BRAKING DEVICE FOR A TRAILER

Abstract: A braking device for a trailer, having two brake blocks (4 and 5) for applying a pressure on a brake disc (2), at least one (4) of the brake blocks being pivoted on a pushing rod (7), which, when the brake is applied during forward travel of the vehicle, will be pressed side ways against a check block (14) on the brake actuation lever (9), thus boosting the braking power. The brake actuation lever (9) is eccentrically pivoted on a ratchet wheel (11) turning on an axle attached to the frame (3), the ratchet wheel being rotated by means of pawls (12a) as the brake actuation lever (9) is turned, with the result that the brake actuation lever (9) will move closer to the brake disc (2) as the brake blocks become thinner with wear. When the vehicle is reversed, the brake disc will rotate in the reverse direction and the pushing rod (7) will turn backwards without obstruction, so that no braking occurs.

Description: BRAKING DEVICE FOR A TRAILER The present invention concerns a braking device for a trailer, consisting of a frame and a brake actuation lever pivoted on it, a br disc rotating with the hub of the wheel, and brake blocks pressed against the disc during braking, with a pushing rod movably attached between the brake actuation lever and one of the brake blocks, and wi a check block preventing free movement of the rod in the direction of ' rotation of the brake disc during forward travel of the vehicle. The braking systems generally used in trailers almost exclusively emp mechanical drum brakes, which are simple in construction and permit e implementation of brake boosting and automatic release at reversal. I many cases the trailer, e.g. a caravan, is almost as heavy as the car itself, but it still has only two wheels for braking. Under these circumstances, due to the high power needed for braking, drum brakes suffer from overheating and consequent reduction of braking power whe the brake is repeatedly applied. Another drawback with drum brakes is that they need to be readjusted from time to time as the brake lining wear, which is done manually and in most cases only after the brakes have become incapable of braking. Because of the increased power dema disc brakes are also used in trailers. Such brakes are often hydraulically powered and have no boosting. Hydraulic operation invol structural complexity and an increased need for maintenance and consequently high cost of the braking device. On the other hand, brak boosting is important, since only two wheels are available for brakin A method for readjustment of the brakes to compensate for wear is presented e.g. by the US patent 3tSil-8,704, in which the position of t brake rod transmitting the braking power is automatically adjusted by means of ring-like adjustment plates mounted as a pack on the rod, th plates being moved one by one over a shoulder on the rod as the wear the braking surfaces reaches a certain degree. However, this solution based on hydraulic transmission of the power for pressing the brake blocks themselves and also for the adjustment of the rod position. In another known solution, automatic release of the brake during reversi has been arranged by providing the braking device, in addition to the I braking cylinder itself, with a control valve to permit the flow of th hydraulic fluid only when the vehicle is moving forward and braking capacity is required. The control valve is mounted on a movable frame which, when the vehicle is reversed, turns around in the direction of rotation of the wheel, whereby the control valve shuts down the flow o the hydraulic fluid, thus preventing braking. This is in itself a workable solution, but it is also based on hydraulic operation, which, as stated above, has its drawbacks. The object of the present invention is to eliminate the drawbacks mentioned and ' to provide a cheap and reliable braking device for trailers. The braking device of the invention is characterized in that one of the brake blocks -is pivoted on the pushing rod, which again is pivoted on the brake actuation lever, and that a check block is attach to the brake actuation lever in such manner that, when the brake is applied, the pushing rod is pressed sideways against the check block, t us forcing the brake actuation lever to turn further, increasing the braking power. An advantageous embodiment of the invention is characterized in that t check * block is placed between the brake block and the pivot of the pushing rod. The solution presented by the invention has the advantage of providing simple method of brake boosting as well as brake release at reversal. The -kke pivots, levers and the check block are so positioned relative each other that, when the brake is applied while the vehicle is travelling in the forward direction, brake boosting will function automatically. When the vehicle is being reversed, the brake blocks te to move clear of the brake disc and no braking takes place. Another embodiment of the braking device of the invention is characterized in that it incorporates a ratchet wheel rotatably mounte on the frame by means of an axle, the brake actuation lever being eccentrically pivoted on the ratchet wheel, said ratchet wheel consisting of an upper and a lower tooth disc, with two pairs of pawls I u pressed by springs against the toothed quadrants of the discs, one p of pawls serving to rotate the ratchet wheel and the other pair to prevent backward rotation, the former pair being pivoted at one end o the brake block and the latter pair on the frame of the braking devic This arrangement provides the advantage of automatically compensating for the wear of the brake blocks. Another advantageous embodiment of the braking device of the inventio is characterized in that the teeth on the tooth discs are so position relative to the pawls that the lower one in a pair of pawls rests at bottom of an indentation on the lower tooth disc when the upper one rests at the middle of an indentation on the upper tooth disc. Another advantageous embodiment of the braking device of the inventio is characterized in that the tooth discs are staggered relative to ea other in such manner that the tip of a tooth on the lower disc is aligned with the middle -point of an indentation on the upper disc. Another advantageous embodiment of the braking device of the inventio is characterized in that the length of one of