NL2033693B1

NL2033693B1 - Chopper device

Info

Publication number: NL2033693B1
Application number: NL2033693A
Authority: NL
Inventors: Willem Van Toor Jan
Original assignee: Hamamelia B V
Priority date: 2022-12-08
Filing date: 2022-12-08
Publication date: 2024-06-14
Also published as: EP4630609A1; WO2024123173A1

Abstract

Chopper device for cutting a ﬁbre filament into ﬁbre pieces, comprising: a frame, comprising a plate member provided with at least one opening therethrough; a pair of mutually counter-rotatable rollers which comprises a driven roller and a cooperating roller, each rotatably mounted to the frame, wherein the pair of rollers is arranged to receive the filament between the rollers and engage the received filament on either side thereof, wherein at least one of the rollers is tangentially provided with blades for cutting the engaged ﬁlament into ﬁbre pieces; an electric drive, mounted to the frame and arranged to rotationally drive the driven roller, wherein the pair of rollers and the electric drive are respectively mounted on opposite sides of the plate member, wherein the electric drive comprises a stator and a rotor shaft rotatably arranged in the stator and coaxially coupled to the driven roller; and at least one bearing arranged to rotatably support at least one of the rollers, wherein the bearing is positioned in the opening of the plate member.

Description

CHOPPER DEVICE

The present invention relates to a chopper device for cutting a fibre filament, particularly filaments in a strand, into fibre pieces.

It is known to divide fibres into pieces of a specific length such that the fibre pieces can be added to material to improve properties of that material. Hereto, the fibres are often supplied in long bundles that are fed into a cutting device, also known as a chopper, in which the bundles are cut between rollers. In a conventional chopper at least one of the rollers is provided with cutting blades. Another roller may have recesses in its cylindrical outer surface wherein, where the rollers meet each other, the outer edge of a cutting blade can reach into such a recess and thereby cut the bundle of filaments so that the filaments break. A strand, which can be a bundle of glass or carbon filaments or any other material, can thus be cut into short lengths to be worked into a material such as plastic, for example for the purpose of reinforcing the plastic.

To work the fibre pieces into a resin material, it is known to mount a chopper device on a handheld resin spray gun to form a chopper gun assembly, wherein the fibre pieces are added to a stream of resin ejected from the spray gun onto an object to be sprayed with the resin material provided with the fibre pieces, for instance in an open moulding process.

For rotationally driving a roller, existing chopper handguns are provided with an air motor which can be decoupled from the chopper for servicing. While chopping fibres, considerable forces act on the motor. For instance, the roller shaft that is driven by the motor is to withstand the radial forces exerted by the other roller. In addition to the resulting bulkiness of such known air motors, which weigh at least 1 to 2 ke, the air motors have the drawback that they require frequent servicing.

Moreover, it has been found that the air motors have a short lifetime in general.

It is known that the rotational speed of the rollers affects the rate of producing cut fibres. In turn, the fibre dosage that is added to the resin affects the properties of the final product. Accurately dosing is a challenge when using air motors, as the rotational speed changes with a changing load on the chopper, or due to wear, resistance or air pressure changes. At times, the air motors cannot be controlled sufficiently for ensuring that the filaments are accurately cut and that optimal fibre pieces are obtained.

In some solutions, the air motor is replaced by a separate servomotor that is to be coupled to the driven roller of the chopper. As the components of the servomotor such as the shaft and the bearings are insufficiently robust for chopping fibres, the servomotor is coupled to the roller via a transmission, in particular a gearbox or an additional coupling. As an alternative, simply a more robust servomotor may be selected. Adding the transmission, or selecting a more robust servomotor, increases the total weight of the chopper device, which is then less suitable for handheld applications.

It is therefore an object of the present invention, amongst other objects, to provide a chopper device wherein at least one of the aforenoted drawbacks are at least partially alleviated.

