Abstract:
An ink builder to build an ink for a hard copy device. The ink has at least one property that deteriorates in storage. The ink builder comprises an ink tank and apparatus for building ink in the ink tank from a plurality of components and/or an ink maintaining apparatus arranged to inhibit deterioration of the at least one property of the ink in the ink tank. The ink builder may be used in cooperation with a separate hard copy device to which the ink tank can be transferred. Methods of producing hard copies using such a hard copy device are also disclosed.

Description:
BACKGROUND  
       [0001]     In some printers and other hard copy devices, the composition of the ink used is continually monitored and adjusted and/or replenished in use. For example, in a liquid-ink electrostatic printer, the ink solution may consist of a blend of ink concentrate and conductivity agent in an oil. In use of such an electrostatic printer, the ink solution is replenished by a solution often consisting of fresh oil, ink concentrate, and conductivity agent as needed. The solution is constantly mixed, for example, by being circulated by a pump, to produce a uniform composition.  
         [0002]     If the level of ink concentrate or conductivity agent becomes too high, or if the ink solution becomes contaminated, or if it is desired to substitute a different ink solution, it has in the past been generally necessary to drain the relevant ink tank on the printer, clean the ink tank and pipe-work, refill the ink tank with clean oil, and build up the ink solution to a usable concentration of ink concentrate and conductivity agent. Both the cleaning and the rebuilding of the ink solution take considerable time, during which the printer is unable to print. Because the ink solution generally requires continual mixing, if the printer is powered down for an extended length of time the ink concentrate and oil content separates, and must be cleaned out either at shutdown or at startup, and the ink solution must be rebuilt before the printer can be brought back into operation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]      FIG. 1  is a schematic view of one embodiment of printing system according to the invention.  
         [0004]      FIG. 2  is a schematic view of parts of one embodiment of an ink building section of a printer forming part of the printing system shown in  FIG. 1 .  
         [0005]      FIG. 3  is a schematic view of parts of one embodiment of an ink builder forming part of the printing system shown in  FIG. 1 .  
         [0006]      FIG. 4  is a perspective view of one embodiment of an ink tank.  
         [0007]      FIG. 5  is a perspective view of one embodiment of a motor lift unit for use with the ink tank shown in  FIG. 4 . 
     
    
     DETAILED DESCRIPTION  
       [0008]     Referring to the accompanying drawings, and initially to  FIG. 1 , one embodiment of a hard copy production system according to the invention is a printing system indicated generally by the reference numeral  10 . The printing system  10  comprises a hard copy device that in this embodiment is a printer indicated generally by the reference numeral  12  and an ink builder indicated generally by the reference numeral  14 . In this embodiment, the printer  12  is a seven-color liquid-ink electrostatic printer. The printer  12  has a photoconductive cylinder  20 , with the usual imaging and cleaning stations  22 ,  24 , and seven developing stations  26 . The image formed on the photoconductive cylinder  20  may be transferred to a blanket  28 , and from the blanket to a sheet of paper or other print medium  30 . A controller  40  controls the operation of the printer  12  through control lines  32 .  
         [0009]     The seven developing stations  26  may be used for primary colors such as cyan, yellow, magenta, black, orange, violet, (CMYKOV) and a spot color. Other combinations of colors may be used, for example, cyan, yellow, magenta, black (CMYK) primary colors may be used while orange and/or violet may be replaced by a second and third spot color. Alternatively, fewer than or more than seven developing stations  26  may be used. The CMYK or CMYKOV colors are usually overlaid to build up the various colors needed for a color image. Spot colors may be used in commercial printing, for example, to print a distinctive color associated with the customer. A spot color is usually laid down in a separate page space from the CMYK or CMYKOV overlay. However, a spot color is sometimes laid down on top of a single other color to form a “duotone.” 
