Retainer for self-standing packaging bags supplied to a bag-packing packaging machine

A retainer with a bottomed retaining hole and a pair of insertion grooves so that a self-standing packaging bag in a closed state is set in the retaining hole and insertion grooves and then the bag is opened and kept opened during packaging operations. The retaining hole that is vertically formed accommodates the body portion of the self-standing packaging bag, and both side edges of the bag are inserted in the insertion grooves which are vertically installed in symmetrical positions on both sides of the retaining hole. The depth of the bottomed retaining hole and insertion grooves is set to be smaller than the length of the self-standing packaging bag, the spacing between the end portions of the insertion grooves is set to be equal to or greater than the width of an unopened self-standing packaging bag, and the angle between the inside surfaces of the retaining hole and insertion grooves is set at or about 90 degrees.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a retainer for accommodating a
 self-standing packaging bag that can stand by itself in an open state and
 for supplying such bags to a bag-packing packaging machine.
 2. Prior Art
 Japanese Patent Application Laid-Open (Kokai) No. S58-73501 discloses one
 type of a bag-packing packaging machine.
 This machine is designed so that packaging bags (which are empty) are
 accommodated in retainers, and the retainers are continuously conveyed.
 Various packaging operations such as filling the bags with contents to be
 packaged and sealing the bag openings, etc. are performed during the
 conveying process.
 Each retainer is provided with a hollow space and a pair of vertical side
 grooves. The hollow space has a shape that corresponds to the
 cross-sectional configuration of the body portion of the packaging bag in
 an open state (i.e., a state in which the opening of the bag is open and
 the body portion of the bag is inflated), and the pair of vertical side
 grooves guide the side edges of the packaging bag. The packaging bag in a
 closed state is put in the hollow space and is opened and filled with the
 contents by a filling device.
 Accordingly, the above-described filling device requires a bag-opening
 means such as a vacuum suction picker; and as a result, the structure of
 the device is extremely complicated. Furthermore, the retainer does not
 have any means for maintaining the opened packaging bag "as is" in its
 open state. Accordingly, even though the packaging bag once opened has
 some degree of shape retention if the bag is a self-standing bag, the bag
 opening tends to close as a result of vibration during the conveying
 process and of the recovery force of the packaging bag itself. Thus, when
 the bag is successively filled with liquid and solid substances during the
 conveyance, it is necessary to install a bag-opening means for each of
 liquid and solid substances in the filling devices.
 Another prior art, Japanese Utility Model Application Laid-Open (Kokai) No.
 S58-904 discloses that an open self-standing packaging bag (empty bag) is
 placed in a retainer, the retainer is successively conveyed to a filling
 station and sealing station, etc., and various packaging operations such
 as filling of the bag with contents and sealing of the bag opening, etc.
 are successively performed.
 The retainer of this prior art includes a plate which has a retaining hole
 and insertion grooves. The retaining hole is in a shape that more or less
 coincides with the cross-sectional shape of the body portion of a
 self-standing packaging bag of an open state, and the insertion grooves
 are formed so that both side edges of the packaging bag are inserted and
 held therein. Thus, in this retainer, the packaging bag of an open state
 is set in the retaining hole and insertion grooves of the plate. However,
 there is no clear description about the means that keeps the open state of
 the bag in this prior art; therefore, it appears that the bag opening
 cannot be prevented from closing by way of recovery force of the packaging
 bag.
 Still another prior art, Japanese Patent Application Laid-Open (Kokai) No.
 H10-236448 discloses a retainer that is equipped with a packaging bag
 retaining means. With this retainer, a packaging bag is held in an open
 state, and the bag can be reliably positioned at a specified location.
 However, the structure of the retainer of this prior art is complicated,
 and the maintenance and cleaning is not accomplished easily.
 SUMMARY OF THE INVENTION
 The present invention is devised in light of the problems with the
 above-described conventional retainers.
 The primary object of the present invention is to provide a retainer which
 can maintain the open state of a self-standing packaging bag during
 various packaging operations after the self-standing packaging bag is set
 in the retainer in a closed state. Also, the retainer of the present
 invention does not have a complicated structure.
