IMPROVED MIXER

Field of the Invention

The present invention relates to concrete mixers, particularly to skid mounted concrete mixers.

Background to the Invention

Construction sites often have stationary concrete mixers on location for the storage of prepared concrete prior to the concrete being utilised by piling machines. These stationary concrete mixers generally have a rotatable drum mounted to a frame known as a skid. The inlet to the skid mounted mixer is a cone which reduces in diameter to a mouth into which concrete can be poured from a loading hopper.

The skid mounted concrete mixer is filled periodically by a truck mounted concrete mixer which brings prepared concrete to the construction site. The truck mounted mixer has a discharge chute which is used to transfer concrete from the truck to the skid mounted concrete mixer drum via the loading hopper and the inlet cone.

The design of conventional skid mounted mixers is such that the inlet to the skid mounted mixer's loading hopper is higher than the discharge chute of the truck mounted mixer. To align the loading hopper and the discharge chute, to permit the transfer of concrete, the truck has to be elevated from ground level. Elevation is normally achieved by building a ramp structure. However, as the discharge chute is mounted to the rear of the truck, the truck has to reverse up the ramp. Once aligned the transfer of concrete can take place into the drum via the truck mounted mixer discharge chute and the skid mounted mixer loading hopper.

From a health and safety perspective, it is not desirable to have a ramp on a construction site or to have a truck reversing up a ramp.

Conventional skid mixers are also designed to be tilted from a substantially horizontal configuration to an inclined configuration. This tilting is achieved by the provision of a pair of hydraulic rams located at either side of the mixer drum. Such an arrangement also has drawbacks; as the concrete is mixed, for example, the load of concrete moves from side to side in the drum with the result that the contents of the drum are unevenly distributed, that is, when the drum is heavier on one side than the other. If the contents are unevenly distributed as the drum is lowered, it has been known for one of the rams to stick.

Summary of the Invention

According to a first aspect of the present invention there is provided a concrete mixer for mounting on a skid, the mixer comprising: a rotatable drum; and an inlet cone having a first end in fluid communication with the drum and a second end adapted to receive a loading hopper, the inlet cone having an internal surface extending from the first end to the second end, wherein at least a portion of the internal surface defines zero taper or a taper which increases radially from the first end to the second end. In at least one embodiment of the present invention, a concrete mixer having an inlet cone with the above described structure has a mouth (defined by the second end of the cone), which is low enough to receive concrete from a truck mounted concrete mixer without requiring the truck to be elevated.

For the avoidance of doubt, the term "inlet cone" is used as it is a term in the art. To fall within the scope of the present invention, the inlet cone does not have to be conical.

Preferably, more than 50% of the internal surface defines zero taper or a radially increasing taper from the first end to the second end.

Most preferably, more than 50% of the internal surface defines a radially increasing taper from the first end to the second end. In one embodiment, the internal surface diverges from the first end to the second end.

Preferably, the diameter of the first end is less than the diameter of the second end. This directly contrasts with the inlet cones of the prior art in which the first end is of greater diameter than the second end. Preferably, the inlet cone is attached to the drum such that the inlet cone rotates with the drum.

The first end may be provided with an attachment device for attaching to the drum.

In one embodiment, the inlet cone can be retrofitted to the drum. The attachment device may be a funnel circumferentially mounted around the first end.

Alternatively, the attachment device may be a flange or other suitable attachment device.

In a further alternative, the attachment device is a surface adapted to be welded to a drum surface.

The inlet cone may be adapted to be retrofitted to a conventional inlet cone.

The first end of the inlet cone could be attached to the mouth of a conventional inlet cone. Such an arrangement is advantageous because the mounting of the inlet cone to a conventional inlet cone further distances, in use, the user from the drum of the truck mixer.

In one embodiment, the inlet cone attachment device is adapted to be attached to a drip ring mounted to the mouth of a conventional inlet cone. Preferably, in this embodiment, the attachment device is a flange circumferentially mounted to the inlet cone first end.

Preferably, the inlet cone comprises at least one helical vane.

Preferably, the/each helical vane extends radially inwardly from the internal surface of the inlet cone. Helical vanes assist in the transfer of concrete from the inlet cone into the body of the drum and if the drum is lowered whilst the load of concrete is not evenly dispersed in the drum, one of the rams may jam.

Preferably, the inlet cone comprises four or more helical vanes. A four-start arrangement is preferred.

Preferably, each vane completes at least one helical turn over the length of the inlet cone.

Preferably, the/each vane defines a variable depth.

