GB2111199A

GB2111199A - Movement monitor

Info

Publication number: GB2111199A
Application number: GB08234432A
Authority: GB
Inventors: Douglas Simpson
Original assignee: GEC Mechanical Handling Ltd; GEC Elliott Mechanical Handling Ltd
Current assignee: Alstom Automation International Ltd
Priority date: 1981-12-02
Filing date: 1982-12-02
Publication date: 1983-06-29

Abstract

A movement monitor for giving an indication of the speed and/or direction of a body, more particularly a chain conveyor, having uniformly spaced repetitive features (2) capable of being sensed to indicate movement of the body, incorporates a plurality of detection means (3, 3A, 3B) disposed along the path of movement of the body for sensing the passage of a said feature (2) with the spacing of the detection means such that a number of output signals is generated in turn by movement of the body a distance equivalent to the distance between adjacent features. The distance (7A, 7B) between adjacent detection means (3A, 3B) is preferably P+/-P/n where P is the distance between adjacent features (2) and n is the number of detection means. <IMAGE>

Description

SPECIFICATION Movement monitor This invention relates to a movement monitor mainly for use on a chain conveyor system: On chain conveyor systems an indication of the direction of movement, and the speed of the conveyor is commonly required. The indication of movement could be in the form of pulsed output obtained by using a physical feature of the chain to operate a transducer. This method of transducer operation by the passage of identical links has a severe limitation in that a chain link is usually constructed in such a manner that only one distinctive physical feature, such as a connecting roller, capable of effecting the operation of the transducer exists for each link and consequently only one pulsed signal is available for the movement of the link past a given datum.

One object of the present invention is to more closely monitor chain conveyor movements, although the invention also has application to other moveable members having repetitive physical features as will be apparent from the following description.

According therefore to the invention in its broadest aspect a movement monitor for giving an indication of the speed and/or direction of movement of a body having repetitive features spaced uniformly along it, and capable of being sensed to indicate the passage of the body, incorporates two or more detection means disposed along the path of movement of the body and each arranged to sense the passage of a said repetitive feature, the spacing of the detection means being such that a respective number of output signals are generated in turn by the movement of the body a distance equivalent to the distance between said features.

The detection means may be spaced uniformly apart in the direction of movement of the body with the distance between the first and last of the detection means less than the distance between said repetitive features. Preferably, however, the spacing of the detection means is such that the distance between the first and the last is greater than the distance between adjacent repetitive features of the body, with the distance between adjacent means equal to P+P/n where P is the distance between adjacent repetitive features and n is the number of detection means.

As applied to a chain conveyor system comprising a plurality of individual links each having a distinctive feature capable of being sensed to indicate the passage of the link, a movement monitor in accordance with the invention comprises two or more detection means disposed along the path of movement of the chain and each arranged to sense the passage of said distinctive feature of a link, the spacing of the detection means being such that a respective number of output signals are generated in turn by the movement of said conveyor a distance equivalent to the length of one link.

Whilst the detection means may be uniformly spaced along the path of movement of the conveyor chain, all within the length of one link, the spacing between two adjacent detection means is preferably greater than or less than the length of one link, by a distance equal to P/n where P is the link pitch length and n is the number of detection means.

The detection means may be photo-electric detectors, or may comprise transducers able to transform physical movement into an electrical, pneumatic hydraulic or similar output signals. In the case of a movement monitor applied to a conveyor chain these signals can be used to provide an indication of direction, acceleration, and speed of movement, amount of stretch or contraction of the chain or chain breakage.

The distinctive features may constitute integral parts of the respective links of a conventional conveyor chain, such as connecting rollers, or may be provided by elements which are attached thereto.

A movement monitor in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings of which Figure 1 shows a monitor having its transducers spread within the length of one link of the driving chain of a chain conveyor, and Figure 2 shows a monitor having its transducers spread over several chain links.

On previous system where a greater number of pulses than one per chain link is required in order to more closely monitor the chain movement, it has been customary to make a mechanical coupling to the chain and, by means of appropraite mechanical gears, operate a mechanism which could provide the transducer with a signal of chain movement at the desired frequency which was directly related to chain movement speed and direction.

