[0001] This invention relates to a formwork system as utilised by the construction industry
to provide what is known in the art as soffit, table or flying formwork/falsework.
The invention particularly relates to a lightweight formwork system wherein the majority
of its components are manufactured of an aluminium alloy by extrusion techniques.
[0002] It is an object of the present invention to provide a new or improved particular
component part of a formwork system, namely retaining means for releasably connecting
a screw jack to a main leg of the system.
[0003] In accordance with the present invention there is provided in a formwork system comprising
a plurality of vertically disposable main legs, ledgers and bracing wherein each main
leg is provided with an end plate at each end thereof to which a rotatable female
threaded element of a screw jack is securable; releasable retaining means engaging
a flange portion of said female threaded element and said end plate and being releasably
secured to said end plate whereby said female element is retainable captive to said
end plate in freely rotatable relation thereto.
[0004] Said releasable retaining means conveniently comprises a metal plate having a central
semi-circular slot formed therein extending from an edge thereof with a peripheral
rim of said slot being offset from the plane of the plate whereby the plate is releasably
securable to a said end plate of a main leg with the said rim of the slot engaged
over a said flange portion of a female element of a screw jack.
[0005] Said metal plate is conveniently provided with an aperture alignable with an aperture
provided in a said end plate of a main leg whereby said metal plate may be bolted
through said aligned apertures to the main leg end plate.
[0006] Other features of the invention will become apparent from the following description
given herein solely by way of example with reference to the accompanying drawings
wherein:
Figure 1 is an isometric view of one form of a lightweight formwork system showing
the various components thereof and arranged with a central downstand section;
Figure 2 is a similar isometric view to that of Figure 1 but showing a different configuration
of the formwork system including a downstand and a walkway;
Figure 3 is a further similar isometric view to that of Figure 1 showing an alternative
configuration of the formwork system to provide a table form;
Figure 4 is a diagrammatic isometric detail illustrating the engagement of the end
elements of the ledger frames with a main leg;
Figure 5 is a diagrammatic transverse cross-sectional view through the clamped ledger
frame end element and main leg of Figure 4;
Figure 6 is a detail isometric view of the T-shaped bolt utilised to clamp the ledger
frame to the main leg;
Figure 7 is an isometric view showing the attachment of a primary beam to the top
horizontal element of a ledger frame;
Figure 8 comprises diagrammatic isometric views of alternative head fittings at the
upper end of a main leg for supporting a primary beam thereon;
Figure 9 is an isometric exploded view illustrating releasable retaining means constructed
in accordance with the invention for attaching base or head screw jacks to the lower
and upper ends respectively of a main leg;
Figure 10 is an isometric view of a ground engaging jack base member for supporting
a main leg;
Figure 11 is an isometric view of a bracing collar securable about a main leg for
the attachment of bracing; and
Figure 12 is an isometric view of the bracing collar of Figure 11 clamped around a
main leg adjacent an end plate thereof.
[0007] The lightweight formwork system described and illustrated herein in accordance with
the invention includes a plurality of components, the majority of which are manufactured
as aluminium alloy extrusions. Referring to Figures 1 to 3, the systems illustrated
therein comprise a plurality of horizontally spaced vertically disposed main leg assemblies
10, a plurality of ledger frames 12 each interconnecting and being releasably securable
to adjacent pairs of main legs, a plurality of horizontally spaced apart horizontally
disposed primary beams 14 supported either directly on the main legs or on the ledger
frames, and a plurality of horizontally spaced apart horizontally disposed secondary
beams 16 supported on the primary beams. Additionally there is shown base and head
screw jacks 18 and 20 attached to the respective lower and upper ends of each main
leg, jack base members 22 and bracing collars 24 for receiving bracing 26 and 28 for
supporting the ledger frames.
[0008] For ease of understanding, the various components of the system will now be individually
described in more detail with reference to the relevant drawings as follows.
Main Leg Assembly
[0009] Each main leg assembly 10 comprises a main leg proper 30 manufactured as an aluminium
alloy extrusion of the profile shown in Figures 4,5, 9 and 12. Thus the profile comprises
a substantially square hollow centre section 32 with integral flanges 34 defining
four longitudinally extending T-shaped slots 36 with the mouth of each slot facing
outwardly of the leg. Each main leg also has secured thereto, as by welding, at each
of its upper and lower ends an end plate 38 which in the embodiment illustrated in
Figures 9 and 12 is of octagonal configuration. Each end plate 38 has an aperture
40 extending therethrough for the purpose further described hereinafter.
