Abstract:
The present invention relates to the automatic balance adjusting centrifuge that enhances the efficiency of space utilization by simplifying the structure as well as supports a precise movement by improving the structure of the balance weight transport apparatus in the automatic balance adjusting centrifuge that compensates the unbalance of the centrifugal force by transferring the balance weight equipped in the rotor rotational arm. According to the automatic balance adjusting centrifuge of the present invention, the structure is simplified as well as the precise and exact transfer of the balance weight is possible by connecting the balance weight with the axis of the motor directly and adopting the length sensor. Furthermore, the efficiency of space utilization is enhanced because the axis of rotation of the balance weight transfer motor is in radial direction of the rotational arm.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Korean patent application No. 10-2008-0067109 filed on Jul. 10, 2008, all of which is incorporated herein by reference in its entirety for all purposes. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an automatic balance adjusting centrifuge, and particularly to an automatic balance adjusting centrifuge compensating for the imbalance of the centrifugal force by transferring balance weights equipped in rotating arms. 
     2. Description of the Related Art 
     As is well known, a centrifuge is an essential equipment which is widely used over medical and physiochemical fields, and is an instrument which separates sample elements by rotating a rotor equipped with buckets containing samples at a high speed to provide the samples with high centrifugal acceleration. Thus, high density elements in the samples are placed at the outer layer along the radial direction of the rotor and low density elements in the samples are placed at the inner layer along the radial direction. 
     In the operation of the centrifuge, imbalance of the centrifugal force is inevitably created by the weight differences among buckets due to the discrepancy in the number of samples within each bucket or in the total weight. However, the conventional centrifuge without the automatic balancing function brought about a problem of imposing the laborious works on users, such as measuring the weight of each sample manually to load the samples with an identical weight on a rotor symmetrically. 
     To address this problem, the applicant has already suggested several automatic balance type centrifuges and reserved the rights in United States as patents. To be concrete, United States patent registration number U.S. Pat. No. 7,285,085 B2 (registered date: Oct. 23, 2007) (hereafter, it is referred to Preceding Invention; PI) discloses an automatic balance type centrifuge including a rotor, wherein the rotor comprises: a plurality of rotating arms, e.g. three rotating arms, which support buckets containing samples, have the same radial length from a rotational shaft for centrifuging, and are disposed around the rotational shaft with equal angles; a balance weight installed to be movable along the radial direction of each rotating arm so as to compensate for the imbalance induced by the centrifugal force during centrifugal separation process; and a balance weight transfer mechanism transferring each balance weight horizontally along the radial direction of each corresponding rotating arm. In PI, detection of imbalance of the centrifugal force, that is, imbalance of bucket weights, for example, can be carried out by an electronic scale which is installed in separate from the rotor and goes up and down in the lower part of each bucket. 
       FIGS. 1 ,  2 , and  3  are perspective view of a rotor of a centrifuge proposed in the PI, exploded view, and the cross-sectional view, respectively. As shown in  FIG. 1  through  FIG. 3 , the rotor of the centrifuge of the PI can comprise the three rotating aims  29  supporting sample-loaded buckets  31 , a balance weight  15  installed in each rotating arm  29  to compensate for the weight imbalance of the rotor during the centrifuging process, and a balance weight transfer mechanism transferring the balance weight  15  along the radial direction of each rotating arm  29 . 
     In the configuration described in the above, the rotating arm  29  can be formed by cutting away some portion equi-angularly, which is supposed to install buckets  31 , from a disk with a prescribed thickness, and in the present preferred embodiment, each rotating arm  29  maintains 120.degree. interval with each other. And at both sides of each rotating arm  29 , bucket supporting pins  33  are formed to support the buckets  31  to be assembled so that adjacent rotating arms  29  cooperate to support the buckets  31 . 
     Meanwhile, in each rotating arm  29 , a slot  29   a  is formed along the radial direction to guides the balance weight  15  to be transferred along the horizontal direction, and is preferably implemented as a rectangle-type long groove. The balance weight  15  is preferably implemented as the form of hexahedron in order not to be rotated in the slot  29   a , and has the female screw (not illustrated) formed in the center. 
     Each balance weight transfer mechanism can comprise a balance weight transfer motor  5  installed at the center part of the rotor, whose shaft is in the line of the vertical axis; a worm  7  coupled with the end of the shaft of the balance weight transfer motor  5  by shaft coupling; a balance weight transfer shaft  17  which is installed in a longitudinal direction within the slot  29   a  and of which an outer circumferential surface a male screw is formed on to couple with a female screw of the balance weight  15  by screwed connection; a worm gear  19  coupled with the worm  7  by gear coupling and also coupled with one end of the balance weight transfer shaft  17  by shaft coupling; a thrust bearing  21  and a radial bearing  23  which are coaxially coupled with each end of the balance weight transfer shaft  17  respectively. 
