WO2005121604A1

WO2005121604A1 - Gearbox for a motor vehicle and a method for production of a gearbox

Info

Publication number: WO2005121604A1
Application number: PCT/SE2005/000797
Authority: WO
Inventors: Johan TRÄFF
Original assignee: Scania Cv Ab (Publ)
Priority date: 2004-06-08
Filing date: 2005-05-30
Publication date: 2005-12-22
Also published as: SE0401458L; SE528294C2; DE112005001329T5; SE0401458D0

Abstract

A transmission device (1) is described which comprises at least a first endwall (3) and a second endwall (4) which are arranged substantially parallel with one another, and a mainshaft (8, 10). The transmission device (1, 101, 201) has a casing (2, 102, 202) with an inside surface and an outside surface each arrived at by parallel movement of a straight line along a curve in space, with the endwalls (3, 4, 103, 104, 203, 204) arranged each on their respective side of the casing (2, 102, 202) and at least one fastening means (19, 22, 45, 46) arranged to exert upon the distal surfaces of the endwalls (3, 4, 103, 104, 203, 204) a force against one another inwards towards the casing (2, 102, 202). A method for manufacture of such a transmission device (1, 101, 201) is also described.

Description

GEARBOX FOR A MOTOR VEHICLE AND A METHOD FOR PRODUCTION OF A GEARBOX.

Technical field

The present invention relates to a transmission device for a motor vehicle according to the preamble of claim 1 and to a method for production of such a transmission device.

Description of state of the art

Motor vehicles are mostly equipped with transmission devices such as gearboxes, differential locks and transfer gearboxes. A commonly occurring type of transmission device is gearwheel gearboxes which usually comprise a housing with a mainshaft and a countershaft which are arranged in parallel. The mainshaft comprises an input shaft and a primary shaft which are usually adapted to being lockable relative to one another. An input shaft is connected to the engine via a clutch, and a gearwheel arranged on the input shaft drives a gearwheel arranged on the countershaft. A number of gearwheels arranged in mutually engagement in pairs are arranged on the primary shaft and the countershaft. The gearwheels on the primary shaft are adapted to being lockable relative to the primary shaft. The ratio between the primary shaft and the countershaft depends on which gearwheel is locked relative to the primary shaft. A gear control element in the gearwheel gearbox is arranged to enable the gearwheels on the primary shaft to be locked securely. It is possible, by means of a gear carrier connected to the gear control element, to change the gearwheel which is to be locked relative to the primary shaft,

Today's gearboxes often comprise a cast casing in which the shafts are arranged. An example of such a gearbox is described in US patent 5,284,067. Fastening points for fastening the gearbox in the motor vehicle are arranged on the gearbox. Most such fastening points are situated at different locations depending on the vehicle in which, the gearbox is to be installed. It is sometimes also desired to arrange equipment items on the gearbox, in which case equipment fastening points for such items are provided. The locations of the fastening points and equipment fastening points respectively vary depending on the motor vehicle in which the gearbox is to be fitted and the equipment which is to be installed on the gearbox. It is also usual that it is desired to modify the gearbox with regard to the number of gear steps. If it is desired to increase the number of gear steps, the length of the shafts in the gearbox and the number of gearwheels arranged on the shafts have to be increased. Providing space for longer shafts in the gearbox entails lengthening the gearbox. If changes have to be made to the gearbox housing with regard to the length of the gearbox housing, the fastening points or the equipment fastening points, however, the casting mould used has to be modified, but mould modifications are expensive.

Another problem with the state of the art is that the casting technique used entails subsequent machining to give the castings sufficient dimensional accuracy.

The problems described above with respect to gearwheel gearboxes apply also to other transmission devices for a motor vehicle, such as differential locks and transfer gearboxes.

There is thus a need for a transmission device for a vehicle which solves the problems of the state of the art and can be modified more easily than known transmission devices without having to modify any casting mould.

Summary of the invention

One object of the present invention is to provide an alternative to known transmission devices for motor vehicles.

Another object of the present invention is to provide a transmission device which is less expensive to produce than today's transmission devices.

A further object of the present invention is to provide a transmission device which can be modified more easily for different motor vehicles than known transmission devices.

Another further object of the present invention is to provide a transmission device on which it is easier to install equipment without modifications to the transmission device. Yet another object of the present invention is to provide a method for manufacture of a transmission device which is less expensive than the methods for manufacture of a transmission device according to the state of the art.

These objects are fulfilled by a transmission device and a method according to the independent claims. Further advantages are afforded by the features defined in the dependent claims.

