US3079791A

US3079791A - Pick up for torque-measuring apparatus

Info

Publication number: US3079791A
Application number: US760949A
Authority: US
Inventors: Oswald Karl
Original assignee: Messen-Jaschin GA
Current assignee: Messen-Jaschin GA
Priority date: 1957-09-14
Filing date: 1958-09-15
Publication date: 1963-03-05
Anticipated expiration: 1980-03-05

Description

March 5, 196 3 K. MOSWALD PICK up FOR TORQUE-MEASURING APPARATUS 6 Sheets-Sheet 1 Filed Sept. 15, 1958 March 5, 1963 K. OSWALD 3,079,791

7 PICK UP FOR TORQUEMEASURING APPARATUS Filed Sept. 15, 1958 s Sheets-Sheet 2 Fig.4

March 5, 1963 K. OSWALD 3,079,791

PICK UP FOR TORQUE-MEASURING APPARATUS I Filed Sept. 15, 1958 e Sheets-Sheet a March 5, 1963 K. OSWALD 3,079,791

PICK UP FOR TORQUE'MEASURING APPARATUS Filed Sept. 15, 1958 e Sheets-Sheet 4 Fig.9

4 l l I I 1 ns 33 l W A i if CI 30 34 L March 5, 1963 K. OSWALD PICK UP FOR TORQUEMEASURING APPARATUS Filed Sept. 15, 1958 6 Sheets-Sheet 5 March 5, 1963 K. OSWALD 3,079,791

' PICK UP FOR TORQUE-MEASURING APPARATUS Filed Sept. 15, 1958 e Sheets-Sheet e PHIK UP FUR TGRQUE-MEASUREQG APPARATUS; Karl Oswald, Sari-zen, Switzerland, nssignor to G. A.

Messen-Jasehin, Sarnen, Switzerland, a corporation of Switzerland Filed Sept. 15, F958, Ser. No. 76%,94? Claims priority, application dwitzerland Sept. 14-, 1%? 11 Claims. (Cl. 73-136) The invention relates to a transmitter or pick-up for a torque-measuring instrument, the transmitter or pickup having toothed rims which are secured at spaced positions to a shaft, the torque of which is to be measured. The rims are co-axial with the shaft and they co-operate With a stator to bring about, in the case of each toothed rim, a cyclic variation in some electrical parameter. The two cyclic variations are compared in further apparatus which gives an indication of the torque on the shaft. This may involve supplying to an indicator two cyclically varying voltages, induced in two dilferent magnetic fields, and having an indicator which gives a torque indication in dependence upon the phase difference between the two voltages.

In known pick-ups of this type, each toothed-rim carrier is mounted on the shaft by means of a cylindrical or conical surface. Due to the axial extent of this surface, which in practice cannot be brought to bear completely against the cooperating surface of the shaft, the exact extent of the measuring section, i.e. the axial distance apart of the supporting positions of the two toothed rims on the shaft, is unknown, which may result in errors of measurement. Furthermore, in the known pick-ups, the stator is supported independently of the two toothed rims. The often unavoidable eccentricity of the toothed rims with respect to the shaft axis results in a variation of the distance of the toothed rims from the stator parts influenced by them during a revolution of the shaft, which likewise leads to errors of measurement.

in the pick-up according to the invention, these disadvantages are avoided. For this purpose, the pickup according to the invention comprising a shaft, first and second toothed rims co-axial with the shaft, first and second cylindrical support members surrounding the shaft and to which the first and second toothed rims, respectively, are fixed, first and second fixing means secured to the first and second support members, respectively, and making substantially line contact with the shaft around first and second spaced peripheral lines on the shaft, whereby the first and second rims will turn in accordance with the turning of the shaft at said first and second lines, respectively, a stator adjacent the toothed rims, magnetic means in the stator for co-operating with the teeth for the generation of alternating current when the shaft turns, and bearings engaging the stator and one of the support members at spaced locations distributed around the entire circumference of said one support member and supporting the stator in space and locating it both axially and radially with respect to said one support member.

Since the toothed rims are each connected to the shaft only on a circular, i.e. peripheral, line on the latter, the length of the measuring section situated between these two peripheral lines is exactly determinable. Measuring errors due to eccentric mounting of the toothed rims on the shaft cannot occur, since the stator is mounted on one of the toothed rim supports itself.

