Year: 1886

page_text: Date of Application, 3rd Apr., 1886.
Complete Left, 16th Dec., 1886.
Complete Accepted, 21st Jan., 1887.
I, GUSTAV DAVERIO, Engineer, residing at Zurich, Switzerland, do hereby declare
the nature of this invention to be as follows:-
--
My invention relates to screens for middlings-purifiers, and the improvements
consist in the means employed for stretching the gauze, constituting the sifting surface
of the screen, as well lengthwise as transversely, and for allowing a sheet of gauze
composed of pieces of different fineness, to be shifted lengthwise in the frame of the
screen, so that the desired piece may come into operation.
For this purpose I provide the longitudinal parts of the frame near their bottom
edge with a groove narrow outside and widened inside, while into each edge of the
gauze is sewed a cord having such thickness that the said edge thus strengthened,
may be passed into the said groove lengthwise, but that the cord will prevent the
gauze from slipping out transversely. At the ends of the frame are mounted rollers
provided with ratchet wheels, with which engage palls pivoted to the frame. The
gauze being fixed with its ends to these rollers, may, by a rotation of the rollers, be
shifted one way and the other in the frame, its edges sliding in the said grooves; and,
after having been stretched by the same means, it is kept tight by the ratchet-wheels
and the palls.
For stretching the gauze transversely I place in the middle of the frame a bar
movable in guides and adjustable by a screw or otherwise, and between the said bar
and either side-part of the frame I arrange a number of oblique struts forming knee-
levers, so that when the said har is drawn in the proper direction, the struts will press
against the said side-parts. In order to allow this pressure to be transmitted to the
gauze, the joints of the frame are arranged to yield to the requisite extent.
GUSTAV DAVERIO.
By his Agent, Carl Pieper.

page_text: I, GUSTAV DAVERIO, Engineer, residing at Zurich, Switzerland, 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 relates to screens for middlings-purifyers, and the improvements
consist in the means whereby the gauze constituting the sifting-surface of the screen
is stretched, as well lengthwise as transversely, and by which a sheet of gauze
composed of pieces of different fineness, may be shifted lengthwise in the frame of the
screen, so that the desired piece will come into operation.
A screen involving my invention is represented on the annexed sheet of drawings
by Fig. 1 in sectional elevation, and by Fig. 2 in plan. Fig. 3 is partly a transverse
section and partly an end view, and Fig. 4 an end-view showing the frame expanded.
The frame of the screen consists of the two longitudinal parts a, and of the end-
parts d, connected to the former by dovetail joints. To the bottom edge of each part a
is secured a ledge 1, between which and the part a is formed a narrow groove b,
opening out towards the inner space of the frame and widened at its bottom. To each
edge of the gauze c is sewed a cord having such thickness that the said edge thus
strengthened, may be passed into the groove lengthwise, but that the cord will prevent
the gauze from slipping out of the groove transversely. At the ends of the frame are
mounted in brackets two rollers e adapted to be rotated by means of a key applied
to a square on one of their pivots, and provided with ratchet-wheels h engaged by the
palls i. To these rollers the gauze, after having been introduced with its strengthened
edges into the grooves b, is fixed with its ends, and the excess in length of the same is
rolled on one or on either of the rollers e. Moreover the gauze may, by a rotation of
the rollers, be shifted lengthwise in the frame, so that, if it is composed of portions of
different fineness, the required portion may with facility be taken into use. While
being thus shifted, the gauze slides with its edges in the grooves b; and, after having
been stretched by means of the rollers, it is kept tight by the ratchet-wheels and the
palls.
For stretching the gauze transversely I place in the middle of the frame a bar o
movable in guides, and between the said bar and either side-part a of the frame I
arrange a number of oblique struts q, forming knee-levers, so that when the bar o is
drawn in the proper direction, the struts q will press against the parts a. In order to
cause this pressure to be transmitted to the gauze, the frame-parts a and d are not
fixed to each other, but so connected by means of the aforesaid dovetail joints that the
parts a are capable of sliding on the tenons of the parts d, and of yielding to the
required extent, as shown by Fig. 4. For adjusting the bar o, the same is provided
at one end with a screw p, passing through the opposite frame-part d and carrying
outside of the latter a thumb-nut; but any other suitable contrivance may be
employed in place thereof.
If the gauze is to be shifted in view of taking into use a portion of different fine-
ness thereof, it is first slackened transversely by turning back the nut of the screw p;

page_text: the gauze is then rolled from one roller e to the other by as much as is required, and
finally its lateral tension is restored. This may be done even while the machine is
working. The operations of changing the degree of fineness of the gauze and of
stretching the same are thus considerably simplified as compared with the arrange-
ments herebefore employed, and the exchangeable gauze frames at present in use are
done away with.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed, I declare that what I claim is :
e,
1. In a screen, the combination, with the frame-parts a having the grooves b
widened at the bottom, of a sheet of gauze c having cords sewed to its edges and
passed with the said edges into the grooves b, and the rollers to which the gauze is
fixed with its ends, and which are provided with means for preventing them from
rotating contrary to the longitudinal tension of the gauze, substantially as and for the
purpose specified.
2. The combination, with the frame-parts a being in yielding connection with the
frame-parts d, and having the grooves b widened at the bottom, and the gauze c having
cords sewed to its edges and passed with the said edges into the grooves b, of the
struts 9 and the adjusting-bar o, substantially as and for the purpose specified.