TECHNICAL FIELD The technical design concerns the towing device consisting of removable towbar and a towing bracket fixed to the vehicle structure.

BACKGROUND OF THE INVENTION In current practice there are many various design types of towing device.

These are represented, for instance, by older towing device types rigidly fixed to the automobile load bearing structure. They present increased hazard in case of collision with other vehicles or traffic participants because of towing de- vice parts overlapping the body contour.

Modern towing device types are fitted with a detachable towbar already making thus possible to remove the towbar in an easy way, if the use of trailer is not required. These types consist of a fixed part-the towing bracket fixed to the vehicle structure and detachable towbar. The detachable towbar may con- nected to the fixed part through couplings of various design, such as the bolted connection specified by the CS Patent No. 255740. Because of its difficult in- stallation requiring additional tooling this design brings some disadvantage.

Other known designs employ structures based on a principle of eccentric coupling as shown, for example, in the Czech Utility Models Nos. 4501,3529 and/or CH Patents Nos. 675859 and 675860. These designs meet current re- quirements for towing device types in a great deal. Their basic drawback, how- ever, is the necessity of applying a considerable force to fix the eccentric part.

Various levers and nuts serving to this purpose usually decrease the vehicle

road clearance or are accessible only with difficulties or do not allow to apply sufficient pull. Spontaneous loosing of the towbar at grossly uneven roads may even happen.

Further designs, based on partially or fully through members forming a transverse section of detachable towbar. These design types are described, for instance, in the Czech Utility Models Nos. 2544,2545,2599,2600,2670 and others. Their shortcomings being similar to those set out above are character- ised by awkward placements and/or poor accessibility of auxiliary clamping elements such as handles, nuts, etc.

Other designs may also be based on non-circularity principles, as shown in the Patents Nos. FR 2697471 and 2647394. These ones suffer from insuffi- cient locking against disengagement and possibility of mutual shift between the fixed part and detachable towbar.

In the existing types of detachable towing device their towbar hole axes in the bracket are parallel with vehicle longitudinal axes. This set-up brings about a certain drawback of necessity to create structures strong enough to prevent any disconnection of the towbar out of the bracket and, in some cases, the shape and position of these brackets may also bring additional troubles if they interfere with vehicle bumpers. These problems are removed in case of a bracket where the towbar hole axis is positioned vertically. Such design types are described in applications Nos. WO 97/04972, Czech Utility Models 6485, 5692,5156,7330 and others. On the other hand, in case of these structures the towbar manufacture is too complicated, the bar itself is robust and, in fact, sin- gle-purpose only which means that a single towbar is, in principe, suitable for one car type only while the other one would require a completely different tow- bar of another geometric shape.

SUMMARY OF THE INVENTION The above mentioned drawbacks are coped with to a great degree by the towing device consisting of detachable towbar and bracket fixed to the car structure according to this invention. In this principe the towbar is fitted with a fixed pivot the axis of which is in a cross direction to bar axis; the towbar, at the same time possesses a sliding index placed in the bar cavity. The index and towbar axes make an angle from 0 to 50°. The bracket is formed by the base wall parallel with the towbar axis and fitted with a mounting piece forming a re- cess for the fixed pivot support projecting out of it on one side while the other side wall is fitted with a hole for fixing the index. At the recess place the base wall is sloped towards the towbar axis in an angle from 10 to 60°. The fixed pivot and sliding index can be positioned on a segment connected to the towbar and the bracket can be fitted with the index cavity. In this case the cavity is fit- ted with a contact face accommodating the segment. The sliding index is then suitably fitted with a pressure spring acting along the index axis. The sliding index may be also fitted with a circumferential groove to accommodate a latch.

An index carrier, connected with a towbar handling member, is fixed to the sliding index in a suitable manner.

The towbar can be fitted with an end stop shaped as a lever and this lever can posses a hole for a padlock.

A push end supporting the sliding index is suitably placed in the bracket bottom part. The pawl unlocking element can be placed in the bracket as well.

The handling member and/or sliding index are fitted with a locking element (a safety lock) preventing an undesirable self-loosening.

Both the towbar and bracket can be easily manufactured for such as- sembly structure which, in turn, offers high rigidity and strength. This design provides sufficiently accurate mutual arrangement of separate functional parts.

