Patent Publication Number: US-6220483-B1

Title: Dispensing assembly for dispensing two liquid components

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation application of PCT/NL97/00645 filed Nov. 25, 1997. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a dispensing assembly for dispensing two liquid components, comprising an outer piston pump concentric with an inner piston pump for the components to be dispensed, with a common control part, which piston pumps are provided with resetting means and each comprise a piston chamber with a piston and an inlet and an outlet, which outlet can be placed in communication with an outflow opening, with the interposition of a non-return valve under pre-tension, and which inlet can be placed in communication with a source for component to be dispensed, with the interposition of a non-return valve, while the pistons of the piston pumps comprise a channel for conveying the liquid component in question to an outflow opening. 
     BACKGROUND OF THE INVENTION 
     Such dispensing assemblies with so-called double, concentric pumps are generally known in the prior art and are used for dispensing many kinds of liquid components from containers. Such liquid components are not particularly limited and vary from aqueous liquid components to paste-like materials. 
     Examples of components to be dispensed are, for example, adhesives with a hardener, paints with a hardener, cosmetic products with reactive components, detergents with reactive components etc. 
     The ratio between the quantities of the components to be dispensed can be set as desired by a suitable choice of the dimensions of the parts in question. 
     The outflow openings for the components in question can be in the form of individual outflow openings, but they can also be in the form of a common outflow opening, with the interposition of a mixing chamber section or otherwise. 
     All known dispensing assemblies have the major disadvantage that partial vacuum possibly occurring outside the outflow opening causes an inadequate seal to be obtained between the concentric inner and outer piston. This can occur, for example, in an aircraft. In that case, material may be sucked out of the outer piston chamber, through between the pistons, and consequently out of the container for the particular component which may be connected to the outlet of the outer piston chamber, and out of the outflow opening. This is, of course, undesirable. Constituents are in fact often dispensed with such dispensing assemblies in practice, which are sticky after drying or otherwise. When there is accidental outflow of such constituents, the subsequent functioning of the dispensing assembly may be seriously impeded, if not rendered impossible. 
     The control part used in the case of such dispensing assemblies is generally a push-button on the dispensing assembly, which push-button interacts with both pumps. It is undesirable for said button to be soiled with material for dispensing, since a user operates the dispensing assembly by pressing with a finger on the push-button. 
     Moreover, the entire assembly is often shut off by a sealing cap or sealing cover, which can also be undesirably soiled by the abovementioned escaping component. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a solution to the abovementioned problems, and to that end the invention is characterized in that the inner piston pump comprises an inner piston which has a small free stroke relative to the other parts of the assembly, in that a stationary stroke limiting part with a stop is present in the outer piston chamber of the outer piston pump, which stroke limiting part under friction can interact with a stop on the inner piston, in order to limit the movement distance thereof and permit the movement thereof only under friction, and in that the outer piston and the inner piston comprise carrier means which can interact in a sealing manner with each other and form an active non-return valve for the outlet of the outer piston chamber, all the above in such a way that when there is a resetting movement the outer piston can carry along the inner piston and seal the connection between the outer piston chamber and an outflow opening. 
     Owing to the small free stroke of the inner piston and the presence of the carrier means, an excellent seal is obtained between the outer piston and the inner piston, which ensures that no material can be sucked through between the pistons if a partial vacuum occurs. In other words, the non-return valve in the outlet of the outer piston chamber is formed by the carrier means mentioned earlier. Unlike many non-return valves used in the prior art, said non-return valve is an active non-return valve, and not a passive one. A partial vacuum outside the dispensing assembly, i.e. outside the outflow opening, also promotes the sealing action of said non-return valve. All the above will be explained in greater detail further on, in the description of the drawings. 
     In a special embodiment of the dispensing assembly according to the invention, the stationary stroke limiting part defines an annular intermediate piston chamber which by way of one or more narrow passages is in communication with the outer piston chamber, and the stop on the inner piston forms an intermediate piston in the intermediate piston chamber. 
