Wide type school bag
Patent Information
- Application Number
- JP2017004437U
- Authority / Receiving Office
- JP · JP
- Patent Type
- Utility models
- Current Assignee / Owner
- Filing Date
- 2017-09-28
- Publication Date
- 2025-09-03
- Estimated Expiration
- 2027-09-28
AI Technical Summary
Conventional school bags lack sufficient storage capacity for bulky items like gym clothes and school lunch bags, leading to instability and potential injuries due to swinging during movement, and existing slide fasteners fail to effectively widen the storage compartments to accommodate larger items.
A school bag design featuring a telescopic widening mechanism in the sub-storage chamber with a stretchable gusset that can change from a standard width to a wider size, equipped with a reinforcing plate and a slide fastener system allowing easy expansion and contraction, ensuring stable storage of bulky items.
The design allows for stable storage of bulky items within the school bag, preventing swinging and potential injuries by expanding the sub-storage chamber, thus enhancing safety and usability.
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an improvement of a schoolbag that enables the depth width of the sub-storage room of the schoolbag to be widened.
Background Art
[0002] Conventionally, a schoolbag is formed by successively connecting a main storage room for storing textbooks, notebooks, etc., a sub-storage room for storing various teaching materials, and a front pocket for storing small items in the front-rear direction. Also, recently, the main storage room of the schoolbag is formed in a so-called wide size in order to store A4-sized files and memo pads other than teaching materials. On the other hand, schoolchildren need to carry not only textbooks, notebooks, clear files, pencil cases, arithmetic teaching materials, etc. stored in the schoolbag, but also bulky gym clothes, lunch bags or water bottles.
[0003] The above-mentioned bulky gym clothes, lunch bags or water bottles do not fit in the main storage room or the sub-storage room of the schoolbag, and are hung on the nasu ring provided in the large gusset part of the schoolbag and carried. Therefore, when a schoolchild running to school, the hanging heavy gym clothes bag or lunch bag is likely to swing up and down and left and right. Due to the swinging of this gym clothes bag or lunch bag, the center of gravity of the schoolbag moves, making it difficult for the schoolchild to run or be swung, and there is a risk of injury, such as the gym clothes bag or lunch bag getting caught on the branches of a tree on the way to school or the side mirror of a passing car, which is very dangerous.
[0004] On the other hand, since the slide fastener is easy to handle and inexpensive for opening and closing the opening of the schoolbag, it is widely used. In particular, the slide fasteners used for schoolbags and backpacks are widely used, which are "stop products" type slide fasteners in which either the stop piece on the starting side or the end side is joined.
[0005] In particular, since it is necessary to improve the storage capacity of the main storage room and the sub-storage room of the schoolbag, a schoolbag in which a slide fastener is attached to the gusset part of the schoolbag to improve the storage capacity is known (Patent Documents 1 and 2).
Prior Art Documents
[0006] [Patent Document 1] Utility Model Registration No. 3161321 [Patent Document 2] Utility Model Registration No. 3190801
[0007] However, in the school bag described in Patent Document 1, the slide fasteners attached to the two gussets and the bottom of the secondary storage compartment are of the so-called "stopper product" type, with one or both stopper pieces at the starting or ending point being connected. Therefore, when the slide fastener is pulled to open the opening, the two gussets and the bottom expand into an isosceles triangle shape in cross-section, but the opening width of the secondary storage compartment remains at its original width and cannot be widened. As a result, bulky items such as gym clothes, lunch bags, or water bottles cannot be stored inside.
[0008] The school bag described in Patent Document 2 has slide fasteners attached to three sides of the main storage compartment: the gussets on both sides and the bottom. By opening and closing the slide fasteners, the gussets on both sides and the bottom can be expanded and contracted.
