Abstract:
A sheet cleaning apparatus having sets of cleaning rollers, wherein the rollers are integrated into a removable cartridge structure. Couplers are provided at roller shaft ends to connect to the roller drive. The cartridge is received in a slide carriage, permitting the cartridge to be readily removed from the apparatus by sliding the carriage out, and lifting the cartridge out from the slide carriage. With this arrangement, the down time for the sheet cleaning apparatus is minimized, since the sheet cleaning apparatus can be provided with two cartridges, and the cartridge needing maintenance can simply be quickly removed and replaced with a fresh cartridge. The production line can quickly be put back into operation, and the removed cartridge can be serviced off line for subsequent use.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to an improved apparatus for cleaning dust and other surface particulate contaminants from material in sheet form. 
     BACKGROUND OF THE INVENTION 
     This invention is an improvement to the sheet cleaning apparatus described in U.S. Pat. No. 5,349,714, the entire contents of which are incorporated herein by reference. These apparatus are typically arranged in a printed circuit board production line, with other, very expensive machines. When the sheet cleaning apparatus needs servicing, typically to clean the sheet cleaning rollers (52, 54, 56, 58, shown e.g. in FIG. 8), the apparatus must be disassembled to remove the rollers, or the operator must clean the rollers in place. With either technique, considerable time is required for this maintenance procedure, idling not only the sheet cleaning apparatus but the other, very expensive machines on the production line. 
     It would therefore be advantageous to provide a sheet cleaning apparatus which can be quickly serviced to minimize the machine down time. 
     SUMMARY OF THE INVENTION 
     To overcome the foregoing problems, a sheet cleaning apparatus is described, having one or more sets of cleaning rollers, wherein the rollers are integrated into a removable cartridge assembly. Couplers are provided at roller shaft ends to connect to the roller drive. The cartridge assembly is held in a slide carriage, permitting the cartridge assembly to be readily removed from the apparatus by sliding the carriage out, and lifting the cartridge out from the slide carriage. With this arrangement, the down time for the sheet cleaning apparatus is minimized, since the sheet cleaning apparatus can be provided with two cartridges, and the cartridge needing maintenance can simply be quickly removed and replaced with a fresh cartridge. The production line can quickly be put back into operation, and the removed cartridge can be serviced off line for subsequent use. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     These and other features and advantages of the present invention will become more apparent from the following detailed description of an exemplary embodiment thereof, as illustrated in the accompanying drawings, in which: 
     FIG. 1 is a front view of a sheet cleaning apparatus embodying the invention. 
     FIG. 2 is a side cross-sectional view taken along line 2--2 of FIG. 1. 
     FIG. 3 is a side view illustrating the relative orientation of the sheet cleaning rollers and the roller cleaning adhesive rolls. 
     FIG. 4 is a simplified perspective view illustrating an exemplary motor/gear drive arrangement for driving the roller couplers. 
     FIG. 5 illustrates the sheet cleaning apparatus with the roller cartridge exposed and removed from the cartridge slide arrangement for replacement. 
     FIG. 6 is an exploded view of the drive end of the cartridge roller assembly. 
     FIG. 7 is an isometric view of a roller lifting device employing in the apparatus of FIG. 1 to bias the position of the upper set of sheet cleaning rollers upwardly for separation from the lower set of sheet cleaning rollers when the apparatus is not in use. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1-7 illustrate an exemplary embodiment of a sheet cleaning apparatus 50 embodying the invention. The apparatus 50 includes two pairs of sheet-contacting cleaning rollers 52, 54 and 56, 58. Rollers 52 and 54 are disposed in vertical alignment adjacent each other to define a nip 62. The surfaces of the cleaning rollers 52, 54, 56, 58 are defined by a layer of resilient compressible material which has a surface tack or adhesion sufficient to transfer dust and other foreign particulate contamination from a sheet coming into compressive contact with the roller surface. It is also desirable that the roller surfaces be smooth, in order to obtain complete contact with the surface of a sheet pressed against the surface. Typically, the roller surfaces will have a Shore A durometer value of up to 35. 
     In order to clean the surfaces of the sheet cleaning rollers 52-58, rolls 64, 66 of adhesive-coated tape are provided. These rolls 64, 66 are disposed so as to be in contact with respective surfaces of rollers 52-58 during sheet cleaning operations, as shown in FIG. 3. In a general sense, the rolls 64, 66 are defined by rolls of tape having the adhesive coating on the outward facing sides. The external surface of each of the rolls 64, 66 has a surface tack which greatly exceeds the surface tack of the sheet cleaning rollers 52-58, in order to transfer the foreign particles from the sheet cleaning rollers 52-58 to the surfaces of rolls 64, 66. 
     To the extent just described, the apparatus 50 is similar to that described in U.S. Pat. No. 5,349,714. 
