GB2469337A

GB2469337A - Apparatus and method for combining a primary material with an additive

Info

Publication number: GB2469337A
Application number: GB0906242A
Authority: GB
Inventors: Alaric Waterson
Original assignee: CLAYTON ENGINEERING Ltd
Current assignee: CLAYTON ENGINEERING Ltd
Priority date: 2009-04-09
Filing date: 2009-04-09
Publication date: 2010-10-13
Also published as: GB0906242D0

Abstract

The apparatus and method, particularly for processing material excavated from roads so that it can be used as backfill, comprises weighting an additive in a first receptacle 14 and providing a second receptacle 6 for receipt of the primary material and the additive, the second receptacle being provided with further weighting apparatus to determine the weight of the primary material and the additive, after which the relative weight of the two components can be determined. The second receptacle may include a mixing system 12 that may comprise a pugmill mixer and which may include an inclined surface which enables material to travel from the inlet to the outlet due to gravity. Additive may be released from the first receptacle by a screw feed 8 onto a feedbelt 10 which is used to transfer primary material to the secondary receptacle. Also claimed is a pugmill mixer.

Description

Machine Aspects of the present invention relate to a machine and method for combining an additive with a primary material in a controlled manner, and a machine for mixing the additive and primary material.

As an example excavated material is traditionally taken away to landfill where it is dumped. This material is generated often as a result of excavating existing highways, footpaths and cycle ways for example. Quarried aggregate is then required to refill the excavation in order that the sufficient material properties are achieved for the refilled area. Examples of such excavations could be where maintenance is required and pipes or replacements must be installed, or for example in providing signs or lighting on road ways. In order to improve this wasteful procedure, trench arisings (excavated material) are mixed with a proprietary binding material product which turns the arisings into a useable backfill within a short space of time by stabilising the arisings and improving the S..

*. strength reducing the possibility of shifting or movement. Accordingly, trench arisings S...

that would otherwise have to be put into landfill can be recycled avoiding the need for *: landfill tax and reducing the quantity of quarried aggregate required to reinstate the excavation. S... * S 20

A first aspect of the present invention provides an improved and more accurate method of S...

* * combining at least two constituent components, which may be used for providing a controlled product for use for example in backfill for excavation.

According to a first aspect of the present invention there is a method of combining an additive with a primary material, the method comprising the steps of: a) determining the weight of an additive; b) transferring the additive and a primary material to a receptacle; c) determining the weight of primary material and additive in the receptacle; d) calculating. the relative weight of primary material and additive in the receptacle.

The method according to the present invention is advantageous as the weight of the additive is determined following which the additive and a primary material are transferred to a receptacle and the weight of the combination in materials is determined which then enables the relative weight of the primary material and additive in the receptacle to be calculated. The relative weight means the weight percentage of each of the components of primary material and additive. These values are accurately calculated and can be compared to a desired relative weight value.

Transfer of additive to the receptacle preferably ends prior to release of primary material to the receptacle. Such operation is beneficial as all of the additive is ensured to have entered the receptacle for the requirement of the mixture. This method of operation ensures all guess work is removed from the calculation of the mixture thereby causing the method to be inherently more accurate than a continuous process. Furthermore, transfer :::: 15 of primary material into the receptacle beneficially commences prior to transfer of additive into the receptacle. This furthermore ensures accuracy of the relative I...

components of the mixture.

S S...

The primary material is beneficially transferred to the receptacle by transfer means and the additive is released onto the transfer means. Accordingly, the additive and primary * ** * materials are transferred together via a transfer means into the receptacle.

*5S**S * S The method beneficially further comprises the step of determining when the relative weight of the additive and primary material in the receptacle approximately reaches a selected weight value and once this weight value is reached pausing transfer of primary material and additive to the receptacle. The method is performed in this manner in order that the weight of the material in the receptacle can be accurately determined without additional material entering the receptacle causing inaccuracies to develop.

The method beneficially further comprises the step of comparing the relative weight of primary material and additive in the receptacle which forms a partial batch with a preselected relative weight requirement for a batch. This step is important as each partial batch comprising additive and primary material has a relative weight value of the materials which is then compared with a global requirement for the entire batch. A large number of partial batches are likely to be required to meet the requirement for the weight of a complete batch. The relative weight of primary material and additive being determined is compared with the global batch requirement which informs an operator if the relative weight requirements are not correct.

