US3587685A - Apparatus and methods for debarking logs - Google Patents

Abstract

LOG DEBARKING APPARATUS AND METHODS WHEREIN A LOG TO BE DEBARKED IS PRESENTED TO THE NIP BETWEEN TWO ROTATABLE LOG TURNING MEMBERS AND A TOOTHED DEBARKING MEMBER, THE LOG BEING ROTATED AND SIMULTANEOUSLY MOVED LENGTHWISE TO ENABLE THE DEBARKING MEMBER TO REMOVE BARK FROM THE ENTIRE PERIPHERY OF THE LOG. THE TURNING MEMBERS ARE YIELDABLY, BUT FORCIBLY, MAINTAINED IN ENGAGEMENT WITH THE LOG BY A FLUID PRESSURE CYLINDER, AND THE TURNING MEMBERS ARE CAPABLE OF RELATIVE MOVEMENT TOWARD AND AWAY FROM ONE ANOTHER TO ENABLE LOGS OF IRREGULAR CROSS SECTION TO BE ACCOMMODATED BETWEEN THE TURNING MEMBERS. THE SPEED OF ROTATION OF EACH TURNING MEMBER IS THE SAME WITH ROUND LOGS BUT IS AUTOMATICALLY VARIABLE TO ENABLE THE PERIPHERAL SPEED OF EACH TURNING MEMBER TO CORRESPOND TO THE PERIPHERAL SPEED OF THE LOG AT THE POINT WHERE THE LATTER ENGAGES THE TURNING MEMBERS TO AVOID SLIPPAGE WHEN DEBARKING LOGS OR IRREGULAR SHAPE AND ENSURE THAT BOTH TURNING MEMBERS ARE ALWAYS EXERTING AN EQUAL TORQUE TO ROTATE THE LOG. THE AXES OF ROTATION OF THE TURNING MEMBERS ARE INCLINED TO THE AXIS OF ROTATION OF THE LOG, AND THE AXES OF ROTATION OF THE TURNING MEMBERS ARE AUTOMATICALLY ADJUSTED ACCORDING TO THE DIAMETER OF THE LOG FOR VARYING THE SPEED AT WHICH A LOG IS MOVED LENGTHWISE THROUGH THE MACHINE.

Description

United States Patent [72] Inventors Not-val K. Morey Winn, Mich. Leward N. Smith, Remus, Mich. [21 1 Appl. No. 773,408 [22] Filed Nov. 5, 1968 [45] Patented June 28, 1971 [73] Assignee Morbark Industries, inc.

Winn, Mich.

[54] APPARATUS AND METHODS FOR DEBARKING Primary Examiner-Gerald A. Dost Attorney-Learman, Learman & McCulloch ABSTRACT: Log debarking apparatus and methods wherein -a log to be debarked is presented to the nip between two by a fluid pressure cylinder, and the turning members are capable of relative movement toward and away from one another to enable logs of irregular cross section to be accommodated between the turning members. The speed of rotation of each turning member is the same with round logs but is automatically variable to enable the peripheral speed of each turning member to correspond to the peripheral speed of the log at the point where the latter engages the turning members to avoid slippage when debarking logs or irregular shape and ensure that both turning members are always exerting an equal torque to rotate the log. The axes of rotation of the tuming members are'inclined to the axis of rotation of the log, and the axes of rotation of the turning members are automatically adjusted according to the diameter of the log for varying thespeed at which a log is'moved lengthwise through the machine.

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INVENTORS NORVAL K. MOREY LEWARD N. SMITH BY lku'unun, l zu'lmmz f." M-C APPARATUS AND METHODS FOR DEBARKING LOGS This invention relates to the debarking of logs and more particularly to improved apparatus and methods for the rotation and lengthwise movement of a log relative to a debarking member at speeds best suited for the debarking of the particular log undergoing treatment.

