EP0748938A1

EP0748938A1 - Device and method for pumping mortar

Info

Publication number: EP0748938A1
Application number: EP95201647A
Authority: EP
Inventors: Geurt Gerritsen
Original assignee: BREMAT BV
Current assignee: BREMAT BV
Priority date: 1995-06-16
Filing date: 1995-06-16
Publication date: 1996-12-18

Abstract

A closing device (1,1') used, for instance, in pumping thin-fluid mortar using a piston pump (7), wherein a shut-off body (2) in the open position rests on supports (6) and in the closed position abuts against a seal (4). The shut-off body is movable in a guide between the open and closed position.

The guide is formed by a guiding cage of at least three bars (3, 3') whose centreline is parallel to the direction of travel of the shut-off body.

Piston pump (7) for pumping, for instance mortar, under high pressure, equipped with two driven cylinders (8, 9), each comprising a closing device (1, 1') both on the inlet side and on the outlet side, and a method for pumping mortar under high pressure using such piston pump (7).

Description

The invention relates to a closing device used, for instance, in pumping thin-fluid mortar using a piston pump, wherein a shut-off body in the open position rests on supports and in the closed position abuts against a seal.
In the conventional manner of closing off the inlet opening of a piston pump for pumping thin-fluid mortar, a ball of a relatively large diameter is pressed against a seal or seat. When the pump is being filled by suction, this ball rests on supports. In the area between the supports and the seat, the ball can move freely, with the mortar flow pressing the ball against the seal during discharge and against the supports when the piston pump is being filled.
A disadvantage of this ball closure device is that in the pumping of thin-fluid mortar which may contain pebbles (gravel), such pebbles may become stuck between the ball and the seat during the discharge of the piston pump. Because the ball can tilt and move laterally, the inlet opening is no longer fully closed. The efficiency of the piston pump decreases in that during discharge of the pump a part of the mortar is forced back into the inlet opening again. In particular the water from the mortar is forced back, giving rise to "dry" sand-gravel plugs which may cause clogging of the piston pump and the lines. Moreover, the ball and the seat are subject to wear if mortar is forced back through a narrow gap during the discharge of the piston pump. The ball may, for instance, no longer be spherical and grooves may form in the seat. As a result, the closing device no longer provides a watertight seal, even if no gravel is stuck between the ball and the seat.
The object of the invention is to provide a closing device which also functions properly if pebbles are present in the mortar.
To that end, the invention is characterized in that the shut-off body is movable in a guide between the open and closed position. By virtue of the guide, the sealing face of the shut-off body is pressed straight against the seal. Due to the increasing pressure during discharge of the pump, any pebbles present between the seal and the shut-off body are pushed away.
A particularly suitable embodiment of the closing device according to the invention is formed by a guiding cage comprised of at least three bars whose centreline is parallel to the direction of travel of the shut-off body. Thus, the passage behind the inlet opening remains as large as possible and the guiding of the shut-off body is ensured.
A good result is obtained if the shut-off body has a cylindrical shape. This provides for a good guiding of the shut-off body in the guiding cage.
The seal is formed by a ring having a projecting edge which is directed to the sealing face of the shut-off body. As a result, pebbles which are present between the shut-off body and the seal during the closure of the closing device can be pushed away more easily.
To enhance the pebbles being pushed away, the height of the projecting edge is greater than the diameter of a pebble and the edge is of conical design on its exterior periphery. Upon closure of the closing device, the mortar with the pebbles is pushed away laterally and the chances of a pebble getting stuck are reduced considerably.
The invention further relates to a piston pump for pumping, for instance mortar, under high pressure, which is equipped with at least two driven cylinders comprising a closing device both on the inlet side and on the outlet side. Owing to the proper sealing of the closing devices, the pressure in the piston pump can be raised and the efficiency of the pump can be improved.
The invention also relates to a method for pumping mortar with a piston pump as described above. In the method, just before the end of the pumping stroke of the first piston, the pumping stroke of the second piston is initiated. Then the first piston, after completing the pumping stroke, is moved back at an accelerated pace, in order to be ready to initiate the next pumping stroke just before the end of the pumping stroke of the second piston. The second piston, after completing the pumping stroke, is moved back at an accelerated pace. As a result, the flow of material in the outlet line does not come to a standstill and no pulsatory action is involved. Setting the material flow into motion again, in particular, is accompanied by high pressure peaks. Due to the absence of a pulsating material flow, the transport hose no longer jerks back and forth. Due to the absence of peak pressures, the required power is reduced and moreover the piston pump can work at a higher pressure, which yields a higher efficiency.
The drive of the piston pump using a hydraulic pump can be effected advantageously in that all oil is pumped to the delivery side of the first cylinder, while just before the end of the pumping stroke of the first piston, half of the oil is pumped to the delivery side of the second cylinder, and upon completion of the pumping stroke of the first piston, all oil is pumped to the rod side of the first cylinder, while the oil situated on the delivery side of the first cylinder is passed to the delivery side of the second cylinder, and then upon completion of the return stroke of the first cylinder all oil is pumped to the delivery side of the second cylinder. Just before the end of the pumping stroke of the second piston, the cycle is repeated, with the first and the second piston changed round. In this way the drive of the piston pump, and hence the pumping of the mortar, takes place without pulsations. Also, the material flow remains in motion continuously, so that the occurrence of peak pressures is prevented.
One embodiment of the closing device and of the piston pump according to the invention will be further clarified with reference to the accompanying drawings. In the drawings:

