CA1292926C - Veneer lathes having veneer thickness sensor and thickness control - Google Patents

Abstract

ABSTRACT

A wood veneer lathe that includes a sensor carried by the nose bar and co-acting with the peeling knife to detect and provide an output signal in response to and proportioned to deviations from a predetermined spacing of the nose bar and knife relative to one another. The sensor is located downstream from the point of contact of the nose bar with the block at a position opposite a flat face of the knife and adjacent the latters cutting edge. A particular veneer lathe is disclosed that includes electrohydraulic linear actuators with feedback control means for adjustably positioning the peeling knife. Signals from the sensor, detecting deviations of the peeling knife from its fixed setting, are analyzed by a computer and the latter controls actuators to make suitable knife position adjustments to control the veneer thickness.

Description

iZ9Z9"6 Title: VENEER LATHES HAVING VENEER THICKNESS SENSOR ~ND
THICKNESS CONTROL

This invention relates to lathes for making wood veneer, and more particularly to such lathes in combination with means to measure the thickness of the veneer as it is cut in the form of a ribbon from the log. The signals derived from such measurement are used to contLol the veneer thickness. The invention also concerns novel control means for adjustably positioning and controllably moving the peeling knife of a lathe.

Lathes are used to cut veneer, in the form of a ribbon, from a wood log or block as the block is rotated.
Typically lathes include an arrangement for rotating the wood block, a knife and a pressure bar, and may be either a spindle ox spindleless type. In the spindle type there are two axially spaced head stocks that support thé log and at least one head stock is driven for rotating the wood block. The spindleless type lathe typically has three parallel rollers that hold the wood block captive and at least one of such rollers is driven to rotate the block. In either type an adjustably movable knife is used to peel a ribbon of veneer from the block as the block is rotated. In any veneer forming apparatus the principal objective is to produce a ribbon of veneer that is of uniform and precise thickness.
;,' Veneer must meet certain minimum quality standards and the thickness must be within a few thousands of an inch , of the average. This precise thickness is nece,ssary for ~z`~

the veneer to accept sufficient glue with a roll type spreader or to prevent panel rejection because of being too thin or to avoid excessive sanding losses. Veneer must be strong enough to avoid breakage during handling, and loose enough to be handled by automatic equipment, yet smooth enough to ensure proper glue distribution at the glue spreader. Multi layers of veneer are often laminated together to produce a panel product and uniformity of veneer thickness yields panels that are uniform.
The actual yield and qualit-; of veneer is dependent upon lathe related variables, and as far as veneer quality i3 concerned, control is required for variable parameters such as smoothness, tightness and thickness variability.

With a view to accompllshing the obJective of quality control, most lathes use a nose bar in assoclation wlth the knife.
Veneer thickness control ls the subject of United States Patent No. 4,392,519, lssued July 12, 1983 to H.B.
Calvert, which discloses a nose bar and peeling knife assembly wherein the pitch angle of the peeling ~nife is varied in response to knife deflection. A sensor mounted in the knife holder is used to detect the direction and amplitude of lateral ! deflection of the knife edge from a conditlon of substantial equilibrium during veneer peeling. If the deflection of the knlfe is towards the block the knife i~ said to be "leading", 1~9Z~

and conversely, if the knife is deflected away from the workpiece, it is undergoing "heeling". A leading ~nife usually causes the knife and log to vibrate and the lathe will then produce a corrugated veneer of irregular thickness. A heeling knife tends to move in and out of the log producing alternately thick and thin veneer. A strain guage sensor detects the direction and amplitude of deflection of the knife relative to the knife support bar and from a corresponding signal that is generated a s~gnal responsive controller causes the knife, which is either in a leading or heeling condition, to return to its optimum pitch angle condition. ~ithout deflection sen~ing and controlling means, the pitch angle (being the angle between a horizontal plane and the plane of the cutting edge of the peellng knife faclng the block) will vary from it3 pre-established fietting.
The knife conventionally is guided along curved pitch tracks, or by inclined rails as in the Calvert patent, as it moves into the block so that the pre-established pltch angle is caused to decrease as the diamter of the block being peeled -decreases. The purpose of this is to maintain as close as possible the optimum pitch angle.
In the Calvert form of construction, the signal from the strain guage, which detects blade deflection, is used to effect a correction to the pitch angle as it follows along lts guide tracks, 80 as to maintain the knife in approximate balance, and which is achieved by varying the angle of the 1~9Z~26 inclined rails in response to the signal.
Because Calvert has located the strain guage on the cuttlng knife holder and downstream of the cutting edge of the peeling knife, it iq susceptable to malfunctioning because of debris accumulating in the area of the strain guage. Because of such location the strain guage is also exposed to the deleterious effect of steam and water.

