Positive Displacement Pump

CLAIM OF PRIORITY

The present application claims the benefit of the filing date of German Patent Application No. DE 10 2016 100 957.1, filed on Jan. 20, 2016, which is hereby incorporated by reference in its entirety.

FIELD

The present teachings relate to a positive displacement pump, and more particularly to a rotating externally mounted positive displacement pump.

BACKGROUND

Rotating positive displacement pumps have been known since the early seventeenth century in the form of gearwheel pumps. In modern pumps, the displacing bodies are fastened on shafts which are mounted outside a product section which is flowed through by the product to be conveyed.

The pump is driven from the outside via a motor which drives one of the shafts. The second shaft can be driven by way of the displacing bodies which mesh with one another. However, this leads to pronounced wear of the displacing bodies, in particular in the case of screw-spindle pumps, which wear firstly reduces the service life and secondly leads to product contamination as a result of abrasion, which contamination cannot be tolerated, in particular, if the pump is used in the hygienic field. The hygienic field is to be understood to mean, in particular, the food and cosmetics industry.

Therefore, a design of the pumps has mainly established itself, in which the second shaft is coupled to the first shaft via a synchronizing gear mechanism. The displacing bodies can then be designed in such a way that they operate without contact and practically without wear.

Particularly high requirements are to be made of the bearing system of the shafts in the described pumps. On account of the contactless method of operation, the bearing system has to be very rigid and low in play, in order to avoid undesired contact of the displacing bodies. At the same time, the bearing system has to absorb great axial forces in the case of certain pump types, in particular in the case of single-flow screw-spindle pumps. In order to meet the said requirements, a certain axial spacing is necessary between the radial and axial bearing points, which axial spacing determines the external dimensions of the pumps. As a result of the said spacing, the sufficient cooling and lubrication of the bearings is difficult, in particular at high rotational speeds.

The synchronizing gear mechanism is usually arranged outside the bearing points of the shafts, which additionally increases the overall length of the pump. There are sporadic cases of known pumps, in which the synchronizing gear mechanism is arranged between the bearing points. Since the diameter of the pinions of the gear mechanism is greater than the axial spacing of the shafts, the pinions cannot be introduced into the housing through the bearing bores from either side. Instead, the housing has to be constructed in two pieces, with the bearing bores for the radial bearings being provided in one part and the bearing bores for the axial bearings being provided in the other part. On account of the low permissible positional tolerances, this construction increases the manufacturing and assembly complexity of the pump immensely.

Therefore, what is needed is a pump that exhibits reduced wear of the displacing bodies; reduced product contamination from abrasion; ability to use in the hygienic field; sufficient cooling and lubrication of bearings, especially at high rotational speeds; reduced overall length of the pump; simplified manufacturing and assembly of the pump; or a combination thereof.

SUMMARY

It is therefore the object to provide a pump which is improved, in particular, with regard to the abovementioned disadvantages.

In accordance with the invention, the said object is achieved by way of a rotating externally mounted positive displacement pump having at least two displacing bodies which are driven synchronously with respect to one another and are fastened on the end side on associated shafts, the shafts being mounted in each case by way of a first, radially acting bearing and a second, radially and axially acting bearing, and the shafts being coupled to one another by way of a synchronizing gear mechanism, which positive displacement pump is developed by virtue of the fact that the bearings are fitted into seat bores of a housing which is manufactured in one piece, and that the synchronizing gear mechanism is arranged between the respective bearings.

The corresponding construction of the pump brings about a plurality of advantages. As a result of the single-piece construction of the housing, manufacturing and assembly tolerances of the housing parts with respect to one another are reduced, with the result that the production of the pump becomes simpler and more reliable. Here, within the context of the invention, a single-piece construction of the housing is to be understood to mean any construction, in which all bearing bores of the shaft bearings are provided in the same part of the housing. This does not rule out that the housing comprises further separate parts which do not contain any bearing bores.

At the same time, the overall length of the pump can be reduced, since the synchronizing gear mechanism fits into the spacing which is necessary for functional reasons between the bearing points. The synchronizing gear mechanism can additionally contribute to the sufficient lubrication and cooling of the bearings, by the pinions of the synchronizing gear mechanism dipping into an oil sump in a circulating manner and outputting the oil in the direction of the bearings as an oil mist. Homogeneous lubrication and cooling of all the bearings is made possible with minimum complexity by way of the positioning of the oil sump between the bearing points.

