Note: Descriptions are shown in the official language in which they were submitted.
CA 02545905 2006-05-05
Title
STEPPED CYLINDER PISTON PUMP
Scope of the Invention
[0001] This invention relates to piston pumps and, more particularly, to a
stepped piston
pump with a stepped cylinder to accommodate piston shrinkage or setting.
Background of the Invention
[0002] Piston pumps are well known in which a piston reciprocally slides
within a
chamber. For many piston pumps, the piston includes an annular disc with an
inherent
resiliency biasing a periphery of the disc into engagement with an inner wall
of the chamber
to form a seal therewith. Frequently such discs may permit fluid flow in one
direction
therepast by a pressure differential across the disc urging the disc against
its bias away from
sealed engagement with the inner wall of the chamber and with the inherent
bias of the disc
causing the disc to assume a sealed position.
[0003] The present inventor has appreciated that under various conditions, the
inherent
resiliency of the disc may become impaired such that the disc will not
adequately perform its
function and the pump may have its performance reduced or fail. For example,
the present
inventor has appreciated that with pistons incorporating resilient discs which
are made of
plastic material, that the disc can be subject to setting and shrinkage.
Setting arises, for
example, when a disc is received in a chamber which disc has an initial
inherent bias to
assume a diameter larger than the diameter of the inner wall of the chamber
such that the
disc's inherent bias urges the disc into engagement with the inner wall of the
chamber. That
is, the disc is compressed inside the chamber. If, however, such disc may be
left in such
compressed condition in the chamber for an extended period of time, then the
disc may loose
its inherent resiliency as, for example, tending to set and retain the shape
in which it is held
for an extended period of time and losing its bias to expand further
outwardly. The extent to
which setting of set may arise will determine the extent to which the disc
member forms a
functional seal with the inner wall of the chamber. Set is increased with the
time during
1
CA 02545905 2006-05-05
which the disc is retained in one position. Set with most plastic materials
increases with
increased temperature. For example, with many relatively inexpensive plastic
materials as
may preferably be used to form pistons for pumps, leaving a disc of a piston
in a fixed
condition within a cylinder for a number of days at temperatures in excess of
35 C and
higher can significantly increase the extent to which a set is developed.
Nevertheless, where
the assembled pumps are left, for example, in storage in many climatic
conditions, it may not
be unrealistic for the pumps to be subjected for temperatures in the range of
35 C to 60 C for
hours if not days as in transit, storage and the like.
100041 The present inventor has also appreciated that set and the reduced
inherent
resiliency of a disc may arise when the disc may be subjected to certain
fluids to be
dispensed by the pump including chemicals which negatively affect the
properties of the
plastic with the time that they are left in a particular position.
100051 The present inventor has also appreciated that there are plastic
materials which
may be preferred for use with pistons in pumps which can be subject to
shrinkage when
exposed to increased temperatures for periods of time. Thus, many plastic
discs in piston
pumps will also be subject to shrinkage when exposed to temperatures above,
say, 35 C for
an extended period of time which shrinkage can be enhanced and rendered more
permanent
as when a disc is retained in a compressed condition within the cylinder to
the time that it is
subjected to the elevated temperatures.
Summary of the Invention
[0006] To at least partially overcome these disadvantages of previously known
devices,
the present invention provides a piston pump in which, when the piston is
stored or when the
pump is not operative, the piston is received inside a portion of the chamber
with the piston
in a position having a larger diameter than portions of the chamber in which
the piston is
received when the piston is operative for pumping.
[0007] An object of the present invention is to provide an improved piston
pump
assembly to overcome difficulties which may arise due to setting, the loss of
resiliency or
shrinkage of a piston-forming member.
2
CA 02545905 2006-05-05
[0008] Another object is to provide a piston pump which provides for useful
operation of
the pump even after a piston sealing member may have shrunk or become set to
adopt an
effectively smaller diameter.
[0009] A pump in accordance with the present invention has a piston
reciprocally axially
slidable within a chamber, with the piston assuming an axial set position
within the chamber
when the piston is not in use or when it is stored as after initial assembly.
