Control system for lift trucks

Claim 2

In a control system for a lift truck, said truck having an engine, an acceleration control member, a lift control mechanism, a fuel flow control, and a variable ratio hydrostatic drive for the truck from said engine to propel the truck for ground drive; mechanism operable in proportion to setting of said acceleration control member to actuate said fuel control to propel said truck at speeds controlled in relation to the position of said member, including relatively low speeds; separate connections operated with said lift control to operate said fuel control to increase the speed of said engine; mechanism to vary the hydrostatic drive ratio connection between the engine and the wheels of said truck to allow said increase in speed of said engine to drive said lift mechanism at a relatively high rate of lift while continuing to drive said truck at the speed called for by said acceleration control member, said mechanism comprising: control members responsive to flow rate in a hydraulic line of said hydrostatic drive; connections from said control member constructed and arranged to vary the effective drive ratio thru said hydrostatic drive from said engine to allow said engine to increase in speed as called for by said lift control mechanism while maintaining relatively low ground speed of said truck as called for by said acceleration control member.

Claim 3

A control system as in claim 1 wherein: mechanism operable in proportion to setting of said acceleration control member to actuate said fuel control to propel said truck at speeds controlled in relation to the position of said member, including relatively low speeds comprises: a fluid pump driven by said engine; a variable outlet orifice controlled by said acceleration control member; a main delivery line connecting said fluid pump with said variable outlet orifice; a carburetor valve controlling fuel flow to said engine; a hydraulic actuated cylinder and piston resiliently biased to open said carburetor valve, said valve being actuated toward closure by hydraulic pressure; an auxiliary delivery line connecting said main delivery line with said resiliently biased hydraulic cylinder and piston thereby supplying fluid under pressure to said piston in a direction to close said carburetor valve against the resilient bias.

Claim 4

A control system as in claim 1 wherein: connections from said control member constructed and arranged to vary the effective drive ratio thru said hydrostatic drive from said engine to allow said engine to increase in speed as called for by said lift control while maintaining relatively low ground speed of said truck, comprise: a hydraulic-fluid flow line in said hydrostatic drive, the flow rate thru which is indicative of the speed generated by the drive for propelling said truck; an orifice in said hydraulic-fluid flow line; connections from the upstream side and downstream side of said orifice responsive to pressure drop across said orifice; mechanism responsive to pressure in said connections to vary the effective drive ratio of said hydrostatic drive.

Claim 5

A control system as in claim 2 wherein there is provided: a manually actuated control valve spool member for control and actuation of said lift mechanism; a separate source of fluid pressure for actuating said lift mechanism an auxiliary delivery line from said main delivery line to said control valve spool member; a section of said control valve spool member constructed and arranged tO bleed hydraulic fluid from said main delivery line thru auxiliary delivery line on actuation of said control valve spool causing speed up of the engine to actuate said lift and load support member at a relatively fast rate in proportion to movement of said valve spool member.

Claim 6

A control system for a lift truck, said truck having an engine, an acceleration control member, a fuel control, lift control mechanism, and a variable ratio hydrostatic drive for the truck from said engine to propel the truck for ground drive: said control system comprising: mechanism operable relative to the setting of said acceleration control member to actuate said fuel control to propel said truck at speeds controlled by the position of said member, including relatively low speeds; connections operable with said lift control mechanism, independently of said acceleration control, to increase the speed of said engine to effect a relatively high rate of lift; mechanism varying the hydrostatic drive ratio between the engine and the wheels of said truck constructed and arranged to allow said increase in speed of said engine to increase the lift rate of said lift mechanism while continuing to drive said truck at speeds called for by said acceleration control member.

Claim 7

A control system for a lift truck, said truck having an engine, an acceleration control member, a fuel control, lift control mechanism, and a variable ratio hydrostatic drive for the truck from said engine to propel the truck for ground drive: said control system comprising: mechanism operable relative to the setting of said acceleration control member to actuate said fuel control to propel said truck at speeds controlled by the position of said member, including relatively low speeds; connections operable with said lift control mechanism, independently of said acceleration control, to increase the speed of said engine to effect a relatively high rate of lift; mechanism varying the hydrostatic drive ratio between the engine and the wheels of said truck constructed and arranged to allow said increase in speed of said engine to increase the lift rate of said lift mechanism while continuing to drive said truck at speeds called for by said acceleration control member.

