FIELD OF INVENTION The present invention relates to concrete slip forming methods and machinery. The present invention has particular but not exclusive application for use in forming barrier walls along roads and highways, kerbs, feed bunks and bikeways.

BACKGROUND OF THE INVENTION

Slip forming is an alternative method of construction where concrete is poured into a continuously moving form. Slip forming requires the concrete to be quick setting but be workable so that the concrete can be packed and the emerging structure has integral strength. Slip forming construction forms a continuous, non- interrupted, cast-in-place concrete structures.

In the forming of barrier walls using slip form construction methods, it is necessary to introduce contraction joints or gaps that allow the concrete to expand and contract because of temperature variations and other stresses. With the contraction joints, stresses are relieved along the contraction joint because they are a site of inherent weakness. Contraction joints minimize the formation of cracks in the concrete structure and increase the useful life of the structure.

The contraction joints or gaps are currently formed in slip formed concrete structures by manual cutting with a quick cut saw. The problems with using a quick cut saw to manually cut a gap or recess in the concrete structure is that it is time consuming and labour intensive, failure to create precise and reproducible cuts in the structure and the use of a quick cut saw increases the risk of injury to the workers.

OBJECT OF THE INVENTION

It is an object of the present invention to provide an alternative solution to creating contraction joints or gaps in slip formed concrete structures that alleviates at least in part one or more of the above mentioned problems. SUMMARY OF THE INVENTION

In one aspect the present invention broadly resides in a guillotine assembly for forming a contraction joint in a slip formed concrete structure, including

a one or more blades;

a blade housing to support said one or more blades, the blade housing is adapted to position about the formed concrete structure;

a guillotine means to move the one or more blades between an operative position and an inoperative position; wherein in use the blade housing is positioned about the formed concrete structure and the guillotine means moves the one or more blades from an inoperative position to an operative position where the one or more blades cut into the formed concrete structure.

Preferably there are two blades that substantially oppose each other in the blade housing. More preferably the two opposing blades move together to cut the formed concrete structure on either side of the structure. The two blades preferably move in unison when they move to and from an operational position. Preferably the two blades make incomplete cuts that form recesses or gaps on either side of the slip formed concrete structure.

Preferably the free side of each of the blades have an edge adapted to cut concrete.

Preferably the formed recesses or gaps are substantially symmetrical on either side of the slip formed concrete structure. Preferably the formed recesses or gaps are reproducible along the slip formed concrete structure.

Preferably at least a portion of the blade housing has a shape that is similar to the mould for the slip formed concrete structure.

Preferably the blade housing has a shape similar to the slip formed concrete structure.

Preferably the blades are substantially retained in the blade housing when in the inoperative position.

Preferably the guillotine means includes a ram that actuates the movement of the blades between operative and inoperative positions. The blades are preferably linked together so that when the ram is actuated the blades close towards each other. Preferably the ram is hydraulically actuated. In a preferred form the guillotine assembly is integral with or attachable to a concrete slip forming machine or apparatus. In this form the guillotine assembly preferably operates at set intervals to create contraction joints. Preferably contraction joints are made at intervals of 2.5 to 4.5 meters and more preferably every 3.8 meters.

In an alternative embodiment the guillotine assembly is a stand-alone apparatus that follows the slip forming machine.

In a further form the guillotine assembly is a kit assembly purchased and added separately to the slip forming machine.

In another aspect the invention broadly resides in a slip forming machine having a concrete slip forming portion and a guillotine assembly as described above.

In a further aspect the invention broadly resides in a method of making contraction joints using the guillotine assembly as described above and including the steps of

slip forming a concrete structure;

actuating the hydraulic ram to move the blades into operational position to form cuts on each side of the structure;

releasing the hydraulic ram and the blades so that the blades return to the inoperative position.

Preferably the method is repeated periodically. Preferably the method repeats in making contraction joints at intervals of 2.5 to 4.5 meters and more preferably every 3.8 meters.

In the form where the guillotine assembly is integral with or attached to the slip forming machine, the movement forward of the slip forming machine is coordinated with the making of contraction joints. Preferably the slip forming machine stops when the guillotine assembly operates to make a cut and then proceeds forward again after the cut is made.

Preferably the method of forming a contraction joint is automated.

In another aspect, the invention broadly resides in a method of making at least one contraction joint in a slip formed concrete structure, the method including the steps of:

providing a guillotine assembly having one or more blades and a guillotine means to move the one or more blades between an operative position and an inoperative position; slip forming a concrete structure;

actuating the guillotine means to move the one or more blades into the operative position to form at least one contraction joint into at least one side of the concrete structure;

actuating the guillotine means so that the one or more blades return to the inoperative position.

