The present invention relates to veneer slicers having a staylog for moving a tapered flitch past a knife, and particularly to the means for retaining the flitch on the staylog so as to maintain the veneer-producing zone of the flitch in parallel relation to the knife.

Staylogs for use with veneer slicers are known. Such staylogs hold a flitch and move relative to a slicing knife. As the flitch passes the knife, the knife slices a sheet of veneer from the flitch.

The veneer slicers use a plurality of dogs to hold the flitch in position against a mounting surface on the staylog. The dogs are clamping members that extend from the mounting surface of the staylog and are positioned on either side of the flitch along the length of the staylog. Typically, the dogs include a sharp-edged portion oriented parallel to the mounting surface of the staylog to cut into the flitch and hold it in place against the staylog. The dogs are moved toward each other to pinch the flitch therebetween.

An alternative dogging arrangement is disclosed in U.S. Patent No. 5,150,746 to Weil. Weil discloses a plurality of oval-shaped rotating dogs that include a sharp-edged portion at the ends of the major axis of the oval. The dogs are arranged in parallel rows along the mounting surface of the staylog. A plurality of axially extending grooves are cut into the mounting surface of the flitch. The grooves are cut to align with the rows of dogs and are sized to allow the dogs to fit up into the grooves when the major axis of the oval is aligned with the groove. When the flitch is mounted on the staylog, the oval-shaped dogs extend upwardly into the grooves and are rotated to engage the sharp-edged portion of the dogs with the flitch.

Regardless of whether clamping dogs or rotating dogs are used, conventional flitch mounting techniques require that the flitch mounting surface be positioned adjacent the staylog mounting surface. Unfortunately, these conventional mounting techniques cause some of the best veneer on a log to be wasted.

A flitch is formed by cutting a log down the middle along its longitudinal axis so that the plane formed by the cut defines a flitch mounting surface and the periphery of the log defines a veneer-producing surface. Conventionally, the mounting surface of the flitch is positioned adjacent the mounting surface of the staylog and the veneer-producing outer portion of the log is positioned to be sliced into sheets of veneer by the knife.

In a rotary veneer slicer, however, because the tree trunk is naturally tapered, one end of the flitch is thicker than the other end, and consequently extends a greater distance from the mounting surface of the staylog. As a result, the veneer-producing zone of the flitch is frusto-conical, i.e., trapezoidal in cross-section when viewed from the side of the flitch or from the knife. As the staylog and the flitch are rotated in a rotary veneer slicer, the knife first encounters the thickest portion of the flitch. With each rotation, the knife slices a wider veneer sheet until the entire length of the flitch is exposed to the knife. Once the entire length of the flitch is being sliced, subsequent sheets are of substantially uniform width. However, the initial sheets, which are cut from the best part of the log, are too narrow to be useful, and are thrown away as wasted product. Consequently, some of the best veneer on a flitch is thrown away as waste. In addition, with the prior art methods of retention, the long slots formed along the length of the flitch removed sufficient material from the flitch that the flitch lost its rigidity and would flex in response to the pressure of the slicing knife resulting in, at best, nonuniform and unacceptable slices of veneer.

Therefore, a need exists for a method and apparatus for mounting a flitch on a staylog in such a manner that the flitch is securely retained on the staylog, that the production of desirable veneer from the outside of the flitch is increased and waste is reduced, and that waste is concentrated in the less desirable, inner portion of the flitch.

According to an embodiment of the present invention, a method and apparatus for retaining a flitch on a staylog comprises the use of stationary dog means coupled to the staylog and providing one or more surfaces for engaging the flitch, and pushing means for moving the flitch into engagement with the stationary dog means. The stationary dog means preferably includes a plurality of stationary pin dogs and the pushing means includes a plurality of pusher pins, the pin dogs and pusher pins extending orthogonally from the staylog. Each pin dog includes means for adjustably coupling the pin dog to the staylog and a plurality of annular knife edges for engaging the flitch. Each pusher pin includes means for adjustably coupling the pusher pin to the staylog.

