Shaft seal for a process plant

Abstract

The invention relates to a shaft seal for a process plant, which has at least one housing (14) comprising at least one housing wall (15), and a rotating shaft (13) which extends through an opening in the housing wall (15), wherein the shaft seal is designed as a sealing unit (12) which seals the shaft (13), wherein the sealing unit (12) is connected to the rotating shaft (13) for conjoint rotation therewith, and the sealing unit (12) comprises a sealing disc (7) with a self-lubricating property, which bears slidingly against the housing wall (15).

Description

[0001]Shaft seal for a process engineering plant The invention relates to a shaft seal for a process engineering plant according to the preamble of patent claim 1. A process engineering plant is understood to mean the comminution, agglomeration, separation and screening, mixing, as well as the storage and conveying of materials. An example of a process engineering plant is a mixer or a dosing and conveying screw. The process engineering plant preferably has a housing which forms the product space within which the product is processed. A shaft is arranged within the housing and extends out of the housing. The shaft transmits rotary movements and torques. Such a shaft is supported by bearings, whereby the bearings transmit the occurring radial and axial forces to the housing.The requirement now is to seal the shaft from the housing to prevent material from escaping from the housing. Seals are used in process engineering plants where material systems are transformed through predominantly mechanical influences. The seals are designed to reduce or prevent the ingress or escaping of gases, liquids or solids at the points where components are separated. A distinction is made between static (stationary) seals, which seal between components that are not moving relative to one another, and dynamic seals (motion seals), which are used wherever components move relative to one another. Dynamic seals have the disadvantage that when the rotating shaft vibrates, material can work its way through the seal and ultimately escape from the housing.US 7,178,806 B1 discloses a seal commercially available under the name CinchSeal. Such a seal is preferably used in screw conveyors and bulk material processing plants. The seal consists of a first flange, which is placed outside the housing on the rotating shaft. An elastomer seal and two rotor caps are then arranged on the shaft, which are surrounded by a seal housing. The housing is pressure-tight and is subjected to overpressure. Although the CinchSeal seal can seal off shaft vibrations to a certain extent, its design is very complex because a pressure-tight housing is required. Furthermore, the seal package of the CinchSeal seal must be positioned opposite the rotating shaft.The invention is therefore based on the object of developing a shaft seal for a process engineering plant in such a way that it has a simpler and more cost-effective design. To achieve this object, the invention is characterized by the technical teaching of claim 1. An essential feature of the invention is that the seal package is connected to the rotating shaft in a rotationally fixed manner and that the seal package has a sealing disk with self-lubricating properties that slides against the housing wall. In a first preferred embodiment, the seal package forms a unit that is arranged on the rotating shaft of the process engineering plant. The seal package is connected to the shaft and rotates with it. It is therefore an idler seal. The seal package has a sealing disk that is in contact with the surface of the housing.Thus, there is no relative movement between the shaft and the seal, but rather between the sealing washer and the housing or the bearing mount of the shaft. In a preferred embodiment, the sealing washer is made of polyetheretherketone (PEEK). Preferably, the sealing washer is made of polyetheretherketone + solid lubricant (PEEK-TX), which is particularly suitable for use in the food industry and has high wear and sliding properties. In a further preferred embodiment, the sealing washer is designed as a type of thrust washer, which has high wear resistance and a long service life. The use of such a sealing washer is a cost-effective and space-saving solution for the axial guidance of the shaft relative to the housing or the bearing mount of the shaft.The above-mentioned materials all have self-lubricating properties and are used, for example, as bushings, seals, bearings or retaining rings. The self-lubricating property of the sealing washer means that components in the seal package can be eliminated and, at the same time, maintenance requirements are reduced. The rotating shaft of the process plant extends through an opening in the housing. The opening is designed, for example, as a bore. The seal package is arranged outside the housing on the