Volumetric pump with synchronous gear

Abstract

A positive displacement pump is presented with at least two positive displacement bodies (10, 11) driven synchronously with respect to each other, which are fixed at the end on associated shafts (12, 13) which are coupled to each other by a synchronous gear (30), the synchronous gear (30) comprising - a first pinion (31) which is mounted on a first shaft (12) and a second pinion (32) which is mounted on a second shaft (13) and which meshes with the first pinion, the first pinion (31) and / or the second pinion (32) being mounted on the associated shaft (12, 13) so as to be lockable in different axial positions, different axial positions of the first and / or the second pinion (31, 32) corresponding to different rotational orientations of the shafts (12, 13) with respect to each other.The pump is characterized in that the movement of the first and / or second gear (31, 32) between different axial positions is possible continuously and without disassembling the gear (30). Figure for abstract: Fig. 2.

Description

Title of the invention: Volumetric pump with synchronous gear

[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 section through which the product to be fed passes.

[0002] The pump is driven from the outside by a motor which drives one of the shafts. The second shaft can be driven by the volumetric bodies engaged with each other. However, this leads to high wear of the volumetric bodies, especially for screw pumps, which on the one hand reduces the service life and on the other hand leads to a load on the product due to abrasion, which cannot be tolerated, especially when using the pump in the hygienic field. In particular, the food, cosmetic and pharmaceutical industries are to be understood as a hygienic field.

[0003] It is therefore mainly a type of pump that has established itself, in which the second shaft is coupled to the first shaft by means of a synchronous gear. The volumetric bodies can then be designed to operate without contact and practically without wear.

[0004] On the one hand, in order to keep the gap between the volumetric bodies as small as possible and at the same time to avoid contact with the volumetric bodies, it is necessary to precisely adjust the synchronous gear. From the state of the art, solutions are known for this, in which the pinions or ring gears of the synchronous gear can be rotated relative to the respective shafts. The fastening of the pinions or ring gears is then generally carried out by force-fit connections. Corresponding pumps are known, for example, from DE 10 2016 100 957 A1 and DE 10 2012 001 700 A1

[0005] However, it turned out that the known solutions are difficult to implement, especially for small pumps.

[0006] A synchronous gear is known from GB 343344, the pinions of which are mounted at the end on the shafts and provided with a helical toothed thread. To adjust the synchronous gear, one of the pinions can be removed from the shaft and moved axially by washers. However, this is very time-consuming and requires disassembly of the gear. A similar synchronous gear is known from DE 2532 202 A1, in which a pinion can be moved axially by means of a nut against the force of a spring. However, the corresponding solution does not offer a secure fixation and is therefore not applicable to modern fast pumps.

[0007] The task is therefore to provide a volumetric pump with a synchronous gear, which is improved with regard to the problems described.

[0008] According to the invention, this problem is solved by a volumetric pump with at least two volumetric bodies driven synchronously with respect to each other, which are fixed at the end on associated shafts which are coupled to each other by a synchronous gear, the synchronous gear comprising - a first pinion which is mounted on a first shaft and a second pinion which is mounted on a second shaft and which meshes with the first pinion, the first pinion and / or the second pinion being mounted on the associated shaft in such a way that it can be locked in different axial positions, different axial positions of the first and / or the second pinion with different rotational orientations of the shafts corresponding to each other, the displacement of the first and / or the second pinion between different axial positions being possible continuously and without disassembly of the gear.The continuous adjustment without disassembly of the synchronous gear allows, for example, quick and easy re-adjustment after replacing the volumetric bodies.

[0009] The shafts may be supported respectively in a first radially acting bearing and in a second axially and radially acting bearing, the synchronous gear being arranged between the first bearings and the second bearings. The double bearing of the shafts allows particularly quiet operation of the pump. The arrangement of the synchronous gear between the bearing points reduces the length of the gear, while improving the lubrication of the gears and the bearing points.

[0010] In a possible embodiment of the invention, the first and / or second pinion are axially fixed between two stop nuts which are screwed onto the external threads of the associated shaft. An axial displacement of a pinion can therefore be carried out by simply turning the stop nuts on the respective shafts.

