A novel screw conveyor trough

Abstract

There is provided a material conveying screw feeder, which includes an inlet and an outlet, a trough, a frame, at least one screw which includes screw flights, where the at least one screw is comprised of a first screw portion and a second screw portion, where the first and second screw portions are joined together by a screw joint assembly which is generally located where the first trough section is connected to the second trough section, at least one motor, a control system, which controls the at least one motor, and a plurality of trough load cell measuring devices which are located under the trough, which are used to measure the weight of material in the trough, where the trough load cell measurements are used by the control system to control the screw feeder.

Description

Schenck Process Europe GmbHA NOVEL SCREW CONVEYOR TROUGHFIELD OF TH E INVENTION

[0001] The present invention relates to a material screw feeder. In particular, a screw feeder with a new screw arrangement is described. The screw arrangement comprises a joint assembly, which may comprise at least one universal joint, which reduces torque loads upstream of the joint assembly. The invention seeks to reduce and eliminate erroneous readings on load cells which are used to control the screw feeder.BACKGROUN D OF THE INVENTION

[0002] Screw feeders or conveyors are devices which facilitate the transport of material. Screw feeders provide a way to convey a material in a consistent way, when the material is fed in an inconsistent way.

[0003] Typically, material is dropped into a bin or hopper above the screw feeder where it collects and gathers. The material then drops down into the screw feeder, allowing the material to be processed at a desired and controllable feed rate. The hopper may comprise an agitator, which can remove the material from the hopper at a faster rate.

[0004] The material can therefore be loaded into the hopper at irregular feed rates (via a mechanical loader or excavator for example), and be output from the feeder at a constant and regular flowrate. This is highly desirable for applications where a constant flowrate is important, such as when the material is entering into a furnace for example. Furnaces for energy generation often need to have highly controllable feed rates, and thus a high quality control system for a screw feeder is highly desirable.

[0005] Example materials which may be used in screw feeders may vary from household waste, commercial waste, recycling materials, to industrial materials. Materials may range from Cement, used in the construction industry; to alternative fuels, based on domestic waste. Material screw feeders are widely used in industries such as agriculture, food processing, mining, and pharmaceuticals. They offer a reliable and efficient means of transporting bulk materials over short to medium distances, with the ability to handle a wide range of material types, sizes, and viscosities, all whilst being capable of discharging the materials in a controllable manner.

[0006] The main components of a screw feeder are the hopper or silo, into which the material is loaded into, and the screw conveyor itself, which is located below the hopper. The screw conveyor issimilar to an Archimedes' screw, which comprises an outer housing which channels the material being conveyed, and a type of screw in the middle. There may be more than one screw within the housing, and the pitch between the screw flights may not be constant. The screw rotates about within the housing, and the screw flights cause the material to travel in one direction inside the housing, from the inlet to the outlet.

[0007] To control the material flowrate in a screw feeder, the screw's rotational speed is varied. Increasing the rotational speed increases the material flowrate, and reducing the rotational speed reduces the flowrate. The hopper may also comprise an agitator, which when used may cause the material to exit the hopper with a higher flowrate. Control systems may be connected to be both the agitator and the motor which controls the speed of the screw.

[0008] The control system also may use load cells, which are used to measure the amount of material in one particular area of the system. For example, there may be load cells to weigh the hopper, and load cells to weigh certain areas of the trough. The trough may have a load cell near the inlet end of the trough, and a load cell near the outlet end of the trough. These loads cells aught to be able to measure the amount of material in the particular region with high accuracy.

[0009] An issue with the prior art is that due to the length of the screw inside the trough, large torque forces or moments can be transferred from one end of the screw to the other. For example, if there is a build up of material underneath the outlet end of the screw, this may cause a pitch down motion to the inlet end of the screw- causing the load cell near the inlet end of the screw to read a higher value than reality. This may also happen to the inlet end of the screw, and affect the load cell at the outlet end of the screw.

[0010] A solution is therefore required which creates a more efficient screw feeder, and prevents erroneous load cell measurements from being used to control the system. Erroneous load cell measurements could lead to the system jamming, overflowing, or catastrophically breaking.

