GB2266463A

GB2266463A - Hypodermic syringe

Info

Publication number: GB2266463A
Application number: GB9308571A
Authority: GB
Inventors: Brian Norman Hendy
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-04-25
Filing date: 1993-04-26
Publication date: 1993-11-03
Anticipated expiration: 2013-04-26
Also published as: GB9308571D0; GB2266463B

Abstract

A hypodermic syringe affording incomplete but controlled delivery of its charge and resistant to reverse plunger (20) movement includes an actuator (24, 28) low-geared in relation to plunger movement. Preferably the actuator includes means e.g. frictional resistance to limit such reverse movement. Suitably it is a plastics screw of 1 to 2 pitches per mm. Alternatively, spigot 18 is longer and forms a track on which end-cover 24 may advance until it abuts finger-plate 16 or arrives at a defined intermediate position. The syringe can be as light and portable as a disposable. It makes convenient a simplified insulin regime. <IMAGE>

Description

HYPODERMIC SYRINGE THIS INVENTION relates to a hypodermic syringe and to a control means therefor.

A hypodermic syringe under patient's control, for example for administering insulin, is commonly used to deliver all of its charge at each injection. This has the merit that the dose is definite and reproducible, but is inconvenient for a patient wishing to be away from home for a half day or more and requiring more than one injection during that period, because it necessitates carrying more than one charged syringe or a reservoir of the drug to be injected.

It is known to provide for multiple injections by disposing a reservoir cylinder in a casing and operating a piston stepwise by means of press-button ratchet mechanism. One such device C'XovoPen') is complicated and heavy and does not give the patient confidence because the reservoir is inside the casing and the position of the piston cannot be seen over its full stroke. Another such device ('PenJect'), as described in EP-0037696, has a #transparent barrel, but depends on a complicated mechanism. Such devices contrast with the simplicity, lightness, compactness, sensitivity and directness of present-day disposable syringes.

ACCORDING TO THE INVENTION a hypodermic syringe affording incomplete but controlled delivery of its charge comprises a barrel, a plunger, an intermediate actuator and an indicator of the quantity delivered, and is characterised in that the actuator is low-geared relative to the movement of the plunger.

The actuator can be intermediate and low-geared in virtue of a lever or inclined plane mechanism. Preferably it includes a rotary member to which external force is to be applied and the angular movement of that member is large relative to the movement of the plunger. Xost conveniently it involves a screw operating along the axis of the syringe. The screw thread could be formed on the syringe barrel, for engagement with a female thread in an end-cover member bearing on the syringe plunger head. Wore simply it is a female thread formed in an end-cover member, for engagement with a bolt bearing on the plunger head.

To limit or prevent plunger reverse movement, which would draw air into the syringe needle, the actuator preferably is forward one-way coupled to the plunger, that is, can push it forward but cannot pull it back. Thus the screw means bears on the plunger head, as already mentioned, but is not otherwise coupled to it. Alternatively or additionally the actuator includes frictional means against such reverse movement, for example mutually interfering surfaces at least one of which is made of a plastics material. Thus in the screw means male and female threads are preferably in mutual interference fit, so as to provide positive positioning.

This is more convenient than, for example, a separate locking nut. A screw of thread pitch preferably at least 1, suitably up to 2, per mm < single-start) provides both the large rotary movement and (especially if plastics) the resistance to plunger reverse movement.

The syringe includes means to position the actuator in relation to the barrel. In a first such means an actuator body is unipositional on the barrel and force is applied to the plunger by operating a movable part of the actuator, for example the rotary member.

In a second such means an actuator body or body portion occupies a track on the barrel in the direction of plunger movement and force is applied to plunger by advancing the body or body portion along the track. The low gearing and preferably also the frictional property of the actuator are effective to limit reverse movement of the plunger, just as in the first means. Using the second means, use of the syringe is more rapid at injection. The track can be cylindrical or not , and can be smooth or splined or coarsely threaded. In the bolt arrangement the end-cover fixing can be for example screw-on or snap-on or bayonet or interference-fit, chosen to suit the positioning means.

The invention provides an actuator separable from the barrel and formed with means, for example screw-on or snap-on or bayonet or interference fit, to position it in relation to a syringe barrel. The means is preferably the same as that of the end-cover that it replaces on the barrel of an existing syringe. Thus, for example, on a Becton Dickinson zMICRO- FINE IV" syringe of 0.5 or 1.0 ml capacity, interference fit is convenient. Conveniently the actuator is supplied in a kit for use interchangeably with the-protective end-cover of an available single-shot syringe The indicator preferably gives a direct indication of the quantity injected. Very suitably it is the graduations on the barrel of the syringe. These should be clearly visible, for example with alternating white and coloured divisions and/or with numbers at least 2 mm high.In an alternative or additional indicator a screw may include a pointer on a scale and/or a pawl on a ratchet-face. The position of the pointer or pawl should be visible or feelable. By simple modification the indication can be made available to a blind patient.