While the piston is
in such set position, the piston is received within a set portion of the
chamber having a larger
circumference than other portions of the chamber into which the piston will
slide when moved
for pumping. The piston may, due to engagement in the larger diameter set
portion of the
chamber, become set to assume the diameter of the larger diameter set portion
of the chamber
or may shrink as to assume the diameter of the larger diameter set portion of
the chamber
which may impair the engagement of the piston in the larger diameter set
portion. However,
on movement of the piston in use into the other portions of the chamber having
smaller
diameters, the effects of set or shrinkage of the piston on engagement with
the chamber will be
reduced. Preferably, when the piston is in the set portion of the chamber,
even after reasonably
expected setting or shrinkage, the piston will continue to engage the wall of
the chamber. It is
within the scope of the invention, however, that when the piston is in the set
position that the
disc not engage the wall of the chamber. Pumps in accordance with the present
invention
provide a stepped chamber with a larger diameter set portion of the chamber to
be a portion or
portions in which the piston is received when not operative and/or is being in
storage
preferably with the set position or positions being a fully retracted position
or a fully
withdrawn position. Preferably, the difference between the diameter of the
larger diameter set
portion and the other portion of the chamber is selected to be as small as
possible to reasonably
accommodate expected set or shrinkage.
[0010] Piston pumps may have pistons with more than one disc to engage the
inner walls
of a piston chamber and a separate stepped arrangement may be provided for
each disc
although this may not be necessary and merely to provide a stepped
configuration for one of
the discs may be adequate to ensure reasonable operation of the pump.
3
CA 02545905 2006-05-05
[00111 The present invention provides by use of a stepped chamber a mechanism
for
accommodating adequate function of the pump notwithstanding set or shrinkage
and, as well,
permits the piston for the pump to be made from more easily handled and less
expensive
materials as, for example, plastics having lower melting and increased
likelihood of set and
shrinkage.
[0012] The invention is for use not only with pistons which have discs which
extend
radially outwardly to engage an inner wall of the chamber but also with
arrangements in which
a chamber may have a annular disc which extends radially inwardly as to engage
a cylindrical
surface on a piston. In the latter case, the diameter of the piston to be
engaged by the radially
outwardly extending disc should be reduced when the piston is in a set
position it assumes
when not in use.
[0013] In one aspect, the present invention provides a pump for dispensing
fluid from a
reservoir comprising:
[00141 a piston-chamber forming member having an inner cylindrical chamber and
an
outer cylindrical chamber, the inner chamber and outer chamber each having a
diameter, a
chamber wall, an inner end and an outer end,
10015] the diameter of the inner chamber being different than the diameter of
the outer chamber,
[0016] the inner chamber and outer chamber being coaxial with the outer end of
the inner
chamber opening into the inner end of the outer chamber,
[0017] the inner chamber in fluid communication with the reservoir,
[0018] a piston forming element received in the piston-chamber forming member
axially
slidable inwardly and outwardly therein,
[0019] a disc on the piston extending radially outwardly,
[0020] the piston forming element slidably received in the piston-chamber
forming member
for reciprocal axial inward and outward movement therein in a cycle of
operation between an
extended position and a retracted position to pump fluid from the reservoir
out a pump outlet,
[0021] an intermediate position between the extended position and the
retracted position,
100221 one of the extended position and the retracted position being a set
position and the
other of the extended position and the retracted position being a temporary
position,
4
CA 02545905 2006-05-05
[0023] in the set position and between the set position and the intermediate
position, the
disc is in the one of the inner chamber and outer chamber having the larger
diameter,
[0024] in the temporary position and between the temporary position and the
intermediate
position, the disc is in the one of the inner chamber and outer chamber having
the smaller
diameter,
[0025] when the disc is in the one of the inner chamber and outer chamber
having the
smaller diameter, the disc engaging the chamber wall thereof circumferentially
thereabout to
substantially prevent fluid flow in that chamber past the disc in at least one
of an inward
direction and an outward direction,
[0026] the pump, after assembly of the piston-chamber forming member and the
piston
forming element, being in the set position or between the set position and the
intermediate
position: (a) when the pump is stored prior to initial use, (b) when the pump
is, after initial
use, between cycles of operation, or, (c) when the pump is stored prior to
initial use and
when the pump is, after initial use, between cycles of operation.
