Abstract:
A dispensing device comprising a container with product outlets, a screw that operates a piston within the container and a torsion spring that biases the screw. The torsion spring includes a hoop having one or more inner tabs. The hoop is frictionally engaged with an interior surface of the container. A boss is fixed to the screw and a flexible arm interconnects the hoop and boss. The torsion spring also includes a spoke that is angularly offset from the flexible arm. Application of a rotational force to the screw urges the piston toward the container outlets, causing the flexible arm to yield, allowing the boss to rotate relative to the hoop until the spoke engages an inner tab. Further rotation releases the hoop from frictional engagement with the container. Once the rotational force is removed, the hoop re-engages the container interior surface and the flexible arm regains its original shape, causing the hub and screw to counter-rotate, which simultaneously moves the piston away from the fluid outlets.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention pertains generally to viscous product dispensing systems. More particularly, the invention pertains to product dispensers that eliminate residual product leakage from the dispenser (commonly known as the “drool effect”) after the actual amount of product that is desired by the user has been dispensed. Additionally, the invention relieves residual pressure within the dispenser which helps reduce product degradation caused by ingredient separation. 
   2. Description of Related Art 
   Systems for dispensing viscous flowable materials such as soft-solid deodorant/antiperspirant products, are well-known in the prior art. Typically, the product is extruded out of a container via a plurality of openings that are located at the top of the container. To do this, a chamber in the interior of a dispenser is loaded with the desired product. The product is supported by an underlying structure, such as a platform, piston or elevator. The user manipulates a thumbwheel or a slider which moves the underlying structure toward the top of the container. This action causes the product to be expelled out through the top openings. 
   One of the inherent problems with the prior art devices is that moving the underlying structure toward the top of the container, decreases the volume of the interior chamber. This pressurizes the product, which causes an additional small amount of product to be expelled through the openings, even after the user has already dispensed the desired amount of product and the user has stopped moving the underlying structure toward the top of the container. The result is a slight oozing, or weeping, of product out of the container top openings (known as the “drool” effect). The drool effect is undesirable in the liquid dispenser manufacturing industry, and it is desired to produce a viscous product dispenser that eliminates this effect. Moreover, the elimination of residual pressure on the product, will inhibit product degradation caused by ingredient separation. This most commonly occurs in fluid and fluid solid multiple component mixtures. 
   U.S. Pat. No. 5,540,361, which issued to Fattori for an invention entitled “Cream Deodorant Dispenser,” discloses an elevator cup 11 with a spring element 12 which extends into a first portion and into a second portion of the elevator cup. Differential flexing between the first portion and the second portion during dispensing of the product results in a retracting force that slightly withdraws the elevator cup when dispensing is stopped. 
   A problem with the Fattori device is that the first portion, second portion and spring element are a continuous structure. This produces an unpredictable diaphragm-like action resulting in erratic movement of the elevator cup. 
   U.S. Pat. No. 5,879,096, which issued to Franta et al. for an invention entitled “Gel/Cream Applicator,” discloses an intermittently rotatable spindle with threads having discrete valleys on their upper surfaces. Pins from an elevator follow the upper surfaces during rotation of the spindle. The elevator slightly retracts to prevent product drool, whenever the pins move into the valleys. 
   The problem with the Franta et al. device is the upper surface valleys provide the same amount of retraction no matter what amount the fluid is pressurized. Therefore, the device does not always compensate for variations in fluid pressure, and unwanted leakage can occur. 
   In light of the above, it is an object of the present invention to provide a dispenser for viscous products that eliminates residual pressure on the product. It is another object of the present invention to provide a dispenser wherein product leakage is prevented when the user stops extruding product from the container. Another object of the present invention to provide a dispenser wherein the user easily manipulates the dispenser to distribute product. Yet another object of the present invention is to provide a dispenser with as few moving parts as possible for increased reliability of operation. Another object of the present invention is to provide a dispenser that is easy to assemble and manufacture in a cost-effective manner. 
   SUMMARY OF THE INVENTION 
   A device for dispensing a viscous product in accordance with the present invention basically comprises a container having a top opening and interior surfaces which define a chamber. A screw and piston assembly extend into the chamber and a torsion spring is attached to the screw. The torsion spring is also frictionally engaged with the interior surfaces to effect a counter rotational force to the screw. 
   The screw is attached for rotation to the bottom of the container so that it extends into the chamber. A piston is threaded onto the screw, and is frictionally engaged with the interior surface of the chamber. Rotation of the screw urges the piston towards or away from the top opening, according to the direction of rotation of the screw. 
