Improvements in Floor Joists, in the Method of Crowning same, and in Machinery therefor.
Year: 1892

page_text: Date of Application, 6th Dec., 1892-Accepted, 7th Jan., 1893
COMPLETE SPECIFICATION.
Improvements in Floor Joists, in the Method of Crowning same, and
in Machinery therefor.
I, JOSEPH FRIEDRICHS, of No. 304, North Eighth Street, in the City of
St. Louis, State of Missouri, United States of America, Gentleman, do hereby
declare the nature of my said invention, and in what manner the same is to be
performed, to be particularly ascertained in and by the following statement :-
My invention relates to the method of, and means for, giving to floor joists the
required curvature or convexity to their upper surfaces to compensate for their
sag when placed in position and made to support a weight or strain, and has for its
object to give each joist, in a group of joists to be used together, a crowning
corresponding to, and compensating for, their relative strengths and consequent
relative sags, when subjected to a given load or strain, adapting the top surfaces of
the different joists to be brought to a common level when thus subjected to such
strain or load.
The object, in any case, of crowning joists, is to give the upper surface a
convexity, or curvature, more or less pronounced, from end to end, to compensate
for the normal sag of the same when supported as a beam at either end. The
degree of curvature thus given is determined by the length, and should, also, be
modified, in each particular piece, to independently compensate for the relative
deflection-resistance of each picce.
Heretofore, this has been done by hand, the curvature given to the upper
surface of the joists being uniformly gauged by a templet, similar for all joists of
the same length. It is evident that, by this method, the joists are all similarly
curved, and that, when placed in position, supported at their ends, the weaker ones
will have more of a sag than the stronger ones, leaving the upper floor-supporting
surfaces uneven and irregular.
My invention consists in an improved method of crowning joists, by which, the
unequal vertical beam-strength of the different timbers is provided for, as hercin-
after described.
The accompanying drawings, in which like numbers of reference denote like parts
in the several figures, serve to illustrate my improved method and one form of
apparatus adapted to put the same in practice.
The machine illustrated, is a simple wood-planing machine, with a longitudinally-
movable bed, on which to support the timbers to be planed and bring them under
the rotating planer-knives, as in an iron-working planer.
Figure 1 is a side elevation of the same;
Figure 2 is a plan-view ;
Figures 3 and 4 are side elevational views of a joist being planed and after
having been planed, respectively; and
Figure 5 is a cross-section, taken on the line 5-5 in Figure 4;
Figure 6 is a vertical section, taken parallel to the length of the machine
through the rollers and cutter-head, showing the spring bearings for the rollers in
elevation;
Figure 7 is a vertical cross-section on line 7-7 in Figure 6; and
Figure 8 is a longitudinal section on line 8-8 in Figure 6;
Figures 9 and 10 are views, similar, respectively, to Figures 2 and 1, showing
the preferred details of the bearings for the presser-rollers shown in Figures 1 & 2.
1, 1, are the side timbers of the machine, to which are secured the vertical
standards 2, and, in which, are formed guide-ways for the sliding bed-plate 3. In
the standards 2, are formed guides for the sliding frame 4, which is vertically
adjustable, by means of the screws 5, one of which is placed on either side of the

page_text: machine, and are connected together by a cross-shaft 6 (see Figure 1) and bevel
gear-wheels 7, so as to operate both ends of the frame 4, together. In the frame 4,
are revolubly mounted the forward and following rollers and the rotary knife-
shaft 9, to the end of which, as shown in Fig. 2, is secured the small drive-pulley 10,
by which means the machine, as a whole, is made to operate through the medium
of the belt 11. It will be readily understood, without more detailed illustration,
that, in the operation of the machine, at the same time that the knife-shaft 9 is
made to rotate, the bed-plate or platform 3 is given a longitudinal movement to
bring the joists 12 in operative position under the rotating knives.
The foregoing description relates to the form of machine illustrated in the first
and second figures of the drawings. While, by the use of the machine, as just
described and as illustrated in the first two figures, the "crowning," as hereinafter
described, can be effectually carried out, yet the details illustrated in Figures
to 10, inclusive, and hereinafter described, are preferably made use of, to more
conveniently, and, strictly speaking, more effectually carry out my method. These
details, indeed, are common to wood-planing machines, to which my method is
adapted, and form no part of this invention, and, in the practice of my improved
method, are made use of for the purposes just stated.
The rollers 8 are journaled in boxes 16, which are provided guide-ways in the
vertically-movable frame 4, the boxes being held in vertically yielding position by
the compression-springs 17 and 17', and this position made adjustable by means of
the adjusting screw-bolts 18, which bear against the upper end of the upper
spring 17. The normal position of the journal-bearing is, in this manner,
determined as a position of equilibrium between the two springs, and this decided
by the tension given to the upper springs by the set or adjusting screws 18. By
these means, the level of the under or effective side of the rollers 8, and the cutting
level of the cutter 9, are adjustable relative to each other. The cut taken by the
knife is, in any instance, therefore, defined primarily by the set position of the
forward roller 8. Thus, when the supporting-frame 4 is screwed down to bear
harder on the timbers, or, what is the same thing, the timbers press harder on these
rollers, as hereinafter explained, in the act of planing, the upper spring will "give"
more or less and the cutter will take a deeper "bite."
Instead of
As illustrated, there are, preferably (for economic reasons), several (6) joists
placed on the sliding platform and secured together by the clamps 13.
laying the joists flat on the plane surface of the sliding platform 3, I interpose
under each end of the joists, a block 14, thick enough to raise the joists far enough
away from the surface of the planer-bed or platform 3, where the joists are carried
in under the action of the knife to be planed, as illustrated in Fig. 3, to allow for
the necessarily consequent deflection of the middle portions of the joists. This
result might, also, be obtained by hollowing the bed of the planer to similarly allow
for the deflection of the joists.
In this manner, the joists, in fact each individual joist, independently of the
others, is, in the operation of crowning, subjected to a strain similar to that when
placed in a building, similarly applied, and under exactly similar conditions--
the ends, only, supported.
1.e.,
As already stated, the amount of cut of the knife 9 is due, primarily, to the
relative position of the cutter-blades and the normal position of the forward roller 8,
but not altogether so. When for instance, in the act of planing, the frame 4 is
screwed down so that, while the ends of the timbers, when they are supported at
the ends only, are immediately below the cutter-head, the roller is forced upward
relative to the cutter, and, therefore, the cut taken will be greater at this point
than at the middle, when it comes under the cutter, in that the timbers "give," and
do not press so hard against the rollers 8, allowing them, by the action of the upper
spring 17, to be depressed relative to the cutter.
It will be evident that the curved form of surface of the upper edge of the joists,
illustrated in Figure 4, will be the result of passing the joists in under the knife and
rollers, in that, the ends being supported, the knife will take out a given cut there,

