Modern Machine-Shop Practice Part 215

Now suppose that lever _u_ is moved to the right, and the belt would be moved from the loose pulley _q"_ to the fast pulley _q_, while the other belt would merely be moved or s.h.i.+fted from one to the other side of loose pulley _q'_.

Similarly if lever _u_, be moved to the left, the belt on the loose pulley _q'_ will be moved on to the fast pulley _q_, and the belt on pulley _q"_ would simply be moved across the face of the pulley, and as the countershaft pulleys for the two pulleys are of different diameters, therefore two rates of motion are obtained.

The shaft _v_, on which pulley _q_ is fast, drives the pinion _l_, which drives _m_, the latter gearing with the rack beneath the carriage.

The carriage is guided by the wheels _z_, which are secured to it, and run on the iron guideways _z'_, the f.l.a.n.g.es of the wheels preventing side play, and causing the carriage traverse to be in a straight line.

WOOD-PLANING MACHINES.

[Ill.u.s.tration: Fig. 3152.]

The simplest form of planing machine for wood work, is the hand planer or buzz planer, as it is termed, an example of this cla.s.s of machine being shown in Fig. 3152, which has been designed and constructed by George Richards, for the use of pattern-makers.

It consists of a frame carrying a revolving shaft, which is by some called the _cutter head_, and by others the cutter bar, and to which the cutters or knives are attached.

The work is rested upon the work table, or else pressed against a guide or _fence_, and fed by hand over the revolving knives, whose cutting edges protrude above the surface of the table, to the amount of the depth of cut it is intended to take.

[Ill.u.s.tration: Fig. 3153.]

In this example, however, the table is made in two sections, the front one of which is below the cutter edges to an amount equal to the depth of the cut, and the back one level with the cutter edge, when the latter is at its highest point in its path of revolution, the construction being shown in Fig. 3153, in which J, J, represents the top part of the main frame of the machine, C the cutter head, B the front or feed table, A the back or delivery table, and W a piece of work being fed in the direction of the arrow.

Upon the upper surface of the frame J, J, and on the feed side of the cutter head is the carriage G, to which are pivoted two links L, L, which support the feed table B. At D is a hand wheel whose screw has journal bearing in a lug from the table, while the screw threads into a nut provided in the carriage. Obviously then by operating the hand wheel D, carriage G is moved along the top of the frame J, and the height of table B is adjusted. Thus if the carriage G is traversed to the left, the link L would fall more nearly to a horizontal position, and table B would lower. Or if G were moved to the right, links L would stand more nearly vertical, and table B would be raised, it being understood that table B is not permitted to move endways. Similarly by means of hand wheel C, carriage H may be moved to adjust the height of table A.

By this construction, the work can bed fairly on the delivery side, as well as on the feeding side of the cutter head, which is not the case when a single table is used.

It is obvious that the work must be fed in opposition to the pressure of the cut, which endeavors to push the work back from the cutter, and this limits the size of work that the machine can operate upon.

[Ill.u.s.tration: Fig. 3154.]

The work can be fed easier however, with a cutter skewed or set out of line with the axis of the cutter head. Thus in Fig. 3154, is the common form of cutter head, carrying two knives placed diametrally opposite, so that the weight of one counterbalances that of the other, and the head will therefore run steadily and smoothly. The knives K, K' are here set parallel with the axis of the cutter head, hence the whole length of the cutting edge meets the work at the same instant, and a certain amount of time must pa.s.s after one cutting edge has left the work before the other cutter edge meets it.

[Ill.u.s.tration: Fig. 3155.]

This is remedied by the construction of cutter head shown in Fig. 3155, in which three cutters are used, and each cutter is set askew, or out of parallel with the axis of cutter head, so that the knife begins to cut at one end, and the cutting action gradually extends to the other, hence the cutting action is more continuous and uniform, and better work is produced, while less power is required to drive and feed the machine.

[Ill.u.s.tration: Fig. 3156.]

Fig. 3156 shows a cutter head with two skew cutters.

The cutter head is provided with a cover or guard, which is arranged as follows: In the table is cut a groove or slideway, in which a slide fits, and to this is attached a thin sheet-iron guard. To the slide is attached a weight, which draws the guard back to the fence after the work has pa.s.sed over the cutter head. By this means the guard covers all the knife edge that protrudes beyond the work, no matter what the width or thickness of the work may be; the guard can however be fixed in position when a number of pieces of the same size are to be planed.

The fence provides a guide surface for the work, and its face may be set at any required angle to the surface of the work table. Suppose, for example, that the sides or edges of a piece of work require to be at an angle of 100 degrees to the top and bottom surfaces, then the top surface may be planed first, and the fence being set at an angle of too degrees to the table surface, the top of the work may be pressed to the surface of the fence while fed across the cutter, and as a result, the side or edge will be planed at 100 degrees to the top.

ROLL FEED WOOD PLANING MACHINE.

[Ill.u.s.tration: Fig. 3157.]

Fig. 3157 represents a roll feed wood planing machine, designed and constructed by George Richards & Co., of Broadheath, near Manchester, England, the construction being more fully shown in the detailed figures following. The machine consists essentially of a framework, carrying a cutter head with two knives, and having a pair of feed rolls, in front and a pair behind it. The front pair feed the timber to the cutter head and the back pair deliver it from the cutter head.

[Ill.u.s.tration: Figs. 3158, 3159.]

