GB2485819A

GB2485819A - Transfer plate for a delivery mechanism

Info

Publication number: GB2485819A
Application number: GB1020012.9A
Authority: GB
Inventors: Milan Fuchs
Original assignee: Radix Systems Ltd
Current assignee: Radix Systems Ltd
Priority date: 2010-11-25
Filing date: 2010-11-25
Publication date: 2012-05-30
Also published as: GB201020012D0

Abstract

A delivery mechanism for an inspection or sorting apparatus comprises an object source 110 operable to supply objects to be sorted and a transfer plate 130 having a smooth surface and being mechanically coupled 135 at a first end to the object source and positioned to transfer objects supplied by the object source over the smooth surface and on to a chute 140, and wherein a second, free end of the transfer plate is arranged to move freely with respect to the chute. Preferably, the object source is a vibratory feeder such that the transfer plate mechanically excited the objects it transfers. The transfer plate may be rigid or flexible; preferably, the transfer plate is sigmoid in shape and its flexibility varies over at least part of the length between the source and the chute. The transfer plate may be coupled to the course by a fastener, or it may be integral to the source. A separate vibration source may be provided for the transfer plate.

Description

DELIVERY MECHANISM FOR INSPECTION OR SORTING APPARATUSES

AND DELIVERY METHOD

The present invention relates to a delivery mechanism for inspection or sorting apparatuses and a delivery method.

The automated inspection or sorting of commodities such as rice, beans or other objects typically involves delivering a stream of such objects from a reservoir along a chute to an inspection or sorting station. The inspection or sorting station typically comprises an optical system for inspecting each object, coupled in the case of a sorting station to means by which defective objects (for example those of an undesired size or colour) can be rejected.

The accuracy of these processes can be improved if the orientation of the objects can be made more regular vhilst maintaining or improving the spacing of the objects within the delivery stream.

is The orientation of the objects can made more regular by adding grooves or channels along the length of the chute, causing the objects to align themselves with the grooves or channels as they pass along the chute to the inspection or sorting station. Typically the grooves are chosen to have a size responsive to one dimension of the object, so that for example in a rice sorter, the grooves may be slightly larger than the diameter of a grain of rice. This will encourage the rice to align itself longitudinally in the direction of travel along the chute, so simplifying inspection and, if necessary, rejection of the rice.

However, the grooves represent a potential constriction to the movement of some objects, for example when the objects are of a non-standard size or where by chance several objects enter a groove at substantially the same time. In such eases a first object may pass along the groove more slowly than later objects, resulting in subsequent objects within the groove catching up and forming clusters of objects by the time they reach the inspection or sorting station. Such clusters are hard to inspect and are likely to lead to sorting errors.

Moreover, when a defective object is present in a cluster, it is therefore likely that otherwise acceptable objects will be rejected along with the defective object, leading to unnecessary waste. However, to reduce the rate of instances of clustering it becomes necessary to limit the flow rate of objects passing along the chute, resulting in lower throughput and efficiency.

To mitigate this problem, a delivery mechanism may comprise a known chute described in GB application 2416533 (Sortex Ltd). This chute comprises a first smooth portion and a second portion having grooves parallel to the length of the chute. The objects are dropped onto the fir st smooth portion, where they can separate out and become more uniformly spaced before entering the grooves or channels of the second portion, thereby reducing the chance of clusters forming.

However, there is still scope to improve upon this approach in order to further increase object throughput and efficiency. The present invention seeks to mitigate this problem.

In a first aspect of the present invention, a delivery mechanism for an inspection or sorting apparatus is provided in claim 1.

In a second aspect of the present invention, a delivery method for delivering an object in an inspection or sorting apparatus is provided in claim 14.

Further respective aspects and features of the invention are defined in the appended claims.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: is Figure 1 is a schematic diagram of a known delivery mechanism and sorting / inspection apparatus; Figure 2 is a schematic diagram of a delivery mechanism in accordance with an embodiment of the present invention; Figure 3 is a schematic diagram of a delivery mechanism in accordance with an embodiment of the present invention; Figure 4 is a schematic diagram of a delivery mechanism in accordance with an embodiment of the present invention; and Figure 5 is a flow diagram of a method of delivery in accordance with an embodiment of the present invention.

