GB2329680A - Paste dispenser - Google Patents

Abstract

A dispenser for dispensing a measured dose of a viscous substance comprises a piston (9, Fig 1) which is driven by a worm gear 11 having ratchet teeth 11b which engage with ratchet teeth 13b on an inner surface of a pinion 13. The pinion 13 also has teeth 13a on its outer surface which engage with teeth 15a on a rack 15. In use, actuation of a button 5 moves the rack 15, causing subsequent movement of the piston (9). The dispenser has a dose limiting mechanism comprising a setting clip 19 which may be inserted into one of several holes 17a in a plate 17 at the time of filling the dispenser, the clip 19 acting as a stop for an eccentric tab 13c on the pinion 13, limiting the rotation of the pinion 13 and hence the advance of the piston (9) to a pre-set amount.

Description

Paste Dispenser The present invention relates to dispensers for pastes, gels or other viscous substances and in particular to a paste dispenser which can dispense a precise dose of paste.

In this document the term "paste" is used to refer to all pastes, gels, resins or similarly viscous substances.

A number of designs for paste dispensers are known which comprise a cylinder to contain the paste, a piston to drive the paste out of a nozzle and a central worm gear to displace the piston. Various different mechanisms for turning the worm gear have been proposed. For example, GB 2,146,612 A discloses a toothpaste pump in which depression of a button adjacent the nozzle causes an angled projection to engage an angled slot in a rotatable member attached to the worm gear. EP 0,193,688 B discloses a metering tube intended to dispense accurate doses of a paste which has a body of noncircular cross-section and a knob of similar cross-section directly attached to the worm gear at the opposite end from the nozzle. It is intended that the user may judge how much paste has been dispensed by observing how far the knob has been turned relative to the base.

DE U1 G 94 06 792.9 discloses a paste dispenser in which a telescoping member that drives a piston is extended via bevel gears driven by a trigger mechanism on a handle attached to the side of the tube.

According to the present invention there is provided: a paste dispenser comprising: a main body for containing a paste to be dispensed and having a dispensing nozzle at a distal end thereof; a piston disposed within said main body for driving said paste toward said nozzle; a non-return drive train for advancing said piston toward said nozzle in response to a user actuation; and a limiter for limiting the movement of the drive train to a selected amount in response to each user actuation so that a selected dose of paste is dispensed from the nozzle in response to each actuation.

Preferably the drive train comprises: a worm gear connected to said piston whereby rotation of said worm gear in a first sense advances said piston toward said nozzle; a ratchet gear for driving said worm gear when rotated in said first sense but not when rotated in the opposite sense.

The arrangement of rack and ratchet gear acting as pinion enables the drive mechanism to be situated at a convenient location on the dispenser body and to be driven simply by a button or the like.

The limiter ensures that a single actuation of the device by the user rotates the worm gear and thereby advances the piston by a predetermined consistent amount. This then ensures the device dispenses a known consistent amount of paste per actuation. The limiter is preferably arranged so that the amount of paste dispensed can be adjusted. In a preferred embodiment the dispensing amount is set, by positioning a peg in one of a number of pre-provided holes, to one of a plurality of amounts at the time the device is filled.

The nozzle of the device is preferably of a shape that can be easily and comfortably placed in or gripped by the mouth of an animal without damage thereto.

Preferably, the actuator is positioned on the side of the device at or near the opposite (proximal) end to the nozzle.

The paste used in the device may be a medicinal or veterinary product or food supplement. The device then enables a pre-set dose of the product or supplement to be easily dispensed directly to an animal.

An exemplary embodiment of the invention will be described below with reference to the accompanying drawings, in which: Fig. 1 is a side view, partly sectioned, of a paste dispenser according to the present invention; Fig. 2 is side view, showing hidden detail, of the piston and worm gear of the dispenser of Fig. 1; Fig. 3 is an exploded perspective view of the back cover and drive mechanism of the dispenser of Fig. 1; Fig. 4 is a cross-sectional view showing the drive mechanism of the dispenser ofFig. 1; Figs. 5 A and B are respectively side and end views of the setting clip of the dispensor of Fig. 1; and Fig. 6 is an end view of the setting plate of the dispensor of Fig. 1.

