Optimized vertical adjustment of a patient couch

Abstract

A medical device (1) has a patient bed (2) whose position can be adjusted in the vertical direction by means of a drive (5). A control device (9) controls the drive (5) whenever it receives a travel command (F) from an operator (12) on the basis of which the patient bed (2) is to be moved upwards, in response to the travel command (F) initially in such a way that the drive (5) moves the patient bed (2) downwards during an initial period. Only then does the control device (9) control the drive (5) in a lifting period immediately following the initial period in such a way that the drive (5) moves the patient bed (2) upwards.

Description

[0001] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

[0002] The present invention is based on an operating method for a medical device having a patient bed whose position can be adjusted in the vertical direction by means of a drive, wherein a control device controls the drive in response to the drive command whenever it receives a travel command from an operator on the basis of which the patient bed is to be moved upwards, such that the drive moves the patient bed upwards.

[0003] The present invention further relates to a control device of a medical device having a patient bed whose position can be adjusted vertically by means of a drive. The control device is programmed with a control program so that the control device executes such an operating method. The control program comprises machine code that can be directly processed by the control device, and the processing of the machine code by the control device causes the control device to execute such an operating method.

[0004] The present invention further relates to a medical device having a patient bed whose position can be adjusted in the vertical direction by means of a drive, wherein the medical device has such a control device which carries out such an operating method for adjusting the patient bed in the vertical direction.

[0005] The aforementioned items are well known. In particular, various medical imaging modalities, such as CT systems, C-arm systems, and MRI systems, feature a standard location for height-adjustable patient beds.

[0006] In some cases, a drive is used for the lifting axis of a patient bed that acts on the bed via a self-locking gear. The use of such a gear offers several advantages, but also has several disadvantages.

[0007] The most important advantage is that a separate brake is not required to secure the patient table at a specific height. Instead, it is only necessary to disconnect the power supply to the drive. Another advantage is that any potential interference with the magnetic field of an MRI system caused by an electromagnetically actuated brake cannot occur. Another advantage is the relatively low cost. Furthermore, only a few parts are susceptible to failure, and few service calls are required.

[0008] One disadvantage is that the efficiency is relatively low. It can range, for example, between 20% and 25%. This requires a relatively high drive power. This also applies to all other energy supplies, such as a power supply, the dimensioning of an inverter feeding the drive, and, in the case of a mobile medical device, an on-board battery.

[0009] The most problematic case is when various circumstances coincide which require a particularly high torque and / or particularly high power. One circumstance arises when a particularly heavy load has to be lifted. This can be particularly common when a patient is lying on the patient couch and the patient has a large mass. Another circumstance is when the patient couch has not been moved for a certain period of time before being moved upwards. In this case, the lubricating oil which lubricates the contact surfaces of the drive train - for example a gearing - and thereby significantly reduces the frictional force is forced out of the contact surfaces of the drive train. In this case, there is therefore direct metal-to-metal contact at the contact surfaces. The oil film only builds up again during travel.Another issue arises when the lubricating oil is at a relatively low temperature. This causes the lubricating oil to be more viscous and thicker, so it takes longer for the oil film to build up. If these conditions occur together, the drive may not start.

[0010] To solve these problems, it is of course possible to dimension the power supply accordingly. However, in this case, the power supply would have to be very large, which would involve a corresponding increase in volume and corresponding costs.

[0011] In addition, the German patent application DE 10 2021 210 095 A1 discloses solutions for keeping the muscle force manually applied by an operator for a horizontal movement of a patient couch, which can vary greatly depending on the position of the patient couch, its direction of travel and the weight of the patient on it, essentially constant.

[0012] The object of the present invention is to create possibilities by means of which a reliable start-up of the drive can be achieved even when the disadvantageous circumstances explained above occur.

[0013] The object is achieved by an operating method having the features of claim 1. Advantageous embodiments of the operating method are the subject of dependent claims 2 to 7.

