IIMECHANICAL MOVEMENTS

Fig. 87. Bobbin case

Fig. 88. Bobbin case in position

Fig. 89. Bobbin in position in bobbin case—Method of threading

The bobbin case (Fig. 87), fixes to a stud in the centre of the hook. It is held in position, that is, kept from revolving with the hook, by means of a stop pin, Q, fitting between a holder. The tension is obtained by a spring, R, which is regulated by turning a small screw, S, to the right to tighten and to the left to loosen.Fig. 88shows the bobbin case in position, with the holder raised ready for taking it out of the machine.Fig. 89shows the bobbin in position in the bobbin case and methodof threading, andFig. 91, the direction the cotton should draw off the bobbin when it is in the machine. It will be noticed that the cotton pulls in the opposite direction to which the hook travels, as shown by an arrow inFig. 88. The bobbin case holder (Fig. 91), should prevent the bobbin case from revolving with the hook. As parts wear, the bobbin case is liable to slip past the holder, causing the cotton to be stranded and broken. When such isthe case the holder should be bent as shown by (Fig. 92), but it must not fit so tightly against the bobbin case as to cause the cotton to become trapped. The holder is held rigid by means of a catch and spring T (Fig. 88). Should the catch or holder become worn, fit new parts by driving out the pins U and V. Any sharpness or roughness on the forked part of the holder should be removed. Should the stop pin Q (Fig. 87) become loose, it should be soldered and well cleaned with an emery cloth. The centre tube of the bobbin case should also be kept quite firm. Should it become loose, place it over some hard substance, rivet it until tight, and thoroughly smooth with very fine emery cloth.

Fig. 90. Direction cotton should draw off

Figs. 91 and 92. Bobbin case holders

Fig. 93. Take-up spring

The take-up spring (Fig. 93) is attached to the face plate, and is shown in position inFig. 83. Replace a new one as follows: First take out the set screw W (Fig. 93), and remove the complete thread controller from the face plate. Then take out the screw and withdraw the old spring. Place the ring part of the new spring inthe recess between plate Y and back plate Z, and replace the screw X, being careful not to get the spring fastened under the screw head. This done, fix the spring and other parts on the face plate. A small barrel with a slot in it receives the coiled portion of the spring. See that the part of the spring that is turned in enters the slot in the barrel, then replace the screw W, but before tightening this screw, see that the hooked part of the spring A´ rests on the regulator B´, which determines the amount of action given to the take-up spring. By raising it, less action is given. The amount of pressure on the spring is regulated by adjusting the barrel in the face plate. Take off the face plate, loosen the screw C(Fig. 83), fix a screw-driver in the rear of the barrel (seen inside the face plate), turn it toward you for more pressure, and backward for less and tighten the set screw C.

Figs. 94, 95, 96. Presser foot with details

Presser feet are made solid for ordinary purposes, although alternating feet can be fitted when desired. Figs.94, 95, and 96show a pressure foot, collar, and spring. To fix this foot, remove the ordinary presser foot, turn the foot bar round by loosening the set screw, so that the groove made for the reception of the presser foot is directly behind the needle. Put on the collar (Fig. 95), then turn the foot (Fig. 94), and screw it in position. Next place the spring each side at the pointsD´(Fig. 94), press down the collar (Fig. 95), and secure it by its set screw. The springs will act on each half of the foot, and keep them firm, though the material be uneven. The foot is particularly useful when overseaming a hem or the top band of a lady's boot, etc. To time the hook and needle, raise the connection rod so as to produce no throw, and tighten the screw as inFig. 81. Then take off the needle plate and remove the slideE´(Fig. 81) under which will be seen a crank and screws.

