Vacuum printing apparatus and process method

Information

  • Patent Grant
  • 6253674
  • Patent Number
    6,253,674
  • Date Filed
    Monday, November 15, 1999
    24 years ago
  • Date Issued
    Tuesday, July 3, 2001
    22 years ago
  • Inventors
  • Examiners
    • Hilten; John S.
    • Grohusky; Leslie J.
    Agents
    • Learned, Jr; Samuel M.
Abstract
A vacuum printing apparatus and process method whereby the application of a decorative imprint in either a single or multi-color rendition to the felt cover playing surface of a pool or billiard table is accomplished without there being any resultant dimensional or thickness irregularity in the playing surface which would otherwise interfere with the course of a ball during play.
Description




BACKGROUND OF THE INVENTION




This invention relates to the apparatus and process method for application of decorative imprints in either single or multi-color renditions to the felt cover playing surface of either a pool or billiard table.




It is well known in pool and billiard table art that a primary requirement for pool and billiard table surfaces, if there is to be accurate play, is that such surfaces must be absolutely flat and true with no thickness or dimensional irregularities that would interfere with the course of either a cue or game ball during play. Thus, the application of any decorative imprint to the felt surface covering for a pool or billiard table top was not heretofore satisfactorily accomplished as an interfering playing surface irregularity was thereby incorporated and inherent to any such decorative application. Being illustrative of the foregoing point, as in the case of placement of a “spot” on either a pool or billiard table for spotting the cue ball, illustratively taught in Nathan, U.S. Pat. No. 1,143,222 dated Jun. 15, 1915, there is disclosed the use of a “—thin, tough material, as for instance linen or silk fabric,—over which the balls may roll with the least deflection.” (emphasis added).




Another pool table teaching showing playing surface decorative imprints is as set forth in Galedrige, U.S. Pat. No. 3,399,890 dated Sep. 3, 1968, which teaches the use of novel markings upon a pool table playing surface, wherein, however, no method or procedure is described or disclosed regarding the nature or character of the marking medium or application thereof.




The imprinting methodology as herein taught employs the use of a vacuum frame apparatus to effect the drawing of the printing ink or paint through an imprint stencil and into the pool or billiard table felt covering fabric to thereby eliminate the adverse effects of the incorporation of thickness and dimensional irregularities. Although the vacuum frame apparatus for photostencil preparation as taught in Smith, U.S. Pat. No. 4,649,817 dated Mar. 17, 1987, is structurally similar, the methodology and functional aspects thereof are applied to the art of stencil preparation as opposed to stencil printing per se, and are thus clearly distinguished.




When the application of decorative imprints in either single or multi-color rendition to a pool or billiard table felt cover playing surface is desired, without the incorporation therein of either thickness or dimensional irregularities which would otherwise interfere with the course of either a cue or game ball during play, the instant invention provides a new and novel apparatus and process method for accomplishing the same.




SUMMARY OF THE INVENTION




It is the principal object of the present invention to provide a vacuum printing apparatus and process method for application of decorative imprints to the felt cover playing surface for a pool or billiard table.




Yet another important object of the present invention is to provide a vacuum printing process method whereby a decorative imprint may be applied to the felt cover playing surface of a pool or billiard table without incorporating a resultant dimensional or thickness irregularity in the playing surface which would in any way otherwise interfere with the course of a ball during play.




A further object of the present invention is to provide a vacuum printing process method which enables the application of decorative imprints in either a single or multi-color rendition upon the felt cover playing surface of a pool or billiard table.




A still further object of the present invention is to provide a vacuum printing apparatus and process method which enables the application of various customized decorative imprints to the felt cover playing surface for a pool or billiard table.




Another object of the present invention is to provide a vacuum printing apparatus and process method whereby the respective ink or paint medium layers comprising a multi-color decorative imprint, which are sequentially applied to the felt cover playing surface of a pool or billiard table, are respectively and successively impregnated to adhere within the felt material fabric structure.




Yet another object of the present invention is to provide a vacuum printing apparatus and process method which further enables the application of a decorative imprint to the playing surface of a pool or billiard table which will retain the applied color vibrance and distinctive shape outline when repeatedly subjected to the rigors of game play over an extended time.




