US2239615A - L-shaped cutter knife - Google Patents

Description

April 22, 1941. A MELDE LSHAPED CUTTER KNIFE Filed Feb. 9, 1940 flu wt'EWZ/de ATTORN EY i atentecl Apr. 22, 1941 L-SHAPED CUTTER KNIFE.

August G. Melde, Seattle, Wash., assignor to Henry Disston & Sons, Inc., Seattle, Wash., a corporation of Washington Application February 9, 1940, Serial No. 318,074

3 Claims.

This invention relates to the art of cutter knives. More particularly this invention relates to L-shaped cutter knives of the milled to pattern type which are secured to rotating cutter heads.

L-shaped cutter knives are commonly used in the wood-working arts, A rotating cutter head is provided with a plurality of substantially radially extending cutter shank receiving slots, into each of which slots the shank member portion of an L-shaped cutter knife is positioned and secured. The knife portion of the L-shaped cutter knife is formed integral with and extends at an angle to said shank member portion, as 105, thus forming the L shape.

Cutter knives are generally designated in the trade as either a. milled to pattern type or a ground to pattern type. In a milled to pattern type, the pattern is formed in the knife which is intersected by the grinding face in a common plane, thus forming the cutting edges. On the other hand, a ground to pattern type of knife is one where the pattern is formed by grinding the knife with configurations following the pattern to be formed so that the grinding face is in as many planes as the particular pattern requires. L-shaped milled to pattern type of knives are also known to the trade as Generated knives and Peripheral milled knives.

In milled to pattern types of cutter knives the patterns most commonly employed arefor: flooring, ship-lap, double V ceiling, bullnose casing, stepping, cribbing, shelving, molding and many others. In a milled to pattern knife for cutting flooring there are two pattern surfaces, while in knives for cutting bullnose casing, stepping, cribbing and others there are a multiplicity of such surfaces. The particular problem which this invention solves is present when a plurality of pattern surfaces are present.

In order to illustrate the invention, by way of example cutter knives having a plurality of pattern surfaces and used in making ship-lap are illustrated and described, However, it is to be expressly understood that the invention is not limited to knives for cutting any such specific pattern and that the same is illustrated and described only by way of example of L-shaped milled to pattern cutter knives having at least two pattern surfaces.

L-shaped knives are characterized by a relatively long life in that the knives may be ground and reground because of the great amount of ma terial present in the knife member portion.

A particular difficulty heretofore existing in the art was the care and precision and calculation necessary in grinding or sharpening the L-shaped mllied to pattern type of cutter knives. In an L-shaped cutter knife for cutting ship-lap, the outer end of the cutter knife was ground at an angle as 35 to provide the cutting edges. The cutting edges so provided cut in more, than one cutting circle to provide the desired pattern- Referring to Figure 1, the cutter knife must cut away material from the stock to form the surfaces l0, l I and [2 of the board 9, The cutting edges I3 and M of the L-shaped cutter knife must thus cut in radially spaced cutting circles. In regrinding the cutter knife, care must be taken to insure that the cutter knife will cut the same pattern after sharpening, By cutting the same pattern it is meant that the relative positions of the surfaces [0, l I and I2 of the board 9 must be maintained uniform despite the fact that the cutter knives must be sharpened frequently from time to time. For reasons hereinafter explained, the grinding angle of the prior art cutter knives (which angle corresponds to grinding angle 2'! of Figs. 3 and 4) must be gradually and continually changed with continued sharpening so that the same pattern will be maintained. When it is remembered that a number of cutter knives are operating together on the same cutter head and each must cut the identical pattern. for accuracy and efiiciency, and that cutter heads commonly employ two to sixteen cutter knives, a practicaldifliculty was encountered when the knives must be resharpened in properly calculating the grindin'g angle so that each cutter knife would cut the identical and original pattern. This practical difficulty in the art Was greatly enhanced by the fact that cutter knives are generally sharpened at the mill where the use of not always possible.

