Improvements for lighting within a skinner.

Abstract

The invention improves illumination within a hazardous volume along the length of the blade of an operator-driven skinner. Light-emitting diodes (LEDs) in arrays or singly are disposed about both ends of, and shine deep into the hazardous volume. Additionally, the LEDs may be energised alternately in order that each electronic camera sees reflected or scattered incident light and is not blinded by light from the opposite side.

Description

[0001] Title: IMPROVEMENTS FOR LIGHTING WITHIN A SKINNER.

[0002] Field:

[0003] The invention relates to improvements for the machines known as “skinners”, “denuders”, or as “flaying machines”. They separate layered parts of carcasses in meat or like processing plants. The invention relates to improvements to optical sensing of an instantaneous position of a worker’s hand or hands in relation to a fixed blade of the skinner, in order to protect the user’s hands from trauma caused by the blade. In particular the invention relates to lighting the hazardous volume within which a worker’s gloved hand may come into hazardous proximity in relation to the blade, for the benefit of electronic cameras.

[0004] Definitions

[0005] Skinner. The kind of skinner referred to herein is a stand-alone machine, not linked to a conveyor. An operator stands at the machine, grasps an item to be skinned, and feeds items to be skinned toward the blade, using his or her properly gloved hands with gloves of a contrasting colour. A transverse gripping roller grips the underneath of the item and carries it toward a rear, fixed knife 105. Surface velocity of the feeder roller is typically 700 mm per second. Waste material taken in a thin layer passes under the blade; food material passes over it. For example an ox tongue is skinned in several passes to remove the epithelium, fascia, and other materials covering the muscle. The Applicant’s skinners include a digital processor.

[0006] Hazardous volume. During skinner operation, the operator holds the item to be skinned with one or more hands, while assisting the feeder roller to bring the item to the blade. The hazardous volume is located over the top of the rotatable feeder roller 103 (see Fig 1) and is just in front of an edge of a fixed blade 105. It is situated across the rear of an operator work area, in front of the blade. It is elongated to at least the blade length of for instance 500 mm. The hazardous volume is often concealed from above. The hazardous volume is viewed by cameras at each end of the blade looking along the blade. If a hand or finger approaches the blade within the hazardous volume, the skinner controller should recognise the image and take rapid stopping action. Bundle of image-forming rays of light. This term describes the information-carrying light arising within the hazardous volume to one or more lenses when in use. It is abbreviated herein to “image light”.

[0007] LED. A common abbreviation for “light emitting diode”.

[0008] Optical Axis. If more than one camera, viewpoint, or equivalent are in use, the optical axis is a mean of individual camera, viewpoint, or equivalent axes.

[0009] Electronic camera. This name refers to cameras used in machine-vision applications such as the skinner. Currently preferred Teledyne “Blackfly” colour cameras are described at https: / / www.teledynevisionsolutions.com / en- 150 / products / blackfly-s-usb3 / ?model=BFS-U3- 04S2C-CS&vertical=machine%20vision&segment=iis

[0010] Problem to be solved:

[0011] The invention relates to operator safety. Since the hazardous volume of a manually operated skinner may be concealed from above, from time to time, by parts of the object being processed an optical operator protection system having a “from above” layout like that for bandsaws is infeasible. The Applicants have previously used a view along the length of the typically 500 mm blade of the skinner revealing the hazardous volume in front of and right up to the blade.

[0012] Better illumination of the interior of the long and usually enclosed (except at the ends) hazardous volume increases the quality of an image from an electronic camera. It reduces inherent noise in the image, and allows the camera lenses to be stopped down in order to achieve a greater depth of field. As a result, a positive identification of even a small part of a glove within the hazardous some can start an ‘instant stop’ response.

[0013] Prior Art

[0014] The Applicants have previously described optical sensing systems adapted to detect an operator's hand close to, and especially in dangerous proximity to a cutting blade of a machine. WO2017196187A1 is for a bandsaw. At least one electronic camera looks down on to the bandsaw table and a braking system stops the bandsaw blade within 20 milliseconds of optical detection of a hazard.