The method may further comprise the step of releasing the primary material and additive from the receptacle.

The method beneficially further comprises the step of preparation of a second partial batch of primary material and additive, wherein the value of the weight of additive transfer to the receptacle is increased or decreased to cause the relative weight value of *:: : : 15 the first partial batch and second partial batch in combination to generally correspond to a preselected relative weight value of the batch.

A significant benefit of this method of combining two materials is that a plurality of * : ::* partial batches may be prepared and the relative quantities of material in each partial batch are determined such that the next partial batch produced is prepared taking into account any errors in each partial batch in the next subsequent partial batch produced.

This means that the apparatus may only be paused for a short time period when the material in the receptacle is weighed until the machine restarts thus producing a product with accurate relative quantities of material at high speed.

The method may further comprise the step of mixing the primary material and additive, and the mixing step is beneficially subsequent to determination of the relative weights of the additive and primary material.

A second aspect of the present invention provides an improved machine for providing a controlled product for use for example in backfill for excavation.

According to a second aspect of the present invention there is a machine for combining a primary material with an additive, the machine comprising: -a first receptacle for receiving an additive; -a weighing arrangement for determining the weight of the additive in the first receptac Fe; -a second receptacle for receipt of the primary material, wherein the first and second receptacle are configured for transfer of additive from the first to the second receptacle; and -a weighing arrangement for determining the weight of the primary material plus additive in the second receptacle, The present invention provides the advantage in that accurate weight percentage of *::: : 15 additive may be added to a primary material enabling subsequent mixture to be used with **1* confidence for the desired purpose. For use as backfill, this means that the product must be of sufficient strength.

S S...

* . The apparatus preferably further comprises means for determining the relative weight of the additive compared to the primary material. S...

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S.....

* The machine preferably further comprises a mixing means arranged to mix the primary material and additive. In one embodiment the mixing means may be located in the second receptacle however alternatively the mixing means may be configured to receive material from the second receptacle. The mixing means may be mounted to the second receptacle.

The mixing means beneficially includes one or more shafts having a plurality of mixing paddles mounted relative thereto. The mixing means is even more beneficially a pug mill mixer.

The mixing means preferably comprises a chamber having an inlet and an outlet and a shaft mounted in the chamber, wherein the chamber comprises a gravity feed surface arranged such that material travels gravity wise between the inlet and the outlet. The benefit of such an arrangement is significant in that improved mixing is achieved as gravity assists in the mixing. Material falls due to gravity thereby improving mixing capability through reduction in compaction of the material to be mixed. The gravity feed surface is preferably inclined. The shaft is preferably substantially parallel to the gravity feed surface. One or more shafts may be provided, the shafts mounted substantially parallel to an adjacent shaft.

The machine may further comprise a transfer arrangement for transferring the mixed material away from the mixing means. Such as a transfer arrangement may comprise a feed belt.

:::.. 15 The release means is preferably a screw feed which controls release of the additive from the first receptacle.

The machine preferably further comprises a transfer means for transferring primary material to the second receptacle. The release means is preferably configured to release additive onto the transfer means. The transfer means preferably comprises a feed belt. S...

* : * A third aspect of the present invention provides an improved pug mill mixer.

According to a third aspect of the present invention, there is a pug mill mixer comprising a chamber having an inlet and outlet and a shaft mounted in the chamber, the shaft having a plurality of mixing blades mounted thereon, wherein the chamber comprises a gravity feed surface arranged such that material travels gravity wise between the inlet and the outlet.

The gravity feed surface is beneficially inclined ensuring that the material travels between the inlet and outlet utilising the effects of gravity.

The shaft is preferably substantially parallel to the gravity feed surface. The mixer preferably further comprises a support means for supporting the chamber. The support means is preferably configured to be adjustable to effect change of the incline of the gravity feed surface. The support means is beneficially configured to effect change of incline of the chamber additionally.

The support is beneficially configured to be adjustable to enable the angle of the shaft to the horizontal to be adjusted.

