Sawing System For Sawing Of Logs Sorted To Diameter Class

Abstract

Log infeed apparatus for a sawmill includes log-holding arms depending from separate carriages on an overhead trackway. The trackway is positioned so that the lower, log-gripping portions of the arms move the log in the feeding line for the saws. A first endless drive line moves connected carriages at a first speed along the trackway, and a second endless drive line moves connected carriages at a second speed greater than the first speed along the trackway to facilitate the gripping and release of logs by the arms. Each log-holding arm has both a fore log-gripping device facing in the infeed direction and a rear log-gripping device facing in the opposite direction so that a single arm can support opposite ends of two longitudinally adjacent logs in the feeding line.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device for feeding logs through one or several successive saws or other log-processing machines.

2. Description of the Prior Art

The device can be regarded as a development and improvement of the log-feeding device described in U.S. Pat. No. 3,503,428.

In the log-feeding device of the type described in the above-mentioned patent it is necessary to have two log-holding arms for each log to be fed through the saw or the row of saws. One of these log-holding arms holds the log at its fore end, whereas the second log-holding arm holds the log at its rear end so that the log is held between the two log-holding arms. Consequently, according to the prior art, between two successive logs being fed through the saw or the row of saws, there are always two log-holding arms. The leading arm holds the rear end of the preceding log, and the second or following arm holds the fore end of the succeeding log. Further, a certain space or gap cannot be avoided between the two successive log-holding arms holding longitudinally adjacent logs because of the different way in which these arms function. The fore log-holding arm is kept stationary while the rear log-holding arm is moved by means of the endless drive chain forwardly toward the rear end of the log until contact is made, after which the log is moved forwardly toward the stationary fore log-holding arm until the fore end of the log reaches this fore log-holding arm and the log is grasped between the two log-holding arms.

The gap between two successive logs being fed through the saw or row of saws, which cannot be avoided in the above-mentioned prior art feeding device is not very harmful in a saw-mill in which the logs are not sorted and grouped according to their diameters before the sawing. In such a sawmill a certain interval or gap between successive logs is necessary to provide time for resetting the saws from a setting suitable for the saw-ing of a log of one diameter to a setting suitable for the sawing of a following log having a different diameter.

However, in many sawmills logs are sorted and grouped into different diameter classes before the sawing of the logs so that all logs in the same diameter class can be sawn successively with the same setting of the saws. In this way it becomes possible to saw a large number of logs without changing the setting of the saws. In this way the necessary time for the resetting of the saws can be saved, whereby at least theoretically a larger production capacity can be reached. It becomes also possible to use saws, as for instance frame saws, the setting of which cannot be changed automatically and rapidly. In such a sawmill, however, the intervals or gaps between successive logs which are unavoidable in the prior art feeding device cause an undesired reduction of the production capacity of the sawmill.

SUMMARY OF THE INVENTION

An object of the present invention is therefore to provide an improved feeding device of the general type previously described in which the gaps or intervals between successive logs are reduced considerably.

According to the invention the above object is achieved in a log-feeding device wherein one log-holding arm can at the same time hold the rear end of a preceding log and the fore end of a following log. Thus the gap or space between two successive logs being fed simultaneously through the saws corresponds to the dimension in the feeding direction of a single log-holding arm. Consequently, the logs are fed very closely spaced through the saws, whereby a high production capacity is possible.

As compared with the log-feeding device described in the above-mentioned patent, the log-feeding device according to the invention simplifies substantially the grasping of the logs between the log-holding arms at the input side of the saws.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages will become more apparent from the following detailed description which proceeds with reference to the accompanying drawings, in which:

FIG. 1 shows schematically and by way of example a side view of a sawmill including a number of log-processing machines positioned one after the other along a processing line and provided with a log-feeding device according to the present invention;

FIG. 2 is a plan view of the same sawmill, in which the log-holding arms and their trackway have been omitted for the sake of clarity;

FIG. 3 is a section at a larger scale through the sawmill along the line III--III in FIG. 1;

FIG. 4 is a section at a larger scale through the sawmill along the line IV--IV in FIG. 2;

FIG. 5 shows schematically and at a larger scale a side view of a preferred design of the lowermost end of the log-holding arms; and

FIG. 6 shows schematically a plan view of a sawmill comprising two parallel processing lines, each including several processing machines positioned one after the other along the processing line, and a log-feeding device according to the invention.

