GB2261650A

GB2261650A - Lifting pin

Info

Publication number: GB2261650A
Application number: GB9124780A
Authority: GB
Inventors: Frederick John Humphries; Robert David Partridge
Original assignee: LANESFIELD ENGINEERING SEALS L
Current assignee: LANESFIELD ENGINEERING SEALS L
Priority date: 1991-11-21
Filing date: 1991-11-21
Publication date: 1993-05-26
Also published as: GB2261651B; AU2950192A; GB9224376D0; FI933271L; WO1993010321A1; CA2100871A1; EP0568677A1; GB9124780D0; AU655337B2; GB2261651A; FI933271A0; FI933271A7

Abstract

A concrete body 21 has a threaded socket 20, to receive a lifting pin (10) having a shank 16 threaded so as to prevent accidental unthreading. The shank has one side wall 17b of the threads which is longer and steeper than the other 17a. Prof. the pin head 11 is connectable to a lifting clamp (30, Fig 2, not shown). <IMAGE>

Description

LIFTING SYSTEM The invention relates to a lifting system and more particularly to the system of lifting a heavy object such as a concrete body to be placed in an intended location. One specific use in which the invention is seen to good effect is in the placement of segments to build up a tunnel lining. For convenience the invention will be described with reference to that particular use that the invention is not to be limited thereby.

It is known to cast a threaded socket in a concrete segment and to locate a threaded pin in that socket. The pin comprises a shank which is received in the socket and a head which can be engaged by the end of an articulated arm mounted on a crane or the like by which the concrete segment can be lifted into place.

The hand is disengaged following which the pin is removed and then grout can be pumped through the socket to fill a space behind the segment, e.g. the annulus between the tunnel lining and the tunnel bore wall. Unfortunately, this method of lifting is unreliable because the pin can unthread itself from the lifting mechanism especially when the concrete segment tends to rotate. Clearly this has safety implications.

It is one object of this invention to provide a system for lifting which is of improved security. According to the invention in one aspect there is provided a method of lifting a concrete body for placement, e.g. as a segment of a tunnel lining, the method comprising (i) engaging a lifting pin in a threaded socket therefor in the body, the pin having a head and a threaded shank, and (ii) engaging the head of the pin in the hand of an articulated arm and then moving the arm to lift the body to the intended place, wherein the shank of the pin has a threaded portion shaped to prevent unintentional unthreading of the pin from the socket.

Preferably the threads of the threaded portion comprise sloping side walls, one of which is relatively steeper and longer than the other. Preferably the threads are in a helix and include a three point start.

The threaded socket is preferably formed of Nylon or like plastic and has side flanges to anchor the socket in the concrete body.

The shank may include a frustoconical portion between the threaded portion and the head of the pin.

It is preferred that the head of the pin is generally spherical, and is mounted on a neck portion.

Most preferably the method includes the step of locating the hood of a lifting means over the head of the pin, the hood containing a clamping device actuable to engage the head of the pin, and engaging the clamping device with the pin. Preferably the clamping device comprises an upper bulb like body surrounded by a plurality of segmental fingers, the lower portion of the fingers being shaped to engage the head of the pin, and actuating cam means to urge the fingers to engage the head of the pin.

Preferably the method includes the step of actuating the cam means from outside the hood.

In another aspect the invention provides a lifting pin comprising a head and a shank, the shank having a threaded portion, the threads being arranged in a helical path, the walls of the threads being shaped to prevent unintentional unthreading from a socket for the threaded shank.

In another aspect the invention provides a lifting device comprising a hood adapted to fit over the head of a pin, the hood containing finger means for engaging the head of the pin, cam means for moving the finger means into and out of engagement with the head of the pin, the cam means being engageable from outside the hood.

In order that the invention may be well understood it will now be described with reference to the accompanying diagrammatic drawings, in which Figure 1 is a side elevation of one embodiment of a lifting pin according to the invention overlying and partly in a socket therefor set in a concrete segment; Figure 2A is an elevation partly in section of a lifting device about to engage the pin of Figure 1 and Figure 2B is a sectional view taken along lines II-II on Figure 2A; Figure 3A corresponds to Figure 2A showing the device in clasping engagement with the pin and Figure 3B is a sectional view taken along lines III-III on Figure 3A; and Figure 4A is a plan view and Figure 4B a vertical section of a plug used to seal the socket shown in Figure 1.

The lifting pin 10 comprises an elongate steel body comprising a spherical head 11 on top of a neck 12 mounted on an annulus 13 having side flats 14. The pin may be made in any convenient way, for example by being machined from a length of bar. Below the annulus is a frustoconical portion 15 beneath which is a helically threaded shank 16. The threading is of helical form, each thread 17 comprising one relatively longer side wall 17A and one relatively shorter sidewall 17B. The thread is a three point start for speed of insertion into a socket 20.

