By the other method, which is known as " trepanning," the holes for the reception of the bunches are bored not quite through the stock, and these are crossed by other holes bored transversely through the sides ; the bristles, being then inserted, are secured by wires put through the transverse holes. These last are then stopped up with plugs of the same material as the stock (which is also the back), so that they are invisible, and the brush looks to be made of one solid piece.
Pe Woodbury Machine.—Quite a revolution in the manufacture of some kinds of " compound " brushes was caused by the invention of the Woodbury brush machine, whose object is to produce a brush having its bunches of bristles firmly bound and securely held in the back, without the use of any cement or independent fastening beyond that employed in binding the bunches together, the back remaining in one solid piece. The backs, which are introduced to the machine ready made, are prepared in the following way :—The position of the holes is marked by punching with a simple machine and the back is then placed in the boring machine, which consists of a two-spurred bit of suit able size, made to revolve very rapidly and which drills the holes as fast as the back can be adjusted, the process being facilitated by a hooked arm whose bent end inserted in a punch mark draws the back just far enough forward to bring it in position under the bit, to have the succeeding aperture made. One. such machine easily bores 50,000 to 60,000 holes per day. A (Fig.
395) represents a portion of the back of a brush, furnished with the usual holes a for the reoeption of the bristles. These are collected into suitable quantities so as to form, when doubled or bent over as usual in the manufac ture of other brushes, bunches B of a size to fit the holes a. A wire b is then passed through the loop formed by the doubling of the bristles, and is afterwards bent spirally around the bunch B, so as to bind it and form screw-threads on it, in order that when the bunch of bristles is screwed into one of the holes a, the wire b will secure the bunch of bristles in the back by forming corresponding female threads in the hole, or by fitting into similar threads previously made there.
The two ends of the wire are either carried around the bristles separately from each other so as to form double screw-threads, or are carried around it side by side. The ends of the wire b serve, upon any tendency to unscrew the bunch, to prevent the backward motion of the bristles, and thus retain them in place, by reason of their (the wires') abrupt termination, or by their being formed so as to ensure engagement with the sides of the hole.
396.
The figures representing the machine are :—Fig. 396, front elevation ; Fig. 397, partially sec tional side elevation ; Fig. 398, sectional plan mainly on line z z on Fig. 397 ; Fig. 399, section of device used in connection with a treadle§ for stopping and starting the machine without arrest ing the motion of the driving pulley ; Fig. 400, elevation as seen from rear of principal mechanism and devices for inserting bristles ; Fig. 401, enlarged section of doubling.and outer plungers and certain attachments working in concert with them ; Fig. 402, view of brush-back oentring mecha nism detached ; Figs. 403, 404, and 405 show respectively enlarged plan of wiring apparatus, elevation of lower portion of doubling plunger, and sectional view of internally threaded screw-nut or mouth-piece at the lower end of the hollow or outer plunger. C is the main frame of the machine, Parrying at its top a main horizontal driving shaft D, which receives its motion from a driving pulley E fitted loose on the shaft. The hub c of this pulley is notched at d (Fig. 399), and works against a disc F which is fast on the shaft D. Pivoted to this disc is a double-armed pawl e, which engages
with and disengages from the notched hub c by a spring f on the face of the disc when pressure is removed from the back of the upper arm of the pawl e, which is done by working a crank lever g by the application of the operator's foot to a treadle connected by a rod h with the lever. On releasing pressure from the treadle, a spring contrivance throws up the treadle, and bears the lever g against the upper arm of the pawl e, till arrested by a stop k on the disc. The pawl is thus thrown and held out of gear with the notched hub c, and the machine is stopped without arresting the motion of the driving pulley. This arrangement forms a very simple, smooth, quiok and efficient stopping and starting device. CI is a secondary shaft arranged vertically within the machine and deriving its motion from the main shaft D by bevel gear 1 (Fig. 397). The shaft serves to work the devices by which the bristles are fed to the plungers that effect their doubling, tbeir binding by the wire, and the introduotion of the bunch into the brush.baek, as well as the devices by which the wire is fed to and through the bristles after doubling, and the mechanism for centring the brush-back under the bunch-inserting devices. These last are worked by the main shaft D ; H is a bed on vvhich the brush-back A lies. This bed is adjustable up and down by means of a slide working in a guide frame a,nd operated by a screw m to set the brush-back to its work, the guide frame also being adjustable laterally in a curvilinear direction by a slot or groove a, (Fig. 396), to give the bed various angular positions to suit backs of different shapes. J is a, horizontal c,omb arranged over an upper table K, which is situated some distance above the bed or table H, but a little to one side or in the rear of it. This comb, whose teeth face the front of the machine, has an intermittent travel in the direction of the arrow (Fig. 398), a tooth or space between two teeth at a time, when feeding the bristles to the bunch-forming and inserting. devices. The bristles o, represented by lines and dots in the figures, are placed within the teeth of the comb, so that they stand in an upright position, projecting for about half their height or length above the comb, and resting at their lower ends on the table K. Each intermittent movement of the comb, which is effected by ft weight p and cord q passing over pulleys, causes a space between two contiguous teeth in the c,omb to be brouzht onnosite a, twisted receiver or gauge L (Fig. 401), into and down tbrough which the bristles in the comb space are passed, by the action of a cross intermittently reciprocating saw or feeder M (Fig. 397). This saw feeder has its motion communicated to it in one direction by a toe cam r (Fig. 398) on the shaft C, working against a roller carried by a rod or arm s, which is guided in its course by travelling along a fixed slot t ; and in the reverse direction is worked by a spring u pulling on the arm s. Each forward motion of the saw feeder projects a certain quantity of the bristles in the comb space facing the spiral receiver L into the receiver, the discharge being aided by a crowding fork N (Fig. 397) operating on the bristles on either side of the receiver, through whose sides they project. This crowding fork receives a reciprocating motion for the performance of its work from a cam v on the shaft C, and a spring w ; also an up and down motion, at the end of its back stroke and when starting forward, by an incline x on the rear sliding portion of tho fork stem, working through a slotted guide and a spring y, which latter also serves to hold the fork down during the remainder of its travel.