DEVICE FOR MOVING THROUGH A GRANULAR MEDIUM

Abstract

A device (1) for moving through a granular medium, the device comprising: a body (2); a rotatable part (4A, 4B) for rotational movement relative to the body about a rotational axis (6), wherein the rotatable part is externally-exposed and arranged to cause agitation of an adjacent portion of a granular medium in which the device is to be provided; a motor configured to cause the rotational movement of the rotatable part; and a protrusion (8) arranged to extend from the body and to limit rotational movement of the body about the rotational axis relative to the granular medium when the motor causes rotational movement of the rotatable part relative to the granular medium.

Claims

1. (canceled)

2. (canceled)

3. (canceled)

4. (canceled)

5. (canceled)

6. (canceled)

7. A device for moving through a granular medium, the device comprising: a body; a rotatable part for rotational movement about a rotational axis, the rotatable part being externally-exposed and arranged to cause agitation of an adjacent portion of a granular medium in which the device is to be provided; a motor configured to cause the rotational movement of the rotatable part; and one or more agitating portions provided with the rotatable part to cause the agitation of the adjacent portion of the granular medium, and wherein at a first rotational position of the rotatable part relative to the body, the device is configured such that a first portion of the rotatable part and the one or more agitating portions cause a first degree of agitation in a first region of the granular medium and a second portion of the rotatable part and the one or more agitating portions cause a second degree of agitation in a second region of the granular medium, and at a second rotational position of the rotatable part relative to the body, the first portion of the rotatable part and the one or more agitating portions cause the second degree of agitation in the second region of the granular medium.

8. The device according to claim 7, wherein the device has a further configuration in which at the first rotational position of the rotatable part relative to the body, the device is configured such that the first portion of the rotatable part and the one or more agitating portions cause the second degree of agitation in the first region of the granular medium.

9. The device according to claim 7, wherein at least one of the one or more agitating portions is moveable between a first position and a second position, the first position extended further than the second position.

10. The device according to claim 9, wherein the device further comprises: a cam, the cam being connected to the at least one of the one or more agitating portions and movable independently of the rotatable part; and a cam motor, the cam motor being operable to cause rotation of the cam relative to the body, wherein rotation of the cam causes movement of the at least one of the one or more agitating portions between the first position and the second position.

11. The device according to claim 10, wherein rotation of the cam to a first cam position causes movement of a first region of the one or more agitating portions to the second position and movement of a second region of the one or more agitating portions to the first position, and wherein rotation of the cam to a second cam position causes movement of a third region of the one or more agitating portions to the second position and movement of a fourth region of the one or more agitating portions to the first position.

12. The device according to claim 7, wherein the rotatable part defines one or more apertures through which the one or more agitating portions may be extended and/or retracted.

13. The device according to claim 7, wherein the device comprises one or more agitating portions provided with the rotatable part to cause the agitation of the adjacent portion of the granular medium, the one or more agitating portions being movable relative to an outer surface of the rotatable part in a direction having at least a component normal to the outer surface of the rotatable part to alter a degree of the agitation of the adjacent portion of the granular medium that is caused when the rotatable part is caused to move relative to the granular medium.

14. A device for moving through a granular medium, the device comprising: a body; a rotatable part for rotational movement about a rotational axis, the rotatable part being externally-exposed and arranged to cause agitation of an adjacent portion of a granular medium in which the device is to be provided; a motor configured to cause the rotational movement of the rotatable part; and one or more agitating portions provided with the rotatable part to cause the agitation of the adjacent portion of the granular medium, wherein the one or more agitating portions is movable relative to an outer surface of the rotatable part in a direction having at least a component normal to the outer surface of the rotatable part to alter a degree of the agitation of the adjacent portion of the granular medium that is caused when the rotatable part is caused to move relative to the granular medium.

15. The device according to claim 7 comprising a sampling portion operable to selectively capture a sample of the granular medium for removal from the granular medium.

16. A device for sampling granular material from within a granular medium, the device comprising: a body; a rotatable part for rotational movement about a rotational axis, the rotatable part being externally-exposed and arranged to cause agitation of an adjacent portion of a granular medium in which the device is to be provided; a motor configured to cause the rotational movement of the rotatable part to thereby move the device through the granular medium; and a sampling portion operable to selectively capture a sample of granular material from the granular medium for removal from the granular medium.

17. The device according to claim 7, wherein a maximum extent of the rotatable part in a direction transverse to the rotational axis is greater than five times a mean maximum extent of grains forming the granular medium.

18. The device according to claim 7, wherein the device comprises a sensor for outputting a signal indicative of a depth position of the device within the granular medium.

19. (canceled)

20. (canceled)

21. (canceled)

22. (canceled)

23. (canceled)

24. (canceled)

25. The device of claim 7, wherein the granular medium is a dry granular medium and comprises foodstuffs, and wherein the granular medium is retained within a silo.