DETAILED DESCRIPTION

The sawmill illustrated in FIGS. 1-4 comprises three log-processing machines positioned one after the other, and more particularly a cant- or plane-reducing machine 8, which cuts or mills two opposite faces on the log, and two double band saws 9, each separating one board from each side of the cant received from the canting machine 8. The feed direction through the machines 8, 9 is indicated with an arrow in FIGS. 1 and 2.

The fresh logs are supplied to the input side of the sawmill by means of a transverse conveyor 1. The logs are resting upon this transverse conveyor 1 with their longitudinal directions parallel with the sawing or feeding line through the machines 8, 9. The transverse conveyor 1 is provided with an end-aligning device 2, which functions to align the logs with their rear ends along a common line.

In the present specification the two opposite ends of a log are called the fore end and the rear end, respectively, in accordance with the direction of movement of the log through the machines. The transverse conveyor 1 delivers the logs one by one to a so-called single-log feeder 3, which is shown more clearly in FIG. 4. From this single-log feeder 3 the logs are supplied one by one and at predetermined intervals to an aligning device 5. This aligning device 5 extends in the direction of the feeding line for the logs at the input side of the machines 8, 9 and consists of a plurality of pairs of rotatable cylinders. Each pair of cylinders is connected to drive means (not shown in detail in the drawing), by means of which the associated pair of cylinders can be rotated in the one or the opposite direction. By rotation of the pair of pairs of cylinders upon which a log is supported at the moment, the log can be rotated about its longitudinal axis and thereby be adjusted into the best position for the processing of the log in the machines 8, 9.

For feeding the logs through the processing machines 8, 9 the sawmill is provided with a log-feeding device according to the present invention. This log-feeding device comprises a plurality of vertical dependent log-holding arms 4, each mounted on a separate carriage 4a. The carriages 4a are supported by and individually movable along a trackway 11, which forms a closed circuit for the carriages. The drawing shows only that part of the trackway 11 which extends parallel to and above the feeding line through the processing machines 8, 9 from their input side to their output side. The remaining portion of the closed circuit trackway 11, that is, from the output side back to the input side, can extend in various ways, as for instance at one side of the processing machines 8, 9 or alternatively below or above the machines.

It should be preferable to locate the "return portion" of the trackway 11 at the one side of the processing machines 8, 9 in the same horizontal plane as the portion of the trackway 11 extending above the feeding line through the processing machines. Such an arrangement is illustrated in FIG. 3.

For moving the carriages 4a and thus also the log-holding arms 4, an endless chain 7, in the following called the feeding chain, is provided. This feeding chain runs over chain wheels 7a and extends parallel to at least the portion of the trackway 11 extending above the feeding line from the input side to the output side of the machines 8, 9. By suitable drive means (not shown in detail in the drawing) this feeding chain 7 is driven with a predetermined speed.

An additional endless chain 6, in the following called acceleration chain, is arranged at the input side of the processing machines 8, 9 in such a way as to extend parallel to the feeding chain 7. This acceleration chain 6 runs over chain wheels 6a. It is continuously driven by suitable drive means (not shown in detail in the drawing) with a predetermined speed which is higher than the speed of the feeding chain 7. A similar additional endless chain 10, also called acceleration chain, is arranged at the output side of the processing machines 8, 9 so as to extend parallel to the feeding chain 7. This acceleration chain 10 runs over chain wheels 10a. It is driven by suitable drive means (not shown in detail in the drawing) with a predetermined speed which is higher than the speed of the feeding chain 7. The direction of movement of the chains is indicated with arrows in FIG. 1.

