Patent Publication Number: US-11045968-B2

Title: Knife assembly

Description:
FIELD OF THE INVENTION 
     The present invention relates to a knife assembly for use in a veneer cutting machine such a rotary veneer lathe and a veneer slicer. 
     BACKGROUND OF THE INVENTION 
     Referring to  FIG. 11 , there is shown in a fragmentary side view of a part of a typical rotary veneer lathe which is disclosed in the Japanese Patent No. 3,689,132. Specifically, the drawing shows a knife blade  57  that is fixedly mounted on a knife carriage  55  of a rotary veneer lathe that is movable toward a log or a wood block  51  held and rotated by spindles (not shown) for a distance corresponding to the thickness of veneer sheet  53  to be peeled by the veneer lathe for each rotation of the wood block  51 . The knife blade  57  has at the tip end thereof a cutting edge  57 C that is formed by a surface  57 A and a bevel surface  57 B of the knife blade  57 . The knife blade  57  fixed on the knife carriage  55  and ready for veneer peeling operation need be precisely set so that the cutting edge  57 C is positioned at a height corresponding to an imaginary horizontal plane passing through the axis of rotation (not shown) of the wood block  51 . If the cutting edge  57 C is positioned away from the desired height, the thickness of the veneer sheet  53  cut by such knife blade  57  is varied and, therefore, veneer with a degraded quality is produced. 
     Continued use of the knife blade  57  for peeling veneer from a rotating wood block  51  causes a wear to the cutting edge  57 C, which in turn causes irregular or rough surface on peeled veneer sheet. Such knife blade  57  is removed from the knife carriage  55  and the cutting edge  57 C is ground by a grinding machine (not shown) to sharpen the cutting edge  57 C. Grinding of the cutting edge  57 C means stock removal and that the position of the cutting edge  57 C with respect to the blade bottom surface  57 D is changed. Specifically, the height of the cutting edge  57 C, or the dimension of the knife blade  57  as measured from the bottom surface  57 D to the cutting edge  57 C, is reduced. For adjustment of the knife blade  57  to position the cutting edge  57 C at the above-described desired height when the knife blade  57  is set in the knife carriage  55  as shown in  FIG. 11 , a plurality of threaded holes  61  (only one hole shown in the drawing) is formed in the bottom of the knife blade  57  at a predetermined spaced distance in the longitudinal direction the knife blade  57  along the cutting edge  57 C and an adjusting bolt  59  is screwed in each of the threaded holes  61 . In  FIGS. 11 and 12 , reference symbol P 1  shows the knife assembly that includes the knife blade  57 , the adjusting bolts  59  screwed in the threaded holes  61  in the bottom of the knife blade  57  and lock nuts  63  that secure the respective adjusting bolts  59  to the knife blade  57 . 
     In such knife assembly P 1 , the distance between the cutting edge  57 C of the knife blade  57  and the top surface  59 B of the adjusting bolt head  59 A is the knife height in the context of the knife height adjustment. Therefore, the knife height adjustment is made so that the cutting edge  57 C of the knife blade  57  of the knife assembly P 1  as mounted on the knife carriage  55  coincides with the aforementioned imaginary horizontal plane. For the sake of description, the knife height is indicated by L 1  in  FIG. 12 . 
     For better understanding of the present invention, the following will describe in detail a procedure for knife height adjustment and mounting of the knife assembly P 1  to the knife carriage  55 . An adjustment jig  64  is used for the knife height adjustment. Referring to  FIG. 12  showing a method for knife height adjustment, the jig  64  includes a base  66  and an upright member  68  that is fixedly mounted in upright position to the base  66 . The distance between the top surface  66 A of the base  66  and the top surface  68 A of the upright member  68  corresponds to the desired knife height L 1 . Numeral  70  designates a dial gauge of a known structure having a spindle  70 A, a gauge head  70 B and an indicator  70 C. The gauge head  70 B is urged by a spring (not shown) to move away from the indicator  70 C. The jig  64  further includes a support block  72 A that supports the dial gauge  70  and a connection block  72  that is fixed to the top surface  68 A of the upright member  68  and to the support block  72 A, thus the dial gauge  70  being held in place in the jig.  64 . The gauge head  70 B is attached to the spindle  70 A and movable by being pushed by an object to be measured. Such movement of the gauge head  70 B and hence of the spindle  70 A is converted into rotation of an indicating needle of the indicator  70 C to show the measurement. 
