US2725084A - Wood-planing machine with angularly disposed cutterheads - Google Patents

Description

Nov. 29, 1955 L. B. CARLSON WOOD-PLANING MACHINE WITH ANGULARLY DISPOSED CUTTERHEADS Filed Nov. 12, 1954 6 Sheets-Sheet 1 Invenioah Zeuw's B. CaflZsow,

Nov. 29, 1955 L. B. CARLSON WOOD-PLANING MACHINE WITH ANGULARLY DISPOSED CUTTERHEADS 6 Sheets-Sheet 2 Filed NOV. 12, 1954 Lewis B. CarZsoaw,

M F W =5 I lg 33 Nov. 29, 1955 L. B. CARLSON 2,725,084

WOOD-PLANING MACHINE WITH ANGULARLY DISPOSED CUTTERHEADS Filed Nov. 12, 1954 6 Sheets-Sheet 3 12204922202 leazzls B 0112 80032 Nov. 29, 1955 L. B. CARLSON WOOD-PLANING MACHINE WITH ANGULARLY DISPOSED CUTTERHEADS 6 Sheets-Sheet 5 Filed Nov. 12, 1954 Lewis .B 0022 80081,

Nov. 29, 1955 B. CARLSON 2,725,084

WOOD-PLANING MACHINE WITH ANGULARLY DISPOSED CUTTERHEADS Filed Nov. 12, 1954 6 Sheets-Sheet 6 lawezzior Lewis B. CaHZsow, by 6:07, M; mm, 142, +40% 1 24 ,350

United States Patent WOOD-PLANING MACHINE WlTH ANGULARLY DISPOSED CUTTERHEADS Lewis B. Carlson, Milton, Mass, assignor to S. A. Woods Machine Company, Boston, Mass, a corporation of Massachusetts Application November 12, 1954, Serial No. 468,347 7 lairns. (Cl. 144-116) This invention relates to wood planing machines of the type in which rotary knife-carrying heads operate on rough boards which are advanced transversely thereto. When such a machine operates on one or both of the wide faces of the board only, it is commonly referred to as a surfacer and there are top surfacers, bottom surfacers and double surfacers. While the word planer may. have a generic significance it is usually used specifically to apply to a machine in which both faces of the board are planed and which also embodies sideheads for operating on the edges of the board. When such sideheads cut a tongue on one edge and a groove on the other, the machine is specifically termed a matcher. In any case additional heads, whether horizontal or vertical, may be also provided to make a hogging out before the final planing cut, and a planer frequently has attached thereto a profiler, so-called, to give a contour to the work as it emerges from the planing heads proper. In the accompanying drawings a planer in the specific sense of that Word is illustrated and the description will correspond, but the application of the invention is not limited to this specific type of machine.

characteristically, in these planing machines rough boards are forwarded along a lateral guide or fence by feed rolls, past the cutting heads, one following another. Feeding-out rolls are provided beyond the cutting heads. When the boards are long, as is the usual case in soft woods, they will span the space between the heads so that a board will be engaged by the feeding-out rolls before leaving the feeding-in rolls. In the case of short pieces, one board pushes the one ahead. The practice is to so operate the machine that the boards of whatever length are not only in end-to-end succession, but in end abutting relation, this being partly from the desire to avoid clipping as hereinafter referred to. Thus the boards are fed to the feeding-in rolls, for instance, by a feed table tending to feed them somewhat faster than feed rolls do, so that the ends are abutted and, to a certain extent, interlocked one with another to prevent the ends moving out of the common plane.

The object of the invention is to provide a new organization of such a machine which will facilitate its work, in particular avoiding difiiculties which arise with the usual planer because of insufficient control of the position of the board being operated on, particularly at the ends thereof, with effects known as clipping, disfiguring the end, and requiring that a portion of the board be cut off and discarded.

