opening of a valve controlled either by the driver, either by an automatic system (ex: traction on the tractor trailer connection hose).

 Other devices act by the mechanical application of the brakes, controlled by cable linkages, but they act on only one axle and only perform a relatively weak application.

 The device according to the invention makes it possible to obtain effective mechanical braking on all of the braked wheels of a trailer, in the event of a coupling break, of parking, and does not allow the brakes to be released during failure of the tractor hydraulic system.

 The device according to the invention is characterized by the combined action of a spring and a double-acting cylinder on each braked wheel, the spring braking the wheel at rest.

 The hydraulic braking line from the tractor, which is by construction a flexible line, is divided into two lines to supply each chamber of the cylinder.

 On the line supplying the cylinder chamber, the movement of which opposes the action of the spring, there is a non-return valve, allowing free passage to the cylinder, and a hydropneumatic accumulator located between the non-return valve and the cylinder. A stopcock allows, by its opening, to put the two pipes in communication.

 The second pipe feeds the chamber of the cylinder working in the same direction as the action of the spring, that is to say the action of effecting the braking.

 When coupling the trailer, an action of the tractor braking will on the one hand cause the accumulator to inflate, and on the other hand, keep the brake applied.

 When the action on the tractor brake is released, the non-return valve will close and the hydraulic energy stored in the accumulator will compensate for the spring force and thus release the wheel brake.

 If the tractor's hydraulic braking circuit does not deliver its nominal pressure (150 bar), the inflation of the accumulator will be insufficient to compensate for the spring force, the wheel will therefore remain braked. Trailer movement is therefore only possible if the tractor brake system is operating normally.

 In normal operation, the forces exerted by the spring and the pressure stored by the accumulator being canceled, the braking pressure moderated by the driver allows normal braking.

 In the event of a coupling breakage, a cord connecting the tractor to the stop valve will open the valve, thus causing the discharge of the accumulator throughout the circuit, or on the road if the trailer-tractor connection hose was torn off when it broke, allowing the springs to brake the wheels.

 When parking the trailer, opening the tap will allow the accumulator to discharge in the tractor, thereby releasing the action of the springs.

 Alternatively, the cylinder can be located directly in the drum and act on the jaws, thereby reducing the size of the entire system.

 Figure 1 shows the device according to the invention.

 Figure 2 shows a variant of this device.

 The device shown in Figure 1 consists of a hose (1) connecting the tractor to the trailer which is divided into (2) in two separate circuits.

 The non-return valve (3) allows passage to the hydropneumatic accumulator (5) when the pressure has reached the value of the spring (4), then the line (17) goes towards the chambers (7) of the jacks 8, 9, 10 and 11 via a conduit made in the rod (6) of the jacks.

A spring (12), identical on all the cylinders, keeps the brake control levers in the tight position at rest.

 The second line (14) supplies the chamber (15) of the jacks. The stop valve (16) makes it possible to put the lines (17) and (14) in communication for discharging the accumulator (5). This opening of the tap (16) can be controlled from the tractor by the cord (18).

 According to a preferred embodiment, the cylinders 8, 9, 10 and 11 have a diameter of the chamber (15) of 25 mm, and a diameter of the rod of the chamber (7) of 14 mm.

These cylinders have a stroke of 50 mm. The springs (12), mounted around the cylinders, work in compression, with a wire diameter of 8 mm, exert a force of 375 kg per cylinder when the cylinders are in the retracted or released brakes position, and 225 kg when the cylinders are fully extended or the brakes are applied.

 This spring force is balanced by a pressure of 117 bars produced by the accumulator, the volume of which depends on the number of cylinders.

 According to a variant of the invention, the jack (19) is located inside the drum and directly actuates the jaws. The chambers (20) and (21) are connected to the line (17) and to the accumulator (5). The spring washers (22) tend to keep the cylinder extended and to apply the jaws to the drum.

 The device according to the invention is particularly intended for braking agricultural trailers comprising several axles fitted with brakes.

Claims (6)

 1) Hydraulic braking device for agricultural trailer with several braked axles, characterized by the combined action of a spring (12) with a jack (8, 9, 10 or 11) by braked wheel, and by the hydraulic supply of cylinders in two circuits (14) and (17), the second of which is fitted with a non-return valve (3) and a hydropneumatic accumulator (5). A tap (16) allows, by its opening, to connect the circuit (14) and the circuit (17).  2) Device according to claim 1 characterized in that each brake is kept applied, in the rest position, in the event of a coupling breakage or failure of the tractor or trailer hydraulic circuit by a spring (12).  3) Device according to claim 1 characterized by a jack (8, 9, 10 or 11) with double effect on each braked wheel.  4) Device according to claims 1 and 2 characterized in that a hydropneumatic accumulator (5) allows normal operation, after filling through the valve (3), cancel the effect of the spring (12) and release the brake to allow moderate braking.  5) Device according to claim 1 characterized by the valve (16) allowing by its opening to release the action of the spring (12) by the discharge of the hydropneumatic accumulator (5) in the two circuits (14) and (17) , or on the road if the circuit breaks.  6) Device according to claims 1, 2, 3, 4 and 5 characterized in that the restricted volume of the jacks (8, 9, 10 and 11) and their spring (12) allows them to be included in the drums.