CA1065188A

CA1065188A - Piston pump for conveying semi-fluid materials

Info

Publication number: CA1065188A
Application number: CA273,969A
Authority: CA
Inventors: Heinz Bille
Original assignee: Maschinenfabrik Walter Scheele GmbH and Co KG
Current assignee: Maschinenfabrik Walter Scheele GmbH and Co KG
Priority date: 1976-03-17
Filing date: 1977-03-15
Publication date: 1979-10-30
Also published as: DE2611124C3; DE2611124A1; FR2344730A1; GB1555629A; DD129480A5; FR2344730B1; DE2611124B2; JPS52129003A; JPS5740354B2

Abstract

ABSTRACT OF THE DISCLOSURE

A piston pump for conveying cement has a piston moveable in an annular working chamber to save space. To reduce sealing problems, the piston is displaced to and fro along a circular path in the working chamber between end positions, and a control device located immediately adjacent the end positions and interrupting the circular path of movement of the piston connects the working chamber in front of the piston to an outlet passage and behind the piston to an inlet passage.

Description

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The present invention relates to a piston pump for conveying semi-fluid materials, for example cement.
It has previously been proposed to provide a cement convey-ing pump with two working cylinders extending parallel to one another, and having inlet and outlet openings controlled by a control device so that an approximately continuous flow of material is produced. In this previously proposed cement conveying pump, two separate working cylinders with pistons movable to and fro therein are indispensible. For increasing the continuity of the material flow and reducing wear in the vicinity of the control device, the length of the working cylinders is suitably large, so that comparatively long conveying strokes are required.
To save space, and to improve the continuity of the material flow, cement pumps with annular working chambers, in which a piston is moved along a circular path, are also known. This form of working chamber makes it possible to provide a conveying stroke of large length in a relatively small space. The cement pumps with circular working chambers known from German Offenlegungschrift 1941409 are provided with at least one piston which is moved uninterruptedly in a rotational direction and also have a control device by means of which a working chamber can be connected before the piston, in a direction of movement, to a pressure or outlet duct and behind the piston, in the direction of movement, to a suction or inlet duct.
These known piston pumps with circular working chambers have the disadvantage that the control device has parts extending into the working chamber which must be removed frcm ; 30 the working chamber as the piston passes thereby.

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Alternatively, the piston can be withdrawn in a radial direction as the piston passes by the control device.
In ~oth cases, sealing problems arise during the passage of t:he piston past the control device, and these problems can hardly be overcome, in particular with an abrasive material, such as cement. For these reasons, cement pumps with annular working chambers have not come into widespread use, in spite of their advantageous construc-tion, which enables a very large working chamber l~ngth to be accommodated within a small space.
It is accordingly an object of the present invention to provide a novel and improved piston pump which has an annular working chamber and can be used for conveying abrasive materials, and which mitigates the above-mentioned sealing problem.
According to the present invention, there is provided a piston pump for the transport of viscous materials and, in particular, concrete, comprising: a housing including a ring-shaped body having a U-shaped cross-section which has defined therein an annular-shaped working space, and a ring-shaped cover which closes said working space; a piston, slidably mounted within said annular-shaped working space, for oscillating movement; a pressure conduit and a suction conduit, each of which is commun-icative with said working space; control means for connecting the portion of said working space, which lies in front of the moving piston, to said pressure conduit and for simultaneously connecting the portion of said working space which lies in back of the moving piston, to said suction conduit; said control means, including a member which is disposed in said annular-shaped working _ ~_ A~

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space; and means for reversibly driving said piston so thalt said piston moves in an oscillating manner in said annular working space, reversing its direction when said piston nears said member of said control means disposed in said annular-shaped working space, said means for driving inc:Luding a drive ring, slidably supported on the under-side of said cover, to which said piston is secured, said piston projecting downwardly therefrom into said working space of said body.
Due to the to and fro movement of the piston, the piston and the control device, which extends into the annular shape of the working chamber, are not damaged.
The control means can therefore, without further measures, be constructed as in conventional two cylinder piston pumps. In this connection, preferred constructions are available which can handle even - 2a -A

