Rotatable Cutter Spindle

The present invention relates to a rotatable cutter spindle for cutting wooden chips of a predetermined length.

In order to produce flat chips of high quality it has been known for a long time to provide a cutter spindle in which a cutter is arranged on a supporting body inclined relative to the axis of the latter. In such a case, a pulling cut is performed which guarantees a wooden chip with a smooth cutting surface and a high quality upper surface. Such a cutter spindle is disclosed in the German Pat. No. 1,251,937.

In the known cutter spindles a so-called toothed cutter has been used. It is formed as a strip-shaped cutter whose radially outer portions are provided with cutting edges. Each of the toothed cutters removes a material along the region corresponding to half of the cutter length. In order to guarantee a complete material removal, the toothed cutters are offset relative to one another by half of the tooth length. The length of the chips is determined by the portion of the cutters provided with the cutting edges, so that when such cutters are utilized a splitting cutter can be abandoned which latter was necessary in the cases when cutters with continuous cutting edges were utilized.

The cutter spindles with toothed cutters inclined relative to the spindle axis have been proved to be satisfactory for manufacturing high quality flat chips for many years. The only adherent disadvantages thereof are constituted by the fact that they have relatively small material removal capacity inasmuch as in order to cut over the entire length of the cutter spindle it is necessary to have two cutters, and that the number of the cutters to be mounted to the cutter spindle is limited on construction grounds. Purely theoretically it is possible to double the material removal capacity for a given cutter spindle, when the toothed cutter can be replaced with a cutter with continuous cutting edges. However, a splitting cutter which has to be provided in such a case occupies an additional space. The splitting cutter is expensive and involves expensive manipulations for insertion of the same into the cutter spindle inasmuch as this cutter, similarly to the chip cutter, becomes quickly blunted and as a rule must be replaced by a new one. Moreover, the splitting knife affects the desirable support of wood before the chip cutter and increases the separation of the material.

Some other cutter spindles are disclosed in the German Design Patent MR No. 52 published in 1957, in the German Pat. Nos. 936,294 and 2,241,938, and in the German Auslegeschrift Nos. 1,021,565 and 1,076,936.

Accordingly, it is an object of the present invention to provide a rotatable cutter spindle for cutting chips of a predetermined length, which avoids the disadvantages of the prior art.

More particularly, it is an object of the present invention to provide a rotatable cutter spindle which has an improved material removal capacity and provides for manufacturing chips of higher quality, as compared with the known cutter spindles.

In keeping with these objects, and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a rotatable cutter spindle which has a plurality of cutters mounted on a supporting body in spaced relationship to one another and inclined relative to the axis of the body so that each of the cutters includes an acute angle with the axis and has a leading end and a trailing end and defines cutting angles which differ from one to another of these ends. Each of the cutters has alternately arranged radially outer cutting edges and radially inner cutting edges of which the radially inner cutting edges are formed by grooves which are provided in the cutters and which have a depth which increases from the leading end toward the trailing end of each cutter. The radially outer cutting edges are arranged at a first, circular surface, and the radially inner cutting edges are arranged at a second common circular surface.

In this construction, since the grooves forming the radially inner cutting edges have a depth that increases from the leading end toward the trailing end of the cutter, they compensate for the inclined position of the cutter and the differing cutting angle resulting in differing radial extension of the inner cutting edges. The required depth of the grooves depends upon the radius of the cutter spindle, the length of the cutter spindle or the length of the cutter, the angle of the bevel cut as well as the cutting angle. The depth of the grooves can be relatively easily diametrically determined, as will be seen hereinbelow.

The invention provides for a considerable increase of cutting capacity as compared with the known cutter spindles, with maintaining the advantages resulting from inclined position of the cutter. The cutter in accordance with the present invention can be relatively easily manufactured inasmuch as simple and precise grinding of the grooves can be performed by an automatic grinding machine. It is further essential that finish grinding of the cutter can be performed by conventional surface grinding machines so that the radial outer cutting edges and radial inner cutting edges can be simultaneously grinded without changing the distance between the cutting edges. The grooves may be so dimensioned that a groove located at the leading end of the cutter has a minimum depth whereas a groove located at the trailing end of the cutter has a maximum depth.

