PRESSES, DRAWING. SHEET METAL.—Toole Drawing Presses.—The most impor tant recent improvement in drawing presses is the perfecting of an arrangement for operat ing the blank-holder by means of toggles, which entirely dispenses with cams of any descrip tion. Two rock shafts are placed across the back and front of the frame, to which the blank-holder yokes are connected by toggle links. These rock shafts are operated from a crank on the outer end of the main shaft, by a peculiar system of link work, which im parts, through the blank-holder, a much more uniform pressure to the blank than can be maintained in cam drawing presses, The strain arising from the pressure put upon the blank is transferred through the straight ened toggles directly to the frame of the press, instead of falling on the main shaft, thus relieving entirely the bearings from all fric tion and wear due to the blank holding. Bet ter and smoother work, with fewer wasters, greater durability, and less consumption of power, are the princi pal advantages gained through this toggle movement.
In presses of this • type, made by the E. W. Bliss Co., of Brooklyn, N. T.. the main frame of the usual sizes is made of a single casting. The main shaft is of forged steel, with a crank slotted out to operate the plunger. This plunger is guided on the inside of the blank-holder slide and connected to the crank by a pitman with steel adjusting screw, provided with right and left-hand ratchet collars for quickly adjusting same. The adjustment of the blank-holder is made by means of four steel screws. In the larger sizes, power is communicated to the back shaft through a powerful friction clutch, which, in con nection with the au tomatic brake, places the movements of the press entirely under the control of the op erator, so that the press can be stopped and started instantly at any point of the stroke.
Fig. 1 shows one of the snuffler sizes of press made by the E. W. Bliss Co. This press is adapted for operating double-ac tion dies in the manu facture of brass, tin, and other sheet-metal shells not exceeding 3b in. in diameter or in. in depth. This includes a large vari ety of lamp and burn er work, tin boxes and covers.
Manufacturers of metal goods of various kinds have discovered that ni any articles which have heretofore been roduced by p casting them, or by expensive processes of forging, can be made by the process of cold drawing, provided the proper machine is constructed, and the tools used with it are made with due regard to the behavior of the metal worked in the drawing press. Many comparatively thin and light articles, which have heretofore been cast, are
now being drawn out of sheet metal, and the drawing process is found to have so many advantages peculiar to itself that the limits within which it is applied are constantly being extended.
A recent example is afforded by the machine shown in Fig. 3, designed and built by the same corporation to be used in drawing the common kitchen sink out of sheet steel, instead of casting, as has hitherto been the practice. The machine is remarkable in respect to the size of blank it will work ; its great power and strength ; in having an engine directly at tached for driving, and in many of its features of construction. Fig. 2 gives a general view of the machine, and Figs. 3 to 8 show some of the details of construction and method of operation ; Fig. 3 being a side view; Fig. 4 a front view from the left of the machine: Fig. 5 a sectional plan ; and Fig. G a side view from the right of the machine.
The machine consists essentially of a heavy base in two parts, upon one of which is the upright engine for driving, and the clutch mechanism, while from the other portion rise the uprights upon which are the guides for the blank-holder, and which support the crank shaft and other mechanism seen at the top of the machine. The uprights are connected at the top by a heavy beam, which crosses from one to the other above the crank shaft. They are not subjected to tensile stress dining the work ing of the machine, this stress be ing borne by the four bolts, b, b, b, Fig. 5, which are 5 in. diameter, and pass through the uprights from the base of the ma chine to the top, nuts being fitted at top and bottom. The engrav ing shows the machine with the die removed, but it will be understood that this is secured to the base of the machine between the uprights, and may be of any desired form for the work to be done, and blanks up to 60 in. by 38 in. can be worked. At the four corners of the uprights are the guides for the blank bolder, 13 (Figs. 4 and 5), these guides being formed in part by the plates, c, c, c, c, which are bolted to the uprights. To the inner sides of the blank-holder are secured by heavy bolts the two guides, g, g, upon which the punch-slide works. The latter slide derives its motion from the crank shaft, 0, Fig. 3, which, driven at a uniform speed by means of the large gear, G, imparts to this slide a motion analogous to that of the piston of an engine.