US3724134A

US3724134A - Door control mechanism

Info

Publication number: US3724134A
Application number: US00161042A
Authority: US
Inventors: M Verdone
Original assignee: Singer Co
Current assignee: Singer Co
Priority date: 1971-07-09
Filing date: 1971-07-09
Publication date: 1973-04-03
Anticipated expiration: 1990-04-03

Abstract

A mechanism for controlling the partial opening of a cover, or door, of a cabinet upon release of a latch and for thereafter retaining the door in a fully open position following the exertion of an additional opening effort.

Description

United States Paten 0 1 Verdone 1 Apr. 3, 1973 541 DOOR CONTROL MECHANISM 2,454,450 11/1948 Hendricks ..220/35 x 2,686,340 7/1954 Shepard et al ..49/386 [75] Invent 3,001,227 9/1961 Long etal ..220/35 x 2,252,685 7/1941 Babcock ..l6/l80 x [73] Assignee: The Singer Company, New York,

N Y Primary Examiner-Kenneth Downey An -Ch I R.L h k t l. 22 Filed: July 9, 1971 ares epc m y e a [21] Appl. No.: 161,042 [57] ABSTRACT A mechanism for controlling the partial opening of a [52] US. Cl ..49/379, 220/35 cover, or door, of a cabinet upon release of a latch [51] Int. Cl. ..E05f 1/00 and for thereafter retaining the door in a fully open [58] Field of Search ..49/379, 386; 220/35; 16/180 position following the exertion of an additional opening effort.. [56] References Cited 9 Claims, 6 Drawing Flgures UNITED STATES PATENTS 3,233,276 2/1966 Swanson et al. ..l6/l80 X PATENTEUAPN I973 3,724,134

SHEET 2 OF 3 m g n r g o DOOR CONTROL MECHANISM BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to door-opening devices and more particularly to a mechanism for partially opening the hinged door of boxes or containers, such as cabinets for housing electrical and electronic equipment, stereo and other high-fidelity instruments, data disc files, etc., and for thereafter retaining the door in a fully open position.

2. Description of the Prior Art In certain prior art devices, the cover or door of an article, such as the deck lid of an automobile, is provided with a latch and a door opening mechanism for lifting the cover to an open position once the latch is released. The door opening mechanism typically comprises a pair of torsion bars mounted in such a way that each bar is twisted a predetermined amount as the cover is closed and latched. When the latch is released, the potential energy stored in each bar provides the motive force for raising the cover against the force of gravity.

In such a device, the optimum size of the bars required to lift and hold the door is determined by the size and weight of the door, and also by the desired angle of inclination made by the open door with reference to the closed position: as any one of these factors is increased, the stiffness of the bars must be correspondingly increased.

In many applications, the stiffness required to provide the desired angle of cover inclination in the open configuration is exceedingly great. As a consequence, the operator force required to close the door is correspondingly great. Such an arrangement usually results in the application of excessive strains to the door and the associated mounting elements, resulting in early mechanical failure of the system, which is highly undesirable. Further, in those applications which require the door to be opened and closed in a repeated manner, this arrangement also suffersfrom the disadvantage that the excessive operator force required for each closing leads to operator fatigue.

In other prior art devices, the cover of an article is provided with a knob or handle for manually lifting the cover, and a means, such as an over center spring of the type shown in U.S. Pat. No. 2,201,333 to Carlson, for retaining the cover in an open position at a predetermined angle. In a typical device of this kind, as the cover is opened, the over center, or toggle, spring opposes the upward cover movement with a force of increasing magnitude until the spring passes slightly over center, after which the spring assists the upward cover movement with a force of decreasing magnitude until the cover reaches the fully opened position. Similarly, as the cover is moved toward the closed position, the toggle spring opposes this movement with a force of increasing magnitude until the spring passes slightly over center in the downward direction, after which the spring assists the downward cover movement with a force of decreasing magnitude until the cover reaches the fully closed position. Thus, in either direction the force of the toggle spring acting on the cover comprises an opposing force of increasing magnitude during a first range of cover movement followed by an assisting force of decreasing magnitude during a second range of cover movement.

It is important to note that the maximum force exerted by the spring on the cover occurs at the center position and that this force abruptly reverses direction once this position is passed. Because of this sudden reversal of direction at greatest magnitude, there occurs a sudden acceleration of the cover whenever the center position is just exceeded. This sudden acceleration is highly undesirable and, if unchecked can result in mechanical failure of the cover and the cover mounting members.