The drawing shows in sectional elevation a syringe according to the invention.

The syringe has barrel 10 having needle 12 and needle-cover 14. At its actuation end it has finger-plate 16 and spigot 18. Barrel 10 carries clear graduations (not shown). Plunger 20 is formed with head 22, to be pressed (if in single-shot use) by the thumb while the first and second fingers bear under finger-plate 16. Spigot 18 is in interference fit with end-cover 24, which is formed with female thread 26 in which operates nylon X4 bolt 28 having a shallowpitch thread.

(The X4 bolt has 1.5 pitches per mm in a single-start thread). End-cover 24 replaces a protective cover with which the single-shot syringe is supplied. Apart from the needle and possibly the threaded members of the actuator, the syringe and actuator are made of plastics materials as in conventional disposable syringes.

Operation of the syringe is typically as follows. Barrel 10 is filled from a reservoir with a days supply or part of a day's supply of short-acting insulin and the reservoir is returned to storage. Bolt 28 is unscrewed far enough to clear head 22 and end-cover 24 is slid over spigot 18 until it abuts the outer side of finger-plate 16. when an injection is required, for example before each meal, the needle is inserted at the body injection site and bolt 28 is turned until the required part of the charge #as shown by the graduations) has been injected. Then the needle is sterilised by dipping in industrial methylated spirit, the needle-cover 14 is replaced and the syringe put away until next needed. Bolt 28 stays in position, and thus prevents reverse movement of plunger 20 such as might permit ingress of air; this is the result of the relatively fine pitch andmutual interference fit of the male and female screw.

Suitably either or both screws is made of a sufficiently rigid plastics material, such as an engineering polymer for example nylon 66.

The syringe as shown is an example of the first means of positioning the actuator in relation to the barrel. For the second means spigot 18 is longer and forms a track on which end-cover 24, the actuator body, can advance. In operation, barrel 10 is filled as described and bolt 28 is unscrewed, but then end-cover 24 is slid only to an intermediate position along spigot 18. Preferably end-cover 24 and spigot 18 are formed each with one or more annular grooves in which lie O-rings or circlips or balls, so as to define one or more such intermediate positions. Then bolt 28 is turned until it just contacts plunger head 22. When an injection is required, end-cover 24 is advanced along (lengthened) spigot 18 until it abuts the outer side of finger-plate 16 or arrives at a defined intermediate position.

The total volume of barrel 10 is typically in the range 0.5 to 5.0 ml, in particular 0.5 or 1.0 ml as in standard sizes.

Typically the stroke of the plunger is 50 mm, corresponding to 75 revolutions of bolt 28. A typical single dose is in the range 1 to 20 units of insulin, that is, 0.01 to 0.2 ml, and the sensitivity is such that a half unit can be measured. Then a further injection is to be made, the syringe is ready for use at once or after simple adjustment, until its whole volume has been used.

Especially in away-from-base conditions this is much more convenient than charging an empty syringe, injecting all of its charge in one go. and refilling it when the next injection is required.

If desired, the threaded length of bolt 28 can be less than the total traverse of plunger 20 if the first injection is made just after filling barrel 10; then the sliding-on of end-cover 24 pushes plunger 20 in until stopped by the outer side of finger-plate 16.

The actuator can readily be made to fit standard syringes.

It can be supplied in a kit comprising actuator, syringe and also needle steriliser (such as a small container of industrial methylated spirit or other sterilant). Such a kit will normally be light in weight and easily fit into a pocket or handbag. A kit for longer term use can include a containing box having a space for one or more syringes, possibly up to 10 or more per actuator, and strong enough to protect its contents. The box can, if desired, be thermally insulated.

The invention makes convenient an insulin regime using multiple injections of only one type of insulin, preferably the fast acting type, though not limited thereto. This is distinct from the 'traditional two injections per day of a mixture of short- and mediums acting insulin. Since no single large injection is made, and since there is no risk of mistakenly using short-acting instead of longer-acting insulin, there is less risk of hypoglycaemia. It is particularly desirable for an individual to be able to judge the required dose in terms of intended exercise and food intake.

