SWITCHOVER DEVICE FOR A THICK-MATTER PUMP

Abstract

A switch-over apparatus for a thick-matter pump includes a housing that forms a pre-fill vessel, which has first and second inlet/outlet openings and an outlet opening positioned on opposite sides of the housing. The apparatus further includes a pivot body positioned within the housing and that forms a duct. The duct includes a duct inlet configured to pivot between the first and second inlet/outlet openings and includes a duct outlet configured to align with outlet opening. The pivot body forms at least one seal chamber adjacent the duct inlet or duct outlet. The apparatus further includes an elastic seal positioned within the seal chamber and includes a support strip positioned within the seal chamber between the elastic seal and the pivot body. The seal strip forms first and second oblique-cut ends.

Description

The invention relates to a switchover device for a thick-matter pump as well as to the use of a support strip in such a switchover device and to the use of a pivot body of such a switchover device.

A switchover device for thick-matter pumps can be configured, for example, as a transfer tube of a concrete pump. With such a switchover device, concrete is pressed at high pressure by means of two delivery cylinders via the transfer tube into a concrete delivery tube. The pressure in the transfer tube of a concrete pump which may pump concrete by several hundreds of meters up onto building structures such as bridges or skyscrapers ranges at up to 160 bar for concrete pumps of the present generation. With a further increase in pump capacity to is allow for pumping concrete up to levels higher than 500 meter, pump pressures of 300 bar will be needed in future which will expose the seals of the delivery system to extreme strains and stresses.

With a switchover device of this type, the flow of concrete and/or thick-matter from a pre-fill vessel is pressed into a sucking delivery cylinder and from a pumping delivery cylinder into the delivery line. Inasmuch as these are two-cylinder thick-matter pumps, the inlet and the outlet of the pivot body swinging to and fro in the housing at the cycle of the piston strokes are connected to each other through a passage duct in the pivot body.

This switchover technique puts high demands on the seals of the switchover device, particularly in order to avoid that the concrete, and particularly the water contained therein, is pressed from the passage duct of the pivot body into the pre-fill vessel. In particular, the water contained in the concrete has the property of improving fluidity and thus transportability of concrete in the delivery line. Moreover, too dry concrete leads to clogging in the delivery line and may entail costly repair measures if concrete hardens in the deliver line.

For this purpose, a rubber seal made of hard rubber is usually laid into the seal chambers of the pivot body, said rubber seal pressing the pivot body against the two opposite sides of the housing of the switchover device. Frequently, a hard metal ring is inserted in addition to the rubber seal so that the rubber seal is not directly moved to and fro at the housing wall due to the pivoting motions of the pivot body, but the rubber seal presses the hard metal ring to the housing sides.

During the pumping procedure, due to the high pressure of the concrete in the passage duct of the pivot device, the rubber seal is pressed outwardly, in particular into a gap between the hard metal ring and the seal chamber. Owing to the abrasive effect of concrete, this entails high wear and tear of the rubber seal. Since an exchange of a rubber seal is very costly and leads to standstill periods of the concrete pump, it is necessary to reinforce the rubber seal in the outer circumference in order to reduce this wear and tear.

In the printed publication DE 31 13 787 it was already proposed to provide a rubber seal for a switchover device of the afore-mentioned type, which is not equipped with the said hard metal ring, with a metallic support ring on the outer circumference of the rubber seal which prevents the seal exposed to high pressure from penetrating into the gap between passage duct and pre-fill vessel and thus preventing its premature wear and tear.

A metal support ring of this type, however, is costly in manufacture and needs to be produced with utmost precision, in particular for a kidney-shaped seal, in order to fulfill the set task. Moreover, such a support ring does not have the elasticity required to sufficiently adapt itself to the circumferential shape of the seal chamber.

It is the object of the present invention to improve the seal of the switchover device of a thick-matter pump by way of simple and low-cost measures with the aim to increase stability of the existing rubber seal.

The present invention achieves this object by way of a switchover device for a thick-matter pump in accordance with claim 1.

Advantageous embodiments of the present invention are indicated in the dependent sub-claims.

The present invention proposes to arrange a support strip around the elastic seal and/or the rubber seal within the seal chamber of the pivot body, said support strip supporting the elastic seal towards the outside in order to prevent the elastic seal from migrating into the gap between the seal ring and the shoulder of the seal chamber.

Preferably, this support strip is made of elastic plastic, the hardness of which is higher than the hardness of the elastic seal. On the one hand, this ensures that the support strip itself cannot migrate into the gap between the seal ring and the shoulder of the seal chamber because of an alteration in its shape, and on the other hand, owing to the existing elasticity of the support strip, it can easily be adapted to the shape of the seal chamber, which for example may be round or kidney-shaped.