[0014] According to the invention, an operating method of the type mentioned at the outset is designed in that the control device, whenever it receives a travel command from an operator on the basis of which the patient bed is to be moved upwards, does not immediately control the drive in such a way that the drive moves the patient bed upwards, but in response to the travel command, first controls the drive in such a way that the drive moves the patient bed downwards during an initial period, and only then controls the drive in a lifting period immediately following the initial period in such a way that the drive moves the patient bed upwards.

[0015] By moving the patient table downwards at the beginning of the travel process, the weight of the patient table and the patient lying on it does not have to be overcome. All other circumstances being equal, this requires less drive power than would be needed to move the patient table upwards. However, as the patient table moves downwards, the oil film builds up. As a result, when the patient table is subsequently moved upwards, the weight of the patient table and the patient lying on it must be overcome in addition to the frictional force. With regard to the frictional force, however, it can no longer occur that the high frictional force that occurs when metal slides against metal has to be overcome.Rather, only the considerably lower frictional force has to be overcome, where the oil film is present between the metal surfaces, which significantly reduces friction.

[0016] As a result, it is possible to dimension the drive's power supply relatively small and yet still ensure reliable start-up of the drive even during a lifting movement (i.e. moving the patient bed upwards) with high load.

[0017] The amount by which the patient bed is lowered during the initial period can be determined as needed. In many cases, this amount can easily be set so small that it is unnoticeable by either the patient lying on the bed or the operator.

[0018] As already mentioned, a further disadvantage is that the lubricating oil can be relatively cold and therefore relatively viscous, at least at the start of a travel movement. The procedure according to the invention does reliably ensure that the drive starts up, i.e. that the lifting movement begins. However, it can happen that the lubricating effect of the lubricating oil is not yet optimal and that the drive is therefore overloaded when the patient bed is moved upwards, i.e. during the lifting period. To avoid this, the control device iteratively controls the drive during the lifting period in such a way that the lifting speed at which the patient bed is moved upwards is increased continuously or in steps. The control device carries out two tests here. Firstly, the control device checks whether the lifting speed reaches a predetermined setpoint.Second, the control unit checks whether an electrical operating variable of the drive reaches a predetermined limit. The control unit stops increasing the lifting speed as soon as the lifting speed reaches the predetermined speed setpoint or the electrical operating variable of the drive reaches the predetermined limit. The electrical operating variable of the drive can be, as required, the current, the voltage, the power (i.e., the product of current and voltage, possibly taking into account a phase shift), or an operating frequency of the supplying converter.

[0019] The lifting speed is therefore increased to the setpoint speed whenever possible. However, the increase in the lifting speed is stopped before the setpoint speed is reached, as soon as the electrical operating variable of the drive reaches the predetermined limit. This procedure can therefore reliably prevent overloading of the drive.

[0020] Of course, if the control unit receives a corresponding movement command from the operator, it must also be possible to lower the patient bed by controlling the drive accordingly. Therefore, whenever the control unit receives a movement command from an operator to lower the patient bed, it controls the drive in response to the movement command during a lowering period in such a way that the drive lowers the patient bed.

[0021] In order to be able to move the patient bed downwards upon receiving a command to move it upwards, the corresponding downward travel path must be available at the time the command is received. There are various options for reliably providing this travel path.

[0022] One possibility is that when the patient bed is moved downwards, the control device stops controlling the drive as soon as the patient bed reaches a predetermined minimum distance from the lowest possible position.

[0023] A further possibility is that when the patient bed is moved downwards, the control device controls the drive at least in a final period immediately following the lowering period in such a way that the drive moves the patient bed upwards if the patient bed is moved downwards to a position during the lowering period which is less than a minimum distance from a lowest possible position.

[0024] In many cases, the drive for adjusting the patient support vertically drives a helical worm shaft. In this case, the control device is preferably designed to terminate the final period as soon as the drive has rotated the worm shaft by a predetermined first rotation angle, in particular by a maximum of 360°. This ensures that after the final period, a predetermined second rotation angle is always available for starting the drive when moving the patient support downwards during the initial period.

