The invention relates to the construction and dismantling (herein striking-down or simply “striking”) of falsework in the construction industry. “Falsework” is the name given to the framework for supporting a structure under construction which is not yet capable of supporting itself For example, the structure may be one created by the on-site pouring of wet concrete into a mould supported by the falsework. That mould would be vertically or horizontally supported by the falsework, which typically would comprise an array of posts. Vertical or horizontal posts of the falsework typically are adjustable in length, which can be achieved by having a threaded post positioned relative to its base post by means of adjustment of a screw collar. The falsework would take the load of the mould and ultimately of the wet concrete mix poured into that mould. Once the concrete has set, or once the constructed structure has otherwise been rendered self-supporting, the striking can take place. After the wet concrete has been poured into the moulds, however, the loads on each screw collar of the falsework are potentially very high indeed, making the striking process very difficult. The invention provides a novel power tool for turning screw collars on falsework posts during either the installation or the striking of falsework, but particularly during the striking process.
A falsework post can achieve adjustability in length by having a threaded member inserted into a hollow member where their relative positions are controlled by a screw collar as shown in
When an area of falsework is used to support moulds for a massive concrete structure such as a road bridge or an elevated highway, the loads supported by each post of the falsework can be very high indeed. This makes the unscrewing of the individual screw-threaded nuts or collars on the posts during striking a very difficult operation. One collar design comprises an internally screw-threaded cast nut or cylinder with two or four externally projecting lugs which permit a user to grasp and turn the collar to raise or lower it on an externally screw-threaded portion of its post while it is not under load.
The recommended method of freeing tight collars under load during the striking of falsework is to fit a torque bar on the collar and apply a load by hand. When the collar is under load, a torque bar can be coupled to the collar and engaged with some or all of the lugs, in order safely to obtain the necessary leverage to turn the collar. Torque values needed to strike falsework posts on a construction site may be as high as 900 N.m. Using a torque bar approximately 1 metre in length as shown in
Another method of freeing tight collars is to apply an impact load at the free end of the torque bar by hitting it repeatedly with a heavy hammer or sledgehammer. Frequently, however, this is difficult for a number of reasons; (a) the space limitations to install a torque bar may restrict this method, (b) the concurrent holding of a torque bar and the swinging action of a hammer (especially a sledgehammer) is ergonomically difficult, (c) even with a torque bar held securely in place ready for hitting, there may be insufficient room for a proper swing of the hammer and (d) the hammer swinging operation cannot always be performed easily as the site worker may have to swing the hammer from a compromising position (i.e. perched from an access tower or platform.) It is therefore not unusual for workers to omit the torque bar, and attempt to loosen collars by impacting the projecting lugs of the collars directly with a heavy hammer or sledgehammer. This latter operation is also faster to perform compared to having to set up a torque bar—hence direct impacting of the collar tends to be adopted as the only convenient method.
There are several consequences for directly impacting the collars with one or a series of hammer swings. The first consequence is damage to the collars. The collar lugs may become significantly deformed to the point that the collars can no longer accept the torque bar. Likewise the collar may become significantly deformed so that the lugs no longer provide enough surface for a hammer impact to be effective, or the lugs may break off. The collars themselves can also fracture. Therefore replacement and inspection costs for the collars can be significant in order to manage the safety of the falsework.
Another consequence is safety for the site workers. As the torque required to release the load of the collar is high, and the length of the collar lugs are short, this results in the site workers having to apply a series of relatively powerful hammer swings (usually using a sledgehammer). With cramped spaces, and usually having two site workers for the falsework striking operation, there have been several instances where site workers have been accidentally hit by the sledgehammer swinging action.
A third consequence of this method is increased levels of noise. Instead of performing the recommended method of applying a non-impact load on a torque bar, the magnitude of the hammer impact and the frequency of the swings create a level of noise that is significant even for a building site. Especially where concrete building structures are created in urban environments in the vicinity of businesses and residential sites, the series of hits, especially occurring concurrently with other striking, can create a significant disturbance. There have been instances where the United Kingdom Health and Safety Executive have issued notices to construction companies prohibiting them from creating significant noise during the striking of falsework.