The cause of this clipping effect may be explained as follows. The stream of boards is forwarded, in endabutting relation, past the cutterheads along a horizontal supporting surface or bed, and various hold-down means are provided for keeping the boards flaton this bed. In particular, at the intake side of the top cutterhead this takes the form of a chipbreaker shoe which is mounted for vertical movement to accommodate varying thicknesses of the boards. The edge of the shoe extends parallel to the axis of the cutterhead and its rearward face is usually contoured to approximate the cutting circle in order to maintain control of the board as long as possible. However, there is an interval where the trailing edge of the forward board and the leading edge of the succeeding board pass out from under the chipbreaker shoe but have not arrived at the knives of the cutterhead. If the board Patented Nov. 29, 1955 is somewhat crooked or has been distorted by the latter hold-down means of the machine sothat it is under considerable strain, the trailing edge of the forward board may spring upwardly or the leading edge of the succeeding board may similarly move upwardly and the cutterhead will cut diagonally to the face of the board, making a taper or bevel at that end. This is known as clipping and, since boards are cut in standard lengths of feet a considerable portion of the board may be wasted when it is trimmed off to a shorter length. The end-lock provided by the forcible butting together of the ends of the boards resists the movement upwardly of one or both of the ends but, while doubtless improving the situation as regards clipping, is not effective to prevent it entirely.

To one casually examining the drawings which accompany this application, it will appear that a salient feature of the machine shown is the disposition of the horizontal cutterhead at an angle to the liner feed of the machine, and indeed with proper correlation with other features this provides for the improved results to be obtained.

- It would be misleading and incorrect, however, to suggest that the invention consists solely in such a disposition of the top head or cylinder. It is the fact that h skew cut or draw cut across the board is effected, but this is not claimed as novel in itself. Joiners hand planes with the throat and the edge of the plane iron disposed diagonally to the length of the sole, have long been known and are termed skew planes. It would be natural then, when a planing mechanism with a rotary cutterhead was introduced, to suggest that the knives might be similarly placed on the skew relative to the direction of motion relative to the work. The only commercial application of this of which I know was the provision, seventy-five years or more ago, of machines for taking a light finishing cut on previously assembled door frames. These machines had a work table over which single door frames were advanced by hand, above which table was a rotary cutterhead placed at an angle. The door frames, of course, were not assembled from rough lumber but from finished lumber, and this cut was a final smoothing operation after the rails and stiles had been assembled. It is clear that if we have an assembled door and plane it along the length of the vertical stiles we are working with the grain in the customary preferred manner of planing. As the end of our door finally passes out from under the head however, it encounters the rail, the grain of which extends transversely to that of the stiles. Therefore the cutterhead knife, if parallel to the grain in the rail, is likely to knock off the trailing edge. The'diagonal disposition of the cutterhead, Whether or not an advantage in planing the stiles, distributed the splitting strain on the rails to make such damage less likely. I believe that these machines are obsolete, the corresponding operation now being performed by sanding machines. I believe, furthermore, that the diagonal disposition of the head has not hitherto found any application in planers in which the cuts were along the grain of successive boards, the trailing end of each being engaged by a succeeding one.

In present day planers the speeds of feed are very great, being specified in hundreds of feet per minute. The heads also rotate at very high speeds and the aggregate relative speed of the work and the knife is great. In general this is an advantage in cutting, but the out has to go where the parts are moving and, as explained, this causes difiiculty at the ends of the boards which is minimized by the present construction.

With this introduction I may proceed to the detailed description of the illustrative embodiment of my invention, shown by way of example in the accompanying drawings whereir1 Figure 1 is a simplified and diagrammatic plan, of the type known to manufacturers as a floor plan or foundation plan, intended merely to give an overall view of the principal elements of the machine within the restricted scope of a patent drawing;

Fig. ,2 is a corresponding side elevation;

Fig. 3 is a fragmentary longitudinal section in a vertical plane showing the top and bottom cutterheads and mechanism cooperating more directly therewith;

Fig. 4'is a corresponding plan view;

Fig. 5 is a transverse section as seen from the right of Figs. 3 and 4. The reader is looking in the direction of feed at the rear side of the chipbreaker which precedes the top head;

Figure 6 is a side elevation of that chipbreaker and its mounting as seen from the front side, so-called, the left side as one looks forward in the direction of feed;

Fig. 7 is a corresponding fragmentary plan;

Fig. 8 is a vertical section of the chipbreaker showing its construction and mounting at the other, or guide side;

Fig. 9 is a corresponding fragmentary plan; and

Fig. 10 is a diagrammatic section and Fig. 11 is a diagrammatic plan to aid in the description of certain features of operation.

All figures have been simplified by omitting or breaking away various parts which would appear in a complete machine, including details of mounting and drive, shavings disposal and so on which would be well understood by one skilled in the art and the illustration of which would only complicate the drawings and obscure the important features of construction and correlation.

The travel of the stock is from right to left in the figures and unless the context otherwise indicates forward means in the direction of travel, rearward means toward the feeding-in end and in advance of means nearer the feeding-in end.