     In making the knife height adjustment, firstly the gauge head  70 B of the dial gauge  70  is set in contact with the top surface  68 A of the upright member  68  and the measurement on the dial gauge  70  is read and taken as reference value R. Each adjusting bolt  59  is screwed out previously to such an extent that the distance between the cutting edge  57 C of the knife blade  57  and the bolt head surface  59 B of the adjusting bolt  59  is sufficiently larger than L 1 . Subsequently, the gauge head  70 B is lifted up by hand to provide a space between the gauge head  70 B and the top surface  66 A of the base  66  that is large enough for the knife assembly P 1  to be placed in upright position in the space. The knife assembly P 1  is set in the jig  64  with the adjusting bolt head  59 A placed on the top surface  66 A of the base  66  and the surface  57 A of the knife blade  57  placed against the upright member  68 , as shown in  FIG. 12 . The gauge head  70 B is lowered into contact with the cutting edge  57 C of the knife blade  57  and the then measurement on the dial gauge  70  is read and taken as Q 1 . Since the knife assembly P 1  is set in the jig  64  with the cutting edge  57 C of the knife blade  57  positioned above the top surface  68 A of the upright member  68 , the measurement Q 1  is greater than the measurement R or the value L 1 . The knife assembly P 1  is removed from the jig  64  and the first knife height adjustment is made by screwing in the respective adjusting bolts  59 . After such adjustment is over, the knife assembly P 1  is set in the jig  64  again and the dial gauge  70  is read. According to the measurement on the dial gauge  70 , second knife height adjustment is made by turning the adjusting bolts  59  in either direction as required. Such knife height measurement and adjustment are made repeatedly at different points along the knife edge  57 C until the dial gauge reading Q 1  at the different points coincides with the reference value R. The knife height measurement at the different points along the cutting edge  57 C with use of a single dial gauge such as  70  may be accomplished by moving the knife assembly P 1  in the longitudinal direction thereof to change the point of measurement by the single dial gauge  70 . 
     If the measurement Q 1  on the dial gauge  70  made when the knife assembly P 1  is initially set in the jig  64  is the same as R, it means that the knife height is at L 1  or less. Whether the then knife height is the same as L 1  or not cannot be determined from the dial gauge reading. In such a case, the adjusting bolts  59  are screwed out so that the cutting edge  57 C of the knife blade  57  is positioned slightly above the top surface  68 A of the upright member  68  when the knife assembly P 1  is set in the jig  64 . Subsequently, the above-described procedure for the knife height adjustment, that is performed when the cutting edge  57 C of the knife blade  57  is positioned above the top surface  68 A of the upright member  68 , is repeated until the knife height becomes L 1 . After the knife height adjustment is over, the adjusting bolts  59  are secured by tightening the lock nuts  63 . 
     The knife assembly P 1  thus completed is mounted on the knife carriage  55  as shown in  FIG. 11 . In the drawing, reference numeral  65  designates a blade back support plate having a curved surface  63 A at the top end thereof and fixed to the knife carriage  55  by bolts  67 . Reference numeral  55 A designates a mounting surface of the knife carriage  55  for receiving the adjusting bolt head  59 A of the knife assembly P 1 . Numeral  69  designates a plurality of knife clamps (only one clamp shown in the drawing) disposed at a spaced distance in the longitudinal direction of the knife blade  57 . As shown in  FIG. 11 , the knife clamp  69  is pivotally supported by a support arm  71  via a bearing  73  mounted in the support arm  71  so that the knife clamp  69  is pivotable about the bearing  73  as indicated by double-headed arrow. The support arm  71  is fixed to a frame of the knife carriage  55 . The pivoting movement of each knife clamp  69  is effected by a hydraulic cylinder  75  mounted in the knife carriage  55 . Specifically, the hydraulic cylinder  75  has a piston rod  75 A and a pusher  75 B that is mounted at the piston rod end and engageable with the lower end of the knife clamp  69 . Solid line of the knife clamp  69  shows the operative clamping position and phantom line the unclamping or retracted inoperative position of the knife clamp  69 , respectively. 
     In mounting the knife assembly P 1  to the knife carriage  55 , the knife clamps  69  are pivoted to their inoperative position indicated by phantom line ( FIG. 11 ) by retracting the piston rod  75 A of the hydraulic cylinder  75 . The knife assembly P 1  having the knife blade  57  adjusted properly is lifted and moved to the knife carriage  55  by an in-house lifting equipment such as crane. The knife assembly P 1  is set in knife carriage  55  such that the top surface  59 A of the adjusting bolt head  59  is placed on the mounting surface  55 A of the knife carriage  55  and the surface  57 A of the knife blade  57  set against the blade back support plate  65 , as shown in  FIG. 11 . Then, the hydraulic cylinders  75  are operated to extend their piston rods  75 A thereby to turn the knife clamps  69  clockwise about the pivot  73  as seen in  FIG. 11  to their operative clamping positions indicated by solid line, thus the knife assembly P 1  being held down firmly against the blade back support plate  65 . Thus, the knife assembly P 1  is held securely between the knife clamps  69  and the blade back support plate  65 . 
