WO2015134113A1

WO2015134113A1 - Roller with wear indicator

Info

Publication number: WO2015134113A1
Application number: PCT/US2015/010120
Authority: WO
Inventors: Sheila Hamilton; Steven Frank MITCHELL
Original assignee: Itw Cs (Uk) Limited
Priority date: 2014-03-05
Filing date: 2015-01-05
Publication date: 2015-09-11
Also published as: GB201403852D0; GB2523786A

Abstract

A roller comprising a core region and a surface region sheathing the core region; wherein at least one of the core region and the surface region is doped with a first optically detectable dopant and the other of the core region and the surface region is not doped with the first optically detectable dopant.

Description

ROLLER WITH WEAR INDICATOR

The present invention relates to a roller having a wear indicator for use in a contact cleaning process, in particular to a roller comprising a core region and a surface region sheathing the core region.

Contact cleaning is used to clean substrate surfaces. Once cleaned the substrate surfaces may be used in a variety of sophisticated processes such as in the manufacturing of electronics, photovoltaics and flat panel displays. Usually, a rubber or elastomeric cleaning roller is used to remove contaminating particles from a substrate surface and an adhesive roller can then be used to remove the contaminating particles from the cleaning roller. This allows the cleaning roller to maximise its efficiency in removing contaminating particles from the substrate surface.

However, the maintenance of existing contact cleaning machines can be difficult with the removal and replacement of the rollers, both cleaning and adhesive, being time consuming and/or requiring partial disassembly of the area holding the rollers. In addition, the wear rate of the cleaning roller is determined partly by the material forming the roller and partly by the cleaning process being used. Typically rollers wear unevenly, and are prone to pitting, due to the pressure exerted when rolling over the surface of a component such as an electronic substrate. The rate at which a cleaning roller wears is fundamental to the success of the cleaning process. Typically such rollers consist of a homogeneous material. The surface of the homogeneous material wears during the lifetime of the roller. If the roller is not replaced before the surface of the roller no longer contacts the particles of contamination, the contaminant particles are not removed from the substrate surface. In these circumstances the electronic substrate becomes damaged and goes to waste. However, taking a more cautious approach, if the roller is replaced too soon whilst there is still an appreciable working life, the overall cost of the cleaning process increases. This is a key consideration in a multi-step cleaning process. Consequently, there is a need to be able to predict the wear of the cleaning rollers accurately, repeatably and without considerable increased cost in the overall cleaning process. The present invention aims to address these issues by providing a roller comprising a core region and a surface region sheathing the core region; wherein at least one of the core region and the surface region is doped with a first optically detectable dopant and the other of the core region and the surface region is not doped with the first optically detectable dopant.

By using an optically detectable dopant it is possible to monitor the rate of wear of a roller. A threshold optical response from the optically detectable dopant may be predetermined to provide an indication of the wear of the roller. The threshold optical response preferably indicates a condition of wear of the roller at which at least a portion of the surface is worn to a minimum acceptable thickness. This is ideal when the roller is used in a contact cleaning apparatus or process, since the minimum acceptable thickness of the surface region can be used to indicate when the roller should be replaced. In embodiments of the invention, the threshold optical response from the optically detectable dopant may be indicative of a thickness of at least a portion of the surface region tending towards 0mm. It should be understood that the threshold optical response from the optically detectable dopant may be predetermined by the user for a roller of the present invention such that a minimum acceptable thickness of the surface region of the roller remains at the threshold optical response. The minimum acceptable thickness of the surface region may be predetermined by a user.

Preferably the other of the core region and the surface region is at least partially transparent at a wavelength at which the dopant is optically detectable.

More preferably the core region is doped with the first optically detectable dopant. The surface region may be doped with a second optically detectable dopant.

Preferably, the surface region has a thickness T, and the optical response of the surface region at the wavelength is proportional to the thickness. Preferably, the optical response of the surface region is predictable for at least a portion of the thickness T. The optical response may be exponential, linear or logarithmic for at least a portion of the thickness T. More preferably, the optical response of the surface region is approximately linear for at least a portion of the thickness T. The surface region may have a thickness ti, wherein ti < T, at which the optical response indicates an unacceptable thickness of at least a portion of the surface region. In certain embodiments, ti indicates a thickness of at least a portion of the surface region of 0mm. Most preferably, the surface region may have a thickness £2, wherein £2 < T, and t2 > ti at which the optical response demonstrates a measurable threshold level. During use, the surface region wears such that the thickness of at least a portion of the surface region decreases from T to £2.