A delivery mechanism for inspection or sorting apparatuses and a delivery method are disclosed. In the following description, a number of specific details are presented in order to provide a thorough understanding of the embodiments of the present invention. It will be apparent, however, to a person skilled in the art that these specific details need not be employed to practise the present invention. Conversely, specific details known to the person skilled in the art are omitted for the purposes of clarity where appropriate.

Referring to Figure 1, a known sorting apparatus comprises a hopper or other reservoir for holding obj ects 12 and releasing them onto a vibrating tray 14. The tray itself is likely to contain a high density of objects. The vibrations deliver a proportion of the objects to the edge of the tray, from which they fall on to a first smooth portion of a chute 1 6A. The smooth portion of the chute allows the objects to separate and become more uniformly spaced before they enter the grooved second portion of the chute 1 6B. The products subsequently fall from the lower end of the chute into an inspection zone where they are inspected by an optical system 18. If the optical system detects an undesirable property of the obj ect, such as a non standard size or a discolouration, then that object is subsequently prevented from landing in a first receptacle 22A and is diverted to a second, rejection receptacle 22B. The diversion can be achieved using an air jet generator to blow the object onto an alternate trajectory that ends in the second receptacle instead of the first. Other equivalent inspection and sorting techniques will be known to the person skilled in the art.

Referring now to Figures 2 and 3, in a delivery mechanism for an inspection or sorting apparatus according to an embodiment of the present invention, objects to be sorted or inspected such as rice or beans are supplied to a vibratory feeder 110. The supply may be from a hopper or other reservoir (not shown) or from the output of a preceding process, such as a drier or a cleaner (not shown). The vibratory feeder may have side walls (indicated by doffed lines) to prevent spillage. The vibratory feeder itself may have a high density of objects on its surface.

The vibratory feeder is caused to vibrate, for example by being mechanically coupled to an electro-magnet that is excited by a fixed or variable frequency current, although other means to generate suitable vibration will be appreciated by the skilled person. The vibration causes objects on the vibratory feeder to move towards a lip 120 of the vibratory feeder, The proportion of objects moved to the lip of the feeder (i.e. the feeder flow rate) may typically be controlled by the frequency and/or amplitude of vibrations used. In this way, the vibratory feeder operates as an object source for further stages of the delivery mechanism.

In an embodiment of the present invention, attached to the lip of the vibratory feeder a thin smooth metal or plastic sheet is then provided, which acts as a transfer plate 130 between the vibratory feeder and a chute 140. Other suitable materials, such as vulcanised rubber, may also be considered for the transfer plate.

In other words, the transfer plate is positioned to transfer objects supplied by the object source over its smooth surface and on to the chute.

The transfer plate may be substantially rigid (as illustrated in Figure 2) or may be flexible (as illustrated in Figure 3). A first end of the transfer plate may be mounted or fastened on the lip of the vibratory feeder as illustrated in Figure 3 by a bolt 135, although glue or other suitable fastening means are also envisaged. Alternatively the transfer plate may be made integral to the vibratory feeder, for example extending from the lip of the vibratory feeder.

In an embodiment of the present invention, the second, free end of the transfer plate rests freely on the surface of the chute, and as such is not mechanically coupled to the chute and so is able to move freely with respect to the chute whilst remaining in contact with it.

Alternatively, and particularly in the case of a substantially rigid transfer plate, the free end of the transfer plate may optionally be arranged to contact or nearly contact the chute without resting or lying on it, for reasons to be explained later herein.

The chute itself will typically be a grooved chute, but may be a conventional smooth chute or a combination of the two. The chute is typically constrneted from anodised aluminium, although any suitable material (for example steel) is envisaged.

In operation, embodiments of the transfer plate provide several advantages over the prior art. It will be understood that the transfer plate provides an opportunity for objects to separate and become more uniformly spaced as they pass along its smooth surface, both longitudinally and laterally. However in addition it will be appreciated that the transfer plate is mechanically coupled to the vibratory feeder through its fastening or by virtue of being integral with the feeder, and so also vibrates. This beneficially increases the separation and distribution of the objects beyond that possible by simple passive rolling or sliding of the objects over the plate, by mechanically exciting the objects as they progress along the transfer plate.