[0015] The Applicants have also described an optically protected skinner in PCT / NZ2020 / 050142, herein “ ’ 142”. A skinner has a different configuration to that of a bandsaw. In ‘ 142 cameras are directed horizontally along the length of the skinner blade from both sides through an apparatus including deflecting mirrors that extends the effective distance between the camera and the viewed space, the hazardous volume.

[0016] Prior art that relates to hazard protection uses electrical conduction from a wired-in conductive glove when touching the blade. See for instance US 5,122,091 Townsend.

[0017] Summary of Invention

[0018] In a first broad aspect, the invention provides a skinner machine for use by an operator; the machine having a working surface having, with respect to the operator, a near edge, a left side border and a right side border and including a gripping feeder roller intended to carry an item to be skinned against a blade of a fixed knife located along a far edge of the working surface; the skinner machine having an operator safety system including an optical apparatus having a directing mirror and at least one electronic camera together with a processor, intended when in use for detection of a potentially hazardous event namely presence of a gloved hand of an operator within a predetermined hazardous volume located along the edge of the blade and toward the position of the operator and above the edge of the blade, and taking immediate action if so detected; wherein the skinner machine includes a light source at each side of the blade using light-emitting diodes (LEDs) directed into an interior of the hazardous volume.

[0019] In a first variant, the LEDs comprise an array of LEDs upon a surface, disposed in order to emit a flood of light from a lit area directly into the hazardous volume from each end, from around the viewing aperture.

[0020] In one option, an inclined mirror in the shape of a truncated hollow cone having a reflective exterior that surrounds the optical axis receives light emitted across the surface from the LEDs and directs the light close to an optical axis into the hazardous volume.

[0021] Optionally the inclined mirror has the shape of a polygon, having a hollow interior and a sloping reflective outer edge.

[0022] Preferably an edge of the inclined mirror is substantially in contact with the window surrounding the viewing aperture 108 so that, when in use, the inclined mirror excludes direct light from impinging on the window within the viewing aperture thereby degrading the image. Optionally some or all of the LEDs emit light in a selected wavelength or colour, providing increased discrimination between a selected glove colour and a typical red-brown-yellow- white colour of the item to be skinned; for instance blue LEDs for blue gloves or green LEDs for green gloves.

[0023] Preferably each LED is provided within a package that provides a beam width of less than about 30 degrees.

[0024] More preferably each LED package is configured to concentrate the emitted light in a narrow beam to be directed into the hazardous volume.

[0025] Optionally the beam may be collimated by a collimating filter.

[0026] In a second variant, coaxial illumination substantially aligned along the optical axis is provided by fabricating the inclined directing mirror to have a partially reflecting outer surface capable in use of providing a first function of reflecting at least some image light toward the electronic cameras, and a second function of providing illumination substantially along the optical axis through the viewing aperture and into the hazardous volume by at least one LED behind the partially reflective diverting mirror.

[0027] Preferably a mass of light-absorbing substance or baffle is placed in line with a tunnel separating one or more cameras from the hazardous volume, but above the inclined mirror.

[0028] In a second broad aspect, the invention reduces specular reflected light by using a circular polarizing filter placed behind the window.

[0029] Preferably the filter is a circular polarizing filter placed so that, when in use, both emitted light from the array and light returned from the hazardous volume to the camera pass through the filter.

[0030] In a third broad aspect, the invention, through a digital processor, cyclically controls the instantaneous current passed alternately through the left side and the right side LED arrays, while controlling an image capture event in the or each corresponding electronic camera.

[0031] Preferably each array is caused to flash while the camera on the same side captures an image including the hazardous volume, while the array on the opposite side from the camera is turned off. NOTICES:

[0032] In this specification, any references to an electronic camera and illumination assembly, or parts thereof, for one side of a skinner should be interpreted as embracing a mirror image of the same assembly provided on the other side of the hazardous zone of the skinner machine.

[0033] In this specification, reference numerals are provided for clarification only and are not intended to restrict the scope of the invention to the particular embodiments of the components in conjunction with which the reference numerals are used.