It is much preferred that the thickness £2 is pre-determined for a roller according to the invention. By providing a pre-determined threshold thickness of at least a portion of the surface region at which the optical response demonstrates a measurable and determinable threshold level, a user will be provided with a measurable indication of the point when the roller has reached the end of its useful life and should be refreshed or replaced.

Preferably, the roller further comprises a shaft coaxial with the core region. More specifically, the roller further comprises a shaft coaxial with the core region and the surface region.

Preferably the at least the first optically detectable dopant is detectable in a portion of the electromagnetic spectrum. Most preferably, the at least the first optically detectable dopant is one of: luminescent, fluorescent, phosphorescent, reflective or detectable in the visible, infrared or ultraviolet regions of the electromagnetic spectrum. If the core region is doped with the at least first optically detectable dopant, and the at least first optically detectable dopant is luminescent, phosphorescent or fluorescent, the surface region may be transparent to the wavelength at which the dopant luminesces, phosphoresces or fluoresces.

The core region and the surface region may be formed from elastomeric materials. More specifically, the core region and the surface region comprise a homogeneous elastomeric material.

In another aspect the present invention also provides the use of such a roller in a contact cleaning process.

The present invention will now be described by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 is a schematic side view of a contact cleaning apparatus employing a roller in accordance with embodiments of the present invention;

Figure 2 is a schematic cross-section of a roller in accordance with a first embodiment of the present invention;

Figure 3 is a schematic graph showing the optical response of a roller in accordance with the first embodiment of the present invention;

Figure 4 is a schematic cross-section of a roller in accordance with a second embodiment of the present invention; and

Figure 5 is a schematic side view of an apparatus for monitoring the wear of a roller in accordance with a first embodiment of the present invention.

In the present invention it has been appreciated that cleaning rollers can be manufactured in a manner that allows remote and contact-free monitoring of their wear during a contact cleaning process. Rollers comprising a core region and a surface region sheathing the core region can be formed such that at least one of the core region and the surface region is doped with a first optically detectable dopant, where the other of the core region and the surface region is not doped with the first optically detectable dopant. By using optical monitoring of the dopant the rate of wear can be determined from the optical response measured as the surface region is worn during the contact cleaning process. By choosing a dopant and surface region material giving an optical response that is proportional to the thickness of the surface region, a threshold optical response indicating wear can be defined by engineering a measurable change/level in the optical response. This can be achieved by adapting the dopant, the core region and/or the surface region, as described below.

Figure 1 is a schematic side view of a contact cleaning apparatus employing a roller in accordance with embodiments of the present invention. The contact cleaning apparatus 1 comprises a contact cleaning roller 2 and an adhesive roller 3 mounted above a conveyor 4 on which a plurality of substrates 5 for cleaning are carried. The contact cleaning roller 2 is elongate and generally cylindrical in shape, and is mounted on a holder (not shown) having an axis perpendicular to the plane of view about which the contact cleaning roller 2 is free to rotate. The specific structure of the contact cleaning roller 2 is described in more detail below. The adhesive roller 3 is generally cylindrical in shape, and comprises a body having a surface on which adhesive is present, and is also mounted on a holder (not shown) having an axis perpendicular to the plane of view and parallel to that of the contact cleaning roller 2 about which the adhesive roller 3 is free to rotate. The contact cleaning roller 2 and adhesive roller 3 are mounted in such a manner so as to be in contact with one another such that clockwise rotational movement of the contact cleaning roller 2 results in counter-clockwise rotational movement of the adhesive roller 3 and vice versa. The need for the contact cleaning roller 2 and adhesive roller 3 to be in contact will be clear from the description of use below. The contact cleaning roller 2 is also mounted so as to be able to be in contact with the surface of a substrate 5 to be cleaned as it passes on a conveyor located below the axis of the conveyor 4.

