Patent Application
20080054198
In the accompanying drawings, reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale; emphasis has instead been placed upon illustrating the principles of the invention. Of the drawings:
In order to read out the X-ray information stored in the storage phosphor layer 2, the cassette 1 is opened and the storage phosphor plate 2 removed from the cassette 1 by means of a removal device (not shown in detail), and passed to a conveyance device 5 which in the example shown here comprises two mating rolls which convey the storage phosphor plate 2 to a read-out device 6.
In the example shown, the read-out device 6 comprises two further mating rolls which convey the storage phosphor plate 2 through a read-out unit in which the storage phosphor layer 2 is stimulated by stimulation light into emitting emission light which is collected by an optical detector (not shown). The read-out of the storage phosphor plate 2 is implemented here line by line, individual points of a line 4 being respectively irradiated with stimulation light one after the other—as with so-called flying spot scanners—or at the same time—as with so-called line scanners. The design of appropriate read-out units is described e.g. in EP 1 065 523 A2 and EP1 034 443 B1.
In the region of the repository A, a fixing element 13 is provided which can be moved towards the cassette 1 or away from the cassette 1 by a threaded rod 12. In the example shown, the fixing element 13 is a clamping wedge with a screw thread by means of which the clamping wedge is coupled to the threaded rod 12 and can be shifted by the latter.
A first end of the threaded rod 12 is coupled by a coupling 11 to a stepper motor 10 and is driven by the latter, i.e. set in rotation. A second end of the threaded rod 12 is pivotably mounted in a mounting 14 and pre-tensioned axially in the direction of the stepper motor 10 by a spring 15.
In this example the stepper motor 10 is controlled by the control unit 20 in a way such that the fixing element 13 is moved at a high speed over a first stretch s I between a reference position 16 and a position 16′ close to the cassette 1. This is achieved by operating the stepper motor 10 with high frequency electrical alternating currents.
From the number of steps implemented by the stepper motor 10 for the movement of the fixing element 13, information about the respective position of the fixing element 13 in relation to the reference position 16 is calculated in a control unit 20 connected to the stepper motor 10.
In the control unit 20, as well as the number of steps implemented by the stepper motor 10, the motor load of the stepper motor 10 is also recorded, and this provides a measure for the load of the stepper motor 10 while the fixing element 13 is being moved. According to the invention, the position of the fixing element 13 is calculated from the number of steps implemented by the stepper motor 10, and this is checked, and if appropriate corrected, by means of the motor load recorded.
If, for example, the check shows that the motor load recorded exceeds a pre-specified maximum value, it can be concluded from this that an obstacle, for example the operator's hand, is present. In this event, the stepper motor 10 is halted immediately.
The situation can also arise where the cassette 1 is not placed accurately by an operator against the stop edge K, by means of which the fixing element 13 moved towards the cassette 1 comes into contact with the cassette 1 prematurely and pushes the latter over a specific stretch until the cassette 1 is abutted against the stop bar 4. Along this stretch step, losses occur in the stepper motor 10 due to which the stretch s1 covered by the fixing element 13 from the reference position 16 is no longer in proportion to the recorded number of steps. Precise determination of the position of the fixing element 13 purely from the number of steps is no longer possible in this way. According to the invention, in order to check the precise actual position of the fixing element 13, the recorded motor load is used.
In the present example, on the stretch over which the cassette 1 is pushed by the fixing element towards the stop bar 4 an increased motor load is detected which suggests step losses of the stepper motor 10. In this case the stepper motor 10 is controlled in a way such that any step losses occurring when the fixing element 13 is being driven can be avoided, or at least reduced. In the example shown, the rotation speed of the stepper motor 10 is reduced and/or the torque of the stepper motor 10 is increased.
If the motor load recorded while the fixing element 13 is being driven exceeds a pre-specified maximum value, in certain operational states, such as e.g. with a low revolution speed of the stepper motor 10, the position of the fixing element 13 deduced from the number of steps can also be corrected in order to finally obtain the actual position of the fixing element 13. The desired position of the fixing element 13 calculated from the number of steps recorded can be corrected downwardly dependently e.g. upon the respectively recorded level of the motor load in order to establish the respective precise actual position of the fixing element 13.
