AU784912B2 - Spacer - Google Patents

Description

AUSTRALIA

Patents Act 1990 Ronan O'Reilly

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT 9 C9 C

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9CC

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*CC CCC Invention Title: Spacer The following statement is a full description of this invention including the best method of performing it known to us:- 2 Technical Field This invention concerns a spacer suitable for positioning steel bars within drilled holes.

Background Art In forming a steel-reinforced concrete structure, steel members are normally arranged such that they are entirely surrounded by concrete when the concrete is fully poured. Any steel reinforcement protruding from the surface of the concrete will be prone to rusting if exposed to air and moisture, and the rust may then penetrate into reinforcements further within the concrete, resulting in a weakened structure. It is therefore conunon practice to use spacers to prevent the steel from contacting the surface of the mould into which the concrete is to be poured. For example small plastics or metal "chairs", typically about 50-100 mm in height, are used to support steel mesh reinforcements when pouring concrete slabs.

Certain construction situations require steel bars or bolts to be anchored into bedrock. This involves drilling a hole into the rock, inserting a """steel bar or bolt into the centre of the hole, and pumping grout into the gap between the bar and walls of the hole. Standard steel bar diameters are 12, 16, 20 and 24 mm and the thickness of the gap around the bar may be as :'"'"small as 10 mm. The holes are commonly drilled to a depth of 2 m, but in certain applications such as mines, holes with a depth of up to 6 m may be necessary The bars are centred in the holes by sliding a series of washers around the bar before inserting the bar into the hole. However, different-sized S" washers are required for each permutation of hole and bar diameter.

Furthermore, if the hole diameter is close to the diameter of the spacer, there can be difficulty in inserting the bar into the hole without moving the spacer.

.ooooi 30 Disclosure of Invention The invention, as currently envisaged, is a spacer for centring a bar in a hole. The spacer includes: At least three arms. each consisting of an upper member and a lower member joined by a bent elbow.

At least one strap to interconnmmect adjacent upper members or lower members in order to retain the arms side-by-side.

One or more elongate straps may be utilised to connect upper or lower members to each other. The straps may be flexible, or they may be thinned at their connection to the arms to facilitate supply on a roll, wrapping about bar in use and parting to provide a spacer of the required length (number of arms) in any application.

The straps may be in the form of a sticky backing strip to which the adjacent upper or lower members are stuck. The upper members or lower members may be evenly spaced along the backing strip.

A chosen number of the arms, together with the strip to which they are stuck, may be parted from the remainder to form a spacer for use. Parting may be by cutting or tearing.

The strip may be flexible to facilitate not only supply in a roll, but also wrapping of the spacer around the circumference of a bar in use.

The straps may be integrably formed from the same material as the arms.

In this case, adjacent arms may be thinly joined together along their sides. The thin join acting as a hinge to provide a means with which the members can wrap around an object. The thin join further providing an easy .ooooi means to cut or tear away a selected number of arms. It may also be perforated to make it easier to cut or tear.

In use, the arms are oriented along the length of the bar and either the upper or lower members are secured parallel to the bar so that the other members flare out from the bar and the straps serve to distribute the arms around the bar.

S, 25 The spacers may be arranged in one of two configurations. In the first :configuration the straps join the members which are secured to the bar, In this configuration the members which are secured to the bar are spaced apart by the length of the straps. In the second configuration the straps join the members which flare out from the bar.

A spacer of this type has the advantage that it is able to fit with a range of bar and hole diameters. This eliminates the need to manufacture a different spacer for every bar and hole diameter required. Such a spacer is also able to fit a hole which has a varying diameter, such as a hole which has a narrower diameter at the bottom than at the top, or a hole with imperfections such as chipped-off sections or markings left by the drill.

The upper and lower members may join at an obtuse angle at the elbow. The lengths of the upper and lower members may be different. For large holes the longest member will be flared out, and for small holes the shortest member is flared out. The lengths of members may also be shortened on site by clipping off the ends, allowing the spacers to be fitted more precisely to small holes.

In one embodiment. the spacer has three arms and two straps, the straps distribute the arms around bars such that they are arranged at intervals of approximately 1200. The straps are oriented perpendicular to the arms.

The arms may be curved to conform to the surface of the bars. The arms may also be manufactured from a plastic or elastic material which deforms to closely fit the shape of the bar. The surfaces of the arms which come into contact with the bar may have a texture or finish which engages the surface of the bar.

The arms may be constructed such that the elbows may be deformed elastically while the members remain substantially rigid. Alternatively, the arms may be constructed such that the members may be deformed elastically while the elbows remain substantially rigid.

The ends of the arms may terminate in a sharp edge. The sharp edge will not restrict the flared-out members from sliding against the walls of the hole when being inserted, but will grip against the walls of the hole to resist withdrawal of the bar. Metallisation may be applied to the ends of the arms to increase their hardness.

