WO1990008075A1

WO1990008075A1 - Pressurised metering dispenser

Info

Publication number: WO1990008075A1
Application number: PCT/GB1989/001050
Authority: WO
Inventors: Terence Edward Weston
Original assignee: Microvol Limited
Priority date: 1989-01-12
Filing date: 1989-09-07
Publication date: 1990-07-26
Also published as: GB8900670D0

Abstract

A dispenser for dispensing a predetermined volume of liquid through a nozzle (18), has a liquid reservoir (32) of which the upper part (34) contains gas under pressure. The nozzle is connected to a valve spindle (16) and a tube (14) which pass up through the reservoir into a gas chamber (8). When the nozzle (18) is pushed upwards, the metered volume in the tube and spindle is expelled by the pressurised gas. Releasing of the nozzle enables liquid from the reservoir to pass through a port (20) into the spindle (16), and up the tube (14) to refill the metered volume; and on return to its normal rest position the port (20) is again out of communication with the reservoir (32), and any excess liquid in the chamber (8) flows through slots (36) back into the reservoir.

Description

Title: Pressurised Metering Dispenser

Field of the invention

This invention relates to a pressurised metering dispenser, and more particularly to a dispenser for dispensing pre-determined volumes of liquid.

Background to the invention

In PCT International Application Publication No. WO 88/04638, there is described and claimed a pressurised metering dispenser in which in its normal or rest position a liquid metering chamber remains in communication with a main reservoir to receive liquid therefrom. In such an arrangement it has been found that a problem may arise with the refilling of the liquid metering chamber particularly for small volumes or doses to be dispensed, since bubbles are liable to become trapped therein.

It is an object of the present invention to provide an improved dispenser.

Summary of the invention

According to the present invention there is provided a pressurised metering dispenser comprising a reservoir for containing gas under pressure in an upper part and liquid to be dispensed in a lower adjoining part, characterised by a gas chamber formed in and normally communicating with said upper part, valve means extending through said lower part and terminating in an external nozzle, and metering means communicating with the gas chamber and defining a metered volume of liquid, the valve means having a first port communicating with the metering means and a second port communicating with the nozzle and being movable against biasing means between a rest position (in which the gas chamber communicates with the reservoir) and a dispensing position (in which the gas chamber is sealed from the reservoir and the second port is in communication with the metering means, enabling gas from the gas chamber to dispense the metered volume of liquid out through the nozzle so that the pressure in the gas chamber is reduced to ambient pressure), and wherein during the return movement to the said rest position the valve means passes through an intermediate position in which the gas chamber is still sealed from the reservoir but the first port communicates with the liquid in the reservoir, so as to cause the pressurised liquid to refill the metering means against the reduced pressure in the gas chamber.

It has been found that a dispenser in accordance with the invention overcomes the problem of trapped gas bubbles, and gives improved repeatability, ie. reduced variation in the volume of liquid dispensed.

The valve means may be a valve spindle axially slidable in a valve assembly and having an axial bore extending into the gas chamber.

The valve assembly may be formed with a channel with which the first and second ports communicate when in the dispensing position. A groove may be formed above the first port, whereby when the spindle is in the intermediate position liquid can flow through the groove and the channel and up through the bore to the gas chamber.

The channel, the first port and the bore thus together constitute the metering means, and by varying the diameter of the bore, so the desired metered volume of liquid can be readily altered.

The gas chamber may be defined by a cylinder, and the top of the spindle may then be in the form of a piston sealably slidable into the cylinder.

The bottom of the cylinder is preferably slotted to enable excess liquid to flow out of the gas chamber, after the metering means has been refilled.

Brief description of the drawings

The invention will now be described, by way of non- limiting example only, with reference to the accompanying drawings in which:-

Figure 1 is a side view in section of a pressurised metering dispenser embodying the invention in a refilling position;

Figure 2 is an enlarged sectional view of the upper and lower ends of the dispenser of Figure 1 in its rest position;

Figure 3 is a view similar to Figure 2 with the dispenser in a dispensing position; Figure 4 is an enlarged sectional view of the upper end of a modified dispenser in a rest position corresponding to Figure 2; and

Figure 5 is a sectional view of the upper and lower ends of another dispenser similar to that shown in Figures 1 to 3 and suitable for putting into production.

Detailed description of the illustrated embodiment

The dispenser to be described operates generally in the manner explained in the above-mentioned PCT International Patent Application, Publication No. WO 88/04638, and the disclosure of said publication is hereby incorporated in its entirety into the present specification.

Referring first mainly to Figure 1, the dispenser shown has a tubular body 2 closed by an upper cap 4 and a lower cap 6. Mounted under the upper cap 4 in axial alignment with the tubular body 2 is a cylinder 8 in which a valve piston 10 is sealingly slidable. The piston 10 has a bore 12 and provides a sealed fit over a tube 14 communicating with the bore.

