Apparatus For Correcting Misprinted Matter On Sheet Material

Abstract

Apparatus for correcting misprinted matter on sheet material, the means for directing a stream of finely divided particulate abrasive or granular material on the sheet material and means for collecting the spent material immediately after use, in which the projection may take place within an enclosure which is positioned over the sheet material and to which a suction air flow is connected to remove the abrasive material after use.

Description

This invention relates to apparatus of the kind in which granular or abrasive material is directed from a storage hopper on to a surface to be treated. In particular, though not exclusively, it relates to apparatus for correcting misprinted matter or `set-off` on sheet material.

In the practice of printing there are frequent occasions when errors occur on printed sheet material such as documents and the like, which generally means that the matter is wasted and becomes useless. In some cases an erratum slip is attached to the printed article or over-printed thereon, but this is by no means a satisfactory solution to the problem. Occasionally, when an error occurs on a limited number of printed documents or books, it is possible to erase the misprint by hand by the use of a rubber, abrasive powder, or by coating the error with a white material, and then over-print, but this is a slow, costly, and tedious procedure. Another problem occurs with `set-off` which causes a smudge of ink to be picked up on the paper during printing, and which must be removed, especially on printed items of high quality. The object of the invention is to satisfy a need for a method of removing print from paper at high speed automatically or regulated in some manner without substantially damaging its surface, in order that it may then be over-printed with the correct words, diagrams, illustrations or other matter.

The invention consists in a method for correcting a misprint. The invention pertains to an apparatus for correcting misprinted matter on sheet material comprising means for directing a stream of finely divided particulate abrasive material on the sheet material and means for collecting the spent material immediately after use. The invention still further consists in an apparatus as set forth in the preceding paragraph in which the stream of particulate material is projected within an enclosure which is positioned over the sheet material and to which a suction air flow is connected to remove the abrasive material after use. The invention still further consists in an apparatus as set forth in the preceding paragraph in which the particulate material is projected at a pre-determined velocity and angle to the surface of the sheet material in a stream of compressed air through an accelerating nozzle.

The invention still further consists in an apparatus as set forth in the preceding paragraph in which the means for directing abrasive material entrained within a stream of air comprises a storage hopper for the abrasive material, which is closed below by a porous plate and above by a filler closure, a chamber below the porous plate with means for connection to a source of air under pressure, pressure air operated valve means mounted across the hopper just above the porous plate and comprising of first cylinder connected at one end to a second cylinder having a piston with a piston rod co-axial of the first cylinder, a co-axial bore in the cylinder opposite to the second cylinder, which is engageable by the end of the piston rod to close the latter, a radial bore in the first cylinder for the passage of abrasive material from the hopper to the first cylinder, a channel for the passage of air from the first cylinder to the hopper above the level of the abrasive material therein, duct means associated with valve means connected on opposite sides of the piston in the second cylinder for opening and closing the valve, and a nozzle connected by channel means to the co-axial bore in the first cylinder.

The invention still further consists in an apparatus as set forth above in which the means for directing abrasive material entrained within a stream of air comprises a storage hopper for the granular material which is closed below by a porous plate and above by a filer enclosure, a chamber below the porous plate with means for connection to a source of air under pressure, a channel means connected to a source of pressure passing through the storage hopper above the porous plate with a restrictor orifice co-axially inside the channel, a further orifice through the wall of the channel for the passage of abrasive material from the hopper into the channel, and a nozzle connected to the outlet end of the channel means.

The invention still further consists in apparatus as set forth in the preceding paragraph in which the nozzle is mounted in an enclosure of box like form and has a bottom with an aperture therein for the passage of the stream of granular material therefrom on to sheet material positioned adjacent to and below the bottom of the enclosure.

The invention still further consists in apparatus as set forth in the preceding paragraph in which an air pervious seal ring is provided around and below the aperture in the bottom of the enclosure.

The invention still further consists in apparatus as set forth in the preceding paragraph in which the enclosure is provided with a slot in opposite sides thereof, the one open to atmosphere while the other is adapted to be connected to the fan of a dust collector unit.

The invention still further consists in apparatus as set forth above mounted so as to be readily moveable relative to the sheet material so as to direct the stream of abrasive material on to the desired point upon the sheet material.

The accompanying drawings show, by way of example only, a number of the embodiments of the invention in which:

FIGS. 1, 2 and 3 show diagrammatically in cross-section three embodiments of the invention;

FIG. 4 shows a plan view of a complete apparatus;

FIG. 5 shows a side elevation of the apparatus of FIG. 4;

FIG. 6 shows a rear elevation of the apparatus of FIG. 4;

FIG. 7 shows a sectional elevation in detail through the storage hopper of blast enclosure of FIG. 4; while

FIG. 8 shows a sectional elevation in detail through the storage hopper and blast enclosure in a further embodiment.

