Regulation 3.2 AUSTRALIA Patents Act 1990 (Cth) Charbel Houchab DIVISIONAL SPECIFICATION FOR AN INNOVATION PATENT Invention Title: A MIXING APPARATUS The following statement is a full description of this invention, including the best method of performing it known to us: 1 A mixing apparatus FIELD OF THE INVENTION The present invention relates broadly to a mixing apparatus and relates particularly, though not exclusively, to an apparatus for mixing or preparing cement slurries for tiling purposes. 5 BACKGROUND OF THE INVENTION Cement slurries are commonly used in the tiling industry for levelling a wall or floor so as to provide a level and smooth surface to which tiles may be adhered. When water is added to cement and/ or sand, it forms a slurry or gel that may be used for tiling purposes. Cement slurry production requires a source of calcium (usually limestone) and a source of silicon (such as clay 10 or sand), an adhesive and water. The water content in a cement slurry is critical as it affects the properties of the cement slurry such as viscosity, thickening and setting time. The process of hardening or setting is actually a chemical reaction called hydration. The dynamic behaviour of the hydration process is important in a sense that a slurry which either sets too quickly or slowly is a costly failure. Hence meticulous precision in controlling of water content in a cement slurry is 15 required. The specification of Russian patent no. 2236674 by Sljadnev discloses a method designed to determine the water-to-cement ratio of cement slurries. The method disclosed in the Sljadnev patent includes measuring loadings on an electric motor of a concrete mixer thereby determining the water-to-cement ratio from the measurement data. The water-to-cement ratio is determined 20 by way of mathematical calculation using a formula that relates the loadings and the water-to cement ratio. The specification of United States patent application US 2005/0201197 discloses a method for mixing water and non-aqueous materials using measured water concentration to control addition of ingredients. The method disclosed includes a separate tub and mixing head with a plurality of 25 lines connecting to the mixing head to supply the mixing head with water and at least one non aqueous material. The system further includes a sensor that measures concentration of water in the fluid. The specification of UK patent application GB 2145635 discloses an annular trough mixer, The method disclosed includes transducers positioned at the bottom of the annular trough for 30 measuring the water content of the mixture.
2 SUMMARY OF THE INVENTION According to one aspect of the present invention there is provided a mixing apparatus comprising: a vessel being adapted to contain a cement slurry; a detector operatively coupled to the vessel and being at least in part immersed in the 5 cement slurry for detection of its water content; and a water control assembly operatively coupled to the vessel to provide water to the slurry, the control assembly also communicating with the detector whereby at a predetermined water content the provision of water to the slurry is stopped. Preferably the water control assembly includes a water valve operatively coupled to a water 10 supply for the provision of water to the slurry. More preferably the water valve is electrically coupled to a power supply via a control circuit for opening of said valve. Preferably the detector includes a conductive element partly immersed in the slurry and electrically connected to the water control assembly to deactivate the control circuit. More preferably the detector also includes a deactivation circuit interconnecting the conductive element 15 and the control circuit. Even more preferably the deactivation circuit includes a deactivation relay operatively coupled to the control circuit which is deactivated via the deactivation relay at the predetermined water content wherein current flows across the element and the vessel for closure of the deactivation circuit. Preferably the deactivation circuit includes a light source electrically connected to the deactivation 20 relay. More preferably the light source is designed for activation and light emission at the predetermined water content wherein said circuit is closed. Even more preferably the deactivation circuit further includes a light sensor in communication with the light source and operatively coupled to the deactivation relay to deactivate the control circuit for closure of the valve. Still more preferably the deactivation circuit additionally includes adjustment means 25 connected to the light source to adjust the required current for light emission and thus deactivation of the control circuit. Preferably the mixing apparatus also comprises a power relay electrically connected to the control circuit for the supply of control power to the valve for its opening. More preferably the power relay is electrically coupled to a power switch. 30 Preferably the deactivation circuit includes an isolation switch electrically connected to the light source for manual activation of the deactivation circuit.