 More specifically, the self-standing packaging bag retainer according to
 the present invention is characterized by the fact that: a bottomed
 retaining hole, which has a cross section that is capable of accommodating
 the body portion of an open self-standing packaging bag, is vertically
 formed; a pair of insertion grooves into which both side edges of the
 self-standing packaging bag are inserted are vertically formed in
 diametric positions of the retaining hole; the depth of the bottomed
 retaining hole and the insertion grooves is set so as to be smaller than
 the length (or height) of the self-standing packaging bag; and the outside
 surface of the open self-standing packaging bag contacts the inside
 surface of the retaining hole or the inside surfaces of the boundary areas
 between the retaining hole and the insertion grooves; so that the
 self-standing packaging bag is prevented from closing once it is put in
 the retainer.
 In the above structure, it is desirable that the angle formed by the
 direction of an imaginary extension line of the inside surfaces of the
 bottomed retaining hole and the direction of an imaginary extension line
 of the insertion grooves in the boundary areas between the bottom
 retaining hole and the insertion grooves be set exactly at or about 90.
 This angle can vary according to the width of the insertion grooves, the
 shape and material of the boundary areas, the material of the packaging
 bag, and other factors. The object of the present invention can be
 achieved by setting the above-described angle at an angle of up to
 approximately 110 degrees. A desirable (horizontal) cross-sectional shape
 for the bottomed retaining hole is circular, elliptical, racetrack-shaped
 and some other shapes similar to these shapes. In other words, a
 cross-sectional shape which conforms to the outer configuration of the
 body portion of the packaging bag in an open state, or a rectangular
 cross-sectional shape, etc. may be employed.
 Furthermore, the retainer of the present invention may be provided with
 projections in the boundary areas between the retaining hole and insertion
 grooves. The projections respectively protrude inward or toward the inside
 of the retaining hole and are formed continuously on the inside surfaces
 of the retaining hole. With these projections, the side surfaces of the
 opened self-standing packaging bag come into contact with the projections
 so that the self-standing packaging bag is prevented from closing. The
 projections can be formed separate from the retainer main body. In this
 case, the projections are designed so as to undergo elastic deformation
 and to be oriented toward the inside of the retaining hole so that the
 spaces between the tip ends of the adjacent projections become narrower
 toward these tip ends. The opened packaging bag is prevented from closing
 with the use of the thus structured projections.
 Furthermore, in the above-described retainer, it is also possible to form a
 pair of suction plate insertion holes. Preferably, these holes are formed
 in the lower portions of the side walls of the retainer so that the
 suction plate insertion holes are oriented perpendicular to the insertion
 grooves and pass through the retainer from the outer circumferential
 surface to the retaining hole. With this structure, when the bag in the
 retainer is opened, a pair of suction plates are inserted via the suction
 plate insertion holes, and both surfaces of the lower portion of the bag
 are pulled toward both sides of the retainer (in this case, the upper
 portion of the bag, i.e., the portion protruding from the retainer, is
 also simultaneously pulled toward both sides of the retainer). Thus, the
 self-standing bag can be more or less uniformly opened from its bottom to
 the bag opening. When the bag is thus opened, it is preferable to blow
 compressed air into the interior of the bag through the bag opening.
 Furthermore, in the retainer of the present invention, printing holes may
 be formed in appropriate positions in one or both side walls of the
 retainer. The printing holes are oriented perpendicular to the insertion
 grooves and pass through the retainer from the outer circumferential
 surface to the retaining hole. Ink from the print head of an ink jet
 printer can be sprayed onto the surfaces of the packaging bag through
 these printing holes so as to print, for instance, the date of manufacture
 on the bag.
 Furthermore, each of the insertion grooves of the retainer of the present
 invention may be divided into a lower region and an upper region. The
 lower region has substantially vertical inside wall surfaces extending
 from the bottoms of the insertion grooves to a specified height, and the
 upper region has inside wall surfaces that are continuous to the inside
 wall surfaces of the lower region and are inclined outward toward the top
 of the retainer. With this structure, when both side edges of the filled
 packaging bag are gripped and pulled laterally (to the left and right) by
 a gripping means during heat sealing process of the bag, both side edges
 of the packaging bag can easily enter the upper regions of the insertion
 grooves without any great resistance.
 When a closed self-standing packaging bag is set in the retainer, the
 spacing between end portions of the pair of insertion grooves needs to be
 equal to or greater than the width of the bag in a closed state. Moreover,
 when an open self-standing packaging bag is set in the retainer, the
 spacing between the end portions of the pair of insertion grooves needs to
 be equal to or greater than the width of bag in an open state.
