GB2091843A - Flexible shaft coupling - Google Patents

Abstract

A flexible shaft coupling comprises first and second rotary hubs (5, 5') securable by keys (8, 8') to ends of driving (9) and driven (9') shafts, respectively. Central circular portions of abutting pairs of flexible, dished metal foils are secured to the hubs (5, 5') by bolts (7, 7'). Cylindrical rims of the foils are secured to the opposite ends of a surrounding torque transmission sleeve (10) by further bolts (7, 7'). The foils of each pair are formed with obtuse scalene triangular slots (2, 2') which incline in opposite directions and are tangential to the central circular portion of that foil. The slots of the respective foils overlap one another. Drive can be transmitted when the axes of the shafts are parallel but spaced from one another, are relatively inclined and when they are axially relatively movable. The slotted formation of the foils allows high torque to be transmitted without significant torsional distortion thereof and the couplings will transmit drive without significant vibration and incorrect bearing loading. <IMAGE>

Description

SPECIFICATION Flexible shaft couplings This invention relates to flexible shaft couplings of the kind that are used for the interconnection of two rotary shafts which latter are not necessarily in axially aligned relationship.

Generally speaking, it is often difficult to maintain the longitudinal axes of two rotary shafts in exactly aligned relationship by the use of non-flexible shaft couplings. When two shafts are initially non-aligned, or become non-aligned during use, and are tightly interconnected by a non-flexible coupling, the bearings for at least one of those shafts in a supporting member or supporting machine portion are subjected to adverse loading conditions that tend to destroy the bearing much more rapidly than would occur with correct loading. Moreover, if the driving torque in one of the shafts is variable, the nonalignment of said two shafts can cause significant vibration of a least one of them.In addition to rapid bearing wear, such situations can cause breakages of the shafts themselves or of machine portions in which they are situated so that expensive repairs become necessary whilst the machine is out of commission for a considerable period of time. It would therefore be desirable to provide a flexible coupling which can connect two non-aligned driving and driven shafts without exerting potentially destructive forces upon the bearings of those shafts whilst nevertheless transmitting drive from one of the shafts to the other without significant vibration, knocking or the like.

Flexible shaft couplings are, of course, already known and are used directly to interconnect driving and driven shafts associated with pumps, generators, motors, fans and the like and are of several basic types. For example, the known flexible shaft couplings may be classified as being of the flange type, the gear type, the roller chain type, the flexible elastomer type, the spring type and soon. The flexible connecting element in each of these coupling types may be made wholly or principally from rubber, leather, synthetic plastics resin, roller chain, spring steel, toothed gears and so on and the object of the present invention is to provide a novel shaft coupling that has a simple structure, good flexibility and a long working life.

Accordng to the present invention, there is provided a flexible shaft coupling which comprises a first flexible metal foil formed by cutting an annular blank of said foil and expanding the same to produce a dished configuration having a central circular portion surrounded by a plurality of slots which extend substantially tangentially in one direction relative to said central circular portion, the coupling also comprising a second flexible metal foil which is formed similarly to the first foil except that its slots are tangential to its central circular portion in an opposite direction to said one direction, said first and second foils being disposed in abutting relationship with their respective slots overlapping and with their central circular portions secured to a first rotary hub and their substantially cylindrically dished rims secured to a surrounding torque tranmission mem ber, and the coupling comprising a second similarly constructed and symmetrically arranged pair of first and second metal foils which are secured to a second rotary hub and to said surrounding torque transmission member, said first and second hubs being constructed for connection to corresponding shafts in the use of the coupling.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figures 1 and 2 are front elevations illustrating the two metal foils of a pair of such foils that are employed in a shaft coupling in accordance with the invention, Figure 3 is a section taken on the line I-I in Figure 1, Figure 4 is a partly broken away view as seen axially towards the left-hand side of Figure 5, Figure 5 is a sectional view showing the whole of a shaft coupling in accordance with the invention in interconnecting relationship with two shafts, and Figures 6 and 7 are diagrammatic sketches, to a reduced scale, illustrating circumstances in which pairs of non-aligned shafts can advantageously be connected together by a coupling in accordance with the invention.