26. The device of claim 7, comprising a protrusion arranged to extend from the body and to resist rotational movement of the body about the rotational axis relative to the granular medium when the motor causes rotational movement of the rotatable part relative to the granular medium.

27. The device of claim 26, wherein the body, the protrusion, and the rotatable part each have an outer surface area, and wherein the outer surface area of the protrusion contributes less than 15% to the total combined surface area of the body, the protrusion, and the rotatable part.

28. The device of claim 26, wherein the body and the protrusion each have a length, and wherein the length of the protrusion is at least 20% of the combined length of the protrusion and the body.

29. The device of claim 7, wherein the device comprises a tether.

30. The device of claim 26, wherein the protrusion comprises a connector for connecting the body to a tether via the protrusion.

Description

DESCRIPTION OF THE DRAWINGS

[0105] Examples of relevance to the present disclosure will now be described with reference to the following Figures in which:

[0106] FIG. 1A is a perspective view diagram of an example of a device for moving through a granular medium;

[0107] FIG. 1B is a side elevation diagram of the device of FIG. 1A, FIG. 1C is a front elevation diagram of the device of FIG. 1A, and FIG. 1D is a plan view diagram of the device of FIG. 1A;

[0108] FIG. 2 is a contour plot showing an example of the effect of rotation of the rotatable parts (wheels) of the device 1 on the granular medium in which the device travels according to one of the ways in which the device could move;

[0109] FIG. 3A is a perspective view diagram of a further example of a device for moving though a granular medium;

[0110] FIG. 3B is a side elevation diagram of the device of FIG. 3A, FIG. 3C is a front elevation diagram of the device of FIG. 3A, and FIG. 3D is a plan view diagram of the device of FIG. 3A;

[0111] FIGS. 4A to 4F are a series of cut-away perspective view diagrams of the rotatable part (wheel) of the device of FIGS. 3A to 3D;

[0112] FIG. 5 is a flow chart of example steps in a method of moving a device for moving through a granular medium;

[0113] FIG. 6A is a perspective view diagram of another device for moving through a granular medium and capturing a sample of granular material;

[0114] FIG. 6B is a side elevation diagram of the device of FIG. 6A, FIG. 6C is a front elevation diagram of the device of FIG. 6A, and FIG. 6D is a plan view diagram of the device of FIG. 6A;

[0115] FIG. 6E is a cut-away perspective view diagram of the device of FIG. 6A;

[0116] FIG. 7 is a flow chart of example steps in a method of capturing a sample of granular material according to an aspect of the disclosure;

[0117] FIG. 8 is a cut-away front elevation diagram of equipment for removing a captured sample according to an example of the disclosure; and

[0118] FIG. 9 is a diagram showing a further example of a device as disclosed herein.

DETAILED DESCRIPTION OF AN EXAMPLE EMBODIMENT

[0119] It will be understood by those skilled in the art that any dimensions and relative orientations such as lower and higher, above and below, and any directions, such as vertical, horizontal, upper, lower, axial, radial, longitudinal, tangential, etc., referred to in this application are within expected structural tolerances and limits for the technical field (here including devices for moving through granular media) and the apparatus and methods described, and these should be interpreted with this in mind.

[0120] FIG. 1A is a diagram showing an example of a device 1 for moving through a granular medium made up of granular material. The device 1 has a generally spherical shape, and comprises a body 2 and first and second rotatable parts in the form of two generally hemispherical wheels 4A, 4B located at either side of the body 2 and for rotation relative thereto. The device 1 comprises two motors (not shown in FIG. 1A) and a dedicated power source (not shown) each mounted relative to the body 2 and together for driving rotation of the wheels 4A, 4B relative to the body 2, about a rotation axis 6. A protrusion 8 in the form of a narrow, elongate protrusion 8 extends from the body 2. The protrusion 8 extends in a direction transverse to the axis of rotation 6. The protrusion 8 comprises an end portion 10 from which extends a tether 12 in the form of a tether cable 12 for communication of control signals and sensor data between the device 1 and a further component (not shown). The outer surface of each wheel 4A, 4B is provided with a plurality of agitating portions 14 in the form of a plurality of raised bumps 14. FIGS. 1B, 1C, and 1D are side and front elevation diagrams and a plan diagram of the device 1 of FIG. 1A.

[0121] The device 1 is typically provided with a controller (not shown) for controlling operation of the motors and/or of the wheels 4A, 4B. The device 1 may be provided with a processor (in electronic communication with a memory storing computer executable program code) programmed to control the movement of the device 1 through a granular medium, for example by directing the device 1 along a pre-programmed path.

[0122] The device 1 is further provided with one or more sensors (not shown) for sensing one or more characteristics of an external environment of the device 1. For example, in an example embodiment, the device has one or more temperature sensors operable to measure temperature and to transmit a temperature signal (for example, to the controller or to a user or to an external device). The device 1 is provided with one or more surface position sensors operable to detect whether the device 1 is at the surface of the granular medium and to transmit a signal indicative of whether the device 1 is at the surface of the granular medium (for example, to the controller or to a user or to an external device).

