Window and door closing mechanism

Information

  • Patent Grant
  • 6581331
  • Patent Number
    6,581,331
  • Date Filed
    Thursday, January 11, 2001
    23 years ago
  • Date Issued
    Tuesday, June 24, 2003
    21 years ago
Abstract
A opening and closing mechanism for a door or a window including a stationary primary track, a movable secondary track, an operating member with one end pivotally fixed in the primary track and an opposite end movable along the secondary track, and a guide engageable with a guide surface of the operating member. The guide surface is curved along at least a portion of a length thereof such that a tangent to the guide surface at a point where the guide surface crosses a longitudinal center line of the primary track forms an acute angle with the center line. The acute angle is substantially constant throughout the range of pivotal movement of the operating member.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to window closers, window stays and door closers. The invention also relates more generally to mechanisms such as, though not limited to, window closers, window stays and door closers which operate on a wedge principle. For example, the invention may be applicable to scissor-action mechanisms which incorporate a wedge principle of operation.




2. Description of Related Art




Present window closers include latches, chain winders and wire winders. Window latches cannot be used as stays and only latch in the final, lock-up position. Therefore, friction, a notch or some other type of stay is required to maintain a window or door ajar. Chain and wire winders do not require additional stays, however both are vulnerable in the open position to outside factors. Both, the chain and the wire tend to deflect and allow the window to partially close. A latch is usually required to secure the window in the closed position.




Present door closers include spring loaded member mechanisms with hydraulic or pneumatic braking arrangements to prevent slamming of the door. Some less expensive door closers do not incorporate the braking arrangement.




BRIEF SUMMARY OF THE INVENTION




It is the object of the invention to overcome or substantially ameliorate at least one of the above disadvantages and/or more generally to provide improved window and door closing mechanisms.




There is disclosed herein an opening/closing mechanism for a window or door, the mechanism including:




a primary track secured to or formed integrally with a window or door jamb,




a secondary track secured to or formed integrally with a window or door frame,




an operating member pivotally secured at one end thereof to the primary track and/or window/door jamb, and mounted at its other end so as to be linearly moveable along the secondary track, the operating member including a guide surface which extends along the member, the association of the operating member with the primary track being such that a line parallel to the guide surface crosses a longitudinal centre line of the primary track at a substantially constant, shallow, acute angle throughout a substantial range of operation of the mechanism, and wherein the guide surface includes a curved profile along at least a part of its length, and




a guide including means engageable with said guide surface, the guide being retrainedly moveable along said primary track whereupon interaction of the guide with the guide surface causes pivotal movement of said operating member about said one end thereof.




Preferably the guide surface is an edge of a slot formed in the operating member, the line parallel to the guide surface being a centre line of the slot.




Preferably the guide includes a roller car which can roll along the primary track and includes a guide roller which rides along the slot.




Preferably the point of pivotal attachment of the operating member to the primary track is linearly moveable along the primary track, the guide being fixed to the primary track.




There is further disclosed herein an opening/closing mechanism for a parallel opening window, the mechanism including:




a primary track secured to or formed integrally with a window jamb,




a secondary track secured to or formed integrally with a window frame,




a pair of operating members each pivotally secured at one end thereof to the primary track and/or window jamb, and each being pivotally mounted to, and so as to be linearly moveable along, the secondary track, the operating members each including a guide surface which extends along the member, the association of the operating member with the primary track being such that a line parallel to the guide surface crosses a longitudinal centre line of the primary track at a substantially constant, shallow, acute angle throughout a substantial range of operation of the mechanism, and wherein said guide surface includes a curved profile along at least a part of its length, and




a pair of guides, each including means engageable with said guide surface of a respective one of said operating members, the respective guide being restrainedly moveable along said primary track whereupon interaction of the guide with the respective guide surface causes pivotal movement of said respective operating member about said one end thereof.




Preferably each guide surface is an edge of a slot formed in the respective operating member, said line parallel to the guide surface being a centre line of the slot.




Preferably the guide includes a roller car which can roll along the primary track and includes a guide roller which rides along the slot.




Preferably the roller cars are attached to a wire rope or other flexible tension member, which wire rope passes around a sheave to a drum, rotatable by means of a handle, rotation of the handle thus causing movement of the respective roller car to effect movement of the window.