This type of lifting and holding mechanism also suffers from the disadvantage that the cover must be manually lifted each time the cover is opened. Further, the necessary knob or handle is frequently objectionable from the standpoint of esthetic design.

SUMMARY OF THE INVENTION The invention comprises a door opening device which utilizes a torsion bar mechanism employed in conjunction with a latch for lifting a cover from a closed position to a first, partially opened position, and an over center, or toggle, spring mechanism for holding the cover in a second, fully open position once the cover has been manually raised from the first to the second position. Because the torsion bar mechanism is used to lift the cover only to a partially open position, the torsion bars may be of a relatively light construction. The toggle spring mechanism is designed to provide a smoothly decreasing upward force on the cover when the center position is exceeded in the upward direction and also a smoothly decreasing downward force on the cover when the center position is exceeded in the downward direction. The toggle spring mechanism is further designed to provide an upward force on the cover as the latter approaches the closed position in order to counteract the above-noted sudden acceleration of the cover when the center position is exceeded in a downward direction, thereby preventing slamming of the cover. The toggle spring mechanism is additionally designed to permit a range of angular movement of the cover within which the toggle spring exerts no force on the cover.

For a fuller understanding of the nature and advantages of the invention, reference should be had to the following detailed description taken in conjunction with the accompanying drawings wherein like reference characters designate like or similar elements throughout the various views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a frontal elevation of a preferred embodiment showing the latch member;

FIG. 2 is a plan view of the FIG. 1 embodiment showing the disposition of the torsion bars in dash line;

FIG. 3 is a fragmentary sectional elevational view taken on the plane indicated by line 3--3 in FIG. 1 and showing the latch in detail;

FIG. 4 is a fragmentary rear elevational view of the FIG. 1 embodiment, with the back panel broken away to show the toggle springs, the view being taken on the plane indicated by line 4-4 in FIG. 2;

FIG. 5 is a fragmentary, sectional, elevational view taken on the plane indicated by line 5-5 in FIG. 4; and

FIG. 6 is a sectional view similar to FIG. 5, showing the door retained fully open by the toggle spring.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGS. 1 and 2, a container, or cabinet, generally indicated at 10, comprises sidewalls 11 and 12, a bottom plate 13 (FIG. 3), and a back panel 14 (FIG. 4). The panel 14 is secured in place along each of its side edges within

rabbets

15 and 16, formed in the rear edge of the respective sidewalls l1 and 12.

A door or lid, generally indicated at 20, may be formed of wood or metal, but is preferably molded or formed of a thermoplastic material, and includes a top portion 21 and a frontal portion 22 formed at a right angle to the top. Along its rearward edge, the top portion 21 of the door is secured within a groove 23, extending lengthwise of a metallic bar 24 (FIGS. 5 and 6). At each end, the bar 24 is provided with a bore, having engagement with each of respective pins 25 and 26 (FIG. 4) secured on the inner surface adjacent the upper end of flanges 27 and 28 of respective

U-shaped brackets

29 and 30.

- Each of the

U-shaped brackets

29 and 30 is secured by any suitable means, such as nuts and bolts 34, to the formed-over end portion of one arm of respective angle members and 36, secured on the inner surface of sidewalls 11 and 12 (FIGS. 1 and 2). The brackets are supported in a manner similar to bracket 30, as seen in FIGS. 5 and 6. The door 20, when closed, rests against a suitable gasket 37, as indicated in FIG. 3, which is preferably a strip of sponge rubber secured to the laterally extended arm of each

angle member

35 and 36.

Along its lower edge, the frontal portion 22 of the door 20 is secured within a groove 38 (FIG. 3) of a plate 39, having a channel 40 formed therein. The inner surface of the lower flange, or wall, 41 of the channel 40 is inclined outwardly, forming an acute angular edge 42 extending lengthwise of the plate 39. As the door 20 is closed, it becomes latched by the frictional engagement of the angularly formed edge 42, with the inner surface 43 of the substantially V-shaped hook-like portion 44 ofa latch 45 (FIGS. 1 and 3). The latch 45 is molded, or otherwise formed, of a pliant material, such as rubber or plastic, and is secured on the vertically disposed arm of an angle member by means of bolts and nuts 51. At its ends, the angle member 50 is secured by welding or other suitable means to the lower end of each of

angle members

35 and 36, and serves to support the bottom plate 13. When the door is closed, the inner surface of the upper portion of the plate 39 engages a seal strip 48, preferably of sponge rubber, secured along the front edge of the bottom plate 13.

