firstly , a preferable embodiment of the present invention of picture frame is described in accordance with fig1 - fig3 . in fig1 - fig3 is a hollow frame member having the opening 2 along its longitudinal direction to hold a picture face . the end of the frame 1 is cut to 45 ° to form the connection face 3 . to the underside of the end of the frame member 1 an oblong stopper hole 4 is formed in its longitudinal direction . numeral 5 is an l - shaped corner connection fitting , of which each leg part is inserted into the hollow frame members 1 , 1 to connect them perpendicularly and to assemble them as a square frame . numeral 6 is a stopper formed on the under face of the corner connection fitting 5 , and this stopper 6 engages with the stopper hole 4 when the frame member 1 is inserted to the leg of the corner connection fitting 5 , and it is prevented from being pulled out . numeral 7 is a little upwardly projected spring part formed on the upper surface of the leg part of the corner connection fitting 5 . this spring portion 7 is fit to the inside of the frame member 1 without any clearance when the frame member 1 is inserted to the leg part of the corner connection fitting , and the looseness can be prevented . moreover , the corner connection fitting 5 is made symmetrically , making the dashed line c of fig1 as the center . in the frame of this exemplary embodiment , when the frame member 1 shown in fig1 is inserted into each leg of the corner connecting fitting 5 as shown by the arrow , the frame member 1 is inserted into the leg part of the corner connection fitting 5 without any looseness by virtue of the spring part 7 . the connection face 3 is stopped at the centerline c or deep - end of the corner connection fitting 5 , and touches the end . at this time , the end of the stopper 6 located on the leg part of the corner connection fitting 5 meets with the stopper hole 4 , and springs out with the elastic force , and engages with the stopper hole 4 , serving as pull out prevention . this construction is indicated in detail in fig2 and fig3 . fig2 is a perspective view of the fig1 as viewed from the underside , and fig3 is the perspective view of the frame in an assembled condition as viewed from the underside . the stopper 6 is formed to spring out a little initially . when the frame member 1 is inserted into the leg part of the corner connection part 5 , the stopper 6 is pressed down by the inside face of the frame member 1 , and recovers the original position by elastic force when the stopper hole 4 and the stopper 6 coincide with each other , and the stopper 6 engages with the stopper hole 4 . therefore , when the frame member 1 is pulled in the opposite direction of insertion for removing it from the leg part of the connection fitting 5 , they will not be pulled apart . however , when the stopper 6 , which is engaged with the stopper hole 4 , is pressed down by a nail or an end of a bar , the engagement of the stopper 6 and the stopper hole 4 is released and the frame member 1 can easily be pulled out . the corner connection fitting 5 has a cross - section almost the shape of u , and it can be molded as one body with a certain resin having elasticity , therefore , the constituent parts of the frame can be reduced to the frame member 1 and corner connection fitting 5 only . thus , the frame of this exemplary embodiment does not need rivets or screws to assemble the frame members , and requires only a small number of components . this not only reduces assembly man - hours , with simple assembly work and reduced production cost , it is also accompanied with the advantage that the corner connection fitting is inserted into the frame member and is not exposed outside , resulting in a good appearance and no rivet or screw head projecting outside , and the back surface of the frame can flatly contact with the wall . moreover , the frame member , inserted into the leg part of the corner connecting fitting , can be assembled in a stable manner , because the clearance is absorbed by the spring part , and also the frame member can be pulled out easily from the leg part of the corner connection fitting only by releasing the engagement of the stopper and the stopper hole ; therefore , the disassembly or re - assembly of the frame work can be performed simply and in a short time . moreover , the frame surface can be enlarged by pulling out the frame member 1 only a limited amount from the leg part of the corner connection fitting ; therefore , the picture can be changed from the front face under this condition . cutting or adjustment of picture position can also be made easily . moreover , in this corner connection fitting , the stopper can be molded as one body with a resin having elasticity , and the corner connection fitting can be manufactured at low cost . now , another preferable