Clutch

A clutch includes a driving member and a driven member. The driving member includes a rotatable shaft and four breaking blocks radially fixed to the rotatable shaft. Each breaking block includes a thermally deformable main body including an engaging surface, and a heating element and an engaging block formed on the engaging surface. The driven member includes a mounting surface and defines four engagement-receiving portions and a through hole in the mounting surface. The four engagement-receiving portions are positioned and shaped so as when the driving member is assembled to the driven member the four engaging blocks are correspondingly engaged with the four engagement-receiving portions. The rotatable shaft is rotatably inserted through the through hole. The heating element is configured for heating the breaking block to force it to bend the engaging blocks away from the engagement-receiving portions to disengage the clutch.

BACKGROUND

1. Technical Field

The disclosure relates to a clutch.

2. Description of Related Art

A clutch is a device for enabling two rotating bodies to be engaged or disengaged. Current clutches typically include a complicated gear arrangement to engage or disengage the rotating bodies and this increases the cost of the clutches and causes mechanical noise.

Therefore, it is desirable to provide a clutch which can overcome the above-mentioned problems.

DETAILED DESCRIPTION

Referring toFIG. 1, a clutch100, according to an exemplary embodiment, is disclosed. The clutch100includes a driving member101and a driven member102. The driving member101is configured for connecting to a driving device (not shown) such as a motor shaft. The driven member102is configured for connecting to a driven device (not shown) such as a drill chuck.

Also referring toFIG. 2, the driving member101includes a rotatable shaft10, four breaking blocks20, and a holding member30such as a locking pin. The four breaking blocks20are fixed to the rotatable shaft10. The holding member30is longer than the diameter of the rotatable shaft10.

The rotatable shaft10includes a first end11and a second end12. In addition, the rotatable shaft10defines a first through hole13and four block-receiving portions14(seeFIG. 3). The first through hole13extends substantially along a diameter of the rotatable shaft10, adjacent to the second end12. The diameter of the first through hole13is a little larger than the diameter of the holding member30. The four block-receiving portions14are defined in the cylindrical surface of the rotatable shaft10adjacent to the first end11. Each two adjacent block-receiving portions14are about 90 degrees from each other. In this embodiment, each block-receiving portion14is constituted by two first slots, each extending parallely along the circumference of the rotatable shaft10.

Each breaking block20includes a main body21, a heating element22, and an engaging block23. The main body21includes an engaging surface202and an inserting end204, and defines a second slot24. The second slot24extends along a plane substantially parallel to the engaging surface202, and forms a Y-branch at an end opposite to the inserting end204, thereby, forming a deformable portion25. Alternative, in other embodiments, a second slot24′ of a main body20′ can extend without the deformable portion25to facilitate manufacture of the main body20′ (seeFIG. 5). The inserting end204is tightly inserted into a corresponding block-receiving portion14so that the engaging surface202faces the second end12. The main body21is made from thermoplastic material, and can expand when is heated and contract when is cooled down. The thermoplastic material can be doped with heat-conductive particles to increase thermal deformation coefficient of the main body21. In detail, the main body21can be made from general purpose polystyrene (GPPS), polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinylchloride (PVC), or polybutylece terephthalate (PBT). In this embodiment, the main body21is made from PC. The heating element22is formed on the engaging surface202adjacent to the inserting end204. The engaging block23is formed on the engaging surface202distal from the inserting end204.

The driven member102is disc-shaped. The thickness of the driven member102is equal to the distance between the first through hole13and the block-receiving portions14of the rotatable shaft10. The driven member102includes a mounting surface102s, and defines a second through hole102aand four engagement-receiving portions102bin the mounting surface102s. The second through hole102ais in the center of the mounting surface102s. The engagement-receiving portions102bare of equal distance from the center and at 90 degrees from each other on the mounting surface102s. The distance, of the engagement-receiving portions102b, from the center of the mounting surface102sis equal to the distance between the breaking block20and the center of the rotatable shaft10. The four engagement-receiving portions102bare shaped to receive the corresponding engaging blocks23.

Referring toFIG. 3, in assembly, the rotatable shaft10is inserted through the second through hole102ausing the second end12. The holding member30is inserted through the first through hole13so that the four engaging blocks23are correspondingly engaged with the four engagement-receiving portions102band the four breaking blocks20are in contact with the mounting surface102s. The driving member101is engaged with the driven member102and can transmit rotational energy from the driving device to the driven device.

Also referring toFIG. 4, if the driving member101needs to disengage from the driven member to stop the driving device from being driven. Electrical power is applied to the heating element22. The main bodies21are heated and bend upwards to disengage the four engaging blocks23from the engagement-receiving portions102b. As a result, the driving member101becomes disengaged with the driven member102.

It should be understood the second slots24/24′ are for increasing thermal deformation effect of the main body21/20′. In other embodiments, they can be omitted if the thermal deformation coefficient of the main body21/20′ is large and quick enough to enable the clutch100to realize a desired disengagement.

It should be noted that driving member101and the driven member102can be assembled using other techniques, and therefore should not be limited to using the locking pin and the first through hole13. For example, in an alternative embodiment, the rotatable shaft10can defines an annular groove (not shown), and the driving member101is assembled to the driven member102using a retaining ring (not shown). Even using the first through hole13and the locking pin, the positions and structures of the first through hole13and the locking pin are not limited to this embodiment, but can vary within the scope of the disclosure.

It should be mentioned that the four breaking blocks20are not limited to being fixed to the rotatable shaft10using the block-receiving portions14and the inserting end204. Other alternative techniques can be used too. For example, in another exemplary embodiment, the breaking blocks20are integrally formed with the rotatable shaft10.

It is to be understood that the number of the breaking blocks20and the engagement-receiving portions102bis not limited to this embodiment, but can be set depending on design requirements. For example, in an alternative embodiment, only one breaking block is employed. Also, the positions of the breaking blocks20and the engagement-receiving portions102bare not limited to this embodiment. For example, the four breaking blocks20and the four engagement-receiving portions102bare not necessary to be equal-distantly distributed.

It is to be understood that elements from the three embodiments, to the degree practical, could potentially be combined and/or interchanged. Further, where a mating and/or fitting match between parts is prescribed, it is to be understood that such a fit should permit sliding therebetween to allow reasonably easy assembly/disassembly yet should be tight enough to otherwise minimize any potential lateral movement/vibration therebetween.