GB2474085A

GB2474085A - Collapsible access tower

Info

Publication number: GB2474085A
Application number: GB0918287A
Authority: GB
Inventors: John Timothy Stevens
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-10-05
Filing date: 2009-10-19
Publication date: 2011-04-06
Also published as: GB0918287D0; GB0917411D0

Abstract

An access tower 1 comprises a plurality of cells 10, 10A, 10B, , at least one of which is collapsible, arranged one above another, each collapsible cell formed of upper and lower members 12, 14, 16, 18, 20 which are orientated substantially horizontally, and collapsing members 22, 24 which move from a collapsed orientation when the cell is collapsed, to an erected orientation when the cell is in an erected configuration. The top of at least one of the cells extends laterally beyond the top of a cell above it, and at least one cell comprises at least one step 26, 28 located vertically between the upper and lower horizontal members of the cell when it is erected, the or each step being coupled to at least one of the collapsing members 22, 24.

Description

ACCESS TOWER

Background of the Invention

The present invention relates to access towers, particularly, but not limited to, free standing and mobile access towers for providing a working platform raised from the ground.

Access towers are known in general. Some may generally comprise an upper working platform, on which a worker stands, and a support structure, which supports the working plafform to hold it in a position raised above the ground.

It is also known to provide access towers which are collapsible about part of their height so that they can be stored, when not in use. However, access towers can be heavy, and raising and lowering such towers can be difficult and/or dangerous. Further, climbing to the access platform can be difficult for a worker.

Summary of the Invention

The present invention seeks to overcome or ameliorate at least one of the disadvantages associated with the prior art. The present invention provides an access tower which is collapsible at least over a part of its height. The tower may be formed with a plurality of cells, and one or more of the cells may be collapsible. Each cell may be formed of one or more substantially horizontal upper members and corresponding substantially horizontal lower members, joined by collapsing members which move between a collapsed and erected orientation to erect the cell. The upper members of a cell may correspond to the lower members of another cell. The lower member of at least one of the cells may extend laterally further than the upper members in at least one direction.

One or more cells may comprise one or more steps, which may be mounted substantially midway in a vertical direction between the substantially horizontal members when the cell is erected, for example by being coupled to the collapsing members. The, some, or each of the steps may extend laterally beyond the top of the cell to which it is connected when that cell is erected and may withdraw within a volume defined by the upper and lower horizontal members when the cell is collapsed. More than one step may be provided between the upper and lower substantially horizontal members of one or more of the cells. The steps may be coupled to the collapsing members, extending between the upper and lower substantially horizontal members. The collapsing members may be substantially horizontal when they are in the collapsed orientation and may be inclined to the vertical direction when in the erected orientation. They may comprise first and second support members.

The first support members may extend between the upper and lower members. The second support member may be coupled to the first support member a part of the way along the length of the first support member, and coupled to one of the horizontal members of the cell.

The or a step may be coupled to the coupling point between the first and second support members, or may be connected to a different point on the collapsing members, for example to a support member above the coupling point between the two respective support members.

Biasing means may be provided to bias the collapsible members towards the erected orientation. This biasing force may be comparable with the weight of the respective cell and those above it, to provide substantially neutral buoyancy to the cell as it is erected and collapsed.

Locking means may be provided to lock at least one cell in the erected configuration. The locking means may be arranged to be unlocked from a locked position by raising of the upper member of the cell above the level of the erected configuration to allow the cells to be collapsed. The lock may be biased by gravity into a locked position. The lock may be a swing lock, engaging a fixed pin when locked. The pin may be mounted on the first support member and the swing lock mounted on one of the horizontal members of the cell.

Detailed description of an embodiment of the invention Detailed embodiments of the invention will now be described, purely by way of example, with reference to the accompanying figures, in which: Figures 1 and 2 shows an access tower according to an embodiment of the invention in an erected configuration; Figure 3 shows a lock according to the embodiment of the invention; Figure 4 shows the access tower in a partially erected configuration; Figure 5 shows the access tower in a collapsed configuration; and Figure 6 shows a further locking mechanism according to an embodiment of the invention.

As shown in Figure 1, an access tower (I) according to an embodiment of the invention comprises a plurality of cells (10, bA, lOB) arranged one above another. At least one of the cells (10, bA, lOB), (in the present embodiment all of the cells) is collapsible. Each of the cells comprises pairs of substantially horizontal upper and lower members (12, 14; 16, 18; 18, 20) and collapsing members (22, 24), which move from a collapsed orientation, in which, in the present embodiment they extend substantially horizontally when the cell is collapsed to an erected orientation in which, in the present embodiment, they extend at a small inclined angle to the vertical direction when the cell is in an erected configuration. The top of at least one of the cells (16, 18) extends laterally beyond the top of a cell above it (12, 16), shown as X and Y in Figure 1. Further, at least one of the cells comprises at least one step (26, 28), which is positioned vertically between the upper and lower members of the cell when that cell is erected, the or each step being coupled to at least one of the collapsing members (22, 24).