 Accordingly, for bags of the same width, the spacing between the end
 portions of the pair of insertion grooves can be set at a smaller value
 when the bag is set in the retainer in the closed state and not in an open
 state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The retainer 1 shown in FIGS. 1(a), 1(b), 2(a) and 2(b) has an outer
 circumferential shape that comprises mutually parallel flat surfaces 2a
 and 2b and arc-shaped surfaces 3a and 3b which connect these flat surfaces
 2a and 2b (i.e., the retainer has the external shape that is formed by
 making parallel longitudinal cuts on both sides of a solid cylinder).
 Groove-shape engaging cut-outs 4 which are cut in a V shape from the
 arc-shaped surfaces 3a and 3b toward the respective flat surfaces 2a and
 2b are formed at locations approximately 1/3 from the bottom.
 Furthermore, a retaining hole 5 which has a bottom and which has a circular
 cross section is formed in the vertical direction inside the retainer 1.
 Also, a pair of insertion grooves 6 are formed in symmetrical or
 diametrical positions on both sides or on the left and right of the
 bottomed retaining hole 5. Both insertion grooves 6 have the same depth as
 each other with respect to the vertical direction as shown in FIGS. 1(b)
 and 2(b). A hole 7a which passes through to the outside of the retainer 1
 is formed in the center of the bottom 7 of the retaining hole 5 and
 insertion grooves 6.
 The retaining hole 5 has a size and cross-sectional shape that allows the
 accommodation of the body portion of an open self-standing packaging bag,
 and the spacing S between the walls of the end portions of the pair of
 insertion grooves 6 (see FIG. 1(a)) is set to be equal to or greater than
 the width of the packaging bag in a closed state. Furthermore, the
 boundary areas 8 between the inside wall surfaces of the retaining hole 5
 and insertion grooves 6 are formed with curvatures R by chamfering. Also,
 the angle .theta. defined by an imaginary linear extension line (tangent)
 5a of the inside surfaces of the retaining hole 5 and an imaginary linear
 extension line 6a of the inside surfaces of the insertion grooves 6 is set
 to be fairly close to 90 degrees.
 Each of the insertion grooves 6 has a pair of more or less perpendicular
 inside wall surfaces and end portion walls that face each other. Only the
 upper end portions of the insertion grooves 6 are inclined upward and
 outward in the shape of a hopper, so that side edges of a packaging bag
 can be easily brought into the insertion grooves 6.
 The retainer 1 thus formed is continuously conveyed; and during the
 conveying process, various packaging operations such as filling with
 contents and sealing of the bag opening, etc. are performed on the
 self-standing packaging bag accommodated in the retainer 1. One example of
 this process is shown by way of steps (a) through (g) in FIG. 3.
 Step (a): The empty retainer 1 is conveyed to a packaging bag supply
 position.
 Step (b): A packaging bag W is set in the retainer 1 with its part of the
 body portion and its side edges in the insertion grooves 6 of the retainer
 1. In this step, the packaging bag W is in a closed state. Since the
 spacing S between the walls of the end portions of the insertion grooves 6
 are equal to or greater than the width of the bag W, the bag can easily be
 set in the retainer 1.
 Step (c): The bag is opened by an opening device such as vacuum suction
 plates, etc. at a bag-opening position. If necessary, the bag is opened by
 blowing air into the interior of the bag. As a result of this opening
 action, the body portion of the packaging bag W expands (or inflated) in
 the retaining hole 5 of the retainer 1, and the part of the body portion
 of the bag W in the insertion grooves 6 is withdrawn from the insertion
 grooves, leaving the end edges of the bag W (see FIG. 4) in the insertion
 grooves 6.
 Step (d): The retainer 1 is further conveyed; and at a solid content
 filling position, a hopper H is inserted into the bag opening, and the
 opened packaging bag W is filled with solid contents.
 Step (e): Next, at a liquid content filling position, a nozzle N is
 inserted into the bag, and the packaging bag W is filled with liquid
 contents.
 Step (f): At a sealing position, both edges of the packaging bag W are
 pulled side-way by grippers G so that the upper edge of the bag opening is
 closed; at the same time, the bag opening is heat-sealed by sealing bars
 B.
