Abstract:
A dual fluid cartridge which reduces fluid waste while minimally increasing back pressure is disclosed. One embodiment of the dual fluid cartridge disclosed includes a post having a groove formed therein which allows more fluid to be dispensed from the dual fluid cartridge while simultaneously keeping the increase in back pressure within ranges still suitable for handheld cartridge applications.

Description:
BACKGROUND  
       [0001]     Dual fluid cartridges are used to store and dispense two fluids which must be kept separate until the time of use and then, at the time of dispensing, need to be mixed together very quickly in a precise pre-set ratio to ensure that the proper chemical reaction takes place. If the cartridge does not dispense the two fluids properly in the required pre-set ratio, the final fluid mixture may be greatly affected and may not function or adhere as required. Examples of such fluids are those that are used to create thermoset adhesives (i.e., a resin and a hardener).  
         [0002]     Dual fluid cartridges have been used in industry for the last twenty years and, over the years, differing types of dual fluid cartridges have been developed.  FIG. 1  depicts one relatively recently developed dual fluid cartridge that has been particularly effective. Such dual fluid cartridges can be filled relatively easily and can be used in readily available dispensers, such as caulking guns as is shown in  FIG. 2 . An example of such a dual fluid cartridge that is presently in use is depicted in  FIG. 3 . Another example is described and depicted in U.S. Pat. No. 5,310,091, entitled “Dual Product Dispenser”, (“&#39;091 patent”) which is commonly owned with this application and is incorporated by reference herein. However, with designs such as the one depicted in  FIG. 3 , there tends to be a significant amount of residual fluid waste left in the cartridge once the product has been completely dispensed due to the open volume between the cartridge post, such as the post  82  in  FIG. 3 , and the inner diameter of the cartridge delivery tube, such as the delivery tube  54  in  FIG. 3 , through which such post  82  moves. Such residual waste increases cost due to the fluid left in the cartridge and also has the effect of potentially raising serious environmental and disposal issues, depending on the type of fluids being discharged. Much of this waste could be reduced or eliminated if the diameter of the post was increased in relation to the inner diameter of the delivery tube or, vice versa, if the diameter of the inner delivery tube was decreased in relation to the diameter of the post, as depicted in the figures of the &#39;091 patent. However, because the post  82  completely fills the interior of the delivery tube  54  in such an approach, this type of approach has the very undesirable effect of increasing the back pressure generated as the fluids are pushed through the cartridge. This is a very significant drawback, considering that such cartridges are typically used in hand held applications and a cartridge design that generates any significant amount of back pressure causes the cartridge to be very difficult, if not impossible, to use.  
         [0003]     Accordingly, there is a need for a dual fluid cartridge that is effective in reducing the residual waste left in a cartridge after all the product has been dispensed, while at the same time not generating an unacceptable level of back pressure.  
       SUMMARY  
       [0004]     In accordance with one aspect of the present invention, a fluid cartridge for storing and dispensing two fluids including an outer cartridge wall defining an outlet and an open end opposite the outlet. A delivery tube is disposed within the outer cartridge wall and defines an outlet that is co-located with the outlet defined by the outer cartridge wall. A first piston is disposed between the outer cartridge wall and the delivery tube forming a first fluid chamber. A second piston is disposed within the outer cartridge wall between the first piston and the open end of the outer cartridge wall. A post connected to and extending from the second piston is in alignment with the delivery tube. The post has a groove formed in it along the length of the post. A fixed wall is disposed between the first piston and the second piston. The fixed wall and the second piston define a second fluid chamber, and means is present for transmitting force from the second piston to the first piston. According to other aspects of the present invention, the groove formed in the post may be kidney-shaped, square, round, formed in a channel shape or some other shape. The outer diameter of the post may also be approximately equal to the inner diameter of the of the delivery tube. In yet another embodiment of the present invention, passageways may be formed in the second fluid chamber for evacuating air trapped in the second chamber during the filling process.  
