Patent Application
20090162093
The invention relates generally to the field of laser printer toner cartridges and more specifically to the field of remanufacturing such cartridges.
A laser toner cartridge contains a few significant components that directly affect the print quality and durability over time. These significant components are all located in the development section of the cartridge. The above mentioned components are the photosensitive drum that is made of an electrically conducting material such as aluminum, the developing roller, the regulating member and the primary charge roller.
During operation of a laser printer the photosensitive drum rotates as its drive gear is rotated. Specific models of cartridges are known to have specific gear designs. Also, such gears are typically attached to the drum by mechanical techniques, such as described in U.S. Pat. No. 7,248,841, where a mechanical crimping and coupling process was used.
The coating on the photosensitive drum typically wears off after one lifecycle of the cartridge as a result of constant friction between the photosensitive component and the primary charge roller, as well as friction between the developing roller and the printed media. The amount of wear depends on multiple factors such as: type of media printed, average coverage area of the printed documents, type of toner used, type of documents printed (short: 1-2 pages or long: 100+pages) type of coating etc. It was found out that more often than not using the same photosensitive drum for another or second lifecycle, would not produce the same print quality as the original cartridge over the whole second lifecycle of the remanufactured cartridge. Therefore, in conventional remanufacturing processes the photosensitive drum is treated as an exhausted component and is replaced by a new one on all known remanufactured models of cartridges.
While the photosensitive drum can become exhausted during a single lifecycle, the drum's drive gear typically does not become exhausted with such use, and can be re-used. In addition, the original drum's drive gear, or specific features of a drum's drive gear may be the subject of one or more patents, such as for example the particular shape of a drive gear that is unique to a certain product line. In order to reuse a cartridge component conventionally considered to be not reusable, as a precaution in order to avoid possible patent infringement claims and as a way to reduce costs of remanufacturing a toner cartridge, a need exists for a process and associated apparatus by which the drive gear of original equipment toner cartridge photosensitive drums may be reused.
Responding to the aforementioned need, described herein are apparatuses and processes for reuse of an original photosensitive drum drive gear of a laser printer toner cartridge. The process includes removal of the original gear from the original photosensitive drum and installation of the original gear onto a new drum cylinder. The original gear is installed by coupling the prior art gear to the new drum preferably by surface treating the original gear to render it more capable of holding an adhesive, and then using adhesive to couple the original gear to a new drum. Preferably the original drive gear from the original photosensitive drum (also referred to as a “member”) has been used at least one lifecycle, and is then installed on the new photo sensitive member.
Because the design concepts of the original drive gear and the adherence to the original photosensitive drum are essentially different from those of a replacement gear and drum, the original gear is modified to improve its adhesion capability and the thus modified original gear is installed in the drum by an adhesive processes in order to assure durability and consistency of the product over the cartridge's lifecycle. The preferred process for reusing a photosensitive drum drive gear includes removing the original gear from the original photosensitive drum by using a pneumatically operated machine that clamps the drive gear in a fixed position, and then is removed from the drum by twisting the photosensitive cylinder out of position and off of the gear manually. The gear removal optionally can be done automatically as well manually, or by using an electrical clamp or a hydraulic clamp.
The original drive gear is then selectively roughened using blasting media, manual sanding, knurling and/or creating channel grooves on the surfaces of the gear that contacts the drum. Then the part is thoroughly cleaned using an ultrasonic bath or manually cleaned using cleaning solvents such as iso-propanol, MEK (methyl-ethyl ketone), acetone or mild detergents. The electrical contacts of the original gear are straightened out in order to assure electrical continuity once the gear is pushed into a new drum. The inside of the new drum is degreased using a solvent such as iso-propanol, and dried. One area or more close to the end on the internal side of the new drum is preferably laser etched, or otherwise roughened in a patch form in order to remove the anodized layer of aluminum on the drum and thus to provide a path for electrical continuity between the contacts on the drive gear and the drum. The roughened surface of the drive gear is preferably primed using a diluted adhesive in order to achieve high surface contact between the inner surface of the photosensitive drum and the outer periphery of the drive gear shaft.
