Transfer tube and axial sealing ring for a two-cylinder thick matter pump, and two-cylinder thick matter pump

Abstract

The invention relates to a transfer tube (2) for a two-cylinder thick matter pump (I), wherein the transfer tube (2) has a switch tube (12) which is mounted in a filling container (30) of a transfer tube housing (11) so as to be pivotable about a pivot axis (S), wherein the switch tube (12) has an inlet opening (8) which is arranged eccentrically with respect to the pivot axis (S) and an outlet opening (9) which is arranged coaxially with respect to the pivot axis (S), wherein the inlet opening (8) of the switch tube (12) is axially sealed with respect to the transfer tube housing (II) by an inlet seal (17), and the outlet opening (9) of the switch tube (12) is axially sealed with respect to the transfer tube housing (11) by an axial sealing ring (15), wherein the axial sealing ring (15) is formed from at least two materials of different hardness. The invention additionally relates to an axial sealing ring (15) for a two-cylinder thick matter pump (1), and to a two-cylinder thick matter pump (1) having an axial sealing ring (15).

Description

[0001] Two-cylinder thick matter pump

[0002] The invention relates to a diverter pipe for a two-cylinder viscous matter pump. The diverter pipe comprises a diverter pipe pivotably mounted about a pivot axis in a filling container of a diverter pipe housing. The diverter pipe has an inlet opening arranged eccentrically to the pivot axis and an outlet opening arranged coaxially to the pivot axis. The inlet opening of the diverter pipe is axially sealed from the diverter pipe housing with an inlet seal, and the outlet opening of the diverter pipe is axially sealed from the diverter pipe housing with an axial sealing ring. Furthermore, the invention relates to an axial sealing ring of a two-cylinder viscous matter pump and a two-cylinder viscous matter pump.

[0003] Two-cylinder slurry pumps have long been known in the state of the art for industrial applications, such as pumping biowaste, sewage sludge, and the like, but also as concrete pumps for pumping concrete on construction sites.

[0004] In these thick matter pumps, the thick matter, i.e. the material to be conveyed, is sucked in alternately by two conveying cylinders driven by hydraulic cylinders, which open into a pipe switch housing, and is conveyed into a conveying line by means of a pipe switch arranged in the pipe switch housing.

[0005] Due to their shape, these slurry pumps use diverter valves, such as S-diverter valves, rock gate valves, or C-tubes. The diverter valves themselves, as well as the bearings and seals of the diverter valves to the inlets and outlets in the diverter housing, are subject to significant wear and tear and require regular maintenance and, if necessary, replacement. This is particularly difficult with S-diverter valves, as the S-diverter valve typically requires removal from the diverter housing.

[0006] It is therefore an object of the invention to provide a pipe switch for a two-cylinder thick matter pump, the bearing and sealing of which are subject to as little wear as possible in order to minimize the effort required for maintenance and repair of the two-cylinder thick matter pump.

[0007] This object is achieved by a pipe switch for a two-cylinder thick matter pump according to claim 1, an axial sealing ring for a two-cylinder thick matter pump according to claim 14 and a two-cylinder thick matter pump with an axial sealing ring according to claim 15. Due to the fact that the axial sealing ring is formed from at least a first material and a second material, wherein the hardness of the first material and the second material is different, i.e. the hardness of the first material differs from the hardness of the second material, the axial sealing ring can be ideally adapted to the conditions at the transition from the outlet opening of the back and forth pivoting switch pipe to the stationary pipe switch housing.

[0008] Advantageous embodiments and further developments of the invention emerge from the dependent claims. It should be noted that the features listed individually in the claims can also be combined with one another in any technologically expedient manner, thus revealing further embodiments of the invention.

[0009] Advantageously, the second material, oriented toward the outlet opening of the switch tube, has a greater hardness than the first material, oriented toward the tubular switch housing. Due to the greater hardness of the second material, the abrasion resistance of the axial sealing ring is greater in the direction of the pivoting switch tube, so that wear on the axial sealing ring toward the reciprocating outlet opening of the switch tube is minimal.