[0009] However, because both ends of the slide fastener are joined together, if the strap extends to the edge of the main storage compartment's opening, the opening cannot be widened, similar to the aforementioned schoolbag. Therefore, the opening width of the main storage compartment is widened by extending the tabs on both ends of the slide fastener beyond the edge of the opening. However, this presents many problems, such as the tabs on both ends of the slide fastener dangling loosely and making the schoolbag look bad. [Summary of the invention] [Problems the invention aims to solve]
[0010] Therefore, since not all textbooks and notebooks stored in school bags are A4 size, and most textbooks and notebooks are B5 size, the storage capacity of the secondary storage compartment 7, which is usually used to store pencil cases and teaching materials, is improved by making the width of the gusset and the bottom of the secondary storage compartment expandable. This allows B5 size textbooks and notebooks to be stored in this secondary storage compartment, and bulky items such as gym clothes bags, lunch bags, or water bottles to be stored in the main storage compartment, eliminating the need to hang gym clothes bags and lunch bags on the outside of the school bag. The aim is to prevent schoolchildren from falling or getting into traffic accidents while commuting to and from school. [Means for solving the problem]
[0011] This invention relates to a school bag 1 in which a main storage compartment 3 for storing textbooks and notebooks, a secondary storage compartment 7 for storing supplementary materials, and a front pocket section 9 for storing small items are provided in the front-to-back direction on the back side of the back panel 2, and the main storage compartment 3, secondary storage compartment 7 and front pocket section 9 are covered by a flap 10 with one end sewn to the upper end of the back panel 2 so as to be openable and closable, wherein the secondary storage compartment 7 is equipped with an expandable and contractible widening mechanism S that changes the width of the gusset from a standard width X to a wide width Y. Furthermore, the widening mechanism S comprises an inner gusset piece 11 formed integrally with a bottom portion and side gusset portions having a wide width Y, and an outer gusset piece 15 provided on the outside of the inner gusset piece 11, which has a movable gusset portion 19 formed by cutting and separating the center of a gusset portion 17 having a standard width X in the width direction, and an opening / closing zipper 22 attached between the movable gusset portion and the gusset portion 17 so that the gusset portion 17 and the movable gusset portion 19 can be separated and connected. When the width of the sub-storage compartment 7 is changed from the standard width X to the wide width Y, the slider 26 of the opening / closing zipper 22 attached to the outer gusset piece 15 is slid to separate the gusset portion 17 and the movable gusset portion 19, and then the inner gusset piece 11 is widened toward the front pocket portion so that it can be changed into a sub-storage compartment 7 having a wide width Y. Furthermore, the sub-storage compartment 7 is characterized by having a reinforcing plate 40 that is foldable when the gusset width is standard width X and can be laid on the inner bottom surface when the gusset width is wide Y, and is pivotally attached to one end of the inner bottom surface. Furthermore, the inner gusset piece 11 is characterized by having a fold portion 12 and a rib fold 13 that can be folded inward at the center in the width direction of the bottom surface and both side gusset portions. Furthermore, the fastening zipper 22 attached to the cut portion 16 of the outer gusset piece 15 consists of elements 25 on the opposing surfaces of a pair of strips 23a and 23b, a slider 26 that is inserted over the elements 25 of the strips to mesh and separate the elements, a connecting stopper 27 that is detachably attached in a male-female configuration to one end of the strips 23a and 23b, and a stopper portion 38 attached to the other end of the strips 23a and 23b, and is characterized in that the strips 23a and 23b can be separated when the fastening zipper 22 is opened.Furthermore, the connecting stopper piece 27 of the opening and closing fastener 22 has a hook-shaped locking head 29, a support portion 30 through which the slider 26 is inserted, a female stopper piece 28 with a locking groove 31 provided in the width direction on one side of the support portion and the locking head 29, a flat base plate 34 inserted into the locking groove 31 of the female stopper piece 28, and a male stopper piece having locking projections 35 provided on both sides of the base plate 34 at symmetrical positions, which fit onto the locking head 29 of the female stopper piece 28. The connection of the connecting stopper piece 27 is characterized by positioning the slider 26 on the support portion 30 of the female stopper piece 28, then moving the male stopper piece 33 almost parallel to the female stopper piece 28 to engage the locking projection 35 with the locking head portion 29 of the female stopper piece 28, while fitting the base plate 34 into the locking groove portion 31 of the female stopper piece 28 and the groove portion of the slider 26, and pulling down the slider 26 so that the elements 25 mesh with each other and connect.
