Improvements in the Manufacture of Helices or Spirals, and a Method of and Apparatus for Making the same.
Year: 1898

page_text: Improvements in the Manufacture of Helices or Spirals, and a Method
of and Apparatus for Making the same.
I, FRANK C. CALDWELL, of Oak Park, Cook County, State of Illinois, United
States of America, Mechanical Engineer, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement: —
My invention has for its object the production of a continuous spiral conveyor
flight formed from a single strip of metal, and it consists in the novel means for
converting a single continuous strip of metal into such spiral conveyor flight,
and in the novel form of the conveyor flight thus produced. I am aware that
it has heretofore been proposed, in various prior patents, to form a conveyor
flight from a continuous strip of metal, and as a practical manufacturer of con-
veyor flights I am also aware that numerous attempts in this direction have been
made; but to the best of my knowledge no successful method or apparatus for
producing such continuous conveyor Hights has heretofore been devised, and
there is not now, and never has been, upon the market or in practical use any
conveyor flight of this description, all conveyor flights which are now and have
heretofore been in use being built up of separate sections. I have devised novel
and successful means for converting a continuous strip of metal into a conveyor
flight of novel form, by which the work may be easily and expeditiously accom-
plished with complete success and satisfaction.
In carrying out my invention I employ a continuous strip of metal of substan-
tially uniform thickness throughout and I convert this strip of metal into a con-
tinuous spiral conveyor flight of tapering form in cross section by passing it
between a pair of pressure rolls of novel form and especially adapted for the pur-
pose, as hereinafter described. Suitable guides are preferably provided to receive
the spiral strip as it issues from the rolls and direct it therefrom in proper form;.
all as hereinafter more fully explained in connection with the accompanying
drawings, in which Fig. 1 is a detail top plan view showing the two pressure
rolls, the metal strip passing between them, and the guides for receiving and
directing the same; Fig. 2 a detail front elevation of the same parts; Fig. 3 an
enlarged cross section of the metal strip: Fig. 4 an enlarged detail of the rolls,
showing the tapering form of the pass between them: Fig. 5 a cross section of
the strip of Fig. 3 after it has been passed between the rolls; Fig. 6 a middle
longitudinal section through a piece of the completed spiral conveyor; Fig. 7

page_text: a diagram illustrating the method of determining the cross section of the spiral;
Fig. 8 an enlarged and somewhat exaggerated view of the cross section of a spiral
as determined by the method illustrated in Fig. 7; and Fig. 9 a similar view of
the two pressure rolls.
The same letters of reference are used to represent corresponding parts in the
several views.
•
In the course of experiments having for their object the production of a con-
tinuous strip spiral, I have discovered that while a strip of metal of uniform thick-
ness may be readily rolled into a disk or ring of tapering form in cross section by
passing it between a pair of truly conical rolls having their working faces set at the
proper angle. to each other, it is wholly impossible to roll such strip into a helix
or spiral by passing it between such rolls, no matter how proportioned and adjusted
in relation to each other. In the course of repeated efforts to convert a continuous
strip of metal into a spiral by means of such rolls I discovered that the difficulty
and the cause of failure arose from the fact that the pass between such rolls
(under any possible adjustment of them) did not conform to what would necessarily
be the cross section of the strip of metal when transferred into a spiral, inasmuch
as the cross section of a spiral produced from such a strip would be substantially
different from the cross section of a disk or ring produced from it. Following
up this discovery, I ascertained, by further experiments, that if the faces of the
conical rolls were so ground as to produce a pass between them corresponding
to what would be the exact cross section of a strip of metal of uniform thickness
when transformed into a spiral, such strip could then be readily converted into
spirals by passing them between such rolls.
As a result of these experiments I found that a spiral of any given pitch might
be formed from a continuous strip of metal of uniform thickness and of any
desired width by first determining mathematically what would be the exact cross
section of such a spiral, and then providing cone like rolls so shaped and adjusted
that the pass between them would correspond to such a cross section, and so pro-
portioned that the circumference of the rolls at the one end of the pass would
bear the same ratio to their circumference at the other end thereof as the length
of one edge of the spiral strip to be formed bore to the length of the opposite
edge thereof.
