GB2531573A

GB2531573A - Filament winding apparatus

Info

Publication number: GB2531573A
Application number: GB1418819.7A
Authority: GB
Inventors: Lewis Paul; Dewhirst Mike; Odling Simon
Original assignee: Lentus Composites Ltd
Current assignee: Lentus Composites Ltd
Priority date: 2014-10-22
Filing date: 2014-10-22
Publication date: 2016-04-27
Anticipated expiration: 2034-10-22
Also published as: GB2531573B; GB201418819D0

Abstract

A filament winding apparatus comprises a former 14 rotatable about an axis 16, a resin bath 20,and an adjustment pulley 24 rotatable about an adjustment axis 26, rotation of the former 14 about its axis 16 causing a filament 12 to be drawn through the resin bath 20 and around the adjustment pulley 24 to be wound upon the former 14, wherein the adjustment pulley 24 is adjustably mounted to permit displacement of the adjustment axis to vary a length of filament 12 located between the resin bath 20 and the former 14, a motor 40 being operable to displace the adjustment axis 26 of the adjustment pulley 24. A control method suitable for use with the apparatus is further disclosed wherein data representative of the profile of the former and the rotary position thereof are used to control the displacement of the adjustment axis of the adjustment pulley.

Description

Filament Winding Apparatus This invention relates to a filament winding apparatus, and in particular to a filament winding apparatus suitable for use in the formation of composite material products by the wet-winding of resin coated or impregnated filaments onto a former. However, it may also be used in other applications.

A typical wet-filament winding apparatus uses the rotation of a former onto which a filament is to be wound to draw the filament from a spool, the filament passing through a resin bath in which the filament has a resin material applied thereto before being wound onto the former.

In order to produce an end product having the desired properties, it is desirable to ensure that the resin material is held at a substantially uniform temperature and that the filament is drawn through the resin bath at a substantially uniform speed so as to ensure substantially uniform coating or impregnation of the filament with the resin material. The filament should also be of uniform tension.

Where the former is of a uniform circular cross section and is rotated at a substantially uniform speed, then the rate at which the filament is drawn through the resin bath will be substantially uniform. However, where the former is of other shapes, for example being of non-circular cross-section, or having regions along its length of different circumference, then rotation of the former at a substantially uniform speed does not result in the filament passing through the resin bath at a substantially uniform speed, but rather the filament speed through the resin bath will vary significantly. As a result, parts of the filament will carry more resin material than other parts thereof. Consequently, certain parts of the end product may contain more resin than is desired, and other parts may contain less resin than is required. Too much or too little resin material can significantly impact upon the mechanical properties of the product, and so is undesirable. By way of example, the porosity and adhesion of the resin to the filament material can vary undesirably.

It is known to attempt to compensate for the effect outlined hereinbefore by introducing an idler roller or pulley into apparatus, the pulley being mounted upon an arm, the position of which can be adjusted so that, for example, as the rate at which the filament is being drawn arising from the rotation of the former falls, the pulley is moved, for example raised, to ensure that the rate at which the filament passes through the resin bath is maintained at the desired rate. As the rate at which the filament is drawn by the rotation of the former increases, the pulley is moved in the reverse direction to slow the rate of passage of the filament through the resin bath to the desired speed. In such an arrangement, a cam mechanism is used to drive the pulley for movement in synchronism with the rotation of the former.

Whilst such an arrangement can operate satisfactorily, when it is desired to manufacture a product of a different shape, the cam arrangement needs to be changed to ensure that the movement of the pulley continues to achieve a substantially uniform rate of movement of the filament through the resin bath. As a result, such arrangements are complex and inconvenient to use, and changing between the manufacture of products of different designs is cumbersome.

It is an object of the invention to provide an apparatus in which at least some of the disadvantages with known arrangements are overcome or are of reduced effect.

According to the present invention there is provided a filament winding apparatus comprising a former rotatable about an axis, a resin bath, and an adjustment pulley rotatable about an adjustment axis, rotation of the former about its axis causing a filament to be drawn through the resin bath and around the adjustment pulley to be wound upon the former, wherein the adjustment pulley is adjustably mounted to permit displacement of the adjustment axis to vary a length of filament located between the resin bath and the former, a motor being operable to displace the adjustment axis.

