EP1120216B1 - Method and apparatus for mixing and discharging of concrete - Google Patents

Description

The invention relates to a mixing and conveying device for discontinuous, interrupted by charging operations mixture and subsequent promotion of thick materials, especially mortar and concrete, with a connected to a delivery line, a motor-driven agitator mixing vessel containing charged with mixed and conveyed and compressed air for discharging the thick matter through the delivery line can be acted upon, and with a built in the mixing and conveying device or as a separate unit, driven by a combustion or electric motor rotary compressor for generating the compressed air. Furthermore, the invention relates to a method for controlling and operating such a mixing and conveying device.

Such mixing and conveying devices are used in the construction industry for mixing and conveying of thick materials, in particular high solids with low water content such. As mortar and screed concrete used. First, the components of the thick stock, usually sand, binder and water, fed through a feed opening to the mixing vessel and then mixed by the agitator. Then the lid of the mixing tank is closed and the mixing tank is pressurized with compressed air. The thick material is pressed in the form of plugs which are interrupted by compressed air bubbles through a delivery line which is connected to an outlet nozzle in the lower part of the mixing vessel. The interruptions between the plug arise because the blades of the still running agitator sweep periodically the outlet opening in the delivery line. To support the plug conveying is usually compressed air by another Blowed in line in the area of the outlet nozzle. Such mixing and conveying devices are designed with integrated or separate compressor.

In the following, first known devices are described with integrated compressor. In such mixing and conveying equipment usually oil-injected rotary compressors are used in which an electric or internal combustion engine directly or via a belt or gear drive drives the compressor element. For reasons of cost and because of other constructive disadvantages no switchable couplings are used between the drive motor and the compressor element, d. H. the compressor element is always driven with the drive motor running.

The drive of the agitator takes place either via a switchable belt drive and a cardan shaft between the drive motor and agitator or via a hydraulic motor on the agitator and a hydraulic pump on the drive motor.

For cost reasons, it is endeavored to use the power of the drive motor as efficiently as possible, d. H. to achieve the shortest possible mixing and conveying times with the installed engine power for a certain amount of thick material. The known mixing and conveying devices here have deficits that result from the above-described operation and are described below:

Due to the lack of a switchable coupling between the drive motor and the compressor element, the compressor is also driven during the mixing phase, in which there is no compressed air demand for the promotion. Although the compressor is idling, it nevertheless consumes a significant proportion of the drive motor power that is not available for the mixing process.

The required drive torque for the agitator is highest at the beginning of the mixing phase and then decreases rapidly when the feed is mixed to a pasty mass. In addition, the required drive torque for the agitator depends strongly on the speed of the agitator. A reduction in the speed of the agitator at the beginning of the Mixed phase would reduce the required drive torque and (to an even greater extent) the required drive power (as a product of torque and speed), however, there is no efficient way of reducing the speed of the agitator in the known mixing and conveying equipment.

For cost reasons, one dispenses with gearbox with variable transmission ratio between the drive motor and agitator or on controllable hydraulic motors. A change in the speed of the agitator is therefore limited on a change in the drive motor speed and / or in hydraulic motors by a bypass control with high power losses possible. If a combustion engine is used as the drive motor, then a reduction in the speed due to the curve speed-torque curve narrow limits. In addition, a reduced drive motor speed means a reduction in the output of the engine. When using an electric motor as the drive motor, no speed-variable drives come into question for cost reasons.

Therefore, in mixing and conveying equipment according to the prior art, the drive power required for the agitator at the beginning of the mixing phase has a clear maximum. The design or tuning of the drive motor and the agitator must be done for this most unfavorable operating point, otherwise the engine can be strangled by the agitator. In the further course of the mixing phase then the available power of the drive motor is not fully used for mixing.

Even during the production phase, a reduced speed compared with the mixing phase would be desirable, which would be sufficient to maintain the mixing and to support the plug formation. However, the agitator runs in the known mixing and conveying equipment in the funding phase with an unnecessarily high speed and with unnecessarily high drive power, especially when - as in some devices usual - in the funding phase, the speed of the drive motor is further increased to as much as possible Generate compressed air for the promotion. The unnecessarily high The power requirement of the agitator is not available for the generation of compressed air, ie the delivery of thick material.

Another disadvantage of known mixing and conveying equipment with hydraulic pump and motor are the high cost of the additional hydraulic circuit. In the published patent application DE 42 11 139 A1 it is therefore proposed to combine the oil circuit of the rotary compressor and the hydraulic circuit. However, this system has not been successful so far, probably because the high percentage of air in the compressor oil causes significant problems in the hydraulic system.

