GB2395275A

GB2395275A - Sensing rotation of a shaft

Info

Publication number: GB2395275A
Application number: GB0225933A
Authority: GB
Inventors: Niklaas G C Monteyne; Karel Naeyaert
Original assignee: CNH Belgium NV
Current assignee: CNH Industrial Belgium NV
Priority date: 2002-11-07
Filing date: 2002-11-07
Publication date: 2004-05-19
Also published as: GB0225933D0

Abstract

A shaft 14 is disclosed having one end journalled in a support member 12 by means of a bearing 16. A cover 24 is fitted to the opposite side of the support member 12 from the shaft 14 to overlie the bearing 16 and the end of the shaft 14 so as to shield the bearing from dirt. A vane 20 coupled for rotation with the shaft 14 is disposed between the bearing 16 and the overlying cover 24 and a sensor 28 is mounted on the opposite side of the cover 24 for sensing rotation of the vane 20 through the cover 24. This shaft rotation sensing device is suitable for use on the shaft of a film tensioning mechanism of a bale wrapping machine.

Description

- 1 SENSING ROTATION OF A SHAFT

Field of the invention

5 The present invention relates to the sensing of the rotation of a shaft having one end journalled in a support member by means of a bearing, wherein a cover is fitted to the opposite side of the support member from the shaft to overlie the bearing and the end of the shaft, so as to lo shield the bearing from dirt. The ensuing description will

be made by reference to a shaft of a bale wrapping machine but it should be understood that the invention can be applied to the sensing of the rotation of other shafts intended to operate in a dusty or dirty environment, such as 15 in an agricultural vehicle.

Background of the invention

A baler is a machine for towing behind a tractor which 20 cuts grass or hay and compacts it into bales for convenient storage. The bales, which can be square but are assumed herein to be cylindrical rolls, are left in the field for

subsequent collection. A separate wrapping machine is often used to pick up the bales and to wrap them in a plastics 25 film but it is also known to combine the baler and the wrapping machine into one, as in the New Holland 548 Combi, so that bales are transferred directly from the baler to the wrapping machine for wrapping before they are lowered to the ground. The wrapping machine in the New Holland 548 Combi comprises a frame having an inverter "U" shape that is rotatable about a vertical axis. As the frame rotates, the two depending limbs move in a horizontal circle surrounding 35 the bale discharged from the baler. Each of the two arms carries a supply roll of the plastics film and a "pre

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À À À - 2 stretcher" or tensioning mechanism to maintain the film taut. In operation, the bale is rotated about a horizontal 5 axis at the same time as the frame is rotated about a vertical axis. The plastics film is held at its free end by the weight of the bale and the movement of the frame carrying the support rolls acts the draw film from the supply roll. After the bale has been entirely wrapped, the lo plastics films is cut and the wrapped bale is lowered to the ground. The operation of the wrapping machine cannot be monitored from the cab of the towing tractor because the IS driver's view is obstructed by the baler. It is therefore desirable to provide a sensor to warn the driver when, no plastics film is being dispensed, which may occur if the supply roll is exhausted or if the film tears as it is being wound around the bale.

A convenient way of detecting if no film is being dispensed is to monitor the rotation of a shaft, or roller, over which the film is guided. As earlier mentioned, the film is guided over a tensioning mechanism which comprises 25 such a roller and a sensor detecting rotation of a roller of the pre-stretcher will provide the necessary warning of malfunction of the wrapping machine.

The roller, the rotation of which needs to be sensed, 30 iS supported at its opposite ends in bearings that are mounted in brackets which project laterally from the vertical limbs of the wrapping machine frame. Because the wrapping machine has to operate in a hostile environment, the bearings are covered by a protective end cap. This 15 poses a problem as to how one can safely attach to the shaft a device for enabling its rotation to be sensed.

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It is known that the rotation of a shaft can be sensed by attaching to it a vane which is magnetised or made of a ferromagnetic material. In the former case, the magnetised vane can be used to induce a voltage in a stationary coil as 5 it rotates or to operate a reed switch or a Hall effect device. In the latter case, the ferromagnetic vane may alter the magnetic coupling between two coils as it rotates and thereby induce a signal in one of the coils.

lo The design of the sensor is not material to the present invention, which is more concerned with the manner in which it can be attached to the shaft. It is not practicable to mount the vane between the journalled ends of the shaft, because this would interfere with the plastics film guided Is over the shaft and instead the vane has previously been fitted to an extension of the shaft that projects beyond the support bearing and its protective cover. It is also not safe to mount an unprotected vane on a rotating shaft. In the prior art construction, an annular protective cover was

so used and it had to seal against the rotating extension of the shaft making for a complex and expensive construction.

