Anchoring device

Details Anchoring device Anchoring device

2000-03-06

2001-08-14

Wilson, Neill (Department: 3627)

Expanded, threaded, driven, headed, tool-deformed, or locked-thr

Having separate expander means

Bulged by axially contracting ends

C411S037000, C411S072000

Reexamination Certificate

active

06273655

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to an anchoring device, and in particular but not exclusively to an expansible bolt anchoring device.
BACKGROUND OF THE INVENTIONS
Expansible bolt anchoring devices are widely used for attaching articles to, for example, the surfaces of masonry or brick walls or structures. A typical anchoring device comprises a segmented right cylindrical shell, and an expansion member located in the shell. The expansion member may be in the form of a nut mounted on the bolt (a “loose bolt” anchor) or may form the head of the bolt (a “projecting bolt” anchor). The expansion member is initially positioned at the inner end of the segmented shell such that rotation of the bolt, or rotation of a nut on the shank of the bolt, will draw the expansion member into the shell and radially expand the shell. Thus, when the device is located in a hole of corresponding diameter to the segmented shell, tightening the bolt or nut expands the shell radially to engage the hole wall.
Tightening of the bolt or nut in the desired “one-handed” manner requires that the shell engages the hole wall and is held against rotation in the hole. This requires that the shell is a snug fit in the hole, which is often difficult to achieve. In the absence of such a close fit, the shell must be held or jammed in the hole by some other means, such as part-filling the hole with packing material.
The three or four segments which typically form the shell are conventionally formed of cast or pressed metal. The segments are held together in the desired cylindrical form around the bolt by a ferrule placed over one end of the segments. A spring clip also encircles the segments intermediate their ends to prevent the shell segments from falling apart. Not surprisingly, the assembly of expansible bolt anchoring devices is a relatively difficult and time-consuming task and is still, in the main, a manual operation.
The majority of segments utilized in existing anchoring devices are relatively rigid and are only subject to minor deformation on the bolt or nut being tightened to expand the shell to engage the segments with the hole wall. Accordingly, the segments tend to engage the hole wall with a point or line contact, such that pressure forces experienced by the hole wall are relatively high and tend to cause a degree of crushing of the masonry or brickwork. A limited degree of such crushing may be advantageous, serving to anchor the shell securely in the hole. However, in softer materials the surrounding stone may crumble to such an extent that the device will not remain in the surface, requiring drilling of a larger hole and use of a larger diameter device.
Numerous proposals have been made to provide bolt anchoring devices with solid resilient sleeves in place of the conventional segmented metal sleeves. Devices of this type are described in GB-A-685643, GB-A-1530344, GB-A-774002, GB-A-886400, EP-A-0494741, EP-A-0105829 and U.S. Pat. No. 4472088. However, these devices have not been adopted by the industry and the resilient sleeve anchor bolts currently available on the market are provided for non-load bearing applications only.
SUMMARY OF THE INVENTION
According to the present invention there is provided an anchoring device comprising: an elastomeric sleeve for receiving a threaded elongate member; inner first and outer second stopper portions each having tubular portions extending into respective ends of the sleeve, the inner first stopper portion defining a thread for co-operating with the elongate member, whereby movement of the stopper portions towards one another causes the sleeve to expand radially.
The device may be supplied on its own or with an appropriate elongate member, typically a bolt or threaded stud. The bolt may be a hexagonal bolt, eye bolt or indeed any form of bolt. The device may be supplied to a customer as a single part or unit that may then be matched with an appropriate elongate member as desired; this is not possible with prior art devices in which the elongate members are integral parts of the devices and if the member is removed the devices tend to fall apart. This feature greatly reduces the level of stock of devices which must be held, and even where a device is supplied with a particular elongate member this may be readily removed and replaced with another member if desired. Further, the device is intended to be suitable for use in a wide range of applications, including load-bearing applications, unlike the vast majority of anchoring devices currently available, which are intended only for single applications.
In a preferred embodiment the inner first stopper is of metal, typically steel, although other materials, such as polymers and composites may be utilized where the application permits. In certain embodiments, the first stopper portion may itself define a thread for engagement with the threaded inner end of a bolt or the like, and in such embodiments the stopper portion will likely be formed of metal.
Preferably, the tubular portion of the inner first stopper is of a length at least equivalent to the diameter of the threaded elongate member, and is preferably of a length greater than the elongate member diameter. In a preferred embodiment, the tubular portion is around three times the length of the member diameter. Surprisingly, it has been found that the length of the tubular member is important in maintaining the resistance of the device to fatigue. Extensive testing revealed that damage to the sleeve resulting from cyclic axial loading of the device was minimized or avoided when the tubular member was extended. Further, it has been found that providing a relatively long tubular portion facilitates an overall reduction in the sleeve wall thickness and sleeve diameter relative to the diameter of the elongate threaded member, such that the ratio of sleeve wall thickness to elongate member diameter may be between 1:4 and 1:8. Accordingly, the diameter of the bore drilled to accommodate the device may be reduced, allowing the bores to be drilled relatively quickly and with less effort.
Preferably, the inner first stopper consists of a flange for engaging the respective end of the sleeve and an internally threaded tubular portion extending into the end of the sleeve. This arrangement allows a relatively short device to provide a relatively great effective depth, that is the inner sleeve end, which is expanded to grip the bore wall, is adjacent the end of the device. Thus, it is not necessary to drill a bore to accommodate a relatively long inner first stopper extending beyond the sleeve end; when a large number of bores are being drilled to accommodate such devices this aspect of the invention may result in a considerable saving in time and effort.
Preferably also, at least the outer second stopper portion is of a relatively rigid material, typically metal, but possibly a polymer-based material such as polypropylene.
The outer second stopper portion may be provided with a lip, for engaging a hole edge and preventing the device from falling into the hole. In other embodiments, in particular for through bolt applications, the lip may be omitted.
The stopper portions may be provided separately, or may be integral with the sleeve.
Preferably, the tubular portions are an interference fit in the respective sleeve ends or may snap fit in the respective sleeve ends. The tubular portions may be knurled or otherwise finished to provide engagement with the sleeve, or may be bonded to the sleeve ends using a suitable adhesive.
Preferably also, the sleeve is of rubber, and may be a natural rubber or a thermoset or thermoplastic rubber. Preferably, the sleeve material has a tensile strength of between 10 and 25 megapascals (MPa), and satisfactory test results have been obtained using rubber having a tensile strength of 18 MPa. Preferably also, the sleeve material has a compression set of no more than 50%; above this, the set sleeve may tend to “relax”, reducing the holding force provided by the device. Most preferably, the sleeve material is selected such that the slee

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