Note: Descriptions are shown in the official language in which they were submitted.
3~233668
This invention relates to a torque measuring device,
and in particular to a device for the torque exerted on a driven
shaft or rod.
While the device of the present invention is particularly
suitable for use with a Waldo drive system of the type used
to drive a rod driven rotary bottom hole pump, it will be apprec-
fated that the device can be used, in other environments where
it is important to limit torque.
Commonly, it is necessary to provide a device in a drive
system for limiting the output or input torque to prevent the
overloading or stressing of some components of the system. Con-
ventional torque limiting devices rely on a shear pin or slip
clutch arrangement. Such devices possess at least one of the
drawbacks of not providing an indication of operating conditions,
of completely releasing the torque, i.e. of disconnecting the
driven member from the drive which may result in backlash or reverse
rotation, or of requiring constant monitoring to prevent the
burnout of slipping discs. Accordingly, such devices are not
suitable for use on unmanned equipment.
The object of the present invention is to avoid the
above mentioned drawbacks by providing a relatively simple device
which is capable of monitoring torque mechanically.
Accordingly, the present invention relates to a
device for measuring the torque of a rotating shaft comprising
drive hub means for connection to said shaft for rotation therewith;
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follower hub means for rotatable mounting on said shaft
adjacent to one side of said drive hub; first swing means
associated with said drive hub means and said follower hub means
for exerting a force between said hub means substantially at f
pa right angle to the longitudinal axis of said shaft; indicator
means longitudinally movable with respect to said shaft on the
other side of said drive hub means; pin means connected at one
end to said indicator means and extending through said drive
hub means from said indicator means to said follower hub means;
comma means on said follower hub means for receiving said other
end of said pin means, said cam means being inclined with respect
to the longitudinal axis of said pin means, whereby, when the torque
on said shaft exceeds a predetermined level, the length of the
first spring means changes to cause said pin means to move said
inductor means away from said drive hub means a distance directly
proportional to the amount by which the torque exceeds the pro
determined level.
The invention will now be described in greater detail
with reference to the accompanying drawing, which illustrates
aye preferred embodiment of the invention, and wherein:
Figure 1 is an end elevation of a torque limiting device
in accordance with the present invention, with parts omitted;
Figure 2 is a cross section of the whole device taken
generally along line II-II of Fig. 1,
Figure 3 is a longitudinal sectional view of another
lZ33668
embodiment of the torque limiting device of the present invention.
With reference to Figs 1 and 2, a torque measuring device
Jo in accordance with the present invention is intended for use on
a driven shaft 1. The device includes a drive hub 2, which is
fixedly mounted on the shaft 1 for rotation therewith. For such
purpose rectangular grooves 4 and 5 are provided in the shaft 1
and the hub 2, respectively for receiving a key 6. Longitudinal
movement of the hub 2 on the shaft 1 is prevented by a screw 7.
A generally circular plate 8 is integral with one end of the hub
2 and extends outwardly therefrom. Three short segments of the
circular plate 8 are omitted to define three shoulders 9 spaced
equidistant apart. A lug 10 extends outwardly from one end of
each flat portion or shoulder 9.
A follower hub 12 is rotatable mounted on the shaft 1
by means of bearings 13. The bearings 13 are held in position by
rings 14 and a spacer 15. The follower hub 12 partly overlaps
the drive hub 2 and is essentially the same shape as such drive
hub. Lugs 16 extend outwardly from a plate 17 integral with the
hub 12. The lugs 16 are spaced apart from the lugs 10, i.e. are
located at the ends of flat portions 18 (one shown - Fig. 2)
on the plate 17 opposite to the lugs 10. The lugs 10 are inclined
towards the plane of the plate 17 and the lugs 16 are inclined
towards the plane of the plate 8. Axially aligned pins 19 extend
outwardly from the opposed ends of the lugs 10 and 16 for supporting
a helical spring 20.
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An indicator ring 21 is connected to the plate 8 by
bolts 22. Nuts 23 are provided on each side of the ring 21 for
holding the ring 21 on the ends of the bolts. The bolts 22
extend through bushings 25 in the plate 8. The inner ends of the
bolts 22 are defined by conical heads 26 for riding in cams
defined by conical recesses 27 in the plate 17. queue recesses
27 have a deep centre 28, and are inclined upwardly to a shallow
edge 29. A helical spring 30 (one shown) is mounted on each
bolt 22 between -the ring 21 and the bushings 25 for maintaining
the plates 8 and 16 in spaced apart relationship.
During normal operation, the shaft 1 rotates in a
counterclockwise direction as seen in Fig. 2 with the hub I
Because the plates 8 and 17 are interconnected by the spring 20
and the bolts 22, the hubs 2 and 12 rotate together (at least
initially). When the torque on the shaft 1 exceeds a predetermined
upper limit, dependent inter aria on the strength of the springs
20, the heads 26 of the bolts 22 begin to ride up the recesses
27, i.e. from the deep centre 28 towards the shallow edge 29 of
the recesses 27. The distance that the heads 26 ride up the
recesses 27 is directly proportional to the amount by which the
torque exceeds the predetermined level. Movement of the heads 22
along the recesses 27 results in movement of the ring 21 away
from the plate 8. The distance that the ring 21 moves away from
the plate 8 can be measured on a scale 32. A micro switch 33 can
be used with or without the scale 32 to shut off the prime mover
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(no-t shown), to sound an alarm or to cause some other action
indicative of torque overload
When the excess torque is removed, the helical springs
30 on the bolts 22 return the plates 8 and 17 to their normal
spacing, i.e. cause the plates 8 and 17 to move apart so that
the heads 26 of the bolts 22 ride down the recesses 27 to the
deeper centers 28.
It will be appreciated that the helical springs 20 can
be compression or expansion springs. If the springs 20 are
of the expansion type, the inclination of the recesses 27 is
reversed, since the lugs 9 and 16 will move apart rather than
towards each other as when compression springs are used.
Referring to Fig. 3, where whenever possible the
reference numerals of Figs. 1 and 2 have been used, another
embodiment of the invention includes the same basic elements as
the device of Figs. 1 and 2, except that the follower hub 12
includes an elongated sleeve 35 extending away from the plate
17. The outer end 36 of the sleeve 35 includes a splinted passage
37 for receiving a splinted portion 38 of the shaft 1. A portion 39
of the shaft 1 between the bearings 13 and the splinted portion
38 is defined by a spring in the form of a torsion bar. Of course,
the plates 8 and 17 can be circular, i.e. the flat portions 9
and 18 are no longer necessary.