100271 In another aspect, the present invention provides a pump for dispensing
fluid from
a reservoir comprising:
[0028] a piston-chamber forming member having an inner cylindrical chamber, an
intermediate chamber and an outer cylindrical chamber, the inner chamber,
intermediate chamber
and outer chamber each having a diameter, a chamber wall, an inner end and an
outer end,
[0029] the diameter of the inner chamber being less than the diameter of the
intermediate
chamber,
[0030] the diameter of the intermediate chamber being less than the diameter
of the outer
chamber,
[0031] the inner chamber, intermediate chamber and outer chamber being coaxial
with the
outer end of the inner chamber opening into the inner end of the intermediate
chamber and with
the outer end of the intermediate chamber opening into the inner end of the
outer chamber,
[0032] the inner chamber in fluid communication with the reservoir,
[0033] a piston forming element received in the piston-chamber forming member
axially
slidable inwardly and outwardly therein,
CA 02545905 2006-05-05
[0034] an inner disc on the piston extending radially outwardly,
[0035] an outer disc on the piston extending radially outwardly,
[0036] the outer disc located on the piston axially outwardly from the inner
disc,
[0037] the piston forming element slidably received in the piston-chamber
forming member
for reciprocal axial inward and outward movement therein in a cycle of
operation between an
extended position and a retracted position to pump fluid from the reservoir
out a pump outlet,
[0038] an intermediate position between the extended position and the
retracted position,
[0039] in the retracted position and between the retracted position and the
intermediate
position, the inner disc is in the inner chamber and the outer disc is in the
intermediate chamber,
[0040] in the extended position and between the extended position and the
intermediate
position, the inner disc is in the intermediate chamber and the outer disc is
in the outer chamber,
[0041] when the inner disc is in inner chamber, the inner disc engaging the
chamber wall
thereof circumferentially thereabout to substantially prevent fluid flow in
the inner chamber past
the inner disc in at least one of an inward direction and an outward
direction,
[0042] when the outer disc is in intermediate chamber, the outer disc engaging
the chamber
wall thereof circumferentially thereabout to substantially prevent fluid flow
in the intermediate
chamber past the outer disc in at least one of an inward direction and an
outward direction,
[0043] the pump, after assembly of the piston-chamber forming member and the
piston
forming element, being in the extended position or between the extended
position and the
intermediate position: (a) when the pump is stored prior to initial use, (b)
when the pump is,
after initial use, between cycles of operation, or, (c) when the pump is
stored prior to initial use
and when the pump is, after initial use, between cycles of operation.
Brief Description of the Drawings
[0044] Further aspects and advantages of the present invention will become
apparent
from the following description taken together with the accompanying drawings
in which:
[0045] Figure 1 is a schematic cross-sectional side view of a piston pump in
accordance
with a first embodiment of the present invention in an extended position;
6
CA 02545905 2006-05-05
[0046] Figure 2 is a view the same as in Figure 1, however, with the piston in
an
intermediate position;
[0047] Figure 3 is a view the same as in Figure 1, however, with the piston in
a retracted
position;
[0048] Figure 4 is a schematic cross-sectional side view of a piston pump in
accordance
with a second embodiment of the present invention in an extended position;
[0049] Figure 5 is a view the same as in Figure 4, however, with the piston in
an
intermediate position;
[0050] Figure 6 is a view the same as in Figure 4, however, with the piston in
a retracted
position;
[0051] Figure 7 is a schematic cross-sectional side view of a piston pump in
accordance
with a third embodiment of the present invention in a retracted position;
[0052] Figure 8 is a schematic cross-sectional side view of a piston pump in
accordance
with a fourth embodiment of the present invention in a retracted position;
10053] Figure 9 is a schematic cross-sectional side view of a piston pump in
accordance
with a fifth embodiment of the present invention in a retracted position;
[0054] Figure 10 is a schematic cross-sectional side view of a piston pump in
accordance
with a sixth embodiment of the present invention in an retracted position;
[0055] Figure 11 is a view the same as in Figure 10, however, with the piston
in an inner
intermediate position;
[0056] Figure 12 is a view the same as in Figure 10, however, with the piston
in an outer
intermediate position; and
[0057] Figure 13 is a view the same as in Figure 10, however, with the piston
in an extended
position.