[0123] In some alternative examples, the device 1 is also provided with one or more humidity sensors operable to measure humidity and to transmit a humidity signal (for example, to the controller or to a user or to an external device) and/or one or more moisture sensors operable to measure moisture and transmit a moisture signal (for example, to the controller or to a user or to an external device) and/or one or more motion sensors (e.g. one or more accelerometers and/or one or more gyroscopes) etc operable to detect motion and transmit a motion signal (for example, to the controller or to a user or to an external device).

[0124] The inventor has found that, when the device 1 is submerged in a granular medium, rotation of the wheels 4A, 4B about the rotation axis 6 causes the device 1 to travel through the granular medium. Specifically, the two motors generate a torque on the wheels 4A, 4B which in turn generates a rotation torque of the body in the opposite rotational direction. Rotation of wheel 4A can be driven independently of rotation of wheel 4B, and vice versa. When the wheels 4A, 4B are rotated relative to the body 2 with the device 1 submerged within a granular medium, the protrusion 8 resists the rotational movement of the body 2 relative to the granular medium about the rotation axis 6 thus allowing the wheels 4A, 4B to rotate relative to the granular medium about the rotation axis and causing the device 1 to move efficiently through the granular medium, as will be described further with reference to FIG. 2 hereinafter.

[0125] The device 1 can travel vertically and horizontally and transversely through the granular medium and can turn, with the direction of motion being adjustable by adjusting the speed and direction of rotation of the motors (and thus the wheels 4A, 4B). The device 1 can also travel on the surface of the granular medium. The agitating portions 14 cause agitation of the granular material, when the wheels 4A, 4B are rotated. The agitating portions 14 can also provide at least some friction (i.e., grip) between the wheels 4A, 4B and the granular medium during rotation of the wheels 4A, 4B. It will be understood that the speed of rotation of the wheels 4A, 4B can be varied to vary the degree of agitation of the granular medium and/or the degree of grip between the wheels 4A, 4B and the granular medium.

[0126] In practice, movement of the device through the granular medium can be achieved with rotation of the rotatable portions through a wide range of angular velocities, for example between 0.1 Hz (i.e. 0.1 complete revolutions per second) and 10 Hz (i.e. 10 complete revolutions per second), in some cases even up to 100 Hz, with the particular angular velocity selected based on device parameters such as device shape, size and weight as well as the nature of the granular material.

[0127] The tether 12 can be used to retrieve the device 1, for example if the device 1 develops a fault or stops moving.

[0128] FIG. 2 is a contour plot showing an example of the effect of rotation of the wheels 4A, 4B of the device 1 on the granular medium in which the device 1 travels, according to one way in which the device 1 could move. In particular, movement of the rotatable parts 4A, 4B relative to the granular medium with sufficient angular velocity causes the agitating portions 14 to agitate the grains of the granular medium. With sufficient agitation, the grains of the granular medium can be considered to exhibit some liquid-like properties. In this way, the effect can be referred to as liquefaction. Furthermore, the rotation causes the formation of a relatively higher-pressure region 50 within the granular medium on one side of the wheels 4A, 4B of the device 1, generally on a lower-left side of the device 1, and a correspondingly relatively lower-pressure region 52 forming within the granular medium on the opposite side of the device 1. Generally on an upper-right side of the device 1. Accordingly, it will be understood that the device 1 will move in accordance with the pressure gradient defined between the higher-pressure region 50 and the lower-pressure region 52, in particular in the direction of the lower-pressure region 52. FIG. 2 shows the situation with clockwise rotation of the wheels 4A, 4B in the centre of the figure. It will be understood that with anti-clockwise rotation of the wheels 4A, 4B, the higher-pressure region 50 would be located generally on a lower-right side of the device 1, and the lower-pressure region 52 would be located generally on an upper-left side of the device 1. In the example shown in FIG. 2, the density of the device is greater than the density of the granular medium. Accordingly, if the density of the granular medium is instead greater than the density of the device, the mechanism will change, such that the higher-pressure region 50 would be located at least partially above the device and the lower-pressure region 52 would be located at least partially below the device.

[0129] Because the device 1 is provided with a protrusion 8, the protrusion 8 provides resistance against rotation of the device 1 around the rotation axis 6, thus allowing the device 1 to move through the granular medium more efficiently, with less energy lost to unwanted rotational movement of the body 2 relative to the granular medium. Because the protrusion 8 is elongate and narrow, the frictional forces between the protrusion 8 and the granular material when the device 1 moves through the granular medium are relatively small, allowing the device 1 to move through the granular medium with relative ease. Specifically, the frictional forces between the protrusion 8 and the granular medium are small in comparison to the frictional forces between the wheels 4A, 4B and the body 2 when the device moves through the granular medium. As such, the protrusion 8 provides the advantage of limiting rotational movement whilst not contributing significantly to drag on the device 1 as the device moves. This makes the movement of the device more efficient than would otherwise be the case.