According to one refinement of the invention, the pump is developed in such a way that the synchronizing gear mechanism has two pinions which mesh with one another and the diameter of which is greater than the axial spacing of the shafts.

According to a further refinement of the invention, the pinions in each case have a toothed rim which is fastened on a supporting body.

If, according to one preferred embodiment of the invention, the greatest external diameter of the supporting bodies is smaller than the axial spacing of the shafts, the shafts can be pushed with mounted supporting bodies through the bearing bores into the housing. The toothed rims can be pushed over the shafts through a separate housing opening between the bearing points and can be fastened on the supporting bodies.

According to one embodiment of the invention, the supporting bodies are fastened on the shafts in a non-positive and/or positively locking manner. This takes place, for example, by way of shrink-fitting and/or a known feather key connection.

According to one development of the invention, the toothed rims are fastened to the supporting bodies in a non-positive manner. The non-positive connection makes it possible to loosen at least one of the toothed rims and to rotate it on the supporting body for rotational orientation of the displacing bodies with respect to one another. Here, the toothed rims can preferably be rotated freely in a great angular range, particularly preferably by one or several complete revolutions, when the non-positive connection is released.

According to one exemplary embodiment of the invention, the non-positive fastening of the toothed rims on the supporting bodies takes place by means of screwed clamping plates.

In one exemplary refinement of the invention, the pump is a single-flow screw-spindle pump.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a pump in accordance with one aspect of the invention.

FIG. 2 shows a horizontal sectional illustration of a pump in accordance with a further aspect of the invention.

FIG. 3 shows a vertical sectional illustration of a pump in accordance with a further aspect of the invention.

FIG. 4 shows a horizontal section through the seal of the product section of a pump.

FIG. 5 shows a securing plate of a pump.

DETAILED DESCRIPTION

As required, details of the present teachings are disclosed herein; however, it is to be understood that the disclosed teachings are merely exemplary, and the teachings may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present teachings.

The present teachings relate to a rotating externally mounted positive displacement pump having at least two displacing bodies which are driven synchronously with respect to one another and are fastened on the end side on associated shafts, the shafts being mounted in each case by way of a first, radially acting bearing and a second, radially and axially acting bearing, and the shafts being coupled to one another by way of a synchronizing gear mechanism.

FIG. 1 shows a pump 1 in a perspective illustration, which pump 1 includes or consists substantially of a drive section 2 and a product section 3. In the example which is shown, this is a hygienic single-flow screw-spindle pump, though the teachings are not limited to such a pump.

The drive section 2 of the pump 1 has a drive shaft journal 4, by way of which the pump 1 can be coupled to a drive motor (not shown). The product section 3 of the pump 1 has a product inlet 5 and a product outlet 6. In the case of reversible operation of the pump 1, the product inlet 5 and the product outlet 6 can be swapped here in a manner which is dependent on the conveying direction.

The inner construction of the pump 1 is shown in FIGS. 2 and 3. In the product section 3, two displacing screws 7, 8 which engage into one another are arranged which are driven by two parallel shafts 9, 10. The displacing screws 7, 8 are plugged onto the shafts 9, 10 and are fastened releasably to the latter in a positively locking manner, by means of the fittings 11, 12 in the example which is shown.

The shafts 9, 0 extend out of the product section 3 into the drive section 2, where they are first of all mounted by way of radially acting needle bearings 13, 14 and by way of radially and axially acting angular contact ball bearings 15, 16. In the example which is shown, the angular contact ball bearings 15, 16 consist of in each case three bearings which are arranged behind one another and are described as one bearing for the sake of clarity, though a bearing arrangement having more or fewer bearings is also contemplated. The angular contact ball bearings 15, 16 include an inner ring 32, 33; balls 44, 45; and outer rings 26, 27. A synchronizing gear mechanism 17 with pinions 18, 19 which mesh in one another is arranged between the bearings 13, 14, 15, and 16. The synchronizing gear mechanism 17 transmits the movement which is imparted into the shaft 10 via the drive shaft journal 4 to the shaft 9, with the result that the displacing screws 7 and 8 rotate synchronously in opposite directions.

