Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Patent
1995-06-07
1998-04-28
McDermott, Corrine M.
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
604207, 604218, 604224, A61M 500
Patent
active
057438897
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an incrementing mechanism arranged to advance an elongate element through a pre-set distance on each cycle of operation of the mechanism. The invention in particular--but not exclusively--relates to such a mechanism adapted for use in conjunction with a hypodermic syringe, in order to assist the accurate dispensing of a predetermined dose of a medicament each time the syringe is used.
2. Description of the Prior Art
There have been many proposals for mechanisms intended for use with a hypodermic syringe, in order to ensure that an accurately metered dose is dispensed from the syringe. It is further known to provide a mechanism which allows the repeated dispensing of accurately metered, but perhaps individually variable, doses from a charged syringe. Such a mechanism is frequently used by persons who have to receive drugs or medicaments by injection on a frequent and on-going basis. For example, a diabetic may require a dose of insulin to be given by injection two or three times a day in order to maintain the blood-sugar level within an acceptable range, and a mechanism as has been described above conveniently is used with a hypodermic syringe to perform self-injection of the required dose of insulin.
In DE-A-3725210 there is disclosed a device for dispensing doses from a syringe, but the volume dispensed cannot be altered. Friction provided by an O-ring prevents a thrust rod from returning each time the mechanism is to be reset to dispense another dose, but when a spent cartridge of medicament is to be changed for a fresh cartridge, the thrust rod has to be pushed back against the friction provided by the O-ring. This mechanism lacks certainty in its operation, and if the O-ring is to provide sufficient friction to hold the thrust rod against movement during normal resetting, very considerable force will be needed to move the rod at the time of cartridge changing. Also, the O-ring can be expected to wear rapidly, so giving unreliable operation.
The known mechanisms intended for use with hypodermic syringes, to allow repeated dispensing of accurately-metered doses, tend to be somewhat complex and so are relatively expensive to manufacture. There is moreover a requirement to reduce the physical size of the mechanism as much as possible to make it convenient to carry and use as and when required, but this can reduce the reliability or the life of the mechanism. There is also a demand that such mechanisms should be simple and easy to use, in order to minimise the likelihood of erroneous operation.
SUMMARY OF THE INVENTION
It is a principal aim of the present invention to provide an incrementing mechanism suitable for use, for example, with a hypodermic syringe in order to assist the dispensing of accurately-metered doses of a drug or medicament from that syringe.
According to one aspect of the present invention, there is provided an incrementing mechanism to advance an elongate element in one direction relative to an outer tubular body within which the element is mounted, which mechanism comprises, in addition to said element and said body, a driving member slidably mounted on the body and arranged for relative turning movement with respect to the element, an end stop to limit sliding movement of the driving member in one direction, control means selectively to control movement of the driving member in the other direction dependent upon the required incremental movement of said element, automatic one-way clutch means disposed between the driving member and the element and arranged to permit relative sliding movement between the driving member and the element when the driving member is moved in said other direction but connecting the member to the element for simultaneous movement when the member is moved in said one direction, and means resisting movement of the element in said other direction, the one-way clutch means being disengaged upon relative turning movement of the driving member and element.
It will be appreciated that
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McDermott Corrine M.
Rodriguez Cris L.
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