[0011] It is therefore an aim of the present invention, to obviate or mitigate any of the aforementioned problems.SUMMARY OF THE INVENTION

[0012] In one aspect of the present invention, there is provided a material conveying screw feeder, which includes an inlet and an outlet, a trough for containing the material whilst it is inside the conveying screw feeder, a frame which surrounds the trough, where the trough includes a first troughsection, a second trough section, and a trough outlet section which are operatively connected together, and where the trough is supported by the frame, at least one screw which includes screw flights, where when the screw is rotated it conveys material from the inlet to the outlet, where the at least one screw is comprised of a first screw portion and a second screw portion, where the first and second screw portions are joined together by a screw joint assembly which is generally located where the first trough section is connected to the second trough section, at least one motor for driving the at least one screw, a control system, which controls the at least one motor, at least one trough load cell measuring devices which are located under the trough, which is used to measure the weight of material in the trough, where the trough load cell measurements are used by the control system to control the screw feeder.

[0013] The presence of the screw joint assembly may allow the second screw portion to flex and move within limits due to material clumping, whilst not providing any torque forces through the screw joint assembly, meaning that the trough load cell measurements maintain accuracy, especially under the first trough section. Without the presence of a screw joint assembly, large reaction moments would be generated along the second screw portion, which would affect load measurements under the first trough section.

[0014] The material conveying screw feeder may also include a plurality of hopper attachment brackets which comprise hopper load cells. The hopper attachment brackets may be used to attach a hopper onto. The hopper load cells may be used to measure the weight of the contents of a hopper. The hopper load cell measurements may be used by the control system to control the screw feeder, i.e. by controlling the speed of the screw. The hopper load cell measurements may be used in combination with the trough load cell measuring devices, to control the rotational speed of the screw in the screw feeder. May be used to calibrate the second trough section equipped with loadcell used for continuous feeding calculation.

[0015] The first screw portion may be located within the first trough section, and the second screw portion may be located within the second trough section. The first screw portion may be attached to the motor, which is located adjacent to the first trough section.

[0016] The second screw portion may be attached to only the screw joint assembly. Alternatively, the second screw portion may be attached to the screw joint assembly and the trough outlet section. The trough outlet section may comprise a trough outlet section bearing, which receives and supports the second screw portion end. The trough outlet section bearing may comprise a degree of flexibility, to allow the second screw portion to flex and move laterally within limits.

[0017] The screw joint assembly may include a single universal joint. The screw joint assembly may also include another similar type of joint, which may provide a degree of flexibility between the two screw portions.

[0018] The screw joint assembly may include two universal joints connected in series. Having two universal joints in series may result in a system which does not allow for any torque moments to pass through the screw joint assembly. This may be desirable for preventing any erroneous load cell readings. Two universal joints in series allows the second screw portion to move laterally in the vertical and horizontal axis, and prevents any bending moments from being transferred through the screw joint assembly.

[0019] There may also be a plurality of vertical compensators that provide a flexible connection. The vertical compensators may be made from a rubber and / or plastics material / textile. The vertical compensators may be located between the first trough section and the second trough section, and between the second trough section and the trough outlet section. The vertical compensators may allow the second trough section to move laterally in the vertical and horizontal plane, to accommodate fluctuations in material loading within the trough.

[0020] There may also be at least one vertical compensator that provides a flexible connection, which is located between the first trough section and the second trough section.

[0021] There may also be a plurality of horizontal compensators that provide a flexible connection. The horizontal compensators may be made from a rubber and / or plastics material / textile. The horizontal compensators may be located between the trough outlet section and the frame, thus providing a flexible connection between the trough outlet section and the frame. This may allow the trough outlet section to move laterally relative to the frame, to accommodate fluctuations in material loading within the trough outlet section which may be rigidly connected with second trough section equipped with vertical compensators between first and second trough section.

[0022] There may also be a plurality of trough runners which are lengths of material which line the trough along the trough longitudinal axis, to provide a wear surface for the screw flights. The trough runners may be made from any material which is wear resistant, but which is generally softer than the screw flights. This will ensure that the trough runners wear at a faster rate than the screw flights.

[0023] One of the trough load cell measuring devices may be located under the first trough section, and one of the trough load cell measuring devices may be located under the second trough section. There may be more than one trough load cell measuring devices located under each section of the trough, depending on the size of the application.

[0024] The screw feeder may include two screws, where the screws are generally aligned along a longitudinal axis of the trough. The screws may be have a diameter of around 200mm up to around 1000mm, and a length of around 2000mm to 7000mm.

