Abstract:
A method and apparatus for screwing pistons of syringes, each defined by a corresponding cylinder fluid-tightly sealed by a plug made of elastomeric material and a corresponding piston screwed into the plug itself, according to which each cylinder and corresponding piston are coaxially fed along a given path, and are respectively turned to screw the piston into the corresponding plug; the screwing of each piston into the corresponding plug being controlled by measuring either the value of a screwing torque or of a magnitude according to the screwing torque itself.

Description:
[0001]    The present invention relates to an apparatus for screwing pistons of syringes. 
       BACKGROUND OF THE INVENTION 
       [0002]    In particular, the present invention relates to an apparatus for screwing pistons of syringes, each of which has a given longitudinal axis, and comprises a cylinder fluid-tightly sealed by means of a plug made of elastomeric material mounted within the cylinder and an actuating piston screwed into the plug itself. 
         [0003]    The apparatus comprises a feeding line, for feeding in sequence the cylinders and corresponding pistons, which are coaxial to each other, along a given path, and comprises a plurality of first gripping and conveying devices, each of which is pivotally engaged by a corresponding cylinder and a plurality of second gripping and conveying devices, each of which is adapted to receive and hold a corresponding piston; and a rolling block made of elastomeric material arranged along the path to turn each cylinder about the corresponding axis and to fasten the corresponding plug on the corresponding piston. 
         [0004]    The position of the rolling block with respect to the cylinders is selectively controlled so as to prevent, after having completed the screwing, a further rotation of the cylinders, allowing at the same time the sliding of the syringes on the rolling block itself. 
         [0005]    Because the cylinders of the syringes of a given diameter may reciprocally differ due to the contemplated tolerances of the diameter itself and the rolling block may wear, the apparatuses for screwing syringes of the above-described known type display some drawbacks, mainly deriving from the fact that the friction conditions between cylinders and rolling block may vary, thus compromising the correct screwing of each cylinder in the respective plug. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an object of the present invention to provide an apparatus for screwing pistons of syringes which is free from the above-described drawbacks and which is simple and cost-effective to implement. 
         [0007]    According to the present invention, there is provided an apparatus for screwing pistons of syringes as claimed in the attached claims. 
         [0008]    The present invention further relates to a method for screwing pistons of syringes. 
         [0009]    According to the present invention, there is provided a method for screwing pistons of syringes as claimed in the attached claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention will now be described with reference to the accompanying drawings, which illustrate a non-limitative embodiment thereof, in which: 
           [0011]      FIG. 1  is a diagrammatic plan view, with parts removed for clarity, of a preferred embodiment of the apparatus according to the present invention; 
           [0012]      FIG. 2  is a first diagrammatic side view, with parts removed for clarity, of a detail of the apparatus in  FIG. 1 ; 
           [0013]      FIG. 3  is a first diagrammatic side view, with parts removed for clarity, of a detail in  FIG. 2 ; 
           [0014]      FIG. 4  is a second diagrammatic side view, with parts removed for clarity, of the detail in  FIG. 3 ; and 
           [0015]      FIG. 5  is a diagrammatic plan view, with parts removed for clarity, of the detail in  FIGS. 3 and 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    With reference to  FIG. 1 , numeral  1  indicates, as a whole, an apparatus for screwing pistons of syringes  2 , each of which has a given longitudinal axis  3  and comprises a cylinder  4  for containing a product, in the case in point a medical product, a plug  5  made of elastomeric material adapted to fluid-tightly close the cylinder  4  and an actuating piston  6  screwed into the plug  5  itself. 
         [0017]    The apparatus  1  comprises a feeding wheel  7 , which is motorized, in a know manner (not shown), to continuously rotate about a longitudinal axis  8  thereof vertical and perpendicular to the sheet in  FIG. 1 , and is provided with a plurality of pockets  9 , which are uniformly distributed along the periphery of the wheel  7  about the axis  8 , and each comprises two corresponding cylindrical rollers  10  mounted parallel to the axis  8  and reciprocally arranged at a distance smaller than the diameter of the cylinder  4  of a syringe  2 . 
         [0018]    The cylinders  4 , filled with product and fluid-tightly closed by the corresponding plugs  5 , are fed in sequence to the corresponding pockets  9  by a feeding device  11  connected to the wheel  7  at an inlet station  12 , and are withheld in the corresponding pockets  9  by the corresponding upper annular flanges  13  and by a fixed containment slat  14 , which extends about axis  8 , and opens at the station  12  and at an outlet station  15  of the syringes  2  from the wheel  7 . 
         [0019]    As shown in  FIG. 2 , wheel  7  is further provided with a plurality of gripping and conveying members  16 , which are uniformly distributed about axis  8 , are each aligned with a corresponding pocket  9  in a vertical direction parallel to axis  8 , and each comprise two corresponding gripping jaws  18  movable between a clamping position and a releasing position of a corresponding piston  6 . 
         [0020]    With reference to  FIG. 1 , the pistons  6  are fed in sequence to the corresponding members  16  by a feeding device  19  connected to the wheel  7  at an input station  20 , and are withheld by respective members  16  in position coaxial to the corresponding cylinders  4 . 
         [0021]    The apparatus  1  further comprises a first screwing device  21 , which is arranged along a feeding path P of the cylinders  4  between the stations  12  and  15 , and comprises, in turn, a supporting plate  22 , a crank  23  hinged to the plate  22  to oscillate, with respect to the plate  22 , about a fulcrum axis  24  parallel to the direction  17 , and a rolling assembly  25  comprising a belt  26  looped about a pair of pulleys  27 , one fixed to the plate  22  and the other fixed to the crank  23 . 
