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Title:
A PNEUMATIC MATERIALS HANDLING UNIT
Document Type and Number:
WIPO Patent Application WO/2006/056849
Kind Code:
A2
Abstract:
This invention relates to a pneumatic materials handling unit, e.g. one for unloading bulk fluent materials from ships. The unit includes a support structure, a boom (16), and a suction pipe. The suction pipe includes a boom pipe (42), which forms a part of the boom, and a rigid down pipe (20), defining a suction nozzle (74) at its operative bottom end. It includes also a pivot joint (24) via which the boom pipe and the down pipe are pivotally interconnected and, at the joint, an arrangement of at least two telescopically displaceable pipe sections (104, 44.1) that interconnect the boom pipe and the down pipe. This arrangement defines an arc in the suction pipe about the pivot axis of the pivot joint and operatively accommodates pivoting of the joint via telescopic displacement of its pipe sections. The unit provides for effective manoeuvring of its suction nozzle in confined spaces containing materials to be unloaded thereby.

Inventors:
Vorster, Francois Maree (166 Marine Drive, Bluff, 4052 DURBAN, ZA)
Application Number:
PCT/IB2005/003480
Publication Date:
June 01, 2006
Filing Date:
November 21, 2005
Export Citation:
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Assignee:
Vorster, Francois Maree (166 Marine Drive, Bluff, 4052 DURBAN, ZA)
International Classes:
B65G67/60; B65G53/24; B65G53/42; B65G53/52; B67D9/02
Foreign References:
GB1371655A1974-10-23
GB709704A1954-06-02
GB191124023A1912-10-24
DE2048939A11972-04-13
GB2114531A1983-08-24
US4190080A1980-02-26
US3510155A1970-05-05
US4020953A1977-05-03
Attorney, Agent or Firm:
Rotteveel, Martin (Adams & Adams, PO Box 2746 Suite 1, 4 The Crescent, Westway Office Par, Westville 3635 WESTWAY OFFICE PARK, ZA)
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Claims:
CLAIMS
1. A pneumatic bulk materials handling unit which includes a base structure; a boom, pivotally mounted at one end thereof on the base structure to permit pivoting of the boom about a horizontal axis; a suction pipe which includes a boom pipe which forms a part of the boom, extends along the boom, and is operatively connected in communication with a vacuum chamber; a down pipe which is rigid against bending and which defines at its operative bottom end a suction nozzle defining the inlet of the down pipe; and an arrangement of at least two telescopically displaceable pipe sections that interconnect the boom pipe and the down pipe; a pivot joint which pivotally connects the operative top end of the down pipe to the end of the boom remote from the base structure; and displacement means for effecting pivoting of the boom with respect to the base structure and of the down pipe with respect to the boom, the arrangement of telescopically displaceable pipe sections defining an arc in the pipe about the pivot axis of the joint and operatively accommodating pivoting of the joint via telescopic displacement of its pipe sections.
2. A unit as claimed in Claim 1 , in which the at least two telescopically displaceable pipe sections include an end section of the boom pipe and an end section of the down pipe, each of which is rigid and curved about the pivot axis of the joint.
3. A unit as claimed in Claim 2, in which the at least two telescopically displaceable pipe sections includes also an intermediate pipe section which is intermediate the end sections and which is rigid and curved about the pivot axis of the joint.
4. A unit as claimed in Claim 1 , in which the arrangement of at least two telescopically displaceable pipe sections includes a rigid first pipe section which is an end section of either of the boom pipe and the down pipe; and a second pipe section which extends from the proximate end of the other of the boom pipe and the down pipe and which is telescopically displaceable with respect to the first pipe section, flexible about the axis of the joint, and substantially rigid against crosssectional and length deformation.
5. A unit as claimed in any one of the preceding claims, in which the down pipe includes at least two pipe sections that are telescopically displaceable to provide for length adjustment of the pipe, the unit including displacement means for effecting telescopic displacement of the pipe sections.
6. A unit as claimed in any one of the preceding claims, in which the boom pipe includes at least two pipe sections that are telescopically displaceable to provide for length adjustment of the pipe, the unit including displacement means for effecting telescopic displacement of the pipe sections.
7. A unit as claimed in any one of the preceding claims, in which the boom includes a swivel joint and in which the down pipe is fixed against rotation with respect to the side of the swivel joint remote from the base structure about an axis parallel to the boom, the unit including displacement means for effecting swivel of the joint to thereby effect rotation of the down pipe pendulum fashion about the said axis.
8. A unit as claimed in any one of the preceding claims, in which the down pipe includes passage defining means defining a bypass airflow passage of which the outlet is in communication with the passage in the down pipe at a position immediately downstream of the inlet of the down pipe and of which the inlet is at a position remote from the operative bottom end of the down pipe and exposed to the atmosphere.
9. A unit as claimed in Claim 8, which includes flow control means for controlling air flow through the bypass air flow passage.
10. A unit as claimed in any one of the preceding claims, in which the boom includes passage defining means defining a bypass airflow passage connected in parallel with the passage defined in the boom pipe and the unit includes flow control means for controlling air flow through the bypass air flow passage to thereby control distribution of air flow through the boom between the passage in the boom pipe and the bypass air flow passage.
11. A unit as claimed in Claim 10, in which the boom includes screening means at the inlet of the bypass air flow passage for preventing particulate material from entering the passage.
12. A pneumatic bulk materials handling unit substantially as described herein with reference to and as illustrated in the accompanying diagrammatic drawings.
Description:
A PNEUMATIC MATERIALS HANDLING UNIT