[0130] FIG. 3A is a diagram of a further example of a device 100 for moving through a granular medium made up of granular material. The device 100 is generally spherical and includes a body 102 and first and second generally hemispherical rotatable parts in the form of two wheels 104A, 104B mounted at either side of the body 102 for rotation relative to the body 102. The outer surface of each wheel 104A, 104B defines a plurality of apertures 116 through which a plurality of moveable agitating portions 114 may be extended and/or retracted. Here the plurality of agitating portions 114 are provided in the form of generally cylindrical prisms. The body 102 contains two wheel motors (not shown in FIG. 3A), two cams (not shown in FIG. 3A), two cam motors (not shown in FIG. 3A) and a dedicated power source (not shown). Each cam is connected to the plurality of moveable agitating portions 114 of one of the wheels 104A, 104B. The two wheel motors are for driving rotation of the wheels 104A, 104B, about a rotation axis 106. The cam two motors are for driving rotation of the two cams. Two protrusions 108A, 108B, in the form of two narrow, elongate protrusions 108A, 108B extend from the body 102 one each in opposite directions transverse to the rotational axis 106. FIGS. 3B, 3C, and 3D are side and front elevation diagrams, and a plan diagram of the device 1 of FIG. 3A, respectively.

[0131] Rotation of wheel 104A can be driven independently of rotation of wheel 104B, and vice versa. Rotation of the wheels 104A, 104B can be driven independently of rotation of the cams.

[0132] As in the example embodiment shown in FIGS. 1A to 1D and described above, when the device 100 is submerged in a granular medium, rotation of the wheels 104A, 104B about the rotation axis 106 causes the device 100 to travel through the granular medium. Specifically, the two wheel motors generate a torque on the wheels 104A, 104B which in turn generates a rotation torque of the body in the opposite rotational direction. The protrusions 108A, 108B then act to resist the rotational movement of the body 102 about the rotation axis 106 thus allowing the device 100 to travel within the granular medium more effectively.

[0133] As described hereinbefore with reference to FIGS. 3A to 3D, the agitating portions 114 both provide grip and cause agitation of the granular material, when the wheels 104A, 104B are rotated. Rotation of the cam motors drives rotation of the cams, which in turn drives movement of the agitating portions 114 such that the agitating portions 114 are extended and/or retracted through the apertures 116 in the outer surfaces of the wheels 104A, 104B. In this way, both the degree of grip and the degree of agitation of the granular material can be adjusted.

[0134] As a result of the cams provided to engage with the agitating portions 114 of each of the wheels 104A, 104B, it can be seen that the agitating portions 114 on a first side of the wheels 104A, 104B, substantially adjacent the first protrusion 108A, extend further from an outer surface of the wheels 104A, 104B than the agitating portions 114 on a second side of the wheels 104A, 104B, substantially adjacent the second protrusion 108B. Thus, the agitation and/or grip provided by the agitating portions 114 is different at the first side and the second side of the wheels 104A, 104B. The cams are configured to be mounted rotationally independently of the wheels 104A, 104B. In this way, when the wheels 104A, 104B rotate, without rotation of the cams, the agitating portions 114 remain more extended from the outer surface of the wheels in the region adjacent the first protrusion 108A than in the region adjacent the second protrusion 108B. Therefore, a degree of agitation of the granular medium is greater in a region of the granular medium adjacent the first protrusion 108A than in the region of the granular medium adjacent the second protrusion 108B, regardless of the rotational position of the wheels 104A, 104B.

[0135] Put another way, as a wheel 104A, 104B is rotated, the wheel moves from a first rotational position relative to the body 102 to a second rotational position relative to the body 102 (and indeed would typically continue to move to further rotational positions). At a first rotational position of the wheel 104A, 104B relative to the body 102, the agitating portions 114 are positioned (e.g. extended or retracted) such that the agitating portions 114 at a first portion of the wheel 104A, 104B cause a first degree of agitation in a first region of the granular medium and the agitating portions 114 at a second portion of the wheel 104A, 104B cause a second degree of agitation in a second region of the granular medium. Then, when the wheel 104A, 104B is rotated to a second rotational position relative to the body 102, the agitating portions 114 at the first portion of the wheel 104A, 104B cause the second degree of agitation in the second region of the granular medium.

[0136] The advantage of extendible and retractable agitation portions 114 and thus of adjustable grip and an adjustable degree of agitation of granular material (i.e., as the wheels 104A, 104B are rotated) is that this provides improved manoeuvrability of the device 100 as it travels through the granular medium.

[0137] By rotating the cams, the region of the granular medium to be agitated can be changed. It will be understood that the cams can be rotated independently for each of the wheels 104A, 104B.

