Abstract:
An apparatus and method for inserting a stopper into a medical syringe minimizing the amount of entrapped air between the stopper and the contained liquid. The apparatus in a first embodiment utilizes a vacuum to assist inserting the stopper within the syringe. In a second embodiment a vacuum is used to transport the stopper and cause the insertion into the syringe. This method eliminates a mechanical device that transports the stopper to the syringe.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an apparatus and method for inserting stoppers under a vacuum into a syringe filled with liquid.  
       BACKGROUND OF THE INVENTION  
       [0002]     In order to prepare a medical syringe that will be used to inject liquid into a patient, it is critical that the syringe and fluid are free of contamination, biological and chemical. Apparatus used in the process must be made from non-corrosive materials and be located within a controlled atmosphere. Important to the process and apparatus is the prevention of air being retained within the syringe after the filling and stopper insertion processes. The presence of air in the syringe and its possible injection into a patient is undesirable. One of the objectives of syringe filling and closing systems is to minimize the trapped air above the liquid.  
         [0003]     The syringes and stoppers are often standardized by the use of ISO (International Organization for Standardization), e.g. ISO 11040-4 and 5 for glass barrels and plungers for injectables. It is therefore possible to manufacture apparatus to accommodate the various size barrels or syringes and plungers or stoppers.  
         [0004]     All apparatus described herein is typically part of a larger machine that precisely locates multiple syringes below a series of one or more stopper insertion apparatuses and then delivers and inserts the stoppers within the previous filled syringes. Syringes processed by the traditional method contain a relatively large amount of air or gas above the liquid after filling and stopper insertion. This method also requires moving machinery parts to move stopper rams and stopper tubes, inject the stoppers and place the syringes. This machinery releases particles by wear and interferes with the flow of clean air through the machine.  
         [0005]     A description of a typical prior stopper insertion apparatus will be described by referring to  FIG. 1 . The basic function of this system is the insertion of stoppers  1  (also called pistons or plungers) into filled syringes  2 . The syringes are filled with a liquid medium  3 . The main functional elements for this insertion are stopper tubes  4  and stopper rams  5 . Each functional element is moved relative to each other according to a specific timing. The movement and timing of stopper tubes  4  and stopper rams  5  is driven for example by mechanical cams, servos or a robot system. A stopper insertion system includes one stopper tube  4  and stopper ram  5  for sealing one syringe  2  at once or more sets for sealing two or more syringes at the same time. The following description of operation is simplified for only one set.  
         [0006]     The stopper  1  is placed concentric above the stopper tube  4 . By a vertical movement of the stopper ram  5 , the stopper  1  is inserted into the stopper tube  4 . The stopper  1  is compressed inside the stopper tube  4 . Then the stopper tube  4  and stopper ram  5  move down into the syringe  2  up to a specific depth. As long as the stopper  1  remains in the stopper tube  4 , air above the filling level of the filling liquid  3  can escape out of the syringe  2  by passing the gap between stopper tube  4  and the inner surface of the syringe body. The pressure inside the syringe remains almost equal to the system&#39;s environment pressure (P 1 ≈P 2 ). By starting to move up first, the stopper tube  4  releases the stopper  1  above the filling level. After that release the stopper ram  5  also starts moving up. Both functional elements move back to their home position, and the next cycle can start.  
         [0007]     According to the described function of the system, the final position of the stopper  1 A after the insertion into the filled syringe  2  depends on the lowest position of the stopper tube  4  movement and the stopper ram  5  movement. A gas volume between the stopper  1 A and filling liquid  3  remains. The pressure of this gas volume is close to the system&#39;s environment pressure (P 1 ≈P 2 ).  
       SUMMARY OF THE INVENTION  
       [0008]     It is the purpose of this invention to disclose an apparatus and method for inserting a stopper into a syringe using simplified machinery having less moving parts and that permits a minimum volume of air to remain within the syringe after stopper insertion. In a first embodiment the apparatus provides a stopper insertion system that uses vacuum to assist the insertion of the stopper. This method and apparatus reduces the air entrapped above the liquid in a syringe. A preferred embodiment improves this process by eliminating the stopper ram mechanism and causes insertion of the stopper by controlled use of vacuum. This method and apparatus reduces entrapped air and reduces the moving machinery parts required to insert the stoppers. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a side section schematic view of a prior art apparatus for inserting a stopper into a syringe.  
