Pin binding assembly

Information

  • Patent Grant
  • 6174100
  • Patent Number
    6,174,100
  • Date Filed
    Tuesday, December 22, 1998
    26 years ago
  • Date Issued
    Tuesday, January 16, 2001
    24 years ago
Abstract
A binding assembly includes first and second sheet retaining members which are releasably attached to a base member by first and second latching mechanisms. The sheet retaining members include a pair of side members which support a pair of pins and tubes onto which sheets of paper or other materials are placed. Each of the side members includes an engaging rod which is receivable in a channel provided in the base member to retain the sheet retaining members to the base member. Each of the latching mechanisms are independently pivotable about an axis perpendicular to the pins and tubes from a retaining position where the sheet retaining members are constrained to the base member, to a releasing position where the sheet retaining members may be detached from the base member.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a binding assembly for retaining sheets of material, such as paper, and more particularly, to a binding assembly having a pair of side plates which are independently detachable from a base member so that sheets may be inserted or removed from either side of the binding assembly.




2. Description of the Background Art




Various binding assemblies are known in the prior art for retaining sheets of paper or other materials together in an orderly fashion. The binding assemblies are usually attached to a cover member to form a notebook or binder. Typically, a plurality of holes are punched along a side edge of sheets of paper, and pins or tubes of the binding assembly are passed through the holes to retain the sheets of paper together.




One example of such a binding device is shown in U.S. Pat. No. 4,693,625, which shows a binding assembly having a pair of side members which support a pair of pins and tubes onto which the sheets of paper are placed. The side members are detachable from a base member which is fixed to the spine of a notebook cover. Each of the side members includes a pair of engaging rods which are inserted into hollow portions in the base member to retain the side members to the base member. The engaging rods are movable along the length of the respective side member by a sliding plate disposed within the side member which is slidable along the length of the side member. The sliding plate transfers a force provided by a user in a direction of the length of the side member to the engaging rods, so that the side member may be detached from the base member. Unfortunately, the detaching mechanism is complicated, and therefore costly to produce. Further, because the side members must be relatively thick to accommodate the components of the detaching mechanism therein, there remains less room for the sheets of paper for a fixed width of binder cover, and thus the capacity of the binding assembly is limited. Finally, only short portions of the engaging rods are held by the hollow portions of the base member, and therefore the retaining strength is limited.




Another example of a binding device is shown in U.S. Pat. No. 5,330,280, which shows a binding assembly also having a pair of side members which support a pair of pins and tubes onto which the sheets of paper are placed. Each of the side members includes a pair of engaging rods which are inserted into hollow portions in the base member to detachably retain the side members to the base member. The engaging rods are movable along the length of the respective side member by an actuating mechanism which is slidable in the direction of the length of the side member. Similarly to the previously discussed patent, the actuating mechanism transfers a force provided by a user in the direction of the length of the side member to the engaging rods, so that the side member may be detached from the base member. A series of actuating mechanisms are shown in the various embodiments, all of which are extremely complex. However, as the number of components and the complexity of a device increases, the cost to manufacture increases, and the number of components that can malfunction increases. Further, since only short portions of the engaging rods are held by the hollow portions of the base member, the retaining strength is also limited.




A final example of a binding device is shown in U.S. Pat. No. 5,634,732, which shows a binding assembly also having a pair of side members which support a pair of pins and tubes onto which the sheets of paper are placed. Each of the side members includes a pair of fixed engaging rods which are retained by a pair of latches provided on the base member. The pair of latches are movable along the width of the base member by depressing an actuating knob attached to the latches. As the knob is pressed inwardly, the latches move inwardly, and allow the engaging rods to move therepast to release the side member. However, the placement and actuation direction of the latch assemblies promotes inadvertent release of the side members by contact of the actuating knob with the front or rear cover members of the notebook binder. Also, other materials located loosely within the notebook may become wedged between the cover member and the actuating knob, resulting in inadvertent release of the side members. Finally, the latch assemblies are made of plastic material, and are susceptible to increased wear and breakage.




SUMMARY OF THE INVENTION




It is therefore an object of the present invention to provide a binding apparatus which has few components, and which is inexpensive to manufacture.