         [0005]     According to another aspect of the present invention, a fluid cartridge for storing and dispensing two fluids including an outer cartridge wall defining an outlet and an open end opposite the outlet. A delivery tube is disposed within the outer cartridge wall and defines an outlet that is co-located with the outlet defined by the outer cartridge wall. A first piston is disposed between the outer cartridge wall and the delivery tube forming a first fluid chamber. A second piston is disposed within the outer cartridge wall between the first piston and the open end of the outer cartridge wall. A post connected to and extending from the second piston is in alignment with the delivery tube. The post has a groove formed in it along the length of the post. A fixed wall is disposed between the first piston and the second piston. The fixed wall and the second piston define a second fluid chamber, and a transmission structure is present for transmitting force from the second piston to the first piston. According to other aspects of the present invention, the groove formed in the post may be kidney-shaped, square, round, formed in a channel shape or some other shape. The outer diameter of the post may also be approximately equal to the inner diameter of the of the delivery tube. In yet another embodiment of the present invention, a step surface may be formed on the transmission structure and at least one passageway may be formed in the step surface for evacuating air trapped in the second chamber during the filling process. According to another aspect, at least one passageway may be formed in the second piston, and this passageway may be in communication with the passageway formed in the step surface formed on the transmission structure.  
         [0006]     According to another aspect of the present invention, a fluid cartridge for storing and dispensing two fluids including an outer cartridge wall defining an outlet and an open end opposite the outlet. A delivery tube is disposed within the outer cartridge wall and defines an outlet that is co-located with the outlet defined by the outer cartridge wall. A first piston is disposed between the outer cartridge wall and the delivery tube forming a first fluid chamber. A second piston is disposed within the outer cartridge wall between the first piston and the open end of the outer cartridge wall. A post connected to and extending from the second piston is in alignment with the delivery tube. The post has at least one supply window formed therein near the second piston, and the post also has a passage formed throughout the center of the post that is in communication with the at least one supply window at one end and in communication with the delivery tube outlet at the other end. A fixed wall is disposed between the first piston and the second piston. The fixed wall and the second piston define a second fluid chamber, and a transmission structure is present for transmitting force from the second piston to the first piston.  
         [0007]     According to yet another aspect of the present invention, a fluid cartridge for storing and dispensing two fluids to form a product including an outer cartridge wall defining an outlet and an open end opposite the outlet. A delivery tube having an inner diameter is disposed within the outer cartridge wall and defines an outlet that is co-located with the outlet defined by the outer cartridge wall. A first piston is disposed between the outer cartridge wall and the delivery tube forming a first fluid chamber to store and dispense a first fluid. A second piston is disposed within the outer cartridge wall between the first piston and the open end of the outer cartridge wall. A fixed wall is disposed between the first piston and the second piston. The fixed wall and the second piston define a second fluid chamber to store and dispense a second fluid, and a transmission structure is present for transmitting force from the second piston to the first piston, wherein the inner diameter of the delivery tube is of a diameter to allow no more than five milliliters of the second fluid to remain in the second chamber when the product is entirely dispensed. The delivery tube may be formed of an inner surface and an outer surface, wherein the inner surface defines the inner diameter. The delivery tube may also have a sidewall with thickness, wherein the sidewall thickness defines the inner diameter. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0008]     These and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims and accompanying drawings where:  
         [0009]      FIG. 1  depicts a dual fluid cartridge useable in readily available dispensers, such as caulking guns;  
         [0010]      FIG. 2  depicts a dual fluid cartridge with a nozzle attached and with the dual fluid cartridge disposed in a dispenser, with a portion of the dual fluid cartridge and the dispenser broken away;  
         [0011]      FIG. 3  is a longitudinal sectional view of a prior art dual fluid cartridge with the contents of the dual fluid cartridge dispensed, which is depicted along with a portion of an attached nozzle and static mixer in section and the plunger and a portion of the rod of the dispenser depicted in  FIG. 2 ;  
         [0012]      FIG. 3A  is cross-sectional view taken along line  3 A- 3 A of  FIG. 3 ;  