         [0010]     Referring also to  FIG. 2 , each developing station  26  is supplied by a respective ink tank  42 . Each ink tank  42  has a pump  56  under control of the controller  40  that can deliver ink, which in this embodiment is ink solution, from the ink tank through a pipe  58  to the respective developing station  26 . Used ink solution is returned from the developing station  26  through a pipe  60 . In this embodiment, when the printer is in operation, the ink solution is constantly circulated through the pipes  58 ,  60 . This maintains even mixing of the ink solution both in the tank  42  and in the pipes  58 ,  60  and the developing station  26 . Thus, evenly mixed ink solution is immediately available whenever it is needed for printing. In the interests of clarity, only one ink tank  42  is shown in  FIG. 2 . All of the ink tanks  42  have substantially identical connections. The ink tanks can be removed easily from the printer  12 , as is described in more detail below. The pump  56  is equipped with a filter, which is coarse enough to permit the mixed ink solution to flow through it freely, but removes coarse contaminants.  
         [0011]     Each ink tank  42  has a dispenser  62  for colorant, which in this embodiment is ink concentrate, and has feeds for carrier liquid, which in this embodiment is imaging oil, from an oil tank  64  and for conductivity agent from a conductivity agent tank  66 . In this embodiment, the ink concentrate is a can of ink paste. The ink paste is stable in the can, and is suspended in the oil in use. Although the liquid in the tanks  64  is referred to as “ink solution,” in this embodiment the “ink solution” is a suspension of very fine solid ink or toner particles in the imaging oil. In the embodiment shown in  FIG. 2 , the printer  12  has a single, common oil tank  64  with a pump  67 , and a single, common conductivity agent tank  66  with a pump  68 . These deliver oil and conductivity agent through a system of valves  69  to any selected ink tank or ink tanks. Each ink tank  42  also has sensors that monitor the concentration of oil and conductivity agent, the level of ink solution in the tank, and other properties of the ink solution. The controller  40  monitors the condition of the ink solution in the tanks  42  and controls the circulation pump  56  and the feeds from the ink paste dispenser  62 , the oil tank  64 , and the conductivity agent tank  66  so as to maintain the desired color density, conductivity, and other properties in the ink tanks. The oil tank  64  and the conductivity agent tank  66  can be refilled as necessary through inlet funnels  70 ,  72  respectively.  
         [0012]     In some circumstances, for example, when a spot color, that is to say, a color specifically chosen for a particular print job, is to be produced, one of the ink tanks  42  may be provided with two or more ink paste dispensers  62  containing different colors of ink paste. The controller  40  then controls the dispensers  62  to produce an ink solution with a color that is a desired blend of the colors of the ink pastes. Alternatively, a single ink dispenser  62  may be loaded with an ink paste formulated to produce the spot color.  
         [0013]     In the embodiment shown in  FIG. 1 , the ink builder  14  comprises seven ink tanks  42 . However, the ink builder  14  may have more or fewer ink tanks than seven, and may have more or fewer ink tanks than the printer  12 . The ink tanks  42  are easily removable from the ink builder, and are the same as the ink tanks  42  of the printer  12 . When the ink solution is stored in the tanks  42 , it may deteriorate because the suspended ink particles may settle out and the composition of the ink becomes uneven. As mentioned above, each ink tank  42  has a pump  56 . In the ink builder  14 , the pump  56  stirs the ink solution in the tank by circulating it via a pair of pipes  90 ,  92 . Each ink tank has one or more dispensers  62  for ink paste, and has dispensers that in this embodiment are feeds for oil from an oil tank  94  and for conductivity agent from a conductivity agent tank  96 . The feeds for oil and conductivity agent in the ink builder  14  may be similar to the feeds for oil and conductivity agent in the printer  12 .  
         [0014]     When the ink is stored in the ink tank  42 , the ink may deteriorate because of changes in the chemical composition of the ink. As mentioned above, each ink tank  42  also has sensors that monitor the concentration of oil and conductivity agent, the level of ink solution in the tank, and other properties of the ink solution. In the ink builder  14 , the sensors are connected to a controller  100 . The controller  100 , like the controller  40  in the printer  12 , monitors the condition of the ink solution in the tanks  42  and controls the circulation pump  56  and the feeds from the ink paste dispenser  62 , the oil tank  94 , and the conductivity agent tank  96  so as to maintain the desired color density, conductivity, and other properties in the ink tanks. A filter  102  can be connected into the circulation pipe  90  by operating three-way valves  104 . The filter  102  is sufficiently fine to remove the ink and conductivity agent from the ink solution, leaving essentially clean oil. The filtered oil may be returned to the ink tank  42  through the circulation pipe  92 . Alternatively, the filtered oil may be returned to the oil supply tank  94 .  