Adhesive is then applied on the internal surface of the photosensitive drum preferably using an automatic adhesive dispenser or dispensing the adhesive manually. The adhesive is preferably dispensed while rotating the drum. The whole adhesive application apparatus is preferably positioned at an angle in order to allow visual inspection of the quality of the application and the consistency of the dispensed adhesive. The drive gear is preferably aligned on a rotary bearing in order to facilitate aiming at or placing the contact on the area of the inside of the drum intended to provide the path for electrical continuity, such as for example a laser etched patch on the inside of the drum near the end where the gear is installed. Then the drive gear is pushed into the drum preferably using a pneumatic piston in order to prevent possible contamination of the coating that might result during a manual insertion. The electrical continuity between the cylinder or drum and the shaft of the drive gear is then tested. At this stage of the process, new drums having the original drive gears installed are then preferably stacked vertically and left to cure, preferably for not less than 12 hours at room temperature, for example at a temperature in the range of about 60-75 degrees F, with the drive gears facing down. This orientation is preferred in order to assure good flow of the adhesive towards a tapered area of the gear, where it is believed that the strongest areas of bonding results.
These and other embodiments, features, aspects, and advantages of the invention will become better understood with regard to the following description, appended claims and accompanying drawings.
The foregoing aspects and the attendant advantages of the present invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
Reference symbols or names are used in the figures to indicate certain components, aspects or features shown therein. Reference symbols common to more than one Figure indicate like components, aspects or features shown therein.
Hereinafter, preferred embodiments of the present invention will be described with reference to
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Adhesion surfaces 54, 54, shown on the surfaces of a prior art gear in
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Preferably after being primed, and as described below, the drive gear 28 is then positioned onto the rotary insert 136. The gear 28 is then aligned with the drum 22 by manually rotating it so that tabs 36, 38 are aligned, preferably by visual inspection, with laser etched patch 114. Pneumatic switch 140 is then depressed to activate air cylinder 130, which then causes cradle 134 to move in the direction of arrow 138 and insert the gear into to drum at its end 118. Pneumatic momentary switch 140 is then released, causing air cylinder 130 to move cradle 134 in the direction of the arrow 139, that is, to return the cradle 134 back to its home position. An electrical continuity test is then conducted, preferably by contact ground member 48A, shown in
In accordance with embodiments of the present invention the process of removing the original drive gear from a used photosensitive member and installing the used, original drive gear on a new photosensitive member will be described. Removing the prior art gear from the prior art drum cylinder is preferably accomplished by using a pneumatic clamp that holds the drive gear with the assistance of a pneumatic clamp apparatus 70, as shown in
In order to make sure that the presently described embodiments function to attach an original gear to a new drum as well as the original gear was attached to the original drum a series of torque measurements were taken. Those measurements were taken with a JETCO brand torque wrench, 0-100 ft. lb range. In regard to the prior art design, i.e., the original gear as attached to the original drum, the gear failed at 5 ft. lb. In other words at an application of 5 ft. lbs. of torque the gear would break loose from the drum. This value is referred to as the torque failure value, and was used as a benchmark or standard for determining the attachment or adhesion strength of various embodiments as described herein. In other words, in order for a process of attachment of an original gear to a new drum to be considered useful, it must meet or exceed the torque failure value of the original equipment drum and gear assembly.
As described herein four surface preparation methods are preferred: (a) knurling; (b) grooving; (c) media blasting; and (d) primer. The four different techniques were experimented with in order to generate a larger and/or better surface for adhesion, and thus increase the strength of the adhesion, gripping power or mechanical grip of the adhesive to the surface of the gear. It is believed that in the prior art designs only mechanical crimping was employed to attach the gear to the drum, with no adhesive used, and that no consideration was given to the adhesion affinity of the surfaces of the gear and the drum cylinder with respect to each other. The prior art gears intended to be used in the present inventions were made of nylon polymer. As is well known, it is extremely hard to make another structure or item adhere to a component made of nylon polymer, due to the very nature of the nylon polymer.
In order to enable adhesion, it was discovered that surface treatment was needed, and the knurling, grooving and/or media blasting techniques proved to be useful. Furthermore, it has been discovered that the use of all four methods or techniques produces superior adhesion properties after 24 hours from the time of application of the adhesive. It has also been discovered that if used alone, the knurling and grooving processes do not produce such superior results. Rather, for gear-drum assemblies made with only a knurling or grooving surface treatment, a consistent decline in adhesion strength over time, in aggressive environments, such as high humidity and extreme temperature differences, has been found to result.