shaft, with the self-lubricating sealing washer of the seal package being in direct sliding contact with the surface of the housing. The seal package is firmly connected to the shaft and rotates with the shaft. Consequently, the sealing washer also rotates and is in sliding contact with the housing surface. Preferably, the housing wall orthe surface of the housing in the contact area of ​​the sealing washer is free of grooves, so that good sliding friction is achieved. The sealing washer of the seal package has a circular recess for the shaft. A sealing ring, which is designed as a shaft seal and provides a seal against the shaft, is preferably arranged in the recess of the sealing washer. The shaft seal is made of silicone, for example, and is designed as a flat gasket or a grooved ring. In general, the sealing ring provides sufficient sealing against the shaft. To increase the sealing effect, a compressive force is generated on the sealing ring, causing it to expand or squeeze radially. The necessary compressive force is generated by a thrust ring. The thrust ring has an axial projection which, when installed, is in contact with the sealing ring and with which the compressive force is transferred to the sealing ring.The diameter of the projection roughly corresponds to the diameter of the sealing ring. The thrust ring can also be referred to as a driving ring or shaft seal holder and is preferably made of a metallic material. However, other materials such as plastics or fiber-reinforced plastic are also possible. The thrust ring is located between the sealing washer and a mounting flange. The thrust ring is attached to the sealing washer using cylinder head screws (e.g. M5). For this purpose, the sealing washer preferably has holes with internal threads. When fitting the thrust ring, the cylinder head screws are only tightened loosely so that the thrust ring is positioned with a certain amount of play relative to the sealing washer and does not yet squeeze the shaft seal.The mounting flange is mounted on the sealing washer using shaft screws. The shaft screws have a stepped collar that defines the distance between the sealing washer and the mounting flange. These shaft screws are therefore referred to as spacers. The spacers primarily serve as assembly aids. After the seal package has been installed on the shaft, the spacers are removed. To connect the sealing washer to the mounting flange, the spacers are inserted through holes in the mounting flange and screwed into internal threads in the sealing washer. Because the screw head of the spacer is larger than the hole diameter in the mounting flange, a detachable connection is created between the two components. The preload can be increased by placing washers underneath.Since the spacers are screwed into the threads of the sealing washer and the sealing washer is made of plastic, assembly is preferably carried out by hand to avoid excessive forces. Once the seal package has been completely assembled and fitted, the spacers can be removed again. The mounting flange can also be referred to as the base flange and is preferably made of a metallic material. However, other materials such as plastics or fibre-reinforced plastic are possible. The mounting flange has several threaded holes through which the compression springs are inserted. The compression springs are helical compression springs or spiral springs made of metal, which are elastically deformable. Instead of compression springs, however, other elastic elements such as disc springs, rubber elements, hydraulic elements or the like can also be used.The sealing washer preferably has circular recesses aligned with the holes in the mounting flange, into which the compression spring engages and is held securely against possible slipping. After inserting the compression springs into the holes in the mounting flange, the guide screws are screwed into the threads of the holes. The guide screws are M16 screws, for example, which are tightened to a defined torque. The preload on the sealing washer can be adjusted using the guide screws and the compression springs. The assembled seal package is then placed on the shaft and pushed against the housing wall. The surface of the sealing washer is in contact with the surface of the housing. The seal package is attached to the shaft with a rotationally fixed connection. Preferably with a shaft-hub connection.The shaft-hub connection can, for example, be a force-fit connection (frictional connection), a form-fit connection, a preloaded form-fit connection, or a material-fit connection. In a preferred embodiment, the shaft-hub connection has radial pins (e.g. threaded pins, grub screws) which are inserted through holes in the mounting flange and engage in grooves or recesses provided for this purpose in the shaft. After the seal package has been positioned and fixed on the shaft, the cylinder head screws can be