BACKGROUND OF THE INVENTION

[0001] This invention relates to the generation of electrical energy using a conveyor belt as a prime mover. [0002] It can be advantageous under certain conditions to generate electrical energy from a moving conveyor belt which, inherently, embodies mechanical or kinetic energy. For example, at a location which is remote from an electrical source and which is traversed by or which is near to a conveyor belt, a capability to obtain electrical energy without installing electrical cables can present significant benefits. [0003] One approach to the problem is described in US9948163. Use is made of a stator which is configured to be supported by a portion of conveyor beit support structure. A substantially different approach is based on a technique which is used in connection with an exercise treadmill - see EP3246073.

[0004] An object of the present invention is to provide a conveyor pulley generator which is of robust construction and which can be installed in the place of a standard conveyor pulley.

SUMMARY OF THE INVENTION

[0005] The invention provides a conveyor pulley generator which comprises a conveyor pulley which includes a cylindrical shell, mounted for rotation about an axis, and which is configured to be engaged with a conveyor belt, a ring gear which is fixed to and which is rotational together with the shell about the axis, a rotor shaft positioned on and axially aligned with the axis, a gear train which has an input end connected to the ring gear and an output end connected to the rotor shaft, the gear train having a gear ratio of N where N - an electrical generator which is located at least partly inside the shell and which is mounted at least to the rotor shaft, the electrical generator comprising output contacts, a first part for producing a magnetic field and a second part, with electrical windings, which is rotatably movable relative to the first part, wherein one of said first part and said second part in use is rotatable together with the ring gear and the other of said first part and said second part is rotated together with the rotor shaft at a rotational speed R, where R = N x rotational speed of the ring gear, and a counterweight assembly, mounted to the generator, to prevent said first part rotating together with said second part so that said electrical windings are rotatable relative to and through the magnetic field thereby to create an electrical source which is connected to the output contacts.

[0006] The ring gear is connected to the input end of the gear train which is rotational together with the shell, thus R=N (rotational speed of shell).

[0007] The gear train may take on any suitable form which is of a compact nature so that it can be located inside the cylindrical shell. In a preferred embodiment the gear train comprises a series of planetary gears with a sun gear, at the output end of the gear train, connected to the rotor shaft.

[0008] The conveyor pulley may be used as a tail pulley but, preferably is used as a head pulley. [0009] The rotor shaft may be rotatably mounted to spaced apart bearing blocks which are supported on external structure.

[0010] A fan arrangement may be fixed to the rotor shaft so that, in use of the conveyor pulley generator, the fan arrangement exerts a cooling effect on the electrical generator.

[0011] The first part of the generator may be fixed to the rotor shaft, and may be rotatable together with, and in unison with, the rotor shaft.

[0012] The first part of the generator may include a magnetic structure for producing the magnetic field. It is possible to use an external electrical supply to produce the magnetic field or to use a self-excitation process, as is known in the art, to produce the magnetic field. Preferably use is made of permanent magnets for producing the magnetic field, at least during an initial phase of operation i.e. start-up..

[0013] The second part of the generator which may be regarded as a stator, may be fixed to supports, inside the shell, which are attached to an inner surface of the shell. Thus the second part of the generator may be rotatable together with, and in unison with, the shell.

[0014] The cylindrical shell may be rotatably mounted to spaced apart bearings which are supported on the rotor shaft. This configuration allows the rotor shaft to be rotated via the gear train, by drive derived from rotation of the cylindrical shell.

[0015] The output contacts are preferably in the form of slip rings.

[0016] The counterweight assembly may be secured in any suitable way to the gear train so as to be positioned in use below the rotor shaft which is horizontal. In this respect the construction of the invention, wherein planetary gears in the gear train, between the ring gear and the sun gear, is beneficial for a plurality of the planetary gears in the gear train can be arranged, preferably in two functionally identical sets of gears, between two spaced apart supports, e.g. in the form of plates.