[0025] Preferably, the control device is further configured to terminate the initial period as soon as the drive has rotated the worm shaft by the predetermined second rotation angle, and such that the second rotation angle is at most as large as the first rotation angle. This ensures that the reversal of the initial downward movement of the patient support into an upward movement occurs in a timely manner before the patient support reaches its lowest possible position.

[0026] Regardless of the specific procedure for moving the patient bed downwards, the control device is preferably designed such that it terminates the initial period as soon as the drive has rotated the worm shaft by a predetermined angle of rotation, in particular by a maximum of 360°.

[0027] The 360° rotation angle is particularly important because the worm shaft is often horizontally oriented and runs in an oil bath. When performing one complete rotation, there is therefore always an unreliable guarantee that the worm shaft will be wetted with lubricating oil over its entire circumference.

[0028] The object is further achieved by a control device having the features of claim 8. According to the invention, the control device is programmed with a control program so that the control device executes an operating method according to the invention. The execution of the control program causes the control device to execute the operating method according to the invention.

[0029] The object is further achieved by a medical device having the features of claim 9. According to the invention, the control device is designed as a control device according to the invention.

[0030] Preferably, the medical device has a self-locking gear, which the drive drives to adjust the patient bed in the vertical direction. The self-locking gear can, in particular, have a helical worm shaft.

[0031] The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of the embodiments, which are explained in more detail in conjunction with the drawings. Herein, in schematic representation: Fig. 1 a medical facility, Fig. 2 a control device and a drive train, Fig. 3 a part of a drive train, Fig. 4 a flow chart, Fig. 5 a time diagram, Fig. 6 a flow chart and Fig. 7 and Fig. 8 time diagrams.

[0032] According to Fig. 1, a medical facility 1 has a patient bed 2. A patient 3 can be placed on the patient bed 2. The position of the patient bed 2 is, as shown in Fig. 1 is indicated by a double arrow 4, in the vertical direction. The patient couch 2 can therefore be moved up and down in the vertical direction. The movement of the patient couch 2, i.e. the adjustment of the position in the vertical direction, is carried out according to Fig. 2 by means of a drive 5. As a rule, the drive 5 acts on the patient couch 2 via a gear 6, which the drive 5 drives to adjust the patient couch 2 in the vertical direction. The gear 6 can in particular be a self-locking gear, for example as shown in Fig. 3, a worm gear comprising a helical worm shaft 7 and a gear 8. In this case, the drive 6 rotates the worm shaft 7, which in turn acts on the gear 8. The gear 8 acts directly or indirectly on the patient bed 2.

[0033] To control (among other things) the drive 5, the medical facility 1 has according to Fig. 2 has a control device 9. The control device 9 is programmed with a control program 10. The control program 10 comprises machine code 11, which can be directly processed by the control device 9. The programming of the control device 9 with the control program 10 or - synonymous with this - the processing of the machine code 11 by the control device 9 causes the control device 9 to execute an operating method for adjusting the patient bed 2 in the vertical direction, which is described below in connection with Fig. 4 is explained in more detail.

[0034] According to Fig. 4, the control device 9 checks in a step S1 whether an operator 12 has issued a travel command F for vertically moving the patient bed 2. The control device 9 repeatedly executes step S1 until it is issued a travel command F. If a travel command F is issued here, the control device 9 accepts the travel command F in a step S2.

[0035] In step S3, the control device 9 checks whether the travel command F is a travel command to move the patient bed 2 upwards. If this is not the case, the control device 9 proceeds to step S4. In step S4, the control device 9 determines a control signal C for the drive 5, based on which the drive 5 moves the patient bed 2 downwards. In step S5, the control device 9 controls the drive 5 according to the determined control signal C. From step S5, the control device 9 returns to step S1.

[0036] If, on the other hand, the specified travel command F is a travel command to move the patient couch 2 upwards, the control device 9 checks in a step S6 whether the travel command F was just specified, i.e. whether it represents the start of a travel movement of the patient couch 2. If this is the case, the control device 9 proceeds to a step S7. In step S7, the control device 9 determines a control C for the drive 5, on the basis of which the drive 5 moves the patient couch 2 downwards, i.e. opposite to the actually desired direction of travel. The control device 9 then proceeds to step S5. If, on the other hand, this does not represent the start of an upward travel movement of the patient couch 2, the control device 9 proceeds from step S6 to a step S8.In step S8, the control device 9 determines a control signal C for the drive 5, based on which the drive 5 moves the patient bed 2 upward, i.e., in the actually desired direction of travel. The control device 9 then returns to step S5.

