Note: Descriptions are shown in the official language in which they were submitted.
WQ' 19096 PCT/SEg1/00408
2 ~
A ~luid valve device and a positive-displacement ~umP
This invention relates to a fluid valve device ~or con-
trolling the flow of a fluid and to a positive-displacement
pump including such a valve device~
Although not limited exclusively to use as an inlet valve
in a positive-displcement pump, the valve device according to
the invention is particularly useful for such applications. It
therefore will be described herein with special reference to
its use as an inlet ~alve in a positive-displacem~nt pump,
namely a positive-displacement pump in which a reciprocable
displacement member repetitively contracts a pump chamber to
expel liquid received in the pump chamber.
A positive-displacement pump has a pump chamber which
communicates with an inlet and a~ outlet and includes a
movable wall or wall sectlon ~orming part of or cooperating
with the displacement member. A inlet valve controls the flow
of fluid into the pump chamber from the inlet by opening and
closing a flow passage which opens into the pump ~hamber. Most
positive-displacement pumps al80 include an outlet valve which
prevents backflow of fluid from the outlet into the pump
chamber, bu~ in some cases such a valve can be dispensed with~
The flow passage through which the fluid being pumped
enters the pump chamber often causes a serious limitation of
the output and e~ficiency of the pump. ~sually, the fluid
being pumped enters the inlet and the pump chamber at a rela-
tively low pressure: in many case~ the inflow takes place
under the action of a partial vacuum in the pump chamberO In
order that the pump chamber may be ~illed rapidly and with
small losses of energy, the inlet valve has to be able to open
a flow passage of large cross-section area and of a shape such
that the resistance to flow of the fluid is minimized. In
known positive-displacement pumps, this requirement is diffi-
cult to reconcile with the requirem~nt for small dimensions.
This is particularly so in pumps which are ~o oper~te at high
stroke rates.
EP-A-~ 374 115 di~clo~es po~it~ve-displac~ment pump~ which
represent ~n advantag~ou5 solution to the problem o~ providing
for a rapid ~illing of the pump chamber with small energy
losses. An important feature of thi~ solution resides in a
WOS 9~96 PCT/S~91/0040~
~8~8~
.
gap-like flow passage which extends over the entire circum-
ference, or at least over a substantial portion of the circum-
ference, of the pump chamb~r and which can be opened over the
entire circumferential extent thereof to admit fluid into the
pump chamber. In preferred embodiments a variable~volume
supply compartment or reservoir is provided adjacent the inlet
valve on the upstream side thereo~ ~o that a ~upply of fluid
for filling the pump chambex is available very close to the
inlet valve; the supply is replenished during the ejection
stroke of the pump so as to be available again when the next
ejection stroke comm~nces. Because o~ its large circumferen-
tial extent, the flow passage already has a large cross-
section area after a short opening movement of the inlet
valve, and as the inflow into the pump chamber takes place
from all or almo~t all directions, the flow path is relatively
short for most of the fluid that enters the pump chamber.
In some of the embodiments illustrated in the just-
mentioned publication, the inlet valv~ is a mechanical,
posîtiv~ly operat~d valve while in others of the illustrated
embodiment~ a flow-direction controlled non-return valve,
namely a flap valve, is used. In certain other embodiments
which are not illustrated, the inlet valve is a combination of
the two types af valve.
Objects of the present invention are to provide fluid
valve devices which are useful in positive displacement pumps,
especially positive-displacement pumps of the kind discussed
abo~e, and to providé an improved positive-displacement pump.
To this end, there is provided according to the inventlon
fluid valve devices and positive-displacement pumps as defined
in the claims.
As will be~ome clear from the following description, th~
valve device according to the invention is ~either c~ntrolled
mechanically by a positively acting valYe operating mechan~sm
nor controlled by th~ direction o~ the fluid flow through it.
Instead, it is controlled ~y the pre~sure or the force which
the fluid being receiv~d by the vAlve device applies to a
valve member that is movable into and out of ~aling engage-
ment with a valve ~eat. The ~luid whose pre~sure controls the
displacement of the valve member i5 received in a valve cham-
-: - - '
.
