GB2261651A

GB2261651A - Lifting pin

Info

Publication number: GB2261651A
Application number: GB9224376A
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: 1992-11-20
Publication date: 1993-05-26
Anticipated expiration: 2012-11-20
Also published as: FI933271A; AU655337B2; AU2950192A; GB9124780D0; CA2100871A1; GB9224376D0; WO1993010321A1; GB2261651B; GB2261650A; FI933271A0; EP0568677A1

Abstract

A lifting pin (10) has a lifting head (11) and a threaded shank (16), the shank being received in the threaded portion (25) of a socket (20) formed in the concrete body (21) to be lifted. The thread is shaped to prevent unintensional dethreading during lifting. The thread has one side wail (17b) longer and steeper than the other (17a). Preferably the pin head (11) is connectable to a lifting clamp (30, Fig 2, not shown). The pin is used for lifting and placing tunnel lining segments. <IMAGE>

Description

1 LIFTING PIN AND SYSTEM ) ' 'i 1 1) - The invention relates to a lifting

pin and more particularly to a 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 o-r the like by which the concrete segment can be li-ted Jnto place. The arm 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 lin- Lng and the tunnel bore wall. Unfortunately, this method of lifting is unreliable because the pin can unthread itself from the lift Lng 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 and has other advantages.

2 -1 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) (ii) (i j j) engaging a lifting pin in a threaded socket therefor in the body, the pin having a head and a threaded shank, the socket and the pin having complementary threads shaped to cause the pin to interengage with the socket so as to enable the pin to engage the body for lifting and the threads of the pin being shaped to prevent unintentional threading of the pin from the socket; engaging the head of the pin with a lifting device and then moving the body to the intended place, separating the lifting device from the pin and releasing 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. The threads are preferably arranged so that the lead -he so.

in face of each thread, i.e. the one which leads into 4. -ket, --eeper and so presents minimal resist is the shorter and st 1-ance whereas the trailing face presents are larger area for the subsequent unthreading. Preferably the faces are inclined so 4 3 that the pressure generated at the t-railing face is about three times as zreat as at the leading face. Preferably the threads are in a helix. Preferably the threads are shaped so that there is a three point start for speed of insertion of the pin in the socket. The shank may, include a frustoconical portion between the threaded portion and Ithe head of the pin to engage with a complementary portion of the body.

T-he threaded socket is Dre-E-arabl;1 -formed of 1Nylon or plastic langes and has o anchor 4-he socket in the concrete body.

When the socket is cast -i-n the concrete body, the concrete will threads so or-Dvid-"na deep ta-iered 1 e s -c a c e b e'll i_n d t -h shou-",'--.----s f3--' set concrete. As a --esu-',-- of the interengagement of ---" e - the socke'- and 1WI concr& the threads of the pin and those o. L shoulders behind those socket threads, the pin can be used to lift a heavy concrete body. A pin of the invention can be used A to lift a heavy concrete body and the socket can be used for other purposes, e.g. grouting.

The head of the pin may be generally spherical and have sockets to receive a bar used to rotate the pin out of the socket.

Most preferably the method of lifting 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.

4 Preferably the clamping device comprises an upper bulb like body surrounded by a plurality of segmental fingers, the lower portion of the f ingers 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 and each having a relatively steep lead in angled face and a relatively shallow trailing angled face and the head of the pin being shaped for lifting.

In =Ser the ú.nve--i.L1.-ion may be well understood it will now be descr-2.bec-' wit-h reference to the accompanying diagrammatic in -h drawlnzs, --- whic ligure 1, is a side elevation off one embodiment of a lifting pin according to the invention overlying and partly in a sDc.',ze.:: thereffor 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; A 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 --elativeiv shorter sidewall 17B. The ratio of the side walls may be selected so that Ithere is a steep lead-in angle (side wall 17B) and a relatively shallower trailing angle (sidfle_ wall 17A); the ratio may be about 3:1. The thread is a three Doint start for soeedl of insertion into a socket 20.

t 20 is cast in the body of concrete 21. The sock.et 20 The sockel has a conical base porItion 22 having an annular anchoring rim 23 at IkIne 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 nortion 25 4 6 of the socket 21 is threaded in a helix to complement that of the shank 16 of the pin 10. Because the socket 21 is cast in the concrete shoulders of set concrete are present behind the threads of the socket. The socket 20 is made of 2mn 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. Because of the engagement of the threads of the shank and those of the socket and the concrete behind, the pin may be used to li-f t a heavy concrete body. 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 whic-11is shown. A bulb-like body 33) depends from the centre of the hood and is surrounded by a plurality of segmental 34. The inner walls of the fingers 34 have upper and ingers.3 _L - L_ - lower arcuat-e porit-ions 35 adapted to engage the bulb body 33 and the head 1' 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 7 lowered condition shown in Figure 3 the f ingers 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, 'he 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 - -hen be sealle-55.

the placed segment. The mouth of the plug may t The invention is not lim-ted to the embodiment shown. ma17 coMpr'Se the th-eaR--:' portion only and may not full thickness of the body. One more sockets may be body but usually only one is needed. The plug may be destroy the socket. The body need not be a segment be formed of concrete.

-he socket extend the present Der ser--ated to an,:' may not 4 A 1

Claims

1. A method of lifting a concrete body for placement, e.g. as a segment of a tunnel lining, the method comprising (i) (ii) (iii) engaging a lifting pin in a threaded socket therefor in the body, the pin having a head and a threaded shank, the socket and the pin having complementary threads shaped to cause the pin to interengage with the socket so- as to enable the pin to engage the body for lifting and the threads of the pin being shaped to prevent unintentional threading of the pin from the socket; engaging the head of the pin with a lifting device and then moving the body to the intended place, separating the lifting device from the pin, and releasing 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 walls of the threads are shaped so that the pressure generated at the k 1 9 - trailing face is about three times as great as at the lead in f ace.

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

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

A method according to Claim 5, wherein the socket is cast into the body so that concrete shoulders are formed in the threaded portion behind the threads.

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

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

9.

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 1 A - [0 - to engage the head of the pin, and engaging the clamping device to the pin.

10. A method according to Claim 9, 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.

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

12. A lifting pin comprising a head shaped for lifting, 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.

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

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

1 11

15. A pin according to any of Claims 12 to 14, wherein the head of the pin is spherical and is connected by a neck portion to the shank.

16. A method of lifting a concrete body, substantially as described and with reference to the drawings.

17. A lifting pin, substantially as described and with reference to the drawings.

LS/BW/19.11.92 P00586GB.Cl