Another disadvantage of known mixing and conveying devices with belt transmission and cardan shaft are damaging torsional vibrations of the drive train and resulting vibrations, which lead to significant noise and, for example. in the published patent application DE 42 10 430 A1. This type of drive also causes design limitations, which leads to higher production costs. The components such as the switchable belt drive with idler pulley, operating levers, cardan shaft, gearbox to reduce the speed, several bearings, facilities for the lubrication of the bearings, etc. contribute significantly to the manufacturing costs. Another disadvantage is the relatively high maintenance requirements of the switchable belt drive.

Known mixing and conveying equipment with separate compressors z. B. powered by mobile or portable construction site compressors with compressed air. The drive for the agitator usually an electric motor is used. The disadvantage here is that these devices are dependent on an additional power connection, which is not always available on construction sites.

The object of the invention is to improve the known mixing and conveying equipment to the effect that the power of the drive motor optimally used both during the mixing phase and during the delivery phase, reduces the design effort, the manufacturing cost and maintenance and reliability and durability of the device.

To solve the object of the invention, it is proposed to use for the motor drive of the agitator one or more pneumatic motors, which are supplied with a proportion, preferably 20 to 100%, of the compressed air generated by the compressor, and their speed and / or torque and / or Drive power can be adapted by suitable means for influencing the supply of compressed air to the or the compressed air motors and / or the removal of exhaust air from the or the compressed air motors to the various operating phases of the mixing and conveying process.

This includes, in particular, the use of a plurality of compressed-air motors, which individually or in combination drive the agitator so that the speed and / or the drive power and / or the drive torque of the agitator can be changed by connecting or disconnecting individual motors. For this example, a multi-part agitator can be used, the individual parts are each driven separately from a compressed air motor. Alternatively, multiple air motors operating on a common shaft or coupled by a suitable gearbox may drive a one-piece agitator.

Also included is the use of pneumatic motors with multiple inlets for the compressed air and / or multiple outlets for the exhaust air, which are preferably connected to different separate work spaces and / or with different housing sections of the same work spaces and their speed and / or drive power and / or drive torque can be changed by switching on or off the supply of compressed air or discharge of exhaust air at one or more of these inputs and outlets.

Air motors are particularly suitable for this application because of their speed-torque characteristic. They can also provide drive torque well above their rated torque, with their speed decreasing with increasing drive torque.

As a result, compressed air motors are on the one hand able to provide the relatively high drive torque for the agitator at the beginning of the mixing phase put. On the other hand, their speed drops, so that the required for the agitator drive torque compared to known drives with a substantially constant speed is lower. The lower drive torque at a lower speed means that compressed air motors reduce or prevent the maximum drive power occurring in known devices at the beginning of the mixing phase. Compressed air motors must therefore be designed with a comparable mixing effect for a lower power than drives with belt transmission and cardan shaft or hydraulic motor and pump.

The invention will now be described first for mixing and conveying equipment with integrated compressor.

The use of compressed air motors is advantageous in particular because it leads to a decoupling of the rotational speeds of the drive motor and agitator. The drive motor can run both in the mixing phase and in the delivery phase at full power and high speed to deliver as much compressed air for the drive of the agitator and / or for the promotion of thick matter.

The rotary compressors (screw compressors, vane compressors) commonly used in mixing and conveying equipment have compression chambers, which are formed between the rotor (s) and the compressor element housing and which open cyclically during the rotation of the rotor (s), at suction-side control edges close off the suction area, reduce it, open on the pressure-side control edges to the pressure side and push it out to the pressure side against the operating pressure. Openings or connections can be made in the fixed housing regions delimiting the compression chambers, by means of which compressed air with a temporally substantially constant pressure between intake and operating pressure can be taken or supplied to the compression chambers already closed by the suction region in the compressor element. The choice of the position of these connections determines the height of this intermediate pressure.

By changing connection of these connections with the inlets and / or outlets of the compressed-air motors, it is possible to change the pressure difference between the inlets and outlets of the compressed-air motors in a targeted manner. Additionally or alternatively, the inlets and / or outlets can be throttled. Additionally or alternatively, the pressure difference between the inlet and outlet of the air motors can be influenced by a variable bypass. With these measures, the speed and / or torque and / or the drive power of the air motors can be adapted to the operating phases.

In a preferred embodiment of the invention, the compressed air is supplied to the or the compressed air motors at least temporarily with a pressure which substantially corresponds to the operating pressure of the compressor.

