Background The present invention relates to an improved dispenser for viscous materials such as cosmetic and medicament creams.

Dispensers are known where such viscous materials are dispensed by means of a piston that forms the base of a cylindrical container and that in use is advanced so that it exerts pressure upon fluid stored in a cylinder and so discharges the fluid through an aperture or nozzle. However, such dispensers suffer the disadvantage that they continue to dispense fluid for a short time after the user ceases to activate the device. This results in wastage of the material being dispensed; a particular problem when the material is an expensive cosmetic or medicament. An improvement to such a device is disclosed in GB 2472412 A (Levesley).

Summary of the Invention

One aim of the present invention is to provide an improved dispenser. Another aim is to provide a dispenser that is easier and cheaper to manufacture. A further aim is to provide a dispenser with a self adjusting thread member; and a dispenser that operates more smoothly.

In one aspect the invention comprises a dispenser for dispensing a viscous fluid (F) having a body member with an internal female thread the mean diameter of which progressively increases/decreases by a small percentage along the axis of the thread; a male engaging member having a male thread and/or a plurality of thread engaging members/protrusions mounted on a support frame; and first resilient means connected/attached to said support frame that bias said male thread or at least one thread engaging member/protrusion radially outwards; so as in use they continuously abut against said tapered female thread as the male engaging member progressively traverses said female thread. In another aspect the invention comprises a dispenser for dispensing a viscous fluid (F) stored directly within the body of the dispenser, or within a cartridge inserted within the dispenser in which the viscous fluid is forced through a dispensing aperture by advancing a piston member and where the piston is advanced by turning a first thread member that locates in the female thread of a body member wherein the mean diameter of the female thread progressively increases/decreases by a small percentage along the axis of the thread; where upon completion of such turning second resilient means are provided to partly reverse the direction in which the first thread member was turned; a male engaging member having a male thread and/or a plurality of thread engaging members/protrusions mounted on a support frame; and first resilient means connected/attached to said support frame that bias said male thread or at least one thread engaging member/protrusion radially outwards; so as in use they continuously abut against said tapered female thread as the male engaging member progressively traverses said female thread.

Preferably, said small percentage is in the range 0.1 to 2%. Alternatively, the side walls of the thread may inclined at an angle to the axis of the thread in the range 0.05 to 1° and more preferably 0.05 to 0.4°. Preferably, the first resilient means is a spring or a helical spring.

Preferably, said support frame is generally circular or C-Shaped in configuration. Preferably, the first resilient means is a spring member located within said circular or C-Shaped support frame. The frame member may comprise a plurality of radially projecting arms with thread engaging members/protrusions that engage said tapered female thread where one or more of said thread engaging members/protrusions is biased by said first resilient means. Preferably, the first thread member is a male thread on the outside of a piston member. Alternatively, it may be a separate member such that when it is turned it advances along the thread of a main body and pushes the piston member. Preferably, the second resilient means comprises a spring or other resilient member that is either stretched or compressed during turning of the first thread member and which upon completion of such turning by a user returns to its normal length and thereby exerts a force that provides said part reversal in the direction in which the first thread member was turned. The second resilient means may further comprise a male engaging member with a male thread that also locates in the female thread of the main body member and wherein a spring or another resilient member provides bias between the first thread member and the male engaging member. Preferably, in use the male engaging member is prevented from reverse turning under the influence of the second resilient member owing to the presence of a ratchet mechanism or because the male thread of the male engaging member is a sufficiently tight fit within the main body member. Preferably, the first thread member or piston has an abutment member with locating means and the male engaging member has a similar abutment member and locating means and wherein the ends of a spring engage said locating means. The first thread member may be turned by a knob directly or indirectly coupled thereto and the knob may comprise a lower portion of the dispenser. The lower portion of the dispenser may be coupled to the piston by means of a split vane attached to the lower portion of the dispenser. For example, the lower portion of the dispenser may be coupled to the piston by means of a member attached to the piston that is held within a member or members attached to the lower portion of the dispenser.

In another aspect the invention comprises a dispenser viscous fluid dispenser having a main body with: an internal female thread the mean diameter of which progressively increases/decreases by a small percentage along the axis of the thread; into which a piston assembly with a short thread engages and traverses; said piston assembly comprising a male engaging member having a short male thread and/or a plurality of thread engaging members/protrusions mounted on a support frame; and first resilient means connected/attached to said support frame that bias said male thread or at least one of said thread engaging members/protrusions radially outwards; so as in use they continuously abut against said tapered female thread (78) as the male engaging member (80) progressively traverses said female thread (78).

