GB2187962A

GB2187962A - Dosage means

Info

Publication number: GB2187962A
Application number: GB08607178A
Authority: GB
Inventors: Digby Ralf Redshaw
Original assignee: YOUNG ROBERT CO Ltd
Current assignee: YOUNG ROBERT CO Ltd
Priority date: 1986-03-22
Filing date: 1986-03-22
Publication date: 1987-09-23
Also published as: GB8607178D0

Abstract

A hand-held dosage means for delivering an agent for parenteral absorption by an animal comprises in a linear arrangement a disposable nozzle (1) which can be fitted with a hypodermic needle (not shown), a dosage chamber (2) for receiving said agent prior to delivery, a piston (3) which is operated by a trigger mechanism (9) attached to hand grip (10) and a pressurised cartridge (4) which contains a bulk reservoir of the agent (5) in the form of a paste or solution. The chamber has a one-way valve (7) which is normally closed but allows agent delivery on the forward stroke of the piston (3). The piston has a one-way valve (8) which is also normally closed but which allows recharging of the chamber (2) upon the return stroke of the piston (3). <IMAGE>

Description

SPECIFICATION Dosage means This invention relates to means for delivering a controlled dosage of an agent for parenteral absorption by an animal.

The simplest means in existence for administering parenterally a controlled dosage of an agent is the hypodermic needle and syringe for use with solutions or suspensions of the agent.

A syringe is acceptable for solutions or suspensions of low viscosity and for low volume injections. Disadvantages arise where a large number of injections are required, for example, to inoculate a herd of animals. These disadvantages include difficulties in ensuring consistency in the dosage given, inconvenience in use of syringe, risks of cross-infection, and limitations to use of low viscosity media. The viscosity of a given composition may rise to an undesirable level under the cool temperatures prevailing in barns, yards or pastures.

High viscosity results in difficulties in aspiration of a viscous composition into a hypodermic syringe and subsequent discharge of the composition during injection of an animal which requires some effort and is slow. An animal often does not stand still long enough to receive the full dosage, and this presents a further problem in ensuring correct dosage since the animal may dislodge the needle and cause spillage.

There have been several proposals for providing a vaccination gun for injecting humans or livestock consisting of a pistol with a needle syringe and an integral reservoir for the vaccination medium. See for example British Patents 1 026 593, 1 082 582, 1 111 382, 1 118 081/+2, 1 152 285, 1 174 936, 1 198 214, 1 243 574, 1 277 450, 1 284 312, 1 335 797, 1 402 428, 1 464 773, and 1 595 204.

These prior proposals rely in some cases on gravity feed mechanisms which necessitates positioning of a reservoir above the hand piece which is unwieldly and can only be used for freely flowing media. In other cases, the reservoir is positioned below the hand piece and a pump mechanism is required, but again only freely flowing media are acceptable in such devices. Charging and dispensing of dosages is not particularly easy nor accurate in such known devices.

Many of these devices are of complex construction and are too expensive to be discarded after use. Therefore, they must be sterilised to allow re-use. Sterilisation of complex units is difficult and inconvenient.

Of the prior proposals mentioned only GB 1 277 450 discloses a dispensing gun suitable for dispensing pastes. In this gun a container for paste or medicine is mounted in a carriage movable with respect to a fixed thrust member by means of a trigger mechanism which at first causes severing of the container base to act as a piston for driving contents out of the front of the container whilst the container is driven rearwardly over the severed base by actuation of the trigger mechanism.

Operation of this device can become fatiguing when administering a series of dosages due to the physical effort required to discharge a dosage by manual pressure on the trigger.

An object of-the present invention is to provide an improved dosage means which obviates or mitigates the aforesaid disadvantages.

According to this invention there is provided a hand-held dosage means for delivering an agent for parenteral absorption by an animal comprising in a linear arrangement: a) a dosage chamber having a discharge orifice and a one-way valve biased to close said orifice; b) a piston capable of travel within said chamber from one end towards said orifice to effect discharge of the contents of said chamber and return to said one end, which piston has an aperture providing a means of introducing an agent to said chamber, and a oneway valve biased to close said aperture; and c) a pressurised reservoir of said agent having a conduit communicating with said aperture for delivering said agent on demand to the chamber, the said one-way valve in said chamber being biased to counterbalance the pressure in the reservoir.

Preferably, the piston is actuated by a mechanical trigger mechanism attached to a hand grip.

