GB2126690A

GB2126690A - Flexible coupling

Info

Publication number: GB2126690A
Application number: GB08322381A
Authority: GB
Inventors: John Wright
Original assignee: Koppers Co Inc
Current assignee: Beazer East Inc
Priority date: 1982-09-07
Filing date: 1983-08-19
Publication date: 1984-03-28
Also published as: CA1216161A; GB8322381D0; GB2126690B

Abstract

A flexible coupling 10, which is characterised by low torsional stiffness when a relatively low torque load is supplied to shafts coupled thereby, includes a plurality of variable stiffness torque transmitting elements 26, 28 which permit low torsional stiffness at low torque but also permit the coupling to operate at a relatively higher torque load. <IMAGE>

Description

SPECIFICATION A flexible coupling This invention relates to flexible couplings.

Flexible couplings for transmitting torque between misaligned driving and driven shafts by means of elastomeric elements in compression are well known in the art, see U.S. Patent Specifications Nos. 2,764,003 and 2,873,590.

Such couplings have not only demonstrated the ability to compensate for misalignment between a driving member and a driven member, but also the ability to protect the driving and driven members from torsional shock loading and torsional vibration in most applications. Use of such couplings in diesel marine drive systems has presented a unique set of problems because the coupling must be designed to act over a wide range of speeds and therefore over a wide range of torque since in marine propellors the torque is proportional to the square of the speed. It is desirable to provide a torsional stiffness low enough to place the resonances or critical speeds for a particular mode of torsional vibrations below minimum operating speed.When the coupling used is designed to handle the highest torque loadings at full speed, it is sometimes too stiff under low speed, low torque conditions, and torsional resonance may occur at the lower operating speeds. This vibration can damage the propulsion system. However, if the coupling used has a suitably low torsional stiffness, it often cannot handle the high torque developed at higher speeds. This has led to numerous cases of couplings and other drive component failure. Both vibration damage and coupling failure are expensive in terms of repair parts and downtime.

According to the present invention there is provided a flexible coupling, for transmitting torque between driving and driven members, comprising hub means having outwardly extending blade member for mounting on one of said driving and driven members, and sleeve means having inwardly extending blade members for mounting on the other of said driving and driven members, wherein said blade members define at least in part cavities which contain elastomeric elements in compression for transmitting torque between said driving and driven members and wherein the elastomeric elements in compression in each of said cavities include at least two elements having significantly different hardness properties.

The flexible couplings of the present invention overcome the foregoing problems of the prior art by providing a coupling which has low torsional stiffness at low torque loads but which also has sufficient stiffness to handle high torque loads.

Each cavity, formed in part by the blades of the hub means and sleeve means of the coupling, contains a plurality of elastomeric elements of different hardnesses. Under low torque only the lower hardness elements are compressed resulting in a low torsional stiffness. However, at high torque loadings the higher hardness elements also become compressed and limit the torsional windup of the coupling so that the lower hardness elements will not become overstrained.

For a better understanding of the invention, and to show more clearly how the same may be carried into effect, reference will now be made by way of example to the accompanying drawing in which: Figure 1 is a side view, partially in section, of a flexible coupling of the present invention; Figure 2 is a fragmentary end view of the coupling of Figure 1; and Figure 3 is an enlarged sectional view of a portion of Figure 1.

Flexible couplings, by which torque can be transmitted between two shafts by means of elastomeric elements in compression, are fully described in U.S. Patent Specifications Nos.

2,764,003 and 2,873,590. This description is incorporated herein by reference and will only be repeated as necessary for a full understanding of the present invention.

Referring to Figures 1,2 and 3, the flexible coupling of the present invention, generally designated 10, comprises a hub 12 which has blades 14 and is mounted on one of the pair of shafts to be rotated. Preferably, the hub 1 2 is made of cast ductile iron or cast steel. The flexible coupling also comprises a sleeve 1 6 which is mounted on the other shaft and has blades 1 8.

The blades 1 8 in combination with blades 14, a plate 20 and an end plate 22 form cavities 24 in which are contained elastomeric elements 26 and 28. The size of blades 14 and 1 8 and the corresponding size of cavities 24 are design considerations based on the use the coupling is to undergo. These design considerations are well known and understood in the art and will not be repeated here as they form no part of the present invention.

The elastomeric elements 26 are made of a relatively hard, approximately 75 durometer, rubber and are placed on each side of an element 28 in each cavity 24. Elastomeric element 28 is made of a softer rubber, approximately 45 durometer. Eiements 26 which are circular in cross-section have a smaller diameter than the diameter of element 28, and a pin 30 passes through elements 26 and 28 and maintains their concentricity. Pin 30 may be made of metal or plastic or some other suitable material. Under a low torque load only elements 28 are compressed and the coupling has a low torsional stiffness; but as torque increases elements 26 become comrpessed preventing overstraining of elements 28.

