The invention relates to a liquid dispenser, in particular for colorants or tinting pastes for paint . Such dispensers typically comprise a piston pump and a valve allowing the pump to withdraw an amount of colorant from a container, and to dispense it , e . g . , into a receptacle such as a paint can .

Colorants must be dosed and metered very accurately in order to produce a paint matching a desired colour . To this end, some dispensers have pumps capable of dispensing larger volumes as well as smaller volumes .

An example of such a dispenser is disclosed in US 2009/ 0236367 . This system uses a small si zed piston nested in a larger piston pump . The construction is relatively complex and expensive to make . Biasing springs cause unwanted side ef fects .

EP3249222A1 discloses a colorant dispenser with a pump and a cylindrical valve core with a plurality of channels . The channels cause a high flow resistance and make it di f ficult for trapped air to escape from the liquid . The volume between the piston and the dosing outlet is large , so dosing accuracy is low . The dosing process requires a large number of steps to be taken .

It is an obj ect of the present invention to provide a dispenser of a simple and robust design suitable for dispensing larger amounts at high speed and smaller amounts with high accuracy .

The obj ect of the invention is achieved with a dispenser for dispensing a liquid, in particular a colorant for paint , comprising a piston pump and a valve . The piston pump comprises a cylinder and a main piston reciprocatingly fitted inside the cylinder . The valve comprises a valve housing and a valve core within the valve housing, the valve core being rotatable about an axis of rotation (R) . The valve core comprises a main channel , in particular for high speed dispensing of larger amounts , and a secondary dispense channel with a smallest diameter which smaller than the smallest diameter of the main channel , in particular for accurately dosing smaller amounts of liquid . The secondary dispense channel comprises an axial channel section communicating with the piston pump . A secondary reciprocating member fits reciprocatingly inside a pump space comprising the axial channel section in the valve core .

Preferably, the secondary reciprocating member fits reciprocatingly inside the axial channel section itsel f . However, in some cases the pump space may further comprise an intermediate tubular section with one end connecting to the axial channel section, e . g . , a bent section facilitating an upright position of the pump, the secondary reciprocating member fitting reciprocatingly in a free second end of the intermediate tubular section .

The valve core can for example be a ball , a truncated ball , cylinder or ( truncated) cone . The valve core is leak tight disposed within the valve housing and rotatable about the axis of rotation into a number of positions , such as :

- a suction position aligning the main channel with the canister to enable withdrawal of liquid from the canister by means of the piston pump ;

- a fast dispense position aligning the main channel with a dispense opening of the valve housing;

- an accurate dispense position aligning the secondary dispense channel with the dispense opening, and optionally

- a closing position closing of f the main channel as well as the secondary dispense channel .

The secondary dispense channel can have a further channel section e . g . a radial channel section, extending between the axial channel section and an outlet at the outer surface of the valve core . The radial channel section can for example define the smallest diameter of the secondary dispense channel .

The main channel has a relatively large diameter for fast dispensing and/or for dispensing relatively large amounts of the liquid and/or for returning colorant from the pump to the canister .

The valve also comprises a canister connection opening, preferably in the housing of the valve , for connecting a canister to the dispenser .

The secondary reciprocating member can for example be arranged to move with the main piston during at least a part of a pump stroke , so as to be operated by the main piston . To this end, the secondary reciprocating member can be mounted on, or form an integral part of the main piston of the piston pump, preferably on the end of the main piston facing the valve .

Alternatively, the secondary reciprocating member can be separate from the main piston and be biased towards the main piston, e . g . by means of a resilient element , such as a spring . In that case , the secondary reciprocating member can have one end with a flange or broadened head section slidingly locked within the axial channel section, and an opposite end arranged to be moved into the axial channel section by the main piston . To lock the flange or head section of the secondary reciprocating member, the axial channel can be provided with one or more stops , e . g . shoulders or a protruding rim

The secondary reciprocating member can be a closed or solid piston . Alternatively, the secondary reciprocating member may be a hollow member, e . g . , comprising a channel in the direction of the reciprocal movement along the full length of the secondary reciprocating member, e . g . , the secondary reciprocating member being a hollow cylinder or sleeve .

