US1958128A - Safety device for machines - Google Patents

Description

May 8, 1934. M, s GATE 1,958,128

SAFETY DEVICE FOR MACHINES Filed July 8, 1930 5:5 imi@ l Patented May 8, 1934 TES Mrap

cargar oFFllcE SAFETY DEVICE FOR Application July 8, 1930, Serial No. 466,47@

2 Claims.

This invention relates to safety devices for machines, and is especially applicable to machines which are operated intermittently by means of manually actuated clutches; for example, beam presses of the type commonly used for die-stamping sheet material such as sheet-metal, leather, or rubberized fabric.

The chief object of the invention is to prevent operation of the machine while either of the operators hands remains therein. A more specific object is to provide improved safety mechanism automatically preventing operation of the machine while the operators hands are therein, and permitting its operation immediately upon the withdrawal-of his hands.

' Of the accompanying drawing:

Fig. 1 is a front elevation of a beam press embodying my invention in its preferred form, and the work and a. cutting die therein.

Fig. 2 is a detail elevation of the safety device and associated mechanism of the press.

Fig. 3 is a section on line 3-3 of Fig. 1 showing the position of the operators hand with relation to the safety mechanism.

Fig. 4 is a view similar to Fig. 3, the operators hand being removed.

Referring to the drawing, represents generally a beam press comprising an adjustable lower platen 1l, a die-block 12 thereon, adjusting screws 13, 13 for raising and lowering said platen, a movable cross-beam or upper platen 14 mounted upon the upper ends of vertically slidable bars 15, 15, and a cam-shaft 16 for actuating said upper platen through eccentric cams 50, 50, secured to said shaft just inside the end standards 17, 17, said cams coacting with pitmans 5l, 51, hinged as at 52 to crossbars 53, 53 connecting the lower ends of the bars 15, the construction and operation of the parts being well known in the art. The Work 18 is mounted upon the die- block 12, and 19 is a cutting die upon the work in position to be struck by the upper platen 14 upon descent of the latter. The cam-shaft 16 is provided at one end with a male cone-clutch member 20 which coacts with a shiftable, constantly driven, belt pulley 21 constituting a female cone-clutch member, for rotating the cam-shaft 16 to operate the press. The clutch is engaged and disengaged by a forked shipper-lever 22 which is fulcrumed at 23 on a bracket 24 extending from the frame of the press, said lever being actuated by a push-rod 25 hinged to its upper end and connected through a pair of bell crank levers 26, 26, pivoted on the frame of the machine, and links 27, 27, with a treadle 28. The latter is secured at the rear of the machine to a rock-shaft 29 and is connected to the framework of the machine by tension springs 30, 30 which normally hold the treadle in its upper position, with the clutch disengaged. A brake-drum 31 is mounted upon the cam-shaft 16 and coacts with a brake-shoe 32 pivotally mounted upon a bracket 33 extending from the frame of the machine and adapted to be raised against the brake-drum by an arm 34 secured to the rock-shaft 29.

Pivotallymounted upon the framework of the machine, opposite the end of the push-rod 25 remote from the shipper-lever 22, is a latch or pawl 35 adapted alternatively to be raised or lowered to permit or prevent longitudinal movement of the said push-rod, and thereby to control the operation of the clutch. The pawl 35 is adapted to be raised by means of a solenoid 36, the movable core 37 of which is connected at one end to the pawl, and has its opposite end connected by a tension spring 38 to an arm 39 which is part of a bracket 40 by which the solenoid is mounted upon the framework of the machine. The solenoid is energized through thea/electrical conductors 4l, the arrangement being such that when electrical current is flowing through the solenoid its core 37 is raised, against the tension of the spring 38, the pawl 35 being thereby lifted to the position shown in full lines in Fig. 2, where it presents no obstruction to the push-rod 25 and free longitudinal movement of the latter is permitted.

Energizing of the solenoid is eiected automatically, whenever the operators hands are absent from beneath the upper platen 14, by means of light-sensitive mechanism, preferablyr of the type employing a photo-electric tube. The photo-electric tube 42 is mounted upon one of the side frames 17 of the machine at the front thereof at an elevation slightly above the dieblock 12, the said tube being enclosed in a suitable housing 43 which is provided with a, hooded window which is directed toward the opposite side of the machine, the arrangement being such that the tube is shielded from any light other than the source intended for the operation of the device. Mounted upon the opposite side frame 17 of the machine is an electric lamp 44 which preferably is provided with a. shroud or housing 45, the latter being formed with a projector, which may include a condenser lens, for directing a beam of light across the front of the press, toward the photo-electric tube 42. 'Ihe light beam is indicated at 56, Fig. 1, and it is so disposed with relation to the die-block 12 that it is interrupted by the hand, Wrist, or arm of the operator as he manipulates the work 18 upon the die-block or the die 19 upon the work, substantially as shown in Fig. 3.

Power for operating the photo-electric controlled relay mechanism and for energizing the solenoid 36 is supplied through conductor wires 46 which enter a photo-electric controlled relay unit 47 containing the usual thermionic valve cascade amplifier and relays, this unit and the photo-electric tube being of well known construction so that a detail description of its organization and circuit may be omitted herein. The photo-electric tube 42 is connected with the relay unit 47 by conductor Wires 48, and the conductors 41 from the solenoid 36 also are connected with said relay unit, the arrangement being such that when light from the lamp 44 falls upon the photo-electric tube 42, current from the power conductors 46 flows through the solenoid 36 and actuates the latter to lift the pawl 35, thus permitting free movement of the push-rod 25 for manipulating the press clutch. Interruption of the light beam 56, as by the operator inserting his hands between the upper and lower platens of the press, causes such diminution of the current flowing through the tube 42 as to effect the disconnecting of the conductors 41 from the power conductors 46, with the result that the solenoid is de-energized which permits the spring 38 to retract the core 3'7 of the solenoid and thus to move the pawl 35 into the position shown in broken lines in Fig. 2, where it is disposed in the path of longitudinal movement of the push-rod 25, thus disabling the clutch mechanism.

The improved safety device is automatic and practically instantaneous in its operation, so that it in no way curtails the output of the press. It is simple in construction and requires no extensive alteration of existing structures.

The invention may be modified within the scope of the appended claims as I do not limit the claims wholly to the specific construction shown and described.

I claim:

1. In combination with a press, a clutch, a starting member requiring manually to be moved in one direction to engage and in the opposite direction to disengage the clutch, a pawl adapted to be moved into association with the starting member to prevent movement thereof, and a safety device comprising light-sensitive mechanism for so moving said pawl when the operators hands are in a dangerous position in the press.

2. In apparatus of the character described, the combination of a clutch, a starting member requiring to be moved in one direction to engage and in the opposite direction to disengage the clutch, a pawl adapted to be moved into the path of the starting member to prevent movement of the latter, a solenoid adapted to be energized to so move said pawl, and light-sensitive mechanism controlling the action of the solenoid.

IALCOLM S. CATE.

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