Patent Publication Number: US-6669068-B2

Title: Extendable strap and bag provided with the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an extendable/contractible strap and a bag provided with the same. 
     2. Description of Related Art 
     A bag, to which a shoulder strap (shoulder belt) is attached, is convenient, for example, when the load of the bag is heavy or when hands of a user are intended to be made free, because the bag can be retained by hanging the shoulder strap on the shoulder. Usually, the shoulder strap is detachably attached to hooks installed at right and left upper end portions of a main bag body. However, when the shoulder strap is not used, the shoulder strap hangs down from the main bag body, which gives an unseemly appearance. Further, the shoulder strap, which hangs down from the main bag body, may be caught by any object or obstacle, possibly resulting in any accident in some cases. Furthermore, when the bag is temporarily placed on the floor in the airport or on the platform of train, the shoulder strap contacts with the floor, which is unfavorable in view of hygiene. 
     Japanese Patent Application Laid-Open No. 10-117827 discloses a shoulder belt-equipped bag comprising a belt holder provided at a gusset portion of the bag with a belt end which is stickable to the bag by the aid of a Velcro tape. The bag has its shoulder belt which is wound around the outer circumference of the bag. When it is intended to use the shoulder belt, the following operation is performed. That is, the belt end is detached from the bag, and the belt is adjusted to have a desired length. Subsequently, the belt is fixed with the holder. Finally, the belt end is stuck to the bag with the Velcro tape or the like. However, in the case of this bag, it is necessary to attach, to the bag, unique parts such as the belt holder and the Velcro tape. Further, the bag involves the following inconveniences. That is, the bag requires the complicated operation to use the shoulder belt as well as the complicated operation to accommodate the shoulder belt. It is impossible to quickly perform such operations. 
     A first object of the present invention is to provide a strap and a bag provided with the same wherein the strap is shortened to have a length with which the strap does not hang down from a main bag body when the strap is not used, while the strap can be instantaneously stretched to have a sufficient length when the strap is required. 
     A second object of the present invention is to provide an extendable strap which is applicable to a variety of ways of use, including, for example, a strap for a portable telephone. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention, there is provided an extendable/contractible strap device ( 15 ) comprising a first guide ( 3 ) which is formed with a first slit ( 7   b ) and a third slit ( 7   a ); a first strap ( 11 ) which has a first end ( 11   a ) connected to the first guide; a second guide ( 5 ) which is arranged opposingly to the first guide ( 3 ) and which is formed with a second slit ( 9   a ) and a fourth slit ( 9   b ); and a second strap ( 13 ) which has a first end ( 13   a ) connected to the second guide; wherein the first strap has a second end ( 11   b ) which passes through at least one of the second slit and the fourth slit, which returns to the first guide, and which subsequently passes through one of the first slit and the third slit of the first guide, and the second strap has a second end ( 13   b ) which passes through at least one of the first slit and the third slit, which returns to the second guide, and which subsequently passes through one of the second slit and the fourth slit of the second guide. The first end ( 11   a ) of the first strap may be connected to an intermediate or central member ( 3   b ) which is defined between the first slit and the third slit, and the first end ( 13   a ) of the second strap may be connected to an intermediate or central member ( 5   b ) which is defined between the second slit and the fourth slit. 
     According to a second aspect of the present invention, there is provided an extendable/contractible strap ( 35 ) comprising a first guide ( 23 ) which is defined with a first slit ( 27   a ); a first strap ( 31 ) and a second strap ( 33 ) which have first ends ( 31   a,    33   a ) connected to the first guide ( 23 ) respectively; and a second guide ( 25 ) which is arranged opposingly to the first guide and which is defined with a second slit ( 29   a ); wherein the first strap has a second end ( 31   b ) which passes through the second slit ( 29   a ), which returns to the first guide, and which subsequently passes through the first slit ( 27   a ), and the second strap has a second end ( 33   b ) which passes through the second slit ( 29   a ). 
     According to a third aspect of the present invention, there is provided a bag ( 150 ,  180 ) which is provided with the strap device according to the first or second aspect of the present invention. In this specification, the term “slit” means an opening having a slender and rectangular configuration as well as openings having arbitrary cross-sectional configurations including, for example, circular, elliptic, and square configurations. The term “strap” means a string, a cord, a band or the like having a slender and rectangular cross-sectional configuration as well as strings, cords, bands or the like having arbitrary configurations including, for example, elliptic and circular configurations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A shows a schematic view illustrating a structure of a strap device of the present invention, 
     FIG. 1B shows a schematic view illustrating a situation during expansion of the strap device, and 
     FIG. 1C shows a schematic view illustrating a state in which the strap device is extended. 
     FIGS. 2A and 2B show perspective views illustrating first and second guides respectively. 
     FIG. 3A shows a schematic view illustrating a bag in a state in which the strap device is contracted, and 
     FIG. 3B shows a schematic view illustrating the bag in a state in which the strap device is extended. 
     FIG. 4A shows a schematic view illustrating a bag in a state in which the strap device is contracted, and 
     FIG. 4B shows a schematic view illustrating the bag in a state in which the strap device is extended. 