   The torsion spring includes an outer hoop that is frictionally engaged with the interior surface of the container and an inner concentric boss that is fixed to the screw. At least one flexible arm interconnects the boss with the hoop. The flexible arm includes a boss tab that extends radially outward from the boss and merges into an elongated flex portion. The flex portion is connected to the terminal end of an abutment means that projects radially inward from the hoop. 
   To rotationally bias the torsion spring by a predetermined amount, at least one spoke is fixed to the boss so that it extends radially outward a distance sufficient to overlap the abutment means. The spoke is offset radially from adjacent flexible arms by a predetermined angular amount, preferably in a range of thirty to seventy degrees. In an alternative embodiment of the invention, the abutment means may comprise one or more bias tabs. These tabs are unconnected to the flex portion and extend inwardly from selected points of the hoop a distance sufficient to engage a spoke. In this alternative, each spoke will be angularly offset from an adjacent bias tab. 
   When the screw is rotated to dispense product, the piston will move towards the container top openings. The boss will simultaneously rotate with the screw. Since the hoop is frictionally engaged with the chamber interior surface, it remains stationary while the boss rotates with respect to the hoop. This action causes the leg members to twist out of their normal U-shape and develop a counter-rotational bias. As the screw, boss and attached spoke continue to rotate, the spoke will come into contact with the abutment means such as a hoop tab or a bias tab. Once the spoke becomes engaged with a tab, the screw will have been rotated by the predetermined angular amount. Thereafter, further rotation of the screw will overcome the hoop&#39;s frictional engagement with the interior surface of the container, and the entire torsion spring will rotate as an integral unit within the container. 
   When the desired amount of product has been dispensed and rotation of the screw is discontinued, the hoop will frictionally re-engage the interior surface of the container. Upon re-engagement, the twisted leg members will counter-rotate back to their original at-rest position. This causes the hub and screw to likewise counter-rotate in a direction opposite from the original direction of rotation by the predetermined angular amount. The counter-rotation translates into a reverse downward movement of the piston away from the container top openings. This movement neutralizes any pressure build-up in the chamber and thereby prevents unwanted product degradation and subsequent leakage out of the container top openings. 
   To further inhibit undesired product flow out of the container top openings, the openings may have a beveled cross-section. In this variation, each opening will increase in diameter from an outlet diameter to a larger inlet diameter. The larger inlet will provide an enlarged space for accumulating product from any increased pressure that may be present after operation of the screw and piston. Additionally, the inward taper helps to accelerate withdrawal of the product as the piston retracts. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features of this invention will be best understood from the accompanying drawings and description, in which similar characters refer to similar parts, and in which: 
       FIG. 1  is an exploded isometric view of the product dispenser of the present invention. 
       FIG. 2  is a cross-sectional view of a frontal aspect of the dispenser of  FIG. 1 . 
       FIG. 3  is a cross-sectional view of a side aspect of the dispenser of  FIG. 1 . 
       FIG. 4  is an isometric view of the torsion spring for the dispenser of  FIG. 1 . 
       FIG. 5  is a top plan view of the torsion spring and container of  FIG. 1  before operation of the dispenser. 
       FIG. 6  is the same view as  FIG. 5  after initial operation of the dispenser but while the outer hoop portion of the torsion spring is still frictionally engaged with the interior surface of the container. 
       FIG. 7  is the same view as  FIG. 6  after the hoop portion of the torsion spring has disengaged from the container interior surface and is rotating within the container. 
       FIG. 8  is a top plan view of the cap of  FIG. 1 . 
       FIG. 9  is an enlarged cross-sectional view taken along line  9  in  FIG. 8 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the Figures, the product dispenser is shown and is generally designated by reference character  10 . The dispenser comprises a container  12  with a continuous sidewall  14  that extends upwardly from a bottom  16  and terminates at a top opening  18 . Bottom  16  further includes a bottom recess  20  and a bottom opening  22  that is formed in the bottom recess  20 , as shown in  FIGS. 1–3 . Preferably, the container should have an oval shaped profile when viewed in top plan, as best seen in  FIGS. 5–7 . It will be appreciated, however, that square, rectangular or other polygonal profiles (as viewed in top plan) are also envisioned. However, the container should have an interior surface  24  which allows for frictional engagement with other components of the dispenser, as described more fully below. 
   The dispenser of the present invention includes an integrated elevator assembly comprising a screw  30  that extends longitudinally within the container and along the geometrical center axis of the container. The screw is the threaded upper portion of a post  32 . The post projects upwardly from a hub  33 . The hub is centered co-extensively above thumbwheel  34 . 