3 According to another aspect of the invention there is provided a mixing apparatus comprising: a vessel being adapted to contain a cement slurry; an electrical assembly including a conductive element within the vessel for probing the water content of the cement slurry; and 5 a water control assembly operatively coupled to the vessel to provide water to the slurry, the control assembly also communicating with the electrical assembly whereby at a predetermined water content the provision of water to the slurry is stopped. Preferably the water control assembly includes a water valve operatively coupled to a water supply for the provision of water to the slurry. More preferably the water valve is electrically 10 coupled to a power supply via a control circuit for opening of said value. Preferably the conductive element is immersed in the slurry and electrically connected to the water control assembly to deactivate the control circuit for closure of the water valve. More preferably the electrical assembly also includes a deactivation circuit interconnecting the conductive element and the control circuit. Even more preferably the deactivation circuit includes 15 a deactivation relay operatively coupled to the control circuit which is deactivated via the deactivation relay at the predetermined water content wherein current flows across the element and the vessel for closure of the deactivation circuit. According to yet another aspect of the present invention there is provided a mixing apparatus comprising: 20 a vessel being adapted to contain a cement slurry, the vessel having a slurry mixing means; a detector attached to the slurry mixing means for detection of the cement slurry water content; and a water control assembly operatively coupled to the vessel to provide water to the slurry, 25 the control assembly also communicating with the detector whereby at a predetermined water content the provision of water to the slurry is stopped. Preferably the water control assembly includes a water valve operatively coupled to a water supply for the provision of water to the slurry. Preferably the slurry mixing means includes a shaft operatively coupled to a motor. More 30 preferably the detector is mounted to the shaft. Preferably the detector includes two electrodes for contacting the slurry. More preferably the detector includes an electrical circuit that measures the electrical resistance and/or voltage drop of the slurry between the electrodes. Even more preferably the electrical circuit includes a 4 transmitter for transmitting a wireless signal dependent on the resistance and/or voltage drop of the slurry. Preferably the shortest distance between the electrodes is 10-1000mm. More preferably the shortest distance is 100mm. 5 Preferably the mixing apparatus comprises a receiver unit for detecting the wireless signal. More preferably the receiver unit is connected to a receiver circuit, the receiver circuit opening the valve when the resistance and/or voltage drop is above a predetermined value. Preferably the predetermined value is adjustable. BRIEF DESCRIPTION OF THE DRAWINGS 10 in order to achieve a better understanding of the nature of the present invention a preferred embodiment of a mixing apparatus will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic illustration of a mixing apparatus including a water control assembly; Figure 2 is a circuit diagram including a control circuit and a deactivation circuit both forming part 15 of or connected to the water control assembly of the mixing apparatus of figure 1; Figure 3 is a photograph of the mixing apparatus of figure 1 being mounted to a portable frame; Figure 4 is a photograph taken from the top showing the interior of the vessel of the mixing apparatus of figure 1; Figure 5 is a photograph showing the arrangement of a conductive element with the vessel of the 20 mixing apparatus of figure 1; Figure 6 is a photograph showing the location of electronic components, a motor and water valve of the mixing apparatus of figure 1; Figures 7 and 8 are top views of the vessel of another embodiment of the invention, in which the detector is attached to a shaft supporting a mixing blade; 25 Figure 9 is a perspective view of the detector of figures 7 and 8 attached to the shaft; Figure 10 depicts the detector attached to the shaft, according to the embodiment of figures 7-9; 5 Figure 11 is another depiction in exploded view of how the detector attaches to the shaft, according to the embodiment of figure 7-9; Figures 12 and 13 show various views of the detector of the other embodiment of figures 7-11; Figure 14 is a diagram of the electrical circuit within the detector, according to the embodiment of 5 figures 7-13; Figure 15 is a side view of the embodiment of figures 7-13; Figure 16 is a diagram of the electrical circuit within the receiver unit of the other embodiment of figures 7-15; and Figures 17 to 23 are schematic diagrams depicting the general construction and operation of the 10 preceding embodiments of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in figure 1, there is one embodiment of a mixing apparatus generally referenced 1 comprising a vessel 10, a detector 14 and a water control assembly 16. The vessel 10 of this embodiment is adapted to contain a cement slurry 12. The