     The apparatus 50 includes a system for applying a variable preload force, urging roller 64 into engagement with surfaces of rollers 52 and 56, and urging roller 66 into engagement with surfaces of rollers 54 and 58. The system includes pneumatic cylinders 100 and 102 which support the lower tape roller 66, and pneumatic cylinders 104 and 106 which apply pressure to the upper tape roller 64. Cylinder 100 includes a rod 100A driven by a cylinder piston to an extended position. The rod is attached to a coupler 100B which has an opening into which an end of shaft 67 carrying roll 66 is inserted. Cylinder 102 includes rod 102A driven by a cylinder piston to an extended position. Rod 102A is attached to a coupler 102B which has an opening into which the opposed end of shaft 67 is inserted. The roll 66 is therefore supported by the system comprising cylinders 100 and 102 and couplers 100B and 102B. The cylinders 100 and 102 are single acting, spring biased devices, wherein the rods are spring biased to the fully retracted position, and the rods are extended against the bias when pneumatic pressure is applied to the cylinders. Further the compression contact force of the roll 66 in relation to the sheet cleaning rollers 54 and 58 is adjustable by adjusting the pneumatic pressure applied to the cylinders 100 and 102. 
     The system further includes pneumatic cylinders 104 and 106 which apply pressure to the upper tape roller 64. Cylinder 104 includes a rod 104A driven by a cylinder piston to an extended position. The rod is attached to a coupler 104B which has an U-shaped opening into which a portion of shaft 65 carrying roll 64 and adjacent a shaft end is received. Cylinder 106 includes rod 106A driven by a cylinder piston to an extended position. Rod 106A is attached to a coupler 106B which has an opening into which a portion of shaft 67 adjacent the opposite end of the shaft is received. The cylinders 104 and 106 are single acting, spring biased devices, wherein the rods are spring biased to the fully retracted position, and the rods are extended against the bias when pneumatic pressure is applied to the cylinders. Further the compression contact force of the roll 64 in relation to the sheet cleaning rollers 52 and 56 is adjustable by adjusting the pneumatic pressure applied to the cylinders 104 and 106. 
     The shaft 65 is carried by spring-loaded bracket assemblies 72 and 74. Exemplary bracket assembly 72 is illustrated in FIG. 7, and includes outer bracket fixture 72A, sliding bracket 72B which fits within the outer fixture for sliding movement, and bias spring elements 72D and 72E. The spring elements bias the relative position of the sliding bracket 72B to the upper position shown in FIG. 7, and upon application of force, the springs are compressible to permit the bracket 72B to slide down. Assembly 74 is identical to assembly 72. Together, these assemblies bias the upper tape roll 64 to an elevated position out of contact with the cleaner rollers 52, 56 when the machine is idle, i.e. when the pneumatic pressure for the cylinders 104 and 106 is released. This prevents the tape roll surface from adhering to the cleaner roller as a result of extended stationary contact. When the pneumatic pressure is removed from the cylinders 100, 102, the lower tape roll 66 drops by force of gravity out of contact with the lower set of cleaner rollers 54, 58, and is supported by a V-shaped cradle in brackets 76, 78. No spring biasing is employed in connection with brackets 76, 78, since such biasing would tend to keep the tape roll surface in contact with the surfaces of the lower cleaner rollers after the pneumatic pressure is released. 
     In accordance with an aspect of the invention, the cleaner rollers are arranged in an easily removable cartridge assembly 120. The assembly 120 is mounted on a slide assembly 130 which permits the cartridge assembly to be moved from a working position, with the cleaner rollers in position within the apparatus 50 for operation, and a maintenance position (shown in FIG. 5) with the cleaner rollers and the cartridge assembly slid outside the housing 50A of the cleaner apparatus 50 for ready replacement of the cartridge 120. 
     As shown in FIG. 5, the slide assembly 130 includes a carriage member 132 which receives the cartridge assembly 120. Four mounting tabs 122 on the carriage assembly have holes 122A formed therein. The cartridge assembly 120 is dropped and locked into position on the carriage 132, with pins 134 extending upwardly from the carriage 132 and received through holes 122A registering the position of the cartridge 120 on the carriage 132. The cartridge assembly is locked into position by spring-loaded locking tabs (not shown) formed with the pins 134, which locking tabs spring out after cartridge assembly has dropped onto the pins to lock the cartridge in position. This prevents the cartridge from being lifted from the carriage by the tackiness of the roll 64 as pressure is released from the pneumatic system. Other types of locking arrangements can readily be employed. The carriage 132 is mounted between a first set of opposed slide rails 136A, 136B, which in turn are mounted on a second set of opposed slide rails 138A, 138B. The second set of rails 138A, 138B are mounted on bearings (not shown) mounted to the housing 50A to permit the second set of rails to slide outwardly also. The first set of rails is mounted on bearings to permit telescoping of the first and second sets of rails. The slide rails and bearings are parts of a commercially available slide assembly, such as the three-section linear drawer slides marketed by Jonathan Company, Fullerton, Calif., which lock in both the closed and open positions. 
