GB2285110A

GB2285110A - Coupling for a flexible shaft

Info

Publication number: GB2285110A
Application number: GB9425782A
Authority: GB
Inventors: Dirk Volker; Friedrich Henz
Original assignee: Mannesmann VDO AG
Current assignee: Mannesmann VDO AG
Priority date: 1993-12-23
Filing date: 1994-12-21
Publication date: 1995-06-28
Anticipated expiration: 2014-12-21
Also published as: GB9425782D0; GB2285110B; DE4344047A1

Description

2285110 1 COUPLING The invention relates to a plug coupling for connecting

one end of an e.g. flexible shaft to a component or device, in particular a speedometer, in which an outer polygonal portion is provided to be plugged into a corresponding inner polygonal portion.

Speedometer drives generally terminate at an outer square portion, which for connection to the speedometer must be plugged into an inner square portion provided therein. This is only possible if the outer square portion is in this case exactly flush with the inner square portion and if the angular position of the two parts is the same.

Misalignments may be easily compensated by providing is the inner square portion with oblique insert sections.

such oblique insert sections do not allow the outer square portion to be rotated into its correct position if this position does not correspond to the angular position of the inner square portion at the beginning of insertion.

Such misalignments in angular position can be eliminated during manual assembly by rotating the outer square portion and thus the flexible shaft. However, if assembly is carried out automatically, then such misalignments in angular position lead to jamming. A subsequent increase in joining forces then causes 2 destruction of the coupling because of deformation of the square portions, and the flexible shafts in such cases are often bent and thus become unusable.

The object of the invention is to construct a plug coupling of the aforementioned type in such a way that its parts to be connected may be joined together automatically even when they are not arranged completely flush to one another and their angular positions are not in alignment.

In a first aspect, the present invention provides a coupling including a shaf t (or a plug) and a socket having a bore f or receipt of the shaf t. The bore has f irst and second sections, the f irst section tapering f rom a mouth of the bore to a mouth of the second section, and the second section being shaped to permit engagement of the shaft therein. The first section is further shaped so as to urge rotation of the shaft into alignment with the mouth of the second section as the shaft is inserted into the bore, if it is not already aligned therewith.

For the avoidance of doubt, the first section tapers, i.e. gets narrower, towards the mouth of the second section. In other words, a dimension transverse to the longitudinal axis of the bore decreases in a direction from the mouth of the bore to the mouth of the second section.

Preferably, the coupling has a plurality of edges, 3 each edge extending f rom the mouth of the bore to a respective corner of the mouth of the second section, each region between a pair of adjacent edges constituting an alignment portion of said first section, and wherein each alignment portion slopes from a raised region thereof to each of its two said edges.

The first and second sections of the bore may be of any convenient length. Indeed, the second section of the bore may be of little or substantially zero length - in other words, the shaft may be engageable with the mouth of the second section only.

Preferably, the raised region of each alignment portion is located approximately midway between its two said edges.

Preferably, the raised region of each alignment portion is a ridge extending substantially from the mouth of the bore to the mouth of the second section of the bore.

The raised region protrudes in a direction towards the middle of the bore. In other words, if the two edges of a particular alignment portion are straight lines, then the raised region extends out of a plane containing the two edges in a direction towards the longitudinal axis of the bore.

In a preferred embodiment of the present invention, the mouth of the bore is substantially circular.

In a second aspect, the present invention provides is 2 SS 4 a socket f or a coupling according to the f irst aspect. In particular, such a socket may be provided in conjunction with, or as part of, a speedometer and in a third aspect the present invention provides such a speedometer.

In one embodiment, the invention provides a plug coupling in which, on its side facing the outer polygonal portion (or shaft), the inner polygonal portion (or bore) has a widened portion in the shape of a trumpet, its edges extending from the corners of the inner polygonal portion to the end with the largest cross-section like the edges of a pyramid, with two respective transition areas being located between them to form a radially projecting saddle between the adjacent edges.