[0012] Therefore, by operating the widening mechanism S attached to the secondary storage compartment 7 of the school bag 1, the gusset width of the secondary storage compartment 7 can be easily changed from the standard width X to the wide width Y by operating the opening and closing zipper 22 attached to the outer gusset piece 15 to separate the movable gusset piece 19 from the gusset piece 17, and then extending the inner gusset piece 11. As a result, the opening 8 of the secondary storage compartment 7 can be opened wide, allowing for the storage of many textbooks, while bulky gym bags, lunch bags, and even water bottles can be stored in the empty space of the main storage compartment 3. In addition, since there are no protruding parts of gym bags or lunch bags around the school bag 1, injuries caused by bags getting caught can be prevented, allowing for safe commuting to school. Furthermore, by placing a reinforcing plate 40 on the inner bottom surface where the inner gusset piece 11 of the secondary storage compartment 7 is extended, the extended inner gusset piece 11 is prevented from returning to its original shape due to the elastic force of the fold 12, and the wide width Y can be stably maintained. The opening and closing zipper 22, by attaching a connecting stopper 27 to its starting point, can completely separate the movable gusset portion 19 from the gusset portion 17, thereby widening the opening 8. Furthermore, when returning the gusset width of the sub-storage compartment 7 to the standard width X, the auxiliary plate 40 can be raised, and the male stopper 33 of the connecting stopper 27 provided on the starting point of the opening and closing zipper 22 can be moved almost parallel to the female stopper 28 to engage with the female stopper 28, and the slider 26 can be pulled down to engage the teeth of the elements 25, thereby easily connecting the zipper. [Brief explanation of the drawing]
[0013] [Figure 1] This is a perspective view of the school bag according to the present invention with the flap open. [Figure 2] This is a side view of the school bag itself. [Figure 3] This is a plan view of the main body of the school bag. [Figure 4] This is an enlarged plan view of the main part showing the widening mechanism installed in the secondary storage compartment. [Figure 5] This is a side view from the starting point showing the secondary storage compartment in its widened configuration. [Figure 6] This is a side view of the end point showing the secondary storage compartment in its widened configuration. [Figure 7] This is a floor plan showing the secondary storage compartment in its widened configuration. [Figure 8] This is a cross-sectional view taken along the line A-A in Figure 7. [Figure 9] This is a cross-sectional view taken along the line B-B in Figure 8. [Figure 10] This is a close-up view of the main part showing the separated state of the connecting stopper piece of the opening and closing zipper. [Figure 11] This is a cross-sectional view of the center of the female stopper that constitutes the connecting stopper. [Figure 12] This is a close-up view of the main part showing the connected state of the fastening piece of the opening and closing zipper. [Forms for implementing the invention]
[0014] The embodiments of the present invention will be described based on the drawings. Figure 1 is a perspective view of the school bag according to the present invention with the flap open, Figure 2 is a side view of the school bag body, Figure 3 is a plan view of the school bag body, Figure 4 is an enlarged plan view of the main part showing the widening mechanism provided in the secondary storage compartment, Figure 5 is a starting side view showing the secondary storage compartment in a widened state, Figure 6 is an ending side view showing the secondary storage compartment in a widened state, Figure 7 is a plan view showing the secondary storage compartment in a widened state, Figure 8 is a cross-sectional view taken along line A-A in Figure 7, and Figure 9 is a cross-sectional view taken along line B-B in Figure 8. The school bag 1 is formed by a back panel 2 made of natural leather, artificial leather, or synthetic leather, with a main storage compartment 3 for textbooks and notebooks, a secondary storage compartment 7 for supplementary materials, and a front pocket 9 for small items, all located on the back side of the back panel 2. The main storage compartment 3, secondary storage compartment 7, and front pocket 9 are covered by a flap 10, one end of which is sewn to the upper end of the back panel 2, allowing them to be opened and closed. The school bag is also composed of a pair of shoulder straps (not shown) with one end attached to a back ring mounted in the upper center of the back panel 2 and the other end connected to a drawstring located on the bottom surface of the school bag 1.