   The elevator assembly is positioned within bottom recess  20  so that annular lip  25  of hub  33  will engage spaced-apart upwardly and inwardly extending deflectable retention flanges  23 . The flanges define bottom opening  22 . 
   In the above position, screw  30  will extend into the container interior, while the thumbwheel  34  is nested within the bottom recess  20 . Opposing sides of bottom wall  17  are provided with respective cut-outs  21 . The cut-outs provide convenient access to the thumbwheel so that the thumbwheel can be rotated by a user&#39;s thumb and fingers in a manner known in the art. 
   To allow for placement of a viscous product (not shown) therein, a piston  26  is positioned within the container. The piston includes a threaded opening  27  and a skirt  28  that extends around its periphery. The piston has an outer circumference that closely conforms to the geometric profile of the container sidewall when viewed in top plan. Therefore, when the piston is placed within the container and threaded onto screw  30 , the skirt will engage interior surfaces  24  and prevent downward leakage of product into the lower regions of the dispenser. 
   As shown in  FIGS. 1–3 , the dispenser of the present invention also includes a cap  36  that is attached to the inset outer surface  41  of the container sidewall  14 . Once attached, container cap  36 , sidewall  14  and piston  26  cooperate to establish a chamber  38  within the container. The chamber provides for placement and storage of a viscous dispensable product therein, as mentioned above and depicted in phantom by volume  39  in  FIG. 1 . The product may comprise any type, or combination of, flowable material such as a semi-solid stick, paste, dough, putty, a powder or particulate matter, fluid, gel, cream or liquid. 
   The container cap includes a plurality of outlet apertures  40  to provide a path of product communication out of chamber  38 . The outlets function to deliver the product to an end user. A lid  42  can be removably placed over the cap when the dispenser is not in use. 
   The dispenser of the present invention also includes a torsion spring  46  that is fixed to post  32  between piston  26  and hub  33  of the elevator assembly. The torsion spring biases the rotation of the screw in a manner more fully described below, when the operator manipulates the thumbwheel. 
   The torsion spring  46  comprises a plurality of flexible arms  48  that interconnect a hoop  50  with a boss  52 . The boss is oriented concentric to the hoop  50 . The hoop has a diameter that is sufficient to frictionally engage at least opposite portions of container interior surface  24 . The boss includes a center opening  60 . To fix the torsion spring within the container, the screw is inserted into the center opening, until post  32  engages the center opening. In this position, the post may be fixed to the boss by adhesion, fusion-bonding or mechanical means known in the art. 
   In an alternative embodiment of the present invention, the inner surface of center opening  60  and the corresponding outer surface of post  32  may be serrated or polygonal in cross-section. This provides a mechanical connection for ensuring that rotation of spring boss  52  will be in unison with screw  30 . However, outer surface  66  of spring hoop  50  and the corresponding inner surface of the container  24  may be serrated to achieve an audible and tactile click upon rotation of the actuator thumbwheel. This construction may also augment frictional engagement of the spring hoop to the container wall until a calculated degree of rotation is achieved. 
   Referring now primarily to  FIGS. 4–7 , the aforementioned torsion spring  46  is shown in greater detail. Each flexible arm  48  includes a boss tab  54  and a flex portion  56 . For each flexible arm, the boss tab is fixed to boss  52  and extends radially outward until it merges into flex portion  56 . The flex portion has an elongated inverted U-shape having an outer end that merges into an abutment means shown as hoop tab  58 . 
   The hoop tab is fixed to the hoop and extends radially inward to an inner terminal end  65 , where it merges with the flex portion outer end. The boss tab and hoop tab are oriented so that they are about co-planar, while the flex portion extends about perpendicularly from the plane defined by boss tab  54  and hoop tab  58 , as best seen in  FIG. 4 . 
   The torsion spring of the present invention also includes a plurality of spokes  62 , with each spoke corresponding to a respective flexible arm  48 . The spokes are fixed to boss  52  and extend radially and angularly outward to a free end  69  that is beyond terminal end  65  of the hoop tab, for reasons to be described. The spokes are substantially co-planar with the above-mentioned plane defined by the hoop, boss tabs and hoop tabs. Further, each spoke is angularly offset from the corresponding hoop tab for its respective flexible arm by an angle α. The optimum amount of angular offset is determined by the screw thread lead and the desired amount of piston retraction. For a 0.18 inch thread lead and 0.020 inch piston retraction, a 40-degree angular offset is required, as depicted in  FIG. 5 . This feature is application-dependent and customized according to the product being dispensed. Most commonly, the amount of angular offset is within a range of 20 to 70 degrees (a=30–70°). 