Thereto, a chopper device for cutting a fibre filament into fibre pieces is provided, wherein the chopper device comprises: - a frame, comprising a plate member provided with at least one opening therethrough; - a pair of mutually counter-rotatable rollers which comprises a driven roller and a cooperating roller, each rotatably mounted to the frame, wherein the pair of rollers is arranged to receive the filament between the rollers and engage the received filament on either side thereof, wherein at least one of the rollers is tangentially provided with blades for cutting the engaged filament into fibre pieces; - an electric drive, mounted to the frame and arranged to rotationally drive the driven roller, wherein the pair of rollers and the electric drive are respectively mounted on opposite sides of the plate member, wherein the electric drive comprises a stator and a rotor shaft rotatably arranged in the stator and coaxially coupled to the driven roller; - at least one bearing arranged to rotatably support at least one of the rollers, wherein the bearing is positioned in the opening of the plate member.

Herein. the term cutting is used for any action resulting in the separation of a filament into pieces, including bending the filament to break it. The cutting blades for cutting the filaments may be metal blades or may consist of any other suitable material. Furthermore, each roller can also be provided with other blades that are not cutting blades, but that are blades for tensioning the strand by pushing the strand into a zigzag shape between the rollers.

By positioning the bearing in the plate member, wherein the at least one bearing is preferably seated in, fixed to or integrated in the plate member, forces acting on the bearing can be absorbed by the frame more directly such that a material-efficient chopper device can be obtained.

Moreover, as the bearing is positioned in the plate member, a larger bearing can be selected and mounted in a correspondingly sized opening in the plate member, without increasing the overall bulkiness of the chopper device. Larger bearings have the advantage that they can be more robust.

Preferably, the at least one bearing is a rolling bearing, such as a ball bearing.

The position of the bearing enables an electric drive to be coaxially coupled to the driven roller, without the additional weight of an interposed gearbox or additional coupling. Due to the overall weight reduction, the chopper device can be more suitably used in a handheld chopper gun.

Since an electric drive generally requires less servicing than an air motor of corresponding power, the electric drive can be integrated into the frame such that the electric drive can be made more lightweight than the air motor of corresponding power. Moreover, an electric drive can be more energy-efficient than an air motor.

According to an embodiment of the chopper device, the at least one bearing comprises a drive bearing arranged to rotatably support the rotor shaft at a location between the stator and the driven roller. In this case, the plate member is thus provided with an opening at the location of the electric drive and the driven roller, such that the rotor shaft may extend, from the stator to the roller, through the plate member via said opening.

In case a separate motor, which comprises a drive shaft supported by bearings supported by the motor housing, is mounted to the frame, the bearing closest to the driven roller is positioned adjacent the opening of the plate member. By positioning the bearing instead inside the opening, the bearing is positioned closer to the driven roller such that the force acting on the bearing, due to the bending moment resulting from the radial forces on the driven roller. is reduced or minimised.

This way, the drive bearing can withstand the forces exerted on the driven roller more efficiently.

Preferably, the drive bearing is spaced 0.1 to 5S mm from the driven roller as seen along the shaft.

To position the drive bearing close to the driven roller, the electric drive may comprise a housing supporting the drive bearing, wherein the part of the housing that contains the drive bearing extends into the opening in the plate member. It is then preferred if the opening is shaped accordingly to accommodate the part of the housing that contains the drive bearing, preferably in a formfitting manner.

It is however preferred if the drive bearing is fixed to or integrated in the plate member, as opposed to supported by a housing of the electric drive. That is, if the drive bearing is to be supported by the housing of the electric drive, the housing is to be structurally designed to absorb the forces on the drive bearing, with the consequence of an increased overall weight of the electric drive. Bearings of known lightweight electric motors, weighing for instance less than 3 kg, are therefore not sufficiently robust for driving the driven roller for the purpose of cutting fibres. If, instead, the drive bearing is fixed to or integrated in the plate member, a drive bearing can be selected that is more robust than the bearing of a lightweight electric motor that is supported by the motor housing, while the weight of the electric drive, in particular a housing part thereof, can be minimised such that the overall weight of the chopper device can be reduced.

The electric drive then preferably comprises a housing part defining an inner space in which the stator is arranged, wherein the housing part is mounted to the plate member. The housing part can thus keep the stator in place. Preferably, the plate member closes one side of the inner space, such that the stator is kept in place by the housing part together with the plate member. As one side of the inner space is closed by the plate member and the housing part can thus be open on that side, the stator can be housed in a material-efficient manner. This way, the weight of the chopper device can be further reduced.

