IMPROVEMENTS IN HYDRAULIC PRESSES
Year: 1885

page_text: COMPLETE SPECIFICATION
I SYDNEY PITT of Sutton in the County of Surrey, Gentleman do hereby declare
the nature of my invention for "IMPROVEMENTS IN HYDRAULIC PRESSES" (a com-
munication to me from abroad by David Crawley Mayo of the City of Montreal in
the district of Montreal and Province of Quebec, in the Dominion of Canada) and
in what manner the same is to be performed to be particulaily described and
ascertained in and by the following statement
-
This invention relates to an improvement in hydraulic presses more especially of
the class used for pressing plug tobacco, oil cake and like purposes and consists
in an improved form of piston, washer or packing to be used in combination with
any ordinary ram or piston rod, and cylinder
'
In presses of this description at present in use the lower end of the ram has
affixed to it a piston, washer or packing of leather which is of such diameter as to
fit the bora of the cylinder and this leather piston has usually one or more annular
grooves or channels formed in it into which the water presses in raising the 1am
and thus expands the leather at the edges until the piston fits the cylinder very
tightly
Now I have found in making these leather pistons and from long practical trials
of them in tobacco presses that as the leather is forced into shape with a metal
ring pressed over the flat sheet of leather and a metal die block the edges of the
piston or packing are invariably torn or cut in such manner as to render them unfit
for service for any length of time in a hydraulic cylinder
This will be understood when it is borne in mind that the constant action of the
water will swell and destroy the leather whenever a ragged surface is exposed
Another objection to leather packings is that sand or grit finding its way into
the cylinder gets between the piston and cylinder wall and scratches and tears the
packing so as to soon destroy its efficiency
The cost of manufacture is also very high as the best part of a side of sole
leather is used in making each packing

page_text: Again there are serious objections to the fastening of the piston permanently on
the end of the ram which will be comprehended by those accustomed to altering
and working hydraulic presses
By my invention I produce piston, washer or packing which possesses none of
the above disadvantages but combines cheapness with increased utility convenience
and lasting qualities
It consists briefly speaking in a flexible disc of such diameter as to closely fit
the bore of the cylinder and arranged to be raised by the force of the water and
to return again with the ram against the end of which it bears not being
necessarily connected thereto
For more complete comprehension of my invention reference must be had to the
accompanying drawing in which letters of reference similar to those used herein
indicate like parts, and where-
Figure 1 is a vertical sectional elevation of part of a hydraulic press showing
my improved piston within the cylinder
Figure 2 18 a perspective view of my piston in its simpler form and adapted to
be used with a flat ended ram
Figure 3 is a sectional view of a modification adapted for use with a ram having
a reduced end.
Figure 4 18 & perspective view of a piston of this kind
Figures 5 and 6 are respectively a plan and cross section of one of my pistons
having a core or centre of wood or other hard material
A 18 the hydraulic cylinder of any of the usual patterns, having the usual water
pipe a and carried by framing B. Inside this cylinder works the usual screwed
ram C on its upper end being carried the press platform D. The ordinary clamping
collar E 18 interposed between this platform and a shoulder B¹ of the frame, so that
as the ram is forced up by the hydraulic pressure, and the press platform brought
into action, this clamping collar E (being threaded on the ram) is screwed down
hard against the shoulder B¹ and thus retams the press in its position until the
articles acted upon have received the required amount of pressure.
All of the above parts are now embodied in hydraulic presses used in tobacco
factories for pressing plug tobacco, and I have only thus described them to ensure
a clear understanding of the operation of my improvement.
This improvement is in the piston, washer or packing F which is made of
flexible material, preferably vulcanized india rubber, and is simply dropped into the
cylinder A, and the ram 18 then inserted when the piston is ready to rise and fall
therewith, no attachment of the latter to the ram being necessary, although there
is nothing to prevent my rubber piston from being secured to the end of the ram
if desired.
In Figures 3 and 4 I have shown the piston F provided with a cylindrical
recess which receives the reduced end of the ram at present used with the
leather packings. This is done as a matter of convenience to render unnecessary
the planing off of the end of the ram
I however prefer to make the ram C with a plain end as shown in Figure 1 and
construct the piston F in the shape of a perfectly flat disc of rubber having by
preference a slightly bevelled edge f' the larger diameter being at the upper side
and I usually harden or stiffen this upper edge and the top face of the piston (or if
desired the whole exterior of the disc) with canvas or other suitable material as
at f so as to present a better wearing surface
This hardened or stiffened portion is also for the purpose of preventing the
rubber when softened (as it is slightly from the constant action of the water)
from oozing or spreading between the ram and the cylinder wall
In Figures 5 and 6 I have shown my piston with a central core f³ of wood or
other hard material retained in connection with the rubber by an annular flange as
shown in dotted lines or in any approved manner. This construction will be useful
In cases where the cylinder is of large diameter,

page_text: Many other like modifications can be adopted without departing from my
invention.
It will be understood that the water pressing upon the underside of my rubber
piston will cause it to expand at the lower edge and fit the cylinder tightly like
the upper hardened edge ƒ³
The advantages to be derived from the use of my invention will be apparent as
it can be readily seen that by having the loose piston a great deal of labour in
fitting and repairing will be avoided-and the flexible material of which it is made
will ensure the close fitting and efficient operation of the packing
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
1 A piston or packing for a hydraulic cylinder consisting of a loose disc of
flexible material placed within the cylinder and adapted to move with the ram
2 A piston or packing of a hydraulic cylinder composed of a flat disc of
vulcanized rubber
3 A piston or packing for a hydraulic cylinder composed of a disc of vulcanized
rubber hardened or stiffened on one or all of its surfaces.
CARPMAEL & Co,
Agents for the Applicant.