US3849835A

US3849835A - Spring hinge for bifold doors

Info

Publication number: US3849835A
Application number: US00290401A
Authority: US
Inventors: T Jerila
Original assignee: Acme General Corp
Current assignee: Acme General Corp
Priority date: 1972-09-19
Filing date: 1972-09-19
Publication date: 1974-11-26
Anticipated expiration: 1991-11-26

Abstract

A spring hinge is provided for bifold doors such as are commonly used on closets. The hinge has an over-center spring action that closes the doors when they are nearly closed and opens the doors when they are nearly open and retains the doors in those positions respectively. A power pack having two pivotally interconnected U-shaped rigid members displaces the driving spring away from tne ends of the doors to provide clearance. In one embodiment the power pack connects to the respective hinge leaves by way of a bearing tooth on each hinge leaf and bearing faces on the rigid members of the power pack. The spring on the power pack between the rigid members acts to urge the bearing faces towards each other. A line between the bearing teeth lies on opposite sides of the hinge pivot axis when the hinge is in its open and closed positions, respectively. In one embodiment of power pack, the rigid members are formed of sheet metal and pivotally interconnected without a pin joint. In another embodiment the power pack is molded of plastic with an integral web between the rigid members forming the pivot. A pin type pivot may also be used between the power pack and the hinge leaves. The hinge leaves are corner connectors for doors having a thin panel, end rail and side stile.

Description

i United States Patent U91 .1 erila 11 3,849,835 [451 Nov. 26, 19 74 1 1 SPRING HINGE FOR BTFOLD DOORS [75 Inventor: Torsti T. T. Jerila, Baldwin Park,

Calif.

['73] Assignee: Acme General Corp., Monrovia,

Calif.

[22] Filed: Sept. 19, 1972 [21] Appl. No.: 290,401

521 U.s.'ci. 16/182 Primary Examiner-Paul R. Gilliam Assistant Examiner-William E. Lyddane Attorney, Agent, or Firm-Christie, Parker & Hale [5 7 ABSTRACT A spring hinge is provided for bifold doors such as are I v commonly used on closets. The hinge has an overcenter spring action that closes the doors when they are nearly closed and opens the doors when they are nearly open and retains the doors in those positions respectively. A power pack having two pivotally interconnected U-shaped rigid members displaces the driving spring away from tne ends of the doors to provide clearance. in one embodiment the power pack connects to the respective hinge leaves by way of a bearing tooth on each hinge leaf and bearing-faces on the rigid members of the power pack. The spring on the power pack between the rigid members acts to urge the bearing faces towards each other. A line between the bearing teeth lies on opposite sides of the hinge pivot axis when the hinge is in its open and closed positions, respectively. In one embodiment of power pack, the rigid members are formed of sheet metal and pivotally interconnected without a pin joint. In another embodiment the power pack is molded of plastic with an integral web between the rigid members forming the pivot. A pin type pivot may also be used between the power pack and the hinge leaves. The hinge leaves are corner connectors for doors having a thin panel, end rail and side stile.

37 Claims, 18 Drawing Figures PATENTLD 137261974 SHEET 5 BF 6 1 SPRING HINGEYFOR' BIFOLD DOORS installation has four door panels with two mounted to swing towards each jamb. At each side one of the panels pivots relative to the jamb in substantially the same manner as any door. The second panel is mounted on hinges to the edge of the first panel and typically pivots in'the oppositedirection from the first panel. The far edge of the second panel is typically guided by tracks at the top and'bottom of the door respectively so that the far edge travels within the door frame. Thus, when the bifold door is closed both the first and second panels are within the door frame and in alignment. When the bifold door is opened the first panel pivots at the jamb and its opposite edge moves out; the second panel pivots so that its face approaches the face of the first panel. The edges of the two doors where they are pivoted together also move out from the door frame. The furthest edge of I the second panel moves along the tracks towards the jamb.

, as 3/16 or A inch thick plywood, forming the main face of the door. A metal stile is provided along each side edge of the panel and a metal rail is provided at the top and the bottom. A comer connector secures the adja-- cent rail and stile together at each corner. Since hinges cannot be secured to the 'panel in any practical manner, the comer connectors on adjacent doors may be pivotally interconnected to form a hinge. Such hinge cannot extend any substantial distance beyond the end of the doors or it will interfere with the guide track. In addition, a hinge at the bottom of the door might become tangled with shag carpeting or the like It is desirable in a bifold closet door to have some means for assuring that the door stay closed, that is, that the two adjacent panels are in substantial alignment. Preferably, this function is added to the structure of the hinge and when associated with a corner connector issubject to the same constraint that it should not extend much beyond the end of the door. Connections between the edge stiles at some point between the ends of the doors are generally not satisfactory since the engagement of the stile with the panel is not suffficiently uniform to assure good alignment in all installations.

It is therefore desirable to provide hinges for bifold doors that urge the door towards a closed position and hence hold the panels in alignment. Such a hinge should be useful with thin panel doors having peripheral stiles and rails. The hinge leaves should engage the door with sufficient rigidity to resist cave-in if the door is pushed in the wrong direction. It is also desirable that the hinge urge the door towards its open position, particularly for retaining it in such position. Preferably such hinges are economically mass produced and are simple to install.

BRIEF SUMMARY OF THE INVENTION opened position. Preferably the line of application of spring force to the hinge leaves moves over center for alternatively urging the hinge towards its open position or closed position. The spring power pack preferably engages the top of the hinge leaves by way of a window through each of the leaves and has its spring located below the top of the hinge. This can, for example, be

done readily by interconnecting spring support members in scissors fashion.

DRAWINGS These and other features and advantages of the present invention will be appreciated as the same becomes better understood by reference to the following detailed desciption of presently preferred embodiments when considered in connection with the accompanying drawings wherein:

FIG. 1 is a view of a pair of bifold doors indicating the location of application of hinges constructed according to principles of this invention; I

FIG. 2 is a perspective view of a spring hinge constructed according to principles of this invention with bifold doors in their closed position;

FIG. 3 is an end view of the hinge of FIG. 2 in its position when the doors are open;

FIG. 4 is a side view of the hinge from the inside of the doors;

FIG. 5 is a horizontal cross section through the stile I and panel of a door illustrating in end view one hinge FIG. 9 is an inside view of one-half of the power pack of FIG. 8;

FIG. 10 is an outside view looking out towards-onehalf of the power pack of FIG. 8;

FIG. 1 1 is a detailed cross section of an integral hinge or pivot between two halves of the plastic power pack of FIG. 8;

FIG. 12 is a fragmentary side detail of a hinge leaf engaging portion of the plastic power pack of FIG. 8;

FIG. 13 is a fragmentary cross section indicating the engagement of the plastic power pack with an aperture through the hinge leaf;-

FIG. 14 illustrates the two moieties of another sheet metal embodiment of power pack useful in a spring hinge for bifold doors;

FIG. 15 illustrates in perspective a spring for the hinge; 1

FIG. 16 is a fragmentary detail of another hinge leaf engaging portion for a plastic power pack;

FIG. 17 is a fragmentary cross section indicating engagement of the portion of FIG. 16 with an aperture through a hinge leaf; and FIG. 18 is an end view of another embodiment of spring hinge.