Preferably, the housing part comprises an end member closing a side of the inner space opposite the one side closed by the plate member, wherein the rotor shaft extends through the housing. The end member is preferably provided with an end bearing fixed therein and arranged to rotatably support the rotor shaft. If the rotor shaft is supported at one end by the end bearing in the end member and further supported by the drive bearing at the opposite end of the housing, the rotor shaft and the driven roller together can be efficiently supported by only two bearings.

According to a preferred embodiment of the chopper device, the driven roller is mounted directly onto the rotor shaft. This way, a single shaft suffices, as it can generally withstand, in an efficient manner, more loading than a shaft coupling. Mounting the driven roller on the rotor shaft thus has the advantage that a compact, lightweight and/or robust chopper device can be obtained. As such, as opposed to mounting the driven roller on the shaft of a conventional air motor, the robust shaft on which the driven roller is mounted is used for the rotor of the electric drive.

According to a further embodiment of the chopper device, the at least one bearing comprises a cooperating roller bearing arranged to rotatably support the cooperating roller. Positioning the bearing for the cooperating roller in the opening of the plate member allows the cooperating roller to have a small diameter relative to the driven roller.

The chopper device may further comprise a tensioning roller, rotatably mounted to the frame and arranged to pretension the filament to be received between the driven roller and the cooperating roller, Preferably, the tensioning roller is counter-rotatable relative to one of the pair of rollers, wherein the tensioning roller and the one roller are arranged to receive the filament therebetween and engage the received filament on either side thereof. This way, it can be ensured that the filament is tensioned before entering engagement by the pair of rollers for cutting the filament. The 5 one roller is for instance the driven roller. Preferably, the diameter of the one roller is at least 1.5 times, preferably at least twice, the diameter of the tensioning roller. This prevents the fibre filament from remaining in contact with the tensioning roller and allows the fibre filament to be fed to the pair of rollers and be received therebetween.

As such, according to another aspect of the present invention, a chopper device for cutting a fibre filament into fibre pieces is provided, preferably according to any of the embodiments described above, wherein the chopper device comprises: - a frame; - a pair of mutually counter-rotatable rollers which comprises a driven roller and a cooperating roller, each rotatably mounted to the frame, wherein the pair of rollers is arranged to receive the filament between the rollers and engage the received filament on either side thereof, wherein at least one of the rollers is tangentially provided with blades for cutting the engaged filament into fibre pieces; - a tensioning roller, rotatably mounted to the frame and arranged to pretension the filament to be received between the driven roller and the cooperating roller, wherein the diameter of at least one of the driven roller and the cooperating roller is at least 1.5 times, preferably at least twice, the diameter of the tensioning roller.

Preferably, wherein the one roller that is provided with blades is tangentially further provided with pressure ribs extending substantially in axial direction, wherein the other roller is provided with recesses corresponding to the blades, wherein the blades are arranged to sequentially move into corresponding recesses during rotation, preferably while remaining spaced from side walls of the recess, whilst the neighbouring pressure ribs on either side of the blade in the recess abut the other roller. It is then further preferred if the one roller provided with the blades is dimensioned such that a blade of the roller touches the fibre before the next pressure rib contacts the other roller.

Preferably, the pressure ribs comprise elastic material and are shaped in such a manner that a deformation of the elastic material upon compression substantially comprises the bending of a radially outwardly extending part of the pressure rib. As a result, the material is loaded in flexion more than in compression, which enables a greater movement at a substantially constant pressure force. For example, the radially outwardly extending part of the pressure rib may be zigzagged in shape, as seen in the plane of rotation.

For a compact chopper device, it is preferred if each roller is rotatably mounted to the plate member of the frame.

According to a preferred embodiment of the chopper device, the stator has a stator diameter in a direction perpendicular to the rotor shaft and a stator length in a direction parallel to the rotor shaft, wherein the stator diameter exceeds the stator length. This allows the drive to supply enough torque to start the chopper device in high-torque applications, for instance in the case of cutting fibres of a particular type, whereas conventionally a gearbox is employed to boost the start-up torque of the motor. Preferably, the outer stator diameter is at least 1.5 times, preferably at least twice, the stator length.