The particulate material is directed on to the paper A, at a finite angle to it, either by conveying it in a compressed air stream B, through an accelerating nozzle C, or centrifugally directing it by means of a multi-bladed wheel D, into which the material is fed. Immediately after impingement on paper, the spent granular material is removed by suction. This may be achieved by means of a recovery annulus E, closely surrounding the accelerating nozzle as shown in FIG. 1, a separate recovery nozzle F, close to and at an angle to the accelerating nozzle or multi-bladed wheel, as shown in FIG. 2, or finally, by mounting the accelerating nozzle or wheel inside a viewing cabinet G, through which a recovery air flow H, is induced, as shown in FIG. 3.

Where the recovery annulus is used, surrounding the accelerating nozzle, an air pervious ring I, may seal the annulus against the paper being treated. This ring may consist of a bristle brush, or porous plastic, etc., to prevent the particulate material from escaping into the surrounding atmosphere but at the same time allow air to be drawn into the annulus.

Amongst the abrasives which can be employed are angular aluminous oxide, silicon carbide, etc., although the invention is by no means limited to the use of these substances. The most suitable range of size for the abrasive is between 6-16 microns and 19-47 microns, i.e. sizes 600 and 320. It is projected on to the paper at an angle of from 90.degree. to 15.degree. to its plane by means of compressed air preferably at a pressure of 10 to 50 lbs per square inch or, alternatively, centrifugally propelled. It has been found that the more acute the angle is to the plane of the paper, the more rapidly will the print be removed, although there is a danger that the surface of certain types of paper may be more liable to damage if the angle at which the abrasive is directed is excessively acute. It has been found that by using 400 mesh alumina powder directed at an angle of 40.degree.-50.degree. to the surface, it is possible to remove black print from high quality coated paper in 2 to 3 seconds using compressed air at 30 lbs per square inch pressure. Where large areas of print are to be removed, a means is provided to enable the means for propelling the abrasive and the suction nozzle to be traversed across the paper.

In its normal form, the machine for carrying the process out in this invention consists of a means of transferring sheets of paper or the like singly on to a flat bed as is the common practice in printing, after which the abrasive is projected on to it from a stationary or moving source. In the latter case, the speed of movement of the abrasive stream across the paper source can be up to 100 feet per minute, although a speed of 10 to 30 feet per minute is usually adequate.

Alternatively, it may only be required to delete a small spot for correction. This can be most readily achieved by mounting the blast and recovery means on an arm which can be raised and lowered on to the sheet for spot blasting. The sheets can either be stocked in a pile and the top sheet removed between each spot blast or, alternatively, the sheets can be fed into position against a register between each spot blast.

In such cases, when an accelerating nozzle is used, the nozzle bore can be as small as 0.25mm to provide a narrow blast pattern. Where a large blast stream is produced such as with centrifugal acceleration of the particulate material, a stencil J made of rubber, steel or other suitable material can be applied to the paper to restrict the area on to which the particulate matter is projected.

After the misprinted matter has been removed, the paper may be over-printed correctly. This can be carried out on a separate machine, but on continuous applications the print erasure and over-printed operations can be carried out more conveniently on the same machine successively, by synchronizing the paper feeding, particulate material application and over-printing processes, so that a sufficient time is allowed for the misprinted matter to be removed.

A further embodiment consists of a storage hopper 1, see FIGS. 4-7, within which is stored abrasive material 2. Beneath the storage hopper is mounted a feed valve 3, which meters a controlled quantity of the abrasive material into an air stream in which it is conveyed along a blast hose 4, made of rubber, plastic, or similar flexible material and through a nozzle 5. This accelerates the flow of air and abrasive material and directs it in a concentrated stream 6, towards a sheet material 7, being treated. In order to obtain a very small stream for the rectification of single spots, the nozzle may be as small as 0.25mm in bore.

The nozzle 5, is positioned inside an enclosure 8, to retain the stream of air and abrasive and prevent it spreading beyond the particular area being treated. Connected to the enclosure is an outlet duct 9, which may, for instance, being made of a circular or rectangular tube, with a transition piece 10, forming a recovery slot 11, across the width of the enclosure. This outlet duct 9, is connected to a suction air flow to remove abrasive material and debris from the enclosure. One convenient method is to connect a Dust Collector/Fan unit (not shown) to the end of the outlet duct 9, by means of a flexible vacuum hose 12, FIG. 5. In the opposite face of the enclosure to the recovery slot is an air entry slot 13, which provides a flow of air at high velocity across the base of the enclosure to remove the spent abrasive material immediately after impact on the sheet material.

