WO1995008450A1

WO1995008450A1 - Torsion spring axle

Info

Publication number: WO1995008450A1
Application number: PCT/SE1994/000873
Authority: WO
Inventors: Runo Nord
Original assignee: Runo Nord
Priority date: 1993-09-23
Filing date: 1994-09-21
Publication date: 1995-03-30
Also published as: AU7793194A; SE9303106D0; SE503320C2; SE9303106L

Abstract

A torsion bar axle assembly comprises an axle part having a polygonal cross-sectional shape and provided with a transverse arm (6), which part is put into a wider casing (8) likewise having a polygonal cross-sectional shape, spring bars (9) of elastic material being disposed in spaces between the axle part (7) and the wider casing. A movable clamp body (11) is disposed within the casing (8). In an adjustment position remote from the axle part this clamp body (11) allows free axial movement of the spring bars (9) and the axle part (7) into and out of the casing. In a position closer to the axle part said body squeezes the bars and the axle part in an axially immovable actively springy condition within the casing.

Description

TORSION SPRING AXLE

Technical field of the inven ion

This invention relates in a first aspect to a torsion bar axle assembly of the type comprising at least one axle part ha¬ ving a polygonal cross-sectional shape and provided with a transverse arm, which part is put into a wider casing likewise having a polygonal cross-sectional shape, spring bars of elastic material, especially rubber, being disposed in spaces between planar exterior surfaces on the slender axle part and angled interior surfaces on the wider casing, and means associated with the casing for varying the sizes of said spaces in order, on one hand, to allow free axial movement of the spring bars and/or the axle part into and out of the casing and, on the other hand, to fasten the bars as well as the axle part in an axially immo¬ vable, actively springy condition within the casing.

Prior art

Axle assemblies having springy torsion bars are widely used for the suspension of the wheels of trailers. In conventio¬ nal, previously known embodiments, such trailer axle assemblies consist of a box girder, square in cross-section, the length of which is substantially equal to the width of the trailer and which, at each one of the two opposite open ends thereof, pre- sents an axle part immovably mounted by means of four rubber bars, said axle part presenting a square cross-sectional shape like the box girder, although being more slender than the box girder, the axle part having, at its free end protruding from the box girder, a crank-like transverse arm on which the wheel or a brake drum is rotatably journalled. When this transverse arm is subjected to pendulous motion, e.g. due to shock loads during ride, the square axle part tends to turn relative to the surrounding box girder; what is, however, counteracted by each one of the four elastic rubber bars which exert resilient spring forces on the axle part which always aim at returning the axle part to an initial starting position. These rubber bars are inserted in the spaces being triangular in cross-section which are formed between the outside of the axle part and the interior corner portions of the box girder, with a very tight fit against the confining surfaces. More specifically, the rubber bars are already at the manufacturing plant inserted in the appropriate positions in the box girder by means of a special mounting method by which the rubber bars are freezed or cooled down to a temperature at which they have a minimal volume before mounting, whereafter the same in this shrunk condition are inserted into said spaces and, by assuming the temperature of the surrounding, allowed to expand to a volume which secures a powerful permanent fastening of each axle part in the box girder. On the upper side of the square box girder special brackets are attached, by wel¬ ding, at a predetermined distance from each other. By means of these brackets a platform assembly can be mounted on the axle assembly. Due to the fact that the rubber bars do not withstand high heat these brackets have to be welded on the box girder be- fore the axle parts and the associated rubber bars are mounted in the end portions of the box girder. After delivery of such trailer axle assemblies individual components, such as axle parts or transverse arms, cannot be dismounted from the remai¬ ning axle assembly. For this reason the axle assembly has to be replaced in its entirety after possible crashes or damages on individual components. A serious disadvantage of such trailer axle assemblies is precisely that the axle assembly, being ex¬ tensive in total, has to be replaced even if only small damages would occur, i.e. on one of the wheel suspensions. Another dis- advantage is that the axle assembly has to be delivered with a predetermined centre distance between the two brackets for the mounting of a platform. Since the width of different trailers may highly vary from one model to another a great amount of dif¬ ferent axle assemblies have to be stock-kept not only for the construction of new trailers, but also for repairing purposes. By the fact that components cannot be welded to the box girder forming the axle after the mounting of the rubber bars and the associated wheel-supporting axle parts the trailer design itself is furthermore complicated, especially when the trailer should be manufactured in a tippable version.