Now turn the machine back as atFig. 88, lift up the bobbin case holder by pressing the catch T,and remove the bobbin case. Take off the hook guide cap by removing the two screws. Turn the hand wheel F (Fig. 81), toward you, until the needle bar has descended to its lowest point of travel, and loosen the crank screw farthest from you. Having done this, continue turning the hand wheel until the needle bar has risen. With the lowest mark level with the rocking frame casting, at this point, examine the hook, the point of which should be just up to the needle. If otherwise, loosen the other screw in the crank under the plateE´(Fig. 81). Be sure the needle bar mark is level with the rocking frame, place the hook with its point just up to the needle, and tighten the crank set screw, being careful to have no end play to the short shaft. Again examine the needle bar and hook and if in proper time finally secure crank set screws and replace the fittings previously removed. Thread the machine as indicated (Fig. 81). Set the needle as high in the bar as it will go, with the long groove facing the operator, and thread the needle from the long groove side. The stitch regulator will be found at F´ (Fig. 81). The raising of it will shorten and the lowering of it will lengthen the stitch. The feed should be set about one thirty-second of an inch above the needle plate when at its highestpoint. To raise the feed, turn the machine back as inFig. 88. Near to the partG(Fig. 88) will be found a large set screw. Loosen it and press the leverH(Fig. 88) upward raising the feed barJas high as required, and tighten the set screw atGfirmly. To remove the feed for cleaning and sharpening, take off the needle plate, under which will be seen two feed set screws. By unscrewing these, the feed can be lifted out.

One of the modern machines on the market is the Wheeler and Wilson, known as the Number 61, which is of rotary hook principle. The hook forms part of the under shaft, somewhat similar to that known as the D9 W and W. This hook and shaft revolves in two long bearings, and is held in position by a fluted wheel, which forms a collar at the right-hand end; thus when set properly no end play is permitted. This is an advantage over the boat-shaped shuttle machine. In the latter, the shuttle rocks about, becomes worn on the surface, often blunt pointed by striking the needle. As it wears, it becomes loose in the carrier, thus giving it freedom to roll away from or toward the needle, as well as making its action with relation to the needle very uncertain; and on account of the number of little loosenesses in fittings that this uncontrolled shuttleproduces, missed stitches are frequent, and difficult to remedy, unless a number of new fittings are obtained or old ones repaired.

If there is any alteration required in the time of the rotary hook referred to, it can be made to the smallest fractional part of an inch very quickly and easily, and the movement can be relied on. The shaft to which it is secured is positive in its action (no variable motion), and at every stitch will meet the needle at exactly the same spot. This is an improvement over the boat-shaped shuttle, which has to have a certain amount of play or slackness to allow the loop to extricate itself; and this slackness increases as the machine is worked, so that the shuttle action often becomes very erratic.

Sometimes a carrier becomes sprained at one end, thus allowing the shuttle too much freedom. If at the heel end, the carrier should be removed and placed in a vise (heel uppermost). The heel should be given a light blow with a hammer, thus bending it into correct position, but it must never be allowed to incline toward the shuttle; it should stand perfectly square, and have the upper corners rounded off. If inclined toward the shuttle, the loop may occasionally hang on the heel, and cause an irregular tension.

Fig. 97. Bobbin case holder

In some machines the bobbin case holder (Fig. 97) rests on the casting seen inFig. 81. It is secured by a large set screw, D (Fig. 97). For general use, this screw should be adjusted to allow number 40 cotton to pass freely over the bobbin case. The holder should not be removed, except when adjustment or repair is needed. The vertical portion is hinged to the base, and is kept upright by a lock spring and stud. If the spring is pressed from the stud, the vertical or ring part can be drawn back for placing in or taking out the bobbin case. The face of this portion must be perfectly square with the bottom of the base, otherwise it may cause considerable trouble. A slight adjustment can be made by loosening the two screws and moving the lock spring. A set square, E, should be used for testing the accuracy of this part as shown (Fig. 98), F representing the bobbin case holder.

Fig. 98. Set square

The thread controller is similar in design to several others, but its movement is regulated by a small lever (Fig. 99) which receives its motionfrom a link attached to the foot bar bracket set screw, and this may be seen through a hole in the face plate. At G (Fig. 99), this lever engages with a stop washer located behind the thread controller plate. The washer is recessed to form a stop, at the same time to give sufficient clearance for the action of the spring; thus as the foot bar rises and falls, so does the thread controller spring. It is a common practice when cleaning a machine to remove the face plate, thus detaching the link referred to, and not connecting it again when replacing the face plate. From this, trouble arises. The tension pulley should be placed on its stud, the large boss being toward the face plate.

