EP0057288B1 - Two cylinder pump for viscous materials, particularly a concrete pump with a connecting element pivoting in front of a two orifice plate beside the cylinders - Google Patents

Description

The invention relates to a two-cylinder thick matter pump according to the preamble of claim 1.

Such pumps have to cope with a conveying medium which generally consists to a relatively large extent of hard and differently sized particles which are formed by the sand and gravel grains in concrete. In operation, the switching element executes a large number of movements in time with the piston strokes in the cylinders in order to connect the respective delivering cylinder to the delivery line and the aspirating cylinder to a prefilling container. The cutting ring acts on the one hand as a metallic seal with the spectacle plate and, on the other hand, breaks solid bodies which are contained in the medium to be conveyed and which cannot move away from the parts moving relative to one another during the movement of the switching element. The cutting ring must therefore be held on the eyeglass plate with considerable pressure. On the other hand, it must be able to move relative to the spectacle plate and the switching element to compensate for the wear that forms on it and on the spectacle plate.

It is known to mechanically pretension the cutting ring with the switching element (DE-OS 2362670); for this purpose, it is provided that the switching element, which is designed as a swivel tube, is elastically connected via a swivel arm to a switching shaft which is axially movable for pretensioning the swivel arm. The disadvantage here, however, is that elastic deformation of the mechanical parts creates a gap on the eyeglass plate and the compensation of uneven wear on the eyeglass plate and the cutting ring is not possible.

It is also known to replace this mechanical preload with a hydraulic preload (DE-OS 2 835 590), which is so variable that the greater contact pressure is generated when the switching element designed as a swivel tube is aligned with one of the cylinder openings. On the other hand, the contact pressure is practically eliminated from the beginning to the end of the swiveling movement. This results in a gap formation that is dangerous because of the hard particles in the material being conveyed. In addition, the oil hydraulic preload is questionable because of the possible damage to the concrete from the hydraulic fluid.

In a further advanced solution (DE-OS 2 632 816), on the other hand, the pretensioning of the cutting ring is applied without loading the switching element designed as a swivel tube via the swivel arm described, by connecting the cutting ring to the swivel arm with a joint. As a result, however, uneven wear of the cutting ring and the spectacle plate cannot be compensated for in all directions, so that sooner or later there is a gap that can no longer be eliminated.

It is known (DE-OS 2 903 749) to use the hydrostatic forces of the conveyed material to press the switching element designed as an S-shaped swivel tube hydrostatically and by axially pressing together a square sealing ring clamped on the delivery line side in the direction of the spectacle plate. However, the mechanical compression of the rubber-elastic ring generates only slight axial forces because the seats allow the rubber-elastic ring to deflect inwards over the entire length of its axially inner surface. In this device, the cutting ring is supported on a bearing in which spherical surfaces cooperate with one another in order to give the cutting ring a possibility of movement which enables the wear on the spectacle plate and the cutting ring to be compensated for.

The arrangement of the sealing ring, the swivel tube specified by the desired functions and its S-shape lead to difficulties.

Because the friction of the material to be conveyed in such a swivel tube results in a particular drop in pressure. The pressure drop in the operation of the pump can suddenly increase significantly, for. B. if a plug is formed in the switching element. In this case, the cutting ring is practically only elastic and therefore preloaded with a force that is far too low. The gimbal mounting of the cutting ring in turn causes considerable difficulties.

A previously known solution (DE-OS 2614895) is based on the idea of achieving the hydrostatic differential pressure on the one hand by means of a low load on the sealing surface of the cutting ring with the hydrostatic pressure of the conveying medium in favor of a greater load on the rear side of the cutting ring with this pressure presses the cutting ring onto the spectacle plate with increased force and, on the other hand, prestresses the sealing ring necessary for sealing the cutting ring, which can also be rectangular, radially in such a way that the sealing ring in turn slightly elastically prestresses the cutting ring. Under operating conditions, however, this radial prestress cannot be converted into a notable prestressing force of the cutting ring on the spectacle plate. However, since the pump not only has to work in the pressure mode, but also in the suction mode, the sealing ring is often lifted off its seat during the suction mode of the pump and is lost in the pumped medium.

