Volumetric pump with rotating seal

Abstract

A positive displacement pump (1) is provided with a rotationally driven positive displacement body (10, 11), which is fixed in a product space (51) through which the product to be supplied flows on an associated shaft (12, 13), the shaft (12, 13) penetrating into the product space (51) through a front wall (50) of a supply section (5) of the pump (1), and the passage of the shaft (12, 13) through the front wall (50) being sealed by means of a rotary seal (52), the rotary seal (52) having a first stationary ring (53) and a second ring (54) co-rotating with the positive displacement body (10, 11). The pump is characterized in that the stationary ring (53) is inserted into the shaft passage in the direction of the product space (51) and is supported directly on a spring element (56). Figure for abstract: Fig. 3

Description

Title of the invention: Volumetric pump with rotary seal

[0001] Rotary positive displacement pumps have been in the form of primitive gear pumps since the beginning of the 17th century. In modern pumps, the positive displacement bodies are fixed on shafts, which are preferably arranged outside a product space through which the product to be fed passes.

[0002] In order to prevent unintentional leakage of the product from the product space on the one hand and to protect the product from external impurities on the other hand, the passage of the shaft into the product space must be sealed.

[0003] A known measure for sealing the shaft against the wall is, for example, the use of shaft sealing rings. However, these are only partially reliable and severely limited in pressure, and are particularly not feasible if the type of product to be fed requires a particularly secure seal, for example in the transport of toxic substances or in the field of hygiene, for example in the food, cosmetics and / or pharmaceutical industry.

[0004] In these areas, the use of rotary seals has prevailed, which guarantees a very safe and reliable seal. However, this is achieved by a complex structure of the seal. The seal generally has at least one rotating section connected to the shaft and a fixed section mounted in the wall.

[0005] For safe operation of the seal, the fixed section must be secured axially. To achieve this, this section usually has a flange that is screwed into the wall using several screws.

[0006] In many cases it is not desirable or simply not possible to arrange the flange in the product space, as this affects the flow of the product and the corresponding contours are difficult to clean. Therefore, the mounting of the flange must be carried out outside the product space.

[0007] This is detrimental for various reasons. For flange mounting, the shaft must be completely removed from the product space or the pump housing must be removed from the shaft with all components in contact with the product. For many pumps, this requires complete disassembly of the pump drive. Since the mounting of the rotating section of the rotary seal can only be carried out from the product side, the pump must always be completely disassembled, for example for seal maintenance.

[0008] Known solutions, in which the fixed section can also be mounted from the direction of the product space, are generally complex, since the Fixing the fixed section is not trivial here. For example, DE 10 2016 100 959 Al describes a pump in which the sliding rings of the seal are arranged in a separate sleeve, which is complexly protected against displacement. This complex structure is problematic, especially for small pumps.

[0009] It is therefore a question of providing a volumetric pump with a rotary seal, which is improved with regard to the problems described.

[0010] According to the invention, this problem is solved by a volumetric pump with a rotationally driven volumetric body, which is fixed in a product space through which the product to be supplied flows on an associated shaft, the shaft penetrating into the product space through a front wall of a supply section of the pump, and the shaft passage through the front wall being sealed by means of a rotary seal, the rotary seal having a first stationary ring and a second ring rotating with the volumetric body; which is further formed by the fact that the stationary ring is inserted into the shaft passage from the direction of the product space and is supported directly on an elastic element.

[0011] Thanks to the corresponding design, a very efficient and durable seal can be provided with a very simple structure.

[0012] The spring element may be inserted into the shaft passage from outside the product space. The shaft passage may have an internal projection that prevents the spring element from entering the product space. In addition, the spring element may be axially supported on a snap ring that is inserted into a groove in the shaft passage.

[0013] The stationary ring and / or the projection may include alignment features that prevent rotation of the stationary ring in the shaft passage. Several, for example three, radial surfaces may be provided for this purpose.

