Apparatus for preventing electrostatic charge build-up on CRT monitors
TECHNICAL FIELD OF THE INVENTION 
     This invention relates to CRT monitors and, more particularly, to preventing electrostatic charge build-up on the display screens thereof. 
     BACKGROUND OF THE INVENTION 
     In using a computer-controlled CRT monitor (preferably of the graphics display type) as a visual aid in circuit pack assembly and/or testing operations, for example, excessively high values of electrostatic charge normally tend to build up on the cathode ray tube (CRT) screen (or face plate) of such a monitor. Such an electrostatic charge can often seriously impair, if not destroy, the operating functions of many types of IC devices, particularly those of the mos-type, should they be brought into the field of such charge during routine handling at an assembly or test station. 
     When monitors of the above type have been employed in high volume applications heretofore, they have also typically been arranged in multiple rows, and independently housed. Such an arrangement not only requires considerable costly factory floor space, but has not been conducive to the utilization of any common means associated with the monitors for overcoming the troublesome problem of electrostatic charge build-up on the screens thereof. 
     SUMMARY OF THE INVENTION 
     It, therefore, is an object of the present invention to prevent the build-up of electrostatic charge on the screen of one or more CRT monitors in a simplified, inexpensive and reliable manner and, in so doing, in no way interfering with the necessary work functions, or comfort, of an operator. 
     In accordance with the principles of the present invention, the above and other objects are realized in one preferred embodiment through the use of a de-ionizing air generating system which is applicable for use with any type of CRT monitor. The generating system includes an ionized air blower, a fan-out nozzle, a forming nozzle and shields to provide and direct a continuous, low velocity, laminar-type stream of de-ionizing air across the entire outer surface of the CRT monitor screen, from the top to the bottom thereof in accordance with several preferred illustrative embodiments. Considered more specifically, the initially ionized air produced (or generated) by the blower, upon being channeled into a laminar-type air stream, and then directed across an energized CRT monitor screen (or face plate), actually becomes what is referred to hereinafter as a de-ionizing air stream. The rate at which such a de-ionizing stream becomes de-ionized is accelerated in accordance with the principles of the present invention (because of progressively becoming more neutralized) when directed across, and subjected to an electrostatic charge tending to otherwise build-up on, the screen of an energized monitor. 
     Significantly, it is such a controlled and confined de-ionizing air flow that advantageously has been found to prevent any build-up of detrimental electrostatic charge on the monitor screen. In addition, neither the de-ionizing air generating system nor the confined flow of de-ionizing air produced thereby, in any way interferes with the work functions required of any operator. 
     In accordance with other embodiments of the invention, a common de-ionizing air generating system may be employed with two or more CRT monitors, and may be secured either to the cabinet of each monitor, or to an auxiliary housing employed to enclose both the generating system and whatever number of monitors are employed therewith. In two preferred multi-monitor assembly embodiments, for example, four CRT monitors are uniquely clustered to conserve space in diametrically disposed, offset pairs within a common quadrangular housing, together with a de-ionizing air generating system that is secured to only the housing. Such an arrangement advantageously allows the use of either a single, common de-ionized air blower, or a pair of such blowers, each associated with a different pair of monitors, to direct a uniformly distributed flow of such air to all four monitors in a simplified and inexpensive manner. With the de-ionizing air generating system being secured to only the housing, any of the monitors may be readily removed therefrom for repair or replacement. Additional embodiments of the invention disclose how a common de-ionizing air generating system may be employed with any number of CRT monitors, whether arranged in a predetermined cluster, or in a row. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a CRT monitor assembly, including a cabinet-confined monitor, and a de-ionizing air generating system mounted on the cabinet, the latter being adapted to provide and direct a confined, laminar-type stream of de-ionizing air across the monitor screen so as to prevent detrimental electrostatic charge build-up thereon in accordance with the principles of the present invention. 
