GB2049618A

GB2049618A - Hoists

Info

Publication number: GB2049618A
Application number: GB8006233A
Authority: GB
Original assignee: A Rohe GmbH
Current assignee: A Rohe GmbH
Priority date: 1979-05-29
Filing date: 1980-02-25
Publication date: 1980-12-31
Also published as: DK445979A; IT1125640B; GB2049618B; IT7927144A0; DE2921834C2; DE2921834A1

Abstract

A hoist, particularly a two-post vehicle hoist, has a carriage (2) movable on a post (1) and carrying pivoting load-carrier arms (3). Stays (4) pivoted to the arms pass through locking means (20, 21) pivoted to brackets (14) on the carriage. Each locking means comprises a casing (5) containing a fixed jaw (9) and a movable jaw (8) between which the stay is gripped. The movable jaw is connected to a cam follower shoe (10) by rods (11, 12) which slide in the fixed jaw and on which compression springs (13) are mounted. The post carries a linear cam (15) which extends into the path of the shoe so that as the carriage approaches the ground the shoe engages the linear cam and the movable jaw is moved away from the fixed jaw to release the stay. When the carriage is again raised, the shoe moves off the linear cam and the stay is automatically reclamped between the jaws. <IMAGE>

Description

SPECIFICATION Hoists This invention relates to hoists of the kind comprising an upright, a carriage movable up and down the upright, and a load-carrier arm connected to the carriage by a pivot having a vertical axis. While the invention may be applied to such hoists for various purposes and of various constructions it is particularly applicable to twopost hoists for vehicles, each post having two pivoted load-carrier arms to provide four-point support for the vehicle being lifted; for convenience the invention will be described in connection with such hoists.

While it is necessary for the arms to be pivoted to the carriage in order to provide adjustment to accommodate vehicles of different size, it is important that the arums should not pivot during use; there is a considerable tendency for the arms to slip when the support points on the vehicle are damaged or uneven or dirty. It has therefore been proposed to employ locking means to hold the arms against pivoting. However, none of the constructions so far proposed is wholly satisfactory.

According to the present invention, a hoist comprises an upright, a carriage movable up and down the upright, a load-carrier arm connected to the carriage by a pivot having a vertical axis, a stay connected to the arm by a pivot having a vertical axis spaced from the first axis, and a clamp on the carriage, the clamp comprising two jaws between which the stay passes.

Preferably, the post carries a linear cam and the carrier carries a cam follower engageable with the cam over part at least of the travel of the carriage on the post, the cam follower being coupled to one of the jaws to separate the jaws during movement of the carrier over part of its travel. For example, the cam may be so shaped and positioned that the locking means is released as the carriage approaches the ground and is reengaged as the carriage is raised again. Thus the stays may be released when the carriage is right at the bottom so that the load-carrier arms can be adjusted beneath a vehicle.Then as the loadcarrier arms engage with the support points on the vehicle they can. still move to take up their best positions but shortly thereafter, and possibly before the full weight of the vehicle has been lifted off its wheels, the cam followers may leave the cams to re-engage the locking means.

The invention may be carried into practice in various ways but one hoist embodying the invention and a modification of the hoist will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a plan view of the hoist; Figure 2 is a fragmentary elevation of the hoist looking in the direction of the arrow II in Figure 1; Figure 3 is a partly sectioned fragmentary elevation looking in the direction of the arrow Ill in Figure 1; and Figure 4 is a view similar to Figure 3 of a modification that may be applied to the hoist.

The plan view of Figure 1 shows two carrying arms 3 and a post 1 of a two-post hoist. The opposite post is not shown. A carriage or slide 2 adapted to move vertically on the post 1 carries carrier arms 3 which are articulated to the slide 2 by vertical pivots 1 6. The carriage 2 has two brackets 14 with a locking means 20 or 22 interconnecting each bracket 14 and the corresponding carrier arm 3.

Each locking means 20 or 22 comprises a stay in the form of a rod 4 which is pivotally connected at one end to the arm 3 by a pivot 6 and extends at its other end through a clamp 21 or 23 which is pivotally mounted on the respective bracket 14 by a vertical pivot 7. Each clamp comprises a casing 5 of hollow square section within which is contained a fixed jaw 9 and a movable jaw 8 which can slide along the interior casing 5 but is a good fit therein so that it cannot move sideways.

The rod 4 passes through bores 1 7 in the side walls of the casing and passes between the fixed jaw and the movable jaw. The movable jaw 8 is formed with screw-threaded bores in which are fitted screwthreaded slide rods 11, 12 which are guided in bores in the fixed jaw 9. The slide rods are also fixed to a cam-follower shoe 10 which protrudes partly from and is slidable in the'casing.