Detailed Description of the Drawings
[0058] Reference is made to Figures 1 to 3 which show a liquid dispenser 10
having a
pump assembly 12 attached to a reservoir 13 in accordance with the present
invention.
7
CA 02545905 2006-05-05
[0059] The reservoir 13 is a container with a threaded neck 14. The pump
assembly 12
has a piston chamber-forming body 16 defining a chamber 18 therein in which a
piston
forming element or piston 20 is slidably disposed for reciprocal movement to
dispense fluid
from the reservoir. The chamber 18 is defined inside side walls 42 of an inner
tube 26. The
chamber 18 is closed at an inner end wall 23 and open at an outer end 24.
Openings 22 in the
end wall 23 of the chamber 18 are in communication with the fluid in the
reservoir 13. A
one-way valve 25 across the opening 22 permits fluid flow outwardly from the
reservoir 13
into the chamber 18 but prevents fluid flow inwardly.
[0060] The piston chamber-forming body 16 has the cylindrical inner tube 26
defining
the chamber 18 therein. An outer tubular member 28 is provided radially
outwardly of the
inner tube 26 joined by a radially extending shoulder 27 to the inner tube 26.
The outer
tubular member 28 carries threads 29 thereon which engages the threaded neck
14 of the
reservoir 13 to form a fluid impermeable seal therewith.
[0061] Fluid from the reservoir 13 is in communication with the piston chamber
18 via
the opening 22.
[0062] The one-way valve 25 has a shouldered button 30 which is secured in a
snap-fit
inside a central opening in the end wal123 of the chamber 18. A flexible
annular rim 31 is
carried by the button 30 and extends radially outwardly to the side wall 42 of
the inner tube
26. When the pressure in the chamber 18 is less than that in reservoir 13, the
rim 31 is
deflected away from the walls of the inner tube 26 and fluid may flow from the
reservoir 13
through exit openings 22 and past the rim 31 into the chamber 18. Fluid flow
in the opposite
direction is blocked by rim 31, which is biased radially outwardly into the
side wall 42 of the
inner tube 26.
100631 Two circular inner and outer discs 33 and 34 are located on the stem
spaced from
each other. The inner disc 33 resiliently engages the side wall of the chamber
18 to permit
fluid flow outwardly therepast by resilient deflection away from the side wall
when the
pressure in the chamber 18 inward of the disc 33 is greater than the pressure
outward of the
disc 33. Inner disc 33 prevents fluid flow inwardly therepast. Thus, the inner
disc 33
8
CA 02545905 2006-05-05
functions as a second one-way valve. The outer disc 34 engages the side wall
of the chamber
18 to prevent fluid flow outwardly therepast.
[0064] The piston stem 32 has a hollow passageway 34 extending along the axis
40 of
the piston 20 from a blind inner end 38 to an outlet 36 at an outer end.
Inlets 37 to the
passageway 34 are provided on the stem 32 between the inner disc 33 and outer
disc 34. By
reciprocal movement of the piston 20 in the chamber 18, fluid is drawn from
reservoir 13
through exit openings 22 past the inner disc 33 and via the inlets 37 into the
passageway 34
and along the passageway 34 to exit the outlet 36.
[0065] The piston-forming element or piston 20 is preferably a unitary element
formed of
plastic. The piston 20 has a hollow stem 32.