Substrates 5 to be cleaned are processed as follows. A substrate 5 is positioned on the upper surface 6 of a conveyor 4, which in Figure 1 moves from right to left as indicated by arrow A. The substrate 5 to be cleaned passes underneath the contact cleaning roller 2, which rotates in a clockwise direction as indicated by arrow B. Before coming into contact with the contact cleaning roller 2, the upper surface of the substrate 5 is covered with debris 7 requiring removal, such as dust. The contact cleaning roller 2 contacts the upper surface of the substrate 5, removing the debris 7 by means of an electrostatic removal mechanism, where the inherent polarity of the material used to form the contact cleaning roller 2 attracts the debris 7 and causes it to stick to the surface of the contact cleaning roller 2. The relative attractive force between the surface of the contact cleaning roller 2 and the debris 7 is greater than that between the debris 7 and the surface of the substrate 5, hence the debris 7 is removed. The now clean substrate 5 continues along the conveyor 4 to a removal station (not shown) and the lower surface 8 of the conveyor passes back, forming a loop, in a left-right direction in Figure 1, as indicated by arrow D. In order to clean the contact cleaning roller 2, the adhesive roller, rotating in a counter-clockwise direction as indicated by arrow C contacts the surface of the contact cleaning roller 2. At this point the adhesive force between the debris 7 and the adhesive present on the surface of the adhesive roller 3 is greater than the electrostatic force holding the debris 7 onto the surface of the contact cleaning roller 2, and the debris is removed. The contact cleaning roller 3 then rotates to present a clean surface to the next substrate 5 to be cleaned.

Figure 2 is a schematic cross-section of a roller in accordance with a first embodiment of the present invention. The roller is used as a contact cleaning roller in a contact cleaning system 1 as described above. The roller 10 comprises a core region 11 sheathed in a surface region 12. The roller 10 is elongate and generally cylindrical in shape, and is mounted via a mounting mechanism onto a holder (not shown) for use in a contact cleaning system 1. The roller 10 may further comprise a shaft (also not shown) coaxial with the core region 11 and the surface region 12. This may be used to aid in mounting the roller 10, and in the rotational movement of the roller 10 in use. Preferably, such a shaft is formed from metal (stainless steel, for example) or plastic (polycarbonate, polyethylene terephthalate or similar, for example). In this embodiment, the core region 11 is doped with an optically detectable dopant, and the surface region is not doped with the optically detectable dopant. Preferably this is a luminescent or phosphorescent material. Most preferably, the optically detectable dopant is a phosphorescent pigment, comprising one or more of strontium aluminate, radium sulphide or zinc sulphide.

The surface region 12 has a thickness T, and is formed from a material that is at least partially transparent at a wavelength at which the dopant is optically detectable. Both the core region 11 and the surface region 12 are formed from an elastomeric material, such as, for example, rubber or other natural or synthetic elastomer material. Preferably the elastomer materials are homogeneous. In the initial unused and unworn state, the thickness T of the surface region 12 is such that the optically detectable dopant is minimally detectable, for example, sufficiently detectable to verify that the dopant is present in the core region 11. The optically detectable dopant is detected by looking at the optical response of the roller 10, for example, by measuring an intensity of the luminescence or phosphorescence. In order to measure the optical response it may be necessary to use a specific optical source or a specific detector, for example, one that is able to detect luminescent or phosphorescent material, as discussed below. In use, the surface region 12 wears as it comes into repeated contact with substrates 5 to be cleaned. It may be that the wear is even, in that the outer surface of the surface region 12 is gradually worn away, or uneven, such that the outer surface of the surface region 12 is pitted and damaged. During use, the surface region 12 wears such that the thickness of at least a portion of the surface region 12 decreases from T to and then to ti. In undesirable circumstances, the entire thickness T of the surface region 12 is worn away, with the core region 11 being exposed. In any event, the wear of the outer surface of the surface region 12 results in the optical response of the optically detectable dopant increasing. This is illustrated schematically in Figure 3.

Figure 3 is a schematic graph showing the optical response of a roller in accordance with the first embodiment of the present invention. The x-axis represents the thickness of the surface region 12, T, and the y-axis represents optical response, in this case, the intensity / of the luminescence or phosphorescence of the core region 11 detected through the surface region 12. The optically detectable dopant and the material forming the surface region 12 are chosen such that the optical response of the surface region 12 is approximately linear for at least a portion of the thickness T of the surface region 12. At a point where the thickness of the surface region 12 is t\ where ti < T, the optical response represents an undesirable thickness of at least a portion of the surface region and a point at which the roller 10 is beyond its useful life. The continuing optical response plateaus and changes little between ti and t3 when the surface region is completely eliminated. As the core region 11 begins to wear after t3, the optical response decreases further compared to the initial optical response, although in this example remains linear. However, the optical response may be exponential, logarithmic or a step change at this point. It is desirable, therefore, for the user to be able to change the roller 10 before the optical response at t\ is achieved. Consequently a second point i¾ can be defined, wherein at the optical response demonstrates a measurable threshold level. This threshold may be defined for the roller either with or without a calibration of the initial optical response. Preferably is defined as a thickness at which it is most desirable to change the roller 10, rather than being a critical point in terms of the maximum useful lifetime of the roller 10. Consequently rather than an unacceptable minimum thickness, as with ti, t2 represents a workable minimum thickness indicating that the workable lifetime of the roller 10 has been achieved.

