GB850614A - Improvements in and relating to apparatus for forming slots and the like in a workpiece - Google Patents

Abstract

850,614. Woodworking. EDUCATIONAL SUPPLY ASSOCIATION Ltd. May 8, 1959 [Feb. 13, 1958], No. 1125/58. Class 145. Apparatus for cutting mortice slots has a scraper tool 29 formed with a flat with sharpened edges at its work-engaging end and the tool is fed into the workpiece 35 at one extremity of the width of the slot, moved towards the centre of the slot, disengaged from the workpiece to allow swarf to be removed by an air nozzle 38, fed into the workpiece at the other extremity of the slot and returned again towards the centre of the slot ; this cycle is repeated until the full depth of slot has been cut. As shown, two tools 29 and 30 operate on workpieces held against fences 37 and are mounted on rocking plates 18, 21 pivoted in links by which they are joined to a third rocking plate 13 pivoted at 51. The plate 13 is joined by a connecting rod 11 to a crank 10 on a shaft 7 driven by a motor 4 and the shaft 7 also has a cam 40 which through a follower 41, lever 42 and link 44 rocks two bell-crank levers 45, 46 by which the tools are raised and lowered to give the cutting cycle described above. The parts so far described are carried by a verticallyslidable plate 3 having followers 62, 63 engaging a pair of cams 66, 67 which are interconnected by a chain 72. A sprocket 75 on the cam 62 is connected by achain 76 to a ratchet member 78 slidable in a plate 90 carried on two pivoting arms 92, 93. Another drive from the motor drives a cam shaft 87 at slow speed and cams 88 and 89 on this shaft engage respectively a follower 99 on a pawl carrier 98 and a follower 94 (not shown) on the plate 90 itself. The cam 89 has a dwell for threequarters of its circumference and the cam 88 has a gradual lift over the corresponding part of its circumference, this lift moving the pawl carrier 98 so that a pawl 100 moves the ratchet 78 gradually by one step until a pawl 91 engages the next ratchet tooth and prevents backward movement. Through the chain 76, the movement of the ratchet rotates the cam 66, 67 so that the plate 3 and thus the tools are elevated by # inch to cut into the workpiece. The subsequent fall and rise in both cams allow the plate 90 and ratchet 78 to move rapidly back and then forward again so that the tools are lowered by # inch and then raised again by # inch to restore the increment of feed by # inch. This lowering allows swarf left in the slots despite the blowing during each traverse of'the tools to be ejected. To set the apparatus to cut a desired depth of slot, a pin 103 is inserted in a selected hole in a plate 102 moving with the ratchet 78 and when the ratchet has been advanced step by step so that this pin engages a stop member 109 on the pawl carrier 98, the pawl carrier is held clear of the cam 88 and there is relative movement between the plate 102 and the ratchet 78. A vertically slidable plate 108 moves with the plate 102 and pins 104 and 105 on the plate 108 engaging in inclined slots 106 and 107 formed on the plate 108 force the plate downwards to hold the pawls 91 and 100 out of engagement with the ratchet 78. The plate 3 then falls under its own weight and pulls the ratchet back to initial position. The pivot point 51 of the rocking plate 13 is carried by linkage of which an arm 52 normally rests on the upper edge of the plate 3 and therefore rises with the plate during feed so that rectangular slots are formed. If, however, the arm 52 is raised in a slot 57, the pivot 51 can move down in relation to the rising plate 3 and as the virtual pivot point of the tools lies in the same horizontal plane as the pivot 51, the swing of the tools will gradually increase so that dovetail slots are formed.