     When the dispensing assembly is being used, the intermediate piston chamber will be filled through the narrow openings with component from the outer piston chamber, so that on movement of the inner piston a damping of the movement thereof will be obtained, which has a very advantageous influence on the operation of the entire dispensing assembly. This in fact means that when the assembly makes a dispensing stroke the active non-return valve formed by the carrier means is opened in a reliable manner. 
     In particular, the limiting part is formed by a bush fixed on the inner piston chamber and having on one end an inward directed collar which can interact with the intermediate piston, in which case by grooves and/or ribs on either the inside wall of the bush or the outside wall of the inner piston chamber, or both, one or more passages are formed, so that the intermediate piston chamber is in communication with the outer piston chamber. This advantageous embodiment will be explained in greater detail further on, in the description of the drawings. 
     In the case of many dispensing assemblies, in particular dispensing assemblies for components with relatively low viscosity, there is a so-called start-up problem, in other words, when the assembly is being used for the first time it takes some time before material can actually be dispensed, and the user has to press the dispensing assembly several times, sometimes even more than 25 times, before the components can be dispensed. 
     In order to solve this problem, according to the invention, at least the inner piston chamber is filled with a start-up agent prior to a first use of a dispensing assembly. 
     A start-up agent is also known as a primer and serves to ensure that the assembly can operate and dispense material already at the first service stroke. An example of a suitable primer is glycerol. The viscosity of the primer is preferably slightly higher than that of the material to be pumped. Of course, the primer ultimately to be used will depend on the material to be dispensed. The primer is preferably inert relative to the material to be dispensed. 
     The carrier means on the inner piston and the outer piston are advantageously designed in the form of sealing collars on said pistons, which collars are bevelled in the same direction and fit into each other. Using suitably bevelled sealing collars on the pistons ensures that when there is a resetting movement of the outer piston, a very good seal supported by external partial vacuum is obtained between the two pistons. 
     The friction action between the stroke limiting part and the inner piston can be carried out in many different ways. For instance, the mutual dimensions of the parts in question can be selected in such a way that friction is obtained. However, it is advantageous if the outside wall of the inner piston is provided locally with friction ribs which extend in the intended direction of movement of the inner piston, but are situated at a distance from the stop thereof, which distance is equal to or greater than the axial distance of the stop from the stroke limiting part. All the above will be explained in greater detail in the description of the figures. The material of the inner piston is generally a relatively soft plastic material, and the stroke limiting part is often made of a harder, more rigid plastic. By not providing the ribs over the entire outside wall of the inner piston, it is ensured that relaxation (creep) of the material of the inner piston does not cause the necessary friction to decrease, or even disappear, after some time, prior to use for the first time. Instead of or in addition to the above, friction ribs can also be present on the inside wall of the stroke limiting part, which friction ribs extend in the intended direction of movement of the inner piston, but are situated at a distance from the stop thereof, which distance is equal to or greater than the axial thickness of the intermediate piston near the inside wall of the stroke limiting part, all the above being for the same reasons as those in the case of the friction ribs mentioned earlier. 
     The inner piston has a small free stroke, and said free stroke is in particular such that it is just sufficient to be able to release the carrier means on the inner piston and the outer piston and open the communication between the outer piston chamber and a dispensing opening. 
     The non-return valve in the outlet of the inner piston chamber is advantageously designed in the form of a non-return valve with a ball pre-tensioned by a spring in a seat. 