Preferably there is associated with each operating member a scissor member, each respective scissor member being pivotally interconnected to both the primary and secondary tracks.




There is further disclosed herein an opening/closing mechanism for an awning type window, the mechanism including:




a slide rod secured to or formed integrally with a window jamb,




a track secured to or formed integrally with a window frame,




an operating member pivotally, slidably attached at one end thereof to the track and slidably attached at the other end thereof to the slide rod so as to pivot about the longitudinal axis of the slide rod and an axis normal thereto, the operating member including a guide surface which extends along the member, wherein a line parallel to the guide surface and the longitudinal axis of the rod cross each other at a substantially constant, shallow, acute angle throughout a substantial range of operation of the mechanism, and




rotational means associated with the window jamb and engageable with the operating member so as to slide said one end thereof along said rod and pivot same about both said axes.




Preferably the mechanism includes a base frame that includes a pair of bearing blocks, a guide block and a swing block, the bearing blocks supporting said slide rod.




Preferably a slide block is slidably attached to the slide rod and the operating member is pivotally affixed to the slide block.




Preferably one elongated edge of the operating member is smooth, whereas the opposed edge is provided with a curved rack of gear teeth.




Preferably there are two bearing blocks supporting the slide rod and between which the slide block slides and wherein there is provided a connecting rod between the guide block and the swing block along which the slide block also slides, the connecting rod being parallel to the slide rod and maintaining the guide block and slide block in aligned association when pivoting about the longitudinal axis of the slide rod.




Preferably the rotational means includes a gear mounted upon the guide block, the gear being inter-engaged with the rack of teeth.




Preferably the gear is driven by a drive gear which is rotated by means of a handle.




There is further disclosed herein an opening/closing mechanism for a door, the mechanism including:




a pair of guide rods secured to the door jamb,




a track secured to the door,




an operating member pivotally secured at one end thereof to said guide rods and pivotally mounted to the track so as to be linearly moveable therealong, the operating member including a guide surface which extends along the member.




a guide including means engageable with said guide surface,




the association of the operating member with the track being such that a line parallel to the guide surface crosses a straight line passing through the centre in between the guide rods and the point of pivotal attachment of the operating member to the door jamb at a substantially constant, shallow, acute angle throughout a substantial range of operation of the mechanism.




Preferably the guide surface includes a curved profile along at least a part of its length.




Preferably the guide surface is an edge of a slot.




Preferably the guide includes a guide roller received within the slot.




Preferably the line parallel to the guide surface is the centre line of the slot, operation of the mechanism.




Preferably the angle varies by providing a fluctuation or fluctuations in the curve of the guide surface.




Preferably, in all of the above embodiments, the angle of crossing is substantially constant. In the door opening/closing mechanism, this angle may be varied by providing a fluctuation or fluctuations in the curve of the guide surface to decelerate the door during its closing movement.




Typically, the primary slide track is affixed to the head of the door jamb through the end blocks and the secondary slide track is affixed to the top of the door. When the door is opened, one end of the operating member moves with it through the pivotally attached slide engaged in the secondary slide track. The other end of the operating member pivots on a pivot pin affixed to the near end block, one side of the slot in the operating member exerting force upon the roller affixed to the sliding block and forcing the sliding block to slide towards the near end block, thereby tensioning the spring. When the door is released, the spring recoils and forces the sliding block towards the outer end block, exerting force through the said roller upon one side of the slot in the operating member, causing the operating member to pull the door shut through the pivotally affixed slide engaged within the secondary slide track affixed to the door.











BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS




Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings.





FIG. 1

is a schematic plan view of a closer;





FIG. 2

is a schematic perspective view of a closer having a scissor mechanism;





FIG. 3



a


is a side view of a directly operated roller car;





FIG. 3



b


is an end view of a directly operated roller car;





FIG. 3



c


is a top view of a directly operated roller car;





FIG. 4



a


is a side view of a remotely operated roller car;





FIG. 4



b


is an end view of a remotely operated roller car;





FIG. 4



c


is a top view of a remotely operated roller car;





FIG. 5

is a schematic plan view of a gear driven closer;





FIG. 6

is an enlarged, partial slide elevation of a gear driven closer;





FIG. 7

is a schematic plan view of a door closer;





FIG. 8

is a schematic illustration depicting a method adopted in determining the curvature of the guide surface, and





FIG. 9

is a schematic illustration depicting a refined means of determining the curvature of the guide surface so as to maintain a constant crossing angle.