In the drawings like reference numerals designate like parts.

Figure 1 shows a dispenser according to an exemplary embodiment of the invention which is particularly adapted for dispensing measured doses of veterinary pharmaceuticals or dietary supplements to animals. As shown, the dispenser has a main body 1 with a nozzle (not shown) at its distal end and a back cover 3 on its proximal end.

The back cover 3 contains the drive mechanism for the device, described below, and an actuating button 5 protrudes from one side. A cap 7 is provided with an elongate outward projection 7a for piercing an internal seal (not shown) before first use of the device and a shorter inward projection 7b for keeping the nozzle clear once the seal has been broken.

The main body 1 is round in cross-section but may be of another shape, e.g.

oval, if desired. The exterior may be contoured or knurled for ease of gripping provided that the internal cross-section is uniform up to the tapered end 1 a.

The distal end 1 a of the main body is tapered smoothly and shaped so as to be easily inserted into or grasped by the mouth of an animal without causing damage or discomfort. The size and shape of the device and the end 1 a will be determined according to the type and age range of the animals to be dosed. If the device is to be used for other purposes, the shape of the end 1 a and the nozzle arrangements may be varied appropriately.

Figure 2 shows the piston 9 and worm gear 11 which fit inside the main body for forcing the paste out of the nozzle. The proximal end 9a of the piston 9 is shaped to match the interior cross-section of the main body 1 and has an annular projection 9b to make a paste- or water-tight seal to the internal surface of the main body. The distal end 9c of the piston 9 is shaped to match the internal surface of the tapered end la of the main body. This is to ensure that there is no dead space in which paste can remain so that all paste can be ejected and used.

A groove (not shown) is provided on the piston to engage a matching longitudinal rib (not shown) on the internal surface of the main body. This is to prevent the piston rotating within the dispenser and may not be necessary if the piston and main body are not circular in cross-section.

The worm gear 11 has a two-start helical thread along most of its length which engages a correspondingly threaded bore (not shown) in the piston. Rotation of the worm gear relative to the piston (which is prevented from rotating relative to the main body) causes it to advance along the gear. The pitch of the threads determines the rate of advance of the piston and hence the amount of paste dispensed for each revolution of the worm gear.

The proximal end of the worm gear 11 is unthreaded but has ratchet teeth 1 lib by which it is driven to rotate.

The drive mechanism and back cover 3 are shown in exploded form in Figure 3.

The worm gear 11 extends through plate 17 and pinion 13 so that its proximal end is received in a socket 3 a at the rear of the back cover 3. The pinion 13 has ratchet teeth 1 3b on its inner surface which engage the ratchet teeth 1 lib on the worm gear 11.

The ratchet teeth are arranged so that rotation of the pinion in one sense, in this case anti-clockwise as viewed from the distal end, causes the worm gear to rotate and hence the piston to advance. On rotation in the other sense, the ratchet teeth do not engage so that the pinion returns to its original position without rotating the worm gear. The pinion also has teeth 13a on its outer surface which engage with corresponding teeth 15a on rack member 15. The engagement of rack member 15, pinion gear 13 and worm gear 11 is shown in Figure 4 which is a cross-sectional view looking from the distal end of the dispensor. In Figure 4 the device is in its unactuated position. Actuation of the button5 will push the rack member 15 down casuing the pinion gear 13 and worm gear 11 to rotate anti-clockwise. On return, the ratchet teeth 1 lb will slip over the angled faces of the ratchet teeh 13b so that the wormgear does not turn back.

A mounting point 13d is provided for a helical spring which serves to bias the pinion to return against the driving direction.

The rack member 15 has at its upper end a stock 1 sub which engages button 5 which projects through the back cover 3 so as to be operable by the user. The back cover 3 has an enlarged cross-section relative to the main body to accommodate the lateral motion of the rack member 15 when operated by the user.

