GB2034003A

GB2034003A - Shaft Coupling Assemblies

Info

Publication number: GB2034003A
Application number: GB7937425A
Authority: GB
Original assignee: Danfoss AS
Current assignee: Danfoss AS
Priority date: 1978-10-30
Filing date: 1979-10-29
Publication date: 1980-05-29
Also published as: JPS5560723A; GB2034003B; DK449479A; FR2440488A1; SE7908664L; DE2847190C2; DE2847190A1

Abstract

An end portion 6 of a first shaft 2 is provided with a flat 10 parallel to its axis and an end portion 12 of a second shaft 4 has an axial cylindrical bore 16 for receiving the end portion of the first shaft. A spring 24 is held in transverse recesses 20, 22 in the second shaft, and has a curved portion 30 which is engageable with the flat 10 to prevent relative rotation between the shafts. The spring may however serve to absorb torsional shock loads. This construction renders unnecessary the provision of a bore of D-shaped cross-section, or of a transverse clamp screw, as in some prior assemblies. <IMAGE>

Description

SPECIFICATION Improvements in and Relating to Shaft Assemblies This invention relates to a shaft assembly comprising two shafts, wherein the end of the first shaft is provided with a flat on the periphery parallel to its axis and the end face of the second shaft has an axial recess for receiving the one shaft end and a counterabutment in the recess supported against the flat for preventing rotation of the one shaft relatively to the other.

In a known assembly of this kind, the crosssectional shape of the recess in the end face of the second shaft is adapted to the cross sectional shape of the end of the first shaft that is to be inserted in this recess. Further, a clamping screw is passed through the wall of the recess in the second shaft, this screw pressing against the flat of the end of the second shaft inserted in the recess. This assembly is difficult to make the actuate in so far that the formation of a flattened recess calls for an expensive shaping process such as casting, and the production and manipulation of the clamping screw as well as the construction of a tapped hole for receiving the clamping screw are comparatively expensive operations.

The invention is based on the problem of providing a shaft assembly that is easier to produce and operate.

According to the invention, this problem is solved in that the counterabutment is a spring which is stressed when bent and is inserted in recesses of the second shaft that are transverse to the rotary axis of the shaft, and the recess is a coaxial bore.

The recesses are easier to produce than a tapped hole because they do not have a screwthread. The coaxial bore is likewise easy to produce. It need not be made by casting.

Similarly, a spring which is only stressed when bent is easy to make. Insertion of the spring in the recesses is likewise simple. To couple the ends of the shafts, they need only be inserted in one another. A clamping screw and its operation are dispensed with. At the same time, the spring absorbs torsional shock loads.

Preferably, the spring is a leaf spring. A leaf spring is simple to make and presents a comparatively large counterabutment face for the flat which comes to lie thereagainst and thus offers a high resistance to relative rotation.

The spring may be curved in its central region with the convex side of the curve facing the flat in the coupled condition. The curve provides a high spring stiffness and on the other hand prevents lateral displacement of the spring transversely to the rotary axis of the shaft.

The recesses and the sections of the spring received by them can be rectilinear. This simplifies production of the recesses and a proper fit of the spring in the recesses.

It is favourable if the recesses are disposed in a plane parallel to the rotary axis of the shaft and preferably remote therefrom. This enables both recesses to be made in one operation. A spacing between the plane and the rotary axis of the shaft prevents undue weakening of the first shaft by the flat and permits the use of a comparatively short and thus stiff spring.

If the recesses are formed from the end face of the second shaft, the spring can be easily inserted in the recesses from the side of the end face.

If the recesses are parallel to the axis and straight and pass through the wall of the shaft, they can be simply cut in one operation from the end face.

Further, the ends of the spring may project beyond the outside of the second shaft and be flanged. The flanged spring ends provide additional lateral anchoring of the spring.

Further, the end of the second shaft having the recesses may have a larger external diameter than the remaining part of the second shaft. In this way, the coupling end of the second shaft has the stiffness required to transmit the desired torque without the need for making the rest of the second shaft excessively large.

The other end of the second shaft may likewise have a flat. The second shaft will then function as an extension of the first shaft to which a third shaft with an appropriately shaped coupling end may be joined.

Next, the end face of the shaft end to be inserted in the bore may have a chamfer at least at the edge of the flat. This chamfer serves as a ramp for the spring and therefore facilitates introduction of the end of the first shaft in the hole against the spring force.

The present invention also provides a shaft assembly comprising two shafts, wherein an end portion of one shaft is provided with a flat parallel to its axis and an end portion of the other shaft has an axial bore for receiving the end portion of the said one shaft, wherein a spring is held in recesses of the said other shaft that are transverse to the axis of the shaft, the spring being engageable with the flat to prevent relative rotation between the shafts.

A shaft assembly constructed in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawing, wherein: Fig. 1 is an exploded side elevation of the shaft coupling without the spring and shown partly as a longitudinal section; Fig. 2 shows the right-hand shaft of Fig. 1 as viewed from the right-hand end; Fig. 3 shows the right-hand shaft of Fig. 1 as viewed from the left-hand end and with the spring inserted; Fig. 4 is a plan view of the spring when unstressed, and Fig. 5 is a side elevation of the spring when unstressed.

