Patent Publication Number: US-2013237399-A1

Title: Centrifuge comprising visual and/or tactile indicator for indicating the accurate mounting of the rotor on the drive shaft, and corresponding rotor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application is a Section 371 National Stage Application of International Application No. PCT/EP2010/0066821, filed Nov. 4, 2010, which is incorporated by reference in its entirety and published as WO 2011/054906 on May 12, 2011, not in English. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     None. 
     THE NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT 
     None. 
     FIELD OF THE DISCLOSURE 
     The field of the disclosure is that of the designing and manufacture of centrifugation equipment. More specifically, the disclosure pertains to centrifuges used in the fields of biology to centrifuge the products contained in receptacles placed in housings made in the rotor or carried by the rotor. 
     BACKGROUND OF THE DISCLOSURE 
     Classically, the centrifuge comprises:
         a drive shaft,   a rotor designed to be mounted removably on the drive shaft in a mounting position for which the drive shaft and the rotor are coupled in rotation,   a device for the axial locking of the rotor on the drive shaft, comprising a male element carried by the rotor, elastically stressed and capable of occupying a position of cooperation with a female element presented by the drive shaft.       

     In centrifuges of this type, the axial locking of the rotor on the drive shaft must be obtained as reliably as possible. Indeed, during the operation of the centrifuge, an insufficient axial locking may entail a major risk of accident due to the untimely detachment of the rotor. 
     Various solutions have been proposed in the prior art to achieve an axial locking of the rotor on the shaft by means of coupling systems provided with axial locking systems that can be unlocked from the exterior. However, these devices require that the operator should mount the rotor on the drive shaft with great attention and high precision in order that the locking means will take a position in which they ensure highly efficient axial locking. Indeed, these locking means have to be positioned axially in an appropriate way, failing which the rotor can get disengaged from the drive shaft when the centrifuge is put into rotation or during its operation, with possibly drastic consequences in terms of deterioration of the equipment or, at worst, drastic consequences for the personnel present in the vicinity of the centrifuge. 
     One solution described in the patent document EP-0 712 667 has been proposed to overcome this drawback. According to this technique, the male element of the locking device is mounted on the rotor and unlocking means actuatable from the exterior of the rotor are designed to enable the operator to place the male element in a position where it is clear of the retaining hollow feature. At the same time, the free end of the drive shaft has guiding means working together with complementary means fixedly joined to the rotor to bring the rotor, during the engagement of the shaft in the rotor, to pivot about its axis from any unspecified starting angular position and descend along the shaft until it reaches a position in which the rotor is joined rotationally with the shaft, the male element being then pushed back elastically into the female element to ensure an axial locking of the rotor. 
     One advantage of this technique is that the male element and the female element can be made with a profile of a depth sufficient so that, when the rotor reaches its mounting position, there is an audible click loud enough to inform the operator that the locking has truly been engaged. 
     However, in most cases, a centrifuge is present in a room in which there are also other centrifuges and/or other apparatuses. The centrifuges and/or the other apparatuses present prove in practice to be relatively noisy during operation. As a result, it can happen that the operator mounting the rotor on the drive shaft of the centrifuge will not perceive the audible click which may be concealed by the surrounding ambient sound. 
     This may have the following consequences:
         either the operator may repeat the operation until he is totally assured that the rotor is properly mounted on the drive shaft;   or the operation of the centrifuge may be launched whereas the mounting has not been done accurately.       

     Naturally, it is also possible that the mounting will have been done correctly. 
     In other words, it can be understood that even when there are locking means producing an audible click, the quality of the mounting of the rotor on the drive shaft remains random. 
     SUMMARY 
     An illustrative embodiment of the present disclosure relates to a centrifuge, the design of which enables an operator to know unambiguously whether the axial locking of the rotor on the drive shaft has been properly done. 
     An embodiment of the invention provides a centrifuge of this kind that provides for optimal axial locking. 
     An embodiment of the invention provides a centrifuge of this kind in which the means for rotational coupling of the rotor with the drive shaft are simple in design and practical for the operator in terms of mounting. 
     An embodiment of the invention provides a centrifuge of this kind that enables the easy and speedy dismounting of the rotor from the drive shaft. 
     Thus, through an embodiment of the invention, the operator has available a simple and efficient means giving him a clear and unambiguous indication that the rotor has been accurately mounted on the drive shaft. 
     Indeed the operator, by a simple glance and/or a simple touch check (or “feel check”), can ascertain that the rotor is occupying a position on the drive shaft that ensures its axial locking. 
     The operator will thus be perfectly reassured, and will be able to launch the centrifugal operation in total safety. 
     According to the principle of an embodiment of the invention, the rotor carries an annular cage provided with at least one radial passage through which said visual and/or tactile indicator is configured to be presented in protrusion, said male element being pivotally mounted about a pivoting pin parallel to the axis of said drive shaft. 
     Thus, when the indicator protrudes through the radial passage of the annular cage, the operator can:
         either visually check the presence of indicator outside the annular cage, the indicator possibly also carrying a color code (such as a green patch) giving the “green light”;   or pass his fingers around the annular cage, the protruding presence of the indicator being thus easily detected by touch.       