DETAILED DESCRIPTION OF THE INVENTION




In

FIGS. 1 and 3

of the accompanying drawings, there is schematically depicted a mechanism for opening and closing windows. The mechanism includes an operating member


1


typically interconnected between a primary slide track


4


and a secondary slide track


6


. The primary slide track


4


is intended to be secured to a window jamb whereas the secondary slide track


6


is intended to be affixed or formed integrally with a window frame. The near end of the operating member


1


is anchored on the centre line


3


to the primary slide track


4


by a pivot pin


2


. The outer end of the operating member


1


is fitted with a pivoted slide


5


which is engaged into the secondary slide track


6


. A roller car


9


incorporates guide wheels


14


which keep it constantly aligned with the centre line


3


of the primary slide track


4


.




A guide roller


7


is affixed to the body of the roller car


9


and is engaged in the slot


8


of the operating member


1


.




The centre line


10


of the slot


8


in the operating member


1


crosses the centre line


3


of the primary slide track


4


at an acute angle


13


which remains substantially constant through all stages of operation of the operating member


1


, thereby providing ease of operation and self locking capability.




When the roller car


9


operates in direction


11


, the guide roller


7


exerts force upon the upper side of the slot


8


, causing the operating member


1


to travel in direction


12


, moving the pivoted slide


5


and the secondary slide track


6


to a desired position. The purpose of the curved portion of the slot


8


is to ensure that a substantially even force is exerted between the operating member


1


and the guide roller


7


throughout the operation of the device.




The roles of the pivot pin


2


and the guide roller


7


may be reversed, whereby the pivot pin


2


would be mounted on a car not unlike the roller car


9


which can travel along the centre line


3


of the primary slide track


4


. The guide roller


7


would be affixed to the primary slide track


4


.




In

FIGS. 2 and 4

of the accompanying drawings, there is schematically depicted a remotely controlled opening and closing mechanism for parallel opening windows. In this embodiment, the near ends of the operating members


1


are anchored by pivot pins


2


to the outer ends of the primary slide tracks


4


. The outer ends of the operating member


1


incorporate pins


15


which serve as axles for guide wheels which travel within the secondary slide track


6


. At centres


16


, directly in the middle between the anchor pivot pins


2


and the axle pins


15


, there are pivotally attached sets of scissor members


17


, the pivotal centres


16


being directly in the middle between the scissor members' pivotal anchors


18


and pins


19


which serve as axles for guide wheels which travel within the primary slide tracks


4


.




The roller car


20


in

FIG. 4

is fitted with guide wheels


14


which travel within the primary slide track


4


. A guide roller


7


and a wire rope anchor block


21


are affixed to the body of the roller car


20


. The roller car


22


is a mirror image of the roller car


20


.




The body of the roller car


23


is extended in relation to the roller cars


20


and


22


and the roller


7


is here fitted at position


24


. The roller car


25


is a mirror image of the car


23


.




A flexible wire rope


26


is anchored at point


27


to the reel


28


, runs a number of turns around the reel


28


, passes around the sheave


29


, through the anchor block


21


of the roller car


25


where it is anchored, continues to and around sheave


30


, through the anchor block


21


of the roller car


22


where it is anchored, continues to and around sheave


31


, passes under the reel


28


to and around sheave


32


and through the anchor block


21


of the roller car


23


where it is anchored onto and around sheave


33


, through the anchor block


21


of the roller car


20


where it is anchored, continues to and around sheave


34


, continues to and around the reel


28


to the anchor point


35


where it is anchored and terminated after forming a continuous loop. When the crack member


36


is operated in an anti-clockwise direction, the shaft


37


operates the reel


28


, the flexible wire rope


26


coming from the sheave


32


is wound onto the reel


28


and the flexible wire rope


26


leading to the shave


29


is unwound from the said reel


28


. The arrows show directions of travel of roller cars


20


,


22


,


23


and


25


.




The roller cars move in unison. The guide rollers


7


affixed to the roller cars exert force upon the sides of the slots


8


in the operating members


1


, causing motion to the operating members


1


and through pivots


16


, to the scissor members


17


, providing parallel motion of the secondary slide tracks


6


towards and in respect to the primary slide tracks


4


.




