WO2006125998A1

WO2006125998A1 - Vibratory conveyor

Info

Publication number: WO2006125998A1
Application number: PCT/GB2006/001929
Authority: WO
Inventors: Timothy John Blackwall Moulsdale; Ran Mendelewicz
Original assignee: Wright Machinery Ltd
Current assignee: Wright Machinery Ltd
Priority date: 2005-05-27
Filing date: 2006-05-26
Publication date: 2006-11-30
Anticipated expiration: 2007-11-27
Also published as: GB2426562A; GB2426562B; GB0510897D0

Abstract

A vibratory conveying apparatus (10) for moving materials, comprising: a base (12) ; a conveying member (18) supported from the base by at least one resilient support (34) ; a drive (38) arranged to excite said conveying member into vibration; and an absorbing mass (40) supported from the base by at least one resilient support (42) such that movement of the absorbing mass is substantially parallel to that of the conveying member, and that a line passing through the absorbing mass' centre of gravity (44) and the conveying member's centre of gravity (36) is substantially perpendicular to the at least one resilient conveying member support, wherein the natural frequency of the absorbing mass is arranged to be substantially equal to the natural frequency of the conveying member, or a multiple thereof, whereby when the conveying member is excited into vibration by the drive, the absorbing mass vibrates substantially in phase opposition to the conveying member, resulting in the absorption of energy from the base .

Description

VIBRATORY CONVEYOR

The present invention relates to a conveying apparatus, and particularly to an excited-conveyor vibratory conveying apparatus.

Vibratory conveying systems are often used to transport objects or particulate material and are in widespread use in view of their versatile material-handling capabilities. Such devices typically include a generally elongate conveying member that is vibrated by an associated drive system so that material is conveyed along the length of the conveying member.

In general, a vibratory device is connected to a support frame to excite or vibrate the support frame, with the vibrations being transferred to the conveying member through springs. Such systems are known as two-mass vibratory conveyor systems or excited frame vibratory systems.

Conventionally a two-mass, vibratory conveyor of the base-excited conveyor design includes a trough supported by springs from a base support structure that is vibrated by an eccentric rotating mass. The vibration is transmitted to the trough through the springs.

Attempts have been made to design such a system in which the vibration amplitude of the base structure is minimised while the conveying member is vibrated at its natural frequency of maximum amplitude.

A known approach to reducing vibratory movement of the base structure has been to make the base structure very substantially heavier than the conveying member.

Other developments in prior art two-mass conveyor designs have been concerned with the alignment of the directed force exciting the conveyor with the centres of gravity of the conveyor apparatus. Carmichael, U.S. 4,313,535, discloses a base-excited conveyor in which a linear drive is arranged to generate a force drive line that is co-linear with a line passing substantially through the centres of gravity of the conveyor-bed mass, the conveyor mass, and the base mass. Still further, a base-excited conveyor in which the centre of gravity of the base can be displaced from the line of linear force which includes the centre of gravity of the conveyor-bed mass is disclosed in EP-A-O 881 172.

US 2001/0019009 Al also discloses a base-excited conveyor arranged such that centres of gravity of the conveyor-bed mass, the conveyor mass, and the base mass are co-linear with the force drive line, as taught by Carmichael. US 2001/0019009 discloses the use of an electromagnetic drive that eliminates the transients occurring during start-up and shutdown of the conveyor.

A conveyer system with a conveying tray and a counter mass is disclosed in United States Patent No. 5,462,155. The conveying tray and the mass are driven in opposing directions and are physically constrained to vibrate reciprocally by a coupler which is provided between the tray and the mass.

US 3,668,939 proposes a vibratory conveyor comprising a set of counter- masses mounted from the base, the counter-masses being designed to resonate at the frequency of a force driving the conveying system.

Although such base-excited conveyor designs attempt to minimise the forces transmitted to the support structure, it remains that a relatively heavy support structure or restrictions on apparatus alignment are required.

The invention provides a vibratory conveying apparatus for moving materials, comprising: a base; a conveying member supported from the base by at least one resilient support; a drive arranged to excite said conveying member into vibration; and an absorbing mass supported from the base by at least one resilient support such that movement of the absorbing mass is substantially parallel to that of the conveying member, and that a line passing through the absorbing mass' centre of gravity and the conveying member's centre of gravity is substantially perpendicular to the at least one resilient conveying member support, wherein the natural frequency of the absorbing mass is arranged to be substantially equal to the natural frequency of the conveying member, or a multiple thereof, whereby when the conveying member is excited into vibration by the drive, the absorbing mass vibrates substantially in phase opposition to the conveying member, resulting in the absorption of energy from the base.

