GB1561377A

GB1561377A - Scaffolding

Info

Publication number: GB1561377A
Application number: GB692476A
Authority: GB
Original assignee: GKN Mills Building Services Ltd
Current assignee: RMD Kwikform Ltd
Priority date: 1977-02-15
Filing date: 1977-02-15
Publication date: 1980-02-20

Description

(54) SCAFFOLDING (71) We, GKN MILLS BUILDING SER- VICES LIMITED, formerly Mills Scaffold Company of Winchester House, 55 Uxbridge Road. Ealing, London, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to builders scaffolding and in particular to support scaffolding for formwork.

In casting concrete decking, the concrete is supported on pouring by formwork eon- sisting of moulds or panels which in turn are supported on a gridwork of beams, the beams in turn being supported by a plurality of props or other vertical scaffold element.

all hereinafter referred to as props.

Each prop has at the upper end thereof a drop head assembly (hereinafter referred to as being of the kind specified) comprising an inner member arranged to be disposed vertically when the assembly is in use and having a head plate at the top thereof; a drop head mounted on the inner member and having means thereon to engage the beams which support the moulds or panels.

the drop head being movable on the inner member between an upper position and one or more lower positions; and striking means for supporting the drop head in its upper position, said striking means being operable to permit the drop head to move to its lower position(s).

In the upper position of the drop head of a drop head assembly of the kind specified the beams supported thereby in turn support the panels or moulds in operative positions for casing. The lowering of the drop head to a lower position lowers the beams with the panels or moulds, from said operative position, to enable the beams and moulds or panels to be struck and used again while the concrete completes its curing supported by the head plates. Thus, the concrete will be supported for a certain time by the moulds or panels and then, when it is partly cured, the moulds or panels with their supporting beams will be struck and the concrete will be allowed to complete its cure supported only by the head plates.

Normally the inner member of a drop head assembly of the kind specified will be secured to the upper end of the prop but the inner member could be provided by the upper part of the prop itself.

The object of the present invention is to provide an improved drop head assembly of the kind specified.

According to a first aspect of the invention we provide a drop head assembly of the kind specified in which the inner member is provided with projections; the drop head is provided with a first set of recesses on an upper portion thereof, the recesses permitting, when aligned with said projections, the upper portion of the drop head to move past the projections; the striking means comprises a striking element associated with the drop head and having recesses co-operable with said projections such that, in a first relative position of the element and the members the element is supported on the projections against downward movement and supports the drop head in said upper position whereas, in a second relative position of the element and the member, down- ward movement of the element and thus of the drop head is permitted; the arrangement being such that, with the drop head in its upper position, movement of the striking element to its second relative position allows said head to move to a first lower position in which the projections contact and support said upper portion of the drop head whereupon said head may be turned about the longitudinal axis of the member to bring said first set of recesses into alignment with the projections thus permitting said head to move further downwardly on the member to a second lower position.

When using a drop head assembly in accordance with the present invention support formwork is in its operative position. the striking element will be in its first position, and will be holding the drop head in its upper position. When the time comes to strike the formwork, the striking element on each prop is moved to its second position. This will secure an initial lowering of the drop head on each prop to its first lower position thus lowering the beams with their supported moulds or panels. Normally the beams and moulds or panels can now be removed. In some coffered constructions the moulds may form recesses whose depth is greater than the length of the first drop of the assembly so that the beams and moulds have to be removed together except where the moulds have stuck to the soffit when the beams are removed first.The removal of the beams allows all the moulds to be removed except those adjacent to the props whose withdrawal is impeded by the drop heads. These can now be turned and thus allowed to make their second drop thus freeing the remaining moulds for removal.

Preferably the inner member and the drop head carrying interfitting parts which prevent relative rotation between the drop head and member about said axis when the drop head is in its upper position.

Conveniently the drop head may have a portion which engages the projections on the inner member in order to prevent the above rotation.