       FIG. 11  also shows a state in which the wood block  51  is being cut to produce a veneer sheet  63  of a predetermined thickness. As the veneer sheet cutting is continued, the cutting edge  57 C of the knife blade  57  is worn gradually and the cutting performance of the knife blade  57  is deteriorated accordingly, which means that the cutting edge  57 C of the knife blade  57  need be ground. In such a case, the knife assembly P 1  having the worn knife blade  57  is removed from the knife carriage  55  to be replaced with a new knife assembly having a ground knife blade. The knife assembly P 1  may be released by retracting the hydraulic cylinders  75  and removed from the knife carriage  55  by using the above-mentioned lifting equipment. The new knife assembly may be mounted onto the knife carriage also by using the lifting equipment. According to a conventional practice, removal, transportation and installation of a knife assembly have been carried out by using lifting equipment or the like because the knife blade is too heavy to carry by hands and hence laborious and dangerous to do so. 
     In general, handling of a knife assembly such as P 1  having a worn knife blade with lifting equipment such as crane involves moving a hook of the equipment to the knife carriage, lowering the hook, engaging the hook with the knife assembly in the knife carriage, lifting the knife assembly from the knife carriage and moving the knife assembly to any suitable place for storage. Furthermore, handling of a knife assembly having a ground knife blade involves moving the hook of the equipment to the knife assembly, lowering the hook, engaging the hook with the knife assembly, lifting the knife assembly and moving and lowering the knife assembly to the knife carriage. As mentioned above, a knife blade is generally extremely heavy, weighing hundreds of kilograms. If the above operations to handle a heavy knife assembly is performed quickly in order to increase the working efficiency, it may invite a hazardous situation in that the moving knife blade may be brought into contact with maintenance personnel or nearby equipment. In order to avoid the hazardous situation, handling of the knife assembly in removing the knife assembly having a worn knife blade from the knife carriage and installing a new knife assembly with a ground knife blade onto the knife carriage need be carried out slowly and with great care spending a long time, which affects the working efficiency and hence the productivity of veneer peeling by a veneer rotary lathe. 
     If the knife blade such as  67  is made thinner to reduce its weight, the above operations in removing and installing the knife assembly may be carried out by hand, so that the time spent for the handling of the knife assembly may be shortened as compared with a case in which the lifting equipment is used for movement of the knife assembly. It is be to be noted that the position of the adjusting bolt screwed in the threaded hole must not be changed relative to the knife blade. However, a knife blade which is made thinner reduces its effective thickness at position where the adjusting bolt receiving holes are formed and, therefore, the knife blade tend to be deformed or displaced relative to the adjusting bolts under the influence of external force acting on the knife blade during veneer cutting by the veneer lathe. Consequently, the dimension between the top surface of the adjusting bolt head and the cutting edge of the knife blade, which correspond to the desired knife height, may be altered, with the result that veneer of the required quality may not be produced. 
     The present invention provides a knife assembly including a knife blade, a knife blade holder that is fixed to the knife blade at a position adjacent to the base end of the knife blade, and an adjusting bolt that is screwed through a threaded hole formed in the knife holder. 
     SUMMARY OF THE INVENTION 
     The present invention, which has been made in light of the above-identified problems, is directed to providing a knife assembly the knife blade of which can be made thinner and hence less heavy than heretofore and that maintains proper relative position between the knife blade and the adjusting bolt and also permits easy handling of the knife assembly. 
     In accordance with the present invention, there is provided a knife assembly that is adapted for use in a veneer cutting machine such as a rotary veneer lathe and a veneer slicer and permits the use of a knife blade which is thinner and hence less heavy than heretofore. The knife assembly includes a knife blade, at least one knife blade holder that is fixed to the knife blade and a knife adjusting bolt with a lock nut. The knife blade has first and second surface across the thickness of the knife blade, a bevel surface formed on the first blade surface side, a cutting edge formed by the bevel surface and the second blade surface and a base end surface located opposite from and extending parallel to the cutting edge. The knife holder includes a holder block having a first support surface that is in contact with and supports a part of the first blade surface and a second support surface that is in contact with and supports a part of the base end surface of the knife blade. The holder block has formed therethrough in height direction of the knife blade a threaded hole through which the knife adjusting bolt is adjustably inserted. 
     According to one aspect of the invention, the knife assembly includes a plurality of knife blade holders each including a holder block of an L-shape having a vertical portion and a horizontal portion in cross section taken perpendicularly to the knife blade thickness, in which the first support surface supporting the first blade surface is formed in the vertical portion and the second support surface supporting the base end surface of the knife blade is formed in the horizontal portion of the L-shape of the holder block, respectively. The knife holder is fixed to the knife blade by means of a bolt inserted through a hole formed through the holder block and screwed in a threaded hole formed through the knife blade. 
