WO2019036746A1

WO2019036746A1 - Improved slip joint

Info

Publication number: WO2019036746A1
Application number: PCT/AU2018/000147
Authority: WO
Inventors: David Heszberger
Original assignee: David Heszberger
Priority date: 2017-08-25
Filing date: 2018-08-24
Publication date: 2019-02-28
Also published as: CN111194373A; CN111194373B; AU2018320980B2; AU2018320980A1

Abstract

The invention provides a slip joint (10) for use under a first structural component (50) to be supported on or connected to a second structural component (52). The slip joint (10) has a strip (12) for spanning the second structural component (52). The strip (12) has opposing sides (18) and (20) and a skirt (22) and (32) at each opposing side (18) and (20). Each skirt (22) and (32) is substantially perpendicular to the strip (12). Each skirt (22, 32) is removable after the first structural component (50) is located in place.

Description

Improved Slip Joint

FI ELD OF I NVENTION

This invention relates to an improved slip joint for use in construction. BACKGROUND ART Slip joints are used in construction where a component such as a slab, concrete beam or load-bearing brickwork is supported on or con nected to another component, such as a wall or pier. It is necessary to allow for a certain amount of movement between the components, whether this is caused by expansion or contraction or by small ground movement. A slip joint is intended to provide a low-friction interface between the components for these purposes and also to ensure load transfer, avoiding localised fretting.

Slip joints are common ly provided in sheets or strips of differing lengths, being cut to size or annexed end to end to suit the application.

During construction, slip joints must be held in place while the component to be supported is positioned. Adhesive is normally used, together with tape if required. The process is labour-intensive.

In addition, a slip joint can be rendered ineffective if a slab, for example, is formed incorrectly and vertically hinders the slip joint from working.

It is desirable to provide an improved slip joint which, at least in some embodiments, permits one or more of the following: faster installation, reduced labour costs, improved amou nt of slip between components, prevention of vertical hindrance, faster removal of concrete formwork and a cleaner finish along su pporting walls or piers by reducing concrete runs.

STATEMENT OF I NVENTION Accordingly, the invention provides a slip joint for use under a first structural component to be supported on or connected to a second structural component in construction, the slip joint including:

- a strip for spanning the second structural component, the strip having opposing sides; and

- a skirt on each of the opposing sides, the skirt being substantially perpendicular to the strip and adapted to be removable after the first structural component is in place.

The first structural component may be a concrete slab such as cast in-site slab or a post- tensioned slab. As other examples, the first structural component may be load bearing brickwork or a concrete beam. The second structural component may be a pier or a brick wall, for example. If the second structural component is a brick wall, it may be a single brick wall or a double brick wall, or as desired.

The strip in the slip joint of the invention may be of any suitable length and width. A preferred length is 3 metres, which is manageable on site and easy to transport. The width of the strip is preferably designed to accommodate the various masonry walls and other materials used in structures supporting concrete or other cementitious material pours on construction sites. Preferably, the width of the strip is chosen to suit the span of the second structural component, so that the fit with the skirts is suitable but not overly tight. Examples of preferred widths are set out in the description below referring to the drawings.

Preferably, the strip is made of material which is easily cut to size.

The strip may be made of two or more layers of material. In a preferred embodiment, the strip is made of two annexed layers.

Optionally, the strip includes at each opposing side an anchor, which assists the strip to remain attached to the first structural component during the process of removing the skirts after the first structural component is in place. Each anchor preferably extends for the length of the slip joint Each skirt may be made of a single thickness of material. It is more preferred, however, that each skirt is double-walled with a space between the walls. In this embodiment, the double-walled skirt may include one or more transverse connectors to aid strength. Preferably, each skirt is the same length as the strip.

Optionally, each skirt has a drip nib at an outer edge of a lower part of each skirt, for enabling any concrete slurry to drip away from walls of the second structural component. Each drip nib preferably extends for the length of the slip joint

The slip joint of the invention may include means to assist the slip joint to remain in position while the first structural component is being formed or positioned. The means may include grips or teeth located on the inside of each skirt and designed to grip the sides of the second structural component. As one example, the means may comprise one or more elongated teeth, inclined towards the strip at about 45 degrees, so that once the slip joint is placed in situ the teeth engage the sides of the second structural component and resist removal. Preferably, there are at least two elongated teeth on the inside of each skirt, each running the length of the skirt.

Each skirt is designed to be removable after the first structural component is in place. Removal of the skirt is of significance, because it can create a space between the first structural component and the second structural component. This created space allows for differential movement between the first and second structural components and can overcome the problem encountered when a poorly laid slab would hinder functioning of a prior art slip joint

For this purpose, the skirt preferably includes a weakened area or tear away point where each skirt joins the strip. Other configurations that allow a skirt to be removed are within the scope of this invention.