         [0022]    The radial position of the plate  22  with respect to the piston  8  is selectively adjusted according to the diameter of the cylinders  4 , while the tension of the belt  26  is maintained substantially constant by means of a spring  28  arranged between the plate  22  and the crank  23 . 
         [0023]    The apparatus  1  is further provided with a second screwing device  29 , which is arranged along the path P downstream of the device  21  in the sense of rotation of the wheel  7 , and comprises a slide  30  slidingly coupled to a fixed frame  31  of the apparatus  1  to carry out rectilinear movements in a direction substantially radial with respect to axis  8  with respect to the frame  31  and under the bias of an actuating device  32 . 
         [0024]    As shown in  FIGS. 1 ,  3 ,  4 , and  5 , the device  32  comprises an actuating cylinder  33 , in the case in point an electromagnet of known type, which is fixed to the frame  31 , extends radially with respect to the axis  8 , and has an outlet rod  34  connected to the slide  30  by means of the interposition of a rocker arm  35 , which is hinged to the frame  31  to oscillate, with respect to the frame  31  itself, about a substantially horizontal fulcrum axis  36  traversal to direction  17 , and comprises two arms, the ends of which are fork-shaped, and are coupled one to the slide  30  and the other to the rod  34  by means of corresponding coupling pins  37  slidingly engaged in the ends themselves. 
         [0025]    The device  29  further comprises a crank  38 , which is pivotally engaged to the slide  30  to oscillate with respect to the slide  30  itself about a fulcrum axis  39  parallel to the axis  36 , is coupled to the slide  30  with a given side clearance in a tangential direction parallel to the path P, and carries connected a rolling block  40  made of elastomeric material facing the path P itself. 
         [0026]    The position of the crank  38  about the axis  39  is selectively controlled by means of an adjustment screw  41 , which extends through the slide  30 , is screwed into the crank  38 , and has a head  42  arranged in contact with the slide  30  on opposite side of the crank  38 , and is maintained by a spring  43  interposed between the slide  30  and the crank  38  itself. 
         [0027]    The device  29  is associated to a measuring device  44  comprising, in the case in point, a force sensor  45 , in the case in point a load cell, which is fixed to the slide  30  by means of a supporting bracket  46 , is arranged upstream of the block  40  in the sense of rotation of the wheel  7 , and cooperates with an actuating pin  47  which extends parallel to the path P, is screwed through a supporting bracket  48  fixed to the crank  38 , and is arranged upstream of the sensor  45  in the sense of rotation of the wheel  7  and in contact with the sensor  45  itself. 
         [0028]    The operation of the apparatus  1  will now be described with reference to  FIG. 1 , assuming the screwing of a piston  6  in the plug  5  of the corresponding cylinder  4 , and starting from an instant in which the belt  26  and the block  40  are correctly positioned with respect to the path P and the pin  47  is correctly positioned in contact with the sensor  45 . 
         [0029]    The cylinder  4  and the piston  6  are fed by the devices  11  and  19 , respectively, to the stations  12  and  20 , respectively, in phase with a pocket  9  and with the corresponding member  16 , respectively, are transferred to the pocket  9  and to the member  16 , respectively, so as to be reciprocally coaxial, and are advanced by the wheel  7  about the axis  8  (clockwise in  FIG. 1 ). 
         [0030]    At this point, the cylinder  6  is lowered by the member  16  into the cylinder  4  and in contact with the plug  5 , and the cylinder  4  comes into contact with the belt  26 , which imparts a rotary movement to the cylinder  4  itself about the axis  3  (anticlockwise in  FIG. 1 ) so as to partially screw the plug  5  onto the piston  6  itself. 
         [0031]    Subsequently, the cylinder  4  comes into contact with the rolling block  40 , which imparts a rotary motion to the cylinder  4  itself about the axis  3  (anticlockwise in  FIG. 1 ) so as to completely screw the plug  5  onto the piston  6 . 
         [0032]    Due to the friction force between the cylinder  4  and the block  40  and the rotation of the wheel  7  about the axis  8 , the crank  38  and, thus, the pin  47  are laterally moved parallel to the path P and in the same sense as the wheel  7 , and the pin  47  is clamped against the sensor  45  with a clamping force according to the tightening torque of the plug  5  on the piston  6 . 
         [0033]    Because the devices  32  and  44  are connected to an electronic control unit (not shown) of the apparatus  1 , the device  44  allows to: 
         [0034]    control the movement of the slide  30  from an advanced operating position, in which the block  40  is arranged in contact with the cylinder  4 , to a retracted resting position, in which the block  40  disengages the cylinder  4  itself, when the value of the clamping force measured by the device  44  is at least equal to a threshold value chosen in an interval of values comprised between a minimum value corresponding to a correct screwing of the plug  5  on the piston  6  without sliding of the cylinder  4  on the plug  5  and a maximum value over which the cylinder  4  slides on the plug  5  itself; 
         [0035]    compare the value of the clamping force measured by the device  44  with the above mentioned range of values and selectively control the advanced operating position of the block  40  by means of the screw  41  so that the value of the clamping force measured by the device  44  is comprised in the range of values; and 
         [0036]    control the correct screwing of each piston  6  into the respective plug  5 . 
         [0037]    According to a variant not shown, the apparatus  1  comprises an ejector device mounted upstream of the device  29  to reject the syringes  2  when the value measured by the device  44  is different from at least one threshold value, and is in particular lower than the mentioned minimum and/or maximum of the mentioned maximum value. 
         [0038]    According to a further variant not shown the measuring device  44  is eliminated and replaced by a measuring device mounted on each pocket  9  and/or on the corresponding member  16  to directly measure the screwing torque of each piston  6  in the corresponding plug  5 .