THIS INVENTION relates to a pneumatic materials handling unit.

The invention relates, more particularly, to a pneumatic bulk materials handling unit for displacing bulk fluent materials, e.g. for unloading such materials from bulk carriers such as ships, barges, and the like, for onward transportation, or for loading such materials from stockpiles, for onward transportation.

A known type of pneumatic bulk materials handling unit will now be briefly described in its operative configuration on a quay. The unit includes a support structure supported on the quay. The support structure is either fixed to the quay or movable thereon, e.g. on rails. The unit includes also a boom and a suction pipe. The boom is pivotally mounted at one end thereof on the base structure to permit pivoting of the boom about a horizontal axis. The suction pipe includes a boom pipe, which forms a part of the boom, extends along the boom, and is operatively connected at its downstream end in communication with a vacuum chamber. The suction pipe includes also a down pipe which is rigid against bending and which defines at its operative bottom end a suction nozzle defining the inlet of the down pipe. The unit includes also a pivot joint which pivotally connects the operative top end of the down pipe to the end of the boom remote

from the base structure and displacement means for effecting pivoting of the boom with respect to the base structure about a horizontal axis and of the down pipe with respect to the boom. In use of the unit, with its boom pipe connected in communication with a vacuum chamber, the nozzle is inserted into a bulk fluent material to be displaced. Due to pneumatic action, the material is displaced into the down pipe via its inlet, via the down pipe, via the boom pipe, and into the vacuum chamber. From the vacuum chamber, it is then onward transported via any suitable means, e.g. via at least one cargo vehicle. The unit includes also displacement means for effecting displacement of the nozzle, usually in three dimensions. Insofar as bulk fluent materials handling units of the above general type are known, they will not be elaborated on herein. The invention relates to a pneumatic bulk materials handling unit of the above general type.

According to the invention there is provided a pneumatic bulk materials handling unit which includes

a base structure;

a boom, pivotally mounted at one end thereof on the base structure to permit pivoting of the boom about a horizontal axis;

a suction pipe which includes

a boom pipe which forms a part of the boom, extends along the boom, and is operatively connected in communication with a vacuum chamber;

a down pipe which is rigid against bending and which defines at its operative bottom end a suction nozzle defining the inlet of the down pipe; and

an arrangement of at least two telescopically displaceable pipe sections that interconnect the boom pipe and the down pipe;

a pivot joint which pivotally connects the operative top end of the down pipe to the end of the boom remote from the base structure; and

displacement means for effecting pivoting of the boom with respect to the base structure and of the down pipe with respect to the boom,

the arrangement of telescopically displaceable pipe sections defining an arc in the pipe about the pivot axis of the joint and operatively accommodating pivoting of the joint via telescopic displacement of its pipe sections.