In carrying out my invention, therefore, the first step consists in determining
the exact mathematical cross section of the spiral to be produced, and in then
providing the necessary cone like rolls having their working faces so shaped that
when the rolls are properly assembled the pass between them will conform to the
cross section of the spiral to be produced, and so proportioned that their circum-
ference at one end of the pass (i.e. end of the working portion thereof,) will bear
the same ratio to their circumference at its opposite end as the length of one edge
of the spiral strip to be formed bears to the length of the opposite edge thereof.
The cross section of the spiral may be arrived at by either an arithmetical or
geometrical solution of the problem. I have illustrated the latter method in
Figs. 7 and 8 which may be briefly explained as follows:-In Fig. 7 let A C
equal the circumference of the conveyor flight at its outer edge, A S its circum-
ference at its inner edge, and A B the pitch of the helix. CB will then equal
the length of the helix at the outer edge of the flight, and S B its length at the
inner edge of the flight.
Dividing the line S C. (the width of the flight) into any convenient number of
parts, A R, A Q, A P, &c. will represent the circumference of the circles con-
centric to A S and within A C, and R B, Q B, P B, &c. will represent the corres-
ponding helices.
Lines drawn from A perpendicular to the lines S B, RB, Q B, etc. will inter-
sect the latter at the points S¹, R¹, Q¹, &c. Let SI B equal the thickness of the
metal s¹¹ at the inner edge of the conveyor flight, then R¹ B, Q' B, PB &c. will
represent the thickness of the metal at the points r¹ b, q¹ b, pb etc. where the
helices R BQ BP B, &c. are taken.

page_text: Assuming, now the thickness of the inner edge of the spiral which it is desired
to produce to be one eighth of an inch, for instance, the dimension S¹ B will be
scaled to such thickness, and the dimensions R¹ B, Q¹ B &c. be then read by the
same scale. By using the thicknesses thus found the cross section of the spiral
may be delineated as shown in Fig. 8 and its faces will be seen to be slightly
curved inwards. The necessary contour of the rolls can be readily determined
therefrom.
In the present instance the rolls A B, Figs. 12 and 4 are formed upon the upper
ends of shafts or spindles A B₁ having convergent axes and suitably journalled
in bearings in the frame work C of the machine, and driven at a uniform speed
by any suitable means. The circumference of the rolls at the narrower end of
the working part of the tapering pass between them bears the same ratio to their
circumference at the wider end thereof that the length of the outer edge of the
helix to be formed bears to the length of the inner edge thereof, while at 'all
intermediate points the circumference of the rolls corresponds to the length of the
intermediate helices of the spiral. The departure of the rolls from a truly conical
shape is not appreciable in views of the size found on Sheet I of the drawings,
but will be readily understood from Sheet 2, and the explanation heretofore of
the method of determining the shape of the rolls.
When the rectangular metal strip is passed between these rolls it is expanded
from its inner toward its outer edge in exactly the proportion's necessary to con-
form it in cross section to the cross section of a spiral, and the ratio of feed at
äll points between its opposite edges is such as to draw the strip in evenly between
the rolls throughout its width, and deliver it therefrom in the form of a spiral.
In Fig. 1 E represents the metal strip, which is fed to the rolls A B through a
suitable guide way F, and as it issues from the rolls it passes between two
guides G G consisting in this instance of adjustable screws mounted in sup-
ports Hupon the frame work. As seen in Fig. 2 the guide G bears against
one side of the metal strip near its lower or outer edge, as it issues from the
rolls, while the guide G¹ bears against its opposite side near its upper or inner
edge. These two guides are so set and adjusted as to properly direct the strip
from the rolls in the spiral form shown in Figs. 1 and 2. The action of the rolls
themselves upon the strip causes the strip to tend to issue from them in spiral
form, and under some conditions and for some purposes the guides may perhaps
bé dispensed with, but they are advantageous and desirable for insuring a uniform
pitch in the spiral, even if not absolutely essential in all cases, and may be em-
ployed in the form shown or in any other suitable form for the purpose and they
may be arranged to direct the strip into a right hand spiral, or a left hand one,
as desired.
