Field of the Invention

The present invention relates to a test system comprising at least a first and a second reciprocating movable load carriage, which first and second reciprocating load carriages are connected by spring means.

The present invention further relates to a method for test of heavy loads at a test system, which test system comprises reciprocating movable carriages interconnected by spring means, which reciprocating carriages are connected to a force generating apparatus.

The present invention further relates to the use of the test system and the method for test. Background of the Invention

WO04005879A1 concerns an apparatus for applying at least one load to a specimen according to one embodiment of the invention may comprise a mass. An actuator mounted to the specimen and operatively associated with the mass moves the mass along a linear displacement path that is perpendicular to a longitudinal axis of the specimen. A control system operatively associated with the actuator operates the actuator to reciprocate the mass along the linear displacement path at a reciprocating frequency, the reciprocating frequency being about equal to a resonance frequency of the specimen in a test configuration. EP 1349676 concerns a drive unit comprising a at least one motor, which motor is connected to at least one first spring, which first spring is connected to at least one movable mass, which movable mass is connected to at least one second spring.

Object of the Invention

The object of the invention is to perform a vibration test at heavy components. Description of the Invention

This can be achieved if the system described in the preamble to the claim 1 is further modified by that the reciprocating moveable load carriages are supported at a support platform, the said spring means comprises a plurality of springs, which plurality of springs are supported by at least one support unit.

Hereby can be achieved, that even a very heavy load placed on one of the reciprocating movable load carriages can be tested. In the test system as described there must be more or less a balance between the two reciprocating movable load carriages, so that they are to be loaded with more or less the same mass. Therefore, if only one item has to be tested, a dummy load of approximately the same weight has to be placed on the opposite load carriage. The system will operate most effectively if two equal devices can be tested at the same time, and these two devices have more or less the same weight. If the same weight is placed on both load carriages can reciprocating movement be started, and an oscillation of the movable load carriages will begin. The frequency as such could be in the area from 1-10 hertz and the amplitude could be from 20-200 millimetres. In that way it should be possible for different loads to achieve an acceleration in the area from 2-15 G. It will be possible by this invention to test loads with a weight as high as 2 tons on each of the reciprocating movable load carriages. Even heavier loads could be tested. If a test system is constructed in a larger size, extremely heavy loads could be tested. For many heavy constructions there is always a need for a test, before the constructions are delivered to a customer. Often only calculation of vibration stability is achieved, because testing is impossible. Especially for heavy wind mill components, it is important that a vibration test can be performed so that vibrations that occur in a nacelle can be simulated. Since the oscillations will be achieved in a mechanical oscillating system, only a limited energy supply is necessary for keeping the oscillations for a longer time period. The energy supply depends on frictional force between the movable load carriages and the support.

The support unit can be operable to support a mostly non-moving point of said spring means. Since the spring means are relatively long, they have a length of maybe 3 meters or more, these springs need one or more supports, and knowing the oscillation frequency and the way these oscillations take place during the springs, there will probably be achieved a note just in the middle of the spring where the spring is non-moving, because the moving carriages are moving opposite each other. Exactly at the note where the spring is in rest, it is easy to place a support unit at the spring. This support unit can then rest on the support for the movable carriages. It is possible that the oscillation frequency is selected so that more notes exist at the spring means and therefore more support units could be placed below the springs. Especially if even longer or bigger operators for oscillations are constructed, there will be a need for further support units.

In an alternatively embodiment the support unit can be operable to support at least one moving point of said spring means, said support unit is moveable relative to the support platform. If a situation occurs where for example there is some weight difference be- tween the loads, the point of non-moving of the spring will probably be changed or maybe even not exist, therefore it can be important that the support unit is movable relative to the support platform. Even at a start up it can be necessary that the support unit is moving maybe only a few millimetres, but if an oscillation occurs with a difference in the loads, there will be introduced a movement of the middle point of the spring. Therefore it is important that the support unit is movable.

