Patent Application
20080185226
The invention relates to a lubricant tank according to the preamble of claim 1 and a lubrication system according to the preamble of claim 11.
In lubrication systems with a lubrication pump it is known (DE 200 21 026 U) to equip the lubricant tank (for grease or oil) with a follower piston tensioned by gravity, so that the lubricant is securely guided into the inlet chamber of the lubrication pump. In lubrication pumps that do not always have a vertical working position of the lubricant tank, e.g. in the rotating hub of a wind power station, the gravitation cannot permanently tension the follower piston as desired. Therefore, it is known in practice to have the follower piston tensioned by a spring arrangement to ensure secure feeding of the follower piston and thus also the lubricant, e.g. also under the influence of centrifugal forces. Depending on the size of a machine to be lubricated, e.g. a wind power station, for ensuring the envisaged maintenance intervals with e.g. equally efficient lubricant locations, various sizes of lubricant tanks that are always made to measure are employed. The various tank sizes cause cost-intensive part variety. Such a lubricant tank contains at least one to two kilograms of lubricant, or, depending on the demand, even more. In case of larger lubricant tanks, the spring arrangement consists e.g. of a conical spring with a predetermined loaded length of spring, a predetermined spring rate and a predetermined spring characteristic. As the conical spring has to control the complete stroke itself, there is a problem in that with full lubricant storage volume and highly compressed conical spring, the effective force at the follower piston is undesirably high, and it becomes too weak for a secure function of the lubrication pump when the storage volume has become clearly smaller or shortly before the point of time for maintenance has come.
The object underlying the invention is to provide a lubricant tank and a lubrication system which ensure high operational reliability with economical and simple construction.
The object is achieved with the features of claim 1 and subclaim 11.
The disadvantage of an initially too high tensioning force and a too weak tensioning force towards the end is eliminated in a large lubricant tank with economical and simple construction by subdividing the spring arrangement into a row of individual spring units, i.e. if a size or length of the lubricant tank is required where an individual spring unit would necessarily result in the above-mentioned disadvantages. By the subdivision of the spring arrangement into individual spring units connected in series, a stepwise elongation of the travel of the spring system without simultaneous clear increase of the initial force exerted on the follower piston and also without too drastic a reduction of the final force is achieved. Here, the knowledge that a row of spring units permits a long travel of the spring system, and if the weakest spring unit is not compressed to block, it always acts with the force of the weakest spring unit is utilized. With a size of the lubricant tank with which the used stroke distance of the follower piston can be controlled by one single spring unit without any problems, however, only one spring unit has to be employed. In larger lubricant tanks, however, two or more spring units are connected one after the other to prolong the travel of the spring system to be used with favourable forces as desired in a modular manner. In this manner, the desired support of the lubrication pump is in each case ensured via the used stroke distance and the lubricant is securely fed. In this manner, the operational reliability is increased in a simple manner. This can be particularly practical in wind power stations where the lubricant tank rotates and where possibly even centrifugal forces act which could affect the feeding of the lubricant into the inlet chamber of the lubrication pump. The increased operational reliability by the subdivision of the spring arrangement, however, can also be practical for lubricant tanks or lubrication systems designed for other cases of application.
Conveniently, each spring unit is a conical spring. This conical spring can have a simple design, i.e. consist of one spring wire, or it can have a multiple design, i.e. be wound from several spring wires or formed from conical springs fitted into each other. For a conical spring has the advantage of a short loaded length of spring in a completely compressed state, so that with a given fitting length, a long spring stroke can be utilized until the tension of the spring is completely or largely released.
Alternatively, each spring unit can also be a coil spring in simple or multiple design. As a further alternative, it is conceivable to form each spring unit of a disk spring stack.
For the spring units connected in series to correctly cooperate, it is practical to arrange an intermediate plate between each of them which is smaller than the inner cross-section of the outer envelope of the lubricant tank. However, embodiments where the ends of abutting spring units match such that an intermediate plate is dispensable are also conceivable.
For a favourable power transmission it is practical, if conical springs are used, to support them each in pairs with their large-diameter or small-diameter ends at a common intermediate plate. The intermediate plate can also consist of two plates each of which is e.g. mounted to one spring end.
For the effective force to develop in a predetermined manner over the used stroke of the follower piston, it is practical to combine conical springs with identical designs in the spring arrangement.
If, however, a special course of the development of the spring force over the stroke is desired, the conical springs can also be designed with different loaded lengths of spring and/or different spring rates and/or different spring characteristics.
It would also be conceivable to provide different types of springs in the installed spring units.
To avoid the disadvantage of having a wide part variety for various sizes of lubricant tanks (various tank fixing flanges, follower plates, metal parts, tank lids and the like), according to a further, important aspect of the invention, the lubricant tank is modularly made from an outer envelope kit in various sizes each with a different length of the outer envelope but with the same inner cross-section. Thus, for various tank sizes, the same tank fixing flanges, follower pistons, intermediate plates, tank lids and the like can be used. This selection of the respective proper outer envelope from a kit with different lengths of outer envelopes is particularly profitably combined with the measure of subdividing the spring arrangement into individual spring units arranged in series as of a certain size of the lubricant tank or length of the outer envelope.