The present invention, like Calvert discussed above, uses a sensor that co-acts with the knife, but unli~e Calvert provides a direct measurement of the veneer thickness as the veneer is being peeled from the log. The novel sensor arrangement of this lnvention can be utili~ed with known pitch angle ad~uRtment means ~uch as hitherto taught by Calvert in the aforementioned United Stateq Patent, or variable length cylinder méans as disclosed herein. In an extremely simple appllcation the sensor can be used merely to measure the thickness of the veneer or for example the start up of a run and if any change is necessary it can be done by manual ad~ustment.
In the Calvert apparatus, deflection of the cutting knife relative to the structure on which the cutting knife is mounted is monitored and this provides perhaps in one sense an indication of veneer thickness, i.e, thicker or thinner than normal, because what i8 being ~ensed i~ whether the knife i8 a heeling or leading knife, or in equilibrium. In accordance 129Z~26 with the present;invention, a direct measurement of the veneer thickness is sensed by continuously monitoring the relative position of the peeling knife and the lathe nose bar. This is achieved by locating the sensor means so that it is carried by or otherwise associated with the nose bar ltself, and so positioned that a signal from the sensor can co-act with the knife (e.g. being reflected therefrom), whereby blade movement relative to the nose bar is directly measured and such measurement is a direct function of changes in the thickness of the veneer being peeled. This sensor is normally located in reflective relationship to a major plane of the cutting knife (preferrably closely ad~acent the knife's cutting edge). A
commercially available sensor suitable for such purpose is the Kaman Di placement Measuring System.
As the Qen~or i5 ~paced from the peellng knlfe and at no t~me is ln direct contact with the ~nife, its operation is not adversely affected by the hostile environment resulting from steam, water and debrls encountered during veneer production. Further, the sensor being on the pressure or nose bar permits using the invention on both conventional and "spindless" veneer lathes.
In accordance with the present invention the lathe, with the veneer thic~ness sensor, can have a solid, non-rotating, elongate nose bar, which nose bar has been traditional ln the industry, or a rotatable tdriven or ldler) pressure roller whlch displays all of the attrlbutes of a 12~Z~26 conventional non-rotating nose bar, but provides greater support to the bloc~.
In addition to the above features, where a pressure roller i8 used as a nose bar, and whether or not the pressure roller is used on a conventional or spindless lathe, the pressure roller itself can it3elf advantageously include a plurality of knife~ e projections for incising or tenderi~ing the veneer.
In accordance with a further aspect of the present invention there is provided veneer lathes having log and/or knife peeling position adjusting means and which are responsive to a veneer thickness sensor.
In accordance with a further aspect of the present invention there i8 provided in a veneer lathe of the type lncludlng means for ~upporting a bolt of wood and rotating such bolt about itc longitudinal axis and a veneer peeling knife and pressure nose bar disposed in a predetermined spaced relationship relatlve to one another, said peeling knife and pressure nose bar being supported on a movable carriage for peeling veneer in ribbon-form from the outside of said bolt as the latter is rotated, the improvement compri~ing sensor means carried by said nose bar and co-acting with said knife to detect variations in said predetermined spacing of the peeling knife and nose bar and providing output signals in response and proportioned to such variations.
In accordance with a further aspect of the present .

invention there,is provided a veneer lathe comprising ~ a) a rigid frame structure having head stocks for carrying and rotating a log to be peeled into a ribbon of veneer;
(b) a nose bar and peeling knife mounted in predetermined spaced relationship relative to one another on a carriage;
(c) means reciprocally mounting said carriage on said frame structure for movement toward and away from said log;
~d) power means for moving sald carriage toward said log at a predetermined rate to peel a ribbon of veneer from the log as it 18 rotated;
(e~ means pivotally mounting said carriage for movement about an axis parallel to the axis of rotation of the log for permitting ad~ustlng the knife pitch angle;
(f) power means for selectively pivoting said carriage; and (g) means mounting said carriage permitting movement of the same to selectively vary the gap between the . knife tip and point of contact of the nose bar.. with the log.
In accordance wlth a stlll further aspect of the present lnvention there i5 provlded a veneer lathe o the type including means for supporting and rotating a bolt of wood about its longitudlnal axis and a veneer pèeling knife and pressure nose bar assembly having a predetermined flxed spaclng l~Z9Z6 therebetween and.which is supported on a movable carriage for peeling veneer in ribbon form fromthe outside of said bolt as the latter is rotated, the improvement comprising sensor means carried b~ said nose bar and operative to detect and provide an output signal in response to variations in said predetermined fixed spacing of the ~nife and nose bar and magnitude of such variation and means for adjustably repositioning the peeling knife in response to commands from a controller acting in response to signals from said sensor means.