 Step (g): At a discharge position, the sealed packaging bag W is taken out
 of the retainer; and the retainer is collected and conveyed back to the
 packaging bag supply position.
 Generally, the open self-standing packaging bag has some degree of shape
 retention characteristics (a property of tending not to return to its
 original state). However, the bag opening tends to be closed as described
 above due to the vibrations during conveying and the recovery force of the
 packaging bag itself. When the retainer 1 of the present invention is
 used, the outer surfaces of the packaging bag W come into contact with
 portions near the boundary areas 8 that are between the retaining hole 5
 and the insertion grooves 6; as a result, recovery (or closing) of the
 packaging bag is prevented, and the bag can be held in more or less the
 initial open state during conveying and the subsequent filling process.
 The reason that the recovery or closing of the opening is prevented is as
 follows: in the above-described retainer 1, the retaining hole 5 has a
 circular cross section, and the angle .theta. defined by the extension
 line 5a of the inside surfaces of the retaining hole 5 and the extension
 line 6a of the inside wall surfaces of the insertion grooves 6 is set so
 that this angle is about 90 degrees; accordingly, almost all of the
 recovery force (or closing force) of the packaging bag W in an open state
 becomes a component that presses perpendicularly against the inside
 surfaces of the retaining hole 5 and boundary areas 8, and the component
 that is oriented along the outer surfaces of the packaging bag W (i.e.,
 the component that acts to pull the bag out of the insertion grooves 6)
 becomes extremely small.
 In order to prevent closing of the opening of the bag in this way, it is
 desirable that the angle .theta. is set to be about 90 degrees. By way of
 disposing an element that has a large coefficient of friction (e. g.,
 rubber) on the inside surfaces of the retaining hole 5 and/or the inside
 surfaces of the boundary areas 8, the permissible range of this angle
 .theta. can be increased.
 It is also possible to set the angle .theta. to be less than 90 degrees as
 seen in the retainer 11 shown in FIG. 5(a). This arrangement is effective
 in preventing recovery or closing of the bag; however, with this
 arrangement, the inside surfaces of the retaining hole 5 protrude slightly
 inward in the vicinity of the boundary areas 8, and the resistance during
 bag opening process tends to increase. Accordingly, it is desirable that
 the angle .theta. not be set at an angle of any less than approximately 80
 degrees. The retainers 12 and 13 shown in FIGS. 5(b) and 5(c) illustrate
 other examples of the retainer that have different retaining hole shapes.
 In the above-described retainers 1 and 11 through 13, a narrower width P of
 the insertion grooves is more effective in preventing recovery or closing
 of the open packaging bag W. However, if the width P is too narrow, it is
 difficult to accomplish a quick set of the packaging bag W in the
 retainer. Furthermore, the curvature R of the boundary areas 8 is provided
 so as to prevent damages and pinholes in the bag surfaces when the
 packaging bag W is pulled out of or brought into the insertion grooves.
 However, if this curvature is too great, the bag can easily be closed by
 itself. Accordingly, the width P and the curvature R of the boundary areas
 should be set in view of the above-described factors and with
 comprehensive consideration given to the size of the angle .theta. and the
 materials of the boundary areas and packaging bag, etc. For a standard
 self-standing packaging bag (that has a bag width of approximately 60 to
 150 mm), these values may be determined using an insertion groove width P
 of approximately 1 to 5 mm (i.e., in terms of the relationship to bag
 thickness, a width of (bag thickness +3 mm) or less) and a boundary area
 curvature radius R of approximately 1 to 5 mm as guidelines.
 FIG. 6 shows another embodiment of the retainer of the present invention in
 which the shapes of the retaining hole and insertion grooves are different
 from those of the previous embodiments.
 In the retainer 14 shown in FIG. 6, projections 15 are integrally formed in
 the boundary areas between the retaining hole 5 and the insertion grooves
 6. These projections 15 are oriented toward the inside of the retaining
 hole 5 and protrude in such a direction that the projections 15 approach
 each other. The surfaces of the projections 15 are formed so as to be
 smoothly continuous to the inside surfaces of the retaining hole 5 and
 insertion grooves 6. The angle .theta. between an imaginary linear
 extension line 5a of the retaining hole 5 and an imaginary linear
 extension line 6a of the insertion grooves 6 is slightly greater than 90
 degrees. In this retainer 14 of FIG. 6, however, since the projections 15
 are formed so as to substantially constitute portions of the inside
 surfaces of the retaining hole 5, the substantial angel .theta. is similar
 to that of the retainer 11 described in the previous embodiment, thus
 assuring a good recovery-preventing effect. The spacing q of the tip ends
 of the projections 15 is determined based upon the same factors as the
 previously described width P of the insertion grooves.