DESCRIPTION FIG. 1 illustrates rather generally the location of hinges for bifold doors. The doors as seen in FIG. 1 are viewed as if one were standing inside a closet lookiing towards the doors in a nearly closed position. Such doors 20 and 21 are formed of two panels. The first door 20 has pivots 22 at the top and bottom to flt in brackets (not shown) in a door frame adjacent a jamb for mounting the pair of doors. The other door has guides 23 at the top and bottom for riding in a track (not shown) in the door frame. Spring hinges 24 interconnect the two doors 20 and 21 at the top and bottom corners. Generally speaking, hereinafter description of the hinges will consider that the hinge is mounted at the top of a pair of doors and top and bottom may be used in that context in describing various aspects of the structure. It will be apparent, of course, that a substantially identical structure is employed at the bottom of the door. If desired one or more center hinges (not shown) can be mounted between the end hinges 24 for increased stiffness.

FIG. 2 illustrates in perspective a spring hinge constructed according to principles of this invention mounted at the top of a pair of doors which are illustrated in their closed position. FIG. 3 is a top view of the spring hinge, deleting the doors, with the hinge in the position it would have with the doors open.

FIG. 4 is a side view of the hinge from the inside of the doors looking out, with the hinge in a position it would have with the doors closed. Although it may seem contrary to the apparent structure of the hinge itself, reference will be made hereinafter to the hinge in its closed position representing that condition when doors attached thereto are closed, that is, with their panels lying in substantially the same plane.

The doors as seen in FIG. 2 each comprise a flat panel 26 such as plywood, composition board or the like about 3/ l 6 inch thick. Along the edge of each door is a stile 27, each of which is roll formed from flat sheet and has an identical cross section (the two stiles are, of course, reversed relative to each other so as to be symmetrical about the plane between the door edges). Rails 28- are fitted along the top edge of each door panel 26. Similar stiles and rails are employed on the other edges of the panels to complete the door.

As best seen in FIG. which comprises a horizontal cross section looking upwardly one-half of the hinge, the stile 27 has a front wall 29 in engagement with the front face 31 of the panel 26. A hollow raised flange 32 is provided along the length of the stile. A jamb edge or side wall 33 is adjacent the edge of the panel and is opposed to a similar side wall (not shown in FIG. 5) on the adjacent stile on the other door. Typically, the side wall 33 is at an angle of less than from the front wall 29 when the stile is used on a 3/16 inch panel. This permits the springiness of the stile to acommodate a A inch panel, if desired and the stile wall -33 is at about 90 from the panel in that case.

A back wall 34 is approximately parallel to the front wall 31 and is spaced a substantial distance away from the rear face 36 of the panel in order to provide stiffness. Extending between the back wall 34 and the rear face 36 of the panel is an inner leg 37. At the inner end of the inner leg there is an inwardly directed foot 38 that engages the rear face 36 of the panel. A slot 39 is provided through the inner leg 37 as best seen in FIG. 2.

Thus, it will be seen that the stile has a generally G- shaped cross section (illustrated inverted in FIG. 5) with the top of the G corresponding to the front wall 29 and the bottom of the G corresponding to the back wall 34. The panel enters the mouth of the G between the crossbar (foot 38) and the top. The springiness of the sheet metal forming the stile accommodates some variation in thickness of door panel.

The rail 28 which is best seen in the vertical cross section of FIG. 6 and in FIG. 2, is essentially an inverted U-shaped member fitted over the top edge of the panel and sufficiently springy to frictionally engage it. A face flange 41 within the hollow rail engages the front face 31 of the panel. Space is left between the fact 40 of the rail and the face flange 41 to accommodate a portion of the hinge described hereinafter and also to provide good abutment at the end of the rail against the side of the flange 32 on the stile. This prevents the end of the rail from slipping between the panel and stile. It is convenient also to provide a turned in rear flange 42 on the rail which provides a rounded portion so that the door panel can easily be inserted during assembly and which also contributes to the springiness of the rail. The top 43 of the rail normally has a slight clearance beyond the edge of the door panel. A pair of slots 44 extends through the top of the rail adjacent the face flange 41.

Referring again to FIG. 2 and incidentally FIGS. 3 to 6, the hinge between the two doors is made of two hinge leaves 46 that are an allochiral pair except for one minor feature. Each hinge leaf has an extending ear 47 and a hinge pin 48 preferably in the form of a short loose rivet extends through the two ears 47 to define the pivot axis of the hinge. One of the ears 47 is offset from the top of the hinge leaf by an amount equal to the thickness of the metal used to form the hinge leaf so that the two ears can fit together for forming a pivot. Otherwise the two hinge leaves are similar in shape.

Since doors formed of thin panels with peripheral stiles and rails are quite light weight, the short hinge pin formed by the rivet 48 when a hinge is used at both the top and bottom of the door has been found sufficient. Typically, the entire hinge leaf is blanked and bent from sheet steel and bearing loads on the pivots are not excessive.

Each hinge leaf is essentially L-shaped with a top arm 49 extending over the rail 28 and a downwardly extending leg 51 (FIGS. 4 to 6) extending inside the stile 27.

The laterally extending arm 49 has a top face 52 that flts over the top 43 of the rail. Nearer the front of the door a pair of spaced apart tangs 53 extend downwardly through the slots 44 in the top of the rail. As

best seen in FIG. 6 these tangs bear against the face flange-41 of the rail which is in engagement with the front face 31 of the panel. The hinge leaf arm also has a flange 54 extending down from the top 52 on the back side of the rail, that is, nearer the rear face 36 of the panel. The flange 54 bears against the corner 56 between the top and back of the rail. The hinge leaf thus firmly grips the rail and has tangs 53 in effective engagement with the front face of the door panel so that the hinge leaf is securely held in alignment with the font of the panel. The rather widely spaced apart tangs 53 and the elongated flange 54 on the arm of the hinge leaf assure accuratealignment of the rails and therefore 1 also the door panels. It will be apparent that a single transfer through the finger 62 to the rest of the hinge. To release the hinge leaf from the stile in the rare case where it is desired to remove'the hinge, one need only strike the barb with a punch to bend the finger 62.

. stiles and pressing down until the tangs 53 enter the front face of the doors. The two stops are in tight ennot readily be pushed past their aligned, closed 'positron.

An additional tang 57 also extends downwardly from the top of the hinge leaf into the interior of the front flange 32 on the stile. An edge of the tang 57 engages the frontface 31 of the door panel. If desired, the stile may include an additional folded portion on the front flange that lies adjacent the front face of the panel and essentially makes the front flange 32 a box section. When that is done the tang 57 has an edge engaging this additional flange. This third tang 57 serves to further assure alignment of the hinge leaf with the door panel. In addition, it helps secure the stile in fixed relation to the end of the rail as determined by the spacing of the slots 44 from the end of the rail. In a stile where the front flange 32 is deleted, the third tang 57 may also be deleted.

As best seen in the horizontal cross section of FIG. 5, the downwardly extending leg 51 of the hinge leaf has an approximately, U-shaped cross section over much of its length. The bight 58 of the U is adjacent the side wall 33 of the stile. The bight of the U-shaped portion of the leg extends upwardly and connects the leg to the arm of the hinge leaf at a fold 60 (FIG. 2). A plane leg 59 of the U-shaped cross section is relatively nearer the door panel and approximately parallel thereto. The span of this plane leg 59 is sufficient to engage the inner leg 37 of the stile. The other leg of the U'shaped cross section has a slot 61 (FIG. 4) extending upwardly from its lower end. This slot defines a finger 62 extending downwardly along the leg. A barb 63 on the end of the finger 62 snaps into the slot 39 through the inner leg 37 of the stile. The finger and barb cooperate with the stile in a manner somewhat similar to related elements in US. Pat. No. 3,450,426. The barb also picks up loads due to the weight of the door for slots 44 and the tang 57 enters the forward flange 32. As the hinge is pressed further down the barb snaps into the slot 39 and installation is complete.