     FIG. 5 shows a schematic view illustrating a portable telephone to which the strap device shown in FIG. 1 is installed. 
     FIG. 6A conceptually shows another strap device of the present invention, and 
     FIGS. 6B and 6C show structures of first and second guides respectively. 
     FIG. 7A shows a schematic view illustrating a structure of a strap device according to a sixth embodiment of the present invention, and 
     FIG. 7B shows a schematic view illustrating a process of expansion of the strap device shown in FIG.  7 A. 
     FIG. 8A shows a schematic view illustrating a structure of a bag equipped with a strap device according to a seventh embodiment of the present invention, and 
     FIG. 8B shows a schematic view illustrating a state in which the strap device shown in FIG. 8A is extended. 
     FIG. 9A shows a schematic view illustrating a structure of a bag equipped with a strap device according to an eighth embodiment of the present invention, and 
     FIG. 9B shows a schematic view illustrating a state in which the strap device shown in FIG. 9A is extended. 
     FIG. 10A shows a schematic view illustrating a structure of a bag equipped with a strap device according to a ninth embodiment of the present invention, and 
     FIG. 10B shows a schematic view illustrating a state in which the strap device shown in FIG. 10A is extended. 
     FIG. 11A shows a schematic view illustrating a state in which a strap device according to a tenth embodiment of the present invention is contracted, and 
     FIG. 11B shows a schematic view illustrating a state in which the strap device is extended. 
     FIG. 12A shows a schematic view illustrating a state in which a guide to be used for a strap device according to an eleventh embodiment is unlocked, and 
     FIG. 12B shows a schematic view illustrating a state in which the guide is locked. 
     FIGS. 13A and 13B show top views of a bag illustrating a twelfth embodiment in which a lock adjuster is provided on a side wall of a main bag body. 
     FIGS. 14A and 14B show top views illustrating operation performed when a strap is accommodated in the twelfth embodiment. 
     FIG. 15A shows a sectional view illustrating an exemplary structure of a guide to be used for the strap device, and 
     FIG. 15B shows a sectional view illustrating another exemplary structure of a guide. 
     FIG. 16 illustrates a structure and operation of a lock mechanism to be used for the strap device of the present invention. 
     FIG. 17 illustrates a different strap device which may be provided on the bag shown in FIG.  16 . 
     FIGS. 18A to  18 E conceptually show a variety of passage ways for straps to pass through the guides in the strap device of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
     First Embodiment 
     A first embodiment of the strap of the present invention will be explained with reference to FIGS. 1A to  1 C,  2 A, and  2 B. A strap device  15  comprises a first guide  3 , a second guide  5 , a first strap  11 , and a second strap  13 . As shown in FIG. 2A, the first guide  3  is a substantially rectangular frame with mutually parallel slits  7   b,    7   a  which are formed at upper and lower positions respectively with a central member (bridge)  3   b  which intervenes therebetween and which extends in the longitudinal direction at a central portion of the frame. A first end  11   a  of the first strap  11  is secured to the central member  3   b.  The first strap  11  has a width which is slightly narrower than those of the slits  7   a,    7   b  and a thickness which is not more than ½ of those of the slits. The first strap  11  is composed of a flexible member such as polyethylene or nylon having a smooth surface. As shown in FIG. 2B, the second guide  5  is also a substantially rectangular frame based on the same material and the same structure as those of the first guide  3 . The second guide  5  has parallel slits  9   a,    9   b  which are formed at upper and lower positions with a central member  5   b  intervening therebetween. A first end  13   a  of the second strap  13  is secured to the central member  5   b.  The second strap  13  has the same size as that of the first strap  11 , and it is formed of the same material as that of the first strap  11 . As shown in FIGS. 7 and 13, the straps  11 ,  13  may be wound around the central members  3   b  ( 40   b,    60   b ),  5   b  respectively, and the first ends  11   a,    13   a  of the straps may be joined by stitching to the straps themselves. 
     As shown in FIG. 1A, the first guide  3  and the second guide  5  are arranged so that their sides, on which the straps  11 ,  13  extend, are opposed to one another. A second end  11   b  of the first strap  11 , for which the first end  11   a  is secured to the central member  3   b  of the first guide  3 , extends toward the second guide  5 , and the second end  11   b  passes through the slit  9   a  of the second guide  5 . The second end  11   b,  which has passed through the slit  9   a  of the second guide  5 , turns back to pass through the slit  9   b,  and the second end  11   b  travels toward the first guide  3 . Subsequently, the second end  11   b  passes through the slit  7   a  of the first guide  3 , and the second end  11   b  is positioned at the outside of the area which is interposed between the first guide  3  and the second guide  5  (on the outlet side of the first guide). A second end  13   b  of the second strap  13 , for which the first end  13   a  is secured to the central member  5   b  of the second guide  5 , extends toward the first guide  3 , and the second end  13   b  passes through the slit  7   a  of the first guide  3 . The second end  13   b,  which has passed through the slit  7   a,  turns back to pass through the slit  7   b,  and the second end  13   b  travels toward the second guide  5 . The second end  13   b  passes through the slit  9   a  of the second guide  5 , and the second end  13   b  is positioned at the outside of the area which is interposed between the first guide  3  and the second guide  5  (on the outlet side of the second guide). 