         [0013]      FIG. 4  is a longitudinal sectional view of a filled embodiment of a dual fluid cartridge of the present invention, which is depicted along with a portion of an attached nozzle and static mixer in section and the plunger and a portion of the rod of the dispenser depicted in  FIG. 2 ;  
         [0014]      FIG. 5  is a longitudinal sectional view of the dual fluid cartridge depicted in  FIG. 4  in an intermediate dispensing position;  
         [0015]      FIG. 5A  is cross-sectional view taken along line  5 A- 5 A of  FIG. 5 ;  
         [0016]      FIG. 6  is a longitudinal sectional view of the dual fluid cartridge depicted in  FIG. 4  with the contents of the dual fluid cartridge dispensed;  
         [0017]      FIGS. 7A and 7B  are differing views of a rear piston assembly of the prior art dual fluid cartridge depicted in  FIG. 3  showing air passageways;  
         [0018]      FIGS. 8A and 8B  are differing views of a rear piston assembly of an embodiment of the dual fluid cartridge of the present invention depicted in  FIG. 6  showing air passageways;  
         [0019]      FIG. 8C  is a detail view of the area  8 C of  FIG. 8B ; and  
         [0020]      FIGS. 9-11  are longitudinal sectional views of other embodiments of a dual fluid cartridge of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0021]     Referring to  FIG. 1 , a dual fluid cartridge  20  is depicted. The dual fluid cartridge  20  has an outlet  71  which includes an externally threaded outer outlet wall  21 . As explained in detail below, the dual fluid cartridge  20  stores two fluids separately from one another until a user is ready to mix the fluids together using a dispenser. In  FIG. 2 , the dual fluid cartridge  20  is shown disposed in a dispenser  22 , which in  FIG. 2  is depicted as a standard manual caulking gun. However, it should be understood that the dual fluid cartridge  20  may be used with any form or type of dispenser  22  and is not limited to just manual caulking guns. For example, other dispensers  22  may have different shapes or sizes and may be actuated pneumatically, hydraulically, by battery power or by some form of mechanical drive, such as an actuating screw. The dispenser  22  shown in  FIG. 2  has a plunger  24  which is connected to a rod  26  that extends through a handle  28  of the dispenser  22 . The rod  26  has ratchet teeth  30  formed on the rear portion of the rod. The dispenser  22  also has a trigger  32  which, when actuated, engages the ratchet teeth  30 , advancing the plunger  24  forward. The continued actuation of the trigger  32  causes the plunger  24  to eventually engage and apply pressure against the rear portion of the dual fluid cartridge  20 , which, as explained in more detail below, causes the two fluids stored in the cartridge  20  to be dispensed and mixed together.  
         [0022]     The dual fluid cartridge  20  in  FIG. 2  also has a nozzle  34  attached to the end of the cartridge  20 . In this embodiment, the nozzle  34  is attached to the dual fluid cartridge  20  by screwing a retaining nut  36  on to the threaded outer outlet wall  21  of the cartridge  20 . Typically, the nozzle  34  contains a static mixer  31  within it. The static mixer  31  mixes the two fluids stored in the dual fluid cartridge  20  together as the dispenser  22  dispenses them from the cartridge  20 .  
         [0023]     Referring to  FIG. 4 , a longitudinal sectional view of an embodiment of a dual fluid cartridge  20  of the present invention is depicted. This embodiment of the dual fluid cartridge  20  defines a first fluid chamber  40  and a second fluid chamber  42  for storing and dispensing a first fluid  48  and second fluid  50  respectively. In this embodiment of the dual fluid cartridge  20 , the cartridge  20 , in addition, includes an outer cartridge wall  52 , a delivery tube  54 , a first piston  58  having an o-ring  59 , a compression wall  60  having an o-ring  61  and a rear piston assembly  62 . The outer cartridge wall  52  in this embodiment is a cylindrical wall defining a hollow interior  64 . In a preferred embodiment, the outer cartridge wall  52  of the cartridge  20  is an industry standard design that is designed to fit into a standardized piece of dispensing equipment, such as a caulking gun as described above. The outer cartridge wall  52 , in this embodiment, defines an opening  66  at one end and at the other end defines two discharge openings  72 ,  74  and includes the external threaded outer outlet wall  21 .  
         [0024]     The delivery tube  54  of the cartridge  20  is disposed within the hollow interior  64  of the outer cartridge wall  52 . In this embodiment, the delivery tube  54  snaps into locking engagement with the outer cartridge wall  52 , such that the delivery tube  54  is in fluid communication with the discharge opening  74 . It is foreseen that the outer cartridge wall  52  and the delivery tube  54  may also be formed integral with one another. The compression wall  60  in this embodiment is formed integral with the delivery tube  54  which fixes the compression wall  60  in place.  
         [0025]     The first piston  58  of the dual fluid cartridge  20  is disposed within the cartridge  20  between the exterior of the delivery tube  54  and the interior of the outer cartridge wall  52 . In this embodiment, the first piston  58  surrounds the exterior of the delivery tube  54 . The first piston  58 , in conjunction with the exterior of the delivery tube  54  and the interior of the outer cartridge wall  52 , defines the first fluid chamber  40 .  