     According to another aspect of the invention, the knife blade has formed in the bottom thereof a rectangular recess that is recessed from the base end surface toward the cutting edge and having a recessed bottom surface extending parallel to the base end surface. The holder block is generally of a cuboid shape having formed therein a void portion in the form of a recess of a cuboid shape having three adjoining surfaces. The holder block further has a solid portion located adjoining to the void portion and having at the top thereof a surface that extends parallel to the base end surface of the knife blade. The solid portion of the holder block has a shape that is complementary to that of the rectangular recess formed in the knife blade. The knife holder is fixed to the knife blade with the solid portion of the holder block fitted in the complementary shaped rectangular recess of the knife blade, in which one surface of the three adjoining surfaces of the cuboid-shaped recess of the holder block is in contact with a part of the first blade surface and the surface of the solid portion of the holder block is in contact with the bottom surface of the rectangular recess of the knife blade, or alternatively another surface of the three adjoining surfaces of the cuboid-shaped recess is in contact with the a part of the base end surface of the knife blade. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is side view of a knife assembly for use in a rotary veneer lathe according to a first embodiment of the present invention; 
         FIG. 2  is a fragmentary front view of the knife assembly of  FIG. 1  as mounted on a knife carriage of the rotary veneer lathe; 
         FIG. 3  is a fragmentary partially-sectional side view taken along line I-I and viewed in arrow direction of  FIG. 2 ; 
         FIG. 4  is a fragmentary partially-sectional side view showing a part of a knife carriage in which a knife clamp is placed in its retracted position away from a blade back support plate; 
         FIG. 5  is a fragmentary partially-sectional side view similar to  FIG. 4 , showing a state in which the knife assembly is set between the knife clamp and the blade back support plate in the knife carriage; 
         FIG. 6  is a fragmentary partially-sectional side view similar to  FIG. 5 , showing a state in which the knife clamp is moved with the knife assembly away from the blade back support plate; 
         FIG. 7  is a perspective view showing a knife blade holder and a knife height adjusting bolt of a knife assembly according to a second embodiment of the present invention; 
         FIG. 8  is a fragmentary perspective view showing a knife blade of the knife assembly of the second embodiment; 
         FIG. 9  is a fragmentary perspective view showing a state in which the knife blade holder is fixed to the knife blade in the knife assembly of the second embodiment; 
         FIG. 10  is a fragmentary partially-sectional side view showing the knife assembly of the second embodiment as mounted in a knife carriage; 
         FIG. 11  is a fragmentary partially-sectional side view showing a conventional knife assembly for use in a rotary veneer lathe; and 
         FIG. 12  is a schematic diagram illustrating a method of knife height adjustment of the knife assembly of  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The following will describe the first embodiment of a knife assembly according to the present invention with reference to  FIGS. 1 through 6 . It is noted that the knife assembly according to the embodiments of the invention is of a type that is applicable to a rotary veneer lathe. 
     Referring to  FIG. 1 , there is shown a knife assembly P 2  according to the first embodiment of the present invention. The knife assembly P 2  includes a knife blade  7 , a plurality of knife blade holders  9  (only one holder shown in the drawing) and a knife height adjusting bolt  15  with a lock nut  13 . The knife blade  7  has a first surface  7 D and a second surface  7 A formed across the thickness of the knife blade  7  and extending parallel to each other, a bevel surface  7 B formed on the first surface  7 D side of the knife blade  7 , a cutting edge  7 C formed by the second surface  7 A and the bevel surface  7 B, and a base end surface  7 F extending opposite from and parallel to the cutting edge  7 C. The knife blade  7  has a length or the dimension as measured along the cutting edge  7 C. In the description of the embodiments of the present invention, the dimension of the knife blade  7  as measured from the blade base end surface  7 F to the cutting edge  7 C will be referred to as the height in association with the knife height adjustment described earlier. The knife blade  7  has formed therethrough in the thickness direction thereof a plurality of threaded holes  7 G (only one hole shown in the drawing) at positions adjacent to the base end surface  7 F and spaced at a predetermined distance along the longitudinal direction of the knife blade  7 . 