         [0010]      FIG. 2  is a side section of a first embodiment of the present invention for an apparatus for inserting a stopper into a syringe.  
         [0011]      FIG. 3  is a view of the  FIG. 2  apparatus at the start of the stopper insertion cycle.  
         [0012]      FIG. 4  is a view of the  FIG. 2  apparatus after the start of the stopper insertion cycle.  
         [0013]      FIG. 5  is a view of the  FIG. 2  apparatus near completion of the stopper insertion cycle.  
         [0014]      FIG. 6  is a side section schematic of a preferred embodiment of the present invention at the start of the stopper insertion cycle. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]     This first embodiment will be described by referring to  FIG. 2 . The basic function of this system is the insertion of stoppers  10  (also called pistons or plungers) into filled syringes  12  with vacuum assist. The syringes are filled with a liquid medium  14 . The main functional elements for this insertion are stopper tubes  16  and stopper rams  20 . The stopper tubes  16  have one or more radial ports  18  which are connected to a vacuum system. A vacuum system, for example, could include a vacuum pump and a vacuum valve. Each functional element is moved relative to each other according to a specific timing. Vacuum supplied by the vacuum system is activated and deactivated according to the stopper tube&#39;s  16  and stopper ram&#39;s  20  movement. The movements  22  and  24  and timing of stopper tubes  16  and stopper rams  20  are driven for example by mechanical cams, servos, or a robot system. A stopper insertion system can include one stopper tube  16  and stopper ram  20  for sealing one syringe  12  at once or more sets for sealing two or more syringes at the same time. The following description is simplified for only one set. A description of one cycle will refer to  FIGS. 3, 4  and  5 .  
         [0016]     Referring to  FIG. 3 : The stopper  10  is placed concentric above the stopper tube  16 . By a vertical movement of the stopper ram  20 , the stopper  10  is inserted into the stopper tube  16  up to a specific depth as shown. The stopper  10  is compressed inside the stopper tube  16 . By reaching this specific depth, the stopper  10  seals the upper opening of the stopper tube  16  but remains above the radial vacuum port(s)  18 .  
         [0017]     Referring to  FIG. 4 : The stopper tube  16  and stopper ram  20  move down until the sealing element  26  touches the syringe&#39;s  12  body. The stopper tube  16  follows the movement of the stopper ram  20 , so there is no relative movement between these two components. The stopper  10  remains in its specific position proportional to the stopper tube  16 . The sealing element  26  seals the stopper tube against the syringe  12 . A vacuum chamber is formed including the stopper tube  16  and syringe  12 . After the vacuum chamber is formed, the vacuum is activated for the duration of 0.01 seconds to 4 seconds. The vacuum chamber is evacuated up to a pressure between 0.01 millibar and 300 millibar. During the evacuation the stopper tube  16 , stopper ram  20  and stopper  10  remain in position as shown.  
         [0018]     Referring to  FIG. 5 : After that specific duration of evacuation the stopper tube  16  and sealing element  26  remain in position. The stopper ram  20  moves down until the stopper  10  is released out of the stopper tube  16 . When the stopper  10  reaches the vacuum connection port  18 , no further vacuum in the syringe  12  can be reached by evacuating the vacuum chamber. After the stopper  10  has passed the depth of the vacuum connection port  18  the stopper tube&#39;s  16  section above the stopper  10  (including the vacuum connection port  18 ) is vented up to the system&#39;s environment pressure P 1 . A force which is caused by the pressure difference between inside the syringe  12  and the environment (P 1 &gt;P 2 ) moves the stopper  10  down to a final position where the pressure difference is almost equalized with ambient pressure by the compression of the remaining gas volume between the filling liquid  14  and the stopper  10 . The stopper ram  20  and stopper tube  16  return to their home position by upward movements  22  and  24 . A new cycle can start.  
