Cylindrical and rotatable resonating assembly for use in electrostatographic applications

Abstract: A cylindrical and rotatable resonating assembly, generally for use in electrostatographic applications. The resonating assembly is preferably positioned along a longitudinal axis generally transverse to the process direction of movement of a toner bearing member, for applying uniform vibratory energy thereto. The cylindrical form of the resonating assembly allows for rotation of the assembly while remaining in contact with the image bearing member to reduce frictional forces between a contact surface of the resonating assembly and the image bearing member which, in turn, reduces wear of the resonating assembly as well as the image bearing member. The resonating assembly may include a plurality of discrete individual resonator elements, each including a vibratory energy producing segment, such as a piezoelectric transducer, for generating vibratory energy and a waveguide segment coupled to the vibratory energy producing segment for transporting the vibratory energy from the transducer to the image bearing member.

Description: The present invention relates generally to an apparatus for applying vibratory energy to an adjacent surface and, more particularly, relates to a cylindrical and rotatable resonating assembly useful in applying vibratory energy to a pliable or flexible surface, such as a belt type member as may be found in an electrostatographic printing machine. It has been found that various steps in the electrostatographic printing process can be enhanced through the use of vibratory energy, wherein vibratory energy is applied to a pliable or flexible surface having toner particles residing thereon. The vibratory energy operates to reduce the adhesive forces between the toner particles and the surface on which the toner particles reside to enhance the release of the toner particles from the surface. Alternatively, vibratory energy can be used to generate heat in the toner or a support surface for enhancing heat driven processes such as fusing. One exemplary process in which the application of vibratory energy has been shown to be particularly useful is the transfer step of the electrostatographic printing process. Generally, the process of transferring charged toner particles from an image bearing support surface, such as a photoreceptor, to a second support surface, such as a copy sheet or an intermediate transfer belt, is enabled by overcoming adhesion forces holding toner particles to the image bearing surface. In a conventional electrostatographic printing machine, transfer of toner images between support surfaces is accomplished via electrostatic induction using a corona generating device, wherein the second supporting surface is placed in direct contact with the developed toner image on the image bearing surface while the back of the second supporting surface is sprayed with a corona discharge. The corona discharge generates ions having a polarity opposite that of the toner particles, thereby electrostatically attracting and transferring the toner particles from the image bearing surface to the second support surface. Since the conventional process of transferring development materials to a copy sheet involves the physical detachment and transfer-over of charged toner particles from an image bearing surface to a second, the critical aspect of the transfer process focuses on applying and maintaining high intensity electrostatic fields and/or other forces in the transfer region in order to overcome the adhesive forces acting on the toner particles. The use of vibratory energy to assist in this process has been disclosed, for example in US-A-3,854,974, as a means for enhancing toner release from an image bearing surface. More recently, systems incorporating a resonator, suitable for generating focused vibratory energy, arranged along the back side of the image bearing surface for applying uniform vibratory energy thereto, have also been disclosed, as, for example, in US-A-4,987.456; US-A-5,005,054; US-A-5,010,369; US-A-5,016,055; US-A-5,081,500; and US-A-5,210,577. In such systems, toner transfer is enhanced due to the mechanical release of the toner particles from the image bearing surface so that effective toner transfer can occur despite the fact that the electric field alone in the transfer zone by itself may be insufficient to attract toner from the image bearing surface to the second support surface. Similar applications for advantageously utilizing vibratory energy in the electrostatographic printing process have been directed toward sonic toner release in a development subsystem as disclosed in US-A-4,833,503; acoustic cleaning assist as disclosed in US-A-5,030.999 and generating heat for ultrasonic fusing as disclosed in US-A-5,339,147. As disclosed in the above referenced patents, a typical resonator suitable for generating focused vibratory energy generally includes a transducer element coupled to a resonating waveguide member having an operational tip which is brought into contact with an adjacent surface for coupling the vibratory motion thereto. The shape of the waveguide member being designed to respond to the vibrational