[0025] The at least one screw may extends along a longitudinal axis of the trough and extends between the inlet and the outlet of the trough. The longitudinal axis may be parallel to the longest length of the trough.

[0026] In another aspect, there is provided a material feeding system which includes: a hopper and a material screw feeder, where the hopper includes an agitator, and where the trough load cell measuring devices are used to vary the speed of the agitators depending on the material distribution within the trough.

[0027] A method of conveying material via a screw feeder, using the apparatus defined in any of the previous aspects. Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.

[0028] The control system may be configured to adjust the flow rate control devices on a hopper, such as an agitator. The agitator may be configured to increase agitation when the trough may be lacking material

[0029] The method may also further include using the trough load cell measuring devices to measure the weight distribution within the trough, and using this weight distribution data to as input data for the control system of the screw feeder to use to vary the speed of the motor. The motor speed may vary in real time, to accommodate live fluctuations in material within the trough.

[0030] The method may further include using the hopper load cells to measure the weight within the hopper, and using this weigh data as input data for the control system of the screw feeder to use to vary the speed of the motor. Again, the control system may work in conjunction with both the hopper load cells and the trough hopper load cells to vary the speed of the motor. The screw joint assembly arrangement may prevent erroneous results from being transferred through the system as bending or moment forces.

[0031] The method may also include the feature that the input data is updated with a frequency of around 0,5s - 20s. This may result in a real-time update of the control system, and effectively results in a feedback loop.

[0032] The method of conveying material may also include wherein if the weight of the material in the trough is increasing at a greater rate than the weight of material in the hopper, then the controlsystem increases the speed of the motor. Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Embodiments of the present invention will now be described, by way of example only, with reference to the following figures:

[0034] FIG. 1 illustrates a screw weigh feeder according to the prior art;

[0035] FIG. 2 illustrates an embodiment of the present invention; FIG. 3 illustrates an embodiment of the present invention;

[0036] FIG. 4 illustrates a cross section of the embodiments shown in FIG. 2 and FIG. 3;

[0037] FIG. 5 illustrates a detailed view of the screw joint assembly of the embodiment in FIG. 4;

[0038] FIG. 6 illustrates another embodiment of the present invention;

[0039] FIG. 7 illustrates the screw joint assembly of the previous embodiment, showing the vertical and horizontal axis; and

[0040] FIG. 8 illustrates another embodiment of the present invention.DETAILED DESCRIPTION

[0041] FIG. 1 illustrates a screw weigh feeder according to the prior art. A breakdown of how a screw weigh feeder works is as follows:

[0042] 1. The bulk material to be conveyed is introduced into the hopper of the screw feeder. This may be done manually or via an automated system, depending on the capabilities of the system.

[0043] 2. The screw is rotated via a motor or engine, which therefore causes the material from the hopper to move through the trough of the screw feeder. As the screw rotates, the flutes which create the helix push the material from the hopper to the outlet of the device.

[0044] 3. Control of the flow is done by adjusting the rotational speed of the screw. There may be more than one screw inside the trough. Furthermore, there may be agitators or a similar device to loosen the material from sticking to the sides of the hopper. This may encourage the material to move from the hopper 104 to the trough 108

[0045] 4. The material is then discharged at the outlet of the trough.

[0046] The screw feeder 102 according to the art comprises a hopper 104, a screw 106, a trough 108, a motor 110, a hopper inlet 112, and a trough outlet 114. As described, the material is loaded into the hopper 104 via the hopper inlet 112. The hopper 104 can generally store more material than the trough 108.

[0047] As shown in FIG. 1, a typical material distribution 120 within the trough 108 can be seen. The material distribution 120 is shown to be biased towards the trough outlet 114, meaning there is more material (and therefore more weight) at the trough outlet 114 than at the base of the hopper 104.

[0048] In practice, the material distribution 120 can significantly vary from what is shown. However, one common trait with the material distribution 120 is that it is uneven, and is rarely ever evenly distributed throughout the trough 108.

[0049] Additionally, systems according to the art may have hopper load cells 122, located on the hopper 104; and trough load cells 124a, 124b located below the trough 108. These load cells in combination may be used to monitor the weight of material 118 in the hopper 104 and the weight of the material 118 in the trough 108. These weights may be used in combination to control the speed of the screw 106, by varying the speed of the motor 110.