Preferably, the support strip is made of a teflon material. Teflon has got the property of not being attacked so severely by the abrasive properties of concrete as other rubber or plastic materials, and thus it has got a long service life.

Preferably, the support strip made of plastic and/or teflon contains bronze, whereby its properties improve further, the said bronze portion in particular increasing the crushing strength of the teflon strip, thus preventing the risk of migrating into the gap between the seal ring and the shoulder of the seal chamber.

Preferably, the support strip has a thickness of 1 to 3.5 mm. The support strip is particularly well suited for fulfilling the intended task, if it is approx. 2.5 mm thick. If the support strip is thinner than 1 mm, it itself does not have the necessary stability required to prevent migration of the elastic seal, and the support strip itself might migrate into the gap between the seal chamber and the shoulder of the seal chamber. If the support strip is too thick, it is no more sufficiently elastic to allow for easy insertion into the seal chamber and it would demand unnecesarily much space in the seal chamber.

The support strip is preferably cut off from a tape which for example can easily be procured on a roll.

It is furthermore preferred to cut off the support strip to a length that is determined by the outer circumference of the seal chamber. Since the outer circumference of the seal chamber is relatively constant with all pivot bodies of a product series, the support strip can simply be cut to the length of the circumference of the seal chamber, before the support strip is laid into the seal chamber.

The support strip is preferably cut off by an oblique cut to the necessary length and after inserting the support ring, the cut faces should lie as closely as possible next to each other. This ensures that the elastic seal cannot migrate at a circumferential point into a gap of the support strip, thereby restricting its function and/or being exposed to increased wear and tear at the gap. Preferably, the remaining gap in the support strip after inserting into the seal chamber is smaller than 1 mm.

In accordance with an advantageous embodiment of the present invention, one opening of the passage duct of the pivot body is kidney-shaped, with the elastic seal also being kidney-shaped and being supported by the support strip in the seal chamber.

With further preference, wear plates are arranged at the insides of the housing in the area of the inlet openings and/or outlet openings. These wear plates are preferably made of a metal having a hardness which is higher than the housing itself, so that the insides of the housing are exposed to less wear and tear in the area in which the pivot body is swung to and fro at the housing wall. Moreover, the wear plates can be exchanged, if required, without necessitating an exchange of the entire housing.

Practical examples of the present invention are elucidated and explained in the following by way of drawings, where:

FIG. 1: is a schematic representation of a top view on a switchover device of a thick-matter pump;

FIG. 2: is a side view of the switchover device from FIG. 1;

FIG. 3: is a schematic view of a section through a seal chamber (Detail A) according to prior art in technology;

FIG. 4 is a schematic view of a cut through a seal chamber (Detail A) according to prior art in technology during a pumping procedure;

FIG. 5 is a schematic view of an elastic seal with a support strip according to the present invention;

FIG. 6 is a support strip according to the present invention in unrolled status;

FIG. 7 is a perspective view of the cutting edge of a support strip according to the present invention;

FIG. 8 is a schematic view of a cut through a seal chamber (Detail A) according to the present invention during a pumping procedure.

FIG. 1 illustrates a schematic view from the top onto a switchover device 1 for a thick-matter pump. The switchover device is mainly comprised of an open-top pre-fill vessel 20 with the housing sides 2a, 2b, 2e, 2f and a bottom 2c, in which a pivot body 3 is arranged. The pivot body 3 mainly comprises a passage duct 17 with an inlet opening 13 and an outlet opening 14. The switchover device 1 is suitable, for example, to deliver the concrete conveyed by hydraulically driven delivery cylinders 18a, 18b connected to the inlet and outlet openings 19a, 19b through the passage duct 17 of the pivot body 3 in the direction of the outlet opening 14 into a concrete delivery tube 17. In FIG. 1, the delivery cylinder 18b sucks concrete in a suction stroke from the pre-fill vessel 20 and the delivery cylinder in a simultaneous delivery stroke pushes the concrete through the passage duct 17 of the pivot body 3 into the concrete delivery tube 21. On a periodical alteration of the piston movement of the delivery cylinders (18a, 18b), the pivot body 3 is swiftly switched over by means of a non-illustrated hydraulic unit.

To ensure a leakproof sealing of the pivot body 3 with the opposite housing walls 2a and 2b, the pivot body 3 is pressed by means of the sealing system (Detail A) explained later between the housing walls 2a and 2b, but still remains movable for the switchover movement.