A significant advantage of the invention is that vibration of the base can be substantially reduced without needed a massive base, whereby the mass of the conveyor base can be reduced so as to reduce costs. In addition, the vibratory conveying apparatus can transfer less vibration into the floor or ceiling supports.

The absorber mass may be arranged to vibrate with a natural frequency that is substantially equal to a multiple of the conveying member's natural frequency, the multiple being 10 or less, preferably 5 or less, and most preferably 3 or less.

The absorber mass can be arranged such that a line passing through the absorbing mass' centre of gravity and the conveying member's centre of gravity is substantially perpendicular to the at least one resilient conveying member support.

The resilient supports may be of any such suitable form for supporting the conveying member or the absorbing mass. Once such example of a suitable resilient support is a spring that restricts movement of the conveying member to a generally single plane. The resilience or stiffness of the spring may be adjustable so that the natural frequency of the conveying member or the absorbing mass can be altered as required.

The base of the vibratory conveying apparatus may be supported from a mounting frame via vibration isolators. This helps to further reduce any vibratory forces that may act on the floor or ceiling that supports the vibratory conveying apparatus. To provide superior flexibility for the operation of the vibratory conveying apparatus the drive may be an electromagnetic drive. Unlike mechanical drives such as counter rotating mass drives, an electromagnetic drive does not have a transient stage and can be operated at a required frequency immediately. Use of an electromagnetic drive also enables the operation of the conveying apparatus to be more easily controlled.

To ensure that the absorbing mass and conveying member vibrate at the desired frequencies independently of temperature changes, the resilient absorbing mass supports may be made from the same non-elastometric material as the resilient conveying member supports.

The base will generally be arranged such that it has a natural frequency that is different from the natural frequency of the conveying member and its supporting springs. Such an arrangement further avoids unwanted vibrations and movement of the base by reducing the possibility that vibratory forces exerted upon the base by the vibration of the conveying member may excite it.

For a better understanding of the invention, embodiments will now be described, purely by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of an exemplary embodiment of a vibratory conveyor according to the invention;

Figure 2 is a schematic diagram of the vibratory conveying apparatus shown in Figure 1 ;

Figure 3 is an illustration of the relationship between the centres of gravity and the resilient supports for conveying apparatus shown in Figure 1 ; and

Figure 4 is a diagram of a vibratory conveyor according to an alternative embodiment of the invention. While the present invention is susceptible of embodiment in various forms, there is described and shown in the drawings presently preferred embodiments. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.

Referring to Figure 1, a vibratory conveying apparatus 10 is supported by a base 12. The base 12 is an elongate frame generally extending in an intended direction of movement of material from a rear end 14 to a front end 16.

The vibratory conveying apparatus 10 includes an elongate conveying member or tray 18 that extends between a rear end 20 and a front end 22.The conveying member 18 includes a conveying bed 24 for receiving material to be moved. The conveying bed 24 includes side-walls 26 that extend between the rear end 20 and the front end 22. The conveying bed 24 supports the material as it is being conveyed from the rear end 20 to the front end 22.

The conveying member 18 is mounted via a resilient support (not visible) to the base 12. The resilient support may comprise beam springs or leaf springs to enable the conveying member 18 to move in a generally forward and rearward reciprocating motion with respect to the base 12.

The vibratory conveying apparatus 10 includes a vibratory drive means (not shown) for vibrating the conveying member 18 in the intended direction of conveying.

An absorbing mass (not visible) is mounted via at least one resilient support (not visible) to the base 12 such that the movement of the absorbing mass is parallel to the movement of the conveying member 18.

During the operation of the vibratory conveying apparatus 10, the conveying member 18 is vibrated by the vibratory drive means with the material progressively moving from the rear end 20 to the front end 22. The absorbing mass also vibrates to counteract the vibration of the conveying member 18, resulting in the absorption of energy from the base. By arranging the absorbing mass and its resilient support to have the same natural frequency as the conveying member 18 (and its resilient members), the absorbing mass can vibrate out of phase with the conveying member 18 in order to minimise the forces transmitted to the base 12.