     In addition to the above valve, or instead thereof, the inner piston, which relative to the other parts of the assembly has a small free stroke at the outflow end, comprises a valve which is preferably pre-tensioned in the outflow direction, which valve can be opened by interaction with the control part. It is particularly preferable for said outflow end of the inner piston to comprise an inward directed collar which forms a seat for a ball present in the piston, which ball is held in the seat by a spring, and the control part comprises a bar-shaped part which during the dispensing of material can press the ball off the seat against the action of the spring. All the above will be explained in greater detail in the description of the figures. The spring used in the case of this non-return valve is preferably a spring with a relatively low spring force, which is just sufficient to hold the ball in the seat. It must be ensured that at the start of dispensing, i.e. at the moment at which the control part of the dispensing assembly is operated, said non-return valve is opened first. It is particularly advantageous for the abovementioned spring also to serve as a pre-tensioning means for the ball of the non-return valve in the outlet of the inner piston chamber, in other words, the spring is a dual-action spring for providing pre-tension on two non-return valves in the outlet of the inner piston chamber. 
     The invention also relates to an aerosol comprising two compartments for components and a dispensing assembly, characterized in that the dispensing assembly is a dispensing assembly according to the invention. 
     The aerosol preferably comprises a main container which is in communication with the inlet of one piston chamber, and an auxiliary container which is accommodated in the main container and is in communication with the inlet of the other piston chamber. 
    
    
     The invention will be explained in greater detail below with reference to the appended drawing: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a diagrammatic cross-section of a dispensing assembly according to the invention; 
     FIG. 2 shows an enlargement of a part A from FIG. 1; 
     FIG. 3 shows a cross-section of a modified embodiment of a dispensing assembly according to FIG. 1; and 
     FIG. 4 shows a modified embodiment of the dispensing assembly according to FIG.  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 1 an embodiment of a dispensing assembly is indicated diagrammatically by reference number  1 , which dispensing assembly can be fixed on a suitable container (not shown) by means of a fixing collar  2  comprising an internal screw thread  3 . 
     Said dispensing assembly  1  comprises two concentric piston pumps, an outer piston pump  4  and an inner piston pump  20 . The outer piston pump  4  will be discussed first of all. Said outer piston pump  4  comprises an outer piston chamber  5  and an outer piston  6 . A spring  7  is present as the resetting means. Said piston chamber  5  can be placed in communication with an outflow channel  8  and by way of a channel  9  with an outflow opening  10 . The outer piston  6 , which is a hollow piston, also comprises a bevelled, inward directed collar  11 . 
     The outer piston chamber  5  comprises an inlet  12  with a non-return valve  13 , which non-return valve comprises a ball  17  accommodated between a seat  14 , a flange  15  and ribs  16 . 
     The inner piston pump  20  comprises an inner piston chamber  21  and a hollow inner piston  22 . The inner piston chamber  21  comprises a non-return valve  23  in an inlet  24  for said chamber  21 , which non-return valve  23  comprises a ball  28  disposed between lugs  25  on ribs  26  and a seat  27 . 
     A non-return valve  29  is also present in the hollow piston  22 , which non-return valve comprises a ball  30  accommodated between a seat  31  and a spring  33 . Recesses are present between lugs  32 , for an improved throughflow. By way of the non-return valve  29 , the inner piston chamber  21  can be placed in communication with an outflow channel  35  which by way of a channel  36  is in communication with the outflow opening  10 . 
     The inner piston  22  also comprises on the outside a bevelled collar  51  with a stop  52  which can interact with the bevelled, inward directed collar  11  on the outer piston  6 . 
     The inner piston  22  comprises piston sections  40  and  41  combined to form a unit, and has a small free stroke relative to the other parts of the assembly, including the section  42 . Said piston section  41  comprises a stop  43  which by interaction with a stop  44  on the control part  50  (a push-button) limits the movement of the piston  22 . The section  41  is accommodated so that it glides, as it were telescopically, in the section  42  of the control part  50 . For this purpose, the section  41  comprises circumferential protuberances  47 , which provide for the seal of the two parts relative to each other. 
     The dispensing assembly  1  can be operated with the control part  50 , for example by pressing with a finger thereon. 
     The dispensing assembly also comprises a stroke limiting part  55 , which will be described further on with reference to FIG. 2, in which an enlarged detail of the encircled part A is shown. 