The movable jaw 8 is biased towards the fixed jaw 9 by compression springs 1 3 which are mounted on the slide rods 11, 12 between the fixed jaw 9 and the shoe 10 so that the rod 4 is gripped between the jaws by the spring force. The rod 4 is formed with a screwthread and each of the jaws has a part cylindrical groove formed with a complementary screwthread so that when the rod 4 is gripped between the jaws it cannot move axially. Various alternative jaw and rod forms are possible; for example the rod may have complete circumferential ribs alternating with complete circumferential grooves and the jaws may have complementary ribs and grooves. In another arrangement the rod and the grooves in the jaws are smooth, the surfaces of the grooves being formed by a friction material.One or both of the jaws may be plane with the rod of circular or, more preferably, polygonal cross-section. In yet another arrangement, the rod is a toothed rack and one of the jaws is formed with complementary teeth.

At its bottom end, the post 1 carries a vertically extending abutment or linear cam 1 5 which is in the path of the shoe 10 as the carriage 2 descends on the post. When the shoe 10 engages the abutment the shoe is moved inwardly of the casing 5 and the movable jaw 8 is moved away from the fixed jaw 9 thus opening the locking means 20 or 22 and releasing the rod 4 so that the arm 3 can now be pivoted to a new position.

When the carriage is next raised, the shoe 10 will run off the abutment 1 5 and the lock will be re engaged automatically.

Figure 4 shows a modified construction in which the casing 5 of the locking means is disposed vertically and below the bracket 14. In this case the shoe 20 does not engage directly with the abutment 1 but there is an intermediate bell-crank lever 1 8 which is pivoted to the casing 5 and carries a cam-follower roller 1 9.

In another modification, not shown, the casing 5 of the locking means is disposed vertically and above the bracket 14, the shoe 10 then being at the top and forming a button or pad which can be depressed manually to release the locking means.

Claims

1. A hoist comprising an upright, a carriage movable up and down the upright, a load-carrier arm connected to the carriage by a pivot having a vertical axis, a stay connected to the arm by a pivot having a vertical axis spaced from the first axis, and a clamp on the carriage, the clamp comprising two jaws between which the stay passes.

2. A hoist as claimed in Claim 1 in which the stay has a circular cross-section and the jaws have plane clamping surfaces.

3. A hoist as claimed in Claim 1 in which the stay has a circular cross-section and one jaw has a plane clamping surface and the other jaw has a clamping surface which is of the same profile as the stay.

4. A hoist as claimed in Claim 1 in which the stay has a circular cross-section and each jaw has a clamping surface of part-circular profile to match that of the stay.

5. A hoist as claimed in Claim 1 in which the stay is formed with a male screwthread and at least one of the jaws has a clamping surface formed with a corresponding female screwthread.

6. A hoist as claimed in Claim 1 in which the clamping surface of at least one of the jaws is formed with a plurality of axially consecutive annular ribs.

7. A hoist as claimed in Claim 6 in which the stay is formed with a plurality of axially consecutive recesses matable with the annular ribs.

8. A hoist as claimed in Claim 1 in which the stay is a toothed rack and one of the jaws has complementary teeth.

9. A hoist as claimed in any of the preceding claims in which one of the jaws is fixed and the other is movable and is rigidly connected to a thrust member.

10. A hoist as claimed in Claim 9 in which the thrust element is connected to the movable jaw by a guide member which passes through and is slidably guided by the fixed jaw.

11. A hoist as claimed in Claim 10 which includes a spring between the fixed jaw and the thrust element biasing the movable jaw towards the fixed jaw.

12. A hoist as claimed in Claim 9 or Claim 10 or Claim 11 in which the post has an abutment acting as a cam which is engaged by a cam follower on the carriage to move the thrust member to move the movable jaw away from the fixed jaw during movement of the carriage through part of its travel.

13. A hoist as claimed in Claim 12 in which the cam follower is afforded by a part of the thrust member.

14. A hoist as claimed in Claim 12 which includes a lever one part of which carries the cam follower and another part of which engages the thrust member.

1 5. A hoist as claimed in any of Claims 9 to 14 in which the movable jaw and the thrust member are mounted in a casing which is pivotally mounted on a bracket carried by the slide.

1 6. A hoist as claimed in Claim 1 5 in which the iongitudinal axis of the stay and the axis of the pivot between the casing and the bracket intersect.

17. A hoist as claimed in Claim 15 or Claim 16 in which the pivot between the load-carrier arm and the carriage and the pivot between the casing and the bracket are at a fixed distance from one another and from a triangle with the pivot between the stay and the load-carrier arm.

18. A hoist as claimed in any of the preceding claims in which the pivot between the stay and the arm has a vertical axis.

19. A hoist as claimed in Claim 1 in which the post carries a linear cam and the carrier carries a cam follower engageable with the cam over part at least of the travel of the carriage on the post, the cam follower being coupled to one of the jaws to separate the jaws during movement of the carrier over part of its travel.

20. A hoist substantially as described herein with reference to Figures 1 to 3 of the accompanying drawings.

21. A hoist as claimed in Claim 20 modified substantially as described herein with reference to Figure 4 of the accompanying drawings.