[0066] The piston chamber-forming body 16 is preferably injection moulded as a
unitary
element. The one-way valve 24 and the piston forming element 20 are separate
elements.
[0067] In Figures 1 to 3, the piston 20 is reciprocally movable in a single
stroke of
operation from an extended position as shown in Figure 1 to the retracted
position shown in
Figure 3 and then back to the extended position of Figure 1. In moving between
the extended
position of Figure 1 and the retracted position of Figure 3, the piston moves
through the
intermediate position shown in Figure 2.
[0068] In accordance with the first embodiment illustrated in Figures 1 to 3,
the piston 20 is,
after each stroke of operation, to be retained in the extended position until
next activated. In this
regard, in accordance with the first embodiment, a spring member (not shown)
biases the piston
20 to the extended position with a stop mechanism (not shown) preventing
further outward
movement of the piston than the extended position of Figure 1. Such spring
biased soap
dispensers are well known in which a user will move the piston from the
extended position to
the retracted position against the bias of a spring and the spring will return
the piston to a fixed
extended position in which position the piston will remain until next
activation by a user.
[0069] As seen in Figures 1 to 3, the side wall 42 of the chamber has three
portions, an
inner chamber portion 44 of a constant diameter, an outer chamber portion 48
of a constant
diameter greater than the diameter of the inner portion and a transition
portion 46 which
decreases in diameter outwardly from the inner portion 44 to the outer portion
48. As seen, a
9
CA 02545905 2006-05-05
first transition line 45 is disposed between the inner chamber portion 44 and
a transition
portion 46. Another transition line 47 is disposed between the transition
chamber portion 46
and the outer chamber portion 48.
[0070] In the extended position as shown in Figure 1, the outer disc 34 is
received in the
outer chamber portion 48 and the inner disc 33 is in the inner chamber portion
44. In moving
the piston inwardly from the extended position shown in Figure 1, the outer
disc passes
through the transition portion into the intermediate position illustrated in
Figure 2 in which
the outer disc 34 is first received within the inner chamber portion 44. In
moving between
the intermediate position shown in Figure 2 and the retracted position in
Figure 3, the outer
disc 34 is maintained within the inner chamber portion 44. A pump may be left
in the
extended position shown in Figure 1 for long periods of time and under
elevated temperature
conditions. In the extended position as seen in Figure 1, the outer disc 34
preferably, at least
when initially constructed, has an inherent bias such that the peripheral
edges of the disc 34
are, due to the inherent bias of the disc, urged outwardly into the inner wall
of the outer
chamber portion 48. With the passage of time, the outer disc 34 may become
subject to set
or shrinkage such that it loses its resiliency and is biased outwardly with
reduced force.
Notwithstanding any setting or shrinkage of the outer disc 34, on movement of
the outer disc
34 to the intermediate position of Figure 2, the outer disc 34 becomes
received within the
inner chamber portion 44 having a reduced diameter increasing the extent to
which the outer
disc 34 engages the inner wall of the chamber, thus providing for improved
pumping as
contrasted with a pump in which the entirety of the chamber had the diameter
of the outer
chamber portion 48.
[0071] Reference is made to Figures 4 to 6 which illustrate a pump assembly
similar to
that in Figures 1 to 3 and which the same reference numerals are used to refer
to the same
elements. One difference in the second embodiment in Figures 4 to 6 is that
the inner wall
42 of the chamber 18 has five portions, an inner chamber portion 50, an inner
transition
chamber portion 52, an intermediate chamber portion 54, an outer transition
chamber portion
56 and an outer chamber portion 58. Each of the inner chamber portion 50,
intermediate
chamber portion 54 and outer chamber portion 58 have a constant diameter,
however, with
CA 02545905 2006-05-05
the diameter of the inner chamber portion 50 being less than the diameter of
the intermediate
chamber portion 54 and the diameter of the intermediate chamber portion 54
being less than
the diameter of the outer chamber portion 58. In the embodiment of Figures 4
to 5, the pump
is to remain in the extended position of Figure 4 when not in use and is to be
moved in a
cycle of operation from the extended position of Figure 4 through the
intermediate position
of Figure 5 to the retracted position of Figure 6 then back through the
intermediate position
of Figure 5 to the extended position of Figure 4. In the extended position,
the outer disc 34 is
in the outer chamber portion 58 and the inner disc 33 is in the intermediate
chamber portion
54. From this position, the piston is initially moved inwardly to the
intermediate position of
Figure 5 in which the outer piston 34 is in the intermediate chamber portion
54 and the inner
disc 33 is in the inner chamber portion 50. In sliding between the
intermediate position of
Figure 5 and the retracted position of Figure 6, the outer disc 34 continues
to remain in the
constant diameter intermediate chamber portion 54 and the inner disc 33
remains in the
constant diameter inner chamber portion 50.