A transmission device according to the invention comprises at least a first endwall and a second endwall which are arranged substantially parallel with one another. The transmission device also comprises a mainshaft which is supported in the opposing endwalls and which runs through at least one of the endwalls. The transmission device is distinguished by the fact that it comprises at least one casing with an inside surface and an outside surface which are each arrived at by parallel movement of a straight line along a curve in space and have a longitudinal axis whereby the endwalls are arranged on opposite sides of the casing along the longitudinal axis, and that it comprises at least one fastening means adapted to exerting upon the distal surfaces of the endwalls a force against one another along the longitudinal axis inwards towards the casing.

A surface arrived at by parallel movement of a straight line along a curve in space is the definition of a general cylinder surface. A usual particular case of such a cylinder surface is a circular cylinder surface arrived at by parallel movement of a straight line along a circle, perpendicular to the circle. In this application, however, cylinder surface comprises all forms of cylinder surfaces such as oval cylinder surfaces, square cylinder surfaces, triangular cylinder surfaces and all other forms of cylinder surfaces.

The shape of the inside surface may differ from that of the outside surface, in which case the casing is of varying thickness.

The straight line which by parallel movement defines the cylinder surface may be defined as being parallel with the longitudinal axis. The transmission device may take a large number of different forms. For example, the transmission device may be a differential lock, a transfer gearbox or a gearwheel gearbox.

The casing may be produced in any of a number of different ways. The casing is preferably made by extrusion, in which case the longitudinal axis is defined by the direction in which the casing is extruded. Extrusion is a cost-effective method for production of tubes and allows great variation in tube shape. An extruded casing is less expensive to produce than cast casings according to the state of the art, and entails less subsequent machining than cast gearbox housings. It is also possible to produce endwalls from ordinary sheetmetal, which endwalls can, after cutting of the sheetmetal, be machined to form endwalls.

The fastening means may be configured in a large number of different ways. According to one alternative, the fastening means is arranged through both of the endwalls. An advantage of this is that the gearwheel gearbox can be made light and compact and that it is possible to use the fastening means between the endwalls as support for items inside the gearwheel gearbox. Alternatively, the fastening means may take the form of a screw and a thread in the casing, in which case the screw runs through a hole in the endwall.

The fastening means may thus be configured in a large number of different ways. According to one variant, the fastening means takes the form of a rod threaded at at least one of its ends and provided with a nut at the threaded end and a dolly at its other end, whereby the dolly abuts against one endwall and the nut abuts against the other endwall. The force by which the nut is clamped on the rod determines the force on the endwalls. The dolly may be configured in a number of different ways. The rod is preferably threaded at both ends, in which case the dolly takes the form of a nut threaded on the rod. It is of course possible to have a fastening means without any thread. The transmission device may also comprise at least one countershaft supported in the endwalls, with at least one countershaft gearwheel, in which case the mainshaft comprises at least one gearwheel in engagement with one of said at least one countershaft gearwheel on the countershaft. There are countershafts in many different transmission devices, e.g. in gearwheel gearboxes and transfer gearboxes. In gearwheel gearboxes a number of countershafts may be arranged in order to distribute the torque over a number of countershafts.

The invention affords particularly great advantages for gearwheel gearboxes. A gearwheel gearbox comprises at least one countershaft, with a number of countershaft gearwheels arranged on said one countershaft, in which case the mainshaft comprises an input shaft with at least one gearwheel in engagement with a countershaft gearwheel on the countershaft, and a primary shaft with a number of primary gearwheels which are lockable relative to the primary shaft for choice of ratio and are each in engagement with their respective countershaft gearwheel on the countershaft.

In cases where the transmission device is a gearwheel gearbox, it may also comprise a gear control element for effecting the locking of gearwheels on the primary shaft. The gear control element may be integrated with one of the endwalls but may alternatively take the form of a separate element arranged between one of the endwalls and the casing. The gear control element is held firmly in position by the fastening means. In cases where the fastening means runs through both of the endwalls, the gear control element is held in position by the force which acts upon the distal sides of the two endwalls. The gear control element may also be provided with a flange to prevent any possibility of its moving transversely relative to the longitudinal axis of the casing.

The gear control element comprises a gear carrier for effecting the locking of gearwheels on the primary shaft, which gear carrier may comprise a gear carrier stem. The gear carrier stem may be arranged on plain bearings for sliding in the longitudinal direction of the casing. The primary shaft may of course also be lockable relative to the input shaft, in which case said locking is effected by the gear carrier.

