Patent Application
20150300331
The present invention relates to a pump mechanism having multiple cylinders, whose axes are situated around a crankshaft to enclose predetermined angles, and whose pistons are each functionally connected to a connecting rod mounted on a crank on the crankshaft.
Multiple cylinder pump mechanisms are used in process pumps for delivering large delivery streams or at high pressures. Usually, diaphragm pump heads are used as the pump heads in this case. Since the diaphragms used therein are only capable of limited deflection, diaphragm pump heads having very large diameters are required for large delivery volumes. If such large diaphragm pump heads are to be operated using a multiple cylinder mechanism, the intervals of the pump head holders and/or the cylinders must therefore also be large enough. In typical pump mechanisms, the individual cylinders are typically situated in parallel and mounted horizontally on a crankshaft which also lies horizontally. In this case, a large cylinder interval in the connection area for the pump heads also requires a large mounting interval on the crankshaft. In the event of multiple cylinders and large pump heads, the crankshaft must be designed correspondingly long. This in turn requires special properties of the crankshaft, in particular in regard to stability and flexural strength. High costs in production and storage result due to this and due to the large amount of space required. Efforts to develop high-performance pump mechanisms which require less space have resulted from this.
A multiple cylinder diaphragm pump, in which the cylinder pistons are mounted on a single eccentric on a crankshaft, is known from German Utility Model DE G8521520.1 U1. The individual cylinders are situated radially around the crankshaft in this case. The crankshaft itself is accordingly comparatively short. In order to achieve uniform superposition of the partial delivery streams of the individual cylinders, the angles at which the cylinders stand to one another are distributed uniformly around 360°. The radial arrangement of the cylinders is connected to significant disadvantages, however. Firstly, the overall pump is thus relatively protrusive, and the space required by the pump is still unsatisfactory, in addition, the accessibility of the rear cylinders is significantly restricted when the pump is installed. Furthermore, the piping requires a special outlay.
From this background, it is the object of the present invention to specify a pump mechanism which is especially compact and has a short crankshaft while simultaneously having good accessibility to the individual cylinders.
The object is achieved by a pump mechanism having multiple cylinders, whose axes are situated around a crankshaft enclosing predetermined angles, and whose pistons are each linked to a connecting rod mounted on a crank on a crankshaft, each connecting rod being mounted on its own crank and the cranks having a predetermined angular offset to one another. The angular offset of these cranks is selected according to the present invention as a function of the angle which the cylinder axes enclose in such a way that the phase shifts between each two pistons of the cylinders actuated in sequence during a rotation of the crankshaft are equally large.
The angles which the cylinder axes enclose are to be viewed in this case in projection on a plane perpendicular to the longitudinal axis of the crankshaft. The cylinder axes actually do not intersect, since the attack points of the connecting rods on the particular cranks are offset along the longitudinal axis of the crankshaft. In the projection, however, the cylinder axes intersect in the crankshaft and extend therefrom radially. The angular distribution between the cylinder axes may be selected nearly arbitrarily around the crankshaft. Only the minimum angle between two neighboring cylinder axes is predefined by the dimensions of the cylinder and the pump heads to be attached. Both symmetric arrangements having regular angular intervals of the cylinders and also asymmetric arrangements are possible. The manifold possibilities of the geometric arrangement offers the advantage that the pump may be adapted to many different construction conditions, for example, when it is to be integrated into a more complex facility.
In order that the most uniform possible torque curve during a rotation of the crankshaft is achieved in spite of an asymmetric arrangement of the cylinders around the crankshaft, the angles at which the cranks stand to one another are tailored to the angular distribution of the cylinders. The cranks, on which the connecting rods of the individual cylinders are mounted, must therefore be offset to one another around the axis of the crankshaft by a specific angle in each case. The angular offset between the cranks is then selected so that the phase shifts between the work cycles of two sequentially actuated pistons are each equally large. In a three-cylinder mechanism, the phase difference between the work cycles of two cylinders, independently of the spatial arrangement of the cylinders, is thus 120° in each case. In a four-cylinder mechanism, the phase difference of two sequentially actuated cylinders is 90° in each case. In this way, it is ensured that the partial delivery streams of the individual cylinders are superimposed uniformly and pressure pulsations which are too strong do not occur. A more uniform delivery stream using arbitrary angles of the cylinder axes may thus be produced through the angular offset of the cranks.