[0014] The spring element may comprise one or more Belleville springs, sinusoidal springs, wave springs or similar spring elements. The spring element may be arranged between planar support rings. The use of suitable spring elements ensures uniform support of the stationary ring over the entire circumference.

[0015] The stationary ring may be sealed against the passage of the shaft by an elastomer seal.

[0016] In a possible version of a volumetric pump according to the invention, the co-rotating ring can be housed in a receiving sleeve which is mounted on the shaft. To do this, the receiving sleeve can be fixed between a stop shoulder of the shaft and the volumetric body.

[0017] The co-rotating ring and / or the receiving sleeve may in turn include alignment features that prevent the co-rotating ring from rotating relative to the shaft. One or more radial surfaces may be provided for this purpose.

[0018] The co-rotating ring may be sealed against the receiving sleeve by another elastomer seal.

[0019] In a preferred embodiment of the invention, the positive displacement pump is a screw pump.

[0020] Below, the invention is explained in more detail with the aid of a few examples. The embodiments shown in the figures only serve to better understand the invention, without limiting it.

[0021] These illustrations are:

[0022] [Fig.l]: a volumetric pump with connected drive motor;

[0023] [Fig.2]: the internal structure of the volumetric pump of [Fig.l] in a sectional view;

[0024] [Fig.3]: the internal structure of the volumetric pump of [Fig.l] in another sectional view.

[0025] [Fig.l] shows a positive displacement pump 1 with connected drive motor 2 in a perspective view. The motor 2 is a commercially available electric motor, the structure of which need not be discussed further in the following. The pump 1 comprises a coupling section 3 in which a shaft (not shown) of the pump 1 is removably connected to the drive motor 2, a gear section 4 and a feed section 5. In the feed section 5, volumetric bodies not shown are arranged, which feed a liquid or pasty product from an inlet nozzle 6 to an outlet nozzle 7 when the pump is running. The gear section has a service hatch 8 which is closed by a cover.

[0026] [Fig.2] shows the internal structure of the pump 1 in a horizontal longitudinal section, the coupling section 3, the gear section 4 and the feed section 5 being recognizable.

[0027] In the feed section 5, two cooperating volumetric bodies 10, 11 are arranged, which in this case are feed screws whose flanks fit into each other with a small clearance. The volumetric bodies 10, 11 are fixed at the end to shafts 12, 13 which extend parallel to each other from the feed section 5 through the gear section 4 to the coupling section 3.

[0028] The shaft 12 serves as a drive shaft and is equipped with a coupling in the coupling section 3 for connection to an output shaft of the motor not shown. The type of coupling may vary depending on the requirements of the field respective application. For larger pumps, rigid couplings are conceivable, for smaller pumps, for example, bellows couplings are conceivable. The pump shown in the present embodiment is designed for very small flow rates, a sliding claw coupling 15 is provided here, of which only a hub 16 and a damping body 17 are visible in [Fig. 2]. The coupling section 3 shown also has a flange 18 for connection to the motor 1. In other embodiments, the flange 18 can be omitted. A shaft seal 19 prevents oil from entering the coupling section 3.

[0029] The shaft 13 functions as a driven shaft and terminates at the transition between the gear section 4 and the coupling section 3.

[0030] The shafts 12, 13 are respectively mounted in the gear section with a first radially acting bearing 20, 21 and with a second radially and axially acting bearing 22, 23. The first bearings 20, 21 are designed as needle bearings to ensure precise radial guidance of the volumetric bodies 10, 11 in the feed section 5 of the pump 1. In the present example, the second bearings 22, 23 are designed as double angular contact ball bearings and serve, in addition to the precise guidance of the shafts 12, 13, to absorb the axial forces generated by the feed principle of the pump 1.

[0031] Between the first and second bearings 20, 21, 22, 23, a synchronous gear 30 is arranged to drive the shaft 13. The synchronous gear 30 comprises a first pinion 31, which is fixed on the first shaft 12, and a second pinion 32, which is fixed on the second shaft 13.

