DAMPENING FEED APPARATUS

Abstract: A dampening solution feed apparatus for an offset printing press has a form roller (20) in rolling contact with the plate cylinder (10) of the press, and a second roller (22) is provided in contact with the form roller (20). A supply of dampening solution is fed to the form roller and the rollers are arranged to rotate such that excess solution on the form roller is returned to a reservoir (26) between the rollers.

Description: DAMPENING FEED APPARATUS The present invention relates to dampening systems for offset lithographic printing presses. The major components of the offset press are the plate cylinder, blanket cylinder, dampening system, and inking system. Secured around the plate cylinder is a printing plate upon which is imposed a photographic image. The image is defined by a gradation of oleophilic dots over a hydrophilic background, the intensity of the image being directly proportional to the concentration of such dots. The function of the dampening system is to thoroughly moisten only the background of the plate with a substantially aqueous solution. Then grease-based ink is rolled over the plate and adheres only to the oleophilic dots to create an inked image which is transferred to an adjacent blanket cylinder and subsequently to the paper to be printed. The dampening system is a critical element of the press. If the quantity and application of the moistening solution is not precise, the solution and ink will incorrectly coat the respective hydrophilic and oleophilic areas, and the finally printed image will be distorted. Conventional dampening systems control the amount of solution transferred to the form roller adjacent the plate cylinder by adjusting the rate of oscillations of a ductor roller which reciprocates back and forth from a solution reservoir to the train of dampening rollers. The amount of solution which is then actually transferred to the plate is controlled by adjusting the pressure between the form roller and the plate cylinder. Excess solution is nipped between the form roller and the plate cylinder and accumulates on the form roller. This excess solution must eventually be reduced by decreasing the number of oscillations of the ductor roller, or it will accumulate enough to result in over-moistening of the printing plate. Additionally, in order to absorb a sufficient quantity of moistening solution for subsequent application to the printing plate, the form rollers are covered with a-highly absorptive material such as a molleton. The covers, however, ultimately become fouled with ink which collects and finally prevents moistening solution from transferring to the background areas of the printing plate, until such covers are replaced. As a result of these and other disadvantages of prior art dampening systems, sharply defined prints are difficult to obtain without a great deal of control and attention. An object of the present invention is to p#rovide a dampening solution feed apparatus for an offset lithographic printing press with which the above-mentioned problems can be overcome or at least appreciably reduced. According to the invention therefore there is provided a dampening solution feed apparatus for a printing press having a plate cylinder around which is secured an offset lithographic printing plate, said apparatus com prising a first member in the form of a roller adapted to make rolling contact with said plate cylinder to apply dampening solution thereto, a second member such as a roller mounted for sliding or rolling contact with the surface of said first member, and dampening solution supply system adapted to supply dampening solution to the surface of said first member, characterised in that said first and second members are adapted to rotate in use such that excess dampening solution on the first member is returned to a reservoir defined between said first and second members. Most preferably, said second member is also in the form of a roller although it is possible to use other devices such as a squeegee or scraper. Thus, for example, a reservoir of dampening solution may be positioned below the first roller, and the first roller may lie partially submerged within said reservoir abutting a squeegee at one end of the reservoir. With this arrangement, the amount of solution actually applied can be controlled by adjusting the pressure between the first and second rollers and between the first roller and the plate cylinder. Excess moisture which is retained on the first roller is continuously returned directly to the reservoir. When the apparatus is used with a conventional plate cylinder which includes a recessed clamping section for mounting the printing plate, excess solution which is nipped between the cylinder and the first roller is also returned directly to the reservoir upon each pass of the recessed section. Thus, the solution cannot readily accumulate and eventually over-dampen the plate. Also, since the reservoir is in direct