':
WO 19096 rCT/S~91/00408
~84~8~
ber d fined by the valve member and preferaly acts on the
valve member over a thrust sur~ace l~cated downstream of the
- flow passage which the valve member opens when it disengages
from the valve seat.
S Additional objects, ~eatures and advantages of the inven-
tion will become apparent from the following description of
embodiments of the invention, reference being had ko ~he
accompanying drawings.
Figs. 1 and 2 are diaqrammatic vertical sectional views af
a valve device according to the invention ~hown in closed
po~ition in Fig. 1 and in apen position in Fig. Z:
Figs. 3 to 6 are diagrammatic vertical sectional views of
a positive-displacement pump for pumpi~g liquid and show four
successive phases of a pumping cycle.
The fluid valve device shown by way of example in Figs. 1
and 2 camprises a body or hou~ing 11 having an inlet 12 with
an associated feed conduit 14 for a fluid, namely a liquid,
the passage of which the valve device controls in a two-
position or on-o~f mode (open-closed valve).
A vertically extending outlet conduit for the fluid being
passed through the valve device is designated by 15. Th~ lower
portion 17 of the outlet conduit is flared and has a down-
wardly facing annular rim 17A which ~orms a stationary valve
seat.
A valve chamber 20 in the valve deYice is defined later-
ally by a vertically displaceable valve member 21 in the
housing 11. The valve member 21 is in the shape vf a short
length of tube which i~ constricted at its upper snd to form
an annular sealing portion 21A adapted to engage and seal
against the annular valve seat 17A on the flared lower portion
17 of the outl~t conduit 15.
The lower ~nd o~ the valve member 21 is ~lared and con-
stantly i5 in ~liding sealing engagement with the inner side
of a cylindrical, downwardly directed portion llA of the
housing 11~
An intermediate cylindrical portion o~ the valve member 21
constantly is in ~liding sealing engagement with an annular,
inwardl~ directed lip llD o~ the housing. Between this lip and
the flared lawer valve member end, the valve member 21 to-
'
WO ~i9096 PCr/SE91/0040~
~c~
4gether with the housing portion llA defi~es a compartment V
which is filled with air and in open communication with the
surrounding atmosphere through an opening S. As the valve
member 21 moves axially towards and away from the valve seat
17A, the air compartment V accommodates the variations in
volume which the valve cham~er 20 undergoes.
At its upper portion llB the housing 11 defines a supply
compartment or reservoir 22. This compartment or r~servoir is
open at the top of the housing and holds liquid up to a level
which may vary but is here presumed always to be higher than
the level of the val~e seat 17A. If desired, a water seal (not
shown) may be provided on the upstream ~ide of the valve seat.
Figs. 1 and 2 show no bottom wall or other downward limi-
tation of the valve chamber 20. Depending on the application
of the valve device, there may be a fixed or movable bottom
wall. A movable bottom wall may be in th~ ~orm of a pump
piston which is movable up and down in the lower housing
portion llA as in the positive-displacement pump described
below. It is not necessary, however, for the valve device to
include a bottom wall of the valve chamber. What is required
is only that the pressure wlthin the val~e compartment 20 may
be varied in the manner explained below.
Taking the position shown in Fig. l as the initial posi-
tion, the operation of the illustrated valve device is as
~ollows:
In the position shown in Fig. 1, the liquid pressure in
the valve compartment 20 is presumed to be of a value related
to the head pressure in the supply compartment or reservoir 22
such that the upwardly directed fluid ~orce applied to the
valve member 21 prevails over the downwardly directed fluid
furce or the sum of the lat~er and the weight of the valve
member (this weiyht, howev~r, is presumed to be small or fully
or almost fully balanced by an Archimedean force and/or a
spring force). Consequently, the ~ealing portion 21A of ~he
valve member 21 is held in ~ealing engagement with the annular
valve seat 17A. The upwardly directed ~orce may result ~rom,
for example, the head pressure of a column of liquid in the
outlet conduit 17 or a pressure produced by a piston
accommodated in the housing portion llA.
,: :
':: . ' '
. . . . .
.