[0032] In order to align the volumetric bodies 10, 11 relative to each other in such a way that the flanks of the volumetric bodies do not touch each other, a rotational alignment of the shafts 12, 13 relative to each other is necessary. For this purpose, the synchronous gear is designed to be adjustable, which is described in more detail below.

[0033] The pinions 31, 32 have oblique teeth in the version shown. The first gear 31 is mounted on the shaft 12 in such a way that an axial groove not shown in [Fig. 2] engages on the inner peripheral surface of the first gear 31 via a key 35 which is inserted into the shaft 12. In the direction of the coupling section 3, the first gear 31 rests against a stop shoulder 36 of the shaft 12. On the side of the supply section 5, a first stop nut 38 is screwed onto an external thread 39 of the shaft 12 and fixes the first gear 31 on the stop shoulder 36. The first stop nut 38 has a threaded section which engages in the external thread 39 of the shaft 12. A fastening section connects to the threaded section. In the fastening section, a threaded rod 40 is provided which acts on the shaft 12 outside the external thread 39 to secure the first stop nut 38 so that it cannot come loose.

[0034] The attachment of the second pinion 32 to the shaft 13 is similar to the attachment of the first pinion 31 to the shaft 12. The second pinion also has an axial groove not shown in [Fig. 2], which engages via a key 42 of the shaft 13. However, in the direction of the contact section 3, the pinion 12 does not rest on a fixed stop shoulder, but on a second stop nut 44, which is screwed onto a first external thread 45 of the shaft 13. A third stop nut 48 is screwed onto a second external thread 49 of the shaft 13, so that the second pinion 32 is axially fixed between the second stop nut 44 and the third stop nut 48.

[0035] The second and third stop nuts 44, 48 each have, like the first stop nut 38, a threaded section and a fastening section. The grub screws in the fastening sections serve to fasten the stop nuts 44, 48 to the shaft 13.

[0036] Since there is little space available between the shafts 12 and 13, the threaded section and the fastening section of the first stop nut 38 and the third stop nut 48 are axially reversed relative to each other. In this way, the respective fastening section can be designed with a larger diameter to provide sufficient thread depth for the threaded rods, while the respective threaded section is designed with a smaller outer diameter.

[0037] To align the feed flanks of the volumetric bodies 10, 11, the second pinion 32 can now be moved axially relative to the first pinion 31 by turning the second and third stop nuts 44, 48. The helical toothing of the pinions 31, 32 causes the shaft 13 to rotate relative to the shaft 12. In this way, the feed flanks of the volumetric bodies 10, 11 can be oriented so that they do not touch each other during operation of the pump 1.

[0038] In the example shown, the second pinion 32 is slightly shorter than the first pinion 31, so that it completely overlaps the first pinion 31 over the entire axial adjustment range. Alternatively, the second pinion 32 may be longer than the first pinion. The difference in length of the pinions corresponds at least to the axial adjustment range of the second pinion 32.

[0039] The external threads 39, 45, 49 of the shafts 12, 13 are preferably designed in such a way that the stop nuts 38, 44, 48 cannot loosen even without the action of the headless screws in the usual direction of rotation of the pump.

[0040] In alternative versions not shown here, the axial groove of the second pinion may be slightly helical. The shaft 13 is then slightly rotated during axial movement. The total rotation of the shaft 13 in the event of The displacement of the second pinion then results, depending on the orientation of the helical groove, from either the sum or the difference of the pitches of the groove on the one hand and the tooth flanks of the pinions on the other. A helical groove can also be used in combination with straight-toothed pinions. In another alternative version, both pinions can be axially adjustable. If the pinions have axial grooves with different pitches, an adjustment of the synchronous gear can be achieved by an identical displacement of both pinions. This can be advantageous if uneven wear of the tooth flanks of the pinions causes problems.