[0037] The approach of Fig. 2 thus causes the control device 9 to first actuate the drive 5 in response to the actuation command F whenever it receives a travel command F from the operator 12 on the basis of which the patient bed 2 is to be moved upwards, in such a way that the drive 5 moves the patient bed 2 downwards, and only then to actuate the drive 5 in such a way that the drive 5 moves the patient bed 5 upwards.

[0038] This procedure is described below in Fig. 5 is shown again in the form of a time diagram, in which the angular position α of the worm shaft 7 is shown as a function of time t. The greater the angular position α of the worm shaft 7, the further the patient bed 2 is moved upwards.

[0039] The travel command F for moving the patient support 2 upwards is given to the control device 9 at a time t1. At time t1, the worm shaft 7 has an initial angular position α1. Starting at time t1, the worm shaft 7 is rotated to an angular position α2 that is smaller than the initial angular position α1. The angular position α2 is reached at a time t2. From the time t2 reaching the angular position α2, the worm shaft 7 is rotated to angular positions α that increase, not only beyond the angular position α2, but also beyond the angular position α1. The patient support 2 is thus moved upwards. The time period from time t1 to time t2 is referred to below as the initial period. The time period beginning at time t2 is referred to below as the lifting period. The lifting period lasts as long as the patient support 2 is moved upwards.Obviously, the lifting period immediately follows the initial period.

[0040] The extent δα by which the angular position α2 is smaller than the angular position α1 can be determined as required. As a rule, the extent δα is smaller than 360°, often even considerably smaller than 360°, for example 180° or less, 120° or less, or 90° or less. In some cases, it may be possible for the initial period to be determined as such, and the extent δα as such is therefore not fixed. In other cases, it is possible for the extent δα to be predetermined as such, so that reaching the angular position α2 as such, i.e., rotating the worm shaft 7 by a predetermined rotation angle as such, terminates the initial period.

[0041] The following is in connection with Fig. 6 explains a currently preferred implementation of step S8.

[0042] According to Fig. 6, a lifting speed v and an electrical operating variable I of the drive 5 are known to the control device 9 in a step S11. The lifting speed v is the speed at which the patient couch 2 is moved upwards. The electrical operating variable I in this case is the current supplied to the drive 5. However, it can also be a different operating variable. The operating variable I is generally specified to the control device 9 as a measured variable or derived by the control device 9 from measured variables. The lifting speed v can be measured or determined by the control device 9, for example, from a sequence of recorded heights of the patient couch 2 or from actual position values ​​of the drive 5.

[0043] In a step S12, the control device 9 checks whether the lifting speed v is less than a predetermined speed setpoint v*. The speed setpoint v* can be known to the control device 9 in any way, in principle. For example, it can be specified in the control program 10, determined during commissioning of the medical device 1, or re-specified to the control device 9 by the operator 12 at any time during ongoing operation.

[0044] If the lifting speed v is not less than the speed setpoint v*, the lifting speed v has reached the speed setpoint v*. In this case, the control device 9 proceeds to step S13. In step S13, the control device 9 determines the control C for the drive 5 such that a speed change δv has the value 0, thus maintaining the lifting speed v. Otherwise, the control device 9 proceeds to step S14.

[0045] In step S14, the control device 9 checks whether the electrical operating variable I is less than a predetermined limit value I0. The limit value I0 can, in principle, be known to the control device 9 in any desired manner. The above statements regarding the speed setpoint v* apply analogously.

[0046] If the electrical operating variable I is less than the limit value I0, the control device 9 proceeds to step S15. In step S15, the control device 9 determines the control C for the drive 5 such that the speed change δv has a value above 0, thus increasing the lifting speed v. The increase can occur continuously or in steps. Otherwise, the control device 9 proceeds to step S13.