exemplary embodiment of the frame of this invention will be described in accordance with the fig4 through fig1 . in fig4 through fig9 is a hollow frame member of which an upper part is formed in a semicircular shape having an opening 12 on the inside along its length for holding a picture . its ends are cut to 45 ° to form the connection face 13 . further , on the underside of the end of the frame member 11 , an oblong stopper hole 14 is formed in the longitudinal direction . moreover , on the underside of the end of the opening 12 of the frame member 11 , a groundpaper base 18 of a certain width is formed . numeral 15 is an l - shaped corner connection fitting formed to nearly u - shaped cross - section , of which each of the leg parts is inserted into the frame member 11 , and the members are connected to be perpendicular to each other so that a square frame assembly can be made . numeral 16 is a stopper formed on the lower face of the leg part of the corner connection fitting 15 having two stage engaging parts 16 - a and 16 - b in the direction of insertion . when the frame member 11 is inserted to the leg part of the corner connection fitting 15 , the second engaging part 16 - b of the stopper 16 and the first engaging part 16 - a are successively engaged with the stopper hole 14 , and it is designed so that the frame member 11 is prevented from coming out at each of the engaging positions . numeral 17 is a guide formed on the upper surface of the leg part of the corner connection fitting 15 in the longitudinal direction in a manner to project a little upwards , so that it touches the inside of the semi - circular form of the upper face of the frame member 11 and guides the insertion and withdrawal of the frame member 11 . the corner connection fitting 15 is made symmetrically , making the dashed line of fig4 as the center . in fig9 shows a groundpaper , 21 is a picture such as a jigsaw puzzle and 22 is a transparent plate . in the frame of this second exemplary embodiment , when the frame members 11 , 11 shown in fig4 are inserted to each of the leg parts of the corner connection fitting as shown by the arrow mark , the frame members 11 , 11 are guided by the guides 17 and inserted to the leg part of the corner connection fitting 15 smoothly , and the connection faces 13 , 13 stop at the innermost of the corner connection fitting 15 , and correctly meet each other as shown in fig5 . during this process , the second stage engaging part 16 - b located at the mid - part of the stopper 16 on the leg part of the corner connection fitting 15 first coincides with the stopper hole 14 and springs out by the elastic force ; however , the frame member 11 is further inserted and the first stage engaging part 16 - a at the end of the stopper 16 coincides with the stopper hole 14 and springs out by elastic force , thus engaging with the stopper hole 14 , and preventing withdrawal . this structure is described in detail in fig6 and fig7 . fig6 is a perspective view of fig4 as viewed from the underside , and fig7 is a perspective view of fig5 as viewed from the underside . the stopper 16 is formed stepwise so that both the first engaging part 16 - a and the second engaging part 16 - b are projected a little outside initially . when the frame member 11 is inserted to the leg part of the corner connection fitting 15 , the stopper 16 is first pressed down by the inside face of the frame member 11 ; however , when the stopper hole 14 and the second engaging part 16 - b coincide , it recovers a little by the elastic force and the second stage engaging part 16 - b engages with stopper hole 14 , and when the frame member 11 is further inserted and the stopper hole 14 coincides with the first stage engaging part 16 - a , the stopper 16 recovers to the original position with its elastic force , and the first engaging part 16 - a of the stopper 16 engages with the stopper hole 14 . therefore , when the frame member 11 is pulled in the direction opposite to that of insertion with the intention of removing the frame member 11 from the leg part of the corner connection fitting 15 under the condition that the engaging part 16 - a or 16 - b is engaged with the stopper hole 14 , the member 11 will not be pulled out . secondly , in the case of changing pictures , the user can press down the stopper 16 and release the engagement of the first stage engaging part 16 - a and the stopper hole 14 , as shown in fig8 and pull out the frame member 11 a little . then the second stage engaging part 16 - b and the stopper hole 14 engage , and the pulling out of the frame member 11 is prevented . namely , when the stopper 16 is pressed lightly by a finger , and the frame member is pulled a little , the second stage engaging part 16 - b engages with the stopper hole 14 , and the frame member is a little expanded and stopped . therefore , if the same process is performed to the four corners of the assembled frame , the frame area made by the frame members 11 , 11 will be expanded . then the user can place the frame to make the front side face him to mount the groundpaper 20 on the groundpaper base 18 . the picture 21 is placed on it , and then a transparent plate 22 is placed upon it . the frame members 11 are pushed into the leg parts of the four corner connection fittings 15 , then the first stage engaging parts 16 - a engage into the stopper holes 14 and the frame is completed , with the edge portions of groundpaper 20 , the picture 21 , and the transparent plate 22 being held and fixed in the opening 12 of the frame member 11 . this operation requires only that the frame member 11 be pressed in the direction of arrow mark . the operation is very simple , and the user is required to pay attention only to the setting of the picture 21 . moreover , to disassemble the frame , the user can press down the stopper 16 in fig8 release the engagement of the second stage engaging part 16 - b and stopper hole 14 , and pull out the frame member 11 ; then the frame member 11 is separated from the corner connection fitting 15 , and the frame can easily be disassembled . now the procedure to change pictures using the frame of this exemplary embodiment is described in the order of process in accordance with fig1 through fig1 . to change pictures , pull both corners of the frame member 11 outwardly while pushing down the stopper 16 with your thumb and index finger . when this operation is performed for all four corners , the frame is expanded as shown in fig1 , and the picture in the frame is able to be taken out . then , insert another picture as shown in fig1 , and push the frame members 11 into the leg parts of the corner connection fittings . when all the four corners are processed like this , the other picture is set in the frame as shown in fig1 and the replacement of the picture is completed . all these operations can be performed from the front side of the frame , and the setting is easy and the replacement is very simple . change of picture can also be made by the frame of the exemplary embodiment shown in fig1 - fig3 by the same procedure as shown in fig1 - fig1 ; however , with the frame of the second exemplary embodiment shown in fig4 - fig9 the dimensions of the expanded frame area are controlled uniformly by means of the double staged engaging parts 16 - a and 16 - b of the stopper 16 , preventing the frame member 11 from being pulled out of the leg part of the corner connection fitting 15 by applying too much force , and the replacement operation is more easy . further , in the frame of the exemplary embodiment of fig4 - fig9 guides 17 are formed on the leg parts of the corner connection fittings 15 ; however , spring parts 7 may be used instead of the guides 17 as in the first exemplary embodiment shown in fig1 - fig3 and conversely in the exemplary embodiment shown in fig1 - fig3 guide 17 as shown in the exemplary embodiment shown in fig4 - fig9 may be used instead of the spring 7 . moreover , in the frame of the second exemplary embodiment shown in fig4 - fig9 the groundpaper base 18 is prepared as one body with the opening part 12 of the frame member 11 for the easy installation or replacement of picture ; however , the groundpaper base 18 may be formed with the opening part 2 of the frame member 1 in the first exemplary embodiment shown in fig1 - fig3 . moreover , it is needless to say that also in the frame of the exemplary embodiment shown in fig4 - fig9 the corner connection fitting 15 has the section of about u - shape , and the stopper 16 is molded as one body with a plastic resin having elasticity , the detailed sectional form being designed to be most suitable to the sectional form of the frame member 11 .
hollow frame members , having openings to hold a picture along its longitudinal direction , and having connection faces cut to 45 ° at its ends , receive each insertable leg part of an l - shaped corner connection fitting . the frame members connect to each other in perpendicular relationship to form a square form . one stage or two stage engaging means consisting of stoppers and stopper holes at the corner part of the frame members enable expansion of the frame surface , allowing for assembly or disassembly , and easier replacement of pictures . spring parts or guides are formed on the corner connection fittings , to eliminate looseness of the frame members , and to make insertion and withdrawal smoother . the stoppers can be formed as one body with the corner connection fittings with a resin having elasticity to make the manufacturing of the corner connection fitting easier . the frame is formed with a groundpaper base at the opening part to make setting or changing of the puzzle or photo easier .