PI : Ovo : Loe ; TS ey ear oe ey 5 >. tet ES peg ee ee yee Mee 4 Fe LATIN A x Cr eRe oe ee al 3 Sa Ko pe D Be 0 ais : ee Be Ay Be CAN We \ A er AS ae Cd A ob PLA ; a fy ay A : ry A eee OE S Ly Ye ey 5 ae ee, on EORSREK ee Ly BESS ae wee: Y esa Ro se OSTA I aS RAT cae cant he eae aah . 4 Z ‘oe rr Ll fh ary « “oF A NS 5 A SoS AR, 3 Sp. Pn Mek Se eH ss : y A Fog te / Saw, CF heir f. \ oh J i ed atten Or =a ¥ g iF ce 3 ‘> S “Fe CY ee Dt PT avs Ry » pe AY a : te es “ % f oe sey Pet PA tS aL RAD . ACRES Has rd Ca oy i> ca FOS HO ees SE Phe ea PRL eae Py i xe ee Te RON : be LD A we , ; De Ps Uy . f \" — sf s x { f * \ b Ss ie rf Cre, ¥ é or 5 ety S / 2 1) oS b ) aN AG PBN . Soe hh POE hs iat pe ey Poe : LP CS t ERD sey A | Tee oe ; if Sage we: MY Ce a cL eee Roos et PTY IAL < oe A yar Z er nese THESIS SAFE T Y DEVICES AS APPLIED T O THE MANUFACTURING PLANT. REWRY Je MASTENEROOR, Hk. S. "SAFETY FIRS T" MAY 1,191 2. THESIS INTRODUCTION The. suc ject of safety devices for the pre- vention of industrial accidents is so broad that it would be impractical for any one person to attempt a general discussion of the subject. We must look for specialization along various lines of engineering. The expert, competant to provide for the ordinary manufac- turing plant could hardly be expected to provide equ- ally well for. the railroad system or the mine. In the following pages only such safeguards as apply to the manufacturing plant will be considered, and these will be treated in as brief and concise a Manner as possible. Many devices in common use are of little value and a few are a menance in themselves. Such devices will not be described, or if they are, it will be for. the purpose of warning against their use. If an appliance is known to be patented this fact will be stated, or if it is adapted from some published article due credit will be given. It will only be possible however to give credit in a few cases as a great majority of the safeguards described are those that have come under. the observation of the writer and their origin is unknown to him. The illustrations shown will be general in character intended to illustrate the principle in- volved and , with a few exceptions, will not apply A02744 directly to specific cases. They are intended more particularly as a guide to the designer. The writer believes the subject of safety devices is one. that ought to be given more attention in the technical school as the average graduate has little conception of what constitutes an adequate safeguard. The proper place to equip a machine with safeguards is in. the drafting room when the machine is being designed. It is therefore of prime irpor- tance that. the designer have a clear conception of what is necessary in this respect. It has been the writer's experience that. the average designer is wor fully deficient in. this respect. This is a wrong condition of affairs and one that should be corrected at the earliest possible moment. The technicel school could do much towards advancing the knowledge of the student along these lines without unduly interfering with the regular work. It should be incorporated as a part of the regular courses in machine design and shop methods. The campaign now under way for lessening the number of industrial accidents must necessarily be largely a campaign of education. The workman must be taught to avoid dangerous places, they must be taught that all moving machinery is dangerous even though it may look innocent, they must be taught to keep in mind at all times the necessity for care. It is thus that habiés are formed and when CAUTION BECOMES A HABIT ACCIDENTS WILL BE FEW. NECESSITY FOR SAFETY DEVICES It is not possible to obtain accurate statistics regarding the number of industrial accidents in the United States. Conservative estimates made by the Bureau of Labor places.the total mortality among adult male wage earners at from $0,000 to 35,000 anually. in addition to these there are approximately two million non-fatal accidents annally, entailing a vast amount of suffering and financial loss, as well as shortening the natural life of the victim or leaving him in a crippled condition. The mumber of these accidents that could be prevented by the installation of proper safety devices can only be estimated but we can forma fair estimate by comparison with sole country whose statistics are available. The German government has collected exact information along. these lines in connection with the Workmens Compensation insurance in that country. From this it appears that apout 58 per cent of the accidents are the result of negligence on the part of the employer or employee, and therefore prevent- able, and 42 per cent to the inevitable risks of employment. Following is a classified list of the causes of accidents as published: Inevitable risk--------------—.----42.06per cent. Want of skill and carelessness----2.265 ™ "' Want of guards-------------------- 7,82 "' " "" Deficient factory arrangements---- 7.15 " Acting against rules-------~------- 5.14 per cent. Fault of other (third) person----- 5.2@ "— " Fault of employers and workmen---- 4.66 '"' " Not using guards------ ------------ 192 " =" Insufficient instruction---------- 1.8 " " Superior force, casualty, etc.