In addition, it has the disadvantage that the rubber-elastic sealing ring and the cutting ring are practically only pretensioned by the hydraulic pressure, because therefore a sufficient pressure of the cutting ring on the spectacle plate is not achieved during the pivoting movement of the switching element or the switching process. Wear can only be compensated by retightening the Swivel tube bearing possible with the help of several tie rods. However, this is associated with considerable dangers for the pump, because even slight deviations of the swivel axis from its structurally predetermined position lead to considerable damage and destruction on the switching element. Uneven wear cannot be compensated for practically on the cutting ring, so that a gap formation is inevitably associated with such wear phenomena. In addition, it is practically impossible to prevent this ring from lifting off its seat by means of metallic spreading devices which are incorporated into the sealing ring, which is made of an elastomer.

The invention is based on a further likewise known two-cylinder thick matter pump (DE-A-2 829 181). Here, the rubber-elastic ring sits only in corresponding recesses of the cutting ring and the switching element, so that there is an annular space between the outside of the rubber-elastic ring and the axial guidance of the cutting ring, which is acted upon by the pressure of a buffer medium made of oil or fat. Apart from the fact that such a buffer medium is a concrete pest that can easily get into the pumped concrete and cause the concreting to fail, the pressures of the buffer medium cannot be made as high in all phases of the switching element as those on the rubber-elastic ones Ring-acting concrete press.

The invention has for its object to achieve a reliable pressure of the cutting ring on the eyeglass plate and an automatic compensation of wear on the eyeglass plate and the cutting ring without a loss of the rubber-elastic ring to a pump of the latter type even during the switching process fear.

This object is achieved according to the characterizing part of claim 1.

This ensures that a long-stroke spring can be realized with the rubber-elastic ring. As is known, this ring forms a Poisson body, which does not change its volume when pressed together. Here, one chooses in realizing the invention, on the one hand, the axial mobility of the cutting ring limited by the stop faces so that the rubber-elastic ring is not lifted and squeezed out of its seats and z. B. can be carried away by the material to be conveyed. On the other hand, the surface of the rubber-elastic ring which is exposed between the two ring extensions can be matched to the dimensions of the seats in such a way that this ring cannot deflect when pressurized and can generate the desired axial contact force. In this case, the rear length of the cutting ring, which is immersed in the guide under operating conditions, can be dimensioned so short that the cutting ring is axially readjusted when worn and carries out a wobbling movement during switching over with uneven wear and compensates for this.

With such a long-stroke rubber-elastic ring spring, the ring spring surface exposed between the seats can be removed from the hydrostatic pressure of the material to be conveyed and nevertheless the mechanical preload of the ring spring can be used to press the cutting ring onto the spectacle plate. These embodiments of the invention are the subject of claim 2. You can with hydrostatic pressure of the cutting ring by hydrostatic _. Combine table forces on differential surfaces on the cutting ring.

In other cases, the rubber-elastic ring, in turn, and thus also its seating surfaces on the cutting ring, are exposed to the hydrostatic pressure of the conveyed material and mechanically pretensioned so that the cutting ring is pressed onto the spectacle plate. Such embodiments are the subject of claim 3. These embodiments can also be combined with a hydrostatic prestressing of the cutting ring by differential surfaces.

In general, it can be assumed that the gap pressure is not constant when viewed over the end face of the cutting ring on the side of the spectacles plate, but is distributed according to a function according to which the pressure drops from the inside to the outside. Since the counter surface loaded with the hydrostatic pressure on the cutting ring and if the seat of the rubber-elastic ring is inside, the seat surface of the cutting ring is also fully loaded with the hydrostatic pressure, the hydrostatic contact pressure of the cutting ring over differential surfaces can generally be with a cylindrical one Reach the inside surface of the cutting ring. This is the subject of claim 4. However, the size of this hydrostatic pressure can be varied until the differential forces arising on the ring surfaces of the cutting ring are completely compensated.

This is done by the conical surfaces characterized in claim 5. The embodiment according to claim 6 is a further means for this, in particular for the hydrostatic compensation.

