The present invention relates to a clamp for retaining an elongate object, such as an electrical cable, in a desired position and orientation.

It is known to clamp an electrical cable between opposed upper and lower clamp members each having a curved clamping surface for engagement with the outer surface of the cable. Such a clamp is illustrated in Figure 1 . Each clamp member 10,12 is typically formed by bending a strip of stainless steel to define a curved clamp portion 14 and a box-like attachment portion 16. Opposed holes are punched or drilled into the upper and lower walls of the attachment portion for receiving a nut and bolt arrangement for drawing the two clamp members towards each other to clamp a cable therebetween. The bolt may be used to attach the clamp to a support structure such as a rail or the like.

However, the inner clamp surfaces of each clamp member are substantially smooth which can cause the cable to slip both axially and rotationally within the clamp and in turn damage the cable insulation over time. Furthermore, the clamp portion 14 of each clamp member is susceptible to axial movement with respect to the attachment portion 16 when the cable is subjected to axial loading which can undesirably cause fatigue and failure of the clamp.

It is an aim of certain embodiments of the present invention to provide an improved cable clamp configured to grip a cable located therein and to resist axially loading of the cable in use.

According to a first aspect of the present invention there is provided a clamp member for retaining an electrical cable, wherein the clamp member is formed from a strip of material comprising a first end region defining a curved clamp portion having an inner concave clamp surface for engagement with an outer surface of an electrical cable, and an opposed second end region defining an attachment portion for attaching the clamp member to a support surface, wherein a plurality of spaced apart ribs of the second end region respectively engage in correspondingly spaced apart grooves of the first end region. Optionally, each of the plurality of grooves extends substantially into and along an outer convex surface of the clamp portion in a direction substantially perpendicular to a longitudinal axis of the cable in use.

Optionally, each of the plurality of grooves defines an inwardly extending rib for gripping the outer surface of the cable in use.

Optionally, the attachment portion comprises a first wall region extending away from an inner end region of the clamp portion, a second wall region extending substantially perpendicularly from the first wall region, and a third wall region extending substantially perpendicularly from the second wall region, and substantially parallel with the first wall region, towards the clamp portion.

Optionally, the third wall region is substantially tangential to the clamp portion.

Optionally, the first and third wall regions each comprise a hole in axial alignment with each other for receiving a bolt to secure the clamp member to the support surface.

Optionally, each of the holes comprises a curved edge surface.

Optionally, each of the plurality of spaced apart ribs of the second end region of the strip extends along the third wall region.

Optionally, the second wall region comprises a plurality of spaced apart grooves in an outer surface thereof defining corresponding ribs in an inner surface thereof.

Optionally, the strip of material comprises metal and is formed by bending. According to a second aspect of the present invention there is provided a clamp assembly for retaining an electrical cable, comprising: a pair of clamp members each according to the first aspect of the present invention and arranged in opposed orientations with respect to each other for retaining an electrical cable therebetween; and a bolt located through aligned holes in the attachment portion of each clamp member to draw the clamp members together and secure the clamp assembly to a support surface.

According to a third aspect of the present invention there is provided a method of manufacturing a clamp member for retaining an electrical cable, comprising: forming a strip of material having a first end region and an opposed second end region such that the first end region defines a curved clamp portion having an inner concave clamp surface for engagement with an outer surface of an electrical cable, and the second end region defines an attachment portion for attaching the clamp member to a support surface, wherein a plurality of spaced apart ribs of the second end region respectively engage in correspondingly spaced apart grooves of the first end region.

Optionally, forming comprises bending a strip of metal.

Optionally, bending comprises bending the strip of metal about three fold lines to define a first wall region extending from an inner end of the clamp portion, a second wall region extending substantially perpendicularly from the first wall region, and a third wall region extending substantially perpendicularly from the second wall region, and substantially parallel with the first wall region, towards the clamp portion.

Optionally, the method comprises forming at least one hole in the attachment portion for locating a bolt to secure the clamp member to the support surface.

Description of the Drawings

Certain embodiments of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 illustrates a known cable clamp; and

Figure 2 illustrates an isometric view of a clamp assembly according to certain embodiments of the present invention.