Although the electric drive may be a servo drive, the electric drive is preferably a brushless DC drive comprising a permanent magnet arranged on the rotor shaft, wherein the stator surrounds the permanent magnet. The rotational speed of the driven roller can be accurately controlled with the brushless DC drive relative to, e.g., an air motor, since the brushless DC drive can be controlled regardless of, e.g., a changing load on the chopper or other factors. The brushless DC drive generally weighs less relative to a servomotor and is, moreover, more energy efficient. Relative to the servo drive, the brushless DC drive enables a sensor-less control of the drive of the chopper device. As a sensor in a servomotor is susceptive of failure and generally requires frequent servicing, the chopper device can be driven more reliably by the brushless DC drive without requiring frequent maintenance. This further allows the drive to be further integrated into the frame of the chopper device, such that the weight of the chopper device can be further minimised. Hereto, itis preferred if the permanent magnet of the motor is mounted on the same shatt as the driven roller.

As such, although brushless DC motors are known to be lightweight relative to, e.g., servomotors, the components of separately available brushless DC motors are not sufficiently robust for withstanding the forces resulting from chopping fibre filaments. Instead of increasing the weight of the DC motor to adapt the motor to the large forces, it is preferred to fix the drive bearing into the plate member of the frame, as explained above.

Moreover, the brushless DC drive enables a power supply without encoder or sensor wiring, as used for a servo drive, and thus allows a three-core connector cable for controlling the drive.

Hence, a chopper device with a simple drive can be obtained.

The above advantages of the brushless DC drive in a chopper device can also be achieved, to a greater or lesser extent, when the at least one bearing is not positioned in the opening of the plate member of the frame as in the above embodiments. As such, according to another aspect of the present invention, a chopper device for cutting a fibre filament into fibre pieces is provided, preferably according to any of the embodiments described above, wherein the chopper device comprises: - a frame; - a pair of mutually counter-rotatable rollers which comprises a driven roller and a cooperating roller, each rotatably mounted to the frame, wherein the pair of rollers is arranged to receive the filament between the rollers and engage the received filament on either side thereof, wherein at least one of the rollers is tangentially provided with blades for cutting the engaged filament into fibre pieces; - an electric drive, mounted to the frame and arranged to rotationally drive the driven roller, wherein the electric drive comprises a stator and a rotor shaft rotatably arranged in the stator and coaxially coupled to the driven roller, wherein the electric drive is a brushless DC drive comprising a permanent magnet arranged on the rotor shaft in the stator.

Further provided is a chopper gun assembly, comprising a chopper device for cutting a fibre filament into fibre pieces as described above, and a spray gun device arranged to spray out the fibre pieces. Due to the low weight of the chopper device, the chopper device can be conveniently mounted on the spray gun to form a handheld chopper gun assembly. Alternatively, a robot arm, in particular a robot arm with a limited lifting capacity, can be provided with the chopper gun assembly.

As a further alternative, a concrete mixing transport vehicle, in particular a truck, may be provided with a chopper device for cutting a fibre filament into fibre pieces as described above, wherein the transport device is arranged to mix the fibre pieces with concrete. As trucks often have a 12 V - 36 V power source, the lightweight electric drive of the chopper device can be conveniently powered by the power source of the truck, which is particularly advantageous at a construction site with limited access to grid power.

Hereafter, the invention is further elucidated with reference to the attached drawings, wherein: - Figures | and 2 represent isometric views, from different sides, of a chopper handgun assembly comprising a chopper device and a spray gun device; - Figures 3 and 5 represent various views of the chopper device, as such, of the chopper handgun assembly shown in Figures 1 and 2;

- Figure 4A represents a front view of the chopper device shown in Figures 3 and 5; - Figure 4B represents a front view of a variant of the chopper device shown in Figure 4A; - Figure 6 represents a cross-sectional view of the chopper device shown in Figures 3, 4A and 5.