Each carriage 4a is provided with suitable coupling means (not shown in detail in the drawing) by means of which the carriage can be connected selectively either to the feeding chain 7 or to any one of the acceleration chains 6 and 10. A suitable coupling means is shown, for example, in prior U. S. Pat. No. 3,503,428. The coupling means can be actuated by stationary actuating means along the trackway 11 so as to disconnect the carriage 4a completely from all chains. Such a stationary actuating means is provided at least at the position 50 behind the rear end of the aligning device 5 at the input side of the machines 8, 9. Thus in this position the carriages 4a with the log-holding arms 4 can be disconnected from the driving chains and be kept stationary.

As illustrated schematically in FIG. 4, the lowermost end of each log-holding arm 4 is provided with a fixed foregripping portion 13 having a fore log-holding surface provided with spikes 13a facing forwardly, that is, in the direction of movement of the arm. Such arm also includes a rear gripping member 14 pivoted in the arm 4 and having a rear log-holding surface provided with rearwardly facing spikes 14a. The fixed portion 13 with its spikes 13a is intended to act against the rear end surface of a log in front of the log-holding arm 4, whereas the member 14 with its spikes 14a is intended to act against the fore end surface of a log following after the log-holding arm. The two relatively movable members 13 and 14 of the arm are urged in a direction away from each other by an intermediate resilient and/or shock-absorbing member 15.

In continuous operation the log-feeding device operates in the following manner. When a log has been delivered by the single-log feeder 3 to the aligning device 5, a carriage 4a with a log-holding arm 4, previously disconnected from all drive chains and kept stationary in waiting position 50, is coupled to the acceleration chain 6. Thus this log-holding arm moves forwardly toward the rear end of the log just delivered to the aligning device 5. When the arm contacts the log, the arm starts to push this log along the aligning device, while simultaneously any necessary aligning or adjusting of the log can be carried out. In order to reduce the shock between the log-holding arm and the log, the log can be started up by means of a separate pusher or starter 16, before the log-holding arm 4 reaches the rear end of the log.

Because acceleration chain 6 has a higher speed than feeding chain 7 and because the preceding log-holding arms 4, between which logs are already held, have their associated carriages 4a coupled to feeding chain 7, the log moved forwardly along aligning device 5 by the log-holding arm 4 coupled to acceleration chain 6 eventually catches up with the preceding log-holding arm and pushes its fore end against the movable member 14 of this preceding log-holding arm. Due to the higher speed of acceleration chain 6 as compared with feeding chain 7, resilient member 15 between the member 14 and 13 in the preceding log-holding arm is compressed at the same time as spikes 14a are pressed into the fore end of the succeeding log. When the resilient member 15 is compressed to a predetermined extent and thus a corresponding predetermined clamping force is attained for the log between the rearmost log-holding arm and the next rearmost log-holding arm, the rearmost log-holding arm, up to now connected to acceleration chain 6, is automatically disconnected from this chain and instead connected to feeding chain 7. Therefore this rearmost arm is moved on with the clamped log through the processing machines 8, 9 with the speed of feeding chain 7.

In this way the logs are successively supplied to the aligning device 5 at the input side of the machines 8, 9 and grasped between the log-holding arms 4. Obviously therefore, the logs will be fed through the processing machines 8, 9 with only a small gap or space between successive logs corresponding to the dimension of a single log-holding arm in the feed direction.

When the logs have been grasped or clamped between the log-holding arms, they do not have to rest upon any support means but can be supported entirely by the log-holding arms 4. Of course, however, it is also possible to have supporting members or surfaces for the logs which extend along the entire path of movement for the logs through the machines 8, 9 to the output side.

When the boards separated from the log by means of the band saws 9 have been removed in a suitable manner (not illustrated in detail in the drawing), the remaining parts of the logs, the so-called cants, are released from the log-holding arms. This is achieved in the following manner. When a log-holding arm has been moved by means of the feeding chain 7 to a predetermined position at the output side of the machines 8, 9, the carriage 4a associated with said log-holding arm is automatically dis-connected from the feeding chain 7 and instead connected to the acceleration chain 10 which is driven with a higher speed than the feeding chain 7. This may be done in the manner suggested, for example, in prior U. S. Pat. No. 3,503,428. The speed of the log-holding arm is consequently increased so that the distance increases between this log-holding arm and the next following log-holding arm, the latter still being driven by the slower feeding chain 7, whereby the grip of the log previously held between these two log-holding arms is released.

