The invention relates to an automatically-closing connector for connecting a liquid injection head to an injection outlet.
The connector is suitable in particular for medical use and more particularly for connecting an injection head and a catheter tube or other duct of a liquid pathway to enable liquid to be inserted into the body.
Automatically-closing connectors are known that comprise a case which defines a housing which is accessible via an injection inlet duct opening out into the housing through an end wall of the housing, said chamber communicating with an injection outlet, and the inlet duct being designed to enable the injection head to be inserted with lateral sealing into said duct towards the housing, and the connector including a closing piston which is movable in the housing and in the inlet duct between an upstream position in which it closes the duct and towards which it is urged by resilient return means, and a downstream position in which it no longer closes the duct and towards which it is pushed by the injection head when the injection head is inserted into the inlet passage.
An example of such a connector is described in European patent EP 0 544 581 and the corresponding U.S. Pat. No. 5,380,306.
Withdrawing the injection head after an injection operation can cause the patient""s blood to flow back into the liquid pathway which connects the connector to the patient, thus running the risk of said pathway subsequently being blocked by coagulated blood.
To avoid this back flow, it is known to provide the connector with a compression chamber that is accessible to the liquid injected by the injection head and which communicates with the outlet of the connector, said chamber being designed so that its volume varies under the effect of the displacement of the closing piston so that withdrawing the injection head causes the volume of the chamber to be reduced and excess liquid to be expelled from the chamber towards the outlet, thereby establishing pressure that opposes the back flow of blood in the pathway leading to the patient.
Publication WO 98/17192 describes an example of a connector implementing that concept.
In that example, the compression chamber is constituted inside the closing piston which is complex in structure.
An object of the invention is to provide a connector which has a compression chamber while remaining simple in structure.
According to the invention, this is achieved by a connector which comprises a case which defines a housing which is accessible via an injection inlet duct opening out into the housing through an end wall (4) of the housing, said housing communicating with an injection outlet of the connector, and the inlet duct being designed to enable the injection head to be inserted with lateral sealing into said duct towards the housing, the connector including a rigid and non-deformable closing piston which is movable in the housing and in the inlet duct between an upstream position in which it closes the duct and towards which it is urged by resilient return means, and a downstream position in which it no longer closes the duct and towards which it is pushed by the injection head when the head is inserted into the inlet passage, the connector having a compression chamber accessible to the liquid injected by the injection head and which communicates with the outlet of the connector, the volume of said chamber varying under the effect of the displacement of the closing piston so that withdrawing the injection head causes the volume of the chamber to be reduced and excess liquid in the chamber to be expelled towards the injection outlet, wherein the closing piston is rigid and non-deformable, wherein said compression chamber is a space constituted in the housing around the closing piston and defined upstream by said end wall of the housing and downstream by a peripheral sealing gasket (referred to as the xe2x80x9cdownstreamxe2x80x9d gasket) carried by the piston, wherein the outlet of the connector is situated downstream from said gasket, and wherein the closing piston has an internal passage which presents an inlet that opens out into said space and which presents an outlet which communicates with the outlet of the connector.
The terms xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d relate here to the travel direction of the fluid going from the injection head towards the outlet of the connector.
Advantageously, the portion of the piston that moves in the inlet duct carries a peripheral sealing gasket (referred to as the xe2x80x9cupstreamxe2x80x9d gasket) which provides sealing for the duct around the piston.
Preferably, the closing piston has a proximal portion on which both the upstream and downstream sealing gaskets are fitted, and a distal portion of tubular shape that is directed downstream.
These two portions can be made together or they can be fitted one to the other. They are advantageously molded out of synthetic resin.
Such a piston structure is remarkably simple.
In a preferred embodiment, the distal tubular portion has the internal passage of the piston passing longitudinally therethrough.
The outlet of the connector can be constituted, for example, by a catheter tube or other liquid duct permanently fixed to the connector, or else via an outlet coupling formed on the connector and which enables a catheter or other liquid duct to be coupled thereto.
Advantageously, the connector has a fixed gasket placed in the housing around the piston upstream from the outlet of the internal passage of the piston and downstream from the downstream gasket of the piston so as to define a sealed space around the piston between these two gaskets, into which space the injection liquid cannot penetrate and in which it is possible to place a spring which returns the piston upstream.
In a particular embodiment, the fixed gasket is a part disposed so as to cover the distal end of the piston with lateral sealing of the piston, said gasket having a resiliently-opening slot such that the gasket allows the piston to pass therethrough when the piston is pushed downstream by the injection head.