     The knife blade holders  9  are disposed on the first blade surface  7 D side of the knife blade  7  at positions where the threaded holes  7 G are formed through the knife blade  7 . Each knife blade holder  9  includes a holder block  9 A having an L-shape as seen in the side view of  FIG. 1  and a fixing bolt  11 . The holder block  9 A has a vertical or first support surface  9 B that is formed in the vertical portion of the L-shape of the holder block  9 A and in contact with and supports a lower part of the first surface  7 D of the knife blade  7  and a horizontal or second support surface  9 E that is formed in the horizontal portion of the L-shaped holder block  9 A and in contact with and supports a part of the base end surface  7 F of the knife blade  7 . As shown in  FIG. 1 , the first support surface  9 B and the second support surface  9 E of the holder block  9 A and the first surface  7 D and the base end surface  7 F of the knife blade  7  are formed flat, so that the above-mentioned contacts are provided by surface-to-surface contact. The holder block  9 A has therethrough a hole  9 C formed extending perpendicularly to the first support surface  9 B at such a position that the hole  9 C is coaxial with its corresponding threaded hole  7 G in the knife blade  7 . The knife blade holder  9  is fixed firmly to the knife blade  7  by the fixing bolt  11  that is inserted through the hole  9 C in the holder block  9 A and screwed into the threaded hole  7 G in the knife blade  7 . The fixing bolt  11  has such a length that the end of the fixing bolt  11  opposite from the bolt head is positioned within the knife blade  7  without extending out from the blade second surface  7 A. 
     Referring to  FIGS. 1 and 2 , the holder block  9 A has therethrough a threaded hole  9 D that is formed extending vertically or in perpendicular relation to the hole  9 C formed through the holder block  9 A. The aforementioned knife height adjusting bolt  15  is screwed through the threaded hole  9 E of the holder block  9 A and secured by the lock nut  13  that is screwed on the adjusting bolt  5  against the bottom of the holder block  9 A. Specifically, the adjusting bolt  15  is screwed through the threaded hole  9 E and secured by the lock nut  13  with a part of the adjusting bolt  15  of a certain length extending out from the bottom of the holder block  9 A so that the knife assembly P 2  has the desired knife height L 1 . 
     Before mounting the knife assembly P 2  to a knife carriage  1  ( FIG. 3 ), the adjusting bolt  15  is screwed in or out of the holder block  9 A for the knife height adjustment so that the distance between the cutting edge  7 C and the top surface of the adjusting bolt head  15 A becomes the desired knife height L 1 , as shown in  FIG. 1 . Because this knife height adjustment is performed substantially in the same manner as described with reference to  FIG. 12 , detailed description of the adjustment will not be reiterated. After the knife height adjustment is over, the position of each adjusting bolt  15  relative to the knife blade holder  9  may be secured by tightening the lock nut  13 . In so doing, the knife assembly P 2  is made ready for installation onto the knife carriage  1 . 
     Referring to  FIGS. 2 and 3 , the knife carriage  1  has a plurality of blade clamps  21  (only one clamp shown in the drawings). The blade clamps  21  are disposed on the front side of the knife carriage  1  at a predetermined spaced distance in the longitudinal direction of the knife blade  7  for clamping or holding down the knife blade  7  against a blade back support plate  3  that is fixed to the knife carriage  1  by bolts  5  and supports the knife blade  7  from behind the knife blade  7 . As shown in  FIG. 2 , each blade clamp  21  is located between any two adjacent knife blade holders  9 . The knife carriage  1  has a plurality of blade clamp support arms  17  projecting horizontally from the knife carriage  1  and spaced in the longitudinal direction of the knife blade  7 . Each blade clamp  21  has formed therein and on opposite sides thereof a pair of recesses  21 B and has a pair of shafts  21 A disposed within the recesses  21 A and extending in the longitudinal direction of the knife blade  7 . A bearing  19  is mounted on each shaft  21 A. Each blade clamp  21  is pivotally supported by two adjacent knife clamp support arm  17  by way of the bearings  19  and the shafts  21 A. The provision of the recesses  21 B in the blade clamp  21  permits the pivoting motion of the blade clamp  21  about the shafts  21 A without interfering with the knife clamp support arm  17 . 
     Additionally, each blade clamp  21  has formed at the center in the lower end thereof a recess  21 C to receive therein one end of a piston rod  25 B of a hydraulic cylinder  25  which will be described later. Specifically, a shaft  21 E is fixedly mounted to the knife clamp  21  extending in the longitudinal direction of the knife blade  7  in the recess  21 C of the blade clamp  21  and the piston rod  25 B of the hydraulic cylinder  25  is pivotally connected at the one end thereof to the shaft  21 E by way of a connection member  25 C provided at the one end of the piston rod  25 B and a bearing  21 D mounted on the shaft  21 E. The hydraulic cylinder  25  shown in  FIG. 3  is provided for each blade clamp  21  and connected pivotally at the proximal end  25 A thereof to a frame of the knife carriage  1 . The hydraulic cylinder  25  has a hydraulic pump motor (not shown) and a piping (not shown either). The blade clamp  21  is driven to rotate about the shaft  21 A by its corresponding hydraulic cylinder  25 . The hydraulic cylinder  25  is operable in response to a signal generated by manual operation of a control by a lathe operator. 