In the constructions of torque pick-ups known heretofore, the arrangement is always such that the pick-up rotor runs in the stator. Such an arrangement, however, is n ot always ree from transmission errors, and results in such errors even if the two transmission elements, namely the rotor toothed rims and the pick-up magnet systems on the stator lie very close together. In order to avoid the above- Federated Perla-r. E3, 1983 ice mentioned technical drawbacks, it is possible in a special embodiment to construct a pick-up in which the stator, independently of the rotor formed by the toothed rims, is pressed resiliently against the running surfaces of the rotor, so that the distance between the magnet poles of the magnet systems mounted on the stator and the toothed rims is maintained constant as the rotor turns.

Constructional examples of the subject of the invention are represented in the accompanying drawings, wherein:

FIGURE 1 shows a part of an axial section through a pick-up,

FIGURE 2 a detail of the pick-up in an axial section offset relatively to the section according to FIGURE 1,

FIGURE 3 a detail of FIGURE 1 in end view,

FIGURE 4 a part of the stator of FIGURE 1 in end view,

FIGURE 4:: a part of a radial section through an alternative form of pick-up rotor,

FIGURE 5 a part of an axial section through a second example of the pick-up according to the invention,

FIGURE 6 an end view of the pick-up according to FIGURE 5 on a smaller scale,

FIGURE 7 a detail of FIGURE 5 in plan on a larger scale,

FIGURE 8 a third example of a pick-up according to the invention in end view,

FEGURE 9 an wial section analogous to FIGURE 5 through a fourth example of a pick-up according to the invention,

FIGURE 10 an axial section of a pick-up according to the invention with a first example of a device for zeropoint calibration,

FIGURES 11 and 12 in side view and end view, respectively, the pick-up with a second example of a device for zero-point calibration, and

FIGURES l3 and 14 in side view and end view the pick-up with a third example of a device for zero-point calibration.

in FIGURES 1-4 of the drawings, the torque on a shaft 1 is to be measured by reference to the amount by which one end of a test section a of the shaft turns relative to the other end. Mounted on said shit 1, at a small distance apart within the measuring section a are two toothed rims 2 and 3, the teeth of which are of equal pitch and of magnetic material. The toothed rim 2 is formed as end flange of a cylindrical support 4-, which is mounted co-axially and with radial spacing relatively to the shaft 1. The end of the support 4 carrying the toothed rim 2 is supported on the shaft 1 by means of a ring 5 mounted on the shaft so as to turn relative to the shaft. The other end of the support 4 is held by a ring the inner edge of which remote from the support 4 is bevelled. This bevelling and the adjacent end face of a clamping ring 7 partly define an annular recess between the two rings 6 and 7 and the shaft 1, in which ecess lies a ring 3 of round wire. By means of screws, not shown, the clamping ring 7 is fixed to the ring 6, the wire ring 8 being pressed against the shaft 1. The

wire ring 3 makes line contact with the shaft at the peripheral line on the shaft 1 representing one boundary of the measuring section a, and against said shaft, so that the support aand with it the toothed rim 2 is firmly connected to the shaft 1 at the desired position. The second toothed rim 3 is connected to one end of a cylindrical shell 9, surrounding the shaft 1 with radial spacing and co-axially, the other end of said shell being fixed to the external periphery of an annular disc 10 coaxial with the shaft l. The annular disc 19 is anchored by its inner edge to a ring 11, the inner edge of which, remote from the disc, is bevelled. By means of screws, not shown, a clamping ring 12 is fixed to the ring 11, and together with the bevelling on the ring 11 partly defines an anul'ar recess facing the shaft 1. In this recess lies a ring 13 of round wire, which like the wire ring 8, is pressed on the shaft 1 along a peripheral line on the latter, representing the corresponding limit of the measuring section a, and thus connects the support 9, with its toothed rim 3 firmly to the shaft at the desiredposition. Mountedin the toothed rim 2 at intervals apart on the circle are bushes 14, each of which has an end part which is eccentric relative to the bush axis and which carries a ball bearing 15.