• Fig. 1 schematisch zur Wiedergabe des Bewegungsablaufs des Schaltorgans eine Ansicht der Öffnungen der Förderzylinder einer Zweizylinder-Kolbenpumpe gemäß der Erfindung im Schnitt längs der Linie I-I der Fig. 2,
• Fig. 2 einen Schnitt längs der Linie II bis IX der Fig. 1,
• Fig. 3 in der Fig. 2 entsprechender Darstellung diese Ausführungsform in vereinfachter Wiedergabe sowie darunter eine schematische Darstellung der hierbei auftretenden statischen Drücke, welche unmittelbar auf den Schneidring einwirken,
• Fig. 4 bis 7 in der Fig. 3 entsprechender Darstellung abgeänderte Ausführungsformen der Erfindung,
• Fig. 8 eine weiter abgeänderte Ausführungsform und,
• Fig. 9 einen besonderen Betriebszustand dieser Ausführungsform, jeweils in den Fig. 3 bis 7 entsprechender Darstellung.

The details, further features and other advantages of the invention result from the following description of several embodiments with reference to the figures in the drawing. It shows

• 1 schematically shows the openings of the delivery cylinders of a two-cylinder piston pump according to the invention in section along the line II of FIG.
• 2 shows a section along the line II to IX of FIG. 1,
• Fig. 3 in Fig. 2 corresponding representation this embodiment in a simplified representation as well as below it a schematic representation of the static pressures occurring which act directly on the cutting ring,
• 4 to 7 in the representation corresponding to FIG. 3 modified embodiments of the invention,
• 8 shows a further modified embodiment and,
• Fig. 9 shows a special operating state of this embodiment, each in Figs. 3 to 7 corresponding representation.

The pipe-side openings of the two delivery cylinders of a two-cylinder thick matter pump are shown by their inner edges at 1 and 2 in FIG. 1. A switching element 3, which is not shown in its details, swings over an arc 4 about the pivot axis 5 drawn at 5 in FIG. 1. In its end positions indicated by the dash-dotted lines 6 and 7, the switching element 3 in each case closes the connection from the relevant delivery cylinder the delivery line, not shown, while the other delivery cylinder is connected to a prefilling container from which it can suck concrete. Therefore, the pressure in the switching element briefly collapses during the switching movement if the conveyed medium can escape in the prefilling container.

According to FIG. 2, the housing 8 receiving the mouths of the delivery cylinders is covered with an eyeglass plate 9; this has recesses 10 for each feed cylinder, which are aligned with corresponding recesses 11 in the housing 8. The eyeglass plate 9 is fastened to the housing 8 by means of screws 12 with countersunk heads 13.

The connection to the switching element 3 produces a cutting ring 14 according to the exemplary embodiments shown. In a departure from the exemplary embodiments, the cutting ring 14 could be mounted in an intermediate ring. It lies in a guide, generally designated 15, which is formed in the cylinder-side end 16 of the switching element 3. The guide consists of a cylindrical surface 17 at the end 16 of the switching element 3 and a corresponding cylindrical surface 18 on the cutting ring 14. In operation, the cutting ring 14 normally plunges into the guide 15 with its length a. Stop faces 19, 20 on the end face of the end 16 of the switching element 3 or an outer ring flange 21 of the cutting ring 14 serve as stops which limit the immersing length of the cutting ring.

The embodiment of the invention shown in FIGS. 1 and 2 is drawn out in FIG. 3 with its functionally important parts. The cutting ring 14 encloses an opening 1 or 2 in the end positions of the switching element 3. If the pivoting movement is carried out during the switching process, the material to be conveyed must be severed shortly before reaching the end positions, which jams between the cutting ring and the spectacle plate. In order to achieve a full contact of the cutting ring 14 during the cutting movements occurring here between the cutting ring 14 and the spectacle plate, the cutting ring 14 is only guided for a short length, namely the length labeled a, and is supported on a rubber-elastic ring spring 23. The initial cross section of the ring spring is that of a rectangle. It is arranged so that its shorter sides of the rectangle 24 and 25 are oriented radially, while the longer sides of the rectangle 26 and 27 run axially. When installing the ring spring, it is mechanically axially preloaded. As a result, the ring spring deforms in an arc shape on an exposed surface between the seats.