In the debarking of logs it is quite common for successive logs to be of considerably different diameters and, in many cases, a single log will have cross-sectional shapes and sizes which are quite irregular. Such irregularities in a single log occur for various reasons, such as malformation during growth of the tree from which the log is cut; the presence of knots, and the like. irregularly shaped logs have been difficult to debark heretofore because of the inability of the log turning members to accommodate themselves automatically to changes in the log configuration. As a result, it frequently occurs that the rotational speed of a log is improper with respect to its diameter, the rate of lengthwise movement of the log is improper for its diameter, and wear producing slippage occurs between the log and the log turning members.

An object of this invention is to provide apparatus and methods which overcome the disadvantages referred to above.

Another object of the invention is to provide apparatus and methods wherein the speed of rotation imparted to a log by rotatable log turning members is adjusted automatically according to the diameter of the log.

A further object of the invention is to provide apparatus and methods wherein the rate of lengthwise movement of a log through the debarking station is adjusted automatically in accordance with the diameter of the log.

A further object ofthe invention is to provide apparatus and methods for rotating a log while the latter is being debarked and wherein the log rotating members accommodate themselves automatically to the contour of the log.

Another object of the invention is to provide log turning and feeding mechanism having individually drivable turning means and wherein the torque imparted to the log by each turning means is substantially uniform regardless of the relative speeds of rotation of the several log turning members.

Other objects and advantages of the invention will be pointed out specifically or will become apparent from the following description when it is considered in conjunction with the appended claims and the accompanying drawings, wherein:

FIG. 1 is a diagrammatic end view of the apparatus illustrating two different positions of adjustment of the log turning and feeding mechanism;

FIG. 2 is an end elevational view of the apparatus;

FIG. 3 is atop plan view;

FIG. 4 is a fragmentary, enlarged, side elevational view of the right-hand end of the apparatus shown in FIG. 2;

FIG. 5 is a fragmentary, perspective view of the apparatus shown at the left-hand end of FIG. 4;

FIG. 6 is a diagrammatic view illustrating how the apparatus is adaptable for use with irregularly shaped logs; and

FIG. 7 is a schematic diagram of a pressure fluid drive and control system for the machine.

The apparatus comprises a base frame 1 on which are mounted spaced, upstanding support members 2 having spaced apart end plates 3 between which is mounted a rockable table 4 that supports a rotatable log debarking member 5. The debarking member comprises a shaft 6 journaled in bearings 10 fixed to the table 4. Fixed to the shaft is a cylinder or drum 7 provided with a plurality of chipping teeth 8 which engage a log and chip the bark therefrom in a known manner. The table 4 is mounted for rocking movement by means of trunnions 11 supported on the side members 3, the arrangement being like that disclosed in US. Pat. No. 3,016,074, granted Jan. 9, I962.

The member 5 is adapted to be rotated in the direction of the arrow 0 by means of a sheave 9 fixed to the shaft 6 and around which may be trained a belt 12 that also is trained around the drive wheel of an internal combustion engine (not shown). A log L (see FIG. 1) may be supported on end plates 10a for engagement by the chipping teeth 8.

Mounted at one side of the frame I is a yoke 15 which is pivoted at its lower end in trunnions l6 by means of a pivot in 17. The yoke 15 thus is capable of rocking about a horizontal axis which is substantially parallel to the axis of rotation of the debarking member 5. Extending between the frame 1 and the yoke 15 is a fluid pressure operated ram 18 having its piston rod 19 pivoted to an arm 20 on yoke 15. The cylinder 21 of the ram is pivoted to the machine frame 1. A source of pressure fluid (to be referred to hereinafter) constantly, but yieldably, acts on the ram 18 in such manner as to contract its length, thereby urging the yoke 15 to rock counterclockwise as viewed in FIG.

At the free end of the yoke 15 is a bushing 22 in which is journaled a swivel shaft 23. The shaft 23 is fixed to a carrier 24 in which a cylindrical log turning or feeding member 25 is journaled by means of a shaft 26. The periphery of the member 25 is studded with a plurality of teeth 27 so as to provide a nonslip surface for the cylinder 25. The turning member is mounted for rotation in the direction of the arrow 11 and is driven by a chain 28 that is trained around a sprocket wheel 29 fixed to the cylinder 25 and around a sprocket wheel 30 that is fixed to the shaft 31 of a hydraulic motor 32 which is mounted on the carrier 24.

