Document XR1Yzr07Jde3krnNn92eZM9O4

Principles of Guarding and Transmission Guards 2 Determine distance S --the distance from the vertical line of the rolls to a point where a 13/)26-m vertical space exists on each side of the travel line of the stock (total mp width of 3/,, m ), as shown in Fig 24-20 3 At this point, begin the layout of the dimensions shown centered on the travel line m Fig 24-17 Outline the guard sections, giving the required opening be tween sections (One edge of each sec tion will touch a clearance line, the other will touch the safe opening layout at the proper point to give the required opening ) Determine the necessary dimensions for properlv locating the guard from this final layout The width of the guard sections can also be determined in addition to locating dimensions 4 Before the guard is put m operation, check carefully for hand travel under the guard, stability of mounting, and rigidity of con struction Inrunning rolls --stock traveling over one roll before entering nip zone Fig 24-21 shows an inrunning roll nip where the stock travels over a portion of one roll before en tering the nip The stock in such an arrange ment is fed either under or over a barrier To design a properly placed barrier guard under such conditions, it is suggested that the following procedure be used 1 Draw a hil 1-scale outline of the nip zone with the travel line of the stock indicated on the roll Indicate the clearance line on the top roll If more than a '/e-in clearance is required, the top edge of the guard should be located m accordance with the safe opening layout 2 Determine distance S --the distance of the center line of the roll to the point where there is a Vin space between the rolls 3 At this distance begin the layout (on the roll with the stock travel) of the safe open ing dimensions, as shown in Fig 24-17 (Layout can be made on roll surface with `/rin divider steps ) Outline the guard section (one edge touching clearance line and the other touching the safe opening layout at the proper point to give the re quired opening) Determine the neces sary dimensions for properly locating the guard from this final layout The width of the guard can also be determined in ad dition to locating the dimensions 4 Before the guard is put m operation, check carefully for hand travel under the guard, stability of mounting, and rigidity of con struction Guard construction To assure maintenance of the dimensions established for safe openings, it is important that the guards be constructed to minimize the possibility of distortion or movement which would destroy the effectiveness of the guard All guard parts should be strong enough to withstand expected stress Fasten ings should be secure and of such design as to prevent the guard proper from shifting Any guard with openings over'/, m should be considered more or less a ` precision" con struction and checked frequently for align ment and condition Depending upon the need for visibility and rigidity and the method of feeding for a particular guard, the designer can use the layouts shown in Figs 24-19, 24-20, and 24-21 to select the guard sections best suited to his needs Figs 24-22 and 24-23 show typical guard designs for a roll nip with and without a feed table Working from a layout similar to this one, the designer can determine the location, size, and shape of the necessary guard sec tion to meet his particular requirements References American Mutual Insurance Alliance, 20 North Wacker Dr , Chicago, III Safe Openingsfor Some Point of Operation Guards, Technical Guide for Accident Prevention No 2, January 1949 American Standards Institute, 1430 Broadway, New York, N Y, 10018 Safetii Requirements for Floor and Wall Openings, Railings, and Toe Boards, A12 Safety Requirements for Mechanical Power-1 ransmission Apparatus, Bio 1 688