     Meanwhile, in transferring the balance weight  15  horizontally within the slot  29   a , a position sensor  13 , preferably a limit switch, is required to sense the fixed reference position, and the position sensor  13  may be installed at proper position of the slot  29   a , preferably at a support bracket  11  installed by extending downward from a balance weight cover  9  (slot cover  9 ). Non-described reference numbers  3  and  1  in the figures indicate a supporting frame to support the balance weight transfer motor  5  and a motor cap  1  to cover the top of the supporting frame  3 , respectively, and another non-described reference number  9  indicates a slot cover to cover the top of the slot  29   a . The reference number  25  and  27 , respectively, indicate housings to fix a thrust bearing  21  and a radial bearing  23  inside the slot  29   a.    
     However, in the conventional automatic balance adjusting centrifuge as described in the above, there has been a difficulty of designing/manufacturing for enhancing the contact ratio of tooth surface between a worm and a rack-type worm wheel, because it uses a worm shaft-coupled with a balance weight transfer motor, a worm gear tooth-coupled with the worm, and a balance weight transfer shaft coaxial-coupled with the worm gear, as balance weight transferring means. 
     Furthermore, there have been some problems such that accuracy falls down because of analogizing the current position of a balance weight with the number of rotation of the balance weight transfer motor implemented simply by a step motor, structure is complicated because of separating a balance weight transfer shaft from a motor shaft, and the efficiency of space utilization is low because of installing the balance weight transfer motor as the shaft faces to vertical direction. 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     The present invention is proposed to solve the problems described above. The object of the present invention is to provide an automatic balance adjusting centrifuge that enhances the efficiency of space utilization by simplifying the structure of a balance weight transfer mechanism in an automatic balance adjusting centrifuge compensating for imbalance of the centrifugal force by transferring a balance weight equipped in a rotating arm as well as enables a balance weight to move precisely by improving the structure. 
     Technical Solution 
     To achieve the above object, an automatic balance adjusting centrifuge of the present invention includes a rotor with a plurality of rotating arms which have the same radial length from a rotational shaft for centrifuging, are disposed with equal angles around the rotational shaft, and support buckets containing samples, wherein the automatic balance adjusting centrifuge comprises: a motor installed in each rotating arm for its rotational shaft, outer circumferential surface of which a male screw is formed on to transfer a balance weight, to face to the radial direction; a balance weight having a female screw formed through its body horizontally to be combined with the male screw by screwed connection, a guiding means to guide the straight-line motion of the balance weight; a reference position sensing means to sense the reference position of the balance weight; a current position sensing means to sense the current position of the balance weight; a controlling means to calculate the distance between the reference position sensed by the reference position sensing means and the current position sensed by the current position sensing, and to control the motor to transfer the balance weight for a set length. 
     In the above configuration, the guiding means comprises two or more through-holes formed in the balance weight and guide bars inserted into each through-hole in parallel with the rotational shaft for transferring. 
     The current position sensing means comprises a gear disk which is made of magnetic substance, is coupled with an end of the rotational shaft by shaft-coupling to rotate with the rotational shaft, and has a plurality of teeth formed on the circumferential surface with an equal interval; and hall sensors installed on the same plane with the gear disk at regular intervals. 
     On the other hand, the current position sensing means may comprise a capacitive sensor including: a dielectric fixed bar installed on the balance weight to the direction for transferring the balance weight; and a pair of fixed electrodes installed along the transfer path of the dielectric bar, sandwiching the dielectric bar and facing with each other. 
     Meanwhile, the reference position sensing means comprises any one of a physical contact type sensor, a light receiving type sensor, and a magnetic field sensing type sensor. 
     Advantageous Effects 
     According to the automatic balance adjusting centrifuge of the present invention, the adoption of a length sensor and the direct connection between a balance weight and a motor shaft enable to transfer the balance weight precisely and correctly and also to simplify the structure of the centrifuge. Furthermore, the efficiency of space utilization is enhanced because a rotational shaft of a motor for transferring the balance weight is disposed in the radial direction of the rotating arm. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a rotor of a centrifuge proposed in the PI. 
         FIG. 2  is an exploded view of a rotor of the centrifuge proposed in the PI. 
         FIG. 3  is the cross sectional view of a rotor of the centrifuge proposed in the PI. 
         FIG. 4  is a plane view of a rotor of an automatic balance adjusting centrifuge according to one embodiment of the present invention. 
