1. Field of the Invention
The invention concerns a thick matter pump, with two delivery cylinders communicating with a material feed basin via openings situated on an end face, with two hydraulic drive cylinders connected to a reversible hydraulic pump via connections at the piston rod side or piston head side, with a swing oil line connecting the drive cylinder ends opposite to the pump with each other, the drive pistons of the drive cylinders and the delivery pistons of the delivery cylinders being pair-wise rigidly connected with each other via common piston rods, with equalizing lines connected in the area of the two ends of the drive cylinders bridging over the drive pistons at their respective end positions and containing a check or back pressure valve, and with two position sensors provided a defined distance from one of the ends of the drive cylinders, connected to a control device and emitting an end position signal as the associated piston passes by, for controlling the reversal of the hydraulic pump.
2. Description of the Related Art
Two-cylinder thick material pumps of this type are known, in which the two position sensors are provided on one of the two drive cylinders (EP-B 0 446 206). On the other drive cylinder no monitoring of the end position is carried out. It has been found that, depending upon the pressure relationships existing within the cylinder, leakages bypassing the piston can occur, which result in an accumulation of swing oil or in a loss of swing oil, which in turn can result in an advancing or retarding of one of the pistons.
Thus, for example in the case that low oil pressure oil is being supplied to the piston rod side, as for example during the cleaning operation with water, there may result an accumulation of swing oil. This leads thereto, that the piston in the second cylinder is caused to advance, as a result of which this piston when in the end position can come into an undesired slamming mechanical contact with the cylinder. On the other hand, in the case of a high-pressure operation, that is, in the process of thick material conveyance, there can result a loss of swing oil loss as a consequence of a leakage oil bypassing the piston. Thereby in the second cylinder the piston stroke is shortened, so that in the delivery cylinder a clot or plug—hardened concrete—can form. This concrete clot is not pushed out of the delivery cylinder but rather is sucked back in during each suction stroke of the delivery cylinder. It eventually hardens and leads to an elevated friction wear in the delivery cylinder.
In the case of the piston head side connection of the drive cylinder to the hydraulic pump, there results in the low-pressure operation a loss of swing oil. This results in advancing of one of the pistons and in the undesired end-position slamming of the piston in the second cylinder. In high-pressure operation there results in this situation an accumulation of swing oil, which due to the premature switching-over in the first cylinder, can lead to development of a plug in the second cylinder with the above described disadvantages.
Beginning therewith, it is the task of the invention to provide a sensor arrangement in a thick material pump of the type described in the above introductory portion, which prevents both the end position slamming in the case of low pressure operation as well as clot formation in high pressure operation.
The solution of this task is proposed by the combination of characterizing features set forth in Patent Claim 1. Advantageous embodiments and further developments of the invention can be seen from the dependent claims.
The inventive solution is based upon the idea that, by an appropriate arrangement of position sensors on the drive cylinders, a clot development in the delivery cylinders as well an end positioning slamming can be avoided, while with supplemental correcting means an automatic stroke equalization can be achieved. In order to achieve this, it is proposed in accordance with the invention, that the two position sensors are positioned at a specified distance from the piston rod side ends of both drive cylinders, and that in addition a correction sensor is provided at a defined distance from the piston head end of one of the drive cylinders, which in place of the piston rod sided position sensor of the other drive cylinder for a time is activateable for triggering a reverse process. The correction sensor thereby has the task, of carrying out an automatic stroke correction, when the drive piston in the concerned drive cylinder no longer passes over the position of the correction sensor, when on the basis of an internal leakage oil situation this results in a stroke shortening.
Preferably, the correction sensor is activated in defined time intervals respectively for one reversal process. In a preferred embodiment of the invention the requisite amount of reversal occurs. This can occur thereby, that the correction sensor is activateable in the case of a missing piston signal from the correction sensor and the existence of a piston signal of the position sensor associated with the oppositely lying drive cylinder. Therein it has been found to be of advantage, when the control device includes a delay circuit or delay software with a time constant corresponding to at least twice the stroke time of the drive piston for activation of the correction sensor, which is triggered upon missing a piston signal of the correction sensor and the existence of a piston signal at the oppositely lying drive cylinder associated piston sensor, and is reset upon occurrence of the piston signal at the correction sensor. In many application situations it is however sufficient, when the correction sensor is activateable in defined time intervals respectively for one reverse process.
For enhancing the operational reliability it has been found to be of advantage, when respectively two redundant position sensors are provided on the piston rod side.
