Patent Description:
In the waste management industry, industrial and domestic waste is increasingly being sorted in order to recover and recycle useful components. Each type of waste, or "fraction" of waste can have a different use and value. If waste is not sorted, then it often ends up in landfill or incineration which has an undesirable environmental and economic impact.

Industrial waste may be passed to waste management centres because handling and disposing of waste is time consuming and requires specialist equipment. Accordingly, a waste management centre may sort waste to collect the most valuable and useful fractions. For example, industrial waste may include mixed wood and metal fractions (as well as other fractions) and sorted wood and metal fractions can be reused and sold to recyclers. Waste which is sorted into a substantially homogeneous fraction is more desirable and economical for recyclers. This is because less processing of the material is required before being recycled into new products and materials.

It is known to sort domestic and industrial waste in different ways. For many years waste has been manually sorted by hand on a conveyor belt. However hand sorting waste can be arduous and dangerous to the human sorter depending on the type of industrial or domestic waste being sorted. Furthermore, some waste sorting plants which use human sorters require multiple shifts in order to increase the output of sorted waste.

One approach for improving the safety and the output of waste sorting is to automate one or more aspects of the waste sorting. The automation can comprise a controller sending control and movement instructions to a manipulator for interacting with the physical objects. The combination of a controller sending control instructions to a manipulator can also be referred to as a "robot".

One such robotic waste sorting system is a "delta" robot suspended over a conveyor belt which moves objects to be sorted. The conveyor belt passes under the delta robot and within a working area of the delta robot. A working area of a robot is an area on a surface within which the robot is able to reach and manipulate an object. A working volume is the physical space within which the robot is able to move and manipulate an object. The working volume is determined by the height above the working area where the robot can manipulate an object.

The working volume / area can also include chutes which are not part of the surface of a conveyor belt.

A delta robot comprises a servo housing and a plurality of arms which are connected to one or more servos for moving the arms. The arms extend down from the servo housing to a base which is coupled to a manipulator. The arms are connected via universal joints at the base.

Whilst a delta robot can be relatively effective at picking small light objects, the delta robot is not suitable for lifting heavy objects. Furthermore since the manipulator is suspended from the servo housing, the servos must have sufficient power to move the manipulator and the object. This means that the manipulators coupled to delta robots must be as light as possible to increase the maximum lift capacity of the delta robot.

Disadvantageously, the dimensions of the working volume for a delta robot varies across the width of the working space. In particular, the working volume is an inverted cone and becomes narrower as the manipulator moves away from the servo housing. In practice, this may mean that a delta robot cannot manipulate objects at the same height across the width of a conveyor belt and that delta robots are only suitable for working with narrow conveyor belts. This can be problematic because objects can be piled on each other making identifying and picking objects harder. This can limit the design choices and use applications when using a delta robot for waste sorting.

A delta robot is not particularly robust and the universal joints of a delta robot are particularly susceptible to wear and malfunction. Another consideration of a delta robot is that the movement of one or more arms causes movement in the other arms. Accordingly, whenever a delta robot moves, control instructions must be sent to each servo because each arm must move when the manipulator of the delta robot is moved. The non-linear control instructions to move the arms of the delta robot means that increased computational processing is required to control and move the delta robot within the working area / working volume.

Another known robot for automatic sorting of waste is a "gantry" robot. A gantry robot comprises a frame or gantry which engages the floor and bridges over a working area such as a conveyor belt. The gantry supports the weight of the manipulator and an object that the manipulator grips. The gantry robot comprises one or more axes of control which move in a straight line (e.g. linear). Normally the axes of control of a gantry robot are arranged at right angles to each other.

A gantry robot may pick objects from the conveyor belt and drop the picked objects into a chute. A chute comprises an opening which is in communication with a bin or another conveyor belt for receiving a particular fraction of waste. The picked objects placed in the bin or on the conveyor belt can then be moved to another location or step in waste processing. This means a picked object of a certain waste fraction is dropped into the corresponding chute. Known gantry robots have a four or more chutes located at the four corners of the rectangular working space for receiving the different fractions. A problem with this arrangement is that the manipulator is required to travel a large distance if subsequent picks are from differing fractions. This means that a manipulator may be able to successfully pick and drop fewer objects into the correct bin due to the required travel time of the manipulator.

Delta and gantry robots used for waste sorting require regular maintenance because the working environment is dusty. The size of configuration of waste sorting robots can mean that they can be difficult to access and perform maintenance. In particular, waste sorting gantry robots can be assembled and operated in environments which are dangerous. It is desirable to make maintenance of the waste sorting robots as simple as possible to reduce the down time of the waste sorting robot.

<CIT> discloses an automatic shielding test device for a four-shaft direct manipulator. The automatic shielding test device is used for testing an electronic communication product in a shielded environment. The automatic shielding test device for the four-shaft direct manipulator comprises the components of a cabinet, a material inlet mechanism, a four-shaft direct manipulator, at least one shielding testing unit, a material discharging mechanism and a testing control mechanism.

<CIT> discloses a holding position distinguishing device and sorter.

<CIT> discloses a sorting mechanical arm for linear output of forming machine parts. The sorting mechanical arm comprises a linear output machine frame, a sorting mechanical arm body, an electromagnet, a portal frame and a linear output conveying belt.

<CIT> discloses a robot system for screening specified object in waste.

Embodiments of the present invention aim to address the aforementioned problems.

According to an aspect of the present invention there is a waste sorting robot according to claim <NUM>.

Accordingly the chute is located at a predetermined, known location with respect to the gantry frame. This means that the waste sorting gantry robot can be programmed to operate correctly in the factory and does not have to be configured according to the installation site.

Optionally the chute comprises a chute opening positioned at a predetermined distance from the conveyor. This means that the manipulator and controller do not have to be reprogrammed for each installation due to varying size and relative position of the chute with respect to the gantry frame. Indeed, the chute and chute opening will always remain in a fixed position, so the control and installation of the manipulator is simpler. Optionally the chute is integral with the gantry frame. This means that a user of the waste sorting gantry frame cannot move the chute relative to the gantry frame after installation. This means that the waste sorting robot cannot accidentally misalign the chute with respect to the gantry frame.