     Furthermore, as shall be seen more clearly here below, the centrifuge effect caused by the rotation of the centrifuge may be profitably used to increase the cooperation of the male element or elements with the female element present on the drive shaft. 
     In this case, said male elements comprise, on one side of said pivoting pin, an engaging termination for engaging with said female element and, on the other side of said pivoting pin, an ear-shaped attachment that is to form visual and/or tactile indicator. 
     Such an arrangement enables a simple and efficient operation wherein, when the engaging termination penetrates the female element of the drive shaft, the corresponding male element pivots in such a way that the corresponding ear-shaped attachment gets off-centered and provides a visual and/or tactile indication. 
     Advantageously, said male element or elements are mounted at the upper part of the rotor. 
     Thus, the male element or elements occupy a position that easily enables the operator to check the visual and/or tactile indication. 
     According to another characteristic of an embodiment of the invention, the rotor carries a diametral rod designed to get housed in a diametral slot of said drive shaft to ensure the rotational coupling of said rotor with said drive shaft. 
     Thus, a simple and efficient coupling is obtained, involving operations for manufacture and mounting that are simpler than the classic prior-art solutions resorting to snugs and/or cotter pins penetrating the housings and/or the grooves of the drive shaft. 
     In this case, said rod is mounted in a cap overhanging said annular cage. 
     Advantageously, said rotor has means for identifying the orientation of said rod. 
     Thus, the operator, can easily orient the rotor relatively to the drive shaft in making the identifying means coincide with the orientation of the slot of the drive shaft visually located beforehand. 
     It will be noted that another types of rotational coupling can be implemented without departing from the framework of the invention, for example through the use of a grooved or hexagonal drive shaft, the rotor then having a central hollow with a corresponding shape. 
     According to another characteristic of an embodiment of the invention, the centrifuge comprises means for compensating for axial clearances, these means advantageously comprising a ring mounted slidingly on the drive shaft and against which the rotor is to take support, a spring being coupled to said ring and to said shaft so as to act in compression against the downward thrust of said rotor. 
     It will be noted that such compensation means fulfill a twofold function:
         that of compensating for the axial clearance between the male element or elements and the female elements presented by the drive shaft so as to axially press the male element or elements on the interior of the female element;   that of facilitating the withdrawal of the rotor from the drive shaft, by exerting an upward thrust on the rotor when the male element or elements are disengaged from the female element of the drive shaft.       

