GB2475690A

GB2475690A - Counterbalanced "C" frame lifting device

Info

Publication number: GB2475690A
Application number: GB0920660A
Authority: GB
Inventors: Jonathan Luke Chant
Original assignee: Hoerbiger UK Ltd
Current assignee: Hoerbiger UK Ltd
Priority date: 2009-11-25
Filing date: 2009-11-25
Publication date: 2011-06-01
Also published as: GB0920660D0

Abstract

A "C" frame 5 has a pivoting lift bracket 2 and a pivoting counterbalance arm 11 with attached counterweight 6 to counterbalance the lift item (fig 4), the lift bracket 2 and counterbalance arm 11 pivoting about a vertical axis and being mechanically linked to ensure they rotate in unison. The lift point 8 of the "C" frame 5 may be in line with the axis of rotation of the pivoting brackets. This mechanism allows the lift item to be pivoted on the lift bracket whilst the centre of gravity of the "C" frame 5 remains unchanged. The angular position of the lift bracket may be controlled via a hand wheel 3. The linear position of the pivoting counterweight 6 along the counterbalance arm may be adjustable for lift items of differing mass. The pivoting counterweight 6 may be detachable to enable the frame to remain in balance when the lift item is detached. A fixed counterweight 9 may be provided whose linear position is initially adjustable to balance the "C" frame 5. A handle 4 may be provided to manoeuvre the "C" frame 5. The apparatus allows heavy machinery to be lifted and manoeuvred in restricted spaces.

Description

Counterbalanced "C" Frame Lifting Device This invention relates to a counterbalanced "C" frame lifting device.

The maintenance of many items of large machinery involves the lifting of heavy components in to restricted spaces where the only available line of lift is not vertically in line with the centre of gravity of the item to be lifted. In this instance, a "C" Frame lifting attachment would typically be used. However if the lift item must be turned on the lifting bracket to insert it in to position, the "C" frame becomes unbalanced. This effect becomes more pronounced the further away from the lift items centre of gravity the lift item is attached. Due to space constraints of the installation position, the lift item often has to be attached at one end of the lift item, away from the lift item's centre of gravity.

In this instance, heavy lift items will cause the "C" frame to become extremely unbalanced posing a danger to the operator, and risking damage to the lift item and machinery.

To overcome these issues, the present invention proposes a "C" frame lifting device with a pivoting lift bracket, and a pivoting counterbalance arm with counterweight, to counterbalance the item to be lifted. The pivoting counterbalance arm, located at the top of the frame, is mechanically linked to the pivoting lift bracket, located at the base of the frame. The lift point of the "C" frame is at the top of the frame in line with the axis of rotation of the lift bracket and counterbalance arm.

The mechanical linkage, between the pivoting counterbalance arm and the pivoting lift bracket, counterbalances the lift item as it is turned on the lift bracket. The fact that the lift point of the "C" frame is in line with the axis of rotation of the lift bracket and counterbalance arm, means that the centre of gravity of the "C" frame remains unchanged as the lift bracket is rotated. This arrangement enables the lift item to be attached to the lift bracket at one end of the item, away from the lift items' centre of gravity and ensures that the lift bracket does not obstruct the items lift path as it is installed. Therefore items can be safely lifted and manoeuvred into position where there are space constraints at the lift item end (for example, lifting and positioning an item in to an enclosed space with limited access from the sides).

Preferably, the angular position of the lift bracket, and thus the counterweight, are controlled via a hand wheel at the bottom of the frame vertical member.

Preferably, the linear position of the pivoting counterweight along the counterbalance arm, perpendicular to the axis of rotation, is adjustable for lift items of differing mass.

Preferably, the pivoting counterweight is detachable from the pivoting counterbalance arm to enable the frame to remain in balance when the lift item is detached from the lift bracket.

An example of the invention will now be described by referring to the accompanying drawings: * Figure 1 shows a schematic of a counterbalanced "C" frame lifting device with mechanically linked pivoting lift bracket and counterbalance arm.

* Figures 2 to 5 illustrate the operation of the counterbalanced "C" frame lifting device with mechanically linked pivoting lift bracket and counterbalance arm.

In figure 1, a counterbalanced "C" frame lifting device (5) is fitted with a pivoting lift bracket (2) and a pivoting counterbalance arm (11). The pivoting lift bracket, at the base of the frame, is mechanically linked via a chain and sprocket arrangement to the pivoting counterbalance arm at the top of the frame. The linkage between the pivoting lift bracket and the pivoting counterbalance arm is via a spindle that runs inside the vertical section of the "C" frame. The angular position of the lift bracket and counterbalance arm are controlled by a hand wheel (3) at the base of the frame vertical.

The linear position of the pivoting counterweight (6) along the counterbalance arm, perpendicular to the axis of rotation, is adjustable via a lead-screw (7) to counterbalance lift items of differing mass. The pivoting counterweight is removable to enable the "C" frame to remain in balance when the lift item is detached from the lift bracket. The linear position of the fixed counterweight (9) is also adjustable, however once the "C" frame has been balanced, this counterweight will not need to be adjusted. A handle (4), attached to the frame vertical, allows the "C" frame to be easily manoeuvred. The "C" frame can be attached to a crane hook at the eyebolt (8), which is located at the top of the frame. Indexing plungers (10), attached to the frame below the pivoting counterbalance arm, fix the position of the arm when the Counterbalanced "C" Frame is not in use.

Figures 2 to 5 illustrate the counterbalanced "C" frame in use, lifting a typical machine component in to a machine housing with restricted access (the machine housing is shown as a cross section for clarity). In figure 2, the machine component, attached to the pivoting lift bracket, is offered up to the access window. In figure 3, the hand wheel at the base of the frame vertical is turned to rotate the component on its lift bracket, and in turn, rotate the counterbalance arm. In figure 4 the component is further rotated and advanced until it is aligned with its housing bore. In figure 5, the frame is manoeuvred axially to the housing to locate the component in the housing bore. At this point the lift item is secured into position. Before the lift item is detached from the lift bracket, the pivoting counterweight is either removed or wound towards the axis of rotation. In this way the "C" frame remains in balance whilst the frame is withdrawn.

Claims

Claims 1. A counterbalanced lifting device comprising a "C" frame with a pivoting lift bracket at the base of the frame, and a pivoting counterbalance arm at the top of the frame, which are mechanically linked to enable the angular rotation of the lift item attached to the lift bracket, whilst the counterweight attached to the top bracket counterbalances the lift item.
2. A counterbalanced lifting frame according to claim I in which the axis of rotation of the lift bracket and counterbalance arm are aligned with the lift point at the top of the frame to enable the frame to remain in balance when the brackets are turned.
3. A counterbalanced "C" frame according to claim I in which the linear position of the pivoting counterweight along the counterbalance arm, perpendicular to the axis of rotation is adjustable to enable the frame to balance whilst lifting loads of differing mass.
4. A counterbalanced "C" frame according to claim I in which the means of rotation of the lift bracket and hence the pivoting counterweight is provided by a hand wheel at the bottom of the frame vertical.
5. A counterbalanced "C" frame according to claim I in which the pivoting counterweight is detachable from the pivoting counterweight arm to enable the frame to remain in balance when the lift item is detached from the lift bracket.