GB2126911A - Concrete mixer - Google Patents

Abstract

Concrete mixer, particularly a truck-mounted concrete mixer, having a mixing drum (1) containing a vibrator adapted to be actuated by means of a fluid; the vibrator comprises at least one container (4) having a resiliently variable volume and being adapted to be alternately filled with the fluid and emptied thereof for expanding and contracting its volume, respectively. The fluid employed for this purpose is preferably the mixing water used for the concrete mixture. <IMAGE>

Description

SPECIFICATION Concrete mixers The present invention relates to a concrete mixer of the type defined in the generic clause of claim 1.

Already known from DE Patent Application 32 01 162.08 is a concrete mixer of this type, the mixing drum of which encloses at least one vibrator adapted to be energized by the supplied concrete mixing water. To this purpose the mixing water itself is supplied in a pulsating manner or is employed for driving an unbalanced turbine or energizing a pulsator means. The vibrator may be formed by a section of the water supply duct adapted to be set into vibrations by the pulsating water supply or as a separate vibration body adapted to be energized by the pulsating supply water jet impinging thereon. This type of vibrators is suitable for achieving the desired mixing effect during the supply phase of the concrete mixing water only.

Another type of vibrator which may also be employed in a concrete mixer is known from DE-OS 20 05 547. This type of vibrator essentially comprises a closed space filled with a liquid medium. The vibrator further inciudes a loop-shaped conduit for a pressure medium operable to generate cavitation phenomena within the liquid by sudden contractions, such cavitation phenomena resulting in the desired vibrations occurring in a resilient section of the conduit, whence they are transmitted to the liquid medium and thus to the walls of the vibrator. A vibrator of this type is of expensive construction.Its efficiency is unsatisfactory, as the vibrations generated in the pressure medium conduit by the cavitation phenomena therein have to be transmitted to the housing wall through a liquid medium before they can become effective in the material to be mixed.

The initially described vibrators which are energized by the concrete mixing water have a much higher degree of efficiency, although still not optimum.

It is an object of the present invention to provide a concrete mixer of the type set forth in the introduction, the vibrator(s) of which are of simplified construction and operate at a high degree of efficiency.

This object is attained according to the invention by the characteristic feature of claim 1.

The flow energy of the fluid is utilized for the volume variations of the container, whence the cinetic energy is directly transmitted to the material to be mixed. This results in optimum utilization of the input energy. Further advantages are the relatively inexpensive construction and simple maintenance.

The characteristic of claim 2 permits the frequency of the pulses generated by the vibrator to be increased without correspondingly increasing the load on the individual container.

Also increased is the vibrator surface in contact with the material to be mixed. Moreover, two containers may be disposed within the drum in such a manner that they direct their vibration pulses to different parts of the mixing drum.

The characteristic of claim 3 results in a further structural simplification, particularly with a view to the installation of the vibrator in a concrete mixer.

The employed fluid may for instance be air, a pressure medium, or water.

Emptying of the container results in a reduction of the volume thereof under the action of the atmospheric pressure and that of the mixture around the container. This reduction of volume may additionally be accelerated by the employ of the characteristic of claim 4.

Claims 5 to 7 relate to structural embodiments of containers offering different advantages with regard to their manufacture and operation. These embodiments may thus be selected with a view to the size and/or operating parameters of the respective concrete mixer.

In a preferred embodiment of the mixer according to the invention as set forth in claim 8, a particularly simple and economical construction is made possible by the provision that the vibrator is energized by the available fluid. It is thus possible to empty the respective containers by directly supplying the mixing water therefrom to the material to be mixed. A more effective supply of the water required for mixing may be carried out in accordance with claim 9. Claims 10 to 12 finally relate to a preferred arrangement for the supply of water to the containers and to the interior of the mixing drum.

Various embodiments of concrete mixers constructed in accordance with the invention shall now be described with reference to the accompanying drawings, wherein: Fig. 1 shows a diagrammatic view of a concrete mixer drum including a vibrator an energizing means therefore, Fig. 2 shows an alternative embodiment of a mixer drum with a vibrator and energizing means, Fig. 3 shows a further embodiment, Figs. 4 to 6 shows different views of a vibrator in different operative conditions, Fig. 7 shows a flow circuit diagram, Fig. 8 shows a longitudinal section through a distributor, Fig. 9 shows a cross-sectional view of the distributor taken along the line IX-IX in fig. 8, with the distributor in one operative position, and Fig. 10 shows a view similar to fig. 9 in another operative position of the distributor.

