Document 71v1VVk01VjLM8eL9Yr21ogma

COLD FORMING OF METALS Measures to preveut accidental tripping of the press in addition to placing a guard over the pedal include 1 A safety spring on the tnp rod 2 Aisles of ample width for trucking ma terial to the presses. 3 Aisles adjacent to the press used only for necessary trucking of dies and stock. 4 Enough working space between adjacent machines in the same line 5 Unauthorized persons kept away from the area 6 Operators protected from interruption. 7 The operator, and all other persons not concerned, kept away from die press when it is being set up 8 A closely supervised, mandatory rule prohibiting the operator from "tiding" the pedal The operator should remove his foot from the pedal immediately each time he trips the press 8 Flywheel brakes Flywheels -- especially on large presses--continue to coast for some tune after the power source has been turned off, and they have been known to cycle a press when the actuat ing control (or controls) was tripped A flywheel brake will stop the flywheel within 10 to 20 seconds Smgle-stroke attachments Through com mon usage the term "nonrepeat" has more or less come to mean both the nonxepeat device which is installed in the clutch mechanism by the manufacturer of the clutch and the smgle-stroke device which is attached to the tnp rod and which dis connects the pedal after each stroke of the press (Fig 23-20) A press with a positive clutch should have a single-stroke attachment which dis connects the pedal or operating lever after each stroke A single-stroke spring device should de pend on spnng action only if it is a com pression spring encased in a close-fitting* tube or closely wound on a rod The type wound on a rod is preferable because it permits easy detection of a broken spnng ".-e space between the coils should be less than the diameter of the wire Of necessity, a smgle-stroke device is made inoperative when the press is used on continuous operation In this case the die should be completely enclosed, regardless of the method of feeding When the press is set up for other than continuous work, it is of the utmost importance that the sin gle-stroke device be reconnected If the press is controlled by means of a hand lever, the lever should have a spnng latch to prevent accidental or premature tapping If a hand operated press requires more than one operator, the hand lever should be interlocked Feeding and ejecting devices Primary operations, as discussed under "Definitions," are normally conducted with random length strip slock or coiled stock Strip stock is usually manually fed Coiled stock can be fed either manually or by means of a roll feed or hitch feed Automatic roll feeds are often used on continuous operations of blanking from strip stock. Small gears on the roll feed should be enclosed and the run-in nip point of the feed rolls should also be guarded. These precautions are especially impor tant where women operators are employed, even though they wear hair nets or closefitting caps Automatic push or pull feeds are similar to roll feeds and are used mostly in blank ing larger pieces When coiled stock is used with a reel and roll feed or hitch feed, a feed table is gen erally unnecessary Where coiled stock is used with a stock reel but not with a roll feed, a feed table helps the operator backgauge the stock efficiently and feed it to die die with minimum effort In manual feeding of strip stock, a feed table eliminates unnecessary motion and re duces operator fatigue The feed table should be adjusted to the height at which the operator can work with minimum effort Ejection mechanisms eliminate the need for the operator to place his hands in the danger zone to remove the processed piece They also speed up the cvcle of operation, and, because the processed piece must be out oe the way before the next piece can be loca* or blanked, they are obviously nec- essa. o make feeding possible In tne development of ejection facilities, two problems must be solved how to strip the piece from the punch or the die, and how to eject the piece from the die and the press to a container or conveyor 23-22