US3006392A

US3006392A - Knife holder for lathes

Info

Publication number: US3006392A
Application number: US799141A
Authority: US
Inventors: Harold F Elford
Original assignee: ELFORD PLYWOOD MACHINERY Inc
Current assignee: ELFORD PLYWOOD MACHINERY Inc
Priority date: 1959-03-13
Filing date: 1959-03-13
Publication date: 1961-10-31
Anticipated expiration: 1978-10-31

Description

Oct. 31, 1961 H. F. ELFORD 3,006,392

KNIFE HOLDER FOR LATI-IES Filed March 15. 1959 Harold Fflf'ord IN V EN TOR.

United States Patent Ofifice 3,006,392 Patented Oct. 31, 1961 3,606,392 KNIFE HOLDER FDR LATI-IES Harold F. Elford, Portland, Oreg., assignor to Elford Plywood Machinery, Inc., Portland, Oreg., a corporation of Oregon Filed Mar. 13, 1959, Ser. No. 799,141 7 Claims. (Cl. 144212) This invention relates to veneer lathes, and more particularly to an improved construction for mounting the cutting knife (or knives) of a veneer lathe, wherein the knife may be readily removed for sharpening and subsequently set back on the lathe and secured in fixed position, with a minimum amount of adjustment and down time.

Veneer lathes used in cutting a thin sheet of veneer from a peeler log conventionally have an elongated knife (or, in some instances, a series of aligned knife sections) which is held fast while the log periphery is rotated against the knife for the production of a veneer sheet. It is important that the knife be securely held, so that the veneer sheet produced will be of uniform thickness. In addition, it is necessary that the knife be sharp, in order for a clean cut to'be made. The necessity for maintaining the edge of the knife sharp has dictated the use of a detachable knife, which may be removed at intervals and then sharpened while separated from the lathe. The mounting for the knife should be readily detachable and also be capable of firmly holding the knife in place.

. Conventional knife mountings have had the disadvan- -tage of requiring extensive adjustment every time the knife .is removed and then remounted. Adequate supportfor a knife has also sometimes been lacking. In-

adequate provision for the support of a knife has made 1 necessary the use of relatively thick, heavy knives, which are more costly and require a longer time to sharpen.

Generally, it is an object of this inventionr to provide an improved knife holder construction which firmly holds a relatively thin knife rigidly throughout its length, and

which enables speedy dismounting and remounting of the knife.

A more specific object of the invention is to provide a knife-holder construction wherein the knife throughout its length is held in place by means of a plurality of novel clamping members or levers, each of which is camactuated by a novel cam mechanism into clamping engagement with the knife to hold the knife in place.

Another object of the invention is to provide a construction wherein each of the clamping members is provided with a pivotable clamping shoe portion at that end which bears against the knife, this clamping shoe portion being operable to distribute clamping pressure from the clamping lever to the knife over an enlarged area, without producing high and low pressure spots. The pivot connection enables the shoe to yield as it transmits a clamping force from the clamping member to the knife.

In an embodiment of the invention, it is contemplated that each clamping member have a separate cam mechanism, each of which may be actuated independently of the others. Thus the amount of clamping pressure generated by a given clamping member is determined by the extent the cam mechanism for the member is turned. The cam mechanism also. features a slidable mounting for the rotatable cam of the mechanism, which accommodates shifting movement of the cam rotation axis to ward and away from the pivot axis for its associated clamping member. This enables the rotatable cam to slide and to center itself with respect to a cupped wear surface which is provided the clamping member and which engages the cam surface of the cam. The cupped wear surface provides a bigger area of'contact with the cam and makes possible a firmer grip between the clamping member and cam. The shifting action allowed the cam takes care of the tendency of the cupped Wear surface to shift out of alignment with the cam rotation axis due to the pivotal movement which is allowed the clamping member. The loose mounting for the cam rotation axis also simplifies problems of installation.

Another feature of the invention is the Provision of a pivot mounting for each of the pivoted clamping levers or members which accommodates adjustment of the pivot axis for the member in a direction toward and away from a plane passing through the cutting knife. This adjustment provides a means for setting the clamping pressure produced by the clamping member when the cam is turned to approximately an overcenter position, which is the optimum position for the parts with the knife clamped in place, as this overcenter position is the most stable. The pivot mounting for the clamping shoe portion for each clamping member is important in conjunction with this adjustment feature, due to the fact that adjustment of the pivot axis for a clamping lever would have the elfect of repositioning the face of the clamping shoe with respect to the knife if this clamping shoe were fixed in position on the end of the clamping member. The adjustability of the pivot axis for the clamping lever is also important in conjunction with the sliding mounting for the cam for actuating the lever, since it enables the cam to truly center itself in the cupped wear surface irrespective of the position of the clamping lever pivot axis.