The measurable threshold level is engineered to allow the easy detection of a point at which it is necessary to change the roller 10. At this point there is sufficient surface region 12 remaining on the core region 11 to avoid damage to the substrates 5 to be cleaned but this is an acceptable minimum indicating that the useful lifetime of the roller 10 has been achieved. Figure 4 is a schematic cross-section of a roller in accordance with a second embodiment of the present invention. In this embodiment, the roller 20 comprises a core region 21 and a surface region 22 sheathing the core region, but unlike the first embodiment, the surface region 12 is doped with a first optically detectable dopant. Therefore to determine the wear of the roller 20 a decrease in optical response is measured, since as the surface region 22 is worn away the amount of dopant present decreases until a pre-determined threshold in optical response (ie a fading of luminescence or phosphorescence) is detected. In this embodiment there is no need for the core region 21 to be doped, and it may be at least partially transparent at a wavelength at which the dopant is optically detectable.

In the above embodiments the roller 10, 20 is formed from an elastomeric material. Both the core region 11, 21 and the surface region 12, 22 may be formed from the same elastomeric material, or from different elastomeric materials if desired. For example, the materials may have different optical, mechanical or thermal properties. It may be desirable if one of the core region 11, 21 and the surface region 12, 22 is doped with a first optically detectable dopant to dope the other of the core region 11, 21 and the surface region 12, 22 with a second optically detectable dopant. This may make the pre-determined measurable threshold optical response at t2 easier to detect in certain circumstances. Although in the above embodiments the dopant used is luminescent or phosphorescent, it may be desirable to use other dopants that are also detectable in a portion of the electromagnetic spectrum. For example, the dopant may be one of luminescent, phosphorescent, fluorescent, reflective or detectable in the visible, infra red or ultraviolet regions of the electromagnetic spectrum. If the core region 11, 21 is doped with the at least first optically detectable dopant, and the at least first optically detectable dopant is luminescent, phosphorescent or fluorescent, the surface region 12, 22 is transparent to the wavelength at which the dopant luminesces, phosphoresces or fluoresces. In the above embodiments the surface region 12, 22 is a single layer sheathing the core region 11, 12. However it may be advantageous to use a surface region 12, 22 having at least two layers, where each layer is provided with a different or differing amount of optically detectable dopant, or has different materials properties. Such layering would allow the pre-determined measurable threshold to be determined at a point adjacent where the layers meet. For example, if an inner surface region layer was provided with a first optically detectable dopant providing a first colour/luminescence/fluorescence/phosphorescence/reflectivity and an outer surface region layer was provided with a second optically detectable dopant providing a second colour/luminescence/fluorescence/phosphorescence/reflectivity then the pre- determined measurable threshold may be detected as a colour/response change. The at least one optically detectable dopant may be present at 0 to 5% weight/weight. Preferably the at least one optically detectable dopant is present in a range of between 0.1 and 5% weight/weight. Figure 5 is a schematic side view of an apparatus for monitoring the wear of a roller in accordance with a first embodiment of the present invention. The roller 10 is used in a contact cleaning system 1 as described above. The apparatus comprises a roller 10, having a core region 11 and a surface region 12, mounted by means of a shaft 13 onto a holder (not shown), mounted above a conveyor 4 and in contact with an adhesive roller 3.

An excitation energy source 14 is positioned with respect to the roller 10 such that it is operable to emit excitation energy in a direction E toward the roller 10 comprising the optically detectable dopant. In this example, the optically detectable dopant is a phosphorescent pigment material that is detectable at 300nm. The excitation energy source 14 is positioned to emit excitation energy onto the surface region 12 such that the phosphorescent material emits detectable light in a direction F. Preferably the excitation energy is emitted from the excitation energy source 14 at a wavelength of 300nm. An optical detector device 15 is positioned with respect to the roller 10 such that it is operable to detect an optical signal emitted by the optically detectable dopant in response to it absorbing excitation energy from the excitation energy source 14. Preferably the excitation energy source 14 may be an ultraviolet light source. The excitation energy source 14 may be a tungsten white light source, an LED source or other similar source of excitation energy.

