This invention relates to an attachment assembly. In particular, it relates to an attachment assembly that includes a connecting device or connecting sub-assembly and an attachment plate, which attachment plate can be connected to multiple load-bearing components. It has particular application where the connecting device or sub-assembly has a preferred axis of loading.
The invention will be described with reference to an embodiment that is used to make connections to a harness for use in climbing or working at height. A widely-used type of harness used by arborists (an example being shown in Figure 1) incorporates a flexible load-bearing member 2 commonly referred to as a "rope bridge" that extends between two forward connection arrangements 4. The rope bridge serves as a primary component that transfers load from the harness into a rigging system through one or more connecting lines. It is usual to provide a metal connecting component on the rope bridge that can be connected to the rigging system for example through a carabiner. At its simplest, the connecting component can be a metal ring 6, which is advantageous because it can rotate on the rope bridge, so distributing wear evenly around the ring. However, when a user wishes to make more than one connection to the connecting component, use of a ring can be problematic since connected components and lines can become entangled during use of the harness. To address this, there have been various proposals to provide a connection assembly that includes a connecting plate having multiple through holes to which connections can be made. However, all of these have known assemblies have various disadvantages that can result in uneven wear, twisting of the connection assembly as a result of asymmetric loading, and difficulty in connecting to the harness.
An aim of this invention is to provide an improved connection assembly that allows multiple connections to be made through a functional component or sub-assembly to an external anchorage such as the rope bridge of a harness.
To this end, the present invention provides an attachment assembly comprising:
- an attachment plate that has one or more attachment apertures; and
- a connecting arrangement that is connected to the attachment plate and is suitable for connection with an external component; wherein:
- the connecting arrangement has a loading axis, along which axis load from the attachment plate and the external component is preferentially directed; and
- the connection between the attachment plate and the connecting arrangement is configured such that the attachment plate can pivot with respect to the connecting arrangement about an attachment plate axis that is normal to the loading axis.
Allowing the attachment plate to pivot with respect to the connecting arrangement in this way allows the attachment plate to adapt its alignment to compensate for asymmetric loads connected to the attachment plate to ensure that the connecting arrangement is loaded, as nearly as possible, along its loading axis and that loading off the loading axis is minimised. The connecting arrangement is capable of withstanding loads that are off-axis from the loading axis, but it is strongest when loads are applied to it as close as possible to the loading axis.
Typically, the attachment plate axis intersects the loading axis.
The connecting arrangement may include a swivel that comprises first and second bosses interconnected for rotation about a swivel axis, the swivel axis being the loading axis of the connection arrangement, and the attachment plate being connected to the second boss such that the attachment plate can pivot with respect to the second boss about the attachment plate axis. It is preferable to avoid off-axis loading of the swivel since this can cause increased wear and friction in the swivel.
The connecting assembly may be rigidly attached to the first boss of the swivel or, alternatively, the connecting assembly can pivot with respect to the first boss of the swivel, typically about an axis that is normal to the swivel axis.
Alternatively or additionally, the connecting arrangement may include a continuous loop or an openable loop which may be in the form of a carabiner body, the loading axis extending through a rope basket of the carabiner body. Off-axis loading of the carabiner body is preferably to be avoided because the carabiner achieves its maximum strength only when loaded on the loading axis.
The connecting assembly is typically suitable for connection with a rope bridge of a harness whereby load can be transferred from the harness through the attachment assembly to one or more external components connected to the attachment plate.
For example, the connecting assembly may include a pulley block that has a sheave carried for rotation about a sheave axis within a pulley body. Such a connecting assembly can travel along the rope bridge with minimal friction and even distribution of wear. In embodiments in which the connecting assembly includes a continuous loop or an openable loop, the loop may be suitable for surrounding the rope bridge of a harness.
The attachment plate typically includes a planar region through with the or each attachment aperture is formed and a yoke region by which it is connected to the second boss of the swivel. The attachment plate may include several planar regions each having one or more attachment aperture.
From a second aspect, this invention provides a harness that includes a flexible load-bearing member that extends between two forward connection arrangements and an attachment assembly that embodies the first aspect of the invention carried on the flexible connecting member.
From a third aspect, this invention provides safety apparatus comprising a harness embodying the second aspect of the invention and a rigging system, in which one or more components of the rigging system are connected to the attachment plate.