This application is a continuation-in-part of an application filed November 8, 1957 having Serial No. 695,263, and now abandoned and entitled, Knife Holders for Wood Veneer Lathes.

Other objects, advantages, and features of the invention will become apparent as the following description is read in conjunction with the accompanying drawings wherein:

FIG. 1 is an end elevation of a Veneer lathe and knife holder constructed according to an embodiment of this invention, with portions broken away to illustrate details of construction;

FIG. 2 is a front view of portions of the knife-holding mechanism illustrated in FIG. 1;

FIG. 3 is a view corresponding to the view of FIG. 2 but illustrating another embodiment of the invention;

FIG. 4 is a side view of the knife-holding mechanism illustrated in FIG. 3;

FIG. 5 is a perspective view of portions of the camactuating mechanism used in the construction of FIGS. 3 and 4; and

FIG. 6 is a perspective view of another portion of the same cam-actuating mechanism. Referring now to the drawings for a description of the mvention, and in particular to FIGS. 1 and 2, 10 indicates generally a veneer lathe of the type used in peeling thin sheets of veneer from a peeler log, the log being indicated in dotted outline at 11. The log is supported on the lathe on suitable spindles, exemplified by the spindle shown in outline at 12.

The lathe includes a frame or mounting base 16 of an inverted, V-shaped cross section, as can best be seen by the outline shown in FIG. 1. The frame supports a knife 17 and holder mechanism, generally indicated at 18. Frame 16 has a front wall 20 mounting the knife holder mechanism, and a sloping rear wall 21, which provide support for a veneer sheet cut by the lathe as it travels away from log 11.

The lathe also includes a nose bar 26 which rides against the periphery of a log during cutting, and functions to steady the log so as to prevent thick and thin cutting. Normally the lathe is provided with suitable mechanism for moving frame 16 toward and away from the periphery of the log held by spindles 12, to compensate for the reduction in diameter of the log which occurs during cutting. This mechanism is not illustrated, as it forms no part of the invention.

Concerning the knife and holder mechanism, knife 17 is supported on frame 16 with one of its faces abutting a backing plate 31. The backing plate extends along the rear of the knife substantially the length of the knife, and when assembled on the lathe, constitutes part of the mounting base for the knife.

Arranged along the forward or other face of the knife is a clamping plate 32. The clamping plate in the embodiment-illustrated has a length which is substantially equal to the length of the knife and backing plate 31. The backing and clamping plates (which constitutes brace plates in the device) provide two rigid surfaces on either side of the knife, which act to make the knife rigid when the two surfaces are brought together. Thus, using the construction contemplated, a relatively thin knife may be employed, which is easy to sharpen; and this type of knife may be used without the disadvantages normally attending such use, i.e., appreciable flexing of the knife during the cutting operation.

An elongated support bar 37 supports the lower edge of knife 17. The bar is movable up and down on the frame by means of jack screws 38 mounted at intervals on'frame 16 beneath the support bar with their upper ends abutting the bar. Thus, when the knife is sharpouter ends of the bolts 46 and washers 48 seat in dishedout recesses 47 formed in the clamping members. The bolt connection described for each clamping member accommodates pivotal movement of the member about an axis extending transversely of the bolt and substantially parallel to the length of knife 17.

Bolts 46 may be backed out of front wall 20, with the effect of moving the pivot axis for the clamping levers away from the front wall, or to the right in FIG. 1. Thus the bolts constitute means having adjustment mechanism accommodating adjustment of the pivot axes for said members toward and away from a plane passing through the knife. This adjustment is important in connection with the cam-actuating mechanism for each lever, to be described below. The adjustment also is important in conjunction with the pivotal mounting of the brace plate 32 on the upper ends of the levers, since movement of the pivot axis for the levers toward or away from the plane ened and returned to the lathe, the jack screws may be turned so as to raise with the bar and the sharpened edge of the knife supported thereon until the knife edge is properly positioned for cutting.

Holder mechanism 18 further comprises a plurality of elongated clamping members or levers. 36, arranged side by side and extending in a row. These levers extend substantially transversely of the knife. Only a portion of the clamping levers are illustrated in FIG. 2 for reasons of simplicity. It should be realized that, in practice, knife 17 is relatively long, and as many as 8 to 12 clamping members may be present in a conventional lathe. These clamping levers are loosely carried on the front Wall 20 of the lathe, by means to be described.