I-Iinge leaves as described to this point thus serve to hold the rail and stile together, serving as corner connectors for the doors. The hinge leaves are pivotally interconnected and thereby operate in substantially the same manner as conventional hinges. In addition, as hereinafter described, spring loading is applied to the hinge leaves for opening or closing the doors and retaining them in their respective extreme positions.

A window or aperture 64 is provided in the top face 52 of each of the hinge leaves. This window has a generally L-shape with a projection or bearing tooth 66 extending into the window. The bearing tooth points away from the hinge pivot 48. The included angle of the bearing tooth 66 in this embodiment is about Referring to FIG. 2 it will be noted that a line between the points of the bearing teeth 66 on the two hinge leaves lies to one side of the axis ofthe pivot 48 between the two hinge leaves. FIG. 2 illustrates the hinge in its closed position. Referring to FIG. 3 where the hinge is illustrated in its open position, it will be noted that a line between the bearing teeth 66 on the two hinge leaves now lies on the opposite side of the pivot axis from its position, when the hinge was closed. Each of the bearing teeth moves along a circular are about the axis of the pivot 48 as the hinge is moved between its closed and open positions. The two bearing teeth are relatively closer together in the closed position, and in the open position, than they are at the intermediate over-center" point where the line therebetween intersects the pivot axis.

If a force is applied in a direction urging the bearing teeth towards each other, (as, for example, by a tension spring therebetween) the hinge in its closed position will tend to stay closed. Any motion tending to open the hinge must overcome this urging force (and stretch the imaginary tension spring). Similarly when the hinge is in its closed position, any movement tending to open the hinge spreads the bearing teeth further apart and must overcome the urging force. At the intermediate point where the line between the bearing teeth intersects the pivot axis the imaginary spring is stretched to its maximum extent and on either side of this intermediate point this spring would urge the hinge towards either its open or closed position.

Such an over-center action tending to open or close the hinge depending on whether it is more nearly open or nearly closed, respectively, could be obtained by simply providing posts above the top of the hinge at points corresponding to the location of the bearing teeth. A tension spring therebetween would move over center when crossing the pivot axis and provide the opening and closing biasing forces for operating the hinge. Such an arrangement is, however, undesirable since the spring would extend a significant distance beyond the top of the hinge and might interfere with guide tracks or beocme tangled in carpeting. Other means are therefore desirable for applying a force between the bearing teeth without extending any substantial distance above the hinge. A spring power pack is provided for biasing the hinge.

It might be noted that a complete over-center action is not needed. The more important function is to assure that the doors are completely closed and aligned with the stops 55 in engagement. It is not as significant to force the doors to a completely open position. It is therefore feasible to have the spring force applied on one side of the pivot axis when the doors are closed and substantially across the pivot axis when the doors are open. The open position may be less stable, but this is not a substantial problem since the closing spring force exerted at the center position is rather small. Thus it is broadly feasible to have a spring hinge wherein the pivot is on one side of the spring force when the doors are closed and not on the same side when the doors are open. That is, when the doors are open the spring force line may be on or beyond the center position defined by the hinge pivot axis. When on center there is no force tending to either open or close the doors. When beyond center the doors are biased open. It is preferable to bias the doors open as well as closed.

In the embodiment illustrated in FIGS. 2 to 4, the power pack comprises a first rigid spring support member 67 and a second spring support member 68 in many respects similar to the first. Each of the

spring support members

67, 68, is generally U-shaped with a crooked or curved spring arm 69 and a crooked or curved bearing arm 71 aproximately parallel to the spring arm. These two arms are interconnected by a flat bight portion 72. The spring support members are simply blanked and bent from sheet steel. The tip of the bearing arm 71 is bent towards the spring arm to define a bearing surface 73 at approximately a right angle to the principal extent of the bearing arm. The bearing surfaces are preferably substantially normal to a line therebetween. A second bend beyond the bearing surface forms a hook 74 approximately parallel with the principal extent of the bearing arm. As best seen in FIGS. 2 and 3 the power pack is assembled to the hinge leaves with the end of the bearing arm extending through the window 64 so that the hook 74 is beneath the bearing tooth 66 and the bearing surface 73 is in engagement with the tip of the bearing tooth.

'A coil spring 76 (illustrated only in FIG. 2 and deleted from FIGS. 3 and 4) is hooked into a notch 77 at the end of each of the respective spring arms 69. This places the spring parallel to the line between the bearing surfaces 73. When the two spring support members 67'and 68 are interconnected by a pivot transverse to the spring axis, the spring will urge the bearing surfaces towards each other. Such a pivot can be provided by a pin extending parallel to the bight portions 72, however, this tends to present minor manufacturing and economic problems that are preferably avoided.

A pivot between the two bearing support members need only move through a few degrees of arc during operation of the power pack in the bifold door hinge. A

female quasi-cylindrical socket 78 is formed along one edge of the bight portion 72 on the first spring support member 67. A male knife edge is formed on the corresponding edge of the bight portion 72 of the second spring support member 68. When assembled the knife edge 79 rests in the socket 78 and is free to tilt therein about an axis transverse to the arms 69 and 71 on the spring support members. A short tang 81 extends from each of the arms of the first spring support member 67 between the corresponding arms of the second spring support member 68 for inhibiting lateral movement of the knife edge along the quasi-cylindrical female surface, thereby holding the spring support members to gether.

It will be apparent that an extremely blunt knife edge is actually involved in this embodiment corresponding to the thickness of the sheet metal used for forming the spring support members. Such a very im' precise fit at the quasi-cylindrical socket and knife edge pivot is quite satisfactory since operation of the power pack is rather insensitive to location of the pivot, loads on the pivot are rather small, and neither wear nor friction of the pivot is any problem.

The power pack is readily assembled merely by hooking the knife edge 79 into the socket 78 and pivoting to fit the tangs 81 between the arms of the second support member. The spring 76 is then snapped in place in the notches 77. The step 82 adjacent the tangs 81 limits the extent the arms can pivot towards each other under the urging of the spring. This preassembled power pack is then assembled to the hinge when the hinge is in its closed position as illustrated in FIG. 2. The windows 64 through the top of the hinge leaves have a sufficient extent in a direction along the rail arm 49 to provide clearance for the hook 74. The power pack is inserted by pivoting the arms away from each other (thereby stretching the spring) and dropping the hooks through the corresponding windows. When the arms are released the urging of the spring retains the bearing surfaces 73 in engagement with the bearing teeth 66 and inhibits withdrawal of the power pack. The hooks 74 engaging the underside of the hinge leaf also inhibit rotation of the power pack about an axis extending between the bearing teeth. Engagement of the bearing arms 71 with the top 52 of the hinge leaf inhibits rotation about the same axis in the opposite direction.

Thus it will be seen that with the power pack installed on the hinge as above described, the force of the spring is effectively transferred through the spring support members and is applied in a direction between the two bearing surfaces 73. The magnitude of the force exerted by the bearing forces on the bearing tooth is readily selected by the magnitude of the spring force and the relative lengths-of the lever arms formed by the spring arms 69 and bearing arms 71, respectively.