[0017] The plates may be such that the series of planetary gears, and the counterweight assembly, can be mounted to the shell and rotor shaft in a compact arrangement.

[0018] The counterweight assembly may comprise two components, each of a significant and predetermined mass, which are respectively fixed to the plates e.g. to outer surfaces of the plates.

[0019] The counterweight assembly must have sufficient mass to ensure that the rotor shaft can move rotationally relative to the cylindrical shell so that the said windings can be moved through and relative to the magnetic field to generate eiectrica) current.

[0020] The counterweight assembly overcomes rotor shaft inertia and the effects of torque when the cylindrical shell starts to move with belt movement from zero rotational speed to a functional rotational speed. As electrical current is drawn from the generator, the electrical load on the generator is increased and the counterweight assembly prevents the two parts of the generator from rotating in unison. Conversely when the rotor shaft is brought from a functional rotational speed to zero rotational speed, the counterweight assembly helps to constrain movement of the rotor shaft in an opposing direction. Thus, in operation, the counterweight assembly acts against the effects of an electrical load drawn from the electrical generator and ensures that the rotor shaft rotates at a required operational speed relative to the shell. When the electrical load is reduced or brought to zero the counterweight assembly tends to move to some extent to a different angular position relative to the vertical - in this way there is an automatic compensation for the effect of any residual magnetic flux interacting with the windings.

[0021] The electrical generator may include an appropriate number of poles e.g. 4, 6, 8 or 10 and may be configured to achieve a desired operating frequency of, say, 50Hz or 60Hz, according to an operating standard. The ways in which these parameters are established, by varying the windings and magnetic field in the generator, are known in the art and are not repeated here.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention is further described by way of example with reference to the accompanying drawings in which :

Figure 1 is an end view of a conveyor pulley generator according to the invention, with certain components removed to facilitate illustration, at one end of a conveyor belt,

Figure 2 is similar to Figure 1 but with a counterweight assembly removed thereby to illustrate a gear train which is used in the conveyor pulley generator,

Figure 3 is a side view of the conveyor pulley generator removed from a conveyor shell, Figure 4 is similar to Figure 3 but on a different scale showing the conveyor pulley generator inside the conveyor shell and additional structural components of the generator,

Figure 5 is a perspective view of a planetary gear train, depicted from one side in Figure 2, removed from the remainder of the conveyor pulley generator,

Figure 6 is a perspective view of a rotor part of an electrical generator which is used in the conveyor pulley generator, and Figure 7 shows a stator part which, together with the rotor part of Figure 6, makes up the electrical generator used in the conveyor pulley generator.

DESCRIPTION OF PREFERRED EMBODIMENT

[0023] Figure 4 of the accompanying drawings is a side view of a conveyor pulley generator 10, according to the invention. Figure 3 illustrates an electrical generator 12 which is included in the generator and which is formed from a rotor part 16, as shown in Figure 6, and a stator part 20, shown in Figure 7, which, in an assembled condition, is engaged with the rotor part 16.

[0024] The electrical generator 12, in use, is located inside a housing 24 which is supported on spaced apart discs 26 and 28 inside a cylindrical pulley shell 30. The housing 24 shields the electrical generator 12 against the ingress of water and dirt. The shell 30 is designed to be a direct replacement for a conventional conveyor pulley shell as is depicted, somewhat diagrammatically, in Figure 2. Thus the shell 30 includes an outer cover 30A around which, in use, a conveyor belt 34 passes. The pulley shell 30 thus acts as a head pulley. Linear bolt movement thereby imparts rotational movement to the shell. Those aspects are not further described herein for they are conventional.