Another feature of the present invention is that each of the cutters has a chip groove which is subdivided into at least two pockets by a partition extending normal to the axis of the supporting body and having a radially outer edge which lies on a circumferential surface of the supporting body. Each of the cutters may have a front surface, and a projection may be provided which extends from the partition to this front surface of a respective one of the cutters and has a width reducing toward the front surface.

In accordance with still another advantageous feature of the present invention, each of the pockets and each of the outer cutting edges extend over a portion of respective ones of the cutters, which portion is located adjacent to the partition, and the projection of the partition is in alignment with an interface between the outer cutting edge and an adjacent one of the inner cutting edges.

In accordance with a further feature of the present invention, the projection has a flank which faces toward the outer cutting edge and is in alignment with a wall of the partition. This flank also lies in a plane which is normal to the axis of the supporting body. This provides for optimal conditions for running of the chips, and a dynamic pressure of chips in this critical region of the pockets is eliminated.

In accordance with a still further feature of the present invention, each cutter is mounted on a holding member which has a filling piece engaged in the groove of the front surface of the cutter. The holding member may carry a projection and may be provided with a chip guiding surface forming an extension of the pocket. The chip guiding surface may merge in a stepped manner into the outer cutting edges and the inner cutting edges of the cutter.

The filling piece overlaps the projection when the latter engages in a further groove provided in the holding member, and arrests the projection in the latter. The securing means engages the holding member and secures the filling piece to the latter.

In accordance with an additional feature of the present invention the supporting body of the cutter spindle has a stepped surface including portions having a greater diameter at the outer cutting edges and portions having a smaller diameter at the inner cutting edges. The outer and inner diameters may be spaced from one another by a distance which is equal to a distance between the first common surfaces and the second common surfaces at which the radially outer cutting edges and the radially inner cutting edges are arranged, respectively.

A yet another feature of the present invention is that the partition between the pockets may be inclined relative to the axis of the supporting body. In such a construction the partition somewhat deviates in the direction of an angle which is included between the axis of the supporting body and the cutter. By this, natural movement of the chip is enhanced. Moreover, a surface for supporting a wooden material to be cut, is increased.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

FIG. 1 is a top view of a cutter of a rotatable cutter spindle in accordance with the present invention;

FIG. 2 is a view showing a front surface of the cutter shown in FIG. 1;

FIG. 3 is a view showing a section taken along the line III--III in FIG. 2;

FIG. 4 is a schematic view showing the cutter spindle in accordance with the present invention; which includes a supporting body and a cutter inclined relative to an axis of the body;

FIG. 5 is a view showing several sections of the cutter spindle taken along lines Va--Va, Vb--Vb, and Vc--Vc in FIG. 4;

FIG. 6 is a plan view showing a member forming chip pockets, a cutter holding member, and a cutter;

FIG. 7 is a side view of the elements shown in FIG. 6;

FIG. 8 is a rear view of the cutter holding member;

FIG. 9 is a side view of the cutter holding member shown in FIG. 8;

FIG. 10 is a view showing a section of the cutter and the cutter holding member;

FIG. 11 is a view corresponding to the view shown in FIG. 10 by illustrating another embodiment of the present invention;

FIG. 12 is a view showing a section taken along the line XII--XII in FIG. 13; and

FIG. 13 is a section of the member forming chip pockets.

FIGS. 1 and 3 shows a cutter 1 of a rotatable cutter spindle for cutting chips of a predetermined length in accordance with the present invention. The cutter 1 is strip shaped and has alternately arranged radially outer cutting edges 2 and radially inner cutting edges 3. The cutting edges 2 and 3 follow immediately one after another so that the cutter 1 performs material removal work over its entire length.

The radially inner cutting edges 3 are formed by grooves 4 which are provided in a front surface 1a of the cutter and may be manufactured by grinding. The grooves 4 of a single cutter have a differing depth which is identified by reference letter x. As can be seen from FIG. 3, the cutting edges 2 and 3 do not jointly lie in a plane which is formed by the front surface 1a of the cutter.

The cutter spindle is shown in FIG. 4 and includes a supporting body of substantially cylindrical shape 5 on which the cutter 1 is mounted in an inclined position relative to an axis 6 of the supporting body 5. The cutter 1 includes an acute angle .alpha. with the axis 6 of the supporting body 5. Taken into the consideration the direction of rotation which is identified by the arrow in FIG. 4, the right end 1b of the cutter forms a leading end thereof, whereas the left end of the cutter 1c forms a trailing end thereof.