[0072] With the embodiments of Figures 4 to 6, both the outer disc 34 and the
inner disc
33, are in the extended position, in which they may remain when not in use in
a larger
diameter portion of the chamber than in a portion immediately inwardly
therefrom in which
they are substantially constantly retained during use of the pump in pumping.
Thus,
shrinkage or set by either of the outer disc 34 or the inner disc 33 is, to
some extent,
accommodated without performance reduction.
[0073] Figure 7 illustrates a third embodiment of a piston pump in accordance
with the
present invention in which the same reference numerals are used to refer to
the same elements
as in Figure 1. In the embodiment of Figure 7, however, the pump is intended
to be
maintained in the retracted position, shown in Figure 7, when not in use. In
use, the piston 20
is to be moved from the retracted position to an extended position. In the
retracted position,
the outer disc 34 is received in an enlarged diameter inner chamber portion
44. With outward
movement of the piston, the outer disc 34 moves over a transition chamber
portion 46 to an
intermediate position in which the outer disc 34 first enters the outer
chamber portion 48 of
reduced diameter. In reciprocal use of the pump, advantageous pumping occurs
in sliding
11
CA 02545905 2006-05-05
between an intermediate position and a fully extended position or in between
such positions
during which the outer disc 34 is maintained in the outer chamber portion and
the inner disc
33 is maintained in the constant diameter inner chamber portion 44.
[0074] Reference is now made to Figure 8 which illustrates a fourth embodiment
in
which in a manner analogous to that described with reference to Figures 4 to
6, but as in the
embodiment in Figure 7, the piston is to be retained in a retracted position
when not in use.
In Figure 8, there are five portions in the chamber, namely, an inner chamber
portion 50, an
inner transition chamber portion 52, an intermediate chamber portion 54, an
outer transition
chamber portion 56 and an outer chamber portion 58 of the chamber with the
inner chamber
portion 50, intermediate chamber portion 54, outer chamber portion 58 having
substantially
constant but different diameters and with the diameter of the inner chamber
portion 50 being
greater than the diameter of the intermediate chamber portion 54 which is
greater than the
diameter of the outer chamber portion 58. In a fully retracted position as
seen in Figure 8 in
which the piston pump assumes at rest, each of the outer disc 34 and the inner
disc 33 are
received in an enlarged diameter chamber portions compared to the diameter of
the chamber
portions in which the discs are to slide in operation of the pump from an
intermediate
position to an extended position.
[0075] The pump assembly in each of Figures 1 to 8 includes the one-way valve
25 and a
piston 20 with two discs 33 and 34. Figure 9 illustrates a pump assembly which
avoids use
of a separate one-way valve and the piston 20 carries three discs to provide,
in effect, two
one-way valves.
[0076] Referring to Figure 9, the piston has three discs, namely, an outer
disc 34, an
intermediate disc 33 and an inner disc 70. The pump shown is intended to be
maintained in
the extended position shown in Figure 9 when not in use. The outer disc 34 in
the extended
position is received in an enlarged diameter outermost chamber portion 58 such
that on
movement of the piston inwardly for pumping, the outer disc 34 comes to be
engaged within
the smaller diameter intermediate chamber portion 54. The intermediate disc 33
is always
received in the constant diameter intermediate chamber portion 54. The inner
disc 70 is
always received in the constant diameter inner chamber portion 50. A step
shoulder 52 is
12
CA 02545905 2006-05-05
between inner chamber portion 50 and intermediate chamber portion 54. A
transition chamber
portion 56 is between intermediate chamber portion 54 and outer chamber
portion 58.