Referring to the accompanying drawings, a first flexible metal foil 1 (Figures 1 and 3) is formed by cutting an annular blank of said foil and expanding the same to produce the dished configuration that can be seen best in Figure 3 of the drawings by the use of a press and a punch, the metal of said foil having some degree of elasticity. The first foil 1 has a central circular portion whose inner diameter is the same as the external diameter of a shaft 9 which, in the use of the flexible coupling, the first foil 1 closely surrounds together with a first sleeve-like rotary hub 5.A plurality, such as eight, of triangular slots 2 are cut in the first foil 1 at regularly spaced apart intervals around its centre, said slots 2 preferably being of obtuse scalene configuration, as illustrated, in which case the slots 2 are disposed tangentially in one direction relative to the central circular portion of the metal foil 1. The slots 2 extend substantially tangentially relative to the central circular portion of the first metal foil 1 and a study of Figures 2 and 3 of the drawings will show that a second flexible metal foil 1' is provided that is of the same construction as the first flexible metal foil 1 except that slots 2' in the second foil extend substantially tangentially relative to the central circular portion of that foil in a direction which is opposite to said one direction that is mentioned above.The two foils 1 and 1' are placed in abutting relationship with one another as can be seen in Figures 4 and 5 of the drawings so that the respective slots 2 and 2' therein are in overlapping relationship at a number of points around the abutting annular formation and dished configuration foil 1 and 1'. Holes 4 and 4' forthe reception of fastening bolts 7 are formed at 900 intervals around the central circular portions of the two abutting foils 1 and 1' and similarly in the substantially cylindrically dished rims of those foils.Two sets of four bolts 7 clampingly secure the central circular portions to a radial face of the first rotary hub 5 and to one end of a surrounding torque transmission member in the form of a sleeve 10, annular and cylindrical collars 6 being arranged to co-operate with the fastening bolts 7 to ensure firm clamping of the foils to both the first rotary hub 5 and the sleeve 10. In Figure 5 of the drawings, the shaft 9 is a driving shaft carrying the first rotary hub 5 at its end by way of a co-operating key 8.A closely adjacent driven shaft 9' is connected by a key 8' to a second rotary hub 5' and it will be seen from Figure 5 that a pair of abutting metal foils, that is substantially symmetrically identical to the foils 1 and 1', couples the second rotary hub 5' to the opposite end of the transmission sleeve 10 by way of collars 6' and bolts 7' that are substantially symmetrically identical to the collars 6 and bolts 7.

Each metal foil has a portion 3 or 3', extending between the corresponding central circular portion and the substantially cylindrically dished rim of the same foil, which portion 3, 3' is peferably heat treated to enhance both its strength and flexibility.

Figure 6 of the drawings diagrammatically shows the use of the whole flexible shaft coupling of Figure 5 in transmitting drive between two shafts whose longitudinal axes are substantially parallel to one another whilst being spaced apart by a short distance t. Figure 7 shows a similar arrangement but, in this case, the longitudinal axes of the driving and driven shafts are inclined to one another at a small angle 0. In either case, the slots 2 and 2' in the overlapping metal foils are disposed substantially tangentially relative to the hubs 5 and 5', the overlapping arrangement of the slots 2 and 2' in the two foils 1 and 1' of each abutting pair being such that, with a substantially tangential disposition of said slots 2 and 2' relative to the corresponding hubs 5 and 5', there will be substantially no torsional distortion in either pair of metal foils as a result of simple tangential driving tension because the oppositely directed slots 2 and 2' in each pair of foils cause the forces which would tend to produce distortion of the remaining foil portions 3 and 3' substantially to cancel one another out. It will be realised that the same circumstances will apply whichever direction of rotation of the driving and driven shafts is involved. The metal foils can transmit driving torque up to substantially the maximum strength of those foils without causing any significant torsional distortion thereof.Since each of the four foils of the two pairs thereof that can be seen in Figure 5 of the drawings has substantially the shape that can be seen in either Figure 1 and Figure 3 or Figure 2 and Figure 3, the portions 3 and 3' of those foils which extend between the central circular portions and the substantially cylindrical rims thereof (said portions 3 and 3' being formed with the obtuse scalene triangular slots 2 and 2') are able to flex to a significant extent and easily accommodate the circumstances illustrated in Figures 6 and 7 of the drawings whilst transmitting drive from one shaft to the other without any significant vibration or "knock" thus protecting associated shaft bearings from any incorrect loading that would lead to premature failure of those bearings It is noted that the described and illustrated shape of the flexible metal foils 1 and 1' allows some relative axial movements of the driving and driven shafts to be accepted without difficulty either independently of the circumstances illustrated in Figures 6 and 7 of the drawings or in combination with such circumstances.