Furthermore, the compressed air is supplied to the compressed air motors at least temporarily preferably at a temperature which substantially corresponds to the compression end temperature of the compressor, which is usually between 70 ° C and 100 ° C in oil-injected rotary compressors. The compressed air is taken to a point where she has not experienced any appreciable cooling. This allows a relatively high inlet temperature to be processed, so that the outlet temperature of the compressed air from the compressed air motors for thermodynamic reasons safely above the ambient temperature and no harmful condensation can occur. In addition, the maximum operating volume is used.

It may also be advantageous to heat the compressed air prior to its delivery to the compressed air motors in a heat exchanger to a temperature above the compression end temperature of the compressor so as to further increase the working capacity of the compressed air as it expands in the air motors. In mixing and conveying devices with an internal combustion engine as a drive motor, the compressed air can be heated, for example, by heat exchange with the cooling fluid or the exhaust gas flow of the internal combustion engine.

Furthermore, the compressed air can be supplied to the compressed air motors with an oil content for lubrication, preferably with 0.5 to 50 mg of oil per kilogram of air.

Compared to dry operation, this lubrication of the air motors increases their efficiency, their life and their reliability.

When using oil-injected rotary compressors, the desired oil content in the compressed air for the compressed air motors is preferably achieved in that the removal of the compressed air takes place at a suitable location before the fine separation of the oil in the compressor, z. B. in front of the coalescing filter in the oil separation tank.

It is also possible to supply the compressed air to the pneumatic motors at least temporarily with a pressure which is between the suction and the operating pressure. For this purpose, the compressed air can be removed at a suitable point of the compressor element.

In addition, the supply of compressed air to the compressed air motor via one or more valves can be opened and / or throttled and / or closed and / or switched between different sampling points.

The air emerging from the air motors is preferably returned to the circuit of the compressor. This has, inter alia, the advantage that the oil does not escape to lubricate the air motors in the environment, but is returned to the compressor circuit. One possibility is the return to the intake of the rotary compressor, z. B. in the inlet valve.

Another possibility is the return to the compressor element, and at a point where there is a pressure between suction and operating pressure. This intermediate pressure is superimposed by low pressure pulsations whose amplitude corresponds approximately to the pressure difference between two adjacent compression chambers in the region of the return point. In operating conditions in which no recirculation takes place, this can result in pulsating flow processes between the compression chambers and the volume in the return line, which cause power losses. To avoid this effect, it may be advantageous to the exhaust air due to a check valve in the compressor element, wherein between the check valve and the compression chambers in the compressor element, a volume is included, which is smaller than the volume of the compression chamber in the region of the terminal of the return, preferably less than 20%.

Another possibility of removing the exhaust air from the compressed air motor is to connect the outlet of the compressed air motor at the delivery passage with the compressed air supply of the mixing vessel.

The return or removal of the exhaust air can be opened and / or throttled and / or closed and / or switched between different return points via one or more valves.

This is a variety of ways given to influence the or the compressed air motors between inlet and outlet made available pressure difference targeted.

In a particularly preferred embodiment of the invention, the compressed air is supplied to a compressed air motor substantially at the operating pressure of the compressor, while its exhaust air is returned to the suction region or alternatively to the compressor element at a point where there is a pressure between suction and operating pressures the switchover between the two alternative feedbacks takes place via at least one valve. During the mixing phase, the return line at the outlet of the compressed air motor is connected to the intake of the compressor, so that the maximum pressure difference is available for the compressed air engine between inlet and outlet. If this were not the case, then the compressed air motor would have to be unnecessarily large dimensions. During the delivery phase, the return line is connected at the outlet of the air motor with a connection to the housing of the compressor element, at which an intermediate pressure prevails, preferably about 2 to 60% of the operating pressure. By this feedback, the pressure difference between the inlet and outlet of the air motor is reduced and its speed drops to the desired value in the delivery phase.

The return of the exhaust air in already completed compression chambers in the compressor element is particularly advantageous because the supply of the compressed air motor takes place in an inner circuit, so that is substantially the entire intake flow of the compressor element as compressed air for the promotion of thick stock available. The compressor element can therefore be dimensioned substantially smaller than would be the case in a return of the exhaust air of the compressed air motor in the environment or in the intake of the compressor element.

In a further preferred embodiment of the invention, the compressed air is supplied to a compressed air motor substantially with the operating pressure of the compressor, while its exhaust air is fed into the intake of the compressor or in the environment or alternatively in the mixing vessel, wherein the switching between the two alternatives by at least a valve takes place. During the mixing phase, the exhaust air of the compressed air motor is guided in the intake of the compressor or in the environment, so that the maximum pressure difference is available for the compressed air engine between inlet and outlet. If the exhaust air of the compressed air motor is returned to the suction of the Pompressors, then an internal circuit, so that no dusty ambient air, as usually arises when filling the mixing tank, must be cleaned by the inlet filter, resulting in a much longer service life of the filter. If the exhaust air discharged into the environment, z. B. via a blow-off silencer, so the return line can be omitted.

