Patent GB-749822-A (GB)
Title: Improvements in or relating to grinding, polishing and like machine tools
Inventor: JONES REGINALD ARTHUR BISHOP
IPC: B25C1/14
Filed: 1952-09-16
Abstract: 749,822. Shaft couplings; operating clutches. ROLLS-ROYCE, Ltd. Sept. 8, 1953 [Sept. 16, 1952], No. 23283/52. Class 80(2) [Also in Group XXIII] A machine for grinding, polishing &c.. curved edges of articles, e.g. the leading: edges of blades for use in turbines or compressors of gas-turbine engines, comprises a main frame and housing structure 10 including a top plate 11 on which is carried a cradle 13 hanging in a well 12 in the housing 10 and supporting a driven abrasive belt 14, and also comprises a workholder support frame 15 carried on the structure 10. A pair of spaced plates 16, 17 upstanding from the top plate 11 along the back edge of the mouth of well 12 carry the work-holder support frame 15 for swinging movement about a fixed spindle 37. An electric motor 18 within the housing 10 drives through gearing 19, 20 a crank wheel 26; an adjustable crank pin 27 drives through connecting rod 22 a crank arm 23 on a spindle 24 mounted in bearings in the plates 16, 17. During a full rotation of the crank wheel 26 the crank arm 23 is rocked backwards and forwards through about 80 degrees. The spindle 24 of the crank arm drives, through pinions 28, 29 a spindle 30 mounted in bearings in the plate 17. The spindle carries a first coupling member 35 for transmitting drive to the work piece. The end yoke of the coupling member 35 has an arcuate groove 36; in one position of the member 35 the centre of curvature of the groove is on the swinging axis of the work-holder support frame 15. The gear ratio of pinions 28, 29 is such that the coupling member oscillates through an angle of about 160 degrees. A workholder is rotatively supported in the workholder support frame 15. The frame of the work-holder has at one end, a recess and a notch to fit over a central boss 41 and offset tenon 42 on a drive plate 43 secured by nut and bolt 44 to a second coupling member 45. The second coupling member 45 and drive plate 43 are rotatively supported in a ring 47 forming part of the work-holder frame 15; the second coupling member 45 has on one face an arcuate rib 49 adapted to engage in the arcuate groove 36 in the first coupling member 35. The blade is secured in position in the work-holder with the workholder support frame 15 swung upwardly on its'spindle 37 and with the first and second coupling members 35, 45 disengaged; thereafter the frame 15 is swung about its pivot 37 to bring the rib 49 on the second coupling member 45 into engagement with the groove 36 on the first coupling member 35 and thus to bring theaxis of the leading edge of the blade into line with the axis of the spindle 30. A drive can now be transmitted from the pinion 29 through the coupling members 35 45 and drive plate 43 to the workholder. A manually-operable clutch mechanism is provided between the motor 18 and the shaft 21 of the crank wheel 26, the clutch including a trip mechanism so that after the shaft has made one complete revolution the clutch is automatically disengaged. Shaft 90 of motor 18 drives shaft 91 of gear 19 through coupling 92; gear 20 has a hollow shaft 93 which drives the shaft 21 through a dog clutch having one element 94 secured on shaft 93 and the other element 95 rotatable with but slidable along shaft 21 under control of a pivoted striker fork 96. The fork 96 is loaded by compression springs 97, 98; spring 97 is located between fixed abutment 99 and abutment 100 on a slidable collar bearing on fork 96; spring 98 is located between abutment 101 bearing on the opposite side of fork 96 and an abutment 102 movable towards and away from the fork 96 by a cam disc 103 on shaft 21 and having a load land 105 to displace abutment 102 to move fork 96 to disengage dog-clutch 94, 95. Abutment 101 can be displaced by manually-operated lever 106 to permit engagement of the dog-clutch 94, 95. Since the first and second coupling members 35, 45 through which the workholder is rocked, can only be engaged when the crank arm 23 (and thus the crank shaft) is in one particular position it is arranged that they are in this position when the land 105 of the cam disc 103 is in the clutch-disengaging position, and also when the coupling members are in this position the blade mounted in the work-holder is at one limit of its angular' travel.