DRAW HOOK DEVICE

Abstract: A towing bracket device with a detachable towing bracket rod (1) provided with a ball coupling (4), and a fixedly secured retainer (2) is described, with which the towing bracket rod (1) and the retainer (2) can be interconnected by a manually operated coupling (10, 17) with locking device (27, 22, 37) comprising a safety de­ vice. According to the invention, the towing bracket rod (1) and the re­ tainer (2) are interconnectable by helical thread (10, 17), the towing bracket rod (1) or the retainer (2) comprises a locking pin (27), which can be biassed into its operational end position, and onto the locking pin (27) a safety lever (47) is mounted, which can be biassed into its operational end position.

Description: The invention relates to a towing bracket device, comprising a detachable towing bracket rod, provided with a ball coupling, and a retainer that can be fixedly secured to a towing vehicle, with which the retainer and the towing bracket rod can be intercon­ nected by a manually operated coupling with locking device, com­ prising a safety device. In this known towing bracket device, the retainer has a movable locking pin having a handle, which pin co­ operates with the underside of the towing bracket rod and is dis­ placable by the handle movable against a spring force out of co­ operation with the towing bracket rod, while a safety mechanism is present, which blocks the locking pin in its locking position. In this known towing bracket device the towing bracket rod has a rec­ tangular cross-section and the retainer has side walls adapted thereto, which side walls are connected, near their side facing the ball coupling, by a plate, supporting the bottom face of the towing bracket rod, and, at their top side, by a round pin, en­ gaging in a recess in the top face of the towing bracket rod, while the movable locking pin is mounted between side walls, being secured onto a pivoting pin supported in the side walls of the re­ tainer, one of the walls comprising a handle and the other wall being connected to the adjacent side wall of the retainer by means of a pulling spring, which locking pin cooperates self-breakingly with and is biassed against the underside of the towing bracket rod, ending in a circularly arcuate profile at the free end, the distance between the vertical planes through the centre lines of the round pin and the pivoting pin being larger than the distance between the vertical planes through the centre line of the round pin and the centre of the circularly arcuate profile, whereas the angle, enclosed by the connecting lines of the contact point of the locking pin at the circularly arcuate profile to its centre and the centre line of the pivoting pin, is larger than 0° and smaller than 10°. Although it functions properly and also meets the requirements of the "Rijksdienst voor het Wegverkeer" (the Netherlands State Commission for Road-Traffic), this known towing bracket device has the drawback, that the construction is relatively complicated and expensive and that mounting and dismounting it requires a certain skill and strength. Furthermore it is not simply possible with this know towing bracket device to replace an existing one-piece towing bracket device by this known towing bracket device with detachable towing bracket rod. The invention aims to remove the drawbacks of this known towing bracket device. This object is attained, in that, according to the invention, a) the towing bracket rod and the retainer comprise axial helical thread parts that can cooperate with one another, b) the towing bracket rod and the retainer comprise stop surfaces which abut in the operational end position of the towing bracket rod, c) either the towing bracket rod or the retainer comprises an axially movable locking pin, which is biassed in the direction of its operational end position and which in its operational end position can cooperate with a locking surface on a radial cam disc, which is secured to the retainer or the towing bracket rod, the operational end position of the towing bracket rod coinciding with that of the locking pin and d) on the locking pin a manually operable safety lever has been mounted, with which the locking pin can be retracted from its operational position, which is biassed into its operational end position and which, in its operational end position, engages with its free end, in the direction of the towing bracket rod, behind the locking surface of the cam disc and, in axial direction, behind a stop surface. By applying these measures, the towing bracket device according to the invention obtains a simple and quite firm construction, where­ as the detachable towing bracket rod can still be easily mounted and dismounted, since the coupling between the towing bracket rod and the retainer is established by means of axial helical thread parts on the towing bracket rod and the retainer. Furthermore the present towing bracket device meets the require­ ments of the "/Rijksdienst voor het Wegverkeer", because the towing bracket device comprises a locking