In cases where the transmission device is a gearwheel gearbox, it may also comprise a planetary gear connected to the primary shaft. If the gearwheel gearbox comprises a planetary gear, it may also comprise a third endwall and a second casing defining a second inside surface and a second outside surface which are cylinder surfaces according to the foregoing definition, whereby the second casing is arranged between the second endwall and the third endwall, and whereby the planetary gear is arranged between the second endwall and the third endwall within the second casing. Such a third endwall contributes to the stability of the gearwheel gearbox. In cases where the fastening means takes the form of threaded rods, the latter may be configured as rods with two different diameters. A first portion of the rod which runs through the first and second endwalls may for the purpose here concerned have a first diameter and be provided with the same thread at both ends. A second portion of the rod which is a continuation of the first portion and runs through the second endwall has a smaller diameter than the first portion of the rod. With such a rod the nut which is to abut against the second endwall is simply slipped over the second portion of the rod and screwed onto the first portion of the rod. Preferably, a number of rods are arranged as fastening means. The second casing may also be extruded, with the same advantages as described above.

The gearwheel gearbox may comprise seal rings arranged between the casing and the first endwall and between the casing and the second endwall. In cases where there is a separate gear control element, seal rings may be arranged between the gear control element and the casing and between the gear control element and the first endwall.

The outside of the casing in the gearwheel gearbox may comprise at least one groove which runs along the longitudinal axis of the casing and whose width in a direction transverse to the longitudinal axis outwards from the centre of the casing varies and has a local maximum. Such a groove makes it relatively easy to fasten extra equipment securely. In such cases the equipment is arranged on a bracket which substantially corresponds to the shape of the groove. The fact that the groove has a local maximum width means that the bracket with the extra equipment cannot be pulled straight out from the casing transversely to the longitudinal axis. The bracket with the extra equipment may be fixed in the groove so that it also cannot move along the groove.

In a corresponding manner, the inside of the casing in the gearwheel gearbox may comprise at least one groove which runs along the longitudinal axis of the casing and whose width in a direction transverse to the longitudinal axis inwards towards the centre of the casing varies and has a local maximum.

According to a second aspect of the present invention a method is provided for production of a transmission device with at least a first endwall and a second endwall which are arranged substantially parallel with one another, and a mainshaft which is supported in the endwalls. The method is distinguished by the fact that it comprises the steps of providing a tube with a longitudinal axis, of cutting a casing from the tube, of arranging endwalls each on its respective side of the casing, of arranging at least one fastening means to exert a force on distal surfaces of the endwalls inwards towards the casing, and of arranging the shaft supported in the endwalls.

The tube is preferably produced by extrusion, in which case the longitudinal axis is defined by the press direction. The advantages of extrusion were described above in connection with the description of the gearbox according to the invention.

It is of course possible to include further processing steps after the casing has been cut from the extruded tube.

The features described in connection with the transmission device according to the invention may of course in appropriate cases be implemented also in a method for production of a transmission device. The various features described may of course where applicable be combined in the same embodiment. Embodiments of the invention are described below with reference to the attached drawings.

Brief description of the drawings

Fig. 1 depicts in transverse section a gearwheel gearbox according to an embodiment of the present invention.

Fig. 2 depicts in transverse section a gearwheel gearbox according to an alternative embodiment of the present invention.

Fig. 3 is a perspective view of constituent parts of a gearbox according to the embodiment in Fig. 1.

Fig. 4 depicts schematically a transverse section of a differential lock according to an embodiment of the present invention.

Fig. 5 depicts schematically a transverse section of a transfer gearbox according to an embodiment of the present invention.

Description of embodiments

Fig. 1 depicts a gearbox 1 according to an embodiment of the present invention. The gearbox comprises a first extruded casing 2, a first endwall 3, a second endwall 4 and a gear control element 5. The first extruded casing 2 has a longitudinal axis 40 which corresponds to the press direction during the production of the extruded casing. The first endwall 3 and the second endwall 4 are arranged substantially parallel with one another on opposite sides of the casing 2 along the longitudinal axis of the casing. The gearwheel gearbox 1 also comprises a countershaft 6 on which a number of countershaft gearwheels 7 are arranged, an input shaft 8 with at least one gearwheel 9 in engagement with one of the countershaft gearwheels 7 on the countershaft 6, and a primary shaft 10 with a number of primary gearwheels 11 which are lockable relative to the primary shaft 10 for gear ratio selection and are each in engagement with their respective countershaft gearwheel 7 on the countershaft 6.