The dose limiting mechanism comprises setting clip 19 which is inserted into one of the holes 17a in plate 17 when the device is filled. When inserted, wall 19a of setting clip 19 projects through plate 17 and some way beyond. An eccentric tab 13c is provided on pinion 13 extending longitudinally forward such that on rotation of the pinion it will meet wall 19a preventing further rotation. Which hole the setting clip 19 is inserted into determines how far the pinion can rotate before meeting the wall and thus how much paste is ejected on each actuation of the button.

The setting clip and plate are shown in more detail in Figures 5 and 6 respectively. On filling of the dispenser, the angled wall 19 is inserted through the selected hole 17a and is prevented by the adjacent wall 17b from rotating when pressed bytab 13c.

In the present embodiment four holes and a fixed wall are provided at regular intervals in the plate which, with the worm gear pitch, enables the dose to be set at 1, 2, 3, 4 or 5 ml per actuation. The fixed wall limits movement of the pinion at a distance equivalent to a dose of 5 ml if the setting clip is left out. A flange 19b and pointer 1 9c are provided on the clip to assist in setting of the device.

Most parts of the device may be injection-moulded from high-density polyethylene (HDPE), polypropylene (PP) or Acetal so that the dispenser is cheap to manufacture and may be disposed of once empty.

Prior to filling the device the parts are assembled into three assemblies: main body and cap; piston and worm gear; and back cover and drive mechanism. The main body is then filled with paste and the piston and worm gear inserted. The setting clip 19 is then inserted into the appropriate hole in plate 17, or omitted for the largest dose, and the back cover assembly fitted over the projecting end of the worm gear. The back cover is preferably attached to the main body by welding or in some other fashion that makes evident any attempt to dis-assemble the device after manufacture.

The setting clip may be bonded to the plate 17 on filling of the device to provide additional protection against tampering with the dose size.

It will be appreciated that variations and modifications to the above device are possible. For example the dose sizes and number of dose sizes may be changed. In some applications the dose setting clip might be replaced by an extemal control, e.g. a lever, to allow the dose to be set by the user for each use. Some or all of the device may be made more durable and re-useable with, e.g., the paste being provided in a compressible tube that is inserted into the main body of the dispenser and disposed of after use.

Instead of a dose setting clip insertable in one of a number of holes in the plate 17, it would be possible to provide several different plates with fixed walls at different positions corresponding to different dose sizes. On filling of the device an appropriate plate is selected and inserted to regulate the dose size.

Claims (9)

Claims

1. A paste dispenser comprising: a main body for containing a paste to be dispensed and having a dispensing nozzle at a distal end thereof; a piston disposed within said main body for driving said paste toward said nozzle; a non-return drive train for advancing said piston toward said nozzle in response to a user actuation; and a limiter for limiting the movement of the drive train to a selected amount in response to each user actuation so that a selected dose of paste is dispensed from the nozzle in response to each actuation.

2. A paste dispenser according to claim 1 wherein said limiter is adapted to be set to one of a plurality of positions corresponding to different predetermined doses.

3. A paste dispenser according to claim 1 or 2 wherein said limiter is disposed within the main body of the dispenser and is inaccessible after the dispenser has been sealed.

4. A paste dispenser according to claim 1, 2 or 3 wherein said drive train comprises: a worm gear connected to said piston whereby rotation of said worm gear in a first sense advances said piston toward said nozzle; a ratchet gear for driving said worm gear when rotated in said first sense but not when rotated in the opposite sense.

5. A paste dispenser according to claim 4 wherein said ratchet gear has a projecting tab and said limiter comprises a selectively positionable block adapted to contact said projecting tab to limit rotational movement of said ratchet gear.

6. A paste dispenser according to claim 5 wherein said limiting means further comprises a plate member having a plurality of holes at selected positions therein and said block comprises a peg selectively insertable in said holes.

7. A paste dispenser according to any one of claims 4 to 6 wherein said ratchet gear is adapted to be driven by a rack connected to a user actuable member.

8. A paste dispenser according to any one of the preceding claims wherein the distal end of said main body tapers smoothly toward said nozzle.

9. A paste dispenser according to any one of the preceding claims further comprising a user actuable member for driving said drive train, said user actuable member comprising a button provided at or near the proximal end of said main body.

10 A paste dispenser constructed and arranged to operate substantially as hereinbefore described with reference to the accompanying drawings.