contact with the first roller, the roller does not need an absorptive molleton cover to transfer adequate solution. The invention will now be described further by way of example only and with reference to the accompanying drawings in which: Fig. 1 cutaway pictorial view of one form of dampening apparatus according to the present invention; Fig. 2 is an overall pictorial view of the seal of the apparatus of Fig. 1; Fig. 3 is a sectional view of the apparatus of Fig. 1; Figs.4 and 5 are pictorial views of the dampening rollers of Fig. 1 and the plate cylinder illustrating the cyclic return of nipped excess solution back to the reservoir; Fig 6 is a longitudinal sectional view of the arrangement of Fig. 1; Fig. 7 is a sectional view along the line 6-6 of Fig. 1; Fig. 8 is a sectional view along the line 7-7 of Fig. 6; Fig. 9 is a sectional view along the line 8-8 of Fig. i; Fig. 10 is an end view of the embodiment of Fig. 1, illustrating means of attachment; Fig.ll is an end view schematic of an alternate embodiment of a dampening apparatus in accordance with the present invention; Figs. 12 and 13 show a sealing arrangement of an alternative embodiment of the invention; Fig. 14 shows a sprocket arrangement of a further embodiment of the invention; and Fig. 15 shows a solution feed system of a still further embodiment of the invention. As shown in Fig. 1 the press includes a plate cylinder 10 driven by a drive gear 11 within a framework 12. The dampening apparatus itself is enclosed within end housings 13 and an elongate top-cover 14 extending between the housings 13. The dampening apparatus is attached to the press housing in a conventional manner. Various presses are equipped with attachments for dampening solution apparatus. Pressure between the plate cylinder 10 and a form roller 20 is adjusted through these attachments. The dampening apparatus includes a form roller 20 mounted parallel to and in rolling contact with the plate cylinder 10, the second roller 22 lying parallel and tangent to the form roller 20, a reservoir 26 of dampening solution (shown in Fig. 3) located between the form roller 20 and second roller 22 and above their line of tangency 27 (Figs. 4, 5) and a solution fountain bottle 24 positioned immediately above the reservoir 26. The solution fountain bottle 24 is a closed container having a wick 29 which extends horizontally in an arcuate shape almost the entire length of the second roller as shown in Fig. 6. The solution is discharged through an outlet 30 located approximately midway along the length of the wick. By that arrangement, as the level of the reservoir 26 drops below a boundary 31 of the outlet 30, air enters the bottle 24 and allows solution therein to discharge until the level of the reservoir 26 again completely covers the boundary 31 of the outlet 30. Thus, the solution fountain bottle 24 serves to automatically maintain the reservoir 26 at a predetermined level. The boundary of the outlet 30 is generally submerged below the surface level of the reservoir 26. The slightly arcuate configuration of the wick maintains a uniform level of the reservoir across the length of the roller. Therefore, beads of solution will not form. This eliminates the possibility of a bead of solution forming at the outlet 30 while the rest of the reservoir has dried up. If that were to happen, the rollers would run without enough solution to produce clear prints. Fig. 2 illustrates the seal used to prevent solution leakage from the reservoir. Figs. 1, 7,8 depict the position of the seal in the dampening apparatus. The seal comprises a seal carrier 33 and a seal plate 36. The seal carrier 33 is preferably composed of metal while the seal plate 36 is preferably a plastic. The seal plate 36 forms both a circumferential seal with the second roller 22 and an end seal with the form roller 20. The seal is affixed to the end housing 13 by a bolt 35 which extends through a slot 34 in the seal as shown in Fig. 1. A tension spring 38 is attached through an opening 37 in the seal means as depicted in Fig. 7 and 8. The opposing end of the spring 38 is secured to the end housing 13. See Fig. 7. Another spring 39-is biased against the seal carrier 33 adjacent to the end housing 13 as illustrated in Fig. 8. The seal carrier 33 and therefore the seal plate 36 is urged downward and towards the second roller 22 as a result of the tension in the spring 38. At the same time the biased spring 39 urges the seal carrier 33 and therefore the seal plate 36 against the end of the form roller 20. In this manner, the seal continues to be effective even while subjected to wear. As the second roller 22 wears away the seal plate 36, the tension spring 38 assures a tight circumferential seal by pulling the seal plate 36 towards the second roller 22. As the form roller 20 wears away the seal plate 36 the biased spring 39 urges the seal against the end of the form roller 20 so that the end seal remains effective. Adjustments to control the amount