During the delivery phase, the exhaust air from the compressor is fed into the mixing tank, where there is a pressure between the suction and operating pressure of the compressor.

It is then passed substantially all of the compressed air generated by the compressor first by the air motor and then into the mixing vessel for the delivery of mix.

In this arrangement, the operating pressure of the compressor sets in dependence on the total compressed air consumption and is divided into an advantageous self-adaptation to the respective delivery process in a pressure difference between the inlet and outlet of the air motor and a difference between the mixing vessel and the environment.

If the exhaust air of the pressure motor is oil-containing, it can be passed through an oil separation element from which the separated oil is returned to the compressor's circuit before it enters the environment or before it enters the mixing tank.

Foreign objects or very coarse-grained mixed materials can lead to a blockage of the agitator, which can usually be eliminated again by a short-term reversal of the direction of rotation. In a further preferred embodiment of the invention, therefore, the use of a compressed air motor is provided with reversible direction of rotation.

To achieve the object of the invention, a method for controlling and operating a mixing and conveying device is further proposed, in which the compressed air generated by the compressor during the mixing phase substantially only for supplying the or the agitator driving air motors is used and during the delivery phase both for the promotion of thick matter and for the supply of the or the agitator driving air motors.

In particular, several compressed air motors can be used to drive the agitator, of which all but during the mixing phase, not all are supplied with compressed air during the delivery phase.

In a preferred embodiment of this method, the pressure difference between the inlet and outlet of at least one air motor is influenced so that the speed and / or torque and / or the drive power of the agitator during the mixing phase are higher than in the delivery phase of. For this purpose, the pressure difference between the inlet and outlet of the compressed air motors or during the mixing phase is set higher than in the delivery phase.

The change in the pressure difference between the inlet and outlet of the compressed air motors or by targeted throttling and / or switching the supply of compressed air and / or the removal of the exhaust air between various removal and / or return points in the compressor, where essentially the suction pressure , the operating pressure or an intermediate pressure prevails, and / or by changing a bypass between inlet and outlet.

In a further variant of the method, the pressure difference between the inlet and outlet of the compressed air or the motors can also be influenced by the fact that the exhaust air of the air motor or is passed during the conveying process in the mixing vessel. In this builds up a pressure whose height affects the pressure difference and thus the speed and / or torque and / or the drive line of the or the air motors.

It may also be part of the process to release and / or trigger both the supply of conveying air and the reduction of the rotational speed and / or the torque and / or the drive power of the agitator by a manually or automatically operated switching device after closure of the mixing container.

Furthermore, it may be useful to perform the control of the mixing and conveying device so that a possible blockage of the agitator is automatically detected and thereby a temporary automatic reversal of the direction of rotation is triggered. In this case, for example, the fact can be exploited that the compressed air consumption of the compressed air motor at standstill practically goes back to zero.

In addition to the previously mentioned advantages of the solution according to the invention can be reduced by using a pneumatic motor of the design effort and manufacturing costs compared to the known solutions. The switchable belt drive with idler pulley, operating levers, cardan shaft, speed reducer, multiple bearings, bearing lubrication equipment or hydraulic motor with hydraulic pump and all other components of a hydraulic circuit can be eliminated.

Compared to a switchable belt transmission with attached cardan shaft, the solution according to the invention allows greater design flexibility, because only an inlet and exhaust air line must be installed between the compressor and mixing tank. If the exhaust air of the compressed air motor in the delivery phase in the mixing vessel and in the mixing phase passed into the environment, then even only a compressed air line is required between the compressor and mixing unit, whereby in this embodiment, a conventional or only slightly modified construction site compressor can be used. This results in only minor restrictions for the relative arrangement of compressor and mixing tank. It also reduces maintenance and increases reliability. The vibrations and noise emissions of a switchable belt drive with cardan shaft are eliminated.

Most of the items listed for units with integrated compressor also apply to units with separate compressors. In addition, when using compressed air motors for driving the agitator in contrast to the usual drive with electric motors no additional power connection is required. For the supply of the mixing and conveying device with compressed air during the delivery phase a construction site compressor is present anyway (usually with internal combustion engine), which can also supply the compressed air for the air motor to drive the agitator. Drives of other facilities on mixing and conveying equipment (equipment for loading with mix, loading buckets, etc.) can also be driven by pneumatic motors, so that no power supply is required.