[0015] As shown in Figure 3, the main storage compartment 3 of the school bag 1 is formed by folding both sides of the bottom surface, which has a wide gusset, at right angles to form the gussets on both sides as a single unit, and sewing the bottom edge and both sides of the back panel 2 to the back side, and sewing the bottom edge and both sides of the intermediate partition plate 5 to the front side.
[0016] As shown in FIG. 3, the auxiliary storage chamber 7 is provided with an expandable width adjustment mechanism S that can be varied from a standard width X (about 2 to 5 cm), which is the width of the margin of the auxiliary storage chamber, to a wide width Y (about 6 to 12 cm). The width adjustment mechanism includes an inner margin piece 11 having a wide width Y formed by integrally forming a bottom surface portion and both side margin portions, an outer margin piece 15 having a standard width X formed by integrally forming a bottom surface portion and both side margin portions outside the inner margin piece, and a reinforcing plate 40 laid on the inner bottom surface of the auxiliary storage chamber 7 when the inner margin piece 11 is expanded. Needless to say, the above-mentioned standard width X and wide width Y are not limited to the indicated numerical values.
[0017] As shown in FIGS. 4 and 5, the inner margin piece 11 forms a fold portion 12 by folding the center in the width direction of the bottom surface portion and both side margin portions inward, and sews the folded-back portion of the fold portion to provide a rib fold 13 having elastic force. The fold portion 12 facilitates folding inward, and to compensate for the insufficient strength of the margin portion 17 due to the separation of the movable margin portion 19 of the outer margin piece 15, the fold portion 12 of the inner margin piece 11 is sewn in a mountain shape to provide a rib fold 13 to reinforce the insufficient strength of the margin portion due to the extension of the auxiliary storage chamber 7.
[0018] As shown in FIGS. 3 and 4, the outer margin piece 15 is provided with a width adjustment mechanism S in the margin portion 17 composed of a bottom surface portion having a standard width X and both side margin portions. The width adjustment mechanism S is provided with a movable margin portion 19 formed by cutting the center of the margin portion 17 in the width direction so as to be movable, and the belt portions 23a and 23b of the opening and closing fastener 22 are sewn to the cutting portion 16 between the movable margin portion and the margin portion 17 respectively, so that the movable margin portion 19 can be separated from and connected to the margin portion 17.
[0019] As shown in FIG. 8, the reinforcing plate 40 is pivotally attached to one end in the width direction on the inner bottom surface of the auxiliary storage chamber 7 so as to be pivotable toward the main storage chamber 3 side. When the auxiliary storage chamber 7 has the standard width X, the other end side is rotated upward and folded. When the auxiliary storage chamber 7 has the wide width Y, the reinforcing plate 40 located above is pivoted and laid on the inner bottom surface, so that the shape of the expanded auxiliary storage chamber 7 can be maintained.
[0020] Furthermore, when the auxiliary storage chamber 7 is changed from the standard width X to the wide width Y, the reinforcing plate 40 is laid on the inner bottom surface because the movable machi part 19 is separated from the machi part 17 and the strength of the bottom surface part becomes weak, so that the strength of the auxiliary storage chamber 7 can be maintained.
[0021] The opening and closing fastener 22 is a known slide fastener. For example, the trademark "ez-TRAK / Easy Track" of YKK Corporation is preferable. When engaging the elements in the same manner as a normal fastener, this slide fastener can be connected by inserting a stop piece from above the slider. Furthermore, it is used by paying attention to the function that one of the pair of stop pieces provided on the connecting starting point side, which is a feature of this fastener, can be attached to the slider from the horizontal lateral direction and opened and closed.
[0022] As shown in FIG. 5, this opening and closing fastener 22 is provided with elements 25 on the opposing surfaces of a pair of tape-shaped belt parts 23a and 23b. By inserting a slider 26 through the elements and moving it up and down on the elements, the opposing elements 25 can be meshed with each other to connect or separate the opposing belt parts 23a and 23b. Furthermore, at one end of the opening and closing fastener 22, a detachable male-female type connecting stop piece 27 is provided on the starting point side where the elements 25 are meshed, and at the connecting end point on the other end, a stop piece part 38 for preventing the slider 26 from falling off and facilitating the meshing of the elements 25 is attached.
