GB2109485A - Rotational coupling device - Google Patents

Abstract

A rotational coupling device controls the rotation of a driven member by a drive member 10 which has an annular portion 17 defining an inner cylindrical surface 18. A driven member is coaxial with the drive member and carries a locking member 20 which is pivotable about a pin 22 having an axis parallel to and spaced from the axis of the drive member. A portion 24 of the locking member is engageable with the inner cylindrical surface so that on pivoting of the locking member about its axis it can engage and disengage the surface 18 whereby the driven member is driven or not driven by the drive member. The distance from the portion 24 to the axis of the pin 22 about which it pivots is greater than the radius of the surface 18. Portion 24 is biased into engagement with surface 18 by a spring 31 and is disengaged by a mechanism comprising a solenoid or air cylinder 32 actuating a plunger 33 to contact an arm 34 pivoted at 35 and having an end 36 engageable with a pin 29 fixed to the locking member 20. <IMAGE>

Description

SPECIFICATION Rotational control device This invention relates to a rotational control device whereby the rotation of a driven member by a drive member may be controlled.

Many forms of rotational control device have been proposed whereby the rotation of a driven member may be seiected by effecting driving engagement of the driven member by a drive member but such devices suffer from various disadvantages. In some cases the devices utilise wedging elements such as rollers, balls or sprags but these elements cause wear problems due to the repeated wedging action resulting in indentations in the operative surfaces of the member. Other devices use wrapped springs but these limit the size of the device and are also subject to wear due to frictional forces being involved.

An object of the invention is to provide a rotational control device of simple construction which obviates the above disadvantages.

According to the invention a rotational control device includes a drive member having a circular surface directed towards the axis of rotation of the member, a driven member coaxial with the drive member, and a locking member selectively lockable to the drive member and connected to the driven member for rotation therewith, the locking member being pivotable about an axis parallel to and displaced from the axis of rotation of the drive member and arranged such that a portion of the locking member is engageable with said circular surface and is movable, on pivoting of the locking member, about an axis of greater radius than the radius of said circular surface so as to move from a first position in which said portion of the locking member is out of contact with said circular surface and the driven member is not driven by the drive member, to a second position in which said portion is pivoted about its axis and engages said circular surface to lock the driven member to the drive member for rotation therewith.

Further features of the invention appear from the following description of an embodiment of the invention given by way of example only and with reference to the drawings, in which: Fig. 1 is a side elevation of a rotational control device, and Fig. 2 is an end view of the device of Fig. 1 in direction of arrow A.

Referring to the drawings a rotational control device is shown which is hereinafter termed a clutch. The clutch includes a rotational input member 10 which is generally a constantly rotating drive member.

The member 10 is rotatably carried about a shaft 11 on a bush 12 and is secured axially of the shaft 11 by a circlip 13. The member 10 has a cylindrical portion 14 and an integral cup-shaped portion 1 5 coaxial with the portion 14. The cupshaped portion 15 defines an annular rim 17 forming a cylindrical surface 1 8 directed towards the axis of rotation of the member 10. The member 10 is rotatable independently of the shaft 11 in the inoperative condition of the clutch.

A locking member 20 is located within the annular rim 17 and is of generally diamond shape externally. The member 20 has a central circular opening 21 through which the shaft 11 extends, the diameter of the opening 21 being larger than the external diameter of the shaft 11 to allow play between the member 20 and the shaft. The widest external dimension of the locking member 20 is slightly less than the internal diameter of the rim 1 7 so that in a central position of the locking member 20 the input member can rotate freely about the locking member 20.

The locking member 20 is carried on a pivot 22 having an axis 23 parallel to the axis of rotation of the input member 10 and adjacent one end of the diamond. The pivot axis 23 is spaced from the axis of the member 10 a distance which is selected according to the radius of the cylindrical surface 18 so as to give a ratio in the range of between 1.5:1 and 1.75:1 in the radius of the end 24 of the locking member remote from the pivot 22 to the radius of the surface 18, depending on the overall dimensions of the clutch.