[0047] As from Fig. 4, the control device 9 controls the drive 5 whenever it receives a travel command F from the operator 12, based on which the patient bed 2 is to be moved downwards, in response to the travel command F in step S4 such that the drive 5 moves the patient bed 2 downwards. Step S4 or the integration of step S4 into the flow chart of Fig. 4 is, however, advantageously carried out in a certain way.

[0048] For example, it is possible that the control device 9 initially determines the control C of the drive 5 in such a way that the drive 5 moves the patient bed 2 downwards. The control device 9 checks according to the embodiment Fig. 7, however, checks whether the patient bed 2 reaches a predetermined minimum distance from the lowest possible position. If the patient bed 2 reaches the minimum distance from the lowest possible position, the control device 9 stops the control of the drive 5 and thus the downward movement of the patient bed 2. This also applies if the control device 9 continues to receive the travel command F for moving the patient bed 2 downward.

[0049] The lowest possible position is the position from which further downward movement of the patient bed 2 is no longer possible, for example, because a mechanical stop is reached. The minimum distance is determined such that it is at least as large as the downward travel of the patient bed 2, which is performed in step S7. Preferably, the minimum distance is somewhat larger than this travel. The corresponding situation is described in Fig. 7 for the angular position α of the worm shaft 7. amin is the angular position of the worm shaft 7 at which the patient bed 2 reaches the lowest possible position. δαmin is a rotation angle of the worm shaft 7, which corresponds to the minimum distance. The Fig. However, the situation described in Figure 7 is also valid in principle for cases in which the drive 5 acts on the patient bed 2 in a different way.

[0050] Another possibility is described below in connection with Fig. 8. Also in Fig. 8 shows the angular position α of the worm shaft 7. The Fig. However, the situation described in Figure 8 is also valid in principle for cases in which the drive 5 acts on the patient bed 2 in a different way.

[0051] According to Fig. 8, the control device 9 initially controls the drive 5 in response to a travel command F to move the patient bed 2 downwards in such a way that the drive 5 moves the patient bed 2 downwards. At a time t3, the specification of the travel command F to move the patient bed 2 downwards is terminated. At this time, the actual movement of the patient bed 2 downwards is also terminated. The time t3 represents the end of a period which is referred to below as the lowering period. However, upon termination of the travel command F, i.e. upon termination of the lowering period, the control device 9 controls the drive 5 for a short period of time in such a way that the drive 5 moves the patient bed 2 upwards. This period of time, which lasts until a time t4, is referred to below as the termination period. The termination period immediately follows the lowering period.The corresponding procedure, i.e. moving the patient bed 2 upwards during the closing period, can be carried out, for example, in the NO branch of step S1 of . Fig. 4 can be implemented if, in the sequence of steps S1 - S2 - S3 - S4 - S5, when step S1 is executed again, the drive command F is no longer specified and therefore the NO branch of step S1 is switched over.

[0052] It is possible that the control device 9 carries out the functions described above in connection with Fig. 8. However, it is also possible for the control device 9 to only execute this procedure if the patient bed 2 is moved downwards during the lowering period to a position that is less than the minimum distance from the lowest possible position.

[0053] At the end of the period, patient bed 2 is moved upwards. In the case of the screw shaft 7, this corresponds to an amount δα'.

[0054] Analogous to the extent δα by which in Fig. 5 the angular position α2 is smaller than the angular position α1, can also be used in the context of the design of Fig.8, the corresponding extent δα' by which the drive 5 moves the patient bed 2 upwards during the final period can be determined as required. As a rule, the extent δα' is less than 360°, often even considerably less than 360°, for example 180° or less, 120° or less, or 90° or less. In some cases, it may be possible for the final period to be determined as such and the extent δα' therefore not fixed. In other cases, it is possible for the extent δα' to be predetermined, so that reaching the corresponding angular position as such, i.e. rotating the worm shaft 7 by a predetermined angle of rotation as such, terminates the initial period. In the latter case, the angle of rotation corresponding to the extent δα' must be at least as large as the angle of rotation corresponding to the extent δα.Preferably, the rotation angle corresponding to the extent δα' is (slightly) larger than the rotation angle corresponding to the extent δα.