FIG. 5 shows three sections taken through one of the cutters. The left section shown in FIG. 5 is a section taken in the trailing end 1c, the central section is a section taken somewhat in a central region of the cutter, and the right section is a section taken in the leading end 1b. The cylindrical radius of the supporting body 5 is identified by reference letter R, an outer circular surface or orbit at which the radially extending outer cutting edges 2 are arranged is identified by reference number 7, and the inner circular surface or orbit at which the radially extending inner cutting edges 3 are arranged is identified by reference number 8. Reference letter .gamma. identifies an angle included between the front surface 1a of the cutter and a radius r lying at the outer cutting edges 2 (a cutting angle).

In order to attain an identical cutting depth, all inner cutting edges 3 must be located at the same inner circular surface 8. This is guaranteed by corresponding depth x of the grooves 4 which are shown in FIG. 5 in correct scale. The successively positioned grooves 4 of a single cutter have a varying depth that increases from the leading end 1b toward the trailing end 1c of the cutter. The groove located at the leading end 1b has a minimum depth whereas the groove located at the trailing end 1c has a maximum depth.

As can be seen from FIGS. 6 and 7, a member 16 is movably mounted in the cylindrical supporting body 6 of the cutter spindle and a cutter holding member 11 to support the cutter 1 is mounted on the body 5 so that a chip groove 10a is provided therebetween. The chip groove is subdivided into chip pockets 10 by partitions 9. Each of the pockets 10 extends over a distance corresponding to two portions of the cutter. Each partition 9 lies in a plane which is normal to the axis 6 of the supporting body, and a radially extending outer edge of the partition lies in a circumferential surface of the cutter spindle.

Each cutter 1 is mounted by its front surface 1a on a cutter holding member 11. The latter is provided with the correspondingly dimensioned filling piece 12 which engages in the groove 4 of the front surface of the cutter. The holding member 11 carries outer projections 13 which correspond to the parititions 9 and extend to the front surface of the cutter. Each of the projections 13 has a reduced cross section and a thinned end which is located in alignment with an interface between the outer cutting edge 2 and the inner cutting edge 3. Thus, the portion of the cutter corresponding to the pocket 10 and the radially outer cutting edge 2 are extended toward the partition 9. A flank 13a of the projection 13 which faces toward the radially outer cutting edge 2 is located in alignment with the adjacent wall 9a of the partition 9. The filling pieces 12 are used for fixing the projection 13 of the cutter holding member 11.

FIGS. 8 and 9 show that the projections 13 can be replaceably mounted on the holding member 11. The projection engages in a groove 14 of the holding member 11 and is arrested in this position by the filling piece 12 which overlaps the projection and is shown in dotted lines. The projection 13 is subjected to wear in operation and is constituted by a wear resistance material.

FIGS. 10 and 11 show different embodiments of a chip guiding surface 15 between the projections 13. The chip guiding surface 15 merges into a bottom 10a of the pocket 10. The chip guiding surfaces 15 may merge into the radially outer and inner cutting edges in a stepped manner.

The partitions 9 as well as the pockets 10 formed thereby are arranged in a member 16 shown in FIG. 7 which is subjected in operation to the action of centrifugal forces and acts upon the holding element 11. As shown in FIGS. 12 and 13, the partitions 9 can be also formed as replaceable wear resistant members.

The supporting body 5 of the cutter spindle in accordance with the invention is stepped and has portions having an outer diameter 17 at the outer cutting edges 2 and an inner diameter 18 at the inner cutting edges 3. A difference between the outer diameter 17 and the inner diameter 18 may be equal to a distance between the circular surfaces 7 and 8 at which the outer cutting edges 2 and the inner cutting edges 3 are arranged respectively. This is shown in FIGS. 5, 10 and 11 of the drawing.

It is also possible that the partition 9 between the pockets 10 is inclined relative to the axis 6 of the supporting body 5 as shown in dotted lines in FIG. 6. In such a construction the partition 9 somewhat deviates in the direction of the angle .alpha. between the cutter 1 and the axis 6. In this case natural movement of the chip is enhanced, and a supporting surface for a material to be cut is increased.

It will be understood that each of the elements described above or two or more together, may also find a useful application in other types of constructions, differing from the types described above.

While the invention has been illustrated and described as embodied in a rotatable cutter spindle for cutting wooden chips of a predetermined length, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.