By GB 2 061 839 an axle assembly is previously known in which the axle parts of the two wheel suspensions and the asso¬ ciated rubber bars are not mounted in a common box girder but rather in shorter tube pieces which in turn are mounted in a beam of U-shaped cross-section. In this case welding in the U- beam is certainly possible, but still the individual axle part and associated rubber bars are permanently mounted in the asso¬ ciated tube piece without possibility of being dismounted there- from. An additional disadvantage of the axle assembly disclosed in GB 2 061 839 as well as the traditional torsion bar axle assembly discussed above is that the spring-tension or spring- force determined by the rubber bars is given once for all as soon as the bars and the axle part have been initially mounted in the box girder or the tube piece.

The purpose and characteristics of the invention

The present invention aims at eliminating the above men¬ tioned disadvantages of previously known torsion bar axle assemblies. Accordingly, a primary object of the invention is to provide an axle assembly which is simple and cheep to manufac¬ ture at the same time as the same, at need, allows, in a simple manner, the dismounting of individual components in the form of axle parts and torsion bars. Another object is to provide an axle assembly in which the spring-tension can be controlled in a simple manner. A further object of the invention is to provide an axle assembly which in a flexible manner allows welding of other components on the same so as to simplify the building of a platform-forming frame of a trailer. According to the invention at least the primary object thereof is attained by the features stated in the characterizing clause of claim 1. Preferred embodiments of the axle assembly of the invention are further defined in the independent claims 2-6. In a second aspect the invention also relates to a trailer provided with an axle assembly according to any one of claims 1- 6. The basic features of the trailing according to the invention are defined in claim 7. Claim 8 defines a preferred embodiment of this trailer.

Further elucidation of the prior art

US 4 043 571 discloses a wheel suspension including a casing in which an axle part, provided with a transverse arm, is inserted, said axle part being surrounded of torsion bars of an elastic material in the manner stated in the preamble of the appended claim 1. In this case the casing does, however, consist of two mutually movable U-beams which are held together by a set of screws or bolts by means of which the tension in the torsion bars can be controlled. Such screws run the risk of being easily loosened in consequence of vibration or shaking. Furthermore, it is impossible to weld for instance tie-beams to a trailer on the side walls of the casing in as much as the U-beams then would loose their freedom of movement.

Brief description of the appended drawings In the drawings Fig 1 is a perspective, partly simplify exploded view illustra¬ ting the vital components of a trailer according to the invention, Fig 2 is an exploded view illustrating one of two wheel suspen¬ sions included in an axle assembly according to the inven¬ tion, Fig 3 is an enlarged length section, seen from above, through one of two opposite end sections of the axle assembly according to fig 2, and

Fig 4-6 cross-sectional views through the axle assembly accor¬ ding to fig 2 and 3 in three different states in connec¬ tion with the mounting of the axle part and associated torsion bars of the wheel suspension.

Detailed description of a preferred embodiment of the invention

In fig 1 the designation 1 generally refers to an axle assembly which is designed in accordance with the invention and which is included in a trailer which additionally includes a frame 2 for forming a platform, two tie-beams 3, 3' and a coup¬ ling generally designated 4, which in a conventional manner may be attached to the tow hook of a towing vehicle (not shown) , for instance in the form of a private car. At each one of the ends of the axle 1 extending across the frame 2 wheels are arranged, the brake drums of which are illustrated at 5 (only one of the brake drums is illustrated in the simplified view) . The indivi¬ dual brake drum 5 is rotatably mounted at the free end of a crank-like swinging arm 6, which in turn is stiffly connected to an axle part 7 having a polygonal, more specifically square, cross-sectional shape. The main component of the axle 1 is a box girder or tube part 8 which, like the axle part 7, has a polygo¬ nal, quadrangular cross-section. As seen in fig 1 and 2 the individual axle part 7 is mounted in an open end of the box gir- der or tube part 8 along with a number (in this case four) tor¬ sion bars 9 of an elastic material, preferably rubber. It should also be pointed out that the box girder 8 has, on its upper side, two mounting means for the trailer frame 2. These means are generally designated 10 and 10' respectively. The trailer axle assembly shown in fig 1-3 is, as hitherto described, in all essentials previously known.