[0010] Advantageously, the second, harder material is a metallic material. A metallic material has the particular advantage of very high abrasion and wear resistance, which, combined with high rigidity in the transition area from the outlet opening of the switch tube to the tubular switch housing, can be used very effectively to seal the pivoting switch tube.

[0011] In one embodiment of the invention, the first low-hardness material is a plastic or rubber. Rubber and plastic as materials for the axial sealing ring exhibit a certain elasticity, which is particularly advantageous for sealing the transition from the switch pipe to the pipe switch housing.

[0012] According to an advantageous embodiment of the invention, the axial sealing ring is radially mounted in an annular recess of the pipe switch housing. Due to the radial mounting of the axial sealing ring in the annular recess of the pipe switch housing, the axial sealing ring is always positioned centrally in front of the outlet opening of the switch pipe.

[0013] Advantageously, the first material of lower hardness, oriented toward the diverter tube housing, is designed to be pressed radially into the annular recess by the pressure of a medium conveyed by the two-cylinder diverter pump during the conveying of thick solids. Because the first material of lower hardness is pressed radially into the annular recess, the sealing behavior of the axial sealing ring is improved, especially when high pressure prevails in the conveying channel of the diverter tube, so that the axial sealing ring seals particularly well, especially at high conveying pressure in the conveying channel.

[0014] The axial sealing ring is advantageously designed to be fixed in the annular recess by the pressure of a medium conveyed by the two-cylinder slurry pump in the switch pipe by deforming the first material of low hardness. The fact that the axial sealing ring is fixed in the annular recess ultimately means that the axial sealing ring does not move in the annular recess, in particular, it does not rotate in the recess. Wear on the side of the first material of lower hardness in the annular recess due to surfaces rubbing against each other is therefore no longer possible.

[0015] A particularly preferred embodiment is one in which the axial sealing ring is designed to slide, with the second material of greater hardness, on the outlet opening of the switch tube during a pivoting operation of the switch tube. Because the harder, more wear-resistant material of the axial sealing ring slides on the outlet opening of the switch tube, wear on the axial sealing ring on its side oriented toward the pivoting switch tube is particularly low.

[0016] A preferred embodiment of the invention provides a guide bushing arranged in the pipe switch housing, enclosing the outlet opening of the switch pipe, which is designed to radially support the outlet opening of the switch pipe. With such a guide bushing, the outlet opening of the switch pipe is very easily radially supported in the pipe switch housing.

[0017] Advantageously, at least one radial sealing ring is provided in the guide bushing, which, in addition to the axial sealing ring, is designed to seal the outlet opening of the switch tube. This results in a particularly effective seal for the outlet opening of the switch tube.

[0018] In a preferred embodiment, a plain bearing for radially supporting the outlet opening of the diverter tube is arranged in the guide bushing, with at least one first radial sealing ring arranged in the guide bushing being designed to seal the plain bearing from the filling container of the diverter housing. The plain bearing for supporting the outlet opening of the diverter tube can be effectively protected from contamination by the thick material in the filling container with this first radial sealing ring. Advantageously, at least one second radial sealing ring arranged in the guide bushing is designed to seal the plain bearing from the axial sealing ring.In particular, because it cannot be ruled out that with increasing wear of the axial sealing ring, thick material will be pushed from the outlet opening of the switch tube towards the plain bearing, the second radial sealing ring provides additional protection against contamination of the outlet-side plain bearing of the switch tube in the guide bush.

[0019] Advantageously, a wear sleeve encloses the outlet opening of the switch tube. Due to the outlet-side bearings of the switch tube with axial and radial sealing rings, a certain amount of wear will always occur at the outlet opening. However, by using the wear sleeve, the entire switch tube does not always have to be replaced; instead, only the wear sleeve can be replaced. Furthermore, the wear sleeve can be made of a particularly hard material, especially carbide, thus reducing wear to a minimum.