Particularly high requirements are to be made of the bearings 13, 14, 15, 16 and the synchronizing gear mechanism 17 of a single-flow screw-spindle pump 1. The displacing screws 7, 8 engage into one another with a minimum gap without contact, in order to achieve a high degree of efficiency. In order to avoid contact of the displacing screws 7, 8, by way of which contact they can be destroyed, both the synchronizing gear mechanism 17 and the bearing system therefore have to be extremely rigid and low in play. In addition, in particular at high conveying rates and in the case of highly viscous or pasty products, high axial forces act on the shafts 9, 10 as a result of the single-flow construction, which axial forces have to be absorbed by the angular contact ball bearings 15, 16.

In order for it to be possible to withstand the high loads, the bearings 13, 14, 15, 16 have to be cooled continuously. To this end, an oil bath 20 is provided in the drive section 2 of the pump 1. Here, the pinions 18, 19 dip into an oil sump and produce an oil mist in the drive section 2, which oil mist enters into the bearings 13, 14, 15, 16 and at the same time lubricates and cools them.

The shafts 9, 10 are sealed at the product-side end of the drive section 2 by way of shaft sealing rings 21, 22, in order to prevent an exit of oil out of the drive section 2. A further shaft sealing ring 23 is provided for sealing the drive shaft journal 4.

During the assembly of the pump 1, the difficulty arises that the diameter of the pinions 18, 19 is greater owing to their function than the axial spacing of the shafts 9, 10, whereas the diameter of the seat bores 24, 25 for the outer rings 26, 27 of the angular contact ball bearings 15, 16 has to be smaller than the axial spacing of the shafts 9, 10. Therefore, the shafts 9, 10 cannot be introduced with mounted pinions 18, 19 through the seat bores 24, 25 into the drive section 2 of the pump 1.

The assembly therefore takes place as follows: Before assembly, the inner rings 28, 29 of the needle bearings 13, 14, supporting bodies 30, 31 for the pinions 18, 19, and the angular contact ball bearings 15, 16 are mounted onto the shafts 9, 10. To this end, the inner rings 28, 29 of the needle bearings 13, 14 and the angular contact ball bearings 15, 16 are shrink-fitted onto the shafts 9, 10, whereas the supporting bodies 30, 31 are fixed on the shafts 9, 10 by way of feather key connections (not shown).

In the housing 34 of the drive section 2, the outer rings 35, 36 of the needle bearings 13, 14 are fixed with the associated needle cages 41, 42 in corresponding seat bores 37, 38.

The parts 28, 29, 30, 31, 15, 16 which are mounted on the shafts 9, 10 are dimensioned in such a way that their external diameters are all smaller than the axial spacing of the shafts 9, 10, with the result that the preassembled shafts can be pushed through the seat bores 24, 25 into the drive section 2 in the direction of the product section 3. Here, the toothed rims 39, 40 are guided through an assembly opening 43 of the housing while being pushed over the shafts 9, 10. One or more fixing plates 46 is/are then screwed on for axial fixing of the shafts 9, 10 and the angular contact ball bearings 15, 16.

After the shafts 9, 10 are mounted in an axially play-free manner by way of fixing of the angular contact ball bearings 15, 16, the synchronizing gear mechanism 17 is finally assembled in the next step. To this end, the toothed rims 39, 40 which have already been laid loosely over the shafts 9, 10 while the latter were being pushed in are pushed onto the supporting bodies 30, 31, where they are seated with a tight fit and mesh with one another. To this end, the supporting bodies 30, 31 have stop shoulders 47, 48 on the side which faces away from the product section 3. Clamping plates 49, 50, 51, 52 are then placed against the toothed rims 39, 40 from the side which faces the product section 3. The clamping plates 49, 50, 51, 52 are in each case of approximately half-annular configuration and have end-side steps, with the result that in each case two clamping plates can be assembled to form one flush ring. The assembled rings are then fastened to the supporting bodies 30, 31 by means of bolts and press the toothed rims 39, 40 against the stop shoulders 47, 48, as a result of which they are fixed in a non-positive manner.

Production with very low play is possible by virtue of the fact that the seat bores 24, 25 of the angular contact ball bearings 15, 16 and the seat bores 37, 38 of the needle bearings 13, 14 can be made coaxially in the housing 34 which is manufactured in one piece, the risk of a radial offset of the individual seat bores 24, 25, 37, 38 with respect to one another being reduced, in particular.