         [0019]     According to the described function of the system, the final position of the stopper  10 A after the insertion into the filled syringe  12  does not depend on the lowest position of the stopper tube  16  movement and the stopper ram  20  movement. After the stopper  10  is released out of the stopper tube  16 , different forces act on the stopper  10 . The first resultant force is caused by the pressure difference between inside the syringe  12  (F Inside=P 2 *A) and the system&#39;s environment pressure (F Outside=P 1 *A). “A” is the cross-sectional area of the inserted stopper  10 A. The second force is friction between the syringe  12  and the moving stopper  10 . The stopper  10  is forced to move down until these forces are balanced. By this way the remaining gas volume between the filling liquid  14  and the stopper  10  can be reduced in comparison to the stopper insertion prior art.  
         [0020]     The preferred embodiment vacuum stopper insertion apparatus description refers to  FIG. 6 . The apparatus can have one or more devices, but one will be described for simplicity. The basic function of this system is the insertion of stoppers  30  into filled syringes  32  using a vacuum. The syringes are filled with a liquid medium  34 . The main functional elements for this insertion are a stopper tube  36  and a flexible stopper transport device  38 . The stopper tube  36  has one or more radial ports  40  which are connected to a vacuum system. A vacuum system, for example, can include a vacuum pump and a vacuum valve. The stopper tube  36  is moved according to a specific timing. Vacuum is supplied by the vacuum system and is activated and deactivated according to the stopper tube  36  movement and the flexible stopper transport device  38  movement. The movement and timing of the stopper tube  36  and flexible stopper transport device  38  is driven, for example, by mechanical cams, servos, or a robot system. A stopper insertion system can include one stopper tube  36  and flexible stopper transport device  38  for sealing one syringe  32  at one time or more sets for sealing two or more syringes at the same time. The following operational description is simplified for only one set. A description of one cycle follows:  
         [0021]     The stopper tube  36  is moved down until a sealing element  44  touches the syringe  32  body. The sealing element  44  seals the stopper tube  36  against the syringe  32 . A stopper  30  is fed into the flexible stopper transport device entrance  46 . Vacuum between 10 and 800 millibars is activated at port  40 . In comparison to the environment&#39;s pressure P 1 , the pressure P 2  inside the flexible stopper transport device  38  is reduced (P 1 &gt;P 2 ) by evacuation. This pressure difference forces the stopper  30  to move through the flexible stopper transport device  38 . The stopper  30  is compressed as shown at  30 A when it enters the stopper tube  36 . The stopper  30 A seals the stopper tube  36  from the flexible stopper transport device  38 . In that stage, an optional higher vacuum between 0.01 and 300 millibars, P 3  (P 1 &gt;P 2 &gt;P 3 ) can be provided by the vacuum system. Also in that stage, the stopper  30 A can be held on this position by an optional holding device for a specific duration of evacuation. After the evacuation of the smaller vacuum chamber between the stopper  30 A, stopper tube  36  and the syringe  32 , the pressure difference between inside the syringe  32  and above the stopper  30 A (inside the flexible stopper transport device  38  and the upper section of the stopper tube  36 ) forces the stopper  30 A to move down through the stopper tube  36  into the syringe  32  to position  30 B. As an option, the pressure inside the flexible stopper transport device  38  and the upper section of the stopper tube  36  can be increased by venting or providing an additional air pressure supply at port  40  at that stage. The stopper tube  36  returns to its home position by movement  42 , and a new cycle can start. Similar to the vacuum assisted stopper insertion previously described, the final position of the stopper  30 B after the insertion into the filled syringe  32  depends also on the pressure difference P 1 &gt;P 4 . After the stopper  30 B reaches the lowest position, a gas volume between the stopper  30 B and filling liquid  34  can remain. The pressure P 4  of this gas volume would be close to the system&#39;s environment pressure P 1 . Also similar to the vacuum assisted stopper insertion previously described, the final position of the stopper  30 B after the insertion into the filled syringe  32  depends on different forces that act on the stopper  30 B. The first resultant force is caused by the pressure difference between inside the syringe  32  (F Inside=P 4 *A) and the system&#39;s environment pressure (F Outside=P 1 *A). “A” is the cross-sectional area of the inserted stopper  30 B. The second force is friction between the syringe  32  and the moving stopper  30 B. The stopper  30 B is forced to move down until these forces are balanced. In this way the remaining gas volume between the filling liquid  34  and the stopper  30 B is reduced in comparison to the traditional stopper insertion previously described.  
         [0022]     The above embodiments describe a simplified apparatus and method for closing a filled syringe with a stopper that has a minimum of entrapped air.