Preferably, the method further including the step of periodically repeating the method to form a plurality of contraction joints in the concrete structure. Preferably the step of forming the plurality of contraction joints includes forming the contraction joints in the concrete structure at intervals of 2.5 to 4.5 meters. More preferably the contraction joints are formed in the concrete structure at intervals of about 3.8 meters.

Preferably the method further including the steps of providing a slip forming machine attached or integral with the guillotine assembly, and coordinating the forward movement of the slip forming machine with the forming of the at least one contraction joint. Preferably the step of coordinating the forward movement of the slip forming machine with the forming of the at least one contraction joint includes stopping the forward movement of the slip forming machine when the one or more blades move into the operative position. Preferably the step of coordinating the forward movement of the slip forming machine with the forming of the at least one contraction joint includes starting or resuming the forward movement of the slip forming machine once the one or more blades return to the inoperative position. Preferably the step of coordinating the forward movement of the slip forming machine with the forming of the at least one contraction joint are automated. Preferably the steps of actuating the guillotine means are automated.

Preferably the guillotine assembly includes a blade housing to support the one or more blades. Preferably the method includes the step of positioning the blade housing about the slip formed concrete structure.

The features described with respect to one aspect also apply where applicable to all other aspects of the invention. Furthermore, different combinations of described features are herein described and claimed even when not expressly stated. BRIEF DESCRIPTION OF THE DRAWINGS

In order that the present invention can be more readily understood reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein:

Figures 1 and 2 are diagrammatic side views of a slip forming apparatus with the guillotine assembly;

Figures 3, 5 and 8 are diagrammatic views of the guillotine assembly with the blades extended;

Figures 4 and 7 are diagrammatic views of the guillotine assembly with the blades retracted; and

Figure 6 is a diagrammatic side view of the guillotine assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to figures 1 and 2, there is shown a slip forming apparatus 10 with an attached guillotine assembly 1 1 . Concrete is poured into the hopper 12 and compacts to the shape of the mould 14 through the operation of the slip forming process. A formed concrete structure passes through the guillotine assembly 1 1 as the slip forming apparatus 10 moves forward.

With reference to figures 3 to 8, the guillotine assembly 1 1 includes blade housing 15, blades 16 and hydraulic ram 17. The blade housing 15 supports the blades 16. The blade housing 15 has a substantially V-shaped internal configuration 18 that complements the mould or formwork of the slip forming apparatus 10. The opposing sides 19 of the configuration 18 have longitudinal slots 20 through which the blades 16 extend and retract. Each of the blades 16 is attached to a guide 22. Each guide 22 is slideably mounted on an elongate shaft 23. Each guide 22 is also attached to the hydraulic rami 7. When the hydraulic ram 17 is extended, the guides 22 move apart and the blades 16 retract within the blade housing 15. When the hydraulic ram 17 contracts, the guides 22 move together and the blades 16 extend through the slots 20 and oppose each other in closer proximity.

In use, the hydraulic ram 17 is electronically actuated based on distance intervals, timing intervals or manual operation. When the hydraulic ram 17 is actuated, the slip forming apparatus 10 stops moving forward. When the hydraulic ram 17 is actuated, blades 16 extend through the slots 20 as previously described.

The edge 25 of the blades 16 cut into the slip formed concrete structure. The hydraulic ram 17 then extends and the blades 16 retract within the blade housing 15.

Retraction of the blades 16 from the slip formed concrete structure leaves a contraction joint or gap in the structure. The contraction joint is a site of weakness in the structure and allows the concrete to expand and contract without or minimizing the formation of cracks in the structure.

The advantage of the preferred embodiment is that the guillotine action forms reproducible contraction joints regularly spaced along the structure. The guillotine action occurs in less time than the manual making of the contraction joints using a quick cut saw. Consequently, a slip formed structure can be made with less labour costs and time delays. As well the level of risk to injuries is reduced when the guillotine assembly is used.

Please note the internal configuration of the blade housing can have different shapes, not just a substantially V shape, and the shape of the internal configuration depends on the shape of the slip formed structure.

VARIATIONS It will of course be realised that while the foregoing has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is herein set forth.

Throughout the description and claims of this specification the word

"comprise" and variations of that word such as "comprises" and "comprising", are not intended to exclude other additives, components, integers or steps.