[0138] Furthermore, the plurality of agitation portions 114 may be moveable together (e.g. extendible and/or retractable). For example, in one example embodiment, all agitating portions 114 may be extended (or retracted) though their respective apertures 116 together, such as by the same amount, and/or by the same proportional amount. In this way, the device 100 can be configured differently depending on the precise environmental conditions, such as the type of granular medium, or the position of the device within the granular medium (such as whether the device is at the surface or instead submerged within the granular medium).

[0139] In other words, all of the agitating portions 114 can be extended (e.g. fully) when the device 100 is at the surface of the granular medium. Because the agitating portions cause a greater degree of agitation when fully extended, this has the effect of encouraging the device 100 to bury itself in the granular medium when the wheels 104A, 104B are rotated. Conversely, when the device 100 is submerged within the granular medium, the agitating portions 114 can each be (e.g. fully) retracted to limit the frictional forces on the wheels 104A, 104B when the wheels 104A, 104B are rotated, thereby improving the efficiency of the travel of the device 100 within the granular medium.

[0140] FIGS. 4A to 4D are a series of cut-away perspective view diagrams of the rotatable part (wheel) of the device 100 as shown in FIGS. 3A to 3D (protrusion not shown) and discussed above and FIG. 4E is a cut-away front elevation diagram of the rotatable part (wheel) of an example embodiment equivalent to the device 100 as shown in FIGS. 3A to 3D (but having only one protrusion). FIG. 4F is a diagram of internal components of the device shown in FIGS. 3A to 3D, showing aspects of the inner workings of the rotatable part shown in FIGS. 4A to 4E. It will be understood that some components of the device 100 are hidden in some of the figures to better illustrate other components of the device 100.

[0141] Referring to FIGS. 4A to 4F, one example way in which the agitating portions 114 can be controlled to extend through the apertures 116 can be seen. A plurality of agitating portions 114 are provided on an agitating portion undercarriage 113, aligned with a plurality of apertures 116 defined in the wheel 104A. As can be seen in FIG. 4A, the wheel 104A is provided with a plurality of the agitating portion undercarriages 113. Each agitating portion undercarriage 113 is engaged with a track 146, 148, in this example a plurality of tracks 146, 148 (best seen in FIG. 4F), defined within an internal structure within the wheel 104A, in the form of each of two semi-circular portions 138, 142. The agitating portion undercarriage 113 comprises a plurality of track engagement protrusions 113A, 113B, one each for engaging within each of the tracks 146, 148. In this way, the tracks 146, 148 define an extent to which the agitating portions 114 of the agitating portion undercarriage 113 extend through the apertures 116 from the outer surface of the wheel 104A. As the wheel rotates about the rotational axis, the agitating portion undercarriage 113 rotates therewith relative to the tracks 146, 148 which are rotationally independent of the wheels 104A. In this way it will be understood that any lateral movement of the tracks 146, 148 in the internal structure within the wheel, in a direction towards or away from the surface of the wheel 104A, will change the extent to which the agitating portions 114 of the agitating portion undercarriages 113 extend through the apertures 116 at the region of the wheel adjacent the particular portion of the track.

[0142] The tracks 146, 148 of FIGS. 4A to 4F can be moved by two interdependent mechanisms, each of which will now be described.

[0143] Firstly, as shown in FIG. 4A, there is provided a ring piece 126, having defined therein a plurality of arcuate slots 128, in this example six arcuate slots 128. Each of the plurality of arcuate slots 128 extends from a first position to a second position. The second position is radially outward and circumferentially spaced from the first position. A corresponding plurality of expanding arcs 132 are moveably mounted relative to each of the arcuate slots 128 via locating pegs 130 engaged within the arcuate slots 128. In the example shown in FIG. 4A, the locating legs are provided adjacent the second position of the arcuate slots 128, forcing the expanding arcs 132 to a radially outermost position. As shown in FIG. 4D, an opposite side of the expanding arcs 132 defines an expanding arc track 137 for engagement by locator portions 139 of the two semi-circular portions 138, 142. The agitating portion undercarriages 113 engage with the tracks 146, 148 (shown best in FIGS. 4E and 4F) defined in an opposite side of the semi-circular portions 138, 142 to the locator portion 139.

[0144] The ring piece 126 is internally toothed and engaged by a driven gear 154 to cause rotational movement of the ring piece 126 relative to the expanding arcs 132 and thereby cause radial movement inwardly or outwardly of the expanding arcs 132 in a direction transverse to the rotational axis. The retracted position of this mechanism is shown in FIG. 4C.