   In an alternative embodiment of the invention, bias tabs  64  can be included with the torsion spring of the present invention. An exemplary bias tab is shown in phantom in  FIG. 3 . With this configuration, the bias tabs are fixed to the hoop and extend radially inwardly therefrom. For this embodiment, the spokes will be fixed to the boss so that they extend radially outward past the terminal end of the bias tabs. Further, the spokes will be angularly offset from the bias tabs by angle α, instead of being angularly offset from the hoop tab portions of the flexible arms as also discussed above. In this way, the bias tabs will function as a spoke abutment means instead of the hoop tabs. 
   It is to be appreciated that although four spokes and four flexible arms are used in the preferred embodiment, as little as one spoke and corresponding flexible arm structure could be used to accomplish the counter-biasing effect of the torsion spring. It is important that the overall biasing force created by the flexible arm(s) be sufficient to counter-rotate the screw. However, the overall force must be less than the force of frictional engagement between interior surfaces  24  and hoop  50 . 
   To further minimize unwanted product flow from the chamber  38 , a variation of the invention is shown in  FIG. 9 . In this version, the outlet apertures  40  are beveled. More specifically, the apertures have an increasing diameter from a minimum diameter d 1  at outer cap surface  68  to a maximum diameter d 2  at inner surface  70 . This configuration provides an enlarged space for dissipating residual product pressure and a restriction to flow from chamber  38  that occurs during operation of the dispenser. 
   In the preferred embodiment, the screw, container, thumbwheel, cap and lid are preferably injection molded plastic, such as a high density polyethylene (HDPE), a polypropylene, or a resin material having similar physical properties. The torsion spring is preferably made from an acetal plastic or similar material with properties that allow for flexure of the torsion spring during operation of the dispenser. 
   Operation 
   To dispense a viscous product from the above-described device, the user exerts a first rotational force by manually rotating thumbwheel  34  clockwise. This will rotate screw  30  and provide a torque in the direction indicated by arrow T 2  (See  FIGS. 5–7 ). Rotational motion of the screw within a threaded opening  27  of piston  26  becomes translated into axial movement of the piston, which is otherwise constrained from rotational movement. The piston thereby moves toward the container opening, as indicated by arrow A 1  in  FIG. 2 . 
   As the piston moves toward the container top opening  18 , the volume of chamber  38  is decreased. The decrease in chamber volume causes the viscous product therein (which is substantially incompressible) to flow from the chamber through outlet apertures  40  and be delivered for use by the operator. 
   During the above events, the flexible arms  48  yield and flex to allow rotation of the boss and spokes, while the hoop remains stationary by its frictional engagement with interior surface  24 . Rotation continues until the spokes reach the full extent of angle α. At this position, each spoke contacts an inwardly extending respective hoop tab  58  (or bias tab  64  for the alternative embodiment). The overlapping spoke-to-hoop tab engagement is best seen in  FIG. 7 . 
   Once the spoke(s) abut against the hoop tab(s), continued application of sufficient rotational force via thumbwheel  34  will overcome the frictional engagement of circumferential surface  66  of the hoop with interior surface  24  of the container. Simultaneously, the piston continues to move upwardly and expel fluid through outlet apertures  40 . 
   When the desired amount of fluid has been delivered, the user will cease rotating thumbwheel  34 . This action will result in a re-engagement of the outer circumferential surface  66  of hoop  50  with interior surfaces  24 . With the hoop in a stationary mode, the flex portions  56  of flexible arms  48  exert a second rotational force and become unflexed. The arms return to their relaxed state as shown in  FIG. 5 . As the flexible arms return to their relaxed state, boss  52  and the attached screw counter-rotate by angle α, in the direction indicated by arrow T 1 . This reverse rotation will translate into a short downward movement of piston  26  in the direction indicated by arrow A 2 . As the piston moves away from the container top opening, the volume of chamber  38  is slightly increased. The increased volume relieves any residual pressure on the viscous product in the chamber. Dissipation of residual pressure thereby eliminates the cause of unwanted product flow after rotation of the thumbwheel has stopped. Such dissipation also eliminates degradation of product as a result of ingredient separation. 
   While the product dispenser, as herein shown and disclosed in detail, is fully capable of obtaining the objects and providing the advantages above stated, it is to be understood that the presently preferred embodiments are merely illustrative of the invention. As such, no limitations are intended other than as defined in the appended claims.