The structure makes possible to transfer considerably high towbar loads while

the size of structural elements is kept small. The fixed pivot provides accurate positioning of the towbar in the bracket while the sliding index, placed in the towbar cavity, forms a rigid towing-bar-and-bracket connection. Owing to the fact that the index axis may form with the towbar axis an angle ranging from 0 to 50°, no expensive tool or accurate fixtures is required for the installation. The bracket structure formed with the base wall and fitted with a mounting piece forming a recess for the fixed pivot support, is shaped for an easy accommoda- tion of the relevant part of towbar.

The base wall slope over the place of recess in angles ranging from 10 to 60° makes possible to insert easily the towbar into a required position at the bracket. The sloping angle may be chosen according to car type and its spatial arrangement.

If the fixed pivot and sliding index are placed on the segment fixed to the towbar then the racket is fitted with the segment cavity. This design brings about again an advantage of relatively simple manufacture of the towbar con- sisting of two parts-the towbar itself with a ball pivot and the segment. The segment and bracket may be designed as universal parts to which tow bars of various and arbitrary geometrical shapes as may be required by customers and vehicle structures/spatial arrangements. The segment shape, incl. the fix pivot and bracket facilitates an easy placement of the towbar into the bracket cavity.

At its seating into the bracket cavity, the segment forms a self-locking connec- tion at the seating face which is created mainly by bevelling of, at least, one fixed pivot and hole and, if applicable, also the push end which can be of mate- rial possessing better mechanical properties such as strength, wear resistance, etc.

The pressure spring provides the sliding index release to a desired posi- tion preventing, at the same time, its undesirable shifting. The pawl and cir- cumferential groove eliminate a possibility of losing the index if the towbar is

laid off the bracket or carried away, facilitating at the same time the operation of pushing the towbar home to the bracket. The catch driver connected with the towing device lever makes possible to slide the index out of its working position releasing thus the whole towbar out of the bracket. The sliding index may be bevelled at its free end. The lever stop provides formation of a rigid structure and facilitates accurate setting of positions of safety lock holes. The release pawl lever provides an automation of pushing-the-bar-home operation which means that no other fittings and/or handling to secure the bar in bracket are necessary. In this case the safety lock is already the third element applied against undesirable self-loosening of the towbar out of the bracket which im- proves reliability and safety of the whole assembly. The bracket cavity shape arrests the towbar segment against side moving. Except the lever, catch driver control may be designed by the use of various control elements such as a handwheel, grooved or otherwise patterned circular elements, etc. Locking of the catch driver and/or control element by the safety lock further improves safe use of the towing device and prevents self-loosening.

If larger series of towbar s are manufactured it would be expedient, at least in some cases, to produce the towbar together with the segment as one assembly-for instance as a forging-and consequent segment machining per- form with the use of specialised machine tools.

All the above advantages are further extended by the fact that both the bar and bracket, as designed in this way, consist of rather small number of parts which cuts manufacturing and assembly costs down and, at the same time, pro- vides an easy maintenance and minimum of potential defects. This towing de- vice is easy to handle and no additional fittings are necessary. The force nec- essary to secure the towbar in the bracket is, owing to the self-locking principe applied, a minimum one. If the car is used without the towbar then the bracket

accommodates minimum dirt because of its placement; the bracket cavity may be suitably covered, if necessary.

BRIEF DESCRIPTION OF THE DRAWINGS The towing device according to this technical design will be described in a greater detail on the example of a possible concrete arrangement by the use of attached drawings where on Fig. 1 an example of the towing device is shown in a front view while the towbar is outside the bracket. Fig. 2 shows the towbar in the position when pushed home and Fig. 3 when the action is completed. Fig.

4 shows a section through of A-A'plane of Fig. 3. Fig. 5 shows a section through the towing device of B-B'plane as shown on Fig. 4. Fig. 6 shows an- other example of towing device design in a front view while Fig. 7 shows side view of the design as shown on Fig. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLE 1 This model towing device consists of detachable towbar 20 and bracket 10 which is permanently fixed to the car structure. The segment 27, fitted with a self-locking mechanism, is firmly fixed (welded, if possible) to the towbar 20.

The self-locking mechanism is formed by the sliding index 25 with a bevelled free end placed in the segment 27 the axis of which runs in parallel with that one of the towbar 20. The segment 27 is fitted with the fixed pivot 28 on its ex- ternal side the axis of which is perpendicular to that of the towbar 20. The lever 21, interconnected with the catch driver 22 (which is placed in the sliding index 25), is fixed to the side of segment 27. The sliding index 25, placed in the seg- ment 27, is fitted with the pressure spring 26 and the groove 30 along its pe- rimeter to accommodate the pawl 23. The towbar 20 is further equipped with

the stop 24 of the lever 21 in the shape of a pin and the lever 21 is fitted with the hole 29 for the safety lock corresponding with the other hole in the towbar 20. The control lever 21 and/or sliding index 25 are fitted with a safety catch against self-loosing.