On the external periphery of the support 40f the toothed rim 2 are supported a plurality of ball bearings 16, axially parallel to the shaft axis ar d each mounted on "an eccentric end part of a bush 17. The bushes 17 are mounted in a stator disc 18 and can be swung about p v xe o a m (F E .3) fo ra a a u ment of the bearings 16. The arms 19 arepermanently carried by the stator disc. The stator disc 18, supported radially on the support 4 by means of the bearings 16 s p e t fr ota y m n .B ZY I WR Su means may take a form -similarto;-that described below and illustrated in FIGURE 6. The stator disc 18 is provided with detachable cover plates 20 andZl. In an inner flange 22 (FIGURE 2) of the stator disc 18, v coaxial with the shaft, rotatably adjustable pivots 2} are mounted between the bearings 16, the end parts of which pivots, projecting towards the shaft 1 from the flange 22..are eccentric and each carry a ball'bearing 24. The outer rings of said bearings bear against a radial surface on the support 4, so that by means of said bearings 24, the stator is supported axially on the support 4. l

Magnet systems A -A (FIGURE 1) with pole shoes 26 and induction coils 27 are provided at equal intervals apart on a circle,the pole shoes- 26 facing the periphery of the toothed rim 2. Between the magnet systems A A fourv magnet systems 13 -13 with pole shoes 28 and induction coils 29 are provided, the pole shoes 28 facing the periphery of the. toothed rim 3. Between the magnet systems A; and B; there isprovided an identic-a1 magnet system C with pole shoes facing 'one of the toothed rims, while between the magnet systems A and B is mounted afurther magnet system D with pole shoes facing the other toothed rim. The arrangement of the magnet systems on the disc 18 or ping 2'5 is indicated in FIGURE 4. The magnet systems A to A and C and D arefixed on the stator disc '18 by means of bolts passing through round holes in the stator disc and-through arcuate slots in a ring which islet into a recess in the stator ,disc. The remaining magnet systems are fixed on the ring 25 which can be turned about its axis, as far as permitted by the ends of the arcuate slots, in order to adjust the positions of the magnet systems A to A and C and D relative to the other magnet systems. The magnet systems A, and C, as well as A and D serve for calibration and Checking of the measuring instrument. Since the angular. positions, around the ring 25, of the magnet systems A and C, for example, are accurately known, then it is known what the phase difference between the potentials from these two magnet systems really is. It is suflicient, then, to apply the two potentials to the measuringinstrument, which gives anindicati-on of the phase difference. If the indicated phase difference is not the same as the accurately known phase difference, the amplification of the potentials by the instrument requires adjustment until exact correspondence is obtained. The magnet systems A A and 3 -13 serve for torque indioation.

Tne two toothed rims land-3 are made by screwing their blanks together and machining them simultaneous iv. The support 4 is machinedat the same time so that accurate round running of 'the ball bearings 16 with respect to the surface of the supportupon which they bear is ensured. The toothed rims remain screwed together until after their assembly in the pick-up and fixing of the toothed rim 3 to its support 9, 10.

The ball bearings 16 and 24', like the ring 25 carrying the magnet systems B -B are adjusted before the ap plication of the

cover plates

20, 21. The magnet systems li -B are adjusted so that for zero torque a desired phase displacement is adjusted, for which the measuring instrument, not shown, indicates zero.

In the operation of the pick-up, due to the twisting of the measuring section a or of the toothed rims 2 and 3,

occurring during the rotation of the loaded shaft 1, cyclic variation takes place of the magnetic field of the magnet systems of the stator, whereby corresponding alternating voltages are generated in the

coils

27 and 29. The phase difference between the voltages is used for indicating the torque efiective on the shaft 1.

In the example described, the supports of the toothed mims 2 and 3 are clamped on the measuring shaft 1' by means of wire rings 8 and 13 which do not, in fact, follow a complete circle but are split, like piston rings. It is evident that instead of rings of round wire, rings wedge-shaped in cross-section or individual 'balls distributed around the periphery of the shaft couldbeused; In the exampleshown, the magnetic flux in. the magnet systems is varied cyclically for. generating the desired al ternating voltages; similarly, however, the magnitudeof another electrical parameter (for example inductance or capacitance) could be .varied cyclically by the relative movement between stator and toothed rims.