of pressure between the form roller 20 and the second roller 22 are made by adjusting a screw 42 which is threaded through a locknut 43. See Fig. 9. The screw 42 protrudes through the locknut 43 and the end housing 13 into a cam 44. Adjusting the screw 42 causes the cam 44 which is attached to the second roller 22 to travel in a slightly eccentric arcuate path towards the form roller. Adjusting the screw in the opposite direction causes the second roller 22 to travel in a slightly eccentric arcuate path away from the form roller 20. Thus, the pressure between the two rollers is controlled. The cam 44 is affixed to a roller pressure gauge 45 by a screw 47 as shown in Fig. 1. The roller pressure gauge 45 protrudes from the end housing and is marked at predetermined intervals to give a relative reading of the pressure between the form roller and the second roller. An indicator 46 on the end housing 13 enables the reader to gauge the relative amount of pressure between the two rollers. The operator can loosen or tighten the screw 47 and adjust the position of the roller pressure gauge 45 at a zero point. The locknut 43 is loosened and the screw 42 can be adjusted to control the amount of pressure between the second roller and the form roller. The form roller 20 comprises a shaft 50 which is pressed inside a tubular body portion 51. A cylindrical shell 52 is mounted over the tubular body portion 51. The shaft 50 extends beyond the roller 20 on both ends through a pair of bearings 53 (Fig. 8) and is mounted into the end housing 13. The bearings 53 are freely rotatable around the shaft 50. The second roller 22 comprises a shaft 60 which is pressed inside a tubular body portion 61. The tubular body portion 61 is pressed into a cylindrical shell 62. The shaft 60 extends from both ends of the roller. On the end of the shaft where the gears are mounted the shaft 60 extends. through a unidirectional bearing and another bearing which is fitted into the cam 44. The opposing end of the shaft extends through a spacer (not shown) and a bearing (not shown) and is mounted in the end housing 13. A gear 66 fits over the bearing 53 and is in meshing engagement with the drive gear 11. A second gear 68 fits over the central portion of the unidirectional bearing 63 and is in meshing engagement with the first driven gear 66. With this assembly then the drive gear 11 drives the first driven gear 66, and the first driven gear 66 consequently turns the second driven gear 68. As the second driven gear 68 is in tight engagement with the unidirectional bearing, the turning of the gear 68 causes the unidirectional bearing to lock on the shaft, thereby resulting in rotation of the second roller 22. The rotation of the roller 22, in addition to the pressure between the two rollers 20 and 22, causes the form roller 20 to rotate simultaneously therewith. Further, the form roller 20 is aided in its rotation by its contact with the complementarily revolving plate cylinder 10. When the gear 68 is rotated in the opposite direction, the unidirectional bearing disengages and the second roller 22 is prevented from rotation. To summaries the operation, the drive gear 11 rotates the plate cylinder 10 and the first driven gear 66-. The first driven gear 66 rotates the second driven gear 68 which transmits motion through the unidirectional bearing to the shaft 60 of the second roller 22. During operation, the pressure then between the shells 52 and 62 of the form and second rollers 20 and 22 is adjusted by the screw 42 and the pressure between the shell 52 of the first roller 20 is adjusted through the conventional attachment means which may include a bolt or a cam, such that the form roller 20 is driven# by both the second roller 22 and the plate cylinder 10. As should be apparent, the degree of preselected pressure between the rollers, 20 and 22, also determines the amount of solution which is metered from the reservoir 26 to the form roller 20. Similarly, the degree of pressure between the form roller 20 and the plate cylinder 10 determines the amount of the metered solution which actually becomes applied to the printing plate 85 on the plate cylinder 10. Fig. 10 illustrates a means of attachment between the dampening solution apparatus and the press. The dampening solution apparatus can be pivotally raised and lowered about a screw 70, as shown by dashed line 71, by means of a lever arm 18 connected to the housing 13 via a stud 19. The housing 13 is biased in the lowered position against an adjustment bolt 72 by a tension spring 73. Adjustment of the bolt 72 and selection of the spring 73 varies the degree of pressure between the plate cylinder 10 and the form roller 20. The screw 70 secures a connecting arm 74 between the press and the dampening solution apparatus. The connecting arm 74 is secured to the press by two screws 75 and 76. The relative rotation of the form roller 20, second roller 22, and plate cylinder 10 are shown pictorially in Fig. 4. A