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Патент USA US2128783

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Aug. 30,1938.
Filed March 22, '1937
2,128,783: ,
Patented Aug. 30, 1938
sNro‘FFic E»
_ j" 2,128,783
~ ;
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
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
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
lines œ and y.
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
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
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
‘ 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
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.
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