     As appreciated from FIG. 1A, the strap  11  and the strap  13  exist while being folded between the first guide  3  and the second guide  5  respectively. As a result, half portions of the straps  11 ,  13  are positioned and overlapped quadruply between the first guide  3  and the second guide  5 . 
     Next, the operation of the strap device  15  will be explained. Starting from the strap device  15  in the state shown in FIG. 1A, the second ends  11 i b,    13   b  of the straps  11 ,  13  are pulled in directions in which they are separated from each other. In consequence, as shown in FIG. 1B, the first and second guides  3 ,  5  are moved in directions to make approach to one another, while the straps  11 ,  13  are pulled out from the first and second guides  3 ,  5 . When the second ends  11   b,    13   b  are further pulled apart so that they are separated from each other, then the first guide  3  and the second guide  5  make mutual abutment as shown in FIG. 1C, and consequently the straps  11 ,  13  are not pulled out any more. In this situation, almost all of the lengths of the straps  11 ,  13  are pulled out through the respective guides. The length, which is the double of the spacing distance between the first guide  3  and the second guide  5  in the strap device  15  in the state shown in FIG. 1A, is pulled out from each of the guides. The length, which the quadruple of the spacing distance, is obtained for the entire strap device. In order to restore the strap device  15  into the original state as shown in FIG. 1A, the first guide  3  and the second guide  2 , which make the mutual abutment, may be pulled away in mutually opposite directions. Accordingly, the strap, which is extendable to have the quadruple length, is realized. 
     Second Embodiment 
     The bag  150  shown in FIG. 3 has a main body  80 , and a strap device  98  which is placed on the main body  80  in a state shown in FIG.  1 A. The strap device  98  has the same structure as that of the strap device  15  shown in FIG. 1 except that a second strap  13  is longer than a first strap  11  by a predetermined length. The predetermined length is selected on the basis of the thickness of the shoulder of the user. The predetermined length is appropriately 15 to 25 cm. The second ends  11   b,    13   b  of the first and second straps are secured to end portions on the upper surface of the main bag body  80  respectively. Alternatively, the second ends  11   b,    13   b  of the first and second straps may be detachably attached to right and left side wall portions of the main bag body  80  by the aid of unillustrated eggplant-shaped fastener rings (rings). A flexible shoulder pad  70  is allowed to pass through a portion of the strap  11  extending from the second guide  5  toward the outside of the strap device (on the outlet side of the second guide). The shoulder pad  70  may be secured to the second guide  5 . 
     In order to use the strap device  98  of the bag  150  shown in FIG. 3A as a shoulder strap, the shoulder pad  70  may be simply pulled up upwardly. During this process, as shown in FIG. 3B, the straps  11 ,  13  are pulled out from the area between the first guide  3  and the second guide  5  respectively to pull out the length which is about the quadruple of the distance between the first guide and the second guide of the strap device  98  in the state shown in FIG.  3 A. The first guide  3  and the second guide  5  are located at positions slightly deviated leftward from the center of the pulled out straps so as to avoid the shoulder position of the user. The pad  70  is slidably moved on the strap  11 , and it is located at a substantially central position of the pulled out straps to protect the shoulder of the user. Especially, an advantage is obtained such that the center of the pad is necessarily located at the middle of the shoulder when the pad, which has substantially the same length as that of the predetermined length, is attached. When the shoulder strap is not used, the first and second guides  3 ,  5  may be pulled away in mutually opposite directions. The straps are instantaneously restored to the state shown in FIG. 3A in accordance with the simple operation. 
     According to the bag of the present invention, the shoulder strap can be instantaneously pulled out to give a sufficient length from the main bag body only when the shoulder strap is required. When the shoulder strap is unnecessary, then the strap can be restored extremely easily to the state in which the strap is folded on the bag, and the strap does not hang down from the bag. Therefore, the bag, which has the good appearance, which is safe, and which is excellent in functionality, is provided. The strap device of the present invention is usable for any bags having straps or belts, including, for example, brief cases, sports bags, suit cases, garment bags, handbags, knapsacks, tote bags, camera cases, musical instrument cases, and fishing tackle cases. Further, the strap device of the present invention may be attached to any objects to which the shoulder strap is applicable, including apparatuses such as cameras, video cameras, various recording apparatuses, and telescopes, in place of the main bag body. 
     Third Embodiment 
     The bag  180  shown in FIG. 4 has a main body  80 , and a strap device  95  which is placed on the main body  80  in a state shown in FIG.  1 A. The strap device  95  has the same structure as that of the strap device shown in FIG. 1 except that a first strap  11  and a second strap  13  are longer than those shown in FIG. 1A respectively, and their second ends  11   b,    13   b  are connected to one another. The second ends  11   b,    13   b  of the first and second straps travel from the first guide  3  and the second guide  5 , and then they pass through rings  82 ,  84  which are secured to the upper surface of the main bag body  80  respectively. The second ends  11   b,    13   b  are connected to one another after the passage through the rings  82 ,  84 . Accordingly, a strap section  75  is created at the uppermost portion of the strap device. A flexible shoulder pad  70  is allowed to pass through the strap section  75 . 