It has also been discovered that the most preferable or most desirable surface treatment is media blasting using Aluminum-Oxide grit #220 as a blasting media. It is believed that other types of media and grit can be used to achieve a useful result. The blasting pressure was 40-70 psi and the gears were blasted using a media blasting gun commercially available from CYCLONE. As seen in
Preferably the surface treated gear is then cleaned in order to remove all grease and contamination residues as well as media blasting residues. Cleaning preferably was achieved by using air blasting to remove the bigger particles and then by submerging the surface treated drive gears in a conventional ultrasonic bath. Preferably iso-propanol is used in the bath as a degreaser, and the ultrasonic bath is lasts for at least 1 minute. Preferably the cleaned gears are then dried in ambient air for at least 5 minutes. Other techniques can be used to clean the drive gears such as manual brushing, wiping, flushing or dipping numerous times, so long as the end result is a surface treated gear that will adhere to the drum at greater than the torque failure value.
The contact tabs of the original gear are also straightened, preferably after the gear has been surface treated and cleaned. In the preferred embodiments described above, straightening of the contact tabs 36, 38, 40 and 42 was done using pointed pliers. The tabs on the ground plate 34, shown in
As is well known the typical, original photosensitive drum is manufactured with a technique that does not involve anodizing of the aluminum cylinder. As described above, however, the preferred embodiments of the current inventions relate to a new drum cylinder that is manufactured using an anodizing process in order to adhere the photo sensitive coating to the aluminum cylinder surface. The anodizing process is one in which the electrical conductivity property of the anodized metal is greatly reduced. Thus, in order to provide for electrical continuity in a drum-gear assembly having an anodized drum, it is preferred that part of the anodized area of the drum is removed and a conductive path be established. In the event a new drum to be used with an original gear and in accordance with the principles of the present inventions is not anodized, then this part of the process can be skipped.
Preferably a laser etching technique is used to etch a rectangular patch close to the end 118 of the cylinder, as shown at patch 114 in
As described above the original gear, preferably processed as describe above, is adhesively attached to a new drum. In this regard three main groups of adhesives were tested for their adhesion properties in this application. Those three groups were: cyano-acrylates; acrylics; and, epoxies. Samples of these adhesives were applied on the internal surface of a drum cylinder. Because the gear is very close in dimensions to the inner orifice of the cylinder, i.e., a very tight fit, whenever adhesive is applied to the gear's surface, the adhesive will come out when the gear is pushed into the drum. This external adhesive then has the potential to might cause contamination of the outer surface of the drum. In order to avoid or minimize this risk, it is preferable that adhesive be applied on the inner surface of the cylinder. Thus, once the drive gear is installed the adhesive residues are pushed inside the cylinder.
Shown below in Tables 1-3 are results of adhesive testing with a variety of adhesives, surface preparations and test conditions. Adhesive application was tested first without surface treatment to the gear. The first adhesive candidates were in the cyano-acrylate family, because of the ease of use and the low cost. As can be seen in Table 1, two brands of cyano-acrylates were used. The first was Permabond 910 available from Permabond Engineering Adhesives. This is a 100% methyl cyano-acrylate, single part, low viscosity, fast cure cyano-acrylate. The second was Loctite 411 brand adhesive made by Henkel Loctite Corporation. This is also a low viscosity, fast cure cyanoacrylate, specifically, a single part, ethyl cyanoacrylate.
In comparing the adhesion strength, as can be seen from samples 1-6 on Table 1, where no surface treatment was used, the Loctite 411 brand adhesive yields higher adhesion strength with an average failure torque value for the Permabond 910 brand adhesive of 16 and an average failure value of 19.3 for the Loctite 411 brand adhesive. Moreover, the Loctite 411 adhesive is lower in viscosity and easier to apply than the Permabond 910 adhesive.