The scissor mechanism in this embodiment may be modified by shortening the operating members


1


to where they engage the pivoting centres


17


and by modifying the slots


8


as required to provide full closure of the mechanism. In this variation, the secondary slides are no longer required and pivots


18


may be directly affixed to the window.




In

FIGS. 5 and 6

, there is schematically depicted a closer for awning type windows. In this embodiment, the base frame


38


incorporates a bearing block


39


which also serves as a frame side block. The base frame also includes a bearing block


40


and a side block


41


. The bearing blocks


39


and


40


support a main slide rod


42


which in turn supports a swing block


43


, a pivot slide block


44


and a guide block


45


. A connecting rod


46


which is parallel to the main slide rod


42


is firmly affixed to the swing block


43


and the guide block


45


, thereby forming an assembly which allows the pivot slide block


44


to slide freely between the swing block


43


and the guide block


45


and, in addition, allows the three blocks


43


,


44


and


45


to swing in unison, providing a variable operating angle


62


for the operating member


47


which is pivotally affixed to the pivot slide block


44


. The operating member


47


incorporates gear teeth


48


at the outer side of the curved section


49


. The inner side


50


of this curved section


49


is smooth to provide a smooth running surface for the guide roller


51


which is affixed to the guide block


45


. The inner side


50


of the operating member


47


and the datum line of the gear teeth


48


are parallel in relation to each other. The centre line of the curved section


49


of the operating member


47


and the centre line of the main slide rod


42


cross each other at a constant, shallow angle


52


. A slide


53


is pivotally affixed to the far end of the operating member


47


and travels freely within a slide track


54


. The slide track is to be affixed to an awning type window.




A gear


55


is mounted upon the guide block


45


, directly opposite the guide roller


51


. The teeth of the gear


55


mesh with the teeth


48


of the operating member


47


.




The gear


55


of the guide roller


51


provide a firm guide, locating the operating member


47


therebetween, in a similar manner as rollers


7


guide the operating members


1


in the embodiment of

FIGS. 1 and 2

.




A gear


56


which has a greater number of teeth than the gear


55


is affixed to the gear


55


and they rotate in unison on a common axle


57


which is affixed to the guide block


45


. Gear


58


, with a lesser number of teeth than gear


56


is affixed to a shaft


59


. Also affixed to the shaft


59


is a crank handle


60


. A spring loaded catch


61


locks the gear


56


and prevents movement of the operating member


47


. When the crack handle


60


is rotated in an anti-clock-wise direction, the shaft


59


transmits this motion to gear


58


which lifts the catch


61


, allowing gear


56


to rotate and turn the gear


55


which drives, through teeth


48


, the operating member


47


, pulling with it the pivot slide block


44


and with the aid of the guide roller


51


, forcing the slide


53


and the slide track


54


away from the base frame


38


of the closer.




As an alternative to a gear operable mechanism, the rod


42


, instead of being a fixed, smooth surfaced rod might be an externally threaded component adapted to rotate about its longitudinal axis. The slide block


44


might than be internally threaded so as to cooperate with the external thread of rod


42


. The rod


42


could be driven to rotate by means of a “constant velocity” type sequence of universal joints between the end of the rod and a manually rotatable handle.




In

FIG. 7

, there is schematically depicted an automatic door closer. In this embodiment, the primary slide track


63


is affixed to the head of the doorjamb


64


and the secondary slide track


65


is affixed to the top part of the door


66


. The primary slide track


63


incorporates two slide rods


67


anchored within a near side block


68


and the far side block


60


to form parallel slide tracks, along which a sliding block


70


slides freely. A guide roller


71


is affixed to the sliding block


70


and is engaged in the slot of the operating member


73


which is pivotally attached to the near side block


69


by a pivot pin


62


. To the far end of the operating member


73


, there is pivotally attached a slide


74


which slides freely within the secondary slide track


65


. A spring


75


is attached to the far side block


69


and the sliding block


70


. The centre line


76


of the slot in the operating member


73


and the centre line which passes directly through the centres of the guide roller


71


and the pivot pin


62


cross each other and form an acute angle


80


which is substantially constant but may be varied to facilitate increases or decreases in the speeds of operation.