Depending on the application, the inner cross-section of the outer envelope can be round or four-cornered. The contour of the follower piston is adapted to each inner cross-section while the intermediate plates not necessarily have to be adapted to the inner cross-section.
In the lubrication system it is practical to select an outer envelope from a kit with different lengths of outer envelopes having the same inner cross-sections according to the storage volume required for a predetermined maintenance rate of the lubricant consumer, and, as of a predetermined lubricant tank size, to subdivide the spring arrangement into individual spring units and to have these spring units act in series.
With reference to the drawing, embodiments of the subject matter of the invention are illustrated. In the drawing:
A lubrication system S, for example a central lubrication system that can be installed in the hub region of a wind power station, which is operated with a lubricant, such as oil or grease, comprises a lubrication pump P driven by a motor M and a lubricant tank B functionally connected with it. For example, the lubricant tank B is connected to the lubrication pump or a housing containing the lubrication pump or the motor via a tank fixing flange 10. The lubricant tank B has a for example round or four-cornered outer envelope 1b of a length L2 defining an inner cross-section constant over the length. The upper end of the outer envelope 1b is closed by a lid 2. In the outer envelope 1b, a follower piston T is guided in a sealed and displaceable manner (seals 6) and limits a lubricant collector chamber F and is tensioned by a spring arrangement A towards the lubrication pump P. The spring arrangement A is supported, for example, at the lid 2.
The outer envelope 1b can be a commercially available plastic or metal pipe or profile. For designing various sizes of lubricant tanks B, outer envelopes of various lengths are selected from a kit, while the tank fixing flange 10, the follower piston T and the lid 2 can each have the same design. The selected size of the lubricant tank depends on the lubrication demand of the machine or device to be lubricated, and possibly also on the maintenance rates which are predetermined. Normally, the sizes of the lubricant tanks of such lubrication systems start with contents of 1 to 2 kg, and there are no limits upwards.
In the lubricant tank, a level monitoring device is provided which consists of a switch tube 4 penetrating the follower piston T, with a switching component situated at the bottom and a plug connection 5 provided outside at the lubricant tank B. The switch tube 6 is necessary for various tank sizes in various lengths, while the plug connection 5 can always be the same. These measures, i.e. to use outer envelopes having various lengths but the same inner cross-section and only switch tubes of various lengths, reduces the part variety in the manufacture of lubricant tanks B having various sizes.
The spring arrangement A in the embodiment which is shown in
The two conical springs 7 can be identical, i.e. have the same loaded length of spring, the same spring rate and the same spring characteristic. However, it is also conceivable to design the one conical spring different from the other conical spring 7 to achieve a different force characteristic.
Conical springs, such as the shown conical springs 7, have the advantage of a very short overall length in a compressed state and thus the advantage of a long usable spring stroke. Furthermore, for this purpose of application, they have favourable spring characteristics. It is desirable to have a spring characteristic where the difference between the spring force acting on the follower piston T with a compressed spring and with a more tension-released spring is as low as possible and changes as linearly as possible between these force values.
Alternatively, each spring unit E1, E2 could also be formed of a coil spring, or else of a disk spring stack or of an annular spring stack. It would be furthermore conceivable to employ spring units consisting of plastic material. A spring of the one type could also cooperate with a spring of another type in the same lubricant tank. An intermediate plate 3 is not absolutely necessary; however, it can be practical between the spring units for perfect power transmission.
In
As required, in one spring unit E1, E2, two or several individual springs can also be combined. In this manner, all desired force relations and characteristics can be realised according to the function. In the embodiment in
Basically, for achieving a long travel of the spring system via which the follower piston is tensioned with force, the invention consists in subdividing the spring arrangement into units and in connecting these units in series, if with only one spring unit an unfavourably high initial force would result, and possibly in selecting and designing the spring units such that they are alike, and even an individual one of such spring units can be used for a small tank size in an individual arrangement. This principle can be conveniently combined with various lengths of outer envelopes having the same inner cross-section to reduce the part variety in the manufacture of lubricant tanks of various sizes, so that finally, for example, one single type of the spring unit, the tank fixing flange, the follower piston, the intermediate plate, the lid and the level sensor can be used for all tank sizes, while the outer envelopes and the switch tubes have various lengths, but are conveniently also cut from continuous lengths.
Lubrication systems equipped with such lubricant tanks are not only practical for wind power stations where the lubricant and the follower piston are possibly even subjected to centrifugal forces counteracting the feeding of lubricant to the lubrication pump, but also for other employments where a secure feeding of the lubricant to the lubrication pump is important.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 2004 009 387.1 | Jun 2004 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2005/006259 | 6/10/2005 | WO | 00 | 11/29/2007 |