As shown in FIGURE 40, instead of providing salient teeth on the rotor, .the parts 2 and 3 may be formed with blindbores 2A of equal depth, diameter and spacing, so that the rotor parts between the teeth simulate. salient teeth. s 1

In the example according to FIGURES S to 7, 30 is the measuring shaft with test section a. Two

toothed rims

31 and 32 are mounted on said. shaft 30 at a short distance apart. Thevtoothed rim 31 is formed as end flange of a cylindrical support 33, which isimounted coaxially and with a radial spacing relative to shaft'fitl. One end of the support 33 is fixed on shaft 31) by means of a clamping ring 34 of round wire. The wire ring 34 makes line contact with the shaft at a peripheral 'line on shaft 30 so that the support 33 and with it the toothed rim 3-1 can be rigidlyconnected to the shaft 3% atthe desired position, i.e. at the end of the measuring section a. The

second toothed rim 32- is secured to. one end of a cylindrical shell 35, surrounding the shaft 3% with radial spacing and co-axially, the other end of said shell being secured'to the external periphery of an annular disc 36 co-axial with the shaftEil. The annular disc'36 is fixed .to the shaft 30 by means of a clamping ring 37 of round wire like the support 33 around a peripheral line on said shaft representing the corresponding limit of the measuring section a; thus the support 3'5, 36 withpits toothed nim 32 is rigidly connected to the shaft 36 at the desired position. Mounted in the toothed rim 31, spaced apart on a circle, are pins 38 (FIGURE 5 only one visible). The end part of each pin projecting from the toothed rim 31 is eccentric relatively to the pin axis and carries a ball bearing 39. The toothed rim 32 fixed to the shell 35- is mounted on said ball bearings 39. The eccentric pin 38 permits adjustment of the bearings 39 in the radial direction. t

The two

toothed rims

31 and 32 are each provided on their periphery with a cylindrical bearing surface 41) of the same diameter; a further bearing surface 41, situated in a plane at right-angles to the shaftaxis is also provided on each-of the'end sides, facing away from each other, of the two toothed rims 3i and 32. A segment-shaped stator carriage $3 is mounted by means of ball bearings 42 on said bearing surfaces 49, 41 of thetwo

toothed rims

31, 32. In the radial direction, the stator carriage 43 is pressed against the bearing surfaces 40 by means of a resilient system 44a (e.g. suitable springs), which is supported at a fixed point, situated outside the pick-1p so that any play between bearing rollers and cylindrical bearing surface is avoided. In the axial direction, each of the two ball bearings 4-2, running on the bearing surface 41 of the toothed rim 31, is pressed against the hearing surface 41 of the toothed rim 31 by means of a spring 44b (FIGURE 7), supported on the carriage 43 itself and engaging a pivotal arm 4-5 carrying the ball bearing. The carriage 43 carries the magnet systems 46, the magnet poles 47 of which stand opposite the toothed rims 3i and 32.

If, due to a displacement of the middle of the shaft 353 or to non-circularity, produced for example by clamping of the toothed rims, the two rotor toothed rims 3f, 32 run eccentrically, the carriage 43 adapts itself to these movements, so that the pick-up gap between the toothed rims and the magnet poles remains constant and no fluctuations can occur in the transmitted measured values. The only condition which must be made from the manufacturing side is that the two cylindrical bearing surfaces 443 must be absolutely parallel to each other. This can be obtained, however, without trouble in manufacture by machining die two surfaces together in one clamp on the lathe. The arrangement described makes it possible to manage with one set of magnet systems; at the s .e time, by the incorporation of an adjusting system 48 (FIGURE 6), consisting of screwthreaded posts 48A and 5-313 pivotally connected to the stator and a fixed support 48D, respectively and provided with left and right hand threads, respectively, in combination with a turnbuckle The latter can be turned to effect movement of the carriage around the rotor, whereby it is possible to obtain a zero-point adjustment. When the turnbuckle is not being turned, the

posts

48A and 48B prevent the stator from turning around the axis of the rotor. Similar or comparable means may be provided in the other en bodiments to adjust the position of the stator and to prevent from rotating once it has been adjusted.

For a so-called internal compensation of transmission errors, it has been found to be particularly advantageous, instead of a single transmission magnet system, to arrange three or more such systems around the periphery of the pick-up rotor. Such an arrangement is shown in FIGURE 8, in which the construction of the individual stator carriages 43 is the same as in the example last described. in the arrangement as shown in FEGURE 8, the three carriages 43 are so arranged that they can be moved in the radial direction, while remaining constant relatively to each other in th lr segmental or angular spacing 06. For this purpose, the guiding of the carriages 43 is effected by means of bolts 49 running in radial slots. For zero-point adiustment, the stator ring db carrying the radially slidable carriages 43 with the magnet systems can be turned about the center P. F1. ing of the stator ring 5% is effected by means of clamping slit 52 co-operating with an eccentric 51..

in other respects, the construction according to PEG- URE 8 corresponds to that according to FEGURES 5-7, exce t that here instead of a single spring 44a for pressing the individual carriages 43 against their bearing surfaces it), two such springs re provided.

