Shaft of a screw pump

Abstract

Externally mounted, twin-spindle screw pump with attachable feed screws (6), characterized in that the shafts (1, 2) have only a single outer diameter over their entire length and all machine elements (3, 4, 5, 6, 7, 8) to be mounted on these shafts (1, 2) have the nominally same inner diameter.

Description

[0001] Externally mounted, twin-screw pumps with overhung impellers have two shafts mounted radially and axially in rolling bearings in at least one housing body. The pump's helical impellers are slid onto them and secured using conventional shaft-hub connections. The drive torque is transmitted from one spindle shaft to the other via a pair of pinions fixed to the spindle shafts. This gives this pump design the advantage of contactless impellers, as the gap between the spindle flanks is larger than the clearance between the gears. To seal the shafts against the atmosphere, they are equipped with shaft seals such as mechanical seals or shaft seals.The shafts of the pumps described above are provided with shaft shoulders of different diameters and lengths at the respective positions for mounting rolling bearings, shaft seals, gears, and the actual conveyor screws. A pump of this type was disclosed in DE 102 57 859 A1 and further optimized in DE 10 2016 100 957 A1, among others.

[0002] However, all known pumps of this type have the disadvantage that the production of the shafts requires complex manufacturing due to the large number of component-specific steps for assembling the machine elements described above, which increases the product costs and has a very disadvantageous effect, especially for smaller pump sizes, since there is great competition with various alternative pump designs.

[0003] The invention specified in the claims is based on the object of eliminating this disadvantage. An embodiment of the invention is described with reference to Fig. 1 and Fig. 2 explains. They show: Fig. 1 shows the longitudinal section of a screw pump with the features according to the invention, Fig. 2 shows an example of the milling on the otherwise smooth shaft for the positive connection of the shaft and hub part. For better clarity, the Fig. 1, the machine elements shown are numbered only for shaft (1), for shaft (2) the described design is essentially identical.

[0004] According to the invention, the inner diameters of the various necessary components such as rolling bearings (3), shaft seals (5), gears (4) and conveyor screws (6) are standardized so that the shafts (1, 2) are completely free of steps of different diameters, i.e. they are smooth shafts with only a single outer diameter. This means that ground precision shafts can be used for both pump shafts. These are sourced from large-scale production and can also be surface-hardened, which has a positive effect on the wear properties of the shafts, particularly in the case of shaft seals with shaft sealing rings. The shafts designed in this way only need to be cut to size and machined on the end faces, although no accuracy beyond the general tolerances is required.

[0005] The basic requirement for this shaft design is that all components to be mounted on the spindle shaft have the same nominal inner diameter. The axial positioning and fixation of the components on the smooth spindle shaft is achieved using clamping or adjusting rings (7). The narrow diameter tolerance of conventional precision shafts enables the secure installation and operation of the axial and radial bearings, as well as the shaft seals. According to the invention, the required distance between the individual bearings and between the bearings and the gear is determined by means of spacer sleeves (8) pushed onto the shaft.

[0006] The invention further provides for axially fixing the pump screws by means of a centrally inserted fastening screw (9) and for using the clamping force generated by the screw connection, within certain limits, also for the radial transmission of torque. For high torques to be transmitted, the screw hub can also be positively connected to the shaft by providing the shaft with a one- or two-sided flattening below the screw hubs and constructing the screw hub in negative form with the same shape. Claim 1 is not affected by this, since even with the introduction of the flattening, the actual shaft diameter remains constant over the entire length.

[0007] In the simplest case, the gears can be clamped to the shafts using grub screws, similar to an adjusting ring. To transmit high torques, the shafts can be flattened under the pinion hubs. Alternatively, the shaft clamping sets already used in conventional pumps can also be used here to create a frictional connection between the shaft and gear hub. List of reference symbols 1.2 wave 3 rolling bearings 4 gear 5 Shaft seal 6 conveyor screw 7 Clamping or adjusting ring 8 spacer sleeve 9 Fixing screw 10 Milling QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 102 57 859 A1

[0001] DE 10 2016 100 957 A1

[0001]

Claims

[1] Externally mounted, twin-screw pump with attachable feed screws (6), characterized by that the shafts (1,2) have only a single outer diameter over their entire length and all machine elements (3,4,5,6,7,8) to be mounted on these shafts (1,2) have the nominally same inner diameter. [2] Screw pump according to claim 1, characterized by that gears (4) and rolling bearings (3) are arranged between clamping rings or adjusting rings (7) on the shafts (1,2) and are thus fixed in their axial position. [3] Screw pump according to one of the preceding claims, characterized by that spacer sleeves (8) are provided between the machine elements (3,4) arranged between adjusting or clamping rings (7). [4] Screw pump according to one of the preceding claims, characterized bythat the torque is transmitted from the shafts (1,2) to the conveyor screws (6) by the frictional engagement applied by the screw connection (9). [5] Screw pump according to one of the preceding claims, characterized by that the shafts (1,2) in the area of ​​the hubs of conveyor screws (6) and gears (4) are partially provided with millings (10) for positive torque transmission.

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