device, the operational end po­ sition of which coincides with that of the screw coupling between the towing bracket rod and the retainer and the locking device is secured by a safety lever, preventing, even if the bias on the locking pin in the direction of its operational end position would fall off, e.g. by the snapping of a tension spring, the locking pin from moving out of its operational end position, because the safety hook in its operational end position engages with its free end, in the direction of rotation of the towing bracket rod, behind the locking surface of the cam disc and, in axial direc­ tion, engages behind a stop surface. In a preferred embodiment of the towing bracket device according to the invention a) the towing bracket rod comprises a sleeve with internal helical thread and the retainer compreses external helical thread, which helical thread is trapezium thread, b) the sleeve, in the extension of the helical thread part, com­ prises a cylindrical bore with a truncated conical bottom, consti­ tuting the one stop surface, c) the retainer, in the extension of the helical thread part, has a cylindrical bore and at its free end a truncated conical end face, constituting the other stop surface, and d) the locking pin at its free end comprises a locking surface, abutting, in the operational end position of the locking pin, the locking surface on the cam disc, in which the locking surfaces enclose a sharp angle α with the longitudinal centre line of the towing bracket rod and the retainer, said angle being larger than 0° and smaller than 10°. In this embodiment of the towing bracket device according to the invention, the towing bracket rod and the retainer are properly axially centered with respect to each other, and by means of the trapezium thread a very high pulling force can be transferred be­ tween the retainer and the towing bracket rod, so that the present towing bracket device is suitable for heavy trailers and the clearance in the coupling between the towing bracket rod and the retainer arising after long-term use is removed by the sharp angle α between the locking surfaces on the cam disc and the locking pin. Since this angle α is larger than 0° and smaller than 10°, it performs a self-breaking action, i.e. that the locking pin cannot be pushed back by exerting a torque on the towing bracket rod. In a particularly efficient embodiment of the towing bracket de­ vice according to the invention a) the trapezium thread has double threads with a pitch angle of ± 6° and b) the locking surfaces enclose an angle α of 7° with the longi­ tudinal centre line of the towing bracket rod and the retainer. In this embodiment of the present towing bracket device, the coup­ ling between the towing bracket rod and the retainer can be estab­ lished and interrupted by a short turn, while the pitch angle of the trapezium thread itself also exerts a self-breaking action. On account of the angle α of 7° between the locking surfaces and the longitudinal centre line of the retainer and the towing bracket rod, an optimum self-breaking action may be performed among the locking surfaces themselves, and at the same time, the locking between the locking pin and the cam disc can be easily manually removed. The invention will be further elucidated with an embodiment on the basis of the drawing. Fig. 1 is a partial top view and a partial longitudinal section of the towing bracket device according to the invention, Fig. 2 is a side view of the towing bracket device according to the invention and Fig. 3 is a section along the line III-III in fig. 2. The towing bracket device according to the invention comprises a detachable towing bracket rod 1 and a retainer 2. The towing bracket rod 1 has at its one end a perpendicularly bent part 3 with a ball coupling part 4 and a cylindrical sleeve 6 is mounted to the free end of the round rod portion 5, said sleeve having a round opening 7 on the side of the rod portion 5, fitting onto the rod portion 5. The sleeve 6 is secured by a welding seam 8 onto the rod portion 5. Between the far end of the rod portion 5 and the bore 7, a welding seam 8′ may have been applied in the sleeve. It is also possible that the rod portion 5 is secured to the sleeve 6 in a different manner, e.g. by means of helical thread. The rod portion 5 can also have a cross-section other than round, in which the bore 7 is than adapted to the cross-section of the rod portion 5. The sleeve 6 is provided at its end facing away from the rod por­ tion 5 with a bore 9 with internal helical thread 10, which pre­ ferably comprises double-threaded, right, trapezium helical thread with a pitch angle of ± 6°, a tooth depth of 5 mm, a top angle of 30° and a pitch of 20 mm. A cylindrical bore 11 with a smaller diameter connects to the bore 9 with helical thread 10, said bore 11 having a truncated conical bottom 12, constituting a stop cam, as will be further explained hereafter and which can connect to the bore 7 for the rod portion 5. On the retainer 2, which may comprise a round rod portion 13, the cross-section of