Patent Abstract:
A liquid container includes a liquid pack having a flexible pouch holding the liquid, a container body containing the liquid pack, an expandable-and-contractile stirring chamber formed in the container body, and a pressurized fluid supply passage for supplying a pressurized fluid into the stirring chamber. At least a part of the stirring chamber is formed of a low-rigidity member. A pressurized fluid is supplied through the pressurized fluid supply passage into the stirring chamber to press and deform the low-rigidity member by the pressure of the pressurized fluid. The deformed low-rigidity member presses and deforms the flexible pouch of the liquid pack. The liquid container prevents the uneven distribution of ingredient concentration in the liquid contained in the liquid container without complicating and enlarging a liquid-consuming apparatus.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2004-67789, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The present invention relates to a liquid container for holding a liquid to be supplied to a liquid-consuming apparatus. 
   2. Description of the Related Art 
   A liquid-ejecting apparatus provided with an ejecting head that ejects a liquid is a representative conventional liquid-consuming apparatus. An ink-jet recording apparatus provided with an ink-jet recording head for recording images is a typical example of the liquid-ejecting apparatus. Other examples of the liquid-ejecting apparatus are an apparatus provided with a coloring matter ejecting head for fabricating color filters for liquid crystal displays, an apparatus provided with an electrode forming material (conductive paste) ejecting head for forming electrodes for organic EL displays and field emission displays (FEDs), an apparatus provided with a bioorganic material ejecting head for manufacturing biochips, and an apparatus provided with a sample ejecting head as a precision pipette. 
   The ink-jet recording apparatus, which is a representative liquid-ejecting apparatus, is used prevalently nowadays for printing operations including color printing operations because the ink-jet recording apparatus generates comparatively low noise during a printing operation and is capable of forming small dots in a high dot density. 
   A liquid supply system for supplying a liquid to the liquid-consuming apparatus represented by the ink-jet recording apparatus supplies the liquid from a liquid container holding the liquid to the liquid-consuming apparatus. Generally, the liquid container used by the liquid supply system is a cartridge capable of detachably attached to the liquid-consuming apparatus to facilitate the user&#39;s work for replacing the liquid container with a new one when the liquid contained in the liquid container is exhausted. 
   Generally, the ink-jet recording apparatus is provided with a carriage carrying a recording head that ejects ink drops and capable of reciprocating along the recording surface of a recording medium. An ink supply system for supplying ink from an ink cartridge to a recording head mounts the ink cartridge on a carriage and supplies the ink from the ink cartridge to a recording head while the ink cartridge is reciprocated together with the recording head. Another ink supply system mounts an ink cartridge on the case or the like of the body of an apparatus, and carries ink from the ink cartridge to a recording head by a flexible tube or the like forming an ink passage. 
   Recently, the pigment ink is used prevalently for printing high-quality, highly weatherproof images. Although the pigment ink is capable of printing images excellent in print quality, pigment particles of the pigment ink contained in an ink container sediment so that pigment content is distributed unevenly in the ink container. Consequently, the ink-jet recording apparatus is unable to print images in an expected print accuracy after the ink-jet recording apparatus has been kept inoperative for a long time. 
   An ink-jet recording apparatus proposed in JP-A 60-110458 (Patent document 1) is provided with an ink stirring mechanism including a rotor and a magnetic stirrer. An ink-jet recording apparatus proposed in JP-A 11-10902 (Patent document 2) includes a main tank provided with a stirring member and a stirring bar, a subtank connected to the main tank by an ink circulating line. These mechanisms proposed in Patent documents 1 and 2 are intended to prevent the uneven distribution of pigment content by forcibly stirring the ink held in the ink container. 
   These mechanisms proposed in Patent documents 1 and 2 need a device including a complicated mechanism, such as the stirrer, and power for driving the complicated mechanism and, consequently, the construction of the recording apparatus is inevitably complicated. The magnetic stirrer and a stirrer driving unit, namely, driving devices for rotating the rotor and the stirring member, need to be disposed near the ink container, which places restrictions on the configuration of the recording apparatus and the recording apparatus is inevitably large. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in view of the foregoing problems and it is therefore an object of the present invention to provide a liquid container which makes the construction of a liquid-consuming apparatus into which the liquid container is incorporated neither complicated nor large and can prevent the uneven distribution of ingredient concentration. 