The invention, see Figure 1, simplifies this mechanism and provides signals to monitor these and additional chain characteristics by using a single physical feature of a chain link 1, such as connecting roller 2, to operate in turn a number of transducers 3 located at appropriate positions along a section of the length of the chain, which is shown only in part. The transducers provide an input to a signal modulating device (not shown) feeding indicating or control circuits, the number of transducers being equal to the number of pulses required to be generated on movement of a single chain link past a given datum.In many cases, however the space available for positioning the transducers 3 along the length of a single link will be inadequate to accommodate them, and to overcome this problem the transducers are conveniently located as at 3A, Figure 2, such that movement of equivalent single features on other links can be monitored in such a manner that when the output from all transducers is modulated on to a common signal iine the resultant signal is identical to that which would be present if the transducers monitored the movement of a single link only. In Figure 2 it is seen that the spacing 7A between adjacent transducers is greater than the length of one link, by an amount equivalent to 1/n of the link length where n is the number of pulses required to be generated on passage of a single chain link past a given datum.However, a spacing 7B of 1/n less than one link length could alternatively be used to give a similar output, as indicated at 3B in Figure 2.

Mathematically the spacing of the transducers can be stated as: For Figure 1 distance 5=P/n; For Figure 2 distance 7A=1 +P/n; or distance 7B=P-1/n where P=chain pitch length n=number of pulses required for one complete movement of chain pitch past a datum.

The type of transducer that is used in the invention are photo electric, but obviously other types of transducer could be used, which are able to transform physical movement into an electrical, pneumatic, hydraulic or similar output signals.

The output waveform signal of the transducer could be of any characteristic suitable for interfacing with a receiving device. These signals can be used to provide an indication of direction, acceleration, and speed of movement, amount of stretch or contraction of the chain or chain breakage. For the purposes of monitoring chain movement it is desirable that the waveform approximates to a squarewave with equal mark to space ratio at the highest chain speed.

Although the invention is mainly applicable to chain conveyors, it may also be used tQ advantage with other movable objects such as belt conveyors, wire ropes, cables having or suitably provided with uniformly spaced repetitive features.

Claims

1. A movement monitor for giving an indication of the speed and/or direction of movement of a body having repetitive features spaced uniformly along it, and capable of being sensed to indicate the passage of the body, incorporates two or more detection means disposed along the path of movement of the body and each arranged to sense the passage of a said repetitive feature, the spacing of the detection means being such that a respective number of output signals are generated in turn by the movement of the body a distance equivalent to the distance between said features.

2. A movement monitor according to Claim 1 wherein the detection means are spaced uniformly apart in the direction of movement of the body with the distance between the first and last of the detection means less than the distance between said repetitive features.

3. A movement monitor according to Claim 1 wherein the spacing of the detection means is such that the distance between the first and the last is greater than the distance between adjacent repetitive features of the body, with the distance between adjacent detection means equal to PlP/n where P is the distance between adjacent repetitive features and n is the number of detection means.

4. A movement monitor for a chain conveyor system comprising a plurality of individual links each having a distinctive feature capable of being sensed to indicate the passage of the link, comprising two or more detection means disposed along the path of movement of the chain and each arranged to sense the passage of said distinctive feature of a link, the spacing of the detection means being such that a respective number of output signals are generated in turn by the movement of said conveyor a distance equivalent to the length of one link.

5. A movement monitor according to Claim 4 wherein said detection means are uniformly spaced along the path of movement of the conveyor chain all within the length of one link.

6. A movement monitor according to Claim 4 wherein said detection means are uniformly spaced along the path of movement of the conveyor chain, with the spacing between two adjacent detection means either greater than or less than the length of one link by a distance equal to P/n where P is the link pitch length and n is the number of the detection means.

7. A movement monitor according to any preceding claim wherein said detection means are photo-electric detectors.

8. A movement monitor according to any preceding claim wherein said detection means are electro/mechanical transducers.

9. A movement monitor according to any preceding claim wherein said detection means produce a pneumatic or hydraulic output signal.

10. A movement monitor substantially as shown in and as hereinbefore described with reference to Figure 1 or 2 of the accompanying drawing.

1 A chain conveyor system incorporating a movement monitor according to any preceding claim.