[0034] Throughout this specification unless the text requires otherwise, the word "comprise" and variations such as "comprising" or "comprises" will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. Each document, reference, patent application or patent cited in this text is expressly incorporated herein in their entirety by reference. Reference to cited material or information cited in the text should not be understood as a concession that the material or information was part of the common general knowledge or was known in New Zealand or in any other country.

[0035] LIST OF FIGURES

[0036] Fig la: Oblique elevation view of an Example 1 illumination board in place behind a window, with surface mount LEDs.

[0037] Fig lb: An example prior-art package for a LED lamp.

[0038] Fig 2: Diagram of a vertical cross section of part of a skinner including the window, the LED array and the inclined mirror to the tunnel extending downward.

[0039] Fig 3: Diagram of a vertical cross-section; illumination using a partly silvered mirror.

[0040] Fig 4a: A low-profile illumination board having a tapered cylindrical mirror. (Example 2)

[0041] Fig 4b: Cross-section at A— A’ of the low-profile illumination board of Fig 4a.

[0042] Fig 5: Graph of flashed LED array currents for both sides, and image acquisition times.

[0043] Introduction:

[0044] For operator protection, optical identification of a hazard within a skinner machine requires continuous surveillance of an elongated hazardous volume, bounded along one side by the cutting edge 105 (See Fig la) of the fixed knife blade 106 and extending toward the operator (not shown, at far left) for a distance that provides enough stopping time to bring the feeder roller 103 and any items accompanying the feeder roller to a halt before the blade cuts the hand, causing trauma. In the Applicant’s models, the feeder roller surface moves at typically 700 mm per second. The stopping time is less than 20 milliseconds. That determines an example fore-and-aft axis for the hazardous volume to be at least (0.7 x 20 mm) = 14 mm depth toward the operator, a length of about 500 mm and a height of about 15 mm above the blade. According to the invention, the hazardous volume is surveilled from both ends.

[0045] An operator of a skinner machine could inadvertently bring a gloved hand to the fixed knife of the machine while holding an item down on to the motorised feeder roller, which holding action is often required during operation. The hand may be currently hidden by part of the item being skinned. Or, the glove itself could become trapped by the surface of the feeder roller and drawn under the fixed knife. Unlike the open disposition of cutting edge and table top for a bandsaw, a skinner or a derinder might be performing a cut or separation that is concealed underneath a covering layer of the item. It is already common practice that meat industry workers wear latex gloves in a strong blue or green colour.

[0046] One need for good lighting arises from use of stopped-down telephoto (long focal length) lenses in combination with the existing tunnel apparatus in order to increase the thickness of a volume inside which objects are sufficiently well focused (larger depth of field). Since a telephoto lens is normally associated with a limited depth of field, the illumination should be as bright as possible to allow the lens to be stopped down so that a useful depth of field is obtained.

[0047] If an image from the electronic cameras used in this apparatus is viewed as a video clip, one can see significant overlaid noise, arising in part because the lenses have been stopped down. Noise adversely affects discrimination of pixels by the processor while it is looking for contiguous groups of pixels having a colour that is a contrast with the background meat, before deciding if any such group is sufficiently close to the blade to justify stopping the machine. Therefore it is desirable to increase the intensity of illumination through the hazardous volume, each side of which may be 300 mm deep and about 15 x 15 mm in height and width, with little space outside.

[0048] The stripper roller of a skinner is inaccessible to the operator during a skinning operation.

[0049] Preferred Embodiments: A typical skinner as shown in the Applicant’s prior-art ‘142 has bilateral symmetry. This application is intended to improve on the lighting aspect of ‘142 in which the Applicants described “an included high-intensity strip light source sealed inside a trough 815”. The strip light runs along the length of the elongated hazardous volume. The present application describes three Examples having a light source directed through a window 104 at both ends of the blade into the hazardous volume. Two Examples are for LED light emitted close beside a ray path carrying image light to be focused by the electronic cameras; the third mixes light into the centre of the ray path using a partly reflective diverting mirror 206. A fourth Example describes benefits of processor control of LEDs in order to improve image collection.