The seat of the annular spring 23 consists, on the one hand, of the cylindrical extension 29 of the guide surface 17, which accordingly extends axially, and also the radial surfaces 30 and 31, which in the exemplary embodiment are formed by back-turning of the switching element 3 or the cutting ring 14. This results in all embodiments, as shown in the example in FIG. 4, ring extensions 33, 34 on the switching element 3 or on the cutting ring 14, which on opposite sides, which are provided by the seat surfaces 30 and 31, partially covered partial surfaces 35, 36 of the rubber-elastic ring spring 23. In the exemplary embodiment according to FIG. 3, the partial area 28 between the two ring extensions 33 and 34 remains free and is accordingly subjected to the hydrostatic pressure. During the pumping stroke, the cutting ring 14 is therefore pressed onto the spectacle plate 9 both by the mechanical prestressing of the ring spring 23 and by a load on the seats of the ring spring formed on the cutting ring with the hydrostatic pressure of the delivery medium. The centering diameter Dz is predetermined by the guide 15. The inner boundary of the bearing surface of the cutting ring 14 on the eyeglass plate is determined by the diameter Di, while the outer boundary of this bearing surface has the diameter Da. The following can be assumed with sufficient accuracy: As long as the centering diameter ends closer to the outer diameter of the contact surface, there is an excess of the hydrostatic pressure in the pressing direction of the cutting ring on the eyeglass plate. If the centering diameter halves this contact surface, there is a pressure equilibrium. If it is even smaller, a hydrostatic differential pressure results which tries to lift the cutting ring off the glasses plate. This allows the force generated by the preload of the ring spring to act alone or to supplement it hydrostatically.

By a sufficient fit play, which is shown at 32 in Figure 3, wear can be carried out on the eyeglass plate or on the sealing surface 37 of the cutting ring 14 facing this, a wobbling movement and thereby a total surface support both in Ensure new condition as in advanced wear condition.

The hydrostatic forces are drawn on the lower illustration in FIG. 3. The cutting ring 14 has a cylindrical inner surface 38. While the back of the cutting ring, generally designated 39, which is acted upon by the hydrostatic pressure up to the surface 29, is radially substantially uniformly loaded by the hydrostatic pressure, the hydrostatic pressure drops as if the curve 40 is shown on the front 41, from the inside to the outside. The resulting forces are shown by arrows at 42 and 43; it can be seen that the hydrostatic forces which load the cutting ring 14 in the direction of the spectacle plate 9 are greater than the forces 43.

In the embodiment according to FIG. 4, due to a conical recess 44 of the end face 41 of the cutting ring 14, the force 45 acting on it in a lifting sense is approximately as great as the force 46. However, the forces 47 and 49 also act on the cutting ring 14 however, are essentially balanced. Nevertheless, the prestressing force of the ring spring 23 achieves sufficient tightness and particularly low wear in most media.

5, the biasing forces of the cutting ring 14 lie approximately between those of FIGS. 3 and 4. The forces 50 and 51 are balanced. The forces 52 and 53 are not the same size. The force 52 presses the cutting ring 14 hydrostatically onto the spectacle plate. At the same time, the particularly short cutting ring 14 is hydrostatically loaded and mechanically preloaded with the aid of the differently designed ring spring 23 in the direction of the spectacle plate. A support ring 54 improves the mechanical properties of the rubber-elastic ring and enables a greater fit clearance, which is shown at 56. In this way u. a. transfer the switching force from the switching element 3 to the cutting ring without metallic contact.

According to the illustration in FIG. 6, the cutting ring guide with the aid of the surfaces 17 and 18 is not axially present as in FIG. 2, but axially behind the ring spring 23, the stop surface 19 being attached to the end face of the cutting ring 14, while the ring flange 21 is on the outside of the switching element 3. In contrast to the embodiment according to FIGS. 1 to 3, the counter surface 20 therefore lies on the switching element 3.

The hydrostatic contact forces 59 and 60 are so unequal that the hydrostatic contact force 59 acting in the direction of the spectacle plate 9 is greater than the separating force 60.

In the exemplary embodiment according to FIG. 7, the axial seat surface 31 of the rubber-elastic ring spring 23 in the cutting ring 14, which, moreover, has the general shape shown in the exemplary embodiment according to FIG. 6, is moved radially outwards, relative to the corresponding seat surface 30 in the switching element 3 The hydrostatic contact forces 61, 62 are, however, of the same size. Therefore, in this embodiment, the cutting ring 14 is pressed mechanically with the ring spring 23 and not hydrostatically onto the spectacle plate 9.