[0011] The stop nuts may be removably secured to the associated shaft by means of fastening means. To this end, the stop nuts may each have a threaded section and an axially adjacent fastening section, the threaded section engaging the external thread of the associated shaft and the fastening means being arranged in the fastening section so as to act on it outside the external thread of the shaft. In this way it is ensured that the external thread of the shaft is not damaged by the fastening means. Grub screws, for example, may be used as fastening means.

[0012] In one version of the invention, the first pinion can be fixed in different axial positions on the shaft, while the second pinion cannot be fixed on the shaft. only in a single fixed axial position. The second pinion can be fixed axially between a fixed stop shoulder of the associated shaft and a stop nut. In this way, the number of threads required and therefore the manufacturing effort can be reduced.

[0013] In an advantageous development of the invention, the first and second pinions may have internal axial grooves, the associated shafts having drivers which engage in the respective axial grooves. A corresponding version allows on the one hand easy mounting of the pinions on the shafts and on the other hand provides a secure, axially sliding and at the same time rotation-resistant connection.

[0014] In one possible version, the first and second pinions may have helical teeth, so that a relative axial displacement of the first and second pinions relative to each other causes a rotational displacement of the associated shafts. In another version, the axial groove of the first and / or second pinion may be inclined relative to the longitudinal axis, so that an axial displacement of the respective pinion on the associated shaft causes a rotational displacement of the associated shaft.

[0015] The shafts of the positive displacement pump may be arranged in a one-piece bearing housing. The bearing housing may have first bearing bores for receiving the first radially acting bearings, second bearing bores for receiving the second axially and radially acting bearings, and a service hatch. The one-piece design of the bearing housing allows for precise manufacturing of the bearing bores in a single clamping operation.

[0016] The largest outer diameter of the shafts may be smaller than the diameter of the second bearing bores, so that the shafts may be fully inserted into the bearing housing from the direction of the second bearing bores.

[0017] Below, the invention is explained in more detail with the help of some examples. The embodiments shown in the figures only serve to better understand the invention, without limiting it.

[0018] These illustrations are:

[0019] [Fig.l]: a volumetric pump with connected drive motor;

[0020] [Fig.2]: the internal structure of the volumetric pump of [Fig.l] in a sectional view;

[0021] [Fig.3]: the internal structure of the volumetric pump of [Fig.l] in another sectional view.

[0022] [Fig.l] shows a positive displacement pump 1 with connected drive motor 2 in a perspective view. The motor 2 is an electric motor available in trade, the structure of which is not to 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.

[0023] [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.

[0024] 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.

[0025] 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 can vary depending on the requirements of the respective field of 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.

[0026] The shaft 13 functions as a driven shaft and terminates at the transition between the gear section 4 and the coupling section 3.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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 fixing section, a threaded rod 40 is provided which acts on the shaft 12 outside the external thread 39 to fix the first stop nut 38 so that it cannot come loose.

[0031] 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.

[0032] 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 fix the stop nuts 44, 48 on the shaft 13.

[0033] 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 with respect to each other. In this way, the respective fastening section can be designed with a larger diameter to provide a depth sufficient thread for threaded rods, while the respective threaded section is designed with a smaller outer diameter.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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 when the second pinion is moved 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 hand. A helical groove may also be used in combination with straight-toothed pinions. In another alternative version, both pinions may be axially adjustable. If the pinions have axial grooves with different pitches, an adjustment of the synchronous gear may be achieved by an identical movement of both pinions. This may have advantages if uneven wear of the tooth flanks of the pinions causes problems.

[0038] The assembly of the shafts 12, 13 and the synchronous gear 30 in the gear section 4 of the pump 1 is carried out as follows:

[0039] 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.

[0040] 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 that the second pinion 32 and the third stop nut 38 slide on the shaft 13.

[0041] 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.

[0042] [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].

[0043] [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 hole prevents the spring pack 56 from falling out of the passage opening 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.

[0044] 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.

[0045] In an alternative embodiment not shown, the projection 58 may be formed by another rod.

[0046] 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.