Fig. 1 shows a closing device, which is arranged both at the inlet opening and at the outlet opening of a piston pump and is depicted in cross section;
Fig. 2 is a top plan view of a piston pump with two cylinders and an outlet manifold; and
Fig. 3 is a cross section of the piston pump along the line III-III in Fig. 2.

The closing device 1 which is shown in Fig. 1 is arranged behind the inlet opening of a piston pump casing, depicted in part. The outlet opening comprises a similar closing device 1'. The closing device 1, 1' is equipped with a guiding cage which consists of four bars, of which only two 3, 3' are shown. Within this guiding cage a shut-off body 2 is arranged so as to be freely movable. The shut-off body 2 has a cylindrical shape and is preferably of hollow design. In the open position, the stroke of the shut-off body 2 is limited by a support 6 in the form of two round bars. In the closed position, the shut-off body 2 is pressed against a seal in the form of a ring 4. Owing to the round shape of the bars 3, 3' of the guiding cage and the bars 6 of the supports, the mortar flow is disturbed to the least possible extent during the filling and discharge of the piston pump.
In order to reduce the chances of a pebble getting stuck between the sealing ring 4 and the shut-off body 2, the sealing ring 4 can be provided with a projecting edge 5. This projecting edge 5 points to the sealing face of the shut-off body 2. Due to this edge 5 the pressure between the sealing ring 4 and the shut-off body 2 is increased. To that end, the sealing ring 4 is manufactured from a hard and impact-resistant material.
Further, the height of the projecting edge 5 is greater than the diameter of a pebble and the edge is of conical design on the exterior perimeter thereof. As a result, upon closure of the closing device 1, 1' the mortar with the pebbles is displaced laterally and the chances of a pebble getting stuck are reduced considerably.
In Fig. 1 the outlet side of the piston pump also comprises a closing device according to the invention.
It will be clear that within the framework of the invention the shut-off body 2 can also have a different, non-cylindrical shape, and so can the bars 3, 3' of the guiding cage.
In Fig. 2 a piston pump 7 is shown in top plan view. This piston pump 7 is equipped with two parallel, driven cylinders 8, 9. Arranged at the outlet openings of the two cylinders 8, 9 is a manifold 12, which ends in a common duct.
As shown in Fig. 3, both the inlet opening and the outlet opening comprise a closing device 1 and 1', respectively. By virtue of the proper sealing of the closing devices 1, 1', the pressure in the piston pump 7 can be raised and the efficiency of the pump can be improved.
A particularly suitable method for pumping mortar with a piston pump as described above proceeds as follows. Just before the end of the pumping stroke of the first piston 10, the pumping stroke of the second piston 11 is initiated. Then the first piston 10, after completing the pumping stroke, is moved back at an accelerated pace in order to be ready to initiate the next pumping stroke just before the end of the pumping stroke of the second piston 11. The second piston 11, after completing the pumping stroke, is also moved back at an accelerated pace. As a result, the material flow in the outlet duct 12 does not come to a standstill and no pulsatory action is involved. Setting the material flow into motion again, in particular, is accompanied by high pressure peaks. Due to the absence of a pulsating material flow, the transport hose no longer jerks to and fro. Due to the absence of peak pressures, the required power is reduced and moreover the piston pump 7 can work at a higher pressure, which yields a higher efficiency.
The piston pump 7 can be equipped with two hydraulic pumps or one hydraulic pump for both cylinders (the hydraulic pump is not shown). A highly advantageous method for pumping mortar with a piston pump comprising a hydraulic pump for driving the cylinders is characterized in that all of the oil is initially pumped to the delivery side of the first cylinder 8. Just before the end of the pumping stroke of the first piston 10, half of the oil is pumped to the delivery side of the second cylinder 9 and the other half still to the first cylinder 8. Upon completion of the pumping stroke of the first piston 10, all of the oil is pumped to the rod side of the first cylinder 8, while the oil located on the delivery side of the first cylinder 8 is guided to the delivery side of the second cylinder 9, so that the second cylinder 9 is also driven. After the return stroke of the first cylinder 8, all of the oil is pumped to the delivery side of the second cylinder 9, until, just before the end of the pumping stroke of the second piston 11, half of the oil is pumped to the delivery side of the first cylinder 8. The other half is still being pumped to the second cylinder 9. Upon completion of the pumping stroke of the second piston 11, all of the oil is pumped to the rod side of the second cylinder 9, while the oil located on the delivery side of the second cylinder 9 is guided to the delivery side of the first cylinder 8, so that the first cylinder 8 is also driven. In this manner, the drive of the piston pump and hence the pumping of the mortar takes place without pulsations. Also, the material flow remains in motion continuously, so that the occurrence of peak pressures is prevented.