While my invention has been designed more especially for the production of
spiral conveyor flights, and while, being a manufacturer of conveyors; that is the
only use I have made of it, it will be evident that it may be advantageously em-
ployed for the production of spirals for other purposes than conveyor flights, such;
for instance, as springs; and that spirals may be formed of strips of different
widths and thicknesses, and of varying pitch, and of varying internal diameter
of bore, by properly arranging the size, proportions and adjustment. of the rolls.
In the practical use which I have thus far made of my invention, I have heated
the metal strips before passing them through the rolls, to facilitate the action of
the rolls upon them, but I contemplate the employment of heavier and more power-
ful rolls by which the strips may be rolled into form without heating.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, I declare that what
I claim is:-
1. As a new article of manufacture, the herein described spiral formed from
a continuous strip of thin wrought metal, as set forth.
2. As a new article of manufacture, the herein described spiral formed from a

page_text: continuous strip of thin wrought metal of substantially uniform thickness and
tapering in cross section from its inner toward its outer edge, as set forth.
3. As a new article of manufacture, the herein described spiral rolled from a
continuous strip of thin wrought metal of substantially uniform thickness, said
spiral tapering in cross section from its inner toward its outer edge and having
its sides curved slightly inward, as set forth.
4. The herein described method of making continuous strip spirals, consisting
in forming the spiral from a thin strip of wrought metal by passing the same
between suitable pressure rolls having a tapering pass between them correspond-
ing to a cross section of the spiral to be produced, as set forth.
5. The herein described method of making continuous strip spirals, consisting
in forming the spiral from a thin strip of wrought metal of uniform thickness
by passing the same between suitable pressure rolls having a tapering pass between
them corresponding to a cross section of the spiral to be produced and adapted to act
upon such strip of metal and gradually expand it from its inner toward its outer
edge and bring it into the form of a spiral tapering in cross section from its inner
toward its outer edge, as set forth.
6. The herein described apparatus for producing spirals from continuous strips
of thin wrought metal, consisting of a pair of cone like pressure rolls having
convergent axes and so shaped and proportioned as to provide a tapering pass
between them corresponding to a mathematical cross section of the spiral to be
produced the circumference of said rolls at the narrower end of the pass between
them bearing the same ratio to their circumference at the wider end of the pass
as the length of the outer edge of the spiral to be produced bears to the inner
edge thereof, and means for driving said rolls, as set forth.
7. The herein described apparatus for producing spirals of the form specified,
consisting of a pair of cone like rolls having convergent axes and so proportioned
and sét relatively to each other as to provide a pass, between them tapering from
their apices toward their bases and corresponding to a mathematical cross section
of the spiral to be produced, suitable guides for receiving the strip as it issues
from the rolls and directing it in spiral form therefrom, and means for driving
the rolls, as set forth.
8. The herein described apparatus for producing spirals of the form specified con-
sisting of a pair of cone like rolls so proportioned and set relatively to each other
as to provide a pass between them tapering from their apices toward their bases
and corresponding to a mathematical cross section of the spiral to be produced,
the two guides located on opposite sides of the path of the strip as it issues from
the rolls and bearing against the opposite sides of the same near its outer and
inner, edges, respectively, and means for driving the rolls, as set forth.
9. The herein described apparatus for producing spirals of the form specified,
consisting of the cone like rolls A B carried by the end of the shafts A B and
having the tapering pass between them, the guide way F for the metal strip E,
located upon the entering side of the rolls, the adjustable screws G G¹ located upon
the opposite side of the rolls and operating as guides for the outer and inner edges
of the spiral strip as it issues from the rolls, and means for driving the shafts A¹
B¹, as set forth.
Dated this 18th day of August 1990.
HERBERT HADDAN & Co.,
Agents to Applicant, 18, Buckingham Street, Strand, London.