Fig. 1

ein Steuerungsschema eines erfindungsgemäßen Misch- und Fördergerätes in der Mischphase;

Fig. 2

ein Steuerungsschema eines erfindungsgemäßen Misch- und Fördergerätes in der Förderphase;

Fig. 3

ein Steuerungsschema eines erfindungsgemäßen Misch- und Fördergerätes mit einer alternativen Ventilanordnung im Leerlauf;

Fig. 4

die Drehzahl-Drehmoment-Kennlinie eines typischen Druckluftmotors und eines typischen Rührwerks zu Beginn und am Ende der Mischphase. Wobei die Bezeichnungen der einzelnen Kurven folgende Bedeutung haben:

• a: Drehzahl-Drehmoment-Kennlinie des Druckluftmotors
• b: Erforderliches Antriebsmoment des Rührwerks zu Beginn der Mischphase
• c: Erforderliches Antriebsmoment des Rührwerks am Ende der Mischphase
• d: Betriebspunkt von Rührwerk und Druckluftmotor zu Beginn der Mischphase
• e: Betriebspunkt von Rührwerk und Druckluftmotor am Ende der Mischphase
• N_B: Drehzahl von Rührwerk und Druckluftmotor zu Beginn der Mischphase
• N_E: Drehzahl von Rührwerk und Druckluftmotor am Ende der Mischphase
• M_B: Drehmoment von Rührwerk und Druckluftmotor zu Beginn der Mischphase
• M_E: Drehmoment von Rührwerk und Druckluftmotor am Ende der Mischphase

Fig. 5:

ein Steuerungsschema eines erfindungsgemäßen Misch- und Fördergerätes mit einer Anschlußvariante der Komponenten im Leerlauf; Alternative (gestrichelte Linien) mit ölhaltiger Antriebsluft;

Fig. 6:

ein Steuerungsschema eines erfindungsgemäßen Misch- und Fördergerätes mit einer weiteren Anschlußvariante der Komponenten im Leerlauf.

In the following the invention will be described with reference to an embodiment, but without limiting the generality of the invention to this example. Show it:

Fig. 1

a control scheme of a mixing and conveying apparatus according to the invention in the mixing phase;

Fig. 2

a control scheme of a mixing and conveying apparatus according to the invention in the funding phase;

Fig. 3

a control scheme of a mixing and conveying apparatus according to the invention with an alternative valve arrangement at idle;

Fig. 4

The speed-torque characteristics of a typical air motor and a typical agitator at the beginning and end of the mixing phase. Where the names of the individual curves have the following meaning:

• a: Speed-torque characteristic of the compressed air motor
• b: Required drive torque of the agitator at the beginning of the mixing phase
• c: Required drive torque of the agitator at the end of the mixing phase
• d: Operating point of agitator and air motor at the beginning of the mixing phase
• e: Operating point of agitator and air motor at the end of the mixing phase
• N _B : Speed of agitator and air motor at the beginning of the mixing phase
• N _E : Speed of agitator and Air motor at the end of the mixing phase
• M _B : Torque of stirrer and air motor at the beginning of the mixing phase
• M _E : Torque of stirrer and air motor at the end of the mixing phase

Fig. 5:

a control scheme of a mixing and conveying apparatus according to the invention with a connection variant of the components at idle; Alternative (dashed lines) with oily drive air;

Fig. 6:

a control scheme of a mixing and conveying apparatus according to the invention with a further connection variant of the components at idle.

An internal combustion engine 1 drives via a clutch 2, the compressor element 3. This sucks in ambient air through the inlet valve 4, compresses them under injection of oil, which is supplied via the injection line 5, and conveys the compressed air-oil mixture via the pressure line 6 in the Oil separation tank 7. Here, most of the oil is separated from the air stream and collects in the lower part of the oil separation tank 7. From there it is pressed by the operating pressure through the cooler 8 back into the injection line 5. A bypass 9 with a thermo valve 10 controls the final temperature of the oil or the compression end temperature.

Via a pressure line 11 compressed air is passed with operating pressure to the compressed air motor 12, which drives the agitator 13 in mixing tank 14. In the pressure line 11, a 2/2-way valve 15 is provided, with which the compressed air supply of the compressed air motor 12 can be released and interrupted. The exhaust air of the compressed air motor is passed via an exhaust duct 16 to a 3/2-way valve 17.

In the one switching position of the 3/2-way valve 17, the exhaust air is passed via line 18 into the inlet valve 4, in the other switching position in a return port 19 on the housing of the compressor element 3. The return port 19 is provided with an opening in a housing portion of the compressor element 3 connected to the operating in the compression chambers, an intermediate pressure of about 50% of the operating pressure prevails.

The mixing vessel 14 can be charged via an opening 20 with mixed and conveyed material, closed by a cover 21 and set with the lid 21 under pressure.