U.S. Patent No. 2,804,891 discloses a veneer lathe, in which a flitch 13 is clamped onto staylog C between a set of short fixed dogs 54 and a set of short movable clamping dogs 53, which extend into two channels cut longitudinally in the flitch. The veneer lathe of U.S. Patent No. 2,804,891 has no features permitting a tapered flitch to be mounted with its outer veneer-producing surface substantially parallel to a veneer knife, and consequently, short waste strips will be removed from the large end of a tapered flitch until sufficient material has been removed from the large end to expose the entire length of the flitch to the veneer knife.

A further embodiment of the present invention comprises means for retaining a tapered flitch on the staylog of a rotary veneer slicer with the outer surface and veneer producing zone of the flitch substantially parallel to the slicing knife. The flitch is formed to include a plurality of holes for receiving the pin dogs and pusher pins. The holes are deeper in the thick end of the tapered flitch and shallower in the thin end. However, all of the holes terminate at substantially the same distance from the outer surface of the flitch and cooperate to define a surface, or plane, upon which the flitch rests. The invention is not limited to use on rotary slicers, but can be incorporated into a reciprocating veneer slicer.

The staylog includes a longitudinal axis, an axially extending channel, and a pusher bar movably disposed in the channel for axial movement therein. The pushing means includes driving means for axially moving the pusher bar in the channel and at least one pusher pin coupled to the pusher bar for movement therewith. The pusher pin extends orthogonally from the pusher bar and includes means for adjusting the orthogonal extension of the pusher pin from the pusher bar.

The driving means includes at least one hydraulic piston coupled to the pusher bar for moving the flitch into engagement with the stationary dog means. The driving means can also include a second hydraulic piston coupled to the pusher bar for moving the flitch out of engagement with the stationary dog means.

The invention also includes an embodiment of a method for retaining a flitch on a staylog for slicing veneer from the flitch. The method comprises the steps of providing a flitch having a first plurality of holes for receiving a plurality of stationary pin dogs, positioning the plurality of stationary pin dogs in the first plurality of holes, and moving the flitch into engagement with the pin dogs to retain the flitch on the staylog.

The moving step includes the step of providing a plurality of pusher pins and the flitch includes a second plurality of holes for receiving the plurality of pusher pins. The moving step further includes the step of providing means for moving the pusher pins to move the flitch into engagement with the pin dogs.

Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.

• Fig. 1 is a top plan view of a staylog according to the present invention with a flitch (in dotted lines) mounted thereon;
• Fig. 2 is a side elevation of the staylog and flitch of Fig. 1;
• Fig. 3 is an enlarged top plan view of one end of the staylog and flitch of Fig. 1;
• Fig. 4 is an enlarged side elevation of the end of the staylog and flitch of Fig. 1;
• Fig. 5 is an enlarged end view of the staylog of Fig. 1;
• Fig. 6 is a side view of a stationary pin dog according to the present invention;
• Fig. 7 is a side view of a pusher pin according to the present invention;
• Figs. 8a-8b show illustrative positions and depths of plunge cuts made by a dado saw;
• Figs. 9a-9b show a dog configured to match a plunge cut of Figs. 8a-8b;
• Fig. 10 illustrates the dogs of Figs. 9a-9b installed on a conventional staylog: and
• Figs. 11a-11b show an alternative embodiment of the dog of Figs. 9a-9b.

An embodiment of the present invention includes apparatus for retaining a flitch 13 on a staylog 10. The apparatus includes stationary dog means coupled to the staylog 10 for engaging the flitch 13 and pushing means for moving the flitch 13 into engagement with the stationary dog means. The stationary dog means preferably includes stationary dogs 54 that further include a plurality of flitch engagement surfaces 80. The pushing means preferably includes a plurality of pusher pins 56 coupled to the staylog 10. The pusher pins 56 move the flitch 13 into engagement with the flitch engagement surfaces 80 which bite into the flitch 13 to retain the flitch 13 on the staylog. An embodiment of the invention also includes a method of retaining a flitch 13 on a mounting surface 18 of a staylog 10. The method comprises the steps of providing the mounting surface 18 with a plurality of stationary flitch-engaging surfaces, providing the flitch 13 with a plurality of engagement surfaces adapted for engagement with the plurality of stationary flitch-engaging surfaces, placing the flitch 13 on the staylog 10 with its engagement surfaces adjacent the plurality of stationary flitch-engaging surfaces, and moving the flitch 13 relative to the staylog 10 for engagement of the flitch-engaging surfaces of the staylog 10 with the engagement surfaces of the flitch 13 and retention of the flitch 13 on the staylog 10.