     FIG. 2 is a side elevational view of the CRT monitor assembly of FIG. 1, with the cathode ray tube of the monitor shown in phantom; 
     FIG. 3 is a side elevational view illustrating an embodiment of the invention similar to that of FIG. 1, but distinguishing therefrom by having the major portion of the de-ionizing air generating system mounted beneath the monitor, so as to effect a laminar-type flow of de-ionizing air across the monitor screen from the bottom to the top thereof in accordance with the principles of the present invention; 
     FIG. 4 is a side elevational view illustrating an embodiment of the invention also similar to that of FIG. 1, but distinguishing therefrom by having the major portion of the de-ionizing air generating system mounted on one side of the monitor cabinet, so as to effect a flow of de-ionized air laterally across the monitor screen; 
     FIG. 5 is a perspective view of a CRT monitor assembly, including a common auxiliary housing for a cabinet-confined monitor, and a de-ionizing air generating system, the latter being adapted to provide and direct a confined, laminar-type stream of de-ionizing air across the monitor screen in accordance with the principles of the present invention. 
     FIG. 6 is a side elevational view, partially broken away, of the CRT monitor assembly embodiment of FIG. 1, with the cathode ray tube of the monitor shown in phantom; 
     FIG. 7 is a perspective view of a CRT monitor assembly, partially broken away, illustrating the manner in which four monitors are arranged in a particular cluster within a common housing, together with a de-ionizing air generating system secured to only the housing, the generating system including two de-ionized air blowers, each one being associated with a different pair of CRT monitors to provide, through the ducting and nozzles coupled thereto, a uniformly distributed, laminar-type stream of de-ionizing air across the screens of the associated monitors in accordance with the principles of the present invention; 
     FIG. 8 is a plan view of the CRT monitor assembly of FIG. 7, showing in greater detail the manner in which the four monitors are arranged in a particular cluster within the common housing, and selectively coupled to the two de-ionizing air generating system blowers; 
     FIG. 9 is a fragmentary side elevational view, partially broken away, illustrating the ducting, and fan-out and forming nozzles associated with two of the four CRT monitors arranged in the cluster depicted in FIG. 6; 
     FIG. 10 is a plan view of a CRT monitor assembly similar to that of FIGS. 7-9, but distinguishing therefrom by utilizing a single de-ionized air blower common to all four CRT monitors; 
     FIG. 11 is a schematic plan view of a CRT monitor assembly wherein two monitors are arranged in a back-to-back relationship, with a common de-ionizing air generating system, and 
     FIG. 12 is a schematic plan view of a CRT monitor assembly wherein two (or optionally more) monitors are arranged in juxtaposed relationship, with a common de-ionizing air generating system. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It should be appreciated that while the invention is described in detail herein primarily in regard to preventing electrostatic charge build-up on CRT monitors employed in connection with the assembly and/or testing of circuit packs, or boards, utilizing IC devices, the elimination of such electrostatic charges may be of equal importance and significance in diverse other applications and environments. 
     As previously noted, it has been found that the operating functions of many types of IC devices, particularly those of the aforementioned mos-type, can be seriously impaired, if not destroyed, should they be brought into the field of a CRT-generated electrostatic charge, often exhibiting voltage levels on the order of 4,000 to 5,000 volts, albeit with extremely low levels of current. 
     With particular reference now to the first of several preferred embodiments of the invention, FIGS. 1 and 2 depict a CRT monitor assembly 10 that includes a video display monitor 11 and a de-ionizing air generating system 12, the latter being mounted on the top surface of a conventional cabinet 13 that normally forms part of the monitor. An optional auxiliary housing for such a composite assembly will be described hereinbelow in connection with a related embodiment of the invention depicted in FIGS. 3 and 4. 
     The monitor 11 in FIG. 1, as well as in all of the embodiments, may be of a conventional type utilizing either black and white or color display circuitry, with the appropriate cathode ray tube. The monitor may also have computer-controlled display capability, as desired for the particular application of concern herein. 
     In accordance with the principles of the present invention, the de-ionizing air generating system 12 includes an ionized air blower 14, with an output port 14a (see FIG. 2) coupled to an associated duct 16 which, in turn, is coupled to a wedge-shaped fan-out nozzle 18. The latter communicates with an arcuate air stream-forming nozzle 21, and two monitor side shields 23 and 24. It should be understood, of course, that while the duct 16, fan-out nozzle 18 and forming nozzle 21 are described as being formed of separate, but interconnected parts, they could also be readily fabricated initially during manufacture as a composite one or two-piece unit. One preferred type of de-ionized air blower found to be very effective for the purpose in question is sold by the 3M Company, as Model No. 905, and is adapted to function as either a single or dual output port type. 