The use of telescopically displaceable pipe sections for accommodating pivoting of the pivot joint in the pneumatic bulk materials handling unit of the invention ensures that the radius of curvature of the suction pipe in the region of the joint is maintained constant irrespective of the pivot position of the joint. It is envisaged that efficiency of the suction pipe insofar as flow of material therethrough is concerned may thus be maximized.

The displacement means may include at least one of electrically, pneumatically, and hydraulically powered displacement means. The same applies to any other displacement means referred to hereinafter. The unit may include also control means for controlling its displacement means. The unit typically is human operable.

The at least two telescopically displaceable pipe sections of the suction pipe may include an end section of the boom pipe and an end section of the down pipe, each of which is rigid and curved about the pivot axis of the joint. As such, the at least two telescopically displaceable pipe sections may include also an intermediate pipe section which is intermediate the end sections and which is rigid and curved about the pivot axis of the joint.

Alternatively, the arrangement of at least two telescopically displaceable pipe sections may include

a rigid first pipe section which is an end section of either of the boom pipe and the down pipe; and

a second pipe section which extends from the proximate end of the other of the boom pipe and the down pipe and which is telescopically displaceable with respect to the first pipe section, flexible about the axis of the joint, and substantially rigid against cross-sectional and length deformation.

The down pipe may include at least two pipe sections that are telescopically displaceable to provide for length adjustment of the pipe. As such, the unit may include displacement means for effecting telescopic displacement of the pipe sections.

The boom pipe may include at least two pipe sections that are telescopically displaceable to provide for length adjustment of the pipe. As such, the unit may include displacement means for effecting telescopic displacement of the pipe sections.

In a particular embodiment of the unit of the invention, its boom includes a swivel joint. The down pipe is fixed against rotation with respect to the side of the swivel joint remote from the base structure about an axis parallel to the boom. The unit includes displacement means for effecting swivel of the joint to thereby effect rotation of the down pipe pendulum fashion about the said axis.

The down pipe may include passage defining means defining a bypass airflow passage of which the outlet is in communication with the passage in the down pipe at a position immediately downstream of the inlet of the down pipe and of which the inlet is at a position remote from the operative bottom end of the down pipe and exposed to the atmosphere. The unit may include flow control means for controlling air flow through the bypass air flow passage.

The boom may include passage defining means defining a bypass air flow passage connected in parallel with the passage defined in the boom pipe. As such, the unit may include flow control means for controlling air flow through the bypass air flow passage to thereby control distribution of air flow through the boom between the passage in the boom pipe and the bypass air flow passage. The boom may include screening means at the inlet of its bypass air flow passage for preventing particulate material from entering the passage, in use of the unit.

The invention is described below by way of an example of an embodiment of a pneumatic bulk materials handling unit, in accordance with the invention, with reference to and as illustrated in the accompanying diagrammatic drawings. In the drawings:

Figure 1 shows a diagrammatic side elevation of an embodiment of a pneumatic materials handling unit, in accordance with the invention, in the form of an unloader unit mounted on a quay;

Figure 2 shows a diagrammatic long section of a major portion of a boom of a suction pipe of the unloader unit of Figure 1 ;

Figure 3 shows a diagrammatic long section of a length of the boom of Figure 2 including a swivel joint;

Figure 4 shows a diagrammatic cross-section through the boom of Figure 2 along the line IV-IV of Figure 3 and in the direction of the associated arrows;

Figure 5 shows a portion of the down pipe of the suction pipe of the unloader unit of Figure 1 , in diagrammatic partial long section;

Figure 6 shows diagrammatically an arrangement forming a part of the unloader unit of Figure 1 , the arrangement including a length of the suction pipe (shown in long

section) of the unit and a pivot joint of the unit and being shown in a first operative configuration thereof;

Figure 7 shows diagrammatically the arrangement of Figure 6, in a second operative configuration thereof;

Figure 8 shows a diagrammatic side elevation of the unloader unit and quay of Figure 1 , particularly illustrating respective angular ranges within which its boom and down pipe are displaceable;

Figure 9 shows a diagrammatic front elevation of the unloader unit and quay of Figure 1 , particularly illustrating an angular range within which its down pipe is displaceable;

Figure 10 shows diagrammatically an alternative to the arrangement of Figure 6, in a first operative configuration thereof; and

Figure 11 shows diagrammatically an alternative to a part of the boom of Figure 2.