It might be noted that functionally the power pack is analogous to a scissors linkage. A closing force exerted on the spring arms acts through the pivot to cause the bearing arms to exert a closing force. If desired, instead of employing U-shaped spring support members pivotally interconnected along an axis extending along the bight of the U, one can use pivotally interconnected straight spring support members in direct scissors fashion. One difficulty raised by such an arrangement, however, is that the power pack extends a substantially greater distance away from the hinge pivot axis and may, for example, interfere with objects in a 9 closet when the doors are closed. In the illustrated arrangement the power pack intrudes into a-closet a mini-' mum distance and the spring is removed to a position below the top of the hinge so as not to interfere with the tracks at the ends of the doors. a

The power pack applies the spring force in a direction along the line between the bearing teeth 66 thereby urging the hinge towards its closed positions when it is more nearly closed and towards its open position when it is more nearly open. The bearing arms of the spring support members can be connected to the hinge leaves by ordinary pivot pins rather than the illustrated arrangement, however, this raises minor manufacturing or economic problems which are preferably avoided. The number of parts required to make a complete spring hinge is also increased with a concomitant increase in cost. Each of the hinge leaves must pivot through an angle of only about 90 in passing between the open and closed positions. It therefore becomes feasible to employ the pointed tip of the tooth 66 and the flat bearing surface 73 as a knife edge and plane pivot. Such a knife edge is not quite a point contact since the tooth has a finite bearing surface on the plane. With steel parts having the relatively small bearing loads applied by the power pack, the contact area is very small and the motion is effectively one of tilting,

thereby causing very little friction or wear. The included angle of the tooth should be no more than 90 to keep the bearing surface from engaging the side of the tooth.

It is apparent that the relative positions of the bearing tooth and plane surface can be reversed. That is, the bearing tooth can be on the power pack and the bearing surface can be in the window on the top of the hinge leaf. The illustrated arrangement is preferred because of manufacturing considerations. The important consideration is that there be at least 90 of clearance be-,

I tween the bearing tooth and the bearing surface. That is, the total included angle of both the bearing tooth and bearing surface be no more than about 270. This is needed since collectively the hinge halves must pivot through 180 and the connection between the power pack and each hinge leaf must swing through 90. Many intermediate arrangements between the knife edge and plane with an included angle of no more than 270 will be'apparent toone skilled in the art. Even arrangements with an obtuse included angle in both the bearing tooth and the bearing surface may be suitable so long as some means is provided for preventing the points of the two obtuse angles from slipping laterally from each other, thus, for example, a minor indentation may be provided at the apex of one of the obtuse angles.

I Some small additional angular clearance is preferable between the bearing tooth and surface so that the motion of the hinge is limited by other builtin stops. The hinge extends to alignment in its closed position as lim- I since they tend to bind when one attempts to close them. Instead the doors diverge at about 10 to give the second door some lead so that it will slide along the track when the first door is pushed in a direction parallel to the door frame. The engagement of the rails with the power pack may be suitable means for maintaining such divergence, but it is preferred that an auxilliary stop be added after the doors are hung. This permits doors with installed hinges to lie parallel for packing and shipping.

The power pack hereinabove described and illustrated in FIGS. 2 to 4, is conveniently blanked and bent from cold rolled sheet steel. It has also proved highly advantageous to form a power pack of injection molded plastic. When such a power pack is molded of polypropylene, the living hinge properties inherent in this plastic can be utilized. Other suitable plasticsinclude some varieties of nylon and acetal resins. Fibers in this plastic are readily oriented by stressing (possibly while slightly warm) to provide a flexible hinge that can be cycled a great number of times without failure.

FIG. 7 illustrates in perspective the general arrangement of such a molded plastic power pack. As illustrated in this embodiment the power pack is formed of two rigid spring support members 86 which are an allochiral pair. Each of the spring support members has a spring arm 87 on which a spring 88 is mounted as hereinabove described.

A bearing arm 89 is parallel to the spring arm 87 on each half of the power pack. The spring arm in such an embodiment may be approximately semi-circular for enhanced rigidity with a relatively thin section. The bearing arms are preferably made relatively thin so as to have minimum height above the top of the hinge leaves when the power pack is installed.

At the end of each of the bearing arms 89 there is an offset hook 91 for fitting through the window in a hinge leaf and holding the power pack against removal in the manner hereinabove described. A bearing face 92 is on the end of the bearing arm adjacent the hook 91. A shallow groove 93 is provided in the center of the bearing face to provide a region of contact with the bearing toothon a hinge leaf. The bearing tooth (not shown) on a hinge for use with a plastic power pack is preferably provided with a radius as hereinafter described in greater detail because the bearing strength of the plastic is not as great as that of steel and it is desirable to have a larger area of contact between the'tooth and bearing surface when one or both of the parts is made of plastic than when both are made of steel. A point or knife edge contact by steel on the plastic would introduce an unacceptably high localized bearing load. When the bearing tooth with a radius on the end thereof is used it may not be necessary to provide a preformed groove 93 since the tooth will make its own groove in a few cycles of operation. Thereafter wear of the polypropylene as the hinge is used is only minimal.

The two rigid bearing support members 86 are interconnected at their bight portions by a thin web 94 of polypropylene integral with the spring support members. Such a web between the two halves will flex a very large number of cycles and thereby provides a pivotal interconnection between the two spring support members. When the plastic power pack is injection molded, the two halves are fonned in an unfolded" position, that is, with the web 94 extending substantially straight between the two halves lying side by side with the bearing surfaces 92 on the two halves being in pproximately the same plane. Thereafter the two halves are folded towards each other to a position such as that shown in FIG. 7 for receiving the spring 88. This bends the web 94 as shown to provide a pivotal interconnection between the bearing support members.

FIGS. 8, 9 and 10 illustrate in bottom, inside, and outside views respectively another embodiment of molded plastic power pack. In each of these figures one-half of the power pack is illustrated and it will be understood that an allochiral half is omitted. In the three views of FIGS. 8 to 10 the omitted half of the power pack would be lying adjacent the illustrated half in the position occupied during molding of the plastic part before the integral hinge is bent, that is, in top view the power pack would look something like one-half of a figure 8 rather than the approximately circular position illustrated in FIG. 7. FIGS. 11 to 13 are fragmentary views showing details of the plastic power pack.

The top portion of the power pack is approximately a semicircular bearing arm 96. This bearing arm is bowed upwardly at its middle portion and a shallow relief cavity 97 is provided on the underside for clearance over the pivotal interconnection between a pair of hinge leaves of the same general type hereinabove illustrated in FIG. 2. The lower part of the spring support member comprises a spring arm 98 with a notch 99 towards the outside thereof for receiving a tension spring (not shown). Interconnecting the bearing arm 96 and the spring arm 98 is a bight portion 101. To provide sufficient strength in the bight portion it is formed with a generally S-shaped or Z-shaped wall 102 best seen in FIG. 8, extending between the bearing arm and the spring arm. Reinforcing webs 103 extend across the crooks of the S-shaped wall and define recessed pockets 104 facing towards both the inside and outside of the power pack half. These pockets are provided rather than merely making the bight portion of one mass of plastic in order to keep the section thickness of the plastic relatively uniform throughout the molded part. Stiffness can also be enhanced with a steel insert in the bight.

An integral web 106 of polypropylene extends between the bight portion of the illustrated half of the plastic power pack and that half deleted from FIGS. 8 to 10. The web 106 is initially molded approximately flat on its inside face and concave on its outside face as best seen in the lower right portion of FIG. 8. When the hinge is folded as illustrated in FIG. 11 to bring the two spring support members into face to face proximity the web 106 is bent so that the initially flat face is rather sharply concave towards the inside of the power pack and the originally concave portion of the web on the outside is now convex.

At the outer end of the bearing arm 96 there is a hok 107 shown from three directions in FIGS. 8 to 10, andd in the enlarged side view in FIG. 12. In addition, a cross section through the base of the hook is illustrated in FIG. 13 along with a window 108 through the top of a hinge leaf not otherwise illustrated but in most respects similar to that hereinabove described and illustrated in FIGS. 2 to 4.