A staylog 10 according to the present invention can include a cast cylinder 12 that defines end portions 14, 15 and a central portion 16 extending therebetween. As shown in Figs. 1-2, a flitch 13 is mounted to the staylog 10 between the end portions 14, 15 and includes a mounting surface 17 and an outer veneer-producing surface 19. As shown in Fig. 5, the flitch mounting surface 17 extends from the wide end 17a at the thick end of the flitch 13 to the narrow end 17b at the thin end of the flitch 13.

The central portion 16 of the staylog 10 is milled to include a flat mounting surface 18 formed by a pair of mounting rails 16a and 16b defining an axial channel 20 therebetween extending along the longitudinal axis 11 of the cylinder 12. A pusher bar 22 is slidably disposed in the channel 20 and extends substantially along the length of the channel 20, the pusher bar 22 being several inches shorter than the channel 20 in order to allow for axial movement of the pusher bar 22 in the channel 20. The pusher bar 22 is sized to extend upwardly in the channel 20 so that the top surface 24 of the pusher bar 22 is substantially coplaner with, and forms part of, the mounting surface 18.

The mounting surface 18 includes a plurality of threaded pin dog apertures 26. The threaded apertures 26 are arranged in pairs along the length of the central portion 16, with the apertures of each pair disposed on opposite sides of the channel 20, as shown in Figs. 1 and 3. A pin dog 54, shown more clearly in Fig. 6, is threaded into each pin dog aperture 26 to provide a plurality of stationary pin dogs extending orthogonally from the mounting surface 18.

The top surface 24 of the pusher bar 22 includes a plurality of threaded pusher pin apertures 28 arranged in spaced-apart relation along the length of the pusher bar 22. A pusher pin 56, shown more clearly in Fig. 7, is threaded into each pusher pin aperture 28. A preferred arrangement of pin dogs 54 and pusher pins 56 is shown in Figs 1, 3 and 5 but other arrangements can be used without departing from the scope of the invention.

The end portions 14, 15 of the staylog 10 are essentially mirror images of each other, and include a central bore 42 that extends coaxially along the longitudinal axis 11 of the cylinder 12 and opens into the central channel 20. Piston housings 44, 45 are attached to the end portions 14, 15, respectively, and form cylinders 46, 47 which enclose drive pistons 48, 49, respectively. The pistons 48, 49 are positioned for movement along the axis 11. Pusher blocks 53a, 53b are disposed in the central bore 42 adjacent each end of the pusher bar 22. Piston rods 50, 51 are attached to the pistons 48, 49, respectively, and extend into the bore 42 to abut the pusher blocks 53a, 53b, respectively.

The pistons 48, 49 are controlled in a conventional manner by control means 60 which directs the flow of operating fluid from a reservoir (not shown) to one of the pistons 48, 49 and simultaneously permits a return flow of operating fluid from the other piston 49, 48 to the reservoir. Thus, application of operating fluid to piston 48 extends the piston rod 50 to drive the pusher block 53a and pusher bar 22 to the right. At the same time, operating fluid is vented from piston 49 back to the reservoir to prevent piston 49 from blocking movement of the pusher bar 22 to the right. Application of operating fluid to piston 49 extends the piston rod 51 to drive the pusher block 53b and pusher bar 22 to the left. At the same time, operating fluid is vented from piston 48 back to the reservoir to prevent piston 48 from blocking movement of the pusher bar 22 to the left. It will be appreciated that a single piston and piston rod can be attached directly to the pusher bar 22 to move the pusher bar 22 in both directions. In that case, the operating fluid would be directed to opposite sides of the piston.