Fig. 99. Lever

Thread a machine as follows: From the reel pin to nipper F (Fig. 81), round tension pulley G as the arrow indicates, down and into thread controller H up to take-up lever, threading over the roll and through the slot from the top of lever, then down the thread guide J, into guide K, and through the needle-eye from right to left.

In the ordinary boat-shaped shuttle, the looping up of the thread is not difficult. The needle, as it descends, enters an opening or cavity in the carrier, one side of which forms a support for the needleand guards it from contact with the shuttle point. Now, it is important that there be clearance for the needle. If the carrier stands so prominent as to spring the needle out of its true vertical line it will carry it away from the shuttle, and give the latter a chance to miss the loop.

Fig. 100 A, B, C, D. Carriers and drivers

Then there are carriers and drivers of varying heights. Those of the raised kind are preferable, if properly fitted. By "raised" is meant that they are higher, so as to form a better guard for the needle, as previously referred to (Fig. 100 A, in which E indicates the portion of raised carrier, F the shuttle point, and G the needle). But sometimes they are too high, and permit the needle-eye to be buried in the carrier, thus preventing the proper formation of the loop. This can be so bad as to cause very frequent missing; or it may be of such a slight character as to cause a miss-stitch only now and then. Occasionally, a needle bar has to be lowered, and that is sufficient to causethe same fault. The eye of the needle should always be about one thirty-second of an inch above the upper edge of the carrier, and the latter should be shaped so as to allow that amount of clearance the whole of the time the needle is rising to form the loop, until the shuttle point has well entered the same.Fig. 100 Bshows how a carrier is hollowed to give the necessary clearance to the needle eye.

Fig. 101. Sewing machine items

When a machine is reasonably tight in all parts, gauges and setting marks may be adhered to for the preliminary adjustments; and then if the machine works erratically, other adjustments must be made. Where no marks or gauges are furnishedfor the adjustment of the needle bar, it should be so set as to allow the shuttle or hook to enter the bold part of the loop formed from the needle. A good rule is to set the needle bar so that the needle-eye is about1⁄32inch below the point of the shuttle M (Fig. 100 C) when the latter is up to the centre of the needle groove. But this may have to be varied from1⁄64-inch to3⁄32-inch. In boat-shaped and similar shuttle machines, a good rule is to set the needle so that the eye N will pass just below the lower side of the shuttle O as the latter is passing through the loop as inFig. 100 D, P, indicating the level of the bed plate.

Whatis meant by this term is that these devices are intended for the transmission of motion. Motion in mechanics may be simple or compound. Simple motions are those of straight translation, which if of indefinite duration must be reciprocating, or what is called oscillating or helical.

Compound motions consist of combinations of any of the simple motions. Perpetual motion is an incessant motion conceived to be attainable by a machine supplying its own motive forces independently of any action from without, or which has within itself the means, when once set in motion, of continuing its motion perpetually, or until worn out, without any new application of external force. The machine by means of which it has been attempted, or supposed possible to produce such motion, is an invention much sought after, but physically impossible.

Fig. 102. Coffee mill and details

The illustrations herewith exhibit a number ofdevices of various kinds, well known to the practical mechanician and professional engineer, and usually called mechanical movements. It is estimated there are no less than 1,500 of these movements doing service at the present day; but many of them are, of course, quite complex, and difficult to master. In this book, I show about one hundred of the simplest sort, or those in common use. Their usefulness will at once be appreciated if we refer toFig. 102, which shows a machine for grinding or breaking up substances within its capacity. It contains within itself the true principle of the little mill used to grind coffee. The word "grind" in this connection is scarcely the right one, as the mill rather "crushes" or breaks up, than grinds. You will notice coffee, ready for use, is coarse and unlike flour in texture, the latter being "ground" fine and smooth. In grinding, the abrading surfaces are brought very much closer together than in the breaking or crushing processes. In a coffee mill, the berries or grains drop into a vacancy, left between the revolving cone and the walls of the mill. The vacancy between the walls and the cone is a little less at the bottom where the crushed coffee is discharged, and this enables the small and large grounds to fall into the drawer. The detailedplan in illustration (Fig. 102) shows a mill complete, as well as the various parts. It will be noticed that the cone (Fig.5), is corrugated or grooved as shown (Fig.4). Figs.6and7show sections of lining at B and C (Fig.3). A shows the hopper into which the coffee berries are placed before grinding. Figure9shows the crank detached, and Figs.8and10show the remaining parts of the machine, while Figs.1and2show the handle and drawer. The latter is to receive the ground or crushed coffee after it has gone through the mill. Further description is unnecessary if we take for example the movement represented atFig. 150, which is a sort of ball-bearing motion,only instead of small balls wheels are used. Besides being made use of in bicycles in small balls, it is used as depicted for "hanging" grindstones, and for many other similar purposes.