The drive section 2 of the pump is adjoined by the product section 3 which is constructed from an intermediate flange 53 with a product inlet 5, a conveyor housing 54 and a closing flange 55 with a product outlet 6. The intermediate flange 53 is supported by way of an attachment collar 56 on the housing 34 of the drive section 2, with the result that a leakage space 58 is formed between it and the one drive-side wall 57. The said leakage space 58 ensures that oil from, the drive section 2 can exit from the pump if one of the shaft sealing rings 21, 22 fails, without contaminating the conveyed product, which is of elementary significance, in particular, in the use of the pump in the hygienic field, such as in the food or cosmetic industry.

The shafts 9, 10 protrude into the product region through seal seats 59, 60 in the wall 57 and are sealed during the passage through the wall 57 by way of slide ring seals 61, 62 the location of which are generally pointed to in FIGS. 2 and 3. The construction of the said seals will be explained in greater detail in the following text using FIG. 4.

The slide ring seals 61, 62 are of identical construction, for which reason only the slide ring seal 61 will be described here. All specifications also apply likewise to the slide ring seal 62.

The slide ring seal 61 is constructed in two stages and therefore has a stationary section 63 and two rotating sections 64, 65. The first rotating section 64 is seated on the drive side on the shaft 9 and is held axially and rotationally by way of pins 66, 67 which are screwed into the shaft 9. The stationary section 63 includes two sliding rings 68, 69 which are supported on one another by way of a spring ring 70. The unit comprising the two sliding rings 68, 69 and the spring ring 70 is enclosed in a sleeve 71 which is inserted into the seal seat 59 and is supported axially here on a projection 72.

The second rotating section 65 in turn includes a sliding ring 73 which is surrounded in a pot 74 which is supported on a step 75 of the shaft 9 and is clamped fixedly there by way of the displacing screw 7. Drivers 76 are screwed into the pot 74, which drivers 76 prevent a rotation of the sliding ring 73 with respect to the pot 74.

The sliding ring 68 is pressed against the rotating section 64 and the sliding ring 69 is pressed against the sliding ring 73 by way of the force of the spring ring 70, as a result of which they bear tightly against one another and seal the product space 77 with respect to the leakage space 58 (see FIGS. 2 and 3). Here, in particular, the sliding rings 69 and 73 may be manufactured from product-compatible and low-wear material.

The intermediate space between the sliding rings 68, 69, 73 and the shaft 9 is flushed by way of a product-compatible liquid which can be, for example, distilled water. This serves to cool the sliding rings and to transport away product constituent parts which possibly pass between the sliding rings. Inward and outward transport of the liquid takes place via channels in the wall 57, which channels are not shown for the sake of clarity.

During operation of the pump 1, it can occur that a vacuum prevails in the product space 77. In order to prevent the sleeve 71 from being pressed into the product space 77 by way of the ambient pressure, as a result of which in the worst-case contaminants can pass into the product, the sleeve 71 protrudes beyond the wall 57 on the drive side and has a circumferential groove 78 there. Fingers 79, 80 (FIG. 5) of a securing plate 81 which is pushed into the leakage space 58 from the outside engage into the said groove 78. As a result, the sleeve 71 is locked axially, with the result that it cannot be pressed into the product space. At one location, the groove 78 has an axial milled-out section 82 which interacts with a projection 83 of the securing plate 81, in order to secure the sleeve 71 against rotation.

The securing plate 81 is shown in greater detail in FIG. 5. The securing plate has two outer fingers 79, 80 and a middle web 84 which are adapted in terms of the contour to the groove bottom of the groove 78. Overall, they enclose an angle of about 180° or greater, with the result that, when the securing plate 81 is pushed in, the fingers 79, 80 are bent outwards elastically and then spring back into their starting position. The elastic deformation may be assisted by way of slots 85, 86 which engage over securing bolts 87 (FIG. 4) while the securing plate is pushed in. A small bracket 88 may be provided in the center of the web 84, which bracket 88 is used to form the projection 83. To this end, as shown in FIG. 4, a small plate 89 can be fastened on the bracket 88, for example by way of spot welding. As an alternative, the bracket 88 itself can be bent or beaded somewhat out of the plane of the securing plate 81, in order to form the projection 83.

