Patent GB-1109961-A (GB)
Title: Improvements in or relating to log sawmills
IPC: B27B15/08
Filed: 1965-11-10
Abstract: 1,109,961. Sawing. B. I. ACKERFELDT 10 Nov., 1965 [5 Oct., 1965], No. 47771/65. Heading B5L. A log sawmill comprises at least one saw unit 1 having at least one vertical blade, an imaginary sawing line constituting a preferred path of movement from an input side to an output side, an overhead track 8 extending above the saw unit parallel to the sawing line, and at least one log holding device 7b, 7f having substantially downwardly extending fore and rear log holding arms 6b, 6f for engaging the fore and rear end surfaces, respectively, of a log 33 located in the sawing line for moving the log past the saw. The Specification describes two embodiments, the first suitable for small sawmills and the second suitable for larger sawmills. In the first embodiment, the saw 10 is in the form of a band saw and the input and output sides consist of conveyers formed by rollers 2, 3 associated with transverse conveyers for feeding logs to and from the respective conveyers. The input side also has tables 4 which are vertically movable and have support plates 5 for lifting the logs from the rollers 2 to permit rotation of the logs so that they may be sawn at a preferred orientation. A stop 32 initially positions the log for engagement by the holding device which consists of a fore carriage 7f and a rear carriage 7b provided with rollers engaging a track formed by a beam 8. The fore carriage 7f carries an arm 6f which is pivotably moved from a horizontal inoperative position to a vertical operative position by a motor 16, Fig. 3, wherein it is releasably retained by a latch 18. The fore carriage is provided with clamps 21, 22 which are engageable with the upper run of a drive member 11 in such a manner that the carriage can only move relative to the drive member in the direction opposite to the direction of sawing. The clamp 21 is, however, connected by a lever to a roller which is engageable with a cam 25 to release the clamping effect when the fore carriage is in a position in which a triangular member 31 is engaged by a pawl 26 urged by a spring 29 about a pivot 22 movable along a slot 28 on the beam 9, a cam 30 lifting the pawl when it, and hence the carriage, has moved a sufficient direction to the right. The rear carriage 7b is similar to the carriage 7f but is permanently connected to the upper run of the drive member 11 which is entrained about pulleys 12, 13, one of which is driven. In operation, a log is deposited on the rollers 2 and moved against the stop 32. The tables 4 are then raised to permit rotating the log on the plates 5. At this time, the fore carriage 7f is in the position shown in solid line in Fig. 1, where it is retained by the pawl 26, the clamps 21, 21 being released by the cam 25. The holding arms 6b and 6f are thereafter lowered and the drive member started so that the rear carriage 2b moves and its arm 6b engages the rear end of the log which is thereby moved to engage the holding arm 6f of the fore carriage 7f. The carriage 7f is moved against the force of the spring until the cam 25 disengages the roller 24, so that the clamps 21, 22 engage the drive member 11 which can still move relative to the carriage 7f until the cam 30 lifts the pawl 26 to permit the carriage to move at the speed of the drive member, the arms 6b, 6f holding the log with a force dependant on the strength of the spring 29. The carriages move the log past the saw 10 and over the output conveyer 3 whereat the arms 6b, 6f are moved to their horizontal inoperative positions to release the log. The drive member 11 is then reversed to move the carriages back to their initial position. During such movement, timber can be fed past the saw by means of feed rollers 34 which press the timber against a guide 35. In the second embodiment, the saw is in the form of a pair of band saws 36, Figs. 5a, 5b, 6a, 6b and the fore and rear carriages are movable from the input side to the output side along an endless track 52, there being preferably nine pairs of carriages 43f-43b ... 51f-51b. The drive member 55, which follows the same path as the endless track, consists of a double chain entrained about pulleys 56, 57 one of which is continuously driven, and a fore carriage, for example 43f, is guided by rollers along the track and has a sprocket 61, Fig. 9, which is engageable with one run of the chain 55 and carried by a holder 62 connected by a pivot 63 to the carriage. A pair of jaws 66 are spring-loaded against the sprocket to prevent rotation thereof in one direction so that the carriage is movable with the chain in one direction but can move relative to the chain in the opposite direction. Each fore carriage also carries a latch 67, by which it is connectable to an adjacent r ea carriage, and a plate 69 engageable by a pawl 20, Fig. 5b, movable against a spring about a pivot 71 slidable in a slot 72, the pawl being movable by a cam 74. Each rear carriage, for example 43b, Figs. 11 and 12, (not shown) also has a sprocket 75 engaging the chain 55 and a pair of jaws 83 for clamping the carriage to the chain, the holder 76 for the sprocket being resiliently mounted on the carriage. Both the fore and rear carriages have fixed depending holding arms for engaging the fore and rear surfaces of the logs, the lower ends of the arms being engaged by a guide 60 as the logs are moved from the input to the output sides. The logs may be fed from a transverse conveyer 117, Fig. 6b to a feeding device consisting of pairs of supports 89b, 89f, ... 94b, 95f movable around an endless track comprising rails 95, each support consisting of a pair of discs 105, Fig. 13, connected for rotation by a belt 106. A drive member consisting of a double chain 96, which follows the rails 95, is entrained about pulleys 97, 98, one of which is driven. Each support is connectable to the chain by clamp jaws 103 engaging sprockets 100 whereby the support is movable in one direction with the chain but can move relative thereto in the opposite direction. An operating lever 104 is engageable with cam plates at selected parts along the track to release the clamp jaws. When a log is on the discs 105, the latter may be rotated by a wheel 112 driven by a motor 109 on a carriage 107 to rotate the log about its longitudinal axis to a preferred position. In operation, a log 118 is fed by the transverse conveyer 117 on to a pair of supports 89b, 89f which at that time are stationary but may be engaged automatically or manually with the chain 96 by movement of the cam plates permitting the jaws 103 to grip the sprockets 100. The carriage 107 is movable with support 89b and the motor 112 can be operated to rotate the log if desired. During the movement of the log along the track 95, a cam plate 86, Fig. 6b, is moved to an inoperative position so that a rear holding carriage 51b is driven by the chain and pulls a following fore carriage connected to it by a latch 67. The log is now in the position 119 and is engaged by the rear carriage 43b and is moved until it engages a fore carriage 43f which has been disengaged from a rear carriage by a cam releasing the coupling latch 67 and is positioned on the track by the pawl 70. The movement of the rear carriage urges the log against the fore carriage which moves against the spring 73 until the cam 74 lifts the pawl 20 allowing the carriages to convey the log past the saws 36, the pieces cut from the sides of the logs being moved away from the sawing line by screw conveyers 32, 38. The log is moved to the position 121 whereat a cam 83 has acted to retain a preceding rear carriage 47b and the fore carriage 46f is automatically coupled to that rear carriage 47b by the latch 67 and pushes the latter from the cam 83 so that it reengages the drive chain 55. At the same time, a switch 122 is operated and a cylinder 85 moves a cam 84 to disengage the rear carriage 46b from the chain so that the log is released and conveyed away from the sawing line by a conveyer 42. The fore carriage 46f, in its movement, operates a further switch 123 to cause the cylinder 85 to return the cam 84 to its inoperative position so that the rear carriage 46b is again driven by the chain 4 to a position where it is disengaged therefrom by the cam 83 to await the following fore carriage 45f.