energy applied to the base thereof via the transducer so as to achieve a significant gain In vibrational motion at the operational tip of the waveguide. The resonator is situated such that the operational tip thereof is placed in intimate contact with the surface to which the vibrational energy is to be applied for inducing vibration thereof. The resonator device is generally fixedly positioned relative to the moving surface to which the vibrational energy is to be applied. For electrostatographic printing applications, it is essential that the vibratory motion transmitted from the resonator tip to the surface to be vibrated is uniform, since nonuniform vibratory motion can lead directly to image quality defects. Although nonuniformity in the vibratory motion may stem from nonuniform frequency response in a resonator assembly, it has been found that a number of problems related to nonuniformity develop as a result of for example, abrasive action caused by continuous motion of a moving surface i.e., a photoreceptor belt, against the fixedly positioned resonator tip causes excessive wear and deterioration of the resonator tip which, in turn, changes the resonant frequency thereof. In addition, in the case of an endless moving surface having a seam, the seam may generate a significant torque spike as it passes against the resonator tip, causing abrupt vibration along the moving surface. Since the vibratory energy is transmitted to a moving surface in contact with the vibratory energy producing member, it is also desirable to provide a vibratory energy producing member that reduces drag forces on the moving surface. Various concepts have been disclosed in response to the problems associated direct contact between the resonating waveguide and the surface to be vibrated. One exemplary solution is disclosed in commonly assigned US-A- 5,512,989, wherein a coupling cover is bonded to the exposed end of the resonator such that vibratory energy can be efficiently and effectively transmitted from a vibratory energy source to a surface without the problems typically associated therewith. In another solution, the resonator assembly includes a vacuum apparatus including a vacuum plenum defining an opening adjacent the image bearing member, the vacuum apparatus providing sufficient force at the vacuum plenum opening to draw the image bearing member toward the waveguide member and a coupling cover including a pair of resilient cap members, each cap member being mounted on the vacuum plenum along the opening thereof so as to be interposed between the vacuum plenum and the image bearing member. In addition to facilitating critical alignment specifications, this apparatus minimizes undesirable cross process direction components of vibration by introducing a coupling cover to the interface between a resonator and the image bearing surface. The present invention is directed towards an alternative solution to the problem of nonuniform vibratory energy caused, in particular, by the contact between the resonating waveguide and the moving surface and, more specifically, the wear and drag forces induced in the operational tip of a conventional stationary resonating waveguide member. Specifically, the present invention contemplates a cylindrical resonating assembly which may be rotatably mounted to reduce wear along the surface thereof. This cylindrical resonator assembly offers operational advantages, as well as manufacturing expediencies, over the conventional stationary resonating assemblies disclosed in the prior art. US-A-5065194 discloses a resonator made from a piezoelectric film wrapped around a tubular member. The film is in contact with a photosensitive belt but the tubular member and the piezoelectric film are both non-rotatable and energisation of the film merely causes an agitating or vibrating motion. FR-A-2280115 discloses a cylindrical rotatable resonator in contact with the front or back side of a photoconductive belt. In one embodiment the resonator includes a transducer divided into elements spaced around the surface of the cylindrical resonator to cause it to vibrate. In a first aspect, the invention consists in a cylindrical resonating assembly, including a rotatable shaft member, and a substantially cylindrical transducer mounted on said rotatable shaft member; characterised in that the shaft member is electrically conductive and coupled to an AC voltage supply providing an electrical bias to drive the transducer to thereby generate vibrational energy, and a substantially cylindrical resonating waveguide is mounted on said transducer and coupled thereto for transmitting the vibrational energy from said transducer. The transducer may include a piezoelectric material for generating vibratory energy in response to an electrical input, wherein the assembly further includes an A.C: voltage supply for providing the electrical input to said transducer. The cylindrical resonating assembly may further include a controllable voltage source coupled to each of said plurality of discrete transducer elements for providing an individual input to each of said plurality of discrete transducer elements for tailoring the vibratory energy output thereof. Preferably, each of the