Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
RECIPROCATING PUMP
The invention concerns a reciprocating pump whose plunger is sealed
relative to the cylinder with the aid of packings and connected with a
plunger rod which runs in a stuffing box coordinated wi~h ~he pump
cylinder cap and is driven in reciprocating fashion.
A problem associated with reciprocating pumps of that type is making
them safe to r~m dry. Dry running sf the pump involves the danger that
the packings in the area of plunger and stuffing box will overheat and
burn, especially when relatively high sealing pressures are required.
Therefore, the problem underlying the invention is advancing the reci-
procating pump of the initially mentioned type to the effect that over
long periods of time it will be safe to run dry in the packing area of
the stuffing box and the plunger, without coolant proceeding lnto the
pump cylinder.
Basing on a reciprocating pump of the initially mentioned type, the
invention suggests solving this problem by providing the plunger rod and
the cylindrical walls of the pump cylinder across their entire length
with pass-through openings for a cooling medium flowing through these.
The lnventionally suggested cooling of the plunger rod and cylindrical
walls of the pump cylinder results in a continuous dlrect cooling of the
sealing faces of the packing which are incontact with the plunger rod
and/or the cylindrical walls of the pump cyllnder, so that the packing
material cannot burn even when the pump runs dry. The coolant in the
flow-through openings being encapsulated relative to the interior of the
pump cylinder, no coolant can proceed into sald interior. Being good
heat conductorq, the metallic walls between the friction faces and the
coolant can dissipate the heat generated by dry running of the recipro-
~ I
- 2 - ~ ~5~3
cating pump considerably faster than can the poorly heat-conductive
packing material.
The flow-through openings in the plunger rod and the cylindrical walls
of the pump cylinder are suitably connected to a common coolant circuit.
Thus it is possible to favorably make do with only one coolant circuit.
Particular advantages result when the reciprocating pump is driven by ahydraulic cylinder and the hydraulic working medlum for the drive cylin-
der is likewise the cooling medium. This invPntional design of the recl-
procating pump requires no longer a separate coolant circuit. Available
in this case anyway, the hydraulic circuit is rather used for cooling.
A suitable embodiment of the inventional reciprocating pump provides for
a hollow design of the plunger rod and for likewise utilizing it as the
cylinder part of the hydraulic drive, which is mounted shiftably on the
stationary ram and the drive rod connected with it~ In addition to a
continuous cooling of the plunger rod, this offers the advantage of a
particularly short overall length, making it possible to give the entire
pump aggregate including drive a very compact design. Another signif-
icant advantage is that the outside of the plunger rod, with this
design, makes no longer contact with the hydraulic drive medium, thus
eliminating the danger of hydraulic drive medium migra~ing into the pump
cylinder. Especially this design, therefore, is suited for foodstuff
pumping. `
To avoid wlth the latter deslgn flexlble pressure medlum connections, afurther provision consiats in feedlng the hydraulic drive medium to the
hydraulic drive cylinder via the stationary ram rod and the statlonary
ram, these two belng provlded with approprlate feed bores.
Since the latter deaign involves relatively large reclprocatlng masses 3
the fixed ram is on both end faces suitably provided wlth shock absor-
bers for limit position damping. Avoided thereby are ~olting blows when
reaching the limit positions.
The shock absorbers consist suitably of rubber rings which bear, inside,
on the driving ram rod and/or a corresponding cylindrical extension on
the solld face of the drivlng ram while leavlng toward the lnslde wall
~ 3 ~ ~ ~S~8~
of the cylinder part of the drlve cylinder an annular space with a de-
finitive volume which, while the rubber rlngs undergo defor~ation as
they strike the ends of the cylinder part, fill up with rubber substance
which upon complete filling of the annular gap becomes practically ln-
eleastic. Such shock absorbers are simple in design and pr~ctically non-
wearing. Kinemat~cally reversed, of course, the rubber rings may as well
be provided on the ends of the cylinder part while leaving open, toward
the driving ram rod, an appropriate annular space of definitive volume.
.