     In order to use the strap device  95  of the bag  180  shown in FIG. 4A as a shoulder strap, the shoulder pad  70  may be simply pulled up upwardly. As a result, as shown in FIG. 4B, the straps  11 ,  13  are pulled out from the first guide  3  and the second guide  5  through the rings  82 ,  84  respectively. In a state shown in FIG. 4B, the length, which is about the quadruple of the distance between the first and second guides of the strap device  95  in the state shown in FIG. 4A, is pulled out. The pad  70  is slidably moved on the strap  11 , and it is located at an approximately central position of the pulled out straps to successfully protect the shoulder of the user thereby. In order to make restoration to the state shown in FIG. 4A, the first and third guides  3 ,  5  may be pulled away from each other. 
     Fourth Embodiment 
     The size of the strap device  15  shown in FIG. 1 may be miniaturized as a whole. As shown in FIG. 5, the second end  11   b  of the first strap  11  may be connected to a portable telephone by the aid of a thin string  21 . In this case, the width of the strap is preferably 5 to 8 mm. The second end  13   b  of the second strap  13  may be connected to a clip  125  to pinch a pocket or the like in order to avoid any falling off. When the portable telephone  123 , which is accommodated in a chest pocket or a trousers pocket, receives a telephone call, the portable telephone  123  can be taken out of the pocket to make approach to the ear, without disengaging the clip  125  from the pocket. During this operation, the strap is pulled out from the guide. For example, a key, a key holder, a flashlight, a lighter, an azimuth magnet, or a tool may be attached to the strap device in place of the portable telephone  123 . A neck-hang type strap may be provided by lengthening the strap length. In the case of the neck-hang type strap, the second ends  11   b,    13   b  of the straps may be connected to one another by the aid of the clip  125  or without using the clip  125 . 
     Fifth Embodiment 
     The strap device  35  shown in FIG. 6A is provided with a first guide  23  and a second guide  25  which are opposed to one another. The first guide  23  has a first slit  27   a  and a third slit  27   b  which are formed under and over a central member  23   b  respectively. The first guide  23  is formed as a frame member in the same manner as the first guide  3  shown in FIG.  2 A. However, as shown in FIG. 6B, the first guide  23  is different from the first guide  3  shown in FIG. 2A in that a first end  31   a  of a first strap  31  and a first end  33   a  of a second strap  33  are secured to a lower surface and an upper surface of the central member  23   b  of the first guide  23  respectively. A second guide  25  has second slits  29   a,    29   b  which are formed over and under a central member  25   b  respectively. The second guide  25  is formed of the same frame member as that of the second guide  5  shown in FIG.  2 B. However, as shown in FIG. 6C, the second guide  25  is different from the second guide  5  shown in FIG. 2B in that a second end  33   a  of a second strap  33  is not secured to the second guide  25 . 
     A second end  31   b  of the first strap  31  extends from the first guide  23  toward the second guide  25 , and it passes through the second slit  29   a.  The second end  31   b  of the first strap  31  turns back, and it passes through the fourth slit  29   b  to return to the first guide. Further, the second end  31   b  of the first strap  31  passes through the third slit  27   a  of the first guide. A second end  33   b  of the second strap  33  extends from the first guide  23  toward the second guide  25 , and it passes through the second slit  29   a.  The length of the second strap  33  is slightly longer than the half of the length of the first strap  31 . Accordingly, the length of the strap portion protruding to the outer side of the second guide  25  (outlet side) is longer than the length of the strap portion protruding to the outer side of the first guide  23  (outlet side). 
     The strap device  35  is operated as follows. That is, when the second end  31   b  of the first strap  31  and the second end  33   b  of the second strap  33  are pulled out in directions in which they are separated from each other, then the first guide  23  and the second guide  25  are moved to make approach to one another, and they finally make mutual abutment. In this situation, almost all of the entire lengths of the first strap  31  and the second strap  35  are pulled out from the first guide  23  and the second guide  25  respectively. That is, the strap is pulled out toward the left in the drawing from the first guide  23  to give the length which is about the double of the spacing distance between the first guide and the second guide in the state shown in FIG.  6 A. The strap is pulled out toward the right in the drawing from the second guide  25  to give the length which is approximately the same as the spacing distance. The length, which is about the triple of the spacing distance, is obtained as a whole. In order to make restoration to the state shown in FIG. 6A, the first guide  23  and the second guide  25  may be pulled away so that they are separated from each other. 
     The strap device  35  can be attached to a main bag body in the same manner as in the bag shown in FIG. 3. A pad ( 70 ) may be allowed to pass through a second strap portion between the second end  33   b  of the second strap  33  and the second guide  25 . When the shoulder strap is required, the pad can be pulled up from the bag to instantaneously stretch the strap. The strap device  35  can be also used as shown in FIG. 4 such that the second ends of the straps may be connected to one another, and a connecting portion may be provided on the bag. Further, alternatively, the size of the strap device  35  may be also miniaturized so that the strap device  35  may be used as a strap for the portable telephone as shown in FIG.  5 . 
