GB879272A - Improvements relating to guns for applying viscous materials such as mastics - Google Patents

Abstract

879,272. Piston extrusion apparatus. EXPANDITE Ltd. May 13, 1960 [April 14, 1959; April 1, 1960], Nos. 12664/59 and 11607/59. Class 102(2). An extrusion gun for dispensing mastic materials includes a squeeze-grip mechanism which in its completely released position permits movement of a clutch plate to allow movement of a rod on which the extrusion piston is carried into an inoperative position and which in its other than completely released position moves the clutch plate under the action of a spring into a position in which the gun is ready for another operating stroke of the piston. As shown in Fig. 1, a square section piston rod 11 carrying a piston 17 passes through a plate 14 formed on a casing 1 secured to the barrel 15 by a screw-threaded ring 16. The rod also passes through a thrust plate 9, spacer 21, a clutch plate 19 and the rear end of the casing 1 and springs 20, 22 urge the thrust and clutch plates respectively rearwardly. On the movement of a lever 3 fulcrumed on a pin 4, passing through the casing and the spacer, towards a fixed handle 2, an arm 5 carried by the lever tilts the thrust plate 9 to grip the rod 11 and carry the latter forward to extrude mastic through a nozzle connected to a cap 24. At the same time a nose portion 26 of the lever moves away from the clutch plate 19 which is then tilted by its spring 22 about a set screw 23 to also grip the rod 11 and be moved forward by the rod until it is again in a substantially vertical position and free with respect to the rod. On partial release of the lever, the piston 17 tends to move backwards under the pressure of the mastic so that the plate 19 tilts clockwise to again grip the rod to prevent any appreciable rearward movement of the piston. At this stage nose portion 26 does not come into contact with the clutch.plate 19 so that the latter remains in a position for further forward movement of the piston. On complete release of the lever 3, the parts assume the inoperative position shown in Fig. 1., whence the piston 17 moves backwardly under the pressure of the mastic. In an alternative construction an L-shaped clutch plate 35, Fig. 3, pivoting about a pin 36, in the inoperative position of a squeezegrip mechanism constituted by a handle 2a on the casing 1a and a lever 3a, engages a depending arm 46 of a cage 37. The cage 37 is frusto-pyramidal in shape and houses a pair of hardened steel rollers 38 which on pressure on the lever 3a engage the sloping face of the cage and grip the rod 11a. At the same time the arm 46 moves down an extension 47 of the clutch plate 35. The clutch plate is then tilted by its spring 44 about the pin 36 to grip the rod which is then moved forwardly to extrude the mastic. As before a partial release of the lever 3a leaves the parts in position for the next forward stroke of the piston whilst full release of the lever renders them inoperative.