The clamping levers have upper ends which engage clamping plate 32. These upper ends are also pivotable relative to this clamping plate. The plate constitutes a pressure shoe operable to transmit to the knife pressures produced by the clamping levers. The pivot allowed between the upper end of each clamping lever and the plate orvshoe 32 is important, as it enables angular shifting of the clamping plate to a position wherein its entire inner surface abuts the plane of the outer face of knife 17. Were a rigid connection employed, either the top or bottom edge of the pressure plate might hear heavily against the knife with the other edge riding almost free of the knife, the exact condition resulting depending upon the thickness of the knife and upon the position of the pivot axis for the clamping levers relative to the plane of the knife. Thus each clamping member or lever is provided at its upper end with a rounded shoulder 41 which extends transversely across this upper end. The shoulders 41 of the various clamping levers fit into an elongated groove 42 prepared in the outer face of clamping shoe or plate 32 and rotate within this groove. Clamping members 36 may be secured directly to the plate, as by screws 43 in serted through accommodating, loosely fitting bores provided in the upper ends of the members. A pair of compression springs 44 are also shown, which keep each clamping member 36 snugly against plate 32, while permitting ball-and-socket type of movement between the CWO.

.As already stated, the clamping members are pivotly connected immediate their ends to mounting base 16. The connection is made through bolts 46 which are secured to wall 20. A pair of these bolts are shown for each clamping lever, and these are inserted through loosely fitting bores 46a provided in the clamping levers. The

of knife 17 has the effect of changing the angular relationship of these levers and the plane of knife 17.

In the embodiment of FIGS. 1 and 2, each clamping member is biased to swing in a clockwise direction in FIG. 1 and away from a clamping position by a nut and bolt assembly 51 and spring 52. Each assembly 51 is threaded through an enlarged bore formed in wall 20 of the frame. Spring 52 encircles the bolt portion of assembly 51 and is seated between a set of washers 53.

In the embodiment of FIGS. 1 and 2, the clamping members are swung simultaneously about their pivot connections and into the clamping position of FIG. 1 by a cam-actuated mechanism, indicated generally at 61. Mechanism 61 comprises an elongated shaft 62 extending along the length of the knife beneath the knife and having a handle 63 atfixed to one end thereof. The shaft is rotatably mounted on the front face of wall 20 in plural brackets 64, which are slidable up and down on the front face of wall 20.

Joined to shaft 62 and spaced along the length of the shaft are a plurality of cam elements 71. These are cylindrical in shape, and are mounted on shaft 62 with their axial centers off-set from the axial center of shaft 62. Rotation of the shaft operates to rotate the cam elements in unison. Each of the cam elements has a cylindrical cam surface which is rotatable within a cupped wear surface portion 72 provided at the base or the lower end portion of each member. The cupped wear surface provides an enlarged area of contact between the lower arm of each clamping lever and its associated cam, and this extended area of contact means that the cam memher, when moved to a position causing clamping pressure in a clamping member, tends firmly to be held in place, and is prevented from gradually loosening. The cam construction and wear surface described is to be distinguished from a cam mechanism wherein only line contact between a cam and the surface it engages is provided.

It will be noted that. as the lever members are pivoted about the pivot connections provided by bolts 46, the lower ends of the levers move to the right in FIG. 1, and also slightly upwardly, due to the arcuate movement which results from their pivot mounting. As a result, some vertical shifting of the cupped wear surfaces occurs relative to front wall 20. It is for this reason that the cam members and cam shaft are supported on the front of wall 20 by means which accommodates shifting of these parts toward and away from the pivot axes for the clamping members 36. By providing for this shifting or sliding movement, the cams tend to center themselves in the respective wear surfaces and maximum outward pressure on the lower end of the clamping levers occurs when the cams are moved approximately to a true overcenter position. This is desirable, as it is in this position that the cams are most firmly held and prevented from joggling to a position wherein loosening takes place,

With the mounting just described, for any given knife thickness, bolts 46 are adjusted so that, in approximately a truly overcentered position for the cams, the requisite clamping pressure exists in the upper ends of the levers. After adjustment, the knife used is easily removed after first swinging the cams away from their overcenter position. The knife is readily remounted and held fixedly in place with the same clamping pressure as previously, by swinging the cams back to their overcenter position.