[0020] Further features, details, and advantages of the invention will become apparent from the following description and from the drawings, which show exemplary embodiments of the invention. Corresponding objects or elements are provided with the same reference numerals in all figures. They show:

[0021] Figure 1 Side view of a two-cylinder thick matter pump according to the invention,

[0022] Figure 2 sectional view of a switch pipe in a pipe switch housing according to the invention,

[0023] Figure 3 sectional view of the mounting and sealing of the outlet opening of a switch pipe according to the invention,

[0024] Figure 4 exploded view of the bearing and sealing of the bearing of the outlet opening of an S-pipe switch according to the invention, Figure 5a-d views of an axial sealing ring according to the invention in a first variant,

[0025] Figure 6a-d views of an axial sealing ring according to the invention in a second variant,

[0026] Figure 7 sectional view of the outlet seal of the pipe switch according to the invention, and

[0027] Figure 8 Sectional view of the inlet seal of the pipe switch according to the invention.

[0028] Figure 1 shows a side view of a two-cylinder thick matter pump 1 with a pipe switch 2 according to the invention. The two-cylinder thick matter pump 1 comprises two parallel hydraulic cylinders 3, in which two hydraulic pistons 5 alternately drive two delivery pistons 7, coupled to the hydraulic pistons 5, in two delivery cylinders 6. Via the thick matter feed 28, for example a hopper or a conveyor screw arrangement, the thick matter to be conveyed is filled into the filling container 30 of the pipe switch 2 and sucked in by the respective suctioning delivery cylinder 6 through openings in the pipe switch housing 11, to which the delivery cylinders 6 are connected from the outside. As soon as the suction process of one of the delivery cylinders 6 is completed, the inlet opening 8 of the switch pipe 12 is pivoted in front of the opening of the delivery cylinder 6, which is then filled with thick matter.The delivery piston 7, which then moves towards the pipe switch 2, presses the thick material to be conveyed through the delivery channel 16 of the switch pipe 12 towards the outlet flange 29, to which, for example, a delivery line is connected, in order to convey the thick material to the intended location. Depending on the design and size of the two-cylinder thick material pump 1, a delivery pressure of 80 bar or more can occur in the delivery channel 16. In particular, the outlet opening 9 of the switch pipe 12, which is radially mounted in a guide bushing 14 and has a transition to the outlet flange 29, must be very well sealed to prevent the thick material from penetrating from the delivery channel 16 into the outlet-side radial bearing of the switch pipe 12, which would cause the bearing to wear out very quickly, particularly when conveying abrasive thick materials, or even be destroyed, and require replacement.

[0029] As can be seen from Figure 2, the diverter tube 12 is pivoted in the filling container 30 by one or two pivoting drives, for example hydraulic cylinders 13, arranged outside the diverter tube housing 11, via the drive shaft 10. The distance of the inlet opening 8 of the diverter tube 12 from the wall of the diverter tube housing 11, and thus also the contact pressure of the inlet seal 17, can be varied using the adjusting screw 35.

[0030] In the area of ​​the outlet opening 9 of the pipe switch 2, between the outlet opening 9 and the outlet flange 29, an axial sealing ring 15 is arranged, which axially seals the outlet opening 9 against the guide bush 14 surrounding the outlet opening 9.

[0031] Figure 3 shows the axial sealing ring 15 together with the plain bearing 23 arranged in the guide bushing 14 and the sealing arrangement consisting of the first, second and third radial sealing rings 20, 21, 22 at the outlet opening 9 of the switch pipe. Figure 3 clearly shows that the axial sealing ring 15 is formed from a first material 15a and a second material 15b. In this exemplary embodiment, the first material 15a is a rubber and the second material 15b is a metallic material. The first material 15 and the second material 15b form a composite body in which the two materials 15a, 15b are permanently joined to one another during production, for example by injection molding or gluing, or are at least connected to one another in a rotationally fixed manner, for example by toothing, and thus together form the axial sealing ring 15.