Further details of the control of the compressor and the mixing and conveying device are not shown here for simplicity.

As shown in Fig. 1, in the mixing phase, the lid 21 is opened and the 2/2-way valve 22 is closed for the conveying air. The compressor essentially generates compressed air for supplying the compressed air motor 12. The 2/2-way valve 15 is open and releases the compressed air to the compressed air motor. The 3/2-way valve 17 connects the outlet of the air motor with the inlet valve 4 of the compressor. As a result, the air motor is supplied with the maximum pressure difference, so that it operates at a relatively high speed, relatively high torque and relatively high drive power. Before switching to the delivery phase, the lid 21 must be closed.

As shown in Fig. 2, flows in the delivery phase compressed air from the oil separator 7 through a coalescing filter 23, the open 2/2-way valve 22 and the pressure lines 24 and 25 in the mixing vessel 14 and the delivery line 26. The 3/2-way valve is in the other switching position and lets the exhaust air of the compressed air motor now flow into the return port 19 of the compressor element. There prevails an intermediate pressure, so that the compressed air motor is present a smaller pressure difference than during the mixing phase. This reduces both the compressed air consumption of the compressed air motor, as well as its speed, its torque and its drive power.

Because the compressed air for supplying the compressed air motor in the delivery phase in an inner circuit, consisting of the compressor element 3, the pressure line 11, the exhaust duct 16, the 3/2-way valve 17 and return port 19 on the compressor element 3, is guided, is essentially the entire intake flow of the compressor element to promote the thick material available.

Fig. 3 shows an alternative control scheme in which instead of the 2/2-way valve 15 and the 3/2-way valve 17, a 3/3-way valve 27 is used to control the air motor 12. In addition, an additional adjustable throttle point 28 is shown in the line to the return port 19 through which a further adjustment of the speed, torque or drive power of the compressed air motor in the delivery phase is possible. The valves 22 and 27 are shown in the switching position for idle or standstill of the mixing and conveying device.

In the region of the return port 19, a check valve 29 is arranged, which in the mixing phase, d. H. when the return line is closed by the valve 27 and no exhaust air of the compressed air motor 12 flows via the return port 19 into the compressor element, prevents pulsating flows between the compression chambers and the return line.

As shown in Fig. 4, the air motor operates at the beginning of the mixing phase, when the mix still opposes the agitator a relatively high resistance, with lower speed and higher torque, than at the end of the mixing phase. This adjustment results automatically by the course of the speed-torque curve of the air motor and proves to be advantageous over known drives, which operate during the mixing process at a substantially constant speed.

FIG. 5 shows an alternative embodiment, in which the compressed air is led directly from the compressor element 3 to the compressed air motor 12 both in the mixing phase and in the delivery phase. The outlet of the compressed air motor 12 is connected to a 3/3-way valve 17. The valve enables the position Standstill A, Mixing B and conveying C. In position A, the exhaust air duct 16 is blocked and compressed air motor 12 is at a standstill. In the mixing phase (position B), the exhaust air of the compressed air motor 12 is guided through the exhaust duct 16 into the inlet valve 4. As a result, the maximum possible pressure difference across the pneumatic motor 12, so that it operates at a relatively high speed, relatively high torque and relatively high drive power. In addition, in this position, a closed circuit for the compressed air supply of the compressed air motor 12 in valve position C, the exhaust air line 16 is connected to the compressed air supply 30 de mixing vessel 14. In the compressed air supply 30 is an oil separation element 31 to separate the oil from the compressed air and due to a return line 32 in the compressor element 3.

In addition, a bypass line 34 is provided with a throttle valve 35 between the inlet and outlet of the pneumatic motor 12, with which the pressure difference across the compressed air motor 12 can be limited. In the throttle valve 35 may be z. B. act to a minimum pressure valve that opens when exceeding a certain pressure difference and limits this to a certain value.

FIG. 6 shows a further possibility for interconnecting the components. The exhaust duct 16 of the compressed air motor 12 is here analogous to Fig. 5 with a 3/3-way valve 17, which has the same switching capabilities connected. The difference from the embodiment in Fig. 5 is that the mixing process (valve position B), the compressed air is given through the exhaust duct 16 via a blow-off muffler 33 directly into the environment. If oil-containing compressed air is required for lubrication of the compressed-air motor, instead of the coalescing filter element 23 in the oil separation tank 7, an oil separation element 31 can be integrated into the exhaust air line 16.