     Sixth Embodiment 
     The strap device  300  shown in FIGS. 7A and 7B has approximately the same structure as that of the strap device shown in FIG. 3 except that the strap device  300  is provided with a lock mechanism, and a guide  5  is secured to an end portion of a shoulder pad  70 . A guide  40 , which corresponds to the guide  3  shown in FIG. 3, has a central member  40   b  to which a first end  11   a  of a strap  11  is connected by circumscribing the first end  11   a  therearound and stitching the first end  11   a  and the strap  11  together. A lock adjuster  60  is attached to a strap portion between a second end  11   b  of the strap  11  and the guide  40 . Slits  62 ,  64  are formed through a main body  60   a  of the lock adjuster  60 . The second end  11   b  of the strap  11  is allowed to pass through the slits  62 ,  64 , and thus the lock adjuster  60  is attached so that the position of the lock adjuster  60  may be changed on the strap  13 . The lock adjuster  60  has a lock pawl  60   b  which is provided at the tip of the main body  60   a  and which is flexibly deformable with respect to the main body  60   a.  An upper frame  40   c  of the guide  40  constitutes an engaging section for making engagement with the lock pawl  60   b.  A lower frame  5   c  of the guide  5  is secured to the-tip of a pad  70 . A first end  13   a  of the strap  13  is connected to a central member  5   b  of the guide  5  by circumscribing the first end  13   a  therearound and stretching the first end  13   b  and the strap  13  together. A second end  13   b  of the strap  13  passes through a slit between the central member  40   b  and the upper frame  40   c  of the guide. After that, the second end  13   b  passes through a slit between the lower frame  40   a  and the central member  40   b  of the guide  40  to return to the guide  5 . The second end  13   b  passes through a slit between the lower frame  5   c  and the central member  5   b  of the guide  5 , and it passes through the space between the pad  70  and a pad cover  70   a  attached to the pad  70 . 
     As shown in FIG. 7A, in the state in which the strap device  300  is contracted, the lock pawl  60   b  of the lock adjuster  60  is engaged with the upper frame  40   c  of the guide  40 , and the guide  40  is fixed to the lock adjuster  60 . Accordingly, even when any unintentional force is applied to any portion of the strap device  300 , especially to the guide  40 , the straps are prevented from being loosened, i.e., from being extended to protrude. In order to pull out the straps from the strap device  300 , the following operation is performed. That is, the lock pawl  60   b  is flexibly deformed with respect to the main lock adjuster body  60 , for example, the lock pawl  60   b  is urged downwardly to disengage the lock pawl  60   b  from the upper frame  40   c  of the guide  40 . Subsequently, the pad  70  is pulled up upwardly, or the end  13   b  of the strap is pulled out from the pad cover  70   a,  and thus the straps  11 ,  13  are pulled out from the area between the guides. As a result of this operation, the guide  40  and the guide  5  make mutual approach as shown in FIG. 7B to extend the strap device. It is noted that the lock mechanism is not limited to the form shown in the drawings. It is possible to adopt various known lock mechanisms. The lock pawl  60   a  may be provided on the side of the guide  40 . Alternatively, the lock pawl-engaging section may be provided on the lower frame  40   a  of the guide  40 . Further, the engagement between the upper frame  40   c  and the lock pawl of the lock adjuster  60  is not limited to the mechanical engagement, and any magnetic force-based coupling may be adopted. Alternatively, a detachable Velcro tape may be provided for the guide  40  and the strap  11  or the main bag body to connect them. 
     Seventh Embodiment 
     The strap device  400  shown in FIGS. 8A and 8B is constructed in the same manner as the strap device shown in FIG. 3 except that the strap device  400  is provided with a lock mechanism and a shoulder pad is provided between guides. As shown in FIG. 8A, a main bag body  80  is provided with a pair of lock members  47  by the aid of short webs  170 . Each of the lock members  47  has a lock pawl  47   a  at the tip. Each of the guides  43 ,  45  has approximately the same structure as that of the guide  40  shown in FIG.  7 A. An engaging section, with which the lock pawl  47   a  of the lock member  47  is detachably engageable, is provided for each of lower frames  43   c,    45   c  of the guides  43 ,  45 . 
     As shown in FIG. 8A, when the lower frame  43   c  of the guide  43  and the lower frame  45   c  of the guide  45  are engaged with the lock pawls  47   a  respectively, the straps  11 ,  13  cannot be extended to protrude from the guides  43 ,  45 , because the movement of the guides  43 ,  45  with respect to the straps  11 ,  13  is restricted. In this state, the straps (bundle of quadruple straps), which are disposed between the guide  43  and the guide  45 , function as a grip. The grip can be gripped more easily by covering the straps  11 ,  13  with an openable/closable pad cover  195  as shown in FIG.  8 A. 