Referring now to FIGS. 3, 4, 5 and 6, these figures illustrate another embodiment of the invention. In this embodiment, the clamping members or levers are pivoted into clamping engagement independently of each other, by means of a separate cam-actuating mechanism provided each member. Further, a segmented clamping plate, i.e., plural clamping shoes are employed.

Considering now this embodiment, the knife 17 is held in place by a plurality of clamping members 81. These clamping members are pivoted intermediate their ends on the front face of the wall 20 by nut and bolt assemblies 82. The pivot connections for members 81 is similar to the pivot connections already described for clamping members 36, and each accommodates shifting of the pivot axis for a clamping member in a direction away from the plane of knife 17.

At the upper or clamping end of each clamping member is an individual clamping shoe 86. Each has an elongated groove 87 which fits over a transverse shoulder 88 at the upper end of the clamping member. The shoes are held in place by side clips 89 having turned over, outer ends, and inner ends welded to the shoe. The shoulder and groove accommodate pivotal movement between each clamping shoe and the upper end of its associated clamping member, similar to the movement described in conjunction with the first embodiment.

The lower end of each clamping member 81 is bifurcated, and terminates in two leg portions 91, 92. Each leg portion has, on the inner side thereof, a cupped wear surface 96. These cupped wear surfaces perform the function of wear surfaces 72 of clamping members 36.

Held in the space between the front face of wall 20 and the inner side of each clamping member is a cam shaft treating element 101, a stub cam shaft 102, and a T-shaped double cam element 103. These parts constitute the camactuating mechanism for each clamping member. The parts are held loosely adjacent the face of front wall 20, with the seating element free to slide up and down on the wall, to accommodate vertical shifting of the rotation axis for the cams.

Shaft seating element 101 (shown disassembled from the mechanism in FIG. 5) abuts the outer face of wall 20. The shaft seating element has mounting portions 111, 112 at its ends, which are provided with suitable bores 113 for the reception of the ends of shaft 102.

Shaft seating element 101 mounts shaft 102 and double cam element 103 (the two latter parts are shown separate from the rest of the mechanism in FIG. 6) with shaft 102 inserted through bores provided in eleme 103 as shown in FIG. 6. When the entire cam mechanism is assembled as in FIGS. 3 and 4, the central portion of shaft 102 engages and rotates against a semicylindrical built-up surface 116 of element 101, and the ends of the shaft 102 extend outwardly through the bores 113. Portions 117, 118 to either side of surface 116 and inwardly of mounting portions 111, 112 are concavely configured, and receive cylindrically surfaced, cam ends 119 of element 103 without contacting the same. The cylindrical surfaces of the cam ends of element 103 are aligned on a common axis, which is offset from the center axis of shaft 102.

In operation, rotation of cam element 103 functions to move the surfaces of ends 119 against wear surfaces 96, and this is accompanied by pivotal movement of a clamping member in a clamping direction. The reaction force created by movement of the cam ends against wear surfaces 96 is transmitted through stub shaft 102 to seating element 101, and from thence to wall 20.

Double cam element 103 has a center leg 12-1 which takes the shape of a socket for a handle (indicated in outline in FIG. 4). .Handle 122 is removable from the socket, and thus may be used for rotating all the cam-actuating mechanisms for the various clamping levers.

In some veneer lathes, instead of one elongated knife, several knife sections laid end to end are employed. The use of separate and independently operable cam-actuating mechanisms for each clamping lever enables the removal of one knife section independently of the remainder, which is an important advantage.

While there has been described several embodiments of the invention, it is recognized that changes in the parts and their arrangement are possible, without departing from the spirit of the invention. It is desired to cover all modifications and variations which would be apparent to one skilled in the art, and that come within the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a veneer lat-he, the combination of a mounting base; an elongated, relatively thin knife supported thereon; a plurality of elongated clamping members arranged transversely of said knife with one set of ends overlapping one side of said knife; means pivotally connecting the clamping members intermediate their ends to said mounting base for pivotal movement of the members about pivot axes extending substantially parallel to the length of said knife; the latter means having adjustment mechanism accommodating adjustment of the pivot axes for said members toward and away from a plane passing through said knife; pivotable pressure shoe means pivotable relative to said overlapped set of ends of said clamping members interposed between said knife and said overlapped set of ends and operable to transmit pressure from said set of ends to said knife; and a rotatable cam for each clamping member mounted between i the other end of the member and said mounting base operable on rotation of the cam to generate clamping pressure in the clamping member; each cam having a shiftable mounting accommodating shifting of its rotation axis toward and away from the pivot axis for the clamping member simultaneously with rotation of the cam.