On that side of the frame opposite the yoke 15 is fixed a pair of uprights 35 in which is journaled a substantially horizontal shaft 36 that is carried by a yoke 37. The yoke 37, therefore, is capable of rocking movement about the axis of the shaft 36. Rocking movement of the yoke 37 is effected by means of a motion transmitting linkage generally designated 38 which interconnects the yokes l5 and 37. The linkage 38 comprises a plate 39 fixed to the yoke 15 and projecting from one side of the latter. To the plate 39 is pivoted one end of a connecting rod 40 the opposite end of which is pivoted to a lever 41 (see FIG. 5) which is pivoted at 42 to one of the uprights 35. Also pivoted to the lever 41 is one end ofa link 44, the opposite end of which is pivoted at 45 to the yoke 37. The construction and arrangement of the linkage 38 are such that movement of the yoke 15 either toward or away from the yoke 37 imparts corresponding movement to the latter. That is, the yokes l5 and 37 move conjointly and relatively toward and away from one another. The relative lengths of the yokes l5 and 37, however, are such that the extent of movement of the yoke 15 is greater than that ofthe yoke 37.

At the upper end of the yoke 37 is a bushing 49 in which is journaled a swivel shaft 50. To the shaft 50 is fixed a carrier 51, similar to the carrier 24, and in which is journaled a shaft 52 that is fixed to a log turning member or cylinder 53 having studs or teeth 54 similar to the teeth 27. The member 53 is adapted to be driven in the direction of the arrow 0 by means of a chain 55 that is trained around a sprocket wheel 56 carried by the cylinder 53 and around a sprocket 57 fixed to the shaft 58 ofa hydraulic motor 59 which is similar to the motor 32. Motors 32 and 59 may be the Char-Lynn motors manufactured by Char Lynn Co. of Eden Prairie, Minnesota, U.S.A.

As is illustrated most clearly in FIGS. 1, 2 and 3, the axes of rotation of the turning members 25 and 53 are tilted or inclined relatively to each other and to the axis of rotation of the debarking member 5. In FIG. 1, the axis of rotation of the debarking member 5 is indicated by the letter X, the axis of rotation of the turning member 25 is indicated by the reference character Y, and the axis of rotation of the turning member 53 is indicated by the letter Z. If that end of the machine adjacent the driving sprocket of the debarking member 5 is referred to as the forward end of the machine, then the axis Y is inclined downwardly and forwardly relative to the axis X and diverges from the latter in the forward direction. The axis Z is inclined upwardly and forwardly relative to the axis X and diverges from the latter in the forward direction.

The relationship among the three axes is important to the proper feeding of a log through the machine inasmuch as the relative positions of the axes of the turning members with respect to one another and with respect to the axis of the debarking member 5 determines the rate of forward movement of the log. If a log is relatively small diameter, it should be fed through the machine at a faster rate of speed than that at which a log of greater diameter is fed. The reason for this is twofold: firstly, a greater diameter log has a greater circumferential surface which must be presented to the debarking member 5 in order to remove all of the bark and, consequently, its rate of lengthwise movement must be such as to enable the entire circumference to be acted upon by the debarking member. Secondly, the length of time any given portion of a log remains in the debarking zone subjects the surface of the log to the chipping action of the teeth 8. If a portion of a log continues to be revolved in the debarking station following the removal of its bark, then the chipping teeth may remove portions of the exposed wood surface. Apparatus constructed in accordance with the invention provides for the automatic adjustment of the relative inclination of axes Y and Z inversely to the diameter of a log to be debarked, thereby providing automatic adjustment of the speed of lengthwise movement ofthe log through the machine.

Means for adjusting the axis of the turning member 25 comprises a linkage generally designated 60 having a link 61 pivoted at one end to a rigid member 63 that is fixed to the frame I. The opposite end of the link 61 is pivoted as at 64 to a bell crank 65 that is pivoted at 66 on the yoke 15. The crank 65 also is pivoted at 67 to one end of a connecting rod 68, the opposite end of which is universally pivoted at a ball joint 69 to the carrier 24.