Safety apparatus embodying this aspect of the invention may include a main working line which is under tension during normal use, and a backup safety line that is under significant tension only upon failure of the main working line. These lines could both be connected to the attachment plate. In the event that the main working line fails there will be a sudden shock load as the tension transfers across to the safety backup line. The benefits of the attachment plate will pivot to dynamically adjusting its position to re-align with the preferred loading axis. This is particularly important where high peak loads occur.
Safety apparatus embodying this aspect of the invention may include two separate and spaced anchors connected to the attachment plate. These anchors enable an arborist to position themselves accurately beneath or between the anchors when it is not possible to find a suitable anchor directly above. This requires the arborist to continuously adjust the tension in both positioning systems as they move. There is a benefit to eliminate bending fatigue on the components by allowing the attachment plate (which the positioning systems are attached to) to dynamically adjust to equalise the load vectors from both anchors.
An embodiment of the invention will now be described in detail, by way of example, and with reference to the accompanying drawings, in which:
- Figure 1 shows a known harness with which embodiments of the invention might typically be used;
- Figures 2 and 3 are front and side views of an attachment assembly embodying the invention;
- Figure 4 is a rear view of the embodiment of Figures 2 and 3 in an alternative configuration;
- Figures 5 and 6 show the embodiment of Figures 2 and 3 in further alternative configurations of the embodiment of Figures 2 and 3;
- Figure 7 shows an alternative embodiment of the invention;
- Figure 8 shows a second alternative embodiment of the invention;
- Figures 9 and 10 show a first alternative attachment plate for use with embodiments of the invention; and
- Figures 11 and 12 show a second alternative attachment plate for use with embodiments of the invention.
With reference to the drawings, a connection assembly embodying the invention comprises three sub-assemblies: a pulley block 10, a swivel 12 and an attachment plate 14.
The pulley block 10, which constitutes a connecting assembly in this embodiment includes a sheave 20 carried on an axle 22 between two plates 24, 26 that constitute a pulley body. The sheave 20 is free to rotate on the axle 22 about a sheave axis ASh.
The swivel 12 in this embodiment is constructed in accordance with the disclosure of EP-A-3 088 769, the content of which is incorporated herein by reference. This is advantageous because such swivels have an advantageously compact structure, but other forms of swivel could be used instead.
The swivel 12 includes interconnected first and second bosses 30, 32. The bosses 30, 32 are mechanically interconnected such that they are free to rotate with respect to one another about a swivel axis ASw. which constitutes a loading axis of the connection assembly.
The first boss 30 is connected to the pulley block 10, a portion of the first boss 30 extending between the plates 24, 26 where it is retained by a retaining bolt that is held in place by a machine screw. The retaining bolt has a head 34 that is not round in cross-section (rounded triangular in this example) and is received within a correspondingly shaped, close-fitting recess in the second plate 26 whereby its rotation is prevented. The machine screw has a shaft that is threaded into a tapped axial bore of the retaining bolt and a head 36 that is received into a recess in the first plate 24. In this embodiment, it is intended that the pulley block 10 and the swivel 12 can be separated by the user, so the head 36 of the retaining bolt is formed with a recess for cooperation with a standard tool, such as an Allen key.
In this embodiment, the plates 24, 26 and the first boss 30 are shaped with co-operating formations, shown generally at 28 that prevent rotation of the plates 24, 26 with respect to the first boss 30 about the retaining bolt. In this embodiment, the co-operating formations are flats that extend perpendicular to the swivel axis ASw.
The second boss 32 has outwardly-directed flat bearing surfaces 40 and an axle bolt hole that extends through the second boss perpendicular to the bearing surfaces 40.
The attachment plate 14 has a planar region 44 and a yoke region 46. The yoke region 46 has a U-shaped cross-section with two legs that have spaced, mutually-facing, parallel bearing surfaces that are spaced apart by a distance just greater than the spacing of the bearing surfaces 40 of the second boss 32. An axle bolt hole extends through the yoke region 42 perpendicular to the bearing surfaces. The planar region 44 has a plurality of attachment holes 48 formed through it. In this example, there are three holes disposed symmetrically on the planar region 44 and each hole is circular. However, a lesser or greater number of attachment holes 48 may be provided and they may vary in shape.