Claim 8

A mechanism as in claim 5 wherein there is provided: a fluid pump driven by said engine; hydraulic actuated means controlled by said lift control mechanism and said acceleration control member for varying the hydrostatic drive ratio between the engine and the wheels of said truck to allow said increase in speed of said engine to increase the lift rate of said lift mechanism while continuing to drive said truck at speeds called for by acceleration control member.

Claim 9

In a control system for an industrial vehicle having a fluid pressure operated lift mechanism and further hydraulic control mechanism for other components of the vehicle; a manually actuated control valve member for controlling actuation of said fluid pressure operated lift mechanism; a separate source of fluid pressure for actuating said lift mechanism said control valve member including means to bypass fluid from said further hydraulic control mechanism thereby to compensate for variations in at least one of said other components on actuation of said control valve member for control of the lift rate of said lift mechanism; such structure assuring that said lift mechanism may be actuated at a relatively high rate of lift without undesired variation in said further hydraulic control mechanism.

Claim 10

In a control system for an industrial vehicle having a fluid pressure operated lift mechanism and further hydraulic control mechanism for other components of the vehicle; a manually actuated control valve member for controlling actuation of said fluid pressure operated lift mechanism; a separate source of fluid pressure for actuating said lift mechanism said control valve member including means to bypass fluid from said further hydraulic control mechanism thereby to compensate for variations in at least one of said other components on actuation of said control valve member for control of the lift rate of said lift mechanism; such structure assuring that said lift mechanism may be actuated at a relatively high rate of lift without undesired variation in said further hydraulic control mechanism.

Claim 11

In a fluid pressure operated lift mechanism and a control for governing the output of an engine; a fluid pump driven by said engine; an acceleration control member for said engine; a variable outlet orifice controlled by said acceleration control member; a main delivery line connecting said fluid pump with said outlet orifice; a carburetor valve controlling fuel flow to said engine; a hydraulic actuated cylinder and piston resiliently biased to open said carburetor valve, said valve being actuated towards closure by hydraulic pressure; an auxiliary delivery line connecting said main delivery line with said resiliently biased hydraulic cylinder and piston at a position between said engine-driven pump and said variable orifice thereby supplying fluid under pressure to said piston in a direction to close said carburetor valve against the resilient bias; whereby movement of said acceleration control member from one setting to a new position to change said variable orifice will result in change of engine output followed by compensating change in said carburetor valve and gradually reach a balance corresponding to the setting of said acceleration control member; a manually actuated control valve member for controlling actuation of said fluid pressure operated lift mechanism; a separate source of fluid pressure for actuating said lift mechanism; said control valve memBer including means to bypass fluid from said main delivery line connecting said fluid pump with said outlet orifice on actuation of said lift control valve member whereby said engine output may be increased independently of said acceleration control member for the purpose of actuation of said lift mechanism.

Claim 12

In a fluid pressure operated lift mechanism and a control for governing the output of an engine; a fluid pump driven by said engine; an acceleration control member for said engine; a variable outlet orifice controlled by said acceleration control member; a main delivery line connecting said fluid pump with said outlet orifice; a carburetor valve controlling fuel flow to said engine; a hydraulic actuated cylinder and piston resiliently biased to open said carburetor valve, said valve being actuated towards closure by hydraulic pressure; an auxiliary delivery line connecting said main delivery line with said resiliently biased hydraulic cylinder and piston at a position between said engine-driven pump and said variable orifice thereby supplying fluid under pressure to said piston in a direction to close said carburetor valve against the resilient bias; whereby movement of said acceleration control member from one setting to a new position to change said variable orifice will result in change of engine output followed by compensating change in said carburetor valve and gradually reach a balance corresponding to the setting of said acceleration control member; a manually actuated control valve member for controlling actuation of said fluid pressure operated lift mechanism; a separate source of fluid pressure for actuating said lift mechanism; said control valve memBer including means to bypass fluid from said main delivery line connecting said fluid pump with said outlet orifice on actuation of said lift control valve member whereby said engine output may be increased independently of said acceleration control member for the purpose of actuation of said lift mechanism.