According to the invention, the gantry frame comprises a maintenance door for accessing the manipulator and / or the conveyor. According to the invention, the maintenance door is moveable to a position which covers at least a portion of the chute opening. According to the invention, the maintenance door covers the chute opening when the manipulator and / or the conveyor is accessible. Optionally the maintenance door is pivotable about a hinge at the bottom of the maintenance door. This means that the manipulator and the waste sorting gantry robot can be easily accessible. The maintenance door covers the chute and prevents an operator from falling down or tripping on the chute whilst inspecting the manipulator or other parts of the waste sorting gantry robot.

Optionally the maintenance door comprises steps. Advantageously, the steps provide additional grip and stability for an operator when climbing up to inspect the waste sorting gantry robot.

Optionally the waste gantry robot comprises a lock-out sensor wherein the maintenance door actuates the lock-out sensor when the maintenance door is opened. This means that the waste sorting gantry robot is switched off when an operator is inspecting the internal parts. This helps safeguard the operator during maintenance and inspection.

Optionally the waste gantry robot comprises at least one latch for opening the maintenance door. Optionally the maintenance door abuts the conveyer when the maintenance door is in an open position. This means that the maintenance door rests and remains in place when in the open position. Optionally the maintenance door is covered by an external access door.

In this way, the maintenance door cannot be accidentally opened because the operator must open an external door before opening the maintenance door first.

Optionally the opening is between <NUM> to <NUM> wide by <NUM> to <NUM> long. This means that the opening is sufficiently large to receive most types and sizes of waste objects.

Optionally the opening is adjacent to the conveyor in the working area. This means that the manipulator does not have to travel far to throw or drop a picked object into the chute.

Optionally at least a portion of the chute is integral with the gantry frame. Optionally the chute is in communication with a receptacle for receiving the sorted waste objects. Optionally the gantry frame comprises a floor plate comprising an opening connected to the chute. This means that if a hole in the floor for receiving the sorted objects is larger than the chute opening, the sorted objects can fall through the hole whilst protecting the operator from falling down the hole. Optionally, the gantry frame comprises a conversion adaptor for coupling the chute to a floor hole wherein the dimensions of the chute and the floor hole are different. This means that the chute which is fixed to the gantry frame can be coupled to a hole in the floor independent of the size or location of the floor hole.

Optionally the waste sorting robot comprises an enclosure mounted to the gantry frame. Optionally the enclosure surrounds the chute. This means that the enclosure can protect the manipulator. Furthermore, the enclosure prevents the operator from accidentally touching the manipulator during operation.

Various other aspects and further embodiments are also described in the following detailed description and in the attached claims with reference to the accompanying drawings, in which:.

<FIG> shows a schematic perspective view of a waste sorting robot <NUM>. In some embodiments, the waste sorting robot <NUM> can be a waste sorting gantry robot <NUM>. In other embodiments other types of waste sorting robots can be used. For example, the waste sorting robot <NUM> can be other types of robot such as robot arms, SCARA assemblies, or delta robots.

In some embodiments, the waste sorting robot <NUM> is a Selective Compliance Assembly Robot Arm (SCARA). The waste sorting SCARA <NUM> may move in the X, Y, and Z planes like the waste sorting gantry robot, but incorporate movement in a theta axis at the end of the Z plane to rotate the end-of-arm tooling e.g. the gripper assembly <NUM>. In some embodiments, the waste sorting robot <NUM> is a four axis SCARA robot <NUM> that consists of an inner link arm (not shown) that rotates about the Z-axis. The inner link arm is connected to an outer link arm (not shown) that rotates about a Z elbow joint (not shown). The Z elbow joint is connected to a wrist axis (not shown) that moves up and down and also rotates about Z. In some embodiments the waste sorting SCARA <NUM> comprises an alternative configuration which has the linear Z motion as the second axis.

For the purposes of brevity, the embodiments will be described in reference to waste sorting gantry robots <NUM>, but any of the other aforementioned robot types can be used instead or in addition to the water sorting gantry robot <NUM>.

The waste sorting gantry robot comprises a controller <NUM> for sending control and movement instructions to a manipulator <NUM> for interacting with the physical objects 106a, 106b, 106c. The combination of a controller sending control instructions to a manipulator can also be referred to as a "robot". The controller <NUM> is located remote from the manipulator <NUM> and is housed in a cabinet (not shown). In other embodiments, the controller <NUM> can be integral with the manipulator and / or a gantry frame <NUM>.

The manipulator <NUM> physically engages and moves the objects 106a, 106b, 106c that enters the working area <NUM>. The working area <NUM> of a manipulator <NUM> is an area within which the manipulator <NUM> is able to reach and interact with the object 106a 106b, 106c. The working area <NUM> as shown in <FIG> is projected onto the conveyor belt <NUM> for the purposes of clarity. The manipulator <NUM> is configured to move at variable heights above the working area <NUM>. In this way, the manipulator <NUM> is configured to move within a working volume defined by the height above the working area <NUM> where the robot can manipulate an object. The manipulator <NUM> comprises one or more components for effecting relative movement with respect to the objects 106a, 106b, 106c. The manipulator <NUM> will be described in further detail below.

The physical objects 106a, 106b, 106c are moved into the working area <NUM> by a conveyor belt <NUM>. The path of travel of the conveyor belt <NUM> intersects with the working area <NUM>. This means that every object 106a, 106b, 106c that is moving on the conveyor belt <NUM> will pass through the working area <NUM>. The conveyor belt <NUM> can be a continuous belt, or a conveyor belt formed from overlapping portions. The conveyor belt <NUM> can be a single belt or alternatively a plurality of adjacent moving belts.

In other embodiments, the physical objects 106a, 106b, 106c can be conveyed into the working area <NUM> via other conveying means. The conveyor can be any suitable means for moving the objects 106a, 106b, 106c into the working area <NUM>. For example, the objects 106a, 106b, 106c are fed under gravity via slide (not shown) to the working area <NUM>. In other embodiments, the objects can be entrained in a fluid flow, such as air or water, which passes through the working area <NUM>.

The direction of the conveyor belt <NUM> is shown in <FIG> by two arrows. The objects 106a, and 106b are representative of different types of objects to be sorted having not yet been physically engaged by the manipulator <NUM>. In contrast, the object 106c is an object that has been sorted into a particular type of object. In some embodiments, the manipulator <NUM> interacts with only some of the objects 106c. For example, the waste sorting gantry robot <NUM> is only removing a particular type of objects. In other scenarios, the manipulator <NUM> will interact and sort every object 106a, 106b, 106c which is on the conveyor belt <NUM>.