The optical detector device 15 is circumferentially offset from the excitation energy source 14. The distance of the circumferential offset between the excitation energy source 14 and the optical detector 15 will depend upon the decay time of the phosphorescence of the phosphorescent pigment material. The phosphorescent decay curve may not be linear. It is much by preference that the circumferential offset between the excitation energy source 14 and the optical detector 15 for any given phosphorescent pigment is selected to ensure there is sufficient detectable phosphorescence to detect.

The optical detector 15 may be an optical cell. In embodiments of the invention, the detector 15 may be a current charge device (CCD), for example.

In operation of the apparatus, the ultraviolet excitation energy source 14 emits excitation energy and the phosphorescent pigment in the adhesive material begins to phosphoresce. As the roller 10 rotates, the activated phosphorescent pigment emits an optically detectable signal which, in turn, is detected by the optical detector 15 as the surface region 12 rotates.

Although in the above exemplary embodiments an ultraviolet light source is used. Depending on the optically detectable dopant selected it may be desirable to use a visible, infrared or other light source.

When a new, unused roller 10 is mounted into the apparatus, the apparatus is calibrated by measuring the baseline phosphorescence of the surface region 12 in an uncontaminated condition. As the roller 10 is used and the thickness T of the surface region 12 decreases, the detector 19 monitors the change in phosphorescence relative to the baseline until a pre-determined threshold level of change in phosphorescence is reached, equating to a thickness of the surface region 12 of t2. Although less desirable, alternatively, the detected phosphorescence at ti may be measured. At either point, for example, an alarm could be triggered to alert the operator that the roller 10 should be changed. It is less desirable to measure the phosphorescence at ti as opposed to the pre-determined threshold level as at least a portion of the surface region at ti is completely worn away and, therefore, there is an increased risk that the substrates to be cleaned will be damaged beyond use at this point. It is much by preference that the pre-determined threshold level of phosphorescence is measured wherein at least a portion of the thickness of the surface region remains intact.

A processor unit 16 may be programmed to monitor the change in the optical signal detected by the optical detector 15. The processor unit 16 may provide an alarm signal when the threshold or abrupt change in the optical signal relative to the baseline phosphorescence is detected.

Alternative arrangements of detector and light source may be required if other optical properties are to be used to determine the amount of wear of the roller 10. For example, having a light source and optical detector positioned next to one another is particularly useful if a reflective optically detectable dopant is used.

These and other embodiments of the present invention will be apparent from the scope of the appended claims.

Claims

1. A roller comprising a core region and a surface region sheathing the core region; wherein at least one of the core region and the surface region is doped with a first optically detectable dopant and the other of the core region and the surface region is not doped with the first optically detectable dopant.

2. Roller according to claim 1, wherein the other of the core region and the surface region is at least partially transparent at a wavelength at which the dopant is optically detectable.

3. Roller according to claim 1 or 2, wherein the core region is doped with the first optically detectable dopant.

4. Roller according to claim 1, 2 or 3, wherein the surface region is doped with a second optically detectable dopant.

5. Roller according to any of claims 1 to 4, wherein the surface region has a thickness T, and wherein the optical response of the surface region at the wavelength is proportional to the thickness.

6. Roller according to claim 5, wherein the optical response of the surface region is predictable for at least a portion of the thickness T.

7. Roller according to claim 6, wherein the surface region has a thickness at which the optical response demonstrates a pre-determined threshold level.

8. Roller according to claim 6 or claim 7, wherein the surface region has a thickness ¾ wherein < T, at which the optical response demonstrates a measurable threshold level.

9. Roller according to claim 7 or 8, wherein during use, the surface region wears such that the thickness of at least a portion of the surface region decreases from T to t2.

10. Roller according to any preceding claim, wherein at least the first optically detectable dopant is detectable in a portion of the electromagnetic spectrum.

11. Roller according to any preceding claim, wherein at least the first optically detectable dopant is one of: luminescent, phosphorescent, fluorescent, reflective or detectable in the visible, infrared or ultraviolet regions of the electromagnetic spectrum.

12. Roller according to claim 11, wherein if the core region is doped with the at least first optically detectable dopant, and the at least first optically detectable dopant is luminescent, phosphorescent or fluorescent, the surface region is transparent to the wavelength at which the dopant luminesces, phosphoresces or fluoresces.

13. Roller according to any preceding claim, wherein the core region and the surface region are formed from elastomeric materials.

14. Roller according to claim 13, wherein the core region and the surface region are formed from the same elastomeric material.

15. Roller according to any preceding claim, further comprising a shaft coaxial to the core region.

16. Roller according to any one of the preceding claims, wherein the roller is a cleaning roller.

17. Use of a roller according to any preceding claim in a contact cleaning process.