The socket 20 is cast in the body of concrete 21. The socket 20 has a conical base portion 22 having an annular anchoring rim 23 at the lower face 21B of the concrete body. The top portion 24 of the socket is funnel shaped, having an annular rim 24A set in the upper face 21A of the body 21. The intermediate portion 25 of the socket 21 is threaded in a helix to complement that of the shank 16 of the pin 10. The socket 20 is made of 2mm nominal thickness in a plastics such as NYLON.

In use, to lift the body 21 the pin 10 is threaded into the socket 20, the shape of the threads of the helix serving to engage the parts together and to lock them against unintentional unthreading. The body may then be lifted using the lifting device 30 shown in Figures 2 and 3. The device comprises a hood 31 having a central socket 32 in the roof thereof for connection to an articulated limb or crane chain, neither of which is shown. A bulb-like body 33 depends from the centre of the hood and is surrounded by a plurality of segmental fingers 34. The inner walls of the fingers 34 have upper and lower arcuate portions 35 adapted to engage the bulb body 33 and the head 11 of the pin 10 respectively. The outer surface of the fingers has a depression 36 at a position about 2/3 of the height.Opposite cam members 37 are present along the side walls of the hood 30, and can be moved vertically by bars 38 projecting beyond the hood and travelling in slots therefor. The slots are inclined along a helical path. When the cam members 37 are lowered from the raised condition shown in Figure 2 to the lowered condition shown in Figure 3 the fingers are brought together so that they engage the head 11 of the pin 10, the free ends 39 of the fingers resting against the wall of the neck 12. In this condition the concrete body 21 may be lifted, with confidence that the pin 11 is securely clamped to the lifting device 30 and is also held secure against any movement (axial or torsional) relative to the socket 30. After placement, the fingers 34 of the clamping device 30 are released from the head 11 of the pin 10 and the pin 10 is then unthreaded.

A plastics plug 40 shown in Figure 4 is then threaded into the socket 20, the plug corresponding in shape to the interior of the socket. The plug has a bore 41 and a blind end wall 42. The plug is used to block the socket 20 after pumping of grout behind the placed segment. The mouth of the plug may then be sealed.

The invention is not limited to the embodiment shown.

Claims

1. A method of lifting a concrete body for placement, e.g. as a segment of a tunnel lining, the method comprising (i) engaging a lifting pin in a threaded socket therefor in the body, the pin a head and a threaded shank, and (ii) engaging the head of the pin in the hand of an articulated arm and then moving the arm to lift the body to the intended place, the shank of the pin having a threaded portion shaped to prevent unintentional unthreading of the pin from the socket.

2. A method according to Claim 1, wherein the threads of the threaded portion each comprise sloping side walls, one of which is relatively steeper and longer than the other.

3. A method according to Claim 1 or 2, wherein the threads are in a helix and include a three point start.

4. A method according to Claim 1, 2 or 3 wherein the threaded socket is formed of Nylon or like plastic and has side flanges to anchor the socket in the concrete body.

5. A method according to any preceding Claim, wherein the shank includes a frustoconical portion between the threaded portion and the head of the pin.

6. A method according to any preceding Claim, wherein the head of the pin is generally spherical.

7. A method according to Claim 6, wherein the head is mounted on a neck portion.

8. A method according to any preceding Claim including the step of locating the hood of the lifting means over the head of the pin, the hood containing a clamping device actuable to engage the head of the pin, and engaging the clamping device to the pin.

9. A method according to Claim 8, wherein the clamping device comprises an upper bulb like body surrounded by a plurality of segmental fingers, the lower portion of the fingers being shaped to engage the head of the pin, and actuating cam means to urge the fingers to engage the head of the pin.

10. A method according to Claim 9, including actuating the cam means from outside the hood.

11. A lifting pin comprising a head and a shank, the shank having a threaded portion, the threads being arranged in a helical path, the walls of the threads being shaped to prevent unintentional unthreading from a socket for the threaded shank.

12. A pin according to Claim 11, wherein the threading includes a three point start.

13. A pin according to Claim 11 or 12, including a frustoconical portion between the head and the threaded portion of the shank.

14. A pin according to any of Claims 11 to 13, wherein the head of the pin is spherical and is connected by a neck portion to the shank.

15. A lifting device comprising a hood adapted to fit over the head of a pin, the hood containing finger means for engaging the head of the pin, cam means for moving the finger means into and out of engagement with the head of the pin, the cam means being engageable from outside the hood.

16. A device according to Claim 15, wherein the cam means is connected to bar means projecting outside of the hood, th bars means being arranged to travel in slots therefor between one condition where the finger means are remote from the head of the pin and another condition where the fingers means engage the head of the pin, the slots lying along a helical path.