- -
~' ' : - ' ' . " '
WO '19096 P~T/SE91/004U8
In the illu~trated exemplary embodiment of khe fluid valve
device, the upwardly directed fluid force i~ applied to the
valve member 21 over an annular ~urface A on the inner side of
the valve member. ~he surface area of this surface A (thru~t
surface) as projected in the dir~ction of the axis L of the
valve device, or, in other words, the surface area which
determines, in conjunction with the pre~sure in the valve
chamber 20, the magnitude of the upwardly directed ~luid force
on the valve member, is determined by the outer diameter D of
the valve member and the diameter d of the circular or narrow
annular area over which the valve ~ea~ 17A is engaged by the
sealing portion 21A (for convenience, the radial width of the
surface of engagement between the valve seat 17A and the
sealing portion 21A o$ the valve member 21 is disregarded
here).
The downward ~luid ~orce is applied to the valve member 21
over a likewise annular but smaller surface B (thrust surface)
on the outer side o~ the valve member~ The ~urface area of
this surface B as pro;ected in the direction of the axis L is
determined by the diameter Dd of the cylindrlcal intermediate
portion of the valve member and the above-mentioned diameter
d.
In the illustrated embodiment o~ the fluid valve device,
the air compartment V constantly is in open, unrestricted
communication with the surrounding atmosphere and thus is
always subjected to the atmospheric pre~sure. Con~equently,
the upwardly facing annular ~urface C on the outer side of the
valve ~ember 21 - the axially projected or effectiva surface
area o~ this surface C is determined by the outer diameter D
o~ the flared lower valve member portion and the outer dia-
meter Dd of the cylindrical intermediate valve m~mber por-
tion.- is not acted on by any forc~ tending to di~place the
valva member upwardly or downwardly.
~hen the pressure in the valve chanber 2o drops ~;uffi-
ciently ~ar below the pressure in the supply compartment orreservoir 22, e.g. because a pre~sure generated by a piston
(not shown) in the housing portion ~lA di~appears and/or the
momentum of an upwardly moving liquid column in the outlet
condoit 15 tend~ to produce ~uotlon in the vnlve compartrent,
': '
:.
W0' `9096 PCr/SE91/OOqO8
~8 ~81
a situation develops in which the downward force acting on the
valve member 21 prevails and moves the valve member down-
- wardly.
As a conse~uence, an annular gap-like flow passage 23 is
opened between the valve member 21 and the valve seat 17A, see
Fig. 2. Because of the annular configuration o~ this 10w
passage 23, tha cross section area the flow passage presents
to the liquid flow through it already is substantial after a
short downward movement of the valve member. Hence, the liquid
in the supply compartment or re~ervoir 22 can flow into the
valve chamber 20 almost unimpededly, that is, without under-
~oing any significant pressure drop.
A ~ollowing increase of the pressure in the valve chamber
20 with respect to the pressure in the supply compartment or
reservoir 22 will cause the upward fluid force acting on the
valve member to prevail ~o that the valve member 21 is r2-
turned to the closed position shown in Fig. 1. Such returning
of the valve member may take plac~ even before the pressure in
the valve chamber 20 exceeds the pressure in the supply com-
partment or reservoir 22, because the effective (axiallyprojected) surfac~ area o~ the downwardly $acing thrust sur-
face A is larger th~n the e~ective (axially projected) sur-
face area of the upwardly ~acing thrust surface B.
In Figs. 3-6, which show a positive-displacement piston
pump includlng an inlet valve in the form of a one-way fluid
valve device embodying the principles o~ ~he invention, the
reference numerals and letters used in Figs. 1 and 2 are also
used to designate pump elements which correspond, in respect
of their functions, to the ~alve elements forming part o~ the
valve device of Figs. 1 and 2.
The pump ~hown by way of example in Figs. 3-6 comprises a
rigid, generally circular cylindrical pump housing 11. An
inlet opening 1~ is provided in the circumferential pump
housing wall llA, and an outlet opening 13 is prov~ded in the
top end wall llC. A radiaI inlet conduit 14 conveving a sub-
~tantially continuous ~traam o~ liquid opens into the inlet
opening 12, and the outlet opening 13, which is located on the
vertical axis o~ the pu~p housing 11, opens into an upwardly
extending axial outlet conduit 15.
.
