Electrode friction chuck

A friction chuck for securing a test probe within a platform holder. The chuck, formed of elastomeric material, comprises a chuck body with an axially extending bore and a plurality of downward extending fingers disposed around the outer circumference of the projection of the chuck bore. Each finger has an interior bulge that extends into the projection of the chuck bore. The bulges define a segmented aperture of a diameter less than the diameter of the chuck base. When a test probe is inserted into the chuck bore it engages the fingers and bends them outwardly. There is sufficient friction between the fingers and the test probe so that the probe is secured by the fingers. The fingers have sufficient flexibility so the probe position may be changed by hand adjustment.

FIELD OF THE INVENTION 
This invention relates to a friction chuck for holding a test electrode and 
particularly to a friction chuck having fingers that can secure the 
electrode at any position along the length of the electrode, and can 
secure electrodes of varying diameter. 
BACKGROUND OF THE INVENTION 
Electrode holder assemblies are often seen in chemical laboratories and 
other locations where it is necessary to perform either qualitative or 
quantitative analyses on various sample solutions or substances. The 
assemblies are used to support one or more test probes or electrodes that 
are immersed in a sample of a substance in order to obtain a desired 
analytic test parameter from the substance. An example of such probes is a 
pH meter test electrode that is used to find the H+ ion concentration of a 
sample. 
A probe holder assembly usually has a probe holder platform or bracket 
through which the electrode is inserted so to bring it into contact with 
the test samples. Typically, the platform has a mounting bore, or slot, 
through which the electrode is inserted. The electrode is held in the 
mounting bore by cap on the probe that has a diameter larger than the 
bore, or by a thumb-screw clamp that extends into the bore to fasten the 
electrode. Alternatively, the tip of the electrode rests on the bottom of 
the container for the test sample, in which case the platform provides 
only lateral support for the probe. 
Each of these arrangements has disadvantages. For example, electrodes 
having caps that rest on the top of the holder platform are not 
height-adjustable. Thus, if electrodes of different heights are 
simultaneously used with the same supporting platform the sensor elements 
of the probe will be at different vertical positions. Thus one probe may 
rest on the bottom of the sample container, while the tip of another probe 
may be above the top of the sample. 
Thumb screw mechanisms permit height adjustment of the probes relative to 
the platforms. However, they pose a breakage problem when delicate probes 
are used. 
There are also disadvantages to having the bottom tip of the electrode rest 
in the sample container. For example, it would interface with the 
operation of a magnetic stirring bar in the bottom of the container. Most 
importantly, in many test electrodes the actual sensor element or membrane 
is located at the bottom tip of the electrode, and having that tip in 
contact with the bottom of the sample container will interfere with proper 
functioning of the electrode. 
A need therefore exists for a new improved retainer for supporting a probe 
on a probe holder platform so that the probe can be supported in any 
desired position relative to the platform. The retainer should also 
accommodate electrodes of varied diameter, and can be easily used without 
posing a probe breakage problem. 
SUMMARY OF THE INVENTION 
The invention comprises a friction chuck composed of an elastomeric, 
non-conducting material, such as polyurethane, that is inserted into the 
mounting bore of the electrode holder platform. The chuck body is provided 
with a bore through which an electrode probe is inserted. Extending 
downward from the chuck body, beneath the electrode platform, are a 
plurality of fingers that extend downward and inward. The top and bottom 
ends of the chuck are provided with circular flanges so the chuck can be 
snap fitted into the electrode holder platform mounting bore. 
The lower ends of the fingers define a circle of a smaller diameter than 
the diameter of any probe to be accommodated by the platform. Owing to the 
elasticity of the the chuck material, when an electrode is inserted into 
the chuck, the fingers bend outward and thus exert an inward force on the 
probe. The resulting friction force between the fingers and the probe is 
then sufficient to securely hold the electrode at any desired position 
along the length of the electrode, yet it permits easy hand adjustment of 
probe positions. 
Also, it will be apparent that this arrangement allows a chuck to retain 
probes of differing diameters, so that probes can be readily interchanged 
for different tests.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown in FIG. 1, a probe friction chuck 10 of this invention is composed 
of elastomeric material. The chuck 10, has a tubular body 12 that is 
disposed in a bore 40 of a probe platform holder 38. A probe 46, extending 
through the bore is supported by the chuck 10. 
More specifically, as shown in FIG. 2, the chuck body 12 has an upper 
circular flange 16 that has a beveled top surface 18 and a cylindrical 
side wall 20. At the bottom of the chuck body is a lower flange 22 having 
a triangular cross section with a top surface 24 that extends horizontally 
outward from the chuck body. The flanges 16 and 22 retain the chuck in the 
bore 42. 
Extending downward from the chuck body 12, from beneath the bottom flange 
22, are a plurality of fingers 26. Each finger 26 has an interior bulge 30 
spaced above the free end of the finger that extends into the projection 
of the chuck bore 14, extending through the chuck body 12 (FIGS. 1 and 3). 
Thus the bulges 30 define a segmented aperture 36 having a smaller 
diameter that that of the bore 14. 
As is seen in FIG. 1, when the probe 46 is inserted into the chuck it 
passes freely through the bore 14. However, it has a greater diameter than 
the segmented aperture 36. It therefore engages the bulges 30 and bends 
the fingers 26 outwardly. The resilient actions of the fingers 26 combine 
with the relatively high coefficient of friction of the fingers to 
friction-secure the electrode between the fingers. 
Owing to the elastomeric properties of the chuck, once the probe 46 is 
inserted into the aperture 36, the chuck 10 will secure the electrode at 
any location along the length of the electrode, yet the relative position 
of the probe in the platform holder 38 may be changed by simple hand 
adjustment. 
The chuck 10 is readily displayed in the platform bore 40 by simply pushing 
downward into the bore. The lower flange 22 bends and compresses inwardly 
and then, when the illustrated position is reached, it pops out to serve 
as a retaining member.