The relatively simple construction oftheflexible shaft coupling that has been described allows it to be manufactured both quickly and inexpensively and, should the replacement of any part thereof become necessary after an extended period of use, replacement of the worn or damaged part can usually be undertaken without delay merely be releasing some of the bolts 7 and/or 7'. Despite is small size in relation to the diameters of the driving and driven shafts 9 and 9' (Figure 5), the coupling can transmit a high torque for a long period of time without deterioration, the inertia which is attributable to the coupling being only relatively small.The same coupling can transmit drive between shafts whose axes are parallel, to, but spaced from, one another or shafts whose axes are inclined to one another by a small angle and/or shafts which are axially movable relative to one another to a small extent, the coupling acting in each case to damp any tendency to vibration so that its use promotes both smooth and silent machine operation.

Since a coupling in accordance with the invention relies upon the transmission of torque via tensile forces in metal foils of a simple shape, no frictional action is involved and there is no need to use any grease or other lubricant so that there is no tendency to collect dust, fluff and other dirt as can present a significant disadvantage to the use of many already known shaft couplings. Moreover, no frictional wear is involved and no non-metallic materials, such as rubber, are employed that tend to harden or otherwise age after extended use, particularly in an industrial environment. Thus, a shaft coupling in accordance with the invention can be relied upon, when correctly employed, to transmit drive from one shaft to another, even when those shafts are not in absolutely correct axial alignment and/or are axially movable relative to one another to some extent, for a very long period of time without deterioration.

Claims (11)

1. A flexible shaft coupling which comprises a first flexible metal foil formed by cutting an annular blank of said foil and expanding the same to produce a dished configuration having a central circular portion surrounded by a plurality of slots which extend substantially tangentially in one direction relative to said central circular portion, the coupling also comprising a second flexible metal foil which is formed similarly to the first foil except that its slots are tangential to its central circular portion in an opposite direction to said one direction, said first and second foils being disposed in abutting relationship with their respective slots overlapping and with their central circular portions secured to a first rotary hub and their substantially cylindrically dished rims secured to a surrounding torque transmission mem ber, and the coupling comprising a second similarly constructed and symmetrically arranged pair of first and second metal foils which are secured to a second rotary hub and to said surrounding torque transmission member, said first and second hubs being constructed for connection to corresponding shafts in the use of the coupling.

2. A coupling as claimed in claim 1, wherein each of said slots is of triangular configuration.

3. A coupling as claimed in claim 2, wherein each of said slots is of obtuse scalene triangular configuration.

4. A coupling as claimed in any preceding claim, wherein each flexible metal foil comprises eight of said slots arranged at equiangular intervals around the centre of that foil.

5. A coupling as claimed in any preceding claim, wherein the expansion of each annular foil blank to produce the required dished configuration thereof is effected by a press and a punch.

6. A coupling as claimed in any preceding claim, wherein said pairs of first and second metal foils are secured to the first and second rotary hubs and to the surrounding torque transmission member by corresponding sets of bolts.

7. A coupling as claimed in claim 6, wherein each set of bolts comprises four bolts spaced apart from one another at equiangular intervals around the centre of the respective pair of foils.

8. A coupling as claimed in claim 6 or 7, wherein said sets of bolts clamp the pairs of foils to the rotary hubs and to the surrounding torque transmission member with the aid of annular and cylindrical clamping collars, respectively.

9. A coupling as claimed in any preceding claim, wherein each of said rotary hubs is constructed and arranged for mounting at one end of a respective driving or driven shaft with the aid of a key.

10. A coupling as claimed in any preceding claim, wherein the surrounding torque transmission member is in the form of a surrounding sleeve.

11. A flexible shaft coupling substantially as herein before described with reference to the accompanying drawings.