The bottom of the tube 14 is connected to a valve spindle 16 the bottom of which terminates in a nozzle 18 extendin out through the lower cap 6. The spindle has an upper radial port 20, which communicates via a central bore 22 in the spindle with the tube 14, and a lower radial bore 24 which communicates with the nozzle 18.

Referring now also to Figure 2, which shows the dispenser in its normal or rest position, the spindle 16 is biased into its lowermost position by a spring 26 acting on the piston 10 and thereby through the tube 14 onto the spindle 16.

The spindle 16 is vertically slidable in a two-part valve assembly 28 which is sealed to the body 2 by an O-ring seal 30.

As best seen in Figure 1, the body 2 constitutes a main reservoir which is typically half filled with a liquid 32 to be dispensed, and the remaining volume above the liquid is filled with an inert gas 34 such as Nitrogen, pressurised typically to a pressure of 8 bar.

The lower end of the cylinder 8 is formed with slots 36 so that in the rest position of Figure 2 the gas chamber defined by the cylinder remains in communication with the pressurised gas 34 through the slots 36.

Above the upper port 20 the spindle has a land area 38 which, in the dispensing position of Figure 3, is in sealing engagement with an annular seal 40 in the top part of the valve assembly 28.

An axial groove 44 is provided in the valve spindle 16 immediately above the land 40, so that in the position of Figure 1 liquid 32 can flow past the seal .40, along a channel 42 formed in the valve assembly and into the upper port 20.

Operation

The operation of the dispenser will now be described, starting with the dispenser in the rest position shown in Figure 2 .

Let it be assumed, as will become clear from the following description of the operation, that the tube 14, the bores 12 and 22 and the channel 42 (which together constitute the metered volume of liquid to be dispensed) are completely filled to the top. On operating the dispenser by pushing up the nozzle 18 and spindle 16 to the uppermost position of Figure 3 (there being provided a stop to prevent further upward movement, not shown) the piston 10 closes off pressurised gas from the gas chamber formed by the cylinder 8, while at the bottom of the spindle the upper and lower ports 20 and 24 become aligned respectively with the top and bottom of the channel 42. The metered volume of liquid contained in channel 42, port 20, bore 22, tube 14 and piston bore 12 are thereby now connected with the nozzle 18 which is open to atmosphere. The pressure in the gas chamber thus expels this metered liquid, until the pressure in the gas chamber drops to substantially atmospheric pressure, when the full volume of metered liquid will have been dispensed.

When the nozzle 18 is released and allowed to move downwardly under the bias of the spring 26, the lower port 24 moves past a seal 46 at the bottom of the channel 42 whilst the groove 44 passes the seal 40 and comes into communication with the upper port 20 via the channel 42. Since the gas chamber in the cylinder 8 is now at atmospheric pressure, whereas the liquid 32 is pressurised by the gas 34 to about 8 bars (and not less than 2 bars when the liquid 32 is practically depleted), the liquid is forced up the tube 14, pushing any air bubbles ahead of it. Some surplus liquid will then spill out of the bore 12 into the gas chamber. This refilling operation only takes a short period of time, of the order of a few hundredths of a second, before the spindle is again returned by the spring 26 to its lowermost position shown in Figure 2. The gas chamber is now again in communication with the main reservoir, via the slots 36 at the bottom of the cylinder 8, enabling the gas chamber to become recharged with gas under pressure and allowing surplus liquid to flow over the inclined upper face of the piston 10 and back into the reservoir to join the main liquid 32. Complete and rapid drainage of such surplus liquid is assisted by adding a surfactant to the liquid.

In the modified dispenser shown in Figure 4 similar parts are indicated by the previous reference numerals but increased by 100.

The cylinder 108 in this case has holes 109 formed at the top which communicate with the reservoir of pressurised gas 134. The piston 110 has a lower slidable seal 111, similar to that of piston 10, and an upper slidable seal 113 which always remains within the cylinder 108. An annular space 115 is formed between the seals 111 and 113, and this communicates with the bore 112 in the tube 114 via a radial opening 117 in the piston.

The space 115 constitutes the gas chamber which, when the nozzle (eg.as nozzle 18) is pushed upwards, becomes enclosed within the cylinder 108 and causes the metered liquid in the tube 114 to be expelled. As previously, when the nozzle is then returning downwards under the bias of a compression spring (not shown) acting upon the seal 113, the chamber 115 will be at atmospheric pressure and therefore draws in liquid into the metered volume of the tube 114 etc.

The main difference of this embodiment over the previous one is that the volume of the gas chamber remains unaltered during operation. However by including an upper seal 113, the drainage of surplus liquid is also acilitated.