   To solve the problems, the present invention provides a liquid container holding a liquid to be supplied to a liquid-consuming apparatus, including: a liquid pack including a flexible pouch formed of a flexible material and holding the liquid; a container body for containing the liquid pack; an expandable-and-contractile stirring chamber formed in the container body; and a pressurized fluid supply passage for supplying a pressurized fluid into the stirring chamber; wherein at least a part of the stirring chamber is formed of a low-rigidity member having a low rigidity, and the low-rigidity member is deformed by supplying the pressurized fluid into the stirring chamber through the pressurized fluid supply passage to press and deform the flexible pouch of the liquid pack by the low-rigidity member. 
   Preferably, the low-rigidity member of the stirring chamber presses and deforms a part of the flexible pouch of the liquid pack. 
   Preferably, the low-rigidity member includes a flexible film. 
   Preferably, the stirring chamber is formed by attaching the flexible film of a predetermined shape to an inner wall surface of the container body. 
   Preferably, the pressurized fluid supply passage is formed by sealing a groove formed in an inner surface of the container body with the flexible film. 
   Preferably, the stirring chamber has an open passage communicating with an interior space of the container body surrounding the stirring chamber, and the open passage exerts a resistance against flow of the pressurized fluid to generate a pressure sufficient to press and deform the flexible pouch of the liquid pack when the pressurized fluid is supplied into the stirring chamber. 
   Preferably, the open passage is formed by sealing a groove formed in the inner surface of the container body with a film. 
   Preferably, an interior of the container body is a sealed space, and the liquid is discharged by pressing the liquid pack by pressure of the pressurized fluid supplied through the open passage. 
   Preferably, the liquid container further includes a pressure chamber containing the liquid pack and formed to press the liquid pack by the pressurized fluid supplied into the pressure chamber, and the stirring chamber is formed in the pressure chamber. 
   Preferably, the liquid container further includes a connecting passage connecting the stirring chamber and the pressure chamber to carry the pressurized fluid supplied through the pressurized fluid supply passage into the stirring chamber to the pressure chamber. A resistance against the flow of the pressurized fluid flowing through the connecting passage is higher than a resistance against the pressurized fluid flowing through the pressurized fluid supply passage. 
   Preferably, the stirring chamber is disposed so as to press a lower part, with respect to a direction in which gravity acts, of the flexible pouch of the liquid pack while the liquid container is in use. 
   Preferably, the liquid container further includes a stirring bar placed in the flexible pouch to enhance a stirring effect of flow of the liquid in the flexible pouch of the liquid pack caused by a deformation of the low-rigidity member of the stirring chamber. 
   Preferably, the stirring bar is disposed near a part, which is to be deformed by the low-rigidity member of the stirring chamber when the low-rigidity member is deformed, of the flexible pouch of the liquid pack. 
   Preferably, the stirring bar is disposed above a part, which is to be deformed by the low-rigidity member of the stirring chamber when the low-rigidity member is deformed, of the flexible pouch of the liquid pack. 
   Preferably, the liquid pack is provided with a spout through which the liquid contained in the liquid pack is discharged, and the stirring bar has one end fixed to the spout. 
   Preferably, the liquid container is a liquid cartridge which is configured to be detachably attached to a container holding part of the liquid-consuming apparatus. 