The operation of the adjusting linkage 60 is controlled by movement of the yoke 15. For example, if the yoke is moved clockwise from the position shown in FIG. 2, the bell crank 55 will tend to move clockwise with the yoke. As the yoke moves clockwise, however, the link 61 will exert a force on the bell crank, rocking it counterclockwise. This movement of the bell crank 65 will be transmitted by the connecting rod 68 to the carrier 24 so as to swivel the latter, together with the turning member 25, in such direction as to decrease the degree of inclination of the axis Y to the axis X. That is, the axis Y will be more nearly parallel to the axis X so as to decrease the lengthwise thrust imposed by the member 25 on a log. This position of the member 25 is illustrated in chain lines in FIG. 1.

Means for adjusting the axis of the turning member 53 comprises a linkage generally designated 70 which constitutes a connecting rod 71 pivoted at 72 to the lower end of the lever 41 and universally pivoted at its upper end at a ball joint 73 to the carrier 51. The operation of the linkage 70 is responsive to rocking movement of the yoke 37. For example, if the yoke 37 is moved counterclockwise from the position shown in FIG. 2 by the linkage 38, the lever 41 will be rocked clockwise as viewed in FIG. 2 (or counterclockwise as viewed in FIG. 5) exerting a downward thrust on connecting rod 71 which is transmitted to the carrier 51 to swivel the latter in a direction to minimize the inclination of the axis 2 relative to the axis X. As a consequence, the lengthwise thrust imposed on a log by the turning member 53 will be reduced.

The geometry of the linkage systems 38, 60 and 70 is so selected that, regardless of the positions of the turning members 25 and 53, a radial line extending from the axis of rotation of the member 25 will intersect a radial line extending from the axis of rotation of the member 53 at a point which corresponds to the axis of rotation ofa log interposed between the members 25 and 53 and the debarking member 5. This characteristic of the apparatus is illustrated in FIG. 1 wherein the axis of the log L is indicated by the letter R.

Another factor which influences the rate of rotation of a log about its own axis and the rate at which the log is fed lengthwise through the machine is the speed at which each of the turning members and 53 is rotated. To prevent slippage between the turning members and a log to be turned thereby, it is important that the peripheral speed of each turning member coincide with the peripheral speed of the log at the points where the latter engages the turning members. If a log is substantially cylindrical the peripheral speed at each point about the circumference of the log will be substantially uniform. Under these conditions, the speeds of rotation of the two turning members will correspond. It is quite unusual, however, for a log to be of uniform diameter. This is due to many reasons which are of no particular significance to the description of the present invention. It is sufficient that it be recognized that logs are of somewhat irregular cross section, rather than being truly cylindrical. In the debarking of an irregularly shaped log one point on the circumference of the log may have a peripheral speed somewhat different from that of another point on the circumference of the same log. Unless the turning members are capable of adjusting their speeds to the different peripheral speeds of the circumference of the log, slippage between the log and at least one of the turning members inevitably will result.

Apparatus constructed in accordance with the invention includes control means 75 (see FIG. 7) for controlling the speeds of rotation of the log turning members 25 and 53. The control means comprises a reservoir 76 from which hydraulic fluid may be withdrawn by a pump 77. A pressure relief valve 78 is interposed between the discharge side of the pump 77 and the reservoir 76. Fluid fromthe pump 77 is delivered to a manually operable reversing valve 79 having an operating handle 80 controllable by the machine operator. The valve 79 has a neutral position, a forward position and a reverse position. Regardless of whether the valve 79 is in its forward or reverse position, fluid is delivered to a union 81 between two identical, fixed flow, pressure compensated valves 82 and 83, each of which is adjusted so as to be capable of accommodating somewhat less than the entire discharge from the pump 77. For example, each of the valves 82 and 83 may be set to, at a maximum, accommodate approximately 75 percent of the output of the pump 77. Under normal operation the relative speeds of turning members 25 and 53 will never exceed a situation in which one turning wheel motor would require more than 75 percent of the pumps capacity. Flow through valves 82 and 83 is free up to a maximum of 75 percent of the pumps flow capacity in a typical machine.