         FIG. 5  is a perspective view of a balance weight transfer mechanism according to one embodiment of an automatic balance adjusting centrifuge of the present invention. 
         FIG. 6  is a cross-sectional view sectioned along the line  6 - 6  in  FIG. 5 . 
         FIG. 7  is a perspective view of a balance weight transfer mechanism according to another embodiment of an automatic balance adjusting centrifuge of the present invention. 
         FIG. 8  is a cross-sectional view sectioned along the line  8 - 8  in  FIG. 7 . 
         FIG. 9  is a block diagram of the electrical part in the automatic balance adjusting centrifuge of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, preferred embodiments of the automatic balance adjusting centrifuge of the present invention are described in detail referring to the accompanying drawings. 
       FIG. 4  is a plane view showing a rotor of an automatic balance adjusting centrifuge according to one embodiment of the present invention. As shown in  FIG. 4 , the automatic balance adjusting centrifuge of the present invention can include a rotor having three rotating arms  29 ′ to support buckets  31 ′ loading samples as described in PI, and a balance weight transfer mechanism  100 , including a balance weight  160  to compensate for the weight imbalance of the rotor and a balance weight transfer motor  120  to transfer the balance weight  160  horizontally along the radial direction of each rotating arm  29 ′, is installed in each rotating arm  29 ′. 
     In the configuration described in the above, the rotating arm  29 ′ can be formed by cutting away some portion equi-angularly, which is supposed to install buckets  31 ′, from a disk with a prescribed thickness, and in the present preferred embodiment, each rotating arm  29 ′ maintains 120.degree. interval with each other. And at both sides of each rotating arm  29 ′, bucket supporting pins (not illustrated) are formed to support bucket  31 ′ to be assembled so that adjacent rotating arms  29 ′ cooperate to support the buckets  31 ′. 
       FIG. 5  is a perspective view of a balance weight transfer mechanism in the automatic balance adjusting centrifuge according to one embodiment of the present invention, and  FIG. 6  is a cross-sectional view sectioned along the line  6 - 6  in  FIG. 5 . As shown in  FIGS. 5 and 6 , according to one embodiment of the balance weight transfer mechanism  100  in the automatic balance adjusting centrifuge of the present invention, the balance weight transfer motor  120  is installed and fixed in each rotating arm  29 ′ for a rotational shaft  122  of it to face to the radial direction of the rotating arm  29 ′, and it is supported and fixed by a motor bracket  130  preferably at a inner side of the rotating arm  29 ′, that is, at a position near to a rotational shaft for centrifuging. The rotational shaft  122  of the transfer motor comprises a screw bar of which circumferential surface a male screw is formed on, and the end thereof is supported by a bearing  142  mounted in the bearing housing  140  to be rotatable. 
     Meanwhile, a balance weight  160  can be implemented with rigid materials in the shape of rectangle (or disk) and can be coupled with the male screw of the transfer motor rotational shaft  122  by screwed coupling because a female screw is formed through the center of the body thereof. Moreover, 4 through-holes  161  piercing the body horizontally are formed in the vicinity of each corner of the balance weight. Thus, the motor bracket  130  and the bearing housing  140  includes 4 guide bars  150  inserted into each through-hole  161  of the balance weight  160  and installed in parallel so that the guide bars guide the balance weight  160  to do a straight-line motion in spite of the torque of the transfer motor rotational shaft  122 . The diameter of the through-hole  161  is a little bit longer than the diameter of the guide bar  150 . Thus, the bushing  152  having the diameter almost equal to the diameter of the guide bar is inserted to any one (or two) of through-hole  161  to prevent the balance weight  160  from fluctuating during the moving process. 
     Meanwhile, this preferred embodiment adopts a capacitance type sensor to detect the current position of the balance weight  160 , and a dielectric fixed bar made of dielectric material is installed at the proper place, for example, at upper side of the balance weight  160  to the direction for transferring the balance weight. 
     The length of the dielectric bar  170  is longer than the transferable distance of the balance weight  160 . In the figures, the reference number  110  represents a base cover that is mounted on the top of the motor bracket  130  and the bearing housing  140 , and a sensor circuit board  180  is installed under the base cover  110 . A path  182  for the dielectric bar is formed on the sensor circuit board  180  along the longitudinal direction, and electrodes is disposed at both end of the path  182  for dielectric bar to sense the capacitance that is varied according to the position of the dielectric bar  170 . 