The control means 60 includes control valves and actuating means connected as necessary to direct the operating fluid to the pistons 48, 49 and return the fluid to the reservoir. Operator input means 62 controls the flow of operating fluid by directing the control means 60 to direct operating fluid to piston 48 to drive the pusher bar 22 to the right or direct operating fluid to piston 49 to drive the pusher bar 22 to the left. Operator input means 62 can include actuating levers, push buttons or the like to indicate a desired direction of pusher bar movement.

As shown in Fig. 6, preferred pin dogs 54 include a lower threaded portion 70, a central polygon-shaped portion 72, and an upper flitch-engaging portion 76. The lower threaded portion 70 includes external threads for threadedly engaging the pin dog apertures 26. When used in conjunction with shims or washers, the lower threaded portion 70 also provides means for adjusting the orthogonal extension of the pin dogs relative to the mounting surface 18. The central polygon-shaped portion 72 is preferably hexagonal for engaging a wrench (not shown) for screwing the pin dog 54 into the pin dog aperture 26. The upper flitch-engaging portion 76 includes a scalloped side wall 78 defining a plurality of annular knife edges 80 for engaging a flitch 13. The annular knife edges 80 are axially spaced along the pin dogs 54 so as to be positioned at various distances from the staylog 10.

Preferred pusher pins 56 include a lower threaded portion 82, a central polygon-shaped portion 84, and an upper flitch-engaging portion 86. The lower threaded portion 82 and the central polygon-shaped portion 84 are substantially similar in design and identical in function to their counterparts 70, 72, respectively, on the pin dogs 54. The upper portion 86 includes a cylindrical side wall 88 for moving the flitch 13.

The description that follows relates to the invention as it may be incorporated into a rotary veneer slicer, although it will be clear to those skilled in the art that the invention can also be incorporated into veneer slicers that remove veneer from a flitch with non-rotary motion.

A flitch includes, generally, a conical portion corresponding to the base of the tree from which it was taken, and veneer taken from this portion of the flitch is frequently of the highest quality. As the flitch is normally mounted to the staylog, its outer surface and veneer-producing zone are not parallel to the slicing knife so that upon rotation of the staylog, only narrow waste sliced veneer is produced from the thicker end of the flitch. In the invention, the veneer-producing zone, which is generally a cylindrical segment, most generally a semi-cylindrical portion, is arranged with its axis of rotation parallel to the mounting surface and axis of rotation of the staylog.

For example, the flitch 13 can be prepared for slicing by boring holes in the mounting surface 17 for receiving, and providing engagement surfaces for, the pin dogs 54 and the pusher pins 56. As shown in Fig. 4, a first plurality of pin dog-receiving holes 90 are sized to fit and positioned to engage the pin dogs 54, and a second plurality of pusher pin-receiving holes 92 are sized to fit and positioned to engage the pusher pins 56. The pin dog-receiving holes 90 are formed to extend a predetermined distance from the mounting surface 18 of the staylog 10 into the flitch 13 so that all of the holes 90 terminate at a first distance 94 from the veneer-producing surface 19, thereby forming a veneer-producing zone 21, best illustrated in Fig. 4. Likewise, the pusher pin-receiving holes 92 terminate at a second distance 96 from the veneer-producing surface 19, wherein the first distance 94 can be equal to the second distance 96. The primary factors in determining the first and second distances 94, 96 is maximizing the depth of the veneer-producing zone 21 while affording maximum surface contact between the pusher pins 56 and the pusher pin-receiving holes 92 as well as maximum engaging contact between the pin dogs 54 and the flitch 13.

The flitch 13 is positioned on the staylog 10 with the pin dogs 54 and pusher pins 56 disposed in their respective holes. When positioning the flitch 13 on the staylog 10, the flitch 13 is aligned so that the veneer-producing zone 21 is parallel to the mounting surface 18 of the staylog 10.

When a tapered flitch is to be sliced with a rotary veneer slicer, as shown in Fig. 4, due to the taper of the flitch 13, the mounting surface 17 of the flitch 13 will be positioned at an angle to the mounting surface 18 of the staylog 10. Consequently, the holes 90, 92 will have different depths in order to provide a constant-thickness veneer-producing zone 21.