Diagrammatically shown in fig. 1 are a mixing drum 1 and a water tank 2 of a concrete mixer.

The conventional mounting of the drum on a truck as well as further accessories have been omitted for the sake of clarity. Fixedly attached to the interior wall surface of drum 1 are helical mixing elements 3. Provided adjacent the drum bottom 1 b is an auxiliary mixing aid in the form of a vibrator comprising a container 4 of a resilient material. Container 4 is secured to a carrier 5 projecting into the interior of drum 1 from the bottom 1 b thereof. Carrier 5 includes a conduit 6 (only diagrammatically shown in the drawing) extending through the drum bottom and leading to a distributor 7 outside of the drum. Connected to distributor 7 is a pressure outlet 8 of a pump 9, the inlet of which is connected to another part of distributor 7 via a suction line 10. The inlet of pump 9 is additionally connected to water tank 2.

Associated to distributor 7 is a drive source 11 for a control member 1 2 adapted to alternately connect conduit 6 to the pressure side and the suction side of pump 9. For promoting the mixing operation within drum 1 by the employ of the vibrator, pump 9 and drive source 11 are put into operation. This results in container being intermittently filled so as to be expanded to a substantially spherical shape, and being subsequently emptied so as to decrease its volume. This pulsating volume variation continuously transmits vibration energy to the material to be mixed, specifically in an area adjacent the bottom of the drum, whereat the greatest amount of the material is encountered.

The energy induced into the water by pump 9 is thus transmitted to the material to be mixed with a high degree of efficiency.

Shown in fig. 2 is a mixing drum including a vibrator arrangement substantially similar to the embodiment of fig. 1, with the various parts being therefore designated by the same reference numerals. This embodiment differs from the one of fig. 1 by the following features: Carrier 5 carries two containers 4' connected to dist-;butor 7 by a common conduit 6. The configuration of containers 4' is shown in figs. 4 to 6 on an enlarged scale. The container 4' has a substantially drum-shaped body formed of an annular wall 13 provided with annularflanges 14 at both ends, and of a pair of diaphragms secured to respective ends in such a manner that filling of the container 4' causes them to assume an outwards projecting convex shape (fig. 5), while emptying of the container causes them to assume the concave configuration shown in fig. 6.The latter movement is aided by a tension spring 1 6 disposed within container 4' coaxial with annular wall 13. Tubular spigots 17 are provided for connecting container 4' to conduit g.

In fig. 2 containers are arranged in such a manner that their annular wall 13 faces the drum bottom 1 b. In fig. 5, they are secured to carrier 5 in such a manner that the diaphragms on the one side face the drum bottom 1 b, while those on the other side face the drum opening. In addition, the concrete mixer of fig. 3 differs from the one described above by the construction of the distributor 7', which is only shown diagrammatically in fig. 3. Details of this distributor are shown in figs. 8 to 10.

Shown in fig. 7 is a flow circuit diagram for the embodiment of fig. 3. From water tank 2, a conduit including a throttle 1 8 leads to the suction side of the pump 9. The pressure side of pump 9 is connected to distributor 7' through a pressure conduit 8. A suction conduit 10 connects another portion of distributor 7' to the suction side of pump 9. Distributor 7' contains a rotary valve member 12 adapted to be driven from drive source 11 so as to alternately connect pressure conduit 8 and suction conduit 10 to conduit 6' leading towards vibrator containers 4' within mixing drum 1, while the latter is alternately rotated in opposite directions. Containers 4' are arranged in such a manner that one of them is being filled while the other one is being emptied and vice versa.From the pressure side of pump 9, an auxiliary conduit 21 including a shut-off valve 22, a flow meter 23 and a further throttle 24 leads to the interior of mixing drum 1 to connect therein with at least one spray head 25. This auxiliary conduit serves for supplying the mixing water to the interior of drum 1.