   The liquid container according to the present invention having the above-mentioned characteristic features makes the construction of the liquid-consuming apparatus to which the liquid container is mounted neither complicated nor large, and can prevent the uneven distribution of ingredient concentration in the liquid held in the liquid container. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become apparent from the following description taken in connection with the accompanying drawings, in which: 
       FIG. 1  is a plan view of an ink-jet recording apparatus provided with an ink cartridge in a preferred embodiment according to the present invention; 
       FIGS. 2A ,  2 B and  2 C are a side elevation, a sectional view take on the line B-B in  FIG. 2A  and a side elevation of an essential part of a container body, respectively, of the ink cartridge in the preferred embodiment; 
       FIG. 3  is an exploded perspective view of the ink cartridge shown in  FIGS. 2A to 2C ; 
       FIG. 4  is an exploded perspective view of the ink cartridge shown in  FIGS. 2A to 2C , taken from a direction different from that from which the exploded perspective view shown in  FIG. 3  is taken; 
       FIGS. 5A and 5B  are an enlarged side elevation of an essential part of the container body of the ink cartridge shown in  FIGS. 2A to 2C  and a plan view of a section in a plane including a compressed air supply passage, respectively; 
       FIGS. 6A ,  6 B and  6 C are a vertical sectional view, a sectional plan view of a section in a plane including a spout, and a sectional plan view of a stirring chamber in an expanded state, respectively, of the ink cartridge shown in  FIGS. 2A to 2C ; 
       FIG. 7  is a partly cutaway perspective view of an ink pack included in the ink cartridge shown in  FIGS. 2A to 2C ; 
       FIGS. 8A ,  8 B and  8 C are views of a U-shaped member included in the ink cartridge shown in  FIGS. 2A to 2C , taken from different angles, respectively; 
       FIGS. 9A ,  9 B and  9 C are sectional views of the ink cartridge shown in  FIGS. 2A to 2C  in a state where the ink cartridge is fully filled with the ink, a state where the ink cartridge is not pressed and the ink is being consumed and a state where the ink cartridge is pressed and the ink is being consumed, respectively; 
       FIG. 10  is a perspective view of an essential part of a container body included in an ink cartridge in a modification of the ink cartridge shown in  FIGS. 2A to 2C ; 
       FIG. 11  is an exploded perspective view of an ink cartridge in another modification of the ink cartridge shown in  FIGS. 2A to 2C ; 
       FIGS. 12A ,  12 B and  12 C are a perspective view, a side elevation and a sectional view taken on the line A-A in  FIG. 12B , respectively, of an essential part of the container body of the ink cartridge shown in  FIG. 11 ; and 
       FIGS. 13A and 13B  are perspective views of the ink cartridge shown in  FIG. 11  in a state where the ink cartridge is being assembled and a state where the ink cartridge is completed, respectively. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An ink cartridge, namely, a liquid container, for an ink-jet recording apparatus in a preferred embodiment according to the present invention will be described with reference to the accompanying drawings. 
   First, an ink-jet recording apparatus provided with the ink cartridge embodying the present invention will be described with reference to  FIG. 1 . 
   Referring to  FIG. 1 , an ink-jet recording apparatus  100  has a main case  101 , a platen  102 , a guide rod  103 , a carriage  104 , a timing belt  105 , a carriage driving motor  106 , and a recording head  107 , namely, a liquid ejecting head. The ink-jet recording apparatus  100  is provided with valve units  108  and a pressurizing pump  109 . 
   The main case  101  is a box of a shape substantially resembling a rectangular solid. The main case  101  is provided with a cartridge holder  110  in a right end part, as viewed in  FIG. 1 , thereof. Four ink cartridges  1 , namely, liquid containers, in a preferred embodiment according to the present invention, are detachably mounted on the cartridge holder  110 . The four ink cartridges  1  contain a black ink, a yellow ink, a magenta ink, and a cyan ink, respectively. 
   The platen  102  is extended parallel to a scanning direction in which the recording head  107  moves in the main case  101 . The platen  102  supports a recording medium, not shown, fed by a paper feed means, not shown. The recording medium is fed in a feed direction perpendicular to the scanning direction. 
   The guide rod  103  having the shape of a bar is extended parallel to the scanning direction parallel to the platen  102  in the main case  101 . The guide rod  103  penetrates the carriage  104  so that the carriage  104  is slidable on the guide rod  103  to guide the carriage  104  disposed opposite to the platen  102  for reciprocation in directions parallel to the scanning direction. 
   The carriage driving motor  106  is interlocked with the carriage  104  by the timing belt  105 . The carriage driving motor  106  is supported on the main case  101 . The carriage driving motor  106  operates to drive the carriage  104  through the timing belt  105  for reciprocation along the guide rod  103  in directions parallel to the scanning direction. 
   The recording head  107  is provided with a plurality of nozzles to eject ink drops toward the platen  102 . The valve units  108  are mounted on the carriage  104 . The valve units  108  hold the inks temporarily, adjust the pressures of the inks and supply the inks of adjusted pressures to the recording head  107 . This ink-jet recording apparatus  100  is provided with four valve units  108  respectively for the black ink, the yellow ink, the magenta ink and the cyan ink. 