the pawls in a pair exceeds that of the other one by an amount equal to half the distance between two successive teeth on a tooth disc. Another advantageous embodiment of the braking device of the inventio is characterized in that the pivot of the brake actuation lever is eccentrically positioned on the ratchet wheel in such manner that, as the brake blocks become thinner with wear, the brake actuation lever, carried by its pivot as the ratchet wheel is turned, moves closer to brake disc. An advantage common to all the embodiments mentioned above is that th permit fine adjustment of the brakes to compensate for the wear of th brake blocks. Even with a rough pitch of the teeth, adequate results will be achieved. - ft - A further advantageous embodiment of the braking device of the invent is characterized in that each tooth disc has two separate toothed quadrants, one for turning the wheel, the other for preventing revers rotation of the same, the two quadrants being eccentrically arranged relative to each other in such manner that the radial centre of the turning quadrant is on the pivot of the brake actuation lever, wherea the radial centre of the retaining quadrant coincides with the centre the ratchet wheel axle. This arrangement ensures that the distance between the teeth and the pawls remains constant, thus offering the advantage of reduced wear and a smoother automatic adjustment of the brakes. In the following, the invention is described in greater detail by the aid of an example, reference being made to the drawings attached, wherein: Fi ' g. 1 presents the braking device in side view, mounted on the axle of a wheel on a vehicle and seen in section along the line 1- in Fig. 2 so as to show the ratchet wheel mechanism unsection Fig. 2 presents the same braking device in top view, seen in section along the line 2-2 in Fig. 1; Fig. 3 presents the ratchet wheel mechanism; and Fig. ft presents a pair of pawls in engagement with the teeth on the ratchet wheel discs. There are two brake blocks H and 5t placed on either side of the brak disc 2. The brake block 5 is fixed on the frame 3. which is mounted s as to be movable in the axial direction of its supporting tenons 17 to ensure a balanced distribution of the braking force applied on the brake disc via the brake blocks ft and 5. The brake block ft is attache at its middle to the pushing rod 7 by means of a pivot 6. When the br actuation lever 9, part of which is visible in the figure, is pulled e.g. by means of a wire cable, the lever will turn on its pivot 10, thereby moving the pushing rod 7 attached to it by means of the pivot and thus pressing the brake block , pivoted on the other end of the 7, against the brake disc 2. Because of the friction, the brake block now tends to move in the direction of rotation of the brake disc 2, s that when the vehicle is moving forward, i.e. in the diretion indicat by the arrow in the figure, a force is exerted on the rod 7. pressing sideways against the check block 1ft and thus increasing the torsion o the brake actuation lever 9, thereby increasing the braking force. Wh the brake is released, the brake actuation lever 9 is returned to its rest position by means of a spring 15. When the vehicle is being reversed, the brake disc 2 will rotate in the opposite direction, i.e the dircetion indicated by the arrow shown with a broken line. The br block ft is free to move in this direction because the pushing rod 7 c turn unobstructed until it reaches the limit of its range of movement After reversal, the brake block is returned to its normal position a spring 16. The wear of the brake blocks is compensated for by means of a ratchet wheel mechanism 11 employing an eccentric arrangement, actuating the trunnion 10 of the brake actuation lever 9. The tooth discs 21 and 22 the ratchet wheel 11 are attached to the frame 3 by means of bearings their centres 20, and the two discs are fixedly joined by the trunnio 10 of the brake actuation lever 9 located between the upper 22 and th lower 21 tooth disc. The trunnion 10 is eccentrically positioned relative to the ratchet wheel axle 20. Moreover, the tooth discs 21 a 22 are staggered relative to each other in such manner that the tip o tooth on the lower disc 21 is aligned with the middle point of an indentation on the upper disc 22. There are two pairs of pawls 12, on for turning the ratchet wheel 11, the other for preventing it from turning in the reverse dircetion, the former pair 12a being pivoted o trunnion 6 attached to the brake block and the latter pair 12b on a trunnion 19 attached to the frame 3. the two pairs of pawls being pla on opposite sides of the ratchet wheel 11. The two pawls in each pair 12a and 12b are connected to each other by a slat 18, to which a pressure is applied by a spring 13 pressing the the pair of pawls against the toothed quadrants 23a and 23b of the ratchet wheel 11 in such manner that each pawl in the pair is able to function independen of the other one. For improved adjustment of the brakes, one of the pawls in each pair is longer than the other by an amount equal to hal the distance between two successive teeth on a tooth disc 21, 22. Wit wear of the brake blocks, the brake actuation lever 9 will turn throu a greater angular distance and at the same time, by means of the pawl 12a, it will turn the ratchet wheel 11 so that, when one or both of t brake blocks ft and 5 are worn to a certain degree, one of the retain pawls 12b will be able to engage another tooth on the quadrant 23b, w the result that the brake actuation lever 9t being pivoted on the ratchet wheel 11, is brought closer to the brake disc 2. The tooth di 21 and 22 are not exactly round in form, the toothed quadrants 23a an 23b having slightly differing radial centres. The radial centre of th quadrant 23a, which engages with the pawls 12a turning the wheel, is the trunnion 10 of the brake actuation lever 9, whereas the radial centre of the quadrant 23b, which engages with the retaining pawls 12 coincides with the centre of the hub 20 of the ratchet wheel 11, attached to the frame 3 with bearings. With such a form of the toothe quadrants, the distance between the teeth and the pawls remains constant. It is obvious to a person skilled in the art that the embodiments of invention are not restricted to the example presented above, but that they can vary within the scope of the following claims.