     Referring again to  FIGS. 2 and 3 , the knife carriage  1  has a plurality of auxiliary blade clamps  23 , each disposed between the knife blade  7  and its corresponding blade clamp  21 . As shown in  FIG. 3 , the auxiliary blade clamp  23  has therein adjacently to the upper end thereof a recess  23 A having a shape that is complementary to the shape of the upper end portion of the blade clamp  21  so as to receive therein the upper end portion of the blade clamp  21  thereby to position the blade clamp  21 . Though not shown in the drawings, the auxiliary blade clamp  23  has therein on the side thereof that is adjacent to the blade clamp  21  a plurality of permanent magnets to fix the blade clamp  21  against the auxiliary blade clamp  23  by magnetic attraction, as shown in  FIG. 3 . As with the blade clamp  21 , each auxiliary blade clamp  23  is positioned between any two adjacent knife blade holders  9  of the knife assembly P 2  mounted in the knife carriage  1 . As shown in  FIG. 3 , part of the surface of the auxiliary blade clamp  23  facing the knife blade  7  is recessed at  25 B toward the blade clamp  21  to secure tight contact between the auxiliary blade clamp  23  and the knife blade  7 . As shown in  FIG. 3 , the knife carriage  1  has a mounting surface  1 A that is provided by the top surface of a replaceable insert block which is made of a hard material and removably inserted in a groove formed in the knife carriage  1 . 
     The following will describe procedures for mounting and removing the knife assembly P 2  to and from the knife carriage  1 . In mounting the knife assembly P 2 , all blade clamps  21 ,  23  are moved to their retracted inoperative position away from the blade back support plate  3 , as shown in  FIG. 4 . The retraction may be accomplished by retracting the hydraulic cylinders  25  to pivot the blade clamps  21 ,  23  in counter-clockwise direction indicated by arrow in  FIG. 4 . Then, the lathe operator may insert the knife assembly P 2  by manual work into a space then formed between the auxiliary blade clamps  23  and the blade back support plate  3  and sets the knife assembly P 2  so that the head  15 A of the adjusting bolt  15  is in contact with the mounting surface  1 A and the second surface  7 A of the knife blade  7  is in contact with the blade back support plate  3 , respectively, as shown in  FIG. 5 . With the knife assembly P 2  thus set in the knife carriage  1 , the hydraulic cylinders  25  are operated to pivot the blade clamps  21 ,  23  in clockwise direction in  FIG. 5  to move the blade clamps  21 ,  23  to the position shown in  FIG. 3  so that the blade clamps  21 ,  23  hold down the knife assembly P 2  firmly against the blade back support plate  3  thereby to fix the knife assembly P 2  to the knife carriage  1 , as shown in  FIG. 3 . 
     The knife assembly P 2  set in the knife carriage  1  is used for peeling veneer from a wood block as described earlier with reference to  FIGS. 11 and 12 . When the cutting edge  7 C of the knife blade  7  is worn to such an extent that the knife blade  37  need be reground, the knife assembly P 2  is removed from the knife carriage  1 . In removing the knife assembly P 2 , the hydraulic cylinders  25  are operated to move the blade clamps  21 ,  23  away from the blade back support plate  3  by retracting the hydraulic cylinders  25  to the position shown in  FIG. 6 . 
     As the blade clamps  21 ,  23  are retracted to the inoperative position, the knife assembly P 2  is turned by its own weight with the blade clamps  21 ,  23  about the adjusting bolt head  15 A to the position shown in  FIG. 6 . The lathe operator or maintenance personnel may remove manually the knife assembly P 2  from the knife carriage  1  for regrinding of the knife blade  7 . After the regrinding and the subsequent knife height adjustment are over, the knife assembly P 2  is ready to be mounted on the knife carriage  1 . As apparent from the foregoing description, the knife assembly P 2  according to the above-described embodiment may be made lighter in weight than heretofore, so that removing and mounting of the knife assembly P 2  from and to the knife carriage  1  may be accomplished with ease and less time. 
     The second embodiment of a knife assembly according to the present invention will now be described with reference to  FIGS. 7 through 10 . Coordinate axes L, H and T appear in  FIGS. 7, 8 and 9 , wherein L represents the longitudinal direction, H the height direction and T the thickness direction of the knife blade  37 , respectively. 
