EP3653880B1 - Rotary pump with mechanical seal - Google Patents

Description

The invention relates to a rotating pump with at least one driven conveying element, which is arranged in a product space through which the product to be conveyed flows and is driven by means of a shaft protruding from the outside into the product space, and wherein the shaft is sealed against a wall of the product space, the The seal is designed as a mechanical seal to be mounted on the product side and comprises a form-fitting position securing device in order to prevent the mechanical seal from twisting and shifting of the mechanical seal in the direction of the product area.

Correspondingly constructed pumps are known both as flow pumps and as positive displacement pumps.

A well-known measure for sealing the shaft against the wall is, for example, the use of shaft sealing rings. However, these are only reliable to a limited extent and are particularly out of the question if the type of product to be conveyed requires a particularly secure seal, e.g. when conveying toxic substances or in the hygienic area, e.g. in the food and cosmetics industry.

In these areas, the use of mechanical seals has established itself, which ensure a very good seal. However, this is paid for by the complex structure of the seal. The seal generally has at least one rotating section connected to the shaft and a stationary section mounted in the wall.

For the seal to function reliably, the stationary section must be secured axially and against rotation. Here, the axial securing must also prevent the mechanical seal from shifting in the direction of the product space, since otherwise the function of the seal cannot be guaranteed in the event of a negative pressure in the product space. For this purpose, this section usually has a flange or a receptacle which is fixed in the wall in a force-fitting and / or form-fitting manner, for example by screwing with several screws or by shrinking.

In many cases, especially in the case of pumps for hygienic products such as food or cosmetics, it is not desirable or simply not possible to arrange a flange or a receptacle in the product space, as this impairs the product flow and the corresponding contours are difficult to clean. Therefore, the assembly of the flange must be carried out from outside the product area. This is disadvantageous for several reasons.

To assemble the flange, the shaft must be pulled completely out of the product space. With many pumps, this requires a complete separation of the product area and the pump drive. Since the rotating section of the mechanical seal can only be installed from the product side at the same time, the replacement or maintenance of the seal is very complex. In addition, when the product space with the installed stationary section of the seal and the pump drive are brought together, there is a risk that the seal will be damaged by uncontrolled contact with the shaft.

From the EP3214311A1 a pump is known in which the shaft is sealed by means of a mechanical seal to be mounted on the product side, the mechanical seal being secured in bearings by a securing element arranged outside the product space. Here, however, the fastening of the securing element is difficult because it is located in a narrow leakage space between the wall of the product space and a bearing housing.

From the US 2012/0213657 A1 and the EP 0 884 478 A1 Rotating pumps with a mechanical seal that can be mounted on the drive side are known, in which a stationary ring of the mechanical seal is secured with screws running through a wall of the drive housing.

It is therefore the object of the invention to provide a rotating pump which is improved with regard to the problems described.

This object is achieved according to the invention by a rotating pump with at least one driven conveying element, which is arranged in a product space through which the product to be conveyed flows and is driven by means of a shaft protruding from the outside into the product space, and the shaft against a wall of the product space is sealed, the seal being designed as a mechanical seal to be mounted on the product side and comprising a form-fitting position lock to prevent the mechanical seal from twisting and shifting of the mechanical seal in the direction of the product space, which is further developed in that the position lock is perpendicular to an axial direction of the Includes shaft extending through the wall securing element.

Because the securing element runs through the wall perpendicular to the axial direction of the shaft, the securing element ends outside the product space in an area in which the securing element can easily be handled.

In a preferred embodiment of a pump according to the invention, the mechanical seal can comprise a stationary sleeve inserted into the wall, in which a first sliding ring is received, and a rotating sleeve fastened on the shaft, in which a second sliding ring is received, the securing element can engage in a recess of the stationary sleeve. In this embodiment, the position of the mechanical seal can be secured in a particularly simple manner.

According to the invention, the securing element comprises a pin guided through a bore in the wall.

The bore has an enlarged diameter at an end remote from the seal and is provided with an internal thread. Furthermore, the pin is received with one end remote from the seal in a sealing screw which is screwed into the bore. As a result, on the one hand, the pin is fixed in the bore in a particularly simple manner, and on the other hand, the bore is sealed against the environment so that no air can be drawn through the bore into the product space when a negative pressure occurs in the product space.