tightened, whereby the thrust ring exerts a compressive force on the sealing ring, which is compressed or squeezed and presses further against the shaft. This further increases the sealing effect between the sealing washer and the shaft.The shaft screws, which were used as spacers and assembly aids, can then be unscrewed from the mounting flange. The entire seal package now rotates with the shaft. Sealing is achieved via the sealing washer and the sealing ring. The pressure force on the sealing washer can be adjusted using the compression springs on the mounting flange and the spacers. Preferably, in the seal package according to the invention, the diameters of the sealing washer and the mounting flange are the same. However, the invention is not limited to this. Rather, it is possible for the sealing washer, for example, to have a smaller diameter than the mounting flange. Or the sealing washer can have a stepped collar, which reduces the contact area between the housing surface and the sealing washer.In a preferred embodiment, the process plant is a mixer or kneader used in the food industry. The sealing package according to the invention thus has the following functional principles: • The preload is adjustable using spacers (=shaft screws) and compression springs; • The sealing package is pushed onto the shaft and held in its final position; • The sealing package has a mounting flange that is clamped to the shaft with three threaded pins (grub screws); • Once the sealing package is firmly seated on the shaft, the four spacers are removed again.• Due to the axial fixation of the mounting flange on the shaft, the compression springs now exert a compressive force on the sealing washer, pressing it against the sealing surface of the housing wall; • There is no relative movement between the rotating shaft and the sealing washer, but rather a relative movement between the sealing washer and the rigid housing wall; • Cylindrical pins are located between the sealing washer and the mounting flange, which drive the sealing washer when the shaft rotates. The subject matter of the present invention arises not only from the subject matter of the individual patent claims, but also from the combination of the individual patent claims with one another.All information and features disclosed in the documents, including the abstract, in particular the spatial configuration depicted in the drawings, are claimed as essential to the invention, insofar as they are novel, individually or in combination, compared to the prior art. The invention is explained in more detail below with reference to drawings illustrating only one embodiment. Further essential features and advantages of the invention will become apparent from the drawings and their description.They show: Figure 1: Perspective view of the seal package Figure 2: Exploded view of the seal package Figure 3: Schematic representation of the seal package on the shaft Figure 4: Top view of the seal package showing the sections AA, BB and FF Figure 5: Schematic representation of section AA Figure 6: Schematic representation of section BB Figure 7: Schematic representation of section FF Figure 8: Schematic side view of the seal package Figure 9: Another embodiment of the seal package with grooved ring Figure 10: Schematic representation of the seal package in the installed state on a shaft Figure 1 shows the seal package 12 according to the invention in the assembled state. The seal package 12 consists of a round sealing disc 7 made of a self-lubricating material. The sealing disc 7 has a plurality of recesses 23 in which the compression springs 3 are arranged.The compression springs 3 are located between the sealing washer 7 and the mounting flange 1. Figure 1 shows the assembled seal package 12, but the seal package 12 is not yet mounted on a shaft. For this reason, the spacers 9 are still located in the respective bores of the mounting flange 1 and the corresponding threads 24 of the sealing washer 7. Figure 2 shows the seal package 12 in an exploded view. The sealing washer 7 is preferably made of the material PEEK-TX and has a circular recess 18 in the center for the shaft 13. The round shaft seal 5 is inserted into a holder 25 in the circular recess 18 of the sealing washer 7. The thrust ring 4 is placed on the sealing washer 7 and fastened with cylinder head screws 6. The thrust ring 5 has a round shoulder whose diameter approximately corresponds to the diameter of the recess 18.When the sealing package 12 is assembled, the shoulder presses on the shaft seal 5. The thrust ring 4 is designed as a driving ring and has a total of four protruding eyelets for cylindrical pins 10 on its circumference. The cylindrical pins 10 are arranged opposite the sealing washer 7 and enable axial movement of the thrust ring 4. The compressive force on the shaft seal 5 can be adjusted using the cylinder head screws 6. The fastening flange 1 is