The angles of a plurality of the paddles related to the longitudinal length of the shaft are beneficially adjustable. A door is beneficially provided arranged to control exit of the material from the mixer. The door may be sliding. The door may be operable statically meaning that the aperture is adjusted and set to suit a specific mixture or maybe used dynamically to hold the mixture in the mixer for a specific period of time before the door is opened and the mIxture released.

* The present invention will now be described by way of example only with reference to * ::* the accompanying drawings in which: *..: Figure 1 is a schematic representation of a machine according to an exemplary * : * embodiment of the present invention.

Figure 2 is a schematic representation of the side view of a mixer according to an exemplary embodiment of a second aspect of the present invention.

The machine as described by way of example only has been described in particular with respect to the recycling of trench arisings through the addition of some sort of binding material in the manufacture of a hydraulically bound material. The machine is not restricted for this use as defined in the appended claims and may have numerous applications in the manufacture of mixed materials which require the mixture of an additive with an input material which may be granular or cohesive and be derived from a number of sources.

Referring to Figure 1, there is a hopper 2 into which trench arisings are tipped. This material has beneficially undergone a prior crushing operation to provide particles of size or approximate diameter below a desired threshold value. An operator may use a tele-handler or similar industrial material transporting a vehicle, or may provide a conveyer or feed belt to feed such trench arisings into the input hopper 2. The input hopper 2 in one example has a two metre square open top and is arranged such that an input screen can be fitted. Adjacent the exit point from the hopper is a shredder arrangement 4 arranged to shred any large sizes of particle comprising an amalgamation of smaller particles that have formed. This shredding ensures a material having particles of less than a predetermined diameter or size from leaving the hopper.

The feed belt transfers the input trench arisings from the input hopper 2 to a weighing hopper 6. The rate of transfer is beneficially at a constant volume flow rate. The feed I...

belt is angled relative to the horizontal to elevate the trench arisings up to the weighing S..

*..: hopper 6, and this feed belt passes under the discharge from a screw feed 8 which discharges doses of a binding material onto the trench arisings. Such binding material is known in the art and may comprise constituent components such as a polymer hydrogel * or a cement material. The binding material falls Onto the trench arisings as the trench S.....

* arisings pass up the feed belt 10.

The belt operates at a constant speed and is periodically stopped briefly to create a small batch of material within an otherwise continuous process. In order to ensure accuracy of the relative weights of binder material to primary material, it is necessary to ensure that all of the binder material for each small batch is added to the hopper 6. Accordingly, the operation for providing each small batch starts with primary material entering the hopper 6 without binder material. The binder material release is therefore slightly delayed until release onto the primary material on the feed belt 10. For each small batch, the complete weight of binder is released, following which primary material continues to be released into the hopper 6 to achieve the pre-selected approximate weight. This ensures that all of the binder for a small batch enters the weighing hopper 6. Such a method of operation ensures all guess work is removed from the calculation of the mix, thus the method is inherently more accurate than a continuous process.

The weighing hopper 6 is mounted on a load cell system. This allows the approximate weight of the material in the hopper 6 to be monitored whilst the material is being discharged from the belt. Periodically, the feed belt 10 is stopped thereby allowing an accurate measurement of the material weight in the hopper 6 to be recorded. This material comprises the trench arisings and the binding material. Once the weight has been recorded by the weighing system and recorded via a control and recordal system, a trap door opens in the base of the weighing hopper 6 thereby dumping the material into the pug mill mixer 12.

The binder hopper 14 is located above the feed belt and stores a quantity of the binding material. The screw feed 8 in the base of the hopper is used to regulate dosing of the *s..

binding material onto the trench arisings on a volumetric basis. The screw feed S is run* periodically such that a discreet quantity of binder material is associated with each batch *. of material in the weighing hopper. The binder hopper 14 is mounted on a load cell system so that the actual weight of binder material in each batch is recorded by the : weighing system.