S 25 Brief Description of Drawings An example of the invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a pictorial view of the spacer when not in use.

Figure 2 is a pictorial view of the spacer in place around a bar.

Figure 3 is a sectional view of the bar and spacer of Figure 2 taken along the section 3-3, when inserted into a hole.

Figure 4 is an elevation of a 12mrm bar with a spacer, inserted into a mmn diameter hole, looking into the hole.

Figure 5 is an elevation of a 16mm bar with a spacer, inserted into a 44 mm diameter hole, looking into the hole.

Figure 6 is an elevation of a 20 mm bar with a spacer, inserted into a 48 imm diameter hole. looking into the hole.

Figure 7 is an elevation of a 24 mm bar with a spacer, inserted into a 52 mm diameter hole, looking into the hole.

Figure 8 is a sectional view along the centre of a spacer arm.

Figure 9 is a pictorial view of an alternative arrangement of the spacer when not in use.

Figure 10 is a pictorial view of a further alternative view of the spacer when not in use.

Best Modes for Carrying out the Invention Referring to Figure 1, a moulded plastics spacer 1 has three arms 10, 11 and 12, each arm having an upper member 20 joined by a bent elbow 30 to a lower member 40. Adjacent lower members 40 are connected by elongate straps 50 which are oriented perpendicular to the lower members. The spacers could be provided with more than three arms, and they could be cut down to the required number of arms at the time of use.

The lengths of the upper and lower member are 70 mm and 40 mm respectively, and they have a cross-section of 10 mm x 5 mm. The angle 20 formed between the upper and lower members is 1470. The arms have an inner surface 60, two sides 65. an outer surface 70, and arm ends 75. A leading edge 76 is formed at the junction between the outer surface 70 and ooo the ends 75. The straps 50 are positioned 11 mm from the elbow, they are 13 mm long with a rectangular cross-section of 5 mm x 3 mm. The ends of the straps meet the side walls 65 of the lower members, and the underside 55 of each strap 50 is aligned with the underside 60 of the lower members The transverse cross-sections of the lower and upper members are slightly arched with an inner radius of 6mm. The arched shape approximately conforms to the circumference of steel reinforcements bars with diameters in the range 12 mm to 24 mm.

The upper and lower members are elastically deformable and the elbow is relatively stiff.

The spacers may be used with a bar in one of two configurations.

Figures 2 and 3 show the spacer 10 in use with a bar 80 in the first configuration, where the lower members 40 are secured parallel to the bar by tying wire or a cable-tie 90 around them. In this configuration the straps space arm 10 from arm 11, and arm 11 from arm 12. The gap 85 between arms 12 and 10 is determined by the circumference of the bar 80. The upper members 20 are free to flare out from the elbows 30 so that the leading edge 76 engages the wall of hole 100.

In the second configuration the upper members 20 are secured parallel to the bar and the lower members 40 are caused to flare out from the bar by the straps 50. The spacer has a width which ensures gap 85 is slightly open even when the spacer is placed on the smallest bar. This ensures that when the spacer is strapped to the bar the gap does not completely close, since this would limit the tension with which the spacer grips the bar.

The plasticity of the members causes them to deform to fit the shape of the bar when secured firmly in place with wire or cable ties 90, thereby increasing the contact area between the spacer and bar. Maximising the contact area reduces the likelihood of the spacer slipping on the bar once secured into place.

When several spacers are secured to the bar, the bar is inserted together into a hole 100 drilled in a rock wall with the flared-out members trailing behind the members secured to the bar. In Figure 3. the flared-out upper members 20 engage with the walls of the hole 100 and position the bar 80 in 20 the centre of the hole.

Figures 4 to 7 show the same spacer being used to centre bars with different diameters in different sized holes.

Figure 4 shows the spacer centring a 12 mm diameter steel bar 81 within the walls 101 of a 40 mm diameter hole. The upper members 20 are S: 25 secured parallel to the bar 81, and cannot be seen. The lower members flare out from the bar 81 and engage with the walls 100 of the hole. Since the straps 50 are connected between the flared-out lower members 40, there is room for the upper members 20 to sit closely together around the bar 81, with :a small gap 86. of about 2 mm, between arms 10 and 12.

In Figure 5, the spacer is centring a 16 mm diameter bar 82 within the walls 102 of a 44 mm diameter hole. The configuration of the spacer is the same as in Figure 4, that is, the lower members 40 are flared out from the bar 82 and the upper members 20 are secured parallel to the bar 82. The gap 87 between arms 10 and 12 is greater than gap 86, about 6 mm, but the arms are still spread fairly evenly about the bar.