It is another object of the present invention to provide a binding apparatus in which the capacity of the binding assembly is increased.




It is yet another object of the present invention to provide a binding apparatus in which longer portions of the engaging rods are held by the latching mechanism, and therefore the retaining strength is increased.




It is yet still another object of the present invention to provide a binding apparatus which minimizes the possibility of inadvertent release of the sheet retaining members from the latching members.




These and other objects of the present invention are fulfilled by a binding apparatus including a base member and a sheet retaining apparatus having at least one pin. Either the sheet retaining apparatus or the base member includes an engaging rod, and the other one of the sheet retaining apparatus and the base member includes a latching member for securing the sheet retaining apparatus to the base member. The latching member is pivotable about an axis substantially parallel to the engaging rod from a retaining position where the sheet retaining apparatus is secured to the base member, to a releasing position where the sheet retaining apparatus may be detached from the base member.




Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.











BRIEF DESCRIPTION OF THE DRAWINGS




The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein:





FIG. 1

is a perspective view of the binding assembly of the present invention in an assembled condition;





FIG. 2

is a perspective view of the binding assembly of the present invention in a partially disassembled condition;





FIG. 3

is an exploded perspective view of the binding assembly of the present invention;





FIG. 4

is an enlarged cross-sectional view of the latching mechanism of the present invention;





FIG. 5

is an exploded view of an alternative arrangement of the pins and tubes of the binding assembly of the present invention;




FIGS.


6




a


-


6




c


are end views showing the releasing of the pin side of the binding assembly of the present invention;




FIGS.


7




a


-


7




c


are end views showing the releasing of the tube side of the binding assembly of the present invention; and




FIGS.


8




a


-


8




c


are end views showing the releasing of both the pin side and the tube side of the binding assembly of the present invention.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




Referring in detail to the drawings, and with particular reference to FIGS.


1


-


3


, a binding apparatus


10


of the present invention is shown. The binding apparatus


10


includes first and second sheet retaining members


12


,


14


which are releasably attached to a base member


16


by first and second latching mechanisms


18


,


20


, respectively.




The first and second sheet retaining members


12


,


14


each comprise a side plate


22


having a generally rectangular shape. The side plate


22


has a cut-away portion


24


located centrally along one edge


25


thereof. Remaining portions of the side plate


22


which are adjacent to the cut-away portion


24


form a pair of spaced-apart extensions


26


. The ends of each of the extensions


26


are rolled inwardly to form a pair of engaging rod support pipes


28


having a tubular configuration. An engaging rod


30


extends along the side plate


22


between the engaging rod support pipes


28


. The two ends of the engaging rod


30


are fixed to the engaging rod support pipes


28


.




A second edge


31


opposite to the first edge


25


may be turned inwardly at a right angle to the side plate


22


, or may be folded over to form a hem edge, in order to reduce sharp edges and to reinforce the side plate


22


. The side plate


22


further includes a pair of apertures


32


extending therethrough. The centers of the apertures are spaced apart by a distance corresponding to the distance between a pair of holes in sheets of material to be held by the binding apparatus


10


.




In the first sheet retaining member


12


, a pair of pins


34


are fixed to the side plate


22


and extend inwardly therefrom. The pins


34


are preferably solid and have a generally circular cross-section. A first end


36


of each pin


34


includes a circular flange


38


having a diameter larger than that of the pin


34


. The first end


36


of each pin


34


is inserted through the apertures


32


in the side plate


22


until the flanges


38


abut an inner surface


40


of the side plate


22


. The first end


36


of each pin


34


is thereafter enlarged, for example, by pressing the first end


36


of the pins


34


against an outer surface


42


of the side plate


22


to form an enlarged head, to securely fasten the pins


34


to the side plate


22


. A second end


44


of each pin


34


is rounded to reduce sharp edges and to assist with the placement of sheets of material onto the pins


34


.