In Figure 1 , an embodiment of a pneumatic materials handling unit, in accordance with the invention, in the form of an unloader unit, is designated generally by the reference numeral 10.

The unloader unit 10 includes

a base structure including both a fixed frame 12, which is mounted on a quay 13, and a rotatable frame (not shown) mounted on the fixed frame 12 via rotation gear 14 to rotate about a vertical axis 15;

a boom 16, which is pivotally mounted at one end thereof on the rotating frame to permit pivoting of the boom with respect to the frame about a horizontal axis 18;

a down pipe 20 defining at its operative bottom end an inlet 22;

a pivot joint 24 which pivotally connects the operative top end of the down pipe 20 to the end of the boom 16 remote from the rotating frame; and

a swivel joint 26 in the boom 16.

Reference will be made below to various displacement means of the unloader unit 10. Insofar as such displacement means is of a conventional nature it will, in general, not be illustrated or described in detail. Although particular forms of displacement means will be referred to by way of example, it must be appreciated that alternative forms may similarly be used. Such displacement means may generally include at least one of electrically, pneumatically, and hydraulically powered displacement means. All the displacement means of the unloader unit 10 are controlled via control means of the unit, which will also not be described in detail herein, as it is also of a conventional type. Such control means may be human operable.

The unloader unit 10 includes a number of components that are carried on the rotating frame (not shown). These include a body 28; machinery 30, housed in the body 28; a vacuum vessel 32, partially housed in the body 28 and defining therein a vacuum chamber 34; a discharge arrangement 36 of the vacuum vessel 32 via which the vessel can discharge its contents through the rotation gear 14; and an air transfer pipe 38. The machinery 30 includes a vacuum pump, which is connected in fluid communication with the chamber 34 via the air transfer pipe 38 and an arrangement of filters 40 within the vessel 32, and a hydraulic pump system, including a control system (not shown), for powering and controlling the hydraulic displacement means of the unit 10, some of which will be referred to below.

Discharge of any contents of the vessel 32 via the discharge arrangement 36 may particularly occur onto a load carrier vehicle (not shown) or a conveyor belt (not shown) positioned under the discharge arrangement, in use of the unloader unit 10.

With reference to both Figures 1 and 2, the boom 16 includes a boom pipe 42 including pipe segments 44.1 , 44.2, 46.1 , 46.2, and 46.3, the last-mentioned three being telescopically displaceable to provide for length adjustment of the boom pipe 42. The boom 16 includes also displacement means (not shown) including hydraulic cylinders for effecting such telescopic displacement. The end of the pipe segment 46.3 at the vessel 32 defines an outlet 47 of the boom pipe 42. The outlet 47 is exposed to the vacuum chamber 34.

The boom 16 includes also passage defining means including a bypass pipe 48 including three pipe segments 50.1 , 50.2 and 50.3 that are telescopically displaceable and disposed around the boom pipe 42. Between the pipes 42 and 48, a bypass air flow passage 52 is defined. The segments 50.1 and 50.3 are fixed with respect to the segments 46.1 and 46.3, respectively. The passage 52 has an annular outlet 54, which is exposed to the vacuum chamber 34 (see Figure 1 ) of the vessel 32 of the unloader unit 10. The pipe segment 46.1 includes, at the end of the passage 52 remote from the outlet 54, a perforated section 56, defining therethrough a plurality of apertures 58 via which the passage 52 is in communication with the passage defined in the pipe segment 46.1. The bypass air flow passage 52 is thus in parallel with a major portion of the passage in the boom pipe 42.

The boom 16 includes a sleeve member 60 disposed around the pipe segment 46.1 and slideable along a part of its length. The length of the sleeve member 60 is equal to that of the perforated section 56. The sleeve member 60 is incrementally displaceable between an open position as shown, adjacent to the perforated section 56, and a closed position (not shown), in which it is disposed around the entire section 56 and closes off all of the apertures 58. For effecting such incremental displacement of the sleeve member 60, the boom 16 includes displacement means including a rack and pinion combination 62 and a hydraulic motor (not shown) acting on the pinion gear of the combination. The position of the sleeve member 60 thus determines the effective inlet size of the bypass air flow passage 52 and, as will be referred to below, serves as air flow control means for operatively controlling air flow via the bypass air flow passage 52.

