Patent Application
20080086816
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments, which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken in a limiting sense.
The imaging device 100 comprises an imaging gantry 105 that includes a bore or tunnel 110 for receiving a patient 115. In one embodiment as shown in
The table assembly 202 is said to be in a collapsed position when the distance between the table top 206 and the table base 208 along the vertical axis is minimum.
The belt drive assembly 204 configured to drive the single cross bar assembly 210 comprises one or more geared motors (not shown). The geared motor (not shown) can be a stepper motor or a servomotor. A single geared motor (not shown) can be used along with other support accessories in a simple and effective way. The belt drive assembly 204 further comprises one or more timer belts 214 driven by the geared motor (not shown). One or more drive pulleys 216 and 217 can be mounted on the geared motor (not shown) to drive the timer belt 214.
The support rails 420 are provided for co-operation during a longitudinal movement of the single cross bar assembly 428. The single cross bar assembly 428 may be slidably mounted on the first roller assembly 405. Structurally, the single cross bar assembly 428 comprises a pair of cross bars namely a first cross bar 430 and a second cross bar 435. The second cross bar 435 is movably coupled to the first cross bar 430 by a pivot 437. Further, each cross bar 430 and 435 in the single cross bar assembly 428 comprise a first end 440 and 450 and a second end 445 and 455.
The first end 440 of the first cross bar 430 is coupled to the timer belt 414 by a fastening device. One skilled in the art shall however appreciate that the timer belt 414 and the first cross bar 430 can be coupled to each other by similar techniques such as but not limited to a pivot and a hinge, and all such techniques lie within the scope of this embodiment of the invention. The timer belt 414 drives the first cross bar 430 of the single cross bar assembly 428 along the first roller assembly 405.
Further, the single cross bar assembly 428 consists of two rigidly held pivot points 457 and 459 and two robust sliding points 460 and 462. The first end 440 of the first cross bar 430 is coupled to the first roller assembly 405 via the first sliding point 460, where as the second end 445 of the first cross bar 430 is pivoted to the table top 424. Further, the first end 450 of the second cross bar 435 is pivoted to the table base 422, where as the second end 455 of the second cross bar 435 is coupled to the second roller assembly 410 via the second sliding point 462. One skilled in the art shall however appreciate that the patient positioning system 400 can comprise multiple single cross bar assemblies and each single cross bar assembly can be arranged in a substantially similar fashion to yield a collectively operable cross bar assembly. Further, multiple connections in each single cross bar assembly 428 can be varied in a complementary fashion to provide a substantially similar operation of the single cross bar assembly 428.
The belt drive assembly 418 when clubbed with the single cross bar assembly 428 provides flexibility to design a table assembly 426, which can be displaced to multiple positions along a vertical axis. Energization of the geared motor 412 imparts driving motion to the drive pulleys 416 and 417 causing the displacement of the timer belt 414. The linear motion of the timer belt 414 causes the single cross bar assembly 428 to move along a vertical axis. The movement of the single cross bar assembly 428 results in a vertical movement of the table assembly 426. Further, the direction of movement of the table assembly 426 along the vertical axis varies with the direction of rotation of the geared motor 412.
In an exemplary embodiment, the table assembly 426 and the belt drive assembly 418 may be configured such that a clockwise rotation of the geared motor 412 leads to the linear motion of the table assembly 426 in a vertically upward direction, whereas an anticlockwise rotation of the geared motor 412 leads to the linear motion of the table assembly 426 in a vertically downward direction. Thus, the rotary motion of the geared motor 412 causes the table assembly 426 to oscillate between the collapsed position (as shown at
In an embodiment, the belt drive assembly 418 can further comprise a clamping device. The clamping device can be placed along a longitudinal axis of the timer belt 414 to hold the table assembly 418 at a fixed position along the vertical axis. Providing the clamping device avoids unnecessary stressing of the timer belt 418 and the geared motor 412. Further, the clamping device imparts redundancy in displacing the table assembly 426 along the vertical axis.
In an exemplary embodiment, the belt drive assembly 418 comprises a timer belt 414 and two drive pulleys 416 and 417. One of the drive pulleys 416 and 417 is an idle pulley 416 and another is a driver pulley 417. A compact geared motor 412 coupled with an absolute encoder (not shown) drives the driver pulley 417. The driver pulley 417 drives the idle pulley 416 coupled through the timer belt 414. The linear motion of the timer belt 414 in a horizontal plane results in the linear motion of the table assembly 426 in a vertical plane. As a continuously variable belt drive assembly 418 drives the table assembly 426, the movement of the table assembly 426 along the vertical axis is continuous.