Referring to Figs. 1 and 2, the boards are fed in at the right, as by means of a feed table, so-called, over a bed 10 which, in cooperation with other physically separate parts, provides a horizontal support throughout the length of the machine, except where it is interrupted to permit the bottom head to operate. They are taken by two pairs of feed rolls 12, 12, the off edge of the board is guided by a guide or fence 14, shown in Fig. l by a single dot-and-dash line. The feed rolls 12 advance the boards in a continuous series in end-to-end relation past several cutterheads, the boards moving first beneath the chipbreaker shoe 16, not shown in Figs. 1 and 2 but mounted on the standards 18 (Fig. 2) (which also carry in the usual manner the top head yoke, not shown) then, in

succession, under the top head 20, over the bottom head 22 which operates in a gap in the bed and, when four sides of the board are to be planed, between the sideheads 24, which may form part of a matcher works. The board B is then taken by feeding-out rolls 26 to con tinue its movement toward the left. In Fig. 1 the motors shown at 28 at the left are for the cylinders 29 of a profiling attachment which are indicated in Fig. 2, such an attachment being a common adjunct in machines of this type, but the presence or absence of which is'of no significance as regards the present invention.

The cutterheads and 22 are of any usual or suitable type utilizing knives which extend lengthwise in positions corresponding to elements of a cylindrical surface and rotating so that the knife in making the cut moves generally in the opposite direction to the travel of the board.

As appears clearly in Fig. l, the axes of the top and bottom heads 20 and 22 are inclined to the longitudinal line of themachine, making an acute angle with the guide 14 as measured at the right of the figure, the angle illustrated being about 65 Coming now to Fig. 3 it may be noted that for clearness the cutterheads are shown as circles and the adjacent parts of chipbreaker shoe 16 to correspond. The sectioning plane as regards these parts might be considered as inclined at the angle of 65 to the longitudinal center line of the machine. Other parts however are shown as if the section were by a plane parallel to the longitudinal line. In other words the eccentricity of diagonally disposed parts which theoretically should appear in a section by the latter plane and which would show,.for example, the cutterheads as ellipses with parts at the further side in elevation, has been suppressed. This will not be misleading in view of Fig. 4.

As seen in Fig. 3 the board B advances over the platen 30 (which is in effect a continuation of bed 19) and which may be adjusted along diagonal ways 32 in customary manner, and is yieldably held thereagainst by the chipbreaker shoe 16 movably mounted in a manner to be described on lateral cheek pieces 34 which extend bracketlike from the standards 18 at either side of the machine. Herein the chipbreaker is in one piece across the width of the machine. A sectional chipbreaker would in elfect be several shorter chipbreaker shoes in alignment and utilizing intermediate supporting means.

The name chipbreaker shoe chances to be suggestive of the cross sectional shape of the part 16 as illustrated. It has an extended toe portion 36 which is parallel to the axis of the head and extends as closely to the bottom line of the head as is possible consistently with clearing the cutting circle of the knives. It carries a facing or top' lift 37 which as seen in Fig. 5 may be formed in sections, and its rearward face 38 (the vamp of the shoe) is curved to correspond to the cutting circle. The shoe is movably mounted to permit it to accommodate itself to the varying thicknesses of the work, and the pressure exerted thereby may be controlled by springs. Herein compression springs 40 increase the pressure due to its weight. As a homely simile we might compare the shoe with the pushing blade of a snow plow rigged diagonally at the front of a truck. In the present case the relative arrangement of the cutterhead and chipbreaker and a mounting of the latter which permits it to maintain close approximation to the cutterhead at all times is of great importance.

It is clear that the chipbreaker cannot, when approximating closely to the lower right quadrant of the cutting circle, merely move vertically without interfering with the same. If it retreats too far it will not break the chip and the board may be split instead of cut. It is desirable that it move on simple rotating bearings for ease and rapidity of motion. If it were pivoted to swing about an external axis parallel to that of the cutterhead it would not respond properly to the longitudinally mov ing boards. On the other hand if the axis were transverse to the machine, perpendicular to the guide, the toe of the chipbreaker would not maintain its parallelism to the cutterhead axis and would not bear uniformly on the work.

In the example of the invention shown the chipbreaker shoe 16 is supported from the cheeks 34 for movement bodily in a plane longitudinal of the machine under the control of linkwork which gives a compound movement to the toe portion 36 which remains always parallel to the cutterhead axis but moves upwardly and rearwardly in a path closely approximating the adjacent are of the cutting circle.