A concrete mixer having a flow conduit arrangement of this type operates as follows: Pump 9 is driven to withdraw water from tank 2 and to supply it under pressure to distributor 7' via pressure conduit 8 and, if valve 22 is open, to the interior of drum 1 through spray nozzle 25. Drive source 11 is energized so as to rotate valve member 12'. The rotary speed of valve member 12' may be empirically adjusted to the desired vibration frequency. The rotation of valve member 12' causes conduits 6' leading to vibrator containers 4' to be alternately connected to the suction side and pressure side of pump 9. Rotary valve member 12' is designed in such a manner that each container is filled and emptied at the same frequency, any one of the containers being filled, while the other one is being emptied. If no mixing water is required, shut-off valve 22 remains closed.Pump 9 is additionally provided with clutch means enabling the water supply to containers 4' to be likewise interrupted. It is also possible to provide a bypass conduit from water tank 2 directly to spray nozzle 25, so as to permit mixing water to be supplied to drum 1 with the vibrator inoperative.

Fig. 8 shows a longitudinal section through distributor 7' in a slightly diagrammatic representation. Distributor 7' comprises a stationary housing 26 in which rotary valve member 12' is mounted by means of bearings 27.

Housing 26 and rotary valve member 12' are of substantially tubular shape closed by a bottom wall. Valve member 12' is additionally formed with a stub axle 12'a extending through the bottom of housing 26 for connection to drive source 11. Located within rotary valve member 12' is a substantially cylindrical core 28 connected to drum 1 so as to rotate in unison therewith. The interior of core 28 is provided with conduit sections 6a and 6b pertaining to the conduit 6' leading to one of the containers 4' each. In addition, core 28 contains a section of auxiliary conduit 21. Corresponding to the number of containers 4', housing 26 is formed at one of its sides with two passages 29 for the connection of pressure conduit 8, and on the other side, with two passages 30 for the connection to suction conduit 10. Immediately adjacent housing 26 pressure conduit 8 and suction conduit 10 are each divided into two branches for connection to the respective two passages 29 and 30 as indicated by phantom lines in fig. 8. The two connection passages 29 and the two connection passages 30, respectively, for the two containers 4' are located behind one another in the longitudinal direction of housing 26, so that the axes of the first connection passages 29 and 30 and those of the second connection passages 29 and 30, respectively, are located in a common plane. The two connection passages 29 and the two connection passages 30 are preferably located radially opposite one another with their axes in longitudinal alignment.The openings of conduit sections 6a and 6b on the peripheral surface of core 28 are arranged in such a manner that rotation of core 28 causes the opening of conduit section 6a and conduit section 6b to be alternately aligned with the connection passages 29, 30 of the first pair and of the second pair, respectively.

Rotary valve member 12' is formed with window-shaped through openings 31 and 32 extending over part of its circumference. The interior surface of rotary valve member 12' facing towards core 28 is formed with annular grooves 31 a, 32a extending from the respective opening 31 or 32 around the remainder of the circumference. In the longitudinal direction of rotary valve member 12', the spacing between openings 31 and 32 and grooves 31 a, 32a, respectively, associated therewith corresponds to that of the pairs of connection passages 29 and 30, respectively, in housing 26, and to that of the openings of conduit sections 6a, 6b in core 28.

As more clearly evident from figs. 9 and 10, openings 31 and 32 and grooves 31a and 32a associated therewith serve to alternately connect conduit sections 6a and 6b, respectively, to connection passages 29 and 30 for pressure conduit 8 and suction conduit 10, respectively, the position of rotary valve member 12' shown in fig. 9 corresponding to that shown in fig. 8, while fig. 10 shows the position of rotary valve member 12' after rotation by a certain angle. In the position of rotary valve member 12' shown in fig. 9, opening 31 has just started to open the flow connection to connection passage 29. In this position, water flows under pressure from pressure conduit 8 through connection passage 29, opening 31 and conduit section 6a and connecting conduit 6' into container 4'.In the position shown in fig. 10, rotary valve member 12' has rotated by a certain angle so as to shut off connection passage 29, while connection passage 30 of suction conduit 10 is now opened. Water is now evacuated from container 4' through conduit 6', conduit section 6a, groove 31 a, opening 31 and connection passage 30 to the suction side of pump 9. As conduit section 6a is connected to connection passages 29 and 30 in the above described manner, the other conduit section 6b is connected to connection passages 30 and 29, respectively, in the same manner, but with a phase shift of 1800. If the two connection passages 29 and the two passages 30, respectively, are located diametrally opposite one another, as indicated above, openings 31 and 32 of rotary valve member 12' will also be formed at diametrally opposite locations.Preferably each opening 31 and 32 extends over about 1400 of the periphery of the rotary valve member 12', the remainder of its periphery being occupied by the respective grooves 31 a and 32a which are closed towards housing 26. The size and/or arrangement of the openings may of course be modified as required, for instance so as to result in a certain overlap in order to avoid pressure shocks.

