IMPROVEMENTS IN FILTERS, AND IN THE METHOD OF CLEANING THE SAME
Year: 1874

page_text: LETTERS PATENT to Edward Perrett, of 23, Abingdon Street,
Westminster, Civil Engineer, for the Invention of IMPROVEMENTS
PROVISIONAL SPECIFICATION left by the said Edward Perrett at the
Office of the Commissioners of Patents, with his Petition, on the
10th December 1874.
- I, EDWARD PERRETT, of 23, Abingdon Street, Westminster, Civil
Engineer, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN FILTERS, AND IN THE METHOD OF CLEANING THE SAME," to be
as follows:-
This Invention has for its object the arrangement of the filtering
material so that it may be readily cleansed.
I take a cylinder or circular basket of wire or perforated metal work
similar to that used in ordinary centrifugal machines for curing sugar,
and place within it and against the inside the suitable filtering material,
which material is returned upwards from the bottom to a ring capable

page_text: of sliding upwards on a central spindle, thus forming a sort of annular
bag between the disc and case of the cylinder.
The material to be filtered is placed in the annular space, and in some
cases the filtering is assisted by giving rotary motion to the cylinder, but
in other cases the annular filtering material and cylinder remains
stationary.
When the filtering material is choked, and it is necessary or desirable
to clean the same, the ring is raised on the central spindle, and the
filtering material is then turned inside out. In the one case the rotary
motion continuing the dirt is thrown off the now exterior surface of the
bag; and in the other case when the bag is inverted rotary motion is
given to the cylinder and bag, and the dirt thrown off as before..
A convenient way of inverting the bag is by means of a screw and
nut carried by the shaft or axis of the filter. The inner edge of the bag
is. attached to a ring, which is connected with the nut. The nut remains
stationary so long as it and the screw rotate at the same speed, but
when the screw is retarded the nut rises, and the bag is turned
inside out.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Edward Perrett in the Great Seal Patent Office 2
on the 10th June 1875.
1
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, EDWARD
PERRETT, of 23, Abingdon Street, Westminster, Civil Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her 3
Letters Patent, bearing date the Tenth day of December, in the
year of our Lord One thousand eight hundred and seventy-four, in
the thirty-eighth year of Her reign, did, for Herself, Her heirs and
'

page_text: successors, give and grant unto me, the said Edward Perrett, Her
special license that I, the said Edward Perrett, my executors,
administrators, and assigns, or such others as I, the said Edward
Perrett, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention
for "IMPROVEMENTS IN FILTERS, AND IN THE METHOD OF CLEANING THE SAME,'
upon the condition (amongst others) that I, the said Edward Perrett, my
executors or administrators, by an instrument in writing under my, or
their, or one of their hands and scals, should particularly describe.
and ascertain the nature of the said Invention, and in what manner
the same was to be performed, and cause the same to be filed in the
Great Seal Patent Office within six calendar months next and imme-
diately after the date of the said Letters Patent.
"
NOW KNOW YE, that I, the said Edward Perrett, do hereby declare
the nature of the said Invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and
by the following statement thereof, that is to say:-
This Invention has for its object the arrangement of the filtering
material so that it may be readily cleansed.
I take a cylinder or circular bucket of wire or perforated metal work
similar to that used in ordinary centrifugal machines for curing sugar,
and place within it and against the inside the suitable filtering material,
which material is-returned upwards from the bottom to a ring capable
of sliding upwards on a central spindle, thus forming a sort of annular
bag between the disc and case of the cylinder.
The material to be filtered is placed in the annular space, and in some
cases the filtering is assisted by giving rotary motion to the cylinder,
but in other cases the annular filtering material and cylinder remains
stationary.
When the filtering material is choked, and it is necessary or desirable
to clean the same, the ring is raised on the central spindle, and the
filtering material is then turned inside out. In the one case the rotary
motion continuing the dirt is thrown off the now exterior surface of the

page_text: bag; and in the other case when the bag is inverted rotary motion is
given to the cylinder and bag, and the dirt thrown off as before.
A convenient way of inverting the bag is by means of a screw and
nut carried by the shaft or axis of the filter. The inner edge of the bag
is attached to a ring, which is connected with the nut. The nut remains
stationary so long as it and the screw rotate at the same speed, but
when the screw is retarded the nut rises, and the bag is turned
inside out.
The retardation of the screw may be caused by mounting vanes upon
it to catch the air.
When the rotary motion is arrested or the speed reduced the nut and
parts connected with them descend by gravity, so that the action is
automatic.
In order that my said Invention may be most fully understood and
readily carried into effect, I will proceed to describe the Drawings
The Figure shows a vertical section of filtering apparatus constructed
in accordance with my Invention.
a, a, is the frame and case of the machine; it carries the bearings of
the vertical shaft b, on which are fast and loose pulleys to receive a
driving belt and a brake to bring the axis and parts connected with it
rapidly to rest when required. c is the drum or basket fixed upon the
upper end of the shaft b. The sides of the basket are formed of two
concentric cylinders of perforated metal, and between them the bag d
of filtering fabric is received. One of its ends is attached all around the
upper edge of the outer cylinder of the basket, and the other end is
attached around the edge of a disc e. On this disc are lugs e¹, which
receive trunnions f₁ formed on the nut f. The trunnions f' also pass
between guides g fixed into the boss of the basket c, so that the nut is
compelled to revolve with the basket. Between the guides an axis h
with a screw cut upon it is carried; it passes through the nut ƒ, and
consequently so long as the nut remains in the position in which it is
shown in the Drawing the nut will revolve at the same speed as the
basket whenever the basket is rotated. ³ is a fan or fly fixed on the

page_text: top of the axis h, and when the axis is driven at a comparatively high
speed the resistance of the air to the rotation of the fan or fly causes
retardation, the motion of the screw becomes slower than that of the
basket c and nut f, and the nut ascends, the screw carrying the disc e
with it. Thus the filtering bag d is turned inside out, as is indicated in
the Drawing by the dotted lines; the dirt is then thrown off from its
surface by centrifugal action.
When the rotation of the basket is stopped, or when the speed is
sufficiently reduced, the nut and disc descend by their own weight. d¹ is
a heavy metal ring attached to the bag d to carry it down into its place.
k is an upper casing serving to collect the dirt thrown off from the bag,
and it is delivered by the spout k¹.
The liquid to be filtered is introduced by a pipe passing through the
side of the casing k. This pipe is not shown in the Drawing. a¹ is the
spout, which delivers the filtered liquid.
I prefer slowly to rotate the basket whilst filtering in order to
distribute the liquid around it, so that the deposit on the filtering bag
may take place uniformly all round, but this is not essential. The
basket may remain at rest whilst filtering.
What I claim is, the construction of filters substantially as described.
I also claim the mechanism by which the filtering surface is inverted
for the purpose of throwing off the dirt, substantially as described.
In witness whereof, I, the said Edward Perrett, have hereunto
set my hand and seal, this Ninth day of June, in the year of
our Lord One thousand eight hundred and seventy-five.
TT ADD DREDDETT