In the construction shown, the chipbreaker shoe as a unit receives lateral support from the cheek pieces 34 while moving freely between them. As best seen in Figs. 4 and 5, the chipbreaker embodies in its construction two side members 42 supporting the sole and the curved face 38. As seen in Fig. 4, the nigh member 42 (lower in the figure) lies directly against the nigh cheek piece 34 at the .lower portion of the figure, and they are provided with finished surfaces where they contact at the plane X, so that they may slide freely over one another in the movement of the chipbreaker shoe. In the off side, the upper portion viewing Fig. 4, the part 42 is spaced from the adjacent cheek piece 34 so that there is provided on that side of the chipbreaker shoe an extension 43 which has a finished surface cooperating with the finished surface of the cheek piece 34 in the plane Y.

Referring now to Fig. 3 and also Figs. 69, the chipbreaker shoe is mounted for movement between the guiding surfaces thus described by means of pivoted links extending between the cheek pieces 34 and the sides 42 and properly correlated to give the desired motion. In the present instance, these links are parallel links defining, with the line of centers on the cheek pieces 34 and the line of centers on the chipbreaker sides 42, a parallelogram the obliquity of which alters as the parts move and the parallelograms, while alike in dimension, are differentially positioned as indicated by the contrast between Figs. 6 and 7 showing the nigh side of the machine, and Figs. 8 and 9 showing the off side.

Referring now to these figures, in Fig. 6 I have shown an upper link 44-n joining the center a on the chipbreaker to the center b on the cheek 34, and a lower link 46-11 joining the center c on the cheek piece to the center d on the chipbreaker.

Referring now to Fig. 8, on the off side an upper link 440 joins center m on the chipbreaker to center 11 on the cheek piece 34, and a lower link 46-0 joins center 0 on the cheek-piece to center p on the chipbreaker. The rectangles abca' and mnop are at all times similar in the geometrical sense but they are not in transverse alignment the respective vertices of the latter being displaced longitudinally of the machine farther to the front to correspond with the obliquity of the cutterhead axis and of the toe portion 36 of the chipbreaker. The axes of the bearings and pivot pins at these points, however, are perpendicular to the longitudinal plane of the machine. Thus, if we look at Figs. 6 and 8, and imagine the links to swing clockwise, the toe of the chipbreaker in Fig. 6 will move in a predetermined direction relative to the cutting circle of the head 20, adjacent thereto. Likewise the toe in Fig. 8 will move in the same manner relative to the cutting circle of the head adjacent thereto, and this will be true all across the diagonal width of the cutterhead, the position of the toe 34 and the face 38 relative to the cutterhead and its cutting circle being the same throughout the width of the chipbreaker shoe.

As is seen in the drawings, the lines b-c and m-0 between the fixed centers incline upwardly slightly away from the cutterhead and the lines a-p and m p will move parallel thereto. The lines between the pairs of centers a-p, m-n, d--c, p0, may also incline slightly upwardly and forwardly, or to the left in the figures. The parallelograms are oblique and when the chipbreaker responds to the pressure of the board with an upward movement the partial collapse of the parallelograms will be such that the toe of the chipbreaker will move with a compound movement upward and also slightly to the rear in a path closely approximating the cutting circle of head 40 which is the desired efiect.

At the feeding-out side of the cutterhead 20 the board is held down by an adjustable hold-down 48, the lefthand edge of which, viewing Fig. 3, is close to the cutting circle of the cutterhead 20, opposing the right-hand end of platen 30, and which extends across the gap in the bed through which the lower cutterhead 22 operates and opposes the platen 50 at the forward or feeding-out side or" the lower cutterhead 22,. The hold-down 48 may be of any suitable or conventional construction, except that its rearward edge is disposed diagonally to correspond with the inclination of the cutterhead 26. The board then passes, still under control of the guide 14, between the sideheads 24 if such are present. The chipbreakers and hold-downs which cooperate with the sideheads may be of conventional form and are not illustrated.