In a speci fic embodiment , the axial channel section, the secondary reciprocating member and the main piston are coaxially aligned with the axis of rotation of the valve , e . g . , with the secondary reciprocating member fitting reciprocatingly inside the axial channel section . In that case , the secondary reciprocating member can be moved within the axial channel section at di f ferent positions of the valve core . This is particularly useful , i f the secondary reciprocating member is an extension of the piston head of the main piston .

Since the secondary reciprocating member communicates directly with the axial channel section in the valve core , the channels are short . This results in lower flow resistance and more accurate dosing since the piston and the secondary reciprocating member are close to the dispense opening . Hence , dispensing accuracy can be very high using very small minimum dispenses .

The dispenser of the present invention enables a relatively straightforward and/or robust construction and/or provides a high accuracy, preferably an accuracy of less than about 0 . 0015 ml , which is particularly signi ficant in sample tinting . Also , as the axial channel in the valve core and the further reciprocating member are inherently close to the dispense opening, flow resistance and the ef fects of compressibility of the liquid on dispensing accuracy are reduced .

Optionally, the valve core comprises a return channel establishing fluid communication between the pump and the canister during a dispensing cycle via the secondary dispense channel . In the accurate dispense position of the valve core , the outlet of the secondary dispense channel is aligned with the dispense opening of the valve and the outlet of the return channel is aligned with the canister connection opening of the valve housing . While only small amounts can be dispensed via the secondary dispense channel , excess liquid can be returned to the canister via the return channel . In a more speci fic embodiment , the return channel extends at least in part parallel or at an inclination to the axial channel section of the secondary dispense channel .

The volume of the secondary dispense channel can for example be such that a single stroke of the further piston is suf ficient to dispense the required amount , which for small tints typically is in a range from 0 . 007 to 3 ml . To this end, the secondary dispense channel can have a stroke volume , e . g . , in a range from 0 . 1 to 3 ml . The radial channel section of the secondary dispense channel can for example have a length in a range from 1 to 10 mm and/or a diameter in a range from 0 . 2 to 2 mm .

The lead edge of the further piston can for example be chamfered .

In a speci fic embodiment , the piston pump may for example be arranged in an upward position . For example , the pump space may further comprises a tubular section connecting to the axial channel section in the valve core , the tubular section comprising an upward section slidingly receiving the reciprocating member, which may for example be a piston or a hollow cylinder .

The dispenser of the present invention can for example be used in an apparatus for dispensing a plurality of liquids , in particular colorants for paint , comprising a linear table or a turntable rotatable around a vertical axis of rotation and a plurality of dispensers as described above , attached to and distributed along the edge of the table . The piston pumps can extend hori zontally and, in case of a turntable , radially relative to the vertical axis of rotation .

The invention is further explained with reference to the accompanying drawings showing exemplary embodiments .

Figure 1 : shows an apparatus for mixing and dispensing paint products comprising a number of dispensers ; Figure 2A: shows a dispenser of the apparatus of

Figure 1 in longitudinal cross section;

Figure 2B : shows the dispenser of Figure 2A in cross section along line A-A;

Figure 3A: shows a dispenser of the apparatus of

Figure 1 in cross section in a suction position;

Figure 3B : shows the dispenser of Figure 3A in cross section along line A-A;

Figure 4A: shows a dispenser of the apparatus of

Figure 1 in cross section in a fast dispense position;

Figure 4B : shows the dispenser of Figure 3A in cross section along line A-A;

Figure 5 : shows a dispenser of the apparatus of

Figure 1 in cross section in an accurate dispense position;

Figure 6 : shows a second exemplary embodiment of a dispenser in cross section;

Figure 7 : shows a third exemplary embodiment of a dispenser in cross section;

Figure 8 : shows a fourth exemplary embodiment of a dispenser in cross section;

Figure 9A: shows a fourth exemplary embodiment of a dispenser in cross section during a suction stroke ;

Figure 9B : shows the embodiment of Figure 9A at the start of a small amount dispensing step ;

Figure 9C : shows the embodiment of Figure 9A and

9B during a small amount dispensing step ;

Figure 9D : shows the embodiment of Figures 9A-C during a large amount dispensing step .