A need therefore exists for a tool which can rapidly, safely and reliably turn a post collar even when it is under extreme loads during the striking of falsework, whilst avoiding damage to that collar. A non-impact approach facilitates reduction of collar damage with the added benefit of noise reduction.
The invention provides a tool for turning a screw collar on a falsework post, as defined in claim 1 herein. The tool is a power tool which removes the need for workers to use a heavy hammer or sledgehammer even when striking falsework which is under extremely heavy loads.
The motor may be hydraulic, pneumatic or electrical. Hydraulic motors are preferred, particularly for tools to be used for the striking of falsework, because they have potentially the best balance between delivering high torques, unit weight and speed of operation. The drive engagement means may be driven by the motor directly or through gearing that delivers increased torque. The use of gearing permits the use of a lower torque, lighter motor, but at the expense of the added weight and bulk of the gearing system.
In the following specific description we will refer to the tool as being used during the striking of falsework. It will of course be understood that the same or a similar tool could be used as a kind of powered nut runner for extending the lengths of the individual posts of the falsework before they are subjected to high axial loads for the creation of concrete structures. If the motor is to act in a direction to extend the length of the individual posts, however, it is preferably torque-limited so that on extension of the posts no serious damage to the falsework components or building structure can occur from over-tightening of the collar adapter. If the tool is to be used only for the striking of falsework, it should be designed with a much higher torque motor, preferably one capable of delivering to the collar through the collar adapter a total torque capable of releasing the loads on the falsework , for example at least 785 N.m. and preferably at least 1000 N.m. If the motor is to act bidirectionally, then a torque limiter to prevent damage to the mould or to the construction project should be included for one direction of motor movement, so that the high torque loads on the collar adapter and collar are obtained only during striking of the falsework.
The screw collar can be designed to include integral drive engagement means for drive engagement with the motor drive. Alternatively the drive engagement means may be formed on a collar adapter that is releasably mounted on a conventional manually adjustable screw collar. Such a collar adapter may fully or partially encompass the circumference of the screw collar. The collar adapter would have one or a number of features, such as gear teeth, pawls or dogs, that would engage with a motor drive, which could take the form of a spur gear. The collar adapter would also have features that would drivingly engage with the collar, for example with the lugs of the collar. When the motor housing is mounted on the falsework post, the motor drive member engages with the drive engagement means on the collar adapter. The collar adapter is preferably constructed to envelop the circumference of the screw collar as the collar may need to rotate for up to several rotations for certain falsework striking operations. Thus the collar adapter may be formed to close and releasably to lock around the screw collar so that when it is closed and locked around the screw collar it partially or completely envelops the screw collar. Once the load has been removed from the collar with the tool, the motor housing can be removed from the falsework post and the collar adapter can be reopened for removal, and both may be reusable for another falsework post.
It is also preferable that the drive engagement means, whether that be on the collar or on a collar adapter, should be as far out from the axis of rotation of the collar as is practicable. That provides maximum torque, and makes it possible to obtain a mechanical advantage of torque multiplication, which in turn allows for a reduced torque being required from the motor.
The collar adapter can be a separate component from the motor and motor housing. However it can be integral should the combined weight of the collar adapter, the drive engagement means, the motor housing and the motor be low enough to be used comfortably by the site worker.
The torque created by the motor would be transmitted to the collar or collar adapter via a motor drive member. The motor drive member can be in the form of a gear, the teeth of which engage with the drive engagement means of the collar or collar adapter. Alternatively the motor drive member may be a single lug or dog acting on one or a few features on the collar or collar adapter.
The torque delivered by the motor drive can originate directly from the motor's output shaft or via a gear-reduction assembly such as a gearbox. The decision for integration of a gearbox would depend on its own weight and cost versus weight and cost savings for using a smaller motor when using a gearbox.