plurality of discrete transducer elements provides a substantially similar response amplitude in a predetermined operating bandwidth. Preferably, the resonating waveguide includes a uniform response waveguide segment having a substantially uniform cross-sectional axial dimension. Preferably, the resonating waveguide assembly includes a contoured response waveguide segment having an axial dimension along an interior portion thereof which is substantially less than an axial dimension along an exposed contact surface thereof. Preferably, the transducer includes a radially excited transducer segment having a dominant electrical expansion property in a direction equivalent to the substantially uniform vibratory energy output of said resonator means. Preferably, the transducer includes an axially excited transducer segment having a dominant electrical expansion property in a direction substantially transverse to the substantially uniform vibratory energy output of said resonator means. The cylindrical resonating assembly preferably further comprises bearing members for supporting said rotatable shaft to facilitate rotation thereof. In a further aspect, the invention consists In a system for enhancing release of particles from a substantially flexible surface moving in a process direction, including a resonating assembly for applying uniform vibratory energy to a moving surface, including a cylindrical resonating assembly according to the first aspect, adapted to contact the moving surface along an axis generally transverse to the process direction of travel thereof. In a still further aspect, the invention consists in an electrostatographic printing apparatus including a toner bearing surface moving in a process direction of travel and a cylindrical resonating assembly according to the first aspect having its substantially cylindrical resonating waveguide in contact with a backside of the toner bearing surface to, in use, mechanically reduce adhesive forces between toner particles and the toner bearing surface. These and other aspects of the present invention will become apparent from the following description in conjunction with the accompanying drawings, in which: Fig. 1 is a perspective view of a cylindrical rotatable resonating assembly in accordance with the present invention; Fig. 2 is a cross-sectional view taken along a diameter of one embodiment of a cylindrical resonating assembly in accordance with the present invention, illustrating a radially excited uniform waveguide transducer segment; Fig. 3 is a cross-sectional view taken along a diameter of an alternative embodiment of a cylindrical resonator in accordance with the present invention; illustrating a radially excited contoured response waveguide transducer segment; Fig. 4 is a cross-sectional view taken along a diameter of another alternative embodiment of a cylindrical resonator in accordance with the present invention, illustrating an axially excited uniform waveguide transducer segment; Fig. 5 is a cross-sectional view taken along a diameter illustrating an axially excited contoured response waveguide transducer segment; Figs. 6 to 8 are plan views of various arrangements for providing a segmented cylindrical resonator in accordance with the present invention; Fig. 9 is a plan view of an arrangement providing a partially segmented cylindrical resonator in accordance with the present invention; and Fig. 10 is a schematic side view of an illustrative electrophotographic reproducing machine including an exemplary transfer station incorporating the cylindrical and rotatable resonator of the present invention. For a general understanding of an exemplary printing machine incorporating the features of the present invention, a schematic depiction of the various processing stations of an electrostatographic printing machine is provided in Figure 10. It will be understood that although the cylindrical and rotatable resonator arrangement of the present invention is particularly well adapted for use in a vibrationally assisted image transfer subsystem as depicted herein, the present invention is not necessarily limited in its application to a transfer subsystem and may also be useful in other subsystems in which particle adhesion/cohesion forces are desirably reduced, such as development, fusing, or cleaning subsystems, for example. In addition, the cylindrical and rotatable resonating assembly of the present invention is equally well suited for use in a wide variety of other known printing systems as well as other non-printing related systems, devices and apparatus, wherein vibrational energy may be advantageously applied to a moving surface. The construction of the machine of Fig. 10 is well known in the art and, for conciseness, a detailed description thereof has been omitted from the present disclosure. For further details, reference is made to U.S. application S.N. 08/689,166, a copy of which was filed with the present application, in which the machine described with reference to Fig. 10 thereof. With particular reference to the principle of enhanced toner release as provided by a vibratory energy assisted transfer system, the exemplary transfer station D of Figure 10 also includes a cylindrical