CHAINWORK. 



719 



PLAT* 

 cxxxvu. 



f' l S' 9- 



_. ._ 





Tajnlxjur. that any needle, if broken, injured, or worn out, may 

 In chungrd :u i>V;i-uie. Tin- whip, or yam, is pla- 

 ced upon a hollow tin cylinder, as m tin- former ma- 

 chine, and every thread passes through the eye of the 

 corresponding perforator. The motion given to the 

 perforators is exactly the converse of that in the for- 

 mer machine ; for here the perforation is from be- 

 hind, and the reciprocating motion may either be 

 given by wipers, or by two small cranks upon the 

 ends of the shaft G, which is turned by the ope- 

 rator's hand. The form of the shaft appears in 

 Figure 9. In the front of the cloth is a cross rail, 

 to which is attached a frame carrying a number of 

 perpendicular needles, one being correspondent to 

 each perforator. When the perforators are brought 

 forward, these needles, by the rising of the frame, 

 pass between the perforator and the thread, and thus 

 form a loop, which remains until the perforators are 

 withdrawn and return again, and so on. The proper 

 regulation of this motion is the chief matter of nicety 

 and difficulty in the machine. Copious remarks upon 

 its nature, and the means of effecting it with accu- 

 racy, shall therefore be given in the proper place ; as 

 upon this rests the only difficulty of which this ma- 

 chine appears to be susceptible, and, at the same 

 time, it is of such importance that this motion should 

 be executed truly and steadily, that without that 

 being accomplished all the rest would be nugatory 

 and illusive. The pattern motion is, in this machine, 

 to be given by two spiral worms, which may be six 

 inches in diameter, or even less if desirable. These 

 are represented in Figure 10, and some descrip- 

 tion of them may be necessary. They so far re- 

 semble in principle the transverse wheels of the for- 

 mer machine, that the figure of the pattern depends 

 solely upon the form into which their rims are cut, 

 and this depends upon the principles of calculation 

 already described. Were a motion introduced to 

 shift the contact of the frames at the end of each re- 

 volution, any number of wheels contiguous to each 

 other, upon the same axis, would answer entirely 

 the same purpose ; but forming them as spirals will 

 do equally well, and save some additional machinery. 

 In order to avoid the errors to which the ratchet 

 was sometimes liable, on account of the inertia, it is 

 proposed to substitute in this machine an oblique 

 wheel, with what is generally termed by mechanics a 

 double threaded endless screw. This being turned 

 half a revolution for every shift, the whole shifts 

 will be made with a precision, which may in every 

 instance be relied upon. 



For the purpose of allowing the cutter to come 

 fairly in contact with every part of the circumference 

 of the spiral traverses ; while the pattern is cutting, 

 it will be proper to construct them in pieces equal to 

 one revolution of the spiral, and these pieces may be 

 removed while cutting, and when the cutting is 

 finished, all may be placed on the axis, and se- 

 cured by screws, or any other sufficient fixture. In 

 order to allow the friction wheels, which are in 

 contact with the rims of the spiral, to traverse free- 

 ly along, some such contrivance as that represmt- 

 ed in ?'S ure 10 > ma y be adopted. To the lower 

 extremity of each lever may be fixed a small bow or 

 brace of iron, at right angles to the lever, and se- 

 cured by a screw at D. Two cross shafts, one im 

 mediately above the other, may be fitted to slide 



ITie. 10. 



JQ, 



freely in the brace from tide to side. To each of 

 these a small friction wheel may be fitted* with a 

 groove in the rim, to lay hold upon the circumference 

 of each spiral. When the spirals revolve, the fric- t-I". 



i c i i ii CXXXV II. 



tion wheels, by the action of the hollow groove*, f 

 will be drawn laterally along them from F toward* 

 ; and when they have completed their course, they 

 may be drawn back by a weight or spring, when- 

 ever the groove in the friction wheel is removed from 

 the circumference of the spiral. The perpendicular 

 motion of the cloth frame will be very apparent in 

 the elevation, Fig. 2. ; for the action of the spiral 

 upon the lever L will produce it, by means of the 

 cords OO, passing over the pullies in the cross rail 

 N. If these cords are double, and joined in the 

 middle by the slip-knot used by weavers for the cor- 

 dage of looms, the frame may be tempered to re- 

 move any inaccuracy arising from stretching, with 

 great promptitude and facility. The horizontal mo- 

 tion may be given to the cloth frame by a direct con- 

 nection with the other spiral, as in the former machine. 

 This will perhaps be the most simple and effica- 

 cious mode of giving the traverse motion, where a 

 single row of perforators only is to be used ; but as 

 it may be desirable to increase the quantity of work 

 by using different rows of perforators at the same 

 time, and as no insurmountable objection presents it- 

 self against this amplification of principle, it may 

 now be proper to extend our views to the means of 

 augmenting the scope of the machine, premising that 

 the ratio of increment can never be so well ascertain- 

 ed or productive of actual benefit, as by practical 

 experience. If, in the first instance, we propose 

 to double the number of our perforators, so as 

 to work two rows of figures similar, but invert- 

 ed, we may adopt the machinery represented in 

 Figure 11, with rational hopes of complete suc- 

 cess. But here it will be evident, that from the very 

 nature of our object, we must abandon the plan of 

 giving the lateral or horizontal shift to the cloth, 

 and communicate it to the perforators, as they must 

 now work in inverted directions. It will also be ne- 

 cessary that the vertical needles, which secure the 

 loops in front, must move along with the perforators, 

 and that this must be done with great accuracy. In 

 this case, therefore, the vertical motion may still be 

 given to the cloth, but the lateral one must be com- 

 municated to the perforators. In Fig. 11. if a motion 

 is given to the frame AB, by the action of a spiral 

 traverse upon the lever A, the frame CD will ope- 

 rate constantly in an inverted direction, by means of 

 the pulley and band at G. The upper frame being 

 acted upon by the traverse, is kept pressing upon it 

 by the operation of the weight F, and the lower 

 frame works in constant opposition to it by that of 

 the minor weight E, which preserves the tension of 

 the connecting band at G. If four frames be want- 

 ed, the plan in Fig. 12. will effect it. The motion of Fig. 12. 

 the middle frames 2 and 3, is exactly as before, and 

 the motion is continued to the upper and lower irames 

 by the cross clasps at H and I. A profile of these 

 clasps is given in the small Figure 13. In using an ap- pig. Is. 

 paratus so extensive as this, it will be necessary to 

 devise means, either by hinges or otherwise, for 

 speedily removing and replacing the upper frames, 

 so that all may be accessible for the purposes of re- 

 pair or regulation, without loss of time. 



F>g- 



