Patent GB-959143-A (GB)
Title: Improvements in or relating to sanding machines
IPC: B24B23/06
Filed: 1962-08-03
Abstract: 959,143. Grinding. E. MURSCHEL, and K. MESCHER, [trading as C. F. SCHEER & CIE.]. Aug. 3, 1962 [Aug. 10, 1961], No. 29876/62. Heading B3D. A belt sander comprises a casing, a driving motor supported in said casing, a driving roller arranged in said casing and driven by said motor, a tensioning roller mounted adjacent the motor, a rocker arm pivotally mounted on said casing, a tensioning roller shaft, said rocker arm having rocking bearing means adjustably supporting the tensioning roller shaft within the tensioning roller for rocking adjustable movement, and means for biasing said rocker arm outwardly in a tensioning position. A portable belt sander has a casing 14 with a handle 12 at one end. An electric motor 16 drives a drive roller 18, both motor and roller being carried by a wall 30 of the casing 14. An endless sanding belt 22 travels round the drive roller 18, past a guide shoe 24 on the underside of the motor 16 and round a tensioning roller 20. A suction device 26 having a dust bag 28 is provided on the casing 14. A pin 34 is slidably mounted in a bore in the casing wall 30, rotation of the pin being prevented by the end of a set-screw 40 engaging a groove 36 in the pin. The end of the set-screw 40 selectively engages notches 42 to secure the pin 34 in different axial positions. A rocker arm 46 is pivotally mounted on the pin 34. A torsion spring 50 surrounding the pin 34 has one end bearing against a pin 58 in an adjusting ring 52 and the other end bearing against a part 62 of the rocker arm 46 whereby the latter is urged by the spring away from the drive roller 18 so as to tension the belt 22. To enable the belt 22 to be changed, a control pin 64 slidable in the pin 34 is biased by a spring 72 and its end lies in a guideway formed by a forked extension 66 in the end of the pin 34. The inner end of the rocker arm 46 has a abutment pin 68 with an inclined surface. When the control pin 64 is moved inwardly, so that its end lies out of the path of the abutment 68, the rocker arm 46 can be moved against the spring tension to cause the abutment 68 to lie behind the pin 64. The pin 64 is then allowed to move to the right so that it takes the tensioning force. The end of the rocker arm 46 has therein a bore 86 formed at its inner end with a recess providing a socket for a bearing 88 to permit slight rotational adjustment of the shaft 89 on which the tensioning roller 20 is mounted by ball bearings 90. The roller 22 is retained by a ring 92 secured on the shaft 89. A guide rod 94 extends radially outwardly from the ring 92 and includes an arcuate portion extending circumferentially along the side of the roller and closely spaced therefrom. The outer surface of the guide rod extends by an adjustable amount beyond the surface of the roller. A second guide rod 98 is mounted in an extension 102 of the shaft 89. Any tendency for the belt to slide off either end of the roller causes a rocking movement of the shaft 89 to bring the belt back to correct tracking. A pin 105 extending through the bearing 88 is guided in a slot 108 in the rocker arm 46. One end of the pin 105 is engaged by the end of a spindle 112 threadedly engaged in a part 110 of the rocker arm 46; a spring 115 is located between the other end of the pin 105 and the part 62 of the rocker arm 46. Figs. 8 and 9 illustrate modifications of the mounting of the tensioning roller shafts 128 and 162 respectively.