     With respect to the forming nozzle 21, it is dimensioned and positioned not only to extend laterally across the upper forward edge of the monitor cabinet 13, but is suitably contoured so as to also extend around that cabinet edge and, thereby, direct a laminar-type flow of de-ionizing air downwardly across the entire outer surface of the monitor screen 26. To further control the velocity of the de-ionizing air, an adjustable baffle 16a is mounted within the duct 16. 
     The side shields 23, 24, as positioned on the monitor cabinet 13, essentially form extensions of the forming nozzle 21 and, thereby, further confine the flow of de-ionizing air across only the monitor screen. While the shields are shown as formed with an outward, downwardly extending taper, rectangular shields of suitable width could also be employed with equal effectiveness. As illustrated, the side shields are interconnected by, and may form an integral part of, an intermediate support shield or plate 27. This not only facilitates the mounting of the shields adjacent (and optionally secured to) opposite sides of the monitor screen, but allows an arcuate portion of the forming nozzle 21 to pass through a slot 27a formed in the support plate and, thereby, be supported by the latter. 
     Should it be desired in any particular application to defuse the downwardly directed flow of de-ionizing air upon the latter impinging against, a workbench (or desk top) 31 on which the monitor 11 is mounted, a suitable mesh screen (or porous membrane) 36 could be optionally positioned within a pre-formed slot 37 formed in the workbench, as shown in phantom in FIG. 2. Such an airflow passageway would effectively minimize any possibility of the de-ionizing air being reflected partially outwardly and upwardly to cause a noticeable draft to an operator. In practice, however, when utilizing a low velocity flow of de-ionizing air produced at room temperature, it has been found to present no discomfort to an operator while positioned in close proximity to the monitor. 
     With the flow of de-ionizing air being controlled and confined as described above, it has advantageously been found to completely prevent the build-up of any detrimental electrostatic charge on the outer surface of the monitor screen 26. In addition, neither the de-ionizing air generating system, nor the confined, downwardly directed flow of air produced thereby, as noted above, in any way interferes with either the comfort of an operator or the work functions performed by the latter while positioned in close proximity to the monitor. 
     Should it be desired for any reason to direct the flow of de-ionizing air across the monitor screen from the bottom to the top, rather than vice versa, this may be readily accomplished by simply mounting the major portion of the de-ionizing air generating system beneath the monitor, and preferably beneath the workbench (or desk top) upon which the monitor is supported, as depicted in FIG. 3. With the various elements in FIG. 3 that at least substantially correspond with those in FIGS. 1 and 2 being identified by like, but primed, reference numerals, it is seen that the de-ionized air blower 14&#39;, duct 16&#39;, fan-out nozzle 18&#39; and major portion of the forming nozzle 21&#39; are all mounted on the underside of a workbench 31&#39;, such as by means of suitable support brackets 37. 
     With such an arrangement, the workbench 31&#39; (or desk top) would require a slot 38 formed therethrough in a region along the lower forward edge of the monitor cabinet 13&#39; so as to allow the arcuate, forward end of the forming nozzle to project upwardly therethrough. With the forming nozzle thus directed, it is seen that while the side shields 23&#39;, 24&#39; could be identical to those in the embodiment of FIGS. 1 and 2, it would normally be preferable for the shields to be of maximum width at the base of the monitor, and taper inwardly toward the top thereof so as to more effectively confine the flow of de-ionizing air across the screen 26&#39;. 
     To that end, the side shields 23&#39;, 24&#39; are illustrated as being respectively secured along opposite edges of the monitor cabinet 13&#39;, with an optional interconnecting center leg portion 39 (shown in phantom) secured to or resting on the top edge of the monitor cabinet, and preferably slotted to allow the stream of de-ionizing air to pass therethrough. As previously noted, the shields 23&#39;, 24&#39; could also be formed without any taper, if desired, e.g., be of rectangular cross-section, or have outer edges of any desired compound contour, such as for esthetic reasons, and still accomplish the same desired results. 
