CHAPTER VI.

SAFEGUARDING OF MACHINERY.

INTRODUCTION.

The term "machinery" is here used to include not only manufacturing machines proper, such as rolling machines, punch presses, wood shapers, but also all forms of power-driven mechanism, such as shafting, belting, gearing, and a few stationary structures not usually classified as machinery, such as open vats filled with hot or dangerous liquids. Elevators fall within the meaning of the term, but because of the distinct character and special importance of this topic it is considered in a separate chapter. This seems desirable because the character of the accidents incident to elevators, and the laws relating to their safeguarding, can be easily distinguished from the corresponding facts regarding other forms of machinery.

Broadly speaking, all power-driven machinery is in some degree dangerous to personal safety. If it is not directly menacing, as are low uninclosed belts, unguarded punch presses, etc., it becomes so under certain conditions, as in the attempt to clean when in motion. With machinery as it is, it is practically impossible to remove all these risks. A moment's carelessness may undo the best protective measures so far devised. Nevertheless, by the intelligent use of protective measures of proven efficiency, the danger incident to machinery may be reduced to an almost negligible minimum.

DANGERS OF MACHINERY, AND PROTECTIVE MEASURES.

Before proceeding to a detailed presentation of laws and conditions by States, it seems desirable to offer a brief preliminary outline of the more common dangers connected with machinery and the possible protective measures against such dangers. This is necessary to a proper understanding of the several laws, of the evils they seek to remedy, and of the difficulties and intricacies connected with their proper framing and with their proper administration. The points. touched upon in this outline are those of which State laws most frequently take cognizance.

Factory machinery, excluding elevators, fall into three main classes: Prime movers-steam engines, electric motors, etc.; power transmitters (or mill gearing)—shafting, belting, gearing; and individual manufacturing machines.

The present discussion will limit itself almost entirely to the second and third of these classes of machinery. The prime mover is a fre

quent source of accident, but in nearly all factories the dangers incident thereto are limited to a very small number of adult male employees engineers, firemen, etc.-at work in a special room, engine room or power room. Moreover, the most dangerous feature of any prime mover is perhaps the boiler of the steam engine, and although in many States such boilers are subjected to legal restrictions and public inspection, such restrictions and inspection are usually considered as being separate from ordinary factory inspection. If, indeed, boiler inspection is provided for by law, it is usually intrusted to a force of inspectors with special technical equipment. For these reasons the present investigation paid little attention to the subject of prime movers, and in consequence little attention will be given it in this report.

From the standpoint of safety against accident, the most satisfactory power system yet devised is that of electricity, operating by means of individual motors adjacent and connected with each manufacturing machine used in the plant. This avoids all shafting, belting, and gearing, which in many factories occupy such a large space and are such a constant menace to the safety of employees. The individual motor also has another important advantage. One of the most important safety provisions in a factory is some device for quickly stopping a machine. If, for instance, a man's hand is caught in the cog gearing of a rolling machine, the seriousness of the accident may be greatly diminished, and a fatal issue perhaps avoided, by a quick stopping of the machine. The individual motor is adapted to such quick stopping. The pressing of a button or the moving of a lever, which can be done probably by the victim himself, will immediately cut off the power and bring the moving parts to an almost instantaneous stop.

The individual motor system, therefore, itself supplants many safeguards required for safety's sake by the older system of a central power plant with numerous cumbrous power transmitters. With it, the only important safety provision needed in the factory, except with especially dangerous machines, is the inclosing of exposed moving parts of the motor and machine, either by close-fitting guards or by fences, as the circumstances may direct.

The system of the individual motor is of comparatively recent introduction, and, while it is rapidly extending its field, it is as yet existent in only a comparatively small proportion of manufacturing establishments. The great majority of such establishments are equipped with some form of centrally located prime mover, from which the power is transmitted to the various parts of the factory and to the individual machines by means of shafting, belting, and gearing. This is the system which most State legislatures in enacting laws upon the subject of machinery protection have had in view.

POWER TRANSMITTERS.

It is an accepted principle of safety that every part of the power transmission system, so located as to permit anyone coming into personal contact with it or near enough to have the clothing caught therein, should be fully guarded. Thus, for example, if overhead shafts or pulleys are not within, say, 7 feet of the floor, special guarding is rarely necessary. In practice, however, it is seldom possible to locate all the transmitting mechanism at such a safe height. Even if the main parts are overhead, the subordinate parts connecting with the individual machines are necessarily low. In many factories, moreover, where little care has been taken in the original installation of the transmission system, even the main shafts and belts are low down, sometimes at the floor level and even in open troughs below the floor level.

The danger of personal injury to employees under these circumstances is evident, and even the most reasonable considerations of safety require fencing, or other suitable guarding, to be placed at all exposed mill gearing of this character. Broadly speaking, moreover, such safeguarding should not be limited to places which are dangerous because necessarily frequented by employees. It has been repeatedly demonstrated that it is unsafe to leave unguarded any dangerous condition in a factory because located in a place supposedly never used by anyone as a passageway.