   The pressurizing pump  109  is connected to a pressure measuring device  112  by a connecting tube  111 . Air supply tubes  113  connect the pressure measuring device  112  to the ink cartridges  1 , respectively. The ink cartridges  1  are connected to the valve units  108  by ink supply tubes  114 , respectively. 
   An ink cartridge  1  in a preferred embodiment according to the present invention will be described with reference to  FIGS. 2A to 9C . 
   The ink cartridge  1  includes a container body  11  having the shape of a rectangular solid as shown in  FIGS. 2A to 2C . As shown in  FIGS. 3 and 4 , the container body  11  has a main member  12  having one open side, and a cover  13  for hermetically covering the open side of the main member  12 . 
   A formed film member  14  is attached to the inner surface of the main member  12 . The formed film member  14  is formed of a film and has a solid part of a predetermined three-dimensional shape and a flat part of a predetermined planar shape. A U-shaped member  15  substantially resembling the letter U and an ink pack  10  are contained in the container body  11 . The ink pack  10  includes a flexible pouch  16  holding the ink. 
   As shown in  FIGS. 8A to 8C , the U-shaped member  15  has a pair of restricting parts  17  and a holding cross bar  18  having opposite ends connected to the restricting parts  17 . The restricting parts  17  are in contact with bent walls  16   a  ( FIGS. 3 and 4 ), which bend as the ink contained in the ink pack  10  is consumed, of the flexible pouch  16  to restrict the bent walls  16   a  from bending outward and to make the bent walls  16   a  bend inward. The restricting parts  17  extend substantially over the overall length of the flexible pouch  16  of the ink pack  10  in the back-and-forth direction. 
   As shown in  FIGS. 6A and 9C , each of the restricting parts  17  has a width substantially corresponding to the thickness of an interior space in the container body  11  and has a length substantially corresponding to the overall length of the container body  11  in the back-and-forth direction. As shown in  FIGS. 8A to 8C , each restricting part  17  is provided with a plurality of triangular ribs (transverse contact parts)  17   a  and a longitudinal, straight rib (longitudinal contact part)  17   b . The triangular ribs  17   a  come into linear contact with the bent wall  16   a  of the flexible pouch  16  of the ink pack  10  along the entire thickness of the flexible pouch  16 . The longitudinal, straight rib  17   b  comes into contact with the bent wall  16   a  of the flexible pouch  16  along a straight line in the back-and-forth direction of the ink pack  10 . 
   Referring to  FIGS. 3 and 4 , a holding slope  19  is formed in the back end of the space in the main member  12 . A tapered back end part of the flexible pouch  16  of the ink pack  10  is held between the holding slope  19  and a sloping part  18   a  ( FIGS. 8B and 8C ) of the holding cross bar  18  of the U-shaped member  15  to secure a back part of the ink pack  10 . A holding slope  20  is formed in the front end of the space in the main member  12 . A tapered front end part of the flexible pouch  16  of the ink pack  10  is held between the holding slope  20  and the sloping surface of a front holding member  21  disposed in a front part of the space in the container body  11  to secure a front part of the ink pack  10 . 
   As shown in  FIGS. 3 and 4 , a spout  22  is attached to the front end of the flexible pouch  16 . The spout  22  is fitted in an opening  12   a  formed in the front wall of the main member  12  of the container body  11 . A gap between the spout  22  and the side surface of the opening  12   a  is sealed by a sealing member  23 . The ink contained in the ink pack  10  is discharged through the spout  22 . 
   The open side of the main member  12  is hermetically covered with a film  25  to form a pressure chamber  26  in the container body  11  as shown in  FIGS. 5A and 5B . The recording apparatus supplies compressed air into the pressure chamber  26  to compress the flexible pouch  16  of the ink pack  10  to deliver the ink held in the ink pack  10  to the recording apparatus. 
   As shown in  FIGS. 5A and 5B , a protrusion (low-rigidity member)  14   a  of the formed film member  14  defines an expandable-and-contractile stirring chamber  27  in the pressure chamber  26 . A compressed air supply passage  28  is formed to extend from an outer wall surface of the container body  11  to the inside thereof, so as to supply compressed air into the stirring chamber  27 . A part of the compressed air supply passage  28  is formed by sealing a groove  29  formed in the inner surface of a wall of the main member  12  of the container body  11  with a projecting part  14   b  of the formed film member  14 . 