The motor is conveniently an electrically powered motor, for example a servo motor. Alternatively, a stepper motor may be used. A linear actuator arrangement may convert the rotary motion of the motor into a linear displacement.

By using a motor, preferably an electrically driven motor, to adjust the position of the adjustment axis, it will be appreciated that the apparatus can be readily modified to suit the profile of the former in use at any given time.

The position of the adjustment axis is conveniently controlled by using a controller, for example in the form of a computer, to control the operation of the motor and thereby adjust the position of the adjustment pulley.

The controller is preferably supplied with data representative of the profile of the former and of the rotary position of the former, and controls the operation of the motor to adjust the position of the adjustment axis in response thereto, conveniently to maintain the rate at which the filament passes through the resin bath at a substantially uniform level matching an average filament winding speed onto the former despite an instantaneous filament winding speed varying, in use.

The adjustment axis is preferably substantially parallel to the axis of the former. Such an arrangement is advantageous in that displacement of the adjustment axis is less likely to impact upon winding of the filament onto the former. However, arrangements in which the adjustment axis and the axis of the former are not parallel are also possible.

The apparatus is conveniently arranged for use in the manufacture of fibre reinforced, composite material products. By way of example, the filament could comprise glass, polymer, carbon or other suitable material filaments. However, the invention may be used in other applications. By way of example, it could be used in the formation of potted wire products.

By using the apparatus, not only can the application of the resin material to the filament be of enhanced uniformity, and hence a product manufactured using the filament and resin be of enhanced uniformity, but also manufacturing speeds may be increased. The passage of the filament through a resin bath or the like can result in turbulence within the resin, or aeration thereof, which is undesirable, if the filament speed is too high. In conventional arrangements in which the speed at which the filament passes through the resin bath varies, the winding speed is set to avoid generating such turbulence or aeration at points in time when the filament is moving at its maximum speed. For much of the time the actual speed of the filament through the bath is lower. By the use of the invention, the speed at which the filament is drawn through the bath may be held at its optimum level throughout the manufacturing process, thereby achieving increases in production speed.

Variations in the instantaneous filament winding speed relative to the average winding speed are normally proportional to the variations in the filament path length between the resin bath and the contact point between the filament and the former as the former rotates. Accordingly, the invention may be employed by displacing the adjustment axis to maintain a substantially uniform filament path length between the resin bath and the contact point between the former and the filament, as the former is rotated. According to another aspect of the invention, therefore, there is provided a control method suitable for use with such an apparatus, the method comprising the steps of using data representative of the profile of the former and the rotary position thereof in displacing the adjustment axis of the adjustment pulley to maintain a substantially constant filament path length between the resin bath and a contact point between the filament and the former as the former rotates.

The invention further relates to a control method suitable for use with an apparatus as defined hereinbefore, the method comprising the steps of using data representative of the profile of the former and the rotary position thereof to determine a variance between an instantaneous filament winding speed and an average filament winding speed, and using the determined variance in displacing the adjustment axis of the adjustment pulley to maintain the rate at which the filament is drawn through the resin bath at substantially the average filament winding speed.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation of a filament winding apparatus in accordance with an embodiment of the invention; and Figure 2 is a diagrammatic representation illustrating part of the apparatus of Figure 1.

Referring firstly to Figure 1, a filament winding apparatus 10 is illustrated. The apparatus 10 is intended for use in the winding of a resin impregnated reinforcing fibre or filament 12 onto a former 14. The former 14 is of non-circular cross-section, in this case being of lozenge shaped form, and is mounted for rotation about an axis 16. A motor (not shown) is provided and arranged to drive the former 14 at a substantially uniform rate of rotation. The filament 12, in this arrangement, comprises a glass, carbon or polymer fibre, the filament 12 and resin, once cured, forming a composite material.