The invention is illustrated by way of example in the accompanying drawings wherein:
Figure 1 ls a schematic cross-sectional view of a lathe with a conventional rigid nose bar and peeling ~nife including a ~nife position ad~usting means provided in accordance with the present invention;
Figure 2 is similar to Figure 1 but where the nose bar is a roller type;
Figure 2A is a partial view similar to Figure 2 illustrating a roller nose bar with incising teeth;
Figure 3 is an enlarged, partial cross-sectional, view of the lathe of Figure 1 illustrating a veneer thickness sensor mounted on the nose bar;
Figure 4 iq an enlarged partial cross-sectional view, similar to Figure 3, of the lathe shown in Figures 2 or 3 Z~

illustrating the,sensor mounted on a support for the roller nose bar;
Figure 5 ls a diagrammatic cross-sectional view of a splndleless lathe with a veneer thic~ness sensor mounted on the support of one of the rollers;
Figure 5A is a view similar to Fig. 2A but illustrating a modified mounting for adjusting and controlling the knife position; and Figure 6 is a block diagram of the lathe veneer thickness control system of the present invention actuated by a veneer thic~ness sensor.

Tn Figure 1 there i9 illustrated ln partial cross-section a spindle type lathe where, in a conventional manner, a log or wood block is supported between and on a pair of rotatably mounted chucks at least one of whlch i8 driven to rotate the log about an a~is designated X. A knife 6 is presented to the log and peels therefrom a ribbon 1 of veneer as the log rotates. A nose bar 5 detachably mounted (as by clamps) on a supporting rigid structure SA bears against the outer surface of the log slightly upstream from the cutting tip 6A of the peellng knife 6. The knlfe 6 i9 mounted on a knife holder 6B. The knife holder 6B and nose bar support 5A is a rigid assembly pivotally mounted on the carriage 2. Pivotal movement of the assembly is about the tip of the blade. There 12~2~"6 have been various studies on the effect of varying lathe rela1:ed parameters on quality of the veneer, such as relative posi1:ioning of the nose bar and knife, and two which might be mentioned for those wanting further information are: (a) a report in the Forest Products Journal, October 1966, Volume 16, No. lO, entitled "Effects of Hori-ontal Roller Bar Openings and Quality of Rotary Cut Southern Pine and Yellow Poplar Veneer", by J.F. Lut~ and R.A. Pat~er, and (b) a report in Wood 5cience, January 1980, Volume 12, No. 3, entitled "Effect of Four Foot Lathe Parameters on Veneer Yield and Quality Using Response Serv~ce Analysis", by J.R.T. Haley, W.P. Hancock and ~.G.
Warren.
One of the main ad~ustments or variable~ in a lathe i8 the pitch o~ the knife or the knife angle which must be varied depending upon the kind of wood and the thickness of veneer being produced, and furthermore must be varied as the diameter of the log decreases and the veneer is peeled away from the log. To accommodate the latter, and as previously mentioned, the knife carriage conventionally has been mounted on curved rails or tilted by a cam action during movement, as is the case with the structure illustrated in Figure 2 of Calvert's aforementloned Unlted States Patent No. 4,392,519.
In addition to changing the pitch angle, the kn~fe ls mounted on a carriage movable laterally in a direction toward and away from the spindle axis.
With respect to the present apparatus carriage 2 i~