In some embodiments, the objects to be sorted are waste products. The waste products can be any type of industrial, commercial, domestic, or any other waste which requires sorting and processing. Unsorted waste material comprises a plurality of fractions of different types of waste. Industrial waste can comprise fractions of, for example, metal, wood, plastic, hardcore and one or more other types of waste. In other embodiments, the waste can comprise any number of different fractions of waste formed from any type or parameter of waste. The fractions can be further subdivided into more refined categories. For example, metal can be separated into steel, iron, aluminium etc. Domestic waste also comprises different fractions of waste such as plastic, paper, cardboard, metal, glass and / or organic waste.

A fraction is a category of waste that the waste can be sorted into by the waste sorting gantry robot <NUM>. A fraction can be a standard or homogenous composition of material, such as aluminium, but alternatively a fraction can be category of waste defined by a customer or user. In some embodiments, the waste can be sorted according to any parameter. A non-limiting list of parameters for dividing unsorted waste into fractions is as follows: material, previous purpose, size, weight, colour, opacity, economic value, purity, combustibility, whether the objects are ferrous or any other variable associated with waste objects. In a further embodiment, a fraction can comprise one or more other fractions. For example, one fraction can comprise a paper fraction, a cardboard fraction, and a wood fraction to be combinable to be a combustible fraction. In other embodiments, a fraction can be defined based on the previous purpose of the waste object, for example plastic tubes used for silicone sealant. It may be desirable to separate out some waste objects because they are contaminated and cannot be recycled.

The objects are fed from a hopper or other stored source of objects onto the conveyor belt <NUM>. Alternatively, the waste objects are fed from another conveyor belt (not shown) and there is no source of stored waste objects. In this case, the additional conveyor belt can be fed manually from e.g. an excavator. Optionally, the objects 106a, 106b, 106c can be preprocessed before being placed on the conveyor belt. For example, the objects can be washed, screened, crushed, ripped, shaken, vibrated to prepare the material before sorting. Alternatively, the waste objects 106a, 106b, 106c can be sorted with another robot or mechanical device. The objects 106a, 106b, 106c can be optionally pre-sorted before being placed on the conveyor belt <NUM>. For example, ferrous material can be removed from the unsorted waste by passing a magnet in proximity to the conveyor belt <NUM>. Large objects can be broken down into pieces of material which are of a suitable size and weight to be gripped by the manipulator <NUM>.

The manipulator <NUM> is configured to move within the working volume. The manipulator <NUM> comprises one or more servos for moving the manipulator <NUM> in one or more axes. In some embodiments, the manipulator <NUM> is moveable along a plurality of axes. In some embodiments, the manipulator is moveable along three axes which are substantially at right angles to each other. In this way, the manipulator <NUM> is movable in an X-axis which is parallel with the longitudinal axis of the conveyor belt <NUM> ("beltwise"). Additionally, the manipulator <NUM> is movable across the conveyor belt <NUM> in a Y-axis which is perpendicular to the longitudinal axis of the conveyor belt <NUM> ("widthwise"). The manipulator <NUM> is movable in a Z-axis which is in a direction normal to the working area <NUM> and the conveyor belt <NUM> ("heightwise"). Optionally, the manipulator <NUM> can rotate about one or more axes. In some embodiments a gripper assembly <NUM> coupled to the manipulator <NUM> can rotate about a W-axis. The gripper assembly <NUM> is discussed in further detail below.

The directions of movement of the manipulator <NUM> within the working space along the X-axis, Y-axis and the Z-axis are shown by the two headed arrows with dotted lines. The manipulator <NUM> is moved with respect to the conveyor belt <NUM> by an X-axis servo <NUM>, a Y-axis servo <NUM> and a Z-axis servo <NUM> respectively along the X-axis, the Y-axis and the Z-axis. The servos <NUM>, <NUM>, <NUM> are connectively connected to the controller <NUM> and controller <NUM> is configured to issue instructions for actuating one or more servos <NUM>, <NUM>, <NUM> to move the manipulator <NUM> within the working space. The connections between the servos <NUM>, <NUM>, <NUM> and the controller <NUM> are represented by dotted lines. Each connection between the servo <NUM>, <NUM>, <NUM> and the controller <NUM> can comprises one or more data and / or power connections.

Since the directions of movement of the manipulator <NUM> are substantially perpendicular to each other, movement of the manipulator in one of the axes is independent of the other axes. This means that the manipulator <NUM> movement can be defined in a cartesian coordinate frame of reference which makes processing movement instructions by the controller <NUM> simpler.

As mentioned previously, the manipulator <NUM> is mounted on a frame <NUM>. In some embodiments, the frame <NUM> can be a gantry frame <NUM>. In other embodiments, the frame <NUM> can be other structures suitable for supporting the manipulator <NUM> above the working area <NUM>. For example, the frame <NUM> can be a structure for suspending the manipulator <NUM> above the working area with rods and / or cables. Hereinafter, the frame <NUM> will be referred to a gantry frame <NUM> but can be applicable to other frames for supporting a manipulator <NUM>.

The gantry frame <NUM> comprises vertical struts <NUM> which engage with the floor or another substantially horizontal surface. In some embodiments, the vertical struts <NUM> can be tilted upright struts. In this way, the tilted upright struts are angled to the vertical. The tilted upright struts may be required to mount the gantry frame <NUM> to the floor in a non-standard installation. <FIG> shows the gantry frame <NUM> comprising four vertical struts <NUM> coupled together by horizontal beams <NUM>. In other embodiments, the horizontal beams <NUM> can be tilted lateral beams <NUM>. This may be required if the waste sorting gantry robot <NUM> is being installed in a small or unusual space. In other embodiments, there can be any suitable number of vertical struts <NUM>. The beams <NUM> and struts <NUM> are fixed together with welds, bolts or other suitable fasteners. Whilst the horizontal beams <NUM> are shown in <FIG> to be located above the conveyor belt <NUM>, one or more horizontal beams <NUM> can be positioned at different heights. For example, one or more horizontal beams <NUM> can be positioned underneath the conveyor belt. This can lower the centre of mass of the gantry frame <NUM> and make the entire waste sorting gantry robot <NUM> more stable if the vertical struts <NUM> are not secured to the floor.