It is an object of the present invention to provide a form of L-shaped milled to pattern type of cutter knives which are so designed that the original grinding angle may be maintained throughout the'life of the knives andat the same time the original pattern will be maintained, It is a further object of the invention to provide a cutter knife having at least two pattern surfaces which are angularly positioned relative to each other, so that the grinding face intersecting said pattern surfaces may be ground at a constant predetermined angle throughout the life of the cutter knives.

It is an object of the present invention to provide another form of L-shaped milled to pattern type of cutter knives having at least two pattern precision tools is surfaces and which knives are so designed that the original cutting angle (hereinafter more fully explained but to be distinguished from grinding angle), may be maintained throughout the life of the knives and at the same time the original pattern will be maintained.

The above mentioned general objects of my invention, together with others inherent in .the same, are attained by the mechanism illustrated in the following drawing, the same being preferred exemplary forms of embodiment of my invention, throughout which drawing like reference numerals indicate like parts:

Figure 1 is a perspective view showing two detached L-shaped cutter knives and a piece of board in end elevation therebetween to illustrate the cutting of ship-lap;

Fig. 2 is a perspective view of a cutterhead with a plurality of L-shaped cutter knives in place;

Fig. 3 is a fragmentary sectional view on a larger scale showing a fragment of a cutter head with L-shaped cutter knives of my invention in slots-in said cutter head;

Fig. 4; is a detached View on a scale two times that shown in Fig. 3 of a cutter knive of my invention operatively positioned as respects its center of rotation; and

Fig. 5 is a detached sectional view, on the same scale as Fig, 3, of a cutter knife of my invention designed to maintain the cutting angle constant throughout the life of the cutter knife and at the same time maintain the original pattern.

Referring more particularly to Fig. 2, a cutter head it mountsa plurality of L-shaped cutter knives i l. The spindles (not shown) supporting the cutter head it are adjustable so that the cutter knives i! may be moved toward and away from the board being cut as desired. In view of the fact that a number of types of cutter heads and supporting means therefor are used in the art, and in View of the fact that the same form no part of this invention, they are not illustrated.

Inorder to better explain the invention, I have shown in Fig. 1 two detached L-shaped milled to pattern type cutter knives ll which, upon rotation, will cut their patterns upon the respective edges of the board to form a pattern as ship-lap. The L-shaped cutter knives ll shown in Fig. 1 are paired. The cutting edge M of each cutter knife cuts on the largest cutting circle of the knife, which circle will be termed the extreme swing or extreme cutting circle. These cutting edges M provide the surfaces ill on the board. The cutting edges iii of the cutter knives cut on a cutting circle of less diameter, which circle will be termed the jointing cut circle. The cutting edges 13 provide the surfaces H on the board. The cutting edges it cut the surface l2 on the board which is parallel to the faces of the board.

Referring to Fig. 3, the cutter head H5 is provided with a plurality of substantially radially extending slots l9. The shank portion 25 of a cutter knife is inserted into a slot I9 and securing means, as gib-screws 21, hold the shank portion 25 in the desired position. The knife member portion 22 is formed integral with the shank portion 20. In the particular cutter knife shown in the figures, the knife member 22 forms an angle with the shank member of 105. While this angle may vary, in practical cutter knives now used in the arts it ranges from 95 to 120 and more commonly at either 105 or 110.

The pattern is milled intothe cutter knife H by providing pattern surfaces- 23; 24 and 25.