lZ9;~926 reciprocally movable in a hori~ontal plane to the left and right (double headed arrow A) as viewed in Figure 1 by one or more hydraulic, elëctrohidraulic (or pneumatic) cylinder units lA. The carriage unit 2 can be raised and lowered in a vertical direction (double headed arrow B) by a further hydraulic cylinder (or pneumatic) cylinder unit lB attached at one end to the fixed structure 5 and the other end by pivot pin 7B to the carriage 2.
- The knife carriage 2 is provided with both reciprocal and vertical movement. In addition to this, the knife and nose bar i5 movably mounted on the carriage for movement in an arcuate path (double headed arrow C) about an axls parallel to the axis of rotation X of the log 4 for varying the knife pitch angle. This arcuate movement is effected by a hydraulic cylinder unit lC attached at one end as by a bar Bl to sllde on frame structure S, and at the other end by a pivot pin 7C to the strùcture that carries the nose bar and cutting knife. The bar Bl is movable with the carriage structure 2.
From the foregoing, it can be seen the hydraulic cyllnders lA, lB and lC adjustably control movement and variable positioning of the peeling knife 6 relative to the log or wood block w~ich remainq ln a fixed position. The log during its rotation is further supported by a back up-roll 3 ln a conventional manner, and which ls movable and in pressural engagement with the log. The hydraulic cylinders 1~, lB and lC

12a~26 are each of the electro-h-~draulic type recently comlng into use for controlling machine operations. These servoactuators move loadc~ at high speed with high accuracy and they permit quick changes in machine operation. There are a number of different electro-hydraulic actuators with various feedback systems that may be either mechanical or electrical or a combination thereof. The system~ vary in accuracy, dependability and complexity, and not all are suited for every application. For the present application, the method of feedback control is knowns as the *Tempasonic LTD which is a linear actuator manufactured by a number of companies, including Aeroqu~p Corporation, Moog Inc , and Parker, Hannifin Corp.. The tranc~ducer hac~ no moving parts and thus wear i8 not a problem.
It ~s fairly tolerant of vibratlon and shock loads, and has a po81 tioning accuracy of .001 to .003 inches.
The lathe system lllustrated in Figure 2 is essentially the same as in Figure 1, except for the nose bar.
In the lathe of Figure 2 the nose bar is what is referred to as a "big bar" and conClists of a roller 58 mounted for rotation on a rigid nose bar of mounting structure 5A. The lathe is a spindle type lathe with a roller nose bar, the nose bar being movable along with the cutting knife and therefore somewhat different from the roller nose bar in a centreless lathe, as disclosed in United States Patent No. 4,335,764, issued June 22, 1982 to Charles J. Schmidt.
~ Trade Mark lZ9~26 Figure 2A illustrates a roller nose bar type lathe of Figure 2 but where the roller designated 5B' has ~nife like pro~ections on the peripheral surface for inci~ing the wood prior to peeling the veneer lA from the log 4.
In each of the lathes illustrated in Figures 1, 2 and 2A there is a sensor mounted in such a manner as to determine any deviation or change in positioning of the lathe knife 6 relative to the nose bar. This, by appropriate calibration, gives a direct reading of the thic~ness of the veneer belng peeled.
In Figure 3, which is an enlarged cross-sectional view of the nose bar and log for the lathe of Figure 1, a ~ensor 10 is mounted in the nose bar 5 at a location downstream from the tip 5C of the nose bar that engages the log 4. The no~e bar, downstream from the log engaging tip portion 5C, is recessed so as to provide an exit gap designated EG, at the back face 6B of the knife which is greater than the horizontal gap designated HG between the nose bar tip 5C and the leading cutting edge 6A of the knife. This exit gap EG i~ greater than : the thickness of the veneer designated TH allowing for free f low escape of the veneer as it is peeled from the log.
The sensor 10, in the recessed face 5D of the nose bar, i8 a transducer such as model type KD-2~10-6U manufactured by Kaman Instrumentation Corporation of Colorado Springs, Colorada which serves to continuously measure in electrical lmpulsQ form, in a manner known, the distance and any variation ~292~2~;