Preferably, the dosage chamber and piston are releasable from the trigger mechanism to allow replacement thereof to avoid the need for sterilisation.

Preferably also, the pressurised reservoir is a detachable cartridge.

It is further preferred that the dosage chamber has a disposable nozzle located over said discharge orifice.

The dosage chamber may be provided with adjustable means for limiting the degree of travel of the piston in order to provide means for adjusting the dosage.

The invention will now be described by way of example with reference to the accompanying drawings in which: Fig 1 shows schematically a section through the principle components of the dosage means wherein the chamber is fully charged and ready for discharging a dosage of agent; Fig 2 shows the same components in use with the chamber almost exhausted by the advancing piston; and Fig 3 shows the components operating to recharge the chamber as the piston is returned to its original position.

Example In a first embodiment, a dosage means for delivering an agent for parenteral absorption by an animal comprises a disposable nozzle (1) which can be fitted with a hypodermic needle (not shown), a dosage chamber (2) for receiving said agent prior to delivery, a piston (3) which is operated by a trigger mechanism (9) attached to hand grip (10) and a pressurised cartridge (4) which contains a bulk reservoir of the agent (5) in the form of a paste or solution. The chamber has a one-way valve (7) which is normally closed against the pressure (6) in the cartridge (4). The piston also has a one-way valve (8) which is normally closed.

When in use, the piston (3) is caused to move forward in response to operation of the trigger mechanism (9). The one-way valve (8) is closed and the increase in pressure in the chamber (2) causes the one-way valve (7) to open allowing the agent (5) in the chamber (2) to be discharged through the nozzle (1). During this operation, as the piston (3) moves forward through the chamber (2), the volume left behind the piston (3) is filled with more agent (5) expelled from the cartridge (4) by the pressure (6) therein.

When the trigger mechanism (9) is released the piston (3) is caused to return to its original position. The pressure balance is restored and the one-way valve (7) closes the chamber orifice. However, one-way valve (8) remains open until the piston (3) comes to rest in the original position allowing agent (5) to pass from behind the piston (3) into the chamber (2).

Advantageous features of this invention are: 1) that it provides a fully portable injection system which by adopting an in-line system requires minimum pressure to drive it; 2) that the pressurised bulk cartridge is replaceable and forms an integral part of the instrument in use without the need for feed lines, and its location "in line" provides for ease of use in that it is well balanced and easily held; 3) that the dosage may be easily varied by adjusting the piston travel or by adopting chamber/piston sizes to suit requirements; 4) that it is possible to deliver a plurality of dosages repeatedly and accurately by virtue of a consistently accurate and automatic recharge of the dosage chamber from the bulk reservoir; 5) that it is possible to deliver pastes or solutions with the minimum of conversion steps; and 6) that the hand held unit is re-usable in conjunction with disposable cartridge and fresh sterile syringe assemblies giving considerable cost advantages and freedom from concern over infection arising from sterilisation difficulties.

Claims

1. A hand-held dosage means for delivering an agent for parenteral absorption by an animal comprising in a linear arrangement: a) a dosage chamber having a discharge orifice and a one-way valve biased to close said.

orifice; b) a piston capable of travel within said chamber from one end towards said orifice to effect discharge of the contents of said chamber and return to said one end, which piston has an aperture providing a means of introducing an agent to said chamber, and a oneway valve biased to close said aperture; and c) a pressurised reservoir of said agent having a conduit communicating with said aperture for delivering said agent on demand to the chamber, the said one-way valve in said chamber being biased to counterbalance the pressure in the reservoir.

2. A hand-held dosage means according to claim 1 wherein the piston is actuated by a mechanical trigger mechanism attached to a hand grip.

3. A hand-held dosage means according to claim 1 or claim 2 wherein the dosage chamber and piston are releasable from the trigger mechanism to allow replacement thereof to avoid the need for sterilisation.

4. A hand-held dosage means according to any one of claims 1 to 3 wherein the pressurised reservoir is a detachable cartridge.

5. A hand-held dosage means according to any one of the preceding claims wherein the dosage chamber has a disposable nozzle located over said discharge orifice.

6. A hand-held dosage means according to any ome of the preceding claims wherein the dosage chamber is provided with adjustable means for limiting the degree of travel of the piston in order to provide means for adjusting the dosage.

7. A hand-held dosage means for delivering an agent for parenteral absorption by an animal substantially as hereinbefore described with reference to the accompanying drawings.