These surfaces are intersected by the grinding face 26 to provide the cutting edges [3, l8 and M. The grinding angle 21, which is the angle between the surface and the grinding face 26, is shown in Figs. 3- and 4 as an angle of In the knives commonly used in commercial production, this angle may vary between 20 and 50 and more commonly varies between 30 and Referring more particularly to Fig. 4, the cutting edge M will cut on a cutting circle 45 (extreme cutting circle) and the cutting edge l3 will cut on a cutting circle 45 (jointing cut circle), thus determining the surfaces l0 and II of the board. The distance between these surfaces of the board, that is the surface l2, will be determined by the radial difference between the cutting circles l5 and 45, which difference is the distance 55. As the knife member 22 is ground away in sharpening, subsequent grinding faces, as a subsequent grinding face 28, will be provided. The intersection of a subsequent grinding face 23 with the pattern surface 25 will determine a subsequent cutting edge 35) which is comparable to the cutting edge i l in providing the extreme cutting circle. Also, the intersection of a subsequent grinding face 28 with the pattern surface 23 will determine a subsequent cutting edge 42 which is comparable to the original cutting edge l3 in providing the jointing cut circle. In order to maintain a radial difference between the cutting edges 35 and 42, a distance 5i in a radial direction must be equal to the original radial distance 50. Thus the cutting edge 42 must cut on a cutting circle 48, which is a radial difference away from the cutting circle $1 on which the cutting edge 30 cuts.

From the foregoing, it is clear that the pattern surface 23 must pass through the intersection of the subsequent grinding face 28 and a cutting circle d8. If the subsequent grinding face 28 is positioned relative to the pattern surface 25, so that the grinding angle 53 is equal to the original grinding angle 2'1, then the pattern surface 23 is not parallel to the pattern surface 25.

In the prior art the pattern surface, comparable to the pattern surface 23 of this invention, was parallel to the pattern surface 25. Such pattern surface of the prior art would lie in the plane of line 45 which is parallel to 25. The line 44 intersects the circle 48 at 29' which would therefore represent a cutting edge of the prior art devices. The grinding face of such prior art devices would therefore pass from 30 to 25 along line l5. However, the angle 52 is no longer equal to the original grinding angle 21 and is approximately 25 as, distinguished from the originally selected grindingangle of 35.

In the prior art structures it was therefore necessary to gradually and continually change the grinding angle, as the knife member was ground away, or elsethe-pattern, and particularly the extent of the surface l2 of the board 5, would change.

As. distinguished from such prior art structure where itwasnecessary to continually and gradually change the grinding angle, I provide in the form of my invention shown in Figs. 3 and 4 a knife member where the grinding angle may be maintained constant asthe knife member is being ground away in sharpening and at the same time the pattern maintained. This means that if'the manufacturer specifies that a grinding angle of; 35 ShOllld'lbB' used to provide the desired pattern, that it is only necessary to set a grindingdevtce at a 35 angle in the sharpening of the knife members. i

The dash line 44 is drawn parallel to the surface 25 and the surface 23- (shown by dotted line) forms an angle of approximately two degrees (2) thereto as shown in Figs. 3 and 4. This dotted line 23 represents the pattern surface which is intersected by the grinding face 26 to form the cutter edges cutting on the jointing cut circle, as cutter edge l3, to form the surface II on the board. The cutting edges cutting on the extreme cutting circle, as cutting edge I4, cut the surface l on the board.

The radial distance between the arcs 45 and 46 is the same distance as that between the arcs 47 and 48. In other words, radii from the center 49 will provide equal portions 50 and 54. The distance 59 or 5| will determine the depth of pattern or the surface l2 of the board as the cutting edges of the knife operate in cutting circles about a center. It is apparent that if the surface 23 were parallel to the surface 25 as is dash line 44, then the angle represented by 52 will be approximately 25, whereas the original grinding angle 21 was 35. However, if the surface 23 is provided at an angle in accordance with this invention, the grinding angle 53 may be maintained at 35 and still the depth of pattern determined by the distance 5| will be equal to the original depth of pattern represented by 50 In practice an L-shaped knife is not adjusted more than approximately one-half inch in a radial direction, this for the reason that outward radial movement of the shank member lessens the support from the cutter head. As the knife is \being ground away, some of the adjustment may be taken by moving the spindles toward the work. In commercial practice generally both the spindles are moved toward the work and the L-shaped knives are moved radially outwardly to compensate for grinding away of the knives by sharpening. With my invention, al-

though the knife may be cutting on smaller cutting circles, still substantially the same pattern will be cut on the board.