The device also shown atFig. 139, is one in common use. It is a modification of the sprocket wheel on the bicycle. Many of the devices shown herewith are rarely noticed because of our familiarity with them.

The action of pumps, the working of pistons, the changing of motion, and many other things are shown and explained in the little illustrations given in these descriptions, which do not pretend to be exhaustive, or even full.

Fig. 103. In this the lower pulley is movable. One end of the rope being fixed, the other has to move twice as fast as the weight, and a corresponding gain of power is consequently effected.

Fig. 104is a simple pulley used for lifting weights. In this the power must be equal to the weight to obtain equilibrium.

Fig. 105. Blocks and tackle. The power obtained by this contrivance is calculated as follows: Divide the weight by double the number of pulleys in the lower block; the quotient is the power required to balance the weight.

Fig. 106represents what are known as "White's pulleys", which can be made with separate loose pulley; or a series of grooves can be cut in a solid block, the diameters being made in proportion to the speed of the rope; that is, 1, 3, and 5 for one block, and 2, 4, and 6 for the other. Power as 1 to 7.

Figs. 103, 104, 105, 106, 107. Various phases of block and tackle

Figs.107-108are what are known as Spanish bartons.

Fig. 108is a combination of two fixed and one movable pulley.

Figs.111-113are different arrangements of pulleys. The following rule applies to these: In a system of pulleys where each is embraced by a cord attached to one end of a fixed point, and at the other to the centre of the movable pulley, the effect of the whole will be the number 2 multiplied by itself as many times as there are movable pulleys in the system.

Figs. 108, 109, 110, 111, 112. Other combinations of blocks and pulleys

Fig. 114. Endless chain for maintaining power on going barrel, to keep a clock going while winding,as during that operation the action of the weight or mainspring is taken off the barrel. The wheel to the right is the going wheel, and that to the left the striking wheel. P is a pulley fixed to the great wheel of the going part, and roughened to prevent a rope or chain hung over it from slipping. A similar pulley rides on another arbour,p, which may be the arbour of the great wheel of the striking part, attached by a ratchet and click to that wheel, or to the clock frame if there is no striking part. The weights are hung as may be seen, the small one being only large enough to keep the rope or chain on the pulleys. If the partbof the rope or chain is pulled down, the ratchet-pulley runs under the click, and the great weight is pulled up byc, without taking its pressure off the going wheel at all.

Fig. 115. Triangular eccentric, giving an intermittent reciprocating rectilinear motion, often used for the valve motion of steam-engines.

Fig. 116. Ordinary crank-motion.

Figs. 113, 114, 115. Blocks and rocker

Fig. 117. In this, rotary motion is imparted to the wheel by the rotation of the screw, or rectilinear motion of the slide by the rotation of the wheel. Used in screw cutting and slide lathes.

Figs. 116, 117. Crank and rotary motion

Fig. 118. Uniform circular into uniform rectilinear motion; used in spooling frames for leading or guiding the thread on to the spools. The roller is divided into two parts, each having a fine screw-thread cut upon it, one a right and the other a left-handed screw. The spindle, parallel with the roller, has arms which carry two half nuts, fitting to thescrew, one over the other under the roller. When one half nut is in, the other is out of gear. By pressing the lever to the right or left the rod is made to traverse in either direction.

Fig. 119. A system of crossed levers, termed "lazy tongs." A short, alternating rectilinear motion of rod at the right will give a similar, but much greater motion to the rod at the left. It is frequently used in children's toys. It has been applied to machines for raising sunken vessels; also applied to ship pumps three quarters of a century ago.