It is especially preferred that the slip joint of the invention is made from extruded, high density plastic, to allow the installers to be able to cut and modify the slip joint to suite the various lengths of walls and abutments. There is also an economic advantage in using high density plastic, because the slip joint of the invention can have a pricing structure similar to or less than the price of the current metal type slip joint on the market today. However, it is to be understood that the slip joint may be made from any suitable material or mixture of materials.

In use, the slip joint of the invention is placed in position over the second structural component, such as a supporting wall, with a skirt either side of the wall, the size of the slip joint being appropriate for the width of the wall. The strip is pressed down into place. If present, the grip means engage the side of the second component and resist removal. Unlike prior art slip joints, the strip does not need to be glued down when the grip means are present, avoiding the cost and labour involved in gluing the strip to the second component.

The skirts of the slip joint of the invention can function to lock the slip joint in place, both vertically and horizontally. This contrasts with prior art slip joints, which tend to move or shift before the first structural component has been poured or placed, increasing the risk of a poor joint which does not perform its job of allowing slippage between the first and second structural components.

After the first structural component is formed or located in place, any concrete formwork, usually plywood, is stripped away. The presence of the skirts can make this action easier, especially if the slip joint is made of plastic or other flexible material, which gives way to any additional pressure involved with formwork removal, as well as having low adhesion in relation to the concrete slurry.

The skirts are then removed, leaving the strip in place to act as a slip joint. Removal of the skirts is easily effected by pulling them away from the strip. If present, the weakened area or tear away point can assist. Any concrete of the first structural component which has intruded vertically towards the slip joint is quarantined from the slip joint by a small gap left after removal of the skirts. The slip joint is therefore able to function without being impeded by the intruding concrete. The result is a cleaner wall on the sides of the second structural component and a minimization of concrete runs, reducing clean-up requirements.

The placement of the slip joint of the invention is quick and easy and does not require the labour-intensive step of adhering a slip joint to the second structural component. Any concrete runs collect on the outside of the skirts. When the skirts are removed, the concrete runs are also removed, leaving a clean finish, with function of the slip joint unimpeded.

BRIEF DESCRIPTION OF THE DRAWINGS

5 The invention may be better understood from the following non-limiting description of a preferred embodiment. In the drawings:

Figure 1 is a perspective view of one end of an embodiment of a slip joint according to the invention;

Figure 2 is an elevation of one end of the slip joint of Figure 1; i o Figure 3 is a cross-sectional view of the embodiment in Figures 1 and 2, showing typical but non-limiting dimensions of the embodiment;

Figure 4 is an elevation of the slip joint of Figures 1 to 3 in position between a first structural component and a second structural component; and

Figure 5 shows the view in Figure 4 after removal of the skirts of the slip joint.

15 It will be appreciated that the drawings are not on a common scale.

DETAILED DESCRIPTION OF THE DRAWING

Preferred features of the present invention will now be described with particular reference to the accompanying drawings. However, it is to be understood that the features illustrated in and described with reference to the drawings are not to be 20 construed as limiting on the scope of the invention.

Referring to Figures 1 to 3, slip joint 10 is intended for use between a first structural component 50 (shown in Figures 4 and 5) to be supported on or connected to a second structural component 52 (shown in Figures 4 and 5), in this example being a masonry wall.

25 Slip joint 10 has strip 12 which spans the second structural component 52, to be located in the space marked A. The width of strip 12 is chosen to suit various widths of second structural component 52. As an example, if second structural component 52 is brickwork having a width of 110 mm, space A will be approximately 117 mm wide.

Strip 12 has two layers of high density plastic, 14 and 16, and opposing sides 18 and 20 and is 3 metres long. Layers 14 and 16 may be separated by a suitable material such as 5 graphite to assist in slip joint function. Layers 14 and 16 are intended to remain as a permanent structural feature, being free to slide over each other and allow for structural movement as earlier discussed.

First skirt 22 has its outer wall 24 adjoining side 18, being approximately perpendicular to strip 12. Inner wall 26 of first skirt 22 is spaced from outer wall 24 by about 10 - 12 mm in i o this embodiment. Inner wall 26 is about 1.5 - 2 mm thick, as is outer wall 24, so the actual air space between them is about 7 - 8 mm. Stiffener ribs 28 and 30 connect outer wall 24 to inner wall 26 and strengthen them.

Similarly, second skirt 32 has its outer wall 34 adjoining side 20, being approximately perpendicular to strip 12. Inner wall 36 of second skirt 32 is spaced from outer wall 34 by 15 about 10 -12 mm in this embodiment. Inner wall 36 is about 1.5 - 2 mm thick, as is outer wall 34, so the actual air space between them is about 7 -8 mm. Stiffener ribs 38 and 40 connect outer wall 34 to inner wall 36 and strengthen them.

Each skirt 22, 32 is about 30 - 50 mm high in this embodiment. However, skirts 22, 32 may be provided in a range of heights, as convenient.

20 Grip means 42 are shown in relation to inner walls 26 and 36. As another option, the grip means 42 may be omitted.

For convenience, grip means 42 will be described in relation to second skirt 32 only. There are two grip means 42, being in the form of barbs, on second skirt 32, each being inclined towards strip 12 at an angle of about 45 degrees. Each grip means 42 narrows 25 towards its free end and is co-extensive with the length of strip 12 and the length of skirt 32.

