# US 4,395,189 A · Dual mast lift truck for unbalanced loads and the like > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,395,189 A - Document ID: US4395189A - Status: Granted - Kind: A - Application number: 06/230,611 - Filed: 1981-02-02 - Granted: 1983-07-26 - Earliest claimed: 1981-02-02 - Inventors: Gerard H. Munten - Web page: https://patentgrep.com/patent/US4395189A ## CPC - B66F 9/082: {inclinable} - B66F 9/08: Masts; Guides; Chains - B66F 9/085: {Multiple forks, i.e. more than one pair mounted on a single mast or with more than one mast} - B66F 9/20: Means for actuating or controlling masts, platforms, or forks (power take-off from vehicle transmissions, combined with vehicle propulsion systems B60K) - B66F: HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD ({invalid lifting devices A61G7/10; } mounting artificial islands on piles or like supports E02B17/00; scaffolding combined with lifting devices E04G1/22; lifting devices for sliding forms E04G11/24; lifting of buildings E04G23/06; shores or struts E04G25/00; lifts or other hoisting devices on ladders E06C7/12; props for mining E21D15/00) ## Abstract A conventional lift truck is provided with a dual mast arrangement for handling heavy, unbalanced loads, and other awkward objects. Two masts are individually connected with the truck frame in a side-by-side relationship, and each mast includes a fork which is movable up and down its respective mast. The masts are powered by separate motors, and a controller operates the two motors. The controller is capable of independently moving each fork to individually elevate the forks into abutment with the load, and then raise the load slightly into a position in which the load is balanced on the forks. The controller includes a coupler which translates the forks in unison at substantially the same rate and in the same direction, such that the forks are raised simultaneously to lift the load balanced thereon to a transport position, and are lowered together to set the load down in place. ## Claims ### Claim 1 In a conventional lift truck having a frame with front and rear ends, and means for propelling said truck, the improvement of a dual mast arrangement for handling unbalanced loads and the like, comprising: first and second lift masts connected with the front end of said truck frame in a side-by-side relationship; each lift mast having a fork slideably connected therewith for translating up and down its respective mast; said forks extending generally outwardly from said masts in a generally parallel relationship; means for independently moving said forks along their respective masts, whereby each fork is individually elevated into abutment with a load, and raised slightly to a position wherein the load is balanced on said forks; and coupling means for selectively interlocking said forks and moving the same in unison, substantially simultaneously at the same rate and in the same direction, by manipulation of a single control, whereby said forks are raised together to lift the load balanced thereon to a transport position, and are lowered together to set the load down in place. ### Claim 2 (depends on 1) A lift truck as set forth in claim 1, including: means for pivotally connecting said masts with said truck frame; means for independently pivoting said masts; and means for pivoting said masts substantially simultaneously at the same rate and in the same direction. ### Claim 3 (depends on 2) A lift truck as set forth in claim 2, wherein: said mast pivoting means comprises first and second double acting hydraulic cylinders. ### Claim 4 (depends on 3) A lift truck as set forth in claim 3, wherein: said independent mast pivoting means comprises a pressurized hydraulic fluid system having a valve block with a valve therein for each hydraulic cylinder, and means for communicating each valve with its associated cylinder, whereby selective manipulation of said valves extends and retracts said cylinders to individually tilt said masts. ### Claim 5 (depends on 4) A lift truck as set forth in claim 4, wherein said simultaneous pivot means comprises: a two-way valve disposed in a hydraulic line communicating one of said hydraulic cylinders with said pressurized hydraulic fluid system; said two-way valve having a first position wherein the hydraulic fluid is communicated directly with said one hydraulic cylinder, and a second position wherein the hydraulic fluid is communicated with a divider line; a flow control valve positioned in said divider line downstream of said two-way valve, and including means for dividing the flow of hydraulic fluid therethrough into two equal streams; and means for communicating each of said two equal hydraulic streams from said flow control valve with a different one of said hydraulic cylinders, whereby when said two-way valve is in said second position, said masts are pivoted simultaneously at substantially the same rate and in the same direction. ### Claim 6 (depends on 1) A lift truck as set forth in claim 1, wherein: said independent fork moving means comprises first and second hydraulic cylinders. ### Claim 7 (depends on 6) A lift truck as set forth in claim 6, wherein: said independent fork moving means further comprises a pressurized hydraulic fluid system having a valve block with a valve therein for each hydraulic cylinder, and means for communicating each valve with its associated cylinder, whereby selective manipulation of said valves extends and retracts said cylinders to individually raise and lower said forks. ### Claim 8 (depends on 7) A lift truck as set forth in claim 7, wherein said fork coupling means comprises: a