[0047] In the area where the stationary ring 53 and the co-rotating ring 54 are superimposed on each other, they are lapped with great 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.

[0048] 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.

[0049] 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.

[0050] 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 shaft passage 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.

[0051] 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.

[0052] 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.

[0053] In the embodiment shown, the inlet pipe 6 is screwed into the body of the supply section 5. For this purpose, the inlet pipe is composed of a threaded section 61 and a connecting section 62. The threaded section 61 and the connecting section 62 can be made from different materials. In the embodiment shown, the outlet pipe 7 is made of a single holding with a front plate on the outlet side 70 of the supply section 5. In other embodiments, the outlet pipe 7 can be screwed to the supply section 5 in the same way as the inlet pipe 6. A height-adjustable bearing foot 71 is installed under the pump 1.

Claims

Claims

1. Positive displacement pump with at least two positive displacement bodies (10, 11) driven synchronously with respect to each other, which are fixed at the end on associated shafts (12, 13) which are coupled to each other by a synchronous gear (30), the synchronous gear (30) comprising - a first pinion (31) which is mounted on a first shaft (12) and - a second pinion (32) which is mounted on a second shaft (13) and which meshes with the first pinion (31), the first pinion (31) and / or the second pinion (32) being mounted on the associated shaft (12, 13) so as to be lockable in different axial positions, different axial positions of the first and / or the second pinion (31, 32) corresponding to different rotational orientations of the shafts (12, 13) with respect to each other, characterized in that the movement of the first and / or second pinion (31, 32) between different axial positions is possible continuously and without disassembly of the gear (30).

2. A positive displacement pump according to claim 1, wherein the shafts (12, 13) are supported respectively in a first radially acting bearing (20, 21) and in a second axially and radially acting bearing (22, 23), and wherein the synchronous gear (30) is arranged between the first bearings (20, 21) and the second bearings (22, 23).

3. Volumetric pump according to claim 1 or 2, wherein the first and / or second pinion (31, 32) are fixed axially between two stop nuts (44, 48) which are screwed onto external threads (45, 49) of the associated shaft (12, 13).

4. A volumetric pump according to claim 3, wherein the stop nuts (44, 48) are removably secured to the associated shaft (12, 13) by fastening means.

5. A positive displacement pump according to claim 4, wherein the stop nuts (44, 48) have a threaded section and an axially adjacent fixing section, the threaded section engaging the external thread of the associated shaft and the fixing means being arranged in the fixing section so as to act on it outside the external thread of the shaft.

6. A positive displacement pump according to any preceding claim, wherein the first gear (31) is fixable in different axial positions on the shaft (12), and wherein the second gear (32) is fixable in a single fixed axial position on the shaft (13).

7. A volumetric pump according to claim 6, wherein the second pinion (32) is axially immobilized between a fixed stop shoulder (36) of the associated shaft (12) and a stop nut (38).

8. A positive displacement pump according to any preceding claim, wherein the first and second gears (31, 32) have internal axial grooves, and wherein the associated shafts (12, 13) have keys (35) which engage in the respective axial grooves.

9. A positive displacement pump according to any preceding claim, wherein the first and second gears (31, 32) have helical teeth, such that relative axial displacement of the first and second gears (31, 32) relative to each other causes rotational displacement of the associated shafts (12, 13).

10. A volumetric pump according to claim 8, wherein the axial groove of the first and / or second gear (31, 32) is inclined relative to the longitudinal axis, so that an axial displacement of the respective gear (31, 32) on the associated shaft (12, 13) causes a rotational displacement of the associated shaft (12, 13).

11. A positive displacement pump according to any preceding claim, wherein the shafts (12, 13) are arranged in a bearing housing manufactured as a single piece.

12. A volumetric pump according to claim 11, wherein the bearing housing has - first bearing bores for receiving the first radially acting bearings (20, 21), - second bearing bores for receiving the second axially and radially acting bearings (22, 23), and - a service hatch (8).

13. A positive displacement pump according to claim 12, wherein the largest outside diameter of the shafts (12, 13) is less than the diameter of the second bearing bores.

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