Patent GB-614928-A (GB)
Title: Improvements in or relating to clutches for conveying rotary motion
IPC: F16D27/00
Filed: 1946-02-11
Abstract: 614,928. Clutches. BROCKHOUSE ENGINEERING (SOUTHPORT), Ltd., and GATISS, A. L. Feb. 11, 1946, No. 4191. [Class 80 (ii)] A clutch, especially for use between a fluid transmission and a variable speed gear, is capable of transmitting torque up to a predetermined value before there is relative rotation of the driving and driven members, such rotation synchronizing a positive clutch which is automatically engaged after the predetermined torque has been reached, the positive clutch being automatically disengaged on release of the non-positive clutch. A dog element C is slidably mounted on splines on the driving member A and has dog teeth C<1> engageable with corresponding dog teeth B on a ring B<2> rigid with the driven member B. The element C also has teeth C<2> engageable with teeth D<1> on a shifter D axially and rotatably movable on the driving member A. The element C is normally urged away from the driven member B by the springs C<6> abutting an electromagnetic clutch member F rigid with the driven member. Coacting with the clutch member F is an armature E arranged for limited axial movement on the driving member A, and driven therefrom through springs H abutting at one end against the lugs A<1>, rigid with the member A, and at their other ends against a lug D<3> rigid with the shifter D, and through springs G abutting the lugs D<3> and lugs E<4> rigid with the armature E. The springs H and G are pre-stressed so that the initial stress of G is greater than that of H, and these springs are housed in concentric compartments partially in the armature E and partially in a closure ring J<1>. The lugs D<3> extend through slots E<1> in the armature E so that the shifter D has limited rotational movement with respect to the armature E. In operation, when the electromagnet is energized with the shaft A rotating in a clockwise direction, the armature E suffers a retarding torque relative to the shifter D, thus compressing the springs G and bringing the lugs E<3>, which are rigid with the armature E, out of contact with the spring; this rotation is limited by the side faces E<2> of the slots El contacting the shifter lugs D3. Thus, the drive passes from the shaft A through the lugs A<1>, springs H, lugs D3, springs G and lugs E<4>; and also through member C to shifter D, through the inclined side faces C<3>, D<2> and thence through lug D<3> to armature E and clutch member F. An increased retarding torque on driven member B will result in the inclined faces C<3>, D<2> causing member C to move axially towards driven member B and thus allow shifter D to rotate anticlockwise relative to element C, while the torque transmitted through the springs H on to the shifter D overcomes the initial stress in these springs with the result that member A rotates clockwise relative to the shifter D and so further slides the element C towards the member B. If the dog teeth C<1>, B are not in register, the drive will continue until relative rotation occurs between members E and F due to excess torque, when the teeth will engage and shifter D will rotate anti-clockwise relative to the armature E under the action of the stronger springs G until the spring ends contact the lugs E<3>. In this position, the shifter teeth D<1> are out of register with the teeth C<2> so that the element C is held in engagement with the driven member B for positive drive. For disengagement the electromagnet is de-energized leaving the armature E free to rotate relative to the member A, so that the springs H expand and return the elements to the disengaged position, shifter D being moved out of locking engagement with element C, which latter is disengaged from the driven member B by the springs C<6>. In a modification, baulking means are provided to prevent the dog element C engaging with the driven element B in cases where their relative rotation is substantial.