The angle between the pattern surface 25 and the pattern surface 23 (i. e., the angle between the lines 44 and 23) is shown in the drawing in Figs. 3 and 4 as approximately two degrees (2). However, the angle to be provided will depend on the cutting -circle employed. It will also depend upon the grinding angle desired, 1. e., the extent of the angle 21. Also it will depend upon the angle of the pattern face 25 to the shank 20. As previously stated, the angle of the shank 20 with the pattern face 25 may vary from 95 to 120. Also the angle 21 may vary in practical operation from 20 to 50 and more com-- monly from 30 to 40. The cutting circle or extreme swing may vary from approximately six inches (6") to twenty inches (20"). With such variations in mind, I have found that the angle between the pattern surface 25 and the pattern surface 23 may vary from approximately A! to 2 4 and the depth of pattern maintained uniformly throughout the life of the cutter knife and with a constant grinding angle employed. It is clearly within the knowledge of those skilled in this art to ascertain, in view of the foregoing disclosure, the exact angle to be employed when the above variables have been selected or determined.

By way of summary as to this form of my invention, it is thus apparent that any of the cutter heads, as cutter head 18, of the prior art and mounting means therefor may be employed in my invention. The L-shaped milled to pattern typeof cutter knife of my invention embodies a shank member, as 20, which is positioned substantially radially of the cutter head. The knife member portion 22 is integral with and forms substantially an L-shape with the shank member 20. The knife member 22 is provided with more than one pattern surface, as surfaces 25 and 23. These pattern surfaces are in planes which are not parallel and diverge away from each other as they approach the shank member 20. The cutting edges, as l3, I8 and l4, are provided by a cutting face or grinding face 26 intersecting the pattern surfaces. Two or more cutting edges are thus provided, as 13 and [4,

which operate in cutting circles of different radii. By the angular relation between the pattern surfaces 25 and 23 the predetermined selected grinding angle of the cutting face, as angle 21, may be maintained throughout the life of the cutter knife and at the same time the pattern cut by the cutting edges, as I 3, l8 and I4, will be maintained as the original pattern.

In Fig. 5 I have shown a modified form of the invention where the cutting (as distinguished from grinding) angle and pattern are both maintained constant throughout the life of the knife. The cutting angle of a knife is determinedby the angle between a radius and the grinding face. The cutting angle is so determined as aboard will lie in a plane at a right angle to a radius of the cutting circle. In other words, the finished surface of a board will be tangent to the cutting circles of the cutting edges of the cutterknives.

In Fig.5 it isapparen t that the cutting angle 55 between the original grinding face 56 and a radius 51 is the same as the cutting angle 55 between a subsequent grinding face 58 and a radius 59. 1 The cutting angle 55 is maintained constant at the desired angle, as approximately 15 throughout the life of the L-shaped knife 60, although the angle of grinding of the original grinding face 56 to the pattern surface 6|, 1. e., angle 62, is approximately 35, while the angle of grinding of a subsequent grinding face 58 has increased to approximately 50.

In many instances a particular cutting angle as selected to provide for the most accurate and eflicienrt work. In selecting a particular cutting angle variousf-actors are considered such as the character of the wood as to moisture, hardness, grain, etc. and speed of production. In prior art milled to pattern L -shaped cutter knives if a particular cut-ting angle were selected, the same could not be maintained throughout the life of the knife and at the same time maintain the original pattern. By my invention both the cutting angle and the pattern may be maintained constant throughout the life of the knife if so desired.

In Fig. 5 the L-shaped knife member 88 has a shank portion 20 which is similar to such similarly numbered portion of the previous figures.