     It should also be appreciated that the entire de-ionizing air generating system 12&#39; in FIG. 3 could also be mounted on the top side of the workbench 31&#39;, such that the duct 14&#39;, fan-out nozzle 16&#39; and a portion of the arcuate forming nozzle 21&#39; would be interposed between the base of the monitor cabinet 13&#39; and the top surface of the workbench 31&#39;. This arrangement would obviate the need for any forming nozzle-receiving slot in the workbench, but would require a spaced array of support brackets, or spacer blocks (not shown) to allow the positioning of the de-ionizing air generating system 12&#39; between the CRT monitor and the workbench. 
     FIG. 4 illustrates another alternative arrangement of the de-ionizing air generating systems of FIGS. 1 and 3, with like, but higher-primed reference numerals identifying corresponding elements. As shown, the de-ionizing air blower 14&#34;, duct 16&#34;, fan-out nozzle 18&#34; and forming nozzle 21&#34; are all suitably secured to one chosen sidewall of the monitor cabinet 13&#34; so as to produce and direct a desired laminar-type stream of de-ionizing air across the monitor screen 26&#34; from the chosen side to the opposite side thereof. In all other respects, the monitor assembly 10&#34; of FIG. 4 functions in the same manner, and produces the same beneficial results, realized in accordance with the first two preferred embodiments depicted in FIGS. 1 and 3. 
     Attention is now directed to FIGS. 5 and 6 which illustrate a CRT monitor assembly 40, the latter distinguishing from the monitor assembly 10 of FIGS. 1 and 2 by including not only a CRT monitor 42 and a de-ionizing air generating system 45, but an auxiliary housing 46 therefor, all mounted on a suitable workbench or table 48. More specifically, the housing is adapted to confine not only the monitor 42 (with or without a cabinet) therewithin, but the de-ionizing air generating system 45, with the latter being secured to the housing in spaced relationship from the monitor cabinet, if employed, so as to in any event facilitate the removal of the monitor for repair or replacement whenever desired, or necessary. 
     To that end, a duct 47 is shown with brackets 47a attached thereto so as to facilitate the securement of not only that duct, but the interconnected blower 48, fan-out nozzle 51 and forming nozzle 52, all comprising the de-ionizing air generating system 45, to the top wall 53 of the housing 46. If desired, of course, the composite system 45 could be indirectly secured to either the top wall or sidewalls of the housing 46 through the use of any suitable cross-beams, or girders (neither shown) associated with the housing. 
     In order to facilitate the removal of the monitor 42 from the housing 46, it is preferable that the forming nozzle 52 be releasably coupled to the fan-out nozzle 51, and supported by a slide-out support or shield plate 54, having a laterally disposed slot 54a formed therethrough both to receive and support an arcuate portion of the forming nozzle. By way of illustration, the support plate 54 is shown resting at opposite ends on respectively associated brackets 56 secured to the sidewalls 57 of the housing. As thus mounted, the support plate 54 functions as a slide-out shelf so as to facilitate the removal of the CRT monitor from the housing. Such monitor removal is further facilitated by having a forward top wall portion 53a of the housing pivotally mounted, such as by hinges 59. 
     In situations where the housing 46 is dimensioned to provide close-fit confinement of a given CRT monitor therewithin, the housing sidewalls 57 can be readily formed with tapered forward portions 57a, as illustrated, to also function as side shields, and, thereby, facilitate the confinement of the flow of de-ionizing air 58 (shown by dash lines) across the monitor screen 42a from the top to the bottom thereof. Should such a close-fit relationship not always exist, or be desired, because of the housing being constructed for universal use with many different brands of monitors, for example, separate side shields of the type depicted in the first embodiment of the invention could be readily employed. Such shields, for example, could be secured to, or formed as an integral part of, the removable support plate 54, or be separately secured to the sidewalls 57 or the top wall 53 of the housing, or to the sidewalls of the monitor cabinet, in any suitable manner. In all other respects, the de-ionizing air generating system 45 functions in the same manner as the system employed in the first embodiment depicted in FIGS. 1 and 2 to produce the same beneficial end results. 