     The cartridge assembly 120 is shown in further detail in FIG. 6. Side rails 124A, 124B and end rails 126A, 126B form a carriage structure which carries the lower set of cleaner rollers 54, 58. The rollers rotate on respective shafts 54A, 58A which in turn are mounted on bearings fitted in openings formed in the end rails. For example, bearings 126AA and 126AB are mounted in end rail 126A. Only the drive end of the carriage assembly 120 is visible in FIG. 5. The lower set of rollers are driven by a motor drive 150 (FIGS. 1 and 4) through a drive coupler 160. The roller shafts 54A, 58A have flats 54AA, 58AA formed adjacent the shaft ends to form D-shaped shaft ends for mating with corresponding D-shaped openings 162A, 164A formed in hexagonal male coupler elements 162, 164 to prevent rotation of the coupler elements on the shafts, while permitting axial sliding movement of the coupler elements on the shafts. Springs 166A, 166B are fitted on the shafts and extend between an end surface of rail 126A and the coupler elements 162 and 164 to urge the coupler elements away from the end surface of rail 126A. Snap rings 168A, 168B lock into position in grooves 54AB and 58AB to lock the coupler elements 162, 164 onto the shafts, after assembly of the springs 166A, 166B and the coupler elements onto the shafts. The coupler elements 162, 164 are formed with conical end surfaces 162B, 164B which act as lead-in surfaces to align the male hexagonal coupler elements with corresponding female driven hexagonal coupler elements 170, 172 shown in the isolation perspective view of FIG. 4. The driven coupler elements are mounted on shafts 174, 176. Sprocket gears 178, 180 are mounted on the respective shafts 174, 176, and have an endless chain 182 mounted thereon. The shaft 176 also has a beveled gear 184 mounted thereon, which meshes with beveled gear 186 mounted on the motor shaft 188. The cleaner rollers 54, 58 are driven in the same direction by the motor drive 150. 
     The upper cleaner rollers 52, 56 are not actively driven. Referring again to FIG. 6, the upper rollers are mounted to the cartridge assembly 120 by upper end rails 127A, 127B. The roller shafts 52A, 56A are received in corresponding bores (e.g. 127AA, 127AB) formed in the upper end rails. The upper end rails are slidably mounted on pins 128A, 128B which are received in bores (e.g. bores 127AC, 127AD) formed in the upper end rails. Springs (e.g., springs 129A, 129B) can be fitted on the pins to provide a bias force tending to separate the upper end rails 127A, 127B from the lower end rails 126A, 126B. This in turn biases the upper set of cleaner rollers 52, 56 away from the lower set of rollers 54, 58. The upper set of pneumatic cylinders 104, 106 can exert a force on the tape roll 64 to push the upper set of rollers toward the lower set of rollers. The bias action of the springs, biasing the upper set of rollers away from the lower rollers and therefor tending to increase the nip gap, provides the advantage of facilitating the cleaning of thicker sheets for cleaning without adjusting the apparatus. For some applications, it is preferable to omit the springs fitted on the pins. 
     The cleaning apparatus employs a pneumatic supply and control system similar to that described in U.S. Pat. No. 5,349,714, and illustrated at FIG. 9. Similarly, the control circuit of FIG. 10 in U.S. Pat. No. 5,349,714 can be employed to control the motor drive 150. The pneumatic supply and control system and the motor drive control circuit therefore need not be described in further detail herein. 
     The cartridge assembly 120 can easily be replaced with a fresh cartridge. This can be done by releasing the pressure on the pneumatic cylinders 100-106, so that the tape rolls move out of engagement with the cleaner rollers 52-58. The latch of the slide assembly is then released, and the carriage 132 is pulled from the operating position to the maintenance position shown in FIG. 5. As the carriage is pulled out away from its operating position, the drive coupler elements 162, 164 become disengaged from the mating coupler elements 170, 172, thereby disconnecting the cartridge from the motor drive 150. The cartridge 120 is then removed, without the use of tools in this exemplary embodiment, by lifting the assembly up and out of engagement with the pins 134. Once the cartridge assembly 120 is removed from the carriage 132, it can quickly be replaced by a fresh cartridge with clean sets of rollers 52-58. Once a fresh cartridge is positioned in the carriage 132, the operator slides the carriage into the operating position. As the carriage slides into position, the coupler elements 162, 164 are received within the coupler elements 170, 172. There may be some initial rotational misalignment between the hexagonal mating elements. If so, the springs 166A, 166B compress as the elements 162, 164 are pushed toward the end rail 126A. The conical surfaces 162B, 164B tend to align the mating elements by acting as a lead-in surface. Even if the mating elements do not engage as the cartridge is slid into the operating position, the first time the motor drive is actuated, as the outer coupler elements 170, 172 are turned by the motor drive, the mating elements will come into alignment, and the springs 166A, 166B will urge the elements 162, 164 into an engaged aligned position relative to the outer mating elements 170, 172. 
     The sheet cleaning apparatus can be quickly serviced by replacement of the cartridge assembly 120, thus minimizing the machine down time. The removed cartridge assembly 120 can be serviced off line. The upper set of rollers 52, 56 can easily be removed from the cartridge assembly for cleaning, and to expose the lower set of rollers for cleaning. 
     It is understood that the above-described embodiments are merely illustrative of the possible specific embodiments which may represent principles of the present invention. Other arrangements may readily be devised in accordance with these principles by those skilled in the art without departing from the scope and spirit of the invention.