The beams <NUM> and the struts <NUM> are load bearing and support the weight of the manipulator <NUM> and an object 106a, 106b, 106c that the manipulator <NUM> grasps. In some embodiments, the beams <NUM> and struts <NUM> are made from steel but other stiff, lightweight materials such as aluminium can be used. The vertical struts <NUM> can each comprise feet <NUM> comprising a plate through which bolts (not shown) can be threaded for securing the struts <NUM> to the floor. For the purposes of clarity, only one foot <NUM> is shown in <FIG>, but each strut <NUM> can comprise a foot <NUM>. In other embodiments, there are no feet <NUM> or fasteners for securing the gantry frame <NUM> to the floor. In this case, the gantry frame rests on the floor and the frictional forces between the gantry frame and the floor are sufficient to prevent the waste sorting gantry robot from moving with respect to the floor.

The manipulator <NUM> comprises at least one movable horizontal beam <NUM> which is movably mounted on the gantry frame <NUM>. The moveable beam <NUM> can be mounted in a beam carriage (not shown). The moveable horizontal beam <NUM> is movably mounted on one or more of the other fixed horizontal beams <NUM> of the gantry frame <NUM>. The moveable horizontal beam <NUM> is movable in the X-axis such that the manipulator <NUM> moves in the X-axis when the movable horizontal beam moves in the X-axis. The moveable horizontal beam <NUM> is mounted to the fixed horizontal beams <NUM> via an X-axis servo mechanism <NUM>. In some embodiments, the servo <NUM> is coupled to the moveable horizontal beam <NUM> via a belt drive. In other embodiments, the servo is coupled to the moveable horizontal beam via a rack and pinion mechanism. In some embodiments, other mechanisms can be used to actuate movement of the moveable horizontal beam along the X-axis. For example, a hydraulic or pneumatic system can be used for moving the movable horizontal beam <NUM>.

The X-axis servo <NUM> can be mounted on the moveable beam <NUM> or on the fixed horizontal beams <NUM>. It is preferable for the X-axis servo to be mounted on the fixed horizontal beams <NUM> such that the X-axis servo does not have to exert force moving its own weight.

A manipulator carriage <NUM> is movably mounted on the moveable horizontal beam <NUM>. The manipulator shuttle <NUM> is moveable along the longitudinal axis of the movable horizontal beam <NUM>. In this way, the manipulator carriage <NUM> is movable in the Y-axis relative to the moveable beam <NUM>. In some embodiments, the manipulator carriage <NUM> comprises a Y-axis servo mechanism <NUM> for moving the manipulator carriage <NUM> along the Y-axis. In other embodiments, the Y-axis servo <NUM> is not mounted in the manipulator carriage <NUM> and manipulator carriage <NUM> moves with respect to the Y-axis servo. In some embodiments, the servo <NUM> is coupled to the moveable horizontal beam <NUM> via a belt drive. In other embodiments, the servo <NUM> is coupled to the moveable horizontal beam <NUM> via a rack and pinion mechanism. In some embodiments, other mechanisms can be used to actuate movement of the moveable horizontal beam along the Y-axis. For example, a hydraulic or pneumatic system can be used for moving the manipulator carriage <NUM>.

When the manipulator carriage <NUM> moves along the Y-axis, a gripper assembly <NUM> also moves in the Y-axis. The gripper assembly <NUM> is movably mounted to the manipulator carriage <NUM>. The gripper assembly <NUM> is movable in the Z-axis in order to move the manipulator <NUM> heightwise in the Z-axis direction.

In some embodiments, the gripper assembly <NUM> comprises a Z-axis servo mechanism <NUM> for moving the gripper assembly <NUM> along the Z-axis. In other embodiments, the Z-axis servo <NUM> is not mounted in the gripper assembly <NUM> but is mounted in the manipulator carriage <NUM>. In this way, the gripper assembly <NUM> moves with respect to the Z-axis servo <NUM>. In some embodiments, the servo <NUM> is coupled to the gripper assembly <NUM> via a belt drive. In other embodiments, the servo <NUM> is coupled to the gripper assembly <NUM> via a rack and pinion mechanism. In some embodiments, other mechanisms can be used to actuate movement of the moveable horizontal beam along the Z-axis. For example, a hydraulic or pneumatic system can be used for moving the gripper assembly <NUM>.

As mentioned, the manipulator <NUM> as shown in <FIG> comprises a gripper assembly <NUM>. In one embodiment, the gripper assembly <NUM> comprises a pair of jaws <NUM> configured to grip objects 106a, 106b, 106c. A gripper assembly <NUM> comprising a pair of jaws <NUM> is also known as a "finger gripper. " The gripper jaws <NUM> are actuated with a servo (not shown) for opening and closing the jaws <NUM>. The servo for the gripper jaws <NUM> is connectively coupled to the controller <NUM> so that the controller <NUM> can actuate the opening and closing of the jaws <NUM>. In some embodiments, the gripper assembly <NUM> further comprises a rotation servo (not shown) to rotate the gripper assembly <NUM> and / or the gripper jaw <NUM> about the W-axis. In some embodiments the W-axis and the Z-axis are coaxial, but in other embodiments the W-axis and the Z-axis are offset This means that the gripper jaws <NUM> can be rotated to better grasp long thin objects across their narrow dimensions.

Additionally or alternatively in a more preferable embodiment, the gripper assembly (<NUM>) can be a suction gripper, as shown in <FIG> for gripping the objects using negative pressure. The suction gripper can have a suction cup which is substantially symmetric about the Z-axis. This means that the suction gripper does not need to be rotated about the Z-axis to achieve an optimal orientation with respect to the objects 106a, 106b, 106c. This means that the gripper assembly rotation servo is not required with a suction gripper. In the case with an asymmetrical suction gripper <NUM>, the gripper assembly <NUM> comprises a rotation servo to rotate the gripper assembly <NUM> about the W-axis as previously discussed above.

In other embodiments, the gripper assembly <NUM> of the manipulator <NUM> can be any suitable means for physically engaging and moving the objects 106a, 106b, 106c. Indeed, the manipulator <NUM> can be one or more tools for grasping, securing, gripping, cutting or skewering objects. In further embodiments the manipulator <NUM> can be a tool configured for interacting with and moving an object at distance such as an electromagnet or a nozzle for blowing compressed air.