Still another object of the present invention is to provide a vacuum printing apparatus and process method for application of a decorative imprint to the felt cover playing surface for a pool or billiard table which is accomplished with the use of relatively simple and inexpensive equipment, adapted to be utilized and employed in carrying out the process method by persons of ordinary skill without the need for extensive or prolonged training.











These and other objects, advantages and features of the invention will be readily evident upon a study of the following specification taken in conjunction with the accompanying drawings comprising a part thereof, in which:




BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a top view of the vacuum printing apparatus pool or billiard table felt cover layout and register template.





FIG. 2

is an enlarged sectional view of the felt cover layout template register alignment grid as shown in FIG.


1


and seen along the line


2





2


thereof.





FIG. 3

is an exploded view of the apparatus vacuum printing box assembly.





FIG. 4

is a top view of the apparatus vacuum printing box assembly.





FIG. 5

is a side sectional view of the apparatus vacuum printing box assembly as shown in FIG.


4


and seen along the line


5





5


thereof, additionally showing the printing box assembly stencil support in phantom in the tilted ink or paint medium application operational configuration.





FIG. 6

is a perspective view of the apparatus breakdown rod assembly.





FIG. 7

is an enlarged side sectional view of the apparatus breakdown rod assembly as shown in FIG.


6


and seen along the line


7





7


thereof, with the arrows therein shown indicating the breakdown procedure action.





FIG. 8

is a top plan view of the vacuum printing apparatus felt cover layout template showing an exemplary felt cover alignment and application of register tapes.





FIGS. 9

,


10


, and


11


illustrate a series of three-color stencil templates which will result in sequentially successive printed areas as respectively shown in

FIGS. 9A

,


10


A, and


11


A in the application of an exemplary multi-color decorative indicia imprint to the felt cover playing surface of a pool or billiard table.





FIG. 12

illustrates the spray application of an aerosol adhesive to the back of an exemplary stencil template.





FIG. 13

illustrates the completed exemplary multi-color decorative indicia imprint as the same would appear after application to the felt cover playing surface of a pool or billiard table.





FIG. 14

illustrates the final fixing of the pool or billiard table felt cover playing surface exemplary multi-color decorative indicia imprint as previously shown in FIG.


13


.





FIG. 15

is a process method flow chart diagram illustrating the sequential steps for accomplishing an exemplary multi-color application of a decorative indicia imprint upon the felt cover playing surface for a pool or billiard table as taught by the invention hereof.











DETAILED DESCRIPTION OF THE INVENTION




Referring sequentially to

FIGS. 1

,


3


and


6


, wherein the various working components comprising the apparatus for application of decorative imprints


10


to the felt cover playing surface


12


of either a pool or billiard table are respectively illustrated, being first as shown in

FIG. 1

the felt cover layout and register template


14


, second as shown in

FIG. 3

the vacuum printing box assembly


16


, and third as shown in

FIG. 6

the breakdown rod assembly


18


, all of which in combination cooperatively comprise said apparatus for application of decorative imprints


10


by the process method herein taught.




With regard to the foregoing, and in the continued detailed description as hereinafter set forth, it is to be understood that whether a decorative imprint image


36


is to be applied to a pool table or billiard table felt cover playing surface


12


, the apparatus


10


and method of practice of the instant teaching are the same and for purposes of convenience and simplicity only, the continuing description and discussion will refer to the apparatus


10


and method as applied to pool table use with the understanding that the same is not to be considered limiting, and likewise applies in every respect to billiard table use.




Turning attention now to

FIGS. 1 and 2

for a more detailed description of the felt cover layout and register template


14


, which as shown in

FIG. 1

is fabricated from a suitable rigid board material of an adequate thickness such as plywood or the like, being cut in the shape and to the dimensions of a standard sized pool table top, with appropriate recesses for the corner pockets


20


and side pockets


22


. Additionally cut within the top surface of the felt cover layout and register template


14


is a felt cover registration grid


24


being comprised of a table top longitudinal dimension dividing center line recess


26


, a table top lateral dimension dividing center line recess


28


, and a table top centered rectangular shaped vacuum box resister recess


30


all of which accommodates for purposes of make-ready layout the locating of the felt cover playing surface material center to the vacuum printing frame


32


stencil screen


34


, which in turn enables registration of the decorative imprint image


36


to the center of the pool table felt cover playing surface material


38


thereby allowing for installation centering of the decorative imprint image


36


to the pool table top when the felt cover playing surface material is applied thereto. And, as will hereinafter be more fully described during consideration of

FIGS. 8 through 13

, the registration grid also enables the aligned make-ready setup of sequentially printed stencils in the application of multi-color decorative imprints


10


.