[0050] Example 1:

[0051] LED Board: Fig la is an oblique elevation view 100 of a left side illumination board 101 mounted in proximity to one end of a hazardous zone of a skinner. The board is viewed from the midline and looking slightly backward. A shaped transparent window 104 (indicated by a light hatching, see Figs 2 and 4b) is sealed in place with screws 107 to protect the apparatus from contamination such as expected from high-pressure waterjets during repeated cleaning. As shown in the section view in Fig 2, the window is preferably mounted at a small angle to an optical axis, to avoid direct reflections. A board 101 carrying an array of typically 128 surface-mount LEDs 102 is shown in this example. Each board can produce a steady output of approximately 10,000 lumens. The board 101 comprises a printed-circuit board having circuit tracks for mounting rows each of perhaps 4 to 12 diodes; the series connections being driven in parallel through current- sharing and limiting resistors as is known in the electronic arts. The board may have enhanced heat-sink capability.

[0052] Each LED-carrying board 101 is located behind a transparent, sealed window 104 that includes an imaging aperture area 108. Another illumination board is provided at the far end of the 500 mm long hazardous volume (for the prototype). Therefore illumination to at least 250 mm depth by each board is optimal. That imaging aperture 108 leads reflected or scattered image light arising within the hazardous volume to the 45 degree diverting mirror 203 of Fig 2. The illuminating light is close to the optical axis but it does not arrive straight along the optical axis. Thus a deep, narrow space made during skinning might not receive deep illumination. The LEDs 102 shown in Fig la are surface-mount packages. Without a lens, an emitted cone of light may arise from any one device with a solid angle of about 155 degrees. Surface mount LEDs are available with integral lenses for a more directed light cone. In one alternative, LED packages of a type as shown as 102a in Fig lb may be preferred because they inherently have a much narrower illumination cone of about 30 solid degrees. Some of those packages may be mounted at an angle on to the board 101 and directed toward the hazardous volume, although that may be impossible with robotic assembly machinery. The beam passes through the window 104 into the hazardous zone.

[0053] LED colours: White light is assumed. But LEDs emitting light in a colour like that of the gloves in use, such as blue LEDs for blue gloves, or green LEDs for green gloves would return a relatively bright signal within pixels carrying images of the glove, as compared to the typical reddish to whitish background of meat. The image-analysis part of the processor could operate by testing pixel brightness alone, although colour recognition using white light allows better glove-background discrimination.

[0054] Shrouds: A cover or shroud (not shown) may be installed to at least partially shield the operator’s eyes from direct glare from the LEDs. Alternatively, collimating holes made through a sheet, a manufactured collimating filter, or driving the LEDs to produce intermittent flashes may reduce glare.

[0055] Polarizing Filter: Minimising specular reflection from shiny surfaces uses a circular polarizing filter 202 behind the entire window 104 as in Figs 2 and 3 to improve image quality. Such filters are widely available in sheet form. The filter imposes a circular polarised configuration in a first on the emitted light projected into the hazardous volume. Any specular reflections from object surfaces return polarised image light in an opposite direction, and are blocked from the camera by the filter. But diffusely scattered image light such as that incident on gloves loses polarisation and may be seen by the electronic cameras as a more evenly illuminated image.

[0056] Fig 2 is a vertical cross-section including part of the feeder roller 103 in longitudinal section and part of the LED array 102 on the board 101 behind the sloped sealing window 104. Returned image light from inside the hazardous volume above feeder roller 103 passes through the window at 108 to be reflected from 45 degree diverting mirror 203 along axis 201 and through a sealed tunnel to the electronic camera or cameras (not shown).

[0057] Example 2: Fig 3 is a cross-section through a co-axial lighting arrangement for one of the two sides, illuminating the hazardous volume directly along the optical axis. At least one relatively bright LED 102a is placed on the optical axis 207 behind an inclined diverting mirror 206. Mirror 206 has a partially reflecting (“half-silvered”) reflecting surface, so that the mirror both admits part of a beam of emitted light from the LED into the hazardous volume to the left of the drawing, and deflects part of the returned image light 207 down into the tunnel 201 (not shown). Some light from the LED is inevitably reflected up from mirror 206 and enters a light trap 203 lined with a light- absorbing baffle 204. The baffle prevents the light from returning through the diverting mirror as stray light down to the cameras. Some of the imnage light continues to the LED 102a and is lost. This version ensures that light will reach the bottom of a deep, laterally enclosed hazardous volume.