[0023] As shown in FIGS. 10 and 11, the connecting stop piece 27 of the opening and closing fastener 22 is composed of a female stop piece 28 and a male piece 33. The female piece 28 is formed with a locking head 29 in the shape of a hook, a support part 30 for inserting and supporting the slider 26, and a locking groove part 31 is provided in the one-side width direction of the support part and the locking head 29. The male stop piece 33 is provided with a flat substrate 34 to be inserted into the locking groove part 31 of the female stop piece 28, and locking protrusions 35 to be fitted into the locking head 29 of the female stop piece 28 at both symmetric positions of the substrate 34.
[0024] The connection of the connecting stopper piece 27 is as shown in Figures 10 and 12, by positioning the slider 26 on the support portion 30 of the female stopper piece 28, and then moving the male stopper piece 33 almost parallel in the direction of the arrow shown in Figure 12, thereby engaging the locking projections 35 provided on both sides of the substrate 34 with the locking head 29 of the female stopper piece 28.
[0025] Next, the base plate 34 of the male stopper 33 is fitted into the locking groove 31 of the female stopper 28 and the groove (not shown) of the slider 26. Then, by pulling down the slider, the elements interlock with each other and slide to the opposite stopper 38, thereby connecting the gusset portion 17 and the movable gusset portion 19 to form the outer gusset piece 15.
[0026] Therefore, when connecting the movable gusset portion 19 to the gusset portion 17 of the outer gusset portion 15, the female stopper 28 and male stopper 33 can be easily connected and disconnected simply by moving the movable gusset portion in a nearly horizontal direction, rather than forcibly moving it up and down to connect them, making it easy for even schoolchildren to operate.
[0027] The operation of the embodiment of this invention will be described below. By providing a widening mechanism S in the gusset portion 17 of the secondary storage compartment 7 of the school bag 1, the entire secondary storage compartment 7 can be easily widened from a standard width X to a wide width Y, even by school children.
[0028] By widening the secondary storage compartment 7 from a standard width X to a wide width Y, textbooks, notebooks, and other teaching materials that were previously stored in the main storage compartment 3 can now be stored in the secondary storage compartment 7, freeing up space in the main storage compartment 3. Bulky gym bags, lunch bags, and water bottles can be stored in this freed-up space, eliminating the need for them to hang from the outside of the schoolbag. This helps prevent unexpected injuries and traffic accidents during schoolchildren's commutes to and from school.
[0029] The widening mechanism S provided in the sub-storage compartment 7 consists of a double layer of inner gusset pieces 11 with a wide width Y and outer gusset pieces 15 with a standard width X attached to the gusset portion of the sub-storage compartment 7. A movable gusset portion 19 is provided by cutting a part of the outer gusset portion 15, and an opening / closing zipper 22 is attached between the cut portion 16 of the movable gusset portion 19 and the gusset portion 17. The opening and closing of the zipper allows the gusset portion 17 and the movable gusset portion 19 to be connected and separated.
[0030] Furthermore, after separating the movable gusset portion 19, the inner gusset piece 11 is pulled toward the front pocket to widen the sub-storage compartment 7. The insufficient strength of the gusset portion 17 due to the separation of the sub-storage compartment 7 into the gusset portion 17 and the movable gusset portion 19 is compensated for by placing a reinforcing plate 40 inside the sub-storage compartment 7 on its inner bottom surface, and by providing rib folds 13 on the fold portion 12 of the inner gusset piece 11.
[0031] The opening and closing operation of the widening mechanism S provided in the sub-storage compartment 7 is as shown in Figures 1 to 4. To widen the gusset width of the sub-storage compartment 7 from the standard width X when closed to the wide width Y, the slider 26 of the opening / closing zipper 22 attached to the outer gusset piece 15 of the sub-storage compartment 7 is operated by sliding it from one upper end (stopping piece) of the gusset to the other upper end (connecting stopping piece) of the gusset. Then, by pulling the male stopping piece 33 of the connecting stopping piece 27 in the lateral direction, the base 34 of the male stopping piece 33 disengages from the locking groove 31 of the female stopping piece 28, easily separating the strips 23a and 23b of the opening / closing zipper 22, thereby easily separating the gusset 17 and the movable gusset 19.