The illustration shown in

FIG. 2

is an enlarged side sectional view of the registration grid


24


lateral dimension dividing center line recess


28


profile, specifically to show that the recesses


26


,


28


and


30


of said registration grid


24


provide a means whereby the registration grid


24


can be sensed by finger touch feel through the felt cover playing surface material


38


when it is oriented and laid upon the register template


14


during the make-ready layout procedure for centering a decorative imprint image


36


for printing on the pool table felt cover playing surface


12


, wherein the specific lay-out procedure will be discussed in detail on consideration of

FIG. 8

as hereinafter more specifically set forth.




Considering next

FIG. 3

, wherein is shown an exploded view of the apparatus


10


for application of decorative imprints


36


. The apparatus


10


is comprised of a vacuum printing box assembly


16


which includes a vacuum printing frame


32


to which is attached a vacuum frame rigid bottom enclosement member


40


adapted to connectably support a vacuum conduit


42


by means of a vacuum conduit connector assembly


44


. The vacuum conduit


42


extends from the printing box assembly


16


for connection to a typical vacuum source such as a shop-vac or the like, not shown here but well known in the art, to thereby provide a vacuum differential within the enclosed vacuum printing frame


32


. In order to seal the vacuum printing frame


32


, a pliable material vacuum frame liner


46


such as sheet rubber or plastic is preferably used and installed around the frame


32


and interiorly across the bottom enclosement member


40


of the vacuum printing box assembly


16


. A fine mesh screen


48


is installed over the top of the frame


32


and serves both as a felt material


38


support across the image printing area of the vacuum printing box assembly


16


, as well as a porous vacuum backing through which the printing box assembly


16


vacuum differential draws the printing image ink or paint into the felt cover playing surface material


38


fiber structure to impregnate the ink or paint therewithin. Above the screen


48


is a tensioning frame


50


which is provided and adapted to compressively engage and tautly stretch the felt cover playing surface material


38


image printing area in register over the screen


48


surface prepatory to installing the stencil


52


. Affixedly installed to the bottom enclosement member


40


at either longitudinal underside end of the vacuum printing frame


32


is a spaced set of vacuum printing frame pivotal support mounts


54


, each of which is provided with a frame bolt opening


56


for pivotal bolt engagement assembly to the vacuum printing frame pivot mount


58


.




The vacuum printing frame pivot mount


58


, also shown in the exploded view perspective of

FIG. 3

, is preferably constructed of interconnected horizontal and vertical support members


60


and


62


respectively with interconnecting joining beams


64


, and serves to pivotally support the vacuum printing box assembly


16


during printing operations as is more clearly illustrated and shown in FIG.


5


. Pivot bolts


66


, insertably communicating through the respective frame bolt openings


56


of the vacuum printing frame


32


and through the corresponding pivot mount


58


bolt openings


68


, serve both as pintles for pivotal angular elevation of the vacuum printing box assembly


16


as well as also by means of compression bolt assemblies


70


to frictionally fix the vacuum printing box assembly


16


in an angular elevated position for printing operations as is likewise shown in FIG.


5


.




Turning attention now to

FIG. 4

, wherein is shown a top view of the vacuum printing box assembly


16


, and more particularly showing the tensioning frame


50


grid register marks thereon, being the respective longitudinal center line recess index register marks


72


and the lateral center line recess index register marks


74


which in turn correspond in register alignment respectively to the table top longitudinal dimension dividing center line recess


26


and the table top lateral dimension dividing center line recess


28


as shown upon the felt cover layout and register template


14


illustrated in FIG.


1


. It is by means of these corresponding sets of register marks whereby a pool table felt cover playing surface make-ready layout for printing as set up on the register template


14


is transferred and aligned in register for affixment upon the vacuum printing frame


32


. It will also be noted that the tensioning frame


50


is further provided with a plurality of offset register alignment marks


76


extending in a regularly repeating incremental pattern either side of each recess index register mark


72


and


74


respectively to provide for register adjustment of a stencil or printed image in the longitudinal or lateral planes as may be necessary or desired.