In the second sheet retaining member


14


, a pair of tubes


46


are fixed to the side plate


22


and extend inwardly therefrom. The tubes


46


are hollow and have a generally circular cross-section. A first end


48


of each tube


46


includes a circular flange


50


having a diameter larger than that of the tube


46


. The first end


48


of each tube


46


is inserted through the apertures


32


in the side plate


22


until the flanges


50


abut an inner surface


40


of the side plate


22


. The first end


48


of each tube


46


is thereafter enlarged, for example, by pressing the first end


48


of the tubes


46


against an outer surface


42


of the side plate


22


to form a flared head, to securely fasten the tubes


46


to the side plate


22


. A second end


52


of each tube


46


is angled to assist with the placement of sheets of material onto the tubes


46


, and to assist in guiding the pins


34


into the tubes


46


.




Although two pins


34


and two tubes


46


are shown in the present embodiment, it should be understood that three pins


34


and tubes


46


, or any number of pins


34


and tubes


46


, may be utilized as desired with the present invention.




An alternative arrangement of the pins


34


and the tubes


46


of the first and second sheet retaining devices


12


,


14


is shown in FIG.


5


. Therein, each of the side plates


22


includes a pin


34


and a tube


46


attached thereto, which compatibly mate with a corresponding tube


46


and pin


34


, respectively, on the opposite side plate


22


. Accordingly it can be seen that if the first and second sheet retaining members


12


,


14


are configured as shown in

FIG. 5

, the first and second sheet retaining members


12


,


14


are identical, and interchangeable from one side to the other. Thus, it is only necessary to manufacture a single sheet retaining member which can perform the function of the two different sheet retaining members


12


,


14


shown in the first embodiment, resulting in additional cost savings.




The base member


16


is preferably formed from a flat sheet of metal, and includes a substantially rectangular bottom plate


60


. The bottom plate includes four holes


62


extending therethrough. As shown in FIG.


4




a


for example, rivets


64


extend through the holes


62


in the bottom plate


60


for attaching the base member


16


to a binder cover member


66


.




Four portions from a central area of the bottom plate


60


are punched out and upwardly bent at approximately a right angle to the bottom plate


60


to form two pairs of spaced-apart upstanding supports


68


. Distal ends of the upstanding supports


68


are rolled outwardly to form two pairs of aligned pivot shaft support pipes


70


.




Side edges


72


of the base member


16


are bent upwardly at approximately a right angle to the bottom plate


60


. The side edges


72


and the adjacent side portions of the bottom plate


60


form two sides of an engaging rod receiving channel


74


.




One end


76


of base member


16


is upwardly bent at approximately a right angle to the bottom plate


60


. Corners of the end


76


are removed to form end supports


78


for the latching mechanisms


18


,


20


, which will be described in detail below.




Each of the four corners of the bottom plate


60


includes a rectangular cut-away portion


80


which provides a clearance for the engaging rod support pipes


28


of the side plates


22


when the sheet retaining members


12


,


14


are assembled with the base member


16


.




The first and second latching mechanisms


18


,


20


each include a latching member


90


which has a generally L-shaped cross section as shown in FIG.


4


. The L-shaped cross section comprises a back portion


92


, a bottom portion


94


, and a corner portion


96


therebetween.




The back portion


92


has a cut-away portion


98


located centrally along an upper edge


100


thereof. Remaining portions of the back portion


92


which are adjacent to the cut-away portion


98


have ends which are rolled inwardly to form a pair of pivot shaft support pipes


102


having a tubular configuration. A pivot shaft


104


extends along the back portion


92


of the latching member


90


between the pivot shaft support pipes


102


. The two ends of the pivot shaft


104


are located within the pivot shaft support pipes


102


. A helical torsion spring


106


surrounds a portion of the pivot shaft


104


which is located in the cut-away portion


98


of the back portion


92


.




One end of each of the latching members


90


includes a finger pad


108


which provides a convenient pressing point accessible by a user for actuating the latching mechanisms


18


,


20


.




The latching mechanisms


18


,


20


are assembled to the base member


16


by aligning the pivot shaft support pipes


70


,


102


of the base member


16


and the latching mechanisms


18


,


20


, and then inserting the pivot shaft


104


through the aligned pivot shaft support pipes


70


,


102


so that the torsion spring is located in the cut-away portion


98


of the back portion


92


. In this assembled condition, the bottom portion


94


of the latching member


90


forms a third side of the engaging rod receiving channel


74


.