Claims: CLAIMS 1. Braking device for a trailer, consisting of a frame (3) and a brak actuation lever (9) pivoted on it, a brake disc (2) rotating with the hub (1) of the wheel, and brake blocks (4 and 5) pressed against the disc during braking, with a pushing rod (7) movably attached between t brake actuation lever (9) and the brake block (4), and with a check block (1ft) preventing the free movement of the rod in the direction of rotation of the brake disc (2) during forward travel of the vehicle, c h a r a c t e r i z e d in that the brake block (4) is attached to the pushing rod (7) with a pivot (6) and the pushing rod (7) is attach to the brake actuation lever (9) with a pivot (8), and that the check block (1ft). is attached to the brake actuation lever (9) in such manner that, when the brake is applied, the pushing rod (7) is pressed sidewa against the check block (1 ), thus increasing the braking torsion of t lever (9). 2. Braking device according to claim 1, c h a r a c t e r i z e d in that the check block (14) is placed between the brake block (4) and the pivot (8) of the pushing rod. 3. Braking device according to claim 1 or 2, c h a r a c t e r i z e in that it incorporates a ratchet wheel (11) rotatably mounted on the frame (3) by means of an axle (20), the brake actuation lever (9) bein eccentrically pivoted on the ratchet wheel (11), said ratchet wheel consisting of an upper tooth disc (22) and a lower tooth disc (21), wi two pairs of pawls (12a and 12b) pressed by springs (13) against the toothed quadrants of the discs, one pair of pawls (12a) serving to rotate the ratchet wheel (11) and the other pair (12b) to prevent reverse rotation of the same, the former pair (12a) being pivoted at o end on the brake block (4) and the latter pair (12b) on the frame (3) the braking device. 4. Braking device according to claim 1, 2 or 3. c h a r a c t e r i z e d ' in that the teeth on the tooth discs (21 22) are so positioned relative to the pawls (12a and 12b) that the l one in a pair of pawls (12a or 12b) rests at the bottom of an indentation on the lower tooth disc (21) when the upper one rests at middle of an indentation on the upper tooth disc (22). 5. Braking device according to claim 4, c h a r a c t e r i z e d in that the tooth discs (21 and 22) are staggered relative to each o in such manner that the tip of a tooth on the lower disc (21) is ali with the middle point of an indentation on the upper disc (22). 6. Braking device according to claim 4, c h a r a c t e r i z e d in that one of the pawls in a pair (12a and 12b) is longer than the other by an amount equal to half the distance between two successive teeth on a tooth disc. 7. Braking device according to one of the above claims, c h a r a c t e r i z e d in that the eccentrical positioning of th pivot (10) of the brake actuation lever (9) on the ratchet wheel (11 such that, as the brake blocks become thinner with wear, the brake actuation lever (9), carried by its (10.) pivot as the ratchet wheel ( is turned, will move closer to the brake disc (2). 8. Braking device according to one of the above claims, c h a r a c t e r i z e d in that each tooth disc (21 and 22) has t separate toothed quadrants, one (23a) for turning the wheel, the oth (23b) for preventing reverse rotation of the same, the two quadrants being eccentrically arranged relative to each other in such manner t the radial centre of the turning quadrant (23a) is on the pivot (10) the brake actuation lever (9) whereas the radial centre of the retai quadrant (23b) coincides with the centre of the axle of the ratchet wheel (11). H

Inventors: SIMONEN TENHO RAIMO JUHANI, SIMONEN, TENHO, RAIMO, JUHANI
Applicants: SIMONEN TENHO RAIMO JUHANI, SIMONEN, TENHO, RAIMO, JUHANI
Application year: 1985
Main classification: F16D65
IPC codes: B60T7, F16D55, F16D65