The hook 107 has an approximately cylindrical portion 109, except for a cut-away side to provide sufficient clearance for the hook to pass through the window 108. Four tapered ribs 111 extend beyond the cylindrical portion for reinforcement and provide a taper the cylindrical part 109 and the bearing arm 96 exposes a surface 112.

Referring to FIG. 13 a bearing tooth 113 extends into the window 108 in a manner analogous to the bearing tooth 66 seen in FIGS. 2 and 3. In this embodiment the bearing tooth has a rounded end portion 114 extending through an angle of about 270 around the end of the bearing tooth. A mating groove 116 is formed in the surface 112. As mentioned hereinabove the bearing groove 116 may be provided initially in the molding process or it may occur after a few cycles of operation of the power pack in conjunction with a hinge. The mating of the rounded end 114 on the bearing tooth and the bearing surface 116 assures a sufficient contact area therebetween for sustaining the loads between the plastic power pack and the hinge leaf. There will be some sliding between the rounded end of the bearing tooth and the plastic bearing surface but since the loads are relatively small very little wear occurs and such a hinge and power pack may be operated through many hundreds of thousands of cycles.

FIG. 14 illustrates an additional embodiment of spring power pack which may be blanked and bent from sheet steel. As illustrated in this embodiment the two spring support members 120 are essentially similar to those hereinabove described and illustrated in FIGS. 2 to 4. Each spring support member has a bearing tooth on a hinge leaf. A spring arm 123 is connected to each bearing arm by a bight portion 124. The bight portion on one of the spring support members has an inwardly folded flange 125 having slots 126 at each end. The bight portion on the other spring support member has an inwardly directed flange 127 that when assembled is approximately opposite the flange 125 on the first spring support member.

A hook 128 extends from the second flange 127 a short distance from the end thereof. A tang 129 extends from the flange at the opposite end thereof. At some point between the ends, preferably nearer the tang 129, and spaced from the end of the second flange there is a raised post 131. More than one such post may be provided, if desired. To assemble the two spring support members the hook 128 is inserted through one of the slots 126 and the spring support member is slid downwardly so that the tang 1 2 9 fits through the other slot. The post 131 limits the extent that the two spring support members can approach each other since it bears against the flange 125. When this power pack is so assembled with a spring between the spring arms 123 and the hooks through the windows of hinge leaves, the flange 125 can rock on the knife edge post 131 and hook 128 and provide a pivotal interconnection between the two spring support members. The spring force tending to pull the spring support members together is counteracted by the post 131. The separating force acting on the hooks 122 at the upper end is counteracted by the hook 128. these two force couples keep the spring support members stable in all operating positions.

FIG. 15 illustrates in perspective a U-spring which can be substituted for the power pack in engagement with hinge leaves. The U-spring has a pair of opposed bearing arms 133, each of which terminates in a hook 134. The hooks 134 are stepped down from the plane of the bearing arms 133 to define bearing surfaces 136. The hooks and bearing surfaces fit through windows in a hinge leaf and cooperate with the bearing tooth in illustrated in'FIGS. 2 to 4. Interconnecting the two bearing arms 133' and folded from the same sheet of steel is an elastic bight portion 137.

The bightportion is itself substantially U-shaped and the upper part of the central bight is relatively narrow to provide clearance for the rails (not shown) when the power spring is assembled on a hinge. The lower part of the bight portion is relatively enlarged for optimum stress distribution.

When the U-spring is engaged with a pair of hinge leaves, movement of the hinge leaves flexes the elastic bight portion 137 and the elasticity thereof spring biases the hinge in substantially the same manner as the power pack.

According to another arrangement not illustrated herein, a torsion spring having a single torsion loop with its axis parallel to the hinge pivot axis and end prongs fitting through windows in the top of the hinge leaf may provide the over-center operation of the hinge. Similarly, as illustrated ,in FIG. 18 a C-shaped spring 151 similar'to a retaining ring may be riveted through apertures in the mp of the hinge leaf by rivets 152. The other parts of the spring hinge are numbered the same as in FIGS. 1 to 6. Many other spring arrangements will be apparent for alternatively biasing the hinge leaves towards their closed or opened positions.

FIGS. 16 and 17 illustrate another embodiment of hook for a molded plastic power pack and a corresponding hinge. leaf window suitable for practice of this invention. As illustrated in this embodiment there is a short cylindrical post 141 extending downwardly from one bearing arm 142 of a molded plastic spring power pack. A cylindrical hook 143 is beyond the cylindrical post 141 and eccentric therewith.

The hinge leaf 144 has a keyhole shaped window 146 in substantially the same position as a corresponding window in the embodiment illustrated in the embodiment illustrated in FIGS. 2 to 4-. At one side of the window relatively nearer the hinge pivot axis (not shown) the window hasa concave cylindrical surface 147 having the .same radius as the cylindrical post 141. Typically the center portion of this cylindrical surface 147 is between the hinge pivot axis and the center of the post. The cylindrical bearing surface on the hinge leaf engaging the cylindrical post provides a pivotal interconnection between the power pack and a hinge much in the manner hereinabove described. The plastic post rotates within the window in the'hinge leaf during operation, but since the bearing area is quite large and the -a hinge pivot interconnecting the first and second hingeleaves forpivoting between an open position and a closed position; I

a first spring support member having a general U- shape with a first end in pivotable engagement with the first hinge leaf;

a second spring support member having a general U- shape with a first end in pivotable engagement with the second hinge leaf;

said hinge pivot being on one side of a line between v the loci of pivotable engagement of the respective spring support members with the hinge leaves in the closed position and not on the same side of the line in the open position; means for pivotably interconnecting the first and second spring support members in scissors fashion comprising a pivot having a pivot axis along the bight of the U, said pivot axis being substantially parallel to the pivot axis of the hinge pivot; and

spring means on the same side of the pivot axis of the spring support members as is the pivot axis of the hinge pivot interconnecting the second ends of the respective spring support members for urging the second ends towards each other.

-.2. A spring hinge as defined in claim 1 wherein the means for pivotably interconnecting the first and second spring support memberscomprises:

- a quasi-cylindrical socket on the bight of the first spring support member, the interior of the socket facing the hinge pivot axis; and

a knife edge on the bight of the second spring support member engaging the interior of the socket.

3. A spring hinge as defined in claim 1 wherein the hinge leaves each comprise a window through the top of each hinge leaf and a bearing tooth extending into the window, and wherein each spring support member comprises a hook extending down through a respective one of said windows and a bearing surface in engagement with the respective bearing tooth for pivoting about an axis parallel to the pivot axis of the hinge pivot; and each spring support member has a bearing arm extending over a respective hinge leaf and each hook comprises a stud-like projection below the bearsaid hinge pivot being on one side of a line between the loci of pivotable engagement of the respective spring support members with the hinge leaves in the closed position and not on the same side of the line in the open position;

means for pivotably interconnecting the first and sec-- ond spring support members in scissors fashion; and

- spring means interconnecting the second ends of the respective spring support members for urging the second ends towards each other; and wherein the hinge leaves each comprise a window through the hinge leaf and a bearing tooth extending into the window, and

each spring support member comprises a hook extending through a respective one of said windows and a bearing surface in engagement with the respective bearing tooth.

5. A spring hinge as defined in claim 4 wherein each spring support member has a bearing arm extending over a respective hinge leaf and each bearing surface comprises an end extension of the bearing arm going through the respective window and each hook comprises an extension beyond the bearing surface and fitting under the bearing tooth.