Claims

1. A flexible coupling, for transmitting torque between driving and driven members, comprising hub means having outwardly extending blade members for mounting on one of said driving and driven members, and sleeve means having inwardly extending blade members for mounting on the other of said driving and driven members,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A flexible coupling This invention relates to flexible couplings. Flexible couplings for transmitting torque between misaligned driving and driven shafts by means of elastomeric elements in compression are well known in the art, see U.S. Patent Specifications Nos. 2,764,003 and 2,873,590. Such couplings have not only demonstrated the ability to compensate for misalignment between a driving member and a driven member, but also the ability to protect the driving and driven members from torsional shock loading and torsional vibration in most applications. Use of such couplings in diesel marine drive systems has presented a unique set of problems because the coupling must be designed to act over a wide range of speeds and therefore over a wide range of torque since in marine propellors the torque is proportional to the square of the speed. It is desirable to provide a torsional stiffness low enough to place the resonances or critical speeds for a particular mode of torsional vibrations below minimum operating speed.When the coupling used is designed to handle the highest torque loadings at full speed, it is sometimes too stiff under low speed, low torque conditions, and torsional resonance may occur at the lower operating speeds. This vibration can damage the propulsion system. However, if the coupling used has a suitably low torsional stiffness, it often cannot handle the high torque developed at higher speeds. This has led to numerous cases of couplings and other drive component failure. Both vibration damage and coupling failure are expensive in terms of repair parts and downtime. According to the present invention there is provided a flexible coupling, for transmitting torque between driving and driven members, comprising hub means having outwardly extending blade member for mounting on one of said driving and driven members, and sleeve means having inwardly extending blade members for mounting on the other of said driving and driven members, wherein said blade members define at least in part cavities which contain elastomeric elements in compression for transmitting torque between said driving and driven members and wherein the elastomeric elements in compression in each of said cavities include at least two elements having significantly different hardness properties. The flexible couplings of the present invention overcome the foregoing problems of the prior art by providing a coupling which has low torsional stiffness at low torque loads but which also has sufficient stiffness to handle high torque loads. Each cavity, formed in part by the blades of the hub means and sleeve means of the coupling, contains a plurality of elastomeric elements of different hardnesses. Under low torque only the lower hardness elements are compressed resulting in a low torsional stiffness. However, at high torque loadings the higher hardness elements also become compressed and limit the torsional windup of the coupling so that the lower hardness elements will not become overstrained. For a better understanding of the invention, and to show more clearly how the same may be carried into effect, reference will now be made by way of example to the accompanying drawing in which: Figure 1 is a side view, partially in section, of a flexible coupling of the present invention; Figure 2 is a fragmentary end view of the coupling of Figure 1; and Figure 3 is an enlarged sectional view of a portion of Figure 1. Flexible couplings, by which torque can be transmitted between two shafts by means of elastomeric elements in compression, are fully described in U.S. Patent Specifications Nos. 2,764,003 and 2,873,590. This description is incorporated herein by reference and will only be repeated as necessary for a full understanding of the present invention. Referring to Figures 1,2 and 3, the flexible coupling of the present invention, generally designated 10, comprises a hub 12 which has blades 14 and is mounted on one of the pair of shafts to be rotated. Preferably, the hub 1 2 is made of cast ductile iron or cast steel. The flexible coupling also comprises a sleeve 1 6 which is mounted on the other shaft and has blades 1 8. The blades 1 8 in combination with blades 14, a plate 20 and an end plate 22 form cavities 24 in which are contained elastomeric elements 26 and 28. The size of blades 14 and 1 8 and the corresponding size of cavities 24 are design considerations based on the use the coupling is to undergo. These design considerations are well known and understood in the art and will not be repeated here as they form no part of the present invention. The elastomeric elements 26 are made of a relatively hard, approximately 75 durometer, rubber and are placed on each side of an element 28 in each cavity 24. Elastomeric element 28 is made of a softer rubber, approximately 45 durometer. Eiements 26 which are circular in cross-section have a smaller diameter than the diameter of element 28, and a pin 30 passes through elements 26 and 28 and maintains their concentricity. Pin 30 may be made of metal or plastic or some other suitable material. Under a low torque load only elements 28 are compressed and the coupling has a low torsional stiffness; but as torque increases elements 26 become comrpessed preventing overstraining of elements 28. Claims

1. A flexible coupling, for transmitting torque between driving and driven members, comprising hub means having outwardly extending blade members for mounting on one of said driving and driven members, and sleeve means having inwardly extending blade members for mounting on the other of said driving and driven members, wherein said blade members define at least in part cavities which contain elastomeric elements in compression for transmitting torque between said driving and driven members and wherein the elastomeric elements in compression in each of said cavities include at ieast two elements having significantly different hardness properties.

2. A flexible coupling as claimed in Claim 1, wherein each of said driving and driven members is a shaft and wherein each of said cavities contains at least one elastomeric element having a relatively low hardness and at least one elastomeric element having a relatively high hardness.

3. A flexible coupling as claimed in Claim 2, wherein said elastomeric elements in compression in each cavity include one element of relatively low hardness located between two elements of relatively high hardness.

4. A flexible coupling as claimed in Claim 3, wherein the elements having a relatively high hardness have a smaller diameter than the element having a relatively low hardness.

5. A flexible coupling as claimed in Claim 3 or 4, wherein a pin member maintains the concentricity of the elastomeric elements.

6. A flexible coupling as hereinbefore described with reference to, and as shown in, the accompanying drawing.