In Figure 3, a length of the boom 16 (see Figure 1 ) including its swivel joint 26 is shown. Figure 4 shows a cross-section through the boom 16 showing certain details of the swivel joint 26. The joint 26 includes end lengths of the pipe segments 44.2 and 46.1 , the former being received in the latter in a configuration permitting swivel of the former with respect to the latter about the centre line of the segments; two plates 66 and 68 projecting from the pipe segments 44.2 and 46.1 , respectively; and displacement means including two hydraulic cylinders 70.1 and 70.2 acting between the plates 66 and 68. As is clear from Figure 4, contraction of the cylinder 70.1 and a corresponding extension of the cylinder 70.2 operatively effects swivel of the pipe segment 44.2 with respect to the pipe segment 46.1 in one direction and vice versa. Such swivel will cause pendulum fashion rotation of the down pipe 20 with respect to the centre line of the boom 16, as will be referred to below with reference to Figure 9.

With reference again particularly to Figure 1 , the down pipe 20 includes pipe segments 72.1 , 72.2, and 72.3, the latter two being telescopically displaceable to provide for length adjustment of the pipe 20, and a nozzle arrangement 74. The down pipe 20 is rigid against bending.

In Figure 5, a part of the down pipe 20 including its nozzle arrangement 74 is shown in partial long section. The nozzle arrangement 74 includes a rigid outer pipe 76 disposed around the free end portion of the pipe segment 72.3 of the down pipe 20 with clearance provided between the pipe segment and the pipe to define between them a bypass air flow passage 78. The bottom end of the outer pipe 76 projects past the free end of the pipe segment 72.3 and defines the inlet 22 of the down pipe 20. The arrangement 74 includes a frustoconical perforated member 80 carried by the bottom end of the pipe segment 72.3 and extending from it to the inner surface of the end of the pipe 76 with rotation of the pipe 76 around the member 80 being permitted. The member 80 defines therethrough a plurality of circumferentially spaced apertures 82 comprising outlets of the bypass air flow passage 78.

To the top of the pipe 76 is attached a flange-like gear 84. The gear 84 is supported on a flange 86, attached to the pipe segment 72.3, and can rotate with respect to it. As such, the pipe 76 is suspended from the flange 86. The arrangement 74 includes displacement means for effecting rotation of the pipe 76 around the pipe segment 72.3. The displacement means includes the gear 84 and a drive assembly including a stepper motor 88 driving, via a reduction gearbox 90, a gear 92 that is engaged with the gear 84. As such, through stepped rotation of the motor 88, stepped rotation of the pipe 76 with respect to the pipe segment 72.3 may be effected.

The gear 84 and the flange 86 define through them arrangements of circumferentially spaced apertures 94 and 96, respectively. These arrangements are such that the angular position of the gear 84 relative to the flange 86, as determined by rotation effected by the stepper motor 88, determines the degree to which the respective apertures 94 and 96 are in register. With the respective apertures at least partially in register, they define inlets for the bypass air flow passage 78. The motor 88, the reduction gearbox 90, the gear 92, the gear 84, and the flange 86 thus operatively serve as air flow control means for controlling air flow through the passage 78, as will be referred to again later herein.

With reference to Figure 6, the pivot joint 24 includes a first arm 98 mounted on the pipe segment 44.1 and a second arm 100 on which the pipe segment 72.1 is mounted. The arm 100 is pivotally mounted on the arm 98 to pivot about an axis 102. The joint 24 has displacement means including two hydraulic cylinders 103 (only one shown here) on opposite sides of the arms 98 and 100 for operatively effecting pivoting of the joint.

The unloader unit 10 includes also a pipe segment 104 which is fixed to the pipe segment 72.1. The pipe segment 104 is flexible about the axis 102 of the joint 24, and substantially rigid against cross-sectional and length deformation. An end portion of the pipe segment 44.1 is curved about the pivot axis 102.