The input shaft 8 and the primary shaft 10 together constitute a mainshaft. The mainshaft and the countershaft 6 extend through the casing 2 and are supported by bearings 12 arranged in the endwalls 3, 4. The mainshaft also runs through both of the endwalls 3, 4. The gear control element 5 is provided with a first flange 13 on the side which is arranged against a first endwall flange 14 of the endwall 3, and a second flange on the opposite side which is arranged against a first casing flange 16 of the casing 2. The second endwall is provided with a second endwall flange 17 arranged against a second casing flange 18 of the casing on the side opposite to the first casing flange 16. A first rod 19 has a first rod portion 20 and a second rod portion 21. A second rod 22 has a first rod portion 23 and a second rod portion 24. The first rod portions 20, 23 of the rods 19, 22 have larger diameters than the second rod portions 21, 24 and are threaded at both ends. The first rod portions 20, 23 run through the first endwall 3, the casing 2, the gear control element 5 and the second endwall 4. At each end of the first rod portions 20, 23 there are nuts 25 which are screwed onto the first rod portions 20, 23 and exert a force against the distal sides of the endwalls 3, 4.

The gear control element 5 comprises a number of gear carriers 26, only one of which appears in the drawings, for locking any of the primary gearwheels 11 on the primary shaft 10. The gear ratio between the input shaft 8 and the primary shaft 10 depends on which of the primary gearwheels 11 is locked to the primary shaft 10. The input shaft 8 is lockable relative to the primary shaft 10 by means of the gear carrier 26. When the input shaft 8 is locked to the primary shaft 10, none of the primary gearwheels 11 are locked to the primary shaft 10. The gear carrier 26 comprises a gear carrier stem 50 and effects locking of the primary gearwheels on the primary shaft in a manner known to a specialist within the field.

A second extruded casing 27 is arranged between the second endwall and a third endwall 28, whereby a third casing flange 29 of the second extruded casing 27 is arranged against a third endwall flange 30 of the second endwall 4. A fourth casing flange 31 of the second extruded casing 27 is arranged against a fourth endwall flange 32 of the third endwall 28. A rubber gasket 33 is arranged between the flanges at each flange recess in order to seal the joint between the flanges. As may be seen in the drawings, the rubber gaskets are arranged between surfaces whose perpendiculars are transverse to the longitudinal axis 40. An output shaft 34 is supported in the third endwall 28. The primary shaft 10 and the output shaft 34 are connected together by a planetary gear 37. The second rod portions 21, 24 are arranged through the third endwall 28. The third endwall 28 is clamped firmly to the second extruded casing 27 by nuts 38 which are screwed onto the distal ends, relative to the first rod portions 20, 23 , of the second rod portions 21 , 24.

The function of the gearwheel gearbox 1 with the planetary gear 37 will not be described in detail here, since the function is already known to specialists from similar gearwheel gearboxes 1.

Fig. 2 depicts a gearwheel gearbox according to an alternative embodiment of the present invention. The gearwheel gearbox corresponds largely to the gearwheel gearbox in Fig. 1 but has only two endwalls 3, 4. The dolly 51 on the rods takes the form of a protrusion on the rods 19, 22.

Fig. 3 is a perspective view of constituent parts of the gearbox according to the present invention. The drawings shows the first extruded casing 2 with an inside surface and an outside surface which are both cylinder surfaces according to the foregoing definition. A groove 41 running along the whole length of the casing is arranged in the extruded casing. The width of the groove in a direction transverse to the longitudinal axis outwards toward the periphery of the casing varies and has a local maximum. The groove thus has in a direction outwards towards the periphery of the casing from the local maximum a decreasing width and a local minimum. The groove 41 may be used for fastening extra equipment securely to a retainer 42 which is adapted to the groove by having a width which is greater than the local minimum and smaller than the local maximum. Such a retainer 42 is thus adapted to being pushed into or out of the groove via one of the groove's ends in the direction of the longitudinal axis. The gear carrier stem 50 is arranged to slide in plain bearings 52 arranged in the endwalls 3, 4.