Claims

A closing device used, for instance, in pumping thin-fluid mortar using a piston pump, wherein a shut-off body in the open position rests on supports and in the closed position abuts against a seal, characterized in that the shut-off body (2) is movable in a guide (3, 3') between the open and closed position.
A closing device according to claim 1, characterized in that the guide (3, 3') is formed by a guiding cage having at least three bars (3, 3') whose centreline is parallel to the direction of travel of the shut-off body (2).
A closing device according to claim 1 or 2, characterized in that the shut-off body (2) has a cylindrical shape.
A closing device according to claim 3, characterized in that the shut-off body (2) is hollow.
A closing device according to claims 1-4, characterized in that the seal (4) is a ring having a projecting edge (5) which is directed to the sealing face of the shut-off body (2).
A closing device according to claim 5, characterized in that the height of the projecting edge (5) is greater than the diameter of a pebble.
A closing device according to claim 6, characterized in that the projecting edge (5) is conical on the exterior perimeter thereof and has a rounded top.
A closing device according to claims 5-7, characterized in that the seal (4) is a sealing ring of hard and impact-resistant material.
A piston pump for pumping, for instance mortar, under high pressure, comprising a closing device according to any one of the preceding claims, characterized in that the piston pump (7) is equipped with at least two driven cylinders (8, 9), which comprise a closing device (1, 1') both on the inlet side and on the outlet side.
A method for pumping mortar with a piston pump according to claim 9, characterized in that just before the end of the pumping stroke of the first piston (10), the pumping stroke of the second piston (11) is initiated, then the first piston (10), after completing the pumping stroke, is moved back at an accelerated pace in order to be ready to initiate the next pumping stroke just before the end of the pumping stroke of the second piston (11), and the second piston (11), after completing the pumping stroke, is moved back at an accelerated pace.
A method for pumping mortar with a piston pump according to claim 10, comprising a hydraulic pump for driving the cylinders, characterized in that all of the oil is pumped to the delivery side of the first cylinder (8), while just before the end of the pumping stroke of the first piston (10), half of the oil is pumped to the delivery side of the second cylinder (9), while upon completion of the pumping stroke of the first piston (10) all of the oil is pumped to the rod side of the first cylinder (8), while the oil located on he delivery side of the first cylinder (8) is passed to the delivery side of the second cylinder (9), and then upon completion of the return stroke of the first cylinder (8) all of the oil is pumped to the delivery side of the second cylinder (9).