Claims (30)

1. A mixing and conveying apparatus for the discontinuous mixing interrupted by feeding operations and the subsequent conveyance of thick substances, in particular mortar and concrete, comprising a mixing vessel (14) which is connected to a conveyor conduit and which includes a motor-driven agitator mechanism (13) and which is fed with material to be mixed and conveyed and which can be subjected to the action of compressed air for discharge of the thick substances through the conveyor conduit (26), and a compressor element (3) for producing the compressed air, which is integrated into the mixing and conveying apparatus or is in the form of a separate unit and is driven by an internal combustion engine or electric motor,
   characterised in that
   the motor drive for the agitator mechanism (13) is afforded by one or more compressed air motors (12) which are supplied with a part of the compressed air produced by the compressor element (3).
2. A mixing and conveying apparatus according to claim 1 characterised in that the compressed air feed and/or discharge of the compressed air motor or motors (12) is controlled by means of a control device which permits adaptation of the rotary speed and/or the torque and/or the drive power output of the compressed air motor or motors (12) to the various operating phases of the mixing and conveying process.
3. A mixing and conveying apparatus according to claim 1 or claim 2 characterised in that a plurality of compressed air motors (12) drive the agitator mechanism (13) individually or by way of a transmission in such a way that the rotary speed and/or the drive power output and/or the drive torque of the agitator mechanism can be altered by switching individual motors (12) on or off.
4. A mixing and conveying apparatus according to claim 1 or claim 2 characterised in that compressed air motors (12) with a plurality of inlets for compressed air and/or a plurality of outlets for the exhaust air are used, which are preferably connected to different separate working spaces and/or to different housing portions of the same working spaces, wherein the rotary speed and/or the drive power output and/or the drive torque of the compressed air motors (12) can be altered by switching on or off the feed of compressed air or the discharge of exhaust air at one or more of said inlets and outlets.
5. A mixing and conveying apparatus according to one or more of claims 1 to 4 characterised in that the pressure difference between the inlet and the outlet of at least one compressed air motor (12) is influenced at least at times by a variable bypass (9) between the inlet and the outlet.
6. A mixing and conveying apparatus according to one or more of claims 1 to 5 characterised in that the compressed air of at least one compressed air motor (12) is supplied at least at times at a pressure which substantially corresponds to the operating pressure of the compressor element (3).
7. A mixing and conveying apparatus according to one or more of claims 1 to 5 characterised in that the compressed air is fed at least at times to at least one compressed air motor (12) at a temperature which substantially corresponds to the final compression temperature of the compressor element (3).
8. A mixing and conveying apparatus according to one or more of claims 1 to 5 characterised in that the compressed air is heated at least at times before it is fed to at least one compressed air motor (12) in a heat exchanger to a temperature above the final compression temperature of the compressor element (3).
9. A mixing and conveying apparatus according to one or more of claims 1 to 5 characterised in that the compressed air is fed to at least one compressed air motor (12) at least at times with an oil content for lubrication, preferably with 0.5 to 50 mg of oil per kilogram of air.
10. A mixing and conveying apparatus according to claim 9 characterised in that when using oil-injected rotational compressors as the compressor elements (3) the desired oil content of the compressed air for at least one compressed air motor (12) is achieved by the compressed air being taken off at a suitable location upstream of fine separation of the oil in the compressor element (3).
11. A mixing and conveying apparatus according to one or more of claims 1 to 5 characterised in that the compressed air for at least one compressed air motor (12) is taken off at least at times at a location of the compressor element (3) at which a pressure between the intake pressure and the operating pressure obtains.
12. A mixing and conveying apparatus according to one or more of claims 1 to 11 characterised in that the supply of compressed air to at least one compressed air motor (12) can be opened and/or throttled and/or closed and/or switched over between different take-off locations by way of one or more valves.
13. A mixing and conveying apparatus according to one or more of claims 1 to 5 characterised in that the exhaust air of at least one compressed air motor (12) is recycled at least at times into the circuit of the compressor element (3).
14. A mixing and conveying apparatus according to one or more of claims 1 to 5 characterised in that the exhaust air of at least one compressed air motor (12) is recycled at least at times into the intake region of the compressor element (3), preferably into the inlet valve.
15. A mixing and conveying apparatus according to one or more of claims 1 to 5 characterised in that the exhaust air of at least one compressed air motor (12) is recycled at least at times into the compressor element (3) at a location at which a pressure between the intake pressure and the operating pressure obtains.
16. A mixing and conveying apparatus according to claim 15 characterised in that the exhaust air is recycled into the compressor element (3) by way of a check valve (29), wherein enclosed between the check valve (29) and the compression chambers in the compressor element (3) is a volume which is smaller than the volume of the compression chamber in the region of the connection of the recycling means, preferably less than 20%.