2. In a veneer lathe, a mounting base; an elongated knife supported thereon; a plurality of elongated clamping members arranged transversely of said knife with one set of ends overlapping one side of said knife and their other set of ends disposed downwardly therefrom; adjustable screw means extending through an intermediate portion of each clamping member securing the same to said mounting base; said adjustable screw means pivotally supporting the clamping member for pivotal movement about an axis extending parallel to the length of said knife and accommodating adjustment in the position of the pivot axis toward and away from a plane passing through said knife; pivotable pressure shoe means pivota-ble relative to said overlapped set of ends of said clamping members interposed between said knife and said overlapped set of ends and operable to transmit pressure from said set of ends to said knife; a cam for each clamping member and a mounting for the cam rotatably supporting the cam between said mounting base and the other end of the member; the mounting for the cam including shiftable means enabling shifting movement of the cam on said mounting base toward and away from the pivot axis for the clamping member; and means for actuating the cam for each clamping member independently of the cams for the other clamping members.

3. In a veneer la-the having a frame portion, a knife supported on the frame portion, and plural clamping lever portions pivoted on the frame portion for clamping the knife to the frame portion, the improvement comprising cam mechanism for each clamping lever portion for generating clamping pressure in the lever portion by pivoting of the clamping lever portion, said cam mechanism comprising a rotatable cam having a curved cam surface and a mounting for the cam rotatably supporting the cam, said mounting for the cam being supported on one of said portions and including shiftable means accommodating shifting of the cam rotation axis toward and away from the pivot axis for the clamping lever portion simultaneously with rotation of the cam, and a curved wear surface provided the other of said portions contacting the cam surface of the cam and constructed to be pressed on by said cam surface on rotation of said cam.

4. In a veneer lathe having a frame, a knife supported on the frame, and plural clamping levers pivoted on the frame for clamping the knife to the frame, the improvement comprising cam mechanism for each clamping lever for generating clamping pressure therein, said cam mechanism comprising a cam having a curved cam surface anda mounting for the cam rotatably supporting the cam, said mounting being supported on said frame and including shiftable means accommodating shifting movement of the cam rotation axis toward and away from the pivot axis for the clamping lever simultaneously with the rotation of the cam, and a curved wear surface provided the clamping lever contacting the cam surface of its cam.

5. In a veneer lathe having a frame portion and a knife supported on the frame portion, plural clamping lever portions for clamping the knife to said frame portion, a pivot connection connecting each clamping lever portion to the frame portion, said pivot connection having adjustment mechanism accommodating shifting of the pivot axis for the lever portion toward and away from a plane passing through said knife, and cam mechanism for each clamping lever portion for generating clamping pressure therein by pivoting of the clamping lever portion, said cam mechanism comprising a cam having a curved cam surface and a mounting for the cam rotatably supporting the cam, said mounting being supported on one of said portions and including shiftable means accommodating shifting movement of the cam rotation axis toward and away from the pivot axis for the clamping lever portion simultaneously with rotation of the cam, and a curved wear surface provided said other portion contacting said Cent surface and constructed to be pressed on by said cam surface on rotation of said carn.

6. In a veneer lathe having a frame, a knife supported on the'frame, and plural clamping levers pivoted on the frame for clamping the knife to the frame, the improvement comprising cam mechanism for each clamping lever for generating clamping pressure in the lever, said cam mechanism comprising a camhaving a cam surface and a cam shaft joined to said cam, a seating member slidable on the frame rotatably mounting the cam shaft, a cupped wear surface provided on the clamping lever, said cupped wear surface contacting the cam surface of the cam, and means operatively connected to the cam shaft and cam for rotating the same.

'7. In a veneer lathe, the combination of a mounting base; an elongated, relatively thin knife supported on said -mounting base; and clamping means for clamping rigidly the knife to said mounting base; said clamping means comprising an elongated brace plate substantially coextensive in length with said knife mounted over one side of said knife and making the same rigid; and a plurality of clamping members arranged transversely of the knife and pivotaliy connected intermediate their ends to said mounting base; the pivot connections for said clamping members accommodating pivotal movement of the members about axes extending substantially parallel to the length of the knife and having means enabling adjustment of these pivot axes toward and away from a plane passing through the knife; said clamping members being spaced at regular intervals along the length of the knife; each of the clamping members having an end portion overlapping the brace plate and connected to the brace plate by means accommodating pivotal movement between the two; and cam means operatively interposed between each clamping member and the mounting base for generating clamping pressure in the clamping member.

References Cited in the file of this patent UNITED STATES PATENTS Germany Sept. 10, 1930