and rotatable resonator in accordance with the present invention, comprising a vibratory energy producing device or resonator 100 which may include a relatively high frequency transducer element driven by an AC voltage source 98. The resonator 100 is arranged in contact relationship with the back side of belt 10 for applying vibratory energy thereto so as to shake and loosen the developed toner particles on the belt while in imagewise configuration. This vibratory energy induces mechanical release of the toner particles from the surface of the belt 10 by dissipating the attractive forces between the toner particles and the belt 10. Preferably the resonator 100 is situated at a position corresponding to the location of transfer corona generator 44 so that the loosened toner particles are simultaneously influenced by the electrostatic fields generated by the transfer corotron for enhancing the transfer process. In a preferred arrangement, the resonator 100 is configured such that the vibrating surface in contact with the belt is transverse to the direction of movement 16 of the photoconductive belt 10. Since the belt 10 has the characteristic of being nonrigid and somewhat flexible or pliable, to the extent that it can be effected by the vibrating motion of the resonator 100, vibration thereof causes mechanical release of the toner from the surface of belt 10 which, in turn, allows for more efficient electrostatic attraction of the toner to a copy sheet during the transfer step. In addition, vibratory assisted transfer, as provided by resonator 100, also provides increased transfer efficiency with lower than normal transfer fields. Such increased transfer efficiency yields better copy quality, as well as improved results in toner use and a reduced load on the cleaning system. As previously discussed, exemplary vibratory transfer assist subsystems are described in US-A-4,987,456; US-A-5,016,055 and US-A-5,081,500, among various other commonly assigned patents. Further details of vibratory assisted toner release in electrostatographic applications can also be found in an article entitled "Acoustically Assisted Xerographic Toner Transfer", by Crowley, et al., published by The Society for Imaging Science and Technology (IS&T) Final Program and Proceedings, 8th International Congress on Advances in Non-Impact Printing Technologies, October 25 - 30, 1992. While the above cited references will show that vibratory motion enhanced transfer systems are known, the present invention provides that the resonator 100 is provided in the form of a cylindrical and rotatable apparatus, thereby reducing drag forces between the belt and the resonator and, if so desired, permitting rotation of the resonator in the process direction movement of belt 10 such that friction forces therebetween are minimized for preventing wear of the resonator 100. The specific details of the cylindrical and rotatable resonating apparatus of the present invention will be described hereinbelow. As previously discussed, the principle of enhanced toner release as provided by the vibratory energy assisted transfer system described hereinabove is facilitated by a relatively high frequency cylindrical resonator 100 situated in intimate contact with the back side of belt 10, at a position In substantial alignment with transfer corotron 44. It will be recognized that the cylindrical resonator can be advantageously utilized to impart vibratory energy directly to toner particles residing on the resonator, as in a development system as described in the prior art cited herein. In addition, the cylindrical resonator 100 can be used to generate heat in a substrate or directly to toner particles for fusing and fixing applications as known in the prior art. With particular reference to FIG. 1, the resonator 100 may include a transducer element 90 having a waveguide member 92 which is press fitted or otherwise bonded to the transducer 90. In a preferred embodiment, the transducer 90/waveguide 92 combination making up the resonator 100 is further mounted on a conductive shaft 89 which is further coupled to a power supply such as an A.C. voltage source 98 generally operated at a frequency between 20 kHz and 200 kHz and typically at a frequency of approximately 60 kHz for providing an electrical bias to drive transducer element 90. It will be understood that various frequencies outside of the stated range of 20 kHz and 200 kHz may be utilized depending on the application and environment in which the resonator is being utilized. The shaft 89 generally provides a fixed support for the cylindrical resonator and may provide an axis of rotation for the cylindrical resonator. In this regard, it will be recognized that the cylindrical resonator of the present invention may be configured so as to be a stationary element or as an element that rotates with the transport motion of the belt 10 or surface with which it is in contact. The stationary configuration yields reduced drag relative to prior art devices and allows for exploitation of manufacturability advantages, while rotation of the resonator provides additional reduced friction to further reduce wear of the waveguide member 92. In addition, the rotating