[0025] The shell 30 is designed to carry the weight of the electrical generator 12 which is securely mounted to a rotor shaft 38 inside the shell 30. At respective opposing ends which protrude from the shell 30 the rotor shaft is fixed to high capacity bearing blocks 40 which are attached to external supporting structure, not shown. End caps 42 and 44 fixed to opposing ends of the shell 30 and around the rotor shaft 38 seal an interior 46 of the shell. Each end cap is formed with a respective plurality of air holes 48 to allow for the flow of cooling air, in use, through the interior 46 of the shell, from the cap 42 towards the cap 44 and then to the surrounding environment. The air holes 48 contain splash-proof filter cartridges 48A which prevent the ingress of water into the interior 46 of the shell and which are effective at removing particulates from the air flow, particularly from the environment, into the interior 46.

[0026] The shell 30 is rotatably supported by bearings 50 which are mounted to the rotor shaft 38 and which allow the shell 30 to rotate relative to the rotor shaft 38.

[0027] The rotor part 16 (Figure 6) includes a main field rotor 52, an exciter armature 54, and a permanent magnet field rotor 56, mounted to the rotor shaft 38. The stator part 20 (Figure 7) includes a main field stator 60 which is engaged with the support discs 26 and 28, and an exciter field stator 62.

[0028] When the rotor part 16 is inserted into the main field stator 60, opposing ends of the rotor shaft 38 are respectively supported by the bearing blocks 40. The support discs 26 and 28 are fixed to the housing 24 which may comprise a number of segments which are engaged with one another. The support discs are circumferentially fixed to an inner surface of the shell 30 and are rotatable together with the shell.

[0029] A slip ring assembly 72 is fixed to the rotor shaft 38 adjacent a stationary hub 74. Electrical leads 76 from the stator 60 are connected to a rectifier arrangement 80 which generates a DC source which is applied to the exciter armature 54, to allow for self excitation of the generator 12. Output leads 81 from the stator make contact with the slip rings (not shown) in the assembly 72. Carbon brushes (not shown) in the hub 74 are in electrical contact with corresponding slip rings in the assembly 72 and are connected to output leads 82 and 84 through which in use electrical power is drawn from the conveyor pulley generator. [0030] A cowling 86, adjacent the rectifier arrangement 80. has a roughly conical shape which is designed and oriented to deflect heat produced by the electrical generator 12 towards and through the filter cartridges 48A in the end cap 44 to the surrounding environment.

[0031] A fan 88 and an arrangement 90, comprising a gear assembly 92 and a counterweight assembly 94, are fixed to and are rotatable together with the rotor shaft 38.

[0032] Figure 2 shows the gear assembly 92 from one side while Figure 5 is a perspective view of components, in the arrangement 90, comprising the gear assembly 92 and the counterweight assembly 94.

[0033] The gear assembly 92 includes a ring gear 100 which is attached to and which is rotatable together with the shell 30. The ring gear 100 is connected via a planetary gear train 102 to a sun gear 104 which is fixed to the rotor shaft 38. The gear train 102 includes two sets 102A and 102B of gears which are functionally identical. Therefore only one set 102A of the gears is described.

[0034] The set 102A of gears includes a first pinion gear 106 which is engaged with the ring gear 100 and which is rotatable together with a first outer gear 108 which is meshed with a second pinion gear 110 which is rotatable together with a second outer gear 112.

[0035] The second outer gear 112 is meshed with a third pinion gear 114 which is rotatable together with a third outer gear 116 which is meshed with the sun gear 104.

[0036] The gear ratio of the gear assembly 92 is the product of the gear ratios of the respective meshing gears. The gear ratio is determined according to design criteria. In one non-limiting exampie the gear ratio between the ring gear and the gear 106 is 10.15; the ratio between the gear 108 and the gear 110 is 2; the ratio between the gear 112 and the gear 114 is 1.32; and the ratio between the gear 116 and the sun gear 104 is 1.54. The product of the gear ratios is 41 .27 which means that, in use, the rotor shaft 38, and hence the rotor part 16, rotate at 41.27 times the rotational speed of the shell 30.