As mentioned, the controller <NUM> is configured to send instructions to the servos <NUM>, <NUM>, <NUM> of the manipulator <NUM> to control and interact with objects 106a, 106b, 106c on the conveyor belt <NUM>. The controller <NUM> is connectively coupled to at least one sensor <NUM> for detecting the objects 106a, 106b, 106c on the conveyor belt <NUM>. The at least one sensor <NUM> is positioned in front of the manipulator <NUM> so that detected measurements of the objects 106a, 106b, 106c are sent to the controller <NUM> before the objects 106a, 106b, 106c enter the working area <NUM>. In some embodiments, the at least one sensor <NUM> can be one or more of a RGB camera, an infrared camera, a metal detector, a hall sensor, a temperature sensor, visual and / or infrared spectroscopic detector, 3D imaging sensor, terahertz imaging system, radioactivity sensor and / or a laser. The at least one sensor <NUM> can be any sensor suitable for determining a parameter of the object 106a, 106b, 106c.

<FIG> shows that the at least one sensor <NUM> is positioned in one position. The at least one sensor <NUM> is mounted in a sensor housing <NUM> to protect the sensor <NUM>. In other embodiments, a plurality of sensors are positions along and around the conveyor belt <NUM> to receive parameter data of the objects 106a, 106b, 106c.

The controller <NUM> receives information from the at least one sensor <NUM> corresponding to one or more objects 106a, 106b, 106c on the conveyor belt <NUM>. The controller <NUM> determines instructions for moving the manipulator <NUM> based on the received information according to one or more criteria. Various information processing techniques can be adopted by the controller <NUM> for controlling the manipulator <NUM>. Such information processing techniques are described in <CIT>, <CIT>, <CIT>, <CIT> which are incorporated herein by reference.

Once the manipulator <NUM> has received instructions from the controller <NUM>, the manipulator <NUM> executes the commands and moves the gripper assembly <NUM> to pick an object 106c from the conveyor belt <NUM>. The process of selecting and manipulating an object on the conveyor belt <NUM> is known as a "pick".

Once a pick has been completed, the manipulator <NUM> drops or throws the object 106c into a chute <NUM>. An object 106c dropped into the chute <NUM> is considered to be a successful pick. A successful pick is one where an object 106c was selected and moved to the chute <NUM> associated with the same fraction of waste as the object 106c.

The chute <NUM> comprises a chute opening <NUM> in the working area <NUM> for dropping picked objects 106c. The chute opening <NUM> of the chute <NUM> is adjacent to the conveyor belt <NUM> so that the manipulator <NUM> does not have to travel far when conveying a picked object 106c from the conveyor belt <NUM> to the chute opening <NUM>. By positioning the chute opening <NUM> of the chute adjacent to the conveyor belt <NUM>, the manipulator <NUM> can throw, drop, pull and / or push the object 106c into the chute <NUM>.

The chute <NUM> comprises walls <NUM> defining a conduit for guiding picked objects 106c into a fraction receptacle (not shown) for receiving a sorted fraction of waste. In some embodiments, a fraction receptacle is not required at the sorted fractions of waste are piled up beneath the chute <NUM>. <FIG> only shows one chute <NUM> associated with the manipulator <NUM>. In other embodiments, there can be a plurality of chutes <NUM> and associated openings <NUM> located around the conveyor belt <NUM>. Each opening <NUM> of the different chutes <NUM> is located within the working area <NUM> of the manipulator <NUM>. The walls <NUM> of the conduit can be any shape, size or orientation to guide picked objects 106c to the fraction receptacle. In some embodiments, the successfully picked objects 106c move under the force of gravity from the chute opening <NUM> of the chute <NUM> to the fraction receptacle. In other embodiments, the chute <NUM> may guide the successfully picked objects 106c to another conveyor belt (not shown) or other means for moving the successfully picked objects 106c to the fraction receptacle.

Turning to <FIG>, another embodiment will be discussed. <FIG> shows a schematic perspective view of a waste sorting gantry robot <NUM>. The conveyor belt <NUM> is positioned between the gantry frame <NUM>. For the purposes of clarity, no objects 106a, 106b, 106c have been shown on the conveyor belt <NUM>.

The gantry frame <NUM> as shown in <FIG> comprises a different configuration and construction from that shown in <FIG>. In particular, the gantry frame <NUM> comprises two cabinets <NUM>, <NUM>. The cabinet <NUM>, <NUM> comprise internal struts and horizontal beams similar to those discussed in reference to the embodiments shown in <FIG>. However the cabinet structures <NUM>, <NUM> comprise at least one enclosure <NUM>. The enclosure <NUM> surrounds at least a part of the gantry frame <NUM>. In some embodiments, there can be a plurality of enclosures <NUM>, each surrounding one or more parts of the waste sorting gantry robot <NUM>. The enclosure <NUM> can be a solid sheet material <NUM> or can be perforated so that one or more internal parts of the waste sorting gantry robot <NUM> are visible. The enclosure <NUM> for example, surrounds the chute <NUM> on three sides. The enclosure <NUM> also surrounds at least a portion of the manipulator <NUM>. In other embodiments, the enclosure <NUM> can completely surround and enclose the waste sorting gantry robot <NUM>. In this case, the enclosure <NUM> comprises openings for the waste sorting objects 106a, 106b, 106c to be conveyed into the working area <NUM>. In some embodiments, and as shown in <FIG> the enclosure <NUM> covers the struts and the horizontal beams providing the walls, top and bottoms of the cabinets <NUM>, <NUM>.

The cabinets <NUM>, <NUM> provide shielding for the delicate parts to the manipulator <NUM> such as the servos (not shown for clarity). This helps protect the manipulator from be damaged from stray waste objects. Furthermore the cabinet structures <NUM>, <NUM>, provide a barrier between the moving parts and the human operator. This means that the human operator cannot accidentally stray into the working area <NUM> of the waste sorting gantry robot.

One or both of the cabinets <NUM>, <NUM> can comprise an external access door <NUM>. The external access door <NUM> allows access to the interior of the cabinets <NUM>, <NUM>. The external access door <NUM> is located on a wall <NUM> of the cabinet <NUM>, <NUM> which is opposite the conveyor belt <NUM> and faces outwards. This means that when the external access door <NUM> is opened, the opened access door <NUM> does not interfere with any other part of the waste sorting gantry robot <NUM>.