   The stirring chamber  27  communicates with the pressure chamber  26  by means of an open passage  30 . The open passage  30  is formed by sealing a groove  31  formed in the inner surface of the wall of the main member  12  of the container body  11  with a flat part  14   c  of the formed film member  14 . The groove  31  forming the open passage  30  exerts a resistance against the flow of compressed air supplied into the stirring chamber  27  so that a pressure capable of compressing and deforming the flexible pouch  16  of the ink pack  10  is generated in the stirring chamber  27 . More specifically, the groove  31  forming the open passage  30  has a narrow width and is formed like a labyrinth as shown in  FIG. 5A . Thus resistance exerted by the open passage  30  against the flow of the compressed air is higher than that exerted by the compressed air supply passage  28  against the flow of the compressed air. 
   As shown in  FIG. 5A , compressed air can be surely supplied into the stirring chamber  27  through the compressed air supply passage  28  in a state where the stirring chamber  27  is fully compressed by the ink pack  10  fully filled up with the ink because the groove  29  defining the compressed air supply passage  28  is extended and connected to the entrance of the open passage  30  in the stirring chamber  27 . 
   Referring to  FIGS. 6A to 6C  and  7 , a stirring bar  24  is placed in the flexible pouch  16  of the ink pack  10  and the front end of the stirring bar  24  is fixed to the spout  22 . The stirring bar  24  is provided with many slant grooves  24   a  to enhance the stirring effect of the stirring bar  24 . As shown in  FIG. 6A , the stirring chamber  27  is disposed in a lower part of the container body  11  so as to press a lower part, with respect to a direction in which gravity acts, of the flexible pouch  16  of the ink pack  10  while the ink cartridge  1  is in use. The stirring bar  24  is disposed near and above a part, which is to be deformed due to the deformation of the stirring chamber  27 , of the flexible pouch  16  of the ink pack  10 . 
   Functions of the ink cartridge  1  in this embodiment will be described with reference to  FIGS. 9A to 9C . 
     FIG. 9A  shows the ink pack  10  fully filled with the ink of a new ink cartridge  1 . When the ink pack  10  is fully filled with the ink, the ink pack  10  maintains the same shape both in a pressurized state where compressed air is supplied into the container body  11  and an unpressurized state where compressed air is not supplied into the container body  11 . 
   From a state shown in  FIG. 9A , as the ink is consumed and the quantity of the ink contained in the ink pack  10  decreases, the thickness of an upper part of the flexible pouch  16  of the ink pack  10  decreases as shown in  FIG. 9B  where no compressed air is supplied into the container body  11 . 
   When the pressurizing pump  109  is actuated to supply compressed air through the compressed air supply passage  28  into the stirring chamber  27  in a state shown in  FIG. 9B , the stirring chamber  27  expands so as to bulge out toward the flexible pouch  16  of the ink pack  10  as shown in  FIG. 9C . Consequently, a lower part of the flexible pouch  16  of the ink pack  10  is pressed and partially deformed and the ink contained in the flexible pouch  16  is caused to flow and is stirred. The stirring bar  24  disposed near and above the part of the flexible pouch  16  deformed by the expanded stirring chamber  27  disturbs the flow of the ink in the flexible pouch  16  to enhance the stirring effect of the flow of the ink. 
   The compressed air supplied into the stirring chamber  27  flows through the open passage  30  into the pressure chamber  26 . Consequently, the flexible pouch  16  of the ink pack  10  is compressed and the ink can be urged to flow from the ink cartridge  1  toward the recording apparatus. 
   Thus, at the start of the printing operation of the recording apparatus, the stirring chamber  27  is expanded to carry out an automatic stirring operation for stirring the ink contained in the flexible pouch  16 , before the flexible pouch  16  of the ink pack  10  of the ink cartridge  1  in this embodiment is compressed to supply the ink to the recording apparatus. Since compressed air is not supplied to the stirring chamber  27  while the recording apparatus is not in operation, unnecessary compression of the flexible pouch  16  of the ink pack  10  can be avoided while the recording apparatus is not in operation. The construction of the recording apparatus can be simplified by using a common pressure source for both pressing the ink pack  10  and expanding the stirring chamber  27 . 