which may coincide with that of the rod portion 5, of the towing bracket device according to the invention, a cy­ lindrical sleeve 14 is mounted, e.g. with the aid of welding seams 15 and 16. The sleeve 14 comprises external helical thread 17 of the same construction as the internal helical thread 10 in the sleeve 6. The sleeve 14 has, at the end facing the towing bracket rod 1, a cylindrical part 18 and at its free end a truncated concial end face 19. The cylindrical part 18 closely fits into the cylindrical bore 11 in the sleeve 6 and the end face 19 has the same cone top angle as the truncated concial bottom 12 of the cylindrical bore 11 in the sleeve 6. The sleeve 14 has a cylindrical bore 20, fitting onto the round rod portion 13. In this embodiment, the rod portions 5 and 13 can have the same diameter, as well as the bores 7 and 20. A cam disc 22 is mounted onto the cylindrical sleeve 14, in a plane perpendicular to the longitudinal centre line 21 of the rod portions 5 and 13, e.g. with a welding seam 23. The cam disc 22 is located on the sleeve 14 on the side of the helical thread 17 facing away from the sleeve 6 and close to that far end of said helical thread. The function and shape of the cam disc 22 will be further elucidated hereafter. The rod portion 13 and the sleeve 14 with the helical thread 17 can also be made of one piece. The embodiment according to the invention, however, has the enormous advantage that every existing one-piece towing bracket device can easily be fitted with a de­ tachable towing bracket rod, viz. by simply sawing it through and mounting the sleeves 6 and 14 onto it, etc. A bearing sleeve 24 is mounted on the rod portion 5 at the ex­ terior of the coupling sleeve 6, the centre line 25 of the sleeve 24 being parallel to the longitudinal centre line 21 of the towing bracket device. The bearing sleeve 24 has a U-shaped cross-­ section, the legs of the U being secured to the periphery of the the coupling sleeve 6 by welding seams 25. The bearing sleeve 24 can also have a different shape, e.g. a round one, and be secured in a different manner, e.g. by brackets. The bearing sleeve 24 has a bore 26 in the shape of a part of a cylinder, in which a locking pin 27 is mounted slidable in longi­ tudinal direction. The locking pin 27 has a more narrow section 28, to which a compression spring 29 is mounted in the bearing sleeve 24, said spring being locked in between a shoulder 30 at the locking pin 27 and a shoulder 31 in the bearing sleeve 24, which shoulder 31 can be an end face of a sleeve 32 secured in the bearing sleeve 24. In the a radial bore 33 in the locking pin a pin 34 is fixed, the free protruding end of which is slidably guided in a slot 35 in the bearing sleeve 24, which extends parallel to the locking pin 27. The locking pin 27 has at its end facing away from the rod portion 5 a locking surface 36 enclosing a sharp angle α with the longi­ tudinal centre line 21 of the towing bracket rod 1 and the retainer 2, which angle α is larger than 0° and smaller than 10° and preferably is 7°, as elucidated hereabove. The cam disc 22 is about semi-circular, extends over an angle of about 200° and has (at the left-hand side in fig. 3) a locking surface 37, enclosing the same angle α with the longitudinal centre line 21 as the locking surface 36 at the locking pin 27, and closely abutting the locking surface 36 of the locking pin 27 in the operational end position of the locking pin 27. The shape and the position of the cam disc 22 will be further elucidated hereafter, particularly on the basis of fig. 3. Centre line 38 and 39 are in the horizontal or vertical, respectively, middle plane of the rod portions 13 and 5 of the retainer 2 or the towing bracket rod 1, respectively. The first portion 40 of the cam disc 22, observed in the direction of rotation R, has a con­ stant width of about 5 mm and extends over an angle of 110° be­ tween a line 41, enclosing an angle of ± 20° with the horizontal centre line 38, and the vertical centre line 39. The second por­ tion 42 of the cam disc 22 has, in the direction of rotation R over an angle of ± 45°, a gradually increasing width and is bounded by a straight peripheral face part 43, being substantially perpendicular to the centre line 39. Via a rounding off 44 a sub­ stantially concentric peripheral face part 43 blends with the peripheral face part 43, ending at the level of the horizontal centre line 38, where the radial locking surface 37 is formed on the cam disc 22. Furthermore the cam disc 22 has a stop surface 46 on the side visible in fig. 3, extending over its entire length. The function and working of the cam disc 22 and parts thereof will be elucidated hereafter. The locking pin 27 furthermore comprises a safety device. Accor­ ding to the invention, the safety device comprises a safety lever 47 with two arms 48 and 49, which lever between the arms 47 and 48 is mounted with a bore onto a pivoting pin 50, being diametrially mounted in a fork 51 at the more narrow portion 28 of the locking pin 27. The arm 48 of the lever 47 is