Summary of the invention

25 With a view to mitigating at least some of the problems encountered in the prior art, the present invention provides

a shaft having one end journalled in a support member by means of a bearing, wherein a cover is fitted to the opposite side of the support member from the shaft to so overlie the bearing and the end of the shaft so as to shield the bearing from dirt, characterized in that a vane coupled for rotation with the shaft is disposed between the bearing and the overlying cover and a sensor is mounted on the opposite side of the cover for sensing rotation of the vane s through the cover.

À t À À À À À À The invention offers the advantage that the end cover is not required to make sealing contact with any moving parts. It also offers the advantage that the rotating vane is housed in a closed clean compartment which protects it 5 from snagging against other article and prevents it from causing any damage or injury.

As no modification is required to the bearing end cap, the invention allows a rotation sensor to be added to a lo shaft of an existing installation with minimal disturbance.

In this context, it is advantageous to dimension the vane such that its outer diameter is no greater than the outer diameter of the outer race of the bearing supporting the end of the shaft.

Brief description of the drawings

The invention will now be described further, by way of example, with reference to the accompanying drawing which is 20 a section through the end of a shaft journalled in a support member and fitted with a vane cooperating with a rotation sensor. Description of the preferred embodiment

The drawing shows a detail of a known bale wrapping machine to which a rotation sensor in accordance with the invention has been fitted. The wrapping machine will not be described herein in detail as it is in itself known and as 30 it is only one example of a machine having a shaft to which it is desirable to fit a rotation sensor.

In the drawing, reference numeral 10 designates one of two vertical limbs of a frame having an inverter "U" shape 35 that is rotatable about a vertical axis. The limb 10 carries a plastics film supply roll (not shown) . As the

t - 5 - frame rotates, film is drawn from the supply roll and is wrapped about a bale.

The limb 10 also carries a pre-stretcher of which only s a part is shown in the drawing. Film drawn from the supply roll passes over a series of shafts or rollers, of which only one is shown in the drawing. The shaft 14 is journalled at both its ends in support members 12 formed by brackets that projects laterally from the limb 10, only the lo upper bracket being illustrated.

The shaft 14 is journalled in the support member 12 by means of a bearing 16, shown in the drawing, by way of example, as being a ball bearing with an inner race fitted 15 to the a reduced diameter portion at the end of the shaft 14 and an outer race fitted within a cylindrical collar 26 that is formed integrally with the bracket 12. To protect the bearing 16, a seal 18 is fitted beneath it and above it an end cap 24 is fitted to the collar 26 to prevent any dirt 20 from reaching the bearing 16.

All the elements so far described are conventional and the invention is concerned with the mounting on the shaft 14 of a vane 20 to enable rotation of the shaft 14 to be 25 sensed.

In the prior art, an extension was provided on the

shaft 14 to project beyond the collar 26. Consequently, in order to protect the bearing 16 from dirt, it was necessary 30 to provide a seal to engage the rotating extension of the shaft. Such a seal, aside from being more expensive that a simple cap, is prone to wear.

To avoid this problem, in the present invention a vane 35 20 coupled for rotation with the shaft 14 by a screw 22 is fitted between the bearing 16 and the end cap 24 to lie within the collar 26. The cap 24 is made of a suitable

- 6 - material, such as a plastics material or non-ferrous metal, to allow the rotation of the vane 20 to be sensed by means of a sensor 28 located on the other side of the end cap.

5 The vane 20 has an outer diameter smaller than the outer diameter of the outer race of the bearing 16, which means that it can fit within the collar 26. As a result, no modification is required to the end cap 24.

lo The vane 20 is encased within the sealed clean environment inside the collar. This both protects the vane from damage and prevents it from causing damage or injury.

The vane 20 may have any suitable construction so long 15 as its rotation can be detected by a sensor located on the other side of the end cap 24. It could for example be formed as a disc with magnetic inserts that act on a reed switch, a Hall-effect device or a coil in the sensor 28.

More preferably, the vane 20 is a bar of ferromagnetic 20 material that projects from the opposite sides of the shaft 14 and interacts a magnetic circuit in the sensor 28 as it rotates.

Claims

r. . - 7 CLAIMS

1. A shaft having one end journalled in a support member by means of a bearing, wherein a cover is fitted to 5 the opposite side of the support member from the shaft to overlie the bearing and the end of the shaft so as to shield the bearing from dirt, characterized in that a vane coupled for rotation with the shaft is disposed between the bearing and the overlying cover and in that a sensor is mounted on lo the opposite side of the cover for sensing rotation of the vane through the cover.

2. A shaft as claimed in claim 1, wherein the outer diameter of the vane is no greater than the outer diameter is of the outer race of the bearing supporting the end of the shaft.

3. A shaft as claimed in claim 1 or 2, wherein the shaft forms part of a film tensioning mechanism of a bale 2 o wrapping machine.

4. A shaft having one end journalled in a support member by means of a bearing and fitted with a rotation sensor substantially as herein described with reference to 25 and as illustrated in the accompanying drawing.