Referring to sample or test number 7, when the gear was surface treated with sand blasting and the ethyl cyano-acrylate adhesive was used, the torque failure value was 40, which represents a significant increase in adhesion strength. Referring to samples 8-9, a two-part epoxy adhesive was used. Specifically, Scotch-Weld DP190 brand epoxy/amine adhesive, available from 3M Company was used. The DP190 brand epoxy adhesive had an average failure torque of 14, when no surface treatment was used. When a “primer only” surface treatment was used, the DP190 brand adhesive yielded failure torques of 20, referring to samples 10-11. When the gear was surface treated with sand blasting the DP190 adhesive yielded a failure torque of 15, as shown in sample 12, which compared unfavorably to a relatively high value of 40 for sample 7, in which Loctite 411 adhesive was used with a gear that had been surface treated with sand blasting. Referring to samples 12-13, the DP190 had relatively low failure values when surface treated with sand blasting and sand blasting plus primer, respectively. Referring to sample 14 a two-part acrylic adhesive was used. Specifically, 3M Scotch-Weld, DP-810 brand acrylic adhesive was used. As shown in sample 14, the DP-810 brand adhesive had a very low failure torque of 5, when tested without surface treatment, much lower than either the Permabond 910 or Loctite 411 adhesives when used without surface treatment.
The Table 1 torque tests also showed that in most cases the rupture surface was the plastic of the gear itself, rather than at the adhesion. This means that the gear broke before the adhesion surface was disconnected. As shown in Table 1, in all tests in which a cyano-acrylate adhesive was used, it was the gear itself that failed; not the adhesion. When the epoxy or acrylic adhesives were used, however, in only one instance did the failure result in the gear. All other failures (samples 8-12 and 14) were in the adhesion itself. The results of the tests as shown in Table 1 suggested that the cyano-acrylate adhesives were good candidates, with the Loctite 411 brand adhesive holding the most promise.
Referring to Table 2, new test samples 15-17 were prepared then tested using Loctite 411 adhesive in a thermal cycling chamber. Specifically, a TEST EQUITY 1000 SERIES brand temperature chamber was used, with the samples tested for 10 days with the following temperature cycle that repeated itself during the whole 10 days: (a) 20 minutes ramp up from 25-55 degrees C.; (b) 90 minutes at constant 55 degrees C.; (c) 30 minute ramp down from 55 degrees C. to 10 degrees C.; (d) 90 minutes at −10 degrees C.; (e) 20 minute ramp up −10 degrees C. to 25 degrees C. As can be seen from the results on samples 15-17, the adhesion strength essentially completely failed after the temperature cycle testing. It was observed by visual inspection that in every one of samples 15-17 the adhesive residues were held to the aluminum and none were held to the gear. As a result, it was believed that cyano-acrylates are too brittle for this application. Aluminum and the nylon have much different thermal expansion coefficients, and thus the shear forces on the adhesion surface are believed to be too strong to maintain a bond after temperature cycling of the type exemplified above. In order to overcome this problem, it was believed that surface treatment applied to the gear might reduce or eliminate this problem.
Four types of surface treatment were chosen to be tested: knurling, grooving, sand blasting and primer. All four surface treatments were thermal cycle tested against each other in the thermal cycling chamber. As can be seen from tests 18-20 in Table 2, the failure values for knurling, grooving and sand blasting after the thermal cycling were still significantly lower in comparison to the corresponding values obtained the day after the application of the adhesive, as shown on Table 1, samples 4-6. These results prompted use of primer and sand blasting. Specifically, Loctite 770 brand plastic primer was applied on the gear prior to applying the adhesive. Loctite 770 brand plastic primer is a cyano-acrylate, specifically, an aliphatic amine in a n-Heptane solution. The results are shown samples 21-23 on Table 2. The deterioration of the adhesion strength after the thermal cycle test was also shown to be significant, with the rupture taking place at relatively low values and at the adhesion.
Next, a flexible adhesive system was chosen in an attempt to compensate for the difference in thermal expansion coefficients between the nylon and the aluminum of the gear and drum, respectively. The epoxy adhesive that was tested was the flexible, dual component system DP190 from 3M and as an acrylic system the dual component DP-810 adhesive system from 3M was tested. As can be seen from sample 14 in Table 1, use of the DP-810 adhesive resulted in very low adhesion strength compared to the cyano-acrylates and epoxies. However, the DP190 flexible epoxy system resulted in much better performance than the acrylic system but still exhibited significantly lower failure values than did the cyano-acrylates system in failure testing conducted at time “Zero”, i.e., one day after the adhesive was applied, and as reported in Table 1.