Referring to Figure 2, a schematic diagram of the vibratory conveying apparatus 10 of Figure 1 is shown. The base 12 of the vibratory conveying apparatus 10 is supported via vibration isolators 28 from stationary supports 30 and has a known centre of gravity 32.

The stationary supports 30 are attached to the floor, although alternatively the conveying apparatus 10 may be mounted to an upper support, such as a ceiling.

The vibration isolators 28 are resilient support means for absorbing vertical vibratory forces and may be of any such suitable form, such as rubber mounts or hydraulic dampers for example.

Supported from the base 12 via a plurality of resilient supports 34 is a conveying member 18. The resilient supports 34 are spaced apart along the length of the conveying member 18, at each side, and across the width if required. The supports 34 are arranged to enable the conveying member 18 to undergo vibrational movement in a generally forward and rearward reciprocating motion with respect to the base 12. The resilient supports 34 are attached with suitable fasteners between the supports 34 and the base 12. The length, thickness and number of the resilient supports 34, leaf springs for example, may be varied to adjust the total equivalent resilience or stiffness K with which the conveying member 18 is supported.

In a preferred embodiment, the resilient supports 34 are at a slight incline angle with respect to the longitudinal direction of the base 12 such that support angle between the resilient supports 34 and the longitudinal direction of the base 12 is less than ninety degrees. For example, the angle between the resilient supports 34 and the longitudinal direction of the base 12 may be seventy degrees (70°). This preferred arrangement can result in the vibrational movement of the conveying member 18 having a vertical component which causes the material being conveyed to be thrown into the air at an angle.

The conveying member 18 has a known mass M and a centre of gravity 36. For practical purposes, the mass of the resilient supports 34 is usually negligible compared to the conveying member 18. However, if the mass of the resilient supports 34 is not negligible, the conveying member's centre of gravity 36 may also include a fraction of the weight of the resilient supports 34.

hi practice it is generally not necessary to take into account the material on the conveyor when defining the conveying member's centre of gravity 36. However, if in special circumstances the centre of the gravity 36 of the conveying member 18 is changed due to the additional material, this can also be taken into account when calculating the conveying member's centre of gravity 36.

A vibratory drive 38 is connected to the base 12 and the conveying member 18 for causing vibratory motion of the conveying member 18 in the intended plane. The vibratory drive 38 preferably comprises an electromagnetic drive 38a and an armature 38b, as opposed to a mechanical drive.

The electromagnetic drive 38a connected to the base 12 applies an electromagnetic force to the armature 38b connected to the conveying member 18 to excite the conveying member 18 into motion. Preferably the electromagnetic drive 38a is adapted such that it applies the electromagnetic force at a frequency substantially equal to the natural frequency of the conveying member 18 and its resilient supports 32.

An absorbing mass 40, which may be simply a block of material such as steel, for example, is mounted via a plurality of resilient supports 42 to the base 12. The resilient supports 42 are spaced apart longitudinally along both sides of the absorbing mass 40 and parallel to the conveying member's resilient supports 34 such that the absorbing mass 40 to undergoes vibrational movement parallel to the vibrational movement of the conveying member 18. The length, thickness or number of the resilient supports 42, for example, can be varied to adjust the total equivalent resilience or stiffness k_a with which the absorbing mass 40 is supported.

The absorbing mass 40 has a known mass m_a and a centre of gravity 44. Again, for practical purposes, the mass of the resilient supports 42 is usually negligible compared to absorbing mass 40. If the mass of the resilient supports 42 is not negligible, the absorbing mass' centre of gravity 44 may also include a fraction of the weight of the resilient supports 42.

The absorbing mass 40 is also arranged such that a line passing through the absorbing mass' centre of gravity 44 and the conveying member's centre of gravity 36 is substantially perpendicular to the conveying member's resilient supports 34. This preferred arrangement can reduce the moments acting at on the base.