Preferably, the/each vane defines a greater depth towards the second end than towards the first end.

Preferably, the depth of the/each vane increases linearly from the first end to the second end.

Preferably, the drum comprises at least one vane.

Preferably, an inlet cone vane is attached to each drum vane.

Preferably, an inlet cone vane is integral with each drum vane.

In one embodiment, there are a greater number of inlet cone vanes than drum vanes.

Preferably, there are at least as many inlet cone vanes as there are drum vanes.

Preferably, the drum defines a longitudinal axis.

Preferably, the longitudinal axis is at an angle of less than 10° to the horizontal.

Most preferably, the axis is at an angle of less than 7° to the horizontal.

In one embodiment, the axis is at an angle of less than 4° to the horizontal. A relatively small angle between the axis and the horizontal decreases further the height of the inlet cone mouth with respect to the ground.

Preferably, the drum is rotateably mounted to a frame or skid.

Preferably, the longitudinal axis is at an angle of less than 7° to the frame.

Preferably, the drum is also hingedly mounted to the skid. Preferably, the drum is hingedly mounted such that the inlet cone second end can be raised.

Preferably, the mixer further comprises a lifting mechanism to raise the second end of the inlet cone.

Preferably, the lifting mechanism is a single lifting mechanism. Preferably, the single lifting mechanism is located directly below the drum's longitudinal axis. Surprisingly it had been found that such an arrangement facilitates raising and lowering of the drum when the drum contents are unevenly distributed, that is, when the drum is heavier on one side than the other.

Preferably, the lifting mechanism is hydraulically operated. Preferably, the lifting mechanism comprises a rigid lift. An example of a rigid lift is a Harsh Hoists Rigid Lift

Preferably, the mixer further comprises a loading hopper.

Preferably, the loading hopper has a first end adapted to receive prepared concrete from a truck mounted mixer and a second end adapted to deposit the concrete in the inlet cone.

Preferably, the loading hopper second end, in use, deposits the concrete at or adjacent a mid-section of the inlet cone. Such an arrangement permits the vane height(s) to be deeper towards the mouth of the inlet cone assisting in the prevention of spillage from the inlet cone. Preferably, the loading hopper first end defines a tray. A tray arrangement provides a larger surface area for receiving concrete than a conventional loading hopper. As such the second end of the loading hopper can be lower than the end of a conventional loading hopper.

In one embodiment, the loading hopper has a canopy. A canopy can be provided such that the loading hopper envelopes a truck mounted mixer discharge chute protecting the discharge chute from damage by the inlet cone vanes.

Preferably, the mixer further comprises a discharge hopper. Preferably, the discharge hopper comprises a discharge hopper body and a discharge runnel.

Preferably, the discharge funnel is moveable with respect to the discharge hopper body.

Preferably, the discharge funnel is adapted to direct discharged concrete from the mixer to one or more concrete pumps.

Preferably, the discharge funnel is rotatably mounted to the discharge hopper body.

In one embodiment, in use, the inlet cone is inclined to the horizontal such that, in use, the internal surface second end is closer to the ground than the first end. According to a second aspect of the present invention there is provided an inlet cone or a concrete mixer, the inlet cone comprising: a first end, adapted to in fluid communication with a mixer drum, a second end adapted to receive a feed chute, and an internal surface extending from the first end to the second end, wherein at least a portion of the internal surface defines zero taper or a taper which increases radially from the first end to the second end.

According to a third aspect of the present invention there is provided a loading hopper for transferring concrete to a concrete mixer, the loading hopper comprising: a first end adapted to receive concrete from a source; and a second end adapted to deposit the concrete into a concrete mixer; wherein the first end defines a tray.

According to a fourth aspect of the present invention there is provided a concrete mixer for mounting on a skid, the mixer comprising: a skid; and a rotatable drum having a longitudinal axis; wherein the longitudinal axis is at an angle of less than 7° to the horizontal.

According to a fifth aspect of the present invention there is provided a skid mounted concrete mixer comprising:

a skid; a drum rotatably mounted to the skid; and a scissor lift; wherein at least a portion of the drum can be raised with respect to the skid by means of the scissor lift.

According to a sixth aspect of the present invention there is provided a skid mounted concrete mixer comprising: a skid; a drum rotatably mounted to the skid; and a lifting mechanism for raising at least a portion of the drum with respect to the skid; wherein the lifting mechanism is located directly below the longitudinal axis of the drum.