in the distance between the sensor 10 and the opposed bac~-face designated 6B of the cutting ~nife G. As will be clearly evident from Figure 3, the sensor 10 is located in close proximity or viclnity of the tip 6A of the ~nife, and thus any deviation of the knife from its designated or set position is picked up immediately that such deviation occurs. This allows for implementing corrective immediate action should it be required. The operation of the sensor or transducer 10 is unaffected by the presence and movement of the veneer sheet 1 between the sensor and the cutting blade.
The nose bar illustrated in the lathe of Figre 2 is a roller 5B having a central shaft 20 (Figure 4) ~ournalled by 6uitable mean~ at oppo~ed end~ on bearings on the no~e bar ~upport structure 5A and i5 further supported by a center bearing mid-way along the length of the roll with such bearing being carried by a ~upport 22. Mounted on the support 22 is a sensor 10 spaced a selected distance Y from the rear face 6B of the peeling knife 6. The tip 6A of the peeling knife is spaced from the contact point of the roller with the log providing a horizontal gap HG which is slightly less than the distance between the roller and the rear face 6B of the cutting knife.
The positlonlng of the sensor, relative to the rear face 6B of the blade, i5 co-related to the horizontal gap HG and thereby provides a direct reading, through ~uitable calibration, of the thickness of the veneer being peeled, and any deviation from that thic~ness provides a ~ignal in the form of electrlcal 12~2~26 impulses conducted by way of a wire 30 to a suitable controller rendering commands to actuate cylinders designated in Figures 1 and 7. as lA, lB and/or lC.
The pressure roller 5B, depending upon its appllcation, can vary in diamter from about 1 inch to about 6 inches, and is preferably within the range of 4 to 6 inches.
Further, and again depending upon its application, the pressure roller may simply be an idler, or alternatively a driven roller. Also, the pressure as for example, roller 5~' can be provided with a plurality of cutting teeth about its peripheral ~urface for tenderizing or incising the block, and hence the reaultant peeled veneer.
The lathes lllustrated in the foregoing embodiments are of the spindle type in which the log i5 located between and carrled by end plates or chucks that are rotated about a predetermined axis of rotation. In such lathes it is also known to uses additional rolls as idlers or powered to engage and support the log duriny peeling Figure 5 is a basic sectional view of a spindleles~
or centerless lathe as referred to in the aforementioned United States Patent No. 4,335,~64, and which in turn refer~ to United States Patent Nos. 1,951,834 and 4,073,326, as disclosing centerless veneer lathes.
The centerless lathe conventionally consists of three parallel rollers, one of which is fixed ln position, and the other two movable relative thereto for receiving and 12~Z~2~i holding captive a log. One or more of the rollers are driven to rotate the log, and one or more of the rollers can be provided with incising teeth to tenderi~e or incise the veneer.
Referring to Figure 5 there is illustrated a first roll 5B of the type illustrated in Figure 4, having mounted thereon and carrying therewith a sensor lo, roller 5B being in a fixed location and carried by a structure designated 50. Two further rollers designated Sl and 52 are mounted on structure~
carried by the piston rod of respective Tempasonic* hydraulic cylinder units lD and lE. These hydraulic cylinders lD and lE
are fixed to the mounting structure 50. A further Tempasonic*
cylinder lF is anchored to the support structure 50 and has a pi~ton rod connected to the carriage structure 53 having the peellng knlfe 6 reclprocally mounted thereon. The peeling knife 6 is controllably moved horizontally, as viewed in Figure 5, by a hydraulic Tempasonic* cylinder lG to change selectively a gap designated G.that corresponds to the vertical gag VG of Figure 3.
From this embodiment it is clearly ev~dent log supporting rollers 51 and 52 (at least one of which may be driven) are movable toward and away from roller 5B, the three rollers holding captive a log and rotating the same during peeling of the veneer. The peeling knlfe 6 is controllably varied in pitch by actuation of the hydraulic cylinder lF
(pivoting being about pin 5A) and the gap G, iQ varied by ..
Trade Mark lZ9Z926 actuation of the hydraul~c cylinder lG. Logs to be peeled are infed from a bed 60 on the support structure 50, and which has and inclined portion 61 directed downwardly to the gap between roller 52 and roller 5B.
In the Figure 5 embodiment the veneer thickness can be modified or controlled by actuating cylinder unit G to move knife 6 into or out of the cut, by actuating cylinder unit lF
to pivot the ~nife support frame 53 (pivot of rotation being the knife tip) and/or actuation of cylinder units lD and lE
varying the roll position3 and thus changing the angle at which the block is presened to the knife.
Figure 5A illustrates an alternative to the embodiments of Figures 1, 2 and 2A where the cuttlng knife i8 fixedly ecured to the knife holder. In Figure 5A the peeling knife 6 i5 reciprocally mounted on the knife holder for movement along a path parallel to arrow A-A. The direction of path A-A relative to the log, the location of the knife and/or the pitch of the knife can be chosen as may be required to give the desired thickness control by moving the knife along the predetermined path. Movement of the knife 6 is effected by a ~Tempo~onic cylinder unit ~0 mounted on the knife holder 71.
Log L is rotatably supported between a pair of end plates (not shown) and a roller nose bar 72 is ~ournalled on a rigid bar ~3 and engaged by support rollers 74. The knife 6 is reciprocally mounted in any convenient manner.
~ Trade Mark