The reaction torque generated on the motor drive by the collar is transmitted from the motor to the motor housing, and thence to the falsework structure. The motor housing takes vertical and angular support from the falsework post, preferably by having constructional details which react against features or the profile surfaces of the non-threaded or the threaded portion of the falsework post. Likewise the tool can react against other rigid and stationary component(s) attached to either the non-threaded or the threaded portion of the falsework post. Thus it is an advantage of the invention that the tool does not require the presence of any adjacent structure that can provide a reaction surface for the application of torque to the collar. No such structure may be present in many falsework assemblies. Adjacent falsework posts, even if present, are not generally designed to provide the lateral reaction force that would be required. Also, if the tool were braced against an adjacent structure, there would exist a problem of backlash, i.e. the potential for movement of the tool into contact with the reaction surface when the motor is actuated, which can cause a crushing injury to the operator.
The attachment of the tool onto the falsework post can either be such that the tool is introduced to the falsework while engaged with the post feature(s) and collar adapter, or clamped on the post.
The tool can be open-framed. The preferred solution is to have no moving parts exposed during operation for safety. Thus the motor housing when mounted on the falsework preferably envelops the collar or collar adapter, avoiding exposure of moving parts. When the motor is first actuated, there may be a relative movement of parts as the drive member comes into contact with the drive engagement means but this movement is confined to the interior of the motor housing. Because the motor housing is angularly immovable relative to the falsework post, the operator is protected from the effects of backlash.
If the tool is closed-framed, means are preferably provided to ensure that the motor housing cannot be closed around the falsework post and around the collar adapter unless the collar adapter, of a type that closes and locks around the collar, is first closed and locked around the collar.
a and 2b are isometric views of a portion of one of the posts of
a and 3b are respectively a plan view and a side elevation of typical falsework supporting an edifice under construction, showing the restricted access that is sometimes encountered to make striking difficult;
a to 5c are isometric views illustrating the operation of fitting a collar adapter around a collar of falsework when using a tool according to the invention;
a to 6f are plan views from above illustrating the use of six different collar adapters of tools according to the invention;
a to 8c are isometric views of different embodiments of the motor drive;
a and 9b are isometric views of a tool according to the invention during its installation onto a falsework post;
a and 10b are horizontal sections taken through a falsework post on which is mounted a motor housing of a tool according to the invention, the motor housings of
a and 11b are further horizontal sections taken through a falsework post on which is mounted a motor housing of a tool according to the invention, the motor housings of
a to 18c are isometric views of three different collars with integral drive engagement means, which do not require separate collar adaptors.
a and 3b are respective plan and elevational views of part of a possible falsework location, illustrating how the posts 1 of the falsework may be close to one another or to walls of the construction being built. Those walls may therefore restrict the ability of the site worker to use the lever arm L, and may make striking of the falsework very difficult. Another scenario is that the site worker may need to be lifted closer to the falsework on the platform of a cherry-picker and may even have to lean out over that platform in order to access the collar during striking, which makes the striking both difficult and dangerous. Although not recommended practice, site workers in such situations often hit not the lever arm L but the collar 7 itself with a heavy hammer or sledgehammer during striking in order to release the collar 7. Such an action is shown schematically in
An element of the tool of the invention is a collar adapter 10, to engage with the motor drive, which can preferably close and lock around the screw collar 7 in driving engagement with the collar. One such collar adapter 10 is shown in
Six alternative designs of collar adapter 10 are shown in
a to 8c show three alternative forms of drive member 16. The drive member 16 may be a spur gear with an annular array of gear teeth as shown in
a and 9b illustrate the collar adapter 10 of
a to 18c show alternative designs of collar 7 which have integral drive engagement means 11 in the form of integrally formed gear teeth 11. Such collars do not require the use of collar adapters as do the collars 7 of
a shows a collar 7 which does not include the collar lugs 8 of the other illustrated embodiments of collars 7. The lugs are omitted because the collar 7 of
In use, any of the tools as described above with reference to
Number | Date | Country | Kind |
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1006555.5 | Apr 2010 | GB | national |
This patent application is a continuation of PCT/GB2011/050771, filed Apr. 19, 2011, which claims priority to Great Britain Application No. 1006555.5, filed Apr. 20, 2010, the entire teachings and disclosure of which are incorporated herein by reference thereto.
Number | Date | Country | |
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Parent | PCT/GB2011/050771 | Apr 2011 | US |
Child | 13656269 | US |