Fig. 4 illustrates the diagonal disposition of the cutterheads 20 and 22 relative to guide 14. It will be clear that when the cutterheads rotate counterclockwise viewing Fig. 3 then, because of the diagonal disposition of the knives a component of force will be set up tending to diminish friction.

keep the board pressed against the guide or fence 14, which is smoothly finished and may be chrome plated to This pressure is a decided advantage because good work depends on accurate control and positioning of the boards and the guide line is one of the fixed points from which we work. Since a component of the thrust of the knives is directed to the guide a lesser pressure of the feed rolls will be effective to feed the work. This is desirable because excessive pressure is likely to loosen knots. Also excessive pressure may crush the fiber of the wood and poorly planed surfaces will result. The obliquity of the heads, when utilized in connection with such guide, is of particular importance when sideheads 24 are utilized and insures their proper and economical action, the off head 24, or upper head viewing Fig. 1, being set up to cut just inside of the line of the guide and the nigh head 24 being properly spaced therefrom.

Referring now to Figs. 10 and 11, the importance of the diagonal disposition of the cutterhead when used in correlation with a guide and properly acting hold-down as described in preventing clipping will now be explained. In Fig. 11 the chipbreaker shoe 16 and the hold-down 48 are diagrammatically shown, the numerals being placed in quotation marks to indicate the diagrammatic character of the representation. There is a definite space between their opposed edges to permit the top cutterhead 20 to work, as will be apparent from Fig. 10. The edge or" the knife actually moves through the board for a slight distance at opposite sides of its lowermost point along the dot-and-dash line L in Fig. 11. This is where the knife acts and this is where the board is out. Whatever part of the board is there gets cut. If the end of the board is sticking up into the air the knife digs in and chops the top edge off or, with nothing to break the chip, splits it oil? for an even greater distance. Now I have shown in Fig. 11 between the parts 16 and 48 the abutting ends of two successive boards B. Where the cutterheads and the hold-downs are arranged in conventional manner at rightangles to the length of the machine, the parts of the boards in this space are unsupported throughout their width. But in the construction shown the upper portion of the trailing end of the leading board has not passed out from under shoe 16 and the upper portion of the end of the following board is also beneath it. Indeed, in the case of a board wider than the distance between the edges of 16 and 48 measured perpendicular to the center line the end edge of the board could never be free of at least one of the holddowns. In general, looking at the right-hand or following board in Fig. 11 its lower left-hand corner emerges from under shoe 16 and advances to the cutting line L. The knives first engage the corner and at this time the projecting portion is held down along the diagonal which at its upper end is at the extreme end of the board. Throughout a substantial part of its width the board is still under the shoe. The cut progresses parallel to the diagonal under generally similar conditions. As the board passes the head the lower right-hand corner of its trailing end first moves free of the shoe 16 but the upper right-hand corner is still held. As the cut proceeds diagonally upward in the figure across the end portion of the board conditions are similar until the cut is almost completed.

If we turn Fig. 3 upside down, we will see that, at least schematically, it would represent a planer in which the bottom head came first, the boards moving over a bed 36 at their upper side, and along a guide 14. In practice planers are not usually constructed in that manner. Moreover, if we consider the head 20 alone, its position would then correspond to that of the cutterhead of a so-called bottom surfacer (as it corresponds to the head of a top surfacer in the right side position), and if the shoe 16 were supported in such manner as to press the board against the overhanging bed 30, the operation of the parts would be the same. The details of mechanical construction of such a machine doubtless would be quite different in practice. For instance, the guide would ordinarily be at the other side and, since gravitywould be acting to move-the shoe 16 'away'fromthe work 'instead of toward the same, the shoe would have to be supported or counterbalanced as'by increasing the power of the springs 40, or otherwise. It is not to be expected that a design for a given construction would be exactly suitable for a reversed construction, but the general operation of the parts and the means provided for giving them the proper motions would be generally similar and the machine operate in accordance with the same principles.

I amaware that the invention may be embodied in other specific'forms without departing'from the spirit or essential attributes thereof, and I therefore desire the present embodiment to be considered in all respects as illustrative and not restrictive, as is in fact clear in several matters from the description itself. Reference is to be had to the appended claims to indicate those principles of-the invention exemplified-by the particular embodiment described and which I desire to secure by Letters Patent.

1 claim:

l. A wood-planing machine of the type in which a succession of boards in end-to-end relation are advanced by feeding means over a bed and along a lateral guide into cooperation with the planing means, said planing means comprising at least one rotary cutterhead, having knives the edges of which correspond to elements of a cylinder, said head being driven to move the knives through the boards in a direction opposing the direction of feed, the axis of the head being inclined at a substantially acute angle to the guide measured on the side in advance of the cutterhead, and hold-down means comprising a pressure device for bearing on the work immediately in advance of the cutterheadand having an angularly extending work-engaging surface extending parallel to the axis of the head closely adjacent the cutting circle thereof, a supporting framework for said device and means for connecting the device to said frame work to provide for yielding movement of said surface along a path approximating the adjacent arc of said cutting circle comprising linkwork connected to said device by pivots extending substantially perpendicular to the direction of work feed and by parallel pivots to the framework.