---- 1.3] " " Carelessness-----—------ --- -------- 1.19 " " Unfit clothes-------------- wee-n-- 0.49 " " In considering the above list we must remember that the subject of accident prevention has been given a great deal more attention there than in the United States. The Workmens Compensation laws encourage the invention and application of safety devices and their use has become general throuought the Empire. It is therefore probable that the per cent of prevent- able accidents in the United States is very much more than 58 per cent, probpatly as high as 7O per cent and possibly more. Disregarding the humanitarian feature and considering the subject purely from the financial standpoint the loss is staggering. During 1908 over $22,000,000 was paid in premiums to the insur- ance companies for liability insurance. This repre- sents only a small portion of the loss the total amount of which it is impossitle to estimate with any degree of accuracy. This certainly constitutes a serious drain upor our industries and one that there is no question could be lessened in a very marked degree by the installation of proper safe- guards. It is beyond the province of this thesis to discuss at any length the subjects of libility ‘insurance or workmans cempensation. Many factory owners are no longer carrying libility insurance. They realize it is cheaper to prevent accidents than to pay for them and with the factory that is well equipped with safety devices the amount paid for injuries is. invariably less than the cost of insurance. The subject of compensating for unav- Oidable accidents should go hand in hand with that of accident prevention. Some method should be devised whereby the amount of compensation can be determined without the expense and delay now incident to legal methods. Some of the larger industries, notably the United States Steel Corporation, have adopted a fixed scale of compensation for death or injuries which. they pay without question provided no legal measures are taken. It is the writers opinion that this is the correct solution of the problem and to make it applicable to all industries will require governmental aid and supervision. WHAT CONSTITUTES A SAFETY DEVICE. The term "Safety Device" as used in this thesis does not mean merely a guard for some dan- gerous portion of a machine BUT INCLUDES ALL PREVEN- TATIVE MEASURES, NO MATTER WHAT THEIR NATURE, THAT TEND TO MAKE WOREING CONDITIONS MORE SAFE. Any con- dition or apparatus that will tend to lessen the dan- eer from fire, for instance, or facilitate the escape of the employees from the building in case of fire is as truly a safety device as a gear fuard. a THE TIME TO PROVIDE SAFETY DEVICES. The proper time to provide safeguards is when. the plant is pveing erected or the machine or apparatus is being built. A little attention given to the grouping and arrangement of buildings, pro- viding open passage ways, fire exits, doors opening outward, adequate lighting and ventilation and strict compliance with the underwriters rules will lessen to a marked degree the danger of accidental injury to employees, without materially increasing the cost of construction. When a machine is being designed the necessary safeguards can usually be applied at small expense and they can be so designed that they will harmonize with the lines of the machine and in most cases i:prove its appearance. When machinery is not so guarded it falls upon the user to make it safe by means of patented devices or home made safeguards. It is frequently very difficult to pro- vide efficient safeguards on machines for which no provision has been made for them in the original design owing to lack of clearance or other conditions. It can usually be done however although the result may not be very pleasing to the eye, depending upon the amount of time and money spent upon their de- sign and construction. POINTS TO BE CONSIDERED IN THE DESIGN OF SAFETY DEVICES. The first question to be asked in designing a safety device is, "Does it protect?’ A device that only partly protects is often worse than none at all as it conveys a false sense of security and causes the workman to wholly rely upon it for pro- tection thus inducing him to take chances that he otherwise would not and which the device will not protect against. An incident in point was a large gear provided with a guard that extended only part way around. HP CP CE AT EE EE EE Ge aap eee aa 66 ese eas aaa ae Fig. 17. wu ook Vi ot 1é. Fig. o3f .ord important feature. In Fig. 19. we have probacly the best form of safety compression coupling on the market. As will be seen from.the sketch it consists of a tapered, split bushing threaded at each end. The tapered portion is clamped by two taper bored rings: which are forced on by the spanner nuts as. shown. This is Known as the Collins coupling. When in position on the shaft it presents an absolutely smoothe surface with no projections whatever. In Fig. 20. we have a modification of the same type with the nuts omitted. The bushing is clamped by two wrought iron rings driven on. In both these types. the cushing is usually bored Slightly smaller than the shaft thus securing the clamping and self aligning feature. While it is customary to use a key with these couplings it is not absolutely necessary except in véry heavy work although it is disirable as a pre- cautionary measure. } There are other forms of safety couplings on the market but they are nearly all based on the principles of the above, are more expensive and give no better results. sii co fe Th Wy {a aren Fig. 19. Fig. 20. oUl wit 208 ork GEARS. There are few machines that do not in some manner employ gears. This gearing, no matter what its nature, if unguarded is dan- gerous. Gears are frequently so situated that they are a constant menance. to the operator. they are always a source of danger when cleaning or oiling and are in many cases in close proximity to a passage way through which men are constantly passing. They are usually driven with great power and frequently at high speeds and. their very nature makes them particularly liacle to catch anything coming in contact with them. If a man's sleeve is caught his arm is invariably drawn after it and only in rare instances does he escape serious injury. There is one feature however that keeps down. the number of gear accidents and that is that gears are easily