In conventional, previously known axle assemblies a box girder 8 has, like the axle part 7, had a square cross-section, meaning that four equally large triangular spaces are formed at the corners of the box girders for each one of the torsion bars 9 when the axle part 7 is turned e.g. 45° relative to the box girder. In the present invention the box girder 8 is, however, as is clearly shown in Fig 4-6, designed with a rectangular cross-sectional shape, and besides a special clamp body 11 has been provided within the box girder. More specifically, the box girder 8 is defined by two vertically shown longside walls 12, 12' (see Figure 5) and two horisontal top and bottom walls 13 and 13' respectively, which are wider than the side walls 12, 12 ' . The clamp body 11 is formed by a long and narrow ruler- shaped plate which is disposed in parallel with the side walls 12, 12' and movable to and fro the axle part 7 by means of urging members in the form of screws. In the embodiment shown just a few, e.g. two clamping screws 14 co-operate with the clamp plate 11. These clamping screws are arranged in a central row along one side wall 12 of the box girder 8. In practice, the individual screws 14 may be brought to engagement with inter¬ nally threaded nuts 15 which are welded onto the outside of the box girder in connection with holes in the side wall of the box girder. Between the clamp plate 11 and the associated girder side wall 12 a spacer is provided in the form of a fork 16 comp¬ rising two spaced-apart and mutually parallel shanks 17, 17' which are interconnected by a cross-piece 18 having a threaded hole for a safety screw 19. The two shanks 17, 17' may advanta¬ geously consist of round bars or pipes of metal. One or several stoppers 20, 20' (see figure 2 and 3) are disposed within the box girder 8 at a distance from the open end thereof, the task of which is to define an inner end position for the axle part 7 and the torsion bars 9. The distance between the open end of the box girder 8 and the stoppers 20, 20' should in practice be approximately equal to the length of the torsion bars 9. In practice the stoppers may advantageously consist of transverse pins which are inserted through holes in the side walls 12, 12' of the box girder 8 and are welded to the side walls. When mounting the axle part 7 and the torsion bars the components cannot, accordingly, be pushed in further into the box girder 8 than allowed by the stoppers 20, 20' .

When mounting a wheel suspension at one end of the trailer axle assembly the following measures are taken. The axle part 7 and the elastic torsion bars 9 are inserted along with the clamp plate 11 in the open end of the box girder 8 to an inner end position determined by the stoppers 20, 20' . In an initial con¬ dition shown in figure 4 the torsion bars 9 are substantially tension-free since they are accomodated in rather wide spaces between on one hand the exterior surfaces of the axle part 7 and on the other hand interior surfaces on the box girder 8 and the clamp plate 11. In the next step the clamping screws 14 are tightened, whereby plate 11 is moved towards the axle part 7 while diminising said spaces and compressing the torsion bars 9 so that these bars will firmly clamp the axle part in the posi¬ tion shown in figure 6. Initially the screws are tightened so hard that the two shanks 17, 17' of the fork 16 are accomodated and can be inserted in the space between the plate 11 and the girder side wall 12. Finally the screws 14 are loosened and removed from the clamp plate 11, whereby the fork shanks 17, 17' take over the clamping function of the screws, as is seen in figure 6. In this condition, the torsion bars 9 are held comp¬ ressed while maintaining a spring tension which is determined by the diameter of the fork shanks. By using fork shanks or spaces having varying diameter or thickness the elastic torsion bars 9 can be clamped with different, selectable degrees of compression while providing a desired spring tension.

After mounting the torsion bars 9 as well as the associa¬ ted axle part 7 are easily dismountable. Firstly, the clamping screws 14 are tightened so that the spacer 16 can be withdrawn from the space between the clamp plate 11 and the associated girder side wall 12, whereupon the screws are once again loosened. Then the torsion bars and the axle parts are free to be pulled out of the box girder.

The advantages of the invention are as follows. The two wheel suspensions of a trailer axle assembly can be mounted with their axle parts in one single common and simple box girder and, whenever needed after the initial mounting, be dismounted indi- vidually from the box girder. Additionally it is possible to regulate the spring tension of the bars 9 on any occasion by the simple measure of changing the position of the clamp plate within the box girder by replacing the spacer.

A special advantage is offered by the axle assembly accor- ding to the invention by the possibility of welding various com¬ ponents onto the outside of the axle-forming box girder whenever needed. Such welding is allowable by the fact that the tempera¬ ture sensitive torsion bar may be easily dismounted and removed from the interior of the box girder in connection with the wel- ding. Therefore, the invention, in a special aspect, foresees the possibility of building the platform assembly supported by the trailer axle assembly in a simplier manner than formerly.