Figure 1 shows an exemplary embodiment of a paint mixing and dispensing apparatus 1 . The apparatus 1 comprises a turntable 2 carrying a circular array of canisters 3 . Each canister 3 can be filled with a colorant or tinting paste of a given colour . The apparatus 1 comprises a platform 5 for supporting a paint can . When a paint can is placed on the platform 5 the turntable 2 can be rotated to position one of the canisters 3 holding a tinting paste of a selected colour above the paint can . The apparatus 1 may for example be provided with a user interface 6 allowing input of a desired paint colour by a user . A controller with a data processing unit (not shown) determines a paint formulation with the required amounts of the required tinting pastes providing the desired colour . Each canister 3 holding one of the tinting pastes used in the formulation is subsequently positioned above the paint can on the platform 5 and the required amount of the tinting paste is dispensed into the paint can in accordance with the formulation . These steps are repeated for all of the required colorants of the determined paint formulation . The apparatus 1 typically comprises a sensor 7 to detect whether or not a paint can is present on the platform 5 .

Each canister 3 has a bottom with a tubular passage 8 connected to a dispenser 10 , e . g . , as shown in Figures 2A-5 . The dispenser 10 comprises a valve 11 and a piston pump 12 operatively connected to the valve 11 .

The valve 11 comprises a valve housing 13 with an interior space holding a valve core 14 with a narrow fit allowing rotation of the valve core 14 about an essentially hori zontal axis of rotation R . The valve housing 13 comprises four openings opening into the interior space : a canister connection opening 15 at the top side of the valve housing 13 for connecting to the tubular passage 8 of the canister 3 , a dispense opening 16 opposite to the canister connection opening 15 , a driving axle opening 17 for a driving axle 18 rotating the valve core 14 , and a pump opening 19 opposite to the driving axle opening 17 , connecting to the piston pump 12 . A first seal 16A engages the valve core around the dispense opening 16 . A second seal 15A engages the valve core 14 around a passage opening of a canister channel 15B leading to the canister connection opening 15 .

In the shown embodiment , the valve core 14 is essentially ball shaped, with truncated vertical side faces 20A, 20B perpendicular to the axis of rotation R . A first one of the truncated surfaces 20A is connected to the driving axle 18 extending through the sealed axle opening 17 of the valve housing 13 . In response to signals from the controller, the driving axle 18 drives the valve core 14 to rotate to a selected position .

The piston pump 12 comprises a cylinder 25 and a main piston 26 slidable within the cylinder 25 between a dispensing position and a suction position . The cylinder 25 has one end leak tight connected to the pump opening 19 of the valve housing 13 , and an opposite end comprising a closure 27 with a central opening 28 . The main piston 26 comprises a piston rod 29 with a first end provided with a piston head 30 facing the pump opening 19 of the valve housing 13 , and an opposite second end extending through the central opening 28 in the closure 27 ( see Figure 3A) . This second end is provided with grip 30 operatively connected to an actuator (not shown) moving the piston 12 between the dispensing position and the suction position in response to control signals from the controller . The piston head 30 seals against the inner wall of the cylinder 25 while forming a sliding fit , allowing reciprocating movement .

The pump 12 comprises a secondary piston 40 extending from the piston head 30 toward the valve core 14 . The secondary piston 40 is coaxially aligned with the piston rod 29 , which is in turn aligned with the axis of rotation R .

In the shown embodiment of Figures 2A - 5 , the pump 12 is hori zontal , so entrapped air can escape more easily via the canister . The valve core 14 has a main channel 42 for withdrawing liquid content from the canister 3 in the suction position of the valve core 14 ( shown in Figures 4A and 4B ) , and for dispensing of pump cylinder content when the valve core 14 is in the fast dispensing position ( shown in Figures 4A and 4B ) . The main channel 42 has an axial main channel section 43 and a radial main channel section 44 . The axial main channel section 43 runs between the pump opening 16 in the valve housing 13 and the radial main channel section 44 . The axial main channel section 43 is parallel to the rotational axis R and connects to the space of the pump opening 19 at positions not aligned with the secondary piston 40 . The radial main channel section 44 runs in radial direction from the axial main channel section 43 to the spherical outer surface of the valve core 14 .

The valve core 14 further comprises a secondary dispense channel 46 , better shown in Figure 2A and 2B . The secondary dispense channel 46 has an axial channel section 47 dimensioned and aligned to receive the secondary piston 40 , and a radial channel section 48 with a diameter substantially smaller than the diameter of the main channel 42 .