         [0015]     Referring now to  FIGS. 4 and 5 , each ink tank  42  has its pump  56  inside the tank, so that in use the pump is immersed in the ink solution in the ink tank. The pump  56  is placed low in the tank, with its intake near the bottom of the tank, to avoid uncirculated ink solution settling out at the bottom of the tank. Alternatively, the pump  56  may be equipped with a stirrer or impeller that agitates the ink solution within the tank. The pump  56  is driven by a drive shaft  106  that extends upwards through a top cover  108  of the ink tank  42  to a coupler  110 .  
         [0016]     An outlet  112  of the pump  56  is connected by a hose  114  to a connector  116 , with an O-ring  118 , projecting above the top cover  108 . An inlet  120  for returning ink solution is provided in the top cover  108 . An inlet  122  for ink paste is provided with a smooth bore in which an O-ring can seal, and is connected by a hose  124  to the pump  56 , so that ink paste fed into the ink tank  42  is immediately dispersed in the oil by the pump. A circuit board  126  carrying the various sensors  128  is mounted on the pump  56 . The electrical conductivity of liquid electrostatic ink solution is typically sufficiently low that elaborate measures to protect the circuit board  126  from the liquid ink solution are not generally employed, although some may be employed in some applications. The circuit board  126  is wired to a connector  128  on the top cover  108 .  
         [0017]     A separate connector  130  is provided in the front of the ink tank  42  for water, which circulates through a tube  132  to warm or cool the ink solution in the ink tank  42 .  
         [0018]     Referring now especially to  FIG. 5 , for each ink tank  42 , the printer  12  and the ink builder  14  are provided with a motor lift and tank interface unit  140 , which fits over the top of the ink tank and connects with the top plate  108 . The interface unit  140  has mounted on it an electric motor  142 , with a descending output shaft ending in a coupler  144  that mates with the coupler  110  on the pump drive shaft  106 , so that the motor  142  can drive the pump  56 . The interface unit also has a receptacle  146  for the ink paste dispenser  62 , with an outlet hose  148  leading to a connector  150  with an O-ring seal  152  that fits into the smooth bore of the ink paste inlet  122  on the top plate  108  of the ink tank  42 .  
         [0019]     The interface unit  140  also has an outlet connector  154 , which has a smooth bore that fits over the O-ring  118  on the outlet connector  116  of the ink tank  42 , and is connected to the outlet hose  58  or  90 . The interface unit  140  also has an inlet connector  156 , which opens out through the inlet connector  120  of the ink tank  42 , and is connected to the return hose  60  or  92 . The interface unit  140  also has an electrical connector  158  that mates with the connector  128  and is connected to the controller  40  or  100 . The interface unit  140  is provided with angled slots  160  with horizontal upper ends  162  and horizontal lower ends  164  that are open downwards. By engaging crossbars or studs on a slider that moves backwards and forwards in a horizontal plane, the angled slots  160  enable the interface unit  140  to be raised and lowered by a controlled amount, between a position in which all of the connectors on the interface unit  140  are properly mated with their corresponding connectors on the top cover  108  of the ink tank  42  and a position in which all of the connectors are clear and the ink tank  42  can be removed horizontally from under the interface unit  140 .  
         [0020]     In normal use, the printer  12  prints using ink solutions from the ink tanks  42  in the printer, which are constantly replenished with oil from the tank  64 , ink paste from their respective dispensers  62 , and conductivity agent from the tank  66 . In the course of the printing process, ink and a certain amount of conductivity agent is transferred to the image being printed, while most of the oil is returned to the ink tank  42 . The ink solution in the ink tank  42  is thus both depleted in volume and reduced in concentration of ink and conductivity agent. Consequently, the composition of the ink solution can be maintained by additions of oil, conductivity agent, and ink paste.  
         [0021]     Most of the time, the ink builder  14  maintains the composition of the ink solution in the ink tanks  42  in the ink builder. Once an ink tank  42  is full, and has the correct concentrations of ink and conductivity agent, little or no further additions or removals are generally necessary. The ink builder  14  may have a duplicate ink tank for each color of ink solution that the printer  12  is using. However, where a spot color is being used for a comparatively short job, or for a job that is about to end, a duplicate tank of ink solution of the spot color may be unnecessary. If there is a spare tank in the ink builder  14 , for example, because the ink builder  14  has more tanks than are being used on the printer  12 , or because a tank of a spot color is not being duplicated, the spare tank may be used to build a spot color for a forthcoming job.  
