Pumps – Motor driven – Magnetostrictive chamber
Patent
1988-11-22
1990-07-31
Smith, Leonard E.
Pumps
Motor driven
Magnetostrictive chamber
310 26, 604151, A61M 100, F04B 1700
Patent
active
049446592
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to pumps of a small size particularly though not exclusively implantable pumps which are sufficiently small for use within the human body.
Pumps of small dimensions are used in implantable drug dispensing divices where a medicament is to be dispensed to an ambulatory patient on a regular or intermittent basis over an extended period of time, as where insulin is dispensed in the treatment of diabetes, or where chemotherapeutic drugs are dispersed in the treatment of cancer. In these circumstances it is advantageous in the treatment with the drug to perform an automatic dispensation of the drug without having to rely upon pills or injections. Thus a unit is implated within the patient comprising a reservoir of the drug and a pump, the pump being under control of a control circuit which may be coupled by an electromagnetic transmitter and receiver to an external control source.
Such a device for delivering the drug must be reliable in operation, sealed against body fluids and must hold a sufficient quantity of medication so as to avoid the need for frequent refills and must be refillable when empty. Furthermore, such dispensing systems must be physically small so as to be readily implatable without unnecessary disturbance of the body.
It is known to employ in such dispensing devices pumps such as the peristaltic type or solenoid type. Peristaltic pumps operate by responding to blood pressure within the body and solenoid pumps operate under control of an internal battery connected to a solenoid for operating a suitable pump mechanism. However such pumps are relatively large, and considering their size, are inefficient within the context of implantable units.
SUMMARY OF THE INVENTION
The present invention is based on the concept of a pump which incorporates a mechanism which is actuated by means or a piezoelectric element. Such a pump can be made of a very small size and is therefore suitable for use in an implatable drug delivery system. However, such a pump may be of use in whatever application where the requirement is for a pump of very small size.
The present invention therefore provides in general terms a pump comprising a source of electric power connected to means for cyclically applying electrical voltage to a piezoelectric element for inducing periodic changes in dimension in the piezoelectric element, the piezoelectric element, being physically contiguous with and directly coupled to a movable pump element whereby changes in dimension of the the piezoelectric element induce pumping movement into the movable pump member.
Thus, since all that is required to provide the pump motive power is a piezoelectric element and a source of electrical power, such as for example a battery, and since the piezoelectric element is contiguous with and directly coupled with the movable pump element with no intervening shaft or push rod, the piezoelectric pump may be made very small in dimensions.
The electrical power supplied to the piezoelectric element from the battery may be in pulsed d.c. form or alternatively and as preferred for efficiency it may be AC, with a suitable inverter circuit being provided.
The movable pump member may be of any suitable type, rotatable or displaceable, and the piezoelectric element may be coupled to the pump member in such a way as to induce the required type of movement. In a preferred embodiment, the movable pump member comprises a flexible membrane, movement of which increases or decreases the size of the pump chamber, which is coupled to a drug reservoir and an outlet port by suitable one way valves. Thus a decrease in volume of the pump chamber causes a drug within the pump chamber to be expelled through the valve of the outlet port, the valve at the inlet port remaining closed, whereas when the volume of the pump chamber is increased by movement of the membrane, the one way valve at the outlet port is closed whereas the one way valve at the inlet port is opened to permit further drug to be introduced into the pump chamber. As p
REFERENCES:
patent: 4360019 (1982-11-01), Portner et al.
patent: 4487603 (1984-12-01), Harris
patent: 4496343 (1985-01-01), Prosl et al.
patent: 4596575 (1986-06-01), Rosenberg et al.
patent: 4604090 (1986-08-01), Reinicke
patent: 4619653 (1986-10-01), Fischell
Spencer, W. J. et al., "An Electronically Controlled Piezoelectric Insulin Pump and Valves", May 1978, IEEE Transactions on Sonics and Ultiasonics, vol. SU-25, No. 3, pp. 153-156.
Cox Robert E. L.
Damhuis Eduard H. J.
Labbe Jean-Marie
Kabivitrum AB
Scheuermann David W.
Smith Leonard E.
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