Abstract A portable lift truck has a vertically movable load receiving carriage which is driven up and down by a power drive mechanism, such as a hydraulic cylinder and chains connecting a cylinder to the lift carriage. In the event of a malfunction of the lift mechanism, such as due to chain breakage or a major hydraulic failure, the lift mechanism is prevented from free falling beyond a predetermined speed. Equally spaced stop lugs on the mast are engaged by an arm on a rotatable stop member which is spring loaded to dump rotation of the stop member when the arm engages the stop lugs. If the relative speed between the stop lugs and the rotatable member substantially exceeds the maximum rate of movement obtainable from the drive mechanism, the spring damping will not react fast enough to prevent an interference lug on the rotatable stop member from jamming into the path of one of the stop lugs, thus locking the lift mechanism against further movement before it achieves any excessive speed.
Inventors
👤 A Tang
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-10-27 23:42
CPC Classifications
B; B66; B66F; B66F17/00; B66F17/003
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
179 words
In a lift truck having a lift mechanism including a mast with a vertically movable power operated carriage for lifting and lowering loads, and a drive mechanism connected to raise and lower the carriage, an improved safety apparatus comprising a series of stop lugs spaced equally by a predetermined amount and a spring loaded stop member with an arm arranged to move into engagement with said stop lugs, said stop lugs and said stop member being mounted on relatively movable parts of the lift mechanism such that said arm engages and releases from said stop lugs in succession during raising and lowering of the mechanism, said stop member also having an interfering lug normally out of the path of said stop lugs, and a spring device retarding the motion of said stop member in response to engagement of said arm and said stop lugs whereby the interfering lug will clear said stop lugs only if the relative movement between said arm and said stop lugs does not substantially exceed the maximum rate of movement attainable from said drive mechanism.
Claim 2
Dependent Claim
179 words
In a lift truck having a lift mechanism including a mast with a vertically movable power operated carriage for lifting and lowering loads, and a drive mechanism connected to raise and lower the carriage, an improved safety apparatus comprising a series of stop lugs spaced equally by a predetermined amount and a spring loaded stop member with an arm arranged to move into engagement with said stop lugs, said stop lugs and said stop member being mounted on relatively movable parts of the lift mechanism such that said arm engages and releases from said stop lugs in succession during raising and lowering of the mechanism, said stop member also having an interfering lug normally out of the path of said stop lugs, and a spring device retarding the motion of said stop member in response to engagement of said arm and said stop lugs whereby the interfering lug will clear said stop lugs only if the relative movement between said arm and said stop lugs does not substantially exceed the maximum rate of movement attainable from said drive mechanism.
Claim 3
Dependent Claim
32 words
Safety apparatus for a lift truck, as defined in claim 1, wherein said stop member is rotatably mounted and said arm swings into and out of the path of said stop lugs.
Claim 4
Dependent Claim
39 words
Safety apparatus as defined in claim 1 wherein said interfering lug is arranged to jam against a stop lug in response to excessive carriage speed, and a stop device operates to hold the interfering lug in the jammed position.