[0050] H owever, a problem with the art is that the mass calculations from the trough load cells 124a can be erroneous, due to large torque forces being transmitted through uneven distribution of material in inlet of the trough in combination with varying material pressure from the hopper due to the particle size and partial blockages caused by these particles: for example when feeding household waste. The screw 106 can be spinning at high rotational speeds due to incorrectly reading of the loadcells, and so falsely overfeeding the process.

[0051] This is one of the problems with the art which the invention seeks to solve.

[0052] FIG. 2 shows an embodiment of the present invention, in the same orientation as the embodiments shown in relation to the prior art. A screw feeder 302 is shown. A hopper 304, which may be used in combination with the screw feeder 302 is also shown comprising hopper load cells 322.

[0053] FIG. 2 also shows the weighing system layout of the present embodiment: which is generally shared throughout all of the embodiments shown. The weighing system comprises a plurality of hopper load cells 322 , which are located on the hopper 304. The hopper load cells 322 are located on the hopper 304, and would be attached to the frame 346, which is shown as a dashed line. In this particular embodiment, the hopper 304 is attached to the frame via load cells 322, and the first trough section 308a is attached to the hopper 304 via trough load cells 324a. The first trough section 308a isalso attached to the second trough section 308b via the vertical compensator 340a. In this configuration, a horizontal compensator 342 is also used between the hopper 304 and the first trough section 308a. The horizontal compensator 342 is a flexible connection, which is airtight, but allows for some movement between the components. The horizontal compensator 342 may be made from a rubber / plastics material for example.

[0054] As described in FIG. 1, the material exits the hopper above where the screws 306 can be seen. The screws 306 are then driven by the motors 310, and the material is conveyed to the right of the figure, where it exits via the trough outlet 314.

[0055] In this particular embodiment, there are two screws 306. There may be any number of screws 306, including one single screw 306. With a two screw 306 arrangement, the rotational speed of the screws 306 and the phase between both screws 306 can be varied. The phase between the screws 306 may have a 0 degree offset, or the phase between the screws 306 may have a 90 degree offset, for example. The aim of phase control is to reduce and or eliminate the pulsing motion of the material 118 as it exits the trough outlet 314. Reducing pulsing of material is very beneficial for systems where the material is a fuel for an energy production plant, as burning chambers often require constant flow rate feed rates. Synchronisation of the plurality of screws 306 may be done via sensors located on the shaft of each of the screws 306.

[0056] The screws 306 and the flutes of the screws 306 may be made from abrasion resistant steel. The pitch of the screws 306 may be constant along the length of the screw 306, or the pitch of the screws 306 may vary along the length of the screws 306.

[0057] The screws 306 as shown in this particular embodiment are connected to the motor 310, and are not directly connected to the rest of the system. The screws 306 maintain their orientation and location within the trough 308 via trough runners 316, which are sections of material which line the trough 308 in a longitudinal direction. The trough runners 316 may be made of mild steel for example, and may be purpose built to wear over time- thus acting as a replaceable bearing surface for the screws 306.

[0058] The trough 308 may have a diameter which may be from around 200mm across, to around 1000mm.

[0059] The trough 308 may also comprise a cutting edge which is located across the longitudinal direction of the trough 308, which serves the purpose of restricting the flow to the screw to keep fill ratio within designed range 306.

[0060] FIG. 3 illustrates the embodiment from FIG. 2, with some modifications. The hopper 304 may also comprises an agitator 326 which is used to agitate and disturb any material 318 which may be stuck to the inside walls of the hopper 304.

[0061] The agitator 326 may be one of many agitators 326. The agitators 326 may be coupled to the control system of the screw feeder 302. The agitator 326 and motor 310 may both be used in conjunction with the data from the hopper load cells 322, the trough load cell 324a and the trough load cells 324b.

[0062] For example, in use, the system may measure that there is a lack of material in the trough 308, via the trough load cell 324a, and that there is a buildup of material 318 within the hopper 304. The system may then slow the speed of the screws 306 via the motor 310, and simultaneously increase the velocity of the agitators 326- to increase the amount of the material 318 exiting from the hopper 304. This will then allow the operator to add more material 318 to the hopper 304, thus increasing the speed of the workflow. Therefore, it is crucial that the load measurement devices are measuring accurately.