     Referring firstly to  FIG. 7 , there is shown in perspective view a knife blade holder  30  for a knife assembly P 3  ( FIGS. 9 and 10 ) of the second embodiment. The knife blade holder  30  includes a holder block  31  having therein a cutout void portion and a bolt adjusting bolt  35 . Specifically, the holder block  31  is generally of a cuboid shape having formed therein a cutout void portion in the form of a recess  31 A having three adjoining surfaces  31 D,  31 F and  31 G. The surface  31 F has a height L 3  and a length L 4  and extends parallel to the first surface  37 D of the knife blade  37  when the holder block  31  and the knife blade  37  are assembled together into the knife assembly P 3  shown in  FIG. 9 . Similarly, the surface  31 G has a depth L 2  and a length L 4  and extends parallel to the base end surface  37 E of the knife blade  37 . The surface  31 D has a depth L 2  and a height L 3  and extends perpendicularly to the surfaces  31 F and  31 G. As shown in  FIG. 8 , L 2  corresponds to the thickness dimension of the knife blade  37 . The holder block  31  has a top surface  31 G having a surface area  31 E that is indicated by shading and will be described later. 
     The holder block  31  of the knife blade holder  30  has formed therethrough two holes, namely a threaded hole  31 B extending in height direction H and a hole  31 C extending in thickness direction T, respectively. Specifically, the threaded hole  31 B, which corresponds to the threaded hole  9 D in the first embodiment, is formed through the holder block  31  in height direction H. The hole  31 C, which corresponds to the hole  9 C in the first embodiment, is formed extending through the block holder  31  in thickness direction T and has one end thereof opened through the surface  31 F of the recess  31 A at a position spaced from the surface  31 D at a distance L 6  and from the top surface  31 H of the holder block  31  at a distance L 7 . The adjusting bolt  35 , which corresponds to the adjusting bolt  15  in the first embodiment, is inserted and screwed through the threaded hole  31 B from the bottom side thereof. The adjusting bolt  35  has a lock nut  33 . 
     Additionally, the holder block  31  has a solid portion adjoining to the void portion or the cuboid-shaped recess  31 A in longitudinal direction of the knife blade  37  and having a depth L 2 , a height L 3  and a length L 5 . The surface area  31 E in the top surface  31 H of the holder block  31  forms the top surface of the solid portion. The surface area  31 E is formed extending parallel to and spaced in the axial direction of the adjusting bolt  35  from the surface  31 G. 
     Such holder block  31  of the knife blade holder  30  may be made, for example, by preparing a workpiece having a cuboid shape and made of a hard material such as steel and removing or cutting a part from the block stock, which part includes one vertex of the cuboid shape of the workpiece. As with the first embodiment, the knife assembly P 3  of the second embodiment includes a plurality of the above-described knife blade holders  30 . 
     Referring to  FIG. 8 , there is shown in perspective view the knife blade  37  of the knife assembly P 3  of the second embodiment. As with the knife blade  7  of the first embodiment, the knife blade  37  has a first surface  37 D, a second surface  37 A, a bevel surface  37 B, a cutting edge  37 C, and a base end surface  37 E. The knife blade  37  has formed in the bottom thereof a plurality of cutout rectangular recesses  37 F (only one recess shown in  FIG. 8 ) each recessed from the base end surface  37 E toward the cutting edge  37 C and having a bottom surface  37 H that forms a part of the base end surface  37 E with a length L 5 . As shown in  FIG. 8 , the base end surface  37 E has a length L 5  and two opposite surfaces having a height L 3 . Thus, the rectangular recess  37 F of the knife blade  37  is configured to have a shape that is complementary to that of the aforementioned solid portion of the holder block  31  so that the solid portion is received in the recess  37 F of the knife blade  37 , as shown in  FIG. 9 . To be accurate, the size of dimension of the rectangular recess  37 F is just slightly larger than that of the solid complementary portion of the holder block  31  so that the holder block  31  is received snugly and fitted in the rectangular recesses  37 F. 
     As shown in  FIG. 8 , the knife blade  37  has formed therethrough a threaded hole  37 G, which corresponds to the threaded hole  9 D in the first embodiment. The threaded hole  37 G is formed extending in thickness direction T at a position that is spaced from the right-side surface of the rectangular recess  37 F as seen in  FIG. 8  at the distance L 6  and from an imaginary plane passing through the bottom surface  37 H at the distance L 7  so that the threaded hole  37 G and the hole  31 C of the knife blade  37  are positioned coaxially when the holder block  31  is fixed to the knife blade  37 . 