     In the figures, the reference numbers  184  and  186  represent a light emitting part and a light receiving part, respectively, of a photo-coupler installed on the path  182  for the dielectric bar in order to detect a reference position of the balance weight  160 , and if the dielectric bar  170  does not exist then the light from the light emitting part  184  of the photo-coupler reaches the light receiving part  186 , but if the balance weight  160  retrogrades and the leading end of the dielectric bar  170  arrives at the position of the photo-coupler then immediately the light from the light emitting part is blocked by the dielectric bar  170  so that the arrival of the balance weight  160  at the reference position can be detected. 
       FIG. 7  is a perspective view of a balance weight transfer mechanism  100 ′ in the automatic balance adjusting centrifuge according to another preferred embodiment of the present invention and  FIG. 8  is the cross-sectional view sectioned along the line  8 - 8  in  FIG. 7 . Therefore, the same reference numbers are given for the corresponding components of  FIGS. 5 and 6 , and the detail description about them is omitted. As shown in  FIGS. 7 and 8 , in this preferred embodiment, a hall sensor is adopted as the sensor to detect the current position of the balance weight  160  and the hall sensor  190  is mounted on the sensor circuit board  180 ′ installed under the base cover  110  to face downward. 
     Meanwhile, a gear disk  144  made of magnetic substance, of which the circumferential surface a plurality of teeth are formed on with an equal interval, is fixed and installed on outer circumference of the bearing  142 ′. In this configuration, if the transfer motor rotational shaft  122  rotates then the gear disk  144  also rotates together, so that the hall sensor  190  detects the current position of the balance weight  160  as the indirect mode (described later) by sensing the variation of the magnetic field which is caused by getting near or away of the teeth during the rotating process. 
     Next, the preferred embodiment adopts a lead switch  188  turned on/off by sensing magnetic force as the sensor to detect the reference position of the balance weight  160 , wherein the lead switch  188  is installed at proper position beneath the sensor circuit board  180 ′. Meanwhile, a permanent magnet  162  is mounted on the top of the balance weight  160  for responding to the lead switch  188  so that, if the balance weight retrogrades and the permanent magnet  162  is accurately positioned under the lead switch, the arrival of balance weight  160  at the reference position can be detected by turning on or off the lead switch  188 . 
       FIG. 9  is a block diagram of the electrical part in the automatic balance adjusting centrifuge of the present invention. As shown in  FIG. 9 , the electrical configuration of the automatic balance adjusting centrifuge of the present invention comprises: a key input unit  210  that receives or sets up all kinds of information required to operate the centrifuge; a imbalance detection unit  220  to detect the weight imbalance of the centrifuge rotor; a reference position sensing unit  230  to sense the reference position of the balance weight; a current position sensing unit  240  to sense the current position of the balance weight; a centrifuging motor  255  to rotate the rotor and a driving unit  250  thereof; a balance weight transfer motor  265  to transfer the balance weight and a driving unit  260  thereof; an alarm unit  270  to give an alarm for the occurrence of the malfunction or the over-vibration of the centrifuge; a display unit  280  to display all kinds of information generated during the operation of the centrifuge; and a microcontroller unit  200  to control the overall operation of the centrifuge generally. 
     In the configuration described in the above, a centrifuging motor  255  may be, for example, a brushless DC motor and a balance weight transfer motor  265  may be a step motor. The unbalance sensor can be performed, for example, as described in PI, by an electronic scale that is installed separately from a rotor and goes up and down under the bucket. 
     As described above, the reference position sensing unit  230  can include a photo-coupler or a lead switch, beside that it can comprise a micro switch turned on/off by the physical contact. 
     As described above, the current position sensing unit  240  can include a capacitance type sensor or a hall sensor, and it senses the current position of the balance weight as indirect mode converting the number of tooth into distance in case of the hall sensor, while it senses directly the distance from the reference position to the current position of the balance weight in case of the capacitance type sensor. That is, whenever the hall sensor detects the tooth of the gear disk, it delivers the detection result to the microcontroller unit  200 , and the microcontroller unit  200  counts the number of the tooth by the inside counter, which is reset at the time of arrival of the balance weight at the reference position, and converts the counted number into distance so that it gets hold of the current position of the balance weight and places the balance weight on the desirable position. 
     Finally, the microcontroller unit  200  can comprise a microprocessor and attached memories, and, as described above, the distance conversion table or various kinds of setting values are stored in the attached memories. 
     The automatic balance adjusting centrifuge of the present invention is not to be limited to the above-described embodiments and it can be modified and implemented variously within the technical field of the present invention. For example, the number of rotating aims can be 2, 4, or more. Meanwhile, in case of the photo-coupler sensing the reference position of the balance weight, as described above, the reflective type photo-coupler can be adopted beside the transmissive type.