*.S.S. * I

In use, trench arisings are fed via the feed belt 10 into the weighing hopper 6 and the weight in the weighing hopper 6 is continually monitored for the approximate batch weight. Once the designated weight is approximately reached, then the feed belt is stopped and an accurate measurement of the weight of the material in the weighing hopper 6 is taken. The weight loss of the binder hopper 14 associated with this small batch is also recorded therefore for a small batch the weight of the binder and the weight of the trench arisings plus the weight of the binder is known, therefore the weight percentage of the binder relative to the weight percentage of the trench arisings plus the weight of the binder can be calculated. The weight percentage of the composition of the binder is therefore known for the small batch. If the weight percentage of the binder is not exactly that required for the batch in total, any error that is detected is used as an input to the subsequent small batch via the control system. The operator can input a global percentage requirement for the entire batch (which may be varied depending on S the composition of the input trench arisings) and as each small batch is compared to the global requirement, the subsequent small batch composition can be changed by adding more or less binder as required such that the machine automatically compensates for any variability of feed rate, material density etc. and the accuracy of the whole batch is maximised.

In an alternative embodiment, if the relative weight of binder and primary material in the hopper 6 is not correct, the additional binder or primary material could be added to modify the relative weight. This also ensures accuracy of the mixture.

The pug mill mixer 12 is fitted below the trap door of the weighing hopper. This may be *. a standard known type of pug mill mixer which comprises an exit for release of the mixed material onto a discharge belt 16. A generator 18 may be used to power the machine. a a...

Referring to Figure 2, there is an exemplary embodiment of the pug mill mixer 12. The mixer comprises a shaft 18 having a plurality of paddles 20 extending from the shaft 18.

* The shaft 18 is rotatably mounted relative to the housing 24 and a motive means is a.....

a a arranged to cause rotation of the shaft 18. The housing comprises an opening 26 for receipt of the material to be mixed which in the embodiment as described comprises trench arisings plus a binding material. The mixer further comprises an outlet 28 through which the mixed material passes from the mixer 12. The mixer may further comprise a door arranged to adjust the opening of the outlet and may be arranged to completely shut the outlet thereby preventing mixed material from passing therethrough and may be arranged to adjust the outlet to a desired opening cross sectional area.

in a pug miU mixer as described in the art, the shaft rotates in a plane generally perpendicular to the plane in which gravity generally acts. This means that the axis of rotation of the shaft 18 is generally horizontal relative to the ground. A disadvantage of such an arrangement is that there is some compacting effect associated with pushing the material through the housing thereby reducing the mixing effect. According to a second aspect of the present invention, the mixer 12 can be seen to be tilted relative to the horizontal such that gravity assists the material in the direction of the outlet 28. It will be appreciated that for this to occur then the tower portion 30 of the housing must be tilted in order that material will naturally travel under gravity along a downward slope. As the blades 20 rotate, the material to be mixed is lifted by the blades and thrown around the inside of the housing vigorously in a generally downward direction following the force of gravity thereby providing an aerating mixing effect rather than causing compaction of the material. The housing 24 may be a number of shapes and configurations providing that the material naturally falls under gravity from the opening 26 to the outlet 28.

A support arrangement (not shown) is provided to enable the mixer to be mounted such :::: 15 that the axis of rotation of the shaft 18 is not parallel to the ground or the horizontal. An arrangement may be provided for adjusting the angle of the receptacle and or shaft. This U...

may be provided in order that more dense material is mixed more thoroughly however this adds complexity to the machine. It will also be appreciated that the angle of the blade may be adjitstable relative to the shaft for mixing of material having different densities.

* The present invention has been described by way of example only and it will be appreciated by a person skilled in the art that modifications and variations may be made to the present invention without departing from the scope of protection afforded by the appended claims. _ 11