[0032] The pipe switch 2 has a switch pipe 12 pivotably mounted about a pivot axis S in the filling container 30 of the pipe switch housing 11. The switch pipe 12 has an inlet opening 8 arranged eccentrically to the pivot axis S and an outlet opening 9 arranged coaxially to the pivot axis S. The inlet opening 8 of the switch pipe 12 is axially sealed from the pipe switch housing 11 with an inlet seal 17 (Fig. 2), and the outlet opening 9 of the switch pipe 12 is axially sealed from the pipe switch housing 11 with an axial sealing ring 15 (Fig. 2; Fig. 3). The axial sealing ring 15 is formed from at least a first material 15a and a second material 15b, wherein the hardness of the first material 15a and the second material 15b is different.

[0033] The side of the axial sealing ring 15 facing the outlet opening 9, made of a second metallic material 15b, slides during the pivoting process on the outlet opening 9 of the switch tube 12, on which a wear sleeve 18 is arranged. The wear sleeve 18 is made, for example, of a very hard and therefore wear-resistant metallic material. The second material 15b of the axial sealing ring 15 is, for example, a very hard metal and thus very wear-resistant, so that the sliding process caused by the pivoting of the switch tube 12 causes hardly any wear. On the side facing the pipe switch housing 11, the axial sealing ring 15 is made, for example, of a rubber or plastic.The axial sealing ring 15, or rather the first material 15a of lower hardness, is pressed through the outlet opening 9 of the switch tube 12 with a certain preload into an annular recess 19 in the switch tube housing 11 and is also radially mounted in the annular recess 19. The first material 15a of lower hardness, oriented towards the switch tube housing 11, is designed to be pressed radially into the annular recess 19 by the pressure of the thick material pumped by the two-cylinder thick material pump 1 during the thick material conveyance, whereby the axial sealing ring 15 is fixed in the annular recess 19, so that during the pivoting movement of the switch tube 12, the axial sealing ring 15 does not change its position relative to the switch tube housing 11.Because the axial sealing ring 15 with the first material 15a of lower hardness is pressed into the annular recess 19 by the pressure of the conveying medium, the seal between the axial sealing ring 15 and the radial bearing of the outlet opening 9 of the switch tube 12 is also improved. Over time, a certain amount of wear on the metallic second material 15b and the wear sleeve 18 is to be expected, which can be compensated for over a longer period by the prestressing of the first material 15a of lower hardness of the axial sealing ring 15. Before the axial sealing ring 15 is replaced due to wear, spacers (not shown) inserted into the annular recess 19, for example, can extend the service life of the axial sealing ring 15.