     In order to use the strap device  400  as a shoulder strap, the pad cover  195  is detached from the strap bundle, and the lock pawls  47   a  are disengaged from the lower frame  43   c  of the guide  43  and the lower frame  45   c  of the guide  45  respectively. Subsequently, the strap bundle is pulled up upwardly. Alternatively, the portions of the straps  11 ,  13 , which are located outside the guides  43 ,  45 , are mutually pulled away. Accordingly, the straps  11 ,  13  are pulled out from the guides  43 ,  45  as shown in FIG.  8 B. Further, the portion, at which the guides  43 ,  45  are joined, may be covered with the pad cover  195 . That is, in this embodiment, the strap device  400  functions as the grip in the contracted state, and the strap device  400  functions as the shoulder strap in the extended state. 
     Eighth Embodiment 
     A strap device  500  is provided with a pair of strap devices  115 ,  215  as shown in FIGS. 9A and 9B. Each of the strap devices  115 ,  215  has the same structure as that of the strap device  15  shown in FIG.  1 . Engaging members  49  are provided at both ends of a pad cover  195  which functions as a grip. The engaging members  49  are detachably engageable with lock pawls of a pair of lock members  160  which are provided on a main bag body  80  by the aid of webs  170  respectively. The strap devices  115 ,  215  include straps  13  having first ends which are connected to side walls of the bag respectively, and second ends which are connected to central members  5   b  of guides  5 . A first end of a strap  110  is connected to a central member  55   b  of a guide  55  of the strap device  115 . A second end of the strap  110  extends toward the guide  5 , and it circumscribes around a central member  5   b  of the guide  5  to make return. The second end of the strap  110  passes through a slit between a central member  55   b  and an upper frame  55   a  of the guide  55 , and it is connected to a strap  110  of the strap device  215  at the inside of the pad  195  which is disposed at the center of the bag. 
     As shown in FIG. 9A, in a state in which the lock pawls of the lock members  160  are engaged with the engaging members  49 , the straps  13 ,  110  of the strap devices  115 ,  215  cannot be pulled out, and the pad cover  195  functions as the grip. On the other hand, when the lock members  160  are disengaged from the engaging members  49 , and the pad cover  195  is subsequently pulled up upwardly, then the straps  11 ,  13  are pulled out through the guides  5 ,  55  as shown in FIG.  9 B. Thus, the strap devices  115 ,  215  function as a shoulder strap. In order to make restoration to the state shown in FIG. 9A, the guides  5 ,  55  of the respective strap devices may be pulled away in directions so that they make separation from each other. 
     Ninth Embodiment 
     An embodiment, in which a strap is successfully allowed to function as a grip, is shown in FIG. 10A as a modified embodiment of FIG.  4 . As shown in FIG. 10A, a pad cover  195  is a cover made of, for example, leather, which can detachably cover a bundle of straps ( 11 ,  13 ,  75 ) which are quintuply overlapped. When the pad cover  195  covers the bundle of straps ( 11 ,  13 ,  75 ), the respective straps  11 ,  13 ,  75  cannot be moved, because they are restricted by the pad cover  195 . Therefore, the pad cover  195  functions as the grip. When it is intended to use the straps as a shoulder strap, then the pad cover  195  may be detached from the strap bundle, and the strap  75  may be pulled up upwardly. Further, as shown in FIG. 10B, when the pad cover  195  is installed to a central portion of the pulled out strap  75 , the pad cover  195  is successfully allowed to function as a shoulder pad. The second end of the strap  110  of each strap device may be directly connected to the pad cover  195 . 
     Tenth Embodiment 
     In place of the provision of the pad  70 , guides  3 ,  5  may be provided with pads, respectively, or may be formed integrally with the pads as a modified embodiment of the bag shown in FIG.  3 . As shown in FIG. 11A, the entire guides  3 ,  5  are covered with guide covers (pads)  30 ,  50  formed of a flexible material such as rubber, except for strap passage windows  30   a,    30   c,    50   a,    50   c.  When the straps  11 ,  13  are pulled out, then the guides  3 ,  5  make approach to one another, and the guide covers  30 ,  50  make tight contact with each other as shown in FIG.  11 B. In this example, since the pads are attached to the respective guides  3 ,  5 , a length of the strap  11  can be equal to that of the strap  13 . 
     Eleventh Embodiment 
     As shown in FIG. 12, a lock mechanism may be provided for only a guide  3 . The lock mechanism has a lock arm  90  which is rotatable about the center of a rotary shaft  90   c  penetrating through a central member  3   b  of the guide  3 , projections  92  which are provided on both side surfaces of an upper frame of the guide  3 , and projections  94  which are provided on both side surfaces of a lower frame of the guide  3 . The lock arm  90  is a rectangular frame. Arms  90   b,  which are connected to the rotary shaft  90   c,  are bent at intermediate positions so that L-shaped configurations are formed respectively, and they are connected to a lock bar  90   a  which traverses the straps. When the straps are made free from the guide  3  as shown in FIG. 12A, the arms  90   b  are prevented from counterclockwise rotation by the projections  92 . Therefore, the straps  11 ,  13  are slidably movable with respect to the guide  3 . On the other hand, when the straps  11 ,  13  are prohibited from the movement with respect to the guide  3 , then the arms  90   b  are flexibly bent to ride over the projections  92  so that the arms  90   b  are rotated in the counterclockwise direction, and the arms  90   b  are further flexibly bent to ride over the projections  94  as shown in FIG.  12 B. In this state, the lock bar  90   a  presses the strap bundle composed of the straps  11 ,  13 . Therefore, it is impossible for the straps  11 ,  13  to make any sliding movement in the slits of the guide. 