Accord~ng to another inventional design of ~he reciprocating pump, the
plunger rod of the pump cylinder i8 at the same time the ram rod of the
drive cylinder9 the cylinder part of the latter being fixed and sccommo-
dating in axially shiftable fashion the drive ram connected wlth its
rod, where the rod consi~ts of an external pipe and an internal pipe ar-
ranged concentrically in the former and spaced radially from it, and
where the hydraulic driv~ medium flows at least during part of the
stroke through the annular space between the external and the internal
pipe.
This inventional -design of the reciprocal pump offers over the first
design the advantage that the drive ram may have a diameter of arbitrary
size permitting the admission of greater drive forces.
In order to make the hydraulic working medium of the hydraulic cylinderflow through the common plunger rod at least during part of the driving
strokel the driving ram rod features at an axial spacing from the ram a
second ram, the interior of the internal pipe connects with the annular
space between both rams, the annular space beLween internal and external
pipe of the driving ram rod connects directly beside the second ram with
the annular space between the cylinder part and the ram, the wall of the
cylindrical part of the hydraulic cylinder is provided with two pressure
medium sockets which are connected with a common pressure medium line,
the axial spacing of ~he sockets corresponding with the`axial length of
the second ra~, whlle the spacing between the hydraulic cylinder cap and
the flrst pressure medium socket is smaller or equal to the axial spac-
ing between the two drive rams. The particular advantage of thi~ measure
is that a quantity of hydraulic working medlum which i6 sufficient for
cooling can be fed to the common rod of drive ram and pump plunger,
- 4 -
without requlring the provision of a pre~sure medium connection which
moves along wlth the rod.
~n embodiment of the invention will be more fully explained hereafter
with the aid of the drawing.
Fig. 1 shows a horizontal section of an inventional reciprocating pump
in a flrst design;
Fig. 2, a horizontal section of an inventional reciproca~ing pump in
a second design;
Fig. 3, a horizontal section of an inventional reciprocating pump in a
third design.
.
In Fig. 1, the reciprocating pump housing is marked 1 and features two
inta~e chambers 2 and 3 as well as a pressure chamber 4 which connects
through check valves 5 and 6 and/or 7 and 8 with the one and!or the
other end of the pump cylinder 9.
A double-acting plunger 1~ reciprocates in the pump cylinder 9. Ring-
shaped packings li provide a seal between the plunger 10 and the inside
wall of the pump cylinder 9. The packings 11 consists preferably of a
self-lubricating material capable of running dry. The cylindrical walls
of the pump cylinder 9 are provided with flow-through openings 9a for a
coolant passing through them, the openings extendlng over the entire
axial length.
Attached to the plunger 10 i~ a plunger rod 12 passing through a stuf- !
fing box 13. The plunger rod 12 is hollow and accommodates inside a
fixed drive ram 14 which is connected with an as well fixed ram rod 15.
The hollow plunger rod 12 runs on the fixed drive ram 14 and i~s as well
fixed ram rod 15, forming together with it the double-acting drive
cylinder 12, 14, 15 whose cylinder part (plunger rod 12) i6 axially
shiftable. Bores 16 and 17 in the fixed ram rod 15 and the fixed ram 14
serve the alternating hydraulic medium admlssion to the pressure spaces
of the drive cyllnder 12, 14, 15.
The hydraulic drlve medlum i8 supplled by a hydraulic circui~ 18 featur-
ing a pump 18a, reverAing valve 18b, and a reservoir 18c. This hydraulic
circuit 18 includes the flow-through openings 9a in the cylindrlcal
_ 5 - ~ ~5~
walls of the pump cylinder 9, the bores 16 and 17, and the pressure
spaces of the drive cylinder 12, 14, 15~ Thus, the hydraulic medium
cools both the cylindrical walls of the pump cylinder 9 and the plunger
rod 12 across their entlre length, digsipating continuously and inten-
sively the heat generated on the frlction faceg of the packlngs 11
and/or 13a. This contlnuous cooling prevents a burning of the packings,
even when running dry for a longer time. The inventional pu~p is thus
absolutely safe to run dry.