In addition, the free end of the transfer plate can vibrate and hence move with respect to the chute. Consequently in the event that two objects leave the free end of the transfer plate in close succession at the same lateral position, the relative motion of the transfer plate with respect to the chute can reduce the chance of the two objects entering a same groove in the chute, and so reduces the chances of them clustering. It will also be appreciated that due to this relative motion, as noted above a substantially rigid transfer plate may therefore optionally be spaced slightly apart from the chute to prevent damage to either the plate or the chute. In this case, optionally a short flexible lip may be provided at the end of such a rigid transfer plate to rest on or contact the chute.

Thus both the absolute motion of the transfer plate and its relative motion with respect to the chute each separately serves to improve the uniformity of distribution of obj ects arriving on the chute itself Consequently, for a given target level of clustering events or sorting errors, all else being equal it is possible to increase the flow rate of objects compared to the prior art system, and so improve throughput and efficiency.

In addition, the transfer plate provides the further advantage that the objects do not drop freely from the vibratory feeder on to the chute. Rather, the objects experience only a first slight drop equivalent to the thickness of the vibratory feeder lip at the top of the transfer plate as they move on to the transfer plate, and a second slight drop equivalent to the thickness of the transfer plate at the free end as they move off it and on to the chute.

oreover, the first slight drop may be further reduced or eliminated by mounting or integrating the transfer plate in line with the lip.

It will be understood that a thin' transfer plate will typically have a thickness similar to or less than the effective height of the objects it transfers, particularly near its free end in contact with the chute. However this may be overridden over all or part of the plate for the purposes of achieving mechanical strength or another desired property.

Reducing the drop experienced by the objects provides a number of advantages.

Firstly, reducing the drop onto the chute reduces the bounce of objects along the chute.

If an object is bouncing it is less likely to be presented to the optical inspection system at a desired orientation or in a desired inspection plane, and may incorrectly appear brighter or darker than it really is due to being closer to or further than expected from an illumination source used for inspection purposes. In addition, the bouncing may affect the trajectory of the object and interfere with the sorting or rejection process.

Secondly, a low angle of incidence between the free end of the transfer plate and the chute (less than 30 degrees, typically less than 15 degrees, preferably less than 5 degrees and still more preferably in the order of 1 or 2 degrees) reduces cumulative wear on the chute due to object impact. A low angle of incidence also contributes to a reduced rebound angle for any object bounce that occurs.

Finally, reducing the drop experienced by the objects reduces damage to them and hence also reduces rejections by the sorter. In addition, even where damage from a drop is typically too small to directly cause such rejections, it can result in an accumulation, of particulate debris on the chute that results in some objects travelling more slowly, and hence causes clustering or even blockages, so indirectly causing unnecessary rejections. By reducing the drop and so reducing damage, the rate of indirectly caused rejections is reduced, and additionally the need for maintenance and clearing of debris is also reduced, thereby further improving throughput and efficiency.

Referring now also to Figure 4, in which similar components to those of Figures 2 and 3 are similarly numbered, in a variant embodiment of the present invention a transfer plate 130' may have a changing thickness or other parameter to provide varying flexibility (i.e. a stiffhess profile) over at least a part of the length of the transfer plate, in order to provide a suitable shape of transfer plate for objects to move down to the chute. In the example of Figure 4, a vibratory feeder 110' does not have a lip, and so a transfer plate 130' with a tapering thickness and hence increasing flexibility over a first portion of its length is used to provide a small initial drop onto a largely horizontal transfer plate that then gently curves down to the chute 140.

More generally, the transfer plate can thus be either straight or curved along its length between the vibratory feeder and the chute. A sigmoidally shaped transfer chute, for example forming a curve with a single point of inflection, provides a substantially continual and gradual transition between the direction of object travel on the vibratory feeder and the direction of object travel on the chute. It will be appreciated that as a result this provides a low angle of incidence between the transfer plate and the chute.