detector 14 Is operatively coupled to 15 the vessel 10 and at least in part immersed in the cement slurry 12 for detection of its water content. The detector 14 includes a conductive element in the form of an elongate conductor 22 which is made of aluminium and partly immersed in the slurry 12. The aluminium conductor 22 is also electrically connected to the water control assembly 16 to deactivate the control circuit 25 for closure of the water valve 18. The water control assembly 16 is operatively coupled to the vessel 20 10 to provide water to the slurry 12. It also communicates with the detector 14 whereby at a predetermined water content the provision of water to the slurry 12 is stopped. The water control assembly 16 includes a water valve 18 which is operatively coupled to a water supply (not shown) for the provision of water to the slurry 12. Alternatively, if there is no mains water supply, water may be pumped from a water reservoir or tank. The water valve 18 is 25 electrically coupled to a power supply 20 via a control circuit 25. The control circuit 25 provides manual control for opening of the water valve 18. The power supply in this embodiment includes a transformer (not shown) which transforms the voltage from 240VAC to 12V DC. Alternatively, the power supply may be in the form of one or more batteries such as a 9 Volt bank of batteries. The detector 14 also includes a deactivation circuit 24 interconnecting the aluminium conductor 30 22 and the control circuit 25. The deactivation circuit 24 includes a deactivation relay 26 which is operatively coupled to the control circuit 25. The control circuit 25 is deactivated via the 6 deactivation relay 26 at a predetermined water content wherein a current flows across the aluminium conductor 22 and the vessel 10 for closure of the deactivation circuit 24. The deactivation circuit 24 includes a light source 28, preferably in the form of a light bulb, which is electronically connected to the deactivation relay 26. The light source 28 is provided for light 5 emission at the predetermined water content when the deactivation circuit 24 is closed. The deactivation circuit 24 further includes a light sensor 30 which is in communication with the light source 28. The light sensor 30 is operatively coupled to the deactivation relay 26 to deactivate the control circuit 25 for closure of the valve 18. It will be understood that the light sensor 30 deactivates the control 25 and closes the valve 18 when the light source 28 illuminates or glows 10 on closure of the deactivation circuit 24. This occurs when the cement slurry 12 is sufficiently conductive which occurs at the required viscosity or "wetness" of the slurry 12. The deactivation circuit 14 additionally includes adjustment means 32 which is connected to the light source 28. The adjustment means 32 may be manually adjusted such that a required current for light emission can be generated to effect deactivation of the control circuit 25. This means that the 15 viscosity or "wetness" at which water addition to the slurry is stopped via the valve 18 may be varied by adjusting the adjustment means 32. The mixing apparatus 1 in this embodiment also comprises a power relay 34. The power relay 34 is electrically connected to the control circuit 25 for the supply of control power to the valve 18 for its opening. The power relay 34 is electrically coupled to a power switch 36 which can be 20 manually operated. The deactivation circuit 24 also includes an isolation switch 38. The isolation switch 38 is electrically connected to the light source 30 via the conductive element 22, or in the alternate position the vessel 10 for manual isolation of the deactivation circuit 24 from the conductive element 22. 25 Referring to both figures 1 and 2, when the water content inside the vessel 10 reaches a predetermined level that the cement slurry 12 becomes conductive, a current will flow between the aluminium conductor 22 and the vessel 10. This results in closure and thus activation of the deactivation circuit 24. The current then flows across the light source 28 causing light emission. The conductivity of the cement slurry 12 is directly proportional to the water content. The 30 intensity of the light emitted from the light source 28 is proportional to the conductivity of the cement slurry 12. Once the light intensity reaches a predetermined level as detected by the light sensor 30, the deactivation relay 26 will be activated thereby providing control power to the water valve 18 for its closure. The control circuit 25 is designed so that water provision to the slurry 12 may be manually effected or reinstated by way of the power switch 36.