6. A spring hinge comprising:

a first hinge leaf;

a second hinge leaf;

a hinge pivot interconnecting the first and second hinge leaves for pivoting between an open position and a closed position;

a window through the top of each hinge leaf, the pivot axis of the hinge pivot being on one side of a line between the windows with the hinge leaves in the closed position and not on the same side of the line with the hinge leaves in the open position;

pivot means extending down through each window, the pivot axes of the pivot means being parallel to the pivot axis of the hinge pivot;

spring means for exerting a biasing force;

means for transmitting the biasing force from the spring to the pivot means for exertion on the hinge leaves in a direction primarily between the pivot means, said spring means being at least partly below the windows; and

means on the portion extending through each window for inhibiting removal of the pivot means from the respective window.

7. A spring hinge as defined in claim 6 wherein the means for transmitting and the spring means are an integral U-shaped member wherein the center portion is elastically deflectable and the arms of the U are substantially rigid, the center portion being approximately normal to the plane of the U as defined by the arms thereof.

8. A spring hinge as defined in claim 7 wherein the pivot means comprises a hook on the end of each arm of the U-shaped member extending through the window.

9. A spring hinge as defined in claim 7 wherein the center portion of the U-shaped member has a U-shape extending a substantial distance beyond the plane defined by the arms, and wherein the upper part of the U- shaped center portion is relatively narrower than the lower part thereof.

10. A spring hinge as defined in claim 6 wherein the hinge pivot is on the other side of the line between the loci of pivotable engagement with the hinge is in its open position.

11. A spring hinge as defined in claim 6 wherein the means for transmitting comprises:

a pair of rigid U-shaped spring support members each comprising a bearing arm connected to the pivot means, a spring arm connected to the spring means, and a bight portion interconnecting the bearing arm and the spring arm; and

means interconnecting the spring support members along the bight portions thereof for pivoting about an axis parallel to the hinge pivot axis.

12. A spring hinge as defined in claim 11 wherein the spring support members are molded plastic and the means for pivoting comprises a flexible web of plastic integral with both spring support members and extending therebetween.

13. A spring hinge as defined in claim 6 wherein the hinge leaves each comprise a window through the hinge leaf having a concave cylindrical bearing face and wherein the means for transmitting the biasing force comprises a hook extending through a respective one of said windows and a cylindrical bearing surface in engagement with the respective bearing face.

14. A spring hinge as defined in claim 6 wherein the pivot means and the means for inhibiting removal comprise; a bearing surface extending through the window and a hook beneath a portion of the hinge leaf adjacent the window.

15. A spring hinge as defined in claim 14 wherein each hinge leaf comprises a cylindrical bearing surface in the window and the pivot means comprises a cylindrical post engaging the cylindrical bearing surface in the window.

16. A spring hinge comprising:

a first hinge leaf;

a second hinge leaf;

spring means for exerting a biasing force;

means for transmitting the biasing force from the spring to the pivot means for exertion on the hinge leaves in a direction primarily between the pivot means, said spring means being at least partly below the window; said means for transmitting comprising:

a pair of rigid U-shaped spring support members each comprising a bearing arm connected to the pivot means, a spring arm connected to the spring means, and a bight portion interconnecting the bearing arm and the spring arm, and

means interconnecting the spring support members along the bight portions thereof for pivoting about an axis parallel to the hinge pivot axis; and

means for inhibiting removal of the pivot means from the respective window; and wherein one of the spring support members comprises a female socket and the other spring support member comprises a male member engaging the female socket for forming the means for pivoting. 17. A spring hinge as defined in claim 16 wherein the female socket comprises a concave cylinder facing the hinge pivot axis and the male member comprises a knife edge fitted into the cylinder.

18. A spring hinge comprising:

a first hinge leaf;

a second hinge leaf;

a window through the top of each hinge leaf, the

pivot axis of the hinge pivot being on one side of a line between the windows with the hinge leaves in the closed position and not on the same side of the line with the hinge leaves in the open position;

' pivot means extending down through each window, the pivot axes of the pivot means being parallel to the pivot axis of the hinge pivot; I

spring means for exerting a biasing force;

means for transmitting the biasing force from the spring to the pivot means for exertion on the hinge leaves in a direction primarily between the pivot means, said spring means being at least partly below the window;

means for inhibiting removal of the pivot means from the respective window;

' the pivot means and the means for inhibiting removal comprising a bearing surface extending through the windowand a hook beneath a portion of the hinge leaf adjacent the window; and wherein each hinge leaf comprises-a bearing tooth in the window in engagement with the bearing surface, the total included angle of the bearing tooth and bearing surface being less than about 270.

19. A spring hinge as defined in claim 6 wherein the means for transmitting and the spring means are an integral C-shaped spring; and wherein the pivot means comprises a rivet through'each window.

20, A spring hinge for a pair of bifold doors each having a door panel, a stile along each of the side edges of the panel, and a rail along each end of the panel comprising;

. first and second hinge leaves, each hinge leaf comprising a leg for engaging a stile and an arm for fitting over the top of a rail and engaging therewith for connecting the rail and stile together;

a hinge pivot interconnecting the hinge leaves for I pivoting between an open position with rails in alignment anda closed position with rails side by side;

spring means below the top of the rail for exerting a biasing force; and

a pair of rigid U-shaped spring support members each comprising a bearing arm pivotally connected to a respective hinge leaf, a spring arm connected to the spring means, a bight portion interconnecting the bearing arm and the spring arm, and means interconnecting the spring support members along the bight portion thereof for pivoting about an axis parallel to the hinge pivot axis for biasing the leaves towards eachother along a line lying on one side of the hinge pivot axis when in the closed position and on the other side when in the open position.

' 21. A spring hinge as defined in claim 20 wherein the socket on one of the spring support members and a male knife edge on the other spring support member engaging the female quasi-cylindrical socket, said male knife edge and female cylindrical socket extending parallelto the hinge pivot axis.

22. A spring hinge as defined in claim 20 wherein the pivotal interconnection between the bearing arm and respective hinge leaf comprises a first bearing surface on the hinge leaf adjacent a window through the hinge I means for pivot ng comprises a female cylindrical leaf, a second bearing surface on the bearingarm engaging the first bearing surface on the hinge leaf, and a hook beneath a portion of the hinge leaf adjacent the window.

23, A spring hinge as defined in claim 22 wherein the first bearing surface comprises a bearing tooth in engagement with the second bearing surface and wherein the total included angle of the bearing tooth and bearing surface is less than about 270.

24. A spring hinge comprising a first hinge leaf;

a second hinge leaf;

a hinge pivot interconnecting the first and second hinge leaves for pivoting between a closed position and an open position;

a first bearing tooth on the first hinge leaf;

a second bearing tooth on the second hinge leaf, said hinge pivot being on one side of a line between the bearing teeth on the two hinge leaves in the closed position and not on the same sideof the line in the open position;

a first spring support member having a first bearing face in engagement with the first bearing tooth;

a second spring support member having a second bearing face in engagement with the second bearing tooth;

means for interconnecting said first and second spring support members;

means for retaining the first and second bearing faces in engagement with the first and second bearing teeth respectively; and

means for urging thefirst bearing face towards the second bearing face in a direction along a line between the two bearing teeth.

25. A spring hinge as defined in claim 24 wherein the hinge pivot is on the other side of the line between the loci of pivotable engagement when the hinge is in its open position. I

26. A spring hinge as defined in claim 25 wherein the first and second bearing teeth each comprise an opening in the respective hinge leaf and a projection extending into the opening from one side thereof, said projection pointing in a direction away from the hinge pivot; and

the bearing faces each comprise a portion of the spring support member extending through the opening.