         [0022]     There are many ink solution variables that affect the print quality. These include, for example, temperature, conductivity, viscosity, and humidity. If the concentration of ink or conductivity agent in the liquid ink solution in one of the tanks  42  on the printer  12  falls below the desired level, the concentration can be increased, by adding more from the ink paste dispenser  62  or the conductivity agent tank  66 , as fast as the pump  60  can mix the addition into the contents of the tank. If the concentration rises too high, it can be reduced only as fast as the ink solution in the tank  42  is used for printing and can be replaced by oil  64 . If a contaminant, including excess moisture, appears in the ink tank  42  it is eliminated in printing only as fast as the contaminated ink solution is applied to printing and replaced with clean ingredients. If sediment builds up in the tank  42  or on the sensors  68 , it can be removed only by draining and cleaning the tank.  
         [0023]     In any of those cases, absent the ink builder  14 , the printer operator would be faced with the choice of using ink solution with an incorrect composition, and potentially producing sub-standard printing, unless and until the error gradually corrected itself, or stopping the press, discarding the contents of the ink tank  42 , cleaning the ink tank and pipework  58 ,  60 , refilling the ink tank with clean oil, and building up the ink and conductivity agent concentrations until the ink solution is usable. Rebuilding the ink solution typically involves adding conductivity agent and ink concentrate manually in stages until the concentrations are approximately at the minimum edge of the usable range, and then allowing the controller  40  to raise the concentrations further as the printer  12  runs. In some embodiments of liquid-ink electrostatic printer  12 , the entire cleaning and rebuilding process can take up to about 30 minutes before the printer can be used again.  
         [0024]     In the present embodiment, if there is a duplicate ink tank of the same color in the ink builder  14 , the operator merely needs to remove the tank of defective ink solution from the printer  12 , clean the developing unit  26  and the pipes  58 ,  60  from the ink tank  42  to the developing unit  26 , and insert the duplicate tank from the ink builder  14 . Depending on the exact design of the printer  12 , the cleaning may merely need squirting a slug of clean oil through the pipes  58 ,  60  from a hand oil can. In some embodiments of a printer, this can take about two minutes instead of about 30 minutes. Alternatively, a spare ink tank  42  containing clean oil may be temporarily inserted into the printer  12 , and the clean oil circulated through the pipes  58 ,  60  and the developing unit  26  to flush them out.  
         [0025]     The operator then inserts into the ink builder  14  the tank  42  of ink solution removed from the printer  12 , and reconditions the ink solution by adding ink or conductivity agent as needed. This may still take 30 minutes, but the printer  12  is running during those 30 minutes with the duplicate tank  42  of ink solution, so little production time is lost. The ink solution seldom becomes defective, and the probability of the same ink solution in both the printer  12  and the ink builder  14  becoming defective at the same time is low.  
         [0026]     If the defective ink solution has too much ink or conductivity agent in it, or is contaminated, the operator sets the valves  104  so as to pass the ink solution through the filter  102 . The filter  102  can remove some of the ink and conductivity agent, leaving oil with a low concentration of ink or conductivity agent that can be built up again. Alternatively, the filter  102  can remove substantially all of the ink and conductivity agent, leaving essentially clean oil that can be re-used, even for ink solution of a different color. Filtration may thus also be used when a tank of spot color needs to be replaced by a different spot color. The old color is filtered out, the oil is reused, and the tank is built up to the new color. The ink and conductivity agent filtered out are discarded. However, a typical ink tank may contain a gallon (3.8 liters) of oil and a few ml of ink and conductivity agent. Typically, about 98% of the content of the tank is the oil, which in this embodiment can be recovered and reused. This process, according to some embodiments, may be beneficial to the environment in comparison with the situation absent the ink builder  14 , where in practice the operator would frequently discard the entire tank of defective oil in order to replace the tank and resume printing as quickly as possible.  