The view shown in

FIG. 5

illustrates the vacuum printing box assembly


16


from a side sectional view, and in phantom shows tilt adjustment and set of the vacuum printing frame


32


in that position generally found to be most convenient for accomplishing printing operations. As shown in the phantom illustration portion of the view, the felt cover playing surface material


38


is stretched in alignment over the screen covered vacuum printing frame


32


and then compressively fixed in taut register by means of peripheral engagement thereof with the tensioning frame


50


being slid down to hold the same in place. The stencil


52


is then fixed in place as will hereinafter be more fully described, afterwhich the printing ink or paint is spray applied through the stencil cut-out by means of an air-brush spray gun


78


employing technique well known in the art, and thereby a decorative imprint image


36


is applied and by means of the operational vacuum differential within the vacuum printing frame


32


the imprint image ink or paint is drawn into the fabric structure of the felt cover playing surface


12


. Preferably, the inks or paints that are employed for imparting the decorative imprint image


36


are of the quick drying type so that the felt cover playing surface material


38


may be removed from the vacuum printing frame


32


soon after application thereof for accomplishing the next step of the process method as herein taught.




Considering now the breakdown rod assembly


18


as shown in

FIG. 6

, which consists of a smooth rod


80


supported horizontally in an elevated position by means of two spaced uprights


82


each of which upright is respectively affixed to a support base


84


. Use of the breakdown rod assembly


18


is as illustrated in

FIG. 7

, wherein the breakdown process consists simply of a taut reciprocative drawing of the decorative imprint image area of the felt cover playing surface


12


back-and-forth across the rod


80


to break down the stiffness of the image impregnated ink or paint within the felt material fabric structure and thereby eliminate any thickness differential in the felt cover playing surface resultant from applied ink or paint in the decorative image imprint area, as well as reinvigorate the porosity of the felt material fabric so that the ink or paint of any subsequently applied colors will likewise be vacuum drawn and impregnated within the felt material fabric structure in a manner similar to that of the first applied or initial color.




In summary, then, the apparatus


10


consists in combination of the felt cover layout and register template


14


with the vacuum printing box assembly


16


and the breakdown rod assembly


18


, all of which are cooperatively employed to carry out the process method hereof for accomplishing decorative imprint image application to a pool table felt cover playing surface material without the incorporation therein of any resultant dimensional or thickness irregularity in the playing surface which would otherwise interfere with the course of a ball during play. The various components of the apparatus


10


as above identified are preferably constructed of wood or metal or plastics, or various combinations thereof, by methods and techniques commonly and suitably employed for fabricating such devices.




Turning now to

FIG. 8

to consider in greater detail use of the layout and register template


14


in accomplishing make-ready steps to prepare a felt cover playing surface


12


for decorative imprint printing, wherein the template


14


is shown in dashed line rendition centered and underlying the felt cover playing surface material


38


, the accomplishment of which centered underlying alignment as above described is the first step in make-ready preparation. Next, the operator, as shown by the operator's hand


86


, finger-feels the longitudinal and lateral dimension dividing center line recesses


26


and


28


through the felt cover playing surface material


38


and affixes register tapes


88


and


90


respectively thereon at the edges of the table top centered rectangular shaped vacuum box register recess


30


, which register tapes correspond in orientation alignment and dimension to the tensioning frame


50


index register marks


72


and


74


as previously shown in FIG.


4


. To further orient and accurize centering location of the felt cover playing surface material to placement upon the vacuum printing frame


32


, the operator also finger-feels the intersecting corners of the table top centered rectangular shaped vacuum box register recess


30


and affixes aligned corner marking tapes


92


as also shown, which corner marking tapes


92


correspond in orientation alignment and dimension to the vacuum printing frame


32


corners. With the foregoing register and alignment markings affixed to the felt cover playing surface


12


, the felt cover playing surface material


38


is then readied for transfer to and mounting upon the vacuum printing frame


32


in preparation for receiving a stencil


52


.




Considering next the series of

FIGS. 9 through 11

in conjunction with

FIGS. 9A through 11A

, which respectively show an exemplary three-color stencil pattern and the corresponding patterns for printing an exemplary decorative imprint image


36


upon the felt cover playing surface material


38


.