     An embodiment of the invention also pertains to a rotor designed to be mounted removably on a drive shaft of a centrifuge, in a mounting position for which said drive shaft and said rotor are rotationally coupled, said rotor carrying at least one male element, elastically stressed and capable of occupying a position of cooperation with a female element presented by said drive shaft so as to ensure axial locking of the rotor on said drive shaft, characterized in that said male element or elements are coupled to a visual and/or tactile indicator giving a visual and/or tactile indication of said position of cooperation of said male element or elements, the rotor carrying an annular cage provided with at least one radial passage through which said visual and/or tactile indicator is to be presented in protrusion, and said male element or elements being mounted pivotally about a pivoting pin parallel to the axis of said drive shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages shall appear more clearly from the following description of an embodiment of the invention, given by way of an illustratory and non-exhaustive example and from the appended drawings of which: 
         FIG. 1  is a view in perspective of the driving means and of an axial locking device of a centrifuge according to an embodiment of the invention; 
         FIG. 2  is a top view of the active part of the axial locking device of a centrifuge according to an embodiment of the invention; 
         FIG. 3  provides a schematic illustration in vertical section of a centrifuge according to an embodiment of the invention; 
         FIG. 4  is a detailed view of the rotor of a centrifuge according to an embodiment of the invention; 
         FIGS. 5 and 6  are partial top views of the locking device for locking a centrifuge according to an embodiment of the invention, respectively in the unlocked position and in the locked position; 
         FIG. 7  is a partial view of the lid and of the means for axial locking of the rotor on the drive shaft of a centrifuge according to an embodiment of the invention; 
         FIGS. 8 and 9  are top views of the means for axial locking of the rotor on the drive shaft of a centrifuge according to an embodiment of the invention, respectively in the locked position and in the unlocked position; 
         FIGS. 10 and 11  illustrate curves of signals detected by tachometric means of a centrifuge according to an embodiment of the invention, respectively in the locked position and in the unlocked position of the means for axial locking of the rotor on the drive shaft. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     As indicated here above, the principle of an embodiment of the invention lies in the fact of associating, in a centrifuge, elements for the axial locking of the rotor on the drive shaft with a visual and/or tactile indicator providing a visual and/or tactile indication when the male element or elements of the axial locking device are in a position of cooperation with the female element of the drive shaft. 
     Referring to  FIG. 3 , a centrifuge according to an embodiment of the invention, in a manner known per se, comprises a vessel (not shown) incorporating:
         a motor unit  100  connected to a drive shaft  1 ;   a rotor  2  mounted removably on the drive shaft  1 , in a mounting position for which the drive shaft and the rotor are rotationally coupled;   a device  3  providing for an axial locking of the rotor to the drive shaft.       

     According to the present embodiment, the axial locking of the rotor to the drive shaft is obtained by the implementing of:
         an annular groove  10  made on the drive shaft forming a female element presented by the drive shaft;   a pair of male elements  300  carried by the rotor and capable of occupying a position of cooperation with the annular groove  10  in being engaged in it under the action of an elastic stress.       

     According to the principle of an embodiment of the invention, the male elements  300  are coupled to visual and/or tactile indicating means (described in greater detail here below) providing a visual and/or tactile indication of the position of cooperation of the male elements  300  with the annular groove  10  of the drive shaft, i.e. the position when the male elements are engaged in the annular groove (the axial locking of the rotor to the drive shaft being then ensured). 
     Referring to  FIGS. 1 to 3 , a more detailed description is provided here below of the device  3  providing for the axial locking of the rotor to the drive shaft. 
     As can be seen in these figures, the device  3  comprises a pair of male elements  300  each mounted so as to be pivoting about a pivoting pin  31  parallel to the axis X of the drive shaft, the pivoting pin  31  of each male element being mounted on a ring  35  embedded in a housing  20  prepared on the upper part of the rotor  2 . 
     Thus, and as can be seen in  FIG. 3 , the device  3  and therefore the male elements  300  of the device  3  are mounted in the upper part of the rotor  2 . 
     The male elements  300  are mounted so as to be diametrically opposite to each other relatively to the axis X on the ring  35 . The same is therefore the case for the diametrically opposite positions of the pivoting pins  31 . 
     Furthermore, each male element  300  is elastically stressed by a spring  301 , one end of which takes support on a male element while the other end is housed in a cavity  350  of the ring  35 , this spring  301  being designed and mounted so as to act in compression in such a way that each spring  301  tends to make the corresponding male element pivot towards its position of cooperation with the annular groove  10  of the drive shaft. 
     More specifically, each male element  300  comprises:
         an engaging termination  30  extending on one side of the pivoting pin  31  and against which the spring  301  takes support, this engaging termination  30  being designed to get engaged in the annular groove  10  of the drive shaft to ensure the axial blocking of the rotor on the drive shaft;   an ear-shaped attachment  32  extending on the other side of the pivoting pin relatively to the engaging termination, this ear-shaped attachment forming a visual and/or tactile indicator as explained here below.       