The step (26, 28) extends laterally beyond the upper member of the cell in which it is formed. As shown in Figure 1, when the cells are in the erected configuration, the steps (26, 28) extend laterally beyond the top of the cell in which they are provided. However, the lower members (18) of one of the cells (1OA) extend laterally beyond the step (26). In this manner, the steps and the laterally extending portions of the lower members of each cell together form an inclined set of steps which, when compared with a vertically orientated ladder or the like, provide ease of access to a working platform (30) on which the worker stands when the access tower is erected. In the present embodiment, in the lowest cell (lOB) the upper and lower members extend laterally by the same amount. The step (28) extends laterally beyond the upper and lower members (18, 20). In the second cell from the base (1OA) the lower member (18), which also forms the upper member of the lowest cell (lOB), extends laterally beyond the upper horizontal member of the second cell from the bottom (bA). The step (26) extends laterally beyond the upper member (16) of the second cell from the bottom (IOA) but extends laterally to a lesser extent than the lower horizontal member (18). In the present embodiment, the top cell (10) does not provide a step and, when erected, the height difference between the upper and lower horizontal members (12, 14) is less than for the bottom and second from bottom cells (lOb, lOa).

The collapsing members each comprise two support members (22, 24). In the present embodiment, one end of each support member is pivotably attached to one of the upper and lower members of the cell. In the present embodiment, one end of each first member (22) is pivotably connected to an upper member of a respective cell. One end of the second support member (24) is pivotably connected to the lower member of the respective cell, and also pivotably connected part way along the length of the first support member (22). Of course, this arrangement may be reversed, with the first support member sliding along the upper, rather than lower, horizontal member in a cell. The free or running end of each first support member (22) is coupled to the respective lower member so that it can run along the length of the support member in the direction that the step laterally extends, so that, together, the first and second support members (22, 24) act in a scissor motion as the cell is erected and collapsed. As each cell is collapsed, the running end of each first support member (22) slides away from the ends of the horizontal member to which it is mounted. Coupled between respective first and second support members (22, 24) is a biasing means in the form of a spring (32), which biases the first and second members towards an erected orientation. The spring (32) is a tension spring, which acts to pull the running end of each first support member (22) towards the pivoting end of a respective second support member (24), that is attached to the lower member of the cell.

As shown in Figure 2, the steps (26, 28), together with the upper members of the cells (12, 16, 18) form a number of equally spaced steps from the ground to the working platform (30). The uppermost cell (10) does not comprise a step. However, such a step could be provided.

Figure 3 shows a locking means for locking the first support member (22) of each collapsing member to the lower member (16, 18, 20) of a cell. The figure shows the locking means in two configurations. In the present embodiment, the locking means is in the form of a swing lock (40), which includes a pin (42), fixed to the first support member (22). The pin (42) is captive in a horizontally extending through or blind, hole (44) in the lower member, which allows the pin (42) to move horizontally, while restraining it against vertical movement. The swing lock (40) also has an abutting portion (46) which, when in the locked configuration, abuts against the pin (42) to prevent the pin (42) from moving horizontally in a direction to allow collapse of the cell. The swing lock also includes an inclined portion (48), which the pin (42) acts against as the upper member (12, 16, 18) of the cell is raised, so moving the pin (42) on the first support member (22) towards the end of the horizontal member (18), away from the abutting portion (46). As the pin (42) moves against the inclined surface (48), the swing lock (40) is rotated about a pivot (50), which raises the abutting portion (46) so that the pin (42) is no longer constrained by the abutting portion (46). The lock (40) continues to pivot until it tips over and is retained by gravity in an unlocked configuration.

The cell may then be collapsed by allowing the pin (42) to travel in the horizontal hole (44) so lowering the upper member (12, 16, 18) of the cell.

The weight of the cell, and any cells above it, is offset by the biasing force of the spring (32).

Figure 4 shows a partially collapsed view of the access tower (1). As can be seen, the lowest cell (lOB) is collapsed and the upper and lower members (18, 20) have been brought together in the vertical direction. Further, the step (28) is not shown in Figure 4 as it has been retracted into the space within the upper and lower members (18, 20). In order to do this as shown in Figure 1, the step (28) is coupled between the coupling point between the first and second support members (22, 24) and is also supported in a substantially horizontal orientation by a retaining member (34) which supports the step (28), and is connected to the step (28) away from the coupling point, to the first and second support members, to an upper region of the first support member (22). The retaining member (34) is pivotably connected to the first support member (22) and is coupled to the step (28) so that the step (28) can be raised relative to the first support member (22) by pivoting about the coupling point between the step (28), first and second support members (22, 24) as the cell is collapsed. A similar provision is made for the cell of the centre cell (lOa). Figure 5 shows the access tower (1), with all three cells collapsed. The working platform is provided with a retaining cage to protect the worker about which allow the vertically member (36) to fold to a horizontal configuration, thus lowering the upper horizontal bar (38). When the cells are collapsed the height across the whole tower is the same, as on the region of each horizontal member which extends laterally further than the horizontal member directly above it, a raised section is provided, the height of which corresponds to the height of that cell when it is collapsed.