[0077] Reference is made to Figure 10 which illustrates a sixth embodiment in
accordance with the present invention. As seen in Figure 10, the inner tube 26
is shown to
have an inner chamber portion 50 of a first constant diameter, an inner
transition chamber
portion 52, an intermediate chamber portion 54 of a constant diameter, an
outer transition
chamber portion 56 and an outer chamber wall portion 58 of constant diameter.
The inner
transition chamber portion 52 bridges between the inner chamber portion 50 and
the
intermediate chamber portion 54, and has a diameter less than the diameter of
the
intermediate chamber portion 54. The outer chamber portion 58 has a diameter
less than the
intermediate chamber portion 54. The pump is shown in four positions, a fully
retracted
position as illustrated in Figure 10, an inner intermediate position as shown
in Figure 11, an
outer intermediate position as shown in Figure 12 and a fully extended
position as shown in
Figure 13. The pump of Figures 10 to 13 is intended to be stored and shipped
in the fully
retracted position as illustrated in Figure 10, for example, as (a) merely
assembled and not
coupled to a bottle reservoir or (b) assembled and coupled to a bottle but not
engaged on a
dispenser. In the fully retracted position, the outer disc 34 is received
within the reduced
diameter inner transition chamber portion 52. U.S. Patent 5,975,360 issued
November 2,
1999 to Ophardt discloses in Figure 8 a piston pump which is assembled and
coupled to a
bottle in a retracted position but which, when coupled to a dispenser as shown
in Figure 8 of
that patent, is at rest in an extended position.
[0078] The pump, after being stored in the retracted position of Figure 10,
may then be
coupled to a dispenser which dispenser firstly holds the pump in a rest
position between
strokes in the extended position of Figure 13 and in use moves the piston
inwardly and
outwardly between the fully extended position of Figure 13 and the inner
intermediate
position of Figure 11. Thus, the operation of the pump is preferably selected
such that after
being placed in a dispenser, the piston 20 is not moved inwardly past the
inner intermediate
position of Figure 11 and, hence, is not again moved to the storage, retracted
position of
Figure 10. In the operative stroking of the pump in use, the piston 20 is
moved between the
13
CA 02545905 2006-05-05
extended position of Figure 13 and the inner intermediate position of Figure
11. The pump is
intended to be held when not in use in the extended position of Figure 13 in
which the outer
disc 34 is engaged in the enlarged diameter outer chamber portion 58. In
operation, the inner
disc 34 substantially only engages and moves along the constant diameter inner
chamber
portion 50 in all movement between the retracted position and the extended
position. The
inner chamber portion 50 is shown to have a diameter the same as the
intermediate chamber
portion 54, however, it may have a diameter which is greater or lesser than
the intermediate
chamber portion 54 with the inner transition chamber portion 52 suitably
modified.
[0079] This embodiment of Figure 10 has the advantage that when the pump may
be
stored prior to use as, for example, in the stored retracted position of
Figure 10, the outer
piston 34 is in the enlarged diameter inner chamber portion 50 of the chamber
and, as well,
when incorporated into a dispenser for use, when not in use, the outer disc 34
is in another
enlarged diameter outer chamber portion 58 of the chamber.
[0080] In accordance with the present invention, pump arrangements are
preferred
wherein the position of the piston when stored or assembled, whether or not
coupled to a
bottle reservoir and whether or not coupled to a dispenser, is the same as the
position of the
piston when at rest in between cycles of operation. Storage of the piston can
include storage
as when a piston pump is assembled but before it may be coupled to a bottle
reservoir and
after the pump assembly may be coupled to a bottle reservoir before the pump
and reservoir
as a sub assembly may become coupled to a dispenser. Storage can also include
a condition
of being coupled to a dispenser ready for use.
