Platform lift

• US 4,600,085 A
• Filed: 11/19/1984
• Issued: 07/15/1986
• Est. Priority Date: 11/19/1984
• Status: Expired due to Fees

• Current Assignee: LaForest, Pierre, Pierre Gagnon
• Original Assignee: LaForest, Pierre, Pierre Gagnon
• Inventors: Gagnon, Pierre, LaForest, Pierre
• Primary Examiner(s): Marmor, Charles A.
• Assistant Examiner(s): Huson, Gregory L.
• Application Number:
  US06/673,108
• Time in Patent Office: 603 Days
• Field of Search: 187/8.59, 187/24, 187/25, 187/9 E, 182/141, 182/63, 254/7 R, 254/7 C, 254/47, 254/89 R, 254/103, 52/7, 52/118, 52/121, 272/21, 272/22
• US Class Current: 187/268
• CPC Class Codes: B66B 9/025 by screw-nut drives
• CPC Class Codes: B66F 7/14 screw operated
• CPC Class Codes: E04H 3/26 Revolving stages; Stages able to be lowered

Abstract

A platform lift mechanism for theaters, concert halls, etc. The lift device is a module or modules formed of four segments telescopically, vertically extendable or retractable relative to each other, except for a fixed base segment. The platform is secured to the uppermost segment. The second segment carries a rotatable nut adapted to raise and lower an elongated complementary screw secured at its upper end to the third segment. When four modules are used, a synchronizing chain is provided to actuate all modules synchronously. A brake and a motor are provided, either for each module or for all of them. A motor control is also provided.

Claims

1. A platform lift comprising at least one module;

said module being formed of four distinct, upright segments, including a first segment adapted to be secured to a supporting surface, a second segment telescopically, vertically slidable relative to said first segment;

a third segment similarly telescopically slidable relative to said second segment, and a fourth segment similarly telescopically sildable relative to said third segment;

said second segment laterally straddling said first segment and said third segment laterally straddling said second segment, and said fourth segment laterally straddling said third segment;

a primary lift means secured to said second and said third segments and adapted to raise and lower said third segment relative to said second segment;

a first passive lift means adapted to vertically displace said second segment relative to said first segment and, a second passive lift means adapted to vertically displace said fourth segment relative to said third segment as said primary lift means is actuated;

guide means between said first and second segments, between said second and third segments, and between said third and said fourth segments;

power means to operate said primary lift means, and a transmission means mechanically connecting the latter to the power means;

the upper portion of said fourth segment adapted to be secured to the underside of a platform to be lifted.

2. A platform lift as defined in claim 1, wherein each of said segments is formed of a pair of spaced girders;

each said girder having an outwardly, laterally projecting flange at both its opposite ends;

said girders of said first segment being joined by a pair of vertically-spaced crossmembers;

said girders of said second segment being joined adjacent their lower ends by another cross-member;

the lower portions of said girders of said third segment being joined by a fourth cross-member;

the lower portions of said fourth segment girders being likewise joined by a fifth cross-member;

the upper ends of said girders of said third segment being joined by a rigid retaining member.

3. A platform lift as defined in claim 2, wherein said primary lift means comprises:

an elongated externally threaded vertical screw rigidly secured at its upper end to said retaining member and having a free lower end;

a nut rotatably mounted in a nut support means which is rigidly secured to the upper portion of said second segment;

said nut having a central internally threaded bore complementary to the threading of said screw;

said screw being threadedly engaged in said bore;

said nut being mechanically connected to said transmission means.

4. A platform lift as defined in claim 3, wherein said first passive lift means consists of a pair of flexible tie members of the same predetermined length, each having one end attached to the upper end of one first segment girder, each passing around a sprocket rotatably mounted at the lower end of each second segment girder, and fixed at its opposite end to the lower end of each third segment girder.

5. A platform lift as defined in claim 4, wherein said second passive lift means consists of a second pair of flexible tie members, each having one end secured to the lower end of one fourth segment girder;

each passing around another sprocket rotatably mounted at the upper end of each said third segment girder;

each having its opposite end secured to the upper end of each second segment girder.