printing plate 85 is wrapped around the plate cylinder 10 and secured at the recessed section 86. Subsequent to the dampening system, ink is applied to the plate 85 by means of a train of ink rollers (not shown). In Fig. 4, the train of ink rollers would be located on the right side of the plate cylinder 10. After the ink is applied to the plate 85, the image thereby created is transferred to a blanket cylinder and then to the paper itself. Application of a proper amount of dampening solution to the printing plate 85 is critical to the appearance of the final image. Therefore, in theory, the pressure between the form and second roller 20 and 22 should be adjusted to meter through to the form roller 20 only an amount which is to be applied to the plate 85, and the pressure between the form roller 20 and plate cylinder 10 should be precisely adjusted to apply that amount to the plate 85. In practice, such precise adjustment is impossible and constant monitoring is necessary. With the present embodiment, a slightly excessive amount of solution is metered through the line of tangency 27 between the form and second rollers, 20 and 22. The form roller 20 and plate cylinder 10 are precisely adjusted, however, to apply only a proper amount of solution to the plate 85. Some of the excess remains on the form roller 20 as surface moisture and is continuously returned to the reservoir 26, while a nip 90 is created by the remainder of the excess where the form roller 20 contacts the plate cylinder 10, as shown in Fig. 4. The nip 90, however, is returned to the reservoir 26 upon each cycling of the recessed section 86 of the plate cylinder 10, as shown in Fig. 5. Since the reservoir 26 is located adjacent the form roller 20, but beyond the uppermost tangent thereof in the direction of rotation, no occasion is presented for the dampening solution to collect where it can drip back to the plate 85. Thus, the present embodiment provides a means for continuously applying a uniform amount of solution to the plate 85 without the necessity of careful surveillance and administration by an operator. There is also another advantage of the present embodiment. Each printing plate 85 necessarily includes heavily inked areas and lightly inked areas, depending upon-the intensity of the image to be finally created. Consequently, after some usage the form roller 20, and perhaps the second roller 22, in the dampening train of rollers, will have corresponding heavily and lightly inked areas. Such phenomenon is advantageous in that the amount of dampening solution actually applied to any particular portion of the plate 85 by the form roller 20 is roughly inversely proportional to the density of the ink on the corresponding portion of the form and second rollers 20 and 22. For example, the heavily inked areas of the form roller 20 will actually apply less dampening solution to the corresponding heavily inked areas on the printing plate 85, as compared to the amount of solution applied by the lightly inked areas, a desirable result since, as discussed in the background above, the intense image represented by the heavily inked areas requires less dampening solution to achieve clarity and definition. However, prior art form rollers generally include highly absorbent covers, such as molleton covers, in order to conduct a sufficient amount of dampening solution, and those covers quickly become fouled with ink to the point where the covers impair the imag#e on the printing plate with too low dampening solution rate. At that time, the operator must replace the fouled cover with a new one, a timely and inefficient procedure. Similarly, the operator must change the cover when switching the printing plate with one which has a completely different image, or else the permanently-fouled cover will find the fouled areas across from low inten sity image areas of the new plate, and the image will be unclear. With the present embodiment, since an ample supply of dampening solution is provided adjacent the form roller 20 and the line of tangency 27 between the form and second rollers 20 and 22, such absorbent covers are unnecessary and not used. It is preferred that the shells 52 and 62, of the form and second rollers 20 and 22 be manufactured from rubber and metal, respectively. Other materials though can be used. Without the absorbent covers then (in fact, it is preferred that no part of the invention apparatus be comprised of ink-absorbent material), the ink which adheres to the rollers 20 and 22 is merely on the surface thereof and is continuously exchanged with ink on the printing plate. Thus during operation of the press, the ink on-the dampening rollers 20 and 22, does not build up excessively. Furthermore, when a new printing plate is mounted on the plate cylinder, after a short period of operation the ink on the heavily inked areas of the form and second rollers, 20 and 22, will be completely removed, and newly-inked areas will appear on the rollers 20 and 