AIR PLUNGER

Abstract: An air plunger (11) to be used in an air cushioning device in a vehicle has the shape of a straight, circular cylinder, which is closed at one end by means of a first end wall (12) and which at the other end has a second end wall (13) with a centre opening (14). The air plunger (11) has an inner supporting element (16) with a first portion (17), which has the shape of a hollow, truncated, straight, circular cone. The smaller end of the truncated cone abuts against the first end wall (12), and the outer diameter of the larger cone end is essentially equal to the inner diameter of the cylinder. The inner supporting element (16) is connected to the cylinder to provide transfer of forces from the jacket of the cylinder to a centre area, defined by the smaller cone surface, of the first end wall (12).

Description: AIR PLUNGER The present invention relates to an air plunger to be used in an air cushioning device in a vehicle, said air plunger essentially having the shape of a straight, circular cylinder, which is closed at one end by means of a first end wall and which at the other end has a second end wall with a centre opening. An air plunger which is intended for use in an air cushioning device in a vehicle, has essentially the shape of a cylinder closed at its ends by means of end walls. A centre opening is formed in one of the end walls. Such an air plunger is usually made of two components, which each consist of a metal sheet compression-moulded to the shape of a cup. One of the two components has in its cup bottom a centre opening and is welded to the other component in such a manner that an air plunger having the above- described shape forms. This results in an air plunger which is tight, apart from the centre opening in one of the end walls. A prior-art air plunger produced in this manner will now be described with reference to Fig. 1, which illustrates a prior-art air cushioning device provided with such an air plunger. The air cushioning device shown in Fig. 1 has an air plunger 1, which consists of two components 2 and 3 which each consist of a metal sheet compression-moulded to the shape of a cup and which are welded together to form an air plunger 1 of the shape described above. The air plunger 1 has in its upper end wall 4 a centre opening 5 which is surrounded by a collar 6 formed on the upper end wall 4. A rubber bellows 7 is at one end attached to the collar 6 and at the other end attached to a top plate 8, which in turn is fixed to a vehicle chassis (not shown) . The lower end wall or bottom 9 of the air plunger 1 is attached to a bottom plate 10 which has a considerably smaller diameter than the air plunger 1 and the bottom 9 thereof. The bottom plate 10 is connected to the wheel axle (not shown) of the vehicle. Fig. 1 indicates the air cushioning device by full lines in an initial position and by dashed lines in a loaded position, in which the top plate 8 has been pressed a distance downwards in the direction of the air plunger 1. During such downward pressing, the rubber bellows 7 rolls against the cylindrical jacket of the air plunger 1, the jacket thus forming a rolling surface for the bellows 7. The load taken up by the air plunger 1 is transferred from the cylinder jacket to the bottom 9 and via the bottom plate 10 to the wheel axle. Since the bottom plate 10 has a considerably smaller surface than the bottom 9, the latter must for reasons of strength have a considerable thickness, which makes the construction expensive. A known proposal for a solution to this problem is shown in Fig. 2. Thus, Fig. 2 shows a further known air plunger 1' which is adapted to be used in an air cushioning device similar to the one in which the air plunger 1 shown in Fig. 1 is used. The air plunger 1' differs from the air plunger 1 shown in Fig. 1 only by the lower component 3 ' having, instead of a circular-cylindrical cup shape, the shape of a truncated conical cup, the smaller cone end of the cup being directed downwards and having essentially the same extent as the bottom plate 10 of the air cushioning device. By the lower component 3' being given this truncated conical shape, that part of its bottom which is formed of the conical portion can be made of a thinner material than the bottom 9 of the air plunger 1 shown in Fig. 1 and yet transfer the same amount of forces to the bottom plate 10. The smaller the cone angle, i.e. the longer the conical portion, the thinner the conical portion can be made, but the longer the conical portion, the smaller height must be given to the component 2', since the air plunger 1' must, for use in an air cushioning device similar to the one in which the air plunger 1 is used, have the same overall height as the latter. When the height of the component 2' and, thus, the height of the cylindrical jacket decrease, also the rolling surface of the bellows 7 is reduced, which is a considerable drawback. When manufacturing an air plunger 1' of the type shown in Fig. 2, it is therefore necessary to make a compromise between the wish to save material in the lower component 3 ' and the wish to give the bellows 7 a large rolling surface. An object of the present invention therefore is to provide an air plunger, in which no such compromise is required, i.e. to provide an air plunger, in which the desired saving of material can be made without necessi- tating a reduction of the rolling surface of the bellows. According to the invention, this object is achieved by an air plunger, which is of the type stated by way of introduction and which is characterised in that it comprises an inner supporting element with a first portion having the shape of a hollow, truncated, straight, circular cone, the smaller cone end abutting against said first end wall and the outer diameter of the larger cone end being essentially equal to the inner diameter of the cylinder, and that the inner supporting element is con- nected to the cylinder to provide transfer of forces from the jacket of the cylinder to a centre area, defined by the smaller cone surface, of said first end wall. Said first portion of the inner supporting element is preferably perforated. The inner supporting element suitably has a second portion, which is formed in one piece with the first portion and has the shape of a hollow, straight, circular cylinder, which is an extension of the larger cone end and has the same outer diameter as the latter. In a preferred embodiment, the inner supporting element has the same height as the cylinder, and said second portion has at its end facing away from said first por- tion has a bent portion adapted to the shape of said second end wall . The cone angle of the truncated cone is in a preferred embodiment about 60°. The invention will now be described in more detail with reference to the accompanying drawings, in which Fig. 1 illustrates an air cushioning device provided with the prior-art air plunger 1 as described above, Fig. 2 illustrates the prior-art air plunger 1' as described above, and Fig. 3 is a sectional view of an air plunger according to the present invention. The air plunger 11 shown in Fig. 3 has the same shape as the air plunger 1 described with reference to Fig. 1 and is adapted to be used in an air cushioning device for vehicles similar to the one in which the above-described air plungers 1 and 1' are used. The air plunger 11 is rotationally symmetrical and has essentially the shape of a hollow, straight, circular cylinder, which is closed at its lower end by means of an end wall or bottom 12 and which at its upper end has an end wall 13 with a circular centre opening 14. The air plunger 11 is suitably made by means of the method and the device as described in our patent application entitled "Method and Device for Making an Air Plunger" which is filed simultaneously herewith. The air plunger 11 is made from a blank which has the shape of a straight, circular cup or can which has the same diameter as the air plunger 11 which is to be made there- of. The bottom of the cup-shaped blank is to constitute the bottom 12 of the air plunger 11 and its circular- cylindrical jacket is to form the circular-cylindrical jacket 15 of the air plunger 11. The jacket of the blank has a circumferential upper portion which is to be formed to the upper end wall 3 of the air plunger 11 by pressure turning. The air plunger 11 has an inner supporting element 16 which is a compression-moulded or pressure-turned metal sheet and has a first portion 17 and a second portion 18. The first portion 17 of the supporting element 16 has the shape of a hollow, truncated, straight, circular cone whose smaller cone end has an end wall 19 abutting against the bottom 12 of the air plunger 11. The end wall 19 is positioned in front of the bottom plate 10 of the air cushioning device and has the same extent as the bottom plate. The outer diameter of the upper larger cone end is equal to the inner diameter of the circular-cylindrical jacket 15. The cone angle 2α is preferably about 60° . The second portion 18 of the supporting element 16 has the shape of a hollow, straight, circular cylinder which is an extension of the larger cone end and has the same outer diameter as the larger cone end, i.e. its outer diameter is equal to the inner diameter of the cir- cular-cylindrical jacket 15. As is evident from Fig. 3, the second portion 18 of the supporting element 16 has at its upper end a bent portion 20, whose shape corresponds to the shape of the transition between the jacket 15 and the upper end wall 13 of the air plunger 11. The bent portion 20 is suitably formed at the same time as the above-described pressure turning is carried out. To this end, a supporting element blank, which is identical with the supporting element 16, apart from the fact that the bent portion 20 has not yet been manufactured, is placed in the above-described cup-shaped blank, of which the air plunger is to be produced. The upper portion of the cup- shaped blank as well as that of the supporting element blank are then given their desired shape. As will be evident, the inner supporting element 16 is thus properly fixed in the air plunger 11 and is connected to the circular-cylindrical jacket 15 so as to be capable of transferring the forces caused by the load on the air plunger 11 to the bottom plate 10. Owing to the fact that the supporting element 16 which is designed in the manner described above is plac- ed inside the air plunger 11, the jacket 15 and the outer part of the bottom 12 can be made thinner while at the same time the jacket can retain its full length, which permits the desired saving of material without necessitating a reduction of the rolling surface of the bellows. The air plunger 11 according to the invention has, compared with the above-described air plunger 1' according to Fig. 2, also the advantage that it can be given the same inner volume as the above-described air plunger 1 according to Fig. 1 by the truncated conical first por- tion 17 of the inner supporting element 16 being formed with apertures .