         [0026]     In this embodiment, the rear piston assembly  62  and the compression wall  60  define the second fluid chamber  42 . The delivery tube  54  provides fluid communication between the second fluid chamber  42  and the discharge opening  74 . The rear piston assembly  62  includes a rear piston surface  80 , a post  82  with a groove  83  formed therein and a transmission structure  84 . In this embodiment, the groove  83  formed along the length of the post  82  is formed in the shape of a kidney, as depicted in  FIG. 5A . A kidney-shaped groove  83  provides a low friction factor; however, it should be understood that the groove  83  is not required to be kidney-shaped. The groove  83  may be formed in any shape appropriate (e.g. square, round or channel). Further, it should be understood that the differing portions  80 ,  82 ,  84  of the rear piston assembly  62  are all integral with one another in this embodiment, but this is not necessary. One of ordinary skill in the art would understand that it is possible that each portion of the rear piston assembly  62  could be its own separate structure. In this embodiment, the post  82  extends from the rear piston surface  80  of the rear piston assembly  62  and aligns with the interior of the delivery tube  54  for subsequent insertion and movement within the delivery tube  54  during dispensing of the fluids from the cartridge  20 . In this embodiment, the transmission structure  84  extends from the rear piston surface  80  of the rear piston assembly  62 , passes snugly between the compression wall  60  and the interior of the outer cartridge wall  52  forming a seal and is in engagement with the first piston  58 .  
         [0027]     To dispense the fluids from the dual fluid cartridge  20 , the rear piston assembly  62  is pressed forward towards the cartridge outlet  71 . In the embodiment described, this is done by actuation of the caulking gun plunger  24 . As the plunger  24  is actuated forward, in the direction indicated by the arrow in  FIG. 5 , the plunger  24  presses against the rear piston assembly  62 . Simultaneously, the rear piston surface  80  pushes against the fluid  50  stored in chamber  42 , the post  82  enters into and moves within the interior of the delivery tube  54  and the transmission structure  84  presses against the first piston  58 . The fluid  50  being pushed by the rear piston surface  80  in the chamber  42  gets compressed by the fixed compression wall  60 , pushing the fluid  50  through the delivery tube  54  and through the discharge opening  74 , where the fluid  50  is discharged from the dual fluid cartridge  20 . At the same time, the pressing of the transmission structure  84  against the first piston  58  causes the fluid  48  in the first fluid chamber  40  to be pressed into the discharge opening  72 , through which the fluid  48  is discharged from the dual fluid cartridge  20 . As the fluids  48 ,  50  are discharged from the dual fluid cartridge through the discharge openings  72 ,  74 , they are mixed together by the static mixer  31  in the nozzle  34 .  
         [0028]     This fluid discharge and mixing process continues as long as the caulking gun plunger  24  is being actuated and as long as fluids are still left to be dispensed from the dual fluid cartridge  20 .  FIG. 5  depicts the dual fluid cartridge  20  with a portion of the fluids  48 ,  50  dispensed from the dual fluid cartridge  20 .  FIG. 6  depicts the dual fluid cartridge  20  with the fluid contents of the chambers  40 ,  42  of the cartridge  20  fully dispensed. In this embodiment of the invention, only 5 milliliters of waste remain of the second fluid  50  when the entire product has been dispensed from the dual fluid cartridge  20 . This is significantly improved over the 11 milliliters of waste of the second fluid  50  that was left in prior art dual fluid cartridge designs, such as the dual fluid cartridge design depicted in  FIGS. 3 and 3 A.  
         [0029]     Referring to  FIGS. 3 and 3 A, the prior art dual fluid cartridge depicted has significant waste due to the amount of space left between the outer diameter of the post  82  and the inner diameter of the delivery tube  54 . When product is fully discharged from the prior art dual fluid cartridge, most of the waste remaining in the cartridge  20  is in the space between the post  82  and the inner diameter of the delivery tube  54 . As noted above, in the prior art embodiment depicted, there is 11 milliliters of waste. Increasing the diameter of the post  82  to take up the space between the post  82  and the inner diameter of the delivery tube  54  to reduce the amount of waste is impractical with the prior art design because as the diameter of the post  82  is increased, the amount of backpressure generated increases significantly as well. In contrast, the kidney-shaped groove embodiment of the present invention depicted in  FIG. 4  reduces residual waste while minimally increasing back pressure because the groove  83  allows the post  82  to move more freely through the fluid being discharged. The kidney-shaped groove embodiment of the present invention requires around 15 pounds of force, while only leaving only 5 milliliters of waste. A cartridge of the prior art design of  FIG. 3  which, by increasing the diameter of the post  82 , achieves comparable residual waste of only 5 milliliters requires a significantly higher force of around 23 pounds—8 pounds more than the kidney-shaped embodiment of the present invention.  