located above the thrust ring 5. The fastening flange 1 has a similar diameter to the sealing washer 7 and is preferably made of a metallic material. Distributed around the circumference are a total of eight holes with internal threads for the guide screws 2. The guide screws 2 are inserted into the holes 21 together with compression springs 3.Preferably, the sealing disc 7 has small recesses aligned with the bores 21 of the mounting flange 1 for the positive-locking reception of the compression springs 3. On the outer circumference of the mounting flange 1, there are further bores for threaded pins 8 and positioning pins 11, which are components of the shaft-hub connection. With the aid of the shaft-hub connection, the entire seal package 12 is firmly connected to the shaft 13 and aligned relative to the shaft 13. The shaft 13 has recesses and / or grooves for this purpose, which in particular enable the seal package 12 to be positioned axially on the shaft 13. The seal package 12 must be positioned such that, when installed, the sealing disc 7 of the seal package 12 is in contact with the housing wall of the process plant. Figure 3 shows the seal package 12 installed on a shaft 13.The shaft 13 has several sections, one section extending through the housing wall 15 of a housing 14 of a process plant. Preferably, one or more bearings for the shaft 13 are located in the area of ​​the housing wall 15, although these are not shown. The seal package 12 has a sealing disk 7 made of a self-lubricating material. The sealing disk 7 is in direct contact with the housing wall 15. Upon radial movement of the shaft 13, the seal package 12 rotates with it, so that sliding friction occurs between the sealing disk 7 and the housing wall 15. According to Figure 3, it can also be seen that the sealing disk 7 has a receptacle 25 within which the shaft seal 5 is arranged. The shaft seal 5 seals the shaft 13 and prevents a substance from escaping from the housing 14. Figure 4 shows the seal package 12 with a top view and the course of the sections AA, BB, and FF.Figure 5 shows section AA of Figure 4. The sealing package 12 essentially consists of a sealing washer 7, a shaft seal 5, a thrust ring 4, and a fastening flange 1. The sealing washer 7 has a receptacle 25 for the shaft seal 5. The receptacle 25 is designed as a shoulder within the recess 18 and prevents the shaft seal 5 from slipping out of the sealing washer 7. On the opposite side is the thrust ring 4, which presses onto the shaft seal 5 with the projection 19 and deforms it. Figure 6 shows section BB of Figure 4. The sealing package 12 is pre-assembled. With the help of the spacers 9, a defined distance is achieved between the sealing washer 7 and the fastening flange 1. The spacers 9 are used for mounting the guide screws 2 and compression springs 3.The spacers 9 can be used to determine the vertical distance between the sealing washer 7 and the fastening flange 1. This is particularly necessary for the correct assembly of the sealing package 12 on the shaft 13. The reference numeral 17 indicates the preload, which can be adjusted during assembly. Figure 7 shows section FF of Figure 4. The cylindrical pins 10 are used to fix the thrust ring 4 and are clamped in the desired position with the positioning pins 10. Figure 8 shows the sealing package 12 in a side view, with the compression springs 3 arranged between the sealing washer 7 and the fastening flange 1. Figure 9 shows a further embodiment of the sealing package 12, wherein the shaft seal 5 is designed as a grooved ring, which is arranged in the recess 18 of the sealing washer 7. The grooved ring is supported on the receptacle 25, which is designed as a radial shoulder.Figure 10 shows the seal package 12 in the installed state. In the housing wall 15 there are two bores 28 and two recesses 26. This only shows an embodiment with an installed shaft 13 and an embodiment without an installed shaft 13, by way of example. The seal package 12 is arranged on a shaft 13 which extends through a bore 28 in the housing wall 15 of a housing 14. In the area of ​​the bore 28, the housing wall 15 has a circular recess 26 with a sealing surface 27 for the seal package 12. When the seal package 12 is installed, the sealing disk 7 rests against the sealing surface 27, whereby when the shaft 13 rotates a relative movement takes place between the sealing disk 7 and the sealing surface 27 of the rigid housing wall 15. Drawing legend 1. Mounting flange 2. Guide screw 3. Compression spring 4. Thrust ring 5. Shaft seal 6. Cylinder head screw 7. Sealing washer 8. Grub screw 9.Spacer 10. Cylindrical pin 11. Positioning pin 12. Seal package 13. Shaft 14. Housing 15. Housing wall of 14 16. Contact surface 17. Preload 19. Projection of 4 20. Shoulder of 7 21. Bore for 2 22. Bore for 9 23. Recess 24. Thread for 9 25. Receptacle for 5 26. Recess for 12 27. Sealing surface of 26 or 15.