Claims (37)

1. In a veneer lathe of the type including means for supporting a bolt of wood and rotating such bolt about its longitudinal axis and a veneer peeling knife and pressure nose bar disposed in a predetermined spaced relationship relative to one another, said peeling knife and pressure nose bar being supported on a movable carriage for peeling veneer in ribbon form from the outside of said bolt as the latter is rotated, the improvement comprising sensor means carried by said nose bar and acting with said knife to detect variations in said predetermined spacing of the peeling knife and nose bar and providing output signals in response and proportioned to such variations.

2. The veneer lathe as claimed in Claim 1, wherein said sensor means, carried by said nose bar, is positioned downstream from the point of contact of said nose bar with said block, and opposite a face of said knife adjacent the cutting edge thereof.

3. The veneer lathe as claimed in Claim 2, wherein said sensor means is located centrally of the longitudinal extent of said nose bar.

4. The veneer lathe as claimed in Claim 3, wherein said nose bar which contacts the bolt of wood comprises a roller.

5. The veneer lathe as claimed in Claim 4, wherein said sensor means is located on a bearing support for said roller.

6. The veneer lathe as claimed in Claim 5, wherein said roller has a diameter from one inch to six inches.

7. The veneer lathe as claimed in Claim 6, wherein said roller includes a multiplicity of incising teeth.

8. The veneer lathe as claimed in Claim 1 wherein the sensor means is a transducer.

9. The veneer lathe as claimed in Claim 4 wherein the sensor means is a transducer.

10. The veneer lathe as claimed in Claim 1 wherein the veneer lathe is a spindle type having headstocks.

11. The veneer lathe as claimed in Claim 4 wherein the veneer lathe is a spindle type having headstocks.

12. The veneer lathe as claimed in Claim 1 wherein the veneer lathe is a centerless type lathe.

13. The veneer lathe as claimed in Claim 4 wherein the veneer lathe is a centerless type lathe.

14. The veneer lathe defined in Claim 1 further including means to selectively adjustably move said carriage in response to signals from said sensor means.

15. The veneer lathe as defined in Claim 14 where said means comprises electrohydraulic actuators with feedback control means.

16. The veneer lathe as defined in Claim 15 wherein said actuators are linear actuators.

17. The veneer lathe as defined in Claim 16 including a first linear actuator for feeding said carriage to the log, a second linear actuator for changing the knife pitch, and a third linear actuator for varying the gap between the knife cutting edge and the point of contact of the nose bar with the log.

18. In a veneer lathe of the type including means for supporting and rotating a bolt of wood about its longitudinal axis and an assembly of a veneer peeling knife and pressure nose bar with the knife and nose bar in predetermined spaced relationship relative to one another, and which assembly is supported on a carriage that moves toward the bolt during peeling veneer in ribbon form from the outside of said bolt as the latter is rotated, the improvement comprising sensor means carried by said nose bar and operative to detect and provide an output signal in response to variations in said predetermined spacing of the knife and nose bar and proportioned to the magnitude of such variation and means for adjustably repositioning the peeling knife in response to commands from a controller acting in response to signals from said sensor means to maintain said predetermined spacing and thereby control the thickness of veneer during peeling.

19. In a veneer lathe of the type including means for supporting and rotating a bolt of wood about its longitudinal axis and a veneer peeling knife and pressure nose bar assembly in which the knife and nose bar are disposed in selected spaced relationship relative to one another, and which assembly is supported on a movable carriage for peeling veneer in ribbon form from the outside of said bolt as the latter is rotated, the improvement comprising sensor means mounted on said nose bar, operative to provide an output signal in response to variations in said predetermined spaced relationship of the knife and nose bar, and proportioned to the magnitude of such variation, and means for adjustably repositioning the peeling knife in response to commands from a controller acting in response to signals from said sensor means.

20. The veneer lathe as defined in Claim 19 including a first linear actuator for feeding said carriage to the log and a second linear actuator for changing the knife pitch angle, said actuators being responsive to signals from said controller and being of the electrohydraulic type with feedback control means.