FIG. 9

illustrates the exemplary first color stencil


52




a


with the resultant first color decorative imprint image


36




a


as being shown in

FIG. 9A

, with

FIGS. 10 and 11

respectively illustrating the exemplary second and third color stencils


52




b


and


52




c


and the corresponding resultant second and third color decorative imprint images


36




b


and


36




c


as being respectively shown in

FIGS. 10A and 11A

. It will be noted that the first color stencil


52




a


as shown in

FIG. 9

, as well as the second and third color stencils


52




b


and


52




c


as respectively shown in

FIGS. 10 and 11

, all bear longitudinal and lateral stencil register marks


94


and


96


which correspond in register and dimensional alignment to the longitudinal and lateral register tapes


88


and


90


that were previously placed upon the felt cover playing surface


12


during make-ready. Thus, when the stencil register marks


94


and


96


of the respective color stencils are successively aligned in printing order sequence with the index register marks


72


and


74


on the tensioning frame


50


, prepatory to the respective stencil affixments for each color to the vacuum printing frame mounted felt cover playing surface material


38


, then the stencil color image for each imprint color will be centered on the felt cover playing surface


12


and successively in register within the printing sequence with the remaining colors of a multi-color decorative imprint image as exemplified by

FIGS. 9A through 11A

and as shown in completion in FIG.


14


.




The view shown in

FIG. 12

illustrates application by an operator


86


of a suitable spray adhesive


98


to the underside surface of the first color stencil


52




a,


being exemplary of the manner in which such stencils are prepared for removable adhesion thereof to the vacuum printing frame mounted felt cover playing surface material


38


for purposes of printing. In the case of multi-color image imprinting, after printing impression and removal of the previous stencil, and completion of the breakdown process as previously described, each successive color imprint stencil within the multi-color series is then similarly prepared and adhered in register to the vacuum printing frame re-mounted felt cover playing surface material


38


for subsequent successive color printing of those colors comprising the decorative imprint image


36


.




In

FIG. 13

is shown the completed exemplary multi-color decorative imprint image


36


, comprised of the successively printed first through third colors as exemplified by


36




a


through


36




c,


as the same would appear in completion upon an exemplary pool table felt cover playing surface


12


. The final step in completing the decorative imprint image process method herein taught is to fix the image


36


by means of heat, which is accomplished by an ironing of the image from the non-imprint side of the felt cover playing surface


12


as shown in

FIG. 14

, for which purpose the operator


86


employs a standard household iron


100


set at a medium heat.




The view shown in

FIG. 15

is a flow sheet for the process printing method herein taught, starting at the outset with a layout of the pool table felt for printing by use of the felt cover layout and register template


14


as previously described and shown in FIG.


8


. The felt cover with register marks is then taken from the template, assembled in register to the vacuum printing frame


32


, and compressively held in place in tautness over the fine mesh stencil screen


48


by means of the tensioning frame


50


as previously described and shown in FIG.


5


. Adhesive is then spray applied to the back of the stencil


52


as shown in

FIG. 13

, and the stencil


52


removably applied in register to the felt cover playing surface material


38


upon the vacuum printing frame. The vacuum is then turned on to draw the stencil


52


and felt cover playing surface material


38


tight to the fine mesh screen


48


, the vacuum printing frame


32


is tilted forward and secured in the operational configuration, and the first stencil color is imprinted by use of the air-brush spray gun


78


as also shown in

FIG. 5

, and by means of the vacuum differential the air-brush ink or paint medium is drawn into and impregnates the felt cover fabric. The vacuum is then turned off and the first color stencil is removed from the felt cover material. When the imprint color ink or paint has dried, the felt cover playing surface material


38


is then removed from the vacuum printing frame


32


and the imprint image is subjected to the break-down process as was previously described and shown in FIG.


7


.




The foregoing process method, from felt registration through imprint image break-down is repeated for each subsequently printed color, as well as for the final imprint color, with the last process step being heat fixing of the completed multi-color imprint image by means of a medium heat ironing from the imprint reverse side as was previously described and shown in FIG.


14


.




In summary, although the vacuum printing apparatus and process method invention hereof, as well as the structural characteristics and manner of employment thereof for accomplishing an imprint in either single or multi-color renditions upon the felt cover playing surface of a pool table have been shown and described in what are conceived to be the most practical and preferred versions, it is recognized that departures may be made respectively therefrom within the scope of the invention, which is not to be limited per se to those specific details as described herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent such devices, apparatus, and methods.