One end


110


of the torsion spring


106


presses against one of the upstanding supports


68


of the base member


16


, and the other end


112


of the torsion spring


106


presses against the back portion


92


of the latching member


90


. The torsion spring


106


biases the corner portion


96


of the latching member


90


toward the side edges


72


of the base member


16


into what shall be considered a retaining position.




Each of the latching members


90


are independently pivotable by an angle of approximately 45 degrees about an axis parallel to the engaging rods


30


and perpendicular to the pins


34


and the tubes


46


from the retaining position to what shall be considered a releasing position by pressing the finger pad


108


. The end supports


78


of the base member


16


offset forces placed on the finger pad


108


, and limit rotation of the latching mechanisms


18


,


20


beyond the releasing position. Also, as shown in

FIG. 4

, the distal end


114


of the bottom portion


94


of the latching member


90


contacts the bottom plate


60


in the retaining position to prevent the torsion spring


106


from biasing the latching member


90


past the retaining position.




The sheet retaining members


12


,


14


are assembled to the base member


16


by placing the engaging rods


30


into a groove provided by the back portion


92


of the latching member


90


and the side edges


72


of the base member


16


. The sheet retaining members


12


,


14


are then pressed downwardly until the engaging rods


30


are located within the engaging rod receiving channels


74


. The back portion


92


of each latching member


90


forms an inclined surface which guides the engaging rod


30


into the engaging rod receiving channel


74


. As the engaging rod


30


slides along the back portion


92


of the latching member


90


and into the engaging rod receiving channel


74


, the engaging rod


30


moves the latching member


90


out of the way toward the releasing position against the biasing force provided by the torsion spring


106


.




Once the engaging rod


30


is located within the engaging rod receiving channel


74


, the torsion spring


106


biases the latching member


90


back to the retaining position to securely fasten the sheet retaining members


12


,


14


to the base member


16


. In the retaining position, the bottom portion


94


and corner portion


96


of the latching member


90


prevent the engaging rod


30


from being withdrawn from the engaging rod receiving channel


74


, as can be seen in FIG.


4


. As shown in

FIGS. 2 and 3

, one section


116


of the corner portion


96


of each latching member


90


is cut away to receive one of the engaging rod support pipes


28


of the side plates


22


.




When the first and second sheet retaining devices


12


,


14


are assembled with the base member


16


, the upper edges


118


of the side plates


22


are substantially aligned with the upper edge


120


of the bottom plate


60


.




FIGS.


6


-


8


show various ways of detaching the sheet retaining members


12


,


14


from the base member


16


. FIG.


6




a


shows an end view of a notebook binder with the sheets of paper lying against, for example, a back cover


122


of the binder cover member


66


. In FIG.


6




b


, the latching member


90


restraining the sheet retaining member


12


having the pins


34


attached thereto is actuated by depressing the finger pad


108


to release that sheet retaining member


12


. Because the sheet retaining member


14


having the tubes


46


attached thereto is still restrained by the engaging rod


30


within the engaging rod receiving channel


74


, the base member


16


is pivotal with respect to the sheet retaining member


14


about the engaging rod


30


to the position shown in FIG.


6




c


where the bottom plate


60


of the base member


16


is substantially parallel to the side plate


22


of the sheet retaining member


14


. At this time, the sheet retaining member


12


with the pins


34


attached thereto may be removed so that papers still held by the tubes


46


at, for example, a front side of the notebook binder, may be removed or other papers inserted.




FIG.


7




a


shows an end view of a notebook binder with the sheets of paper lying against, for example, a front cover


124


of the binder cover member


66


. In FIG.


7




b


, the latching member


90


restraining the sheet retaining member


14


having the tubes


46


attached thereto is actuated by depressing the finger pad


108


to release that sheet retaining member


14


. Because the sheet retaining member


12


having the pins


34


attached thereto is still restrained by the engaging rod


30


within the engaging rod receiving channel


74


, the base member


16


is pivotal with respect to the sheet retaining member


12


about the engaging rod


30


to the position shown in FIG.


7




c


where the bottom plate


60


of the base member


16


is substantially parallel to the side plate


22


of the sheet retaining member


12


. At this time, the sheet retaining member


14


with the tubes


46


attached thereto may be removed so that papers still held by the pins


34


at, for example, a back side of the notebook binder, may be removed or other papers inserted.