In one embodiment, the geared motor 412 can be a dual end shaft motor. Accordingly, two or more drive pulleys 416 and 417 can be placed beneath each end of the dual end shaft motor. The belt drive assembly 418 comprising the dual end shaft motor inherently takes care of the overhang issues. The dual end shaft motor nullifies the overhang effect as equal and opposite force act on both the ends of the dual end shaft motor. Thus, the rating of the double end shaft motor can be lower than the rating of the single end shaft motor.
The patient positioning system 500 further comprises a cross bar assembly 504 comprising at least two multiple cross bar assemblies 516 and 517 for actuating the table assembly 526. Each multiple cross bar assembly 516 and 517 comprises multiple pair of cross bars 520 and 521 coupled to one another by pivots 539 and 540. Each pair of cross bars 520 and 521 comprises a first cross bar 530 and 532 and a second cross bar 535 and 537. Each of the first cross bar 530 and 532 and the second cross bar 535 and 537 comprise a first end and a second end.
In each multiple cross bar assembly 516 and 517, a pair of cross bars at one end of the multiple cross bar assembly 516 is referred as a first pair of cross bars 520 and a pair of cross bars at another end of the multiple cross bar assembly 516 is referred to as a second pair of cross bars 521. In the first pair of cross bars 520, the second cross bar 535 is movably coupled to the first cross bar 530 by a pivot 538. In the second pair of cross bars 521, the second cross bar 537 is movably coupled to the first cross bar 532 by a pivot 537. One skilled in the art shall however appreciate that the first cross bar 530 and 532 and the second cross bar 535 and 537 can be coupled to each other by similar techniques such as but not limited to a hinge, and all such techniques lie within the scope of the invention.
Further, one skilled in the art shall also appreciate that a cross bar assembly configured to drive the table assembly can comprise a plurality of multiple cross bar assemblies. Each multiple cross bar assembly can be structured and arranged in a substantially similar or complementary fashion to be collectively operable.
Each multiple cross bar assembly 516 and 517 comprises two support blocks 572 and 578 and two sliding blocks 574 and 576. The support blocks 572 and 578 are fixed at a single position and are not freely movable. The sliding blocks 574 and 576 translate the rotary motion of the screw shaft 510 into a linear motion, which actuates the multiple cross bar assembly 516 and 517 to move vertically.
A first support block 572 is pivoted to the screw shaft 510 and supports a free end of the screw shaft 510. A second support block 578 is pivoted to the table top 524. A first sliding block 574 is mounted on the drive nut 512 slidably engaged on the screw shaft 510 for a linear translation. A second sliding block 576 is movably coupled to the table top 524.
Further, each multiple cross bar assembly 516 and 517 comprises two fixed pivot points 580 and 584 and two sliding points 582 and 586. The first pair of cross bars 520 is coupled to the screw shaft 510 via a first pivot point 580 and a first sliding point 582. The second pair of cross bars 521 is coupled to the table top 524 via a second pivot point 584 and a second sliding point 586. More particularly, the first cross bar 530 of the first pair of cross bars 520 is coupled to the first support block 572 via the first pivot point 580. The second cross bar 535 of the first pair of cross bars 520 is coupled to the first sliding block 574 via the first sliding point 582. The first cross bar 532 of the second pair of cross bars 521 is coupled to the second support block 578 via the second pivot point 584. The second cross bar 537 of the second pair of cross bars 521 is coupled to the second sliding block 576 via the second sliding point 586.
The two multiple cross bar assemblies 520 and 521 in the patient positioning system 500 comprise the fixed pivot points 580 and 584 and the movable sliding points 582 and 586 arranged in a complementary fashion to each other, as shown in
Turning now to the operation of the patient positioning system 500, a rotation of the screw shaft 510 by the dual end shaft motor 507 causes the drive nuts 512 and 515 to move axially in order to impart axial motion to the connected sliding blocks 574 and 590. As the sliding blocks 574 and 590 move in the horizontal plane, the pair of cross bars 520 and 521 associated with the sliding blocks 574 and 590 move in a vertical plane. The movement of the cross bar assembly 504 along a vertical axis enables a displacement of the table top 524 with respect to the table base 522.
Clockwise rotation of the screw shaft 510 causes a linear movement of the connected drive nuts 512 and 515 in a direction axially opposite to each other. Further, an anticlockwise rotation of the screw shaft 510 results in an axial movement of each drive nut 512 and 515 in a direction opposite to that resulting from the clockwise rotation of the screw shaft 510. The table assembly 526 can be configured to move in upward direction or downward direction along the vertical axis, based on the rotation of the screw shaft 510. The table assembly 526 can thus be oscillated between the collapsed position and the extended position.