two-way valve disposed in a hydraulic line communicating one of said hydraulic cylinders with said pressurized hydraulic fluid system; said two-way valve having a first position wherein the hydraulic fluid is communicated directly with said one hydraulic cylinder, and a second position wherein the hydraulic fluid is communicated with a divider line; a flow control valve positioned in said divider line downstream of said two-way valve, and including means for dividing the flow of hydraulic fluid therethrough into two equal streams; and means for communicating each of said two equal hydraulic streams from said flow control valve with a different one of said hydraulic cylinders, whereby when said two-way valve is in said second position, said forks are raised and lowered simultaneously at substantially the same rate and in the same direction. ### Claim 9 (depends on 8) A lift truck as set forth in claim 8, wherein: said two-way valve includes a lever for manipulating the same, and said lever is disposed adjacent an operator control area of said lift truck. ### Claim 10 (depends on 9) A lift truck as set forth in claim 9, wherein: each valve includes a lever for manipulating the same, and each lever is disposed adjacent said operator control area. ### Claim 11 (depends on 8) A lift truck as set forth in claim 8, including: means for pivotally connecting said masts with said truck frame; means for independently pivoting said masts; and means for pivoting said masts substantially simultaneously at the same rate and direction. ### Claim 12 (depends on 11) A lift truck as set forth in claim 11, wherein: said mast pivoting means comprises third and fourth hydraulic cylinders. ### Claim 13 (depends on 12) A lift truck as set forth in claim 12, wherein: said independent mast pivoting means includes a pressurized hydraulic fluid system, third and fourth valves operatively connected with said third and fourth cylinders respectively, whereby selective manipulation of said third and fourth valves extends and retracts said third and fourth cylinders to individually pivot said masts. ### Claim 14 (depends on 13) A lift truck as set forth in claim 13, wherein said simultaneous pivot means comprises: a two-way pivot valve disposed in a hydraulic line communicating one of said hydraulic pivot cylinders with said second named pressurized hydraulic fluid system; said two-way pivot valve having a first position wherein the hydraulic fluid is communicated directly with said one hydraulic pivot cylinder, and a second position wherein the hydraulic fluid is communicated with a divider line; a flow control pivot valve connected with said second named divider line, downstream of said two-way pivot valve, and includes means for dividing the flow of hydraulic fluid therethrough into two equal streams; and means for communicating each of the two equal hydraulic streams from said flow control pivot valve with a different one of said third and fourth cylinders, whereby when said two-way pivot valve is in said second position, said masts are tilted simultaneously at substantially the same rate and in the same direction. ### Claim 15 In a lift truck having a frame with front and rear ends, and means for propelling said truck, the improvement of a dual mast arrangement for handling unbalanced loads and the like, comprising: first and second lift masts pivotally connected with the front end of said truck frame in a side-by-side relationship; each lift mast having a movable fork connected therewith, and extending outwardly therefrom in a generally parallel relationship, means for translating said fork up and down its respective mast, and means for pivotally mounting said masts on said truck frame; means for independently pivoting said masts; and coupling means selectively interlocking said masts and pivoting the same in unison, substantially simultaneously at the same rate and in the same direction, by manipulation of a single control, whereby said masts are pivoted rearwardly to lift the load balanced thereon to a transport position, and are tilted forwardly to set the load down in place. ### Claim 16 (depends on 15) A lift truck as set forth in claim 15, wherein: said mast pivoting means comprises first and second double acting hydraulic cylinders. ### Claim 17 (depends on 16) A lift truck as set forth in claim 16, wherein: said independent mast tilting means comprises a pressurized hydraulic fluid system having a valve block with a valve therein for each hydraulic cylinder, and means for communicating each valve with its associated cylinder, whereby selective manipulation of said valves extends and retracts said cylinders to individually pivot said lift masts. ### Claim 18 (depends on 17) A lift truck as set forth in claim 17, wherein said simultaneous tilt means comprises: a two-way valve disposed in a hydraulic line communicating one of said hydraulic cylinders with said pressurized hydraulic fluid system; said two-way valve having a first position wherein the hydraulic fluid is communicated directly with said one hydraulic cylinder, and a second position wherein the hydraulic fluid is communicated with a divider line; a flow control valve connected with said divider line, downstream of said two-way valve, and including means for dividing the flow of hydraulic fluid therethrough into two equal streams; and means for communicating each of said two equal hydraulic streams from said flow control valve with a different one of said hydraulic cylinders, whereby when said two-way valve is in said second position, said masts are pivoted simultaneously at substantially the same rate and in the same direction.