For returning the log-holding arms from the output side to the input side along the "return portion" of the trackway 11 (not shown in the drawing), several different arrangements can be used. In the most simple case the feeding chain 7 extends parallel to the trackway 11 along its entire length and is used for moving the carriages 4a of the log-holding arms also along the return portion of the trackway 11. In order to return the log-holding arms from the output side to the input side at a higher speed, it is also possible to use the acceleration chains 6 and 10 or an additional drive chain having a higher speed. If preferable, one or several additional waiting positions for the log-holding arms 4 can be arranged along the return portion of the trackway 11, in which waiting positions the log-holding arms can be completely disconnected from the drive chains and kept stationary.

It is appreciated that independent of the arrangement for moving the log-holding arms along the return portion of the trackway 11, the two acceleration chains 6 and 10 on the input side and the output side respectively can preferably consist of a single chain.

For guiding the log-holding arms 4 in the transverse direction, stationary guide rails 12 can be arranged immediately above the logs, as illustrated in FIGS. 1 and 3. Alternatively, similar guide rails could be arranged at the lowermost ends of the log-holding arms 4 below the logs.

The coupling means on the carriages 4a for the log-holding arms 4 for connecting the carriages selectively to the feeding chain 7 or the acceleration chains 6 and 10 can be designed in several different ways. Thus, for instance, the coupling device for connecting a carriage 4a to the feeding chain 7 can be designed substantially in the manner disclosed in FIGS. 9 and 10 of the above-mentioned patent. Such coupling means includes a chain wheel which is in engagement with feeding chain 7 and against which spring-biased clamps are pressed in such a way that they automatically prevent rotation of the chain wheel in such a direction that the carriage 4a moves at a lower speed than the feeding chain 7. At the waiting position 50 and any additional waiting positions these clamps can be inactivated by means of stationary cam paths so that the carriage 4a can be kept stationary.

Preferably an additional pair of spring-biased clamps are pressed against the chain wheel in such a way that they automatically prevent rotation of the chain wheel in such a direction that the carriage 4a can move at a higher speed than the feeding chain 7. These additional clamps are inactivated by means of stationary guide paths which extend along the acceleration chain 6 and the acceleration chain 10 at the input side and the output side, respectively. They also extend along the return portion of the track wheel 11, if the log-holding arms 4 are to be returned from the output side to the input side by means of any other drive chain than the feeding chain 7.

For the connection of a carriage 4a to the acceleration chain 6 or 10 respectively, a similar coupling device can be used, which consists of a chain wheel which is in engagement with the acceleration chain 6 and 10 respectively. This chain wheel is provided with a friction brake or friction coupling, which prevents the rotation of the chain wheel as long as the driving force exerted upon the carriage 4a on the acceleration chain 6 and 10 respectively does not exceed a predetermined value. At the input side this friction coupling will start to slip, whereby the coupling between the carriage 4a and the acceleration chain 6 is automatically disconnected, when the carriage is slowed down by the log in front of the associated log-holding arm 4 having caught up with the preceding log-holding arm and the necessary clamping force for the log having been achieved.

At the output side, where the carriage 4a is disconnected from the feeding chain 7 and connected to the acceleration chain 10, a stationary activating member is preferably arranged to influence the friction coupling in such a manner that its friction force is temporarily increased. In this way the carriage is automatically switched over from the feeding chain 7 to the acceleration chain 10 so that the log-holding arm 4 associated with the carriage can be pulled away from the fore end of the succeeding log.

FIG. 6 shows schematically how a log-feeding device according to the invention may be used in a saw mill having two groups of processing machines arranged along two parallel processing or sawing lines. For the sake of clarity the log-holding arms and the trackway of the log-feeding device have been omitted in FIG. 6. The one machine group of the saw mill consists of a canting machine 22 and two double band saws 23 and 24. The second group of processing machines consists of a canting machine 32 and three double band saws 33, 34 and 35. The feed directions for the logs through the two machine groups are opposite and indicated by arrows in FIG. 6.