27. A spring hinge as defined in claim 26 wherein the means for retaining comprises a tang on the end of each spring support member beyond the respective bearing face and extending along one face of the projection approximately in the direction of the line between the bearing teeth.

28. A spring hinge as defined in claim 27 wherein the first and second spring support members are opposite arms of a U-shaped member, the central portion of the U-shaped member being elastically bendable.

29. A spring hinge as defined in claim 27 wherein:

each spring support member has a generally U-shape with a bearing arm having the respective bearing face near the end thereof and a spring arm;

the means for interconnecting the first and second spring support members comprises a pivot having a pivot axis along the bight of the U; and

the means for urging comprises a tension spring between spring arms.

30. A spring hinge as defined in claim 25 wherein the first and second spring support members, the means for interconnecting and the means for urging collectively are an intergal U-shaped member having the bearing faces at the opposite ends thereof and wherein the central portion is elastically bendable.

31. A spring hinge as defined in claim 30 wherein each spring support member is on one side of its respective hinge leaf wherein the means for retaining comprises:

a tab on each end of the U-shaped member engageable with the side of the respective bearing tooth opposite from the side the spring support member 32. A spring hinge as defined in claim 24 wherein the first and second spring support members are each a molded plastic member and the means for interconnecting the spring support members comprises a web of plastic integral with both of the spring support members and extending parallel to the hinge pivot axis.

33. A spring hinge as defined in claim 24 wherein the spring support members are molded plastic and the means for interconnecting comprises a flexible web of plastic integral with both spring support members and extending therebetween.

34. A spring power pack comprising:

a first rigid U-shaped spring support member;

a second U-shaped spring support member, said first and second spring support members each comprising a bearing arm, a spring arm and a bight portion interconnecting the bearing arm and the spring arm;

means interconnecting the first and second spring support members along the bight portions thereof for pivoting about an axis along the bight portion;

means on each of the pair of spring arms for connecting a spring therebetween; and

bearing means on each bearing arm for pivotally engaging a mating bearing surface, said bearing means on the respective spring support members facing each other for exerting a compression force therewith.

35. A spring power pack comprising:

a first rigid U-shaped spring support member;

means interconnecting the first and second spring support members along the bight portions thereof for pivoting about an axis along the bight portion comprising a female quasi-cylindrical socket on one of the spring support members and a male knife edge on the other spring support member engaging the quasicylindrical socket, said male knife edge and female quasi-cylindrical socket extending parallel to the bight portions;

36. A spring power pack as defined in claim 35 wherein the bearing means comprises a fiat surface extending substantially normal to the bearing arm towards the spring arm and a hook portion extending beyond the bearing portion in a plane parallel to the plane of the bearing arms.

37. A spring power pack ccomprising:

a first rigid U-shaped spring support member;

bearing means on each bearing arm for pivotally engaging a mating bearing surface comprising a fiat surface extending substantially normal to the bearing arm towards the spring arm and a hook portion extending beyond the bearing portion in a plane parallel to the plane of the bearing arms, said bearing means on the respective spring support members facing each other for exerting a compression force therewith.

Claims

1. A spring hinge comprising: a first hinge leaf; a second hinge leaf; a hinge pivot interconnecting the first and second hinge leaves for pivoting between an open position and a closed position; a first spring support member having a general U-shape with a first end in pivotable engagement with the first hinge leaf; a second spring support member having a general U-shape with a first end in pivotable engagement with the second hinge leaf; said hinge pivot being on one side of a line between the loci of pivotable engagement of the respective spring support members with the hinge leaves in the closed position and not on the same side of the line in the open position; means for pivotably interconnecting the first and second spring support members in scissors fashion comprising a pivot having a pivot axis along the bight of the U, said pivot axis being substantially parallel to the pivot axis of the hinge pivot; and spring means on the same side of the pivot axis of the spring support members as is the pivot axis of the hinge pivot interconnecting the second ends of the respective spring support members for urging the second ends towards each other.

2. A spring hinge as defined in claim 1 wherein the means for pivotaBly interconnecting the first and second spring support members comprises: a quasi-cylindrical socket on the bight of the first spring support member, the interior of the socket facing the hinge pivot axis; and a knife edge on the bight of the second spring support member engaging the interior of the socket.

3. A spring hinge as defined in claim 1 wherein the hinge leaves each comprise a window through the top of each hinge leaf and a bearing tooth extending into the window, and wherein each spring support member comprises a hook extending down through a respective one of said windows and a bearing surface in engagement with the respective bearing tooth for pivoting about an axis parallel to the pivot axis of the hinge pivot; and each spring support member has a bearing arm extending over a respective hinge leaf and each hook comprises a stud-like projection below the bearing arm for inhibiting removal and the bearing surface comprises an undercut portion on the projection, and wherein the spring means is at least partly below the windows.

4. A spring hinge comprising: a first hinge leaf; a second hinge leaf; a hinge pivot interconnecting the first and second hinge leaves for pivoting between an open position and a closed position; a first spring support member having a first end in pivotable engagement with the first hinge leaf; a second spring support member having a first end in pivotable engagement with the second hinge leaf; said hinge pivot being on one side of a line between the loci of pivotable engagement of the respective spring support members with the hinge leaves in the closed position and not on the same side of the line in the open position; means for pivotably interconnecting the first and second spring support members in scissors fashion; and spring means interconnecting the second ends of the respective spring support members for urging the second ends towards each other; and wherein the hinge leaves each comprise a window through the hinge leaf and a bearing tooth extending into the window, and each spring support member comprises a hook extending through a respective one of said windows and a bearing surface in engagement with the respective bearing tooth.

6. A spring hinge comprising: a first hinge leaf; a second hinge leaf; a hinge pivot interconnecting the first and second hinge leaves for pivoting between an open position and a closed position; a window through the top of each hinge leaf, the pivot axis of the hinge pivot being on one side of a line between the windows with the hinge leaves in the closed position and not on the same side of the line with the hinge leaves in the open position; pivot means extending down through each window, the pivot axes of the pivot means being parallel to the pivot axis of the hinge pivot; spring means for exerting a biasing force; means for transmitting the biasing force from the spring to the pivot means for exertion on the hinge leaves in a direction primarily between the pivot means, said spring means being at least partly below the windows; and means on the portion extending through each window for inhibiting removal of the pivot means from the respective window.

9. A spring hinge as defined in claim 7 wherein the center portion of the U-shaped member has a U-shape extending a substantial distance beyond the plane defined by the arms, and wherein the upper part of the U-shaped center portion is relatively narrower than the lower part thereof.

11. A spring hinge as defined in claim 6 wherein the means for transmitting comprises: a pair of rigid U-shaped spring support members each comprising a bearing arm connected to the pivot means, a spring arm connected to the spring means, and a bight portion interconnecting the bearing arm and the spring arm; and means interconnecting the spring support members along the bight portions thereof for pivoting about an axis parallel to the hinge pivot axis.

16. A spring hinge comprising: a first hinge leaf; a second hinge leaf; a hinge pivot interconnecting the first and second hinge leaves for pivoting between an open position and a closed position; a window through the top of each hinge leaf, the pivot axis of the hinge pivot being on one side of a line between the windows with the hinge leaves in the closed position and not on the same side of the line with the hinge leaves in the open position; pivot means extending down through each window, the pivot axes of the pivot means being parallel to the pivot axis of the hinge pivot; spring means for exerting a biasing force; means for transmitting the biasing force from the spring to the pivot means for exertion on the hinge leaves in a direction primarily between the pivot means, said spring means being at least partly below the window; said means for transmitting comprising: a pair of rigid U-shaped spring support members each comprising a bearing arm connected to the pivot means, a spring arm connected to the spring means, and a bight portion interconnecting the bearing arm and the spring arm, and means interconnecting the spring support members along the bight portions thereof for pivoting about an axis parallel to the hinge pivot axis; and means for inhibiting removal of the pivot means from the respective window; and wherein one of the spring support members comprises a female socket and the other spring support member comprises a male member engaging the female socket for forming the means for pivoting.