Figure 5 shows the upper and lower ends of another dispenser which is of a simple design particularly suitable for putting into production. The parts to be described which are similar to those of Figures 1 to 3 ar here indicated by the original reference numerals increased by 200.

The tubular body is in this case replaced by an inverted cylindrical bottle or flask 202 which encloses the upper end 207 of the dispenser and constitutes the main reservoir. The flask 202 is sealingly secured to the valve assembly 228 by a clamping ring 203, so as to retai the liquid under pressure (not shown) in the flask.

An open sided structure 205 extends upwards from the valv assembly 228, enabling liquid to pass through a groove or cut away 244 in the valve spindle 216 and to the channel 242 in the assembly. The structure 205 secures a cylinde

208 within the top of the gas reservoir 234, the closed top of the cylinder being spaced a short distance below the concave upper end 207 of the flask 202.

In this case the cylinder 108 is formed with a lower seal

209 and the tube 214 acts as a valve or piston, with its outside surface sealingly contacting the cylinder seal 209. A short distance beneath its top face the tube 214 has a cut away portion 211, the bottom edge 213 of which determines the final level to which the tube will be filled with the metered volume of liquid. Any excess liquid entering the cylinder 228 during refilling of the tube will then escape in the rest position shown.

The operation of the dispenser of Figure 5 is virtually the same as that of Figures 1 to 3. In contrast to the dispenser of Figure 4 some compression and expansion of the gas in the cylinder 208 will take pace while the top of the tube 214 is pushed into the cylinder in a dispensing position corresponding to Figure 3.

It has been found that the gas dispenser described has a good repeatability, ie. the volume or dose of metered fluid dispensed at each shot only varies by a small amount. The dispenser also overcomes the problems of bubble formation in the metered liquid volume, by driving the gas bubbles ahead of the liquid.

A further advantage of the dispenser is that the metered volume can readily be altered by providing a range of sizes of tube of differing internal diameter. A typical tube may, for example, have a length of about 90mm and an internal diameter of 0.6mm.

Claims

1. A pressurised metering dispenser comprising a reservoir for containing gas under pressure in an upper part and liquid to be dispensed in a lower adjoining part, characterised by a gas chamber (8r 108; 208) formed in and normally communicating with said upper part, valve means (16; 216) extending through said lower part and terminating in an external nozzle (18; 218), and metering means (14; 114; 214) communicating with the gas chamber and defining a metered volume of liquid, the valve means having a first port (20) communicating with the metering means and a second port (24) communicating with the nozzle and being movable against biasing means (26; 113) between a rest position (in which the gas chamber communicates with the reservoir) and a dispensing position (in which the gas chamber is sealed from the reservoir and the second port is in communication with the metering means, enabling gas from the gas chamber to dispense the metered volume of liquid out through the nozzle so that the pressure in the gas chamber is reduced to ambient pressure), and wherein during the return movement to the said rest position the valve means passes through an intermediate position in Which the gas chamber is still sealed from the reservoir but the first port communicates with the liquid in the reservoir, so as to cause the pressurised liquid to refill the metering means against the reduced pressure in the gas chamber.

2. A dispenser as claimed in claim 1 characterised -in that the valve means is a valve spindle (16; 216) axially slidable in a valve assembly (28) and having an axial bore extending into the gas chamber.

3. A dispenser as claimed in claim 1 characterised in that the valve assembly is formed with a channel (42; 242) with which the first and second ports communicate when in the dispensing position.

4. A dispenser as claimed in claim 3 characterised in that a groove (44; 244) is formed above the first port, whereby when the spindle is in the intermediate position liquid can flow through the groove and the channel (42; 242) and up through the bore to the gas chamber.

5. A dispenser as claimed in any one of claims 1 to 4, characterised in that the gas chamber is defined by a cylinder (8; 108; 208), and the top of the spindle is in the form of a piston (10; 110) sealably slidable into the cylinder.

6. A dispenser as claimed in claim 5 characterised in that the bottom of the cylinder is slotted (36) to enable excess liquid to flow out of the gas chamber after the metering means has been refilled.

7. A dispenser as claimed in any one of claims 1 to 6 characterised in that the valve means comprises a replaceable tube (14; 114; 214) extending towards the gas chamber, whereby the tube can be replaced by another tube of different internal diameter to enable the metered volume to be readily altered.

8. A dispenser as claimed in any one of claims 1 to 7 characterised in that the biasing means comprises a helical compression spring (26) mounted in the gas chamber and engageable with the valve means.

9. A dispenser as claimed in any one one of claims 5 to 8 characterised in that the gas chamber is of constant volume and is defined by an upper seal (113) and a lower seal (111) formed on the piston (110).