Advantageously, the plurality of annular knife edges 80 on each pin dog 54 allows each pin dog 54 to engage the flitch 13 without regard to the distance between the flitch mounting surface 17 and the staylog mounting surface 18. Moreover, as shown in Figs. 2 and 4, in those areas where the flitch 13 is thicker, and therefore more massive, more annular knife edges 80 engage the flitch 13 to provide additional holding capability where needed.

Once the flitch 13 is positioned on the staylog, the operator commands the pusher bar 22 to move in a first direction. The movement of the pusher bar 22 causes the pusher pins 56 to move the flitch 13 in the first direction until the flitch 13 engages the annular knife edges 80 on the pin dogs 54. The annular knife edges 80 cut into the flitch 13 and hold the flitch 13 in position.

When the operator is satisfied that the flitch 13 is securely retained on the staylog, the operator adjusts the staylog offset to produce the desired curvature of the veneer-producing surface 19. Staylog offset is the distance between the axis of rotation of the staylog/flitch combination and the longitudinal axis 11 of the staylog 10. As shown in Fig. 5, the curvature can vary between curvatures 19a and 19b, depending on the staylog offset selected by the operator. With maximum offset, the resulting curvature is indicated at 19a. With minimum offset, the resulting curvature is indicated at 19b.

If, because of the forces imposed on the flitch as it is sliced, the engagement between the flitch engaging surfaces at the pin dogs 54 and the engagement surfaces of the pin receiving holes 92 becomes too loose, the operator can command the pusher bar 22 to move in a second direction opposite to the first direction. The movement of the pusher bar 22 causes the pusher pins 56 to move the flitch 13 in the second direction until the pin dogs 54 engage the flitch at different engagement surfaces of the pin-receiving holes 92 for completion of the slicing operation. When the slicing operation has been completed, the pusher bar 22 can be positioned so flitch 13 disengages from the annular knife edges 80. Once the flitch 13 is disengaged from the pin dogs 54, it can be removed and replaced with another flitch 13.

It is understood that the knife edges can be modified to include non-annular knife edges without departing from the scope of the invention. For example, diametrally opposed knife edges could be aligned with the axial movement of the flitch 13 so as to engage the flitch 13 regardless of whether the flitch 13 moves to the right or left. However, annular knife edges are preferred because they provide more flitch-engaging surface area.

Preferred pusher pins 56 do not include knife edges in order to avoid pusher pin engagement with the flitch 13 while disengaging the flitch 13 from the pin dogs 56. If the pusher pins 56 included knife edges, the flitch 13 could remain engaged with the pusher pins, thereby preventing the easy removal of the flitch 13 from the staylog 10.

It will be appreciated that the pin dogs 54 could also be mounted on a conventional staylog and the flitch retained by pushing a movable pin dog toward a stationary pin dog and pinching the flitch 13 therebetween in a conventional fashion. Modifying a conventional staylog to include stationary and movable pin dogs 54 would eliminate the need for pusher pins 56 and pusher pin-receiving holes 92, thereby simplifying flitch preparation while still allowing for multiple knife edges 80 to engage the flitch 13 at various distances from the staylog mounting surface 18.

The preceding description related to dogs 54, 56 used with a non-conventional staylog 10. However, it would be clear to one of ordinary skill in the art that a conventional staylog could be modified to incorporate the present invention without departing from the scope of the invention. For example, Figs. 8-11 illustrate alternative embodiments of the invention that can be incorporated into a conventional staylog.

As generally indicated in Figs. 8a-8b, hole forming means 98, illustratively a dado saw blade 100, can be used to cut dado holes 102 into the flitch mounting surface 104. The dado holes 102 have a generally rectangular opening 106 at the flitch mounting surface 104 (Fig. 8b) and a generally circular depth profile 108 (Fig. 8a). Dado holes 102 can be formed efficiently by moving a dado saw blade 100 along the flitch mounting surface 104 and plunging the saw blade 100 into the flitch at the desired positions to a desired depth, which would be determined by the thickness of the veneer-producing zone 106. Of course, the dado holes 102 can be formed by using other hole forming means, such as a router, drill, lasers, or the like. It is also possible to vary the shape of the dado holes 102 without departing from the scope of the invention. For example, the hole forming means 98 can be used to bore generally rectangular holes having a flat, rather than circular, depth profile.