The pattern surface 6| corresponds to the pattern surface 25 of Figs. 3 and 4 and dash line 64 is parallel to the pattern surface BI and there-' fore corresponds to dash line 44 of said figures. The pattem surface 65 corresponds in function with the pattern surface 23 but the variation in the angle 66 between 64 and 65 is greater than the angle between and 23 of said figures. The

angle 66, to. permit a constant cutting angle 55 and at the same time a constant pattern throughout the lifeof the knife, will vary from approx imately' /2 to 9 for commercial devices. The

variables determining the exact degrees are the same as in the previous figures and include: the cutting circle to be employed, the angle of the L of .the knife, and the selected cutting angle. While the cutting circles and the angle of the L will have the same variations, the cutting angle may vary from 0 to approximately 55.

In Fig. 5 the cutting edges 61 land 68 correspond in function .to the cutting edges l4 and 13 of Fig. 4.

function to the radial distance 59 of Fig. 4. This radial distance 69 is the difference between the two circles H3 concentric about the center ll.

As the knife is ground away in sharpening and a subsequent grinding face 58 is provided the same pattern will be provided, as the radial distance M between the two concentric circles 15 is the same distance as the distance 69. The cutting edges 72 and 13 provided by the grinding face 58 will cut on cutting circles 15 and are spaced apart the distance 14.

Thus by the use of myinvention L-shaped cutter knives may be either ground at a predetermined grinding angle (Figs. 14) or at a predetermined cutting angle (Fig. 5) throughout described my invention and in the claims have claimed such number as the minimum. In so claiming it is to be understood that such term does not limit the maximum number of pattern surfaces which may be present.

Obviously, changes may be made in the forms, dimensions and arrangement of the parts of my invention, without departing from the principle thereof, the above setting forth only preferred forms of embodiment.

I claim:

1. In a device of the class described, a cutter shank adapted to be connected with and positioned generally in a radial direction of a rotary cutter head; a knife member integral with and These cutting edges are spaced apart aradial distance 69 which will correspond in In the interest of i forming substantially an L -shape with said shank member; a first pattern surface on said knife member; a second pattern surface on said knife member extending in a plane diverging away from the plane of the first pattern surface as they approach theshank member; and a grinding face intersecting said two pattern surfaces and ground at a predetermined angular position and forming spaced apart cutting edges operable in radially spaced apart cutting circles when attached to a rotary cutter head, whereby relative radial variation in said cutting circles as the grinding face is reground at said predetermined angular position may be eliminated.

2. In a device of the class described, a cutter shank adapted to be connected with and positioned generally in a radial direction of a rotary cutter head; a knife member integral with and forming substantially an L-shape with said shank member; a first pattern surface on said knife member; a second pattern surface on said knife member extending in a plane diverging away from the plane of the first pattern surface by one-half to two and one-quarter degrees /2 to 2%") as they approach the shank member; and a grinding face intersecting said .two pattern surfaces and ground at a predetermined grinding angle and forming spaced apart cutting edges operable in radially spaced apart cutting circles when attached to a rotary cutter head, whereby relative radial variation in said cutting circles as the grinding face is reground at said predetermined angle may be eliminated.

3. In a device of the class described, a cutter shank adapted to be connected with'and positioned generally in a radial direction of a rotary cutter head; a knife member integral with and forming substantially an L -shape with said shank member; a first pattern surface on said knife member; a second pattern surface on said knife member extending in a plane diverging away from the plane of the first pattern surface by one-half to nine degrees /2" to 9) as they approach the shank member; and a grinding face intersecting said two pat-tern surfaces and ground to provide a predetermined cutting angle and forming spaced apart cutting edges operable in radially spaced apart cutting circles when attached to a rotary cutter head, whereby relative radial variation in said cutting circles as the grinding face is reground to provide said predetermined cutting angle may be eliminated.

AUGUST G. MELDE.

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