In yet another embodiment, a patient positioning system 400 or 500 comprising a table assembly 426 or 526 and at least one cross bar assembly 428 or 504 coupled to the table assembly 426 or 526 is provided. The cross bar assembly 428 or 504 is positioned between the table top 424 or 524 and the table base 422 or 522 of the table assembly 426 or 526. The cross bar assembly 428 or 504 comprises a single cross bar assembly 428 or two multiple cross bar assemblies 516 and 517. The single cross bar assembly 428 comprises a pair of cross bars 430 and 435. Each multiple cross bar assembly 516 and 517 comprises multiple pair of cross bars 520 and 521 coupled to one another by pivots 539 and 540. Each pair of cross bars 520 and 521 comprises a first cross bar 530 and 532 and a second cross bar 535 and 537 movably coupled to each other by a pivots 538 and 537. Further each cross bar 530, 532, 535 and 537 in the pair of cross bars 520 and 521 comprises a first end and a second end.
Each cross bar assembly 428 or 504 comprises multiple hinge points. The multiple hinge points provide an increased flexibility in assembly errors and manufacturing tolerances. Additionally, the multiple hinge points aid in reducing an initial collapsible height of the table assembly 426 or 526. The initial collapsible height of the table assembly 426 or 526 is the height of the table assembly 426 or 526 in a collapsed position.
The patient positioning system 400 or 500 further comprises one of a belt drive assembly 418 and a screw drive assembly 505 configured to drive the table assembly 426 or 526. The screw drive assembly 505 and the belt drive assembly 418 are rotary-to-linear motion converters, configured for driving the cross bar assembly 428 or 504.
The belt drive assembly 418 can comprise one or more geared motors 412. One or more timer belts 414 can be coupled to the geared motor 412. The timer belt 414 imparts the requirement of linear motion of the cross bar assembly 428 or 504 with an increased flexibility. The timer belt 414 coupled to the geared motor 412 is driven through a coupling device such as an electro mechanical clutch (not shown). The timer belt 414 is coupled to the first end 440 of the first cross bar 430 by a fastening device (not shown).
The timer belt 414 at one end is supported by a drive pulley 416, which is coupled to a brake device (not shown) such as an electro mechanical brake to arrest the motion of the timer belt 414 at a required position. The belt drive assembly 418 and the table assembly 426 or 526 can be configured such that, arresting the motion of the timer belt 414 at a predetermined point along the longitudinal axis results in displacing the table assembly 426 or 526 to a predetermined position along the vertical axis.
The belt drive assembly 418 further comprises a first roller assembly 405 coupled to the table base 422 or 522 and a second roller assembly 410 coupled to the table top 424 or 524. Each roller assembly 405 and 410 comprises multiple rollers 415 and a pair of support rails 420. The support rails 420 can be extended generally parallel to each other and between the opposing sides of the table assembly 426 or 526. The support rails 420 can be made from a relatively lightweight, inexpensive, yet rigid and strong material such as aluminum.
Each single cross bar assembly 428 comprises two fixed points 457 and 459 and two sliding points 460 and 462. In an exemplary embodiment, the first end 440 of the first cross bar 430 is coupled to the first roller assembly 405 via the first sliding point 460. The second end 445 of the first cross bar 430 is pivoted to the table top 424 or 524 via the first pivot point 457 and the first end 450 of the second cross bar 435 is pivoted to the table base 422 or 522 via the second pivot point 459. The second end 455 of the second cross bar 435 is coupled to the second roller assembly 410 via the second sliding point 462.
Operation of the geared motor 412 causes rotation of the drive pulleys 416 and 417. The drive pulleys 416 and 417 drive the timer belt 414 extending between the driver pulley 416 and the idle pulley 417, causing a linear motion of the timer belt 414. The linear motion of the timer belt 414 translates into vertical movement of the cross bar assembly 428 or 504. The vertical movement of the cross bar assembly 428 or 504 causes the displacement of the table top 424 or 524 along a vertical axis. Thus the operation of the geared motor 412 results in a continuous movement of the table assembly 426 or 526 along a vertical axis.
The force applied on the belt drive assembly 418 is minimum as the force is applied at locations requiring an optimum force. The application of an external force and unnecessary stresses generated there from can thus be eliminated.