. ~
WO gt/19096 I'C'r/SE91/01)408
Inside the pump housing 11 the pump has a sac or bladder
16 of a thin, highly flexibl~ but ~ubstantially inextensible
film of plastic, such as polyurethane. This sac is sealingly
connected with the inlet conduit 14 and, through the inter-
mediary of a flared inlet sleeve 17 attachPd to the pump hous-
ing, with the outlet conduit 15. The sac 16 and the pump
housing 11 are designed such that the entire pump, or at least
the sac, lends itself to use as a disposable ltem. Throughout
the height of the sac 16, its cro~s-sections taken perpen-
dicularly to the axis L o~ the pump housing are generallycircular or annular.
The bottom wall of the ~ac 16 re~ts on the top side o~ a
vertically movable displacement member or piston 18 which is
caused to reciprocate vertically at a constant or variable
rate by a motor 19. The piston may be positively driven in
both directions, but in the illustrated embodiment it i5
positively driven only upwardly through the delivery stroke.
The downward movement o~ the pi~ton results from gravity, i . e .
the weight of the piston and the weight of the liquid in the
20 pump chamber 20. A contribution to the downward movement of
the piston may al~o ~e qiven by the ~tatic or dynamic pressure
of the liquid being pump~d.
As the sac 16 is not secured to the piston 18, the piston
does not pull the bottom wall of the sac downwardly during the
downward or filling stroke. However, it is within the scope of
the invention to apply a downward pulling force t~ the bottom
wall of the sac.
The lower portion of the sa~ lS de~ines a pump chamber 20
th~ ~ide wall of which, or at lea~t the upper portion thereof,
is configured by a surrounding, ~ubstantially rigld, upwardly
tapering collar 21 the cross-sections of which taken perpen-
dicularly to the pump axis L are circular. Primarily, the
Punction o~ the collar 21, the weight of which is very small,
i5 to impart a stable configuratiorl to the side wall of the
sac 16 at the upper portion of the pump chamber. This stabi-
lis1ng effect may alGo be accomplished by other means, e.g. by
making the side wall o~ the ~ac ~uf~iciently rigld.
As shown in the drawings, in certain phases o~ the cycle
of operation of the pump, the collar 21 extends d~wnwardly
,
W091ll9096 PC~/SE91/00408
z
beyond the t~p portion of the piston 18, which i5 arranyed
such that air can flow freely past the piston into and out of
the air compartment V, which is constantly under atmospheric
pre~sure.
The collar 21 is freely movable axially within the pump
houslng 11, that is, it can move up and down together with the
adjacent portion of the side wall of the sac 16 without being
driv~n by a positive-acting ~echani~m; the forces acting on
the collar 21 and causing its upward and downward movements
are generated by the liguid being pumped, a~ will be explained
in greater detail in conjunctio~ with the description of the
operation of the pump.
In its uppPr portion, the section of the sac 16 which
d~fines the pump chamber 20 merges, by way of a constriction
or waist at the top edge 21A of the collar 21, with a sac
section which defines an annular supply compartment or reser-
voix 22. This reservoir Z2 surrounds and is partly defined by
the outlet sleeve 17 and communicates with the pump chamber 20
through an annular inlet passage 23 de~ined between the top
edge 21~ of the collar 21 and the valve ~eat 17~ at the flared
lower end of the sleeve 17. The inlet conduit 14 is constantly
in open, unrestricted communication with the reservoir 22
which is expandable by the inflowing liquid.
A thru~t ri~g 24, which is constantly uryed downwardly by
a wea~ compression sprinq 25, engages the top wall of the sac
1~, that is, tha wall of the ~ac 16 which forms the top wall
of the re~ervoir 2~. The pressure within the reservoir 22 pro-
duced by the thrust ring ~ very low, however, at least until
the re~ervoir has been substantially expanded and thus has
compres~ed the ~pring heavily.
