Lifting device
AssigneeKabushiki Kaisha Toyota Jidoshokki
InventorsYuki Ueda, Tsutomu Matsuo, Hirohiko Ishikawa
Life of this patent
Estimating the term…
Abstract
An electromagnetic switching valve, for which the maximum opening is set to be small, is disposed on piping between a lift cylinder and a hydraulic pump motor. A pilot check valve, for which the maximum opening is set to be larger than the electromagnetic switching valve, is disposed on piping, different from the piping, between the lift cylinder and the hydraulic pump motor. In addition, during lowering operations, first, the electromagnetic switching valve is opened, and then after the same is opened, the pilot check valve is opened after a prescribed time has passed. Thus, the shock generated when lowering an object to be raised/lowered is reduced and a fork is operated quickly.
Claims6
A lifting device that lifts and lowers a lifting material by supplying and discharging hydraulic oil to and from a hydraulic cylinder, the lifting device comprising:
- a hydraulic pump that supplies the hydraulic oil to the hydraulic cylinder;
- a first oil passage that connects the hydraulic cylinder and the hydraulic pump;
- a second oil passage that connects the hydraulic cylinder and the hydraulic pump;
- and
- an opening-closing unit that opens and closes the first oil passage and the second oil passage, wherein
- the first oil passage has a maximum oil passage area that is smaller than a maximum oil passage area of the second oil passage,
- the first oil passage includes
- a first portion between the hydraulic cylinder and the opening-closing unit, and
- a second portion between the opening-closing unit and the hydraulic pump, and
- the opening-closing unit
- allows the hydraulic oil to flow through the first oil passage when the lifting material is lowered, and
- after the first oil passage opens, allows the hydraulic oil to flow through the second oil passage when a first pressure difference between the first portion and the second portion decreases to a predetermined pressure difference or less,
- wherein the opening-closing unit includes
- a first direction control valve arranged in the first oil passage, wherein the first direction control valve switches a flow direction of the hydraulic oil in the first oil passage, and
- a second direction control valve arranged in the second oil passage, wherein the second direction control valve switches a flow direction of the hydraulic oil in the second oil passage,
- the maximum oil passage area of the first oil passage is determined by a maximum open degree of the first direction control valve,
- the maximum oil passage area of the second oil passage is determined by a maximum open degree of the second direction control valve, and
- the maximum open degree of the first direction control valve is smaller than the maximum open degree of the second direction control valve.
Dependencies are inferred from the claim text.