Thus, in the embodiment shown in fig 1, the two tie-beams 3, 3' converging towards the coupling 4 are directly welded to the axle 1 at their rear ends, more specifically onto one of the two opposite sidewalls of the axle. In this manner the tie-beams 3, 3' and the axle 1 are located in a common horizontal plane. The two mounting means 10, 10' each comprises a pair of spaced- apart lugs or plates 21, 21' having holes 22 for a pivot pin 23 of the frame 22. In figure 2 these lugs are shown spaced from the box girder 8 so as to illustrate that the same can be attached at arbitrary locations along the box girder. The frame 2 may in practice be simply designed by two longside pieces 24, 24', which are interconnected by a suitable number of cross-pie- ces 25. Each of these longside pieces 24, 24' are disposed bet¬ ween the two lugs 21, 21' in each single mounting means 10, 10', whereupon the pivot pin 23, which may advantageously be a screw provided with a nut, is inserted through the holes 22 in the lugs and a through-hole through the associated frame side piece. Via the two pivot pins of the mounting means the frame 2 may, accordingly, be turned or tilted relative to the axle 1 as well as the tie-beams 3, 3' stiffly connected to the same. Thus, according to the invention a tippable trailer is provided in an extremely simple manner (the locking of the frame relative to the tie-beams is realized by means of conventional locking means not shown) .

Conceivable modifications of the invention Naturally the invention is not limited merely to the embo¬ diment described above and shown in the drawings. Thus, the invention can be utilized also in connection with such portion bar axle assemblies which comprise only one set of torsion bars and one turnable axle part . Then the axle part may be connected to other components than a trailer wheel. Furthermore, the axle part may have another polygonal cross-sectional shape than the square shape. In the tension free condition the elastic torsion bars may also have another cross sectional shape than precisely the circular or cylindrical shape shown in figure 4.

Claims

1. Torsion bar axle assembly comprising at least one axle part (7) having a polygonal cross-sectional shape and provided with a transverse arm (6) , which part is put into a wider casing (8) , likewise having a polygonal cross-sectional shape, spring bars (9) of elastic material, especially rubber, being disposed in spaces between planar exterior surfaces on the slender axle part (7) and angled interior surfaces on the wider casing (8) , and means associated with the casing for varying the sizes of said spaces in order, on one hand, to allow free axial movement of the spring bars and/or the axle part (7) into and out of the ca¬ sing and, on the other hand, to fasten the bars as well as the axle part in an axially immovable, actively springy condition within the casing, c h a r a c t e r i z e d in that the casing is in the form of a tube member (8) rectangular in cross-sec¬ tion, including four walls (12, 12', 13, 13') of which two first ones (12, 12 ) are narrower than two second ones (13, 13') , that said means is a clamp body (11) disposed within the tube member, and that a spacer (16) is inserted in a space between the side of the clamp body (11) being directed away from the axle part and a first narrow wall of the tube member (8) .

2. Torsion bar axle assembly as claimed in claim 1, c h a r a c t e r i z e d in that the clamp body (11) is mo¬ vable by means of one or more exteriorly available screws (14, 14') which are mountable in a first narrow wall (12) of the tube member.

3. Torsion bar axle assembly as claimed in claim 1 or 2, c h a r a c t e r i z e d in that the clamp body is in the form of a long a narrow, ruler-shaped plate (11) having a length sub¬ stantially equal to that of the spring bars (9) .

4. Torsion bar axle assembly as claimed in claim 3, c h a r a c t e r i z e d in that the clamp plate (11) extends substantially in parallel with the first narrow walls (12, 12') of the tube member and has a width being substantially equal o the width of the walls.

5. Torsion bar axle assembly as claimed in anyone of the prece¬ ding claims, c h a r a c t e r i z e d in that the clamping screws (14) are arranged in a central row along said first tube member wall (12) and that the spacer consists of a fork (16) having two shanks (17, 17') , which are inserted between the clamp body (11) and said wall (12) at each side of the row of screws (14) .

6. Torsion bar axle assembly as claimed in anyone of the prece¬ ding claims, c h a r a c t e r i z e d in that stoppers (20, 20') are provided within the tube member (8) at a distance from an end thereof for defining inner end positions for the axle parts (7) and the associated spring bars (9) .

7. Trailer having a torsion bar axle assembly according to any¬ one of the preceding claims, comprising two tie-beams (3, 3') converging towards a front coupling (4) and a frame (2) for a platform mounted on top of the axle assembly, c h a r a c t e r i z e d in that the tie-beams (3, 3') are directly connected to the axle assembly (1) by being welded to a frontal side wall (12) thereof so as to be located in a plane in common with the axle assembly, and that mounting means (10, 10') are attached to the upper side of the axle assembly by welding so as to hingedly connect the frame with the axle assembly while providing a tippable trailer platform.

8. Trailer as claimed in claim 7, c h a r a c t e r i z e d in that the individual mounting means (10, 10') comprises a pair of spaced apart lugs (21, 21') having holes (22) for pins (23) which are insertable in holes in longside pieces (24, 24') of the frame (2) as well as in the holes (22) of the lugs.