Claims: CLAIMS 1. An air plunger to be used in an air cushioning device in a vehicle, said air plunger essentially having the shape of a straight, circular cylinder, which is closed at one end by means of a first end wall (12) and which at the other end has a second end wall (13) with a centre opening (14), c h a r a c t e r i s e d in that it comprises an inner supporting element (16) with a first portion (17) having the shape of a hollow, truncated, straight, circular cone, the smaller cone end abutting against said first end wall (12) and the outer diameter of the larger cone end being essentially equal to the inner diameter of the cylinder, and that the inner supporting element (16) is connected to the cylinder to provide transfer of forces from the jacket of the cylinder to a centre area, defined by the smaller cone surface, of said first end wall (12) . 2. An air plunger as claimed in claim 1, c h a r a c t e r i s e d in that said first portion (17) of the inner supporting element (16) is formed with apertures. 3. An air plunger as claimed in claim 1 or 2 , c h a r a c t e r i s e d in that the inner supporting element (16) has a second portion (18), which is formed in one piece with the first portion (17) and has the shape of a hollow, straight, circular cylinder, which is an extension of the larger cone end and has the same outer diameter as the latter. 4. An air plunger as claimed in any one of claims 1-3, c h a r a c t e r i s e d in that the inner supporting element (16) has the same height as the cylinder, and that said second portion (18) has, at its end facing away from the said first portion (17) , a bent portion (20) adapted to the shape of said second end wall (13) . 5. An air plunger as claimed in any one of claims -4, c h a r a c t e r i s e d in that the cone angle (2α) of the truncated cone is about 60°.

Inventors: BENGTSSON ULF, BENGTSSON, ULF
Applicants: BENGTSSON ULF, RAUFOSS SWEDEN AB, BENGTSSON, ULF
Application year: 1999
Main classification: B60G11
IPC codes: B60G11, F16F9