Also, in order to promote the adhesion a different primer was added to the system as a surface treatment. The primer was DP190 adhesive diluted in iso-propanol at a 1:10 ratio. This high dilution ratio yielded a very low viscosity fluid and enabled application of the primer to the adhesion surface of the gear without concern that it would come out and contaminate the drum once the gear was inserted into the drum cylinder. As can be seen from samples 10-11 in comparison to samples 8-9 in Table 1, the presence of the DP190 primer promoted the adhesion significantly in comparison to the tests with the same adhesive but without a surface treatment. The DP190 adhesive and the DP190 adhesive-primer surface treatment system was then used and tested in the thermal cycles testing and using the same chamber and test procedure as referred to above. The results are reported in samples 24-27 in Table 2. Application of primer on the surface of the gear was shown to promote adhesion, but significant deterioration in adhesion strength remained after thermal cycling with and without primer.
A combination of media blasting and primer as a surface treatment was used and tested, with the results reported as sample 13 in Table 1. In this sample the gear plastic failed rather than the adhesion surface, and the bond strength was significantly higher than the samples that used DP190 adhesive and only one of the two surface treatments. The gear-drum assembly having the combination of primer and sand blasting as a surface treatment was then tested in the thermal cycling chamber under the test procedure referred to above. The results are reported in samples 29-34 on Table 2. It can be seen that not only did the bond strength not deteriorate over the time of the test period, but became stronger. As a result, the combination of both sand blasting and priming of the gear's surface was chosen as the most preferred surface treatment and this surface treatment in combination with the DP190 adhesive was chosen as the most preferred technique or method for adhesively attaching a gear to the drum.
In order to further evaluate bond strength in aggressive, corrosive conditions over time, sample gear-drum assemblies were tested in a walk-in temperature humidity chamber made by WATLOW SERIES F4S/D. This testing was conducted at 80% rH and 80 degrees F. for 14 days. The results are reported as samples 35-40 in Table 3. As shown in Table 3, bond strength greatly varies in these samples, but is still significantly higher than 5 ft. lb. standard that was determined by measuring the failure torque for the mechanical coupling of the original gear-drum assembly. From Table 3 it can be seen that the interface of rupture is affected by humidity as well as by thermal cycling and that most of the failures took place at the adhesion (samples 35-40, 43) rather than in the gear plastic (samples 41-42). Also, it may be seen from samples 41-43, the bond strength is very high and the interface of rupture is within the plastic (samples 41-41) or within the adhesion (sample 43), even when using only primer. As a result of the testing reported in Table 3, it is believed that the presence of humidity is not the main cause or even a significant cause of deterioration in bond strength. Even if humidity is significant in some instances, it appears that the flexible epoxy system is superior in adhesion strength to the cyano-acrylates system when performance over time is considered. Referring to sample 28, this sample shows that sand blasting alone as a surface treatment is not enough to yield a successful adhesion over time and that use of the DP190 adhesive was needed to yield successful adhesion over time.
As understood from the above reported results, cyano-acrylates have relatively low torque failure values in temperature cycling tests and the flexible epoxy adhesive, DP190 brand adhesive, performs the best. Even though cyano-acrylate adhesives perform very well, at start, that is soon after curing, torque failure value decreases significantly after thermal cycling. As a result of thermal cycle testing the most preferred process for attaching the gear to the drum includes surface treating the gear that includes a primer prior to applying adhesive. The preferred primer is DP190 adhesive-primer, available from 3M, and this is used when diluted in iso-propanol at a ratio of 1:10. The primer is preferably applied using a swab on the bond area and dried in ambient air for no less than 5 minutes. The dilution 1:10 was derived from the need to keep the primer thickness as thin as possible to prevent run-out of material as the gear is pushed inside the drum cylinder, but nevertheless to provide a useful surface treatment.
Application of the adhesives as reported in Tables 1-3 was conducted with the gear assembly apparatus or machine as illustrated in
Although specific embodiments of the invention have been described, various modifications, alterations, alternative constructions, and equivalents are also encompassed within the scope of the invention.
The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that additions, subtractions, deletions, and other modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the claims.
