Method for manufacturing a pot-shaped pressure vessel, and such a pressure vessel

Abstract

A method for manufacturing a pot-shaped pressure vessel, in particular an air spring pot for a vehicle, comprises the following steps: providing a pot, which comprises a bottom, which comprises at least one aperture, providing at least one screw, which comprises a head and a shank, inserting the shank of the at least one screw through the aperture from an inside of the pot, so that the shank of the screw protrudes from an outside of the bottom, and firmly joining the screw to the bottom of the pot. In the transitional area from the head to the shank at least one screw comprises a connecting section tapering from the head to the shank and extending all round the circumference. In inserting the shank through the aperture the connecting section is brought to bear against the edge of the aperture, and the connecting section is joined to the edge of the aperture along its bearing contact with the latter.

Claims

1. A method for manufacturing a pot-shaped pressure vessel, comprising the following steps: providing a pot having a bottom having at least one aperture defining a central axis and a circumferential edge, providing at least one screw having a head and a shank, said at least one screw, in a transitional area from said head to said shank, having a connecting section tapering from said head to said shank and extending all round a circumference about a longitudinal axis of said screw, inserting said shank of said at least one screw through said aperture from an inside of said pot, so that said shank of said screw protrudes from an outside of said bottom, wherein the full circumference of said connecting section of said screw creates a linear contact with said circumferential edge of said aperture, thereafter adjusting the angular position of the shank of said screw into a selected angular position with respect to said central axis by acting directly upon the shank of the screw, whereby the longitudinal axis of said screw is purposefully oriented at a non-zero angle relative to said central axis and the full circumferential linear contact between said connecting section of said screw and said circumferential edge of said aperture is substantially maintained and, after said adjustment of said shank of said screw into said selected angular position, firmly joining said screw to said bottom of said pot by joining said connecting section to said edge of said aperture, wherein said selected angular position of said shank is maintained during and after said firmly joining of said screw to said bottom.

2. The method of claim 1, wherein said connecting section is joined to said edge of said aperture by resistance welding.

3. The method of claim 1, wherein said connecting section is of conical design shape.

4. The method of claim 1, wherein said bottom of said pot comprises a plurality of apertures each defining a respective central axis, wherein, according to the number of said plurality of apertures, a corresponding number of screws is provided each of which in said transitional area from said head to said shank comprises a respective connecting section tapering from said head to said shank and extending all round said circumference about a respective longitudinal axis of said respective screw, each of said screws being inserted through a respective aperture of said plurality of apertures from the inside of said pot, said respective connecting section being brought into bearing contact with said edge of said respective aperture, and each of said shanks of said screws being oriented in a respective selected angular position with respect to the respective central axis of said respective aperture, and each respective connecting section in the respective selected orientation being firmly joined to said respective edge of said respective aperture.

5. The method of claim 1, wherein said pot-shaped pressure vessel is an air spring pot for a vehicle.

6. The method of claim 1, wherein the angular position of said shank relative to said central axis can be selectively adjusted in all angular directions transverse to said central axis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment of the invention is represented in the drawing and will be described in more detail below with reference to said drawing, in which:

(2) FIG. 1 shows a perspective representation of a detail of a pot-shaped pressure vessel, in particular an air spring pot;

(3) FIG. 2 shows a further enlarged representation of a detail of the pressure vessel in FIG. 1 in a partial section along the line II-II in FIG. 1, FIG. 2 showing an intermediate stage in the manufacture of the pressure vessel; and

(4) FIG. 3 shows the same detail as in FIG. 2 on completion of the manufacture of the pressure vessel.

DETAILED DESCRIPTION OF A PREFERRED EXEMPLARY EMBODIMENT

(5) FIG. 1 represents a detail of a pot-shaped pressure vessel provided with the general reference numeral 10. Further details of the pressure vessel 10 and its manufacture are represented in FIGS. 2 and 3.

(6) The pressure vessel 10 is, in particular, an air spring pot, which is used as a component of an air spring for a vehicle.

(7) The pressure vessel 10 comprises a pot 12, which is integrally formed in one piece from sheet steel, for example in a cold forming process.

(8) The pot 12 comprises a bottom 14 together with a vessel wall 16 extending substantially perpendicularly away from the bottom 14. Approximately centrally in the bottom 14 the pot 12 in the exemplary embodiment shown comprises a trough 18, which serves as seating for the head bearing of a shock absorber (not shown).

(9) In the fitted position of the pressure vessel 10 serving as an air spring pot, the pot 12, with the bottom 14 uppermost, as represented in FIG. 1, is affixed to the underside of a spring dome of the vehicle. In the exemplary embodiment shown three screws 20, 22, 24, as yet to be described below, are fixedly, that is to say permanently, joined to the bottom 14 of the pot 12, and are provided for affixing the pot 12 to the spring dome.

(10) The screw 20 comprises a shank 26, the screw 22 comprises a shank 28 and the screw 24 comprises a shank 30, the shanks 26, 28 and 30 protruding from an outside 32 of the bottom 14 substantially perpendicularly to the outside 32. The shanks 26, 28 and 30 are provided with an external thread.