The filament 12 is stored, prior to winding upon the former 14, upon a spool 18, and it will be appreciated that rotation of the former 14 about the axis 16 draws the filament 12 from the spool 18. After being removed from the spool 18, the filament 12 passes through a resin bath station 20 in which a resin material is applied to the filament 12 before being wound onto the former 14. It will be appreciated, therefore, that the filament 12 is wet-wound onto the former 14.

The former 14 may be moved, axially, during winding to result in the filament being wound along the length of the former 14. Typically, the filament will be wound onto the former 14 in a helical pattern, the winding process continuing with the former moving back-and-forth axially to build up a number of layers onto the former 14. As an alternative to moving the former 14, the filament 12 may be guided by a guide pulley to wind the filament onto the former 14 in such a pattern.

As the former 14 is of non-circular cross-sectional shape, it will be appreciated that the rate at which the filament 12 would typically be drawn from the spool 18 and passed through the resin bath station 20 in a conventional filament winding apparatus would be non-uniform, the speed at which the filament passes through the resin bath station dropping to a relatively low speed when the former is orientated such that the major axis 22 thereof is substantially horizontal, in the orientation illustrated, rising to a maximum when the major axis 22 is substantially vertical. As mentioned hereinbefore, such variations in the speed at which the filament passes through the resin bath station 20 can lead to significant variations in the quantity of resin material applied to the filament 12 and this, in turn, can lead to significant variations in the levels of resin material present in the finished product. Such variations can result in weakening of parts of the finished product, both where excess resin is present and where insufficient resin is present, and the variations in the strength of the product may result in, for example, premature failure thereof or in the product being unsuitable for its intended use.

In accordance with the invention, in the embodiment of the invention illustrated in the accompanying drawings, an adjustment pulley 24 is provided, the adjustment pulley 24 being located between the resin bath station 20 and the former 14. The filament 12 is entrained around the adjustment pulley 24 and a pair of idler pulleys 26, 28. The adjustment pulley 24 is rotatable about an adjustment axis 30 which, in this embodiment, extends parallel to the axis 16 of the former 14. The adjustment pulley 24 is rotatably mounted to a carriage 32 which, in turn, is slidably mounted to a support 34 so as to permit the carriage 32 to be moved between raised and lowered positions, towards and away from the idler pulleys 26, 28. By way of example, the carriage may include a projection 36 slidable with a slot 38 provided in the support 34, the engagement of the projection 36 within the slot 38 guiding the carriage 32 for substantially vertical movement.

The movement of the carriage 32, and hence of the adjustment pulley 24, is controlled using an electrically controlled motor 40. In the arrangement shown, the motor 40 is a servo motor operable to drive a threaded shaft 42 for rotation, the threaded shaft 42 being in threaded engagement with the carriage 32 with the result that, upon operating the motor 40 to drive the shaft 42 for rotation, the carriage 32 is displaced along the shaft 42 as a result of the threaded cooperation therebetween, the direction of movement of the carriage 32 depending upon the direction of rotary movement of the shaft 42.

Whilst a servo motor is used in the arrangement described, a stepper motor or other suitable form of motor could be use. Furthermore, whilst one linear actuator technique for converting the rotary output of the motor 40 into displacement of the adjustment axis 30 is described, a number of other mechanisms may be used to achieve this effect. By way of example, a rack and pinion based system could be used.

It will be appreciated that by displacing the adjustment axis 30 in the upward direction, in the orientation illustrated, the length of the filament path between the resin bath station 20 and the contact point 12a at which the filament 12 contacts the former 14 is increased, and that by displacing the adjustment axis 30 in the downward direction, the filament path is shortened.

The motor 40 is connected to a control unit 46 which is operable to control the operation of the motor 40 and thereby control displacement of the adjustment axis 30 and the position of the adjustment pulley 26, the control unit 46 controlling the displacement of the adjustment axis 30 using data 48 representative of the profile of the former 14 and the output of a sensor 50 providing information regarding the angular or rotatory position of the former 14.