The bracket 10 is equipped with a cavity for the segment 27 in which is the circular recess 13 on one side accommodating fixed pivot 28 and the hole 15 on the opposite side accommodating the sliding index 25. These is also here the contact face 14 in a shape of bevelled area for the segment 27 con- tact. In the bottom of the hole 15 of the bracket 10, the bearing pivot 11 of the sliding index 25 is placed. The top of bracket 10 holds unlocking element 12 of the pawl 23.

The towing device bracket 10 is firmly fixed to the car structure in such a manner that the segment 27 cavity is positioned downwards. The segment 27 is welded to the towbar 20 the shape of which is modified according to the rele- vant shape and structural conditions of the given car design for various towbars 20. One design of the segment 27 and bracket 10 can be thus used for differ- ent towbars 20. During the installation the towbar 20 is deflected downwards and inserted under the car so that the fixed pivot 28 of the segment 27 is homed to the recess 13 in the bracket 10. The bracket 10 position may marked by a small mark. The towbar 20 is then tipped down to the operating position. The unlocking element 12 then disengages the 23 and the pressure spring 26 in- serts the sliding index 25 into the hole 15. By the lever 21 interconnected with the catch driver the mounting of the sliding index 25 is secured in a desired po- sition. After the towbar 20 is loaded, the self-locking connection is further es- tablished between the segment 27 and bracket 10. The lever 21 is fitted by the hole 29 for a safety lock or another safety pin. The extreme position of the lever 21 is secured by the stop 24 placed in the bottom part of towbar 20.

In the course of dismantling operation the safety lock is removed, as well as other safety pins, if used, and the sliding index 25 is, by the use of lever 21 over the catch driver 22, pushed out of the hole 25 in the bracket 10. The tow- bar 20 is then tipped down and pushed out. Afterwards the pawl 23 enters the groove 30 of the sliding index 25 which prevents, among other things, a possi- bility of losing it during the handling and/or transport of the towbar 20.

EXAMPLE 2 Another design example consists of the towbar 20 and bracket 10 which is permanently fixed to the car structure. The towbar 20 is fitted the fixed pivot 28 the axis of which is perpendicular to that of the towbar 20. In the towbar cavity the sliding index 25 is placed the axis of which is which runs in parallel to that of the towbar 20. The bracket 10 is formed by the base wall 16 parallel with the towbar 20 axis. On the face side the mounting 17 is projected beyond the towbar 20. to accommodate the towbar 20. The internal side of the mount- ing is fitted with the recess 13 to accommodate the fixed pivot 28. At the back side, out of the base wall 16 the other wall 18 runs and it is fitted with the hole 15 to accommodate the sliding index 25. The base wall 16 is sloped making an angle of 45° with the towbar 20 axis at the place of recess 13. The sliding index 25 is fitted with the pressure spring 26 in the direction of its axis and the index possesses the groove 30 along its perimeter to accommodate the pawl 23 un- der pressure.

The sliding index 25 is coupled over the rack gearing (not shown) with the handwheel.

The towbar 20 is slid into the bracket 10 at an angle so that the fixed pivot 28 is placed into the recess 13. Afterwards the towbar 20 is tilted down to follow a horizontal level where its upper part runs in parallel with the base wall 16 of the bracket 10. By this the pressured pawl 23 is released out of the groove 30 and disengaged sliding index 25 is then homed by the spring 26

strength into the hole 15 in the wall 18. The whole system is thus arrested in the self-locking manner.

A removal of the towbar 20 out of the bracket 10 is performed by sliding the index 25 out of the hole 15, a consequent tilt-don of the towbar 20 and its withdrawal out of the bracket 10. The sliding index 25 can be removed by the use of the handwheel fixed to the side of towbar 20. The handwheel is coupled, through the rack gearing, with the sliding shaft of the index 25. Turning the handwheel brings the sliding index 25 to the original position and the towbar 20 is released out of the bracket 10.

INDUSTRIAL APPLICABILITY The towing device as described in this technical design will be used in particular with passenger cars and vans.