FIG. 2 shows a side view of the switchover device 1 from FIG. 1, wherein the outlet opening 14 is located on the side facing the viewer and the inlet and outlet openings 13 are located on the side averted from the viewer. From FIG. 2, it is especially the swinging movement of the pivot body 3 in housing 3 that becomes evident, wherein the pivot body 3 in this drawing is located in position (a), that means upstream to the left-side inlet and outlet opening 19a. In both positions (a, b), the kidney-shaped outlet opening 14 of the pivot body 3 remains in a position upstream to the outlet opening 15 of housing 2, but the outlet opening 14 of the pivot body 3 is nevertheless moved to and fro upstream to the outlet opening 15 of the housing side 2b when swiveled about the swivel axis 11 from position a to position b and vice versa. While the change from suction stroke to delivery stroke of the delivery cylinders takes approx. 3 to 15 seconds, depending on the design and size of the thick-matter pump, and since the pivot body 3 stands still during this period of time, the pivot body 3 must be swiveled into the other position within a few tenths of a second during the switchover. On operation of the thick-matter pump 1, a pressure P with up to several hundreds bar prevails in the passage duct 17 both during standstill and during the switchover procedures, and this pressure also takes effect on the sealing unit (Detail A).

FIG. 3 shows a schematic detail view of the sealing system (Detail A) from FIG. 1 in accordance with prior art in non-burdened status. It means the pivot body 3 is pressed to have contact with the housing wall 2b via the elastic seal 16, seal ring 12, hard metal coating 4 and the wear plate 5 mounted to the housing wall 2b, without there being any pressure of concrete in the passage duct 17. The seal ring 12 in this case is shown as a metal ring with a hard metal coating, but it could also be made of a different solid material that offers high resistivity to the abrasive effect of concrete on pumping. The hard metal coating 4 is not absolutely necessary. In the following, however, a configuration with a metal ring having a hard metal coating is described. The elastic seal 16 which may be comprised of a plastic or rubber material and which may be reinforced in the interior with a metal ring serves the task of pre-tensioning the seal ring 12 against the housing wall 2 and/or wear plate 5 in order to seal the passage duct 17 towards the pre-fill vessel. The elastic seal 16 and the seal ring 12 with the hard metal coating 4 are laid into the seal chamber 8 which is confined towards the outside by the nose-shaped shoulder 10. In non-installed status, the elastic seal 16 shown here would have a round cross-section. Owing to the fact that the pivot body 3 is pressed-in between housing walls 2a, 2b, the seal 16 has a slightly oval deformation, whereby the metal ring 12 with the hard metal coating 4 is pressed at pressure p to enter into contact with the wear plate 5.

To allow the metal ring 12 to migrate forward and backwards within the seal chamber 8 which is confined towards the outside by the nose-shaped shoulder 10 so that it will always provide a flush closure with the wear plate 5, a gap 9 having the width d is provided for. Since the metal ring 12 is moved also laterally during the switchover cycles, the width of the gap may vary between 0 and approx. 1 mm in operation. It becomes evident that due to this movement, also the elastic seal 16 being subjected to the contact pressure is laterally moved and tumbled.

FIG. 4 illustrates the sealing system according to FIG. 3 in operation in conformity with prior art in technology. Because of concrete being conveyed, a very high pressure P now prevails in the passage duct 17. This pressure P which presses the metal ring 12 via the seal 16 during the pumping procedure additionally to the wear plate 5, presses the elastic seal 16 in the direction of the nose-shaped shoulder 10, and moreover, the elastic seal 16 is moved laterally to and fro due to the relative movement of the metal ring 12 towards the seal chamber 8 of the metal ring 12.

The pressure P and the motions of the metal ring 12 involve that the elastic seal 16 is not only pressed into the direction of the nose-shaped shoulder 10, but also into the gap 9, whereby on the one hand the metal ring 12 is virtually clamped, but in particular the elastic seal 16 in the area pressed into the gap 9 is subjected to a particular high wear and tear.

FIG. 5 illustrates a kidney-shaped elastic seal 16 as utilized in a switchover device 3 of a thick-matter pump in accordance with FIGS. 1 and 2. Around the elastic seal 16, a support strip 6 made of teflon material is shown which together with the elastic seal 6 is laid into the seal chamber 8 of the switchover device. The teflon material 6 may advantageously be enriched with bronze in order to increase the hardness of the strip.

FIG. 6 shows the support strip 6 in unrolled status. The support strip 6 has the length L which corresponds to the outer circumference of the seal chamber 8. Clearly visible in FIGS. 5 and 6 are the oblique cutting faces 6a of the support strip 6. These oblique cutting faces take the effect that the elastic seal 16 is not point-wise stressed at a circumferential point in case of a slight gap between the ends (2a) of the inserted support strip 16, but stressed obliquely over a longer area, thereby distributing the wear due to a gap between the support strip ends (2a) in the seal chamber 8 at the elastic seal 16 over a broad range.

The cutting angle may amount to approx. 30 degrees as illustrated in the drawing, but it should not be too small so that the ends of the strip 16 do not become too thin and might slide into the gap 9 and/or rotate; however, this angle should not be too large either, because otherwise the elastic seal would be stressed too much at one circumferential point.

