POWER TRANSMISSION ELEMENTS AND MECHANISMS 



205 



GLUE-APPLYING MECHANISMS 



Fig. 438. — Direct glue dabbers such as this 

 are inexpensive and simple, but can be used 

 only when it is permissible for the quantity of 

 glue to be applied to vary and when the applica- 

 tion is to be made in strips or dots. The 

 applicator, of any desired shapes, is held on the 

 end of a bent rod, all parts that immerse in 

 the glue being so shaped as to drain freely and 

 not to splash when entering the glue. A collar 

 on the rod serves as a stop to enable quick 

 resetting after its removal for cleaning, whereas 

 the linkage holding the applicator permits 

 adjustment over a wide range of positions. 

 The glue pot can be removed freely and usually 

 requires no securing device other than means to 

 prevent it from shifting. 



In designing these mechanisms, the device 

 must allow only a minimum of variation in the 

 consistency of the glue at the point of applica- 

 tion. Therefore the glue pot must be amply 

 large so that evaporation of the solvent will 

 affect the glue consistency but slightly. Even 

 in transferring the glue, it should be exposed as 

 little as possible to the atmosphere. In the 

 device shown here, its directness of application 

 and the simplicity of the parts in contact with 

 the glue give it a high rating for continuous 

 good performance. 



Fig. 439. — Example of an indirect type of 

 gluing mechanism, similar in design to the 

 direct type except for the addition of the trans- 

 fer member. This makes it possible to apply 

 glue to top surfaces and also to control in a 

 certain measure the thickness of the layer of 

 glue applied. This mechanism is also of the 

 type that applies strips or dots rather than 

 films. In all these designs, simplicity is of 

 greatest importance in order that the device 

 will be easy to keep clean, lubricated, and 

 adjusted. 



With reference to all types of gluing mecha- 

 nisms, the practice of exposing the glue to the 

 atmosphere after it has been applied and before 

 the closing or uniting operation, in order to 

 partly evaporate the solvent and thus make the 

 glue more tacky, must be avoided. Such a 

 practice usually is a serious source of troubles 

 as many variable factors such as time, tem- 

 perature, and atmospheric conditions enter in 

 and will seriously affect the efficiency of the 

 machine unless compensation can be made for 

 the variation in these factors and the time 

 element can be maintained constant by uninter- 

 rupted operation of the machine. 



