GB2218805A

GB2218805A - Torque measuring device

Info

Publication number: GB2218805A
Application number: GB8911099A
Authority: GB
Inventors: Hans-Juergen Langen
Original assignee: GKN Walterscheid GmbH
Current assignee: Walterscheid GmbH
Priority date: 1988-05-18
Filing date: 1989-05-15
Publication date: 1989-11-22
Also published as: JPH0219732A; IT1233050B; DE3816827A1; GB8911099D0; IT8905163A0; FR2631701A1

Description

1 PD/87127GB1 2'218 8 0 5 TORQUE MEASURING DEVICE The invention relates to

a device for measuring a torque applied to a shaft, comprising a transmitter and a receiver.

There are several prior art processes and devices for measuring a torque, in the case of which the angle of rotation of a shaft to which the torque is applied forms the basis for conversion into the torque value.

It is also known to use the displacement in terms of time of two maximum values measured by proximity sensors cooperating with marker elements attached to the shaft so as to be spaced.

There are also prior art light measuring systems

1 operating with directly radiating light, with the displacement in terms of time of the light passing 15 through being used for torque measuring purposes.

The disadvantage of such known devices is that they provide acceptable results with rotating shafts only. With stationary shafts or with slowly rotating shafts no acceptable values are indicated even if there exists a 20 torque.

1 Such devices cannot be used for machines or equipment in which overloading, for instance during starting, may occur even in the stationary condition. Furthermore, because of their complicated design, such prior art devices find limited application only, i.e. they are predominantly used in laboratories and in connection with test equipment.

2 It is the object of the invention to provide a device for measuring torques applied to a shaft, which is simple in design and sufficiently robust to be suitable to applications other than test equipment and which ensures reliable results even when used in conjunction with rotating as well as at least temporarily stationary shafts subjected to torque.

The invention provides a device for measuring a torque applied to a shaft, comprising a transmitter and a receiver, wherein the transmitter is in the form of a light source generating a diffused light and the receiver is in the form of a light measuring device converting light into a proportional electric signal, especially a photocell or photodiode, and the transmitter and the is receiver are mounted in separate spaces in a housing, the spaces being divided by two slotted discs mounted adjacent to one another, the discs being fixed to the shaft with their fixing points spaced.

The design according to the last preceding paragraph makes it possible to generate a voltage signal which is proportional to the torque applied. It takes advantage of the fact that the amount of light radiating through the apertures is proportional to the area of the passage, a precondition being, however, that diffusely reflected light shines through the apertures and that diffusely reflected light is received at the receiver. Thus, preferably the light source and receiver are not aligned so that light can pass directly from one to the other through the discs. As the two slotted discs are connected to the shaft in such a way that there is a spacing between the fixing points, a sufficiently large angle of rotation is available.

1 C.

3 By using simple means it is possible to provide a measuring device which is not only suitable for being used under test conditions, but also on machinery operating in the open air, i.e. agricultural machinery. The sensors are protected in the housing. Zero reading is permitted by rotating the slotted discs which are preferably fixed on the shaft at an axial distance.

In a further embodiment, the slotted discs are provided with identical apertures arranged so as to overlap by a predetermined amount in the unloaded condition of the shaft. The slotted discs may be arranged in such a way that the apertures are congruent or that there is a certain amount of overlap characterising the zero position from which positive and negative Values are measured. At their radially inner circumference, each slotted disc is connected to one end of a sleeve whose other end is attached to the shaft. This ensures the greatest possible distance between the fixing points.

To achieve complete screening, said other end of the sleeve is connected to a radially outwardly extending flange.

To improve the conditions for ensuring a diffused light, the surfaces limiting the spaces and the surfaces of the slotted discs facing each other are whitened. This may be achieved by providing them with a white coating or covering them with a coat of white paint.

The conditions for generating a diffused light may be improved further by arranging the light source and/or the light measuring device in an indentation in the inner face of the housing.

1 1 4 In a preferred embodiment, the housing is supported on the shaft so as to be non-rotating. This simplifies the connection, via a cable, to a power supply source and the instrument for indicating the torque value.

Finally, in a further embodiment, the apertures of the slotted discs have a shape adapted to achieve a voltage value at the light measuring device which is proportional to the torque applied.

To prevent the results from being falsified, the housing interior is screened against any external light.

The design of an embodiment of a device in accordance with the invention is digrammatically illustrated in the drawings in which:- device; and Figure 1 is a longitudinal section through the Figure 2 is a circuit diagram for the light source; Figure 3 is a circuit diagram for the light meter; Figure 4 is an elevational view of a slotted disc.

The device illustrated in Figure 1 comprises a torque loaded shaft. The housing 2 is supported on the shaft 1 by means of bearings 3. The housing 2 is fixed by means not illustrated so that it is non-rotating, i.e.

it does not participate in the rotation of the shaft 1.

The interior of the housing 2 is screened against any external light. The shaft 1 has a stepped design, i.e.

it comprises a portion 21 with a reduced diameter. The -1 4 In a preferred embodiment, the housing is supported on the shaft so as to be non-rotating. This simplifies the connection, via a cable, to a power supply source and the instrument for indicating the torque value.

The design of an embodiment of a device in accordance with the invention is digrammatically illustrated in the drab-17,-gs in which:- Figure 1 is a longitudinal section through the device; Figure 2 is a circuit diagram for the light source; Figure 3 is a c =cuit diagram for the light meter; and Figure-4 Is an elevational view of a slotted disc.