Claims
  • 1. A vacuum printing apparatus, said apparatus comprising in combination a means for accomplishing layout and register of a decorative imprint to a game table felt cover playing surface material, a vacuum printing box assembly to support the game table felt cover playing surface material and a stencil thereon for accomplishing a decorative imprint transfer to the game table felt cover playing surface material, an air-brush spray gun to apply a color medium to said stencil, a breakdown means to reduce any dimensional irregularities in the game table felt cover playing surface material resultant from the decorative imprint transfer thereto, and a heat means to fix the decorative imprint transfer to the game table felt cover playing surface material.
  • 2. A vacuum printing apparatus according to claim 1 in which the decorative imprint is a single color imprint.
  • 3. A vacuum printing apparatus according to claim 2 in which the color medium for the decorative imprint is an ink.
  • 4. A vacuum printing apparatus according to claim 2 in which the color medium for the decorative imprint is a paint.
  • 5. A vacuum printing apparatus according to claim 1 in which the decorative imprint is a multi-color ink imprint.
  • 6. A vacuum printing apparatus according to claim 1 in which the decorative imprint is a multi-color paint imprint.
  • 7. A vacuum printing apparatus according to claim 1 in which the game table felt cover playing surface material covers a pool table.
  • 8. A vacuum printing apparatus according to claim 1 in which the game table felt cover playing surface material covers a billiard table.
  • 9. A vacuum printing apparatus according to claim 1 in which said means for accomplishing layout and register of the decorative imprint to the game table felt cover playing surface material is a layout and register template.
  • 10. A vacuum printing apparatus according to claim 1 in which said printing box assembly is provided with a vacuum printing frame having an enclosement bottom to support a vacuum conduit connection.
  • 11. A vacuum printing apparatus according to claim 10 in which said vacuum printing frame having said enclosement bottom is sealably lined with a pliable material.
  • 12. A vacuum printing apparatus according to claim 11 in which said vacuum printing frame having said enclosement bottom has the upward facing open side thereof covered with a fine mesh screen.
  • 13. A vacuum printing apparatus according to claim 10 in which said vacuum printing frame is provided with a tensioning frame.
  • 14. A vacuum printing apparatus according to claim 10 in which said vacuum conduit connection supports a vacuum conduit communicating to a vacuum source.
  • 15. A vacuum printing apparatus according to claim 10 in which said vacuum printing box assembly is provided with an angular adjustment means.
  • 16. A vacuum printing apparatus according to claim 15 in which said angular adjustment means is comprised of a vacuum printing frame pivot mount in combination with a set of compression bolt assemblies.
  • 17. A vacuum printing apparatus according to claim 1 in which said breakdown means is comprised of a horizontally disposed smooth rod upwardly supported by a set of spaced uprights.
  • 18. A vacuum printing apparatus according to claim 1 in which said heat means is a household iron.
  • 19. A vacuum printing process method for application of a decorative imprint to a felt cover playing surface material for a game table, said method comprising performing by means of a template a registration layout of said felt cover playing surface material for receiving a decorative imprint stencil, assembling said felt cover playing surface material in registered orientation to a vacuum printing frame, spray applying an adhesive to the back of said decorative imprint stencil and affixing said stencil in register to said felt cover playing surface material assembled to said vacuum printing frame, activating a vacuum source connected to said vacuum printing frame, spray applying a color medium to said stencil to effect a color transfer of said decorative imprint to said felt cover playing surface material, vacuum impregnating said color medium within the fabric structure of said felt cover playing surface material, deactivating said vacuum source and removing said stencil from said felt cover playing surface material, removing said felt cover playing surface material from said vacuum printing frame, reinvigorating the felt fabric structure of said felt cover playing surface material in the decorative imprint image area by subjecting the same to a breakdown process, and fixing the decorative imprint to said felt cover playing surface material by subjecting the same to a heat source.
US Referenced Citations (8)
Number Name Date Kind
1143222 Nathan Jun 1915
2419695 Shuttleworth et al. Apr 1947
3172358 Weiss Mar 1965
3399890 Galedrige Sep 1968
3418931 Wilford Dec 1968
4173928 Mitter Nov 1979
4649817 Smith Mar 1987
4734298 Kikukawa Mar 1988