[0081] While not necessary, it is preferred in accordance with the present
invention that
the piston disc when in a larger diameter portion of a chamber continues to
provide some seal
and engagement between the outer disc and the inner wall of the chamber. In
this regard, it is
preferred that the difference in diameter, for example, in the context of
Figure 1, between the
inner chamber portion 44 and the outer chamber portion 48 is selected to be
not greater than
a difference required to accommodate for expected set and/or shrinkage.
Minimizing this
difference in diameter can be advantageous at least in reducing the extent to
which the
transitional chamber portion 46 may be required and providing for smooth
sliding of the
14
CA 02545905 2006-05-05
piston when subjected to relatively constant axial forces. Preferably, this
difference in
diameter is not greater than an amount selected from the group consisting of:
5% of the
diameter of the inner chamber portion; 2% of the diameter of the inner chamber
portion; 1%
of the diameter of the inner chamber portion and 0.5% of the diameter of the
inner chamber
portion and 0.2% of the diameter of the inner chamber portion.
[0082] The inner and outer discs 33 and 34 illustrated in the preferred
embodiments
preferably have resiliently deformable edge portions with elastic properties
biasing the edge
portion radially outwardly into engagement with the chamber wall. Such
deformable edge
portion may be formed from plastic material which is subject to reduction of
its elastic
properties biasing the edge portion radially outwardly when the edge portion
is held in a set
position for a period of time or when the edge portion is held in the set
position for a period
of time at temperatures above 35 C or 40 C or 50 C or 60 C. In accordance with
preferred
embodiments of the present invention, the piston element is made from a
plastic material
preferably injection moulded as an unitary element from plastic material and,
thus, the
deformable edge portion is preferably formed from a plastic material.
[0083] In accordance with the present invention, the deformable edge portion
may be
formed from relatively inexpensive plastics including polyethylene, low
density polyethylene
and polypropylene so as to advantageously reduce the costs of materials.
[0084] Having regard to typical such plastics which may be used for
construction of the
piston, when the discs on the piston may have a diameter in the range of 5 to
40 mm, it is
preferred that the difference in diameter between the inner chamber portion
and the outer
chamber portion be in the range of about 0.25% and 2%, more preferably, about
0.5% to about
1% with the disc having an inherent unbiased diameter of about 0.5% to 4%
greater than the
diameter of the inner chamber portion, more preferably, about 1% to 2% greater
than the
diameter of the inner chamber portion. In the embodiment of Figure 1, each of
the inner disc
33 and outer disc 34 most preferably has an inherent diameter when unbiased or
compressed of
about 1.5% greater than the diameter of the inner chamber portion 44; and the
outer chamber
portion 48 preferably has a diameter of about one half the sum of the inherent
diameter of the
disc 34 and the diameter of the inner chamber portion 44. In one preferred
embodiment
CA 02545905 2006-05-05
utilizing a low density polyethylene plastic material, the diameter of the
inner chamber portion
44 is about 12.15 mm, the diameter of the outer chamber portion 46 is about
12.25 mm and the
inherent diameter of the outer disc 34 is about 12.33 mm.
[0085] Embodiments as illustrated in Figures 7, 8 and 10 have at least one
chamber portion
of a smaller diameter inward of a chamber portion of larger diameter. However,
preferably,
the piston-chamber forming member 16 is formed by injection moulding as a
unitary element.
Due to the inherent resiliency of the plastic of the piston-chamber forming
member 16 during
injection moulding, a centrally extending core may be provided with an
enlarged portion to
form the undercut, smaller diameter inward chamber portion. The relative
difference between
the diameter of the inner chamber portion and outer chamber portion is
preferably limited to be
no more than about 2%, more preferably, 1% or 0.5% to assist in permitting
manufacture with
such a removable core.
[0086] While the invention has been described with reference to the preferred
embodiments many variations and modifications will now occur to persons
skilled in the art.
For a definition of the invention reference is made to the following claims.
16