Fig. 3 also depicts the first endwall 3 which has a recess 43 provided in it for a bearing for the countershaft 6 and has running through it a hole 50 for a bearing for the input shaft and a hole 44 for four rods 19, 22, 45, 46. The drawing shows the four rods, 19, 22, 45, 46 which are all similar. The first rod has a first rod portion 20 and a second rod portion 21, the diameter of the first rod portion being greater than the diameter of the second rod portion 21. The second endwall element 4 also has holes 47 for bearings and has holes 48 running through it for the four rods 19, 22, 45, 46. The second extruded casing 27 likewise has an inside surface and an outside surface which are both cylinder surfaces according to the foregoing definition, and has the same kind of groove 49 as the first extruded casing 2. The first extruded casing 2 and the second extruded casing 27 are extruded via the same die. The gear control element 5 is aπ-anged for connecting together with the gear carrier 26. Finally, the third endwall 28 has four holes 36 running through it for the four rods 19, 22, 45, 46.

The parts in Fig. 3 are joined together to constitute the gearwheel gearbox in Fig. 1.

A method for production of a gearwheel gearbox according to the invention comprises the steps of extruding a tube with a longitudinal axis defined by the extrusion press direction, of cutting a first casing 2 from the tube, of arranging endwalls 3, 4 each on their respective side of the casing 2, of arranging rods 19, 22 with nuts 25 so that they exert a force on the distal surfaces of the endwalls 3, 4 inwards toward the casing 2, and of arranging the mainshaft, comprising the primary shaft 10 and the input shaft 8, and the countershaft 6, between the endwalls 3, 4, with the shafts 6, 8, 10 supported in the endwalls 3, 4.

Fig. 4 depicts schematically a differential lock 101 according to an embodiment of the present invention. A first endwall 103 and a second endwall 104 are each arranged on their respective side of an extruded casing 102. Nuts 125 are provided at both ends of a first rod 119 and a second rod 122 and press the endwalls 103, 104 inwards towards the extruded casing 102. An input shaft 108 and a primary shaft 110 together constitute a mainshaft. Differential lock discs 131 facing one another are arranged at the proximal ends of the input shaft 108 and the primary shaft 110. Inside the differential lock between the endwalls 103, 104 there is a viscous liquid adapted to becoming sticky when it warms up. The input shaft may for example be connected to the rear wheels of a vehicle (not depicted), whereas the primary shaft 110 is connected to the front axle of the vehicle.

During operation, the input shaft 108 and the primary shaft 110 are allowed to rotate at different speeds. However, when the difference in rotation speed between the input shaft 108 and the primary shaft 110 becomes too great, the viscous liquid will warm up and thereby become sticky. The shafts will then be forced to rotate at the same speed. If the differential lock is arranged between the rear wheels and front wheels of a motor vehicle as described above, the differential lock 101 will thus connect the drive also to the front wheels if the rear wheels start spinning.

Fig. 5 depicts schematically a transverse section of a transfer gearbox 201 according to an embodiment of the present invention. A first endwall 203 and a second endwall 204 are each arranged on their respective side of an extruded casing 202. Nuts 225 are provided at both ends of a first rod 219 and a second rod 222 and press the endwalls

203, 204 inwards towards the extruded casing 202. A mainshaft 208 is supported in the endwalls 203, 204 and runs through the two endwalls 203, 204 and the extruded casing 202. A countershaft 206 is supported in both of the endwalls and runs through the first endwall 203. A countershaft gearwheel 207 is arranged on the countershaft, and a gearwheel 209 in engagement with the countershaft gearwheel 207 on the countershaft 206 is arranged on the mainshaft 208. The countershaft is thus driven by the mainshaft. The transfer gearbox may be connected to the driving shaft of a vehicle (not depicted) to provide power for a power takeoff connected to the countershaft.

The invention is not limited to the embodiments described above of the present invention. A specialist within the field may modify the embodiments described above in many ways without departing from the invention, which is only limited by the attached claims.

Although the casing 2 has been described as an extruded casing, it is of course also possible to produce the casing 2 in other ways known to specialists within the field.

Claims

1. A transmission device (1, 101, 201) for a motor vehicle, comprising at least a first endwall (3, 103, 203) and a second endwall (4, 104, 204) which are arranged substantially parallel with one another, and a mainshaft (8, 10, 108, 110, 208) which is supported in the endwalls (3, 4, 103, 104, 203, 204) and which runs through at least one of the endwalls (3, 4, 103, 104, 203, 204), characterised in that it comprises at least one casing (2, 102, 202) with an inside surface and an outside surface which are each arrived at by parallel movement of a straight line along a curve in space and have a longitudinal axis (40), whereby the endwalls (3, 4, 103 ,104) are arranged on opposite sides of the casing (2, 102, 202) along the longitudinal axis, and that it comprises at least one fastening means (19, 22, 45, 46, 119, 122, 219, 222) arranged to exert upon the distal surfaces of the endwalls (3, 4, 103, 104, 203, 204) a force against one another along the longitudinal axis inwards towards the casing (2, 102, 202).