     Referring to  FIG. 9  showing the knife assembly P 3 , the knife blade holder  30  having the adjusting bolt  35  screwed through the threaded hole  31 B in the holder block  31  is fitted and fixed in the rectangular recesses  37 F of the knife blade  37  with the surface  31 F of the holder block  31  in contact with a part of the first surface  37 D of the knife blade  37  and with the surface area  31 E of the holder block  31  (indicated by shading in  FIG. 7 ) in contact with the bottom surface  37 H in the rectangular recess  37 F of the knife blade  37 , or alternatively with the surface  31 G in the recess  31 A of the holder block  31  in contact with the a part of the base end surface  37 E of the knife blade  37 . As shown in  FIGS. 7 through 10 , the surfaces  31 F and  31 G in the recess  31 A and the top surface  31 H including the surface area  31 E of the holder block  31  and the base end surface  37 E including the bottom surface  37 H of the knife blade  37  are formed flat, so that the above contacts are provided by surface-to-surface contact. With the holder block  31  mounted to the knife blade  37  as shown in  FIG. 9 , the hole  31 C in the holder block  31  is aligned with the threaded hole  37 G in the knife blade  37 . The knife holder  30  may be fixed to the knife blade  37  by the fixing bolt  39  inserted through the hole  31 C in the holder block  31  and screwed tight in the threaded hole  37 G in the knife blade  37 , as shown in  FIG. 9 . The fixing bolt  39  has such a length that no part of the end of the fixing bolt  39  opposite from the bolt head projects out of the threaded hole  37 G of the knife blade  37  when the fixing bolt  39  is tightened. The adjusting bolt  35  screwed through the threaded hole  31 B may be secured by the lock nut  33 . 
     As is apparent from the foregoing description, the surface  31 F of the recess  31 A of the holder block  30  serves as the first support surface and the surface area  31  of the holder block  31  as the second support surface of the present invention, respectively. As indicated above, the surface  31 G of the recess  31 A of the holder block  31  serves as alternative second support surface of the present invention. 
     In this knife assembly P 3 , the knife height adjustment to determine the dimension L 1  ( FIG. 1 ) between the cutting edge  37 C of knife blade  37  and the top surface of the adjusting bolt head is made in the same manner as described with reference to  FIG. 12 . After the knife height adjustment is over, the adjusting bolt  35  may be fixed securely by tightening the lock nut  33 . The knife assembly P 3  having the knife height adjusted properly is mounted to the knife carriage  1  of the veneer lathe in the same manner as with the knife assembly P 2  of the first embodiment. When the cutting edge  37 C of the knife blade  37  is worn calling for regrinding, the knife assembly P 3  is removed from the knife carriage  1  for regrinding and a knife assembly such as P 3  having a reground knife blade such as  37  is adjusted for the knife height and mounted to the knife carriage  1  of the veneer lathe. 
     In the knife assembly P 3  according to the second embodiment in which the threaded hole  31 B for the adjusting bolt  35  is formed through the holder block  31  at a position that is spaced away from the cutout recess  31 A in the longitudinal direction L, the threaded hole  31 B may be located close to the support surface  31 F and hence to the first blade surface  37 D. Therefore, the distance between the knife blade  37  and the adjusting bolt  35  in the knife assembly P 3  is reduced in comparison with the knife assembly P 2  of the first embodiment, as is apparent from comparison of  FIGS. 10 and 3 . This reduction of the distance helps to reduce the moment that is created due to the force applied to the knife blade  37  during veneer cutting and acts on the knife blade  37  in clockwise direction in  FIG. 10 . 
     It is to be noted that the present invention is not limited to the above-described embodiments, but it may be practiced in various ways as exemplified below. 
     In the foregoing embodiments, the holder block  9 A,  31  and the knife blade  7 ,  37  are fixed together through surface-to-surface contact between the knife blade  7 ,  37  and the holder block  9 A,  13 . According to the present invention, however, the support surfaces of the holder block and the base end surface of the knife blade need not be formed flat, but may be formed, for example, with a plurality of projections so that the contact between the knife blade and the holder block of the knife holder may provided by point-to-surface contact. 
     In the first and the second embodiments, the threaded holes  7 G,  37 G are formed through the knife blades  7 ,  37 , respectively. According to the present invention, however, the threaded holes need not necessarily be formed through the entire thickness of the knife blade as long as the holder block may be fixed to the knife blade with an appropriate strength. 
     Additionally, in making the knife assembly P 2 , P 3 , the holder block  7 A,  31  need not necessarily be fixed to the knife blade by means of fixing bolts. According to the present invention, however, the fixing of the holder block to the knife blade may be accomplished by means of adhesive or welding. 
     The adjusting bolts  15 ,  35  in the first and the second embodiments are secured by means of the lock nuts  13 ,  33 , respectively, to prevent loosening of the adjusting bolts. Alternatively, the adjusting bolt may be secured by using double-nut arrangement. 
     In the above-described embodiments, it is so arranged that the end of the fixing bolts  11 ,  39  opposite from the heads does not project beyond the second blade surface  7 A,  37 A of the knife blade  7 ,  37 . According to the present invention, however, the end of the fixing bolt may project slightly from the second surface of the knife blade as long as the knife assembly P 2 , P 3  may be fixed securely to knife carriage  1  without any inconvenience.