US 4,070,940 AGranted

Machine tool with protective light curtain and work stock holding mechanism

AssigneeCaterpillar Tractor Co.

InventorsJohn H. McDaniel, Harry W. Sinnard, Robert W. Thomas

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Abstract

A shear machine having a blade for cutting successive increments of material from flat sheet work stock has a cutting zone guarded by a curtain of light. Photosensitive means actuates a brake to stop blade motion if an object extends through the light curtain towards the cutting zone. Hold-down mechanism is operated by a lever or the like situated outside of the guarded region to enable the final portion of a sheet of work stock to be manually held in place at the cutting zone without penetrating the light curtain. The plane of the light curtain inclines towards the front of the shear machine enabling the hold-down mechanism control lever or the like to be situated on the machine above the cutting zone where it may be reached without interception of the light curtain by the operator.

Claims14

Dependent claims

In combination with a machine tool of the type having guide means with a surface for receiving work stock and having a tool element which is selectively movable to perform a machine operation on said work stock at a predetermined work zone and further having an electrically controlled device for stopping motion of said tool element, mechanism for protecting and assisting an operator stationed in front of said machine tool comprising:

a radiant energy source positioned to direct radiant energy across a planar area extending between said work zone and said operator's station,
a radiant energy sensor positioned to intercept radiant energy which has traveled across said planar area and having means for producing a signal indicative of a decrease of intensity of the intercepted radiant energy, means transmitting said signal to said electrically controlled device to stop motion of said tool element in response to said decrease of intensity of intercepted radiant energy, and
manually operable auxiliary hold-down means for clamping said work stock against said guide means surface, said auxiliary hold-down having an actuating element situated outside the region between said planar area and said work zone.

Dependencies are inferred from the claim text.