Fluid passing the valve 82 is delivered to the hydraulic motor 32 which drives the turning member 25. Fluid passing the valve 83 is delivered to the hydraulic motor 59 which drives the turning member 53. Fluid from the motors 32 and 59 is recirculated to the reservoir.

Associated with the control apparatus 75 is regulating means 85 for controlling the relative separation of the turning members 25 and 53. The regulating means comprises a pump 86 which draws fluid from the reservoir 76 and delivers it to a manually operable valve 87 which is controlled by an operating lever 88. lnterposed between the pump 86 and the reservoir is a relief valve 89. Fluid from the valve 87 is delivered to a manually adjustable accumulator charge valve 90 and thence to the cylinder 21 of the hydraulic ram 18. The accumulator charge valve 90 also communicates with the cylinder 21 via a pneumatic accumulator 91 and a pressure gauge 92. The arrangement is such that the accumulator normally is charged so as to exert a force on the ram 18 tending to move the turning members 25 and 53 toward one another under the yieldable force of the air head in the accumulator 91. When desired, however, the valve 87 may be adjusted by the machine operator so as to introduce hydraulic fluid to the cylinder 21, thereby extending the ram 18 and effecting movement of the turning members 25 and 53 away from one another.

When the machine is in condition for operation, the log turning members 25 and 53 will be located adjacent one another substantially in the positions indicated in full lines in FIG. 1 as a result of the constant bias exerted on the yoke 15 by the regulating means 85. The turning members 25 and 53 will be rotating in the same rotational direction and at substantially the same speed as a result of the operation of the control means 75. The debarking member 5 will be rotating in the direction of the arrow a as a result of the operation of its driving motor. Under these conditions, a log L of substantially trunnions to accommodate the log. As the log is introduced between the rotating members, the engagement of the log with the members 25 and 53 will cause the latter to be spread apart slightly as is permitted by the accumulator 91. The application of force by the log on the turning member 25 tending to move it away from the debarking member 5 will cause the yoke to rock clockwise, as viewed in FIG. I, and such movement of the yoke 15 automatically will be transmitted via the linkage 38 to the yoke 37 to cause the latter to move counterclockwise. The turning members 25 and 53 thus will be moved apart a distance to accommodate the log L therebetween, but the pneumatic head in the accumulator 91 constantly will exert a force on the ram 18 tending to move the turning members toward one another, thereby maintaining the turning members in engagement with the log L and the latter in engagement with the debarking member 5.

The speeds of rotation of the turning members 25 and 53 are determined by the fluid flow through the respective valves 82 and 83. Thus, if a greater quantity of fluid flows through one of the valves, the associated turning member will rotate at a faster speed than that of the other.

The speed at which each turning member rotates is directly proportional to the length of the radial from the axis of rotation of the log to the respective turning members. In the case of the log L, the radial from the axis R to each of the turning members is substantially the same, so the speeds of rotation of the two turning members should substantially coincide. In the case of the log L illustrated in FIG. 6, however, this is not true. In FIG. 6, the radial from the axis R to the periphery of the turning member 53 corresponds to the distance D, whereas the radial distance from the axis R to the periphery of the turning member 25 corresponds to the distance D+, the distance D+ being greater than the distance D.

In the positions of the members illustrated in FIG. 6, the peripheral speed of that portion of the log L adjacent the turning member 25 is somewhat greater thanthat of the portion of the log adjacent the periphery of the turning member 53. If there is to be no slippage of either turning member relative to the log, therefore, the speed of rotation of the turning member 25 must be greater than that of the turning member 53. The amount of hydraulic fluid necessary to drive the member 53 at a speed less than that of the turning member 25 is less than the amount of fluid necessary to drive the turning member 25 at the higher speed. Thus, the two valves 82 and 83 automatically will adjust the flow of hydraulic fluid through the respective motors 32 and 59 so as to drive them at the proper speeds. As a consequence, each turning member will exert exactly the same torque on the log L' even though the speeds of the two turning members differ.