A further example is shown in FIGURE 9. Here again, the

supports

33 and 35', 36 of the

toothed rims

31 and 32 are fixed on the shaft 30 by means of clamping

rings

34 and 37, respectively. Contrary to the previously described examples, however, in this case there is provided on each toothed rim only one conical bearing surface 5'3, upon which act ball bearings 54 mounted on the stator carriage 55. in this case also, the stator carriage is pressed resiliently against its bearing surfaces on the rotor by means of a spring system, not shown, supporte outside the pick-up. instead of the supporting bearings 39 of the example first described, in this case a wire ball bearing 56 is provided between the two toothed rims 31 and 3M.

in the arrangement of a stator supported resiliently against the rotor, it is not absolutely essential for the two pick-up toothed rims 3?. and 32 to be mounted at the smallest possible distances apart. The pick-up toothed rim 33 may be arranged at the distance a from the pick-up toothed 'im 32, in which case the shell tube 35 may be omitted; i.e. two mechanically independent pickup and receiving systems may be mounted on the torquetransmitting shaft 3%. in this case, therefore, one or more stator carriages each associated with both toothed rims, are not provided, but one or more separate carriages are provided for each toothed rim.

in the transmission of torque and power via shaftlines, two different principles may be used for their measurement. The first principle is based on the fact that the twisting of the shaft occurring in the transmission of torque and power is taken as a measure of the power transmission. The second method is based substantially on the fact that strain gauge strips are applied to the surface of the transmission shaft, and these strips lengthen or shorten during the twisting of the powertransmitting shaft in accordance with the geometrical angle of twist. The changes in length are so vetted into voltage variations and these voltage variations are fed to the indicating instrument by means of a slip-ring system and suitable electrical transmission. Common to both principles is the need for a satisfactory so-called zeropoint determination, i.e. adjustment of the measuring instruments to the condition of freedom of the transmission shaft from torque. This requirement first of all assumes that the transmission shaft has no frictional torque, appearing as pre-stress in the transmission shaft and produced by starting up, for example, of a ships engine. That is to say, therefore, at the commencement of calibration or zero adjustment, the shaft must be brought to a stress-free condition, or the pre-stressed condition must be included as fixed magnitude in the zero point. if we now start from the fact that the shaft itself is in a state of freedom from stress, then in the measuring method employing strain gauges, the zero-point calibration can be undertaken in the static condition, i.e. with the shaft at rest. Calibration with strain gauges, however, is generally dependent upon stress and temperature, so that accuracy of measurement can only be at tained with difiiculty over a large range. Generally, in zero point calibration, a so-called precompensation of measuring errors to be found in the temperature expansion of the apparatus, is undertaken, so that then the actual zero is mready displaced by a mean error. if, new, during the loaded state, the measurement deviations do not occur the assumed order of magnitude or direction, the strain gauge measuring method can then lead to considerable errors in indication.

if the measurement is based on the principle of the twisted shaft, and the torque magnitudes are measured by means of a phase displacement, occurring through the mutual displacement of two pick-up toothed rims, there must be rotation of the rotor relative to the stator for any indications to be obtained. For zero-point calibration, therefore, the transmission shaft must normally be rotated and the speed must reach a value dependent upon the transr -ission frequency. In normal ships drive, however, the requirement of so-called dynamic calibration can be satisfied in extremely few cases only, and a method is therefore desirable for enabling zero calibration to be carried out in the phase-displacement measuring method but with the shaft stationary. The method described in the following indicates a technically satisfactory way of doing this.