The position sensors and the correction sensor can be proximity switches or magnetic switches for detecting the passage of the piston in the direction towards the end position, which can be directly connected to the reverse oil flow circuit. It is however basically also possible to provide the position sensors and the correction sensor as signal emitters, which emit an end position signal during the passage by of the piston in the direction towards the end position.
The hydraulic pump is preferably a reversing pump, in particular a slant disc axial piston pump. The same purpose can be accomplished also by a unidirectional conveying hydraulic pump. In this case the pump connections of the drive cylinder are connected with the hydraulic pump via a directional valve.
In principle it is also possible to provide two or more hydraulic pumps, which are connectable to the drive cylinder in parallel arrangement.
In the following the invention will be described in greater detail on the basis of an illustrative embodiment shown in the figures in schematic manner. There is shown in
a and b a schematic of the drive hydraulic for the thick material pump, with reversing pump connected to the piston rod side, with symbolic arrow representation of the leakage flow during low pressure and high pressure operation;
a and b a schematic of the drive hydraulic with reversing pump connected to the piston head side in a representation according to
The thick material pump shown in
The drive cylinders 24′, 24″ are connected at piston rod sided connections 34′, 24″ (
In the illustrative embodiment shown in
Since the drive pistons 30′, 30″ do not lie absolutely fluid-tight in the inner surface of the drive cylinder 24′, 24″, there can occur leakages within the drive cylinder 24′, 24″ during operation according to the magnitude of the piston rod sided and piston head sided pressure differentials existing in the cylinder space. In
In the case of the exemplary pressure relationships shown in
During high pressure operation according to
During piston sided driving according to
During low-pressure operation according to
During high pressure operation according to
The illustrated examples according to
In summary the following can be concluded: the invention relates to a thick matter pump, especially for delivering concrete. The thick matter pump comprises two delivery cylinders 10, which open into a material feed basin 14 via openings 12 situated on the face. The thick matter pump also comprises two hydraulic drive cylinders 24′, 24″ whose pistons 26, 30′, 30″, are rigidly interconnected in pairs via a shared piston rod 28. The drive cylinders 24′, 24″ are connected to a hydraulic reversing pump 42 via piston rod-side and piston head-side pump connections 34′, 34″; 36′, 36″. In addition, they communicate with one another on their ends opposite the pump connections via a swing oil line 44. The drive cylinders and, with them, the delivery cylinders are driven in a push-pull manner via the reversing pump 42. In order to reverse the reversing pump 42, two position sensors 52′, 52″ are provided, which are arranged at a defined distance from one of the ends of the drive cylinders and which respond to a drive piston 30′, 30″ that is passing by. The object of the invention is to prevent the formation of concrete clots inside the delivery cylinders 10 as well as the occurrence of a slamming when the drive pistons 30′, 30″ reach their end of travel. To these ends, the invention provides that both position sensors 52′, 52″ are arranged at a distance from the rod-side ends of both drive cylinders 24′, 24″ and that, in addition, a correcting sensor 54 is arranged at a defined distance from the bottom-side end of one of the drive cylinder 24′. Said correcting sensor can be temporarily activated for initiating a reversing process overruling the rod-side position sensor 52″ of the other drive cylinder 24″.
Number | Date | Country | Kind |
---|---|---|---|
100 36 202 | Jul 2000 | DE | national |
This application is a national stage of PCT/EP01/07415 filed Jun. 28, 2001 and based upon DE 100 36 202.8 filed Jul. 24, 2000 under the International Convention.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP01/07415 | 6/28/2001 | WO | 00 | 1/24/2003 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO02/08605 | 1/31/2002 | WO | A |
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3994627 | Calzolari | Nov 1976 | A |
4490096 | Box | Dec 1984 | A |
5332366 | Anderson | Jul 1994 | A |
5344290 | Benckert | Sep 1994 | A |
5458470 | Mannhart et al. | Oct 1995 | A |
6100608 | Takahashi | Aug 2000 | A |
6171075 | Munzenmaier et al. | Jan 2001 | B1 |
6299416 | Kwag | Oct 2001 | B1 |
6454542 | Back | Sep 2002 | B1 |
6712587 | Gerhardt et al. | Mar 2004 | B2 |
Number | Date | Country |
---|---|---|
38 34 678 | Apr 1990 | DE |
197 16 030 | Mar 1998 | DE |
19716030 | Mar 1998 | DE |
0 446 206 | Jul 1989 | EP |
WO 9006444 | Jun 1990 | WO |
Number | Date | Country | |
---|---|---|---|
20030170127 A1 | Sep 2003 | US |