Figs. 22 and 23 show the truck by itself, g representing the bottom, and h the back, which is provided with slight grooves, into which the wires catch to assure the entire cutting through of the block of jelly; i is the upper part of the truck, which opens by means of a hinge, and when closed is fastened with the pin, k. This upper part of the truck is fastened to the back part of the truck by means of a screw, which allows it to be set higher or lower, according to the size of the block of jelly to be cut; m is the bar of a rack fastened to the truck, and serves for moving the latter. The driving gear, n, the shaft of which carries a crank, o, catches into the rack.
Fig. 23.
Two boards, one on each side of the truck, serve to keep the block of jelly in position, and guide the truck.
With this machine 120,000 to 130,000 cakes can be cut in five or six hours.
3. DRYING THE CAKES OF GLUE.
Drying the cakes is without doubt the most precarious part of the manufacture. The jelly contains a large quantity of water which, to prevent decomposition of the jelly before it is converted into glue, must be evaporated as quickly as possible. In favorable weather, drying may be accomplished either in the open air or in covered sheds.
Drying in the open air is connected with many inconveniences, for if the sun strikes the cakes of jelly when they still contain a large quantity of water, they may become soft so as to run through the meshes of the net, or they may dry so quickly as to prevent them from contracting to their proper size without numerous cracks and fissures. If frost supervenes, numerous cracks may be formed in the cakes from the congelation of their water, or a shower of rain may cause much work and damage. In consideration of all these inconveniences, it is best to conduct the operation in a drying-room.
To insure a constant circulation of air, which is absolutely necessary for the expulsion of the aqueous vapor caused by the evaporation of such a large quantity of water, the drying-room should be at least 10 feet high, even if intended for summer use only, and the windows be provided with Venetian blinds so as to shut out the sun, if necessary, without disturbing the circulation of air.
To dry the cakes in heated rooms in winter is a more difficult matter, as provision has to be made for the removal of the aqueous vapor, and a current of warm dry air has to be kept up at the same time. But such a room is an absolute necessity for the manufacturer on a large scale, who, in order to carry on his business without interruption throughout the entire year, must be independent of the changes of wind and weather.