Title:  Injection device with electronic presentation of set doses

United States Patent:  6,277,098

Assignee:  Novo Nordisk A/S (Bagsvaerd, DK)

Filed:  December 8, 1997

PCT NO:  PCT/DK97/00093

102(e) Date:  December 8, 1997

PCT PUB. Date:  September 18, 1997

Foreign Application Priority Data:  Mar 12, 1996[DK] (0285/96);  Nov 11, 1996[DK] (1264/96);

An injection device has signal generators (11, 12, 13, 14) which are connected to operative elements (8, 3, 5, 4) of the device and which give off signals which represents the operative condition of the device. The signals are sent to an electronic circuit which controls a presentation of the operational condition of the device and presents operational conditions, which are defined as not allowed, as error indications by switching off the display presenting the operational condition of the device. The number of signals from each generator is counted and a number of operations exceeding a pre-set number for the signal generator in question is interpreted as representing a not allowed operational condition.

Description of the Invention

The invention relates to injection devices for the injection of set doses of a medicine, the operational condition of the device being electronically presented by a circuit which receives a pattern of input signals from signal generators connected to the operative elements of the device.

Such an injection device may have the shape of a device comprising a dose setting wheel and an injection button and a protective cap covering at least a needle receiving part of the device and possibly the dose setting wheel. The electronic presentation usually has the shape of a electronic display, but also a speech circuit may be used which in speech summarize the condition of the device. Also an electro-mechanical device presenting a tactile resume may be imagined.

The generators connected to the operative elements of the device may be switches switching on and off a current or they may be active current generators. Generators of the switch type may be connected to the protective cap or the injection push button to indicate one of two alternative positions, i.e. the cap on or the cap off, or the push button projecting or pressed home.

A generator of an active type which itself produces a current when activated may be connected to the dose setting wheel to provide current signals reflecting the turning of this wheel, e.g. a pulse per unit set by turning the wheel and the pulse having a polarity indicating whether the dose setting is increased or decreased by turning of the wheel. The dose setting signals may also be provided by operating a number of switches.

The use of electronic presentation of the device parameters makes it possible to use a display with large digits as opposed to mechanical displays by which the movements of the dose setting wheel and a plunger operating a piston in an ampoule with the medicine to be injected set narrow limits on the size of the displayed digits.

The electronic presentation depends on electric switches and generators which may, e.g. due to wear, fail without warning and cause a false electric signal and consequently a false displaying. But, mechanical wear may or may not reveal itself.

Consequently it is an object of the invention to provide a device by which unreliable electrical or mechanical components are detected before they cause a wrong dosing of the medicine injected by the device.

This may be obtained by a device as the one described in the opening paragraph of this specification, which device is characterized in that it comprises a circuit which receives input signals from signal generators connected to operative elements of the device and gives off a signal which represents the operational condition of the device and controls a presentation of said operational condition.

According to the invention operational conditions which are defined as not allowed may be presented as an error indication. Further according to the invention at least one of the signal generators may be an active generator generating electric signals.

According to an embodiment of the invention the circuit may comprise a storage in which is stored the signal patterns for all allowed conditions of the device, the signals from the signal generators are frequently compared with the stored signal patterns, and if the signal pattern is not found among the allowed patterns an error indication is made.

An error may be indicated by switching off the presentation of the operational condition of the device.

The allowed signal patterns are such patterns which occur during normal not faulty use of the device. Say that the device has a dose setting wheel which is covered by the protective cap when this cap is mounted on the device. In that case a pattern of signals comprising a signal indicating that the cap is on and another signal indicating that the dose setting wheel is operated will not be allowed as the dose setting wheel may not be operated when it is covered by the cap as this represent an obvious logical discrepancy. If locks are provided by which it is intended to exclude concomitant operation of two of the elements of the syringe, then signals indicating that these two elements are nevertheless operated concomitantly will cause an indication of error.

In an embodiment of the device according to the invention the circuit may be designed to count the number of signals send from each of the signal generators, to compare these numbers with set values stored in the circuit, and to give off a signal when one of the numbers exceed the set value for the signal generator in question, which signal provokes an error indication. By this feature it may be ensured that the device is only used for a number of operations and that the device is replaced by a new one before dysfunction due to wear becomes probable.

If a switch is worn to an extent which makes its stability questionable this will be manifested by the fact that the switch appears as off when it should be on or vice versa which soon will lead to a not allowed signal pattern. When this pattern is detected as not being among the allowed patterns the circuit will turn off the electronic presentation of parameters and the device is made not useable.

As a not allowed signal pattern may be induced by an event which is not related to the condition of the device, e.g. a transient electromagnetic field caused by any electric apparatus in the vicinity, the circuit may, when it turns off the electronic presentation, be reset to allow this presentation again. If the turning off of the electronic presentation is due to an event outside the device, the device will be usable again after the resetting but if the not allowed signal pattern was caused by a failing switch, this switch will soon fail again and turn off the electronic presentation.

Another check of the function may be obtained by summing up the number of doses injected since the ampoule was changed. If the accumulated dose exceeds the total content in a new ampoule an error is reported, e.g. by turning off the electronic presentation.

Recognizing that the switches and generators have a greatly enhanced probability of failing when they have been used a number of times the circuit may be designed to count the number of signals sent from each of the signal generators, to compare these numbers with set values stored in the circuit, and to give off a signal when one of the numbers exceed the set value for the signal generator in question, which signal forms a part of the signal pattern representing the condition of the device and makes this a not allowed pattern. Consequently it causes the device to be disabled when the counts for one of the signal generators reach the number set for that generator.

As the disabling of the device on the basis of the counting of signals from the signal generators is predictable, a warning may be presented to the user when one of the generators has produced a number of signals near the set number for this generator. In this way the user may avoid the inconvenience of a suddenly failing device.

To further avoid sudden failing of the device, the battery condition is currently monitored and a low battery is indicated some time before the battery is totally exhausted.

The failing of the switches and generators may not be foreseen and will cause a sudden disabling of the device. For emergency the circuit may then be reset and the device may be used a few times more unless the switches have become so unstable that the device is at once disabled again.

Claim 1 of 17 Claims

What is claimed is:

1. An injection device comprising:

a plurality of operative elements for setting and injecting of set doses of medicine;

signal generators connected to at least two of said operative elements to generate output signals representing operating conditions of said at least two operative elements, wherein the operating conditions indicated by such output signals individually are not indicative of whether an error state exists; and

an electronic circuit coupled to said signal generators for receiving said output signals and for determining whether the combination of said output signals indicates an error state for said device.

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