In one embodiment, the lifting mechanism facilitates raising and lowering of the drum even when the contents of the drum are unbalanced, that is, when the contents of the drum are unevenly distributed within the drum.

Preferably, the lift mechanism is a rigid lift. An example of a rigid lift is a Harsh Hoists Rigid Lift.

It will be understood that preferred or alternative features of any of the aspects listed above may equally be applicable to any of the other aspects and are not repeated for validity.

Brief Description of the Drawings

An embodiment of the present invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a side view of a skid mounted mixer according to a first embodiment of the present invention;

Figure 2 is a perspective view of the inlet cone of the mixer of Figure 1; Figure 3 is an end view of the inlet cone of the mixer of Figure 1 ; Figure 4 is a section view of the inlet cone of the mixer of Figure 1 taken through line A-A on Figure 3; and

Figure 5 is an end view of the mixer of Figure 1 in an inclined configuration.

Detailed Description of the Drawings

Figure 1 shows a skid mounted mixer, generally indicated by reference numeral 10, according to a first embodiment of the present invention. The mixer 10 comprises a drum 12 rotateably mounted to a skid 14, the skid 14 sitting on the ground 5. The mixer 10 further comprises an inlet cone 16 and a loading hopper 26. The inlet cone 16 has a first end 18 attached to, and in fluid communication with, the drum 12, and a second end 20 adapted to receive the loading hopper 26. The inlet cone 16 has an internal surface 24 which defines a radially increasing, or diverging, taper from the first end 18 to the second end 20. Also shown on Figure 1 is a truck mounted mixer 30. The truck mounted mixer 30 has a mixer drum 22 and a discharge chute 28. The discharge chute 28 pours concrete from a truck mounted mixer drum 22 into the loading hopper 26. In turn, under the effects of gravity, the concrete transfers from the loading hopper 26 to the inlet cone 16. As can be seen from Figure 1, the diverging inlet cone 16 permits the concrete to transferred from the truck 30 to the mixer 10 without the need to elevate the truck 30 with respect to the mixer 10.

Referring to Figures 2 to 4, the inlet cone 16 comprises four helical vanes 32a- d, the start of the vanes 32a-32d being spaced equally around the circumference of the second end 20. The vanes 32 increase in height 36 (seen most clearly in Figure 4) from the first end 18 to the second end 20. As the loading hopper 26 (shown on Figure 4 in broken outline) deposits towards the middle 34 of the inlet cone 16, the increase in height of the lowest point 42 of the mouth 40 of the cone 16 caused by the increasing of the vane height 36 is of no consequence. For successful operation, that is such that a truck 30 can deposit into the inlet cone 16 without needing to be elevated, the vane height 36 is most critical towards the middle 34 of the cone 16 where the loading hopper 26 deposits. The increase in vane height 36 towards the second end 20 assists in retaining the poured concrete within the cone 16 prior to transport by the vanes 32 into the drum 12 as the mixer 10 is rotated. As can be seen from Figure 4, the first vane 32a completes an entire turn over the length of the cone internal surface 24, the pitch of the helix being 840mm. The thickness of the cone wall 44 is relatively thin to reduce the height of the cone 16 and the second end 20 is provided with a flange 46 to increase the strength of the cone 16.

The cone first end 18 includes an attachment funnel 50 for receiving an end of the drum 12 and facilitating attachment of the cone 16 to the drum 12. The use of an attachment funnel 50 means the cone 16 can be retrofitted to existing drums 12.

To further facilitate the transfer of concrete from the truck 30 into the mixer 10, the drum 12 is inclined at and an angle of less than 4° to the ground level 38 and the skid 14.

Reference is now made to Figure 1 and Figure 5 which shows an end view of the mixer 10 in an inclined configuration. In the inclined configuration, the inlet cone 16 is pivoted up into the air by a lifting mechanism 70 about a pivot 176 (Figure 1) which connects a drum end 72 to the skid 14.

As can be seen most clearly from Figure 5, the lifting mechanism 70 is located directly below the drum longitudinal axis 74. Such an arrangement facilitates the raising and lowering of the drum 12 even when the concrete within the drum 12 is unevenly distributed. Various modifications and improvements may be made to the above described embodiment without departing from the scope of the invention. For example, a larger or lesser number of vanes could be used in the inlet cone with. The pitch of the vanes could be varied to achieve a greater or lesser throughput of concrete.

Furthermore although an attachment funnel is depicted as the method of attachment to the drum, any suitable method of attachment could be employed. For example, the first end could include a circumferential flange for attachment to a drip ring defined by the mouth of a conventional inlet cone.