In a further preferred embodiment of a pump according to the invention, the shaft can extend outside of the product space into a bearing housing, a leakage space being formed between the wall of the product space and the bearing housing, and the leakage space being covered to the outside by a sheet-like protection guard which can be attached to the wall by means of the sealing screw.

A pump according to the invention can be a twin screw screw pump.

The invention is explained in more detail below with reference to a few figures.

• Figur 1: Eine Pumpe,
• Figur 2: Eine horizontale Schnittdarstellung einer Pumpe.

Show it:

• Figure 1 : A pump,
• Figure 2 : A horizontal sectional view of a pump.

In Figure 1 a pump 1 is shown, which is a single-flow screw pump. The pump 1 has a gear section 2 and a pump section 3.

The gear section consists of a bearing housing 5 with an inspection opening which is closed by a cover 6. The pump section comprises a product inlet 7 and a product outlet 8.

A leakage space is arranged between the gear section 2 and the pump section 3 and is secured by an anti-intrusion guard 9.

The internal structure of the pump 1 is shown in FIG Figure 2 shown. Two displacement bodies 10, 11 in the form of feed screws are arranged in a product space of the pump section 3. By turning the two displacement bodies 10, 11 in opposite directions, the product to be conveyed is removed from the in Figure 2 not visible product inlet to the product outlet 8 promoted.

The displacers 10, 11 are fastened at the ends on shafts 12, 13 and secured there by means of nuts 14, 15. In order to prevent the displacement bodies 10, 11 from rotating on the shafts 12, 13, they can have suitable form-locking elements.

The displacement bodies 10, 11 engage with one another with very little play in order to enable efficient product conveyance. For this purpose, the shafts 12, 13 must be mounted precisely and stiffly. The shafts 12, 13 are supported in the gear section 2.

The bearing housing 5 of the gear section 2 consists of a main body 16 and a closing body 17, which are releasably fastened to one another, for example by means of a screw connection.

For the precise alignment of the closing body 17 to the main body 16, the closing body 17 has a planar first stop surface 18 which rests against a corresponding stop surface of the main body. A surface normal of the stop surface 18 runs approximately parallel to the axial direction of the shafts 12, 13.

Furthermore, the closing body 17 has a circumferential second stop surface 19 which rests on the inside against a corresponding stop surface of the main body 16. A surface normal of the stop surface 19 runs approximately perpendicular to the axial direction of the shafts 12, 13 at each point of the stop surface 19. Starting from the second stop surface 19, the closing body 17 tapers in the direction of the pump section 3.

The main body 16 has receiving bores 22,23 into which radially acting bearings 24,25 are inserted, needle bearings in the example shown. The inner rings of the needle bearings are shrunk onto the respective shafts, while the outer rings and the needle cages of the needle bearings are axially fixed in the receiving bores 22, 23 between a stop shoulder and a clamping ring.

The closing body 17 has receiving bores 30,31 into which radially and axially acting bearings 32,33 are inserted. In the example shown, the radially and axially acting bearings 32, 33 each include three angular contact ball bearings. Other numbers of ball bearings are possible, each of the bearings 32, 33 comprising at least two oppositely positioned angular contact ball bearings for good support.

The inner rings of the bearings 32,33 are fixed on the shafts 12,13 by means of locknuts 34,35. The outer rings of the bearings 32, 33 are fixed in the receiving bores 30, 31 between a stop shoulder and fixing plates 36, 37 screwed to the closing body 17 within the bearing housing 5.

The shaft 10 serves as a drive shaft and therefore has a drive journal 38 which protrudes from the bearing housing 5. For this purpose, the receiving bore 30 is designed as a through hole, while the receiving bore 33 is designed as a blind hole.

Between the radially acting bearings 24, 25 on the one hand and the radially and axially acting bearings 32, 33 on the other hand, a synchromesh gear 40 is arranged, by means of which the shafts 12, 13 are rotationally coupled.