Brief Description of the Drawings

The invention is described by reference to the following diagrammatic drawings in which:

Figure 1 is a sectioned side view of a dispenser according to a first embodiment of the present invention and a fully charged disposable cartridge containing a cosmetic cream; Figure 2 corresponds to Figure 1 but shows the dispenser in a position where the disposable cartridge has been emptied and the lid has been removed;

Figure 3 shows an exploded perspective view of the upper external components of the dispenser of Figure 1 ;

Figures 4 and 5 show exploded perspective views of selected internal components of the dispenser of Figure 1 ; and in particular Figure 5 shows the male engaging member (located within the main body) that overcomes problems associated with prior-art dispensers;

Figure 6 shows an end view of the dispenser of Figure 1 (including the male engaging member) with the actuator casing removed;

Figure 7 shows a perspective views the male engaging member for the dispenser of Figure 1 ;

Figure 8 shows of a male engaging member according to a second embodiment of the invention; Figure 9 shows of a male engaging member according to a third embodiment of the invention; and

Figure 10 shows a male engaging member according to a fourth embodiment of the invention. Detailed Description of Invention

A preferred embodiment of the invention will now be described by reference to Figures 1-7. Figure 1 is a sectioned view of the dispenser (10) with a fully charged disposable cartridge (12) containing a cosmetic cream (F) or similar viscous fluid; for example the cartridge (12) may contain a medicament cream. The disposable cartridge (12) comprises a cylindrical vessel with a tubular side wall (14); a displaceable piston base (16) and a roof portion (18) having a fluid dispensing recess (20) with a central hole (22) (see Figure 3). The disposable cartridge (12) is housed above the main dispensing mechanism (52) and within the generally tubular shaped upper side wall (34) and a lid (see Figure 3). The lid comprises a circular or crescent shaped inner portion (24) with a stopper (26) that seals the central hole (22) of the recess (20); this inner portion (24) engages a surrounding annular portion (28) that has an inner ring- shaped lip (30) that engages the top of the disposable cartridge (12) and an inner female thread (32) that engages a male thread (36) around the top of the side wall (34). The side wall (34) has a plurality of protrusions (54) (see Figure 3) located on the bottom of the side wall (34) and these protrusions fit over (see below) a thin flange (76) located around the outside of the main internal tube body member (70); thus allowing the attachment of the side wall (34) to the main internal tube body member (70).

The lower outer portion of the dispenser (38) (see Figure 4) has a split vane (40) comprising two parallel spaced apart vertical sheets (42) and four adjacent strengthening members (44) integrally formed with the sheets (42) and inner floor (46) of the lower outer portion (38). The lower outer portion (38) can be rotated about the axis A- A' (see Figure 1) owing to a plurality of tongues (48) located on the top and inside of the side wall (50) of the outer portion (38) such that these tongues fit over (see below) side protrusions (74) of the main internal body tube member (70). Thus, a user may twist the lower outer portion (38) part of a turn in order to activate the dispenser. Split vane (40) engages (see Figure 5) a diametric plate (66) that forms an integral part of the main thread member (60). Main thread member (60) comprises a tubular portion (62) with a short (first) outer male thread (64) located at the lower end of the tube (62). The main thread member (60) has two abutment members (68) each with a protrusion (94) located diametrically to each other on the inside surface of the tubular portion (62).

The short (first) thread (64) of the main thread member (60) screws inside the main internal body member (70). The main internal body member (70) has a very slightly tapered (the side walls of the thread are inclined at an angle of 1° to the axis A- A' of the thread) internal female thread (78) that generally corresponds to the first thread (64) on the main thread member (60). Hence, as the main thread member (60) is turned by abutment against the split vane (40) during turning the lower portion (38) of the dispenser; the main thread member (60) advances along the axis A- A' of the main internal body member (70) until it abuts against and pushes the displaceable piston base (16) upwardly, so displacing fluid (F) contained in the disposable cartridge (12) through the central hole (22) of the recess (20).

The dispenser has means to partly reverse the direction in which the main thread member (60) was turned inside the main internal body tube member (70) during use. This comes into effect when the user stops turning the lower portion (38) and results in main thread member (60) retracting very slightly allowing the displaceable piston (16) to do likewise and thereby reducing the pressure of fluid (F) in the disposable cartridge (12). This is advantageous, as it prevents discharge of fluid after the user has stopped turning the lower portion (38) and so avoids waste. This is particularly important when costly creams (for example certain cosmetics) are being dispensed.