Claims

Claims 1. A method of combining an additive with a primary material, the method comprising the steps of: a) determining the weight of an additive; b) transferring the additive and a primary material to a receptacle; c) determining the weight of primary material and additive in the receptacle; d) calculating the relative weight of primary material and additive in the receptacle.
2. A method according to claim I wherein the transfer of additive to the receptacle ends prior to release of primary material to the receptacle.
3. A method acCording to claim 2 wherein transfer of primary material into the receptacle commences prior to transfer of additive into the receptacle. se.
4, The method according to claim I wherein the primary material is transferred to the receptacle by a transfer means, and the additive is released onto the transfer means. *... S..
5. A method according to any of claims 1-2 further comprising the step of determining when the relative weight of the additive and primary material in the receptacle approximately reaches a selected weight value and once this weight value is reached pausing transfer of primary material and additive to the receptacle.
6. A method according to claim 3 further comprising the step of comparing the relative weight of primary material and additive in the receptacle which forms a partial batch with a pre-selected relative weight requirement for a batch.
7. A method according to any preceding claim comprising the step of releasing the primary material and additive from the receptacle.
8. A method according to any of claims 4-5 further comprising the step of preparation of a second partial batch of primary material and additive, wherein the weight of additive transferred to the receptacle is increased or decreased to cause the relative weight value of the first partial batch and second partial batch in combination to generally correspond to a pre-selected relative weight value of the batch.
9. A method according to any preceding claim further comprising mixing the primary material and additive.
10. A method according to claim 7 wherein the mixing step is subsequent to determination of the relative weights of the additive and primary material. * *
11. A machine for combining a primary material with an additive, the machine S...comprising.-a first receptacle for receiving an additive; -a weighing arrangement for determining the weight of the additive in the first receptacle; *5*S�* * a second receptacle for receipt of primary material wherein the first and second receptacle are configured for transfer of additive from the first to the second receptacle; -a weighing arrangement for determining the weight of primary material plus additive in the second receptacle; and -means for determining the relative weights of the additive and primary material.
12. A machine according to claim 9 further comprising a mixing means arranged to mix the primary material and additive.
13. A machine according to claim 10 wherein the mixing means is located in the second receptacle.
14. A machine according to any of claims 10-11 wherein the mixing means includes a shaft having a plurality of mixing paddles mounted thereon.
15. A machine according to claim 12 wherein the mixing means is a pugrnill mixer.
16. A machine according to any of claims 10 or 12-13 wherein the mixing means is 1 0 arranged to receive primary material and additive from the second receptacle.
17. A machine according to claim 14 wherein the mixing means comprises a chamber having an inlet and an outlet and a shaft mounted in the chamber, wherein the chamber comprises a gravity feed surface arranged such that material travels *:::: 15 gravity wise between the inlet and the outlet. * * * ***
18. A machine according to claim 15 wherein the gravity feed surface is inclined. S..S S...
19. A machine according to any of claims 15-16 wherein the shaft is substantially parallel to the gravity feed surface.
20. A machine according to any of claims 9-17 further comprising a transfer arrangement for transferring the mixed material away from the mixing means.
21. A machine according to any of claims 9-17 comprising a release means for releasing additive from the first receptacle.
22. A machine according to claim 19 wherein the release means is a screw feed.
23. A machine according to any of claims 9-20 comprising a transfer means for transferring primary material to the second receptacle.
24. A machine according to claims 19-21 wherein the release means is configured to release additive Onto the transfer means. /
25. A machine according to any of claims 21 to 22 wherein the transfer means comprises a feed belt.
26. A machine as hereinbefore described with reference to the accompanying drawings.
27. A pug mill mixer comprising a chamber having an inlet and outlet and a shaft mounted in the chamber, the shaft having a plurality of mixing blades mounted thereon, wherein the chamber comprises a gravity feed surface arranged such that material travels gravity wise between the inlet and the outlet. * . .
28. A mixer according to claim 25 wherein the gravity feed surface is inclined. * ***
29. A mixer according to any of claims 25-26 wherein the shaft is substantially *::::* parallel to the gravity feed surface. *..

*
30. A mixer according to any of claims 25-27 comprising a support means for ****** * * supporting the chamber.
31. A mixer according to claim 28 wherein the support means is configured to be adjustable to effect change of the incline of the gravity feed surface.
32. A mixer according to any of claims 28-29 wherein the support means is configured to effect change of incline of the chamber.
33. A mixer according to any of claims 25-30 wherein the angle of a plurality of the mixing blades relative to the longitudinal length of the shaft are adjustable.
34. A mixer according to any of claims 25-31 comprising a door arranged to control exit of the material from the mixer.
35. A mixer according to any of claims 25-32 further comprising a control system arranged to control operation of the door. * . * ** * ce Ce * * S...SCGSS S... *. * S S... *..S *...*SSU*C S *