Each pair of rolls is geared together, so that both the top and bottom rolls act to give a positive feed. Immediately in front of the cutter head and between it and the feed rolls (_i. e._ the front pair of rolls), is a pressure bar extending across the full width of the machine, and having at its lower extremity a steel spring which presses the work down to the table, and thus causes it to be planed of an equal thickness throughout its length. Immediately behind the cutter head and between it and the delivery rolls (_i. e._ the back pair of rolls), is a pressure bar that also extends across the machine and prevents the timber from rising up from the table after it has pa.s.sed the cutters, all timber being found to have a tendency to rise after having been acted upon by the cutters. The arrangement of the feed rolls, delivery rolls and pressure bars is shown in Fig. 3158, in which T, T, T, represents three sections of the work table and W, W, a piece of work pa.s.sing through the machine in the direction of the arrow. Feed roller F is fluted to increase its grip upon the work and insure a positive feed.

The lower feed roller F', and the lower delivery roller D', are fixed in position, their upper surface projecting above the work table to about 1/100 inch. This is necessary to take the thrust of the upper rolls (F, D) and prevent them from forcing the work down upon the surface of the table with an undue amount of pressure, which would induce friction and consume an unnecessary amount of power in driving the rolls. The method of adjusting the lower rolls will be explained presently.

Between the cutter head C and the feed roll F is the pressure bar P, and behind the cutter head is the pressure bar B, both these bars being more clearly seen in Fig. 3159, in which the work W is shown entering the machine, and the lower rolls and work table are removed.

Pressure bar P has at its lower end a steel spring J, Fig. 3159, and is supported at each end by circular links Y, projecting into grooves provided in the main frame of the machine, as shown in Figs. 3160 and 3161, in which C is the cutter spindle, Y the circular link at the end of pressure bar P, and _y_ the circular link at the end of pressure bar B, the two fitting into the one stepped groove.

[Ill.u.s.tration: Fig. 3160.]

[Ill.u.s.tration: Fig. 3161.]

This groove is concentric with the cutter spindle C, so that the pressure bars keep at a positive or equal distance from the edges of the cutter, no matter what the thickness of the work or the depth of the cut may be.

[Ill.u.s.tration: Fig. 3162.]

In Fig. 3162, the work is shown pa.s.sing beneath the two upper rollers, and the spring J (which extends the whole length of the pressure bar), is depressed from the weight of the bar. By this construction, the work is pressed to the table at a point as close as possible to the cutters.

The pressure bar P cannot drop beyond a certain point, because of its tail piece _y'_, Fig. 3160, which rests on the top of the frame at _y"_ when the bar P has fallen to its required limit.

The feed pressure bar P is bolted to its circular links, as shown in Fig. 3162, in which Y is a part of the circular link which is bolted to the pressure bar P.

The delivery pressure bar B (Fig. 3160) is riveted to and forms part of its links _y_. It acts through the medium of spiral springs _s_, which are carried in cases or boxes _s'_, which overhang the end of the bar B.

A set screw _s"_ regulates the pressure of the spring, and a screw _a_ (Fig. 3162) regulates the height of the pressure bar.

The adjustments of the feed and delivery rollers are made as follows:

The feed pressure is obtained through the medium of weights, shown at W, W', in Fig. 3163, upon the bars A, A', whose ends are pivoted to the lower ends of links _m_, _n_, the upper ends of which are pivoted to the side frame of the machine.

Bar A engages or rests at _e_, on a lug or projection on the link I, which fits in a recess provided in the side of the frame. This link I, extends up and has a bearing to receive the feed roller (F, Fig. 3160), whose driving gear is shown at O.

It is obvious therefore, that the amount of pressure on the feed roller F may be varied by moving the weight W along the bar A.

Similarly for the delivery pressure roller, the weight W' is adjustable along the bar A', which is pivoted to link _n_, and rests upon I at _e'_. The link I' is guided in ways in the side frame of the machine, and at its upper end carries the delivery roller D, whose driving gear is shown at O' (Fig. 3163).

It is obvious that there are bars A, A', and links I, I', on both sides of the machine, so as to adjust the feed rollers at both ends.

The work table and the two lower rollers are adjusted for different thicknesses of work as follows:

Between the two main side frames M and M', Fig. 3164, are two frames having corresponding inclines or slideways, of which the upper carries the work table and the lower rolls.

[Ill.u.s.tration: Fig. 3163.]

The lower incline sits on ways K, K, Fig. 3164, cast on the side frame, and is capable of being moved endwise by means of the hand wheel R, Figs. 3163 and 3164, which operates a screw threaded into the lower incline. When the lower incline is moved endways, the upper one, which carries the work table, is moved vertically, and as the lower feed rolls are carried by the upper incline, and the upper rolls are guided to move vertically only, the lower rolls maintain their position beneath the upper ones, or in other words, the table and lower rolls move together in a vertical direction only, when the lower incline is operated.

The lower rollers run in bearings formed in the links Q, Q, Fig. 3160, which are pivoted at their other ends to the upper incline. On the sides of the incline are lugs through which pa.s.s adjustment screws _z_, which by operating beneath the outer ends of the links Q, Q, adjust the heights, bearings of the lower rollers so that the uppermost point on the circ.u.mference stands about 1/100 inch above the level of the work table surface.

The upper surface of the lower incline is shown by the dotted line _f_, _f_, _f_, in Fig. 3163.