More particularly, this invention concerns the use of high pressure jets of liquid to remove such concrete scale.

Background to the invention The interior of the bowl of a pre-mixed concrete delivery vehicle contains a fin, or series of contiguous fins, arranged generally in a spiral, to form an auger. When concrete is being transported by the vehicle, the bowl is rotated about its axis so that the auger-like fin (or series of fins) moves the pre-mixed concrete away from the mouth of the bowl. This action keeps the concrete well mixed and prevents spillage of the concrete through the mouth of the bowl. When the pre-mixed concrete is to be removed from the bowl, the direction of rotation of the bowl is reversed, so that the auger-like fin (or series of fins) moves the concrete to the mouth of the bowl, which is usually positioned above a delivery chute.

A consequence of the continual rotation of the bowl when transporting, then discharging, concrete is that there is a slow build-up of concrete in the region where the auger fin meets the bowl. This build-up occurs even if the bowl is washed out each time a load of pre- mixed concrete is delivered. Initially, this build-up of concrete scale is of little consequence, but as the build-up increases, there is a significantly reduced carrying capacity of the bowl, and transportation of the scale requires energy that is wasted.

Thus, periodically, it is necessary to remove the concrete scale from the bowl. The frequency of taking this action depends on the extent to which the vehicle is used to transport pre-mixed concrete. Most operators remove the concrete scale at least twice in a year.

The conventional method of removing scale involves a pneumatic drill or jack-hammer, and picks and cold chisels. It is an arduous manual task, which has a number of disadvantages. Among these disadvantages are: a) some concrete chips may remain in the bowl and these concrete chips, when included in the next load of pre-mixed concrete, can damage a concrete pump that is used to pump the concrete to a required point on a site; b) concrete chips remaining in the bowl may adversely affect the appearance and strength of kerbing and channelling work that may be the use of the next load of pre-mixed concrete; c) adverse health and safety aspects which are associated with such a task, which requires the person who effects the cleaning to climb into the bowl, and then operate potentially dangerous equipment (and possibly use acid to make it easier to dislodge the concrete scale) in a confined space; and d) there is a real possibility-often borne out in practice-that the inside surface of the bowl and/or auger fin will be damaged by a pneumatic drill, a pick or a cold chisel.

Disclosure of the present invention It is an object according to one aspect of the present invention to provide an apparatus for the removal of concrete scale, which alleviates one or more of the aforementioned disadvantages. It is a further aspect according to another aspect of the present invention to provide an improved method for removing the concrete scale.

According to one aspect of the present invention there is provided apparatus for use in removing concrete scale from a bowl interior of a vehicle for transporting pre-mixed

concrete the bowl having an interior surface which includes an auger like element thereon and a mouth for providing access to the bowl interior, the apparatus including: support means including a base and a carriage operatively connected to the base for movement relative thereto between a retracted position and an extended position; a pressure head assembly including a body portion operatively connected to the carriage for pivotal movement relative thereto and a spray head including at least one nozzle operatively connectable to a liquid source adapted to supply at least one jet of liquid at high pressure.

The arrangement is such that the pressure head assembly can be caused to enter the bowl interior through the mouth thereof by movement of the carriage from its retracted to extended position. Further positioning of pressure head assembly within the bowl interior can be effected by pivotal movement of the assembly relative to the carriage.

The base may include a support beam and the carriage may include a mounting arm operatively connected thereto for relative linear movement between the extended and retracted positions. The base may further include a generally upright column, the support beam operatively connected to the column for pivotal movement relative thereto.

Preferably, the column is adjustable in its lengthwise direction.

In one form the spray head may be mounted for rotation relative to said body portion. The body portion may include a rigid member to which a flexible liquid supply hose can be operatively mounted the hose being operatively connectable to a liquid source. A linear actuator such as, for example, a hydraulic ram may be provided for causing movement of the carriage relative to the support beam.

Operation of a preferred embodiment of the invention will hereinbefore be described.

This invention may use a high pressure liquid jet to dislodge the concrete scale.

The high pressure liquid jet (preferably water) is provided by the spray head which is positioned within the bowl so that at least one high pressure liquid jet is periodically

directed onto the concrete scale, preferably where its outer edge abuts (and is temporarily bonded to) the auger fin. Once the concrete scale at this point has been dislodged, the spray head is moved to an adjacent position and the high pressure liquid jet is directed onto a fresh region of the concrete scale. In practice, the high pressure liquid jet is moved slowly around the interior of the bowl, following the fin that constitutes the concrete auger. It may be necessary for the inner surface of the bowl to be subjected to the high pressure water jet more than once to completely remove the concrete scale, particularly if there has been a heavy build-up of the scale over a period of, say, six months or more.

