US3779017A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hydraulic lift
Assignee: Hitachi Ltd
•
Filing: 1972-09-11
•
Granted: 1973-12-18
•
Expires: 1992-09-11
Abstract
Abstract A hydraulic lift having an accumulator and an associated flow restricting valve disposed in a fluid conduit supplying a fluid under pressure for lifting a cage. In the hydraulic lift, the flow restriction of the flow restricting valve is varied in response to variations in the load carried by the cage so as to prevent transient oscillations tending to occur during starting, deceleration and stoppage of the cage.
Inventors
- 👤 F Fujisawa
- 👤 M Takenoshita
- 👤 H Yumino
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 18:37
CPC Classifications
B; B66; B66B; B66B1/00; B66B1/24; F; F15; F15B; F15B1/00; F15B1/02; F15B1/027
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
135 words
A hydraulic lift comprising a hydraulic cylinder having a plunger, a cage arranged for upward and downward movement in response to the vertical movement of said plunger, a tank containing a hydraulic fluid therein, a conduit connecting said cylinder with said tank, a pump for pressurizing the hydraulic fluid drawn from said tank and supplying the fluid under pressure into said cylinder, an accumulator connected to said conduit for absorbing ripples occurring due to pressure variations in the fluid under pressure, a variable flow restricting valve disposed in the path of the fluid under pressure into and out of said accumulator, and means for varying the resistance of said variable flow restricting valve against fluid flow in such a manner that the flow resistance increases with the increase in the load carried by the cage.
Claim 2
Dependent Claim
135 words
A hydraulic lift comprising a hydraulic cylinder having a plunger, a cage arranged for upward and downward movement in response to the vertical movement of said plunger, a tank containing a hydraulic fluid therein, a conduit connecting said cylinder with said tank, a pump for pressurizing the hydraulic fluid drawn from said tank and supplying the fluid under pressure into said cylinder, an accumulator connected to said conduit for absorbing ripples occurring due to pressure variations in the fluid under pressure, a variable flow restricting valve disposed in the path of the fluid under pressure into and out of said accumulator, and means for varying the resistance of said variable flow restricting valve against fluid flow in such a manner that the flow resistance increases with the increase in the load carried by the cage.
Claim 3
Dependent Claim
133 words
A hydraulic lift comprising a hydraulic cylinder having a plunger, a cage arranged for upward and downward movement in response to the vertical movement of said plunger, a tank containing a hydraulic fluid therein, a conduit connecting said cylinder with said tank, a pump for pressurizing the hydraulic fluid drawn from said tank and supplying the fluid under pressure into said cylinder, an accumulator connected to said conduit for absorbing ripples occurring due to pressure variations in the fluid under pressure, a variable flow restricting valve disposed in the path of the fluid under pressure into and out of said accumulator, and means for varying the flow restriction of said variable flow restricting valve in such a manner that the flow restriction increases with the increase in the load carried by said cage.
Claim 4
Dependent Claim
133 words
A hydraulic lift comprising a hydraulic cylinder having a plunger, a cage arranged for upward and downward movement in response to the vertical movement of said plunger, a tank containing a hydraulic fluid therein, a conduit connecting said cylinder with said tank, a pump for pressurizing the hydraulic fluid drawn from said tank and supplying the fluid under pressure into said cylinder, an accumulator connected to said conduit for absorbing ripples occurring due to pressure variations in the fluid under pressure, a variable flow restricting valve disposed in the path of the fluid under pressure into and out of said accumulator, and means for varying the flow restriction of said variable flow restricting valve in such a manner that the flow restriction increases with the increase in the load carried by said cage.
Claim 5
Dependent Claim
64 words
A hydraulic lift as claimed in claim 1, in which said variable flow restricting valve is of the fluid pressure actuated type and responds to variations in the fluid pressure within a high-pressure conduit portion of said conduit due to variations in the load carried by said cage so that the flow restriction increases with the increase in the load carried by said cage.
Claim 6
Dependent Claim
48 words
A hydraulic lift as claimed in claim 1, in which the flow resistance of said variable flow restricting valve is varied in response to variations in the load carried by said cage so as to maintain the damping ratio at or in the vicinity of the maximum value.
Claim 7
Dependent Claim
52 words
A hydraulic lift as claimed in claim 1, in which said accumulator is connected to a high-pressure conduit portion of said conduit between said hydraulic cylinder and a pilot type check valve, and said variable flow restricting valve is disposed in the high-pressure conduit portion between said accumulator and said hydraulic cylinder.
References Cited (Backward Citations)
US3122992A
Cited
US3220312A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-12-17 | 1977-06-18 | 1977-12-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-17 | 1981-06-18 | 1981-12-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-17 | 1985-06-18 | 1985-12-18 | $7700.00 | Window Closed / Lapsed |