 The reason that the mutually parallel flat surfaces 2a and 2b are formed in
 the retainer of the present invention is to insure proper directional
 characteristics during automated conveying by means of a conveyor, etc.
 The reason that the hole 7a is formed in the bottom 7 of the retainer is
 to allow drainage of cleaning water. Furthermore, the V-shaped engaging
 cut-outs 4 formed in the outer circumferential surface of the retainer 1
 are used for positioning the retainer by means of a corresponding
 anchoring means when the conveying is stopped. It goes without saying that
 the engaging cut-outs 4 may have various shapes depending upon the type of
 anchoring means used and other factors. Also, anchoring holes such as
 those described in the above-referred Japanese Patent Application
 Laid-Open (Kokai) No. H10-236448 may be employed.
 Furthermore, by forming a part of the outer circumferential shape in the
 direction of height in a cylindrical shape as shown in the retainer 21
 which will be described later (this is not shown in the structure of the
 above-described retainer 1), such a cylindrical portion can be used as a
 guide when the retainer is conveyed by a conveyor (see FIG. 7).
 Furthermore, this type of retainer can be transferred in a stable fashion
 from the conveyor to a star wheel, which is commonly used when conveying
 such retainers to a filling device. In this case, the stability during
 conveying by a conveyor, etc. is further increased by forming the lower
 portion of the retainer in a cylindrical shape. Moreover, the useful life
 of the retainer can be extended by employing (preferably in a detachable
 manner) a slip material that has a small coefficient of friction and a
 large wear resistance (resin, metal, ceramic, etc.) for the bottom of the
 retainer, or by fastening (preferably in a detachable manner) a protective
 member to the outer circumferential surface (especially to the portions
 that contact guide members, etc. of the conveying means).
 FIGS. 7(a), 7(b) and 8 show further embodiments of retainer of the present
 invention.
 The retainer 21 of this embodiment comprises a central part (cylindrical
 part) 22a which has a cylindrical outer circumferential shape, an upper
 part 22b which consists of mutually parallel flat surfaces 23a and 23b and
 arc-shaped surfaces 24a and 24b that connected the flat surfaces 23a and
 23b, and a lower part 22c which also consists of mutually parallel flat
 surfaces 25a and 25b and arc-shaped surfaces 26a and 26b that connect the
 flat surfaces 25a and 25b. Furthermore, as best seen from FIG. 7(a),
 groove-shape engaging cut-outs 27 which are cut in a V shape from the
 arc-shaped surfaces 26a and 26b toward the respective flat surfaces 25a
 and 25b are formed in the lower part 22c immediately beneath the
 cylindrical part 22a.
 Furthermore, a retaining hole 28 which has a bottom and which has a
 horizontally circular cross section is formed in the vertical direction
 inside the retainer 21, and a pair of insertion grooves 29 are formed to
 the same depth in the vertical direction. A hole 30a which passes through
 to the outside of the retainer is formed in the center of the bottom 30 of
 the retaining hole 28 and insertion grooves 29. Moreover, attachment
 grooves 31 are formed in the vertical direction in the boundary areas
 between the retaining hole 28 and the insertion grooves 29, and soft
 rubber projections 32 which possess elasticity are fitted in these
 attachment grooves 31 so as to face inward. The surfaces of the
 projections 32 are formed so as to be smoothly continuous to the inside
 surfaces of the retaining hole 28. As best seen from FIG. 7(a), the space
 between the tip ends of the adjacent two projections 32 narrows toward the
 tip ends of the projections 32, so that the tip ends lightly contact both
 sides of a packaging bag.