A known form of spray head may be used to effect this scale removal process. The spray head is preferably mounted at the end of a flexible hose which supplies water to the pressure head assembly. The flexible hose may be supported by a rigid rod (which may comprise a rigid tube within which the flexible hose is positioned) that is pivotally connected to an elongate arm that may be extended by the action of a further hydraulic ram. The hydraulic ram is used to move the rigid rod and, with it, the pressure head assembly. The arm is preferably attached to the upper end of a vertically adjustable member.

The vertically adjustable member raises the arm so that it is at a height at which the pressure head assembly is adjacent to the mouth of the bowl. In this position, the rigid rod may be substantially collinear with the arm. The hydraulic ram is then used to extend the arm to carry the pressure head assembly into the bowl. The spray head is then positioned in a required location within the bowl, so that the removal of the concrete scale by a high pressure water jet may commence.

According to another aspect of the present invention, there is provided a method of removing concrete scale from the interior of a bowl of a vehicle used to transport pre- mixed concrete, said bowl containing an auger constructed by a generally spiral arrangement of a fin or a plurality of contiguous fins, said method comprising: a) positioning a pressure head assembly, capable of producing at least one

high pressure jet of liquid, within said bowl, adjacent to said fin or one of said fins ; b) causing said pressure head assembly to direct at least one high pressure jet of liquid against said adjacent region of said fin or one of said fins ; and c) either moving said pressure head assembly within said bowl, so that said pressure head assembly is always adjacent to a face of said fin or fins, or rotating said bowl to cause said pressure head assembly to move along the associated face of said fin or fins.

According to yet another aspect of the present invention there is provided a spray head having a main body, the main body having a hub and a peripheral edge portion including one or more internal passages through which fluid may flow, the passages traversing from the hub to the peripheral edge portion. The arrangement is such that an entry portion of the or each passage is arranged so as to extend generally radially from the hub and an exit portion of the or each passage is disposed at an offset from the hub so that fluid exiting the passage at high pressure would encourage rotation of the spray head about the hub.

Preferably the exit portion of the or each passage exit ends in a bight in the main body of the spray head, disposed within which, at the body perimeter, is a nozzle.

Preferably the spray head angles the nozzle from the radial plane of the spray head at up to 40° to assist with more effective removal of concrete scale from a bowl.

Preferred embodiments of the present invention, will hereinafter be described, with reference to the accompanying drawings.

Brief description of the drawings Figure 1 is a vertical sectional view through the central axis of a schematic bowl of a pre- mixed concrete transporting vehicle.

Figure 2 depicts a pressure head assembly that may be used in the present invention.

Figure 3 is a schematic view of a pre-mixed concrete transporting vehicle, about to have concrete scale removed from its interior by apparatus constructed in accordance with the present invention.

Figure 4 shows, schematically, the preferred location of a pressure head assembly within a concrete-transporting bowl while concrete scale is being removed.

Figure 5A shows a plan view of spray head according to one aspect of the present invention.

Figure 5B shows an elevation view of the spray head.

Detailed description of the illustrated embodiment The bowl 10 shown schematically in Figure 1 is mounted on the tray 11 of a vehicle used to transport pre-mixed concrete. It is rotated by a crown pin 12. Details of the mounting of the bowl on the vehicle are well known to persons of skill in this field, and need not be detailed in this specification. Within the bowl 10, an auger like member in the form of a continuous fin 13, usually extending about 300 mm into the bowl, is welded to the interior surface of the bowl to provide an auger for pre-mixed concrete within the bowl. (A series of contiguous fins may be used instead of a continuous fin to form this concrete auger.) Most of the time when pre-mixed concrete is within the bowl 10, it will be rotated so that the auger moves the concrete towards the base of the bowl-that is, towards crown pin 12.

As noted above, this maintains the mixing of the concrete and prevents spillage from the mouth 14 of the bowl. (When the vehicle has transported the pre-mixed concrete to the required destination, the discharge of the concrete from the bowl is effected in a relatively <BR> <BR> very short time. ) This means that there is a tendency for a small amount of concrete to bond-as concrete scale-to the downwardly facing face 15 of the fin. This small amount

of concrete has often cured to the extent that it is not dislodged when the bowl is cleaned with a conventional water hose when the vehicle has been returned to the concrete mixing plant. Over a period of time, the amount of concrete scale increases until it has a profile, against the face 15 of the fin 13, such as that shown as a dashed line 16 in Figure 1.

As noted above, this build-up of concrete scale is difficult to dislodge, and adversely affects the operation of the pre-mixed concrete delivery vehicle.

The present inventors have discovered that a high pressure water jet, directed against the concrete scale-preferably by directing the jet at the point which the scale has reached on the fin-will dislodge the scale from the fin and also from the inner surface of the bowl.

A pressure head assembly which has been found to be particularly effective for this purpose is the pressure head assembly available from Hamelmann of Germany, which is illustrated, schematically, in Figure 2. This pressure head assembly may generate two water jets at a pressure of between 10,000 psi and 35,000 psi.

