GB1282784A - Reciprocatory saw - Google Patents

Abstract

1282784 Reciprocating saws R SISLER 6 Oct 1969 [4 Oct 1968 15 March 1969] 49032/69 Heading B5L A reciprocatory sawing machine comprises at least one cutting blade 35, Fig. 2, carried by a pair of heads T 1 , T 2 , a pair of supports 1, 2 on which the heads are guided for vertical movement, means for causing rapid downward or upward movement of the heads to carry the blade(s) to or from a cutting position, means to cause slow downward movement of the heads for cutting, means for causing reciprocating longitudinal movement of the blade(s), means for causing vertical movement of the blade(s) at the ends of each longitudinal movement in such a way that a uni-directional cutting movement of the blade(s) results, and means for interrupting the slow downward movement of the blade(s) if an area of unusual hardness is encountered in a material being cut until the area is passed through. In the machine described the heads T 1 , T 2 are moved vertically rapidly by screws 15, 16 driven from a motor 30, and the slow downward movement is produced from a motor 22<SP>1</SP> acting via a pawl and ratchet device 23, 26. Rapid or slow movement is selected by a hand operated lever. In one embodiment each head T 1 or T 2 , Figs. 5, 6, comprises an oil bath in which run a rack 32 connected to a cutting blade 35, and a rack 31 connected to a non-cutting blade 36 which with the other blade, the racks, and freely rotatable pinions 33 form a closed motion linkage. The blades are reciprocated from a motor 37, Fig. 2, by linkage including connecting rods 40. Instead of the racks and oil baths the heads T 1 , T 2 may each comprise a pair of cylinders the pistons of which are connected to the blades and are arranged to move under the control of a common fluid within the cylinders. The blades are lifted or lowered at the end of each longitudinal stroke by mechanism 49 and 50 included between the blades and the heads T 1 , T 2 . Each mechanism includes a pair of pivoted weighted shafts which move relative to the blades as these change direction and which are connected by linkage and bearings to the blades to lift or lower them. In an alternative construction the heads T 1 , T 2 are each in two parts, and the parts carrying the blades are raised or lowered at the end of each stroke by a cam arrangement. When the cutting blade encounters an area of hardness within a material being cut and its downward motion is prevented a device 70 operated by a cam carried by the blade causes a contact to be opened which breaks the circuit of the motor 22<SP>1</SP> and so interrupts the slow downward feed of the heads T 1 , T 2 until the obstruction is overcome. The machine may include a plurality of cutting blades mounted on each pair of heads, and/ or a plurality of pairs of heads. The blades may all be arranged in a common horizontal plane in which case they are all cutting blades.