ELECTRICAL FEMALE CONNECTOR, ESPECIALLY FOR AN IMPLANTABLE HEART STIMULATOR

Abstract: The invention relates to an electrical female connector for affixing a contact pin on an electrode cable in a connector part (14) of a heart stimulator (10). The female connector comprises a sleeve means (20) which is elastic and has a curved shape in the relaxed state, the sleeve means being arranged to be straightened out into an essentially straight conformation when the contact pin is inserted into it and thereupon rebound back to a partially curved conformation so as to clamp the contact pin inside the sleeve means (20).

Description: Electrical female connector, especially for an implantable heart stimulator Field of the invention The present invention relates to an electrical female connector, especially for establishing contact with a contact pin on the proximal end of an electrode cable which is connectable to an implantable heart stimulator, such as a pacemaker or defibrillator, whereby the female connector has an electrically conductive sleeve means, arranged in a connector part of the heart stimulator. The prior art A commonly found connector for this purpose in the general form includes a metal sleeve in which the electrode cable's contact pin is inserted and affixed with a locking screw accessible from the outside of the connector part. The locking screw achieves contact between the sleeve and the pin and simultaneous axial locking of the electrode cable, thereby preventing detachment of the electrode cable from the connector part. This fixation method requires the use of screwdrivers, tiny mechanical screws and special seals for same. Connectors for the said application have also been proposed which are capable of achieving automatic contact between the contact pin and the female connector when the electrode contact pin is inserted into the connector. For example, US-A-4 934 366 and 5 012 807 describe such female connectors which are formed from a torus-shaped spring means which radially presses against a corresponding contact surface on the pin when the pin is inserted, thereby achieving mechanical contact on all sides between the male contact pin on the electrode and the female connector built into the heart stimulator's connector part. Contact points are sealed with separate seals devised on the exterior of the contact pin end of the electrode cable and/or on the inside the connector. EP-A2-0 339 877 shows a connector for a pacemaker, said connector comprising electrically conductive elastomer rings which permit both a positive mechanical connection and, accordingly, electrical contact between contact surfaces and simultaneous sealing to keep fluid from reaching the contact pin. These contact rings do not have any well-defined contact and sealing surfaces, so the electrically conductive elastic rings must be supplemented with separate sealing rings in order to achieve efficient sealing of contact surfaces. US-A-4 848 346 describes a connector for a pacemaker in which the contact means consists of a spring ring which can be expanded by depressing a shaft section, projecting from the connector part, of the spring means, in order to permit the insertion of an electrode cable's contact pin. However, such projecting operating means can cause inadvertent detachment of the electrode cable. Another way of affixing an electrode cable pin in the connector part of a heart stimulator is described in EP-A2-0 590 756. Here, the fixation device consists of a spring plate, molded into the connector, with opposing, resilient gripping tongues designed to grip the cable's contact pin while simultaneously preventing any detachment of the electrode cable from the connector means, the retention force of the clamp thereby increasing when an detachment force is exerted on the electrode cable. The grip of the gripping tongues on the cable end's contact pin could cease if pressure were exerted on the spring plate's opposing, projecting lateral tips. Summary of the invention One object of the present invention is to propose a female connector of the kind cited initially with which a contact pin can be quickly affixed to the connector part with a simple manual operation. For this purpose, the female connector according to the invention is characterized by an elastic sleeve means which has a curved shape in the relaxed state, the sleeve means being arranged so it can be made to assume an essentially straight conformation to permit insertion of the contact pin into the sleeve means. When the contact pin has been inserted into the sleeve means, after the sleeve has been straightened into an essentially straight conformation, which can be accomplished with an external aid in the form of a detachable push means or with the aid of the contact pin itself, the elastic sleeve means strives to resume its original curved shape. This then clamps the contact pin inside the sleeve means as a result of the friction forces between them. In straightening out the sleeve means, the pressure means is arranged to be inserted into a hole, essentially perpendicular to the longitudinal axis of the sleeve means, in the connector part. The pressure means suitably has a shaft part, insertable in the hole, and an external push-button. The sleeve means, which is preferably made of a superelastic alloy of nickel and titanium, such as nitinol, capable of elastically stretching up to about 10%, is suitably embedded in some elastic substance, such as silicone, so the contact sleeve can be elastically suspended in and sealed against the entry of body fluid. In order to achieve positive locking of the contact pin in the sleeve means, an inward-projecting locking pin can be arranged inside the sleeve means so as to engage a circular slot in the contact pin. Description of the drawings The attached drawings show the following: FIG. 1 is a schematic side view of a pacemaker with a unipolar female connector according to the invention, shown with unbroken lines in a pre-tensioned, straightened position and with dashed lines in a relaxed, unloaded, curved state; FIG. 2 is an enlargement (not to scale) of the sleeve-shaped connector in the relaxed, curved state; FIG. 3 shows the sleeve means in FIG. 2 straightened out with an external pressure means to permit insertion of a proximal electrode cable pin into the sleeve means; and FIG. 4 show an active fixation conformation in which the contact pin is kept affixed inside the sleeve means. Preferred embodiment In FIG. 1, a pacemaker, which has an enclosure 12 containing an electronics unit and battery (not shown) , plus a molded-on superstructure or connector part 14 to hold a female connector 16 for connecting the proximal end contact pin 18 (FIGS. 3 and 4) of a conductive electrode cable (not shown) leading to the heart. The female connector 16 according to the invention comprises a sleeve means 20 made of an elastic alloy, preferably a superelastic alloy of e.g. nickel and titanium, such as nitinol, which can be elastically stretched up to about 10%, as opposed to about 0.2% for other alloys. As is best shown in FIG. 2, the sleeve means 20 has a precurved shape in the relaxed, unloaded state and is inside a compartment 22 in the connector part 14, surrounded by a sealing substance 24 made of e.g. silicone (FIG. 1) . In one practical embodiment, the contact pin 18, which is tubular to permit insertion of a stylet, can be about 5.6 mm long and about 1.5 mm in diameter. The sleeve means 20 can have an internal diameter of about 2.0 mm and a wall thickness of about 0.4 mm. The connector part 14 has a hole 26 which opens into the compartment 22 and is essentially perpendicular to the sleeve means 20 opposite the latter's midsection. The hole 26 is a guide hole for a push means 28, insertable therein, which has a shaft section 30, moveable in the hole 26, and a push-button 32. The task of the push means 28, when pressure is manually applied to it in the direction of the arrow A in FIGS. 1 and 3, is to force the curved sleeve means 20 to assume an essentially straight, pre-tensioned conformation, enabling the contact pin 18 on the proximal end of the electrode cable to be inserted into the contact sleeve 20 through an entry hole 34 in the connector section 14. The sleeve 20 is guided on its longitudinal sides by the nearby walls of the compartment 22 to keep the sleeve means 20 from veering during its straightening and can rest on the abutment 21 at the bottom of the compartment 22. FIG. 3 shows in an enlarged view, not to scale, the phase in which the contact pin 18 has just been inserted into the sleeve 20. The inside of the sleeve can have a projecting locking pin intended to engage a corresponding groove or track 38 in the contact pin 18 when perpendicular pressure on the sleeve 20 has terminated, the sleeve thereupon striving to resume its original curved shape in order to clamp the pin 18 in the sleeve 20 and create good electrical contact between them. The locking pin 36 can project about 0.3 mm from the interior wall of the sleeve means 20, and the groove 38 can be about 0.2 mm deep. FIG. 4 depicts the fixation position between the sleeve and the pin, showing how the sleeve 20 has partially rebounded back to its curved conformation and is clamping the contact pin 18 at the points designated with the arrows F. Here, the locking pin 36 has engaged the groove 38 in order to on one hand achieve blocking which prevents axial detachment of the contact pin from the sleeve 20, and on the other hand improve contact between the sleeve and the pin. Appropriate stop means (not shown) can be arranged in the sleeve and/or the contact pin 18 to limit insertion of the pin to a position at which the locking pin 36 is opposite the groove 38. According to an alternative embodiment of the invention, the push means 28 can be excluded and the sleeve 20 can be devised to be straightened out by the contact pin 18 when the latter is inserted into the sleeve. The pin should then be kept in an axially fixed position in relation to the compartment 22. Even if the above-described embodiment of the female connector according to the invention is a unipolar design, the principle can also be applied to bipolar or multipolar contact pins through the provision of a plurality of elastic, precurved contact sleeves.