The interior surface <NUM> of one or both of the cabinets <NUM>, <NUM> comprises an opening <NUM>. This means that the wall of the cabinets <NUM>, <NUM> which is adjacent to the conveyor belt <NUM> is open. Accordingly, the manipulator <NUM> can move within one or both of cabinets <NUM>, <NUM>. This means that the manipulator <NUM> can be controlled to move to a "home" position within one or both of the cabinets <NUM>, <NUM>. Moving the manipulator <NUM> within the cabinet <NUM>, <NUM> makes inspection and maintenance of the manipulator <NUM> easier. In this way, the plane of the working area <NUM> extends into the cabinets <NUM>, <NUM>. The working area <NUM> has not been shown in <FIG> for the purposes of clarity.

The cabinet <NUM> is located above a chute <NUM> and similar to the embodiments discussed in reference to <FIG>, the chute <NUM> comprises a chute opening <NUM> (not shown in <FIG> because this is within the cabinet <NUM>) in the working area <NUM> for dropping picked objects 106c. The chute opening <NUM> of the chute <NUM> is adjacent to the conveyor belt <NUM> within the gantry frame <NUM>. By positioning the chute opening <NUM> of the chute adjacent to the conveyor belt <NUM>, the manipulator <NUM> can throw, drop, pull and / or push the object 106c into the chute <NUM>.

Another embodiment of the chute <NUM> will now be described in reference to <FIG> shows a schematic representation of the gantry frame <NUM>, the conveyor <NUM> and the chute <NUM>. In some embodiments the chute <NUM> comprises a first part <NUM> which is above the floor where the waste sorting gantry robot <NUM> is installed. The chute <NUM> can also comprise a second part which is a guide chute <NUM> coupled to the chute (not shown in <FIG>, but shown in <FIG>) which is not part of the gantry frame <NUM>.

In some embodiments, the chute <NUM> comprises a plurality of chute walls <NUM> which are the walls <NUM> of chute above the floor. The chute walls <NUM> are an integral part of the gantry frame <NUM>.

As shown in <FIG>, a front chute wall <NUM> is located next to the conveyor belt <NUM>. In some embodiments, the height of the front chute wall <NUM> is from the level of the floor to the height of the conveyor <NUM>.

In some embodiments, the front chute wall <NUM> comprises a guard wall <NUM>. The guard wall <NUM> is connected to the front chute wall <NUM> and extends in the Z-axis slightly higher than the front chute wall <NUM>. Accordingly, the guard wall <NUM> prevents objects 106a, 106b, 106c on the conveyor belt <NUM> accidentally sliding and / or falling into the chute <NUM>.

The chute <NUM> further comprises a back chute wall <NUM> which is on an opposite side of the chute <NUM> to the front chute wall <NUM>. The back chute wall <NUM> is higher than the front chute wall <NUM> and the guard wall <NUM>. This allows thrown objects 106c to hit the back chute wall <NUM>. When a picked object 106c hits the back chute wall <NUM>, the back chute wall <NUM> stops the movement of the picked object 106c in the Y-axis -direction and the picked object 106c falls into the chute <NUM>.

In other words, at least a portion <NUM> of the upper part of the back chute wall <NUM> is higher by a distance H above the conveyor belt <NUM> level. The chute walls <NUM>, <NUM> which are perpendicular to the conveyor belt <NUM> extend from a floor level to angled upper parts which meet the front chute wall <NUM> and the back chute wall <NUM>. Thus, the height of the perpendicular chute walls <NUM>, <NUM> varies as the perpendicular walls <NUM>, <NUM> extend from the front chute wall <NUM> to the rear chute wall <NUM>.

In some embodiments, the chute opening <NUM> dimensions are smaller than dimensions of the gantry frame <NUM>, for example as shown in <FIG>. In this way, the walls <NUM> of gantry frame <NUM> are separate from the chute walls <NUM>.

As shown in <FIG>, the chute opening <NUM> in the gantry frame <NUM>, comprises a predetermined size. The size of the chute opening <NUM> can have, different predetermined dimensions.

The chute <NUM> also comprises a lower chute opening <NUM> which is connected to the floor hole <NUM> (not shown in <FIG>, but shown in <FIG>) on the floor. In some embodiments, the chute <NUM> does not vary in cross sectional area along its length and the chute opening <NUM> is the same size as the lower chute opening <NUM>. In some embodiments, the floor hole <NUM> may be larger than the lower chute opening <NUM>. In this case, a floor plate (not shown) which covers the floor hole <NUM> is installed between the gantry frame <NUM> and the floor. The floor plate comprises a hole which is equal to the size of the lower chute opening <NUM>. In this way, the floor plate is large enough to cover the floor hole <NUM> on the floor. This is to prevent anything else, including people, falling into chute <NUM> or the guide chute <NUM>.

In some embodiments, the floor hole <NUM> is smaller than the lower chute opening <NUM>. In this case, a conversion adaptor (not shown) is installed. The conversion adaptor varies in the dimensions of the chute <NUM> from the dimensions of the lower chute opening <NUM> to the dimensions of the floor hole <NUM>. This is to ensure that all the picked objects 106c are able to fall through the floor hole <NUM>. In this way, the conversion adaptor is arranged to couple the chute <NUM> to a floor hole wherein the dimensions of the chute and the floor hole are different. For example, the dimensions of the chute can be smaller in cross section than the floor hole. Conversely, the dimensions of the chute can be larger in cross section than the floor hole. The conversion adaptor can narrow or widen depending on the relative dimensions of the chute and the floor hole.

As mentioned, some gantry frames <NUM> may requires a conversion adaptor. The conversion adaptor is specific to the dimensions of the installation site and the dimensions of the floor hole <NUM>. However, the dimensions of the chute opening <NUM> and the lower chute opening <NUM> can be predetermined and fixed. Alternatively the dimensions of the chute opening <NUM> and the lower chute opening <NUM> can be limited to few predefined dimensions. Advantageously, this means that the gantry frame <NUM> design, including the chute walls <NUM>, will be independent of the installation site.

Since the chute <NUM> is within the cabinet <NUM>, the manipulator <NUM> can move into the cabinet <NUM> to drop a picked object 106c into the chute <NUM>. The chute <NUM> is in communication with a receptacle (not shown) for receiving sorted picked objects 106c. The receptacle can be a bin, hopper, skip or other suitable container for receiving sorted waste products. In other embodiments, the sorted waste is allowed to pile on the floor and each pile of sorted waste can be separated by partitions.