configuration assumes that the cylindrical resonator may be rotated merely by frictional forces generated due to cooperative engagement with the moving surface or may be driven into rotational motion by means of a drive source (not shown) such as a drive motor coupled to shaft 89. The transducer 90 is preferably provided in the form of a piezoelectric material which may be fabricated, for example, from lead zirconate titontate or some form of piezopolymer material. The waveguide member 92, on the other hand, is preferably fabricated from aluminum or various other materials including certain polymers. As shown in FIG. 2, for example, the waveguide member 92 comprises a base portion 96 interfacing with the piezoelectric transducer 90, and an exposed contact surface 99 for contacting the surface to which the vibratory energy from the transducer 90 is to be conveyed. Practical embodiments of a radially excited resonator, as described above, have been reduced to practice by boring a hole in a cylindrical waveguide for receiving a piezoelectric tube therein. In practice, the bore is slightly undersized (e.g. 0.001 to 0.002 inches (25 to 50µm) on the diameter), and the waveguide is heated to provide an expansion of the bore such that the piezoelectric tube may be easily slid into the waveguide bore. Thereafter, upon cooling to room temperature, an intimate compressive fit is achieved between the piezoelectric tube and the cylindrical waveguide for providing an intimate coupling therebetween without the need for adhesive layers. Alternatively, the piezoelectric material can be applied directly to the inner surface of the waveguide by some direct coating method. For example, copolymers of polyvinylidene fluoride (PVDF) could be coated along the inside surface of a waveguide cylinder through the use of spincasting techniques. Of course, this approach would require that the PVDF coating would be subsequently poled with electrostatic fields to provide the material with piezoelectric characteristics. It has been previously shown in the prior art that the advantages and improvements to the electrostatographic process that result from the application of vibratory energy are directly related, at least in part, to the frequency of the vibrational energy applied to the surface on which the toner particles reside, and, perhaps more importantly, to the substantial uniformity of the vibrational energy along the process width of the surface. This characteristic is directly related to the uniformity of the frequency response of the resonator 100 along the length thereof. For example, in an acoustically assisted transfer apparatus, nonuniform frequency response along the length of the resonator results in nonuniform transfer characteristics and may yield inconsistent image quality of output copies. It has also been noted, particularly in the prior art cited herein, that the root problem of such nonuniformity is that mechanical behavior in one dimension effects mechanical behavior in other dimensions, such that the key to uniform frequency response and vibration amplitudes across an ultrasonic resonator of the type used to enhance and enable electrophotographic processes is the decoupling of desired axial resonator motion (motion perpendicular to the surface to be vibrated) from undesirable transverse motion (motion in the cross process direction, parallel to the surface to be vibrated). Such decoupling has been accomplished by segmentation of the transducer and/or waveguides in order to minimize the effect of the undesirable transverse modes along the length of the resonator. Thus, although it is highly desirable, for manufacturing and application requirements, to provide the resonator in the form of a unitary structure, it is also known to segment the resonator into individually vibrating portions for providing improvements to process width vibration uniformity as well as to increase velocity response across the waveguide. As shown in the illustrative embodiment of FIG. 1, the waveguide member 92 may be provided with a series of radial slots positioned along the length of the resonating waveguide and/or the transducer. These radial slots segment the resonator 100 for creating the effect of a plurality of resonating elements to eliminate, or at least minimize, the effect of the undesirable transverse modes of vibrational energy along the length of the resonator. In fact, the resonator 100 may be made up of a plurality of individually excited and discrete waveguide segments which may enable alternative embodiments as well as additional advantageous effects, as will be discussed. In accordance with one embodiment of the present invention, a plurality of cylindrical segmented transducer/waveguide segments are assembled along a single axis to form a full-width resonating apparatus for applying uniform vibratory energy across the entire process width of an image bearing surface. In the most fundamental form, each resonating element includes a waveguide in the form of a so-called uniform waveguide segment having a uniform cross sectional dimension along the width thereof, as shown in the cross-sectional view of FIG. 2. This figure Illustrates a radially excited transducer segment wherein