It is to be noted that the slot in the operating member


73


is not essential to the operation of the closer, only the outer part


77


of the operating member


73


is necessary. However, the inner part


78


does provide additional strength and ease of handling.




When the door


66


is pushed open, the slide


74


, pivotally affixed to the operating member


73


and engaged within the secondary slide track


65


which is affixed to the said door


66


, pulls the free end of the pivoted operating member


73


with it, causing the outer surface


79


of the operating member


73


to exert force upon the guide roller


71


affixed to the sliding block


70


, causing the sliding block


70


to slide along the two slide rods


67


towards the near side block


68


, and tensioning the spring


75


in the process.




When the door


66


is released, the spring


75


recoils and forces the sliding block


70


towards the far side end block


69


, exerting force through the guide roller


71


upon the outer surface


79


of the slot in the operating member


73


, causing the operating member


73


to pull the door


66


shut through the pivotally affixed slide


74


engaged within the secondary slide track


65


, affixed to the door


66


.




In

FIG. 8

there is schematically depicted a diagram which illustrates certain principles of the present invention. Two lines


81


and


82


radiate from a pivot pin


83


. A wedge shape


84


is depicted in three positions to illustrate the relationship between the wedge


84


and the lines


81


and


82


. The lines


81


and


82


represent the lines to two members of a mechanism pivotally interconnected at


83


. The line


81


is stationary, whereas the line


82


moves about the pivot point


83


.




When the wedge


84


is pushed from its original position


86


towards the pivot point


83


, it causes the line


82


to swing in an arc away from line


81


. As can be seen, the angle between the line


82


and the wedge plane


87


changes through this operation, degrading the wedge effect, increasing friction at a contact point between the upper left corner of the wedge and the line and reducing leverage.




If the wedge


84


is replaced by a round shape


88


, representing a roller for example, friction is reduced, the wedge effect is retained, however the leverage is reduced. To circumvent this disadvantage, the line


82


is modified to become the modified line


85


, incorporating a lever


89


and angled segments


90


which cooperate, if crudely, with the wedge plane


87


, thereby forming a substantially constant angle throughout the operation.




The above described principle may be applied in many ways. For example, the lines


81


and


82


can be straight and the form of wedge


84


can be unequal. Alternatively, the wedge


84


can be equal in shape. Either one of the lines


81


and


82


can be stationary or pivotable. The pivot point


83


can be stationary and the wedge


84


or roller


88


can be mobile. Alternatively, the pivot point


83


can be mobile and the wedge


84


or roller


88


can be made stationary. Either line may have a lever section, such as section


89


added to increase leverage. Wedge


84


may be substituted with roller


88


.




Member


81


can be straight and member


82


can be substituted with a modified member


85


. The wedge effect is provided by the wedge


84


, an equal wedge or a roller


88


. Either one of the lines


81


and


85


can be stationary or pivotable. The pivot point


83


can be stationary and the wedge


84


or roller


88


can be mobile. Alternatively, the pivot point


83


can be mobile and the wedge


84


or roller


88


can be stationary.




In

FIG. 9

of the accompanying drawings, the flat segments


90


of

FIG. 8

are refined, the intention being to approximate a smooth curve. This may be attained in the following manner: a number of radial lines are drawn from the pivot point


83


. These radial lines may be drawn at 5° increments. A line is drawn at, say 38° across a first of the radial lines. The point at which this line intersects the next radial line then has another line drawn at 38° therefrom to the next radial line and so on. The angle of 38° is arbitrary as is the choice of 5° for the radial line increments. An angle acuter than 38° would provide a greater wedge effect and increments of less than 5° would provide a smoother curve.




With reference to

FIGS. 1

,


2


,


5


and


7


of the accompanying drawings, line


81


represents the primary track and the line


85


represents the centre line of the slot in the operating member within which the wedge roller


88


is engaged, or the centre line of the body of the operating member. This requires two rollers


91


to provide the desired wedge effect in both directions.




When the wedge roller


88


or rollers


91


are moved towards the pivot point


83


or the pivot point


83


is moved towards the roller


88


or rollers


91


along the primary track


81


, the wedge effect causes the outer end of the operating member


85


to swing in direction


92


.




The reason for so forming the curve in slot


79


is to ensure that a substantially even force occurs between the slot and the guide roller


71


throughout the operational movement of the apparatus. This principle applies to the operating members of all of the above disclosed embodiments.