     As is clear from FIG. 2, the stroke limiting part  55  comprises a cylindrical bush  56  with a flange-shaped base  15 , which rests on the bottom of the piston chamber  5 , is provided locally with passages  58 , and also serves to limit the movement of the ball  17 . Said cylindrical bush  56  comprises on the top side an inward directed collar  59 , which can interact with a stop  60  on the inner piston  22 . The piston chamber  21  comprises a wall  61  with an outside  62 , which outside is kept at a slight distance from the inside  63  of the cylindrical part  56  of the stroke limiting part  55  by ribs  64  present on said wall  63 . 
     Reference number  70  indicates an intermediate piston chamber which is in communication with the piston chamber  5  by way of the channels  71  thus formed. At the position of the intermediate piston chamber  70 , additional ribs  72 , which serve to increase the friction between the stop  60  and the stroke limiting part  50  during movement of the inner piston  22 , are present. 
     The stop  60  therefore serves as an intermediate piston for the intermediate piston chamber  70 . 
     Friction ribs  57 , which can interact with the stop  59  of the stroke limiting part  55 , are preferably present on the outside wall of the section  40 , instead of the ribs  72 , or possibly in addition thereto. 
     The stroke limiting part  55  in practice will be made of a more rigid, harder plastic than the inner piston  22 , and therefore the stop  60 . At rest, the stop  60  is preferably not in contact with the friction ribs  72 , in order to ensure that the friction is not removed by relaxation of the plastic of the stop  60 . 
     The operation of the dispensing assembly  1  according to the invention will be explained in greater detail below. 
     As illustrated in FIGS. 1 and 2, the dispensing assembly  1  is in an initial position (rest position). 
     When being used, the dispensing assembly will be fixed on a container by means of the fixing collar  2 , which container can comprise, for example, a main container which is connected to the inlet  12 , and an auxiliary container which is preferably accommodated in the main container and is in communication with the inlet  24  for the inner piston chamber  21 . 
     When the push-button  50  is pressed, for example by means of a finger, in the first instance the outer piston  6  is moved downwards and the seal between the bevelled collar  11  on the outer piston  4  and the bevelled collar  51  on the inner piston  22  is released, and material can flow out of the piston chamber  5  by way of the annular channel  8  to the outflow opening  10 . The inner piston  22  moves with the section  41  into the section  42 , which is integral with the push-button  50 . This relative movement of the inner piston  22  is supported by the friction between the ribs  57  and the stop  59 , and the friction between the stop  60  and the ribs  72 . This continues until the stop  44  touches the stop  43 , at which moment the inner piston is also moved downwards and material can also move out of the piston chamber  21  by way of the channel  35  to the outflow opening  10 . This free stroke is preferably 0.2-0.4 mm. During this dispensing, material is conveyed out of the inner piston chamber by way of the channel  36  into the channel  9  of the material from the outer piston chamber  5 , with the result that mixing occurs before a mixture is dispensed. It will be clear that two separate outflow openings or a differently designed mixing opening can also be used. A non-return valve or the like is preferably present between the channel  35  and the channel  9 , said non-return valve serving to prevent material from the auxiliary container from being in communication with the environment in channel  35 . In practice, the auxiliary container in fact often contains the so-called reactive component. 
     The non-return valve  29  will be opened by the pretension of the spring  33  only at a certain pressure in the piston chamber  21 , and the non-return valve, which is formed by the two collars  11  and  51 , is opened by the relative movement of the inner and outer piston respectively, which is promoted at the first stroke by friction between the stop  60  and the ribs  62  around the collar  59  and the ribs  57 , but during use is taken over by the component sucked up into the piston chamber  70  from the piston chamber  5 . In other words, the friction of the friction ribs is taken over by the damping action of the piston chamber  70 . 