The pressure head assembly 20 shown in Figure 2 has a body section 21. Water is supplied to the body section 21 through a flexible hose 22 clamped to the entry port member 23 of the pressure head assembly. When the pressure head assembly 20 is in use, two high pressure jets 24 of water leave nozzles 25 in a rotatable spray head 26. In fact, the water jets 24 cause the spray head 26 to rotate. The dimension I of the high pressure head assembly 20 is about 300 mm The pressure head assembly 20 is mounted at the end of a relatively short rigid tube 28, within which the flexible hose 22 is positioned. An alternative to the tube 28 is a rigid rod to which the flexible hose 22 is clamped.

As shown in Figure 3, the rigid tube 28 is pivotally connected at 29 to one end of an arm 30 comprising a short arm member 31 and a long arm member 32. The angle between the elongate direction of the arm member 31 and the elongate direction of the tube 28 is

variable, and is controlled either electromechanically or hydraulically, by known means.

The arm member 31 is movable relative to the arm member 32 under the action of a hydraulic ram 33. A counterweight 35 at the end of arm member 32 which is remote from arm member 31 facilitates rotation of the arm member 32 about a pivot point 36, where the arm member 32 is mounted on a vertically adjustable member 40, in turn mounted on a base 41.

Rotation of the arm member 32 about the pivot point 36 may be effected manually, or it may be effected by electromechanical means (not shown) or by the optional hydraulic ram 42, connected between points 43 (on the arm member 32) and 44 (on the vertically adjustable member 40). Variation of the height of the pivot point 36 at the top of the vertically adjustable member 40 may be effected by a hydraulic ram 42, or by a known form of electromechanical means (for example, a worm and nut, or rack and pinion, arrangement).

The flexible hose 22, which may pass within the arm member 31 (or it may exit the rigid tube 28 near the pivot connection 29), is connected to a water supply 50.

Referring to Figure 5, a further form of spray head is shown generally at 126 according to another aspect of the present invention. In the Figure, like numerals denote like parts in other Figures of this specification. The spray head has a main body having a hub 160 and a peripheral edge portion 161 and has two radial passages 164 forming entry portions of two fluid flow passages and two offset radial passages 166 forming exit portions of fluid flow passages. Nozzles are provided in the exit portions at 125. The nozzles 125 are disposed to provide fluid exiting the nozzles at 1. 5° from the radial plane of the spray head.

This assists the fluid in penetrating the concrete, helping it travel between the steel surface of the bowl and the waste cement.

When the spray head 126 is in use, two high pressure jets 124 water leave nozzles 125, causing rotation of spray head 126 about hub 160.

As shown in Figure 3, the vertically adjustable member 40 is mounted on a platform 45 towards which a vehicle for carrying pre-mixed concrete may drive, in reverse, to position the mouth 14 of the bowl 10 adjacent to the end of the arm member 31. Manipulation of the rigid tube 28 so that the included angle between the elongate direction of the tube 28 and the elongate direction of the arm member 31 is between 140° and 180°, and (if necessary) further driving in reverse of the vehicle carrying the bowl 10, enables the tube 28, and with it the pressure head assembly 20, to be placed within the bowl 10.

Further manipulation of the rigid tube 28 enables the head to be placed, as shown in Figure 4, adjacent to the concrete scale that has built up on the inner surface of the bowl and also on the"downwards"facing face of the fin 13. Activation of the high pressure water jets of the head 20 causes some of the concrete scale to be detached from the bowl surface and/or the fin face.

In principle, the pressure head assembly 20 may be positioned anywhere within the bowl 10. In practice, preferably the high pressure head assembly 20 will be positioned as shown in Figure 4, below the central axis of the bowl 10 (but not at the lowest point possible with the adopted degree to which the arm 30 is within the bowl 10), adjacent to the downwardly facing face of the fin 13. Rotation of the bowl 10, and simultaneous control (manually, and/or hydraulically, and/or electromechanically) of the position of the pressure head assembly 20 by adjustments of the positions of the tube 28, the arm members 31 and 32, and the vertically adjustable member 40, enables the high pressure water jets 24 to be constantly used to dislodge the concrete scale until all the scale has been removed from the bowl 10.

The advantages of the present invention include the following: 1. The concrete scale is removed without arduous, uncomfortable and potentially dangerous activity by a worker.

2. There is very little, if any, possibility that the bowl or fin (s) may be damaged by the

scale removal process.

3. The scale is removed in a short time (compared to the time required to remove the scale manually).

4. The water and concrete mixture that is produced by the scale removal process can be separated into its constituent parts (for example, by sieving and filtration or sedimentation). The removed concrete scale can then be used as clean fill or road base material, and the water can be used, again, in the scale removal process.

This list of advantages is not exhaustive.

It will be appreciated that the embodiment that is illustrated in the accompanying drawings and described above is but one example of the implementation of the present invention.

Variations and modifications of the illustrated embodiment may be made without departing from the present inventive concept.