Claims

AMENDED CLAIMS received by the International Bureau on 4 December 2024 (04.12.2024) 1 . Shaft seal for a process plant, which has at least one housing (14) with at least one housing wall (15), as well as a rotating shaft (13) which extends through an opening in the housing wall (15), wherein the shaft seal is designed as a sealing package (12) which seals the shaft (13), wherein the sealing package (12) is connected to the rotating shaft (13) in a rotationally fixed manner, and - the sealing package (12) has a sealing disc (7) with a self-lubricating property which slides against the housing wall (15), characterized in that the sealing package (12) has a sealing disc (7) and a fastening flange (1), wherein between the sealing disc (7) and the fastening flange (1) guide screws (2) with compression springs (3) are provided, which, starting from the fastening flange (1), exert a compressive force directed in the axial direction of the shaft (13) on the Sealing washer (7).

2. Weife seal according to claim 1, characterized in that the sealing disc (7) consists of polyetheretherketone (PEEK) or polyetheretherketone and a solid lubricant (PEEK-TX). 3< Shaft seal according to claim 1 or 2, characterized in that the sealing disc (12) has a shaft seal (5) for sealing on the outer circumference of the width (13), wherein the shaft seal (5) is designed as a flat seal or as a grooved ring.

4. Shaft seal according to one of claims 1 to 3, characterized in that the sealing disc has a receptacle (25) for a shaft seal (5). AMENDED SHEET (ARTICLE 19) 5. Shaft seal according to one of claims 1 to 4, characterized in that the sealing package (12) has a sealing disc (12) and a fastening flange (1), wherein between the sealing disc (12) and the fastening flange (1) a pressure ring (4) is arranged, which exerts a pressure force directed in the axial direction of the shaft (13) on a shaft seal (5) in the sealing disc (7).

6. Shaft seal according to claim 5, characterized in that the pressure ring (4) is fastened to the sealing disc (7) by means of cylinder head screws (6), wherein the pressure force of the pressure ring (4) on the shaft seal (5) can be adjusted by means of the cylinder head screws (6).

7. Shaft seal according to one of claims 1 to 6, characterized in that the rotationally fixed connection between the sealing package (12) and the shaft (13) is designed as a shaft-hub connection.

8. Shaft seal according to one of claims 1 to 7, characterized in that there is a rotationally fixed shaft-hub connection between the fastening flange (1) and the shaft (13).

9. Shaft seal according to one of claims 1 to 8, characterized in that the fastening flange (1) consists of a metal material.

10. Shaft seal according to one of claims 1 to 9, characterized in that the process plant is designed as a mixer or as a kneader and is used in the food industry.

11. Shaft seal according to one of claims 1 to 10, characterized in that the sealing disc (7) is in sliding contact with the housing surface.

12. Shaft seal according to one of claims 1 to 11, characterized in that at least two compression springs (3) are located between the sealing disc (7) and the fastening flange (1).

13. Shaft seal according to one of claims 1 to 12, characterized in that a total of eight guide screws (2) with eight compression springs (3) are arranged over the circumference of the fastening flange (1). AMENDED SHEET (ARTICLE 19) 14. Shaft seal according to one of claims 1 to 13, characterized in that the sealing disc (7) has circular recesses into which the compression springs (3) engage.

15. Wave seal according to one of claims 1 to 14, characterized in that the compression springs (3) are designed as helical compression springs or spiral springs made of metal. AMENDED SHEET (ARTICLE 19)

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