the orientation of the dominant electrical expansion property of the piezoelectric transducer segment 90 is in the direction of the desired transducer output as indicated by the vertical arrows 102 and 104. In the case of the radially excited uniform waveguide resonator of FIG. 2, piezoelectric transducer 90 generates electrical expansion which, in turn, produces piston-like motion at the contact surface 99 of the waveguide member 92. In an exemplary embodiment of a radially excited transducer segment, a one-half inch (12.7mm) length portion of one inch (25.4mm) outside diameter aluminum waveguide was provided with a one quarter inch bore. Correspondingly, a one-half inch (12.7mm) length of .251 inch (6.38mm) outside diameter piezoceramic element, for example PZT5A available from Morgan Matroch Inc. of Bedford, Ohio, having a wall thickness of approximately .020 inches (5.1mm) was inserted inside the bore of the aluminum waveguide. This particular device exhibited a radial mode resonance frequency of approximately 114 kilohertz with a surface vibrational velocity of 4.4 inches per second per volt (11.2cm/sec/V), as determined via finite element analysis. In this radially excited embodiment, the electrical expansion property is in the same direction as the desired resonator output, as illustrated by the phantom line 103. However, as can be seen from this diagrammatic representation of the resonator output 103, a phenomenon known as "edge effect fall off' characterizes the frequency response of the resonator. This edge effect fall off results from the well-known "Poisson effect" exhibited by all three-dimensional mechanical continuum, wherein expansion in one direction results in dilation in the direction orthogonal to the expansion direction Thus, as shown in FIG. 2, notwithstanding the use of segmentation discussed hereinabove, the frequency response, and resultant vibratory energy produced by the waveguide may be significantly non-uniform. The edge effect fall off phenomenon described above produces yet another source of non-uniform frequency response along the length of the resonator, and also tends to dissipate the energy associated with the resonant condition of the waveguide such that the energy applied to the transducer does not yield maximum frequency response. This outcome can be minimized or eliminated by providing a so-called contoured response waveguide, as shown in FIG. 3. In this alternative embodiment of the present invention, a significant alteration is made to the waveguide segment 92 wherein the axial dimension of a portion of the waveguide is made to be significantly smaller than the longitudinal dimension of both the base 96 and the exposed contacting surface portion 99. This waveguide segment geometry has been shown to minimize or eliminate the edge effect fall off phenomenon as shown digramatically by phantom line 103 such that a more uniform frequency response output is achieved. In addition, in the case of the cylindrical resonator of the present invention, the operating frequency of a contoured response waveguide can be made to be independent of the waveguide diameter such that the specific contoured response waveguide dimensions can be varied without varying the radial dimension thereof to optimize frequency response and uniformity. FIGS. 4 and 5 show additional alternative embodiments of the cylindrical and rotatable resonating assembly of the present invention, wherein an "axially" excited transducer is provided as opposed to the previously described "radially" excited transducer. Axially excited transducers are constructed using piezoelectric disks 91 situated in abutment with a portion of the side edge of the resonating waveguide member 92, wherein the orientation of the dominant electrical expansion property of the piezoelectric disk 91 is in a direction orthogonal to the transducer output direction. Thus, in FIGS. 4 and 5, the electrical excitement of transducers 91 generate vibrational energy along the base of the waveguide in the direction of horizontal lines 106 which, in turn, generates vibrational energy in the direction of vertical lines 108 along the contact surface 99 of the resonator element. An outline of the piston-like motion of the contact surface 99 generated by the axially excited transducer member 91 is again illustrated by phantom line 103. Moving now to FIGS. 6-8, various preferred embodiments for a cylindrical and rotatable resonating assembly for use in electrostatographic applications as contemplated by the present invention are shown, wherein a plurality of narrow-width cylindrical transducer/waveguide member assemblies are stacked together on a common shaft 89 to produce a full-width cylindrical resonating assembly in accordance with the present invention. It will be understood that shaft 89 provides a common longitudinal axis of rotation for the cylindrical and rotating resonator of the present invention, wherein the axis of rotation is generally transverse to the process direction of travel of the surface to be vibrated. With particular reference to FIG. 6, a radially excited segmented uniform waveguide is illustrated, wherein a plurality of narrow width cylindrical uniform waveguide elements 