The drop head may have a second set of recesses on a lower portion thereof, which are located at a different orientation about said axis than the first set of recesses, said second set of recesses being arranged to allow the projections to pass therethrough as the drop head moves from its upper to its first lower position. This arrangement ensures that when the drop head reaches its first lower position the first set of recesses are not aligned with the projections so that the drop head remains supported in its first lower position until the head is turned about said axis to align said first set of recesses with the projections.

Preferably locking means is provided for holding the striking element in its first relative position to hold the drop head in its upper position.

Preferably, means are provided for guiding the striking element for sliding movement relative to the drop head between the first and second relative positions to prevent turning of the element relative to the head about said axis.

Preferably, the drop head has upper and lower support elements for two sets of beams of a formwork. Preferably, also, the projections are provided by a load pin which passes through the inner member.

According to a second aspect of the invention we provide a drop head assembly of the kind specified in which the inner member is of circular cross-section, the assembly comprising co-operable projections and recesses on the inner member and a striking element, the element being arranged so that, in a first relative position of the element and member, the element is supported on the member by the projections against downward movement relative thereto and supports the drop head in its upper position while, in a second relative position of the element and member, the projections and recesses are aligned thus allowing the element to move with the drop head to a lower position, the member and drop head having interfitting parts to prevent relative rotation between the element and member about the longitudinal axis of the member when the drop head is in its upper position.

In a preferred form of the second aspect of the invention the projections on the inner member provide the parts which interfit with parts on the drop head to prevent the rotation thereof when in its upper position.

The invention will now be described in detail by way of example with reference to the accompanying drawings in which: Figures 1 and 2 are side and front elevations of a drop head assembly embodying the invention with the drop head in its upper position; Figure 3 is a plan view of the drop head; Figure 4 is a section on the line 44 of Figure 2 showing details of the drop head only; Figure 5 is a perspective view of a guidance member carried by the drop head; Figure 6 is a section through the striking element, and Figure 7 is an under plan view of the striking element.

Referring now to the drawings, and particularly to Figures 1 and 2, the drop head assembly comprises an inner member 10 having, at its upper end, a head plate 11 which is rectangular. The inner member 10 is of circular cross-section and is tubular.

At its lower end the inner member 10 has a base plate 13 by which it may be secured to a similar plate provided at the upper end of a prop.

Mounted on the inner member is a drop head indicated generally at 14. The drop head is supported in an upper position shown in Figures 1 and 2 by means of a striking element 15, shown in detail in Figures 6 and 7, and projections 16 which are formed by the end portions of a load pin which passes through aligned apertures 18 in the inner member. The load pin is welded to the inner member in order to be retained in position therein.

The drop head comprises, basically, two channels arranged at right angles. There is an upper channel 22 having side walls 23 and a base 24 and there is a lower channel 25 having side walls 26 and a base 27. The base 24 of the upper channel is welded to the side walls 26 of the lower channel.

Referring now to Figure 3, formed in the base 24 of the upper channel is a circular aperture 28 from which extend two recesses 29 which are diametrically opposed and are so dimensioned that the projections 16 of the load pin can pass through the recesses 29.

Similarly, the base 27 of the lower channel 25 is provided, as shown in Figure 4, with a circular aperture 30 and recesses 31 which again are dimensioned to pass the projections 16 of the load pin. It will be seen that, in each case, the recesses lie on either side of the centre line of the base of the channel in which they are formed. Thus the recesses 29 in the base 24 of the upper channel lie an either side of the centre line 32 of the base while the recesses 31 in the lower channel lie on either side of the centre line 33 of the base 27. As will be seen from a consideration of Figures 3 and 4, the centre lines 32 and 33 are at right angles to one another so that the recesses 29 and 31 are out of alignment with each other, the recesses being arranged on mutually perpendicular diameters about the longitudinal axis 34 of the inner member.

U-shaped straps 35 extend across the upper channel 22 providing, with the side walls 23, apertures 36 to receive locating means on formwork beams which support the moulds or panels. Similarly, U-shaped straps 37 extend across the lower channel 25 to provide locating apertures 38 for a second set of formwork beams, which brace the formwork and may support further beams which support moulds and panels as described in the complete specification of our Patent No. 1457136.