22, corresponding with the new heavily inked areas on the new plate. Thus, no down time is needed to replace the covers An alternate dampening apparatus is illustrated in Fig. 11. The apparatus includes a reservoir 100, a solution fountain bottle 101, a second roller 102 lying parallel and tangent to a form roller 103 at a line of tangency 104, and a form roller 103 lying parallel and tangent to a plate cylinder 105 at a line of tangency 106. The second roller 102 lies within the reservoir 100 and rotates so as to continuously provide dampening solution to a supply 107 lying between the form and second rollers 103 and 102, and above the line of tangency 104. Pressure between the form and second rollers, 103 and 102, is adjusted to meter a slightly excessive quantity of solution from the supply 107 to the solution delivery arc 108 of the form roller 103, defined between the line of tangency 104 and the line of tangency 106 in the direction of rotation. Pressure between the form roller 103 and the plate cylinder 105 is adjusted to apply a proper amount of the above-described excessive quantity to the printing plate 109, such that the excess 110 nipped by the form roller 103 and plate cylinder 105 is returned by the solution return arc 115 of the form roller 103, defined between the line of tangency 106 and the line of tangency 104 in the direction of rotation. The line of tangency 104 and supply 107 are located beyond the uppermost tangent 116 of the form roller 103 in the direction of rotation. As solution in the reservoir 100 is used, it is continually replaced by solution in the fountain bottle 101, as described above. The form roller 103 is slightly shorter than the. second roller 102, such that solution is regularly returned from the supply 107 to the reservoir 100 along the paths indicated by the arrows 117 as the supply 107 builds up to an overflowing level. This arrangement eliminates or simplifies sealing at the ends 118 of the form roller 103. Figs. 12 and 13 show another embodiment of a seal that can be used to prevent solution leakage from the reservoir. The seal comprises a seal carrier 233 and a seal 236. A flange or lip 237 is positioned along one edge of the seal carrier. The seal 236 is free to move or float on the carrier 233, except that the lip 233 engages one side of the seal for retaining the seal in relative position on the carrier 233. A projection 239 is positioned on the surface of the carrier 233 that is opposite to the seal 236. A spring 241 is positioned around the projection 239 and acts to bias the seal carrier 233 towards the form roller 20 and second roller 22. The projection 239 locates the spring 241 with respect to the seal carrier 233. The projection 239 and spring 241 extend into an aperture 243 located in the end housing 13. The positioning of the projection 239 in the aperture 243 maintains the seal carrier 233 in the proper relationship with respect to the form roller 20 and the second rol3.er 22. On the top of the seal carrier 233 there is a flange 245 that projects over the top of the seal 236. A spring 247 is positioned in engagement with the flange 245. The other end of the spring 247 extends into a bore 248 located in the upper surface of the seal 236. In the lower end of the seal carrier 233 there is an aperture 249. A member 251 is positioned on the end housing 13 so that the member extends towards the form roller 20. There is an aperture 253 located in the end of the member and is spaced apart from the end housing 13. A spring 255 is connected between the aperture 249 in the seal carrier 233 and the aperture 253 in the member 251. The member 251 is normally positioned at an angle so that the spring will bias the seal carrier towards the form roller 20. In operation the seal 236 is free to float on the seal carrier 233 during the operation of the dampening apparatus. The spring 241 positioned on the projection 239 will bias the seal carrier 233 and the seal 236 towards the form roller 20 and the second roller 22. The spring 247 which is positioned between flange 245 and the upper surface of the seal 236 will bias the seal towards the cylindrical surface of the form roller 20 and the second roller 22. The spring 255 which connects between the aperture 249 in the seal carrier 233 and the aperture 253 in the member 251 biases the seal carrier 233 and seal 236 towards the roller and specifically towards the second roller 22. The lip 237 on the seal carrier 233 engages the seal 236 to urge the seal towards the second roller 22 as the spring 255 biases the seal carrier towards the second roller 22. The springs bias the seal so that the seal will be self-adjusting and continuously provide an adequate seal with the first and second rollers during the operation of the dampening apparatus. The second roller 22 in this embodiment preferably has a copper surface. The ink used in printing adheres to the surface of the copper roller and the ink is retained on both the second roller 22 and form