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abrasive material satisfactorily. The section of the annular working chamber located in advance of the piston, with respect to the direction of movement, serves as the working chamber in the pressure stroke while simultaneously the section of the working chamber located behind the piston, in the direction of movement, serves as the working chamber in the suction stroke.
For each conveying stroke, which is simultaneously the suction stroke, almost the entire length of the annular working chamber is, therefore, available. In particular, when designing the piston, with respect to its shape and material, no account need be taken of the form of the control means, so that, for example, a highly wear-resistant and self-sealing rubber piston can be employed as the piston. Such a well-sealing piston is particularly important in a cement pump, since with even a small leakage, water is expelled from the material being conveyed in the vicinity of the leakage, whereby a solid plug is formed by which the wear is increased and which can lead to blockages in a succeeding duct system. A further advantage of the present piston pump is that the pump can be driven forwardly and back-wardly such that the pump sucks in material through the pressureor outlet passage and presses the material back into the suction or inlet passage. This manner of operation is necessary in order to be able to empty a conveyor system connected beyond the pump. Such reversed operation is not possible with prior system pumps having annular working chambers.
According to a preferred embodiment of the subject matter ~ of the invention, the control means comprise a double-vaned ; valve mounted on a valve shaft in the vicinity of the circular path for to and fro movement, and the inlet and outlet passages comprise connectiOn passages extending in opposite directions radially of the working chamber for communicating with an inlet duct and an outlet duct, respectively. Such double vaned valves have been found to be very suitable for controlling through flow of cement in double cylinder cement pumps. The incorporation of such a valve in a pump embodying the present invention is particularly advantageous since a compact arrangement of the connection passages is made possible, and the deflection of the conveyed material in the vicinity of the control means can be particularly advantageously arranged.
Alternatively, the control means may comprise a dividing wall extending across the working chamber, and the working chamber may communicate at opposite sides of the dividing wall with the inlet and outlet passages, which are parallel to one another, valve means, for example a flat slide valve, a rotary valve or a flat valve, being provided for alternately con-necting the inlet and outlet passages to the inlet and outlet ducts. The use of parts extending into the working chamber is thus avoided in an advantageous manner.
Preferably, the working chamber is provided in an annular body having a U-shaped cross-section forming a recess, the top of the recess enclosed by a corresponding annular cover, and a drive ring being rotatably supported on the underside of the cover and carrying the piston, which projects downwardly into the recess of the annular body. This construction facilitates easy assembly or dismantling, and thus facilitates a simple replacement of worn parts. Moreover, and in a simple manner, the center of the ring is kept free of driving and bearing devices, so that the outlet duct and/or the inlet duct can extend to the center of the ring. The drive ring is preferably supported by ball bearings against the cover and sealed by O-rlngs or annular seals to the annular body.
The drive ring is also preferably formed with an annular gap, the cover closiny the top of the annular gap, and a hydraulic motor mounted on the ~over may have a drive pinion meshing in the ~ap with an annular toothing formed on the drive ring at one side of the gap. This form of drive arranqement avoids, in a particularly advantageous manner, the provision of moving parts on the exterior of the pump.
The gap in the drive ring may be filled with oil under pressure for lubricating the drive pinion and the annular toothing. This oil under pressure also prevents the cement from passing from the working chamber into the vicinity of the bearings and the annular toothing of the drive ring.
To facilitate replaceability, the piston is preferably releasably secured by screws to the drive ring.
In order to allow replacement of the piston, if required, without removal of the cover from the annular body, the control means may be removable from between the end positions, the piston then being movable between the end positions from the working chamber.
The invention will be more readily understood from the following description of the preferred embodiment thereof given, by way of example, with reference to the accompanying drawings, in which:-Figure 1 shows a plan view of a piston pumpembodying the invention partly broken away in section;
Figure 2 shows a view taken in section along the line A-B of Figure l;
Figure 3, which appears on the same sheet as Figure 1, shows a view taken in section along the line C-D
of Figure l; and lQf~Sl~