[0041] The assembly of the shafts 12, 13 and the synchronous gear 30 in the gear section 4 of the pump 1 is done as follows:

[0042] First, the inner rings of the needle bearings 20, 21 are fixed on the shafts 12, 13. Furthermore, the second stop nut 44 is screwed onto the shaft 13.

[0043] Then, the shafts 12, 13 are inserted into the bearing housing of the gear section 4 on the side of the coupling section 3 not yet mounted through the bearing bores of the ball bearings 22, 23. Simultaneously, the pinions 31, 32 and the first and third stop nuts 38, 48 are introduced into the bearing housing through the service hatch 8, so that the first pinion 31 and then the first stop nut 38 slide on the shaft 12, and the second pinion 32 and the third stop nut 38 slide on the shaft 13.

[0044] Then, the outer rings and the cages of the needle bearings 20, 21 as well as the ball bearings 22, 23 are respectively inserted from the outside into the respective bearing bores to support the shafts 12, 13. Finally, the fixing and, if necessary, the sealing of the bearings 20, 21, 22, 23 are carried out with the usual means.

[0045] [Fig. 3] shows the pump 1 in vertical longitudinal section in the axial plane of the shaft 12. For reasons of clarity, it is not necessary to describe again elements already shown in [Fig. 2].

[0046] [Fig. 3] shows how the shaft 12 enters a product space 51 through a front wall 50 of the feed section 5. The shaft passage is sealed here by means of a rotary seal 52, which comprises a stationary ring 53 and a ring 54 rotating with the shaft 12. The stationary ring 53 is supported axially on a spring pack 56, which is inserted into the passage bore through the front wall 50 in the direction of the gear section 4 and is held axially by a snap ring 57. A projection 58 in the passage bore prevents the spring pack 56 from falling out of the shaft passage when the rotary seal 52 is replaced in the direction of the feed section 5. The stationary ring 53 has a smaller diameter than the projection 58 at its end opposite the feed section and thus lies directly against the spring pack 56. In the example shown, the spring pack 56 consists of a sinusoidal spring or a wave spring held between two flat support rings. These springs can, for example, be purchased under the designation "Crest-to-Crest® Wellenfeder" from the company Smalley.

[0047] The stationary ring 53 may have an elevation (not shown) which cooperates with a notch (not shown) of the projection 58 to prevent unintentional rotation of the stationary ring 53 with the shaft 12. Alternatively, several, for example three, cooperating radial surfaces may be provided on the stationary ring 53 and the projection 58. A sealing ring 59 provides a seal between the stationary ring 53 and the passage bore.

[0048] In an alternative embodiment not shown, the projection 58 may be formed by another rod.

[0049] The co-rotating ring 54 is housed in a receiving sleeve 60, which is fixed between the volumetric body 10 and a stop shoulder of the shaft 12. Similar to the stationary ring 53, the co-rotating ring 54 can also be protected against twisting on the shaft 12 by suitable contours. A sealing ring 61 prevents the product from penetrating behind the co-rotating ring 54.

[0050] In the area where the stationary ring 53 and the co-rotating ring 54 are superimposed on each other, they are lapped with high precision, so that they ensure a good seal. The diameter of the rings 53, 54 is enlarged in the contact area. This makes it possible, on the one hand, to obtain better heat dissipation of the product to be fed, so that the service life of the seal 52 increases, and, on the other hand, to reduce the influence of the internal pressure of the product to be fed on the pressing force of the rings 53, 54. In the example shown, the stationary ring 53 and the co-rotating ring have different contours. In principle, the two rings 53, 54 can also be produced as identical parts in order to further reduce the number of different parts.

[0051] The sealing of the shaft 11 against the front wall 51 is carried out analogously by a rotary seal which is not shown for reasons of clarity, but which corresponds in structure and function to the rotary seal 52.

[0052] In addition to the rotary seals shown, a second seal may be provided for each of the shafts 11, 12, which is mounted downstream of the respective rotary seal. A gap between the rotary seal and the additional seal may be supplied with a barrier or flushing fluid.

