Improvement in Packings for Pistons and Piston-rods.
Year: 1889

page_text: Date of Application, 17th Oct., 1889
Complete Specification Left. 2nd June, 1890-Accepted, 19th July, 1890
PROVISIONAL SPECIFICATION.
Improvement in Packings for Pistons and Piston-rods.
I, EMIL DÖNITZ, Engineer, residing at No. 2, Wein Strasse, Berlin, kingdom of
Prussia, do hereby declare the nature of this invention to be as follows :—
The improved packing forming the subject of my invention, consists in an elastic
and impermeable hose, a part whereof is bent over, or tucked up, around the other
part, so that the hose is doubled. The outer or tucked-up part is fastened with its free
end to the inside of the cylinder or sleeve to which it is applied, while the free end of
the inner part is fastened to the piston, plunger or rod paired with the said cylinder
or sleeve, the latter being made so much larger than the piston, &c., as to leave room
for the hose together with a narrow annular space between the two hose-parts.
If under these conditions the pressure of fluid acting inside of the said annular
space is greater than the pressure acting from the outside on the hose, the two hose-
parts will be pressed respectively against the cylinder and the piston, and any motion
of the latter will cause the inner hose-part to move forward and backward within the
outer part, the bend between the parts continually changing its position and following
the piston at half the speed of the latter.
The hose requires to have such elasticity as that it is adapted to widen out peri-
pherally from the small to the large diameter. Preferably it is made of india rubber
with an outer layer of elastic cloth or of longitudinally-arranged threads.
1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvement in Packings for Pistons and Piston-rods.
I, EMIL DÖNITZ, Engineer, residing at No. 2, Wein Strasse, Berlin, kingdom of
Prussia, 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:
The improved packing forming the subject of my invention, consists in an imper-,
meable cylindrical membrane or hose having such peripheral elasticity that one part
or end thereof may be smoothly drawn over, or tucked up around the other part or
end, so that the hose becomes doubled. The outer or tucked-up part is fastened with
its rim to the inside of the cylinder or sleeve to which it is applied, while the rim of
the inner part is fastened to the piston, plunger or rod, paired with the said cylinder
or sleeve, the latter being made so much larger than the piston, &c., as to leave room
for the two hose-parts and a narrow annular space between them.
The packing may be employed in all cases in which the two fluids separated by the
hose, have such relative pressure that the preponderant pressure always acts in the
same direction during the motion of the piston or rod, or in which the preponderant
pressure changes its direction at or near the ends of the strokes.
In the annexed drawing
Fig. 1 is a diagram showing the principle of the invention.
Fig. 2 represents a portion of the hose drawn to a larger scale.
Fig. 3 shows the packing applied to a piston-rod.
Fig. 4 is a sectional view of a cylinder and a plunger, connected together by the
hose-packing.