At the free end of the securing plate 81, a narrow strip may be bent over by approximately 90°±about 10° and therefore acts as a protective hand guard 90 for the leakage space 58. A sufficient gap remains here, in order to tighten the securing bolts 87 by way of a spanner after the securing, plate 81 is pushed in, and thus to fix the securing plate 81.

The mounting and dismantling of the slide ring seals 61, 62 is particularly simple and takes place from the product side with a dismantled closing flange 55.

The rotating section 64 is guided onto the shaft from the product side and is pushed as far as the pins 66, 67 which have already been screwed into threaded bores of the shafts 9, 10 before the mounting of the drive section 2. The stationary section 63 is then guided with the sliding rings 68, 69, the spring ring 70 and the sleeve 71 over the shaft 9 and is pushed as far as into the seal seat 59, the sleeve 71 protruding out of the wall 57 on the drive side as far as the circumferential groove 78. Next, the securing plate 81 is pushed into the leakage space 58, with the result that the fingers 79, 80 and the web 84 engage into the groove 78. Here, the sleeve is oriented in such a way that the projection 83 engages into the milled-out section 82 and thus secures the sleeve against rotation. After the securing plate has been pushed in completely, the securing bolts 87 are tightened, in order to fix the securing plate.

Finally, the rotating section 65 is pushed with the pot 74 and the sliding ring 73 onto the shaft 9 as far as the step 75. The slide ring seals 61, 62 are fixed by way of mounting of the displacing screws 7, 8.

During the mounting of the displacing screws 7, 8, they are preferably oriented with respect to one another before being pushed onto the shafts 9, 10, with the result that the corresponding thread turns engage into one another. The displacing screws 7, 8 and the product-side ends of the shafts 9, 10 have fitting elements of complementary shape, with the result that a rotation of the displacing screws 7, 8 on the shafts 9, 10 is ruled out. The positively locking connection is secured additionally by way of the fittings 11, 12.

Since the displacing screws 7, 8 can be placed on the shafts 9, 10 only in discrete angular positions as a result of the positively locking connection, it is necessary to rotate the shafts 9, 10 with respect to one another, in order to set an optimum contactless orientation of the displacing screws 7, 8 with respect to one another. This is important, in order to avoid premature wear of the displacing screws 7, 8.

To this end, the clamping plates 49, 50 for the toothed rim 39 are loosened somewhat through the assembly opening 43, with the result that the toothed rim 39 can rotate on the supporting body 30. The gap between the displacing screws 7, 8 is then set by way of rotation. In a correct position of the displacing screws 7, 8 with respect to one another, the clamping plates 49, 50 are tightened again, with the result that the toothed rim 39 is fixed again such that it cannot rotate.

After the adjustment of the displacing screws 7, 8, the closing flange 55 is placed onto the conveyor housing. The assembly opening is closed by way of a cover 91 on the drive section 2 of the pump. The pump 1 is ready for use after this.

While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the teachings contemplated. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention. As can be appreciated, variations in the above teachings may be employed.

Unless otherwise stated, all ranges include both endpoints and all numbers between the endpoints. The use of “about” or “approximately” in connection with a range applies to both ends of the range. Thus, “about 20 to 30” is intended to cover “about 20 to about 30”, inclusive of at least the specified endpoints.

The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. The term “consisting essentially of” to describe a combination shall include the elements, ingredients, components or steps identified, and such other elements ingredients, components or steps that do not materially affect the basic and novel characteristics of the combination. The use of the terms “comprising” or “including” to describe combinations of elements, ingredients, components or steps herein also contemplates embodiments that consist essentially of, or even consisting of, the elements, ingredients, components or steps.

Plural elements, ingredients, components or steps can be provided by a single integrated element, ingredient, component or step. Alternatively, a single integrated element, ingredient, component or step might be divided into separate plural elements, ingredients, components or steps. The disclosure of “a” or “one” to describe an element, ingredient, component or step is not intended to foreclose additional elements, ingredients, components or steps.

Relative positional relationships of elements depicted in the drawings are part of the teachings herein, even if not verbally described. Further, geometries shown in the drawings (though not intended to be limiting) are also within the scope of the teachings, even if not verbally described.

Positive Displacement Pump

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