Referring now to the storage hopper 1, this is fitted at the top with a quick-acting filler plug 14, for charging with abrasive material. Beneath the hopper is a cap 15, which retains a porous disc of ceramic or sintered bronze etc., 16, which forms an inner base of the hopper. The porosity of the disc must be such that, while permitting air to flow through, it will not allow the passage of the abrasive material.

Passing horizontally through the storage hopper at a point just above the porous disc is a feed tube 17, containing a stepped bore 18 (FIG. 7). Into the smaller (outlet) bore is fitted the blast hose 4, which is locked by means of a compression ring 19, so that the hose end just projects into the larger (inlet) bore. The inlet end of the feed tube 17, is connected to an adaptor elbow 20, into which in turn is connected an air cylinder 21. A piston rod 22, of a piston in the air cylinder has a conical or similarly shaped projecting end, and is of such a length that when fully extended it seals against the end of the blast hose 4.

In operation, compressed air is admitted through hose 23, via the porous disc 16, into the storage hopper 1, which is thus pressurized. With compressed air supplied to the air cylinder rear hose 24, the piston rod 22, is extended to seal against the end of the hose 4, so that air cannot flow from the storage hopper. When hose 24, is exhausted, and the air cylinder front hose 25 is pressurized, the piston rod retracts and air then flows from the storage hopper through hose 26, along the feed tube 17, and hose 4, and finally through the nozzle 5. This results in a vertical flow of air through the storage hopper which fluidizes the very fine abrasive material, which may be as small as 10 microns in size, and enables it to flow freely. The degree of fluidization achieved is controlled by the vertical air flow which is determined by the bore of the nozzle 5. The porosity of the disc 16, and dimensions of the hopper 1, can also be varied to adjust the fluidization effect. An orifice 27, which may be positioned anywhere around the wall of the feed tube 17, allows the abrasive material to flow into the feed tube and to be carried in the air flow and accelerated through the nozzle 5.

The size of the orifice 27, is selected to provide the correct flow of abrasive material, and on extending the piston rod 22, to contact the hose 4, instant cessation of air and abrasive material flow results. Conversely, by mounting the storage hopper adjacent to the enclosure the length of the hose 4, is kept to a minimum. Thus, when the piston rod is retracted, the flow of air and abrasive material through the nozzle is virtually instantaneous and without surging due to excessive abrasive lying in the hose 4. It is important that, when retracted, the piston rod is well clear of the orifice 27, so that abrasion of the piston rod by the flow of abrasive material is eliminated.

The hose 4, and nozzle 5, can be conveniently mounted in the enclosure inside a tubular holder 28, and set to direct abrasive at a convenient angle on to the sheet material through an aperture 29, in the baseplate 30, of the enclosure. For many applications in the removal of misprinted matter it is desired to restrict the abrading action to a very small area. For this purpose the holder 28, is fixed to direct abrasive material through a very small orifice 31, in a stencil 32, made of abrasion resistant rubber or plastic. The stencil can be readily replaceable to suit the area being treated and retained in position by a simple clip 33.

If it is required to erase more than a single spot from the sheet material, the holder 28, can be flexibly mounted, for instance in a rubber diaphragm 34. This enables the nozzle 5, to be directed over a large area around its mean position by operation of the handle 35. For all methods of operation in order to enable the erasing action to be readily accessed a viewing window 36, is provided in the top of the enclosure.

In operation, the enclosure baseplate 30, may be laid directly on to the sheet material 7, when abrasive material is directed through the nozzle. With such an arrangement fine dust from the erasure operation may penetrate locally between the baseplate and the sheet material around the aperture 29, although this is not normally detrimental to subsequent correction. However, by attaching a seal 37, of air pervious material such as felt around the aperture, air is drawn locally into the enclosure to scavenge any dust, although the abrasive material will not be able to escape from the enclosure. The air entry slot 13, can then be restricted in area or possibly eliminated completely so that all air enters via the aperture 29.

An alternative embodiment of the invention shown in FIG. 8, consists of a storage hopper 58, within which is stored abrasive material 59. Within the storage hopper is a feed valve 60, which meters a controlled quantity of the abrasive material into an air stream in which it is conveyed along a blast hose 61, made of rubber, plastic or similar flexible material and through a nozzle 62. This accelerates the flow of air and abrasive material and directs it in a concentrated stream 63, towards a sheet material 64, being treated.