A flitch-retaining dog 110 for use with the dado holes 102 is illustrated in Figs. 9a-9b. The dogs 110 include an elongated actuating arm 112 and a flitch-engaging portion 116 extending from the actuating arm 112. The flitch-engaging portion 116 is configured to conform to the depth profile 108 of the dado holes 102 and includes a plurality of circular flitch-engaging knife edges 118 configured to run parallel to the depth profile 108 of the dado hole 102. In an alternative embodiment, dogs 122 include straight knife edges 124, as shown in Figs. 11a-11b, configured to run parallel to the veneer-producing surface 120 of the flitch. Of course, if the selected dado holes 102 include a flat depth profile, the dogs can include a rectangular flitch-engaging portion to conform to the flat depth profile.

Dogs 110, 122 can be coupled to a conventional staylog 130, as illustratively shown in Fig. 10. The dogs 110, 122 are mounted to the staylog 130 to form stationary dogs 134 and movable dogs 136 which are movable toward and away from the stationary dogs 150 to move the flitch 13 into engagement with the stationary dogs 134. The stationary dogs 134 extend from the staylog mounting surface 138 and the movable dogs 136 are formed on one end of a pivotable lever arm 140. The lever arm 140 pivots about pivot pin 142 in response to actuation of a conventional hydraulic (or pneumatic) piston-cylinder 144.

The piston-cylinder 144 can be a self-contained unit installed in the staylog 130, as illustrated in Fig. 10. The piston-cylinder 144 includes a connecting rod 146 coupled to a trunion block 150 fitted into the staylog 130 and a first end 148 of the cylinder 144. A piston rod 152 extends from a second end 154 of the cylinder 144 to a connecting pin 156 formed in the lever arm 140.

The narrowest portion of the flitch 13 would be positioned farthest from the staylog mounting surface 104, due to the taper of the log, as previously described with reference to the embodiments of Figs. 1-7.

An important feature of the present invention is the use of individual holes bored into the flitch mounting surface to accept flitch-retaining dogs, with the holes being separated from each other by areas of solid wood. It is the areas of solid wood between the holes that strengthen the edges of the flitch to eliminate flexing of the flitch edge under pressure from the knife. Eliminating flexing at the flitch edge allows a slicer to remove more of the best veneer from the edges without the problem of nonuniform and unacceptable veneer that arises in conventional flitch-retaining methods and apparatus.

In another alternative embodiment of the invention, conventional stationary and movable dogs operate in a conventional fashion to retain the flitch on the staylog. However, the ends of the staylog are differentially offset from the axis of rotation of the staylog so as to maintain the veneer-producing zone parallel to the knife. In being differentially offset, one end of the staylog is offset from the axis of rotation by a greater distance than the other. That permits the thicker end of a tapered flitch to be retained at the same distance from the knife as the thinner end.

In yet another alternative embodiment of the invention, conventional stationary and movable dogs operate in a conventional fashion to retain the flitch on the staylog. However, rather than differentially offsetting the staylog relative to the axis of rotation of the staylog, the staylog mounting surface can be pivoted about one end or about its center in order to orient the mounting surface at an angle relative to the staylog. Rotating the mounting surface relative to the staylog allows the staylog to accommodate the taper of the flitch and retain the veneer-producing zone generally parallel to the knife, while using holes having equal, and minimum, depth for receiving the dogs.

Although the invention has been described in detail with reference to a certain preferred embodiment, variations and modifications exist within the scope of the invention as described and defined in the following claims. For example, although the invention has been described in a rotary veneer slicer where it can be particularly advantageous in reducing waste, it can also be advantageously used in a transversely moving veneer slicer.