In order to raise a cell, the upper member of that cell is raised, aided by the biasing of the spring 32. When the cell in the erected configuration, the swing lock (40) is rotated manually or by gravity to the locking configuration, so capturing the pin (42) against the abutting portion (46) of the lock (40), and locking the cell in the erected configuration. Alternatively, a peg (not shown) on the short support member is used to knock the swing lock back to the horizontal, locked position.

Figure 6 shows a further locking mechanism for the access tower according to embodiments of the invention. The further locking mechanism is a wire locking mechanism which may be used as well as, or instead of, the locking means disclosed in Figure 3.

The locking mechanism comprises a continuous wire loop (60) which is mounted on two wheels (62), mounted towards each longitudinal end of the horizontal member with the wire passing above and below the horizontal holes (44) in which a respective pin (42) slides. Each pin (42) is mounted on a sliding block (64) which is fixed to the wire on one side of its upper and lower paths, and which allows the wire to slide through the sliding block (64) on the other. Thus the sliding blocks (64) can slide in a horizontal plane limited by the extent of the horizontal hole (42). One sliding block (64) is fixed to the wire (60) on its upper path, while the other is fixed to the wire (60) on its lower path. In this way, movement of each of the pins (42) is always by an equal amount and in a mutually opposite direction, so that the upper horizontal member of the cell remains horizontal at all stages of erection.

Figure 6 also shows a locking block (66). In the present embodiment, this comprises a threaded screw (67) and an engaging part (68) mounted on the threaded screw (67). The threaded screw (67) is screwed into a fixed mount (69), which is fixed to the horizontal member between the two wheels (62).

Tightening of the screw (67) into the fixed mount (69) causes the engaging part (68) to be forced onto the fixed mount (69) while trapping sections of the upper and lower paths of the wire (60) between confronting surfaces of the engaging part (68) and the fixed mount (69). Thus, when the screw (67) is tightened, the wire cannot move due to being held securely between the confronting surfaces. Therefore, the blocks (64), and so the pins (42), also cannot move along the horizontal holes (42). In this way, the pins (42), and thus the support members, can be locked in position even if the swing lock (40) is not provided.

The present embodiment has been described purely by way of example, and various additions, omissions and modifications can be made within the scope and spirit of the invention.

Claims

CLAIMS: 1. An access tower, comprising: a plurality of cells, at least one of which is collapsible, arranged one above another, each collapsible cell formed of upper and lower members which are orientated substantially horizontally, and collapsing members which move from a collapsed orientation when the cell is collapsed, to an erected orientation when the cell is in an erected configuration, wherein the top of at least one of the cells extends laterally beyond the top of a cell above it, and at least one cell comprises at least one step vertically between the upper and lower horizontal members of the cell when it is erected, the or each step being coupled to at least one of the collapsing members.
2. An access tower according to claim 1, wherein the or each step extends laterally beyond the top of that cell when it is erected.
3. An access tower according to claim I or 2, wherein the or each step is arranged to collapse within the cell of which it is part as the cell collapses.
4. An access tower according to any preceding claim, wherein the collapsing members are substantially horizontal when in the collapsed orientation.
5. An access tower according to any preceding claim, wherein the collapsing members comprise first support members and second support members, the first support members extending substantially between the upper and lower horizontal members of the cell, the second support member being coupled to the first support member part way along the length of the first support member, and coupled to one of the upper and lower members of the cell.
6. An access tower according to claim 5, wherein the step is coupled to the coupling point between the first and second support members.
7. An access tower according to any preceding claim, wherein biasing means is provided between respective first and second support members to bias the collapsible members towards the erected orientation.
8. An access tower according to claim 7, wherein the biasing force of the biasing means is comparable to the weight of the respective cell and those above it, to provide substantially neutral buoyancy to the cell as it is erected and collapsed.
9. An access tower according to any preceding claim, wherein locking means is provided to lock at least one cell in the erected configuration.
10. An access tower according to claim 9, wherein the locking means comprises a lock which is biased by gravity into a locked position where the cell is held in the erected configuration, and which is moved to an unlocked position by raising the top of the cell beyond the erected configuration, to allow the cell to be collapsed.
11. An access tower according to claim 10, wherein the lock is a swing lock which engages with a fixed pin when locked.
12. An access tower according to claim 11, wherein the swing lock is mounted on a horizontal member of the cell and the pin is mounted on the first support member.
13. An access tower according to any preceding claim, wherein at least two collapsing members are provided, the tower further comprising a rotatably mounted endless wire loop on the lower horizontal member, the collapsing members being mounted on the wire loop so that rotation of the wire loop causes equal movement of each in a mutually opposite direction so that the upper horizontal member of the cell maintains its horizontal orientation as the cell is collapsed and erected.
14. An access tower, substantially as hereinbefore described with reference to any of the accompanying drawings.