Figures 1 and 2 show a chopper handgun assembly 100, comprising a chopper 1 for cutting fibre filaments in a strand into short lengths, and a spray gun 2 of the type that is known in the art. The chopper 1 is mounted on the spray gun 2 via a mounting bracket 3 of the assembly 100. The spray gun 2 comprises a spray gun housing 20, a handle 21 for manually holding the spray gun 2, connectors 22 for supplying liquid resin to the spray gun housing 20, a nozzle 23 for ejecting the resin out of the spray gun housing 20, and a trigger 24 for manually operating the spray gun 2 to spray the resin onto a target. The short fibre pieces produced by the chopper 1 are caught by a funnel 4 of the assembly 100, wherein the funnel 4 is arranged to receive the fibre pieces and guide them into the stream of resin ejected from the spray gun 2 for mixing the fibre pieces with the resin.

The chopper 1 comprises a frame plate 10. The mounting bracket 3 for mounting the chopper 1 onto the spray gun 2 is, at one end, fixed to frame plate 10 and at the other end to the spray gun housing 20. The chopper 1 comprises a driven roller 11, a cooperating roller 12 and a tensioning roller 13, each rotatably mounted to the frame plate 10, and an electric drive 30 mounted to the frame plate 10 and arranged to rotationally drive the driven roller 11.

Referring to Figures 3-5, a feed-in 14 can be seen fixed to, and extending from, the frame plate 10 and arranged to guide a strand of filaments 200 to the rollers 11, 12, 13 in a feed direction F. The cooperating roller 12 is provided with a cover plate 120. In Figure 4A, the respective rotational directions of the driven roller 11, the cooperating roller 12 and the tensioning roller 13 are indicated by arrows R1, R2 and R2, respectively. First, the driven roller 11 and the tensioning roller 13 receive the filaments therebetween and engage the strand of filaments 200 on either side thereof to stretch the filaments. Then, the filaments are guided along the driven roller 11 and received between the driven roller 11 and the cooperating roller 12 and engaged thereby on either side of the strand.

In Figure 4B, a variant of the chopper | in Figure 4A is shown, wherein like elements are indicated by like reference signs. The diameter D1 of the driven roller 11 is about twice the diameter D3 of the tensioning roller 13. A diameter D3 of the tensioning roller 13 that is small relative to the diameter of the roller to which the tensioning roller 13 is counter-rotatable, reduces the risk of the fibre filament 200 from remaining in contact with the tensioning roller 13.

The cooperating roller 12 is tangentially provided with cutting blades 121 with sharp outer edges.

Each edge may be a crenated edge. In other words, the edge is rough and not in a straight line.

Such edges may be obtained by a grinding operation when machining the sharp edge. The driven roller 11 is tangentially provided with recesses 111. Where the two rollers 11, 12 meet each other, the outer edge of a cutting blade 121 can reach into such a recess 111 and thereby cut the bundle of filaments received therebetween so that the filaments break. The cut fibres 201 are received by the funnel 4 shown in Figures 1 and 2, which guides them into the stream of resin ejected from the spray gun 2.

The driven roller 11 and the cooperating roller 12 each comprise a gear 112, 122. The gears 112, 122 intermesh such that the driven roller 11 and the cooperating roller 12, specifically the recesses 111 and the blades 121, mutually counter-rotate at the same tangential velocity. The tensioning roller 13 is similarly arranged to rotate at the same tangential velocity as the driven roller 11, but in this example the rotational motion of the driven roller 11 is transmitted trom the driven roller 11 to the tensioning roller 13 through friction.

In the following, the electric drive 30 is described in more detail with reference to Figures 5 and 6.

The electric drive 30 comprises a frameless electric motor stator 31, a single shaft 32 extending through the stator 31, and a permanent magnet 33 mounted on the shaft 32 to form a brushless DC drive. To keep the stator windings of the DC drive in place, the stator 31 is partly enclosed by a half open drive housing 34, that is fixed to the frame plate 10 of the chopper 1 by conventional fastenings means 340 that allow disassembly of the drive 30 for servicing. The inner space of the drive housing 34 is closed by the frame plate 10 at the open end of the half open drive housing 34.

The drive housing 34 is provided with an outer cooling structure for cooling the electric drive 30.

The cooling structure is formed by parallel cooling ribs 341, each extending annularly along the cylindrical side of the drive housing 34. The electric drive 30 is provided with a three-core cable 35 for supplying power to the drive 30.