Figure 4 shows a detail, taken in horizontal section, of a part of a modified embodiment of the control means.
The cement pump illustrated in Figures 1 to 3 of the accompanying drawings has an annular body 1 of U-shaped cross-section, to which a correspondingly annular cover 2 is secured by screws, the cover 2 being mounted on the annular body 1 by means of annular inserts 3 and 4, and covering and closing the top of the annular recess of the annular body 1, which recess forms a working chamber la of the pump. The annular inserts 3 and 4 are provided with rounded support shoulders 3a and 4a, on which the balls of two axial ball bearings 5 and 6 run. The balls of the ball bearings 5 and 6 support an underlying drive ring 7. This drive ring has, at its upper side, an annular gap 8, which is covered at its top by the cover 2 and the outer side wall of which has an internal annular toothing 9. A drive pinion 10 of a hydraulic motor 11 meshes with this annular toothing 9, the hydraulic ~otor 11 being mounted on the cover 2.
The drive ring 7 is sealed relative to the annular body 1 and the inserts 3 and 4 by O-rings or annular seals 12. The annular gap 8 in the drive ring 7 is filled with oil under pressure.
A rubber piston 14 is secured to the underside of the drive ring 7 by screws 13 and is displaceable, by rotation of the drive ring 7, in the working chamber la of the annular body 1.
The exterior of the rubber piston 14 sealingly contacts the ;- walls of the working chamber la.
The annular working chamber la is interrupted by a control means indicated generally by reference numeral 15, which serves ~; to connect the section of the working chamber la which is under pressure to an outlet duct 21 of the pump and the section of the working chamber la which is under exhaustionwith an inlet duct 19 of the pump.
In the embodiment of the invention illustrated in Figures 1 to 3, the control means 15 comprise a double-vaned flap valve 16, which is pivotable by means of an operating shaft 17. In the vicinity of the valve 16, the inlet duct 19 communicates in a radial direction through a connecting passage 18 with the working chamber la. Opposite the inlet connecting passage 18, the outlet duct 21 and an outlet connecting passage 20 are connected to the working chamber la in the radial direction.
By rotation of the valve 16 by means of the actuating shaft 17, the section of the working chamber la which, depending on the direction of rotation of the piston 14, is under pressure, can be connected to the outlet connecting passage 20 and the section of the working chamber la which is under exhaustion can be connected to the inlet connecting passage 18. The piston 14 is driven to and fro by the hydraulic motor 11 through the drive ring 7 in such a manner that it reverses it's direction of movement at end positions of it's circular path of movement shortly before reaching the control means 15.
The actuating shaft 17 of the control means 15 is mounted on a plate 22, which is screwed from beneath to the annular body 1.
After release of this plate 22, the valve 17 can be withdrawn downwardly from the vicinity of the working chamber la, i.e. from between these end positions. With the valve 17 removed, the rubber piston 14 can ~e displaced beyond either of its end positions into the space previously occupied by the control means 15. In this position, the rubber piston 14 can be released from the drive ring 17 by unscrewing the screws 13, and then falls downwardly through the opening previously occupied by the i~s~
plate 22. In the reverse sequence, and in a corresponding manner, a new piston can be inserted without having to remove th,e cover 2 from the annular body 1. The removable control means 15 thus enables a particularly simple replacement of the rubber piston 14.
A further embodiment of the control means is illustrated in Figure 4, in which the control means takes the form of a fixed separating wall 23 extending across the working chamber la, and the working chamber la communicates at opposite sides of the separating wall 23 with two parallel inlet and outlet passages 24 and 25. These two passages 24 and 25 are alter-nately connected, by means of a flat slide valve, a rotary valve or a flap valve, to an inlet duct and an outlet duct, as, for example, is known with conventional two cylinder cement pumps.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A piston pump for the transport of viscous materials and, in particular, concrete, comprising:
a housing including a ring-shaped body having a U-shaped cross-section which has defined therein an annular-shaped working space, and a ring-shaped cover which closes said working space;
a piston, slidably mounted within said annular-shaped working space, for oscillating movement;
a pressure conduit and a suction conduit, each of which is communicative with said working space;
control means for connecting the portion of said working space, which lies in front of the moving piston, to said pressure conduit and for simultaneously connect-ing the portion of said working space which lies in back of the moving piston, to said suction conduit; said control means, including a member which is disposed in said annular-shaped working space; and means for reversibly driving said piston so that said piston moves in an oscillating manner in said annular working space, reversing its direction when said piston nears said member of said control means disposed in said annular-shaped working space, said means for driving including a drive ring, slidably supported on the under-side of said cover, to which said piston is secured, said piston projecting downwardly therefrom into said working space of said body.

2. The piston pump according to Claim 1, additionally including a pair of connector pipes, disposed opposite one another, one of which is disposed radially inwardly of said working space and the other of which is disposed radially outwardly of said working space, with one of said pipes connecting said pressure conduit to said working space and the other of said pipes connecting said suction conduit to said working space, and wherein said member of said control means comprises a two-bladed wing flap and said control means comprises a rotatably-mounted flap shaft on which said wing flap is mounted, said shaft being reversibly, rotatably driven so that said wing flap alter-natingly connects the portion of said work space on the opposite sides thereof with said pressure and suction conduits through said connecting pipes.

3. The piston pump according to Claim 1, wherein said drive-ring is slidably supported on said cover by means of axial ball bearings, and said drive-ring has O-rings or loop gaskets which abut against said body.

4. The piston pump according to Claim 1, wherein said drive-ring has an outwardly-opening, radially-extending channel formed therein, which is covered from above by said cover, and a gear-ring mounted on the sidewall of said channel, and wherein said drive means includes a drive-motor mounted on said cover, and a drive pinion coupled to said drive motor, which is disposed in said channel and in meshing engagement with said gear-ring.

5. The piston pump according to Claim 1, wherein said channel of said drive-ring is filled with pressurized oil.

6. The piston pump according to Claim 1, wherein said piston is detachably mounted by screws to said drive-ring.

7. The piston pump according to Claim 6, wherein said control means is removably mounted on said body.

8. The piston pump according to Claim 1, wherein said piston is fabricated from rubber.