One way in which the apparatus 10 may be operated is to control the displacement of the adjustment axis 30 to maintain a substantially constant filament path length between the resin bath station 20 and the contact point 12a. By way of example, the data 48, for example derived from CAD software views of the former 14, may be used to model the location of the contact point 12a as the former 14 is rotated, and to calculate an uncompensated filament path length between the resin bath station 20 and the contact point 12a for a number of angles of the former 14. Obviously, the uncompensated path lengths will vary. The control unit 46 uses the uncompensated path lengths to determine appropriate positions for the adjustment axis 30 and controls the operation of the motor 40 to displace the adjustment axis 30 so as to result in the filament path length between the resin bath station 20 and the contact point 12a remaining substantially constant as the former 14 rotates. By achieving a substantially uniform filament path length in this manner, the rate at which the filament 12 passes through the resin bath station 20 will be of enhanced uniformity.

Alternatively, in use, as the former 14 is rotated, the control unit 46 determines a variance between an instantaneous filament winding speed, ie the instantaneous speed of movement of the filament 12 approaching the former 14, which is determined using the data 48 representative of the shape or profile of the former 14 and its angular orientation provided by the output of the sensor 50, and an average filament winding speed, ie the average of the instantaneous filament winding speeds over a full rotation of the former 14. If the instantaneous filament winding speed is lower than the average filament winding speed, then the control unit 46 drives the motor 40 so as to result in upward movement of the carriage 32 and upward displacement of the adjustment axis 30. The upward displacement of the adjustment axis 30 draws additional filament 12 through the resin bath station 20 supplementing that resulting from the rotation of the former 14 alone. As a result, the rate at which the filament 12 is drawn through the resin bath station 20 is increased. By appropriate control over the displacement of the adjustment axis 30, the rate at which filament 12 is drawn through the resin bath 20 can be held at substantially the average filament winding speed despite the instantaneous filament winding speed being at a reduced level. Similarly, if the instantaneous filament winding speed exceeds the average filament winding speed, then by appropriate control over the motor 40 to displace the adjustment axis in the downward direction, the rate at which the filament is drawn through the resin bath station 20 can be held at substantially the average filament winding speed.

It will be appreciated that by controlling the operation of the motor 40 using either technique outlined hereinbefore, therefore, the speed at which the filament passes through the resin bath station 20 can be held at a substantially uniform level despite the instantaneous filament winding speed varying. As a result, the resin bath station 20 is able to operate to apply a substantially uniform quantity of resin material to the filament and so less variation in the quantity of resin material present in the different parts of the finished product can be achieved.

The enhanced uniformity is achieved independently of the actual rotary speed of the former 14 provided the former 14 is rotated at a uniform speed.

The incorporation of the invention into an existing filament winding apparatus simply involves the addition of the adjustment pulley 24 and associated supports and controls, but does not require significant changes to be made to the manner in which the remainder of the apparatus operates. Retrofitting of the functionality of the invention into existing equipment is thus relatively straightforward. The invention may thus be employed without requiring the acquisition of significant additional expensive equipment.

In addition to, or as an alternative to, using data representative of the shape of the product to be formed, the apparatus may incorporate a sensor sensitive to the speed of the filament approaching the former, the position of the adjustment pulley 24 being controlled in response to the measured speed so as to maintain the speed at which the filament is drawn through the resin bath station 20 at substantially a uniform level. By way of example, the sensor could comprise an encoder associated with a pulley around which the filament passes, the encoder measuring the rate of rotation of the pulley.

In the arrangements described hereinbefore the adjustment pulley 24 is moved along a linear path. It will be appreciated that this need not always be the case. By way of example, the pulley 24 could be mounted upon a pivotable arm, the motor 40 controlling the angle of the arm to adjust the position of the adjustment pulley 24. In such an arrangement the adjustment pulley 24 would be movable along an arcuate path. Despite the path followed by the adjustment pulley 24 being different, operation of the invention is substantially as described hereinbefore.

Products manufactured using the invention are of enhanced uniformity, the disadvantages associated with non-uniform quantities of resin being present within the product being avoided.