Figs. 118, 119. Rectilinear motion

Fig. 120. Centrifugal governor for steam engines. The central spindle and attached arms and balls are driven from the engine by the bevel gears at the top, and the balls fly out from the centre by centrifugal force. If the speed of the engine increases, the balls fly out from the centre, raise the slide at the bottom, and thereby reduce the openingof the regulating valve, which is connected with the slide. A diminution of speed produces an opposite effect.

Fig. 121. Water-wheel governor acting on the same principle asFig. 120, but by different means. The governor is driven by the top horizontal shaft and bevel gears, and the lower gears control the rise and fall of the shuttle or gate over or through which the water flows to the wheel. The action is as follows: The two bevel gears on the lower part of the centre spindle, which are furnished with studs, are fitted loosely to the spindle, and remain at rest so long as the governor has a proper velocity; but immediately the velocity increases, the balls flying farther out, draw up the pin, which is attached to a loose sleeve which slides up and down the spindle, and this pin, coming in contact with the stud on the upper bevel gear, causes that gear to rotate with the spindle, and to give motion to the lower horizontal shaft in such a direction as to make it raise the shuttle or gate, and so reduce the quantity of water passing to the wheel. On the contrary, if the speed of the governor decreases below that required, the pin falls and gives motion to the lower bevel gear, which drives the horizontal shaft in the opposite direction, and produces a contrary effect.

Fig. 122. Another arrangement for a water-wheel governor. In this the governor controls the shuttle or gate by means of the cranked lever, which acts on the strap or belt in the following manner: The belt runs on one of three pulleys, the middle one of which is loose on the governor spindle, and the upper and lower ones fast. When the governor is running at the proper speed the belt is on the loose pulley, as shown; but when the speed increases, the belt is thrown on the lower pulley, and thereby caused to act upon suitable gearing for raising the gate or shuttle and decreasing the supply of water. A reduction of the speed of the governor brings the belt on the upper pulley, which acts upon the gearing for producing an opposite effect on the shuttle or gate.

Fig. 123. Another form of steam-engine governor. Instead of the arms being connected with a slide working on a spindle, they cross each other, are elongated upward beyond the top, and connected with the valve-rod by two short links.

Figs. 124, 125. Diagonal catch and hand-gear used in large blowing and pumping engines. InFig. 124the lower steam valve and upper eduction valves are open, while the upper steam valve and lower eduction valve are shut; consequently thepiston is ascending. In the ascent of the piston rod the lower handle will be struck by the projecting tappet, and being raised will become engaged by the catch, so as to shut the upper eduction and lower steam valves; at the same time the upper handle will be disengaged from the catch, the back weight will pull the handle up and open the upper steam and lower eduction valves, when the piston will consequently descend.Fig. 125represents the position of the catches and handles when the piston is at the top of the cylinder. In going down, the tappet of the piston rod strikes the upper handle, and throws the catches and handles to the position shown inFig. 124.

Figs. 120, 121, 122, 123. Governors for steam-engines

Fig. 126. A mode of driving a pair of feed rolls, the opposite surface of which require to move in the same direction. The two wheels are precisely similar, and both gear into the endless screw,which is arranged between them. The teeth of one wheel only are visible, those of the other being on the back or side which is concealed from view.

Figs. 124, 125, 126. Valve Regulation and Feed Rolls

Fig. 127. Link-motion valve gear of a locomotive; two eccentrics are used for one valve, one for the forward and the other for the backward movement of the engine. The extremities of the eccentric rods are jointed to a curved slotted bar, or, as it is termed, a link, which can be raised or lowered by an arrangement of levers terminating in a handle, as shown. In the slot of the link is a slide and pin connected with an arrangement of levers terminating in the valve stem. The link, in moving with the action of the eccentrics, carries with it the slide, and thence motion is communicated to the valve. Suppose the link raised so that the slide is in the middle, then the link will oscillate on the pin of the slide, and consequently the valve will be at rest. If the link is moved so that the slide is at one ofthe extremities, the whole throw of the eccentric connected with that extremity will be given to it, the valve and steam ports will be opened to the full, and it will only be toward the end of the stroke that they will be totally shut; consequently the steam will have been admitted to the cylinder during almost the entire length of each stroke. But if the slide is between the middle and the extremity of the slot, as shown in the figure, it receives only a part of the throw of the eccentric and the steam ports will only be partially opened, and quickly closed again, so that the admission of steam ceases some time before the termination of the stroke, and the steam is worked expansively. The nearer the slide is to the middle of the slot the greater will be the expansion, and vice versa.