[0063] In another example, the material 318 may be building up in the trough 308, leading to high fill ratio of trough situation before the exit of the trough 308. In this case, the trough load cell 324b closer to the trough outlet 314 should have a higher weight reading. Thus, the control system would take action by varying some parameters such as controlling the speed rotation of screw and so keep the set / chosen gravimetric feed rate. As should be apparent, the measurements between the trough load cells 324a, 324b may be very important: and thus the accuracy of the measurements are paramount to the control of the system.

[0064] The above descriptions of the system using the load cell data is a control methodology which may be used with any of the embodiments of the invention. Furthermore, the described methodology of coupling the load cell data with the agitators 326 and motor 310 is merely exemplary, and should not be seen to be limiting. The load cell data may be used with any other control feature which may ultimately adjust the flow rate of the material 318 within the screw feeder 302.

[0065] The locations of the trough load cells 324a, 324b should not be taken to be limiting, but should be taken as being suggestive of a typical location which load cells may be found.

[0066] In this particular example, the hopper 304 is fixed rigidly to the first trough section 308a. This means that the hopper load cells 322 replace the need for the trough load cell 324a which would sit underneath the first trough section 308a. The hopper load cells 322 would measure the weight of material both inside the hopper 308, and within the first trough section 308a. The first trough section308a is also connected to the second trough section 308b via a vertical compensator 340a, which acts like a hinge.

[0067] FIG. 4 shows a cross section of the embodiments which are in FIG. 2 and FIG. 3. The section is shown as cutting through the middle of one of the screws 306. The screw 306 comprises a drive shaft 336 which contains screw flights 334. The screw flights 334 may vary their pitch along the length of the screw 306 to give the desired characteristics. The screw 306 should be taken to be merely exemplary, and should not be construed to be limiting.

[0068] The screw 306 shown is attached to the motor 310 via a shaft with a fixed coupling which provides a generally fixed coupling, to provide a pivot point for the screw 306. Part -way along the length of the screw 306, there is a screw joint assembly 328. In this instance, the screw joint assembly 328 is generally half-way along the length of the screw 306, however this should not be seen to be limiting.

[0069] The screw joint assembly 328 in this embodiment comprises two universal joints 330, which are shown in more detail in FIG. 5. The screw joint assembly 328 effectively splits the screw 306 into two lengths, i.e. a first screw portion 306a and a second screw portion 306b. The first screw portion 306a is attached onto the motor 310 and bearing assembly 332 at one end, and is attached onto the screw joint assembly 328 at the other end. The second screw portion 306b is attached onto the screw joint assembly 328 at one end, and the other end, the second screw portion end 338, is not connected to anything and therefore is free to move / translate up, down, left and right (i.e. in the plane perpendicular to the axis of the screw 306). The second screw portion end 338 is constrained by the trough runners 316, which line the trough 308 along the longitudinal direction, and are arranged circumferentially around the bottom of the trough 308. These trough runners 316 are wearable and replaceable parts which are worn down via the rotational motion of the screw flights 334 rubbing off them. The wear on the trough runners 316 will depend on the type of material 318 being conveyed, as well as the rotational speed of the screw 306.

[0070] FIG. 5 illustrates a detailed view of the screw joint assembly 328 of the embodiment in FIG. 4. Two universal joints 330 are shown, connected together. The first screw portion 306a connects to one of the universal joints 330, and the second screw portion 306b connects to the other universal joint 330. This arrangement would also be present in the other screw 306 within the screw feeder 302 of this present embodiment. Furthermore, the universal joints 330 are covered by a cover plate, which has been cut through in FIG. 5. The cover plate keeps the universal joints 330 free from debris.

[0071] The arrangement of two universal joints 330 within the screw joint assembly 328, in combination with the second screw portion end 338 being unconnected, results in a system whichminimises the influence of loadcell reading of material 318 chocking the screw flights 334, and between the second screw portion 306b and the trough 308. The second screw portion 306b is free to move within the second section of trough equipped with runners 316. As the second screw portion 306b is free to move in the trough, due to the screw joint assembly 328, there is no reaction forces other than torque force transferred through the screw joint assembly 328 to the first screw portion 306a. This means the trough load cell 324b which is generally located closer to the trough outlet 114.