When the log L has been rotated 180 from the position illustrated in FIG. 6, the axis R of rotation of the log L will shift. In this instance, it may be necessary for the speed of rotation of the turning member 53 to exceed that of the turning member 25. The shift in the relative speeds of the turning members is attained automatically however, by means of the aforementioned valves 82 and 83.

The application of equal torques on a log by both turning members 25 and 53 is assured by the setting of the valves 82 and 83 in such manner that neither can accommodate the full output of fluid from the pump 77. Thus, even though the flow of fluid through the valves 82 and 83 will follow the course of least resistance and be diverted to the turning member offering the least resistance to rotation, some of the driving fluid will be diverted to the other turning member, thereby preventing any possibility of freewheeling of one turning member and no driving force being exerted by it on the log. Such slippage causes horsepower and drive problems which do not occur where each turning member in effect chooses its own speed. The speed of rotation of the log turning members 25 and 53 is governed by the flow of oil, whereas the driving torque delivered by each is governed by the pressure of the oil, which remains constant.

Although the speeds of rotation of the turning members 25 and 53 may vary, each will exert its proportionate share of force on a log to feed the latter lengthwise through the machine. This is due to the construction ofthe linkages60 and 70 in such manner that the lengthwise driving force exerted on the logs by the respective turning member is a function of the degree of inclination of the axes Y and Z to the axis X and to the ability of the turning members to exert equal torque on a log therebetween. The capacity of the pump 77 should be so selected that when the turning members 25 and 53 are in their positions of closest proximity, the relative inclination of the axes Y and Z and the relative speeds of rotation of the turning members are such that the log will be fed spirally through the machine at a rate of speed such that the chipping teeth 8 will effect complete debarking of the log.

The rate of lengthwise movement of a small diameter log obviously can be greater than that of a large diameter log inasmuch as the smaller diameter log has a smaller circumference to be debarked. The construction of the linkage 38 is such that the greater the distance apart the turning members 25 and 53 are moved to accommodate the log therebetween, the lesser is the inclination of the axes Y and Z. Consequently, the forward lengthwise speed of movement of a larger diameter log through the machine is less than that of a smaller diameter log.

In the operation of the apparatus, any log that is too large in diameter to enter the bight between the members 25, 53 and 5, when the latter are in their relatively closed positions, may be admitted to the machine upon the operators manipulating the valve 87 so as to enable fluid from the pump 36 to extend the ram 18 and force the turning members 25 and 53 away from one another. Thereafter, when the operator releases the valve operating handle, the accumulator 91 acts on the ram 22 to urge the members 25 and 53 toward one another so as to maintain both turning members in driving engagement with the log.

Logs presented to the debarking machine conventionally follow one another in end-to-end relation. Consequently, any succeeding log that is the same or smaller in diameter than the immediately preceding log may be introduced between the turning members 25 and 53 without the operator's attention to the valve 87.

The disclosed apparatus is representative of a presently preferred embodiment of the invention, but is intended to be illustrative rather than definitive thereof. The invention is defined in the claims.

We claim:

1. Log debarking apparatus comprising a debarking member rotatable about an axis and having axially spaced bark cutting members thereon: a pair of log turning members having log gripping, nonbark removing, torque transmitting parts thereon, each member being rotatable about its own axis, the axis of each of said turning members being inclined relatively to the axis of said debarking member; means for rotating said log turning members in opposite directions normally at the same speed of rotation to spiral the log axially past said debarking member; means rotating said debarking member in a direction to oppose the rotation of the log imparted by said turning members and at a speed to cut bark from the entire circumference of the log; means mounting said turning members for movement toward and away from said debarking member; and means automatically responsive to movement of said turning members toward and away from said debarking member to vary the inclination of said axes in a manner such that regardless of the positions of the turning members, a radial line extending from the axis of rotation of one turning member will intersect a radial line extending from the other turning member at a point substantially corresponding to the axis of rotation of a log gripped between the two turning members.