92 are mounted on a singular piezoelectric transducer element 90, which, in turn, is situated on a common . shaft 89 for producing a full-width cylindrical resonating assembly 100. The shaft 89 can be implemented via various techniques and methods as, for example, by means of an insert molded polymeric resin cast directly into the assembly or as a solid rod inserted therethrough. The shaft 89 is normally supported by bearing members 88 located at opposite ends of the shaft 89 to allow for rotation of the resonating assembly. Preferably, a relatively low modulus material is utilized in the fabrication of the shaft 89 so as to retain isolation between the segments of the resonator. The shaft can be of a homogeneous nature or may be provided in the form of a composite, having a lower modulus layer in contact with the piezoelectric transducer element 90 for further assuring the isolation between resonating segments. Even further isolation may be provided by inserting polymer spacers or washers (not shown) in between each discrete resonator segment. The shaft may preferably be fabricated from an electrically conductive material in order to provide a common electrode for electrical contact to the piezoelectric material of the transducer. One alternative assembly method which lends itself, in particular to the axially excited embodiment described herein includes the use of a shaft 89 which is threaded at opposite ends thereof, wherein a washer 87 and nut 86 combination is secured to each opposed threaded shaft end for applying a sufficient load to compress the plurality of resonator segments mounted thereon, as shown in FIG. 7. Thus, a plurality of axially excited contoured response waveguide members 92 are mounted on the shaft 89 with the interface between each waveguide member being sufficiently compressed to provide vibrational connectivity between each segment. FIG. 7 shows a configuration which is particularly useful for high energy applications such as ultrasonic fusing, wherein the interface between each waveguide segment comprises an individual piezoelectric disc 91. Alternatively, relatively low energy applications such as vibratory assisted development and/or transfer may be more economically facilitated by providing axial piezoelectric elements only at each end of the assembly as shown in the embodiment of FIG. 8. In this embodiment, each waveguide segment interfaces directly with an adjacent waveguide segment for allowing vibrational energy from the piezoelectric discs at each end of the shaft to be transported across each segment via the compressed interface of each waveguide element. In yet another alternative embodiment, the resonator assembly 100 may be provided in a partially segmented embodiment as depicted in FIG. 9. Similar to the configuration of Fig. 8, piezoelectric discs are compressed on both ends of the resonator assembly via a shaft 89 and nut/washer combination. This partially segmented configuration provides a continuous interface between segments of the resonator assembly. It will be recognized that the shaft of this partially segmented configuration could be completely eliminated by providing threaded ends of each end of the partially segmented resonator assembly. While full segmentation may yield ideal overall vibrational uniformity, partial segmentation along the length of the resonator element may be preferred for manufacturing processing (in the case of blade type transducer designs). However, the geometry of cylindrical transducer elements of the present invention also tends to eliminate the manufacturing difficulties of fully segmented blade waveguides such that the cylindrical geometry of the present invention may be advantageously exploited to enable complete segmentation of the waveguide member. As previously discussed, it is highly desirable for the resonating assembly 100 to produce a uniform response along its length for preventing image defects caused by nonuniform transfer characteristics. Although the embodiments shown and described herein have been shown to be effective in providing a full length resonator having substantially uniform frequency response across the length thereof, it has been found that the frequency response and the uniformity of the vibratory energy generated thereby may also vary due to variations in the response to the same or similar electrical input signals. Thus, in order to meet uniformity requirements one might measure the amplitude of response to a common input signal for each individual resonator element prior to inclusion into a given resonating assembly, whereby the given resonating assembly would be made up exclusively of resonator elements having the same or substantially equivalent response amplitudes in a predetermined operating bandwidth. Alternatively, discrete resonator elements can be combined in a resonating assembly regardless of individual amplitude output or frequency response to provide a resonating assembly providing uniform vibratory energy by providing separate and independent voltage potentials to each discrete resonator element. This approach is demonstrated in commonly assigned US-A-5,512,990 and can be facilitated by providing a separately controllable voltage