The nozzle 62, is positioned inside an enclosure 88, to contain the stream of air and abrasive and prevent it spreading beyond the area being treated. Connected to the enclosure is an outlet duct 65, which may for instance be made of a circular or rectangular tube with a transition piece 66, forming a recovery slot 67, across the width of the enclosure. This outlet duct 65, is connected to a suction air flow to remove abrasive material and debris from the enclosure. One convenient method is to connect a dust collector/fan unit (not shown) to the end of the outlet duct 65, by means of a flexible vacuum hose as 12, in FIG. 5. In the top face of the enclosure is an aperture 68, which permits the flow of air to enter at a velocity sufficient to prevent upward escape of abrasive material and thus remove the spent abrasive material immediately after impact on the sheet material. The aperture 68, also serves as a viewing aperture so that the effect of the abrasive impact can be observed.

Referring now to the storage hopper 58, this is fitted at the top with a filling cap 69, for charging with abrasive material. In the base of the hopper a porous disc of ceramic or sintered bronze, etc., 70, is retained by means of bolts or similar devices against a rubber or similar seal 71. The porosity of the disc is such that while permitting air to flow through, it will not allow the passage of abrasive material. Passing horizontally through the storage hopper at a point just above the porous disc is an inlet tube 72, and the blast hose 61. These are locked in position by means of nuts 73, and flexible rings 74, to prevent the escape of abrasive material. Between the tube 72, and hose 61, is fitted the feed valve 60, containing an orifice 75, to control the flow of air along the tube 72. A secondary tube 76, with an orifice 77, causes abrasive material to flow from the hopper 58, at a controlled rate into the tube 76, and along the hose 61, to the nozzle 62, where it is accelerated and directed on to the sheet material.

While in operation, compressed air is admitted through the pipe 78, at a controlled rate such that it passes through the porous disc 70, and fluidizes the abrasive material 59. The abrasive material will then flow readily through the orifice 77, whenever compressed air is admitted to the tube 72, and flows through the feed valve 60, and hose 61. In order to prevent the air flow through the porous disc from pressurizing the storage hopper a hose 87, is connected from the hopper at a point above the level of the abrasive material and into the outlet duct 65.

The orifice 77, can be positioned anywhere around the feed valve 60, and is of a size selected to provide the correct flow of abrasive material.

As indicated in the arrangement in FIG. 8, the hose 61, can be rigidly attached to the enclosure 88, and set to direct the stream of abrasive material at a convenient angle on to the sheet material through an aperture 79, in the base plate 80, of the enclosure. As earlier described, a stencil 81, may be employed, retained in position with a clip 82, and with an orifice 83, to limit the effect of the blast stream on the paper to a specific area.

The nozzle can of course be hand manipulated to be directed over the entire area of the aperture 79, being readily viewable through the upper aperture 68. Again as earlier described, an air pervious seal 84, may be affixed to the base of the enclosure around the aperture to prevent escape of dust or abrasive material on to the surface of the sheet material. It has been found that by shaping the front edge of the rear seal as shown by 85, and omitting the seal across the front edge of the aperture, some of the air drawn through the slot 67, is able to enter the base slot 86, and more effectively sweep dust and abrasive material from the sheet material.

The construction shown in FIG. 8 has applications relating to abrasive blasting generally for example for the industrial cleaning of component parts, with or without an enclosing cabinet.

In order to be able to direct the abrasive material on to any particular area of the sheet material 7, or 64, it is essential that the enclosure be able to be moved readily over the sheet material. It must also be capable of being locked in a pre-determined position, when correcting a batch of sheets. Thus as each sheet is transferred into position for treatment, the same area will be erased for correction. At the same time, it is required for the enclosure to be raised from the sheet material for the treated sheet to be removed and a new sheet inserted. Finally, for simplicity of operation, the control of the stream of abrasive material should be automatically operated by the lowering of the enclosure on to the sheet material. These requirements can be achieved in a variety of manners, and one suitable system is that indicated, which operates as follows:

Positioned around the outlet duct 9, is a lower guide tube 38, (FIGS. 4-6) which may be of nylon or similar low friction material, and rollers 40. These are so adjusted that the guide tubes moves freely over the outlet duct but with the minimum of side movement. The enclosure 8, can thus be extended to reach fully over the sheet material, and be locked in position by the screw 41, which grips the outlet duct in the lower guide tube.

Rigidly attached to the top of the lower guide tube, but at 90.degree. to it, is an upper guide tube 42, which is similarly fitted with side guides 43, and rollers 44. This moves over a transverse bar or tube 45, of sufficient length that the enclosure 8, can fully traverse the width of the sheet material. The upper guide tube can then be locked in position by the screw 46, which grips the transverse tube.