[0037] The main field stator 60 (Figure 7) is fixed to the inner surface of the shell 30 by means of the support discs 26 and 28. The planetary gear train 102 extends between the shell 30 and the rotor shaft 38 to which the rotor part 16 is mounted. When the shell 30 is rotated due to linear travel of the conveyor belt 34 there is a natural tendency for the rotor part 16 to rotate together with the stator part 20. To act against this the counterweight assembly 94, which is pivotal about the rotor shaft 38, includes components 130A and 130B each of which has a substantial and predetermined mass. These components are respectively fixed to outer surfaces of two spaced apart plates 132 and 134 between which the planetary gears in the planetary gear train 102 are mounted - see Figure 5.

[0038] The counterweight assembly 94 acts in a rotational sense on the planetary gear train 102 which is between the ring gear and the rotor shaft 38. The function of the counterweight assembly 94 is such that it ensures that rotational drive from the shell 30 is effectively transferred, via the gear assembly 92, to the rotor shaft 38. The construction of the arrangement 90 is compact and allows for the gear assembly 92 and counterweight assembly 94 to be located inside the cylindrical shell 30.

[0039] A vent ring 136, between the plates 132 and 134, has aeration gaps 138 which, upon rotation of the shell 30, direct air flow over and between, the various gears. [0040] With the conveyor pulley generator 10 in the assembled configuration shown in Figure 4, the shell 30 rotates with a circumferential speed equal to the linear speed of the conveyor belt 34. The rotor part 16 of Figure 6 is then rotated together with the rotor shaft 38 relative to the stator part 20, of Figure 7, which rotates with the shell 30. The arrangement 90 does, in use, swing to some extent through a small angle about the rotor shaft, in a clockwise direction or anticlockwise direction, in response to belt movement, and when the belt stops moving. To counteract the effect of inertia on the electrical generator at start-up, and the effect of momentum on the electrical generator when operation is ceased, reliance is placed on the counterweight assembly 94 which thus allows the rotor shaft 38 to be rotated on the bearing blocks 40, via the gear assembly 92, relative to the shell 30 which is rotatable, on the bearings 50, by movement of the conveyor belt.

[0041] Rotation of the permanent magnet field rotor 56 relative to the stator 60 induces an alternating current into the windings in the stator 60. An automatic voltage regulator 140 (see Figure 4) on an outer side of the housing 24 controls the output of the rectifier arrangement 80 and a DC current is supplied to the exciter assembly 54. A rotating magnetic field is produced which induces an AC voltage into the main stator 60. This voltage is sensed by the automatic voltage regulator 140 and compared to a reference level and the magnetic field is adjusted accordingly thereby to vary the output voltage which is connected to the slip rings in the assembly 72.

[0042] The carbon brushes which are in the hub 74 are in contact with the rotating slip rings and provide an electrical output at the leads 82 and 84. [0043] The number of poles of the electrical generator 12 (comprising the rotor part 16 and the stator part 20), the rotational speed of the rotor shaft 38, and the frequency of the AC output at the leads 82, 84, are linked, as per established relationships, as set out in the following table:

NUMBER OF POLES RPM ~ revolutions per minute Hz

4 1800 60

4 1500 50

6 1200 60

6 1000 50

8 900 60

8 750 50

10 720 60

10 600 50

[0044] The pulley shell 30 rotates at a rotational speed P (which is also the rotational speed of the ring gear) determined by the linear speed of the conveyor belt 34. The rotational speed

R of the rotor shaft 38 is substantially higher than the rotational speed P of the pulley shell

30 due to the operation of gear assembly 92. [0045] The gear ratio N of the gear train is given by the expression N =

[0046] Due to a change in speed of the conveyor belt 34 and when the belt is halted, and due to a change in the electrical load drawn from the electrical generator during use thereof, the counterweight assembly 94 does move in an angular sense, in one direction or the other, to a limited extent about the rotor shaft 38. The leverage effect of the counterweight assembly is increased as it is angularly displaced from a neutral (at rest) position but such displacement does not exceed 90° from the neutral position.