     In this regard, it is understood, of course, that the housing 46 could also be readily constructed to allow the de-ionizing air generating system 45 to be positioned either along one side of the confined monitor, or beneath the monitor. As such, a flow of de-ionizing air could be readily directed either laterally or upwardly across the screen 42a, if desired, in accordance with the principles of the invention disclosed in FIGS. 3 and 4, and described hereinabove in connection with the description of the first embodiment. 
     It should also be appreciated that the blower 49, as well as fan-out nozzle 51, could be independently secured to the housing 46, as is the duct 47, as illustrated. This would depend to a great extent on the strength and rigidity of the material employed to form the duct and nozzles. Similarly, it should be understood that the housing could obviously be dimensioned so as not to include the blower 49 therewithin, if desired. As for the actual configuration of the housing per se, particularly the top thereof, it is only restricted by the requirement of accommodating a given monitor and the de-ionizing air generating system, thus leaving considerable design flexibility relative to its esthetic appearance. 
     Another preferred embodiment of the invention is illustrated in FIGS. 7-9, wherein a CRT monitor assembly 60, supported on a suitable workbench or table 62, includes a special housing 65 of quadrangular configuration, the latter being adapted to confine therewithin a cluster of four CRT monitors 66-69, and a common de-ionizing air generating system 70 associated therewith. The four monitors are arranged in a unique cluster, namely, in diametrically disposed, offset pairs identified by the reference numerals 66, 68 and 67, 69. This clustered arrangement advantageously conserves costly floor space, and also facilitates the simplification of the de-ionizing air generating system 70. 
     Considered more specifically, the system 70 comprises two commercially available dual output port ionized air blowers 71, 72 respectively coupled to a different pair of ducts 76-77 or 78-79 which, in turn, are respectively coupled to an associated one of four fan-out nozzles 81, 82 or 83, 84. The outer flared end of each nozzle is connected to, or merges into, an associated one of four arcuate forming nozzles 86-89. 
     In order to facilitate the removal of any monitor from the common housing 65, the de-ionizing air generating system 70 is secured to the housing in spaced relationship relative to the monitors. This is accomplished, as best seen in FIGS. 7 and 9, by securing the respective ducts 76-79 to an associated girder 96 of the housing through the use of suitable brackets 97. The motor of each blower is shown independently secured to one of two upper girders 98, by means of a suitable clamp 99. 
     Also to facilitate the removal of any monitor from the common housing 65, an arcuate portion of each forming nozzle 86-89 extends through a slot formed in an associated one of four shield or support plates 91-94. In this regard, it is preferable that the plates 91-94 be freely supported at opposite ends on suitable brackets 103, seen in FIGS. 7 and 9. This allows each forming nozzle, together with the associated support plate, to be withdrawn from the common housing 65 and, thereby, completely free the associated monitor for removal from the latter. 
     Each of the support plates 91-94 also preferably forms an integral interconnecting leg portion between a pair of side shields 106-109 in the illustrative embodiment. It is to be understood, of course, that the side shields for each monitor, if desired, could actually comprise outwardly tapered sidewall extensions of the housing, in a manner similar to that depicted in the embodiment of FIGS. 5 and 6, or alternatively be secured to the sidewalls of the associated monitor cabinet, if employed. 
     With the common housing 65 and composite de-ionizing air generating system 70 constructed and assembled as described and illustrated, a distributively controlled portion of de-ionizing air 108 is fanned-out and directed in a continuous, preferably low velocity, laminar-type stream across the entire surface of each of the monitor screens 66a-69a from the top to the bottom thereof. In order to provide greater control over the velocity of the de-ionizing air streams, adjustable baffles 111-114 are respectively mounted inside the ducts 76-79. In this regard, it should be noted that while the CRT monitor assembly 60 requires the use of two de-ionized air blowers, it does have the advantage over a single blower system of providing more precise control over the volume of de-ioning air distributed to the respectively associated pairs of monitors, while also obviating the need of a common interfacing plenum or manifold. 
     As previously noted with respect to the first embodiment described hereinabove, the various parts of the de-ionizing air distribution system coupled to the blowers 71 and 72 may be initially manufactured as either separate or selectively chosen integral parts, as desired. Also, as described hereinabove in connection with the other preferred embodiments of the invention, the direction of flow of the de-ionizing air, if desired, may also extend from the bottom to the top, as well as from one side to the other side of the monitor screens, by simply rearranging the de-ionizing air generating system within the housing in accordance with the principles disclosed relative to the specific embodiments of FIGS. 3 and 4. 
