GB882823A - Impact tool - Google Patents

Abstract

882,823. Percussive tools. OMARK INDUSTRIES Inc. Feb. 7, 1958 [Feb. 19, 1957], No. 4054/58. Class 124. A percussive tool for producing single blows comprises a piston and cylinder, manually controlled means for moving the piston to a position spaced from one end of the cylinder and forming an explosive charge of fuel and air in the space formed, means for igniting the charge and producing a blow, and means for returning the piston to its original position. As shown, a piston 11 in a cylinder 1 has an extension 12 and a rod 40 both projecting beyond the end 4 of the cylinder. A lever 24 having a handle 36 is pivoted at one end to a bracket 25 on the cylinder and at the other to a latch 44, the free end of which engages in a notch 42 on the rod 40. An electric contact 27 mounted on the lever 24 at the opposite end to the latch 44 engages a contact 32 on the cylinder to provide current to a sparking plug to fire the explosive mixture. Movement of the lever 24 in a clockwise direction moves the piston from the end of the cylinder again return springs 76, 78 and opens an inlet valve 20 for the explosive mixture; further movement of the lever enables a cam 54 on the latch 44 to ride upon an adjustable pin 56 and free the latch from the notch, then, since the lever 24 is freed from the force of the springs rapid movement of the lever enables the contacts 27, 32 to close and the explosive mixture is fired. A rod 60 extending through the piston in both directions has a collar 72 in contact with the piston extension 12 and is thus moved by the piston in the working direction. The rod 60 carries a tool, in the example a knife blade C which co-operates with a hook 86, attached to the front end of a tube 70 containing the return springs, to cut the branch B of a tree. The other end of the rod 60 carries an adjustable washer 64 which co-operates with a shoulder 65 in a sleeve 62, which is secured to a projection 10 on the cylinder, to form a stop for the rod.