A first pinion 41 of the synchronous gear 40 is fastened in a rotationally fixed manner on the shaft 10 by means of a feather key connection. The pinion 41 is axially fixed between a stop shoulder of the shaft 12 and the inner rings of the bearing 32.

A second pinion 42 must be attached to the shaft 13 so that it can rotate with respect to one another for the rotational alignment of the displacement bodies 10, 11. For this purpose, the pinion 42 comprises a ring gear 43 which is seated on a sleeve 44. The sleeve 44 is fastened in a rotationally fixed manner on the shaft 13 by means of a feather key connection and, like the pinion 41, is axially fixed between a stop shoulder of the shaft 13 and the inner rings of the bearing 33.

The sleeve 44 has a circumferential projection 45 on which the ring gear 43 rests. A ring 46 rests on the projection 45 from the other side. The ring gear 43 and the ring 46 are screwed to one another and are thus fixed to the projection 45 in a force-locking manner.

To set the correct rotational angular position of the displacers 10, 11 relative to one another, the screw connection of the ring 46 to the ring gear 43 is loosened somewhat so that the ring gear can be rotated against the sleeve 44 and thus against the shaft 13. Is the When the correct position is reached, the screw connection between the ring gear 43 and the ring 46 is tightened again.

When the pump 1 is in operation, an oil sump is provided in the bearing housing 5, into which the pinions 41, 42 of the synchronous gear 40 are immersed. The rotating pinions 41,42 generate an oil mist which cools and lubricates the bearings 24,25,32,33.

To assemble the gear section 2, the inner rings of the bearings 24, 25 are first shrunk onto the shafts 12, 13. Then, one after the other, the pinions 41, 42, the fixing disks 36, 37 and then the bearings 32, 33 are placed on the shafts 12, 13 and fixed by means of the locknuts 34, 35.

Next, the shafts 12, 13 with the bearings 32, 33 are inserted into the receiving bores 30, 31 and fixed to the closing body 17 by screwing the fixing plates 36, 37.

Finally, the closing body 17 with the mounted shafts 12, 13 is inserted into the main body 16. The free ends of the shafts 12, 13 are guided through the receiving bores 22, 23 of the main body.

At its end facing the pump section 3, the closing body 17 is tapered in such a way that it can be inserted into the main body 16 without any problems. Only when the stop surface 19 enters the main body 16 is the closing body 17 guided closely. The stop surface 19 extends in the axial direction of the shafts 12, 13 over a length that is significantly less than the length of the bearings 32, 33, namely less than 35%, preferably less than 30%, particularly preferably less than 25% of the length of the bearings 32.33. In the example shown, the extent of the stop surface 19 in the axial direction of the shafts 12, 13 is approximately 17% of the length of the bearings 32, 33.

The introduction of the closing body 17 into the main body 16 is further facilitated by the fact that the extension of the stop surface 19 in the axial direction of the shafts 12, 13 is less than the length of the radially acting bearings 24, 25. As a result, the shafts 12, 13 are already supported by the bearings 24, 25 before the stop surface 19 enters the main body 16. Thus, the closing body 17 cannot tilt during assembly.

As soon as the stop surface 18 lies completely against the main body 16, the closing body is fixed by screws. The passages of the shafts 12, 13 and the drive journal 38 through the bearing housing 5 are sealed by means of shaft sealing rings.

The passages of the shafts 12, 13 through a wall 50 of the product space are sealed by two identical mechanical seals 51, 52, of which, for the sake of simplicity, only the mechanical seal 52 is described in detail below.

The mechanical seal 52 comprises a stationary sleeve 53 which is inserted into a receiving bore 45 in the wall 50. A first slide ring 55 is received in the stationary sleeve 53 in a rotationally fixed manner. Furthermore, the mechanical seal 52 comprises a rotating sleeve 56 which is fixed on the shaft 13 between a stop shoulder and the displacement body 11. A second slide ring 57 is received in a rotationally fixed manner in the rotating sleeve 56.

The sliding rings 55, 57 rest against one another with planar sliding surfaces and are axially pretensioned against one another by spring elements 58.

