Cable Fastener For Electrocardiograph Electrodes

Abstract

A cable fastener provides an electrically conducting mechanical connection between a standard male snap fastener commonly used as an electrocardiograph electrode and a cable. The male snap fastener is positively held in contact with the cable fastener by a spring.

Description

BACKGROUND OF THE INVENTION

In patient monitoring applications, several different types of cable fasteners have been used to couple electrical impulses from an electrode on a patient's body to a cable connected to an electrocardiograph or other monitoring device. Many of these electrodes, either glued or taped to the patient's body, use a standard male snap fastener. Traditionally the female portion of the snap fastener was intended to mechanically couple to the male portion. The resulting electrical connection, however, is not noise-free and fatigues easily, causing loose connections. Additionally, since it is connected by pressing downward on the patient, a painfully hard push is often necessary to make a good connection. This type of snap fastener though simple and inexpensive to produce is difficult to repair.

Some departures have been made from the above described snap. One example is a hairpin and turn-cam fastener. This type of fastener makes a good electrical connection when new and allows simple application without pressing upon sensitive areas of the patient. The joint between cable and fastener is by a tubular solderless connector which is crimped on the fastener and the cable, and then covered with shrink tubing. Unfortunately the fastener is expensive to make. It offers very little strain relief, and physically fatigues early in life thereby causing loose connections. The electrical contact surface is only four pin point surfaces, which wear away very quickly. The length of the connector provides leverage which, when lifting the cable, often pries the connector off the snap. Because shielded wire cables work best when the exposed metallic fastenings are as small as possible, the length of this type of fastener is much too great to enhance the benefits of shielded cable. Also, whenever a patient rolls upon this type of fastener, he will likely receive a discomforting jab from its end, or cause the fastener to come off the electrode.

SUMMARY OF THE INVENTION

Accordingly it is an objective of this invention to provide a cable fastener which engages male snap fasteners of several manufacturers and slight size variations. The illustrated embodiment of the cable fastener of this invention includes a metal bracket and a spring wire joined together. The metal bracket has a clearance hole which fits over all of the male snaps which are expected to be encountered and has an offset to allow connections to cup-mounted snaps. The spring wire provides mechanical retention, and by holding the bracket in contact with the snap, a durable electrical connection. A partial loop on the spring wire forms a finger pad for engaging and disengaging the fastener from the snap.

The cable fastener mates with the male snap of an electrocardiograph electrode, for example, as it is mounted on a flat surface or seated in a cup depression. The fastener provides a good electrical connection throughout its full life and is small to allow shielding of the cable right up to the skin connection with the patient. It provides axial strain relief for the wire connection, and torsional strain relief of the cable jacket from any molded shell or handle. It is easily applied with one hand without pressing upon patient, and causes no discomfort when the patient rolls upon it. When a sharp yank is applied to the cable, the cable fastener comes off the electrode, rather than the electrode adhesive parting from the skin. Re-application of the cable is faster and safer for patient monitoring than re-application of the electrode. The fastener is able to swivel about the snap while maintaining good electrical and mechanical connections. The fastener is also simple and inexpensive to manufacture.

DESCRIPTION OF THE DRAWING

FIG. 1 is a top view of the preferred embodiment of a cable fastener for electrocardiograph electrodes.

FIG. 2 is a side view of the preferred embodiment.

FIG. 3 is a perspective view of the preferred embodiment showing a connection to a male snap.

FIG. 4 is a perspective view of the preferred embodiment showing a connection to a male snap in a cup shaped depression.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1 and 2 there is shown the preferred embodiment of a cable-to-snap fastener.

The fastener 10 consists of a metal bracket 11 and a spring wire 20 joined together to make one assembly. The metal bracket 11 has a clearance slot 12 which fits over all of the male snaps expected to be encountered and has coupling region connected to a connective region forming a Z-offset 13 to allow connections to cup-mounted snaps.

Referring to FIG. 1 and the pyriform opening shown, the clearance slot 12 has two converging sides which fit around the small diameter of the snap fastener.

Two tabs 14 are provided on the bracket 11 which can be crimped around the lead to provide axial strain relief. The spring wire 20 provides mechanical retention, and by holding the edge of the clearance slot 12 against the electrode snap, provides good electrical connection regardless of cable orientation around snap. A partial loop 21 on the end of the spring wire form serves as a finger pad for right index finger operation to engage or disengage the fastener 10 from the snap. This assembly is intended as both a unit for field repair, to be covered with only shrink tubing after crimp and soldering to lead; and as connector to be factory molded with a plastic handle over the wire-bracket joint. The application of the entire assembly involves grasping the fastener 10 between right thumb and right middle finger, while squeezing the spring 20 with the right index finger toward the tabs 14 enough to set the slot 12 over the snap. The spring 20 is then released to secure the connection. The fastener is removed in a similar manner. The spring wire 20 is attached to the bracket 11 on the underside. It passes above the slot 12 close to the surface of the bracket 11, and is disposed as a terminating portion beneath the bracket 11 and on the opposite side of the connective region of the offset 13 from the clearance slot 12 as shown in FIGS. 1 and 2 so it is protected against damage.

Claims

We claim:

1. A cable fastener for coupling a cable to an electrode for attachment to a patient comprising:

a bracket having a generally planar handle region, a generally planar coupling region and a generally planar connective region;

the coupling region including a clearance slot having a first portion which is wider than a second portion;

the connective region being of predetermined length and having two ends, connected at one end to the coupling region and at another end to the handle region, said handle and coupling regions being essentially parallel and separated by said predetermined length; and

spring wire means comprising:

a. a base portion connected to the handle region,

b. a coil portion connected to the base portion for providing bias force,

c. a straight portion connected to the coil portion and situated entirely between planes defined by the handle region and the coupling region, the straight portion intersecting and disposed across said clearance slot in close proximity to the surface of the coupling region,

d. a partial loop portion connected to the straight portion, the plane of the loop portion being approximately perpendicular to the plane of the coupling region, and

e. a terminating portion, one end of which is connected to the partial loop portion, the other end of which is disposed between the handle region and the coupling region, and on the opposite side of the connective region from the clearance slot.

2. A cable fastener as in claim 1 wherein the bracket includes two bendable tabs for coupling a cable to the cable fastener.

3. A cable fastener as in claim 1 wherein the clearance slot is of a pyriform shape.