In reaching our decision in this appeal, we have given careful consideration to the appellant's
specification and claims, to the applied Paielli and Hanisko patents, and to the respective positions
articulated by the appellant and the examiner. As explained below, we conclude that the references
applied by the examiner are sufficient to establish that the differences between the prior art and the
claimed invention are such that the subject matter of the claims on appeal would have been obvious to
one of ordinary skill in the art at the time of the appellant’s invention and that, consequently, the
rejection should be sustained.
Paielli, like the appellant’s invention, is directed to a capacitive brake wear sensor. Paielli’s
sensor 20 includes a pair of electrically conductive plates 24, 26 separated by a dielectric block 28 and
embedded in a body 22, the body 22 in turn being threaded into an internally threaded opening of a
brake pad 42 so as to bring face 38 of body 22 into position as a continuation of the braking surface 46
of pad 42. The body 22 is preferably of insulating material, such as molded plastic, into which the
preformed assembly of plates 24, 26 and dielectric block 28 are molded. The material 28 separating the
plates 24, 26 may either be a separate block or a portion of the body 22 molded between the plates (col.
1, ll. 35-39). A brake rotor 48 has a surface opposed to braking surface 46. According to Paielli, the
brake rotor 48 can be a drum-type rotor, with the braking surface 46 being of generally cylindrical
contour or, alternatively, a disc-type rotor having a flat braking surface parallel to and spaced from the
flat braking surface 46 of pad 42, and with surface 38 coplanar with surface 46 (col. 2, ll. 49-55).
As explained by Paielli, use of brake pad 42 causes wear at the braking surface 46 and
corresponding wear at surface 38 of sensor 20, including abrasion of the edges of plates 24, 26, so that
wear of the brake pad and sensor body causes a change (reduction) of the electrical capacitance between
plates 24, 26. Paielli also teaches that sensor body 22 and plates 24, 26 should wear as if they were part
of pad 42 to provide an accurate indication of brake wear (col. 3, ll. 2-4).
In the embodiment illustrated in Figures 5 and 6 of Paielli, the sensor plates 24, 26 are connected
as one arm C2 of a capacitance bridge 64, the other arms including capacitors C1, C3 and C4. Signal
conditioning circuitry 74 has an output connected to gauge 52 to provide an indication of brake wear as
a function of a change in capacitance at capacitor C2, while the other capacitors of bridge 64 remain
fixed.
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Last modified: November 3, 2007