In the phase of compressing the spring 15, an increased motor load of the stepper motor 10 is detected in the control unit 20 which, due to the defined mechanical properties of the spring 15, comes within a characteristic value range. Preferably, in this phase the stepper motor 10 is controlled such that its rotation speed is reduced and the torque increased. In this way, on the one hand step losses are avoided, or at least reduced, and on the other hand particularly reliable and sufficiently strong clamping of the cassette 1 is made possible.
Alternating currents 11 and 12 with which the stepper motor 10 is operated are pre-specified by the motor driver unit 21. These are cosinusoidal and/or sinusoidal alternating current sequences, it being possible to control the rotation speed of the stepper motor 10 by specifying the frequency of the alternating currents. The torque of the stepper motor 10 is set by specifying the amplitude of the alternating currents 11 and 12. The respective number of steps to be implemented by the stepper motor 10 is pre-specified by the number of periods in individual alternating current sequences. According to the invention, the aforementioned values are selected and specified dependently upon the number of steps recorded, which is a measure for the desired position of the fixing element 13, and/or the motor load recorded.
For precisely determining, according to the invention, the position of the guide pins 7 relative to a reference position 16, the above comments in connection with the examples shown in
In this example the stepper motor 10 is controlled by the control unit 20 in a way such that initially the guide pins 7 move quickly towards the recesses 8 at high speed, and the speed of the stepper motor 10 is reduced when the guide pins 7 have reached a pre-specifiable position close to the support 3. The guide pins 7 are then engaged in the recesses 8 at a speed which is reduced in relation to the initial speed and finally push the support 3 together with the storage phosphor plate 2 located on top of it into the cassette 1.
By successively, almost continuously recording the motor load of the stepper motor 10 it can be established here whether the support 3—as shown in FIG. 5—is already fully pushed into the cassette 1 and is abutted against the opposite face side of the cassette or against a stop located here. In this case a high motor load is detected in the control unit 20, and directly thereupon the conveyance of the support 3 and the storage phosphor plate 2 back into the cassette 1 is ended by the rotation of the stepper motor 10 being halted.
In this way reliable and precise conveyance of the support 3 together with the storage phosphor plate 2 located on top of it back into the cassette 1 is achieved.
After fixing the support 3 together with the storage phosphor plate 2 in the cassette 1 the stepper motor 10 can now be operated in the opposite rotation direction at relatively high speed in order to bring the bar 19 together with the guide pins 7 back into the reference position 16. This movement is also initially implemented at high speed and close to the reference position 16 at reduced speed. By successively recording the motor load and taking this into account both when establishing the actual position of the bar 19 and when controlling the stepper motor 10 it is guaranteed that the reference position 16 is approached and finally reached with a high level of reliability and precision.
In the exemplary embodiments described in detail above, only two possibilities were shown with which processors, such as the fixing element 13 and the guide pins 7, can be operated according to the invention when processing and reading out storage phosphor plates. Furthermore, there are numerous further possibilities for using the described invention.
Therefore, for example, the distance between the rolls of mating rolls, as in the conveyance device 5 shown in
Further examples of use of the invention are driving devices for opening and closing a flap located on the face side of the cassette, driving mechanisms for fixing and releasing the storage phosphor plate in the cassette, and driving devices for conveying the storage phosphor plate through the apparatus, in particular through the read-out unit, such as e.g. rolls, threaded rods or cables.
In general the invention can advantageously be used for implementing and controlling any mechanical procedures in connection with processing information carriers. As well as precisely determining the position of and controlling mechanical processors, such as e.g. fixing and/or conveyance elements, a further advantage of the invention is that one can dispense with a plurality of different sensors for determining the position of and controlling mechanical processors. The production costs of corresponding systems are considerably reduced in this way.
While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06119718.2 | Aug 2006 | EP | regional |