17. A spring hinge as defined in claim 16 wherein the female socket comprises a concave cylinder facing the hinge pivot axis and the male member comprises a knife edge fitted into the cylinder.

18. A spring hinge comprising: a first hinge leaf; a second hinge leaf; a hinge pivot interconnecting the first and second hinGe leaves for pivoting between an open position and a closed position; a window through the top of each hinge leaf, the pivot axis of the hinge pivot being on one side of a line between the windows with the hinge leaves in the closed position and not on the same side of the line with the hinge leaves in the open position; pivot means extending down through each window, the pivot axes of the pivot means being parallel to the pivot axis of the hinge pivot; spring means for exerting a biasing force; means for transmitting the biasing force from the spring to the pivot means for exertion on the hinge leaves in a direction primarily between the pivot means, said spring means being at least partly below the window; means for inhibiting removal of the pivot means from the respective window; the pivot means and the means for inhibiting removal comprising a bearing surface extending through the window and a hook beneath a portion of the hinge leaf adjacent the window; and wherein each hinge leaf comprises a bearing tooth in the window in engagement with the bearing surface, the total included angle of the bearing tooth and bearing surface being less than about 270*.

19. A spring hinge as defined in claim 6 wherein the means for transmitting and the spring means are an integral C-shaped spring; and wherein the pivot means comprises a rivet through each window.

20. A spring hinge for a pair of bifold doors each having a door panel, a stile along each of the side edges of the panel, and a rail along each end of the panel comprising; first and second hinge leaves, each hinge leaf comprising a leg for engaging a stile and an arm for fitting over the top of a rail and engaging therewith for connecting the rail and stile together; a hinge pivot interconnecting the hinge leaves for pivoting between an open position with rails in alignment and a closed position with rails side by side; spring means below the top of the rail for exerting a biasing force; and a pair of rigid U-shaped spring support members each comprising a bearing arm pivotally connected to a respective hinge leaf, a spring arm connected to the spring means, a bight portion interconnecting the bearing arm and the spring arm, and means interconnecting the spring support members along the bight portion thereof for pivoting about an axis parallel to the hinge pivot axis for biasing the leaves towards each other along a line lying on one side of the hinge pivot axis when in the closed position and on the other side when in the open position.

21. A spring hinge as defined in claim 20 wherein the means for pivoting comprises a female cylindrical socket on one of the spring support members and a male knife edge on the other spring support member engaging the female quasi-cylindrical socket, said male knife edge and female cylindrical socket extending parallel to the hinge pivot axis.

22. A spring hinge as defined in claim 20 wherein the pivotal interconnection between the bearing arm and respective hinge leaf comprises a first bearing surface on the hinge leaf adjacent a window through the hinge leaf, a second bearing surface on the bearing arm engaging the first bearing surface on the hinge leaf, and a hook beneath a portion of the hinge leaf adjacent the window.

23. A spring hinge as defined in claim 22 wherein the first bearing surface comprises a bearing tooth in engagement with the second bearing surface and wherein the total included angle of the bearing tooth and bearing surface is less than about 270* .

24. A spring hinge comprising a first hinge leaf; a second hinge leaf; a hinge pivot interconnecting the first and second hinge leaves for pivoting between a closed position and an open position; a first bearing tooth on the first hinge leaf; a second bearing tooth on the second hinge leaf, said hinge pivot being on one side of a line between the bearing teeth on the two hinge leaves in the closed position and not On the same side of the line in the open position; a first spring support member having a first bearing face in engagement with the first bearing tooth; a second spring support member having a second bearing face in engagement with the second bearing tooth; means for interconnecting said first and second spring support members; means for retaining the first and second bearing faces in engagement with the first and second bearing teeth respectively; and means for urging the first bearing face towards the second bearing face in a direction along a line between the two bearing teeth.

25. A spring hinge as defined in claim 24 wherein the hinge pivot is on the other side of the line between the loci of pivotable engagement when the hinge is in its open position.

26. A spring hinge as defined in claim 25 wherein the first and second bearing teeth each comprise an opening in the respective hinge leaf and a projection extending into the opening from one side thereof, said projection pointing in a direction away from the hinge pivot; and the bearing faces each comprise a portion of the spring support member extending through the opening.

29. A spring hinge as defined in claim 27 wherein: each spring support member has a generally U-shape with a bearing arm having the respective bearing face near the end thereof and a spring arm; the means for interconnecting the first and second spring support members comprises a pivot having a pivot axis along the bight of the U; and the means for urging comprises a tension spring between spring arms.

31. A spring hinge as defined in claim 30 wherein each spring support member is on one side of its respective hinge leaf wherein the means for retaining comprises: a tab on each end of the U-shaped member engageable with the side of the respective bearing tooth opposite from the side the spring support member is on.

32. A spring hinge as defined in claim 24 wherein the first and second spring support members are each a molded plastic member and the means for interconnecting the spring support members comprises a web of plastic integral with both of the spring support members and extending parallel to the hinge pivot axis.

34. A spring power pack comprising: a first rigid U-shaped spring support member; a second U-shaped spring support member, said first and second spring support members each comprising a bearing arm, a spring arm and a bight portion interconnecting the bearing arm and the spring arm; means interconnecting the first and second spring support members along the bight portions thereof for pivoting about an axis along the bight portion; means on each of the pair of spring arms for connecting a spring therebetween; and bearing means on each bearing arm for pivotally engaging a mating bearing surface, said bearing means on the respective spring support members facing each other for exerting a compresSion force therewith.

35. A spring power pack comprising: a first rigid U-shaped spring support member; a second U-shaped spring support member, said first and second spring support members each comprising a bearing arm, a spring arm and a bight portion interconnecting the bearing arm and the spring arm; means interconnecting the first and second spring support members along the bight portions thereof for pivoting about an axis along the bight portion comprising a female quasi-cylindrical socket on one of the spring support members and a male knife edge on the other spring support member engaging the quasi-cylindrical socket, said male knife edge and female quasi-cylindrical socket extending parallel to the bight portions; means on each of the pair of spring arms for connecting a spring therebetween; and bearing means on each bearing arm for pivotally engaging a mating bearing surface, said bearing means on the respective spring support members facing each other for exerting a compression force therewith.

36. A spring power pack as defined in claim 35 wherein the bearing means comprises a flat surface extending substantially normal to the bearing arm towards the spring arm and a hook portion extending beyond the bearing portion in a plane parallel to the plane of the bearing arms.

37. A spring power pack ccomprising: a first rigid U-shaped spring support member; a second U-shaped spring support member, said first and second spring support members each comprising a bearing arm, a spring arm and a bight portion interconnecting the bearing arm and the spring arm; means interconnecting the first and second spring support members along the bight portions thereof for pivoting about an axis along the bight portion; means on each of the pair of spring arms for connecting a spring therebetween; and bearing means on each bearing arm for pivotally engaging a mating bearing surface comprising a flat surface extending substantially normal to the bearing arm towards the spring arm and a hook portion extending beyond the bearing portion in a plane parallel to the plane of the bearing arms, said bearing means on the respective spring support members facing each other for exerting a compression force therewith.