[0072] The trough 308 may be further defined as comprising three distinct sections: a first trough section 308a, a second trough section 308b, and a trough outlet section 344. These three sections are separate from each other, and are either joined together via a fixed coupling (such as being bolted together or hinge), or via a flexible coupling such as the compensators.

[0073] The compensators are flexible connections, which allow a certain degree of freedom between the connected components. For example, the compensators may be made from a rubber or elastic type material, which allows the compensator to stretch and move, but maintain an airtight seal between components.

[0074] The first vertical compensator 340a is at the boundary between the first trough section 308a and the second trough section 308b. The second vertical compensator 340b is located between the second trough section 308b and the trough outlet section 344 which is rigidly fixed to the frame 346, to provide a flexible connection between these components. As there are two vertical compensators 340a, 340b in this embodiment, it results in very little interference on the load cells, when large pressure changes inside the trough occur.

[0075] Figure 6 shows another embodiment of the present invention. In this particular embodiment there are no horizontal compensators 442a, 442b, however the locations are shown for future embodiments. The upper horizontal compensator 442a would join the top of the trough outlet section 444 to the frame 446 which surrounds the trough 408, and the lower horizontal compensator 442b would attach to the frame at the bottom. The frame 446 would ordinarily be bolted to the floor of the warehouse, thus providing a stable base to the trough 408. Therefore, in this embodiment, the trough outlet section 444 is fixed directly to the frame 446, with no flexible connection in-between. The hopper 408 and the first trough portion 408a are connected to the frame via the hopper load cells 422.

[0076] FIG. 7 illustrates the screw joint assembly 428 of the previous embodiment, showing the vertical axis 906 and horizontal axis 908. With the single universal joint 430 set up, the second screw portion 406b is free to translate up, down, left, and right, over the vertical axis 906 and the horizontal axis 908 as shown only at the end of the second portion of screw 406b. This prevents the screw 406from becoming clogged, and therefore affecting the load cells as previously described. This embodiment gives the smaller degree of freedom to the screw joint assembly 428 compare to double universal joint assembly 328.

[0077] FIG. 8 illustrates another embodiment of the present invention, where there is only one universal joint 530 within the screw joint assembly 528, and there is only one vertical compensator 540a, located near the screw joint assembly 528. In this embodiment the second screw portion end 538 is fixed in place, however this should not be seen to be limiting, and the second screw portion end 538 may be loose as in other embodiments

[0078] In this configuration, the influence of material chocking decreases the reaction forces to the loadcell 524b as it moves away from the screw joint assembly 528, i.e. the effect is lessened as the chocking approaches the second screw portion end 538. This is useful in some applications.

[0079] This embodiment of the trough 508 also comprises two horizontal compensators 542a, 542b, and only one vertical compensator 540aThis means that the device is slightly more sensitive to pressure changes inside the trough 508, which may influence the load cells more than the previous embodiment of the trough 308. However, the two horizontal compensators 542a, 542b may desirable for particular applications.

[0080] In this embodiment, there is only one universal joint 530 as shown. This means that the second screw portion end 538 will have less freedom to move, and therefore the second screw portion 506b will experience less wear, than if there were two universal joints.

[0081] As shown, there is only one universal joint 530 within the screw joint assembly 528. This effectively means that the second screw portion 506b in this embodiment will have less freedom to move than the previous embodiment: which is desirable in some circumstances.

[0082] In this embodiment, the screw joint assembly 528 contains a single universal joint 530.

[0083] This trough 508 also has one vertical compensator 540a, located above the screw joint assembly 528, allowing degree of flexibility in the trough walls. The embodiment further comprises two horizontal compensators 542a, 542b.

[0084] Unique to this embodiment, the second screw portion end 538 is located on the outside wall of the trough 508, i.e. the second screw portion 506b passes through the trough outlet section 544, and is inserted into the trough outlet section bearing 548. The trough outlet section bearing 548 supplies the support structure for the second screw portion 506b, meaning that the trough runners 516 are not impacted by the second screw portion 506b, as the second screw portion 506b does not deviate from its standard axis enough.

[0085] This arrangement provides the most support for the screw 506, however if long strips of material are being used, they can wrap around the drive shaft which extends through the trough outlet section 544: leading to blockages. If long strips of material are to be conveyed, the previous two embodiments will be more suited to this type of material.