In this embodiment, first skirt 22 and second skirt 32, as well as grip means 42, are made of high density plastic and are extruded in one piece together with strip 12 in known manner. However, slip joint 10 may be made of other material and/or using other methods.

The junction of layer 14 with first and second skirts 22 and 32 is notched at 44 to provide a weakened area or tear away point. Similarly, the junction of layer 16 with first and second skirts 22 and 32 is notched at 46 to provide a weakened area or tear away point. The weakened area or tear away points allow easy separation of skirts 22, 32 from strip 12.

This embodiment includes the optional features of anchors and drip nibs.

As shown in Figures 1 to 3, anchor 54 is located at side 18, while anchor 56 is located at opposing side 20, each anchor extending along the length of the slip joint 10. Anchor 54 is formed as an extension of outer wall 24. Anchor 56 is formed as an extension of outer wall 34. Each anchor 54, 56 has a nib 58, 60 respectively, facing inwardly towards the other anchor nib. When removing skirts 22, 32, anchor nibs 58 and 60 remain attached to the concrete in first structural component 50.

As also shown in Figures 1 to 3, each skirt 22, 32 has a drip nib 62, 64, respectively, at the lower end of each of outer walls 24, 34. Drip nib 62 is formed as an extension of outer wall 24, while drip nib 64 is formed as an extension of outer wall 34. Drip nibs 62, 64 direct concrete slurry to drip away from sides of second structural component 52 (see Figure 4). Each drip nib 62, 64 extends for the length of slip joint 10.

Referring now to Figure 4, in use slip joint 10 is placed in position over second structural component 52. First skirt 22 lies on one side of component 52 and second skirt 32 lies on the other side of component 52. Grip means 42 (if present) engage the sides of component 52 and resist vertical movement after placement.

First structural component 52 is then formed by pouring within formwork 66 or by being located in place if preformed. Once first structural component 50 has set (if not preformed), each of skirts 22 and 32 is removed by pulling away from strip 12, breaking at notches 44 and 46, leaving strip 12 in place to act as a strip joint. Removal of skirts 22 and 32 creates a space of about 10 mm on either side of layer 16, as shown in Figure 5. Any vertical intrusion of concrete from first structural component 50 does not prevent operation of slop joint 10 because of the spaces created a described.

As seen in Figure 5, the result after formwork 66 and skirts 22, 32 are removed is neat and clean, with an effective slip joint between first structural component 50 and second structural component 52.

Mechanically, slip joint 10 allows for more positive movement at the interface between first structural component 50 and second structural component 52. The two layers 14 and 16 of strip 12 are kept in place and separate, both during placement of first structural component 50 and afterwards. In addition, a gap of 10 mm or more can be maintained on opposing sides of second component 52, while accommodating different wall or concrete heights between first structural component 50 and second structural component 52.

Architecturally, the slip joint of the invention has the benefits of a final clean look and aesthetic appeal. Concrete runs and splatters on the sides of second structural component 52 are minimised, due to the skirts and can be further reduced by the optional drip nibs. The a gap of about 10 mm maintained between strip 12 and first structural component 50 can present as a shadow line formed in the concrete soffit.

INDUSTRIAL APPLICABILITY

The slip joint of the invention represents an advance in the art, reducing labour time, enabling a clean finish, without concrete runs and preserving function of the slip joint. The slip joint of the invention can also allow for easier removal of forms, used in relation to the first structural component.

The slip joint can be designed to give various economic, architectural and engineering benefits, from its easy application through to its aesthetically pleasing end result.

Claims

1. A slip joint for use under a first structural component to be supported on or connected to a second structural component in construction, the slip joint including:

- a strip for spanning the second structural component, the strip having opposing sides; and a skirt on each of the opposing sides, the skirt being substantially perpendicular to the strip and adapted to be removable after the first structural component is in place.

2. The slip joint of claim 1, wherein each skirt has spaced apart inner and outer walls.

3. The slip joint of claim 1 or claim 2, wherein the inner wall of each skirt has grip means for engaging the second structural component.

4. The slip joint of claim 3, wherein the grip means is one or more barbs inclined at an angle of about 45 degrees to the strip.

5. The slip joint of any one of claims 1 to 4, wherein each skirt has a weakened area to assist removal from the strip.

6. The slip joint of claim 5, wherein the weakened area includes a notch.

7. The slip joint of any one of claims 1 to 6, wherein the strip includes an anchor for assisting the strip to remain attached to the first structural component.

8. The slip joint of claim 7, wherein the strip has an upper layer and a lower layer and the anchor is attached to or integral with the upper layer.

9. The slip joint of any one of claims 1 to 8, wherein each skirt has a drip nib at an outer edge of a lower part of each skirt.

10. The slip joint of any one of claims 1 to 9, when made of high density plastic.