Патент USA US2128783код для вставки
Aug. 30,1938. _ A Q_ R_ OWENS BENT PLYWOOD Filed March 22, '1937 _£1291 , ' 2,128,783 2,128,783: , Patented Aug. 30, 1938 sNro‘FFic E» > _ j" 2,128,783 ~ ; kvBENTfPLYWooD - .Y ifcago, Ill., assigner to Wells- l y; Chicago, lll., a corpora ’ ' Applicaties Maranza, 1 Claim. (credi-'sei' 1937,l -serialî Nd. "„132,191 " . My present invention relates to bent plywood , which may be produced according to the method disclosed in my application iiled October 27, 1936, under Serial No.' 107,810, now Patent No. 2,074,854, issued March 23, 1937. It is commonly desired to produce a bend in plywood so as to form a round corner which is suitable for use, in trim, cabinets, furniture pieces of Various kinds, etc. By the improvements of this invention I am en L: abled to provide a bent structure which is ample in strength, which will retain its shape and appear ance indefinitely, and which maybe produced with little or no forces of compression to be over come. As illustrative of the bent plywood and the method employed, reference may be had to the accompanying drawing, wherein: Figure 1 is an edge view of a plywood board in the ñrst stage of its preparation for the bend ing operation; Fig. 2 which is a similar View shows the board in the next stage of its preparation; Fig. 3 which is an edge view shows the board with the bend completed; Fig. 4 shows akmechanism suitable Vfor produc 25 ing the desired bend in the board; Fig. 5 which is a fragmentary longitudinal sec tion on an enlarged scale shows the board as it appears in the first stage of its preparation for the bending operation; Fig. 6 which is a similar View shows the board the second stage of its preparation; and Ain Figs. 7 and 8 are Views corresponding generally 35 lines œ and y. ï Glue is now applied between the back and core, and, while still unset, a bending force is applied to the board in the region between the lines a: and y. This may be done conveniently with the 10 aid of a die F and a form R. Throughout that portion of the board which is thereupon bent the glue is unset at the time, permitting the back to slide freely, as required, so as to obviate com pression. The initial width of the gap between l5 the back ends J" and g may correspond generally with the distance which one or both of these ends of the back will be required to move while taking up a new position during the bending operation. As a result, the gap will be substantially closed 20 so as to restore continuity to the back when the bend is completed (see Fig. 3). The bending force is maintained a suflicient time to allow the glue to set whereupon the band becomes perma nent and the board lmay be removed. ` The back 25 which is the inside ply in the bent‘board will resist unbending of the board due to its exerting a tension force which counterbalances that of the plies to the outside of the bend. A bend of the kind described may be produced 30 from a board having three, four, five or more plies. A board of four plies has been illustrated and -described by way of example. In Figs. 7 to Figs. 5 and 6, respectively, showing a board of ñve plies instead of four plies as is elsewhere illus and 8 I-have shown a five ply board having a second cross band h disposed between the back 35 and core. In preparation for the bend which is trated. to be made it will be desirable, although perhaps ‘ The board now to be described may be of ply wood with a core a of relatively soft wood to one face of which is adhered a cross bandV b` upon which is mounted a veneer face c. Applied to- the The several 40 rear face of the core is a back d. plies are arranged preferably with grains cross wise of each other and are united in the usual manner as by layers of glue e. To prepare the board for the bending operation the back is ñrst loosened from the core between certain imaginary lines œ and y which deñne the region of the board where a bend is to be made. The back is then slitted between these lines or along one of them, the line a: for example, a sufficient strip-like part of its body adjacent the line of severance being removed 'to leave a sub 55 will be understood that the freed portion of the back, including the gap between its facing edges, extends between opposite edges of the board. As shown in Figs. 2 and 6, the back is thereupon left unsupported except in the regions beyond the 5 stantial gap which interrupts the continuity of the back. The two spaced edges of the back which denne this gap are designated as f and g. It not necessary, to produce an interruption in the band as well as the back (see Fig. 8). In such case the cross band is -disconnected from the core 40 between the lines a: and y which deñne the region of the bend, and the back is also disconnected from the cross band whereby, during the bending operation, each of these plies may slide inde pendently, the band upon the core and back, and 45 the back upon the band. At the completion of the bend, these two plies will have substan tially closed the gap between their ends f and y. The essence of my invention resides in freeing one or more plies upon the inner side of the board 50 where compressive forces are developed during a bending operation, in cutting out a narrow sec tion> of such ply or plies so as to pro-duce a gap or Vinterruption lengthwise thereof, in applying glue between such ply or plies and the adjacent 55 2 2,128,7â3 ‘ surface of the board, in applying, while the glue is still unset, a bending force which will produce a sliding movement of the freed ply or plies, thereby avoiding compression thereof, and in maintaining the bending force until the glue has set. These several steps are requisite with a con ventional plywood as now produced, but obvi ously, if the back be initially applied so that it is already freed in part and/0r slitted to provide a gap, then these preliminary steps may be omitted when carrying out the remaining steps of this process. The number of plies at the inner side of the board which are to be loosened in preparation for bending will depend in large part upon the character and thickness of the board, it being important that so much of the inner board face as would ordinarily be subjected to a compressive force while undergoing bending be loosened and»r cut away to induce a sliding action. Ín perform-ing the bend any of the usual expedients may be employed, such as steam, to facilitate shaping of the wood, and heat to accelerate setting of the glue, etc. A resinous glue, either sheet or liquid, will ordinarily be found satisfactory. I claim: ' - A bent board of plywood having its several plies united and extended continuously throughout the bend, the ply to the inside of the bend having l0 a transversely extending section removed there from at a point Within the bend and having its innerrsurface united throughout its extent to the adjacent bent ply with its opposed edges in abut ting relation, whereby to reduce the circumfer ential length of the inner ply without the setting >up of a'compressive force therein. ORVILLE R. OWENS.