6. A platform lift as defined in claim 5, wherein said guide means comprises:

a plurality of axially, longitudinal, inwardly-projecting guide wheels, one at each inner surface corner of said girders adjacent the lower end of each said segment;

each said guide wheel being arranged to rollingly engage the corresponding inner surface of said flange.

7. A platform lift as defined in claim 6, wherein the circumference of said nut is formed with teeth;

said transmission means being a first endless chain entrained around said teeth;

said power means being a motor having an output shaft drivingly connected to said endless chain.

8. A platform lift as defined in claim 7, wherein there are four modules laterally aligned in pairs, one at each corner of said platform.

9. A platform lift as defined in claim 8, wherein said transmission means comprises:

a rigid longitudinally-extending bridge located centrally between each pair of laterally-aligned modules;

a flat plate secured to each of the opposite ends of said bridge;

a pair of flat and rectangular first support members secured to the longitudinal side of each said flat plate and transversely thereto;

the outer longitudinal side of each said first support member being secured to the adjacent said second segment;

a synchronizing second endless chain supported and guided by said support member and drivingly connected to each of said nuts;

said bridge being provided with a pair of longitudinally-spaced chain guide tracks for said synchronizing chain, the latter causing all of said modules to be extended and retracted in a synchronized manner.

10. A platform lift as defined in claim 9, wherein said transmission means further includes a second support member for each of said modules;

each of the second support members being rigidly secured to said nut support means and extending laterally over its corresponding first support member;

a drive extension shaft journalled at its lower and upper ends in each of said first and second support members, respectively;

each said drive extendsion shaft carrying a first sprocket at its lower portion and a second sprocket at its upper end;

said first endless chain extending around its associated said nut and also around its associated said sprocket;

each said first sprocket meshing with said synchronizing endless chain;

said power means including a motor having an output shaft connected to one of said drive extension shaft s.

11. A platform lift as defined in claim 10, wherein said transmission means further comprises a main chain tensioning means and an auxiliarly chain-tensioning means.

12. A platform lift as defined in claim 11, wherein said main chain-tensioning means comprises a slidably adjustable plate mounted on each said first support member;

a pair of central transverse beams, each rigidly secured at its opposite ends to one of said adjustable plates;

the four said adjustable plates each haivng journalled therein one of said first sprockets;

said motor being mounted on one of said beams, a laterally-slidable bearing support plate mounted on each of said second support members;

each said second sprocket having a bearing carried by a said bearing support plate;

whereby each pair of laterally-aligned first and second sprockets, their respective said drive extension shafts and said motor can be laterally adjusted to properly tension said first and said second endless chains;

means to adjustably lock each said adjustable plate.

13. A platform lift as defined in claim 12, wherein said auxiliary chain-tensioning means includes an auxiliary sprocket gear mounted in each of the two corners facing said bridge of each said flat plate;

each said auxiliary sprocket gear meshing with said synchronizing chain and mounted over said flat plate and in a longitudinally-slotted overlying plate, whereby the position of each said auxiliary sprocket gear is secured by tightening an axial bolt.

14. A platform lift as defined in claim 12, wherein said motor is a hydraulic motor provided with an automatic acceleration, deceleration and speed control means.

15. A platform lift as defined in claim 14, wherein said control means comprises a servo-valve of the two spool type having two differential inputs;

one of said inputs being achieved by said hydraulic motor through the intermediary of at least two demultiplication gears;

the other of said inputs being an electric motor;

said servo-valve being hydraulically connected to said hydraulic motor.

16. A platform lift as defined in claim 15, wherein said hydraulic motor is provided with a brake means.

17. A platform lift as defined in claim 16, wherein said brake means comprises:

one of said first rectangular support members being a fixed plate, adjacent, carrying and overlying said hydraulic motor;

a back plate extending parallel to and vertically-spaced above said fixed plate;

a plurality of frictional;

stator disks interposed between said fixed plate and said back plate;

means to immobilize each stator disk;

a plurality of frictional rotor disks alternatively sandwiched between said stator disks;

means to secure said rotor disks to said output shaft;

both said rotor disks and said stator disks being concentrically arranged relative to said output shaft;

further comprising a flexible hydraulic conduit extending in a loop between said fixed plate and said back plate;

said conduit being fed the hydraulic fluid pressure source of said hydraulic motor; and

biasing means to urge said back plate towards said fixed plate.