Claims
  • 1. An opening and closing mechanism comprising:a stationary primary track; a movable secondary track movable with respect to said primary track; an operating member having one end pivotally fixed to said primary track and an opposite end movable along said secondary track, said operating member having a guide surface extending therein, said guide surface having a length; a guide engageable with said guide surface and restrainedly movable along said primary track so as to cause pivotal movement of said operating member about said one end thereof, said guide surface being curved along at least a portion of said length thereof such that a tangent to said guide surface at a point where said guide surface crosses a longitudinal center line of said primary track forms an acute angle with said longitudinal center line, said acute angle being substantially constant throughout an approximately full range of said pivotal movement of said operating member.
  • 2. The mechanism of claim 1, said guide surface being an edge of a slot formed in said operating member.
  • 3. The mechanism of claim 2, said guide comprising a roller car which is rollable along said primary track, said roller car having a guide roller which is ridable in said slot in said operating member.
  • 4. An opening and closing mechanism for a parallel opening window comprising:a stationary primary track; a movable secondary track; a pair of operating members each having one end which is pivotally fixed relative to said primary track, each of said operating members having another end which is movable along said secondary track, each of said pair of operating members further comprising a guide surface extending therein; a pair of guides respectively engageable with the guide surfaces of said pair of operating members and restrainedly movable along said primary track so as to cause pivotal movement of each of the operating members about said one end thereof, each of said guide surfaces being curved along at least a portion of a length thereof of such that a tangent to said guide surface at a point where said guide surface crosses a longitudinal center line of said primary track forms an acute angle with said longitudinal center line, each of said acute angles being substantially constant throughout an approximately full range of pivotal movement of a respective one of said operating members.
  • 5. The mechanism of claim 4, said guide surfaces each being an edge of a slot formed in the respective operating member, each of said slots having a center line parallel to said guide surface.
  • 6. The mechanism of claim 5, each of said pair of guides comprising a roller car which is rollable along said primary track, each said roller car comprising a guide roller which is ridable in a respective one of said slot.
  • 7. The mechanism of claim 6, each said roller car being attached to a flexible tension member, said flexible tension member passing over a drum, said drum being rotatable by a handle, said handle connected to said drum such that a rotation of said handle causes a corresponding movement of said roller cars.
  • 8. The mechanism of claim 4, each of said pair of operating members further comprising a scissor member, said scissor members being pivotally interconnected to each of said primary track and said secondary track.
  • 9. A mechanism comprising:a door; a door jam; a pair of guide rods secured to said door jam; a track secured to said door; an operating member having one end pivotally fixed to said pair of guide rods and another end pivotally mounted to said track so as to be movable therealong, said operating member further comprising a curved guide surface which extends therealong; and a guide engageable with said guide surface and movable along said guide rods so as to cause pivotal movement of said operating member, said operating member being oriented such that a tangent to said guide surface crosses a straight line passing between and substantially parallel to said pair of guide rods at an acute angle, said acute angle being substantially constant throughout an approximately full range of pivotal movement of said operating member with respect to said pair of guide rods.
  • 10. The mechanism of claim 9, said guide surface being an edge of a slot.
  • 11. The mechanism of claim 10, said guide further comprising a guide roller received within said slot.
  • 12. The mechanism of claim 10, said guide surface having a line parallel thereto, said line being a center line of said slot.
  • 13. The mechanism of claim 9, said acute angle being variable by a fluctuation in the curve of said guide surface.
Priority Claims (3)
Number Date Country Kind
PP 3695 May 1998 AU
6430 Oct 1998 AU
7385 Nov 1998 AU
PCT Information
Filing Document Filing Date Country Kind
PCT/AU99/00400 WO 00
Publishing Document Publishing Date Country Kind
WO99/61739 12/2/1999 WO A
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Number Name Date Kind
428624 Morrell May 1890 A
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1432784 Putnam Oct 1922 A
1693690 Corcoran Dec 1928 A
2366613 Hagstrom Jan 1945 A
5035463 Kato et al. Jul 1991 A
5581941 Sill et al. Dec 1996 A
Foreign Referenced Citations (4)
Number Date Country
1 958 413 May 1971 DE
2 058 321 May 1972 DE
2 817 883 Oct 1979 DE
2 228 767 Sep 1990 GB