# US 4,398,640 A · Multi-span skyline logging system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,398,640 A - Document ID: US4398640A - Status: Granted - Kind: A - Application number: 06/238,690 - Filed: 1981-02-27 - Granted: 1983-08-16 - Earliest claimed: 1981-02-27 - Inventors: Shubert J. Hunter - Web page: https://patentgrep.com/patent/US4398640A ## CPC - B61B 7/02: with separate haulage cables - B61B: RAILWAY SYSTEMS; EQUIPMENT THEREFOR NOT OTHERWISE PROVIDED FOR (lifts or hoists, elevators, escalators, moving walkways B66B) ## Abstract An arcuate jack is arranged to be secured to a spar for supporting a skyline over it. A carriage assembly comprises a main carriage arranged to travel on the skyline and a secondary carriage supported on the main carriage for movement between leading and trailing ends of such main carriage. A brake is operative between the main and secondary carriages to control movement of the secondary carriage on the main carriage. The secondary carriage supports a drop line for connection to a load, and a mainline is connected to the secondary carriage for pulling the carrige assembly along the skyling. A guide for the mainline is provided on the spar and is disposed below the jack in an arrangement whereby the pull on the carriage assembly from the mainline is substantially tangent to the arcuate contour of the jack at its entrance end. The brake is arranged to hold the secondary carriage at the trailing end of the main carriage during initial movement of the latter onto the jack and in subsequent movements thereof along the jack to release it for movement toward the leading end of the main carriage, thus providing a weight shift that assists movement of the carriage over the jack. A clearance cam is provided which is arranged to be engaged by the carriage assembly and which is arranged to swing the carriage assembly out at the bottom so that the drop line will bypass the guide. ## Claims ### Claim 1 A multi-span skyline logging system of a type using a spar member, said system comprising (a) an arcuate jack having entrance and exit ends, (b) support means on said jack arranged to secure it to a spar member, (c) a skyline extending over said jack in supported relation, (d) carriage means arranged for movable support along said skyline and over said jack, (e) drop line means on said carriage for connection to a load of logs, (f) mainline means connected to said carriage means arranged to pull the latter along the skyline, (g) guide means arranged to be supported on the spar member over which said mainline is trained for guided movement, (h) said guide means being disposed adjacent to said jack in an arrangement whereby the pull on said carriage means from said mainline is substantially tangent to the arcuate contour of said jack at its entrance end, (i) and interengaging clearance means on said spar member and said carriage, (j) said clearance means including a cam and cam follower, (k) one of said cam and cam follower being disposed on said spar member below said jack and the other of said cam and cam follower being disposed on said carriage means, (l) said cam projecting horizontally outwardly and being arranged when engaged by said cam follower as said carriage means moves over said jack to swing said carriage means outwardly at the bottom to allow bypass of said drop line past said guide means. ### Claim 2 (depends on 1) The multi-span logging system of claim 1 wherein said support means also supports said guide means, and means on said support means arranged to hang it for swinging movement on the spar. ### Claim 3 (depends on 1) The multi-span logging system of claim 1 wherein said carriage means includes a main carriage having leading and trailing ends, means supporting said main carriage on said skyline, a secondary carriage supported movably on said main carriage for movement between the leading and trailing ends of the latter, said mainline being connected to said secondary carriage for exerting the pulling force, and brake means between said secondary carriage and said main carriage, said brake means being arranged to hold said secondary carriage at the trailing end of said main carriage during initial movement of the latter onto said jack and in subsequent movements thereof along said jack to release it for movement toward said leading end of said main carriage to provide a weight shift that assists movement of said carriage means over said jack. ### Claim 4 (depends on 3) The multi-span logging system of claim 3 wherein said main carriage comprises an elongated body member on which said secondary carriage is movably supported, upwardly projecting arms on said body member, and sheave means on said arm arranged for movement on said skyline and over said jack. ### Claim 5 A multi-span logging system comprising (a) an arcuate jack having entrance and exit ends, (b) means on said jack arranged to secure it to a spar member, (c) a skyline extending over said jack in supported relation, (d) a main carriage having leading and trailing ends and arranged for movable support along said skyline and over said jack, (e) a secondary carriage supported movably on said main carriage for movement between the leading and trailing ends of the latter, (f) drop line means on said second carriage for connection to a load of logs, (g) mainline means connected to said secondary carriage arranged to pull the latter along the skyline; (h) and brake means between said secondary carriage and said main carriage; (i) said brake means being arranged to hold said secondary carriage at the trailing end of said main carriage during initial movement of the latter onto said jack and in subsequent movements thereof along said jack to release it for movement toward said leading end of said main carriage to provide a weight shift that assists movement of said carriages over said jack. ### Claim 6 (depends on 5) The multi-span logging system of claim 5 wherein said main carriage comprises an elongated body member on which said secondary carriage is movably supported, upwardly projecting arms on said body member, and sheave means on said arm arranged for movement on said skyline and over said jack.