     FIG. 10 illustrates a CRT monitor assembly 120 which is very similar to that of FIGS. 7-9, by including what may be an essentially identical housing 122, shown only in outer wall outline form, that is adapted to confine therewithin a cluster of four CRT monitors 126-127, and to both confine and support a common de-ionizing air generating system 130 in the same manner as in the embodiment of FIGS. 7-9. Distinguishing from the latter embodiment, however, is the fact that in the embodiment of FIG. 10 only one blower 135 is required. 
     Considered more specifically, the single ionized air blower 135 is coupled through a common plenum 137 to each of four ducts 141-144 which, in turn, are respectively coupled to an associated one of four fan-out nozzles 146-149. The outer flared end of each nozzle is connected to, or merges into, an associated one of four arcuate forming nozzles 151-154. These respective series of interconnected elements each results in a stream of de-ionizing air being directed across the associated screens 126a-129a (shown by dash lines) of the four housing-confined monitors. 
     Optional adjustable baffles 156-159 respectively mounted in the four ducts 141-144 facilitate control over the velocity of the de-ionizing air to the monitor screens. With respect to the generation of the de-ionizing air, it should be understood that while the de-ionized air blower 135 is shown with two output ports communicating with the common plenum 137, a similar blower with only one output port could be readily employed with equal effectiveness, as long as the volume of de-ionizing air generated therewith was adequate for the particular application involved. It should be further understood that while the common plenum 137 is shown as being essentially square in cross-section, it could also be of circular or any other suitable cross section, if desired. 
     The embodiment of FIG. 10 also includes four slotted support plate and integral side-shield assemblies 161-164 which may be constructed and supported on the housing 122 in the same manner as described above in connection with the embodiment depicted in FIGS. 7-9. In all other respects, the various parts of the de-ionizing air generating system 130 are essentially identical to those employed in the embodiment of FIGS. 7-9, and, as previously noted, may be secured to the common housing 122, shown only in peripheral outline form, in the same basic manner described in detail hereinabove in connection with the preceding embodiment. 
     FIG. 11 illustrates another alternative CRT monitor assembly 170 which includes two monitors 171 and 172, positioned in back-to-back relationship on a support bench or table 173, and a de-ionizing air generating system 175 associated in common with both monitors and mounted thereon. The system 175 comprises a common de-ionized air blower 178, which may be of the type employed in any of the other embodiments, in conjunction with two ducts 181, 182, fan-out nozzles 183, 184, forming nozzles 186, 187 and slotted support plate and integral side shield assemblies 188, 189, to provide the desired stream of de-ionizing air across the monitor screens 171a, 172a (shown only positionally by dash lines). 
     FIG. 12 illustrates still another CRT monitor assembly 190 wherein two monitors 171&#39;, 172&#39; are arranged in side-by-side relationship rather than in back-to-back relationship, as depicted in FIG. 11. As the various parts of the monitor assembly 190 at least substantially correspond with those in FIG. 11 in all other respects, they are all identified by like, but primed, reference numerals. The juxtaposed arrangement of the monitors in FIG. 12 has the advantage of allowing any number of such monitors to be arranged in a row, with de-ionizing air directed across the screen of each monitor through the utilization of a single de-ionized air blower, in conjunction with extended ducting or a suitable baffle-adjustable air-distributing manifold (neither shown). 
     When only two monitors are arranged in juxtaposed relationship, as well as back-to-back relationship, as depicted in FIGS. 11 and 12, the utilization of a two-port ionized air blower, connected to the two associated ducts in a manner illustrated in FIG. 8, is of particular advantage in further insuring the equal distribution of air to the two monitors with no specially constructed plenum, or manifold, being required as an interface between the blower and ducting. 
     While several related and preferred CRT monitor assemblies, and sub-assemblies, each incorporating a specially constructed de-ionizing air generating system, have been disclosed herein, it is obvious that various modifications may be made to the present illustrative embodiments of the invention, and that a number of alternative relative embodiments could be devised by one skilled in the art without departing from the spirit and scope of the invention.