The spring means can comprise a two-dimensional array of springs. In order to achieve a sufficiently strong spring, it is necessary to use a number of springs in parallel. A spring of the dimension that should be used, will be extremely expensive and would probably have to be produced once per unit which is to be built. Therefore, it is much more effective to couple a number of springs in parallel. Because of the high number of springs, a two-dimensional array will be highly effective. It is to be understood that the array of springs may by constructed so that the whole array could be replaced. In that way a new array with another combination of springs could easily be placed when a new test has to be performed. Otherwise, adjustment of the number of springs or coupling one or more of the springs inactive could also be a way of adjusting the spring constant so that oscillations could be performed with different loads. The two-dimensional array of springs can comprise an upper row and a lower row of springs, and wherein said support unit is adapted to support said upper row and said lower row of springs. The support unit has to support each row of springs, and in some situations even more than an upper or lower row of springs could be used, so that there could be three, four or five layers of springs. Even with a high number of layers of springs it is necessary to support all of the springs, because the springs are relatively heavy and very long.

The support platform can carry the reciprocating movable load carriages, which recip- rocating moveable load carriages carry a first and a second load under test. By using the two reciprocating movable loads connected by the number of springs, it is possible to test two more or less equal items at the same time.

Each of the reciprocating moveable carriages carries a load of mostly the same weight. Different items can be tested together if they have more or less the same mass. If not, balanced dummy masses could be added to the carriages. But if a number of items have to be tested, it will often be possible to test two equal items at the same time. If heavy constructions are to be tested, it is supposed that there can be a slightly small difference in their weight. If the support unit is able to move only a few millimetres, tests could be performed with small changes in mass. It should be possible to place load sensors because of the relatively long movement of the reciprocating movable carriages.

The reciprocating moveable carriages can be cooperating with a linear guide system. These carriages have to be controlled by a linear guide system. The linear guide system can be formed in a lot of different ways, but one possibility is that the movable carriages are placed on wheels, and these wheels are rotating at rails for giving the best support for the heavy load. Two or more rails can function as the support platform and carry the reciprocating movable load carriages. Hereby the friction between the reciprocating movable carriages and the support can be rather small. That would lead to relatively low energy consumption when the oscillating system is in operation.

The test system comprises at least one first force generating apparatus, at least one activation spring connected to the force generating apparatus, and at least one of the reciprocating movable load carriages is connected to the activation spring. A possible activation could be performed from an electric motor which by an eccentric and a spring is connected to one of the reciprocating movable load carriages. Thereby an oscillation can be started, and by letting the engine operate at a controlled velocity, it is possible to keep an oscillation at a specific frequency.

The test system can comprise at least one linear hydraulic activator connected to at least one of the reciprocating movable load carriages for driving the test system. It is possible that the reciprocating movable load carriages are connected to hydraulic cylin- ders which can be activated by a hydraulic pressure, so that the heavy loads are being moved. Because of the relative low frequency, it is possible by hydraulic valves to activate and deactivate cylinders so that an oscillation can be started. It is possible with oscillating systems driven by hydraulic cylinders also to control the frequency. Hydraulic cylinders can be operating positive and negative in a puss/pull mode. In that way a relative fast acceleration of the oscillating system can be performed.

The object can be achieved if the system described in the preamble to the claim is further modified so that a heavy load is fixated to each of the reciprocating carriages, the spring means is adjusted in accordance with the load and test frequency, the force gen- erating apparatus is started, and the reciprocating movable carriages an the load starts to reciprocate with a selected frequency.