         [0027]     If the printer  12  is shut down for any reason, so that the controller  40  or the pumps  56  stop working, the ink solution in the tanks  42  will gradually separate and become useless. It may be possible to re-homogenize the ink solution when the printer is started up, but that may take considerable time. Alternatively, all of the tanks  42  can be emptied and cleaned before startup or (if the shutdown was planned) on shutdown. The tanks must then be filled with clean oil and the ink solutions rebuilt before printing can resume. However, if the ink builder  14  contains duplicate tanks, it may be possible to keep the ink builder operating during the shutdown. Then, at startup, the good duplicate tanks from the ink builder  14  are swapped into the printer  12 , and printing can start immediately. The empty or separated ink tanks from the printer can then be rebuilt in the ink builder  14  while the printer is operating.  
         [0028]     If a power outage disables the ink builder  14  as well as the printer  12 , of course the ink solutions will need to be rebuilt on startup. However, if the printer  12  is shut down for maintenance, the ink builder  14  may be kept operating. If the printer  12  is shut down overnight or at weekends to save power, the ink builder  14  can economically be kept in operation, because, according to some embodiments, it may be a much smaller device.  
         [0029]     As noted above, it may not be necessary to use all of the ink tanks in the ink builder  14  to duplicate ink tanks in the printer  12 . For example, the ink builder  14  may have more tanks in it than the printer  12 . For example, the printer  12  may not be using every tank, especially if one tank is used only for spot colors, and there is no spot color in the present print run. For example, if the printer is near the end of a run, the operator may judge that the risk of needing to replace the spot color tank is too small to need a duplicate. In any of those cases, an ink tank  42  in the ink builder that is not needed as a duplicate may be used to build a spot ink solution for a future print job.  
         [0030]     If the print job is sent to the printer in machine-readable format, that format may include data specifying the ink colors to be used, including any spot colors. The print job may then be sent first to the controller  100  of the ink builder  14 , which extracts the ink color data. If the ink color data include a color that is not already available, and there is an unused tank  42 , the ink builder  14  may automatically start to build the specified ink solution. If there is no unused tank, the controller  100  of the ink builder may signal to the operator to release a tank from its previous assignment. When the ink solution is ready, the controller  100  of the ink builder  14  may send details of the actual ink solution to the controller  40  of the printer  12 . The printer  12  then adds the new color to its list of available colors. When the printer  12  is ready to start printing the print job including the new color, the printer prompts the operator to change ink tanks. The operator then need merely select the color of the new ink solution from the list of available colors. Introducing a new spot color on the printer can thus be not only quick, but simple.  
         [0031]     In the present embodiment, the controllers  40  and  100  are provided with software to interpret machine-readable document files. An example of such files is a file having data in the Adobe® PostScript® page definition language. The software on the controller  40  is arranged to convert an incoming file in a suitable format into commands causing the printer  10  to print the desired document. The incoming file may include information naming or otherwise specifying colors of ink solution to be used in printing the document. The incoming file may be “pre-separated” into a stack of single-color images, one for each of the developing stations  26 .  
         [0032]     The controller  100  of the ink builder  14  includes software to parse the file and identify the colors specified. If a file has been received that specifies a color that needs ink mixing, for example, a spot color, the controller  100  launches an alert to its operator on a console  170 . A list of the spot colors used within the file is displayed. The controller  100  displays on the console  170  whether or not it recognizes the color names, and specifically lists the name of a color the controller thinks should be mixed as a spot color, rather than being generated on the press from the basic CMYK or CMYKOV colors. The operator has the option of using the color name read from the file (for the mixed ink solution) or of creating a new ink name. As an alternative to using the software&#39;s internal formulations for the needed color, the operator may have the option of measuring the actual color of a sample swatch via a spectrophotometer  172 .  
         [0033]     Having selected one or more colors to be mixed as spot colors, an operator then mixes ink paste and fills a dispenser  62  for each new spot color. An ink profile is created, identifying the ink color and specifying the correct conductivity, density, and other properties to be measured by the sensors  128 . The controller  100  then prompts the user to replace an existing profile for one of the tanks  42  in the ink builder  14 . The controller  100  knows which tank  42  has clean oil in it via the sensors  128  in the tank, and may prompt the operator to select such a tank. If the operator chooses to use a tank full of ink solution, the system prompts the user to run a tank cleaning cycle. After the tank cleaning cycle has been run, and the oil in the tank  42  is satisfactorily clean, the new profile is applied to that tank. The operator mounts the dispenser  62  containing the newly mixed ink paste on the selected tank  42 .  