Referring now to Figures 6 and 7, the striking element 15 is in the form of a plate having a depending flange 39 at one end and an aperture 40 therein. The aperture 40 has a first part 41 which is of a length indicated by the arrow L to clear the projections 16 of the load pin and a second portion 42 which is of a width W slightly greater than the diameter of the inner member 10. The plate has inclined surfaces 43 on its lower surface referred to below.

Referring to Figures 1 and 2, the striking plate is supported on the drop head by means of guides. The base 27 of the lower channel member carries two pins 44 which pass through apertures in the base 27 and are welded therein. The portions of the pins 44 which project below the base 27 thus assist in guiding the striking plate for transverse sliding movement relative to the drop head. A U-shaped guiding strap 45 shown in detail in Figure 5 is also welded beneath the base 27 and further assists in guiding the sliding movement of the striking plate 15 whilst preventing the striking plate turning about the axis 34 relative to the head 14. The portions of the pins 44 which project above the base 27 can be used, if lhe drop head is used to support beams from the upper channel 22 only, to secure tying pieces between adjacent drop heads.These tying pieces will extend at right angles to the beams supported by the upper channel.

The strap 45 is provided with a cut-out 46 which receives part of the inner member 10 as shown in Figure 1. When the drop head is in its upper position, as shown in Figures 1 and 2, the drop head is prevented from rotating about the inner member 10 by the portions 47 of the strap 45 which abut the end portions 16 of the load pin.

Also when the drop head is in its upper position an arcuate part 55 of the aperture 40 in the striking plate 15 abuts the inner member 10 so that the end portions 16 of the load pin engage abutment surfaces 43a to the right of the inclined surfaces 43 shown in Figures 6 and 7. The striking plate is retained in this position, herein referred to as the first relative position of the striking plate, by a sheet metal locking member 48 which is slidable in a slot 49 in one of the side walls 26 of the lower channel 25. This locking member is of a stepped construction and has two flanges 50 and 51 which extend one on each side of the slotted side wall 26.

With the striking plate 15 in the position shown in Figure 1 and 2 and the step 52 of the locking member 48 resting on the bottom 53 of the slot 49, the bottom portion of the locking member projects through the portion 41 of the aperture 40 thus preventing the sliding movement of the striking plate and hence retaining the drop head in its upper position. The locking member 48 is arranged to automatically engage the aperture 40 under the action of gravity when the striking plate is slid to the first relative position shown in Figures 1 and 2.

With the drop heads on the props in their upper positions, as described, two sets of beams will be supported from the upper and lower channels 22 and 25 and moulds or panels will in turn be supported on the upper set of beams, the lower set serving as braces. Concrete will be poured onto the formwork thus provided. When the concrete has set and has cured for some time then the formwork will be struck as follows. Firstly, the locking members 48 will be slid upwardly in their slots 49 to clear the apertures 40 in the striking plates. Each striking plate on each prop will then be moved to the left, as viewed in Figure 1, this movement is facilitated by the inclined abutment surfaces 43, to its second relative position in which the end portions 16 of the load pin come into alignment with the portion 41 of the aperture in the striking plate when the drop head will drop.This is because the recesses 31 in the base 27 of the lower channel are in alignment with the end portions 16 of the load pin when the drop head is in its upper position as shown. The drop head will drop until the lower surface of the base 24 of the upper channel engages the end portions 16 of the load pin. The beams and moulds or panels can now be removed as described above. If some moulds are trapped as, for example, in the making of a coffered construction as described each drop head may be dropped further by turning through 900 about the axis 34 of its inner member 10 so that the recesses 29 in the upper channel 22 are in alignment with the end portions 16 of the load pin and the drop head can then drop until it rests on the base plate 13. There will be enough room between the cast concrete and the drop heads to release the moulds adjacent to the props.

It will be seen, therefore, that the invention provides a drop head assembly in which the drop head can make two drops with two simple movements, the first of the striking element to obtain a first drop and the second movement, a rotation of the drop head to obtain a second drop.

