CA1233668A

CA1233668A - Torque measuring device

Info

Publication number: CA1233668A
Application number: CA000483518A
Authority: CA
Inventors: Les Schubert
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-06-07
Filing date: 1985-06-07
Publication date: 1988-03-08

Abstract

ABSTRACT OF THE DISCLOSURE
A device for measuring the torque of a rotating shaft when the torque exceeds a predetermined level includes adjacent drive and follower hubs on the shaft, the drive hub being connected to the shaft and the follower hub being rotatable on the shaft; a plurality of helical springs extending perpendicular to the longitudinal axis of the hubs interconnecting the hubs;
an indicator ring on the side of the drive hub opposite to the follower hub; and a plurality of pins connected at one end to the indicator ring and extending through bushings in the drive hub into engagement with inclined cams in the follower hub.
When the torque on the shaft exceeds the predetermined level, the force of the springs is overcome, and the pins ride up the cams to move the indicator ring away from the drive hub a distance directly proportional to the amount by which the torque exceeds such predetermined level.

Description

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;

lZ33~68 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.

lZ336~i8 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 ~233668 (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.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A device for measuring the torque of a rotating shaft comprising drive hub means for connection to said shaft for rotation therewith; follower hub means for mounting on said shaft adjacent to one side of said drive hub means, first spring means associated with said drive hub means and said follower hub means for exerting a force between said hub means substantially at a 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; cam 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 pre-determined level, the first spring means causes said pin means to move said indicator means away from said drive hub means a distance directly proportional to the amount by which the torque exceeds the predetermined level.

2. A device according to claim 1, wherein said follower hub means is rotatably mounted on said shaft, and said first spring means extends between the periphery of said drive hub means and the periphery of said follower hub means.

3. A device according to claim 1, wherein said follower hub means includes elongated sleeve means coaxial with the shaft, and splint means connecting the outer free end of said sleeve means to the shaft; and said first spring means includes a torsion spring forming a portion of said shaft in said sleeve means.

4. A device according to claim 2, wherein said drive hub means includes a drive hub plate, and said follower hub means includes a follower hub plate, each said plate being sub-stantially circular and extending outwardly from the centre of the respective hub means, a plurality of flat shoulders on the periphery of each said plate, and a lug extending outwardly from one end of each said flat shoulder, the lugs on the drive hub plate opposing the lugs on the follower hub plate, and said first spring means extending between each pair of lugs on adjacent drive and follower hub plates.

5. A device according to claim 1, 2 or 3, including second spring means on said pin means between said drive hub means and said follower hub means for normally maintaining said hub means spaced apart by a constant distance.

6. A device according to claim 4, wherein the lugs on said drive hub plate and said follower hub plate are inclined towards each other, whereby the longitudinal axis of the first spring means extending between said lugs is perpendicular to the longitudinal axis of said shaft.

7. A device according to claim 1, 2 or 3, wherein said follower hub means overlaps said drive hub means on said shaft.

8. A device according to claim 4, including bushing means in said drive hub plate for slidably receiving said pin means, and a conical head on said other end of said pin means for sliding on said cam means.

9. A device according to claim 8, wherein said cam means includes a plurality of conical recesses in a surface of said follower hub plate adjacent to said drive hub plate.