Claims: Patent claims 1. An electrical female connector, especially for establishing contact with a contact pin (18) on the proximal end of an electrode cable, connectable to an implantable heart stimulator (10) , such as a pacemaker or defibrillator, the female connector (16) comprising an electrically conductive sleeve means (20) , arranged in a connector part (14) , characterized in that the sleeve means (20) is elastic and has a curved shape in the relaxed state, and the sleeve means (20) is arranged to be capable of straightening out into an essentially straight conformation to permit insertion of the contact pin (18) into the sleeve means (20) . 2. A female connector according to claim 1, characterized in that a hole (26) , essentially perpendicular to the longitudinal axis of the sleeve means (20) , is arranged for introduction of a push means (28) designed to exert perpendicular pressure (A) on the sleeve means (20) . 3. A female connector according to claim 2, characterized in that the push means (28) has a shaft part (30) , insertable in the hole (26) , and an external push-button part (32) . 4. A female conductor according to claim 1, characterized in that the sleeve means is arranged to be straightened out by the contact pin when the latter is inserted into the sleeve means. 5. A female connector according to claims 1-4, characterized in that the sleeve means (20) is embedded at least in part in an elastic substance (24) made of e.g. silicone. 6. A female connector according to any of claims 1-5, characterized in that the sleeve means (20) is made of a superelastic alloy, e.g. of nickel and titanium, such as nitinol. 7. A female connector according to any of claims 1-6, characterized in that the sleeve means (20) has an inward-projecting locking pin (36) designed to engage a periphual groove (38) on the contact pin (18) .

Inventors: LINDEGREN ULF, LINDEGREN, ULF
Applicants: LINDEGREN ULF, PACESETTER AB, LINDEGREN, ULF
Application year: 1997
Main classification: A61N1
IPC codes: A61N1