One end of the shaft 32 is rotatably supported by an end bearing 36 supported by an end plate 342 of the drive housing 34. A second bearing supporting the shaft 32, referred to as the drive bearing 37, is fixed to the frame plate 10 of the chopper 1 inside an opening 15 thereof. The shaft 32 extends through the drive bearing 37 to the other side of the frame plate 10, where the driven roller 11 is coupled directly to the shaft 32. In this embodiment, the bearings 36, 37 are ball bearings.

The stator 31 has a stator diameter Ds and a stator length Ls. The stator diameter Ds exceeding the stator length Ls enhances the start-up torque that can be supplied by the drive 30 for starting the chopper 1 in high-torque applications.

In the arrangement shown in Figures 1-6, the rollers 11, 12, 13 radially exert forces on one another during operation. Thus far, mainly light air motors with relatively large bearings have been used in chopper handguns for the purpose of driving the rollers. Such air motors are maintenance- and energy-intensive. By incorporating an electric drive in the frame plate 10 that rotatably supports the rollers 11, 12, 13, the weight of the chopper 1 can be considerably reduced.

The figures and the above description serve to illustrate specific embodiments of the invention and do not limit the scope of protection defined by the following claims.

Claims

CONCLUSIONS

1. A chopper apparatus for cutting a fiber filament into fiber pieces, comprising: - a frame comprising a plate member having at least one opening therethrough; - a pair of mutually counter-rotatable rollers comprising a driven roller and a cooperating roller, each rotatably mounted on the frame, the pair of rollers being adapted to receive the filament between the rollers and to engage the received filament on opposite sides thereof, at least one of the rollers being tangentially provided with blades for cutting the engaged filament into fiber pieces; - an electric drive mounted on the frame and adapted to rotately drive the driven roller, the pair of rollers and the electric drive being mounted on opposite sides of the plate member respectively, the electric drive comprising a stator and a rotor shaft rotatably mounted in the stator and coaxially coupled to the driven roller; - at least one bearing adapted to rotatably support at least one of the rollers, the bearing being positioned in the opening of the plate member.

2. The chopper apparatus of claim 1, wherein the at least one bearing comprises a drive bearing configured to rotatably support the rotor shaft at a location between the stator and the driven roller.

3. Chopper device according to claim 1 or 2, wherein the at least one bearing is fixedly arranged, in particular integrated, in the plate member.

4. A chopper device according to claim 1, 2 or 3, wherein the electric drive comprises a housing part defining an interior space in which the stator is arranged, the housing part being mounted to the plate member, the plate member closing off one side of the interior space.

5. The chopper apparatus of claim 4, wherein the housing portion includes an end member closing a side of the interior space opposite the one side closed by the plate member, the rotor shaft extending through the housing, the end member including an end bearing adapted to rotatably support the rotor shaft.

6. Chopper device according to any one of the preceding claims, wherein the driven roller is mounted directly on the rotor shaft.

7. A chopper device according to any preceding claim, wherein the electric drive is a brushless DC drive comprising a permanent magnet mounted on the rotor shaft, the stator surrounding the permanent magnet.

8. A chopper assembly according to any preceding claim, wherein the at least one bearing comprises a cooperating roller bearing adapted to rotatably support the cooperating roller.

9. A chopper device according to any preceding claim, wherein the stator has a stator diameter perpendicular to, and a stator length parallel to, the rotor axis, the stator diameter being greater than the stator length.

10. A chopper apparatus according to any preceding claim, further comprising a tension roller rotatably mounted to the frame and adapted to pretension the filament to be received between the driven roller and the cooperating roller.

11. The chopper apparatus of claim 10, wherein the tension roller is counter-rotatable relative to one of the pair of rollers, the tension roller and the one roller being adapted to receive the filament therebetween and to engage the received filament on either side thereof.

12. Chopper arrangement according to claim 11, wherein the diameter of the one roller is at least 1.5 times, preferably at least twice, the diameter of the tension roller.

13. A chopper gun assembly comprising a chopper device for cutting a fiber filament according to any one of the preceding claims into fiber pieces and a spray gun device adapted to spray out the fiber pieces.

14. A robotic arm provided with a chopper gun assembly according to claim 13.

15. Concrete mixing transport vehicle equipped with a chopping device for cutting a fibre filament according to any one of the preceding claims 1-12 into fibre pieces, the transport device being designed to mix the fibre pieces with concrete.