devised as a handle, the purpose of which will be explained hereafter. The safety lever 47 is biassed into the operational position according to fig. 1 by means of a compression spring 52 between the arm 48 and the bearing sleeve 24. In this embodiment, the free end 53 of the arm 48 engages, in the direction of rotation R of the towing bracket rod 1 (vide figure 3) behind the locking surface 37 of the cam disc and in axial direction behind a stop surface 54 at the bearing sleeve 24 of the locking pin 27, which stop surface preferably is the end face of the bearing sleeve 24. The other arm 49 of the safety lever 47 is able to cooperate with the end face 56 of the threaded coupling sleeve 6 at the side of the ball coupling 4, when the lever 47 rotates in the direction of the arrow 55. Mounting and dismounting the towing bracket device according to the invention is performed as follows, vide fig. 3, assuming that the retainer 2 with the rod portion 13, the sleeve 14 and the cam disc 22 is mounted to the towing vehicle in the position drawn in fig. 3. The towing bracket rod 1 is, with the locking pin 27 in the posi­ tion in the direction of rotation L, placed just past the line 41 and with the sleeve 6 opposite the sleeve 14 at the retainer 2 and axially pressed towards the retainer 2, the cylindrical part 18 of the sleeve engaging with its free end into the bore 11 in the sleeve 6 and is thus centered. Now the towing bracket rod 1 is turned in the direction R, the helical thread 10 in the sleeve 6 engaging into the helical thread 17 on the sleeve 14 and the locking pin 27 abutting, with part of its end face 57, the stop surface 46 of the cam disc 22. Here it was assumed that the locking pin only abuts the stop surface 46 with its end face 58 when the helical thread 10 and the helical thread 17 are already in engagement. If the locking pin 27 were to protrude somewhat to far forwards and to end up on the radial face 58 of the cam disc during rotation of the towing bracket rod 1, the abutment of the head face 57 of the locking pin 27 against the stop face 46 can be facilitated by a slight bevel or rounding off 59 at the cam disc 22 and/or a slight bevel or rounding off 60 at the locking pin 27. When the head face 57 of the locking pin 27 abuts the stop surface 46 of the cam disc 22, the towing bracket rod can be turned fur­ ther in the direction R, axially pushing back the locking pin 27 by the stop surface 46 by screwing on the helical thread 10 onto the helical thread 17. When the locking pin 27 has passed the vertical centre line 39 in the direction of rotation R, the end face 61 of the end part 53 of the arm 48 of the safety lever 47 contacts the straight peri­ pheral face portion 43 of the cam disc 22, opening the safety le­ ver in the direction of the arrow 55 (fig. 2). When further turn­ ing the towing bracket rod 1 in the direction R the arm 49 of the lever 47 engages the end face 56 of the sleeve 6, retracting the locking pin 27, also by means of the safety lever 47, from its operational position. Subsequently the end face 61 of the safety lever 47 passes the rounding off 44 on the peripheral face of the cam disc 22 and runs onto the substantially concentric peripheral part 45, until the locking face 37 of the cam disc 22 has been passed, the spring 52 pulling the safety lever 47 inwards in the direction of the arrow 62 (fig. 1), establishing the above-described safety position of the locking pin 27. After a slight turn onwards in the direction of the arrow R of the towing bracket rod 1 the locking surface 36 of the locking pin 27 passes the locking surface 37 of the cam disc 22 and the spring 29 biasses the locking pin 27 out of the bearing sleeve 24, the locking surfaces 36 and 37 ending up one on top of the other. In this operational end position of the locking pin 27, the truncated conical stop surfaces 12 and 19 in the sleeve 6, and on the sleeve 14, respectively, abut against each other. Clearance possibly arising in due course in the thread coupling between the towing bracket rod 1 and the retainer 2 can be removed by the locking pin 27, sliding with its locking face further onto the locking face 37 of the cam disc 22. In order to prevent the towing bracket rod 1 from being placed in the wrong position onto the retainer 2, a square-headed bow 63 can be welded onto the sleeve 14 (vide figures 2 and 3), positioned in the direction of rotation L at about an angular distance of 45° from the vertical centre line 39. In order to dismount the towing bracket rod 1, one only has to turn the arm 48, constructed as a handle, with one hand in the di­ rection of the arrow 55, cancelling the safety position of the locking pin 27 and axially retracting the locking pin 27 by the lever action of the arm 49 against the end face 56 of the coupling sleeve 6 and removing the locking of the coupling sleeve 6. After that, by a light blow of the hand against the ball coupling 4 in the direction of the arrow L, the towing bracket rod 1 can be released and in the direction of the arrow L easily be turned loose and removed.