Figs. 127, 128. Link and other motions

Fig. 128represents a mode of obtaining motion from rolling contact. The teeth are for making the motion continuous, or it would cease at thepoint of contact shown in the figure. The fork catch is to guide the teeth into proper contact.

Fig. 129. What is called the Geneva-stop, used in Swiss watches to limit the number of revolutions in winding-up; the convex curved part of the wheel serving as the stop.

Fig. 130. A continuous rotary motion of the large wheel gives an intermittent rotary motion to the pinion-shaft. The part of the pinion shown next the wheel is cut of the same curve as the plain portion of the circumference of the wheel, and therefore serves as a lock while the wheel makes a part of a revolution, and until the pin upon the wheel strikes the guide-piece upon the pinion, when the pinion-shaft commences another revolution.

Figs. 129, 130. Stop and rotary motions

Fig. 131. The two crank-shafts are parallel in direction, but not in line with each other. The revolution of either will communicate motion to the other with a varying velocity, for the wrist of onecrank working in the slot of the other is continually changing its distance from the shaft of the latter.

Figs. 131, 132, 133. Irregular Motions

Figs.132and133. These are parts of the same movement, which has been used for giving the roller motion in wool-combing machines. The roller to which the wheel F, (Fig. 132) is secured, is required to make1⁄3revolution backward, then2⁄3revolution forward, when it must stop until another length of combed fibre is ready for delivery. This is accomplished by the grooved heart-cam C, D, B, e, (Fig. 133) the stud working in the said groove; from C to D it moves the roller backward, and from D to e it moves it forward, the motion being transmitted through the catch G, to the notch wheel F, on the roller-shaft H. When the stud A arrives at the point e in the cam, a projection at the back of the wheel, which carries the cam, strikes the projecting piece on the catch G, and raises it out of the notch in the wheel F, so that while the stud istravelling in the cam from e to C, the catch is passing over the plain surface between the two notches in the wheel F, without imparting any motion; but when stud A arrives at the part C, the catch has dropped in another notch and is again ready to move wheel F and roller as required.

Fig. 134. An arrangement for obtaining variable circular motion. The sectors are arranged on different planes, and the relative velocity changes according to the respective diameters of the sectors.

Fig. 135. Intermittent circular motion of the ratchet-wheel from vibratory motion of the arm carrying a pawl.

Figs. 135, 134, 137, 136. Movements of various kinds

Fig. 136. This represents an expanding pulley. On turning piniondto the right or left, a similar motion is imparted to wheelc, by means of curved slots cut therein, which thrust the studs fastened to arms of pulley outward or inward, thus augmenting or diminishing the size of the pulley.

Fig. 137represents a chain and chain pulley. The links being in different planes, spaces are left between them for the teeth of the pulley to enter.

Fig. 138. Another kind of chain and pulley.

Fig. 139. Another variety.

Fig. 140shows two different kinds of stops for a lantern-wheel.

Figs. 140, 138, 139. Chain pulleys and lantern-wheel

Fig. 141. Intermittent circular motion is imparted to the toothed wheel by vibrating the arm B. When the arm B is lifted, the pawl C is raised from between the teeth of the wheel, and travelling backward over the circumference again drops between two teeth on lowering the arm, and draws with it the wheel.

Fig. 142. The oscillating of the tappet-arm produces an intermittent rotary motion of the ratchet-wheel. The small spring at the bottom of the tappet-arm keeps the tappet in the position shown in the drawing, as the arm rises, yet allows it to pass the teeth on the return motion.

Fig. 143. A nearly continuous circular motion is imparted to the ratchet-wheel on vibrating the leverato which the two pawlsbandcare attached.

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