An operating cycle of the pump will now be explain~d,
starting from the condition or the phasP of the op~rating
cycl~ illustrated in Fig. 3, i~ which the piston 18 is pxe~
sumed to be moving downwardly towards its lower end posltion
and to have reached a point near that end position. The collar
21 i8 at or near a low~r end position ~o that the inlet pas-
sage 23 has it~ maximum or almo~t its maximum height. The
fluid, a liquid, then flows in~o the pump chamber 20 through
the inlet passage 23 without undergoing any signiPicant pres-
,, . . . :
- . `: `,, : '
WO 91 J 19096 pcr/sEs1 /004118
9 2~6~
sure drop. ~he liquid is supplied both directly ~om the inlet
conduit 14 and indirectly from this concluit by way of the
reservoir 22.
Because the inlet passage 23 has a large cros~-s~ction
area for the inflowing li.quid and because its length as mea~
sured in the direction of the liquid flow through it, that is,
in the radial direction, is very ~mall, it present~ an extrem-
ely low rasistance to the flow of liquid from th~ inlet open-
ing 12 and the reservoir 22. For that re~aon, th~ inflow of
liquid into the pump chamber 20 from the reservoir 22 can take
place almost entirely independently of the more or less con-
tinuous inflow from the inlet opening 12 and the inlet cvnduit
14. Thu6, the inflow from the inlet opening 12 and t~e inlet
conduit 14 is virtually unaffected by the diæcharging of the
reservoir 22.
Because the di~charge into the pump chamber 20 o the
liquid accumulated in the reservoir 22 does not inter~ere with
the in~low of liquid rom the inlet opening 12 and the lnlet
conduit 14 and because the resi~tance to flow of liquid
through the inlet passage 23 i~ very ~mall, the reservoir 22
can be discharged extremely rapidly, even though the biasing
action exerted on the liquld in the reservoir 22 by the thrust
plate 24 and the compression 6pring 25 i~ not very ~trong.
Factors which contribute to the rapid discharge of the reser-
voir are:.
- ~he biasing device 24/25 need only accelerate the liquid
volume which is discharged from the reservoir 22, because the
liquid flowing from the inlet 12/14 direct into the pump
chamber 20 need neither be retarded nor be accelerated:
- The distance that the di~charging liquid has to travel
is very short;
- The r~sistance to ~low that the discharging liquid
encounters is extre~ely ~mall.
As long as the liqu~d flows into the pump chamber 20
35 through the inlet pa~age 23 from the inlet 12/14 and the
reservoir 22, the pu~p ¢har~er 20 ~xpands, providQd t:hat: the
pump pi~ton 18 is still free to move downwardly. In the illu
strated embodiment o~ the pump, the expansion take~ place
without any external force tending to pull the bottom wall of
'
. ' , '
WO~i/19096 PCT/SE91/00408
2 ~
the ~ac 16 downwards and thereby tending to produce a sub~
atmospheric pressure in the pump chamber 20 (but as mentioned,
it is within the scope of the invention to provide for ~uch a
force to assist in the expansion of the pump chamber). ~ccord-
ingly, in the illustrated emhodiment of the pump, the fillingo~ the pump chamber 20 is governed by th~ inflow of liquid
from the inlet conduit 14 and the re~ervoir 22.
When the pump piston 18 is ~topped at its low~r end posi-
tion or is stopped b~fore it reaches it~ low~r ~nd position
b~cause it engages the upwardly moving driving member l9A of
the motor 19, the collar 21 and the constricted upper portion
of the side wall 16A of the sac 16 will move upwardly to a
position in which they ssalingly engage the downwardly facing
~alve seat 17A on the flared lower portion of the outlet
sleeve 17 so that the inlet passage 23 is closed and continued
inflow into the pump chamber 20 is prevented. Accordingly, the
collar 21 and the a~sociated portion of the sac ~6 constit~te
an inlet valve member for the pump chamber 20.
The movement of the collar 21 to the just-mentioned posi-
tion (clos~d valve) is governed by the pres~re o~ the li~uidin the pump chamber 20 and the pres~ure in the inlet 12 and
the reservoir 22. The pressure of the liquid in the pump
chamber 20 applies to the ~ac 16, and thus to the collar 21,
an upwardly directed force over a downwardly facing, axially
pro~ected annular thrust ~urPace A on the collar; this annular
thrust surface ha~ an outer diam~ter D and an inn~r diameter
d, see Fig. 3. Thi~ force tends to displace the collar 21
upwardly with respect to the pump piston 18.