     When the push-button  50  is released after dispensing of material, the spring  7  will cause the assembly to move back to the initial position shown in the figures. At that moment the non-return valves  28  and  14  will be opened and material will be sucked out of the containers in question and into the piston chambers  5 ,  21  by way of the inlets  12  and  24 . When the inner piston  22  moves back, the intermediate piston chamber  70  will be filled with material from the outer piston chamber  5  by way of channels  71  and the openings  58 , but also by material passing through between the intermediate piston  60  and the ribs  64  and  72 . For the next working stroke, the downward movement of the inner piston  22  will therefore be damped by the material which is present in the intermediate piston chamber  70  and is forced back by way of the narrow channels  71  to the piston chamber  5  and between the ribs  64  and  72 , to the top side of the stop  60 . The intermediate piston chamber  70  with the piston or stop  60  therefore acts as a damper on the movement of the inner piston  22 . The effect of the friction ribs  72 ,  57  respectively and of the damping by the material present in the piston chamber  70  is particularly important during the return stroke. 
     In the return stroke the outer piston  6  will be moved upward first of all, and then, after the collar  11  has come into contact with the collar  51 , the inner piston is moved upward along with them. The non-return valve formed by said collars  11 ,  51  is an active non-return valve, and the sealing thereof will be promoted by external partial vacuum, in other words a partial vacuum by way of the opening  10 , the channel  9  and the channel  8 . 
     It is advantageous if, prior to a first working stroke, the dispensing assembly at least in the piston chamber  21  contains a so-called primer or start-up agent which considerably shortens the start-up operation, in other words, reduces the number of times that pumping has to be carried out before material is dispensed. Accommodating the primer in the inner piston chamber  21  means that the number of start-up strokes of the outer pump can be made equal to that of the inner piston chamber. By also accommodating primer in the outer piston chamber  5 , the number of start-up strokes of the outer pump can be reduced, but that means that in that case more primer must also be accommodated in the inner piston chamber  21 . 
     An example of such a primer is glycerol. It is also advantageous if the intermediate piston chamber  70  and also the piston chamber  5  are filled with primer. 
     The embodiment according to FIG. 3 largely corresponds to that according to FIG.  1 . However, here the channels  36  and  9  are not in communication with each other and both open out into the environment. The piston section  41  comprises at the top end an inward directed collar  65 , which serves as a seat for a ball  66  which is under pretension from a spring  67 , which rests on a shoulder  68  in the section  41 . The control button  50  comprises a pin  69  which has such measurements that when the control button  50  is pressed, said pin  69  forces the ball  66  off the seal, and the channel  35  can be placed in communication with the outflow channel  36 . 
     The spring  33  from FIG. 1 in this case is no longer necessary, since the inner piston chamber  21  now comprises an active non-return valve in the end of the channel  35 , in the form of a ball  66  which is under spring tension in the seat  65 . Partial vacuum in the environment will seal the last-mentioned valve even better, with the result that it becomes impossible to suck material out of the inner piston chamber  21  and possibly out of the container in communication therewith. Remaining material in the channel  35  cannot come into contact with the environment either. Such material is frequently an active component. 
     The spring  67  preferably has a relatively low spring force, for it must be ensured that at the start of dispensing, i.e. when the control button  50  is pressed, the ball  66  is first lifted off the seat  65  before other non-return valves are opened or the pistons of the pumps in question are moved in the piston chambers. 
     A particularly preferable embodiment of the spring  67  is shown in FIG. 4, in which embodiment the dispensing assembly for the rest is identical to that of FIG.  3 . The spring  67  in this case is a dual-action spring. It is made so long that it serves as a pre-tensioning means both for the ball  66  and for the ball  30 . An additional advantage is that the shoulder  68  can be omitted here, which in FIG. 3 in combination with the seat  65  constitutes an injection moulding problem for the section  41 , since there is in fact a problem with removal from the mould which is to be used for the purpose. This problem does not arise in the case of the embodiment according to FIG.  4 . 
     All parts of the dispensing assembly according to the present invention in practice can be made of suitable plastic. However, the balls and springs are generally made of metal.