FIG.


8




a


shows an end view of a notebook binder with the sheets of paper lying against, for example, the back cover


122


of the binder cover member


66


. In FIG.


8




b


, both latching members


90


restraining both sheet retaining members


12


,


14


are actuated by depressing the finger pads


108


to release the sheet retaining members


12


,


14


. This allows the sheet retaining members


12


,


14


to be completely removed together while retaining the sheets in an orderly fashion, as shown in FIG.


8




c


. At this time, the sheet retaining members


12


,


14


may be relocated into a different binder cover member


66


if desired.




While the present invention has been described with reference to a preferred embodiment with the latching members


90


provided on the base member


16


, it is also conceived that the latching members


90


may be located on the sheet retaining members


12


,


14


, with the engaging rods


30


being provided on the base member


16


. Further, while the pins


34


and the tubes


46


are preferably straight, it is envisioned that curved pins receivable in correspondingly curved tubes could alternatively be utilized if so desired.




The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.



Claims
  • 1. A binding apparatus comprising:a base member; a sheet retaining apparatus having at least one pin; one of said sheet retaining apparatus and said base member including an engaging rod; and a remaining one of said sheet retaining apparatus and said base member including a latching member for securing said sheet retaining apparatus to said base member, said latching member being pivotable from a retaining position where a portion of said latching member engages said engaging rod so that said sheet retaining apparatus is secured to said base member, to a releasing position where said portion of said latching member releases said engaging rod so that said sheet retaining apparatus may be detached from said base member.
  • 2. The binding apparatus according to claim 1, wherein said axis is perpendicular to said pin.
  • 3. The binding apparatus according to claim 1, further comprising a torsion spring for biasing said latching member toward said retaining position.
  • 4. The binding apparatus according to claim 1, wherein said sheet retaining apparatus includes said engaging rod, and said base member includes said latching member.
  • 5. The binding apparatus according to claim 4, wherein said engaging rod extends along a majority of an entire length of said sheet retaining apparatus.
  • 6. The binding apparatus according to claim 4, further comprising:a pair of spaced-apart support pipes extending upwardly from said base member; and a pivot shaft extending along said latching member, said pivot shaft passing through said pair of spaced-apart support pipes to support said latching member.
  • 7. The binding apparatus according to claim 6, further comprising a torsion spring surrounding a portion of said pivot shaft for biasing said latching member toward said retaining position, one end of said torsion spring contacting one of said support pipes, and another end of said torsion spring contacting said latching member.
  • 8. The binding apparatus according to claim 1, wherein a portion of said latching member has an L-shaped cross section comprising a back portion, a bottom portion, and a corner portion therebetween.
  • 9. A binding apparatus comprising:a base member; a sheet retaining apparatus having at least one pin; one of said sheet retaining apparatus and said base member including an engaging rod; and a remaining one of said sheet retaining apparatus and said base member including a latching member for securing said sheet retaining apparatus to said base member, said latching member being pivotable from a retaining position where said sheet retaining apparatus is secured to said base member, to a releasing position where said sheet retaining apparatus may be detached from said base member, wherein said sheet retaining apparatus includes said engaging rod, and said base member includes said latching member, and wherein said base member further comprises an upstanding end, said end including end supports for offsetting forces applied to said latching member during pivoting of the latching member, and for limiting rotation of the latching member beyond said releasing position.
  • 10. A binding apparatus comprising:a base member; a sheet retaining apparatus having at least one pin; one of said sheet retaining apparatus and said base member including an engaging rod; and a remaining one of said sheet retaining apparatus and said base member including a latching member for securing said sheet retaining apparatus to said base member, said latching member being pivotable from a retaining position where said sheet retaining apparatus is secured to said base member, to a releasing position where said sheet retaining apparatus may be detached from said base member, wherein said sheet retaining apparatus includes said engaging rod, and said base member includes said latching member, and wherein a portion of said latching member has an L-shaped cross section comprising a back portion, a bottom portion, and a corner portion therebetween.
  • 11. The binding apparatus according to claim 10, wherein a distal end of the bottom portion of the latching member contacts the base member in the retaining position to prevent the latching member from moving beyond the retaining position.