[0032] As described above, by completely separating the male fastening piece 33 and the female fastening piece 28 attached to one end of the strip fabric 23a and 23b, the movable gusset portion 19 is separated from the gusset portion 17, and by pulling the inner gusset portion 11 toward the front pocket portion 9, the folded portion 12 of the inner gusset piece 11 is extended and the width can be expanded to the width Y, and furthermore, by placing the reinforcing plate 40 installed inside the sub-storage compartment 7 on the inner bottom surface, the width Y can be maintained.
[0033] When closing the widened sub-storage compartment 7, the reinforcing plate 40 laid on the inner bottom surface of the sub-storage compartment 7 is pivoted and raised towards the main storage compartment 3, and the inner gusset piece 11 returns to its original state due to the elastic force of the fold portion 12, while the slider 26 is positioned on the support portion 30 of the female stopper piece 28 provided on the connecting stopper piece 27 of the opening and closing zipper 22 attached to the outer gusset portion 15, as shown in Figures 10 and 12.
[0034] Next, as shown by the arrow in Figure 12, the base plate 34 of the male stopper piece 33 is moved almost parallel to the female stopper piece 28, and the locking projections 35 provided on both sides of the base plate 34 are locked onto the locking head 29 of the female stopper piece 28. Furthermore, the base plate 34 of the male stopper piece 33 is fitted into the locking groove 31 and slider groove of the female stopper piece 28. Then, by pulling down the slider 26, the elements 25 interlock with each other and slide to the opposite stopper piece 38, allowing it to be easily returned to the outer gusset piece 15 having a standard width X.
[0035] The width Y of the sub-storage compartment 7 can be maintained not only by the reinforcing plate 40 laid on the inner bottom surface of the sub-storage compartment 7, but also by storing teaching materials in the sub-storage compartment 7. For example, it can be maintained by storing B5-sized textbooks, notebooks, and communication notebooks (approximately 20 or more can be stored).
[0036] The aforementioned secondary storage compartment 7 can be easily transformed from a standard width X to a wide width Y by a simple operation using the widening mechanism S, even by schoolchildren. This makes it easy and convenient to move textbooks and other materials stored in the main storage compartment 3 to the secondary storage compartment 7, reducing the amount of material stored there. Furthermore, bulky items such as gym bags, lunch bags, and water bottles can be stored in the empty space within the main storage compartment 3. Moreover, by storing bulky items such as gym bags, lunch bags, and water bottles, there are no protruding parts around the backpack, allowing for a safer commute to school. [Explanation of Symbols]
[0037] 1. School bag 2 Back plate 3. Main storage room 4 Large Gusset Pieces 5. Intermediate partition plate 7. Sub-storage room 8 openings 9 Front pocket section 10. Cover 11 Inner gusset flap 12 Folded section 13 Rib folds 15 Outer gusset flap 16 Cut section 17 Gusset 19 Movable gusset 22 Zipper closure 23 Obi fabric 25 elements 26 Slider 27 Connection stopper 28 Female stopper 29 Locking head 30 Support part 31 Locking groove 33 Male stop piece 34 circuit boards 35 Locking protrusion 38 Stop piece part 40 Reinforcement plate S widening mechanism X standard width Y Wide Width
Claims
1. A school bag (1) having a main storage compartment (3) for storing textbooks and notebooks, a secondary storage compartment (7) for storing supplementary teaching materials, and a front pocket section (9) for storing small items, each arranged in the front-to-back direction on the back side of a back panel (2), and further having a cover (10) with one end sewn to the upper end of the back panel (2) that can open and close and cover the main storage compartment (3), secondary storage compartment (7), and front pocket section (9), wherein the secondary storage compartment (7) is equipped with an expandable widening mechanism (S) that can change the gusset width from a standard width (X) to a wide width (Y), The widening mechanism (S) includes an inner gusset piece (11) having a bottom surface portion and both side gusset portions integrally formed with each other, each having a wide gusset width (Y); The bag is made of an outer gusset piece (15) which is formed by cutting a gusset part (17) having a standard width (X) at the center in the width direction outside the inner gusset piece (11) to form a movable gusset part (19), and