21. The veneer lathe as defined in Claim 19 wherein said nose bar has a roller mounted thereon for rolling engagement with the bolt of wood as it is rotated.

22. The veneer lathe as defined in Claim 21 wherein said roller has wood incising teeth projecting from the outer periphery thereof.

23. A veneer lathe comprising:
a) a rigid frame structure;
b) at least three parallel spaced apart rollers for carrying and rotating a log to be peeled into a ribbon of veneer mounted on said frame structure, one of said rollers being a nose bar located in a fixed position on said frame;
and the other rollers being mounted for movement relative thereto;
c) a peeling knife movably mounted on said frame and located in close proximity to said nose bar for peeling a ribbon of veneer from a log held captive between and rotated by said rollers; and d) electrohydraulic power means operative selectively to adjustably move at least one of (i) the knife into or out of the cut, (ii) the knife to vary the pitch angle thereof; and (iii) the movable rollers to control the thickness of the veneer.

24. A veneer lathe as defined in Claim 23 wherein said power means are electrohydraulic linear actuators with feedback control means.

25. A veneer lathe as defined in Claim 23 including sensor means to detect variations in a predetermined spaced apart relationship of the knife and nose bar and provide output signals proportional to said variations and means operative to actuate said power means in response to said signals.

26. A veneer lathe as defined in Claim 23 wherein said knife is mounted for movement relative to the log along a linear path selectively to vary the vertical gap.

27. A veneer lathe as defined in Claim 26 including an electrohydraulic actuator with feedback control means for moving said knife along said linear path.

28. A veneer lathe as defined in Claim 27 wherein at least one of said rollers is an incising roll.

29. In veneer lathes of the type that include means for supporting and rotating a bolt of wood about its longitudinal axis, a veneer peeling knife and a pressure nose bar with the knife and nose bar in predetermined spaced relationship relative to one another for peeling veneer in ribbon form from the outside of said bolt as the latter is rotated, the improvement comprising means mounting said knife for movement along a linear path in a direction into and out of the cut selectively to vary the vertical gap and power means connected to said mounting means for moving the knife, and sensor means mounted on said nose bar to detect variations in said predetermined spaced relationship of the knife and nose bar and provide an output signal proportional to said variations and wherein said power means is actuated in response to such output signal to minimize any variation of veneer thickness during peeling of the same from the bolt of wood.

30. The improvement as defined in Claim 29 wherein the output signals from the sensor are processed by a controller and commands therefrom actuate the power means to maintain a predetermined spacing of the knife and nose bar and thereby control the thickness of veneer during peeling.

31. The improvement as defined in Claim 30 wherein said power means are linear actuators.

32. The improvement as defined in Claim 31 including a first linear actuator for feeding the knife to the log for peeling the veneer, a second linear actuator for changing the knife pitch, and a third linear actuator for varying the gap between the knife cutting edge and the point of contact of the nose bar with the log, and wherein at least one of said actuators are controlled by signals provided in response to variations detected by said sensor means to controllably maintain a desired veneer thickness.

33. A veneer lathe comprising:
a) a rigid frame structure with pivotally mounted headstocks for carrying and rotating a log to be peeled into a ribbon of veneer;
b) a nose bar and peeling knife mounted in predetermined spaced relationship to one another on a carriage;
c) means movably mounting said carriage on said frame structure for movement toward and away from said log;
d) power means for moving said carriage toward said log at a predetermined rate to peel a ribbon of veneer from the log as it is rotated;

e) means pivotally mounting said carriage permitting adjusting the knife pitch angle;
f) power means for selectively pivoting said carriage;
g) means mounting said carriage permitting movement of the same to selectively vary the gap between the knife tip and point of contact of the nose bar with the log, and h) a sensor mounted on said nose bar providing an output signal in response to changes in said predetermined spaced relationship of the knife and nose bar.

34. A veneer lathe as defined in Claim 33 including power means for selectively moving the carriage as defined in paragraph (g).

35. A veneer lathe as defined in Claim 33 wherein said power means are electrohydraulic linear actuators with feedback control means.

36. A veneer lathe as defined in Claim 34 wherein said power means are electrohydraulic linear actuators with feedback control means.

37. A veneer lathe as defined in Claim 34 including at least one of a knife deviation and veneer thickness sensing means and means actuating said power means in response to signals from the sensing means to adjustably control the quality of veneer being peeled from the log.