Moreover, by guiding the striking plate on the drop head so that it cannot rotate relative thereto about the axis of the inner member and by ensuring that when it is in its upper position, the drop head cannot rotate relative to the inner member, it is possible to use conventional circular section tube for the inner member.

If desired the aperture 30 in the base 27 may not be provided with the recesses 31 but may be shaped to allow the end portions 16 of the load pin to pass therethrough at all circumferential locations of the base 27 relative to the inner member 10. If such a construction is used the sliding movement of the drop head on the inner member 10 will be guided by the aperture 28 in the upper channel 22 and the strap 45 beneath the lower channel 25.

Also, if the drop heads of drop head assemblies in accordance with the invention are to be used only to support parallel rows of beams all at the same level with parallel rows of moulds or panels carried therebetween, the props which support the drop head assemblies may conveniently be tied together by tying pieces which extend below at right angles to the rows of beams. Since the inner members of the drop head assemblies of the present invention are of circular cross-section, which is preferably of the same diametraI size as conventional tubular vertical scaffold elements, the above tying pieces can be secured between the props using, for example, the scaffolding fitting and collar arrangement described in our co-pending Patent Application No.

6503/75 (Serial No. 1528961). In such an arrangement the collar could be carried on the lower parts of the inner members 10 but would then require removal before the drop heads were dropped from their upper positions.

WHAT WE CLAIM IS:- 1. A drop head assembly of the kind specified in which the inner member is provided with projections; the drop head is provided with a first set of recesses on an upper portion thereof, the recesses permitting, when aligned with said projections, the upper portion of the drop head to move past the projections; the striking means comprises a striking element associated with the drop head and having recesses co-operable with said projections such that, in a fir.st relative position of the element and the member, the element is supported on the projections against downward movement and supports the drop head in said upper position whereas, in a second relative position of the element and the member, downward movement of the element and thus of the drop head is permitted; the arrangement being such that, with the drop head in its upper position, movement of the striking element to its second relative position allows said head to move to a first lower position in which the projections contact and support said upper portion of the drop head whereupon said head may be turned about the longitudinal axis of the member to bring said first set of recesses into alignment with the projections thus permitting said head to move further downwardly on the member to a second lower position.

2. An assembly according to claim 1 in which the inner member and the drop head carry interfitting parts which prevent relative rotation between the drop head and member about said axis when the drop head is in its upper position.

3. An assembly according to claim 2 in which the drop head has a portion which engages the projections on the inner member in order to prevent rotation thereof when in its upper position.

4. An assembly according to any one of claims 1 to 3 in which the drop head has a second set of recesses on a lower portion thereof, which are located at a different orientation about said axis than the first set of recesses, said second set of recesses being arranged to allow the projections to pass therethrough as the drop head moves from its upper to its first lower position.

5. A drop head assembly of the kind specified in which the inner member is of circular cross-section, the assembly comprising co-operable projections and recesses on the inner member and a striking element,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

the drop head will drop. This is because the recesses 31 in the base 27 of the lower channel are in alignment with the end portions 16 of the load pin when the drop head is in its upper position as shown. The drop head will drop until the lower surface of the base 24 of the upper channel engages the end portions 16 of the load pin. The beams and moulds or panels can now be removed as described above. If some moulds are trapped as, for example, in the making of a coffered construction as described each drop head may be dropped further by turning through 900 about the axis 34 of its inner member 10 so that the recesses 29 in the upper channel 22 are in alignment with the end portions 16 of the load pin and the drop head can then drop until it rests on the base plate 13.There will be enough room between the cast concrete and the drop heads to release the moulds adjacent to the props.

It will be seen, therefore, that the invention provides a drop head assembly in which the drop head can make two drops with two simple movements, the first of the striking element to obtain a first drop and the second movement, a rotation of the drop head to obtain a second drop.

Moreover, by guiding the striking plate on the drop head so that it cannot rotate relative thereto about the axis of the inner member and by ensuring that when it is in its upper position, the drop head cannot rotate relative to the inner member, it is possible to use conventional circular section tube for the inner member.