For the mechanical seal 52 to function reliably, the stationary sleeve 53 must be secured against twisting in the receiving bore 54. At the same time, it must be prevented that the stationary sleeve 53 is pulled out of the receiving bore 54 with compression of the spring elements 58 in the direction of the product space when a negative pressure occurs in the product space.

For this purpose, the stationary sleeve 53 has a recess 60 on its outer circumference, into which a securing element 61 extending through the wall 50 engages. In addition, the stationary sleeve 53 can have a flat surface (not shown) in the region of the recess 60 in order to simplify the correct alignment of the sleeve 53 during assembly.

The securing element 61 comprises a pin 62 which runs through a bore 63 in the wall 50. At an end remote from the mechanical seal 52, the bore 63 is widened and provided with an internal thread 64. A sealing screw 65, in the shaft of which the pin 62 is received, is screwed into the internal thread 64.

The length of the pin 62 is dimensioned such that, when the sealing screw 65 is screwed in completely, it engages positively in the recess 60 of the stationary sleeve 53 without exerting a radial force on the stationary sleeve 53. As a result of a radial force, there would be the risk that the sleeve 53 would be deformed and thus the sealing effect of the mechanical seal 52 would be impaired.

The sealing screw 65 seals the bore 63 from the surroundings of the pump 1, so that no air can be sucked in through the bore 63 in the event of a negative pressure in the product space.

The sealing screw 65 also serves to fasten the access protection 9 to the wall 50.

Maintenance or repair of the mechanical seals 51, 52 can be carried out simply from the product side without opening the bearing housing 5. For this purpose, an outlet cover 70 and a product space section 71 are removed and the displacement bodies 10, 11 are pulled off the shafts 12, 13. The rotating sleeve with the second slide ring 57 can then be pulled off the shaft.

Next, the securing element 61 is released so that the stationary sleeve 53 with the first sliding ring 55 can also be pulled out of the receiving bore 54 in the direction of the product space.

The installation of the mechanical seal 52 takes place in the opposite sequence.

Instead of the single-acting mechanical seals 51, 52 shown, the pump 1 can be equipped with double-acting mechanical seals. Such double-acting mechanical seals can be flushed from the inside during operation; flushing channels (not shown) are provided in the wall 50 for this purpose. In this case, the correct rotational alignment of the mechanical seals in the receiving bores is particularly important so that the flushing openings of the mechanical seals lie against the ends of the flushing channels.

Claims (4)

1. Rotating pump with at least one driven conveying element (10, 11), which is disposed in a product chamber through which the product to be conveyed flows and is driven by means of a shaft (12, 13) extending into the product chamber from the exterior, wherein the shaft (12, 13) is sealed against a wall (50) of the product chamber, and wherein the seal is in the form of a mechanical seal (51, 52) to be mounted on the product side and comprises a positive-locking positional securing means in order to prevent rotation of the mechanical seal (51, 52) and displacement of the mechanical seal (51, 52) in the direction of the product chamber, characterized in that the positional securing means comprises a securing element (61) extending perpendicularly to an axial direction of the shaft (12, 13) through the wall (50), wherein the securing element (61) comprises a pin (62) guided through a bore (63) of the wall (50),
   the bore (63) having an enlarged diameter at an end remote from the seal and being provided with an internal thread (64), and
   the pin (62) being received with an end remote from the seal in a sealing screw (65) which is screwed into the bore (63).
2. Pump according to claim 1, characterized in that the mechanical seal (52) comprises

   - a stationary sleeve (53) inserted in the wall (50) in which a first sliding ring (55) is received, and

   - a rotating sleeve (56) fixed on the shaft (13), in which a second sliding ring (57) is received,

   wherein the securing element (61) engages a recess (60) of the stationary sleeve (53).
3. Pump according to claim 1 or 2, characterized in that the shaft (12, 13) extends outside the product chamber into a bearing housing (5), wherein a leakage space is formed between the wall (50) of the product chamber and the bearing housing (5), and wherein the leakage space is covered to the exterior by a sheet metal-shaped engagement protection (9), which is fixed to the wall (50) by means of the sealing screw (65).
4. Pump according to any one of claims 1 to 3, characterized in that the pump is a twospindle screw pump (1).

Images