IMPROVEMENTS IN PISTONS WHICH WORK WITHOUT FRICTION AND KEEP PERFECTLY AIR- TIGHT.
Year: 1873

page_text: LETTERS PATENT to Johann Heinrich Cohrs, of Steinstrasse, in the
City of Hamburg, Merchant, for the Invention of "IMPROVEMENTS
IN PISTONS WHICH WORK WITHOUT FRICTION AND KEEP PERFECTLY AIR-
TIGHT.
"
Sealed the 3rd February 1874, and dated the 5th August 1878.
PROVISIONAL SPECIFICATION left by the said Johann Heinrich
Cohrs at the Office of the Commissioners of Patents, with his
Petition, on the 5th August 1878.
I, JOHANN HEINRICH COHRS, of Stainstrasse, in the City of Hamburg,
Merchant, do hereby declare the nature of the said Invention for "In-
PROVEMENTS. IN PISTONS WHICH WORK WITHOUT FRICTION AND KEEP PERFECTLY
AIR-TIGHT" to be as follows:-
This Invention relates to pistons for pumps whereby all escape of air or
other fluid is prevented from the cylinder during the working.except
through the proper channels.
The Invention consists in extending the barrel of the pump at the
upward or outer end in a cylindrical or skeleton form to serve as a guide

page_text: to the upper end of a plunger, which may also be of skeleton form
at that part, and provided with rollers or other appliances to reduce
friction, or it may be left plain to bear upon or against the inner side of
the barrel in the to-and-fro or up-and-down strokes. The bottom of the
plunger is disc shaped and has a plate or a block attached to permit of
a cylindrical flexible bag or envelope working freely within the space.
The cylindrical flexible bag or envelope is attached at one end to the
bottom of the plunger in any suitable manner, and at its other end
to the flanges of the pump barrel to form an air or fluid tight com-
partment between the plunger and the end of the barrel. The plunger
can be of any length from top to bottom, and I prefer that the exterior
body of it should be made as I have shown in the accompanying
Drawings in which my Invention is illustrated.
Figure 1 shows in section a pump for the suction and force of air,
gas, water, or other fluid with the piston, such as I have above described
within the barrel. A is the barrel, which is of greater length than
usual, and B is the head of the plunger or piston, the lower portion of
which C is of smaller diameter to permit of the flexible bag or envelope
D passing into the space E, one end of the bag or envelope being
attached to the bottom of the plunger by a plate or block F, and its
other end between the flanges G of the pump barrel. The flexible
bag or envelope D is formed of cured rubber, water and air proof
canvas, or other suitable material which becomes doubled or folded over
in the working of the plunger, as shown in Figures 2, 3, 4, and 5.
SPECIFICATION in pursuance of the conditions of the Letters Patent
filed by the said Johann Heinrich Cohrs in the Great Seal Patent
Office on the 5th February 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHANN
HEINRICH COHRS, of Steinstrasse, in the City of Hamburg, Merchant,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fifth day of August, in the year
of our Lord One thousand eight hundred and seventy-three, in the thirty-
seventh year of Her reign, did, for Herself, Her heirs and successors,

page_text: give and grant unto me, the said Johann Heinrich Cohrs, Her special
licence that I, the said Johann Heinrich Cohrs, my executors, admi-
nistrators, and assigns, or such others as I, the said Johann Heinrich
_Cohrs, my executors, administrators, and assigns, should at any time
agree with, and no others, from time to time and at all times there-
after 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 In-
⚫vention for "IMPROVEMENTS IN PISTONS WHICH WORK WITHOUT FRICTION AND
) KEEP PERFECTLY AIR-TIGHT," upon the condition (amongst others) that I,
the said John Heinrich Cohrs, my executors or administrators, by an
instrument in writing under my, or their, or one of their bands and
seals, 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 immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said Johann Heinrich Cohrs, do hereby
declare the nature of my 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, reference being had to the Drawings
hereunto annexed, that is to say :—
This Invention relates to pistons for pumps whereby all esca pe of air
or other fluid is prevented from the cylinder during the working except
through the proper channels.
The Invention consists in extending the barrel of the pump at the
upward or outer end in a cylindrical or skeleton form to serve as a guide
to the upper end of a plunger, which may also be of skeleton form
at that part, and provided with rollers or other appliances to reduce
friction, or it may be left plain to bear upon or against the inner side of
the barrel in the to-and-fro or up-and-down strokes. The bottom of the
plunger is disc shaped and has a plate or a block attached to permit of
a cylindrical flexible bag or envelope working freely within the space.
The cylindrical flexible bag or envelope is attached at one end to the
bottom of the plunger in any suitable manner, and at its other end
to the flanges of the pump barrel to form an air or fluid tight. compart-
ment between the plunger and the end of the barrel. The plunger can

page_text: be of any length from top to bottom, and I prefer that the exterior body
of it should be made as I have shown in the accompanying Drawings,
in which my Invention is illustrated.
Figure 1 shows in section a pump for the suction and force of gas,
water, or other fluid with the piston, such as I have above described
within the barrel. A is the barrel which is of greater length than
usual, and B is the head of the plunger or piston, the lower portion of
which O is of smaller diameter to permit of the flexible bag or envelope
D passing into the space E, one end of the bag or envelope being
attached to the bottom of the plunger by a plate or block F, and its
other end between the flanges G of the pump barrel.
The flexible bag
or envelope D is formed of cured rubber, water and air-proof canvas or
other suitable material which becomes doubled or folded over in the
working of the plunger, as shown in Figures 2, 3, 4, and 5.
I also use my piston arrangement for compressing air and other
liquids.
Thirdly. The piston can be used as part of a break and re-starter for
tramway carriages, such as is referred to in the Specification of a
previous Patent granted to me, dated 7 December, 1872, No. 8714, the
air piston being applied instead of springs. This modification is shown in
the Figures 6, 7, and 8, of the accompanying Drawings. A is an air-tight
metal cylinder; O is the plunger; D, the flexible bag. The plunger is
connected with a pair of racks a, a, and pinions b, b. When the carriage
is being stopped, these racks and with them the plunger, are pressed
backwards and the air is maintained compressed by the flexible bag.
When the car is about to be brought into motion again the racks are
released and the movements of the same are reversed. The compressed
air now gives the force to push or re-start the carriage forward again by
expanding the bag and pressing the piston forward without reference to
the direction of travel of the vehicle. The pressure can be regulated
by valves in any suitable manner.

page_text: And, Thirdly. I claim the adaptation of my cylinder and piston
arrangement to stopping and re-starting, or assisting to stop and to
re-start tramway carriages, substantially in the manner described and
shown.
In witness whereof, I, the said Johann Heinrich Cohrs, have
· hereunto set my hand and seal, this Thirtieth day of January,
One thousand eight hundred and seventy-four.