I Because of the special shape of its widened section, such a plug coupling causes the outer polygonal portion to rotate when it has reached its widened portion if its position does not correspond to the angular position of the inner polygonal portion. Misalignments in the flush arrangement are also compensated. Therefore, the invention permits automatic plug assembly of those parts of the plug coupling to be connected to one another.

Misalignments in angular and flush arrangement are particularly well compensated, if, according to an advantageous embodiment of the invention, the widened portion forms a circle on the side of its largest crosssection.

It is especially advantageous for use in the case of flexible shafts to be plugged into a speedometer socket, if, according to a further embodiment of the invention, the widened portion slopes down towards the inner polygonal portion as it approaches closer to the inner polygonal portion.

The invention permits various arrangements. For further explanation of its basic principle, one of these arrangements is shown, by way of example only, in the drawings and described below.

Figure 1 shows a perspective view of a socket according to the invention; and Figure 2 shows a top view onto the socket of Figure is Figure 1 shows a socket 1 (which may, for example, be part of a speedometer) with an inner polygonal portion 2 in the form of an inner polygon. This inner polygon portion 2 has a widened portion 3 (the first section of the bore) which, as shown in Figure 1, widens upwards in the shape of a trumpet, its shape being of importance to the embodiment of the invention. The second section of the bore is shown as the central square section in Figure 2, and is of substantially constant transverse crosssection.

Two side surfaces 4,5, each with an upper end edge 6, 7, may be seen of the inner polygonal portion 2. These end edges 6,7 merge into the widened portion 3. Edges 6 8,9 extend from their corners to the side of the largest cross-section of the widened portion 3 up to a circle 10 defining the widened portion 3 there. Between a pair of vertical internal edges 8, 9 two respective transition areas 11, 12 (both part of an alignment portion) are arranged, which abut one another with a raised region such as a ridge or saddle 13 projecting into the widened portion 3 between edges 8,9.

The free end of an outer polygonal portion 14 (which, f or example, may be the end of a speedometer drive), which is to be plugged into the inner polygonal portion 2, is shown above the widened portion 3. If its angular position differs in relation to the inner polygonal portion 2 and its corners strike the walls of the widened portion 3 to the right or left of the saddle 13, then the outer polygonal portion 14 is rotated by application of a low axial force until its side surfaces lie flush with those of the inner polygonal portion 2.

In addition, Figure 2 shows the structure of the plug coupling. It may be seen how the inner polygonal portion 2 gradually widens up to the circle 10. The saddle 13 between edges 8,9 may also be seen. The other corresponding saddles are given the reference numerals 13a, 13b and 13c in Figure 2.

The inner and outer polygonal portions may have any number of sides. In this embodimenz they have four, i.e.

the shaft 14 and socket aperture 2 are square.

7

Claims

CLAIMS:

1. A coupling, including: a shaft; and a socket having a bore for receipt of the shaft; 5 the bore having f irst and second sections, the first section tapering from a mouth of the bore to a mouth of the second section, and the second section being shaped to permit engagement of the shaft therein, the first section further being shaped so as to urge rotation of the shaft into alignment with the mout-h of the second section as the shaft is inserted into the bore, if it is not already aligned therewith.

2. A coupling according to claim 1, wherein the first section has a plurality of edges, each edge extending from the mouth of the bore to a respective corner of the mouth of the second section, each region between a pair of adjacent edges constituting an alignment portion of said first section, and wherein each alignment portion slopes from a raised region thereof to each of its two said edges.

3. A coupling according to claim 2, wherein the raised region of each alignment portion is located approximately midway between its two said edges.

8 4. A coupling according to cla.!,.m 2 or claim 3, wherein the raised regi. )n of each alignment portion is a ridge extending substantially from the mouth of the bore to the mouth of the second section of the bore.

5. A coupling according to any one of the above claims, wherein the mouth of the bore is substantially circular 6. A socket for a coupling according to any one of the above claims.

A speedometer including a socket according to claim 6.

8. A coupling substantially as herein described with reference to the accompanying drawings.