[0034] A wear sleeve 18 with an L-shaped cross-section is firmly attached to the outlet opening 9 of the switch tube 12. The wear sleeve 18, which is manufactured to fit, is applied to the outlet opening 9, for example, after heating, and is firmly connected to the outlet opening 9 after cooling. A plain bearing 23 and a first radial sealing ring 20, a second radial sealing ring 21, and a third radial sealing ring 22 are arranged on the outer circumference of the wear sleeve 18 or in the interior of the guide bushing 14 surrounding the wear sleeve 18. As can be seen from Figure 4, the plain bearing 23 consists of a perforated brass ring and is arranged in a permanent lubrication chamber 32 enclosed by the second radial sealing ring 21 and third radial sealing ring 22. The first radial sealing ring 20 prevents in particular the penetration of thick material from the filling container 30 into the permanent lubrication chamber 32.The second radial sealing ring 21 prevents, in particular, lubricant from penetrating the permanent lubrication chamber 32 toward the filling container 30, because the thick material to be pumped must generally not be contaminated with lubricants or other substances. The third radial sealing ring 22 prevents, in particular, the entry of thick material into the lubrication chamber 32 of the plain bearing 23. Despite the good sealing effect of the axial sealing ring 15, this could penetrate past the axial sealing ring 15 into the area 31 located between the axial sealing ring 15 and the radial sealing ring 22. The first radial sealing ring 20 and the third radial sealing ring 22 are, for example, V-seals made of a self-lubricating polyurethane material with preloaded sealing lips. The sealing lips of the first radial sealing ring 20 are oriented in the direction of the filling container 30 and the sealing lips of the third radial sealing ring 22 are oriented in the direction of the area 31.This arrangement of the radial sealing rings 20, 21, 22 in conjunction with the axial sealing ring 15 and the plain bearing 23 provides a very effective and durable seal and bearing for the outlet opening 9 of the switch pipe 12, allowing very long service and maintenance intervals. Figures 5a) to 5c) show views and cross sections of an axial sealing ring 15 formed from a first material 15a and a second material 15b, each of which has a different hardness. This is the axial sealing ring 15 as described above in conjunction with Figures 2 to 4. This means that the second material 15b of greater hardness is a metallic material and the first material 15a of lesser hardness is a rubber or a plastic.The cross-section shown in Figure 5c) shows the axial sealing ring 15 in a not yet installed state, and Figures 5d), as well as Figure 5b), show the axial sealing ring 15 installed in the pipe switch 2. It is clearly visible that the first material 15a of lower hardness, which is oriented towards the pipe switch housing 12, i.e., pressed into the annular recess 19 by the outlet opening 9 of the switch pipe 12 with the force Fi, is deformed. In addition, the material 15a of lower hardness is pressed radially into the annular recess 19 by the pressure F2 of the conveyed medium, so that the axial sealing ring 15 is firmly embedded in the annular recess 19 and fixed therein. For comparison, the undeformed first material 15a of lower hardness of the axial sealing ring 15 is shown again in dotted lines in Figure 5c.

[0035] Figures 6a) to 6c) show views and cross-sections of an alternatively constructed axial sealing ring 15, which is formed from a first material 15a, a second material 15b, and a third material 15c, wherein the hardness of the first material 15a and the second material 15b differs. As already described in connection with Figure 5, the first material 15a of lower hardness, which is oriented toward the pipe switch housing 11, is, for example, a rubber or a plastic. The material 15b of greater hardness, which is oriented toward the outlet opening 9 of the switch pipe 12, is also a rubber or plastic here, but the second material 15b is harder and therefore more wear-resistant than the softer first material 15a and thus has similar properties to the metallic material 15b of the axial sealing ring 15 shown in Figure 5.An advantage of the second material 15b made of plastic compared to a metallic material 15b is that it is easier to form during production and can, for example, have lubrication grooves 36 through which a liquid contained in the conveyed thick material can flow, whereby the axial sealing ring 15 slides better on the outlet opening 9 and thus wear is reduced. Because the rubber or plastic materials 15a, 15b of the axial sealing ring 15 allow radial deformation of the entire axial sealing ring 15, which can, for example, lead to the axial sealing ring 15 being sucked into the conveying channel 16 in the event of negative pressure in the conveying channel 16 of the switch pipe 12, a third material 15c is arranged, for example, between the first material 15a and the second material 15b.The third material 15c is harder than the first material 15a and the second material 15b, for example, a metallic material or a relatively hard plastic, which effectively prevents radial deformation of the entire axial sealing ring 15. Other combinations of materials of different hardness are conceivable; for example, the first material 15a could be a relatively hard plastic, so that the third material 15c can be omitted. The selection of the materials 15a, 15b, and optionally 15c depends in particular on the consistency and composition of the thick material to be pumped, but also, for example, on the discharge pressure to be applied by the two-cylinder thick material pump 1, and can be adapted as desired by selecting the appropriate hardness of the materials.