an opening / closing fastener (22) is attached between the movable gusset part and the gusset part (17) to enable the gusset part (17) and the movable gusset part (19) to be separated and connected. When the gusset width of the auxiliary storage compartment (7) is changed from the standard width (X) to the wide width (Y), the slider (26) of the opening / closing fastener (22) attached to the outer gusset piece (15) is slid to separate the gusset portion (17) from the movable gusset portion (19), and then the inner gusset piece (11) is widened toward the front pocket portion, thereby changing the width of the auxiliary storage compartment (7) to the wide width (Y). The opening and closing fastener (22) attached to the cut portion (16) of the outer gusset piece (15) has an element (25) on each of the opposing surfaces of the pair of band fabrics (23a, 23b), and a slider (26) that is inserted over the elements to engage and separate the elements (25) with each other; The belt (23a, 23b) comprises a connecting stop piece (27) detachably attached to the starting point side of one end of the belt (23a, 23b) in a male-female type, and a stop piece part (38) attached to the end point side of the other end of the belt (23a, 23b), When the opening and closing fastener (22) is opened, the band fabrics (23a, 23b) can be separated from each other. The connecting fastener (27) of the opening / closing fastener (22) comprises a hook-shaped fastener head (29), a support part (30) through which the slider (26) is inserted, and a female fastener (28) having a fastener groove (31) formed in one width direction of the support part and the fastener head (29). The connector comprises a flat base plate (34) inserted into the locking groove (31) of the female locking piece (28), and male locking pieces (33) having locking projections (35) fitted into the locking heads (29) of the female locking pieces (28) provided at symmetrical positions on both sides of the base plate (34), The connection of the connecting locking piece (27) is performed by positioning the slider (26) on the support part (30) of the female locking piece (28), then moving the male locking piece (33) almost parallel to lock the locking projection (35) with the locking head part (29) of the female locking piece (28), while fitting the base plate (34) into the locking groove part (31) of the female locking piece (28) and the groove part of the slider (26), and pulling down the slider (26) to connect the elements (25) by meshing with each other. The male retaining piece (33) and the female retaining piece (28) are completely separable, By this separation, the movable gusset portion (19) is completely separated from the gusset portion (17), so that the inner gusset piece (11) can be pulled in the direction of the front pocket portion (9), The expansion type school bag is characterized in that the opening (8) of the secondary storage chamber (7) is opened widely by the pulling, and after the pulling, the widened width of the inner bottom surface of the secondary storage chamber (7) can be maintained by laying a reinforcing plate (40) on the inner bottom surface where the inner gusset piece (11) is extended.
2. An expandable school bag as described in claim 1, characterized in that the inner gusset piece (11) has a fold portion (12) and a rib fold (13) that can be folded inward at the center of the width of the bottom portion and both side gusset portions.
3. An expandable school bag as described in Claim 2, characterized in that the rib fold (13) is formed by sewing the folded portion of the fold portion (12) in a mountain shape.
4. An expandable school bag as described in claim 2, characterized in that by pulling the inner gusset piece (11) in the direction of the front pocket portion (9), the fold portion (12) stretches and the gusset width of the secondary storage chamber (7) can be expanded to a wide width (Y).
5. An expandable school bag as described in claim 1, characterized in that when the male retaining piece (33) and the female retaining piece (28) are completely separated, the male retaining piece (33) is pulled laterally, causing the base plate (34) of the male retaining piece (33) to come out of the locking groove portion (31) of the female retaining piece (28).
6. An expandable school bag as described in any one of claims 1 to 5, characterized in that the secondary storage chamber (7) is formed so that it can stand up when the gusset width is the standard width (X) and can be laid on the inner bottom surface when the gusset width is the wide width (Y), and the reinforcing plate (40) is pivotally attached to one end of the inner bottom surface.