In addition to the two dispense channels 42 , 46 , the valve core 14 also comprises a return channel 49 . The return channel 49 has essentially the same geometry as the main channel 42 , with an axial return channel section 50 and a radial return channel section 51 . The axial return channel section 50 runs between the pump opening 19 in the valve housing 13 and the radial return channel section 51 . The axial return channel section 50 is parallel to the axis of rotation R and connects to the space of the pump opening 19 at positions not aligned with the secondary piston 40 . The radial return channel section 51 runs in radial direction from outer end of the axial return channel section 50 to the spherical outer surface of the valve core 14 . The radial return channel section 51 and the radial channel section 48 of the secondary dispense channel 46 extend radially at opposite sides of the axis of rotation R, as for example is shown in Figure 2A and 2B . Consequently, when valve core 14 is in the accurate dispensing position, the radial channel section 48 of the secondary dispense channel 46 is aligned with the dispense opening 16 of the valve housing 13 while the return channel 49 is aligned with the canister connection opening 15 . Only small amounts can be dispensed via the secondary dispense channel 46 . During dispensing via the secondary dispense channel 46 , the return channel 49 serves to return excess colorant into the canister 3 .

Figures 3A and 3B show the dispenser 10 during a suction stroke , when retracting the main piston 26 withdraws colorant from the canister 3 and gradually fills the cylinder 25 of the piston pump 12 . During this step, the valve core 14 is rotated into a position closing of f the dispense opening 16 of the valve housing 13 . The secondary dispense channel 46 and the return channel 49 are closed of f by the inner wall of the valve housing 13 , while the main channel 42 fluidly connects the canister 3 with the interior space of the cylinder 25 of the piston pump 12 . Moving the main piston 26 away from the valve 11 results in suction withdrawing colorant from the canister 3 via the main channel 42 into the cylinder 25 of the piston pump 12 .

The dispenser 10 of the present invention can be used for fast dispensing larger amounts of colorant and for accurate dispensing smaller amounts . Figures 4A and 4B show the dispenser 10 in a position for fast dispensing . In this position, the main channel 42 connects the dispense opening 16 of the valve housing 13 and the pump opening 18 to enable a dispense flow from the cylinder 25 of the piston pump 12 via the main channel 42 to the dispense opening 16 while the main piston 26 is gradually moved towards the valve housing 13 . The main piston 26 stops in response to the controller when a suf ficient amount of colorant is dispensed . In this fast dispensing position, the secondary dispense channel 46 and the return channel 49 are closed of f by the valve 11 .

To prepare for an accurate dispensing cycle via the secondary dispense channel 46 , the valve core 14 is rotated into a position for accurate dispensing as shown in Figure 5 . In this position, the secondary dispense channel 46 is aligned with the dispense opening 16 of the valve housing 13 , and the return channel 49 is aligned with the canister connection opening 15 . The secondary piston 40 is then moved into a position where it j ust closes of f the axial channel section 47 of the secondary dispense channel 46 . The free outer end 52 of the secondary piston 40 is chamfered to facilitate easier positioning of the secondary piston 40 relative to the axial channel section 47 . The secondary piston 40 is then moved deeper into the axial channel section 47 of the secondary dispense channel 46 so as to force colorant through the dispense opening 16 ( see Figure 2A) . Liquid present in the space at the pump opening 19 outside the axial channel section 47 is moved to the canister 3 via the return channel 49 . The small diameter of the radial section 48 of the secondary dispense channel 46 enables very accurate dosing and a signi ficantly improved match between the resulting paint colour and the selected colour .

The secondary piston 40 is moved j ointly with the main piston 26 . To this end, the secondary piston 40 is fixed to the outer end of the main piston 26 , as shown in the embodiment of Figures 2A-5 , or forms an integral part of it . Figure 6 shows an alternative embodiment , having a secondary reciprocating member 40 ' which is aligned with the main piston 26 ' , but forms a separate part . The axial channel section 47 ' of the secondary dispense channel 46 ' has an access opening restricted by an inwardly proj ecting circumferential rim 53 . The secondary reciprocating member 40 ' has a main body 54 extending through the restricted access opening and one end with a broadened head or flange 55 locked within the axial channel section 47 ' by the circumferential rim 53 . A spring element 56 biases the secondary piston 40 ' towards the main piston 26 ' . This simpli fies the step of positioning the secondary piston j ust before the accurate dispensing step, as shown in Figure 4A. During the accurate dispensing step, the main piston 26 ' pushes the secondary reciprocating member 40 ' into the axial channel section 47 ' to force colorant out via the dispense opening 16 of the valve housing 13 .