[0053] The structure of the rotary seal 52 described here is particularly advantageous for small pumps, since it comprises only a minimal number of components and is therefore easy to manufacture, assemble or replace. During initial assembly, the spring pack can be pushed into the passage of the shaft from the side of the gear section 4, so that it rests against the projection 56. Then, the snap ring 57 is inserted into the shaft passage in order to hold the spring pack 56 in the shaft passage.

[0054] The snap ring 57 and the spring pack 56 have a free inner diameter which is greater than the outer diameter of the shaft 12 in the area which projects into the product space 51 of the pump 1. Thus, the assembly of the spring pack 57 and the snap ring 56 can be carried out before the shaft 12 passes through the shaft passage.

[0055] The stationary ring 53 can then be pushed over the shaft 12 from the product space 51 until it is in contact with the spring pack 56. Then, the receiving sleeve 60 with the inserted co-rotating ring 54 is pushed onto the shaft 12 before placing the volumetric body and pressing the receiving sleeve 60 against the stop shoulder of the shaft 12.

[0056] In the embodiment shown, the inlet nozzle 6 is screwed into the body of the supply section 5. For this purpose, the inlet nozzle is composed of a threaded section 61 and a connecting section 62. The threaded section 61 and the connecting section 62 can be manufactured from different materials. In the embodiment shown, the outlet nozzle 7 is made in one piece with an outlet-side front plate 70 of the supply section 5. In other embodiments, the outlet nozzle 7 can be screwed to the supply section 5 in the same way as the inlet nozzle 6. A height-adjustable bearing foot 71 is installed under the pump 1.

Claims

Claims

1. Volumetric pump (1) with a rotationally driven volumetric body (10, 11), which is fixed in a product space (51) through which the product to be supplied flows on an associated shaft (12, 13), the shaft (12, 13) penetrating into the product space (51) through a front wall (50) of a supply section (5) of the pump (1), and the passage of the shaft (12, 13) through the front wall (50) being sealed by means of a rotary seal (52), the rotary seal (52) having - a first stationary ring (53) and - a second ring (54) co-rotating with the volumetric body (10, 11); characterized in that the stationary ring (53) is inserted into the shaft passage from the direction of the product space (51) and bears directly on a spring element (56).

2. Volumetric pump according to claim 1, characterized in that the spring element (56) is inserted into the shaft passage from outside the product space (51).

3. A positive displacement pump according to claim 2, wherein the shaft passage has an internal projection (58) which prevents the spring element (56) from entering the product space (51).

4. Volumetric pump according to claim 2 or 3, characterized in that the spring element (56) bears axially on a ring (57) which is inserted into a groove in the shaft passage.

5. A positive displacement pump according to claim 3 or 4, wherein the stationary ring (53) and / or the projection (58) comprise alignment elements which prevent rotation of the stationary ring (53) in the shaft passage.

6. A positive displacement pump according to any preceding claim, wherein the spring element (56) comprises one or more Belleville springs, sinusoidal springs or wave springs.

7. A positive displacement pump according to any preceding claim, wherein the stationary ring (53) is sealed against passage of the shaft by an elastomer seal (59).

8. A positive displacement pump according to any preceding claim, wherein the co-rotating ring (54) is housed in a receiving sleeve (60) which is mounted on the shaft (12, 13).

9. A volumetric pump according to claim 8, wherein the receiving sleeve (60) is fixed between a stop shoulder of the shaft (12, 13) and the volumetric body (10, 11).

10. A volumetric pump according to claim 8 or 9, wherein the co-rotating ring (54) and / or the receiving sleeve (60) have alignment elements which prevent the co-rotating ring (54) from rotating relative to the shaft (12,13).

11. A positive displacement pump according to any one of claims 8 to 10, wherein the co-rotating ring (54) is sealed against the receiving sleeve (60) by an elastomer seal (61).

12. A volumetric pump according to any preceding claim, characterized in that the pump is a screw pump.

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