In the exemplary embodiment in FIG. 8, on the other hand, the annular spring 23 is removed from the action of the delivery medium, but is mechanically prestressed for all operating states. The guide 15 of the switching element 3 and its ring extension 34 are therefore arranged on the outside. The end face 63 of the switching element 3 and the ring face 64, which is acted upon by the hydraulic pressure for prestressing the cutting ring on the spectacle plate 9, serve as stop faces for limiting the cutting ring movement, although the face 65 is also loaded with the hydraulic pressure, as can be seen from the illustration below 8 results. In this case, the rubber-elastic ring spring 23 loses its sealing function, which in the exemplary embodiment according to FIG. 8 is carried out by an O-ring 66 which is formed in a corresponding groove 67 on the guide surface 17 of the cutting ring 14.

In the exemplary embodiment in FIG. 8, the ring surfaces of the switching element 3 or cutting ring 14, which are acted upon by the hydrostatic pressure, are designed such that the opposing axial ring forces 68 and 69 are unequal. The force 68 acting in the pressing direction is greater than the lifting force 69.

According to the representation of the embodiment of FIG. 8 in FIG. 9, the stop surfaces 63 and 64 lie on top of one another. This happens, for example, through a sudden evasion, i.e. H. Lifting the cutting ring 14 off the eyeglass plate 9, for example if too hard particles have been cut through, as a result of which the annular spring 23 has been compressed beyond its installation dimension. However, this situation occurs only occasionally.

The rubber-elastic ring 23 is generally made of a plastic, apart from the support ring 54 which may be provided. In particular, natural rubber with a soft and elastic design but also butadiene copolymers, for example a butadiene-venylpyridine polymer, are suitable.

With such ring springs, the cutting ring can only be pressed hydrostatically on the spectacle plate during the switching phase and, if necessary, after the hydrostatic pressure has built up.

Claims (6)

1. Two-cylinder pump for viscous material, particularly a concrete pump with a connecting element pivoting in front of a two-orifice plate adjacent the cylinders, which is sealed on the two-orifice plate by means of a rubber-elastic ring with a cutting ring, which is axially aligned on the connecting element and for part of its length by means of an annular extension along the longer cross-sectional side of the rubber-elastic ring overlaps the latter and the socket of the rubber-elastic ring on the connecting element, whereby the sockets of the rubber-elastic ring on the cutting ring and the connecting element each have an annular extension which leaves a partial surface of the cutting ring free, characterised by the fact that the socket of the rubber-elastic ring (23) is formed on part of the aligned length (18) of the cutting ring (14) and that the partial surface (28) remaining free between the annular extensions (33, 34) lies on the opposite side, whereby on the cutting ring (14) and the connecting element (3) stops (19, 20) are provided which limit the length of the cutting ring (14) which enters the cutting ring guide (25).

2. Two-cylinder pump for viscous material according to claim 1, characterised by the fact that the guide (15) of the cutting ring and the annular extension (34) of the connecting element (3) are located on the outer face of the latter, and an end face (63) of the connecting element (3) as well as an annular surface (64) of the cutting ring (14), charged with hydrostatic pressure for the pre-stressing of the cutting ring (14) on the two-orifice plate (9), serve as stop faces.

3. Two-cylinder pump for viscous material according to claim 1, characterised by the fact that with an internal guide (25) for the cutting ring the partial surface (28) of the rubber-elastic ring (23) serving as a seal which remains free is subjected to the pressure of the fluid medium and the stop faces (19, 20) are formed on an end face of the cutting ring (14) and an end face of the connecting element (3) facing it.

4. Two-cylinder pump for viscous material according to one of the claims 1 to 3, characterised by the fact that the cutting ring (14) has a cylindrical inner surface (38).

5. Two-cylinder pump for viscous material according to one of the claims 1 to 4, characterised by the fact that the cutting ring (14) has a conical surface (44) which diverges in the direction of the two-orifice plate (9), and is subjected to hydrostatic pressure of the fluid medium.

6. Two-cylinder pump for viscous material according to claim 1, and one or more of the subsequent claims, characterised by the fact that the socket surfaces (31, 35) of the rubber-elastic ring (23) in the cutting ring are arranged turned radially outwards opposite the socket surfaces (30, 36) in the connecting element.

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