page_text: which cut will be reduced as we approach the middle portion of the length of the
joists, the joists being deflected from the normal by the pressure applied, in a
vertical direction, by the knife and rollers, or, what is the converse of this fact, if
the joints were rigid beams without deflection, the cut would be even throughout the
length of the same.
Moreover, this decrease of cut at the mid-length of the timbers being due to the
deflection of the joists, as beams supported at either end, for a given pressure, the
stronger ones-i.e., those better able to resist this applied strain, will "give" less,
and be cut more in the middle-that is, they will be cut more nearly to a straight
line than the weaker ones, which will "give" more to the applied strain.
There is more than one cause that goes to effect this result. As before stated,
the primary cause of the "crowning" of the group of joists, considered collectively,
is due to the decrease of upward pressure of the joists in their mid-length on the
presser-rollers. But this in itself does not account for the differential planing of
individual weaker and stronger timbers. Consider, for the sake of illustration, the
pressure-rollers removed, then the cutter itself bearing against the upper surface
of the joists, as they are supported at their ends only, the joists will "give" more
or less before the revolving knife, and that, in each individual joist, in the inverse
proportion to its strength and its ability to resist the deflecting strain put upon it
by the cutter. That is, at the middle of the length they will be cut less than at
their ends, and that to a different degree as between weaker and stronger ones.
Now, when the roller-the preceding one, which is the only one that need be
considered is used, the strain is partly borne by the roller and partly by the
cutter, and, while the result as above, when the roller was removed, will not be so
marked, yet it is effected to a comparative degree. It has also been observed, in
the practical use of the planer, as described, where the roller is small--not more
than two and one-half or three inches in diameter-it becomes more or less, in
proportion to the pressure put upon it, imbedded in the fibre of the timber, and
this, of course, modified by the strength of the individual joist, in this manner
presenting more timber to the cutter than if it was not imbedded, and, of course,
comparatively more to the stronger timbers. Now, when this applied strain is
removed; and the joists allowed to assume their normal position, their upper
surfaces, at their mid-length, will be brought to relatively different heights, the
weaker ones, as shown in Fig. 5, those which were less able to resist the deflecting
strain put upon them in the planer, being the higher. When this strain is again
applied, as would be the case where the joists are put into service, as to support a
floor, they will again be brought to a common level.
It is evident, that, when the joists are supported at their ends only, they at once
assume their normal position of deflection, due to their own weight, and that this
enters into and is compensated for by the method described, especially inasmuch as
they are placed, during the act of "crowning," in their natural position-the one
in which they are to be used. This natural deflection also, undoubtedly, helps in
a small measure to obtain the results effected.
It is in this particular that I claim the superiority of my improved method in
practical results over any in use heretofore-in that the joists are planed to a flat
surface when they are being subjected to what can be considered conditions exactly
similar to what they would be subjected when used in actual practice.
It will be evident that, while, as already stated, the essential feature of inven-
tion in the apparatus used to carry out my method is the supporting of the joists
at their ends only, these details relate only to this particular means of carrying my
method into practice, that is, when the deflecting pressure is applied by the means
itself by which the surface of the joists is planed or levelled off, it is enough to
support the joists in such a position to allow these forces to act. The principle
being disclosed, it is obvious that other means might be devised to effect the
results attained. For instance, the joists might be deflected by means other than
the presser-roller and the cutter, and means other than the revolving cutter might
be used to level the surface while the joists are thus deflected.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :
1. The method herein-described for crowning floor joists, which consists in
subjecting the same to a deflecting strain and levelling one surface while so
subjected, substantially as and for the purposes described.
2. The method herein-described for crowning floor joists, which consists in
supporting the same at their ends and planing, or otherwise levelling, the upper
surfaces of the same, substantially as and for the purposes described.
3. In a machine for crowning floor joists, the combination with a levelling
cutter, of a supporting and carrying platform, and means for deflecting the stock
while it is being operated on by the cutter, substantially as and for the purposes
described.
4. In a machine for crowning floor joists, the combination with the cutter of a
supporting and carrying platform, and means supported directly by and carried
with the platform, by which the joists are supported at their ends only, sub-
stantially as and for the purposes described.
5. In a machine for crowning floor joists, the combination with an adjustable
cutter, of a supporting and carrying platform provided with means for supporting
the stock away from the platform, thereby permitting the joists to be deflected
while being cut, substantially as and for the purposes described.
6. As a new article of manufacture, a crowned floor joist, bellied on one side,
said bellied portion being formed by planing, or otherwise levelling, one surface of
the joist while it is being deflected from the normal, substantially as and for the
purposes described.
Dated the 6th day of December 1899
PHILIP M. JUSTICE,
Chartered Patent Agent.