Note: Descriptions are shown in the official language in which they were submitted.
WO93/10321 ~ i3 ~1 ~ P, ~ PCT/GB92/0215~
LIFTING PI~ AND SYST~.~1
The invention relates to a lifting pin and more ~articul~rly to a
system of lifting a heavy object such as a ^oncrete body to be
placed in an intended location. One specifi_ use in which the
invention is seen to good effect is in th~ placement of segments
to build up a tunnel lining. ~or convenience the inven~ion will
be described with reference to that particular use that tns
invention is not to be limited therebv.
It is known to cast a threaded soc~et in a concrste segment and
to locate a threaded pin in that socket. The pin com~rises 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
th li]ce by which the concrete segment can be li~ted into place.
The ~rm is disengaged following which the pin is removed and then
grout can be pumped through the socket to fill ~ 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.
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It is one object of this invention to provide a system for
lifting which is of im~roved security and has other advantages.
WO93/10321 Q ~ PCT/GB92/0215~
Accor~ing 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 2in having a head and a threaded shank,
the socket and the pin having complementary threads
shaped to cause the pin to interengage with ~he socket
so as to enable the pin to engage the body for lifting
and the threads of the pin being shaped to ?reven~
unintentional threading of the pin from the socket;
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(ii) 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
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(iii) 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
in face of each thread, i.e. the one which leads into the socket,
is the shorter and steeper and so presents minimal resistance
whereas the trailing face presents are larger area for the
subsequent unthreading. Preferably the faces are inclined so
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WO93/10321 ~ ~ PCT/GB92/021~
that the pressure generated at the trailing face is about three
times as great 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 shan~ may include a frustoconical portion between
the threaded portion and the head of the pin to engage with a
complementary portion of the body.
~he threaded socket is pre'erably formed of ~ylon or like plastic
and has side flanges to anchor the soc~e_ in the concre~e bodv.
~hen the socket is cast in the concrete body, the concrete will
fill the space behind the threads so providing deep tapered
shoulders of set concrete. As a result of the interengagement of
the threads of the pin and those of the socket and the concrete
shoulders behind those socket threads, the pin can be used to
lift a heavy concrete body. A pin of the invention can be used
to lift a heavy concrete body and the socket can be use~ for
other purposes, e.g. grouting.
The hsad of the pin may be generally spherical and have sockets
to receive a bar used to rotate the pin out of the socket.
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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 clamoing device with the pin.
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WO93/10321 PCT/GB92/0~15~
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Preferably the clamping device comprises an upper bulb like body
surrounded by a plurality of segmental fingers, the lower ?ortion
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
c~m 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 staep
lead in anglsd face and a relatively shallow trailing angled face
and the head of the pin being shaped for lifting.
In order that the invention may be well understood it will now be
described with reference to the accompanying diagrammatic
drawings, in which
~igure 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;
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W093/1032] ~ 3~ ~ PCT/GB92/0215
~igure 3A corresponds to ~igure 2A showing the device in
clasping engagement -~ith the ~in and Figure 3B is a
sectional ~Jiew taken along lines III-III on Figure 3A; and
r igure 4A is a plan view and ~igure 43 a vertical section
of a plug used to seal the socket shown in ~igure 1.
The lifting pin 10 comprises an elongate steel ~ody comprising a
spherical head 11 on top o a neck 12 mounted on an annulus 13
h ving 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 ~ortion 15 beneath -~hich 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 ratio of the side walls
may be selected so that there is a steep lead-in angle (side wall
17B) and a relatively shallower trailing angle (side wall 17A);
the ratio may be about 3:l. 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
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WO93/10321 PCT/GB92/0215'
~ ~`.'3 7 l6
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 2mm nominal thickness in
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 o' the helix serving to
engage the par.s together and ~o locc them against unintenlional
unth~eading. The body may then be lifted using the lifting device
30 shown in Figures 2 and 3. Becaus2 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't a heavy concrete body. The
device comprises a hood 31 having a cen~ral 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
'ingers 34. The inner walls of the fingers 34 have up?er 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
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WO93/10321 h ~ PCT/GB92/021~
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 ~all of the nec3c 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, t~e
flngers 34 of the clamping device 30 are released from the head
11 of the pin 10 and the pin 10 is then unthreaded.
plastics plug 40 shown in Figure 4 is then threaded into the
socket 20, the plug corresponding in shape to the inte ior or the
socket. The plug has a bore 41 and a blind end wall 42. T}le
plug is used to block the socket 20 after pumping of grout behln~
the placed segment. The mouth of the plug may then be sealed.
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The invention is not limited to the embodiment shown. The socket
may comprise the threaded portion only and may not ex_en~ the
full thi.ckness of the body. One more sockets may be present per
body but usually only one is needed. The plug may be serrate~ to
destroy the socket. The body need not be a segment and may not
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be formed of concrete.
