Drive assembly for probe carrier

A drive assembly for a probe carrier such as used for inspection and maintenance of a heat exchanger in a steam driven electric power generation plant includes a motor and speed reducer and drive wheel for pushing a probe carrier through the tubes of the heat exchanger. The carrier may comprise nylon tubing, and the drive wheel includes radially mounted wires with the tips of the wires defining a surface for engaging the tubing. An adjustable pressure plate yieldably biases the tubing into engagement with the drive wheel with sufficient pressure for the wire tips to indent the tubing surface but without penetrating the tubing surface whereby an interference drive of the probe carrier is achieved.

This invention relates generally to inspection equipment for tubular 
products such as coils in heat exchanger, and more particularly the 
invention relates to an improved drive assembly for positioning probes and 
probe carriers during the inspection and maintenance of tubular products. 
Heat exchangers such as used in connection with steam driven electric power 
generators are subjected to very high temperatures and pressures. Further, 
deposits of impurities from the fluids used in the heat exchangers tend to 
build up on the tubes and supports in the heat exchanger which can lead to 
tube thinning and cracking. Thus, the tubes must be periodically inspected 
to ensure safe operation. 
Heretofore, inspection probes have been mounted on flexible tubular 
carriers with the carriers being pushed by a drive assembly typically 
including a smooth friction drive mechanism. Such drive assemblies have 
been relatively complex in structure and susceptible to water, dust, and 
other lubricants which adversely affect the friction drive. 
Accordingly, an object of the present invention is an improved drive 
assembly for a probe carrier and the like. 
Another object of the invention is a drive assembly which provides an 
interference motive force to a carrier. 
Still another object of the invention is a drive assembly which is simple 
in structure. 
Briefly, a drive assembly in accordance with the invention includes a 
motor, means for coupling said motor to a drive shaft, a drive wheel 
mounted on said shaft and having a peripheral surface for engaging the 
probe carrier. 
In accordance with one feature of the invention, the peripheral surface for 
engaging the probe carrier is defined by a plurality of wires radially 
mounted on the wheel. Preferably, the peripheral surface is contoured to 
conform to the surface of the probe carrier. 
Means is provided for urging the probe carrier into engagement with the 
peripheral surface. Preferably, this means includes a pressure plate which 
is mounted to the motor and coupling means with means provided for 
yieldably biasing the pressure plate into engagement with a probe carrier 
positioned between the plate and drive wheel. The pressure plate 
preferably has a contoured low friction bearing surface which engages the 
probe carrier. By adjusting the pressure from the plate, the tips of wires 
in contact with the probe carrier will not penetrate or abrade the carrier 
but will indent or knurl the carrier to provide the interference drive. 
Accordingly, the drive is not affected by contaminants which can operate 
as lubricants in a friction drive. 
The invention and objects and features thereof will be more readily 
apparent from the following detailed description and appended claims when 
taken with the drawings.

Referring now to the drawings, FIG. 1 is a top view of one embodiment of a 
drive assembly in accordance with the present invention, and FIGS. 2 and 3 
are side views and end views, respectively, of the drive assembly. The 
assembly includes a motor 10 which is mounted to a speed reducer 12 having 
a drive shaft 14. As shown in FIGS. 2 and 3, the speed reducer 12 is 
mounted to a suitable support by means of bolts 16. 
Mounted to shaft 14 of the speed reducer 12 is a drive wheel 18 which 
preferably has a contoured peripheral surface for receiving a probe 
carrier 20. Probe carrier 20 may comprise a nylon tube with the inspection 
probe mounted on one end thereof. The drive assembly moves the probe 
through a tubular product by pushing the carrier tubing 20. 
Mounted on the top of speed reducer 12 is a pressure plate 22 which is 
pivotally mounted by means of pillow block bearings 24. Plate 22 
preferably has a contoured bottom surface for engaging probe carrier 20, 
and pressure plate 22 is yieldably biased in engagement with the probe 
carrier 20 by means of a load adjust mechanism including an adjusting bolt 
26 and spring 28 positioned between the handle of the adjusting bolt 26 
and pressure plate 22. Thus, by adjusting the position of bolt 26 the 
tension of spring 28 and consequently the pressure exerted by plate 22 can 
be adjusted. 
In accordance with one feature of the present invention, the drive wheel 18 
comprises a plurality of radially mounted wires with the ends of the wires 
trimmed to define the contour on the peripheral surface for engaging tube 
20. Advantageously, by adjustment of the pressure exerted by pressure 
plate 22, the tips of the wires in contact with the probe carrier do not 
penetrate or abrade the carrier tube but do indent or knurl the carrier 
tube to provide an interference drive. Thus, the presence of water, dust, 
or other lubricants which can greatly reduce the ability of friction 
drives have negligible influence on the interference drive of the 
disclosed assembly. 
FIG. 4 is an end view of a partially disassembled drive wheel in accordance 
with one embodiment of the present invention. The wheel includes a hub 40 
with a plurality of steel wires 42 mounted thereon. In this embodiment the 
ends of the wires 42 nearest to hub 40 are mounted in an adhesive 44 such 
as epoxy or polyurethane resin with circular discs mounted on either side 
of the wires for maintaining lateral positioning of the wires. One disc is 
illustrated by the dotted line 46 while the other disc is removed for 
illustration purposes. The tips of the wires which define the peripheral 
surface for engaging the probe carrier extend beyond the discs, as shown. 
FIG. 5 is a perspective view of another embodiment of a drive wheel in 
accordance with the present invention. Again, the wheel includes a hub 50 
with a plurality of wires 52 extending radially outwardly from hub 50. In 
this embodiment the entire length of the wires is embedded in an adhesive 
with only the tips 54 of the wires which define the peripheral surface 
being exposed. Greater pressure can be exterted against a probe carrier 
using the drive wheel of FIG. 5 due to the entire length of wires being 
molded in adhesive. Further, since only the tip portion of the wires is 
exposed the indentation of the probe carrier by the wires is limited thus 
minimizing the possibility of the wires penetrating and abrading the probe 
carrier. 
In one embodiment of a drive assembly in accordance with the invention a 
three-fourths horse power Reliance EF 56 DC motor was used with a Reliance 
D200 speed reducer. The drive wheel utilized steel wire and the probe 
carrier comprised nylon tubing. The pressure plate was provided with a 
Teflon bearing surface to provide low friction through the carrier 
engaging surface. 
While the invention has been described with reference to specific 
embodiments, the description is illustrative of the invention and is not 
to be construed as limiting the invention. Various modifications and 
applications may occur to those skilled in the art without departing from 
the true spirit and scope of the invention as defined by the appended 
claims.