The basic principle of the method is as follows: the apparatus part acting as rotor in the working condition and rigidly connected to the transmission shaft is used as stator in calibration method, while the apparatus part acting as stator in the normal working condition is now used as rotor for zero-point calibration. In detail,

t, a the included in the line.

this is-efiected by the following device, shown in FIG- URE 10. The ring 61, on which the magnet systems 62 are secured, is originally the stator part of the measuring apparatus. A hollow cylinder 67 is formed integral with the ring 61 and there is mounted on its external periphery two slip rings 63, to which the phase-separated voltages of the magnet systems 62 can be transmitted by means of electric leads. A resilient wheel 64 runs against the inner surface 65 of the cylinder 67 in order to drive the latter. An electric motor 66, mounted on a two part holder 66a to be secured to the transmission shaft, effects drive of the wheel 64 and the transmission of the rotary movement to the

part

67, 61 of the apparatus, which originally was the stator, but for zero adjustment is the rotor of the measuring apparatus. The electrical values are trans mitted to the measuring instruments by means of brushes 63A engaging the slip rings. Since in the measuring method described, phase differences are used for the measurements, slip-ring'transmission does not introduce any transmission errors into the measurement itself, whereas if voltage difierencesare to be measured, slip-ring transmission always gives rise to considerable transmission errors; From the standpoint of transmission accuracy, therefore, the slip-ring method can be used without objection if, and this point is now important, after calibration by means of the slip rings, the line capacitance resulting fromthe slip-ringlength and the slip-ring crosssectionis compensated by a capacitance member to be The value of the transmission capacitance in the static zero-point calibration described above can be fixed, however, without difiiculty, and after zero-point calibration has been effected, the compensation capacitance member can be incorporated in the transmission line or in the measuring part.

In the example according to FIGURES 11 and 12, the driving mechanism is also detachably mounted on the shaft by means ofa clamping holder 66a. The motor 65 drives the rim 67 of the stator by means of the resilient wheel 64. 'In other respects, this construction corresponds to the example described in the foregoing.

If, for technical process reasons, the driving mechanism and the voltage take-ofi device are to be mounted on the shaft while it is at rest during zero-point calibration, it is possible-to proceed in accordance with the example shown in FIGURES '13 and 14. A vertically adjustable shear arrangement 72 is mounted-on a ground beam 71 so that by spindle adjustment-73, the supporting block 74 can be raised or lowered. By means of this shear arrangement, it is now possible 'to support the ground beam 71 positively against the shaft 75. A bracket 76, rotatable on the axis 76a, is coupled to the adjustable shears 72 so that the friction wheel '77, mounted on the shaft of the driving motor 78, is brought into frictional contact with the inner surface of the cylinder disc 79.

In the pick-up constructions so far described, the main principle of which consists in that the generation of the'voltagestakes place inductively, an important question has been left unmentioned, namely that of the optimum tooth-form of the pick-up Wheels. Extensive theoretical and practical investigations have shown that the pick-up wheel, if it is'not to indicate any simulated phase displacements, must first of all be free from pitch errors. This requirement for freedom from pitch errors is solved from the point of view of process technique in modern gear-cutting machines, so that this basic requirement can be regarded as satisfied in construction. Much more difiicult from the point of view of manufacturing technique, however, 'is the second requirement of absolute circular'running of the toothed rim and the associated constant depth of cut of the individual teeth of the pickup wheel. As soon, in fact, as the tooth parts fluctuate, in normally profiled tooth flanks, variations occur in the tooth tip width which cause the magnetic flux formed between the magnet system-and tooth of the pick-up wheel to-undergo a phase displacement, produced by the variable tip width of the tooth of the pick-up wheel. Since the relative displacements of the two toothed rims required for torque indication are in any event small, any variation in the tooth tip widths very soon falsifies the measured result. This circumstance is counteracted by using a tooth form in which the tooth flanks are planes parallel to one another,so that variation in the depth of cut of a tooth cannot produce any variation in the tooth tip width. The result is that with teeth free from pitch errors, the tooth tip widths remain constant, even in the case of Variable tooth parts. Only such a configuration of the teeth permits transmission of the phase displacement of the two pick-up wheels free from error and independent'of mechanical effects.