7 In case of emergency or when the water supply has to be stopped for any reason, the isolation switch 38 may be operated. The isolation switch 38 is connected to the aluminium conductor 22, a frame 46 of the vessel 10 and the deactivation circuit 24. Once the isolation switch 38 is operated, a current will flow directly across the body of the vessel 10 (instead of from the 5 conductive element 22 across the cement slurry 12 to the vessel 10) causing light emission from the light source 28. As described above, once the intensity of the light reaches a predetermined level, the provision of water to the slurry 12 is stopped. The adjustment means 32 which may be used to manually control the intensity of the light emitted from the light source 28. The adjustment means 32 in the embodiment is in the form of a 10 potentiometer. The isolation switch 38 may be manually adjusted while the water provision is closely monitored such that an exact degree of wetness of the slurry 12 may be achieved. Referring to figure 3, a mixer 40 is provided inside the mixing apparatus 1. The mixer 40 is connected to an electric motor 42 which runs on 240V and is located underneath the vessel 10. The transformer 11 is located next to the electric motor 42 transforming the voltage to 12 V DC. 15 The vessel 10 is mounted on a frame 46 with wheels 48 enhancing the mobility of the mixing apparatus 1. The vessel 10 includes a grate 52 which is welded onto the edge 54 of the opening 56 of the vessel 10. Water is supplied into the vessel 10 via the valve 18 and an associated duct 58 which is joined to a conduit 60. The valve 18 is mounted onto the frame 46 and located adjacent to one of the wheels 48. A throttle valve 57 with a handle 59 is provided in the middle of 20 the duct 58 to allow manual regulation or adjustment of water flow. The conduit 60 in this embodiment is permanently affixed by a bracket 61 to and runs along the periphery of the vessel 10. A hole 62 is provided in the vessel 10 through which the conduit 60 passes. The conduit 60 extends across the opening 56 of the vessel 10 being tied to one of the bars 64 of the grate 52. The portion of the conduit 60 which runs across the opening 56 forms part of a sprinkler system 25 having spigots 66. Referring to figures 4 and 5, in this embodiment, the aluminium conductor 22 comprises two portions. The first portion 44 of the aluminium conductor 22 is U-shaped and mounted onto a tiltable lid 50 of the vessel 10. One end of the aluminium conductor 22 is extended in length such 30 that the extended portion is immersed in the cement slurry 12 when in use. The other end of the aluminium conductor 22 curls away from the vessel 10 so as to facilitate smooth engagement with the other portion 68 of the aluminium conductor 22. The portion 68 is mounted to the main body of the vessel 10 via the insulation 70. The insulation 70 however does not cover the full length of the portion 68 leaving a gap 86 in the proximity of the bottom of the vessel 10 between 8 the end section 67 of the portion 68 and the exterior 88 of the vessel 10. In this embodiment, this end section 67 may be pushed against the exterior 88 functioning as the isolation switch 38. Once the end section 67 makes contact with the exterior 88, light will be emitted from the light source 28 to stop provision of water to the slurry 12. Once the lid 50 is closed, the portions 44 5 and 68 are in contact with each other and an electrical current may flow through them. The lid 50 is pivotally hinged to the vessel 10 for maintenance and cleaning. Turning now to figure 6, the electrical and electronic components shown in figures 1 and 2 are contained within a box 72 which is fixed adjacent to the bottom of the vessel 10. The power switch 36 in this embodiment takes the form of an elongate bar 80 which is accommodated 10 within and bolted to elongate channel 82. The power switch 36 is connected to the power relay 34 which is contained within the box 72. The power switch 36 in the form of the bar 80 is activated by being pushed up against the bottom surface 84 of the vessel 10. Once the bar 80 makes contact with the surface 84, water will be provided into the vessel 10. In another embodiment of the invention shown in figure 7, the vessel 102 of the mixing apparatus 15 100 includes blades such as 104 each attached to a shaft such as 106. The shafts are coupled to an electric motor (not shown) via a central axle 108 for driving the blades through the slurry and thus mixing it. Attached to one shaft 110 is a detector 112 which detects the cement slurry water content. Figure 10 is a detail showing how the detector 112 is connected to the shaft 110 via an 20 intermediary angle attachment 114 that passes through the detector and is terminated with a pin 116 for secure attachment of the detector to the angle attachment. The other end of the angle attachment is releasably fixed to the shaft 110 by fixing means such as a bracket and nuts although it will be appreciated that other fixing means could be used. Figure 11 is another exploded view of the detector 112 showing its relationship with the angle attachment 114. A 25 passage 116 through the detector, and through which the angle attachment passes can be clearly seen. Figures 12 and 13 show various views of the detector 112. There are two electrodes or sensors 118 and 120 which are located on opposing faces of the detector. In use, these electrodes are for contacting the slurry, and in association with electrical circuitry within the detector (not shown) 30 measure the electrical resistance and/or the voltage drop of the slurry between the electrodes. The distance between the sensors is important. The optimal distance is 10cm, but a range of 1 100cm is satisfactory. The detector includes two charging points 122 and 124 which allow the charging of batteries contained within the detector. The batteries power the detector.
