Patent GB-913226-A (GB)
Title: Improvements relating to polishing, buffing or like machines
Inventor: ROSS JOHN
IPC: B24B49/00
Filed: 1960-03-24
Abstract: 913,226. Control of motors. MIDWEST SUPPLY & MFG. CO. March 24, 1960, No. 10492/60. Class 38 (3). [Also in Group XXIII] A mechanism for automatically adjusting, during operation, the operating head of a polishing, buffing or like machine to take up wear occurring on a buffing wheel or the like carried by the head, comprises motor-operated means to advance and retract the head relative to a workpiece and control means operative to cause said advance to take place in steps of predetermined direction with intervals therebetween also of predetermined duration. A buffing machine comprises a mounting sleeve 13. An upright way 23 on a part 14 of the sleeve 13 receives a dove-tail slide 22 on a head 15 carrying a buffing wheel 16. For effecting vertical movement of the head 15 relative to the sleeve 13, a screw 24 journalled in the slide 22 meshes with a nut portion on the part 14. A motorized timing and control unit 28 is applied directly to and in fixed driving relation to the top squared end 26 of the screw 24, the unit comprising a housing 30 having a bottom flange 31 with bolt holes 32 for attachment to the top of the slide 22. A worm gear 33 is connected by means 34 in fixed driving relation to the squared end 26 of the screw 24 and meshes with a worm 38 on a shaft 36. One end of the shaft 36 has a squared end 38<SP>1</SP> to receive a hand-wrench. The other end of the shaft 36 carries a pulley 40 driven through a belt 42 by a pulley on the shaft of an electric motor 44 mounted on the top of the housing 30. Lower and upper limit switches 47, 48 of the snap-over type with operating arms 50 are carried by a bracket 49 secured to the part 14. A bracket 51 secured to the head 15 carries vertically spaced cams 52, 53, 54 which operate the switches. The electric control circuit, Fig. 7, is fed by a transformer 60 and includes the limit switches 47, 48, " down " and " up " energizing coils 62, 63 of a reversing starter for the motor 44, a control relay 61, a first timer relay 56 and a second timer relay mechanism 57 having a clutch 59 and a motor 58 controlling multiple contacts including the contacts 58<SP>1</SP>, 58<SP>11</SP>. The Figure shows the positions of the various contacts at the beginning of a complete operating cycle, i.e. when the head 15 is at the top limit of its vertical travel relative to the work. With reset switch 64 closed, circuits are made through contacts 47<SP>1</SP>, contacts 61<SP>1</SP> (a) through contacts 56<SP>1</SP> and contacts 63<SP>1</SP> to the " down " coil 62, and (b) through contacts 58<SP>1</SP> to the first timer relay 56. After a time interval, contacts 56<SP>1</SP> open, so de-energizing the " down " coil 62 and contacts 56<SP>11</SP> close so (a) completing a circuit through contacts 58<SP>11</SP> to the motor 58, and (b) completing a circuit through clutch 59. After a time interval, contacts 58<SP>1</SP>, 58<SP>11</SP> open, so de-energizing timer relay 56, resulting in closure of contacts 56<SP>1</SP> thus again energizing the " down " coil 62. Contacts 58<SP>1</SP>, 58<SP>11</SP> are automatically reset and the downward adjustment of the head 15 is therefore repeated. At the bottom of the travel of the head the central cam 53 snaps the arm 50 of limit switch 47 downwardly, opening contacts 47<SP>1</SP> to break the circuits to both timers 56, 57 and the " down " coil 62 and closing contacts 47<SP>11</SP> to energize the control relay which is held in by contacts 61<SP>111</SP>. The " up " coil 63 of the reversing starter is energized through limit switch 48 and contacts 61<SP>11</SP>, 621. The head 15 is elevated completely to the top of its stroke, whereupon bottom cam 52 trips the arm 50 of limit switch 47 upwardly to its normal position. Continuation of the upward travel causes top cam 54 to trip the operating arm 50 of limit switch 48, thus de-energizing the " up " coil 63. The reset switch 64 is operated to repeat the full cycle. Switches 65, 65<SP>1</SP> are provided for over-riding the automatic operation.