The screw drive assembly 505 used as an alternative to the belt drive assembly 418 comprises one or more dual end shaft motors 507. The dual end shaft motor 507 can be a servomotor comprising shafts that extend outwardly in opposite directions. The screw drive assembly 505 further comprises a screw shaft actuator coupled to the dual end shaft motor 507. The screw shaft actuator comprises a screw shaft 510 coupled to the dual end shaft motor 507 and two or more drive nuts 512 and 515 movably coupled to the screw shaft 510.
Each multiple cross bar assembly 516 and 517 comprises two rigidly held support blocks 572 and 578 and two movable sliding blocks 574 and 576. A first support block 572 is coupled to the screw shaft 510 and a first sliding block 574 is coupled to a first drive nut 512 driven by the screw shaft 510. A second support block 578 is coupled to the table top 424 or 524 and a second sliding block 576 is movably coupled to the table top 424 or 524. Two multiple cross bar assemblies 516 and 517 can be arranged in a fashion complementary each other in order to make the cross bar assembly 428 or 504 operable.
In an exemplary embodiment, the first cross bar 530 of a first pair of cross bars 520 is coupled to the first support block 572 via a first pivot point 580. The second cross bar 535 of the first pair of cross bars 520 is coupled to the first sliding block 574 via a first sliding point 582. Further the first cross bar 532 of a second pair of cross bars 521 is coupled to the second support block 578 via a second pivot point 586. The second cross bar 537 of the second pair of cross bars 521 is coupled to the second sliding block 576 via a second sliding point 584.
Rotation of the screw shaft 510 by the dual end shaft motor 507 causes the drive nuts 512 and 515 to move axially in order to impart linear motion to the connected cross bars. The linear movement of the cross bars along the longitudinal axis results in the linear movement of the connected cross bar assembly 428 or 504 along the vertical axis. As the movement of the cross bar assembly 428 or 504 is continuous, the displacement of the table top 424 or 524 coupled to the cross bar assembly 428 or 504 is continuous.
Some of the advantages of the patient positioning system provided in various embodiments include cost reduction, provision of continuously variable height and reduction in initial collapsible height of the table assembly. The belt drive assembly and the screw drive assembly provide a cost effective solution to attain a vertical displacement without compromising on the specifications.
The initial collapsible height of the table assembly is small compared to the prior art actuators. Several hinge points provided in the cross bar assembly aid in reducing the initial collapsible height of the table assembly and provide increased flexibility in assembly errors and manufacturing tolerances.
The belt drive assembly used in the patient positioning system is simpler and compact compared to a conventional hydraulic drive system. Components such as timer belts and drive pulleys used in the belt drive assembly are easily available at a nominal cost. Critical components used in the belt drive assembly are bought out components and hence replacement or repair cost is reduced significantly. Therefore, the cost savings are reduced greatly when compared to a hydraulic drive system.
The manufacturing and production of the belt drive assembly is simple when compared to the hydraulic drive system. The belt drive assembly requires less assembly time and can be accommodated easily due to the flexibility of the timer belt used in the belt drive assembly. Therefore the manufacturing, assembling, transport and handling of the belt drive assembly is simple, cheap and reliable.
The belt drive assembly when clubbed with the cross bar assembly enables a continuous movement of the table top along a vertical axis. The continuous movement of the table top results in a continuously variable height of the table assembly.
On the other hand, a patient positioning system comprising the screw drive assembly is simpler in transporting, storing, handling, assembling and aligning, compared to the hydraulic drive system.
The screw drive assembly along with the cross bar assembly enables the table assembly to be displaced to multiple positions along a vertical axis when compared to a hydraulic drive system where the movement of the table assembly is restricted to two positions namely a collapsed position and an extended position. Additionally, the screw drive assembly reduces the initial collapsible height of the table assembly when compared to the hydraulic drive system.
The screw shaft actuator provided in one embodiment enables upgrading a patient positioning system comprising a hydraulic cylinder. The hydraulic cylinder being expensive can be replaced at ease with the screw shaft actuator. The patient positioning system can be utilized without significant alterations, by replacing the hydraulic cylinder with the screw shaft actuator. Further, the screw shaft actuators are independent of the constraints such as load, displacement and minimum collapsible height.
In various embodiments of the invention, a patient positioning system for an imaging device and an imaging device using a patient positioning system are described. However, the embodiments are not limited and may be implemented in connection with different applications such as displacement applications. The application of the invention can be displaced to other areas, for example positioning devices. The invention provides a broad concept of a rotary motion translating to a linear motion application, which can be adapted in a similar positioning device. The design can be carried further and implemented in various forms and specifications.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