   The stirring operation by the expansion of the stirring chamber  27  may be performed not only at the start of the printing operation, but also at any suitable time when necessary. 
   The pressurizing pump  109  may be capable of alternately performing a discharge operation and a suction operation to make the stirring chamber  27  perform expansion and contraction alternately. 
   As apparent from the foregoing description, the ink cartridge  1  in this embodiment is capable of surely preventing the uneven distribution of ingredient concentration in the ink contained therein without intensifying the structural complicacy of the ink-jet recording apparatus and without enlarging the ink-jet recording apparatus. When a pigment ink is used for printing, the ink cartridge  1  is particularly effective in preventing the uneven sedimentation of the pigment particles in the ink cartridge  1 . 
   As obvious from  FIG. 9B , the upper bent wall  16   a  of the flexible pouch  16  of the ink pack  10  bends as the ink contained in the ink pack  10  is consumed. The restricting part  17  restricts the bending of the upper bent wall  16   a  so that the upper bent wall  16   a  surely bends inward. Thus it is possible to prevent the outward bending of the bent wall  16   a  of the flexible pouch  16  and resultant increase in resistance against the bending of the bent wall  16   a , and increase in the quantity of the ink that is unused and remains in the ink pack  10 . 
   Since the triangular ribs  17   a  of the restricting part  17  are in contact with the bent wall  16   a  of the flexible pouch  16  of the ink pack  10  over the entire width of the bent wall  16   a  in the direction of the thickness of the bent wall  16   a , the concentration of impulsive force on the folding line of the bent wall  16   a  can be avoided when the flexible pouch  16  of the ink pack  10  is compressed, and the restricting parts  17  are able to hold the ink pack  10  securely in place in the container body  11 . 
   Particularly, in the ink cartridge  1  in this embodiment, the bent walls  16   a  of the flexible pouch  16  of the ink pack  10  are pressed against the restricting parts  17  when the stirring chamber  27  is expanded for a stirring operation. Then, it is very effective to avoid the concentrated, repetitive application of impulsive force on the bent walls  16   a.    
   Unification of the restricting parts  17  and the holding cross bar  18  in a single member reduces the number of parts. 
   The flexible pouch  16  of the ink pack  10  of the ink cartridge  1  in this embodiment is compressed by compressed air when the recording apparatus operates for printing. An ink cartridge provided with an ink pack that is not compressed when the recording apparatus operates for printing may be provided with the foregoing stirring mechanism and restricting parts. 
   An ink cartridge in a modification of the ink cartridge  1  in the preferred embodiment will be described with reference to  FIG. 10 . 
   As shown in  FIG. 10 , restricting parts  17  are formed integrally with a container body  11 . The restricting parts  17  are formed on the inner surface of a main member  12  included in the container body  11  at intervals along the length of an ink pack  10  in the back-and-forth direction. The restricting parts  17  are in contact with the bent wall  16  over substantially entire thickness of the flexible pouch  16  of the ink pack  10 . 
   The ink cartridge in the modification is expected to have the same effect as that of the foregoing embodiment. Moreover, since the restricting parts  17  are formed integrally with the container body  11 , the number of parts can be reduced and manufacturing processes can be simplified. 
   Referring to  FIGS. 11 to 13B  showing an ink cartridge in another modification, a container body  11  includes a main member  12  having an open front end and a cover  13  hermetically covering the open front end of the main member  12 . An O-ring  32  is held between the main member  12  and the cover  13  to seal the container body  11 . The modification does not need any member corresponding to the film  25  shown in  FIGS. 3 and 4 . 
   The upper and the lower walls of the main member  12  of the ink cartridge in the modification are bent inward so as to protrude into the interior of the main member  12  to form restricting parts  17  having a triangular cross section. 
   The ink cartridge in the modification is expected to have the same effect as that of the foregoing embodiment. Moreover, since the ink cartridge in the modification does not need any members corresponding to the film  25  and the restricting parts  17  separate from the main member  12  shown in  FIGS. 3 and 4 , the number of parts can be reduced and manufacturing processes can be simplified. 
   Although the invention has been described in terms of the preferred embodiments thereof with a certain degree of particularity, obviously many changes and variations are possible therein. It is therefore to be understood that the present invention may be practiced otherwise than as specifically described herein without departing from the scope and spirit thereof.

Technology Classification (CPC): 1