 In this retainer 21, since the projections 32 are fitted in the attachment
 grooves 31 so that the projections 32 face inward (or face the retaining
 hole 28), and since the space between the tip ends of the projections 32
 is set so as to be narrow, a part of the body portion of the packaging bag
 (not shown) is withdrawn from the insertion grooves 29 without any great
 resistance when that the bag is opened and inflated; however, the
 projections 32 provides a great resistance against the recovery force (or
 closing) of the packaging bag. As a result, vibration during conveying and
 the recovery force of the bag are resisted and the packaging bag is
 maintained "as is" in an open state. Furthermore, the angle .theta.
 defined by the extension line 28a of the retaining hole 28 and the
 extension line 29aof the insertion grooves 29 is about 90 degrees, and the
 projections 32 are formed so as to virtually constitute a part of the
 retaining hole 28 as in the retainer 14 of the previous embodiment; and
 these features are also effective in preventing recovery or closing of the
 packaging bag.
 The functions of the other elements of the above-described retainer 21 are
 similar to those of the retainer 1 of the previous embodiment. The central
 part 22a is in a cylindrical shape and bulges out in the form of a flange
 as seen from the side as shown in FIG. 8; and positional deviation of the
 retainer 21 is prevented by causing the central part 22a to slide on, for
 instance, guide bars R that are disposed on the conveyor. Furthermore,
 transfer to a star wheel can be stably accomplished as described above.
 The retainer 41 shown in FIGS. 9(a) and 9(b) is similar to the retainer 1
 shown in FIG. 1 (the constituting elements which are the same as in the
 retainer 1 are labeled with the same numbers in FIGS. 9(a) and 9(b)).
 However, this retainer 41 differs from the retainer 1 in that a pair of
 suction plate insertion holes 42 and 43 are formed in both sides of the
 lower portions of the side walls of the retainer 41. The pair of suction
 plate insertion holes 42 and 43 pass through to the retaining hole 5 from
 the outer circumferential surfaces 2a and 2b in a direction perpendicular
 to the axis of the insertion grooves 6.
 During the opening process of a packaging bag in this retainer 41, suction
 plates are respectively inserted through the suction plate insertion holes
 42 and 43, and the lower portions of both sides of the bag are held by
 suction and pulled sideways, so that the lower portion of the
 self-standing packaging bag, which is difficult to open, can be easily
 opened. At the same time, another pair of vacuum suction plates hold both
 sides of the upper portion of the packaging bag (the portion that is
 outside the retainer 41) by vacuum suction and open the bag; and further
 air is blown into the bag if necessary.
 The retainer 51 shown in FIGS. 10(a) and 10(b) is similar to the retainer 1
 shown in FIG. 1 (the constituting elements which are the same as in the
 retainer 1 are labeled with the same numbers in FIGS. 10(a) and 10(b)).
 The retainer 51, however, differs from the retainer 1 in that a printing
 hole 52 which passes through to the retaining hole 5 from the outer
 circumferential surface 2b is formed in the lower portion of the side wall
 of the retainer 51.
 Ink is sprayed onto the surface of a packaging bag (that is in the retainer
 51) from the print head of a fixed jet printer via this printing hole 52,
 so that, for example, the date of manufacture is printed on the bag. The
 printing can be performed on the packaging bag inside the retainer 51 that
 is being conveyed at a constant speed.
 The retainer 61 shown in FIGS. 11(a) and 11(b) is also similar to the
 retainer 1 shown in FIG. 1 (the constituting elements which are the same
 as in the retainer 1 are labeled with the same numbers FIGS. 11(a) and
 11(b)). This retainer 61, however, differs from the retainer 1 in the
 following aspects: each of the insertion grooves 6 consists of a lower
 region 6A which is formed by substantially perpendicular inside wall
 surfaces that extend to a specified height from the bottom of the groove,
 and an upper region 6B which has inside wall surfaces that form
 continuations to the inside wall surfaces of the lower region 6A and
 incline outward toward the top; and the upper regions 6B are formed so as
 to have a considerable depth.
 Because of the thus formed upper regions 6B, a packaging bag can be easily
 inserted into the retainer 61 as in the case of the retainer 1 of FIG. 1.
 In this retainer 61, the end walls also incline outward toward the top in
 addition to the inside wall surfaces in the upper region 6B; however, this
 is not essential. The retainer 61 provides the effects and merits
 described below:
 After the bag is filled with contents, both edges of the packaging bag are
 pulled sideways by grippers G as shown in FIGS. 12 and 13 so as to close
 the bag opening, and then the bag opening is heat-sealed by sealing bars.