page_text: Figs. 6 and 7 are two views of a cylinder and piston with the packing arranged to
be capable of operating under the condition that the preponderant pressure changes its
direction simultaneously with the change in the direction of motion of the piston.
In fig. 1a is a piston, the cylinder in which it moves, and d the hose
constituting the packing. The said hose is fastened to the cylinder by being inserted
with its outer rim between the parts b and b', secured together by screws (not shown
in the drawing). In similar manner the inner end of the hose is fixed to the piston
by being pinched between a surface or shoulder a² of the same and a ring or sleeve a¹.
Preferably the surfaces which hold the rims of the hose, are made conical. The two
spaces of the cylinder are thus completely separated from each other by the hose con-
stituting an impervious membrane, while at the same time the edges of the hose form
the packings between the respective parts bb and a a¹. g is the room left between
the piston and the cylinder for the doubled hose and the annular space between the
parts thereof.
If under these conditions the pressure of fluid acting inside of the space f, is greater
than the pressure acting on the hose from the outside, or, relatively to the figure,
from below, the two hose-parts will be pressed respectively against the cylinder and
the piston, and any motion of the piston will cause the inner hose-part to move
forward and backward within the outer part, the bend c continually changing its
position and following the piston with a speed equal to one half of that of the
latter.
The hose requires to have such elasticity as to be capable of stretching peripherally
from the smaller to the larger diameter.
cloth coated with a layer of india-rubber as shown by the dark line e fig. 1, or it is
For this purpose it is made of an elastic
composed of alternating layers of the said materials. The cloth serves to impart to
the hose the necessary strength for resisting the tensional strain to which it is
exposed, while the india-rubber renders it impermeable. The cloth preferably consists
in plaited or knitted work, and it should not have any seam.
its operation, passes from the smaller diameter through the bend a to the larger
When the hose, during
diameter, it simultaneously becomes shorter, as indicated by fig. 2. For pistons
having a diameter of several decimeters, a hose with a body of woven material of the
ordinary kind may he employed, because in such case the amount by which the hose
has to stretch is but a small fraction of its periphery.
For a given hydrostatic pressure the strain acting lengthwise on the hose, does not
depend upon the area of the piston, but upon that of the annular space f, the width
whereof is sufficient if it is made equal to double the thickness of the hose. In con-
sequence the hose may be thin and the room or space g between the cylinder and the
piston narrow, a width of from 3 to 4 millimeters being sufficient for a hose adapted
to resist a strain of several atmospheres, while, if the pressure is 100 atmospheres, the
width required is not above 8 millimeters.
According to fig. 3, showing the new packing applied to a piston-rod, one end of
the hose is pinched between a bead at the lower end of the tube k and the surface
of a recess in the piston m, the said tube, which is slipped over the piston-rod, being
pressed down by a nut 7. The other end of the hose is held between the bottom of
the stuffing-box and its cover i.
The arrangements shown by figs. 4 and 5 will be understood without any further
explanation.
In respect to the arrangements represented by figs. 3 to 5. it has been supposed that
the preponderant pressure always acts on the same side of the hose, so as to keep the
hose permanently applied with its other side to the surfaces of the cylinder or sleeve
and the piston or rod. If, however, these surfaces are both arranged to extend length-
wise on each side of the points of fixture of the hose, and if the hose has such length
that it is stretched out, either completely or nearly so, at the ends of the strokes of the
piston or rod, the preponderant pressure of fluid acting on the hose, may at these points
change its direction without causing any irregularity in the operation of the packing.
Thus in the arrangement represented by figs. 6 and 7, the hose may bear against the
surfaces of both cylinder-parts bh' as well as against the surfaces of both parts a a¹ of

page_text: ∙the piston, and it is made of the appropriate length as stated. Therefore, if the piston
is at the end of its down-stroke and the preponderant pressure is from below, the hose
will lean against the piston-part a¹, as shown by fig. 6, the bend c being at the top;
whereas if at this moment the direction of pressure changes to act from above, the
hose will be pushed over against the surface of the cylinder-part b, as represented by
fig. 7, and the bend is formed at the bottom. The piston may then rise again
unimpeded. In like manner the change of position of the hose takes place if the
direction of pressure changes when the piston is at the top end of its stroke. During
each course of the piston the preponderant pressure must, however, have uniform
direction; but it is irrelevant whether this direction coincides with that of the motion
of the piston or whether it is contrary thereto. If the preponderant pressure is the
driving power, for instance in piston-water-meters, the position of the hose shown by
fig. 7, corresponds to the end of the downstroke of the piston, that represented by
fig. 6 to the commencement of its upstroke. The contrary is the case if the motion
of the piston produces the preponderant pressure, as in pumps.
The described packing is with advantage applicable in all cases in which absolute
tightness or the least possible friction of the piston is desired, or if a lubrication of the
latter is to be avoided. The packing is therefore serviceable in pneumatic and
hydraulic contrivances, such as railway-brakes, central power-distributing apparatuses,
hydraulic accumulators, lifting-gears and weighing machines, &c., and more particu-
larly it is of importance for regulating, indicating-, measuring-, and signalling-
devices in which the position of a piston is dependent upon the volume of a liquid or
the tension of a gas or saturated vapor.
Having now particularly described and ascertained the nature of this inver-
tion and in what manner the same is to be performed, I declare that what I
claim is:
The combination, with a cylinder or sleeve and a piston or rod working therein
and smaller in diameter than the former, of an impermeable cylindrical membrane
consisting in a hose composed of one or more layers of cloth being elastic peripherall
to the hose, and one or more layers of india-rubber, and means for fixing the said
hose with one end to the cylinder or sleeve and with the other end to the piston or
rod, substantially as described.
Dated the 31st day of May 1800
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.