9 Figure 14 shows the electrical circuit 126 contained within the detector. The rechargeable batteries 128 are connected to the charge points 122 and 124. The heart of the electrical circuit is a PIC 16F84 integrated circuit 130. The sensors 118 and 120 are also connected to the circuit. The circuit includes a transmitter 134 for transmitting a wireless signal that contains information 5 about the resistance and/or voltage drop through the slurry in contact with the sensors 118 and 120, the transmitter comprising an antenna 132 and a integrated transmitter chip 134. As shown in figure 15 the wireless signal is detected by a receiver unit 136 attached to the mixing apparatus 100 and which is preferably outside of the vessel 102. The receiver unit 136 includes a receiver circuit 138 as shown in figure 16. The heart of this circuit is another PlC 16F84 10 integrated circuit 140. The receiver unit 136 processes the signal received by a wireless module RX433 MHz indicated as 142. The integrated circuit 140 compares the resistance and/or voltage information received from the transmitter against a predetermined value held in the receiver unit 136. If the resistance and/or voltage drop is above a predetermined value then the circuit opens the water valve 144 to add more water to the slurry contained in the vessel 102. The valve, which 15 is configured normally closed, is part of a water control assembly as previously described. The predetermined value can be increased by pressing button 148 and decreased by pressing button 146. Other elements of the circuit 138 are a BD136 150 which is a relay switch, and a 780S 152 which is a 15 volt to 25 volt converter. Figure 17 is a high level schematic depicting operation of the embodiment of figure 1. The main 20 purpose of this mixing apparatus is to enable/disable the water valve by in this example measuring the current produced by the cement mix using a light globe, a light operated relay and a solenoid relay. If the critical path from the conductor to the water valve is closed, that is a closed circuit is created, then the apparatus is active. Current will travel from the conductor through the Potentiometer (POT) to the light globe turning it on. A light sensor will detect the 25 luminance of the light (assuming the luminance is above the light sensors threshold) and create a path for current from a 12V source to the water valve via the solenoid relay. As shown in figure 18, when the mixing apparatus is in the off state, contacts 1 and 2 are open and connected to the No Contact pins. When the momentary enable Push Button (PB) is pressed, a closed circuit is created from the source to the ground via the solenoid. This will 30 cause contacts I and 2 to close and come in contact with GND and +ve To Valve. As contact 1 connects to GND from No Contact, the closed circuit will still be continuous allowing the solenoid to keep contacts 1 and 2 closed. As contact 2 connects with +ve To Valve, the 12V power source will enable the valve. As shown in figure 19, to disable the valve, a break in the solenoid current is required. This is 10 created from the light operated relay. When the enable PB (from Block 1) is pressed a current from the aluminium conductor flows through the POT to the light globe. When the light sensor detects the luminance from the globe, it generates a current through the solenoid pulling contact 3 to the +ve pin. This will create a closed circuit from the +ve 12V source to the valve via the 5 solenoid relay. This closed circuit will enable the valve. As long as the luminance emitted from the globe is above the enabling threshold of the light sensor, the circuit will remain closed. However, if the luminance emitted from the globe is below the enabling threshold of the light sensor, contact 3 will open to the No Contact pin effectively creating an open circuit from the +ve source to the relay and turning off the valve. As a precautionary measure, a momentary disable 10 PB is included to shut off the valve by pushing the circuit to ground. The- PB is normally at closed at pin 1. The POT is use to vary the luminance emitted from the light globe. Figure 20 is a schematic of high level hardware for the other embodiment of figures 7 and 8. In this example, the Probe is a slave in its relationship with the Actuator. The Probe is programmed to have limited functionality and will only transmit data when prompted. The Actuator is a master 15 in its relationship with the Probe. The actuator contains all the logic in its operation and is the interface between the Input/Output (1/O) drivers. As shown in figure 21, the Probes acts as a slave to the Actuator. The Probe has two functions which are: (i) to take readings from the contacts and store them into a buffer, and (ii) to wait for a command from the Actuator to send the average reading. 20 As shown in figure 22, the Actuator acts as a master to the Probe. It sends a command to the Probe once every 25 milliseconds and waits for a response. A valid response will be processed and used in the "State Machine" (see figure 23). If the Actuator detects a null response from the Probe or detects that the Probe has not responded then it will try again. If, whilst the Actuator is in auto mode and does not receive a response or receives an invalid response then the Actuator 25 will try again. If the Actuator does not receive a response from the Probe after three attempts, it will take the "State Machine" to idle mode. Figure 23 is a schematic flow diagram describing the general operation of the other embodiment of figures 7 and 8. The "State Machine" controls the operation of the Actuator. It takes instructions from the start, stop and POT value and controls the operation of the light and water 30 valve. Now that preferred embodiments of the present invention have been described in some detail, it should be apparent to those skilled in the art that the mixing apparatus at least in some embodiments has the following advantages: 1. the provision of water supply into the cement slurry is automated; 11 2. the water content in the cement slurry can be controlled with precision and finely adjusted; 3. the mixing apparatus is relatively easy to construct and operate. Those skilled in the art will appreciate that the invention described herein is susceptible to 5 variations and modifications other than those specifically described. For example, the various electronic components in the circuitry may be replaced by others that have the same function. Also, the mixing apparatus of this invention may run on a different voltage. Moreover, the conductive element may be made of a different conductive material which preferably does not corrode in a water environment. The end of the aluminium conductor 22 may be designed to curl 10 toward the vessel 10. The elongate conductor 22 may be made of stainless steel. The elongate conductor 22 may be substituted with the mixer 40 itself which would be electrically insulated from the remainder of the mixing apparatus 1, for example by an insulating bearing. All such variations and modifications are to be considered within the scope of the present invention, the nature of which is to be determined from the foregoing description. It is to be 15 understood that any acknowledgement of prior art in the specification is not an admission that this prior art forms part of the common general knowledge in the relevant art.