[0145] The two semi-circular portions 138, 142 each define semi-circular portions of a circle (i.e., having a substantially constant radius of curvature). As best seen in FIG. 4F, the two semi-circular portions 138, 142 are connected via first and second expandable connections 140, 144 allowing slight lateral movement between the semi-circular portions 138, 142, such that the two semi-circular portions 138, 142 define a circular portion of the tracks 146, 148 for each of the semi-circular portions 138, 142 and a short, approximately straight portion of the tracks 146, 148 in a transition region between the semi-circular portions 138, 142. In this way, it can be seen that in an expanded configuration, the tracks 146, 148 will define a non-circular path. As a result, the agitating portions 114 will be caused to extend further from the wheel 104A when passing through a midway portion of the tracks 146, 148 defined by a central region of each of the semi-circular portions 138, 142. The greater the expansion between the two semi-circular portions 138, 142 at the expandable connections 140, 144, the greater the degree of extension of the agitating portions 114 from the wheel 104A at the central region of the semi-circular portions 138, 142. Similarly, the agitating portions 114 will extend less far from the wheel 104A (or even not at all) in the region of the expandable connections 140, 144. As will be understood, the degree of expansion for the two semi-circular portions 138, 142 is controlled by movement of the expanding arcs 132 as described hereinbefore. In this way, the degree of agitation caused by the agitating portions 114 can be altered. In this way, the tracks 146, 148 defined in the two semi-circular portions 138, 142 can be considered to form a cam piece selectively defining a non-circular path for the agitating portions 114.

[0146] In addition to the mechanism described above, the tracks 146, 148 can be further manipulated by rotation of the cam piece, formed from the two semi-circular portions 138, 142. A first semi-circular portion 142 defines a circular internally-toothed region. The cam piece can be rotated into a desired rotational position my driving the worm gear 150 to engage with further gear 152 to drive the internal teeth of the first semi-circular portion 142. Thus, the first semi-circular portion 142 and a second semi-circular portion 138 can be rotated together relative to the wheel 104A to move the position relative to the body 102 at which the agitating portions 114 extend most from the surface of the wheel 104A, thereby allowing control of the direction of movement of the device 100.

[0147] FIG. 5 is a flow chart of example steps in a method 61 for moving the device. Here, the method is typically performed by a controller and includes the step of receiving 60 a signal indicative of whether or not the device 1, 100, is at the surface of the granular medium. If the signal is a signal indicative that the device is at the surface of the granular medium 68, the method comprises extending 62 the agitating portions 114. The method subsequently comprises moving 66 the wheels 104A, 104B. Conversely, if the signal is a signal indicative that the device is not at the surface of the granular medium 70, the method comprises retracting 64 the agitating portions 114. The method subsequently comprises moving 66 (i.e., rotating) the wheels 104A, 104B. The method may be repeated. In other words, the method subsequently comprises (again) receiving 60 a further signal indicative of whether or not the device 1, 100, is at the surface of the granular medium.

[0148] FIG. 6A is a diagram of a device 200 for moving through a granular medium made up of grains and capturing samples of the grain. The device 200 is generally spherical and comprises a body 202 and first and second generally hemispherical rotatable parts in the form of two wheels 204A, 204B located at either side of the body 202. The outer surface of each wheel 204A, 204B has a plurality of agitating portions 214 as described hereinbefore. In this example, the agitating portions 214 are provided in the form of a series of fins, surrounding the outer surface of each wheel 204A, 204B. The body 202 contains two wheel motors (not shown), and a dedicated power source (not shown). The two wheel motors are for driving rotation of the wheels 204A, 204B, about a rotation axis 206. A narrow, elongate protrusion 208 extends from the body 202. The protrusion 208 is connected to a grain sampler 218. The grain sampler 218 has two connectors in the form of ports 210A, 210B via which the grain sampler 218 is connected to two tethers in the form of an air conduit 220 and a grain conduit 222. The grain sampler also has two grain inlets 224A and 224B for receiving grain to be sampled. FIGS. 6B, 6C, and 6D are side and front elevation diagrams and a plan diagram of the device 1 of FIG. 6A, respectively.

[0149] As in the example embodiments shown in FIGS. 1A to 1D and FIGS. 3A to 3D, and described above, when the device 200 is submerged in a granular medium, rotation of the wheels 204A, 204B about the rotation axis 206 causes the device 200 to travel through the granular medium. Specifically, the two wheel motors generate a torque on the wheels 204A, 204B which in turn generates a rotation torque of the body in the opposite rotational direction. The protrusion 208 (as well as the grain sampler 218 and tethers, here provided in the form of an air conduit 220, and a grain conduit 222) then resists the rotational movement of the body 202 about the rotation axis 206 thus allowing the device 200 to travel within the granular medium.

[0150] As can be most clearly in FIG. 6E, which is a cut-away perspective view diagram of the device 200 of FIG. 6A, in use, an airflow of pressurised air enters the air conduit 220 and travels towards the grain inlets 224A, 224B where the pressurised air mixes with the grains of the granular medium adjacent to the grain sampler 218, encouraging a sample of grain to enter the grain sampler 218 via the grain inlets 224A, 224B, thus capturing a sample of grain. In this example embodiment, the pressurised air and the sample of grain then leave the grain sampler 218 (and the granular medium) via the grain conduit 222. In FIG. 6E, the airflow path for the pressurised air is shown with thin-line arrows through the conduits 220, 222 and the path taken by the grain sample is shown in solid arrows at the grain inlets 224A, 224B. The example device 200 shown in FIG. 6 also includes a cooling air source conduit 240 for receiving cooler air from the air conduit 220 for cooling the components of the device 200 within the body 202 and the wheels 204A, 204B. The air is provided back out of the device via a cooling air exhaust conduit 242 to the grain conduit 222.