The logs are supplied to the saw mill building 48 in the manner described in the foregoing by means of a transverse conveyor 17. They are transferred via an end-aligning device 18 and a single log feeder 19 to an aligning device 20 at the input side of the machine group 22, 23, 24. A log-holding arm (not shown in the drawing), kept stationary in the waiting position 37 at the rear end of the aligning device 20, is connected to the acceleration chain 38, whereby the log-holding arm moves, in the manner described in the foregoing, the log last delivered to the aligning device 20 towards the preceding log-holding arm and clamps the log between itself and said preceding log-holding arm. Thereafter the driving of the rearmost log-holding arm is automatically taken over by the feeding chain 21.

After a log has been fed through machine group 22, 23, 24 held between two log-holding arms driven by feeding chain 21, the remaining cant is dropped onto a transverse conveyor 25 when the log-holding arm holding the fore end of the cant is disconnected from the feeding chain 21 and instead connected to the acceleration chain 39. The transverse conveyor 25 transfers the log via an end-aligning device 26 and a single log feeder 27 to an aligning device 28 at the input side of machine group 32, 33, 34, 35.

The log-holding arms which have been pulled free from the logs by means of the acceleration chain 39 at the output side of machine group 22, 23, 24, are in the illustrated embodiment of the invention driven past the chain wheels 29 and 30 by means of a feeding chain 21 to a waiting position 31 behind the rear end of aligning device 28. From this waiting position 31 a log-holding arm is started, as described in the foregoing, by connecting the arm to acceleration chain 40. Thus the arm will push the cant last delivered to the aligning device 28 forwardly until the fore end of the cant strikes the immediately preceding log-holding arm and is clamped between two log-holding arms. Thereafter the log-holding arm holding the rear end of the cant is automatically disconnected from acceleration chain 40 and connected to feeding chain 21. The cant held between the two log-holding arms is consequently moved by means of the feeding chain 21 through the machine group 32, 33, 34, 35.

It should be pointed out here that the cant has been rotated through 90.degree. about its longitudinal axis relative to its position during the processing in machine group 22, 23, 24. Consequently canting machine 32 cants the two previously unprocessed side faces of the cant, whereafter double band saws 33, 34, 35 separate each two boards from the cant. The portion of the cant remaining after passing through processing machines 32, 33, 34, 35 is dropped onto a transverse conveyor 36 when the log-holding arm holding the fore end of the cant is disconnected from feeding chain 21 and instead connected to acceleration chain 41. The log-holding arm thus released from the log is in the illustrated embodiment returned to waiting position 37 by feeding chain 21.

The boards cut away by band saws 23 and 24 are transferred by a transverse conveyor 45 to a longitudinal conveyor 46. Conveyor 46 conveys the boards to additional processing machines, as for instance board edgers, or to a storing site. The boards cut away by band saws 33, 34, 35 are transferred to conveyor 46 by a transverse conveyor 47.

The remaining center part of the log dropped onto transverse conveyor 36 is normally only cut through its center. This can be done automatically when transverse conveyor 36 transfers the remaining portion of the log to a feeding device 42. From device 42 the log is fed into a center cleaver 43, from which the two boards or planks thus separated are discharged from the saw mill house 48 by a conveyor 44.

It is appreciated that in the plant illustrated in FIG. 6 and described in the foregoing, the four acceleration chains 38, 39, 40 and 41 could be replaced with a single chain running parallel to the feeding chain 21 along its entire length. Alternatively the acceleration chain 38 at the input side of machine group 22, 23, 24 and the acceleration chain 41 at the output side of machine group 32-35 could be replaced with a single chain. In the same way acceleration chain 39 at the output side of machine group 22-24 and acceleration chain 40 at the input side of the machine group 32-35 can be replaced with a single chain.

In the saw mill illustrated in FIG. 6 having two machine groups 22-24 and 32-35 arranged along two parallel processing lines, the fresh logs supplied to the mill are fed through and successively processed in all such processing machines of both groups. However, it is appreciated that the same log-feeding device according to the invention could also be used, if both machine groups 22-24 and 32-35 were used for sawing fresh, not previously processed logs. In such case, new unprocessed logs are supplied to aligning device 28 in front of machine group 32-35 in the same way that they are fed to the aligning device 20 in front of machine group 22-24. Naturally, in this case it might be necessary to arrange the conveyors supplying new logs to the mill and the conveyors removing the boards and the remaining portions of the logs in a different manner, but the log-feeding device according to the invention could remain substantially unchanged.