Claims

CLAIMS1. A material conveying screw feeder, comprising: an inlet and an outlet; a trough for containing the material whilst it is inside the conveying screw feeder; a frame which is proximate to the trough; wherein the trough comprises a first trough section, a second trough section, and a trough outlet section which are operatively connected together, and wherein the trough is supported by the frame; at least one screw which comprises screw flights, wherein when the screw is rotated it conveys material from the inlet to the outlet, wherein the at least one screw is comprised of a first screw portion and a second screw portion, wherein the first and second screw portions are joined together by a screw joint assembly which is generally located where the first trough section is connected to the second trough section; at least one motor for driving the at least one screw; a control system, which controls the at least one motor; and at least one trough load cell measuring device which is located under the trough, which is used to measure the weight of material in the trough, wherein the trough load cell measurements are used by the control system to control the screw feeder.

2. The material conveying screw feeder of claim 1, wherein a hopper is rigidly fixed to the first trough section, and wherein the hopper comprises hopper load cells, wherein the hopper load cells measurements are used by the control system to control the screw feeder.

3. The material conveying screw feeder of claim 1, wherein the screw feeder comprises a plurality of hopper attachment brackets which comprise hopper load cells, which are used to measure the weight of the contents of a hopper, wherein the hopper load cells measurements are used by the control system to control the screw feeder.

4. The material conveying screw feeder of one of claims 2 or 3, wherein the control system is configured to adjust the flow rate control devices on a hopper, such as an agitator.

5. The material conveying screw feeder of any one of claims 1 to 4, wherein the first screw portion is located within the first trough section, and the second screw portion is located within the second trough section.

6. The material conveying screw feeder of any one of claims 1 to 5, wherein the second screw portion is attached to the trough outlet section via a trough outlet section bearing, which receives and supports the second screw portion end.

7. The material conveying screw feeder of any one of claims 1 to 6, wherein the screw joint assembly comprises a single universal joint.

8. The material conveying screw feeder of any one of claims 1 to 6, wherein the screw joint assembly comprises two universal joints connected in series.

9. The material conveying screw feeder of any one of claims 1 to 8, further comprising a plurality of vertical compensators that provide a flexible connection, and which are located between the first trough section and the second trough section, and between the second trough section and the trough outlet section.

10. The material conveying screw feeder of any one of claims 1 to 8, further comprising at least one vertical compensator that provides a flexible connection, which is located between the first trough section and the second trough section.

11. The material conveying screw feeder of any preceding claim, further comprising a plurality of horizontal compensators that provide a flexible connection, and which are located between the trough outlet section and the frame.

12. The material conveying screw feeder of any preceding claim, further comprising a plurality of trough runners which are lengths of material which line the trough along the trough longitudinal axis, to provide a wear surface for the screw flights.

13. The material conveying screw feeder of any preceding claim, wherein there are a plurality of trough load cell measuring devices, and wherein one of the trough load cell measuring devices is located under the first trough section, and one of the trough load cell measuring devices is located under the second trough section.

14. The material conveying screw feeder of any of claims 1-12, wherein the at least one load cell is located under the second trough section.

15. The material conveying screw feeder of any preceding claim, wherein the screw feeder comprises two screws, wherein the screws are generally aligned along a longitudinal axis of the trough.

16. The material conveying screw feeder of any preceding claim, wherein the at least one screw extends along a longitudinal axis of the trough and extends between the inlet and the outlet of the trough.

17. A material feeding system comprising: a hopper and a material screw feeder of any one of claims 1 to 16; wherein the hopper comprises an agitator, and wherein the trough load cell measuring devices are used to vary the speed of the agitators depending on the material distribution within the trough.

18. A method of conveying material via a screw feeder, using the apparatus or system defined in any one of claims 1 to 16 or claim 17.

19. A method of conveying material via a screw feeder according to claim 18, wherein the method further comprises using the at least one trough load cell measuring devices to measure the weight distribution within the trough, and using this weight distribution data to as input data for the control system of the screw feeder to use to vary the speed of the motor.

20. A method of conveying material via a screw feeder according to claim 18 or 19, wherein the method further comprises using the hopper load cells to measure the weight within the hopper, and using this weigh data as input data for the control system of the screw feeder to use to vary the speed of the motor and / or for calibration of the continuous control system.

21. A method of conveying material via a screw feeder according to any one of claims 18 to 20, wherein the input data is updated with a frequency of around 0.5 seconds to 20 seconds.

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