The'device illustrated In Figure 1 comprises a torque loaded shaft- The housing 2 is supported on the shaft 1 by means of bearings 3. The housing 2 is fixed by means not Illustrated so that It is non-rotating, i.e. it does not participate in the rotation of the shaft 1. The interior of the housing 2 is screened against any external light. The shaft 1 has a stepped design, i.e. it comprises a portion 21 with a reduced diameter. The 1 interior of the housing 2 accommodates two slotted discs 4, 5, with sleeves 8, 9 connected to their radially inner circumference. The sleeves 8, 9 have been provided with bores 10, 11 by means of which they are attached to the shaft I so as to be non-rotating relative to the shaft. Such a non- rotating connection may be achieved by a press-fit, i.e. the sleeves 8, 9 with their bores 10, 11, are firmly seated on the portion of the shaft 1 adjoining the portion 21. In the region of the ends of the sleeves 8, 9 by means of which they are fixed to the shaft 1, they are connected to radially outwardly extending flanges 13, 12. Between the inner face 20 of the housing 2 as well as between the faces 23 of the two flanges 12, 13, the faces 22 of the slotted discs 4, 5 and the outer faces 24 of the sleeves 8, 9 there are formed two spaces A and B, i.e. the interior of the housing 2 is divided into two spaces A and B. The spaces A and B are thus divided by the slotted discs 4, 5 which are mounted adjacent to one another, the discs 4, 5 being fixed to the shaft 1 with their fixing points (at 10 and 11) spaced by the length of the portion 21. As can be seen in Figure 4, the slotted discs 4, 5 comprise apertures 6,7. The slotted discs 4, 5 are arranged relative to each other with their apertures 6, 7 in such a way that the apertures 6 of the slotted disc 4 overlap with the apertures 7 of the slotted disc 5 when the shaft 1 is not subjected to any torque. The region of the space A of the housing 2 has been provided with an indentation 15 which accommodates a transmitter in the form of a light source 14 which, by means of a switch 26, may be connected to a power supply source 18. The light source 14 has been designed to produce a diffused light. The region of the space B of the housing 2 has been provided with an indentation 17 for receiving a receiver in the form of a photocell 16 which provides a light measuring 6 device. The light source 14 and the photocell 16 are, thus, mounted in separate spaces A, B in the housing 2. The photocell 16 is connected to a consumption device in the form of a voltage meter 19. On its scale, the voltage meter 19 indicates a torque which is proportional to the voltage measured. It is the torque applied to the shaft 1. When applying a torque to the shaft 1, the positions of the apertures 6 and 8 in the two slotted discs 4 and 5 may change relative to each other because the shaft 1 rotates. As a result, some of the light produced by the light source 14 may pass through the free cross-section of the region of overlap between the two apertures 6, 7 of the slotted discs 4, 5 from space A into space B. The amount of light shining through increases with an increasing torque. In the case of a negative torque the free cross-section is reduced in size, as a result of which the amount of light passing through is reduced. This also makes it possible to identify the effective direction of the torque applied.

The shape of the apertures 6, 7 may be chosen to be such that proportionality is ensured.

To improve the conditions for producing a diffused light, it is proposed to provide the surfaces facing the spaces, i.e. the surfaces 20, 22, 23, 24 of the housing 2, the slotted discs 4, 5, the sleeves 8, 9 and the flanges 12, 13 with a white coat of paint. The surfaces of the two slotted discs 4, 5 facing each other should also be covered with a white coat of paint.

7

Claims

1. A device for measuring a torque applied to a shaft, comprising a transmitter and a receiver, wherein the transmitter is in the form of a light source generating a diffused light and the receiver is in the form of a light measuring device converting light into a proportional electric signal, especially a photocell or photodiode, and the transmitter and the receiver are mounted in separate spaces in a housing, the spaces being divided by two slotted discs mounted adjacent to one another, the discs being fixed to the shaft with their fixing points spaced.

2. A device according to Claim 1, wherein the slotted discs are fixed on the shaft with an axial distance.

3. A device according to either one of Claims 1 and 2, is wherein the slotted discs are provided with identical apertures arranged so as to overlap by a predetermined amount in the unloaded condition of the shaft.

4. A device according to any one of Claims 1 to 3, wherein at their radially inner circumference, each slotted disc is connected to one end of a sleeve whose other end is attached to the shaft.

5. A device according to Claim 4, wherein said other end of the sleeve is connected to a radially outwardly extending flange.

6. A device according to any one of Claims 1 to 5, wherein the surfaces limiting the spaces and the surfaces of the slotted discs facing each other are whitened, especially by a white coating or a coat of white paint.

8

7. A device according to any one of Claims 1 to 6, wherein the light source and/or the light measuring device is arranged in an identation in the inner face of the housing.

8. A device according to any one of Claims 1 to 7, wherein the housing is supported on the shaft so as to be non-rotating.

g. A device according to any one of Claims 1 to 8, wherein the apertures of the_ slotted discs have a shape adapted to achieve a voltage value at the light measuring device which is proportional to the torque applied.

10. A device according to any one of Claims 1 to 9, wherein the interior of the housing is screened against any external light.

11. A device for measuring a torque substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

Published 1989 at The Patent Office. State House, 66,'71 High Holborn. London WCIR 4TP Further copies maybe obtained from The Patent Office. Sales Branch, St Mary Cray, Orpington, Kent BR,9 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87