The attachment plate 14 is connected to the second boss by an axle bolt that passes through the axle bolt holes in the second boss and the yoke region 46 such that the bearing surfaces of the second boss and the yoke region 46 lie closely adjacent to one another. The axle bolt has a head 50 that is not round in cross-section (rounded triangular in this example) and is received within a correspondingly shaped, close-fitting recess one leg of the yoke region 46 whereby its rotation with respect to the attachment plate is prevented. The machine screw has a shaft that is threaded into a tapped axial bore of the retaining bolt and a head 52 that is received into a recess in the other leg of the yoke region 46.
The axle bolt can rotate within the axle bolt hole of the second boss 32 so allowing the attachment plate to rotate on the second boss about an attachment plate axis AP between limits imposed by parts of the attachment plate 14 making contact with the second boss 32. This combined with the rotation permitted by the swivel 12 about the swivel axis ASw allows the attachment plate 14 two rotate with respect to the pulley block 10 about two perpendicular axes.
In Figure 4, the attachment plate 14 has been rotated about the swivel axis ASw such that its planar region 44 is offset at an angle from the sheave 20. In installations in which multiple lines are connected to the attachment holes 48 this can prevent the lines from becoming twisted or enable them to be untwisted.
In Figure 5, the attachment plate 14 has been rotated about the attachment plate axis AP. In this example, the attachment plate is being loaded asymmetrically by a load L from a connector such as a carabiner 56 that is passed through one of its attachment holes 48, the load L being transferred through the attachment assembly to the rope bridge 2, which is under tension. The attachment plate 15 has been rotated about the attachment plate axis AP such that the load L approaches the alignment of the swivel axis ASw so reducing the tendency of the connection assembly to become twisted out of alignment.
When assembled upon a harness, the rope bridge 2 passes through the pulley block 12 between the sheave 20 and the first boss 30. The attachment assembly can be assembled onto the harness in two ways:
- if the rope bridge can be detached from one or other forward connection arrangement so that one of its ends is free, this end can be passed between the plates 24, 26 and then re-fastened to the forward connection arrangement; or
- if the rope bridge cannot be detached from either forward connection arrangement, the retaining screw is unscrewed from the bolt and the connection bolt is then removed to allow the pulley block 12 to be separated from the first boss. The connection arrangement can then be re-assembled with the rope bridge 2 correctly disposed between the sheave 20 and the first boss 30.
In a modification to the above-described embodiment, the co-operating formations 28 that prevent rotation of the plates 24, 26 with respect to the first boss 30 about the retaining bolt are omitted or modified such that the connecting assembly 10 can pivot with respect to the first boss about the retaining bolt.
Figure 7 shows an embodiment in which the connecting assembly 10 is constituted by a C-shaped body 60 on which is carried an openable gate 62 - that is to say, it takes the form of a carabiner. A threaded recess is formed in the body 60 into which the first boss 30 of the swivel (which in this embodiment is externally threaded) is received. In this embodiment, the loading axis AL is coincident with the swivel axis and passes through a rope basket of the carabiner.
As with the first embodiment, the attachment plate 14 is secured to the second boss 32 of the swivel 12 by an axle bolt about which it can pivot. This helps to reduce any tendency for the carabiner to be incorrectly loaded. For example, when the connecting assembly 10 is attached to a rope bridge 2, the bridge 2 tends to remain in the basket of the carabiner body 60 rather than being displaced sideways towards the gate 62.
A simplified embodiment is shown in Figure 8. In this embodiment, the attachment plate 14 is secured directly to the connecting assembly 10 without the intermediary of a swivel. As with the preceding embodiment, the connecting assembly 10 is constituted by a C-shaped body 60 on which is carried an openable gate 62 to take the form of a carabiner. As with the preceding embodiment, the attachment plate 14 will pivot in response to forces applied to it to resist any tendency for a rope that is passing through the body to be displaced from the rope basket and to ensure that the body 60 is loaded close to the loading axis AL. This direct connection can be employed in embodiments that have alternative forms of connecting assembly.
Modifications to the attachment plate can be used in either embodiment. In the example shown in Figures 9 and 10, the attachment plate includes three planar regions 44', 44", 44‴ each having three circular attachment apertures and connected to a common yoke region 42. In the example shown in Figures 11 and 12, the attachment plate includes one planar region 44iv that has a single attachment aperture 38' in the form of an arcuate slot.