The reverse means may be obtained by the addition of a male engaging member (80) having first and second resilient members (106, 96). The male engaging member (80) comprises a frame member (82) with a short C-Shaped tube section having a (second) male thread (84) and also three thread engaging protrusions (100) - equally spaced on the periphery of the frame member (82) either side of the first resilient member (106). The C-Shaped frame member (82) with its attached thread (84) and engaging protrusions (100) are biased radially outwardly by means of a first resilient means (106) located within the C-Shaped tube section (82). In the present embodiment this comprises a generally U-shaped spring member (106) that engages the open ends of the C-shaped frame member (82) by means of small slots (108) in the spring (106) and corresponding protrusions (104) that form part of the end faces of the C-Shaped tube section. This arrangement ensures that the frame member (82) has a slightly greater "diameter" (when unrestrained) than the first male thread (64) and also that as it traverses the tapered female internal thread (78) it radially expands/contracts thus ensuring a continuous tight grip between the male engaging member (80) and the female internal thread (78). Thus, while the first male thread (64) of the main thread member may be readily screwed inside the main body member (70) the second male thread (84) requires the application of considerably more torque to do so. Two further abutment members (88) each with a protrusion (92) are located on the inner cylindrical surface of the frame member (82). The frame member (82) also has a plurality of guide members (90) that comprise arcuate walls formed integrally with the frame member (82). The guide members (90) allow the male engaging member (80) to be placed inside the bottom end of the main thread member (60) such that the first and second male threads (64 and 84) form substantially a single continuous thread that allows the main thread member (60) and the male engaging member (80) to advance together along axis A- A' as they main are turned within the main internal tube body member (70). Two springs (96 - second resilient members) are placed between protrusions 92 and 94 and therefore apply a bias between abutment members 68 and 88 (see Figure 6).

When a user initially turns the main thread member (60) (by means of the lower main portion 38) the springs (96) initially compress until sufficient torque is thus applied to turn the male engaging member (80) also. When the user stops turning the main thread member (60) the springs (96) expand to their at rest length. During this step the tighter fit of the male engaging member (80) ensures that the main thread member (60) turns slightly in a backward direction and so eases the pressure applied to the fluid (F) inside the disposable cartridge (12). In use, extension of the spring (96) (to their rest length) is limited by of the edge (98) of the guide members (90) abutting against an edge of the protruding abutment member (68) of the main thread member (see Figure 6). This prevents the springs (96) disengaging the protrusions (92, 94) when in the rest position.

While the dispenser (10) preferably is used with replaceable disposable cartridges (12) they are not essential. Thus, if the inner wall of the side wall (34) were cylindrically shaped and the piston (16) was. a tight fit within the side wall (34) then the cartridge members 14, 18, 20 and 22 could be omitted.

In the above described preferred embodiment the slight increase in the distance between the outer portion (28) and the main thread (piston) member (60) is provided by finally slightly retracting the piston member (28).

The male engaging member (80) can vary in configuration (for example; as described with the aid of Figures 8 and 9 below) and may be used in a variety of viscous liquid dispensers. Any such dispenser having an internal female thread will probably be manufactured using injection moulding. The injection moulding of such threaded parts normally requires a slightly tapered thread in order to facilitate removal from the mould at the end of the process. Thus, unless such a thread is relatively short any male engaging threaded member may benefit from being able to radially expand to maintain a good grip within the female thread as it traverses such a thread. This is particularly the case where the dispenser has means to partly reverse the direction in which a piston member was advanced during following a dispensing action.

While such a male thread is preferred it is also possible to use a plurality (and preferably three or more) of radially extending arms; these arms forming part of a support frame; each arm having an outwardly biased thread engaging member. Figures 8 and 9 show just two alternatives for male members employing a generally C- Shaped frame member (82). Figure 8 shows a male engaging member (80) where the U-shaped spring (106) of Figure 7 has been replaced by a helical spring (206). Figure 9 shows a male engaging member that has a frame member (82) which is generally circular but that has a weaker unitary U-Shaped (minor) portion (304) within which the first resilient means (a U-shaped spring 306) is housed. Again, like the earlier described embodiments this allows the main portion of the frame member to expand radially outwards as it traverses a tapered female thread. Figure 10 shows an alternative male member (480) that does not employ a C-Shaped frame member but rather employs a plurality of U-shaped radially extending arms (406) that provide resilience; these arms each have an engaging protrusion (500) that cooperate to engage the female internal thread (78). This arrangement ensures that the plurality of arms and engaging protrusions (406, 500) have a slightly greater "equivalent diameter" (when unrestrained) than the first male thread (64) and also that as the male member (480) traverses the tapered female internal thread (78) it radially expands/contracts thus ensuring a continuous tight grip between the male engaging member arms/protrusions (406, 500) and the female internal thread (78). Each arm (406) also has a generally cylindrically shaped protrusion (492); between these protrusions (492) and the main thread protrusions (94) one or more resilient members/springs (96) are located.