(11) The positioning of the shanks 26, 28 and 30 in relation to the bottom 14 and also the orientation of the axes 34, 36 and 38 of the shanks 26, 28 and 30 is determined by the fitting position of the pressure vessel 10 in the vehicle and its attachment to the spring dome, the position of the shanks 26, 28 and 30 on the outside 32 of the bottom 14 and the orientation of the axes 34, 36 and 38 having to conform as precisely as possible to a corresponding hole pattern in the spring dome.

(12) The method of attaching the screws 20, 22 and 24 to the bottom 14 of the pot 12 will be described below on the basis of the screw 20 with reference to FIGS. 2 and 3. The same applies to the other two screws 22 and 24 with regard to their design and their attachment to the bottom 14.

(13) According to FIG. 2 the screw 20, in addition to the shank 26, which has an external thread 40, also comprises a head 42. The head 42 adjoins an end 44 of the shank 26, but not directly, the screw 20 between the head 42 and the end 44 of the shank 26 instead comprising a connecting section 46, which tapers in the longitudinal direction of the axis 34 from the head 42 to the end 44 of the shank 26 and extends around the axis 34 all around the circumference.

(14) The connecting section 46 is, in particular, of conical design shape.

(15) For manufacturing the pot-shaped pressure vessel 10 the pot 12 is first provided in accordance with FIG. 1, together with the screws 20, 22 and 24. The pot 12 is provided in such a way that at the positions of each of the screws 20, 22 and 24 it comprises an aperture, as is shown in FIG. 2 for an aperture 48 for the screw 20.

(16) The shank 26 of the screw 20 is inserted through the aperture 48 from an inside 50 of the bottom 14, until the connecting section 46 of the screw 20 comes into bearing contact with an edge 52 of the aperture 48. The edge 52 is formed by the end of the aperture 48 facing the inside 50 of the bottom 14.

(17) The connecting section 46 here bears with its full circumference against the edge 52 of the aperture 48, the point of contact between the connecting section 46 and the edge 52 being substantially linear owing to the tapering shape of the connecting section 46, because the connecting section 46 runs at an angle both to the inner bottom wall (inner side 50) and to the wall of the aperture 48. This linear bearing contact now makes it possible to orient the axis 34 of the shank 26 precisely. The axis 34 and thereby the shank 26 are oriented by a suitable device (not show), which acts on the shank 26, for example in the area of its tip 54, and orients the shank 26 in the required axial direction and fixes it in this orientation. The fully circumferential, substantially linear bearing contact of the connecting section 46 against the edge 52 of the aperture 48 is retained irrespective of whether the axis 34 needs to be tilted for exact orientation of the shank 26, for example owing to a tolerance in the orientation of the surface of the bottom 14 in the area of the aperture 48.

(18) The orientation of the axis 34 is here possible in all angular directions, this being illustrated by a double arrow 56 for an orientation of the axis 34 in the drawing plane of FIG. 2.

(19) The shank 26 of the screw 20 is oriented according to the predefined pattern of holes on the spring dome.

(20) As soon as the shank 26 is oriented correctly in respect of the direction of its axis 34, the connecting section 46 is firmly joined to the edge 52 along its bearing contact against the edge 52 of the aperture 48, in order to fasten the screw 20 to the bottom 14 of the pot 12. For this purpose the connecting section 46 is joined by resistance welding along its bearing contact with the edge 52 of the aperture 48.

(21) FIG. 3 shows the screw 20 after the resistance welding. The edge 52 of the aperture 48, which is substantially sharp-edged prior to the resistance welding, is slightly blunted after the resistance welding. At the same time the aperture 48 is sealed pressure-tightly by the resistance welding of the connecting section 46 to the edge 52 of the aperture 48. Since no welding filler metal is needed for the resistance welding, the position of the axis 34 of the shank 26 is also maintained in the previously oriented position after the welding, that is to say no distortion and hence no axial error of the shank 26 of the screw 20 occurs. Furthermore, porosity or air inclusions, which can occur in the area of the welding where welding filler metals are used, are avoided.

(22) As can be seen from FIGS. 2 and 3, the bottom 14 in the area of the aperture 48 is only relatively small in extent perpendicular to the longitudinal direction (axis 34) of the screw 20. The vessel wall 16 and the inner vessel wall 17, which is formed by the trough 18, and which to both sides of the aperture 48 extend away approximately perpendicularly from the bottom 14, leave little room for the arrangement, manipulation and attachment of the screw 20 to the bottom 14, since the vessel walls 16, 17 are very closely adjacent. The method according to the invention, however, means that the head 42 of the screw 20 can be selected especially small, just small enough for the connecting section 46 to be in bearing contact with the edge 52 of the aperture 48. This allows the screw 20 to be affixed to the bottom 14, in particular very close to the vessel wall 16 or to the vessel wall 17, the latter being shown in FIGS. 2 and 3.

(23) The other two screws 22 and 24 are similarly inserted through corresponding apertures in the bottom 14 of the pot 12 from the inside 50 thereof, and are attached to the bottom 14 of the pot 12 by resistance welding once the shanks 28 and 30 have been correctly oriented, as described above with regard to the shank 26.