If desired the aperture 30 in the base 27 may not be provided with the recesses 31 but may be shaped to allow the end portions 16 of the load pin to pass therethrough at all circumferential locations of the base 27 relative to the inner member 10. If such a construction is used the sliding movement of the drop head on the inner member 10 will be guided by the aperture 28 in the upper channel 22 and the strap 45 beneath the lower channel 25.

Also, if the drop heads of drop head assemblies in accordance with the invention are to be used only to support parallel rows of beams all at the same level with parallel rows of moulds or panels carried therebetween, the props which support the drop head assemblies may conveniently be tied together by tying pieces which extend below at right angles to the rows of beams. Since the inner members of the drop head assemblies of the present invention are of circular cross-section, which is preferably of the same diametraI size as conventional tubular vertical scaffold elements, the above tying pieces can be secured between the props using, for example, the scaffolding fitting and collar arrangement described in our co-pending Patent Application No.

6503/75 (Serial No. 1528961). In such an arrangement the collar could be carried on the lower parts of the inner members 10 but would then require removal before the drop heads were dropped from their upper positions.

WHAT WE CLAIM IS:- 1. A drop head assembly of the kind specified in which the inner member is provided with projections; the drop head is provided with a first set of recesses on an upper portion thereof, the recesses permitting, when aligned with said projections, the upper portion of the drop head to move past the projections; the striking means comprises a striking element associated with the drop head and having recesses co-operable with said projections such that, in a fir.st relative position of the element and the member, the element is supported on the projections against downward movement and supports the drop head in said upper position whereas, in a second relative position of the element and the member, downward movement of the element and thus of the drop head is permitted; the arrangement being such that, with the drop head in its upper position, movement of the striking element to its second relative position allows said head to move to a first lower position in which the projections contact and support said upper portion of the drop head whereupon said head may be turned about the longitudinal axis of the member to bring said first set of recesses into alignment with the projections thus permitting said head to move further downwardly on the member to a second lower position.
2. An assembly according to claim 1 in which the inner member and the drop head carry interfitting parts which prevent relative rotation between the drop head and member about said axis when the drop head is in its upper position.
3. An assembly according to claim 2 in which the drop head has a portion which engages the projections on the inner member in order to prevent rotation thereof when in its upper position.
4. An assembly according to any one of claims 1 to 3 in which the drop head has a second set of recesses on a lower portion thereof, which are located at a different orientation about said axis than the first set of recesses, said second set of recesses being arranged to allow the projections to pass therethrough as the drop head moves from its upper to its first lower position.
5. A drop head assembly of the kind specified in which the inner member is of circular cross-section, the assembly comprising co-operable projections and recesses on the inner member and a striking element,

the element being arranged so that, in a first relative position of the element and member, the element is supported on the member by the projections against downward movement relative thereto and supports the drop head in its upper position while, in a second relative position of the element and member, the projections and recesses are aligned thus allowing the element to move with the drop head to a lower position, the member and drop head having interfitting parts to prevent relative rotation between the element and member about the longitudinal axis of the member when the drop head is in its upper position.
6. An assembly according to claim 5 in which the projections on the inner member provide the parts which interfit with parts on the drop head to prevent the rotation thereof when in its upper position.
7. An assembly according to any one of claims 1 to 6 in which locking means is provided for holding the striking element in its first relative position to hold the drop head in its upper position.
8. An assembly according to any one of claims 1 to 7 in which means are provided for guiding the striking element for sliding movement relative to the drop head between its first and second relative positions to prevent turning of the element relative to the head about said axis.
9. An assembly according to any one of claims 1 to 8 in which the drop head has upper and lower support elements for two sets of beams of a formwork.
10. An assembly according to any one of claims 1 to 9 in which the projections are provided by a load pin which passes through the inner member.
11. A drop head assembly of the kind specified constructed and arranged substantially as hereinbefore described with reference to and as shown in the accompanying drawings.