The ends of the transverse tube are adapted to locate in two flange mounted ball bearings 47, attached to the vertical end plates 48, of the base frame 49. This enables the transverse tube to rotate about its longitudinal axis which causes the enclosure to be raised or lowered from the sheet material. Connected to one end of the transverse tube is a crank arm 50, attached by means of a pin 51, to a fork 52. The fork is fitted to the piston rod or an air cylinder 53, which in turn is secured on a trunnion 54. Thus as compressed air is admitted to a lower connection 55, the piston rod extends, rotates the transverse tube 45, and raises the enclosure from the sheet material. Conversely, as compressed air is admitted to upper connection 56, the enclosure is lowered into hard contact with the sheet material.

It is a simple matter to co-ordinate the movement of the enclosure and flow of abrasive material by a pneumatic or electro-pneumatic control system to give the following sequence of operation with reference to FIGS. 5-7. When the control system is switched on, compressed air is admitted to hoses 23, 24, and 55. This pressurizes the storage hopper 1, but closes the feed valve assembly 3, to prevent any flow of air and abrasive material through the nozzle 5. At the same time, the enclosure is raised clear of the sheet material. By slackening the screws 41, and 46, the enclosure can be moved in two directions so that when lowered, the stream of air and abrasive material erases any selected region on the sheet material 7. A foot operated control valve can conveniently be employed which exhausts hose 55, and pressurizes hose 56, and after a preset delay period exhausts hose 24, and pressurizes hose 25. This causes the enclosure to be lowered on to the sheet material after which a flow of air and abrasive material takes place through nozzle 5. Conversely, when the foot operated control valve is de-actuated, the feed valve air cylinder 21, first closes to stop the blast stream, and after a preset period the air cylinder 53, raises the enclosure from the sheet material 7. It is thus only necessary to arrange an automatic feed of sheet material between the actuation of the foot operated valve, to remove a misprinted area from a batch of sheets. Due to the suction applied to the enclosure to recover the abrasive material there may be a tendency for the sheet material to adhere to the enclosure as it is raised. This can be overcome by a simple spring plunger 57, located each side of the enclosure and extending freely a short distance below the base plate 30.

Although the above describes one system for the application of our invention, many variations are possible without departing from the basic principle involved.

It is to be understood that the above description is by way of example only and that details for carrying the invention into effect may be varied without departing from the scope of the invention claimed.

Claims

We claim:

1. An apparatus for correcting misprinted matter on sheet material, comprising means for directing a stream of finely divided particulate abrasive material entrained within a stream of air onto the sheet material, and means for collecting spent material resulting from impingement of said abrasive material against said sheet material, an enclosure positionable over said sheet material within which said stream of particulate abrasive material is projected, and means including a source of suction air flow connected to said enclosure; said means for directing said abrasive material comprising a storage hopper for said abrasive material, closure means for said hopper comprising a porous plate at its lower end and a filler closure at its upper end, a chamber below the porous plate and means connecting said chamber to a source of air under pressure, air operated valve means mounted across the hopper just above the porous plate and comprising a first cylinder connected at one end to a second cylinder, a piston in said second cylinder and having a piston rod coaxial of the first cylinder, said rod having a projecting end extending into said first cylinder, a coaxial bore in said first cylinder opposite to said second cylinder, said bore being engageable by the projecting end of the piston rod to close said valve means, a radial bore in the first cylinder for the passage of abrasive material from the hopper to the first cylinder, a channel for the passage of air from the first cylinder to the hopper above the level of the abrasive material therein, duct means associated with said second cylinder to supply air pressure thereto to open and close said valve means, and a nozzle connected by channel means to the coaxial bore in the first cylinder.

2. An apparatus as claimed in claim 1, which further includes channel means connected to a source of air pressure passing through the storage hopper above the porous plate, and a restrictor orifice coaxially inside said channel means, and a nozzle connected to the outlet end of the channel means.

3. Apparatus as claimed in claim 2, said enclosure within which said nozzle is mounted having a wall with an aperture therein for the passage of the stream of abrasive material therethrough onto sheet material positioned adjacent said aperture of the enclosure.

4. An apparatus as claimed in claim 3, in which an air pervious ring is positioned around the aperture in the wall of the enclosure.

5. An apparatus as claimed in claim 4, in which the enclosure is provided with a slot in opposite sides thereof, the one open to atmosphere while the other is adapted to be connected to the fan of a dust collector unit.