Referring to the accompanying drawing, the end portions of two shafts 2 and 4 are connectible to form a coupling for the two shafts.

The end portion 6 of the shaft 2, which can be the driving shaft of, say, an oil pump 8 (which is only shown in outline) has a flat 1 0. A bore 1 6 coaxial with the axis of rotation 14 of the shaft 4 is provided in the end portion 12 of that shaft. The end portion 1 2 has a larger external diameter than the remainining part of the shaft 4 and than the shaft 2. An annular wall 18 of the end portion 12 is provided with two similar slot-shaped recesses 20, 22 which lie in a plane parallel to the rotary axis 14 of the shaft which extend transversely from the inside of the bore 1 6 to the outside of the wall 1 8 and which extend axially into the end portion 12 from the end face of that portion to a predetermined depth less than the axial length of the end portion 12.The spacing of the recesses 20, 22 from the rotary axis 14 of the shaft 4 is somewhat larger than the spacing between the flat 10 and the rotary axis 14 of the shaft 2.

As shown in Fig. 3, a spring 24 is inserted in the recesses 20, 22. The spring is a leaf spring with planar sections 26, 28 which fit in the recesses 20, 22, and with a curved section 30 at the centre. The ends 32, 34 of the spring 24 project beyond the outer transverse ends of the recesses 20, 22 and are flanged to lie along the outer periphery of the end portion 12.

After the spring 24 has been inserted in the recesses 20, 22 the bore 1 6 of the shaft 4 is pushed from the Fig. 1 position over the end portion 6 of the shaft 2 the bore 16 having a diameter which may be substantially equal to that of the shaft 2, thereby coupling the two shafts.

The convex surface of the curved section 30 engages against the flat 10 and stresses the spring 24. The radius of curvature of the curved section 30 is chosen so that when the spring 24 is in place the minimum spacing of it from the axis of the shaft 4 is somewhat less than the spacing of the flat 10 from the rotary axis 14 of the shaft 2. Stressing of the spring 24 provides axial anchoring not only of the spring 24 itself-if it is not a push fit in the recesses 20, 22-but also of the end portion 6 in the bore 1 6 of the shaft 4. In addition, the spring 24 serves as a counterabutment for the flat 10 and thus for securing the shaft 2 and 4 against relative rotation so that the latter are coupled to turn together while being substantially secured against relative axial movement.

A chamfer 36 at the end face of the end portion 6 serves as a ram for the spring 24.

The second shaft 4 is likewise provided with a flat 40 and a chamfer 42 at its other end portion 38. It can therefore likewise be coupled to a shaft having one end shaped in the same way as the end portion 12. In this way, the shaft 4 serves as an extension of, or a coupling adaptor for the shaft 2. By using shafts 4 having end portions 38 of varying the effective diameter of the oil pump shaft 2 can be increased or decreased as required.

The end portion 38 of the second shaft 4 can, however, also be cylindrical and directly form the drive shaft (which can have a diameter larger-as shown-or smaller than the diameter of shaft 2 of a motor.

On the other hand, the shaft 2 may be a drive, rather than a driven shaft, and may, for example, be part of a motor rather than a pump as described above.

Claims

1. A shaft assembly comprising two shafts, wherein an end portion of one shaft is provided with a flat parallel to its axis and an end portion of the other shaft has an axial bore for receiving the end portion of the said one shaft, wherein a spring is held in recesses of the said other shaft that are transverse to the axis of that shaft, the spring being engageable with the flat to prevent relative rotation between the shafts.

2. A shaft assembly as claimed in claim 1, in which the spring is a leaf spring.

3. A shaft assembly as claimed in claim 1 or claim 2, in which the spring is curved in its central region, the convex surface of that region being engageable with the flat.

4. A shaft assembly as claimed in any one of claim 1 to 3, in which the recesses and the sections of the spring received by them are rectilinear.

5. A shaft assembly as claimed in any one of claims 1 to 4, in which the recesses are disposed in a plane parallel to the axis of the shaft.

6. A shaft assembly as claimed in any one of claims 1 to 5, in which the recesses extend axially from the end face of the said other shaft.

7. A shaft assembly as claimed in any one of claim 4 to 6, in which each or the recesses pass through the wall of the said other shaft.

8. A shaft assembly as claimed in claim 7, in which the end of the spring project beyond the outer periphery of the said other shaft and are flanged.

9. A shaft assembly as claimed in any one of claims 1 to 8, in which the end of the said other shaft having the recesses has a larger external diameter than the remaining part of that shaft.

10. A shaft assembly as claimed in any one of claims 1 to 9, in that the other end of the said other shaft also has a flat.

11. A shaft assembly as claimed in any one of claims 1 to 10, in which the end face of the end of the said one shaft has a chamfer at least at the edge of the flat.

12. A shaft assembly substantially as hereinbefore described with reference to, and as illustrated by the accompanying drawing.