I claim:

1. A pick-up for torque measuring apparatus, comprising a shaft, first and second juxtaposed toothed rims in spaced relation co-axial with the shaft whereof the teeth are of equalpitch andare of magnetic material, first and second cylindrical support members surrounding the shaft and to which the first and second toothed rims,

respectively, are fixed, first and second fixing means secured tothe first and second support members, respectively, and making substantial line contact with the shaft around first and second spaced peripheral lines on the shaft, whereby the first and second rims will turn in accordance with the turning of the shaft at said first and second lines, respectively, a stator adjacent the toothed rims, means connected to the stator for preventing it from rotating when a measurement is to he made, magnetic means in the stator for co-operating with the teeth for the generation of alternating current when the shaft turns, ball bearings engaging the stator and one of the support members at spaced locations distributed around the entire circumference of said one support member and supporting the stator in space and locating it both axially and radially with respect to said one support member, and eccentrics upon which the ball bearings are mounted and which are adapted to be turned for adjusting the positions of the bearings.

2. A pick-up for torque measuring apparatus, comprising a shaft, first and second juxtaposed toothed rims in spaced relation co-axial with the shaftwhereof the teeth are of equal pitch and are of magnetic material, first and second cylindrical support members surrounding the shaft and to which the first and second toothed rims, respectively, are fixed, first and second fixing means secured'to the first and second support members, respectively, and making substantial line contact with the shaft around first and second spaced peripheral lines on the shaft, whereby the first and second rims will turn in accordance with the turning of the shaft at said first and second lines, respectively, a stator adjacent the toothed rims, means connected to the stator for preventing it from rotating when a a measurement is to be made, magnetic means in the stator for co-operating with the teeth for the generation of alternating current when the shaft turns, bearings engaging the stator and one of the support-members at spaced locations distributed around the entire circumference of said one support member and supporting the stator in space and locating itboth axially and radially with respect to said one support member, turnable eccentrics mounted on a first of the support members and ball bearings mounted on the eccentrics and engaging a,

bearing surface on the second support member, whereby said second support member is supported with respect to said first support member while being rotatable relative thereto.

3. A pick-up for torque measuring apparatus, comprising a shaft, first and second juxtaposed toothed rims in spaced relation co-axial with the shaft whereof re teeth are of equal pitch and are of magnetic material, first and second cylindrical support members surrounding the shaft and to which the first and second toothed rims, respectively, are fixed, first and second fixing means secured to the first and second support members, respectively, and making substantial line contact with the shafit around first and second spaced peripheral lines on the shaft, whereby the first and second rims will turn in accordance with the turning of the shafit at said first and second lines, respectively, a stator adjacent the toothed rims, means connected to the stator for preventing it from rotating when a measurement is to be made, a set of magnet systerns fixed to the stator for the generation of alternating current when the shaft turns, pole shoe-s of said magnet systems presented to the teeth of one rim, a ring mounted in the stator for turning relative to the stator, another set of magnet systems secured to the ring for the generation of alternating current when the shaft turns, pole shoes of those magnet systems presented to the teeth of the other rim, the magnet systems of the two sets alternating at equal intervals around a circle centered on the shaft axis, and bearings engaging the stator and one of the support members at spaced locations distributed around the entire circumference of said one support member and supporting the stator in space and locating it both axially and radially with respect to said one support member.

4. A pick-up according to claim 3 and further comprising two further magnet systems fixed on the stator and each having a pole shoe, one shoe being presented to the teeth of one rim and the other pole to the teeth of the other rim.

5. A pick-up for torque measuring apparatus, comprising a shaft, first and second juxtaposed toothed rims in spaced relation co-axial with the shaft whereof the teeth are of equal pitch and are of magnetic material, first and second cylindrical support members surrounding the shaft and to which the first and second toothed rims, respectively, are fixed, first and second fixing means secured to the first and second support members, respectively, and making substantial line contact with the shaft around first and second spaced peripheral lines on the shaft, whereby the first and second rims will turn in accordance with the turning of the shaft at said first and second lines, respectively, a stator adjacent the toothed rims, a fixed abutment member adjacent to the stator, spring means effective between said abutment member and the stator for urging the stator towards the toothed rims, means connected to the stator for preventing it from rotating when a measurement is to .be made, magnetic means in the stator for co-operating with the teeth for the generation of alternating current when the shaft turns, and bearings engaging the stator and one of the support members at spaced locations distributed around the entire circumference of said one support member and supporting the stator in space and locating it both axially and radially with respect to said one support member.

6. A pick-up according to claim 5, wherein the spring means urge the stator as aforesaid in both the axial and the radial directions.

7. A pick-up according to claim 5, wherein the stator comprises a carriage in the shape of a segment of a circle, which carriage is urged towards the toothed rims by said spring means.