     Twelfth Embodiment 
     This strap device  700  shown in FIGS. 13A and 13B has approximately the same structure as that described in the sixth embodiment except that the lock adjuster  60  is provided on the main bag body  80 , and an engaging section for making engagement with a lock pawl is provided for a lower frame  140  of a guide. An end of a main body  60   a  of the lock adjuster  60  is attached to a side wall section  80   a  of the main bag body  80  by the aid of a web  63 . In a state in which the strap device  700  is contracted as shown in FIG. 13A, the lock pawl  60   b  of the lock adjuster  60  is engaged with the lower frame  140   a  of the guide  140 , and the guide  140  is fixed to the lock adjuster  60 . A first piece  73   a  of a Velcro tape  73  is adhered to the back surface of a pad  70 . A second piece  73   b,  which adheres to the first piece  73   a,  is attached to the side surface  80   a  of the bag. The pad  70  is detachably attached to the side surface  80   a  of the bag by the aid of the Velcro tape  73 . In order to pull out the straps from the strap device  700 , the lock pawl  60   b  is flexibly deformed with respect to the main lock adjuster body  60   a  to disengage the lock pawl  60   b  from the lower frame  140   a  of the guide  40 . Subsequently, as shown in FIG. 13B, the first piece  73   a  of the Velcro tape is disengaged from the second piece  73   b,  while the pad  70  is pulled in the direction to make separation from the lock adjuster  60  along the side surface  80   a  of the main bag body. As a result of this operation, the straps  11 ,  13  are pulled out from the area between the guides  140 ,  5 . When the straps are completely pulled out, the guide  140  and the guide  5  are joined to one another and integrated into one unit as shown in FIG.  14 A. 
     In order to shorten the pulled out straps, the user grips the pad  70  or the guide  5  with one hand to carry the guide  140  joined to the guide  5  to the lock adjuster  60  so that the lower frame  140   a  of the guide is engaged with the adjuster pawl  60   a  as shown in FIG.  14 B. In this situation, the straps are in a state of being loosened as shown in FIG.  14 . Subsequently, the user pulls the guide  5  in the direction to make separation from the guide  14  (direction of the arrow shown in the drawing) while gripping the pad  70  or the guide  5 . Accordingly, the loosened straps are accommodated into the area between the guides  5 ,  140  to successfully make restoration to the state in which the guides  5 ,  140  are separated from each other as shown in FIG.  13 A. The pad  70  can be fixed to the side surface  80   a  of the bag by adhering the first piece  73   a  of the Velcro tape to the second piece  73   b.  It should be noted that the user can retain the main bag body  80  by gripping a handle  80   c  of the bag with the other hand during the operation for shortening the straps as described above. That is, when the lock mechanism of this embodiment is used, the user can perform the extending/contracting operation for the straps with one hand, while gripping the handle  80   c  of the bag with another hand. Therefore, it is unnecessary to place the main bag body on the floor or on the chair during the extending/contracting operation for the straps. Especially, when the operation for contracting the straps is performed, it is enough to perform the two steps of (i) inserting the lock pawl  60   b  into the lower frame  140   a  of the guide, and (ii) pulling the guide  140 . The simple two steps take only several seconds. It is intended that the side surface of the bag in this embodiment refers to the front face of the bag. However, the side surface of the bag may be the back face of the bag. When the strap device is provided on the front face of the bag, it is possible to give a functional design to the bag. When the strap device is provided on the back face of the bag, the design of the front face of the bag is not deteriorated by the strap. 
     In a modified embodiment of the twelfth embodiment, a strap device as shown in the tenth embodiment may be used in place of the strap device  700 . In this case, as shown in FIG. 17, an engaging section  610 , which is engageable with the lock pawl  60   b,  can be attached through a tape  612  (or directly) to the bottom surface on the side of the strap passage window  30   a  of the guide cover  30 . The second piece  73   b  of the Velcro tape may be attached to the bottom surface of the guide cover  50 . 