At the same time, the collar 21 ~s acted on by, in addi-
tion to the fairly small downward force resulting from theweight of the collar, a downward force re~ulting from the
action o~ the pressure o~ the liquid in the reservoir 22 on an
upwaxdly facing, axially proje~ted annular thruæt ~ur~ace B of
the ~ac. The inner diameter of th~ annular thrust ~urface B is
consta~t and e~ual to the inner diameter d of the first~
mentioned annular thru~t ~urfaae A, and its outer diameter
varies during the movement of the collar 21; as ig apparent
from a comparison of Fig. 3 and Fig. 4, the outer diameter,
and thus the surface area of the annular thrust ~urface B, is
.. . .
' . '~ . ', ' " '
' :-
. ~ . ~ .. . . .
W~ 19096 PCTtSE91/00408
11 z~ S~
at its maximum when the collar i~ in its top position (closed
valve) and decreases during ~he downward movement of the
collar.
During the "steady state" phase of the portlon of the
operating cycle of the pump in which the inflow to the pump
chamber 20, that is, the filling of the pump chambex, takes
place, the interaction of ~orces is ~uch that the collar 21 is
acted on by a resultant force which maintains the collar in
its lowermost position or at any rate at a distance from the
valve seat 17A, so that the valve is kept open.
When the inflow into the pump chamber 20 ceases, which may
result ~rom ~topping the pump piston 18 in its lower end
position, so that continued expansion of the pump chamber is
prevented, or from the motor 19 beginning to move the pump
piston 18 upwardly, or from a backflow tending to develop in
the outlet conduit 15, the resultant liquid-pressure foroe
acting on the collar 21 is reversed, ~o that the collar is
displaced upwardly to the position shown in Fig. 4 (closed
valve). This movement Of the collar 21 can take plac~ even
before there is a tendency to backflow through the passage 23.
Thu~, the clo~ing movement may very well ~ccur or at least be
initiated before such a tendency has developed, that is, even
before the inflow to the pump cha~ber 2~ through the passage
23 ha~ ceased.
When the pump pis~on 18 moves upwardly after the valve
member formed by the collar 21 and the adjacent portions of
the sac sidewall 16A has engaged the ~lared portion or valve
seat 17A of the outlet ~leeve 17, the pump chamber 20 is
contracted by the upwardly moving pump pis~on 18 so that the
liquid in the pump chamber is expelled through the outlet
sleeve 17 and the outlet conduit 15 (Fig. 4). Although the
valve is clo9ed, liquid may still flow to the pump through the
inlet conduit 14, becau~e the liquid ~upplied when the valve
is closed is accommodated by the re~ervoir 22 which expands
against the relatively w~ak force of the ~pring 24 (Fig. 5).
In the initial phase o* the expansion, the ~pring force is
very small, so that the in~low through ~he conduit 14 ma~
~ontinue even when the incoming liquid i~ at a very low pres-
sure. Only when the re~ervoir 22 approaahes its maximum
,
W0~"l9096 PCT/SE91/00408
12 ~8~
volume, the spring force increases su~ficiently to substan-
tially oppose or even stop the inflow.
Naturally, the pump should be dimensioned with con5idera-
tion given to the flow rate of the inflow which it is meant to
handle, so that the re5ervoir 22 can normally accommodate the
liquid ~upplled during the closed phases of the valve without
having to expand to near its maximum volume. This prevents the
inflow to the pump through the inlet conduit 14 from becoming
unduly retarded or even stopped during the discharge or ejec-
10 tion periods when the inlet valve i5 closed.
Whe~ that phase of the operating cycle which comprises theexpulsion of the liquid from the pump chamber ~O approaches or
reaches its end (Fig. 5), the resultant liquid-pressure force
acting on the collar 21 is again reversed 80 that the collar
returns toward the position corresponding to open valve, see
Fig. 6. The inflow into the pump chamber 20 can thus start
again.
Depending on the rate at which the pump piston 18 is
reciprocated and on the momentum of the liquid being dis-
charged from the pump chamber, a portion of the liquid enter-
ing the pump chamber may flow directly out of the pump chamber
throuyh the outlet conduit 15 whil~ the expan~ion of the pump
chamber takes place. It has also been found that when the
stroke rate of the pump i5 sufficiently high, the outgoins
flow is almost constant because of its momentum. The volu-
metric variations of the reservoir 22 over the pump cycle then
are very small.