8. A pick-up according to claim 7 and further comprising means for adjusting the position of the carriage by turning it about the shafit axis.

9. A pick-up according to claim 5, wherein the stator corn-prises a plurality of carriages in the shape of a segment of a circle equally spaced around the shaft axis, which carriages are urged towards the toothed rims by said spring means.

10. A pick-up according to claim 9, wherein the fixed abutment member is a ring which serves as an abutment for the spring means of all the carriages and which is mounted for turning about the shaft axis.

11. A pick-up for torque measuring apparatus, comprising a shaft, first and second juxtaposed toothed rims in spaced relation coaxial with the shaft whereof the teeth are of equal pitch and are of magnetic material, first and second cylindrical support members surrounding the shaft and to which the first and second toothed rims, respectively, are fixed, first and second fixing means secured to the first and second support members, respectively, and making substantial line contact with the shafit around first and second spaced peripheral lines on the shaft, whereby the first and second rims will turn in accordance with the turning of the shaft at said first and second lines, respectively, a stator adjacent the toothed rims, drive means connected to the stator for turning the stator about the shaft axis while the shaft is stationary, means connected to the stator for preventing it from rotating when a measurement is to be made, magnetic means in the stator for co-operating with the teeth for the generation of alternating current when the shaft turns, slip rings and cooperating brushes for conveying from the stator alternating currents generated in the magnetic means thereof, and bearings engaging the stator and one of the support members at spaced locations distributed around the entire circumference of said one support member and supporting the stator inspace and locating it both axially and radially with respect to said one sup port member.

References Cited in the file of this patent UNITED STATES PATENTS 2,217,539 De Bruin Oct. 8, 1940 2,270,760 Mershon Jan. 20, 1942 2,365,564 L-anger Dec. 19, 1944 2,579,629 Tubbs Dec. 25, 1951 2,675,700 Van Degrift et a1 Apr. 20, 1954 2,754,683 Waugh July 17, 1956 2,766,617 Tyler et al. Oct. 16, 1956 FOREIGN PATENTS 763,063 Great Britain Dec. 5, 1956

Claims

1. A PICK-UP FOR TORQUE MEASURING APPARATUS, COMPRISING A SHAFT, FIRST AND SECOND JUXTAPOSED TOOTHED RIMS IN SPACED RELATION CO-AXIAL WITH THE SHAFT WHEREOF THE TEETH ARE OF EQUAL PITCH AND ARE OF MAGNETIC MATERIAL, FIRST AND SECOND CYLINDRICAL SUPPORT MEMBERS SURROUNDING THE SHAFT AND TO WHICH THE FIRST AND SECOND TOOTHED RIMS, RESPECTIVELY, ARE FIXED, FIRST AND SECOND FIXING MEANS SECURED TO THE FIRST AND SECOND SUPPORT MEMBERS, RESPECTIVELY, AND MAKING SUBSTANTIAL LINE CONTACT WITH THE SHAFT AROUND FIRST AND SECOND SPACED PERIPHERAL LINES ON THE SHAFT, WHEREBY THE FIRST AND SECOND RIMS WILL TURN IN ACCORDANCE WITH THE TURNING OF THE SHAFT AT SAID FIRST AND SECOND LINES, RESPECTIVELY, A STATOR ADJACENT THE TOOTHED RIMS, MEANS CONNECTED TO THE STATOR FOR PREVENTING IT FROM ROTATING WHEN A MEASUREMENT IS TO BE MADE, MAGNETIC MEANS IN THE STATOR FOR CO-OPERATING WITH THE TEETH FOR THE GENERATION OF ALTERNATING CURRENT WHEN THE SHAFT TURNS, BALL BEARINGS ENGAGING THE STATOR AND ONE OF THE SUPPORT MEMBERS AT SPACED LOCATIONS DISTRIBUTED AROUND THE ENTIRE CIRCUMFERENCE OF SAID ONE SUPPORT MEMBER AND SUPPORTING THE STATOR IN SPACE AND LOCATING IT BOTH AXIALLY AND RADIALLY WITH RESPECT TO SAID ONE SUPPORT MEMBER, AND ECCENTRICS UPON WHICH THE BALL BEARINGS ARE MOUNTED AND WHICH ARE ADAPTED TO BE TURNED FOR ADJUSTING THE POSITIONS OF THE BEARINGS.