Patent GB-648287-A (GB)
Title: Improvements in or relating to log saw-mills
IPC: B27B29/10
Filed: 1947-12-16
Abstract: 648,287. Log saws. EASTON & JOHNSON, Ltd., and EASTON, S. W. Dec. 16, 1947, No. 33188. [Class 145(ii)] An automatic traverse mechanism for a reciprocating-carriage log saw-mill embodies a thickness control member which comprises a follower member movable from a " start" position to follow the lateral movements of the log-holding means, a stop member adiustable to positions in the path of the follower member spaced from the " start" position by amounts corresponding to the thickness of the plank to be cut plus an allowance for the thickness of the cut, contact between the follower member and the stop member being arranged automatically to stop the lateral movement of the holding means and also to release the follower member to return to the " start position independently of the log-holding means. A log supporting carriage 30 is moved longitudinally by a rack 32 and a pinion 33 driven from an AC variable-speed commutator motor 34 through a gearbox 35, the rack 32 being connected to the carriage by bell cranks 36 arranged in a known manner to laterally side-step the carriage on the idle stroke. The five gripping-dog headstocks 50 for holding the log are moved laterally by racks on their undersides engaged by pinions 52 carried on a shaft 53 which is driven by a traversing motor through a reduction gear box embodying a clutch 58 (not shown) which is disengaged by energizing a solenoid 67. A " Selsyn " transmitter is driven from the shaft 53 and is connected to two " Selsyn" receivers contained in a control cabinet 83. One receiver is directly connected to a pointer which shows the lateral displacement of a datum point on the headstocks from the saw, and the other drives, through a friction clutch 95 actuated by a linkwork and a solenoid 97, a follower arm 96. A pointer 86 is moved over a dial 85, indicating the thickness of the plank by a handle 87 and spur wheels 88 and 89, the latter carrying a block 90, on which is mounted a pair of contacts 91 and 92. When a plank of predetermined thickness is to be cut the handle 87 is turned until the pointer 86 indicates the required thickness and the traversing switch closed. The traversing motor starts and the solenoid 67 de-energizes to engage the clutch 58 (not shown) and the solenoid 97 energizes to engage the clutch 95. As the motor rotates it traverses the log-holding means and rotates the " Selsyn " transmitter. The "Selsyn " receiver then rotates until the arm 96 "shorts" contacts 91, 92 thus causing a relay to operate and energize the solenoid 67 so opening the clutch 58 (not shown). Simultaneously the solenoid 97 de-energizes, opening the clutch 95, and the arm 96 is returned to its "start" position by a spiral spring 98. The " start " position is adjustable to allow for thickness of the cut by means of a knurled nut. The mechanism also comprises an oil pressure system giving a quick return motion to the reciprocating carriage, motordriven saw-tensioning system, a motor driven steady for the cutting stretch of the band, and safety devices for stopping the DC braking of the AC driving motor when the speed of the latter drops to 100 r.p.m. and to prevent operation of the sawtensioning motor for a predetermined time after the stoppage of the DC braking.