     It can be noted that the angular play of the engaging termination  30  of each male element  300 , in the direction along which the termination is off-centered relatively to the axis X is limited by a shoulder  351  made on the ring  35 . 
     At the same time, the diametrically opposite shoulders  351  mutually make a space in which the ear-shaped attachments  32  extend, this space between the shoulders being also designed to enable an angular play of the ear-shaped attachments  32 . 
     Furthermore, the rotor  2  has an annular cage  33  designed to be attached and fixed to the ring  35 , this annular cage  33  demarcating a volume forming a housing for the male elements  300 . 
     Furthermore, the annular cage  33  is provided with a radial passage  330  for each ear-shaped attachment  32 . These radial passages  330  and this sizing of the diameter of the annular cage  33  are designed so as to permit two positions for the visual and/or tactile indicator constituted by the ear-shaped attachments  32 , namely:
         a position of concealment in which the ear-shaped attachments are housed integrally within the annular cage, the ear-shaped attachments being therefore neither visible nor accessible to touch (or almost non-accessible to touch) in this position ( FIG. 5 );   a position for indicating the axial locking of the rotor on the drive shaft in which the ear-shaped attachments protrude through the passages  330  of the annular cage  33 , the ear-shaped attachments being then presented outside the annular cage so as to be visible and accessible to being touched (as can be seen in  FIGS. 4 and 6 ).       

     To further increase the visible nature of the ear-shaped attachments when they are made to protrude through the radial passages  330  of the annular cage, a color indicator  320  (for example green) is attached to the upper face of each ear-shaped attachment  32 . 
     The axial locking of the rotor on the drive shaft is obtained by the device  3  which has just been described. 
     Furthermore, the centrifuge also has a device to measure the rotational speed of the centrifuge, the device comprising:
         a first part called an emitter carried by the rotor  2 ;   a second part capable of detecting a frequency of passage of the emitter part at a fixed point, this second part being mounted preferably on the lid  40  of the centrifuge.       

     These first and second parts constitute a tachometric device by which it is possible to obtain the rotation speed of the rotating assembly constituted by the rotor. 
     According to the present embodiment, the emitting part carried by the rotor is constituted by the indicators  320 , each of them being a magnet. In parallel, the second part capable of detecting a frequency of passage of the emitter part is a radio-magnetic effect sensor  3200  carried by the lid (this sensor being therefore at a fixed point of the centrifuge once the lid is closed). 
     Furthermore, according to another aspect of an embodiment of the invention illustrated by  FIGS. 8 to 10 , one of the male elements  300  of the axial locking device  3  has a target element  321  while the chamber, and preferably the lid according to the present embodiment, carries a device for locating the target element  321 , this assembly being designed to detect the axial positioning of the rotor on the drive shaft in the position corresponding to the position of cooperation of said male element with the annular groove  10  of the drive shaft  1 . 
     This target element is constituted according to the present embodiment by a magnet mounted at one corresponding end of the ear-shaped attachment  32  opposite the end receiving the indicator  320  relatively to the pivoting pin  31 . It can be noted that, according to this device, when the axial locking device is in an unlocked position, the magnet  321  is presented outside the annular cage  33  ( FIG. 9 ) while, inversely, when the axial locking device is in the locked position, the magnet  5  is concealed within the annular cage  33  ( FIG. 8 ). 
     Thus, when the rotor rotates and when the axial locking device is in a locked position ( FIG. 8 ), the radio-magnetic effect sensor  3200  will emit a signal corresponding to a curve of the type shown in  FIG. 10 : two signals evenly spaced out corresponding to the passages of the indicators  320  beneath the radio-magnetic effect sensor  3200 . 
     By contrast, when the rotor rotates and the locking device is not in a locked position ( FIG. 9 ), the radio-magnetic effect sensor  3200  will emit a signal corresponding to the curve of the type shown in  FIG. 11 : three signals corresponding to the passages of the indicator  320  and of the magnet  5  beneath the radio-magnetic effect sensor  3200 , these signals being spaced out unevenly in sets of two (the magnet  321  being closer to one of the indicators  320  than to the other). In this case, the curve is interpreted as representing an unlocked position of the rotor on the drive shaft and the centrifugation cycle is immediately stopped. 
     The rotational coupling of the rotor with the drive shaft is obtained by the implementing of the constituent parts described here below. 
     As can be seen in  FIG. 1 , the rotational coupling of the rotor with the drive shaft comprises:
         firstly, a diametral slot  11  extending from the upper end of the drive shaft  1 ;   a diametral rod fixed to the rotor, designed to get housed in a diametral slot  11  of the drive shaft to provide for the rotational coupling of the rotor with the drive shaft.       