[0058] Dichroic mirrors may be used if the LEDs are selected to emit light in a particular colour range that excites fluorescence, and fluorescent gloves returning light in a different colour are used.

[0059] Example 3:

[0060] Figs 4a and 4b show an alternative low-profile layout of LEDs for paraxial illumination of the hazardous area. Fig 4a is a surface view as seen through the window 104. Light from a radial array of bright LED lamps such as 102a is directed over a mounting board surface toward the optical axis of the image light, traversing the viewing aperture 108. Emitted light is reflected into the hazardous volume from an inclined mirror 301 surrounding and close to the optical axis 207. The individually packaged LED lamps shown here may be replaced by widely available higher-output devices. The LED lamps may be thermally bonded along their sides such as with a thermally conductive paste on to a thermally conductive base board 101 for disposal of waste heat, perhaps using the conductors on the printed-circuit board.

[0061] Fig 4b includes a cross-section of the inclined mirror 301 along the line A— A” of Fig 4a. This example has the shape of a truncated, hollow cone. It may be turned or machined from aluminium or brass, or be moulded from glass or a plastics, and provided with a reflective polish or coating on the outer, sloping side. Each reflecting surface may be slightly curved and may be tilted slightly from 45 degrees to best direct the beam into the hazardous volume. The line of contact of the periphery of the mirror 301 and the window 104 helps prevent stray emitted light from illuminating any surface contaminants on the window surface and being scattered into the cameras. The array and the inclined mirror 301 surrounding the viewing aperture 108 may be circular as shown in Fig 4a or it may be rectangular or have a N-sided polygonal shape.

[0062] Example 4:

[0063] Example 4 (Fig 5) relates to illuminating and viewing each side of the hazardous volume alternately. One advantage of LEDs over other forms of lamp is their substantially instantaneous response to applied current. They may be intermittently driven by a controller (flashed or strobed) in a cyclic manner. Intermittent current pulses provides flashes of light, giving a brighter apparent output for the same mean rate of heat dissipation and can be synchronised in order to flash during image acquisition by the cameras.

[0064] Digital outputs from the embedded digital processor control LED current sources for alternately driving the left hand side and the right hand side LEDs in a flash mode. The processor is programmed to synchronise the flash on one side with the moment at which the electronic cameras on the same side capture an exposure. At that moment the lamps on the opposite side of the hazardous volume are set to be off and do not shine directly into the lens of the active camera.

[0065] To illustrate this, Fig 5 is a drawing from an oscilloscope with left and right channels of LED current amplitude on the vertical scales 401 and 402, and camera sampling signals, against time on the horizontal scale. The current traces 403 and 404 represent an optional steady illumination. If steady emitted light is not necessary, the steady current may be zero. The cycle from 407 to 407’ is repeated perhaps every 5 (200 Hz rate) to 20 (50 Hz rate) milliseconds, dependent for instance on camera exposure duration and image processing time. The cyclic process of alternate flashing continues indefinitely while the skinner is operated.

[0066] An example capture moment is at 407, when the right-hand camera or cameras is or are caused, as at 406, to capture an image of the hazardous volume. Each “flash” command is synchronised with camera acquisition. At that time, the LEDs on the same side are driven at a higher current as shown at 407, and the opposite array of LEDS are turned off, as at 405. Later, at capture moment 408, the left-hand camera or cameras capture an image from the other end of the hazardous volume using a flash of light from the LEDs on the same side, when driven at a higher current as shown at 409. The opposite array of LEDS are turned off, as at 410. Optionally both cameras are triggered to capture an image regardless of which side is flashed, because a back-lit or silhouette image of a gloved hand in proximity to the blade may hold useful information.