The exact character of the guarding devices which should be employed with exposed power transmitters can not be determined, of course, in advance. Conditions differ widely and there are consequent differences in the proper methods of treatment. Certain general principles, however, may be laid down. Thus, main shafts, belts, and pulleys, when overhead but not sufficiently high above the floor to be out of reach of passers-by, may be protected by troughs suspended underneath, so arranged as to prevent the body or clothing of a person from coming in contact with the moving mechanism itself. Gearing near or on the floor level may be protected by a fence sufficiently high to prevent a person from falling against the moving parts, and not so close to such moving parts as to permit clothing or parts of the body being caught when brushing by the fence. Vertical shafts and belting passing through floors are particularly dangerous because of the necessary floor openings and, in consequence, should be fenced with particular care.

SUBORDINATE TRANSMITTERS.

With subordinate transmitters; that is to say, belts, shafts, or gearing leading from the main transmitters to the manufacturing machinery, or from one to another part of this machinery, the attendant dangers are of the same general character as with the main transmit

ters. The possibility of accident, however, is perhaps even greater in the case of the subordinate moving parts of a machine than with the more prominent transmitters, the very prominence of which act in some degree as a warning. Unguarded cogs, wheels, or other moving parts of machines are dangerous not only to the operatives themselves, but also to other employees who pass near such machines, for in a factory workroom machines are almost necessarily arranged in series with passageways, or at least passage room, on one or more sides.

Almost always such dangerous parts can be protected by guards so arranged that the wheels or cogs are shielded at the point where a person's body or clothing may be caught most readily. To provide such guards upon completed machines is usually more difficult than to make such provisions at the time the machine is built, and much of the machinery manufactured at present is fully equipped with protecting devices before it is offered for sale. Nevertheless, there are comparatively few cases in which unprotected gearing on completed machinery can not be rendered comparatively harmless by means of simple safeguards, relatively inexpensive and of established merit, and this without interfering with the operation of the machine.

SET SCREWS.

One of the major sources of accident in connection with transmission shafting is the projecting set screws. The set screw is a small screw placed on the collar of shafting in order to hold the collar to the axle. Frequently its head is square and projecting, and revolving rapidly with the shafting it may easily attract and entangle any loose material coming within its reach. The clothing of anyone coming near to it may be readily caught and if the clothing does not part under the strain, its wearer will be dragged to the shaft and injured.

The set screw may be guarded efficiently and cheaply in any one of three general ways. It may be countersunk below the surface of the collar and worked with a box key or screw driver, or it may be made in hollow form and adjusted by means of a square key, or, finally, the projecting screw head may be protected by means of an additional wooden collar fitting around the original metal collar and with a hole in it to fit over the screw head. By this means a completely smooth surface is attained. The first and second of the enumerated methods require a special form of collar and screw. The third method, however, is adaptable to any existing condition without any change in the metal parts.

BELT SHIFTERS.

It is at present a very general, although not universal, practice in factories to operate all belts on the tight-and-loose-pulley system.

This system, as the name indicates, consists in having a pair of pulleys for every belt connection, one of these pulleys being firmly fastened to the shaft, the other revolving freely on the shaft. When it is desired to put the belt in use, it is swung on to the fixed pulley, and when it is desired to put it out of use it is transferred to the loose pulley, which, swinging freely on the shaft, stops all motion in the belt. The purpose of this is to avoid the primitive and dangerous system of unshipping a belt by simply pushing it off the pulley and either letting it dangle from the shaft or hanging the loose end on a hook. The danger of the "dangling" belt is very great, as an unevenness or a fold in the belt may cause it to catch in the shaft. Such a method of unshipping is rarely employed now except in the case of machines employing a very slow motive power, such as stamping presses, where it is claimed loose pulleys are often impracticable.

The shipping or shifting of belts by hand is extremely dangerous and is rarely if ever necessary. For shifting belts when tight and loose pulleys are used there are numerous mechanical appliances. These are controlled by a lever or cord and permit a belt to be shifted from the one pulley to the other without imposing any danger upon the person doing the shifting. If only a single pulley is used, the shipping and unshipping may be done by properly constructed poles without danger. To do this with an ordinary stick is dangerous as the stick may catch between the pulleys and belt and be thrown or twisted in such a way as to injure the person doing the work.

POWER-CONTROL DEVICES.

From the standpoint of safeguarding against accident, it is of great and evident importance to have some method of rapidly stopping the mill gearing and machinery. Thus, in the event of a workman having a part of his clothes or body caught in a moving belt, the immediate stopping of such belt might prevent a serious accident, whereas a delay of even several seconds might be fatal. The imperative need of power-control devices, therefore, can not be too greatly emphasized. All authorities agree upon their importance, and in several States the law requires their provision. Such devices do not take the place of the fencing, railing, and other guarding devices earlier mentioned, but they offer an invaluable supplement thereto. They are the final resort when other safeguards are impracticable or, even if provided, for some reason fail to fulfill their functions.

As has already been pointed out, the most satisfactory method of quick power control is that offered by the system of having an individual motor for each machine. The individual motor obviates all main transmitting shafts, belts, and pulleys and thus avoids a considerable proportion of the usual machinery accidents. It does not obviate the need of proper guards around the exposed moving parts