It is appreciated that in a saw mill having two parallel processing lines (for instance in the manner illustrated in FIG. 6), a log-feeding device according to the invention will be used very effectively, as the log-holding arms are used for transporting logs substantially along their entire path of movement.

Having illustrated and described what is presently a preferred embodiment of the invention and several suggested modifications, it should be apparent to those skilled in the art that the invention permits of modification in arrangement and detail. I claim as my invention all such modifications as come within the true spirit and scope of the following claims.

Claims

I claim:

1. Apparatus for feeding logs through a sawmill or other log-processing machine, comprising:

plural upright log-holding arms adapted to grip the opposite ends of the logs while feeding the logs through the processing machine,

said log-holding arms being mounted on carriage means supported by and movable along a trackway,

drive means for selectively moving said carriage means along said trackway,

said log-holding arms each being provided with fore log-gripping means facing in the direction of movement of the arm toward said machine for gripping a rear end portion of a log and a rear log-gripping means facing in the opposite direction for gripping a fore end portion of a log in a manner such that each said arm can support opposite ends of two longitudinally adjacent logs.

2. Apparatus according to claim 1 wherein said carriage means comprises a separate carriage for each arm and said drive means is capable of selectively moving one or more of said carriages at the same speed along said trackway and means are provided for selectively moving individual ones of said carriages at an increased speed greater than said first-mentioned speed both at the input side of said processing machine and at the output side thereof to facilitate the gripping and release of logs by said arms.

3. Apparatus according to claim 1 wherein said fore and rear log-gripping members of each arm are movable relative to each other in the direction of movement of said log-holding arm and are urged away from each other by resilient means.

4. Apparatus according to claim 2 wherein said drive means comprises a first endless drive member common to all said carriages, said means for moving said carriages at an increased speed comprising an additional endless drive means driven at a higher speed than said first drive member and arranged to run parallel to said first drive member, said drive means and said moving means including coupling means for selectively connecting and disconnecting each carriage to and from said first drive member and said additional drive means.

5. Apparatus according to claim 4 wherein said coupling means includes means for simultaneously connecting a carriage to said additional drive means while disconnecting the carriage from said first drive member at least at the output side of said processing machine.

6. Apparatus according to claim 4 wherein said additional drive means at the input and the output side of said processing machine is constituted by one and the same endless drive member driven at a higher speed than said first drive member.

7. Apparatus according to claim 4 wherein said trackway forms a closed circuit for the carriages and said additional endless drive means driven at a higher speed than said first drive member extends also along the portion of said closed circuit trackway extending from the output side to the input side of said saw, whereby the carriages can be returned from the output side to the input side of the saw driven by said additional drive means.

8. Apparatus according to claim 4 including stationary means at the input side of said processing machine for influencing said coupling means on said carriages to disconnect the carriages from said first drive member as well as from said additional drive means.

9. Apparatus according to claim 4 wherein at least two saws or other log-processing machines are arranged side by side with their feeding lines substantially parallel but with opposite feeding directions, said trackway for said carriages extending parallel to the feeding line of said first processing machine as well as parallel to the feeding line of said second processing machine, said first drive member extending along said trackway throughout its entire length, said additional endless drive means driven at a higher speed than said first drive member being arranged at the input and the output side of said first machine as well as at the input and output side of said second machine, whereby the same log-feeding device can be used for feeding logs through both said first and second machines.

10. Apparatus according to claim 9 wherein said additional drive means at the input side of said first machine and the output side of said second machine comprises a single endless drive member and that said additional drive means at the output side of said first machine and at the input side of said second machine comprises a single endless drive member.

11. Apparatus according to claim 9 wherein said additional drive means comprises a single endless drive member extending parallel to said first endless drive member.

12. Apparatus according to claim 1 wherein said trackway is an overhead trackway and said log-holding arms are vertically dependent from their associated carriage means supported by said trackway.