17. A mixing and conveying apparatus according to one or more of claims 1 to 5 characterised in that the exhaust air of at least one compressed air motor (12) is passed at least at times into the air supply of the mixing vessel (14).
18. A mixing and conveying apparatus according to one or more of claims 1 to 5 characterised in that the exhaust air of at least one compressed air motor (12) is discharged at least at times into the ambient atmosphere.
19. A mixing and conveying apparatus according to claim 17 or claim 18 and claim 8 characterised in that oil-bearing exhaust air of at least one compressed air motor (12) before passing into the mixing vessel (14) or before issuing into the ambient atmosphere is passed through an oil separator (7) from which the separated oil is recycled into the circuit of the compressor element (3).
20. A mixing and conveying apparatus according to one or more of claims 11 to 15 characterised in that the recycling of the exhaust air of at least one compressed air motor (12) can be opened and/or throttled and/or closed and/or switched over between different recycling locations by way of one or more valves.
21. A mixing and conveying apparatus according to one or more of the preceding claims characterised in that a compressed air motor (12) is used for driving the agitator mechanism (13), to which compressed air is supplied substantially at the operating pressure of the compressor element (3) and the exhaust air of which is recycled into the intake region or alternatively into the compressor element (3) at a location at which a pressure between the intake pressure and the operating pressure obtains, wherein switching over between the two alternative recycling conditions is effected by at least one valve.
22. A mixing and conveying apparatus according to one or more of the preceding claims characterised in that the direction of rotation of at least one compressed air motor (12) can be switched over.
23. A method of operating a mixing and conveying apparatus for the discontinuous mixing interrupted by feeding operations and the subsequent conveyance of thick substances, in particular mortar and concrete, comprising a mixing vessel (14) which is connected to a conveyor conduit and which includes a motor-driven agitator mechanism (13) and which is fed with material to be mixed and conveyed and which can be subjected to the action of compressed air for discharge of the thick substances through the conveyor conduit, and a compressor element (3) for producing the compressed air, which is integrated into the mixing and conveying apparatus or is in the form of a separate unit and is driven by an internal combustion engine or electric motor, characterised in that during the mixing phase the compressed air produced by the compressor element (3) is used substantially only for supplying one or more compressed air motors (12) for driving the agitator mechanism (13) and that during the conveying phase the compressed air produced by the compressor element (3) is used both for conveying the thick substance and also for supplying one or more compressed air motors (12) for driving the agitator mechanism (13).
24. A method of operating a mixing and conveying apparatus according to claim 23 characterised in that when using a plurality of compressed air motors (12) for driving the agitator mechanism (13) during the conveying phase all compressed air motors (12) are supplied with compressed air but during the mixing phase not all compressed air motors (12) are supplied with compressed air.
25. A method of operating a mixing and conveying apparatus according to claim 23 characterised in that the rotary speed and/or the drive power output and/or the drive torque of at least one compressed air motor (12) which is provided with a plurality of inlets for the compressed air and/or a plurality of outlets for the exhaust air is altered by switching on or off the supply of compressed air or the discharge of exhaust air at one or more of said inlets and outlets.
26. A method of operating a mixing and conveying apparatus according to one or more of claims 23 to 25 characterised in that the rotary speed and/or the torque and/or the drive power output of the agitator mechanism (13) is higher during the mixing phase than in the conveying phase by influencing the pressure difference between the inlet and the outlet of at least one compressed air motor (12).
27. A method of operating a mixing and conveying apparatus according to one or more of claims 23 to 26 characterised in that the pressure difference between the inlet and the outlet of at least one compressed air motor (12) is greater during the mixing phase than during the conveying phase.
28. A method of operating a mixing and conveying apparatus according to one or more of claims 23 to 27 characterised in that the variation in the pressure difference between the inlet and the outlet of at least one compressed air motor (12) is effected by variable throttling and/or by switching over the supply of the compressed air and/or the discharge of the exhaust air between different take-off and/or recycling locations in the compressor element (3) or mixing vessel, at which the intake pressure, the operating pressure or an intermediate pressure obtains, and/or by varying a bypass between the inlet and outlet.
29. A method of operating a mixing and conveying apparatus according to one or more of claims 23 to 28 characterised in that after closure of the mixing container (14) a manually or automatically actuated switching device enables and/or triggers both the supply with conveying air and also the reduction in the rotary speed and/or torque and/or drive power output of the agitator mechanism (13).
30. A method of operating a mixing and conveying apparatus according to one or more of claims 23 to 29 characterised in that a possible blockage of the agitator mechanism (13) is automatically detected and triggers a temporary automatic reversal in the direction of rotation of the agitator mechanism (13).

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