The height H of the support strip 6 amounts to approx. 1.5 cm, but it should not exceed the height of the seal chamber 8 in built-in status, because otherwise the support strip 16 is pressed between the metal seal 12 and the upper end of the seal chamber 8, and the elastic seal 16 would no longer be able to fulfill its function of pressing the metal seal 8 to the wear plate. On the other hand, the height H of the support strip 6 should not be much lower than the height of the seal chamber 8, because otherwise a gap would occur above or below the laid-in support strip 6 into which the elastic seal 6 might unintentionally penetrate.

FIG. 7 shows a view of the oblique cutting face 6a of the support strip 6 with the thickness D. The thickness D of the support strip here for example amounts to 2.5 mm, but it could also vary between 1 mm and 3 mm. The minimal thickness D should not be less than the maximal width d of gap 9, because is otherwise there would be a risk in that the support strip 6 migrates into the gap 9 and obstructs the mobility of the metal seal in the seal chamber 8. Conversely, if the support strip is configured with too much thickness, it does not leave sufficient space for the elastic seal 16 in the seal chamber 8.

Figure illustrates a sealing system according to FIG. 1, Detail A, in which the support strip 6 is circumferentially laid around the elastic seal 16 in the seal chamber 8. Here it is clearly visible that at the pressure P of pumped concrete 7 prevailing in the seal chamber 8 which is open towards the passage duct 17 (the direction of flow is illustrated here by way of the larger downwardly directed arrow, whereas the effect of pressure P on the elastic seal 16 is illustrated by way of the smaller arrows directed towards the right side), the elastic seal is deformed only slightly. Furthermore, the metal ring 12 is pushed to and fro during the switchover cycles due to the frictional force F_R.

In this figure, it becomes clearly evident that the elastic seal 16 is pressed into the direction of the nose-shaped shoulder 10 and becomes slightly deformed during this procedure, but the support strip 6 prevents the elastic seal 16 from migrating into gap 9 as it is subjected to pressure P. Thereby, wear and tear to the elastic seal 16 is substantially reduced and the metal ring 12 is not restricted in its mobility.

It should still be noted that the support strip 6 shown here may not only be utilized in the kidney-shaped seal chamber 8 of the switchover device illustrated here, but for example also at the round inlet opening 13 on the other side of the pivot body 3 in order to seal the inlet and outlet openings during the pumping cycle.

Furthermore, the use of such a support strip 16 is not limited to the design version of a switchover device illustrated here, but it could also be utilized for example in S-shaped switchover valves for sealing at inlet and outlet openings.

Claims

1-12. (canceled)

13. A switch-over apparatus for a thick-matter pump, the apparatus comprising: a housing forming a pre-fill vessel having a first and second inlet/outlet opening and an outlet opening positioned on opposite sides of the housing;a pivot body positioned within the housing and forming a duct, the duct including a duct inlet configured to pivot between the first and second inlet/outlet openings and including a duct outlet configured to align with outlet opening, wherein the pivot body forms at least one seal chamber adjacent the duct inlet or duct outlet;an elastic seal positioned within the seal chamber; anda support strip positioned within the seal chamber between the elastic seal and the pivot body, wherein the seal strip forms first and second oblique-cut ends.

14. The apparatus of claim 13, wherein the support strip comprises an elastic plastic having a hardness higher than a hardness of the elastic seal.

15. The apparatus of claim 14, wherein the support strip comprises Teflon.

16. The apparatus of claim 15, wherein the support strip comprises bronze.

17. The apparatus of claim 13, wherein the first oblique-cut end forms a first face that faces a second face formed by the second oblique-cut end.

18. The apparatus of claim 17, wherein a distance between the first and second face less than 1 mm.

19. The apparatus of claim 18, wherein the support strip has a thickness of 1-3.5 mm.

20. The apparatus of claim 19, wherein the thickness is 2.5 mm.

21. The apparatus of claim 13, further comprising: a metal ring at least partially positioned within the seal chamber, wherein the elastic seal is directly coupled to the metal ring, pivot body, and support strip.

22. The apparatus of claim 21, wherein the metal ring includes a bottom surface in direct contact with a wear plate.

23. The apparatus of claim 22, wherein the bottom surface of the metal ring comprises a hard-metal coating.

24. The apparatus of claim 23, wherein the hard-metal coating has a hardness greater than a hardness of the housing.

25. The apparatus of claim 22, wherein the elastic seal is kidney-shaped.

26. The apparatus of claim 22, wherein the metal ring includes a side surface facing the pivot body and wherein the pivot body and metal ring form a gap adjacent the side surface.

27. The apparatus of claim 24, wherein the support strip is configured and arranged to prevent the elastic seal from migrating into the gap.

28. The apparatus of claim 13, wherein the pivot body forms two seal chambers, each chamber having an elastic seal and support strip positioned therein, wherein the support strips each form first and second oblique-cut ends.