At a location not covered by rotary valve member 12', the section of auxiliary conduit 21 contained within core 28 is in constant communication with a circumferential groove 33 formed in the interior wall surface of housing 26 and connected to an outwards opening passage.

The circumferential grooves 31 a, 32a and 33 permit core 28 to be rotated in alternating directions corresponding to the mixing rotation af drum 1 without the flow connections through distributor 7' being interrupted at any time.

Moreover, this arrangement permits the conduit sections 6a, 6b and 21 within core 28 to be disposed at any suitable location therein as long as it is ensured that their openings are aligned with the associated grooves 31 a, 32a and 33, respectively.

The invention is not restricted to the embodiment shown and described. The container(s) may also be of different construction and/or shape. The employ of the anyhow available water from the water tank of the concrete mixer is particularly simple and economical. The containers may also be emptied directly into the drum by the employ of pressure-responsive or otherwise controlled valves. It is also possible to provide a separate fluid container for the vibrator with one or more container(s). The expansion of the containers may also be accomplished by the employ of a different pressure medium or of air instead of water.

Claims (13)

1. A concrete mixer, particularly a truckmounted mixer with a fluid-actuatable vibrator disposed in the mixing drum, characterized in that said vibrator comprises at least one container (4 or 4') having a resiliently variable volume and adapted to be alternately expanded by being filled with a fluid and to be subsequently emptied.

2. A mixer according to claim 1, characterized in that there are provided at least two resilient containers (4 or 4') adapted to be alternately filled and emptied.

3. A mixer according to claim 2, characterized in that said containers (4 or 4') form a closed fluid circuit.

4. A mixer according to any of claims 1 to 3, characterized in that each container contains a spring element (16) for contracting it during the emptying phase.

5. A mixer according to any of claims 1 to 4, characterized in that said container essentially consists of a resilient bladder (4).

6. A mixer according to any of claims 1 to 4, characterized in that said container (4') is formed with rigid wall portions (13) and resiliently expansible diaphragms (1 5) extending therebetween.

7. A mixer according to claim 6, characterized in that said container (4') is in the form of a drum comprising a rigid annular wall (13) and bottom walls (15) formed by diaphragms.

8. A mixer according to any of claims 1 to 7, characterized in that a pump (9) for filling and emptying said container(s) is connected to a water container (2) containing the mixing and cleaning water.

9. A mixer according to claim 8, characterized in that there is provided an auxiliary duct (21) for simultaneously feeding the mixing water to the mixing drum (1).

10. A mixer according to any of claims 2 to 9, characterized in that there is provided a distributor (7t) for alternately connecting said containers (4 or 4') to a supply duct (8) and to a return duct (10), said distributor (7') comprising: a housing (26) fixedly connected to said ducts (8 and 10) and having a circular cross-section at least interiorly, a core (28) projecting into said housing (26) and formed with passage means (6 and 6') leading to each of said containers (4'), and a drivingly operable valve member (12') in the form of a hollow body provided with passages (31 and 32) and mounted for rotation between said housing and said core.

11. A mixer according to claim 10, characterized in that said core (28) is part of the rotary mounting of the drum.

12. A mixer according to claim 10 or 11, characterized in that said core (28) and said housing (26) include sections of said auxiliary duct (21) for the mixing water supply.

13. A concrete mixer substantially as herein described with reference to any one of Figures 1 to 3 and Figures 4 to 10.