The position of the chute <NUM> with respect to the working area will now be discussed in reference to <FIG> shows a schematic plan view of the working area <NUM>. The manipulator <NUM> can move anywhere within the working area <NUM>. The path of the conveyor belt <NUM> intersects with the working area <NUM>. The chute opening <NUM> is located within the working area <NUM>. At least a portion <NUM> of the working adjacent to the conveyor belt <NUM> is within the cabinet <NUM>. The cabinet <NUM> is not shown for the purposes of clarity.

In this way, the gantry frame <NUM> and cabinet <NUM> comprises an integral chute <NUM> for receiving picked objects 106c. The chute opening <NUM> has a predetermined orientation, size and location within the working area <NUM>. The working area <NUM> of the manipulator <NUM> will remain constant with respect to the gantry frame <NUM>. Accordingly, in this way, the chute opening <NUM> is fixed with respect to the gantry frame <NUM> and the cabinet <NUM>. For example, the chute opening <NUM> is located a fixed distance X1, X2 from the edges of the working area <NUM> in the X-axis. Similarly the chute opening <NUM> is a fixed distance Y1 from the conveyor belt <NUM> and a fixed distance from the edge of the working area <NUM> in the Y-axis. The dimensions of the chute opening <NUM> are also predetermined and the distance X3 and Y3 are fixed.

By providing an integral chute <NUM> in the gantry frame <NUM>, this means the distances X1, X2, X3, Y1, Y2, Y3 can be pre-set before the gantry frame <NUM> and the waste sorting gantry robot <NUM> leaves the factory. This means that the distances, size and orientation of the chute opening <NUM> remains constant and will not change when the waste sorting gantry robot is installed.

When fixing the location of the chute opening <NUM> with respect to the gantry frame <NUM>, the distances X1, X2, X3, Y1, Y2, Y3 can be selected. In some embodiments, X3 and Y3 are made a large as possible. Additionally or alternatively in some embodiments Y1 and Y2 are zero. This means that dropping picked objects into the chute <NUM> may be easier.

By fixing the size, orientation of the chute opening <NUM> with respect to the gantry frame <NUM>, the installation of the waste sorting gantry robot <NUM> is simplified. In particular, the chute opening <NUM> is always the same with respect to the gantry frame <NUM>. This means that the parameters for determining instructions for the controller instructing the manipulator <NUM> to drop a picked object do not vary between waste sorting gantry robots <NUM>.

Previously the chute opening could be located anywhere with respect to the manipulator <NUM> and would vary because each site and installation was different. This was because the receptacle for receiving sorted waste objects would not be located in the same place at each site. Accordingly, the chute dimensions and orientation would have to be changed to make sure sorted waste objects were successfully guided to the receptacle. This meant that an engineer would need to be required for installation to measure and reprogram the waste sorting gantry robot parameters once physically installed. By providing an integral chute, the variability of the chute opening between different sites is removed.

In some embodiments the dimensions of the chute opening are between <NUM> ≤ X3 ≤ <NUM> wide by <NUM> ≤ Y3 ≤ <NUM> long. Accordingly, the dimensions of X3 and Y3 mean that most objects can be successfully dropped into the chute opening. In some embodiments, the dimensions are as follows:.

Although not shown in <FIG>, there can be additional integral chutes located within the gantry frame. In this way the walls <NUM> of the chute <NUM> are fixed to the gantry frame <NUM>. The chute <NUM> can be welded, bolted, glued or fastened using any other suitable means to the gantry frame. In other embodiments, the gantry frame <NUM> comprises sheet material <NUM> which form the walls of the cabinets <NUM>, <NUM> and the walls <NUM> of the chute <NUM>. Optionally in some embodiments, one or more walls of the cabinets <NUM>, <NUM> comprise the chute opening <NUM> of the chute <NUM>. In this way, a hole in a plate or wall <NUM> of the gantry frame <NUM> is the chute opening <NUM>. The chute opening <NUM> can be orientated to be in any plane or planes so long as the size of the chute opening <NUM> is large enough to received picked objects 106c.

For example, another chute opening <NUM> can be located within the other cabinet <NUM> aligned along the same line parallel to the Y-axis. Additional chutes <NUM> can be added, for example, four chutes can be arranged each at a corner of the working space <NUM>. Again each of the four chutes <NUM> are integral with the gantry frame <NUM>. In other embodiments, there can be any number of chutes <NUM> for receiving sorted waste objects.

Returning to <FIG>, the chute <NUM> is visible. As previously mentioned, the gantry frame <NUM> comprises an integral chute <NUM> with a chute opening <NUM>. The integral chute <NUM> in some embodiments can be aligned with a hole <NUM> in the floor. This means that the dropped picked objects 106c, fall straight through the integral chute <NUM> and through the floor hole <NUM> and into the receptacle.

In some cases it is not possible to align a receptacle for sorted waste objects directly underneath the waste sorting gantry robot <NUM>. Accordingly, alternatively in some embodiments the integral chute <NUM> is connected to a guide chute <NUM> for guiding the dropped picked objects from the integral chute <NUM> to the receptacle. Both the chute <NUM> and the guide chute <NUM> are connected to the floor hole <NUM>. The guide chute <NUM> can be orientated at a different angle to the cabinet to guide the picked waste objects 106c laterally away from the waste sorting gantry robot <NUM>. In other embodiments, the guide chute <NUM> can vary in cross sectional dimensions to accommodate a difference in dimensions and shape between the integral chute <NUM> (e.g. rectangular) and a hole for a receptacle. The guide chute <NUM> can be flared to widen the chute and the guide chute <NUM> can be narrow to constrain the chute <NUM>. If required the guide chute <NUM> can comprise kinks or dog-legs in order to guide the picked waste objects through narrow or congested spaces. As mentioned previously, additionally or alternatively, another conveyor belt <NUM> can be used to transport picked objects 106c away from the integral chute <NUM>. For example, picked objects 106c fall onto a secondary conveyor belt (not shown).

The waste sorting gantry robot <NUM> will now be further described in reference to <FIG> shows a schematic cross sectional drawing of the waste sorting gantry robot <NUM>. As mentioned with respect to the embodiments shown in <FIG>, one of the cabinets <NUM> comprises an external access door <NUM>. The external access door <NUM> covers the interior of the cabinet <NUM> during operation. The external access door <NUM> can cover one or more control panels.