In addition to such a regime, the invention is useful in for example evaluating the diabetic state by titration against blood glucose levels. It could be particularly useful when a normally well-controlled patient has lost control, for example in illness or after injury.

Claims

1. A hypodermic syringe affording incomplete but controlled delivery of its charge comprising a barrel, a plunger, an intermediate actuator and an indicator of the quantity delivered, characterised in that the actuator is low-geared in relation to the movement of the plunger.

2. A syringe according to claim 1 in which the actuator includes a rotary member to which an external force is to be applied and the movement of that member is large in relation to the movement of the plunger.

3. A syringe according to claim 1 or claim 2 in which the actuator is forward one-way coupled to the plunger.

4. A syringe according to any one of the preceding claims in which the actuator includes frictional means against reverse movement of the plunger.

5. A syringe according to claim 4 in which the frictional means is provided by mutually interfering surfaces at least one of which is made of a plastics material.

6. A syringe according to claim 5 in which the plastics material is nylon 66.

7. A syringe according to any one of the preceding claims in which the actuator involves a screw operating along the axis of the syringe.

8. A syringe according to claim 7 having an end-cover formed with a female thread in which operates a bolt bearing on the plunger head.

9. A syringe according to claim 7 or claim 8 in which the male and female threads of the screw are in mutual interference fit.

10. A syringe according to any one of claims 7 to 9 in which the pitch of the screw thread is 1 to 2 per mm Csinglestart).

11. A syringe according to any one of the preceding claims in which the actuator body is unipositional on the barrel and force is applied to the plunger by operating a movable part of the actuator.

12. A syringe according to any one of claims 1 to 10 in which an actuator body or body portion occupies a track on the barrel in the direction of plunger movement and force is applied to plunger by advancing the body or body portion along the track.

13. A syringe according to any one of the preceding claims in which the actuator is separable from the barrel and is formed with means, for example screw-on or snapon or bayonet or interference fit, to position it in relation to the barrel.

14. A syringe according to any one of the preceding claims in which the actuator is interchangeable with the protective end-cover of a single-shot syringe barrel.

15. A syringe substantially as herein described and as shown in the foregoing drawing.

16. A syringe actuator having any one of the characteristic features set out in claims 1 to 9 and 12.

16. A kit comprising an actuator, at least one syringe barrel, said actuator and barrel(s) being adapted to constitute a syringe according to any one of the preceding claims, and needle steriliser.

AMENDED CLAIMS 1. hypodermic syringe affording incomplete but controlled delivery ol its charge comprising a barrel, a needle, a plunger including a piston, a piston rod and a plunger head), an indicator ol the quantity being delivered and an intermediate actuator which is low-geared in relation to the movement of the plunger, includes a rotary member -to which an external force is to be applied and is separable from the barrel and formed with means to position it in relation to the barrel.

2. A syringe according to claim 1 in which the actuator is forward one-way coupled to the plunger head.

3. A syringe according to claim 1 or claim 2 in which the actuator includes trictional means against reverse movement of the plunger.

4. A syringe according to claim 3 in which the frictional means is provided by mutually interiering suriaces at least one ot which is made of a plastics material.

5. A syringe according jo claim 4 in which the plastics material is nylon 66.

6. A syringe according to any one ot the preceding claims in which the actuator involves a screw operating along the axis ol the syringe.

7. A syringe according to claim 6 having an end-cover formed with a temale thread in which operates a bolt bearing on the plunger head.

8. A syringe according to claim 6 or claim 7 in which the male and tenale threads of the screw are in mutual interference fit.

9. A syringe according to any one of claims 6 to 8 in which the pitch ot the screw thread is 1 to 2 per mm (single-start).

10. A syringe according to any one of the preceding claims in which the actuator body is unipositional on the barrel and force is applied to the plunger by operating a movable part of the actuator.

11. A syringe according to any one of claims 1 to 9 in which an actuator body or body portion occupies a track on the barrel in the direction of plunger movement and force is applied to plunger by advancing the body or body portion along the track.

12. A syringe according to any one of the preceding claims in which the barrel and plunger are those of a conventional single-shot syringe and the actuator is interchangeable with the protective end-cover of the barrel.

13. syringe according to any one of the preceding claims in which the indicator is the graduations on the syringe barrel.

14. A syringe substantially as herein described and as shown in -the toregoing drawing.

15. A kit comprising an actuator, at least one syringe barrel and plunger and a container of needle steriliser, said actuator and bal-relEs) being adapted to constitute a syringe according to any one of the preceding claims.