In the embodiments of the valve device shown in Figs. 1-6
the flow passage 23 is opened all the way round the pump
chamber. Such a continuous flow passage is advantageous,
because the maximum cross-s~ction area and an advantageous
flow pattern are achievedO It is within the scope of the
invention, however, to use a portion of the circumference for
a radial outlet from the pump chamber. This outlet may be
positioned diametrically opposite to the inlet, but it is also
pos~ible to position the inlet and the outlet side by side.
In the just-mentioned case, in which the fluid is dis-
charged from the pump chamber 20 through a radial outlet and
the inlet passage 23 between the valve member 21 and the valve
:
.
WO '`' /19096 l'C'rtSE91/00408
~ 3
seat 17A thus does not extend all the way round the pump
chamber, it may be preferred to mount the valve member such
that it can be pivoted about an axis which is in a plane
parallel to the plane containing the valve seat and which
preferably passes through or near the ends of khe inlet pas-
sage. In such case, the height of the opened passage will
increase gradually from th~ pivot axis to a maximum at the
side of the pump chamber which is diametrically opposite the
outlet.
Several modifications of the valve device and th0 pump
illustrated in the drawin~s can be made within the scope of
the invention.
For example, while in the illu~trated embodiments the
entire fluid force acting on the valve menber in the closing
direction is applied directly on the valve member, lt is
possible within the scope of the invention to apply it in-
directly, at least partly, ~uch as through a mechanical trans-
mission, from a fluid pressure device which converts the fluid
pr~ssure in the valve chamber or the pump chamb~r into an
upward force which is applied to the valve member. Moreover,
in a modification o:E the pump 6hown in figs. 3~6, the pump
piston during its downward movement displaces a fluid volume
in the driving device. This displaced fluid volume is used
during part o~ the downward movement of the pump piston,
2S namely toward the completion o~ the filling of the pump cham-
ber, to cause displacement of a force-transmittning element
upwardly and to thereby apply an upward, that is, closing
force on the valve member~
Within the scope of the invention, it is also possible to
provide for a biasing force, such as a gravity force or a
spring force, constantly acting in the closing or in the
openlng direction on the valve member, so that the valve
member always t~ds to mo~e to a pr~determined position, such
as the closed position, when the ~luid forces which are gene-
rated in normal operation are not present.
In the illu~trated embodimenta, the air compartment v isalways under atmospheric pressure, so that the thrust surface
c does not contribute to the opening or closing ~orce applied
to the valve member. However, especially when the valve device
W~1'19096 PC~/S~1/00~08
14
~ccording to the i~vention is used in a positive-displacement
pump, the pres~ure in the air compartment may be caused to
vary over the pumping cycle. This can be accomplished by
making the air compartment V a part of the total volume of a
fluid system the remaining volume of which is matched with the
maximum and minimum volumes of the air compartment V such that
the pressure in compartment V varies in a predetermined manner
over the pumping cycle and thereby contributes to the fluid
forces acting on the valve member in the direction of movement
thereof.
It should also be noted that even though it is advan-
tageous in some applications of the valve device accoxding to
the invention, the thrust surface B facing the valve seat 17
which is provided in the illustrated embodiments and contri-
butes to displacing the valve member in the opening direction,is not indispen6ahle. Thus, the diameter of the sealing por-
tion 21A of the valve member 21 may be equal or nearly equal
to the diameter which is designated by Dd in the drawings. In
such case, the resulting fluid ~orce is determined only by the
differential pressure over the thrust surfaces A and C.
The positive-displacement pump illustrated by way of
example is particularly suitable for use as a blood pump. In
such use of the pump, the inside of the sac 16 and any other
sur~aces contacted by the blood being pumped should have a
lining or coating of human or animal tissue (such as peri-
cardium of swine) so that the surfaces coming into contact
with the blood have the best possible compatibility with the
blood.
:- .
;:
. . .
.
~ .
., ~ ~. , ., '
.. .. .
.' . - .: . ' .. : .. .. . ' ' .