The arrangement is also such that the natural frequency of the absorbing mass 40 is substantially equal to the natural frequency of the conveying member 18. The requirement for this arrangement can be expressed as:

Matching of the natural frequencies can be achieved by changing the relevant masses, M and m_a> or stiffness, K and k_a, of the resilient supports.

hi a preferred embodiment, the resilient supports 42 that support the absorbing mass 40 are made from the same non-elastometric material as the resilient supports 34 which support the conveying member 18. This minimises any difference between the natural frequency of the absorbing mass 40 and the natural frequency of the conveying member 18 that may be caused by temperature changes

It is also preferred that the base 12 is arranged to have a natural frequency that is different from the natural frequency of the conveying member 18, the absorbing mass 40 and the drive 38. During the operation of the vibratory conveying apparatus 10, the conveying member 18 is excited in to vibratory motion by the vibratory drive 38, preferably at a frequency substantially equal to the natural frequency of the conveying member 18. The absorbing mass also vibrates to counteract the vibration of the conveying member 18, that is in phase opposition, resulting in the absorption of energy from the base. The arrangement such that the natural frequency of the absorbing mass 40 is substantially equal to the natural frequency of the conveying member 18 results in the absorbing mass 40 vibrating out of phase (preferably 180° out of phase) with the conveying member 18, thus absorbing energy and reducing the forces transmitted to the base 12.

The absorbing mass 40 is not directly driven, but reacts to the tendency of the base 12 to move due to the forces applied by the vibrating conveying member 18.

/

Referring to Figure 3, the relationship between the centres of gravity 32,36,44 and the resilient supports 34 for the conveying apparatus shown in Figure 1 is illustrated.

The centres of gravity 36,44 of the conveying member 18 and the absorbing mass 40 respectively, are arranged such that a line through them is perpendicular to the line 46 which illustrates the angle of the resilient supports 34,42.

The force 48 applied by the drive 38 is located at a distance from the line through the centres of gravity 36,44 of the conveying member 18 and the absorbing mass 40. This force 48 can be in along line of varying direction, as indicate by the various arrows extend from the point of force 48.

The centre of gravity 32 of the base 12 is a distance 50, measured longitudinally of the conveyor, from the line through the centres of gravity 36,44 of the conveying member 18 and the absorbing mass 40.

Unlike prior art base-excited conveyors, the alignment of the centre of gravity 32 of the base with the conveying member 18 and the absorbing mass 40 is not of concern. Thus, there is no need to determine the centre of gravity 32 of the base 12. Furthermore, unlike EP 0 881 172 and other similar prior art, there is also no need to align the line of force 48 applied by the drive 38 to pass through the centres of gravity 36,44. Although it may be preferred to arrange the line of force 48 to pass through the centres of gravity 36,44, satisfactory conveyor performance may still be achieved when the centres of gravity 35,44 deviate from the line of force 48 beyond the limit of 0.21 inches per foot length of the conveying member 18 identified in '172.

Referring now to Figure 4, an alternative embodiment of the present invention is shown. The absorber mass 40 is connected via a resilient support 52 to the base 12 and supported on a slide 54. The surface of the slide 54 upon which the absorber mass 40 rests is arranged so that it is inclined at an angle substantially perpendicular to the conveying member's resilient supports 34.

The resilient support 52 is attached to the base 12 using a suitable fastener and arranged such that the absorbing mass 40 can undergo vibrational movement parallel to the vibrational movement of the conveying member 18.

The arrangement is also such that a line passing through the absorbing mass' centre of gravity 44 and the conveying member's centre of gravity 36 is substantially perpendicular to the conveying member's resilient supports 34. This arrangement minimises the moments acting at on the base.

Again, the arrangement is also such that the natural frequency of the absorbing mass 40 is substantially equal to the natural frequency of the conveying member 18.

The operation of the vibratory conveying apparatus 10 is largely the same as in the embodiment of Figure 2. However, the vibratory motion of the absorbing mass 40 to counteract the vibration of the conveying member 18 is realised by the absorber mass 40 sliding over the surface of the slide 54. Again, the arrangement such that the natural frequency of the absorbing mass 40 is substantially equal to the natural frequency of the conveying member 18 results in the absorbing mass 40 vibrating out of phase with the conveying member 18, thus absorbing energy and reducing the forces transmitted to the base 12 and to the supporting structure through the base 12.

Unlike prior art conveying apparatus, in the present invention there exist no restrictions upon the centre of gravity 32 of the base 12, the magnitude of the drive force 48, position of the drive 38 or alignment of the drive force 48. The inclusion of an absorbing mass 40 as a passive element, which counteracts the conveying member's movement, and the arrangement of the centres of gravity 44,36 of the absorbing mass 40 and conveying member 18 with respect to the angle of the resilient supports 34, results in minimal forces being transmitted to the base 12 independently of the orientation and magnitude of the driving force applied the conveying member 18.