2. A wood-planing machine of the type in which a succession of boards in end-to-end relation are advanced byfeeding means over a bed and along a lateral guide intov cooperation with the planing means, said planing means comprising at least one rotary cutterhead, having knives the edges of which correspond to elements of a cylinder, said head being driven to move the knives through the boards in a direction opposing the direction of feed, the axis of the head being inclined at a substantially acute angle to the guide measured on the side in advance of the cutterhead, a pair of checks in advance of said head at either side thereof having interiorly directed smooth guiding surfaces disposed in vertical planes substantially parallel to the line of work feed, a pressure device received between them having cooperating smooth surfaces for guided movement between the first-mentioned ones, said device having a work-engaging surface extending parallel to the axis of the head closely adjacent the cutting circle thereof and means for supporting the device for a guided movement between said cheeks wherein said surface throughout its. length moves in a path corresponding closely to the adjacent arc of the cutting circle.

3. A wood-planing machine of the type in which a succession of boards in end-to-end relation are advanced by feeding means over a bed and along a lateral guide into cooperation with the planing means, said planing means comprising at least a rotary top cutterhead, having knives, the edges of which correspond to elements of a cylinder, said head being driven to move the knives through the boards in a direction opposing the direction of feed, the axis of the head being inclined at a substantially acute angle to the guide measured on the side in advance of the cutterhead, a pair of cheeks in advance of said head ateither side thereof, a pressure device in advance of the head having a work-engaging surface extending parallel to the axis of the head closely adjacent the cutting circle thereof and means for supporting the device from said cheeks for a movement wherein said surface moves through parallel positions inv a path 'corresponding closely to the adjacent arc of the cutting circle said means comprising upper and lower links on each side, the pivotal centers of said links on one side being offset longitudinally relatively to those on the other side in such manner that the connecting lines between their homologous center points are parallel to the axis of the head.

4. A wood-planing machine as set forth in claim 3 wherein the links at either side form the ends of a'parallelogram, and the line between the centers on either cheek inclines ina vertical direction away from the bed and also rearwardly.

5. A wood-planing machine as set forth in claim 3 wherein the links at either side form the ends of a parallelogram, and the line between the centers of each link inclines in a vertical direction toward the 'bed and also forwardly.

6. A wood-planing machine having a bed and a lateral guide along one side thereof,feeding means for'forwarding boards in end-to-end succession'over said bed and along the guide, a rotary cutterhead at one side of the bed the bed having knives disposed to correspond to elements of a cylinder and having its axis inclined at an acute angle to the guide measured on the side in advance of the cutterhead, said head rotating to carry the knives into the boards in a direction opposite to that-of the feed, a board hold-down in advance of and one succeeding said cutterhead having inclined edge portions parallel to the axis of the head and extending into close proximity to the cutting circle thereof, and means foryieldably mounting the first-mentioned hold-down to provide for movement of its said edge portion through a path closely approximating the adjacent arc of said cutting circle.

7. A planer having a bed and a lateral guide along one side thereof, feeding means for'forwarding over said bed and along said guide, a series of boards in end-abutting relation, a first top and second bottom rotary cutterhead each having knives disposed to correspond to elements of a cylinder and having their axes inclined at an acute angle to the guide measured on the side in advance of the cutterhead, said heads rotating to carry the knives into the boards in a direction opposite to that of the feed, holddown devices in advance of the first head, between the two and following the bottom head presenting inclined work-engaging edge portions parallel to the axes of the heads and extending into close proximity to the adjacent cutting circles thereof and a side cutterhead following the other heads having its cutting circle projecting inwardly past the line of the guide for operating on the edge of the board which is pressed against the guide by the action of the top and bottom heads.

References Cited in the file of this patent UNITED STATES PATENTS 4,283 Andrews Nov. 21, 1845 201,624 Norris Mar. 26, 1878 298,454 Eldredge May 13, 1884 390,829 Welch Oct. 9, 1888 452,632 Bennett May 19, 1891 1,292,579 Clement et al. Jan. 28, 1919 2,102,186 Nicholson et al. Dec. 14, 1937 2,312,439 Peterson Mar. 2, 1943 FOREIGN PATENTS 616,952 Germany Aug. 9, 1935

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