     This rod  34  is force-fitted into a cap  340  overhanging the annular cage  33  (the cap  340  and the annular cage forming one and the same part), the rod  34  being introduced through two holes  331  made in the cap  340  so as to be diametrically opposite to each other. 
     It can be noted that the annular cage  33  (and therefore the cap  340 ) is fixedly joined to the rotor by screwing elements that go through holes  332  made in the annular cage  33  and holes  352  made in the ring  35  (the holes  352  of the ring  35  are made so as to be placed in correspondence with the holes  332  of the annular cage  33 ); the result of this assembly is that the rod  34  is joined rotationally to the rotor  2 . 
     Furthermore, the rotor has a device for identifying  36  ( FIG. 4 ) the orientation of the rod  34  so as to enable an operator to present the rotor in an angular position in which the rod is in the alignment of the diametral slot  11  of the drive shaft  1 . 
     According to another characteristic illustrated by  FIG. 3 , a slotted conical ring  12  is mounted so as to be sliding on the drive shaft  1  and a spring  13  is interposed between the ring  12  and a shoulder  14  made on the drive shaft, this spring  13  acting in compression and tending to push back the ring  12  towards the upper end of the drive shaft. 
     The mounting of this ring  12  is designed so that the rotor takes support, by its lower face, on the ring  12 . 
     Thus, the ring  12  and the spring  13  constitute a device for compensating for the axial clearances between the constituent parts of the rotor  2  and the annular groove of the drive shaft. 
     The mounting of the rotor on the drive shaft of a centrifuge according to an embodiment of the invention is done as follows. 
     The operator grasps the rotor and orients it angularly so as to align the identifying device  36 , indicating the orientation of the rod  34 , with the diametral slot  11  of the drive shaft that the operator has preliminarily visualized. 
     The presence of chamfers  110  on either side of the slot  11  at the end of the drive shaft makes it possible to move the engaging terminations  30  of the male elements apart from one another, enabling the rotor to get engaged in the drive shaft. 
     The operator then engages the rotor on the drive shaft. The pressure on the ear-shaped attachments of the male elements can be released, the engaging terminations then sliding, in being supported on the external surface of the drive shaft. The rod  34  gets engaged in the diametral slot of the drive shaft. 
     The operator continues the engagement of the rotor on the drive shaft until the engaging terminations reach the annular groove  10  of the drive shaft. At this stage, under the action of the springs  301 , the engaging terminations  30  penetrate the annular groove  10  of the drive shaft. 
     The simple fact of placing the engaging in correspondence with the location of the annular groove  10  of the drive shaft is enough to give rise to the pivoting of the male elements about their pivoting pin  31 , as indicated by the arrow F 2  in  FIG. 2 . 
     The pivoting of the male elements tends to bring the engaging terminations into a position of cooperation with the annular groove of the drive shaft accompanied by the shifting of each ear-shaped attachment  32  through the corresponding radial passage  330  of the annular cage  33  until the ear-shaped attachments are brought into a position in which they are presented in protrusion through these radial passages and give a visual and tactile indication, indicating that the axial locking of the rotor on the drive shaft has been achieved. 
     It can be noted that when the engaging terminations reach the annular ring  10  of the drive shaft, the rotor reaches a position in which it is supported on the ring  12  mounted slidingly on the drive shaft and presses lightly on this ring. This tends to slightly compress the spring  13  which pushes the rotor back upwards. The result of this is that the terminations are also pushed upwards and are made to abut the interior of the annular ring. The axial play between the thickness of the engaging terminations and the height of the annular groove is thus compensated for. 
     It can be noted that, during the centrifugation, the rotation of the rotor gives rise to a centrifugal effect on the male elements  300  as illustrated by the arrow F 1  in  FIG. 2 . This centrifugal effect tends to increase the gripping force of the terminations for engaging within the annular groove  10  of the drive shaft. The centrifugal effect (illustrated by the arrows F 1 ) thus substantially increasing the clamping force (forces F 2  illustrated in  FIG. 2 ) of the male elements on the drive shaft. 
     To withdraw the rotor from the drive shaft once the centrifugation is terminated, it is enough for the operator to press the ear-shaped attachments  32  so as to make them penetrate the annular cage  33 : this corresponds to a spreading of the engaging terminations apart from each other until they are brought outside the annular groove  10 . At this stage, the spring  13  which had been hitherto compressed tends to push the rotor back upwards through the sliding ring  12 . 
     The operator can then continue the disengagement of the rotor effortlessly.