[0067] A basic circuit to provide two levels of LED current output may be obtained from two digital control lines in parallel for the left side and for the right side. One line drives a corresponding power MOSFET or equivalent to pass current through a predetermined current-limiting device such as a resistor, and then through the corresponding array of LEDs, providing a background amount of light. The other parallel line, if switched ON, delivers a higher current using a second power MOSFET to briefly carry current through a second current limiting device (or none, relying only on resistance within conductors to limit current) and into the same array. Or the MOSFET circuit may be configured to control instantaneous current as is known in the electronic arts.

[0068] Advantages:

[0069] An advantage of placing the LEDs behind a sealed window is that they are protected from mechanical damage or liquids, facilitating cleaning.

[0070] No electrical connection enters the wet working area of the skinner.

[0071] The Example 1, Example 2 and Example 3 types of illumination may be used in combination.

[0072] The Example 2 arrangement provides a low-profile light source aligned along the long axis of the hazardous volume while screening the window from stray emitted light.

[0073] The Example 3 version is coaxial and illuminate to the end of a relatively deep cavity.

[0074] Advantages of the Example 4 synchronisation system include that neither camera is blinded by emitted light from the opposite LEDs. Heat dissipation from the LEDs is reduced. The operator sees less glare.

[0075] Finally it will be understood that the scope of this invention as described and / or illustrated herein is not limited to the specified embodiments. Those of skill will appreciate that various modifications, additions, known equivalents, and substitutions are possible without departing from the scope of the invention as set forth in the following claims.

Claims

WE CLAIM1. A skinner machine for use by an operator; the skinner machine having a working surface having, with respect to the operator’s position, a near edge, a left side border and a right side border and including a gripping roller intended to carry an item to be skinned against a blade of a fixed knife located along a far edge of the working surface; the skinner machine having an operator safety system including an optical apparatus having at least one electronic camera and a processor capable when in use of detecting a distinctive object, namely a gloved hand of an operator, within a predetermined hazardous volume located along the edge of the blade and toward the position of the operator and above the edge of the blade; the safety system taking immediate protective action if so detected; characterised in that the skinner machine includes a light source at each side of the blade that directs light from light-emitting diodes (LEDs) into an interior of the hazardous volume.

2. The skinner machine as claimed in claim 1, characterised in that each light source comprises a plurality of LEDs disposed upon a board and directed perpendicular to a plane of the board and behind a window surrounding a viewing aperture on each side of the working surface.

3. The skinner machine as claimed in claim 2, characterised in that an inclined mirror surrounding the viewing aperture and an optical axis therein is mounted upon the board so that, when in use, the inclined mirror receives light emitted across the surface from the LEDs and directs the light close to an optical axis into the hazardous volume.

4. The skinner machine as claimed in claim 3, characterised in that the inclined mirror has a shape like that of a hollow, truncated cone and an inclined exterior reflective face.

5. The skinner machine as claimed in claim 3, characterised in that the inclined mirror has a hollow polyhedral shape, a series of inclined exterior reflective face, and an open interior.

6. The skinner machine as claimed in claim 1, characterised in that the LEDs have a selected spectral distribution of light which has a peak at the mean wavelengthreflected by the gloves when in use, thereby providing increased discrimination between a selected glove colour and a typical red-brown-yellow-white colour of the item to be skinned; for instance blue LEDs for blue gloves.

7. The skinner machine as claimed in claim 1 and having a diverting mirror having a first function of deflecting image-carrying rays of light originating within the hazardous volume into a tunnel terminated by said at least one electronic camera is provided, characterised in that the diverting mirror has a partially reflective mirror surface capable in use of providing a second function of providing illumination substantially along the optical axis through the viewing aperture and into the hazardous volume by at least one LED behind the partially reflective diverting mirror.

8. The skinner machine as claimed in claim 1, characterised in that the invention reduces specular reflected light by using a circular polarizing filter placed behind each window.

9. The skinner machine as claimed in claim 1, characterised in that an embedded digital processor is programmed in order to control an instantaneous current passed alternately through the left side and the right side LED arrays, while initiating an image capture event in the electronic camera near to the immediately driven LED array; the captured image being used for detection of the coloured object.

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