By the method can heavy loads be placed at the reciprocating carriages and an oscillation is started, because the spring means are connecting to the reciprocating carriages, a highly effective oscillation can be started. This oscillation test could be very helpful for testing heavy mechanical constructions. Not only wind mill wings and other heavy wind mill components could be tested. Many other mechanical apparatus could be tested highly effectively by the oscillations in the frequency areas 1-10 hertz and with amplitude between 0 and 200 millimetres. Thereby a relative high G force at a test items can be achieved. By a method for test as here described, a life time test could be made on rather heavy equipment, before it is sent out into the real live. Thereby a lot of quality breakdowns could be indicated long before a product is sent to the market. The system or method can be used for test of heavy loads. It is possible by the test system to use the system for heavy loads. If particularly heavy loads have to be tested, a test rig could be manufactured just for that purpose. The system or method can be used for test of windmill components. Different wind mill components could be tested in that way. For example all components which have to be placed in a nacelle, such as gearbox and generators can be tested by an oscillation test.

The system or method can be used for test of cars or car components. It should be pos- sible in a test system like this to test a normal car for vibrations.

The system or method can be used for test of off shore components. Heavy off-shore components can be tested, before they are sent to platforms at open sea. The system or method can be used for test of airplane or space components. Many airplane or space components have to be tested, before the components can be used in the airplane or space industry.

The system or method can be used for test of ship components. Also many heavy ship components can be tested by a system as described.

Detailed Description of the Invention

Fig. 1 shows a side view of a possible embodiment for a test system.

Fig. 2 shows a top view of the test system.

Fig 3 shows a sectional top view of the test system.

Fig. 4 shows a first possible embodiment for reciprocating load carriages.

Fig. 5 shows an alternative embodiment of the reciprocating load carriages.

Description of the Drawing

Fig. 1 shows a test system 2 which is one possible embodiment of the invention described in the pending application. The test system 2 comprises a fixture 4 and a number of rails 6 on which rails 6 reciprocating load carriages 8 and 10 are indicated. Spring means 12 are supported by a support unit 14, and the spring means 12 are placed between the frames 15 which frames 15 are part of the reciprocating load carriages 8 and 10. The reciprocating load carriages are supported by the wheels 16 at the rails 6. Further the support unit 14 is supported by a movable support 18 which also interacts with the rails 6.

Fig. 2 shows the same embodiment as does fig. 1 , but seen from the upside. Again, the test unit 2 is indicated with a frame 4, and the frame 4 comprises rails 6. The rails support the reciprocating load carriages 8 and 10, and spring means 12 are carried by the carriage unit 14 and the spring means 12 are placed between the frames 15 which frames are part of the reciprocating load carriages 8 and 10.

Fig. 3 shows a sectional view of the test system 2. The system shown in fig. 3 has the same features as those shown in fig. 2, and these common features will not be further described here. Instead there is a sectional view indicating a mechanical actuator 20 which can interconnect some of the springs that form the spring means 12. Hereby it can be achieved that the spring constant as such can be adjusted by simply coupling some of the springs into a non-active state during oscillation. Thereby different oscillating frequencies can be adjusted before a test is started. The spring constant as such depends on the mass that is to be tested and the selected frequency. Therefore it is highly effective that the spring constant can be adjusted in one or another way.

Fig. 4 shows the reciprocating load carriages 8 and a wheel unit 16 which are supported by a rail 6.

Fig. 5 shows an alternative embodiment where the reciprocating load carriages 8 or 10 are also supported by wheel means 16, but where the wheel 22 together with the support 24 forms a guidance system. By the test system 2 should be understood that also many other embodiments operating in the same way are possible. Test systems could be constructed in such a way that very heavy loads of up to 50 tonnes can be tested. The test system 2 must only be made in some sufficiently larger dimensions. Here the test system 2 is operating at the surface, for example inside a relatively big building. Alternatively a vertical system could be built where one of the reciprocating load carriages form part of a floor where for example a car can be parked when it is to be tested. The spring means and other load carriages could be placed deep below the floor surface, and the downwards load carriage could in fact carry a dummy mass which is more or less like the mass of the car that is to be tested. Another testing example is fixing a windmill wing at both of the load carriages 8 and 10 and then starts an operation test of two wings at the same time.