Claims: Towing bracket device, comprising a detachable towing bracket rod, provided with a ball coupling, a a retainer that can be fixedly secured to a towing vehicle, with which the retainer and the towing bracket rod can be interconnected by a manually operated coupling with locking device, comprising a safety device, characterized in that, a) the towing bracket rod (1) and the retainer (2) comprise axial helical thread parts (10, 17) that can cooperate with one an­ other, b) the towing bracket rod (1) and the retainer (2) comprise stop surfaces (12, 19) which abut in the operational end position of the towing bracket rod (1), c) that either the towing bracket rod (1) or the retainer (2) com­ prises an axially movable locking pin (27), which is biassed in the direction of its operational end position and which in its operational end position can cooperate with a locking surface (37) on a radial cam disc (22), which is secured to the retainer (2) or the towing bracket rod (1), the operational end position of the towing bracket rod (1) coinciding with that of the locking pin (27) and d) on the locking pin (27) a manually operable safety lever (47) has been mounted, with which the locking pin (27) can be retracted from its operational position, which is biassed into its oper­ ational end position and which, in its operational end position, engages with its free end (53), in the direction (R) of the towing bracket rod (1), behind the locking surface (37) of the cam disc (22) and, in axial direction, behind a stop surface (54). 2. Towing bracket device according to claim 1, characterized in that a) the towing bracket rod (1) comprises a sleeve (6) with internal helical thread (10) and in that the retainer (2) comprises external helical thread (17), which helical thread (10, 17) is trapezium thread, b) the sleeve (6), in the extension of the helical thread part (10), comprises a cylindrical bore (11) with a truncated conical bottom (12), constituting the one stop surface, c) the retainer (2), in the extension of the helical thread part (17), has a cylindrical bore (11) and at its free end a truncated conical end face (19), constituting the other stop surface and d) the locking pin (27) at its free end comprises a locking sur­ face (36), abutting, in the operational end position of the locking pin, the locking surface (37) on the cam disc (22), in which the locking surfaces (36, 37) enclose a sharp angle α with the longitudinal centre line of the towing bracket rod (1) and the retainer (2), said angle being larger than 0° and smaller than 10°. 3. Towing bracket device according to claim 2, characterized in that the trapezium thread (10, 17) has double threads with a pitch angle of ± 6° and that the locking surfaces (36, 37) enclose an angle α of 7° with the longitudinal centre line (21) of the towing bracket rod (1) and the retainer (2). 4. Towing bracket device according to claim 2 or 3, characterized in that the cylindrical part (18) of the retainer (2) has such a length that it is centered in the cylindrical bore (11) in the sleeve (6) on the towing bracket rod (1), before the helical thread parts (10, 27) engage each other. 5. Towing bracket device according to one or more of the preceding claims, characterized in that, a) the radial cam disc (22) has a peripheral face (43, 44), the radial distance of which to the longitudinal centre line (21) of the towing bracket rod (1) being larger, over at least a part of its length up to the locking surface (37) of the cam disc (22), than the radial distance between the end face (61) of the safety lever (47) at its operational end portion (53) and the longitudi­ nal centre line (21) of the towing bracket rod (1) and the retainer (2) in the operational end position of the locking lever (47) and the locking pin (27) and b) the radial distance of said peripheral face (43, 44) of the cam disc (22) to the longitudinal centre line (22) gradually increases from a valve, which is smaller than or equal to the latter radial distance. 6. Towing bracket device according to one or more of the claims 1 through 5, characterized in that the safety lever is a dual-armed lever (47), its one arm (48) being a safety arm, arranged as a handle and being connected by a pulling spring (52) to the helical thread sleeve (6), in such a manner that the locking lever (47) is pulled toward its operational position and its other arm (6) being able to cooperate with a radial face (56) of the sleeve (6) on the towing bracket rod (1), in such a manner that the locking pin (27) can be entirely retracted from its operational position with the aid of the locking lever (47), the free end of the other arm (49) abutting the radial face (56) on the sleeve (6). 7. Towing bracket device according to one or more of the preceding claims, characterized in that a) the locking pin (27) is slidably mounted in a bearing sleeve (24) which is attached to the helical thread sleeve (6) on the towing bracket rod (1), b) on the locking pin (27) a helical compression spring (6) is mounted, which is locked up between a shoulder (30) at the locking pin (27) and a shoulder (31) in the bore (26) of the bearing sleeve (24) and c) in a radial bore (33) of the locking pin (27) a pin (34) is secured, the free protruding end of which is slidably guided in a slot (35) in the bearing sleeve (24), which extends parallel to the locking pin (27). 8. Towing bracket device according to any of the preceding claims, characterized in that a) the retainer (2) consists of a rod portion (13), the cross-­ section of which corresponds to that of the rod portion (5) of the towing bracket rod (1), b) a sleeve (14) is secured onto the rod portion (13), comprising the external helical thread part (17) and the cylindrical part (18) and c) the cam disc (22) is secured onto the sleeve (14) on the side of the external helical thread part (17), which faces away from the towing rod portion (5).

Inventors: BRINK, GERARD JACOBUS
Applicants: BRINK B.V.
Application year: 1987
Main classification: B60D1
IPC codes: B60D1