 In the case of the retainer 1, as shown in FIG. 13, the body portion of
 the packaging bag W is bulging outward because of the filled contents. As
 a result, it is difficult to pull both edges of the bag W into the
 insertion grooves 6, which have a narrow width; and the slope of the
 spread of the edges of the packaging bag extending from the vicinity of
 the upper ends of the insertion grooves 6 to the grippers G becomes tight.
 Consequently, the portion between the grippers G is not flatly closed (a
 conical bulge a is formed), and wrinkles tends to be formed in the sealed
 area when the bag opening is heat-sealed by the sealing bars. To the
 contrary, in the retainer 61 shown in FIGS. 11(a) and 11(b), the width of
 the upper regions 6B of the grooves 6 is spread as seen from FIG. 11(b);
 thus, even if the body portion of the packaging bag W bulges due to the
 filled contents, both edges of the bag can enter into the wide upper
 regions 6B without any great resistance. Furthermore, both edges of the
 packaging bag up to the grippers G spread with a gradual slope, and the
 area between the grippers G can easily be closed in a flat manner (i.e.,
 the conical bulge a is reduced in size). Accordingly, when the opening of
 the bag is heat-sealed by sealing bars, wrinkles are less likely occur in
 the sealed area. Furthermore, since the bulge a in FIG. 12 is small
 compared to that in FIG. 13, the amount of residual air inside the bulge a
 is also small, and there is little effect of the air (oxidation caused by
 residual air, etc.) on the contents.
 As seen from FIG. 12, where the height h is from the upper edge of the
 packaging bag W to the lower end of the upper regions 6B, the slope of
 both edges of the packaging bag when pulled by the grippers G increases as
 the bag width increases if h is the same. As a result, the conical bulge a
 increases in size so that wrinkles tend to be formed in the sealed area.
 Accordingly, how deep the upper regions 6B should be set in the insertion
 grooves 6 of retainers varies depending upon the size of the packaging bag
 (i.e., the bag width). Furthermore, gripping by the grippers G and sealing
 by the seal bars are performed for the area extending from the upper edge
 of the packaging bag W to the upper ends of the insertion grooves 6,
 therefore, interference of the grippers G, sealing bars and retainer 61
 must be avoided. Thus, regardless of how small the bag size is, the height
 h must be set greater than a certain value to avoid the interference.
 A desirable depth for the upper regions 6B is experimentally determined
 from the standpoint described above. If the self-standing packaging bag is
 the one that has an ordinary vertical height, the height h is roughly
 0.7.times.d or greater (where d is the bag width) and is also 50 mm or
 greater. The value of h may be selected from a range satisfying both of
 these requirements.
 On the other hand, if the upper regions 6B are formed too deep, the lower
 regions 6A naturally become shallow; and a shallow lower region will
 interfere with the prevention of the recovery of a packaging bag from an
 open state. Accordingly, the height h is set at roughly 1.2.times.d or
 less and is also set at roughly 0.6.times.e or less (where e is the length
 of the packaging bag W); and the value of h may be selected from a range
 satisfying both of these requirements.
 In this way, wrinkles during sealing can be suppressed, and the recovery
 (or closing) of the packaging bag from an open state can also be
 prevented. There may also be cases in which the upper regions 6B are not
 formed in the insertion grooves 6. In these cases, a similar effect can be
 obtained by setting the distance between the upper end of the packaging
 bag and the upper end of the retainer as described above.
 If the angle of inclination of the inside wall surfaces in the upper
 regions 6B is too great, the packaging bag W will tend to close from an
 open state; on the other hand, if this angle is too small, it becomes
 difficult for both side edges of the packaging bag to advance into the
 narrow insertion grooves 6B. Accordingly, although this is not a specific
 limitation, it is advisable to set the inclination of one side of each of
 the upper regions to be in the range of 8 to 37 degrees, preferably in the
 vicinity of 15 degrees.
 As seen from the above, the present invention provides a retainer in which
 a self-standing packaging bag in a closed state is inserted into the
 retaining hole and insertion grooves of a retainer, and the open state of
 the bag that is obtained when the bag is opened following insertion can be
 maintained during various packaging operations. In addition, the retainer
 does not have a complicated structure.