source coupled to individual transducer segments 90 associated with each resonator element 92. In a preferred embodiment, individual contact leads-may be coupled to each transducer element 90 which, in turn, are connected to a circuit board comprising a series of variable resistors which may be remotely controlled through the system controller or some other software controlled microprocessor. The output of each discrete resonator element is adjusted and set via the controller to a predetermined value. Thus, in this alternative embodiment, each resonator element is individually provided with an input voltage in order to tailor the frequency response and amplitude of each element such that each of the plurality of resonator elements provides a substantially uniform frequency response characteristic in a predetermined operating bandwidth. Preferably, the response and amplitude of each element is tailored to produce uniform vibratory energy across the process width of the belt such that nonuniform frequency response in each element may be compensated to produce a resonating assembly having a uniform frequency response across the entire length thereof. It will be understood that the cylindrical resonator assembly of the present invention may be configured in association with a vacuum plenum (not shown) arrangement, including a vacuum supply (not shown) and/or a resonator coupling cover, as shown in the patents referenced herein. In this arrangement, the resonator assembly 100 would be enclosed by a generally air tight vacuum plenum defined by upstream and downstream walls sealed at either end at inboard and outboard sides thereof with the walls of the vacuum plenum extending to a common plane for forming an opening in the vacuum plenum adjacent to the photoreceptor belt 10. The vacuum plenum is coupled to a vacuum or negative air pressure source such as a diaphragm pump, so that the surface to be vibrated is drawn into contact with the resonator for imparting the vibratory energy thereto. This arrangement provides positive contact engagement between the resonator 100 and the photoreceptor 10, while maintaining continuity along the region of contact between the resonator 100 and the belt 10, without regard for irregularities in the contact surface of the resonator.

Claims: A cylindrical resonating assembly (100), including a rotatable shaft member (89); and a substantially cylindrical transducer (90,91) mounted on said rotatable shaft member (89); characterised in that the shaft member (89) is electrically conductive and coupled to an AC voltage supply (98) providing an electrical bias to drive the transducer to thereby generate vibrational energy, and a substantially cylindrical resonating waveguide (92) is mounted on said transducer (90,91) and coupled thereto for transmitting the vibrational energy from said transducer (90,91). The cylindrical resonating assembly (100) of claim 1, wherein said transducer (90) includes a piezoelectric material for generating the vibrational energy in response to the electrical bias. The cylindrical resonating assembly (100) of claim 1 or claim 2, wherein said A.C. voltage supply (98) provides a voltage having a frequency between 20 kHz and 200 kHz, and more preferably at 60 kHz. The cylindrical resonating assembly (100) of any one of claims 1 to 3, wherein said substantially cylindrical resonating waveguide includes a partially segmented body defining a plurality of radial slots extending from an external surface (99) of said waveguide (92) toward said substantially cylindrical transducer (90,91). The cylindrical resonating assembly (100) of any one of claims 1 to 4, wherein said substantially cylindrical resonating waveguide includes a plurality of discrete cylindrical resonating elements (92) arranged along a substantially common plane. The cylindrical resonating assembly (100) of claim 5, wherein said substantially cylindrical resonating waveguide further includes a plurality of discrete cylindrical transducer elements (90,91) each associated with one of said plurality of discrete cylindrical resonating elements (92). A system for enhancing release of particles from a substantially flexible surface moving in a process direction (16), including a resonating assembly for applying uniform vibratory energy to a moving surface (10), induding a cylindrical resonating assembly (100) according to any one of claims 1 to 6, adapted to contact the moving surface (10) along an axis (89) generally transverse to the process direction (16) of travel thereof. An electrostatographic printing apparatus including a toner bearing surface (10) moving in a process direction (16) of travel and a cylindrical resonating assembly (100) according to any one of claims 1 to 6 having its substantially cylindrical resonating waveguide (92) in contact with a backside of the toner bearing surface (10) to, in use, mechanically reduce adhesive forces between toner particles and the toner bearing surface (10).

Inventors: MASHTARE DALE R, NOWAK WILLIAM J, SNELLING CHRISTOPHER, MASHTARE, DALE R., NOWAK, WILLIAM J., SNELLING, CHRISTOPHER
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1997
Main classification: G03G15
IPC codes: B06B1, G03G15, B06B3