Figure 7 shows a further embodiment , which is similar to the embodiment of Figures 2A-5 , except that the piston pump 12" is arranged in a vertical position, and the pump opening 18" is on the top side of the valve housing 13 , next to the canister 3 . A bent pipe section 60 comprises a hori zontal part 61 connected to the axial channel section 47 , and a vertical section 62 receiving the secondary piston 40" . The axial channel section 47 and the bent pipe section 60 form a small pump space 63 where liquid is forced into the radial channel section 48" while the secondary piston 40" moves downward through the vertical section 62 of the bent pipe section 60 .

Figure 8 shows a further embodiment , which is similar to the embodiment of Figure 6 , with the di f ference that the secondary reciprocating member is not a closed piston but a hollow cylindrical part 40 ' ’ with a central channel 64 extending in axial direction, coaxial with the axial channel section 47 ' . The central channel 64 connects the axial channel section 47 ' with the interior of the cylinder 25 . Due to this connection, the axial channel section 47 ' is easier filled with liquid to be dispensed during a suction stroke .

Figures 9A- 9D shows an embodiment , which is similar to the embodiment of Figure 7 , except that the secondary reciprocating member 40 ' ’ ’ is not a closed piston but a separate hollow cylindrical part with a central longitudinal channel 64 ' , like the secondary reciprocating member 26 ' ’ of the embodiment of Figure 8 . The piston pump 12 ' is arranged in a vertical position, and the pump opening is on the top side of the valve housing 13 ' , next to the canister 3 . A bent pipe section 60 ' comprises a hori zontal part 61 ' connected to the axial channel section 47 ' ' , and a vertical section 62 ' receiving the secondary reciprocating member 40 ' ’ ’ . The axial channel section 47 ' and the bent pipe section 60 ' form a small pump space 63 ' . A pump channel 66 connects the interior of the pump cylinder 25 and the main channel 42 in the valve core 14 . The pump channel 66 comprises a first pump channel section 67 enclosing the bent pipe section 60 and a second pump channel section 68 extending vertically and enclosing the vertical section 62 ' receiving the secondary reciprocating member 40 ' ’ .

Between the valve core 14 and the inner walls of the valve housing 13 is a gap 65 which is sealed at the dispense opening 16 by the first seal 16A and at the canister channel 15 by the second seal 15A. The gap 65 is in fluid communication with the first pump channel section 67 .

In Figure 9A, the main piston 25 is moved upward to withdraw liquid from the canister 3 via the main channel 42 . Simultaneously, the upward movement of the piston 25 creates a suction in the small pump space 63 ' generating a secondary flow of liquid from the first pump channel section 67 into the gap 65 between the valve core and the inner walls of the valve housing and subsequently via the radial secondary dispense channel 46 into the axial channel section 47 ' ' .

To dispense a small amount of liquid, the main piston 26 is first moved down to close of f the secondary reciprocating member 40 ' ' , while the valve core 14 is still in the same position ( see Figure 9B ) . Excess liquid flows back into the canister 3 via the main channel 42 and the canister channel 15 . Subsequently, the valve core 14 is rotated until the radial secondary dispense channel 47 is aligned with the dispense opening 16 ( see Figure 9C ) . By moving the piston 26 further down, liquid is dispensed from the small pump space 63 ' via the axial secondary dispense channel 47 . Liquid in the interior of the pump cylinder 25 outside the small pump space 63 ' is returned to the canister 3 via the main channel 42 .

Figure 9D shows how a larger amount of liquid is dispensed . The valve core 14 is rotated into a position aligning the radial main channel section 44 of the main channel 42 with the dispense opening 16 . The piston 26 is then moved down . Liquid is moved from the interior of the pump cylinder 25 and the pump channel 66 via the radial main channel section 44 to the dispense opening 16 . Part of the liquid in the small pump space 63 ' is moved via the secondary dispense channel 46 into the gap 65 and subsequently into the first pump channel section 67 , where it j oins the main flow via the main channel 42 to the dispense opening 16 .