In Figure 6, the spacer is centring a 20 mm diameter bar 83 within the walls 103 of a 48 mm diameter hole. In this situation, the alternative spacer configuration is used in which the lower members 40 are secured parallel to the bar and the upper members 20 flare out from the bar 83. The gap 88 between arms 10 and 12 is small, about 4 mm, and the three arms are spread evenly around the bar.

In Figure 7, the spacer is centring a 24 mm diameter bar 84 within the walls 104 of a 52 mmn diameter hole using a the spacer configuration in which the lower members 40 are secured parallel to the bar 84 and the upper members 20 flare out from the bar 84. The gap 89 between arms 10 and 12 is greater than for the 20 mm bar, about 16 mm, while the separation of the arms remains fairly even.

Figure 8 illustrates how the ends 75 of the arms 10 are undercut at a 450 angle beneath the outer surface, forming a sharp edge 76. This sharp edge 76 enables the flared-out member to grip against the walls of a hole. A coating of metal 140 increases the hardness of the ends 75, and provides increased strength to the grip. This feature prevents the bar from sliding back out of vertical holes.

S" The spacer can in addition be used for centralising sheathed bolts or multi-strand cables. Since multi-strand cables are typically wider in diameter that the bars previously mentioned, more than three arms may be required in order to surround the circumference. For such situations, the straps will be formed from a single strip of flexible sticky material which will be used to connect many arms together. Alternatively the strip may not be sticky and is 25 welded to the arms. The arms will be evenly spaced along the strip, and individually stuck to the surface of the strip. The strip, with the arms attached thereon, is then wrapped around the circumference of the cable.

Referring to Figure 9, a moulded plastics spacer 200 has multiple arms 10, 11, 12 19, each arm having an upper member 20 joined by a bent elbow 30 to a lower memnber 40. The arms have an inner surface 60., two sides an outer surface 70. and arm ends 75. The sides 65 of each arm are positioned parallel to one another. The inner surfaces 60 of the lower members 40 are stuck to a continuous sticky backing strip 51 which is oriented perpendicular to the lower members 40. Each member is individually stuck to the backing strip.

It is envisaged that the spacers will be manufactured on a backing strip having many arms. The spacers will be supplied as a roll, and in use they will be cut or torn on site into lengths of three or more arms as required for the particular application. The number of arms per application will depend on the diameter of the cable or bolt with which the spacer will surround. As in former embodiments, the spacers may be arranged in one of two configurations. In the first configuration the lower members 40 surround the cable. In the second configuration the upper members 20 surround the cable.

In both configurations the members surrounding the cable are secured firnmly in position with wire or cable ties. The spacing between the arms along the roll may be varied according to the application.

In Figure 10, an alternative construction is shown in which many arms of the plastics spacer 200, are integrally moulded side by side, joined by a thin region of the same plastic as the arm. The upper member 20 and lower member 40 of respective arms 10, 11. 12, 19 are six sided. Each respective member has an inner surface 60, an outer surface 70, arm ends 75, and 2 pairs of sides 66; each pair of sides forming an apex 67 to provide the thin e region.

advantage of such a construction, is that the point of contact 68.

S" 20 between adjacent apexes 67, is sufficiently thin to cut with a sharp knife.

Alternatively, the point of contact 68 may be perforated, enabling the members to be simply torn apart without the need for an additional tool. In any event, the thin region acts as a hinge for the spacer, to separates the members which in use are wrapped around the circumference of an object.

It should be appreciated that the invention may be embodied in other o•forms. For instance, the profile of the fingers may be changed in order to reduce, or minimise, the amount of plastics material required. In particular, it is envisaged that longitudinal grooves may be along the surfaces of the U C fingers in order to remove material without compromising the strength.

In addition, some form of gusseting may be provided at the elbows in order to enhance performance.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the 9 invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

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Claims (9)

1. A spacer for centring a bar in a hole, the spacer including: at least three arms, each consisting of an upper member and a lower member joined by a bent elbow; and at least one strap to interconnect adjacent upper members or lower members in order to retain the arms side-by-side.

2. A spacer according to claim 1, wherein one or more elongate straps are utilised to connect upper or lower members to each other.

3. A spacer according to claims 1 or 2, wherein the straps are flexible.

4. A spacer according to claims 1, 2 or 3, wherein the straps are thinned at their connection to the arms.

A spacer according to claim 1, wherein the straps are in the form of a backing strip to which the adjacent upper or lower members are connected.

6. A spacer according to claim 5, wherein the upper members or lower members are evenly spaced along the backing strip.

7. A spacer according to claims 5 or 6, wherein the strip is flexible.

8. A spacer according to claims 1, 2. 3 or 4, wherein the straps are integrably formed from the same material as the arms.

9. A spacer according to claim 8, wherein adjacent arms are thinly joined together along their sides. Dated this eleventh day of December 2000 Ronan O'Reilly Patent Attorneys for the Applicant: FB RICE CO F B RICE &r CO oeooi