An approximation to this shape may be achieved in several ways. Firstly a flexible transfer plate may be mounted so as to produce such a shape, as illustrated in Figure 3.

Secondly, a flexible transfer plate having variable flexibility or stiffness may be employed to achieve such a shape where required, as seen in Figure 4. Thirdly, a substantially rigid transfer plate may be made having a predetermined sigmoid shape.

Further variant embodiments of the present invention include a separate vibration source mechanically coupled directly to the transfer plate, for example in a case where the object supply is not provided by a vibratory feeder but directly from the output of a preceding process.

Referring now to Figure 5, a sorting method comprises: in a first step (slO), disposing a transfer plate having a smooth surface between an object source and a delivery chute such that the transfer plate is not mechanically coupled to the delivery chute; in a second step (s20), receiving an object on to the transfer plate from the object source; and in a third step (s30), mechanically exciting the object as it traverses the smooth surface of the transfer plate to the chute.

It will be apparent to a person skilled in the art that variations in the above method corresponding to operation of the various embodiments of the apparatus as described and claimed herein are considered within the scope of the present invention, including but not limited to: i. the step of mechanically exciting the object comprising in turn mechanically coupling the transfer plate to a vibratory feeder acting as the object source; ii. the step of mechanically exciting the object comprising in turn mechanically coupling the transfer plate to a vibration generator separate to the object source; iii. using either a rigid or flexible transfer plate; iv. using a flexible transfer plate with a varying stiffness profile; and v. shaping or allowing the transfer plate to adopt a sigmoid shape.

Claims

CLAIMS1. A delivery mechanism for an inspection or sorting apparatus, comprising: an object source operable to supply objects to be sorted; a transfer plate having a smooth surface and mechanically coupled at a first end to the object source and positioned to transfer objects supplied by the object source over the smooth surface and on to a chute; and wherein a second, free end of the transfer plate is arranged to move freely with respect to the chute.
2. A delivery mechanism according to claim 1 in which the transfer plate is substantially rigid.
3. A delivery mechanism according to claim 2 in which the free end of the transfer plate comprises a flexible lip.
4. A delivery mechanism according to claim 1 in which the transfer plate is flexible.
5. A delivery mechanism according to claim 4 in which the flexibility of the transfer plate varies over at least part of the length of the transfer plate between the vibratory feeder and the chute.
6. A delivery mechanism according to claim 4 or claim 5 in which the free end of the transfer plate rests on the chute.
7. A delivery mechanism according to any one of the preceding blaims in which the transfer plate is substantially sigmoid in shape.
8. A delivery mechanism according to any one of the preceding claims in which the transfer plate is mechanically coupled at a first end to the object source by a fastener.
9. A delivery mechanism according to any one of claims 1 to 7 in which the transfer plate is integral to the object source.
10. A delivery mechanism according to any one of the preceding claims, in which the object source is a vibratory feeder, and in operation the transfer plate mechanically excites the objects it transfers due to the mechanical coupling of the transfer plate to the vibratory feeder.
11. A delivery mechanism according to any one of claims 1 to 9, in which the transfer plate is mechanically coupled to a vibration source separate to the object source.
12. A delivery mechanism according to any one of the preceding claims in which the free end of the transfer plate is in contact with the chute, thereby presenting a drop for objects on to the chute substantially equal to the thickness of the transfer plate.
13. An inspection or sorting apparatus comprising a delivery mechanism according to any one of the preceding claims.
14. A delivery method for delivering an object in an inspection or sorting apparatus comprises the steps of: disposing a transfer plate having a smooth surface between an object source and a delivery chute such that the transfer plate is not mechanically coupled to the delivery chute; receiving an object on to the transfer plate from the object source; and mechanically exciting the object as it traverses the smooth surface of the transfer plate to the chute.
15. A delivery method according to claim 14, in which the object source is a vibratory feeder and the step of mechanically exciting the object comprises the step of: mechanically coupling the transfer plate to the vibratory feeder.
16. A delivery mechanism substantially as described herein with reference to drawings 2 to5.
17. A delivery method substantially as described herein with reference to drawings 2 to 5.