seen, their danger is generally recognized and men working around them are usually carefull. Therefore the numoer of accidents re- sulting from gears are far less than those result- ing from other parts which, in themselves, are much less dangerous. Nevertheless the fact remains that gearing is extremely dangerous and should in all cases be effectually guarded. Kost builders of high grade machinery now guard their gearing but in cases where it is not guarded or in the case of old machinery it is necessary for the owner to provide suitable guards. In the following illustrations some typical forms of gear guards are shown. These are all practical and easily constructed and each represents some form the writer has either designed himself or observed in actual use. One thing must always be kept in mind in designing gear guards and that is, to ce efficient they must be STRONG and RIGID and COMPLETELY ENCLOSE THE GEAR. The blue prints, Fig's. 2] and 22 show the general arrangement and details of a spur and worm gear drive recently designed by the writer. Here we have the most efficient form of gear guard it is possible. to produce. The gears are comple- -tely enclosed and the guards are so designed that they are a part of the bearing, thus making it impossible for the operator to remove them or in any way tamper with the gears while the machine is in operation. In other words, without the cuards the machine is inoperative. This ideal condition can frequently be attained in the design of new machines but not often when applying guards to old machines. In Fig. 23 we have a cast iron guard for a pair of bevel gears. As will be noted it is cast in one piece and may be lowered in place from above. It covers the gears completely including the shaft ends and keys and may be held in position by lugs cast on the guard in such a manner as to rest on the bearing cap or preferably some portion of the FIG. BZ. machine frame. The pattern work may be symplified by making the zuard of plain rectangular cross section or carrying it straight across between the outside faces of the gears instead of forming it to suit the contour as shown. The same idea can of course be applied to spur gears, sprockets, etc. While the cast iron guard is probably the cheapest form for the machine builder to use, the cost of pattern work makes it more expensive than a. steel one when only one is wanted. I[n Fig. 24 is shown a spur gear and pinion gu@&rd of steel. It is shown with one side closed to pro- tect the ends of. the shafts but may be used on gears located between bearings py simply cutting _the hole for the shafts. through both ends. Fig. 26 shows the same idea arranged to set on the floor when. the gears are so located as.to inake this desirable. These are the standard forms of xuards used by the United States Steel Corporation at the Gary mills. The angles are 1 1/2 x¥ 11/2 x 5/16 and.the plate #12 gauge. A hinged door is provided on the top for oiling and inspection. This is undoubtedly the best form of guard for general mill use. It is strong, neat and efficient. In Fig's. 26 and 27 are shown two types of guards that are frequently used but are not to be recommended. They are illustrated for the pur- pose of pointing out their defects and warning against their use. The first, if the gears mesh Fig. 23. A | Pip | fir! LIM A 4 s/h tI | £4 Wi] ly Wiy fi} id il Pei i py Pg Ptah — fit | | /\\ 1 | | Ht f\ \fbuy Th a : ha l 4 | ; 7 e Be el ah DE Ba et dd \1 a ee “<= 5" —_yoeee eee eee oe ee owe Ge ewe of oe Dp > CE Ge GN Gp GED 4 au Fig. 24. ~ \i I TT i i 7? if I\ ‘’w \ \ J Lf > cm aus Gn» Gua qee=ees eae a= ean pam eww ee ewe eee ee ee co a — Sig. 25. amp a> GP GaP c= Ge ew @p a= Gp x from the top, offers a fair measure of protection but it does not protect the end of the shaft and .it leaves open the possibility of a man's eetting caught between the teeth and the guard on the. ‘outside edge. In case the gears mesh from the bottom it offers but little protection, in fact it makes the probability of serious injury greater in case a man is caught. The writer knows of a guard constructed exactly like this in use at the present time. The gears mesh from the bottom and the guard is cut out as shown exposing the. the end of the shaft and its projecting key. There is no apparent. reason for cutting it out in this way, it is simply a case of careless and thought- less design. The second form is open to all the ovjections of the first and in addition it does noé even afford protection against being caught between the gears when.they mesh from the top. both forms are thoroughly bad and should be avoided in all cases. Fig. 28 shows a punch press equipped with a guard similar to that shown in Fig. 24 except that the sides are made of wire netting about #12 gauge and 1/2 inch mesh. This is not as strong as a guard with plate sides but in places where it cannot be used as a step ladder is strong enough and has the advantage that the gears are visible and can be readily inspected. The lower half of the fly wheel is shown guarded in the Same manner. Fig. 28. / Ts. Vs (Vs ‘re 1 i ee ee == 4] == S51 = == ae ee | p-4—- | Jt Ue 8 \ WV" ‘\ | 4 XN e—-—| sof\ afl “i — = > Con +} Tt + Tr | it at aL 1} t+ ti} / Fig. 29. In Fig. 29 is shown the method of guarding live roll gears in the steel mills. The .top plates are hinged and are made sufficiently strong so. they may be used.to step on in crossing the roll.table. Frequently gears ina manufacturing plant can be boxed in in a similar manner to ad- vantage. Fig. @ shows about the neatest form of guard for the change gears ona lathe or any gearing exposed in a similar manner. [t consists of a steel frame covered with wire netting. It is fastened to the floor and the machine by means of clips or hooks in such a manner as to be easily removable.