[0010] Each main leg assembly 10 also includes either or both base and head screw jacks
18 and 20, a head jack 20 being shown in more detail in Figures 8 and 9. As will be
seen particularly from Figure 9, the head screw jack comprises a central male screw
threaded element 42 of coarse pitch and a winged rotatable female screw threaded element
44 engaged about the male element 42. The female element 44 includes an end flange
46 which, as shown in Figures 8 and 9, rests on the upper end plate 38 of the main
leg with part of the male element 42 extending into the central hollow section of
the leg 30. A pressed metal retainer plate 48 is located to engage over respective
parts of the associated end plate 38 and over the flange 46. As will be clearly seen
in Figure 9, the metal plate 48 has a central semi-circular slot extending from one
edge thereof with a peripheral rim of said slot offset from the plane of the plate
whereby the plate 48 is releasably securable to the end plate 38 with the rim of the
slot engaged over the end flange 46 of the female element 44. The retainer plate is
clamped in position by a bolt 50 passing through an aperture in the plate 48 aligned
with the aperture 40 in the main leg end plate 38 as shown in Figure 9 whereby the
jack 30 is secured to the main leg with the female element 44 being freely rotatable.
A similar arrangement of retainer plate assembly may be provided at the lower end
plate of each main leg to secure a base jack 18 thereto.
[0011] Referring again to Figure 9 it will be seen that the end plate 38 is provided with
four equi-angularly spaced slots 52. Such slots 52 in the end plate 38 enable an additional
main leg 30 to be secured thereto by bolting passing through the slots in adjacent
end plates of the two legs. Also, in some circumstances, a head jack 20 may not be
utilised, and a primary beam 14 may be supported directly on the upper end plate of
the main leg by bolting to the upper end plate 38 through the slots 52.
[0012] The upper end of the male element 42 of the head jack 20 may be provided with differing
head fittings 54 or 56 as shown in Figure 8. For example, the head fitting 54 may
comprise a channel-shaped member 58 within which a primary beam 14 may be disposed,
and include a plurality of apertured lugs 60 for receiving bracing members. Alternatively,
the head fitting 56 may comprise a flat plate 62 having apertures therethrough in
which are engaged T-bolts 64 clampable within the lower slot of a primary beam 14;
the primary beam being described in more detail below. Such a plate type head fitting
56 may also include a plurality of apertured lugs 60 for the securing of bracing members
thereto. In either embodiment, the head fitting 54 and 56 includes a downwardly depending
collar 66 which fits over the upper end of the head jack male element 42 and is secured
thereto by a bissell pin 68 passing through aligned apertures 70 in the collar 66
and a transversely extending bore 72 in the element 42.
[0013] The lower end of a base screw jack 18 is shown in Figure 10 which also illustrates
a jack base member 22 comprising an aluminium alloy casting having a cylindrical central
collar 74 for receiving the lowermost end of the base jack male element 42. The casting
also includes four radially outwardly extending equi-distantly spaced apart wings
76 within each of which is provided an aperture 78 for the securing of bracing 26
thereto. The jack base member also includes a planar base plate 80 and is secured
to the male element 42 by means of a bissell pin 82 extending through aligned apertures
84 in the collar 74 and a bore 86 in the male element 42. As mentioned above, the
base jack member may be secured to the lower end plate of the main leg by a similar
retaining plate 48 to that shown in Figure 9 and thus the effective length of the
main leg assembly 10 may be varied by appropriate rotation of the female elements
44 of the base or head jacks 18 and 20.
[0014] Each main leg assembly 10 may also include a bracing collar 24 as shown in Figures
11 and 12. Such collar 24 comprises a two-part hinged aluminium alloy casting having
central body parts 88 - 90 shaped to fit snugly around the main leg 30 and to be clamped
thereon by a clamping nut and bolt assembly 92. The collar 24 includes four radially
outwardly extending equi-distantly spaced apart wings 94 each having an apertured
lug 96 therein for engagement by bracing members 28. As shown in Figure 12, and at
various positions in Figures 1 and 2, the bracing collar 24 is conveniently clamped
around a main leg 30 immediately adjacent and above the lower end plate 38 of the
respective main leg. Thus, in the downstand beam construction shown in Figures 1 and
2, loading on the ledger frames is transmitted via bracing 28 and collar 24 to the
lower end plate 38 of a respective main leg and thence to the associated base jack
18.
Ledger Frame
[0015] Various ledger frames 12 of the system are shown in Figures 1 to 3 and the manner
of their attachment to the main leg is illustrated in Figures 4 and 5. Referring to
Figure 3, each ledger frame 12 is comprised essentially of upper and lower horizontally
disposed elements 98 and 100, a pair of vertically disposed end elements 102 extending
between the horizontal elements and one or more intermediate vertically disposed elements
interconnecting the horizontal elements 98 and 100. Diagonal bracing 106 may also
be included at one or more positions in each ledger frame. Either or both of the upper
and lower horizontal elements 98 and 100 may be provided with respective upwardly
or downwardly projecting apertured lugs 108 for the securing of bracing members 26
or 28 thereto.