Detailed Description

As illustrated in Figure 2, a clamp assembly 100 includes a lower clamp member 102 and an upper clamp member 104, wherein each clamp member comprises a curved clamp portion 106 extending from a box-like attachment portion 108. Each clamp member 102,104 is identical and formed from a strip of material, such as by bending a strip of sheet metal, e.g. stainless steel. The strip of material has a first end region opposed to a second end region, wherein the first end region defines the clamp portion 106 and the second end region defines the attachment portion 108.

The clamp portion 106 of each clamp member 102,104 defines an inner concave clamp surface 110 for engagement with the outer surface of the cable in use, and the attachment portion 108 is formed by bending about three fold lines to define a first wall region 112 extending from an inner end of the clamp portion 106, a second wall region 114 extending substantially perpendicularly from the first wall region 112, and a third wall region 116 extending substantially perpendicularly from the second wall region 114, and substantially parallel with the first wall region 112, towards the clamp portion 106. A free end region of the third wall region 116 engages with the clamp portion 106 to prevent, or at least limit, movement of the clamp portion 106 in a direction perpendicular to a cable located in the clamp, i.e. upwardly for the upper clamp member 104 and downwardly for the lower clamp member 102.

Opposed and axially aligned holes 118,120 are provided in the first wall portion 112 and the third wall region 116 respectively for receiving a bolt (not shown) engageable with a corresponding nut to draw the upper and lower clamp members 102,104 towards each other such that the first wall regions 112 thereof engage and a cable located between the clamp members is clamped and retained. Each hole comprises a curved edge surface 122 for guiding the bolt into the hole during installation and to eliminate a sharp edge which could undesirably damage the bolt thread. Each hole 118,120 terminates inside the box-like attachment portion 108 with an annular wall 124. Each hole is formed by punching, drilling, or the like.

Each concave clamp surface 110 has a uniform radius of curvature to define part of a circle which is less than semi-circular in cross section. Alternatively, each clamp surface may be substantially semi-circular in cross section or have a non-uniform radius of curvature, e.g. define a plurality of clamp surface portions each having a different radius of curvature for accommodating cables of different diameters.

As illustrated, the curved clamp portion 106 includes a plurality of spaced apart grooves 126 extending into the outer convex surface of the clamp portion 106, i.e. into the surface against which the third wall region 116 engages. The grooves 126 define corresponding ribs 128 on the inner concave clamp surface 110 which increase the bending stiffness of the clamp portion and also act to grip the resilient outer material of the cable to prevent or at least minimise axial movement of the cable with respect to the clamp assembly 100 when the cable is subjected to an axial load.

The third wall region 116 of the attachment portion 108 includes a plurality of grooves 130 in its outer surface which define corresponding ribs 132 on the inner surface which are aligned with the grooves 126 in the convex outer surface of the clamp portion 106. A free end region of each rib 132 engages into a corresponding one of the grooves 126 at an apex region of the convex outer surface of the clamp portion 106 to thereby interlock with each other at the free end region of the third wall region 116. This arrangement desirably adds strength and stiffness to the attachment portion 104 whilst also constraining the clamp portion 106 of each clamp member 102,104 in the axial direction to prevent twisting thereof when the cable is subjected to axial loading. Similar spaced apart grooves are provided in the second wall region 114 to add strength and stiffness thereto.

Aptly, each clamp member 102,104 may be any suitable size to clamp differently sized cables. For example, the clamp assembly 100 may be suitable to accommodate single cables having a diameter of 10-65mm or larger. In use, the lower clamp member 102 may be located on a support surface, such as a rail member, and a cable located on the inner concave surface of the clamp portion 106. The upper clamp member 104 is then located on the lower clamp member 102 and a bolt is located through the holes 118,120 of the clamp members to engage with a corresponding nut to secure the clamp assembly, and the cable clamped therein, to the support surface. Alternatively, either clamp member of the assembly may be used on its own to clamp a cable or the like to a surface, such as a floor or wall, wherein the cable is clamped between the inner clamp surface of the clamp member and the surface.

Certain embodiments of the present invention therefore provide an improved clamp member for a clamp assembly to retain an elongate object, such as an electrical cable, with respect to a support surface and to efficiently resist axial loading of the cable in use, wherein the clamp member has an increased stiffness and strength compared to conventional cable clamp members/assemblies.