[0151] FIG. 7 is a flow chart of example steps in a method of capturing a sample of granular material according to an example aspect of the disclosure. In general, the method 71 includes introducing the device into the granular medium 72. The device is typically any of the devices described hereinbefore including a sampling portion. The method 71 further comprises receiving 74 a control signal. The control signal is indicative of a sampling location at which the device is to sample the granular medium. The method 71 further comprises controlling 76 the device to move through the granular medium to the sampling location in accordance with the control signal. The method 71 further comprises capturing 78 a sample of granular medium at the sampling location. Optionally, the method 71 can also include removing the sample from the granular medium (not shown in FIG. 7).

[0152] Advantageously, a user may then carry out analysis of the sample. However, in alternative embodiments of the method, the sample may not be removed away from the granular medium and instead analysis may be carried out whilst the sample is retained by the grain sampler 218 (and the sample may then optionally be released back to the granular medium or may be removed from the granular medium. In some alternative embodiments of the method, the method may include causing the device to move to the surface of the granular medium (optionally whilst retaining the said sample) where it may be retrieved by a user.

[0153] FIG. 8 is a cut-away front elevation diagram of an example of pressurised air equipment 300 that could be used to provide the pressurised air and for receiving a captured sample, however the skilled person will appreciate that other equipment or methods could also be used. The equipment 300 has a cyclone 340 formed within a cylinder having an inner cylindrical surface 380 and a cone having an inner conical surface 390. The equipment 300 also has a reservoir 350, as well as an outlet connection 360 for connecting the equipment 300 to an external vacuum source. As in FIG. 6E, the airflow path for the pressurised air is shown with dashed arrows and the path taken by the grain sample is shown in solid arrows.

[0154] In use, compressed air enters the pipe at inlet point 370 and travels downward via air conduit 320 (the same conduit as air conduit 220 in FIGS. 6A to 6E) until reaching device 200 where it mixes with granular material entering the grain sample 218 via the grain inlets 224A, 224B. Air mixed with the said granular material then travels upward via the grain conduit 322 (the same conduit as grain conduit 222 in FIGS. 6A to 6E) and then enters the cyclone 340 where the grains move around the vertical axis (not shown) travelling substantially along a path following the inner cylindrical surface 380 until the grains fall under gravity and follow substantially along a path following the inner conical surface 390 and finally to the reservoir 350 where grains are separated from the airflow. The air then travels upward along the vertical central axis (not shown) and exits the cyclone via outlet connection 360. The collected grains can then be conveniently retrieved by a user. In this example, the grain inlets 224A, 224B can be selectively opened and closed by rotation around a vertical axis, such that the inlets of the grain sample 218 become closed off from an external environment of the device 200 (i.e., the granular medium), and the grain pockets 224A, 224B are oriented and open toward the inner conduits 220, 222 to facilitate passage of the sample of granular medium in the grain pockets 224A, 224B into the conduits 220, 222 and away from the device 200.

[0155] The advantage of providing a device 200 for moving through a granular medium made up of grains having a grain sampler 218 is that this allows a sample of a grain to be collected without the need for a user to collect such a sample manually.

[0156] In alternative examples, the tether 12 may include a power cable for supplying power to the device 1, 100, 200 and/or may include one or more communications cable for transmitting information to the device 1, 100, 200 and/or for receiving data from the device 1, 100, 200. The connector 10 may include a slip ring. In some alternative examples the one or more sensors may be mounted on the body 2, 102, 202 or the protrusion 8, 108A, 108B, 208.

[0157] The device 1, 100, 200 may be remote-controlled (in which case the vehicle may include a receiver and a transmitter for communicating with a remote-control unit) or the device 1, 100, 200 may be autonomous. Such a device 1, 100, 200 could be used in underground investigations, for object retrieval, in planetary exploration, or in (cereal, seed or pulse) grain or powder (e.g. cement) silos.

[0158] Where a grain sampler 218 is provided, in some alternative embodiments the grain sampler 218 may be configured to capture a sample of grain but may not have a grain conduit 222, in which case the grain sample may be retrieved when the device 1, 100, 200 moves to the surface of the granular medium. Alternatively, the device 1, 100, 200 may comprise sensors and tests may be carried out on the sample without the sample being removed from the granular medium, in which case the sample may optionally then be returned to the granular medium.