2. A transmission device (1, 101, 201) according to claim 1, whereby the fastening means (19, 22, 45, 46, 119, 122, 219, 222) is arranged in such a way that it runs through both of the endwalls (3, 4, 103, 104, 203, 204).

3. A transmission device (1, 101, 201) according to claim 2, whereby the fastening means comprises at least one rod (19, 22, 45, 46, 119, 122, 219, 222) threaded at at least one end. and provided with a nut (25, 125, 225) at the threaded end of the rod and a dolly (51) at its other end, so that the force by which the nut (25) is clamped to the rod (19, 22, 45, 46, 119, 122, 219, 222) determines the force on the endwalls (3, 4, 103, 104, 203, 204).

4. A transmission device according to any one of the foregoing claims, comprising at least one countershaft (6, 206) supported in the endwalls, with at least one countershaft gearwheel (7, 207), whereby the mainshaft comprises at least one gearwheel (9, 209) in engagement with one of said at least one countershaft gearwheel (7, 207) on the countershaft (6, 206).

5. A transmission device according to claim 4, whereby a number of countershaft gearwheels (7, 207) are arranged on the countershaft (6, 206), whereby the mainshaft (8, 10, 108, 208, 210) comprises an input shaft (8) with at least one gearwheel (9, 209) in engagement with a countershaft gearwheel (207) on the countershaft (206), and a primary shaft (10) with a number of primary gearwheels (11) which are lockable relative to the primary shaft (11) for choice of gear ratio and are each in engagement with their respective countershaft gearwheel (7, 207) on the countershaft (6, 206).

6. A transmission device (1, 101, 201) according to claim 5, which also comprises a gear control element (5) with a gear carrier (26) for effecting the locking of the primary gearwheels (11) on the primary shaft (10), which gear carrier (26) is adapted to running on said at least one fastening means (19, 22, 45, 46, 119, 122, 219, 222).

7. A transmission device (1, 101, 201) according to claim 5 or 6, which also comprises a planetary gear (37) connected to the primary shaft (10, 110).

8. A transmission device (1) according to claim 7, which also comprises a third endwall (28) and a second casing (27) with an inside surface and an outside surface each arrived at by parallel movement of a straight line along a curve in space, whereby the second casing (27) is arranged between the second endwall (4) and the third endwall (28), and whereby the planetary gear (37) is arranged between the second endwall (4) and the third endwall (28) within the second casing (27).

9. A transmission device (1) according to any one of the foregoing claims, comprising seal rings (33) arranged between the casing (2) and the first endwall (3) and between the casing (2) and the second endwall (4).

10. A transmission device (1, 101, 201) according to any one of the foregoing claims, whereby the casing comprises on its outside at least one groove (41) whose width in a direction transverse to the longitudinal axis (40) outwards from the centre of the casing (2) varies and has a local maximum.

11. A transmission device (1, 101, 201) according to any one of the foregoing claims, whereby the casing is extruded, and whereby the longitudinal axis is parallel with the direction in which the casing (2, 102, 202) is extruded.

12. A method for production of a transmission device (1, 102, 201) comprising at least a first endwall (3, 103, 203) and a second endwall (4, 104, 204) which are arranged substantially parallel with one another, and a primary shaft (10) and a mainshaft which are supported in the endwalls (3, 4, 103, 104, 203, 204), characterised in that it comprises the steps of providing a tube with a longitudinal axis (40), of cutting a casing (2, 102, 202) from the tube, of arranging endwalls (3, 4, 103, 104, 203, 204) each on their respective side of the casing (2, 102, 202) along the longitudinal axis (40), of arranging at least one fastening means (19, 22, 45, 46, 119, 122, 219, 222)¹ which exerts a force on the distal surfaces of the endwalls (3, 4, 103, 104, 203, 204) along the longitudinal axis inwards towards the casing (2, 102, 202), and of arranging the shaft (6, 8, 10, 108, 110, 206, 208) between the endwalls (3, 4, 103, 104, 203, 204), with the shaft (6, 8, 10, 108 ,110, 206, 208) supported in the endwalls (3, 4, 103, 104, 203, 204).

13. A method according to claim 12, which also comprises the step of forming the tube by extrusion, whereby the longitudinal axis (40) is defined by the press direction. ^'