2. Apparatus as set forth in claim 1 wherein the greater the distance between said turning members, the lesser the relative inclination of their axes.

3. Apparatus as set forth in claim 1 wherein the lesser the distance between said turning members, the greater the relative inclination of their axes.

4. Apparatus as set forth in claim 1 wherein said moving means acts on one of said turning members, and including motion transmission means interconnecting said one of said turning members with the other.

5. Apparatus as set forth in claim 4 wherein the range of movement of said one of said turning members is greater than that of said other of said turning members.

6. Apparatus as set forth in claim 1 wherein each of said turning members is swivelable and wherein said responsive means includes means for swiveling said turning members.

7. Apparatus as set forth in claim 6 wherein the range of swiveling movement of each of said turning members is substantially uniform.

8. Apparatus as set forth in claim 1 including driving means for rotating said turning members about their respective axes.

9. Apparatus as set forth in claim 8 wherein said driving means includes pressure fluid operated rotary motor means.

10. Apparatus as set forth in claim 9 wherein said pressure fluid means comprises a source of said fluid; pump means having a predetermined fluid pumping capacity; and valve means interposed between said pump means and each of said turning members for delivering fluid from said pump simultaneously to each of said timing members.

11. The apparatus set forth in claim 10 wherein neither of said valve means is capable of accommodating the full amount of fluid discharged by said pump but freely passes fluid below a preset maximum.

12. Log debarking apparatus comprising a debarking member rotatable about an axis; a pair of log turning members each rotatable about its own axis and forming a log receiving nip with said debarking member; means for rotating said debarking member; first driving means for rotating one of said turning members; second driving means for rotating the other of said turning members; and means for normally rotating said turning members at the same speed to process a substantially round log, automatically operating said first and second driving means at such relative speeds as to enable the respective turning members to exert substantially equal torque on a log portion interposed therebetween and avoid substantial slippage between the turning members and log, when the log por tion is substantially out of round.

13. The apparatus set forth in claim 12 wherein said first and second driving means comprise pressure fluid motors, and means for delivering pressure fluid to each of said motors.

14. The apparatus set forth in claim 13 wherein said control means comprises valve means interposed between said delivering means and each of said motors, neither of said valve means being capable of accommodating the full quantity of pressure fluid available from said delivering means.

15. The combination defined in claim 13 in which pump means supplying pressure fluid independently of said means for delivering pressure fluid to each of said motors is provided, and means is operated thereby to bias one of said log turning members normally toward the other to grip a log therebetween, means being provided responsive to movement of the turning members toward and away from the debarking member and each other to vary the inclination of the axes of the turning members.

16. The combination defined in claim 12 wherein said means for rotating said log turning members includes a hydraulic circuit including pump means for furnishing hydraulic fluid, a hydraulic motor for driving each of said turning members, and flow proportioning means reactive to the respective resistance to rotation of each of said turning members to maintain the turning members exerting the same torque on the log, when a portion of the log is out of round in sha e.

1%. A method of debarking a log having at least a portion of noncylindrical shape comprising: introducing a log to the nip between rotatable debarking means and a pair of rotatable log turning and feeding members; engaging said turning members with the periphery of said log to rotate the latter; rotating said log turning and feeding members at such speeds as to enable the respective turning members to exert substantially equal torque on the log and to thereby substantially avoid slippage between the log and turning members, even when said portion is engaged between the turning members; and adjusting said turning members relatively to the axis of rotation of said log so that the axes of rotation of said turning members are inclined relative to the axis of rotation of said log by an amount such as to effect axial movement of the log as the latter is rotated and at such rate as to enable said debarking means to traverse the entire periphery of said log.

18. The method set forth in claim 17 comprising maintaining the speed of rotation of each of said turning members at such rate that the peripheral speed of each turning member corresponds substantially to the peripheral speed of said log at the zones where said log is engaged by said turning members.

19. The method set forth in claim 17 including yieldably but forcibly maintaining said turning members in engagement with said log.

20. The method set forth in claim 17 including varying the inclination of the axes of rotation of said turning members inversely according to the diameter of said log.

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