GB876590A - Improvements in or relating to cement applying apparatus - Google Patents

Abstract

<PICT:0876590/III/1> <PICT:0876590/III/2> In a cement-applying apparatus, the rate of feed of cement in rod form into the apparatus is regulated by the amount of cement in the apparatus immediately available for application to workpieces. The regulating device may take the form of a pressure-sensitive diaphragm or a vane operated by the build-up of adhesive in a part of the apparatus adjacent to the applying member. In a machine for applying cement to the backs of books, Figs. 2 and 7, a rod of solid thermoplastic cement S is drawn into the machine by corrugated roller 20 and a similar co-operating roller, not shown. These rollers are driven by an electric motor through chain drives and a separable clutch 256, 257. The rod of cement is fed along passage 94 into a melting and applying unit constitued by disc 56 rotating in a recess in a heated casing 48, a passageway 160 diminishing in size towards the part indicated 162 being formed between said disc and said <PICT:0876590/III/3> <PICT:0876590/III/4> casing. The backs of books B are passed across that part of disc 56 which protrudes from the casing and receive therefrom a layer of melted adhesive, which is subsequently spread by rotating brush 66. The thickness of the applied layer is controlled by the adjustable doctor roller 120, and any adhesive not applied to the books is returned to the casing and the passage 94 via gear pump 172. When cement is not being removed from the exposed part of disc 56, the consequent increase in pressure at the point 162 operates a pressure-sensitive device connected thereto by a passage, which device operates an electric switch controlling the supply of energy to a solenoid 232 which in turn controls the separable clutch 256, 257 in the feeding device through lever 244. The supply of solid adhesive is thus stopped when no molten adhesive is being removed from the disc. In another embodiment, Figs. 9 and 12, the machine is very similar to that described in the second embodiment of Specification 834,567, having a separate feeding unit 314, melting unit 310 and applying unit 312, the latter being provided with a vane 432 which is normally spring-urged towards the position in which it is shown in the Figure, but which is forced to the other side of slot 428 when, because of non-removal of melted cement by workpieces W, the melted cement accumulates in recess 360 and attempts to escape via passage 364 and the space between the vane and applying disc 350. This movement is used to operate a micro-switch which energises solenoid 444, which by means of link 496 and toggle 490, 492 operates jaws 478, 484 so as to grip the rod of thermoplastic cement R and prevent its being fed into the feeding unit 314.