The pump mechanism according to the present invention is especially suitable for the attachment of piston diaphragm pump heads. For trouble-free operation of piston diaphragm pump heads, horizontal piston axes having valve connections lying one on top of another, which are oriented perpendicularly thereto, are preferred. The crankshaft is thus expediently mounted standing vertically, the cylinder axes pointing horizontally radially away therefrom.
The linkage of the pistons by the connecting rod is preferably performed via a crosshead, which absorbs the transverse components of the rotational movement of the connecting rods originating from the crankshaft.
The cranks for the individual connecting rods and cylinders are distributed along the longitudinal axis of the crankshaft. With a vertically mounted crankshaft, this means that the connecting rod main bearings, using which the connecting rods are each mounted on their own crank, are offset in height to one another. Since the connecting rods extend horizontally from the crankshaft in this case, the outer connecting rod ends are also offset in height to one another. In a preferred embodiment variation, this height offset corresponds precisely to the thickness of the connecting rods. The cranks lie so close to one another that the connecting rods slide on one another without noticeable spatial separation. If the connections of connecting rods to crosshead and crosshead to cylinder pistons are central, a corresponding height offset of the cylinder axes by one connecting rod thickness each results therefrom. The cylinder axes then extend, strictly speaking, in a fan shape or similarly to the steps of a spiral staircase from the crankshaft.
The cylinders in the pump mechanism according to the present invention are preferably situated so that the sum of the angles enclosed by the cylinder axes is less than or equal to 180°. The cylinder axes are thus not distributed around the crankshaft, but rather project from the crankshaft only in a half space. This means that there are preferably two outermost cylinders, whose axes enclose an angle of less than 180° of one another, or which extend parallel in opposite directions from the crankshaft. For the case that the pump mechanism has more than these two outermost cylinders, they are distributed in a fan shape between the two outermost cylinders, while no cylinder axes project into the second half space. The asymmetrical cylinder distribution is taken into consideration by the angular offset of the cranks, so that nonetheless a uniform delivery stream occurs. When the pump is installed in a facility, the restriction of the space for cylinder connections to 180° has the advantage that all cylinders are accessible from one side for maintenance work, for example.
The pump mechanism according to the present invention preferably has three cylinders. If the cylinder axes are distributed on 180°, these cylinders may each be at an angle of 90° to one another.
In an especially preferred refinement, the three cylinder axes are only distributed over an angular range of 90°, however, and the individual cylinders are then each at an angle of 45° to one another. This arrangement allows an even more compact embodiment of the pump. The accessibility from one side is improved even further. Depending on the special requirements, for example, arrangements at angles of 30° and 60° or other angle combinations are also possible.
The pump mechanism may be driven using a worm gear pair or an external geared motor which may be coupled directly to the crankshaft. Therefore, the crankshaft has both a coupling for such an external transmission and also a connection device for a worm gear pair in a preferred refinement. If the pump mechanism is enclosed by a housing, both drive possibilities are expediently possible using the same basic variation of a housing. The worm gear pair may be integrated in the housing, while the external transmission may be mounted externally on the housing in an extension of the crankshaft. The drive motor is then either mounted laterally directly on the housing for the drive via the worm gear pair, or adjoining the housing for drive via the external transmission. A stroke frequency suitable for diaphragm pumps may be generated using both types of drive. Such a frequency is typically below 250 strokes per minute. The drive of the pump mechanism via a worm gear pair has the advantage that multiple pump mechanisms may be chained horizontally via a connection of the worm shafts. A vertical chaining of multiple mechanisms is possible with both types of drive. For this purpose, the crankshafts of multiple pumps may be coupled to one another. In this case, it is possible to position the pump heads on the same side or also alternately.
In a preferred embodiment variation of the pump mechanism having three cylinders, which enclose an angle of 90° overall, the crankshaft is driven via a worm gear pair. The drive motor, whose axis is perpendicular to the crankshaft, of course, is preferably mounted in such a way that its axis encloses an angle of less than or equal to 135° with the axis of the middle cylinder. Cylinders and drive motor are then situated in a fan shape around the crankshaft. If the worm engages on the crankshaft in proximity to the cranks, the crankshaft may be implemented as correspondingly short, and an especially compact flat construction of the pump is possible.