     The guide, which has been described and explained in the foregoing embodiments, may have structures as shown in FIGS. 15A and 15B. A guide  133  shown in FIG. 15A has a central member  133   b  around which the strap is wound. The central member  133   b  is provided in the guide so that the central member  133   b  is offset toward the outlet side of the guide (left side in the drawing) in the lengthwise direction of the guide. Especially, in this embodiment, the central member  133   b  is provided at the outlet end of the guide, for the following reason. According to experiments performed by the present inventor, when the strap is sewed up in a state in which the strap is wound around the central member  133   b  of the guide, a seam  135  is separated from the central member  133   b  (margin for the seam). For this reason, when the first guide  133  is joined to the second guide  133 , there is some possibility that the seam  133   b  may enter the slit of the second guide  133 . Such a situation arises due to the fact that any margin for the seam is necessarily required when the seam  135  is formed by using a sewing machine. In order to avoid such an inconvenience, the guide, in which the central member  133   b  is provided at the outlet end of the guide as shown in the drawing, may be used such that the strip is sewed up at the outside of the guide, and the seam  135  is accommodated in the guide  133  thereafter. 
     In this case, it is desirable that the spacing distance S 1  of the slit, which is formed between the central member  133   b  and the upper frame  133   a  of the guide, has a width so that the two straps pass therethrough to such an extent that the straps are not loosened with respect to the guide. For example, it is desirable that the spacing distance S 1  has a width which is larger than the double of the thickness of the strap by about 0.2 mm to 1 mm. It is desirable that the spacing distance S 2  of the slit, which is formed between the central member  133   b  and the lower frame  133   c  of the guide, has a width so that the three straps pass therethrough to such an extent that the straps are not loosened with respect to the guide. For example, it is desirable that the spacing distance S 2  has a width which is larger than the triple of the thickness of the strap by about 0.2 mm to 1 mm. It is desirable that S 1  and S 2  are related such that S 2  is larger than S 1  by not less than the thickness of the strap. In place of the arrangement in which S 1  and S 2  are different from each other as described above, when the end portion of the strap is folded doubly or more to stitch the folded end portion and the strap together, an obtained stitched portion has a thickness which is not less than size of the slit. Accordingly, the seam is prevented from invasion into the slit. 
     Alternatively, when the margin for the seam can be shortened, the central member may be constructed with mutually independent columnar members for a section  34   d  to which the first end  11   a  of the strap is connected and a section  34   b  around which the strap is wound as in a guide  34  shown in FIG.  15 B. When this arrangement is adopted, then it is possible to obtain a thin thickness W of the guide (guide width in a direction perpendicular to the direction in which the strap is extended), and the strap is moved more smoothly. Further as shown in FIG. 15B, in order to easily perform the operation for pulling away the pair of guides from each other, projections  130  may be provided for an upper frame  34   a  and a lower frame  34   c  of the guide, and the projections  130  can be used to function as a grip. It is effective that the projections are provided on side surfaces (lateral frames) of the guide. 
     In place of the lock mechanisms shown in FIGS. 7A,  7 B,  8 A, and  8 B, a structure may be adopted as shown in FIG. 16, in which the second end  11   b  of the strap is folded back to form a section ll c  at which the strap thickness is increased so that the section  11   c  is inserted into the slit of the guide to make engagement as shown in FIG.  16 . This structure enables the strap to be locked by the guide extremely easily. This structure is especially useful for the strap for the portable telephone shown in FIG.  5 . In place of the overlapped strap, a member, which is insertable into the slit portion of the guide, may be provided in the vicinity of the second end of the strap so that the member is detachable or the position of the member is changeable. This member may be secured to an adjuster (not shown) for regulating the length of the strap. 
     FIGS. 18A-18E show a variety of patterns to be adopted for the straps  11 ,  13  to pass through the slits of the guides  3 ,  5  in the strap device of the present invention. Any one of the patterns is included in any one of the forms of the strap device of the present invention as defined in claims. Among them, in view of the intention to avoid the twist or entwinement of the straps  11 ,  13  when they are pulled out from the guides  3 ,  5 , it is especially advantageous to use the pattern shown in FIG. 18B which is equivalent to one shown in FIG.  7 A. 
     The present invention has been explained above as exemplified by the embodiments. However, the present invention includes a variety of modified embodiments of the embodiments. For example, the strap device of the triple elongation mode shown in FIG. 6 may be used as a strap for the bag or portable telephone shown in other embodiments. Further, the exemplified lock mechanism may be provided for the strap devices (for example guide  5 ) shown in FIGS. 4,  6 ,  8 ,  9  and  10 . Those usable as the material for the strap include leather, artificial leather, and cloth. When a flexible material such as cloth is used, a core material such as gut may be inserted into the interior of the material in order to avoid any twist or entwinement of the strap. The strap device of the present invention is usable for a variety of ways of use in which the extendable/contractible function is conveniently adopted, including, for example, reins or bridles for animals, electric cords, chin straps for caps and helmets, cords for glasses, and belts for clothes such as overcoats. 
     The strap of the present invention can be extended extremely easily to have the length which is the quadruple of the length obtained when the strap is contracted. Therefore, the strap of the present invention is preferably used for a variety of ways of use, including, for example, straps for bags and portable telephones. The strap of the present invention can be produced at low cost, because its structure is simple. As for the bag of the present invention, when the strap is not used, the strap is contracted to have the length at which the strap does not hang down from the main bag body. When the strap is required, the strap can be instantaneously stretched to have the sufficient length. On the other hand, the strap can be contracted easily and instantaneously.