The cabinet <NUM> further comprises a maintenance door <NUM>. During operation when the external access door <NUM> is closed, the maintenance door <NUM> is not visible or accessible. The maintenance door <NUM> is shown in the "closed" upright position. In this way, when the external access door <NUM> is opened, the maintenance door <NUM> is shut and forms an internal barrier, preventing access to the interior of the gantry frame <NUM> and the manipulator <NUM>. In some embodiments, the maintenance door <NUM> is <NUM> meter tall by <NUM> wide. Accordingly, the maintenance door <NUM> is approximately waist high when in the closed position. This means that a human operator cannot trip over and fall into the gantry frame <NUM> when the maintenance door <NUM> is closed. The dimension of the maintenance door <NUM> provide an access space that when the maintenance door <NUM> is opened a person can fit into the interior of the cabinet <NUM>.

The maintenance door <NUM> pivots at the bottom <NUM> of the door about hinge <NUM>. <FIG> shows the maintenance door <NUM> in an inclined "open" position. Accordingly, when the maintenance door <NUM> is opened, the top <NUM> of the maintenance door rotates about the hinge <NUM> and pivots until the top of the door <NUM> rests against the side of the conveyor belt <NUM>. The side of the conveyor belt <NUM> physically stops the maintenance door <NUM> from moving any further towards the conveyor belt <NUM>.

The top of the door <NUM> can comprise rubber stoppers or another shock absorbing material on the side facing the conveyor belt. This means that the maintenance door <NUM> repeatedly being opening against the conveyor belt <NUM> reduces the chance of the conveyor belt becoming damaged.

The maintenance door <NUM> can comprise one or more latches and / or handles for locking the maintenance door <NUM> in the closed position and / or the open position. One or more lock-out sensors (not shown) are connectively coupled to external access door <NUM> and / or the maintenance door <NUM>. The one or more lock-out sensors can be a switch for detecting that the doors <NUM>, <NUM> are open. The one or more lock out sensors are connectively coupled to the controller <NUM>. This means that the controller <NUM> knows that the external access door <NUM> and the maintenance door <NUM> are open and operation of the manipulator is forbidden.

When the maintenance door <NUM> is in the open position, the maintenance door <NUM> covers at least a portion of the integral chute <NUM>. This means that access to the interior of the cabinet <NUM>, the manipulator <NUM> and the conveyor belt <NUM> is not impeded by the opening <NUM> of the chute. In some embodiments, the maintenance door <NUM> completely covers the opening <NUM> of the integral chute <NUM>. This means that is not possible to step into the opening <NUM> of the chute <NUM> and fall over when the maintenance door is in the open position. Advantageously, this means that the space created by incorporating the integral chute <NUM> into the gantry frame can serve a dual purpose. The same space in the gantry frame <NUM> which is used for the integral chute <NUM> during operation is used as an access and maintenance space when the maintenance door <NUM> is in the open position.

The maintenance door <NUM> can comprise one or more latches and / or handles (not shown) for holding the maintenance door <NUM> in the closed and / or the closed position. The latches can be manually operated. Additionally or alternatively, the latches can be automatically operated by the controller <NUM>. The handles can be used to manually lower the maintenance door <NUM> into the open position against the conveyor belt <NUM>.

The maintenance door <NUM> is made from a stiff material such as steel and is arranged to support the weight of a person. Accordingly, it is possible to stand on the maintenance door <NUM> when the maintenance door <NUM> is in the open position.

In some embodiments, the maintenance door <NUM> comprises one or more grips elements <NUM> for increasing the friction between the surface of the maintenance door <NUM> and footwear. In some embodiments, the grip elements are rubber grips, raised bumps in the maintenance door, studs, grills or any other suitable means for providing additional grip on the surface of the maintenance door <NUM>.

Since the maintenance door <NUM> is inclined in the open position, the maintenance door <NUM> can be provided with steps <NUM> as shown in <FIG>. The steps <NUM> provide assistance for a person climbing into the interior of the cabinet and inspecting e.g. the manipulator <NUM>. The maintenance door as shown in <FIG> has five steps, but the maintenance door can have any number of steps depending on the incline and the height of the conveyor belt <NUM> and the manipulator <NUM> above the floor. The steps <NUM> can be integral to the maintenance door <NUM> such that the maintenance door <NUM> comprises folded and bent material formed into steps.

Alternatively, the maintenance door <NUM> can comprise one or more fastening elements for receiving separate steps. In this way, the maintenance door <NUM> is opened and the steps <NUM> or ladder is placed and fastened to the maintenance door <NUM>. For example, the steps can be clipped or bolted into place when the maintenance door is opened <NUM>. Additionally or alternatively the steps <NUM> can hook over the side of the conveyor belt <NUM> for additional stability. In this way, the maintenance door <NUM> manufacture can be simpler. The separate steps and / or ladder can be stored inside the cabinet <NUM> when the maintenance door <NUM> and the external access door <NUM> are closed.

Accordingly, by providing a maintenance door <NUM> in the gantry frame <NUM>, a human operator can inspect and maintain the waste sorting gantry robot from the side quickly and safely. This means that maintenance does not have to be conducted by first crawling along the conveyor belt to access the manipulator <NUM>. This make maintenance safer and quicker.

In other embodiments, the chute <NUM> arrangements as described with respect to the <FIG> can also be used with other types of sorting robot was are not waste sorting robots. For example, the chute <NUM> can be used with industrial robots in the automotive industry, food industry etc..

In another embodiment, two or more embodiments are combined. Features of one embodiment can be combined with features of other embodiments.

Claim 1:
A waste sorting robot (<NUM>) comprising:
a frame (<NUM>),
a manipulator (<NUM>) for interacting with one or more waste objects (106a, 106b, 106c) to be sorted within a working area (<NUM>); and wherein the manipulator (<NUM>) is moveably mounted on the frame (<NUM>) and the manipulator (<NUM>) is moveable within the working area (<NUM>);
a conveyor (<NUM>) for moving one or more waste objects (106a, 106b, 106c) to be sorted within the working area (<NUM>);
a chute (<NUM>) for receiving sorted objects moved by the manipulator (<NUM>) from the conveyor (<NUM>) to a chute opening (<NUM>);
wherein the frame (<NUM>) comprises a maintenance door (<NUM>) for accessing the manipulator (<NUM>) and / or the conveyor (<NUM>) and the maintenance door (<NUM>) is moveable to a position in which the maintenance door (<NUM>) covers at least a portion of the chute opening (<NUM>) and characterised in that the maintenance door (<NUM>) covers the chute opening (<NUM>) when the manipulator (<NUM>) and / or the conveyor (<NUM>) is accessible.