         [0034]     The ink solution is then built by gradually introducing the ink paste from the dispenser  62  and conductivity agent from the conductivity agent tank  96  into the clean imaging oil in the tank  42 .  
         [0035]     When the new ink solution has been successfully built by the ink builder  14 , the system offers to configure the document file interpreting software to recognize the newly mixed color(s) within the file and relate the color(s) named in the file to the ink solution just mixed. If the operator agrees, the system sets up a configuration to recognize the color separation(s) named in the file and then reprocesses the document file to ensure that the configuration is valid and works correctly. If the original document file was pre-separated, not using the spot color that has just been mixed, then the separations must be regenerated using the new spot color. After processing the document file, a press ready file is generated. A preview of that file may be displayed on the display monitor of the console  170  showing all the colors/separations to be printed.  
         [0036]     The document file is then sent to the controller  40  of the printer  12 . When the printer  12  is ready to print that document, the system prompts the user to “replicate” the color on the printer  12  and to select which ink solution tank  42  on the printer is be replaced. The controller  100  sends the profile for the new ink solution to the controller  40 , which loads the profile and associates it with the appropriate tank position. An operator swaps the tank  42  of freshly mixed ink solution from the off-line ink builder  14  with the tank from the printer  12 , and swaps the dispenser  62  containing the ink paste for the new color. The printer  12  is then able to maintain, and print with, the new color.  
         [0037]     Although embodiments of the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of the invention as defined by the appended claims.  
         [0038]     For example, the embodiment described comprises a seven-color printer  12 . The printer  12  may have more or fewer than seven colors, such as one, four, five, or six colors. A six color printer may provide CMYK, orange and purple, or CMYK and two spot colors. A five color printer may provide CMYK plus a spot color. Other color palettes may be used for particular jobs.  
         [0039]     The ink builder  14  need not be a single physical unit. It may have a compact structure, with several ink tanks sharing a single oil tank  94 , conductivity agent tank  96 , filter  102 , and other common resources. However, any configuration that fits the space available in the printshop and serves a suitable function may be used. In a printshop having more than one printer  12 , the printers may share one or more ink builders  14 . In that case, the number of ink builder tanks for a color used by more than one printer may be less than the number of printers. Alternatively, if a particular ink solution becomes unusable very frequently, more than one ink tank duplicating that ink solution may be provided for a printer.  
         [0040]     Although the printer  12  and the ink builder  14  can share some services, they may be as nearly independent as possible, to minimize the number of occasions on which a shutdown of or problem with a common service requires both the printer and the ink builder to be shut down simultaneously. Although the printer  12  and the ink builder  14  may be fairly close together, so that gallon tanks of ink solution can be quickly and easily transferred from one to the other, they may be sufficiently far apart that neither unit needs to be shut down when the other is being serviced.  
         [0041]     Alternatively, an ink builder  14 , especially one that has only one or a few ink tanks, could be used solely for preparing spot colors for future print jobs while the printer  12  is printing a previous job. By reducing the down time when a spot color is changed from 20 or 30 minutes to 2 minutes, this greatly reduces the minimum size of print run for which a spot color is economic.  
         [0042]     Although some embodiments are directed to a liquid-ink electrostatic printer  12 , embodiments of the present invention may be applied to any suitable form of printing ink in which active maintenance may be generally employed to inhibit deterioration of at least one property of the ink and keep it ready for printing. Although some embodiments are directed to a printer  12  receiving as input a file in machine-readable form, embodiments of the present invention may be directed to other forms of hard copy device, including photocopiers and facsimile machines.  
         [0043]     Moreover, the scope of the present application is not intended to be limited to the particular embodiments of invention described in the specification. As one of ordinary skill in the art will readily appreciate from the foregoing description, processes, machines, articles of manufacture, compositions of matter, means, methods, or steps presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized to implement and carry out the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, articles of manufacture, compositions of matter, means, methods, or steps.  
         [0044]     The foregoing describes the invention in terms of embodiments foreseen by the inventors for which an enabling description was available, notwithstanding that insubstantial modifications of the invention, not presently foreseen, may nonetheless represent equivalents thereto.