[0159] FIG. 9 is a diagram showing a further example of a device as disclosed herein. The device 400 is substantially as described with reference to the devices 1, 100, 200 described hereinbefore apart from the hereinafter noted differences. The protrusion of the device 400 extends from the body 402, and is formed from a first protrusion portion 409A and a second protrusion portion 409B. As described with reference to other devices 1, 100, 200, the body 402 also has extending therefrom two rotatable parts 404A, 404B. The first protrusion portion 409A extends from the body 402. The second protrusion portion 409B is detachably connected to the first protrusion portion 409A. In this example, the second protrusion portion 409B may be selected as one of a plurality of different second protrusion portions (alternatives not shown), any one of which can be attached to the first protrusion portion 409A as required. Each of the plurality of different second protrusion portions may be shaped differently, and/or may be provided with different components, such as different sensors. In this way, the first protrusion portion 409A can be provided permanently connected to the body 402 of the device, and the second protrusion portion 409B can be selected for attachment to the first protrusion portion 409A as necessary. The second protrusion portion 409B is typically connected to the first protrusion portion 409A through fastening means, for example in the form of a fastener, such as one or more threaded fasteners like one or more screws or bolts. In this way, the shape and/or functionality of the protrusion 408 can be altered by replacing the second protrusion portion 409B depending on the environmental conditions in which the device 400 is to be operated, or the task to be performed by the device 400.

[0160] Other applications of the device 1, 100, 200, 400 include: the retrieval of seabed or under-seabed objects such as oil pipes, electricity cable networks and seabed monitoring equipment buried by turbidity currents or sand avalanches; freeing vehicles, such as cars, whose wheels are trapped in sand; removal of pipes from the ground; and movable foundations for buildings.

[0161] Further variations and modifications may be made within the scope of the invention herein disclosed.

[0162] In summary, there is provided a device (1) for moving through a granular medium, the device comprising: a body (2); a rotatable part (4A, 4B) for rotational movement relative to the body about a rotational axis (6), wherein the rotatable part is externally-exposed and arranged to cause agitation of an adjacent portion of a granular medium in which the device is to be provided; a motor configured to cause the rotational movement of the rotatable part; and a protrusion (8) arranged to extend from the body and to limit rotational movement of the body about the rotational axis relative to the granular medium when the motor causes rotational movement of the rotatable part relative to the granular medium.

[0163] Throughout the description and claims of this specification, the words comprise and contain and variations of them mean including but not limited to, and they are not intended to and do not exclude other components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

LIST OF REFERENCE NUMERALS

[0164] 1. Device [0165] 2. Body [0166] 4A, 4B. Rotatable part, wheel [0167] 6. Rotational axis [0168] 8. Protrusion [0169] 10. Connector [0170] 12. Tether [0171] 14. Agitating portions [0172] 50. Relatively higher pressure region [0173] 52. Relatively lower pressure region [0174] 61. A method for moving the device [0175] 60. Receive surface position signal [0176] 62. Extend agitating portions [0177] 64. Retract agitating portions [0178] 66. Move wheel [0179] 68. A signal is received indicating that the device is at the surface of the granular medium [0180] 70. A signal is received indicated that the device is not at the surface of the granular medium [0181] 71. A method of sampling granular medium [0182] 72. Introducing the device into the granular medium [0183] 74. Receiving control signal [0184] 76. Controlling device to move through granular medium to sampling location [0185] 78. Capturing a sample of granular medium at sampling location [0186] 100. Device [0187] 102. Body [0188] 104A, 104B. Rotatable part, wheel [0189] 106. Rotational axis [0190] 108A, 108B. Protrusion [0191] 113. Agitating portion undercarriage [0192] 114. Agitating portions [0193] 126. Ring [0194] 128. Arcuate slots [0195] 130. Pegs [0196] 132. Expanding arcs [0197] 137. Expanding arc track [0198] 138. Second semi-circular portion [0199] 139. Locator portions [0200] 140. First expandable connection [0201] 142. First semi-circular portion [0202] 144. Second expandable connection [0203] 146. Outer track [0204] 148. Inner track [0205] 150. Worm gear [0206] 152. Further gear [0207] 154. Gear [0208] 200. Device [0209] 202. Body [0210] 204A, 204B. Rotatable part, wheel [0211] 206. Rotational axis [0212] 208. Protrusion [0213] 210A, 210B. Connector [0214] 214. Agitating portions [0215] 218. Grain sampler [0216] 220. Air conduit [0217] 222. Grain conduit [0218] 224A, 224B. Grain inlet [0219] 240. Cooling air source conduit [0220] 242. Cooling air exhaust conduit [0221] 300. Pressurised air equipment [0222] 320. Air conduit [0223] 322. Grain conduit [0224] 340. Cyclone [0225] 350. Reservoir [0226] 360. Outlet connection [0227] 370. Inlet point [0228] 380. Inner cylindrical surface [0229] 390. Inner conical surface [0230] 400. Device [0231] 402. Body [0232] 404A, 404B. Rotatable part [0233] 408. Protrusion [0234] 409A. First Protrusion Portion [0235] 409B. Second Protrusion Portion