To effect a limit posltion damping of the relatively heavy reciprocating
plunger rod 12, the two end faces of the fixed ram 14 are provided with
rubber rings 19 and 20 which contact the outer circumference of the
drive ram rod 15 and/or a corresponding cylinderical extension 14a of
the ram 14 while leaving toward the inside wall of the plunger rod 12
(cylinder part of the hydraulic cylinder 12, 14, 15) an annular gap with
an exactly defined volume. As the fixed ram 14 strikes the inside ends
of the hollow space of the axlally moving plunger rod 12, these rubber
rings undergo an ela~tic deformation until they completely fill the
annular gap and form a practically inelastlc pad. Reallzed thereby is a
highly effective and practically nonwearing end position damping at
relatively low expense.
I
As far as the parts are concerned whlch pertain to the pump housing and
plunger 10, the embodiment according to Fig. 2 corresponds entirely with
the embodiment according to Fig. 1, for which reason identical designa-
tors are used for identical parts. But the rod 12 of the plunger 10
serves here at the same tlme as rod of the hydraulic cylinder and con-
nects therefore with a double-acting ram 21 which is mounted in axially
shiftable fashion in a fixed cylinder component 22. To effect here as
well a cooling of the plunger rod over it~ entlre length, by the medium
of the hydraulic cylinder 22, 21, 12, the plunger rod 12 consists of an
external pipe 12a and an lnternal pipe 12b which are nested concen-
trically at a radial spacing. Thu~ the internal space 12c of the in-
ternal pipe 12b and the annular space 12b betwcen external pipe 12a and
internal pipe 12b form a flow-through opening through which passes the
hydraulic medium successively, thereby cooling the plunger rod 12 as
required. -
For feeding the hydraulic medium to the plunger rod 12 while avoiding
moving pressure medium connections, the plunger rod 12 features a second
drive ram 23 whi~h is axially gpaced from the ram 21. Moreover, the ln-
ternal space of the internal pipe 12b ig with the annular space between
the two rams 21 and 23 in a connection suited for hydraulic medium con-
veyance. The annular gpace between the external pipe 12 and the internal
pipe 12b connects as well, directly beside the second ram 23, with the
annular space between the plunger rod 12 and the cylinder component 21
o the hydraulic cylinder 2~, 21, 12. Lastly, the wall of the cylinder
component 22 of the hydraulic cylinder 22, 21, 12 features two parallel
pressure medium connections 24 and 25 which are connected to the pres-
sure medium circuit 18 and whose axial spacing equals the axial length
of ehe second ram 23. The space b between the cap of the hydraulic cyl-
inder 22, 21, 12 and the first pressure medium connection 24 is smaller
than or at the most equal to the axial spacing a between the two rams 21
and 23.
1.
As follows from Fig. 2, the hydraulic medium contained before the second
ra~ 23 ~s forced into the annular space between the external pipe 12a
and the Internal pipe 12b as the plunger rod 12 shifts to the right, and
proceeds then through the internal pipe 12b into the annular space be-
tween the two rams 21 and 23 and thence through the pressure medium con-
nection 25 into the pressure medium circuit 18. In converse admission,
the hydraulic medium flows first as well through the plunger rod 12 and
cools it.
As regards the design of the pump cylinder 9, plunger 10, and rod 12,
the embodiment according to Fig. 3 is identical with that according to
Fig. 2, using same designators for identical components.
The plunger rod 12 consists as well of an external plpe 12a and an
internal pipe 12b which nest concentrically while maintaining a radial
spacin~. The internal space 12c of the internal pipe 12 and the annular
space 12d between external pipe 12a and internal pipe 12b form flow-
through openings for a cooling medium which is fed into the plunger rod
12 from a separate coolant circuit 26. In addition, this separate cool-
a~t circult 26 lncludes the flow-through openings 9a in the cylindrical
walls of the pump cylinder 9. Moreover, the separate coolant circult 26
comprises a coolant pump 26a and reservoir 26b.
.
7 ~5~!~83
The plunger 10 of the embodiment according to Fig. 3 ls driven by a
separate hydraulic cylinder 27 whose rode 28 is attached to the outer
end of the plunger rod 12. The pressure medium for the separate hydrau-
lic cylinder 27 is supplied by a separate hydraulic clrcuit 29 comprls-
ing a hydraulic pump 29a, reservoir 29b, and reversing valve 29c. The
hydraulic cylinder 27, facultatively, may be substituted also by another
drive aggregate which effects the reciprocating movement of the plunger
rod 12.