roller 20 in the image area. The retention of the ink in the image area on the rollers improves the quality of the printing produced on the lithographic printing process utilising the dampening system of the present invention. It has also been found to be advantageous to provide chrome, stainless steel or other suitable hardened ends to the second roller 22. The hardened ends of the second roller 22 are positioned to engage the seals 236 located in contact with the end of the rollers. The hardened ends reduce the wear on the second roller in the area of the seals. Accordingly, the life of the second roller is significantly increased by incorporating the hardened ends on, the second roller 22. Fig. 14. shows another embodiment of the dampening apparatus of the present invention. In this embodiment the form roller 20 has a sprocket 203 mounted on the support shaft 205 for the form roller. The sprocket engages a drive gear 11 for the plate cylinder 10 whereby the form roller is driven directly by the plate cylinder 10. The second roller 22 is rotated by frictional engagement with the form roller 20. It is advantageous to drive the form roller 20 directly as there is less chance that the form roller will slip or move with respect to the plate cylinder 10. Thus, there is less chance that the material being printed will be smeared from slippage between the form roller and the plate cylinder. Fig. 15 shows another embodiment for the solution fountain bottle and the wick for supplying dampening solution to to the form roller 20 and the second roller 22. In this embodiment, a solution fountain bottle 224 is positioned in connection with a wick 200 which extends horizontally in an arcuate shape almost the entire length of the second roller. There is a centre opening 230 positioned approximately midway along the length of the wick. Positioned on each side of the centre outlet 230 are two side outlets 229. The side outlets are positioned substantially equidistant from the centre outlet 230. The centre outlet 230 and the two side outlets are positioned substantially along the longitudinal axis or centre line for the wick 200. A valve 270 is positioned in the neck of the bottle 224 and co-operates with the centre outlet 230 and two side outlets 229 to provide solution to the reservoir 26 The valve 270 has a plunger 271 containing a passageway 273. The passageway has an inlet opening 272 and a discharge opening 274. The passageway connects the interior of the bottle 224 with the centre outlet 230 in the wick 200. The plunger also contains a cut-out section 276 on one side that defines a passageway 278 along the side of the plunger. The passageway 278 connects the interior of the bottle with the two side outlets 229 in the wick 200. A spring 275 is positioned around the exterior of the plunger 271. One end of the spring engages a shoulder 277 in the valve and the other end of the spring engages an O-ring seal 279 on the end of the plunger. The spring 275 biases the plunger away from the bottle 224 so that the O-ring seal 281 engages the surface 283 on the valve. The O-ring 281 creates a seal with the surface 283 to prevent solution from flowing from the bottle. When the bottle 224 is positioned on the wick 200 the end of the plunger that is spaced apart from the interior of the bottle engages the centre outlet 230. As the bottle is positioned in engagement with the centre opening 230 the plunger is displaced displaced towards the bottle 224. The displacement of the plunger places the inlet opening 272 in communication with the interior of the bottle so that passageway 274 connects the interior of the bottle with the centre outlet 230. The passageway 278 also connects the interior of the bottle with the two side outlets 229. If the level of the reservoir 26 of dampening solution drops below the discharge end 231 of the centre outlet 230 air will enter the bottle 224 through the centre outlet 230 and the solution in the bottle will flow from the bottle, along the passageway 278, through the side outlets 229 and into the reservoir 26. The solution will continue to be discharged -from the bottle 224 until the level of the reservoir 26 again completely covers the discharge end 231 of the outlet 230. Thus, the arrange#ment of the solution fountain bottle 224 and the wick 200 will automatically maintain the reservoir 26 at a predetermined level. This arrangement for the bottle and wick improves the flow of the dampening solution to the reservoir 26. In addition, a narrower casting can be provided for the wick which allows a narrower bead of dampening solution to be deposited in the nip between the form roller 20 and the second roller 22. The narrower bead of solution allows the wick to be positioned further from the roller so that there is increased clearance between the wick and the rollers. The increased distance between the wick and the roller reduces the chance of contact between the surface of the wick and the surface of the rollers.