         [0030]     The arrangement of the dual fluid cartridge  20  in  FIG. 6  is also how the dual fluid cartridge  20  looks prior to being filled. To fill the dual fluid cartridge  20 , the chambers  40 ,  42  are filled with the appropriate fluids  48 ,  50  through their respective discharge openings  72 ,  74 . The filling process occurs in the reverse manner of the dispensing process described above. During the filling process, air can get trapped in the second chamber  42  between the incoming fluid  50  and the rear piston surface  80 . Air trapped in the chamber  42  can cause a number of problems in the use of the dual fluid cartridge  20 . Most significantly, air trapped in chamber  42  can negatively impact the ability to control the volumetric dispensing ratio of the fluids  48 ,  50  in the chambers  40 ,  42 . Referring to  FIGS. 3 and 7 A-B, to alleviate this problem, the prior art design of  FIG. 3  has a small portion of the sidewall of the transmission structure  84  thickened to form a step  90  adjacent the rear piston surface  80 . The rear piston surface  80  of the rear piston assembly  62  has air passageways  94  formed therein which are in communication with air passageways  96  that are formed in the step  90 . The passageways  94 ,  96  act to allow air to vent past the o-ring  61  of the compression wall  60  into an open chamber  43  when the rear piston assembly  62  is the position indicated in  FIG. 3 . From the open chamber  43 , the air ultimately flows through a series of slots  98  formed along the bottom of the rear piston assembly  62  and out to atmosphere through a separation between the transmission structure  84  and the interior of the outer cartridge wall  52 . As the rear piston assembly  62  is pushed rearward as fluid  50  fills the chamber  42 , the step  90  moves off of the o-ring  61  and the chamber  42  is sealed from the open chamber  43 . Such a prior venting system is described in commonly owned international patent application No. PCT/US03/17997 and U.S. patent application Ser. No. 10/755,796, which are incorporated by reference herein.  
         [0031]     Referring to  FIGS. 6 and 8 A-C, the kidney-shaped groove  83  in the post  82  of the embodiment of the present invention depicted improves the manner in which trapped air is vented from the chamber  42 . In the kidney-shaped groove embodiment of the present invention, air enters the kidney-shaped groove  83  from the second chamber  42  and is pushed into one of three passageways  94 , as opposed one of six passageways  96  present in the prior design as shown in FIGS.  7 A-B. As a result, the groove  83 , along with the reduction in passageways  94 , provides a more directed flow path for venting air trapped in the chamber  42 . This results in a more efficient and effective evacuation of air from the chamber  42 .  
         [0032]     Another advantage of the kidney-shaped groove embodiment of the present invention is that the grooved post  82  of the present invention does not move radially during the filling process as the post  82  of the prior art design is apt to do. Radial movement of the post  82  during the process filling generates inconsistent air flow in the chamber  42  which interferes with effective evacuation of air trapped in the chamber  42 . The post  82  of the prior art design is able to move radially, as indicated by the arrows in  FIG. 3 , due to the space that exists between the post  82  and the inner diameter of the delivery tube  54 . The grooved post  82  of the present invention does not have this problem because the grooved post  82  of the present invention fills the entire inner diameter of the delivery tube  54 .  
         [0033]     It should be understood that many differing embodiments of the dual fluid cartridge  20  of the present invention may be designed and employed. Referring to FIGS.  9 - 11 , several other embodiments of the dual fluid cartridge  20  of the present invention are depicted. Referring to  FIGS. 9 and 10 , in these embodiments, the post  82  is removed and the inner diameter of the delivery tube  54  is reduced to reduce the amount of residual waste left after product is dispensed. In the embodiment of  FIG. 9 , an inner delivery tube  54 A is disposed interior to and formed integral with the existing delivery tube  54 . In the embodiment of  FIG. 10 , the wall of the delivery tube  54  is thickened to reduce the inner diameter of the delivery tube  54 . Referring to  FIG. 11 , this embodiment includes a post  82 , but instead of the post  82  having a groove  83  formed therein, a passage  85  is formed through the center of the post  82 . In this embodiment, then fluid being dispensed from the chamber  42  is pushed through supply windows  87  formed in the top of the post  82  and down through the center passage  85  of the post  82  and into the discharge opening  74 .  
         [0034]     While the invention has been discussed in terms of certain embodiments, it should be appreciated that the invention is not so limited. The embodiments are explained herein by way of example, and there are numerous modifications, variations and other embodiments that may be employed that would still be within the scope of the present invention.