  • 12. The binding apparatus according to claim 10, wherein a side edge of the base member forms an engaging rod receiving channel, and the bottom portion of the latching member partially closes an opening of the engaging rod receiving channel when said latching member is in said retaining position to prevent said engaging rod from being withdrawn from said engaging rod receiving channel.
  • 13. A binding apparatus comprising:a base member; a first sheet retaining member having at least one tube; a second sheet retaining member having at least one pin receivable within said tube; an engaging rod fixed to one of said sheet retaining members; and a latching member provided on said base member for securing said one of said sheet retaining members to said base member, said latching member being pivotable from a retaining position where a portion of said latching member engages said engaging rod so that said one of said sheet retaining members is secured to said base member, to a releasing position where said portion of said latching member releases said engaging rod so that said one of said sheet retaining members may be detached from said base member.
  • 14. The binding apparatus according to claim 13, wherein said engaging rod is fixed to said first sheet retaining member, and further comprising:a second engaging rod fixed to said second sheet retaining member; and a second latching member provided on said base member for securing said second sheet retaining member to said base member, said second latching member being pivotable from a retaining position where said second sheet retaining member is secured to said base member, to a releasing position where said second sheet retaining member may be detached from said base member.
  • 15. The binding apparatus according to claim 13, further comprising:a pair of spaced-apart support pipes extending upwardly from said base member; a pivot shaft extending along said latching member, said pivot shaft passing through said pair of spaced-apart support pipes to support said latching member; and a torsion spring surrounding a portion of said pivot shaft for biasing said latching member toward said retaining position.
  • 16. A binding apparatus comprising:a base member; a first sheet retaining member having at least one tube; a second sheet retaining member having at least one pin receivable within said tube; an engaging rod fixed to one of said sheet retaining members; and a latching member provided on said base member for securing said one of said sheet retaining members to said base member, said latching member being pivotable from a retaining position where said one of said sheet retaining members is secured to said base member, to a releasing position where said one of said sheet retaining members may be detached from said base member, wherein a portion of said latching member has an L-shaped cross section comprising a back portion, a bottom portion, and a corner portion therebetween.
  • 17. The binding apparatus according to claim 16, wherein a side edge of the base member forms an engaging rod receiving channel, and the bottom portion of the latching member partially closes an opening of the engaging rod receiving channel when said latching member is in said retaining position to prevent said engaging rod from being withdrawn from said engaging rod receiving channel.
  • 18. A method of operating a binding apparatus, comprising the steps of:providing a base member; providing a sheet retaining apparatus having at least one pin; providing an engaging rod on one of said sheet retaining apparatus and said base member; providing a latching member on a remaining one of said sheet retaining apparatus and said base member; and pivoting said latching member between a retaining position where a portion of said latching member engages said engaging rod so that said sheet retaining apparatus is secured to said base member, and a releasing position where said portion of said latching member releases said engaging rod so that said sheet retaining apparatus may be selectively assembled with or detached from said base member.
  • 19. The method of operating a binding apparatus according to claim 18, wherein said sheet retaining apparatus includes said engaging rod, and said base member includes said latching member.
  • 20. The method of operating a binding apparatus according to claim 18, further comprising the steps of:providing a second engaging rod on said one of said sheet retaining apparatus and said base member; providing a second latching member on said remaining one of said sheet retaining apparatus and said base member; and pivoting said second latching member between a retaining position where said sheet retaining apparatus is secured to said base member, and a releasing position where said sheet retaining apparatus may be selectively assembled with or detached from said base member.
  • 21. The method of operating a binding apparatus according to claim 18, further comprising the step of pressing said engaging rod against said latching member to pivot said latching member from said retaining position to said releasing position to assemble said sheet retaining apparatus to said base member.
  • 22. The method of operating a binding apparatus according to claim 18, further comprising the step of providing said latching member with an L-shaped cross section comprising a back portion, a bottom portion, and a corner portion therebetween.
US Referenced Citations (5)
Number Name Date Kind
2915068 Miyamoto Dec 1959
4693625 Ohminato Sep 1987
5330280 Kaneda et al. Jul 1994
5634732 Ushirooka et al. Jun 1997
5722783 Kiyomi Mar 1998