An example of the vibratory conveying apparatus shown in Figures 1 and 2 has been manufactured with the following measurements:

Base: length = 880mm; width = 325mm; height = 264mm; and weight = 90kg;

Conveying member: length = 1663mm; width = 300mm; height = 222mm; weight = 38kg;

Absorbing Mass: length = 300mm; width = 190mm; height = 52mm; weight = 15kg;

Conveying member's resilient supports: Equivalent stiffness K=23 N/mm (K/M=0.605);

Absorbing mass' resilient supports: Equivalent stiffness K=9 N/mm (Ka/ma=0.6).

During operation of this example, the overall movement of the base 12 is in the range of 1-4 mm when there is no absorbing mass 40 attached to the base 12 and the overall stroke of the conveying member is approximately 6mm. Inclusion of the absorbing mass 40 can reduce the overall movement of the base to 0.1-1 mm. Such a reduction in vibration of the base means that bases with lighter bases can be used, which in turn means that less expensive and more manageable conveying apparatus can be manufactured.

It will be observed that the absorbing mass can be implemented in various ways and numerous modifications and variations can be implemented without departing from the scope of the invention.

For example, in an alternative embodiment, the absorber mass may be arranged to vibrate with a natural frequency that is substantially equal to a multiple of the conveying member's natural frequency. The requirement for this arrangement can be expressed as:

K k a ^■ — ^■ — = x where α is an integer and x — » 0

M »2

It is believed that practical benefit is obtained for values of α below 10, with α preferably 5 or less, and most preferably 3 or less. However, it is foreseen that future technical advances may enable higher values of α to be successfully employed and it should therefore be appreciated that the use of larger α values is envisaged.

In an alternative embodiment, the resilient supports 34 may be in any suitable arrangement for supporting the conveying member 18.

In further alternatives, the vibratory drive 38 may not be connected to or supported by the base 12 or the conveying member 18 but simply arranged such that the vibratory drive 38 applies a force to the conveying member 18 directly, thus exciting the conveying member 18 into vibratory motion. It also within the scope of the present invention that the vibratory drive may be controllable so that its characteristics, such as drive frequency or magnitude for example, may be altered.

In other alternative embodiments, more than one absorbing mass may be used to counteract the vibration of the conveying member 18. It will be appreciated that such a plurality of masses may all be of equal or differing mass, or any combination thereof. However, to minimise the moments acting at on the base, the masses should be arranged such that a line passing through each absorbing mass' centre of gravity and the conveying member's centre of gravity is substantially perpendicular to the conveying member's resilient supports.

It will be appreciated by those skilled in the art that changes may be made to the embodiments described without departing from the principles of the invention.

Claims

1. A vibratory conveying apparatus for moving materials, comprising: a base; a conveying member supported from the base by at least one resilient support; a drive arranged to excite said conveying member into vibration; and an absorbing mass supported from the base by at least one resilient support such that movement of the absorbing mass is substantially parallel to that of the conveying member, and that a line passing through the absorbing mass' centre of gravity and the conveying member's centre of gravity is substantially perpendicular to the at least one resilient conveying member support, wherein the natural frequency of the absorbing mass is arranged to be substantially equal to the natural frequency of the conveying member, or a multiple thereof, whereby when the conveying member is excited into vibration by the drive, the absorbing mass vibrates substantially in phase opposition to the conveying member, resulting in the absorption of energy from the base.

2. A vibratory conveying apparatus according to claim 1 wherein the multiple of the natural frequency of the conveying member is five or less.

3. A vibratory conveying apparatus according to claim 1 or 2, wherein the frequency of excitation of the drive is substantially equal to the natural frequency of the conveying member.

4. A vibratory conveying apparatus according to any preceding claim wherein the base has a natural frequency that is different from the natural frequency of the conveying member.

5. A vibratory conveying apparatus according to any preceding claim, wherein the at least one resilient support comprises a plurality of springs, preferably leaf or beam springs.

6. A vibratory conveying apparatus according to any preceding claim wherein the base is supported from a mounting frame via vibration isolators.

7. A vibratory conveying apparatus according to any preceding claim wherein the drive is an electromagnetic drive.

8. A vibratory conveying apparatus according to any preceding claim wherein the drive is controllable such that the frequency of the drive force can be varied.

9. A vibratory conveying apparatus according to any preceding claim wherein the at least one resilient absorbing mass support and the at least one resilient conveying member support are formed from the same non-elastometric material.

10. A vibratory conveying apparatus according to any preceding claim wherein the absorbing mass comprises a plurality of sub-masses.