The end 24 of the locking member is arranged to engage the surface 18 upon the locking member 20 being pivoted about the pivot 22 to thereby lock the members 10 and 20 together for rotation.

The locking member 20 is mounted on an output or driven member 25 coaxial with and fixed to the shaft 11, the pivot 22 being carried on the driven member 25. The member 25 has a discshaped portion 26 integral with a cylindrical portion 27. Opposite to the pivot 22 the portion 26 is formed with a radial slot 28 in which is located a pin 29 fixed to the locking member 20, the pin 29 acting as a stop pin to cause the locking member to disengage from a locking conditipn with the input member 1 0. The locking member 20 is biased towards a locked condition with the member 10 by a compression spring 31 which acts between the driven member 25 and the locking member and, when free to move towards said locking condition, the interference between the arcs of the surface 1 8 and the portion 26 is such that a high locking action occurs between the input member 10 and the locking member 20.

To counteract the action of the spring 31 and release the locking member from a locking condition a latch mechanism is provided. This is actuated by a solenoid or air cylinder 32 having a plunger 33 which, when extended, engages a latching arm 34. The arm 34 is pivoted at 35 and the free end 36 of the arm 35 is arranged to coact with the pin 29 against the action of the spring 31 to move the locking member 20 about the pivot 22 and disengage the end portion 24 from said surface 1 8. Thus whenever the clutch is to be operated to disconnect drive between the input member 10 and driven member 25 the latch mechanism is actuated.

The solenoid or air cylinder 32 is carried on a plate 37 mounted on the portion 27 of the member 25 via a bush 38 and is fixed against rotation with the output member by a fixed support (not shown).

The clutch can be arranged to provide a single turn or a half turn of the driven member or infinitely variable clutch operation can be provided. The device can also be used as a free wheel or a back stop device.

The device is suitable as an in-line clutch coupling or in a cantilevered or sandwiched situation. The external periphery of the output member may be used to mount a control ring which is connected to the locking member instead of using the latch, as described. The ring may have two stops one being on the periphery and which disengages the locking member when impacting against the solenoid or air cylinder operated latch.

The second stop may limit disengagement movement.

Alternatively the control ring may include a band brake around its circumference to give the facility of an infinitely variable operation.

A relatively small solenoid or air cylinder can be used to engage or disengage high torque drives with great accuracy.

The clutch may be produced in any size and in various materials to suit the purpose of the clutch.

For example the clutch may be of plastics for use in wet environments such as food processing. For machine tool use the material may be hardened steel.

Claims (7)

1. A rotational control device comprising a drive member having a circular surface directed towards the axis of rotation of the member, a driven member coaxial with the drive member, and a locking member selectively lockable to the drive member and connected to the driven member for rotation therewith, the locking member being pivotable about an axis parallel to and displaced from the axis of rotation of the drive member and arranged such that a portion of the locking member is engageable with said circular surface and is movable, on pivoting of the locking member, about an axis of greater radius than the radius of said circular surface so as to move from a first position in which said portion of the locking member is out of contact with said circular surface and the driven member is not driven by the drive member, to a second position in which said portion is pivoted about its axis and engages said circular surace to lock the driven member to the drive member for rotation therewith.

2. A rotational control device according to claim 1 wherein the locking member is biased towards said second position.

3. A rotational control device according to claim 2 wherein the locking member is movable towards said first position against said bias by latching means to disengage drive between the drive member and driven member.

4. A rotational control device according to claim 3 wherein the latching means includes a plunger acting on an arm to move the locking member towards said first position.

5. A rotational control device according to any one of the preceding claims comprising a rotatable shaft, the driven member being coaxial and fixed for rotation with the shaft, and the drive member being coaxial with the shaft and rotatable relative to the shaft except when the locking member is in said second position.

6. A rotational control device according to any one of the preceding claims wherein the axis of the locking member is disposed at one side of the axis of the driven member, the portion of the locking member which engages said circular surface is at the opposite side of the axis of the driven member, and adjacent said locking member portion is a stop pin engageable to move the locking member towards said second position.

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7. A rotational control device substantially as described with reference to the drawings.