[0036] Figure 7 shows a cross-section through the guide bushing 14, revealing a lubrication supply 34 incorporated into the guide bushing 14. This supply leads to the lubrication chamber 32, in which the plain bearing 23 is arranged, which radially supports the outlet opening 9 of the diverter tube 12. The lubrication chamber 32 can be pressurized with grease regularly or during operation of the two-cylinder slurry pump 1.In order to maintain a certain lubricant pressure in the lubrication chamber 32, which is, for example, greater than the pressure of the thick material in the filling container 30, so that no thick material can penetrate to the plain bearing 23, an outlet valve can be arranged at an outlet opening opposite in the guide bush 14. This outlet valve ensures a minimum pressure of the lubricant in the lubrication chamber 32, but does not permit an excessively high lubricant pressure, which could lead to lubricant penetrating past the first radial sealing ring 20 and the second radial sealing ring 21 into the filling container 30. Figure 8 shows a cross section of the inlet seal 17, which forms the inlet opening.

[0037] 8 of the switch pipe 12 against the pipe switch housing 11 or against the outlet openings of the conveyor cylinders 6. The inlet seal 17 consists essentially of a so-called automatic ring 25 and a cutting ring 26. The automatic ring 25 is made of rubber, for example, and is provided with a certain preload, which can be adjusted, for example, by means of the adjusting screw 35 of the drive shaft

[0038] 10 of the switch pipe 12 is adjustable, so that the automatic ring 25, as shown in Figure 9, protrudes between the projections on the cutting ring 26 and the retaining ring 24. During operation of the two-cylinder thick matter pump 1, the pressure F2 of the pumped medium causes the automatic ring 25 to be compressed radially and expand axially, whereby the cutting ring 27 presses more strongly against the wall of the pipe switch housing.

[0039] 11 and thus seals the inlet opening 17 of the switch pipe 12 particularly well due to the pressure of the thick material. By varying the cutting ring 26 and the retaining ring 24 with differently shaped projections 37, the shape and in particular the thickness of the automatic ring 25 can be changed and thus adapted to different pressure ratios or conveying conditions. The cutting ring 26 has, for example, specially shaped cutting edges 27 on the inside and outside both on its side oriented towards the pipe switch housing 11, which cut off or sever in particular biological or softer thick materials when the outlet opening 17 is pivoted in front of the outlet openings of the conveying cylinders 6 and do not simply push them to the side.

[0040] In the embodiments presented here, the first material 15a of lower hardness is oriented towards the pipe switch housing 11 and, as described above, is fixed in the annular recess and the axial sealing ring 15 slides with the second material 15b of greater hardness on the outlet opening

[0041] 9 of the switch tube 12. It should be noted that designs are also conceivable in which the axial sealing ring 15 is fixed to the outlet opening 9 of the switch tube 12 with the first material 15a, and the second material 15b of greater hardness is oriented toward the switch tube housing 11 and slides thereon. List of reference symbols