The joint 24 is shown in Figure 6 in a limit pivot position in which an angle of approximately 70 ° is defined between the pipe segments 72.1 and the pipe segment 44.2. Through contraction of the hydraulic cylinders, the joint 24 can be displaced into an opposite limit pivot position, as shown in Figure 7, in which an angle of approximately 135 ° is defined between the pipe segments 72.1 and the pipe segment 44.2. The effect of pivoting of the joint 24 will be referred to again in the description of Figures 8 and 9.

In Figure 7, a first pipe section comprising the pipe segment 44.1 and an end section of the pipe segment 44.2 has telescopically received therein a second pipe section comprising the section of the pipe segment 104 which projects from the pipe segment

72.1. The said first and second pipe sections thus form an arrangement of telescopically displaceable pipe sections that accommodate pivoting of the joint 24. In both the pivot positions shown in Figures 6 and 7, the said arrangement clearly defines an arc about the axis 102. The rigidity of the pipe segment 104 against bending about the pivot axis

102 must be sufficient to maintain a substantially constant curvature of the arc when a portion of the pipe segment is not within the said first pipe section. Also, flexibility of the pipe segment 104 permits an end section thereof to be either curved or straight, as is required in the pivot positions shown in Figures 6 and 7, respectively.

The boom pipe 42, the down pipe 20, and the pipe segment 104 define a suction pipe of the unloader unit 10.

In Figure 8, two limit pivot positions of the boom 16 with respect to the base structure of the unit 10 are represented by broken lines 106.1 and 106.2, respectively. The line 106.1 is horizontally disposed whereas the line 106.2 is an angle α of approximately 65 ' above horizontal. The unit 10 includes displacement means including hydraulic cylinders (not shown) for effecting displacement of the boom 16 between its limit pivot positions.

Limit pivot positions of the down pipe 20 (see Figure 1) relative to the boom 16 are represented by broken lines 108.1 and 108.2, respectively. Each line 108.1 is angularly spaced from the corresponding one of the lines 106.1 and 106.2 by an angle β of approximately 70 ° corresponding to the pivot position of the joint 24 shown in Figure 6. Each line 108.2 is angularly spaced from the corresponding one of the lines 106.1 and 106.2 by an angle Y of approximately 135 ° corresponding to the pivot position of the joint 24 shown in Figure 7.

In Figure 8, two limit swivel positions of the down pipe 20 (see Figure 1 ) are represented by broken lines 110.1 and 110.2, respectively, offset from vertical on opposite sides thereof by an angle δ of approximately 20 ° . Pendulum fashion displacement of the down pipe 20 between the two limit positions is provided for by the swivel joint 26 (see Figures 3 and 4).

Clearly, all of the angles referred to above are stated for the purpose of example only and, in alternative embodiments of the pneumatic materials handling unit of the invention, corresponding angles may vary substantially from the values stated above.

With reference to the drawings generally, clearly, through suitable operation of the boom

16, the down pipe 20, the joints 24 and 26, and the rotation gear 14, via the displacement means of the unit 10, the nozzle arrangement 74 can be maneuvered to

reach substantially all positions in the hull of a ship required for unloading fluent material located therein.

With reference still to the drawings generally, typical operation of the unit 10 will now be briefly described by way of example of unloading a bulk fluent material from a hull of a ship (not shown) moored against the quay 13. Through suitable displacement of the boom 16, the joints 24 and 26, and the down pipe 20, the latter is suspended into the hull and the nozzle arrangement 74 lowered into the fluent material. With the vacuum pump of the machinery 30 running, air is displaced from the chamber 34 via the filter arrangement 40 and the pipe 38. A below-atmospheric pressure is thus created in the chamber 34 and, due to the pressure differential between the inlet 22 of the down pipe 20 and the chamber 34, air is displaced from the inlet 22, via the down pipe 20, via the pipe segment 104, via the boom pipe 42, and into the chamber 34. Fluent material at the inlet 22 defined by the nozzle arrangement 74 is displaced along with the air and collected in the vessel 32, from which it can be discharged through operation of the discharge arrangement 36. Insofar as the operation of unloader units of types similar to the unit 10 is known, it will not be elaborated herein in relation to the unit 10 specifically.