[0055] The present invention has many advantages. In particular, the drive 5 and the power supply of the drive 5 can be designed smaller than in the prior art.

Claims

[1] Operating method for a medical device (1) with a patient bed (2), the position of which can be adjusted in the vertical direction by means of a drive (5), wherein a control device (9) initially controls the drive (5) in response to the drive command (F) whenever it receives a travel command (F) from an operator (12) on the basis of which the patient bed (2) is to be moved upwards, in such a way that the drive (5) moves the patient bed (2) downwards during an initial period of time, and only then controls the drive (5) in a lifting period immediately following the initial period of time in such a way that the drive (5) moves the patient bed (2) upwards. [2] Operating method according to claim 1, characterized by , - that the control device (9) iteratively adjusts a control (C) of the drive (5) during the lifting period in such a way that a lifting speed (v) with which the patient bed (2) is moved upwards is raised continuously or in steps, - that the control device (9) checks whether the lifting speed (v) reaches a predetermined speed target value (v*), - that the control device (9) further checks whether an electrical operating variable of the drive (5) reaches a predetermined limit value (I0), and - that the control device (9) stops increasing the lifting speed (v) as soon as the lifting speed (v) reaches the predetermined speed setpoint (v*) or the electrical operating variable of the drive (5) reaches the predetermined limit value (I0). [3] Operating method according to claim 1 or 2, characterized bythat the control device (9) controls the drive (5) whenever it receives a travel command (F) from an operator (12) on the basis of which the patient bed (2) is to be moved downwards, in response to the travel command (F) during a lowering period in such a way that the drive (5) moves the patient bed (2) downwards, but ends the control (C) of the drive (5) as soon as the patient bed (2) reaches a predetermined minimum distance from a lowest possible position. [4] Operating method according to claim 1 or 2, characterized bythat the control device (9) controls the drive (5) in response to the drive command (F) during a lowering period whenever it receives a travel command (F) from an operator (12) on the basis of which the patient bed (2) is to be moved downwards, in such a way that the drive (5) moves the patient bed (2) downwards, but then controls the drive (5) at least in a final period immediately following the lowering period in such a way that the drive (5) moves the patient bed (2) upwards if the patient bed (2) is moved downwards to a position which is less than a minimum distance from a lowest possible position during the lowering period. [5] Operating method according to claim 4, characterized bythat the drive (5) drives a helical worm shaft (7) for adjusting the patient bed (2) in the vertical direction and that the control device (9) is designed such that it terminates the final period as soon as the drive (5) has rotated the worm shaft (7) by a predetermined first rotation angle (δα'), in particular by a maximum of 360°. [6] Operating method according to claim 5, characterized by that the control device (9) is designed such that it terminates the initial period as soon as the drive (5) has rotated the worm shaft (7) by a predetermined second rotation angle (δα), and that the second rotation angle (δα) is at most as large as the first rotation angle (δα'). [7] Operating method according to one of claims 1 to 4, characterized bythat the drive (5) drives a helical worm shaft (7) for adjusting the patient bed (2) in the vertical direction and that the control device (9) is designed such that it terminates the initial period as soon as the drive (5) has rotated the worm shaft (7) by a predetermined angle of rotation (δα), in particular by a maximum of 360°. [8] Control device of a medical device (1) with a patient bed (2) whose position can be adjusted in the vertical direction by means of a drive (5), wherein the control device is programmed with a control program (10) so that the control device carries out an operating method according to one of claims 1 to 7. [9] Medical device with a patient bed (2) whose position can be adjusted in the vertical direction by means of a drive (5), wherein the medical device has a control device (9) according to claim 8, which carries out an operating method according to one of claims 1 to 7 for adjusting the patient bed (2) in the vertical direction. [10] Medical device according to claim 9, characterized by that it has a self-locking gear (6) which the drive (5) drives to adjust the patient bed (2) in the vertical direction.

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