Claims: Claims: 1. A dampening solution feed apparatus for a printing press having a plate cylinder around which is secured an offset lithographic printing plate, said apparatus comprising a first member in the form of a roller adapted to make rolling contact with said plate cylinder to apply dampening solution thereto, a second member such as a roller mounted for sliding or rolling contact with the surface of said first member, and dampening solution supply system adapted to supply dampening solution to the surface of said first member, characterised in that said first and second members are adapted to rotate in use such that excess dampening solution on the first member (20) is returned to a -reservoir (26) defined between said first and second members (20, 22). 2. Apparatus according to claim I, wherein said first and second members are first and second rollers characterised in that sealing means (33, 36) is provided at adjacent ends of said first and second rollers (20, 22) for preventing the flow of said solution over said ends. 3. Apparatus according to claim 2, characterised in that said adjacent ends are coplanar and said sealing means comprises seal plates (36)abutting said coplanar ends. 4. Apparatus according to any one of claims 1 to 3, characterised in that there is provided a supply level maintaining means comprising a vessel (24) of dampening solution mounted over said reservoir (26) of dampening solution, a wick (29) extending horizontally across said reservoir with both ends of said wick extending vertically beyond the middle of said wick defining an arc, a means (30) for delivering said solution through said wick-such that said reservoir of solution is maintained uniformly across the length of the first and second rollers, and said solution passes from said vessel .to said reservoir when the said delivery means is exposed to the atmosphere but no solution passes when said level of said reservoir rises and completely submerges said delivery means. 5. Apparatus according to claim 2 or 3, characterised in that said second roller (102) lies above and partially submerges within a supply of dampening solution, said second roller being longer than said first roller, (103), and means (100, 101) is provided for automatically maintaining the level of said supply constant, whereby dampening solution is continuously fed from said supply to said reservoir' (107) by means of the rotation of said second roller, and whereby dampening solution from said reservoir continuously overflows upon said second roller beyond the ends of said first roller and towards the ends of said second roller, such that the overflow is returned to said supply by gravity and the rotation of said second roller thereby automatically maintaining the level of said reservoir. 6. Apparatus according to claim 2, characterised in that said seal means comprises a carrier (33) with a seal plate (36) adapted to fit in a cavity of said carrier, and means (38) is provided for biasing said seal plate against said rollers (20, 22) so as to form a circumferential seal against said second roller and an end seal against said first roller. 7. Apparatus according to claim 4, characterised in that valve means (270) is positioned on said vessel, said valve means having a passageway (273) to allow air to pass into said vessel #(224) and a passageway (278) to allow solution to pass from said vessel; a centre opening (230) is positioned in substantially the centre of said wick (200), one end of said centre opening being in communication with said passageway in said valve means that allows air to pass into said vessel, the other end of said centre opening being in communication with said supply of dampening solution; and at least one opening is positioned adjacent said centre opening, one end of said opening being in communication with said passageway in said valve means to allow solution to pass from said vessel, the other end of said passageway being in communication with said supply of dampening solution; whereby said solution flows from said vessel, through said passageway to said supply when said centre opening is exposed to the atmosphere and air can flow into said vessel through said centre opening and whereby said solution does not flow from said vessel when said level of said supply covers said end of said centre opening in communication with said supply of dampening solution. 8. Apparatus according to claim 7, characterised in that said valve means contains a movable plunger (271) and said passageway to allow air to pass into said vessel is positioned in the centre of said plunger. 9. Apparatus according to claim 8, characterised in that a resilient member (275) is positioned around said plunger to bias said plunger into seating engagement with said valve means when said vessel is not in position on said wick whereby flow of-solution from said vessel is prevented and said plunger is displaced from seating engagement with said valve means when said vessel is positioned on said wick whereby solution can flow from said vessel 10. Apparatus according to claim 2, characterised in that said sealing means comprises: a seal carrier (233) positioned adjacent said first and second rollers, said carrier having a seal contacting surface; a seal (236) movably positioned on said seal contacting surface of said seal carrier; means (241) for biasing said seal carrier towards said first and second rollers; means (247) for biasing said seal towards the circumferential surface of said first and second rollers whereby said seal is biased against said first and second rollers so as to form a circumferential seal against said second roller and an end seal against said first roller. 11. Apparatus according to claim 10, characterised in that a pin member (239) is positioned on said seal carrier opposite the seal carrier surface, said pin member slidably engaging an aperture (243) in an end housing (13) 12. Apparatus according to claim 10, characterised in that a projection (237) extends from said seal contacting surface towards said seal, said projection being positioned for engaging one side of said seal to urge said seal into engagement with the circumferential surface of said second roller.

Inventors: LOUDON, JAMES ROBERT
Applicants: VARN PRODUCTS COMPANY LIMITED
Application year: 1980
Main classification: B41F7
IPC codes: B41F7