By using the apparatus and method of the invention, not only can the application of the resin material to the filament be of enhanced uniformity, and hence a product manufactured using the filament and resin be of enhanced uniformity, but also manufacturing speeds may be increased. The passage of the filament through a resin bath or the like can result in turbulence within the resin, or aeration thereof, which is undesirable, if the filament speed is too high. In conventional arrangements in which the speed at which the filament passes through the resin bath varies, the winding speed is set to avoid generating such turbulence or aeration at points in time when the filament is moving at its maximum speed, and for much of the time the actual speed of the filament through the bath is lower. By the use of the invention, the speed at which the filament is drawn through the bath may be held at substantially its optimum level throughout the manufacturing process, thereby achieving increases in production speed without causing turbulence or aeration of the resin within the bath.

Whilst the invention is described hereinbefore in relation to the winding of a reinforcing fibre or filament onto a former of lozenge shape, it will be appreciated that the invention is not restricted in this regard. It may be used in the winding of filaments onto formers of other shapes, for example polygon shaped formers, and in the winding of filaments onto formers of non-uniform cross-sectional shape along their lengths. Furthermore, it may be used in conjunction with large, irregularly shaped formers in the manufacture of products. The invention could, for example, be used in the manufacture of bent pipe sections. Such an arrangement may require the use of a fibre pay-out head of increased articulation having a relatively large number of degrees of freedom or, for example, a contained articulating system. However, these represent just some ways in which the apparatus and method described hereinbefore may modified without departing from the scope of the invention as defined by the appended claims.

Claims

CLAIMS: 1. A filament winding apparatus comprising a former rotatable about an axis, a resin bath, and an adjustment pulley rotatable about an adjustment axis, rotation of the former about its axis causing a filament to be drawn through the resin bath and around the adjustment pulley to be wound upon the former, wherein the adjustment pulley is adjustably mounted to permit displacement of the adjustment axis to vary a length of filament located between the resin bath and the former, a motor being operable to displace the adjustment axis of the adjustment pulley.
2. An apparatus according to Claim 1, wherein the motor is an electrically powered motor.
3. An apparatus according to Claim 2, wherein the motor is a servo motor or a stepper motor.
4. An apparatus according to Claim 2 or Claim 3, further comprising a linear actuator arrangement for converting the rotary motion of the motor into a linear displacement.
5. An apparatus according to any of the preceding claims, wherein the adjustment axis is displaceable along a linear path.
6. An apparatus according to any of Claims 1 to 4, wherein the adjustment axis is displaceable along an arcuate path.
7. An apparatus according to any of the preceding claims, wherein the position of the adjustment axis is controlled by using a controller to control the operation of the motor and thereby adjust the position of the adjustment pulley.
8. An apparatus according to Claim 7, wherein the controller is supplied with data representative of the profile of the former and of the rotary position of the former, and controls the operation of the motor to adjust the position of the adjustment axis in response thereto.
9. An apparatus according to Claim 8, wherein the controller is operative to maintain the rate at which the filament passes through the resin bath at a substantially uniform level matching an average filament winding speed onto the former.
10. An apparatus according to any of the preceding claims, further comprising a sensor operable to sense the speed of movement of the filament, the motor being operable in response to the sensed speed.
11. An apparatus according to any of the preceding claims, wherein the adjustment axis is substantially parallel to the axis of the former.
12. An apparatus according to any of the preceding claims, wherein the former is of non-circular cross-section shape, at least in part.
13. An apparatus according to any of the preceding claims and arranged for use in the manufacture of fibre reinforced, composite material products.
14. An apparatus according to Claim 13, wherein the filament comprises glass, polymer, carbon or other suitable material filaments.
15. A control method suitable for use with an apparatus according to any of the preceding claims, the method comprising the steps of using data representative of the profile of the former and the rotary position thereof in displacing the adjustment axis of the adjustment pulley to maintain a substantially constant filament path length between the resin bath and a contact point between the filament and the former as the former rotates.
16. A control method suitable for use with an apparatus according to any of the preceding claims, the method comprising the steps of using data representative of the profile of the former and the rotary position thereof to determine a variance between an instantaneous filament winding speed and an average filament winding speed, and using the determined variance in displacing the adjustment axis of the adjustment pulley to maintain the rate at which the filament is drawn through the resin bath at substantially the average filament winding speed.