The use of telescopically displaceable pipe sections defined by the pipe segments 104, 44.1 , and 44.2 for accommodating pivoting of the pivot joint 24 ensures that the radius of curvature of the suction pipe in the region of the joint is maintained constant irrespective of the pivot position of the joint. It is envisaged that efficiency of the suction pipe insofar as flow of material therethrough is concerned may thus be maximized.

With reference again particularly to Figure 5, the bypass air flow passage 78 provides for air to be displaced therethrough, then via the apertures 82, and then into the passage in the pipe segment 72.3 even when the bottom end of the nozzle arrangement 74 is submerged in bulk fluent material being unloaded by the unit 10 of Figure 1. Air flow into the passage in the pipe segment 72.3 may thus be maintained. By controlling operative air flow through the bypass air flow passage 78 via adjustment of the effective inlet size

of the passage, which is a function of the degree to which the respective apertures 94 and 96 are in register, the effective suction force of the unit 10 on the bulk fluent material can be controlled.

With reference again to Figure 2 of the drawings, for a given total air flow through the down pipe 20 and into the vacuum chamber 34 (see Figurei ) via the boom 16, the air flow through the part of the passage defined in the boom pipe 42 downstream of the perforated section 56 is determined by the airflow through the bypass airflow passage 52. This is determined by the position of the sleeve member 60, as is described above. By increasing the portion of the total air flow that passes through the bypass air flow passage 52, the air flow through the said part of the passage in the pipe 42 is reduced and, particularly, its velocity also is reduced. So is the velocity of material operatively transported by the air flow. By suitably controlling air flow through the said part of the passage in the pipe 42, it is envisaged that, in the case of particulate material being unloaded by the unit 10 of Figure 1 , the velocity of such particles may be reduced to a level at which the degree of fragmentation of the particles upon impact with stationary material in the chamber 34 (see Figure 1) is limited to an acceptable level. The perforated section 56 serves also as screening means for preventing particulate material from entering the bypass airflow passage 52.

Figure 10 shows a part of an unloader unit, in accordance with the invention, including an alternative arrangement of telescopic pipe sections to that shown in Figures 6 and 7. Figure 10 shows many features that are similar to features shown in Figures 6 and 7. Such similar features are again designated by the same reference numerals as before and are not described again.

The arrangement of pipe sections comprises three rigid pipe sections 112.1 , 112.2, and

112.3. The section 112.1 forms a top end section of the down pipe of the unit whereas the section 112.3 forms an end section of the boom pipe 42, particularly of an end pipe segment 113 of the pipe 42. The section 112.2 is an intermediate section intermediate

the sections 112.1 and 112.3 and the joint 24 includes an arm 114 via which the section 112.2 is pivotally connected to the arms 98 and 100. The sections 112.1 to 112.3 define an arrangement of pipe sections defining a constant radius arc around the axis 102 of the pivot joint 24. Through telescopic displacement of the pipe sections 112.1 to 112.3, pivot displacement of the joint 24 is accommodated.

With reference to Figure 11 , instead of the arrangement shown in Figure 2 for controlling air flow through a portion of the passage within the pipe 42 of the unit 10 of Figure 1 , another embodiment of a bulk materials handling unit, in accordance with the invention, includes an arrangement as shown in Figure 11. The unit particularly is an unloader unit similar to the unit 10 of Figure 1 and includes a boom pipe 116 and a bypass pipe 118 running along side it and parallel to it. The bypass pipe 118 defines therein a bypass air flow passage 120 which, at its downstream end, is in communication with the chamber defined in the pressure vessel of the unit and, at its upstream end, to the passage defined in the pipe 116 near its upstream end via an inlet 122. The pipe 118 has air flow control means including a butterfly valve 124 for controlling airflow through the bypass air flow passage 120 - the equivalent of the control of air flow through the bypass air flow passage 52 (see Figure 2) via the sleeve 60. Again, by controlling the air flow through the bypass air flow passage 120, the velocity of the air flow in the pipe 116 is effectively controlled. The purpose of such control is the same as was described above in relation to the unloader unit 10, particularly its boom 16, and, as such, will not be described again.