Patent GB-847931-A (GB)
Title: Automatic back gauge spacer for paper cutters
IPC: B23Q15/22
Filed: 1956-11-08
Abstract: 847,931. Photo-electric machine tool control. LAWSON CO. Inc., E. P. Nov. 8, 1956 [March 14, 1956], No. 34185/56. Class 40(3). [Also in Group VIII] Apparatus for controlling the movement of a member of a machine tool comprises motor means, drivable means connecting the member with the output of the motor means and including clutching means for controlling movement of the member by the motor means, and circuit means for controlling movement of the member comprising first photo-electric means from which a signal is arranged to effect the clutching means so as to drive the member at a slow speed, and second photo-electric means arranged in such a manner that when a signal is derived from it and from the said first photo-electric means the clutching means is effected in such a manner as to drive the member at a fast speed, the first and second photo-electric means being mechanically coupled to move with said member and arranged to produce said signals in response to said movement. In a paper cutting machine having a work-table 100, reciprocating knife, work-clamp, back gauge 105 and carriage 127 coupled thereto, generally arranged as described in Specification 707,090, the carriage 127 is provided with two photo-electric cells 190, 191 which operate relays PR1, PR2 of an electric controller whereby clutches are operated to engage or disengage high or low speed continuously running motors with or from the screw feed driving mechanism of the back gauge 105. The illumination of the photo-cells 190, 191 by a light source 192, is controlled by a plurality of stop members 195, arranged on the machine frame in positions according to a predetermined cutting programme. Upon initially starting the machine the clutch of the low speed motor operates and the back gauge moves forward at a slow speed. A first stop member 195 uncovers the cell 190 to operate a relay PR1 causing the apparatus to assume automatic operation. Continued movement of the back gauge 105 advances the associated carriage to a position wherein the stop unit uncovers both cells 190, 191 to operate both relays PR1, PR2, in which condition the electric controller operates to disengage the clutch of the low speed motor and engage the clutch of the high speed motor to cause fast advance of the back gauge 105. As the back gauge approaches the position for the first cut the next stop unit 195 stops the light to the cell 191 so that the cell 190 only is illuminated, in which condition the clutch of the high speed motor disengages and the clutch of the low speed motor engages so that the back gauge advances slowly. At the position of the cut the stop unit stops the light from reaching both of the cells 190, 191, in which condition both high speed and low speed motor clutches disengage so that movement of the back gauge ceases. A green signal light then indicates to the operator that a cut may be made. The return of the knife after the cutting operation initiates another sequence of back gauge advance movements which continue until the back gauge reaches the position for the next cut as determined by the position of the next stop unit 195. Manually operable reversing means is provided for motivating the high speed motor and correspondingly the back gauge 105 in fast speed reverse movement, said manually operable means over-riding any engagement of the clutch caused by a signal from the photo-cell 190. Specification 707,089 also is referred to.