In all above-mentioned embodiment variations, these cylinders are each offset by one connecting rod thickness in the direction of the longitudinal axis of the crankshaft and do not lie in one plane. This may make increased complexity necessary during connection of the pump, in the piping, for example. This constructive disadvantage may be avoided in a preferred embodiment if one or more connecting rods are bent in such a way that the outer ends of all connecting rods facing away from the crankshaft lie in one plane, while the other ends are mounted next to one another and/or, with a vertical crankshaft, one on top of another on the crankshaft, of course. For a three-cylinder pump, at least two such bent connecting rods are necessary so that all connecting rod ends facing away from the crankshaft may lie in one plane. In another preferred variation, the height offset of the cylinder axes is avoided in that either the connecting rods engage off center on the crossheads or the crossheads engage off center on the pistons. In this way, the crosshead tracks, or at least the cylinder heads, may be brought into one plane. A combination of both cited measures is also expedient.
For the mounting of the connecting rods on the crankshaft, the crankshaft is preferably assembled from at least two parts along its length. The division is expediently located in the area of the cranks. The torque transmission is then ensured by a formfitting shaft-hub connection. Possible embodiments are, inter alia, a multi-tooth or polygonal profile or a feather key. A dividable crankshaft allows the use of multiple identical connecting rods, or at least connecting rods having identically shaped closed main bearings, for all cylinders. Storage and production costs may thus be lowered and/or kept low. For three-cylinder or four-cylinder pump mechanisms, the crankshaft must be assembled from at least two parts for this purpose. For a larger number of cylinders, more parts are correspondingly required.
If an undivided crankshaft is used for a pump mechanism having at least three cylinders, at least one main bearing of the connecting rod preferably has a divided bearing shell. In a three-cylinder mechanism, the middle connecting rod main bearing is then expediently implemented as divided. The mounting of more than two connecting rods on an undivided crankshaft may also alternatively be made possible through different diameters of the connecting rod main bearings. In particular for pump mechanisms having a larger number of cylinders, the combination of a divided crankshaft with divided connecting rod main bearings or connecting rod main bearings of different diameters may be advisable. The crankshaft itself is preferably mounted in at least two main bearings on its ends, on both sides of the cranks For this purpose, both friction bearing and also roller bearing technology may be used.
The pump mechanism is expediently installed in a housing. The housing is preferably manufactured from one part and equipped with a closable opening in each of the floor and the rear wall for mounting. The inner workings of the pump, i.e., the single-part or multipart crankshaft and the connecting rods, may be mounted through these openings.
In a preferred refinement, the crosshead tracks of the cylinders and the pump head holders are integrated in the housing. The individual pump head holders may then be connected to one another. This has the advantage that pressure differences in the housing which arise due to the oscillating movements of the crossheads and pistons may be compensated for even with sealed housing openings, since the required air mass equalization may occur between the cylinders. In addition, the housing volumes connected to one another may be used as a reservoir for hydraulic oil in special construction variations of diaphragm pump heads.
The object of the present invention is also achieved by a pump having a pump mechanism according to the present invention. Diaphragm pump heads are preferably connected to the pump head holders of the cylinders.
In the following, the present invention is explained in greater detail on the basis of exemplary embodiments illustrated in the drawing.
The two other connecting rods 15 are mounted without spacing directly below the uppermost connecting rod 15 on the crankshaft 12. The vertical crankshaft 12 is driven via a horizontal worm gear pair 18 using a drive motor 19. The three connecting rods 15 are each mounted on their own crank 14 on the crankshaft 12. On their other end, facing away from the crankshaft 12, they are linked to a crosshead 16. This converts the rotational movement of the connecting rods 15 into a linear movement. This movement is transmitted to a piston 13 via a piston rod. This in turn links the diaphragms of the attached pump heads 22.
The same exemplary embodiment is shown in
With identically shaped connecting rods and identical attachment of the crosshead tracks 25, pistons 13, and pump heads 22, the pump heads 22 have a height offset b to one another, which corresponds to the thickness of the connecting rods.
Another possibility for compensating for the height offset b is used in the refinements shown in
The pump mechanism 10 may alternately be driven via a worm gear pair 18 or via an external transmission 17 having a drive motor 19 which may be coupled directly to the crankshaft 12.
In order that more than two identical connecting rods 15 may be mounted on the crankshaft 12, the crankshaft 12 is implemented as dividable in a special embodiment.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102005029481.2 | Jun 2005 | DE | national |
The present application is a Continuation of U.S. application Ser. No. 11/473,053, titled “Pump Gear,” filed Jun. 23, 2006, which claims priority to German Patent Application No. 102005029481.2, filed Jun. 24, 2005, the entire disclosures of which being hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11473053 | Jun 2006 | US |
| Child | 14753306 | US |