[0042] 1 two-cylinder thick matter pump

[0043] 2 pipe switch

[0044] 3 hydraulic cylinders

[0045] 4 water tank

[0046] 5 hydraulic pistons

[0047] 6 conveyor cylinders

[0048] 7 delivery pistons

[0049] 8 Inlet opening S-pipe switch

[0050] 9 Outlet opening S-pipe switch

[0051] 10 Drive shaft

[0052] 11 Pipe switch housing

[0053] 12 switch pipe

[0054] 13 Rotary actuator

[0055] 14 Guide bushing

[0056] 15 Axial sealing ring

[0057] 15a first material of lower hardness

[0058] 15b second material of greater hardness

[0059] 16 conveyor channel

[0060] 17 Inlet seal

[0061] 18 Wear sleeve

[0062] 19 annular recess

[0063] 20 first radial sealing ring

[0064] 21 second radial sealing ring

[0065] 22 third radial sealing ring

[0066] 23 plain bearings

[0067] 24 retaining ring

[0068] 25 automatic ring

[0069] 26 cutting ring

[0070] 27 Cutting edge

[0071] 28 Thick material feed

[0072] 29 Outlet flange

[0073] 30 filling containers

[0074] 31 Area

[0075] 32 Lubrication chamber

[0076] 34 Lubrication supply

[0077] 35 Adjusting screw

[0078] 36 lubrication grooves

[0079] 37 lead

Claims

Patent claims 1. Pipe switch (2) for a two-cylinder thick matter pump (1), wherein the pipe switch (2) has a switch pipe (12) pivotably mounted about a pivot axis (S) in a filling container (30) of a pipe switch housing (11), wherein the switch pipe (12) has an inlet opening (8) arranged eccentrically to the pivot axis (S) and an outlet opening (9) arranged coaxially to the pivot axis (S), wherein the inlet opening (8) of the switch pipe (12) is axially sealed with respect to the pipe switch housing (11) by an inlet seal (17) and the outlet opening (9) of the switch pipe (12) is axially sealed with respect to the pipe switch housing (11) by an axial sealing ring (15), characterized in that the axial sealing ring (15) is formed from at least a first material (15a) and a second material (15b), wherein the hardness of the first material (15a) and the second material (15b) is different.

2. Pipe switch (2) according to claim 1, characterized in that the second material (15b) oriented towards the outlet opening (9) of the switch pipe (12) has a greater hardness than the first material (15a) oriented towards the pipe switch housing (11).

3. Rohiweiche (2) according to claim 2, characterized in that the second material (15b) with the greater hardness is a metallic material.

4. Rohiweiche (2) according to claim 2 or 3, characterized in that the first material (15a) with the lower hardness is a plastic or a rubber.

5. Pipe switch (2) according to one of the preceding claims, characterized in that the axial sealing ring (15) is radially mounted in an annular recess (19) of the pipe switch housing (11).

6. Pipe switch (2) according to claim 5, characterized in that the first material (15a) of lower hardness oriented towards the pipe switch housing (11) is designed to be pressed radially into the annular recess (19) during the thick matter conveyance by the pressure of a conveying medium conveyed by the two-cylinder thick matter pump (1).

7. Pipe switch (2) according to one of claims 5 or 6, characterized in that the axial sealing ring (15) is designed to be fixed in the annular recess (19) by the pressure of a conveying medium conveyed by the two-cylinder thick matter pump (1) in the switch pipe (12) by means of deformation of the first material (15a) of lower hardness.

8. Pipe switch (2) according to one of claims 2 to 7, characterized in that the axial sealing ring (15) is designed to slide with the second material (15b) of greater hardness on the outlet opening of the switch pipe (12) during a pivoting operation of the switch pipe (12).

9. Pipe switch (2) according to one of the preceding claims, characterized by a guide bush (14) arranged in the pipe switch housing (11), enclosing the outlet opening (9) of the switch pipe (12) and designed to support the outlet opening (9) of the switch pipe (12).

10. Pipe switch (2) according to claim 9, characterized by at least one radial sealing ring (20, 21, 22) arranged in the guide bush (14), which is designed in addition to the axial sealing ring (15) to seal the outlet opening (9) of the switch pipe (12).

11. Pipe switch (2) according to claim 10, characterized in that a sliding bearing (23) for radially supporting the outlet opening (9) of the switch pipe (12) is arranged in the guide bush (14), wherein at least one first radial bearing (23) arranged in the guide bush (14) Sealing ring (20) is designed to seal the sliding bearing (23) against the filling container (30) of the pipe switch housing (11).

12. Pipe switch (2) according to claim 11, characterized in that at least one second radial sealing ring (21) arranged in the guide bush (14) is designed to seal the plain bearing (23) towards the axial sealing ring (15).

13. Pipe switch (2) according to one of claims 9 to 12, characterized by a wear sleeve (18) enclosing the outlet opening (9) of the switch pipe (12).

14. Axial sealing ring (15) for sealing an outlet opening (9) of a switch pipe (12) of a switch pipe (2) for a two-cylinder thick matter pump (1) with respect to a switch pipe housing (11) of the switch pipe (2), characterized in that the axial sealing ring (15) is formed from at least a first material (15a) and a second material (15b), the hardness of the first material (15a) and the second material (15b) being different.

15. Two-cylinder thick matter pump (1) with a pipe switch (2) according to one of the preceding claims and / or an axial sealing ring (15) according to one of the preceding claims.

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