[0016] Each vertical end element 102 of each ledger frame 12 is illustrated in more detail
in Figures 4 and 5 and comprises a hollow box section extrusion of a substantially
T-shaped profile to provide a longitudinally extending projection 110 engageable within
the mouth of a T-shaped slot 36 on a main leg 30. As stated above, each ledger frame
12 interconnects and is securable to adjacent pairs of main legs 30 and such securement
is effected by the clamping bolt 112 shown in Figures 5 and 6. As is clearly illustrated
in Figure 5, each of such clamping bolts 112 has a T-head 114 engageable within a
T-shaped slot 36 of a main leg 30 and a threaded shank 116 which extends through aligned
apertures 118 in opposed faces of the end element 102 of a ledger frame. A nut 120
with an integral lever arm 122 is threadedly engaged on the bolt shank 116 to engage
that face of the ledger frame end element 102 remote from the projection 110 whereby
tightening of the nut will clamp the frame to the main leg.
The Primary Beams and Secondary Beams
[0017] As illustrated in Figures 1 to 3 of the drawings the primary beams 14 and the secondary
beams 16 are of somewhat similar configuration with the primary beams 14 being disposed
in horizontally spaced relationship and supported either directly by a head fitting
54 or 56 of a main leg assembly 10 or on the upper horizontal elements 98 of the ledger
frames 12. The secondary beams 16 are supported in horizontally spaced relationship
on the upper surfaces of the primary beams 14 and secured thereto in a known manner.
[0018] Referring to Figure 7 each of said primary beams 14 is an aluminium alloy extrusion
comprising two spaced I-section flanged elements 124 integrally interconnected by
a planar central web 126 and also interconnected by two opposed channel-shaped integral
webs 128 each located intermediate the central web 126 and the upper and lower co-planar
flanges 130 of the beam respectively.
[0019] Each of said secondary beams 16 is also an aluminium alloy extrusion conveniently
substantially of the profile illustrated in British Registered Design 995006 comprising
two spaced I-section flanged elements integrally interconnected by a pair of parallel
spaced planar webs intermediate upper and lower co-planar flanges of the beam.
[0020] In the configuration of formwork illustrated in Figure 3, where all of the primary
beams 14 arc disposed in the same horizontal plane, such primary beams 14 are supported
by head fittings 54 or 56 at the upper ends of the head screw jacks 20 of each main
leg assembly 10.
[0021] As shown in part in Figures 1 and 2, where a downstand location is to be provided,
the relevant primary beams 14 are supported directly on the upper horizontal elements
98 of the ledger frames 12 at a lower horizontal level than those primary beams 14
which are supported directly on the main leg assemblies 10. As shown in Figure 7,
in such a downstand location, each primary beam 14 is secured to an upper horizontal
ledger frame element 98 by a U-shaped clip 132 having a T-shaped head 134 at one end
engageable within the T-shaped slot of the primary beam 14 and having a securing flange
136 at the other end through which passes a nut and bolt assembly 138 for clamping
that end of the clip to the slower flanges 130 of the primary beam.
Bracing Members
[0022] As shown in Figures 1 to 3, bracing members 26, 28 may be connected between the ledger
frames 12 and associated main leg assemblies 10. Thus, bracing may be connected between
the wings 76 of the jack base members 22 and the lower horizontal elements 100 of
the ledger frames, or between the wings 94 of the bracing collars and the lower horizontal
elements 100 of the ledger frames, or between the lugs 60 of the head fittings 54
or 56 and the upper horizontal elements 98 of the ledger frames.
[0023] As shown in the table form configuration of Figure 3, the braces 26 may be of the
form described in British Patent 1 599 646 comprising tubular telescopic elements
extending from either or both the upper and lower horizontal frame elements 98, 100
of the ledger frames 12 to a respective main leg assembly 10. In a downstand application
where the ledger frame 12 has to take vertical loading imparted thereto from the primary
beams 14 supported on the ledger frame, the ledger frame 12 is supported in accordance
with the invention by bracing such as is shown at 28 in Figures 1 and 2. Such bracing
28 may comprise a vertically or substantially vertically disposed turn-buckle assembly
extending, as shown in Figures 1 and 2, from the wings 94 of the bracing collar 24
to locations adjacent the ends of the lower horizontal elements 100 of the ledger
frames.