In order to open the door 20, the lower extremity of the hook-like portion 44 of the latch 45 is pushed inwardly or to the right in FIG. 3. In so doing, the round nose 46 of the hook-like portion 44 is moved upwardly along the surface of the vertically disposed arm of the angle member 50. Since the latch 45 is of a pliant or resilient material, the web portion 47 yields as the nose 46 moves upwardly. Thus, the surface 43 of the hooklike portion 44 is moved out of engagement with the edge 42 of the plate 39 releasing the door 20 to the influence of a pair of torsion bars 52 and 53 (FIG. 2) and a pair of toggle springs 66, 67 (FIGS. 4-6).

As shown in FIGS. 4-6, the straight or longitudinally extended portion of each of the torsion bars 52 and 53 extends transversely of the cabinet and is substantially parallel to the axis of the

coaxial pins

25 and 26. Adjacent its one end, the torsion bar or rod 52, rests within a suitable notch in a flange 54 of the U-shaped bracket 30 (FIGS. 5 and 6) and is formed downwardly at substantially a right-angle to the straight portion of the bar, thence laterally to engage in a suitable aperture in the web portion of the U-shaped bracket 30 where it is secured to the web of the bracket by means of nuts 55 threaded onto the rod. Similarly, the one'end portion of the torsion bar 53 rests within a suitable notch in a flange 56 of the U-shaped bracket 29 (FIG. 4) and is formed angularly downwardly and laterally inwardly to engage in a suitable aperture in the web portion of the bracket 29, the bar being secured to the web of the bracket by means of nuts 57, similarly to bar 52, as seen in FIG. 5. At its other extremity, or crank end, the torsion rod 52 is engaged in a circular bore formed in a lug 58 secured, together with a right-angle bracket 59, to the underside of the bar 24, adjacent the right-hand end thereof (FIG. 4).by means of a series of screws 60. Similarly, the torsion rod 53 has its crank end secured in the tubular formation of a lug 64 (FIG. 4), similar to lug 58 and secured, together with a right angle bracket 65, on the underside of the bar 24 adjacent the lefthand end thereof by means of similar screws 60. As the door 20 is moved from an open position to the closed position of FIGS. 3 and 5, the crank end of each of the torsion bars or

rods

52 and 53 is effective to twist the longitudinal portion of the respective bars, which bars remain twisted while the door 20 is latched in its closed position by latch 45.

As shown in FIGS. 4-6, a pair of double coil over center, or toggle,

springs

66, 67 are provided at the upper rear corners of cabinet 10 for a purpose described below. The coils of the spring 66 are coaxial and the free ends 68 and 69 of the respective coils project laterally in opposition, one to the other, and in coaxial alignment parallel to the axis of the coils. The projected free end 69 of the left hand coil (FIG. 4) is engaged in a suitable aperture in the flange 28 of the U- shaped bracket 30, while the extended free end 68 of the other coil is engaged in a suitable aperture in the flange 54 of the bracket. The other end of each of the two coils of the spring 66 provides a looped connection 70 disposed intermediate the

flanges

28 and 54 of the U-shaped bracket 30. The looped connection 70 of the spring 66 is disposed within an enlarged opening 71 in the depending arm 72 of the right-angle bracket 65.

The over-center or toggle spring 67 is formed in the reverse direction from toggle spring 66 and is substantially identical to toggle spring 66, having the laterally projecting free ends 75 and 76 of the two coils engaged in suitable apertures within respective flanges 56 and 27 of the U-shaped bracket 29. The loop connection 77 of the two coils of the spring 67 is disposed within an enlarged aperture (not shown) in the depending arm 78 of the right-angle bracket 59, aperture 80 being identical to the aperture 71 in bracket 65.

When the cover or door 20 is in its closed and latched position shown in FIGS. 3 and 5, the toggle springs 66, 67 are expanded, i.e., the coils .are forcibly unwound by depending arms 72, 78, respectively. In

this position, the connecting loop 70 of toggle spring 66 (FIG. 5) is located to the right of a hypothetical center line through the axis of the hinge pin 26 and that of the coaxial lateral projections 68, 69 of toggle spring 66. Similarly, the looped connection 77 of toggle spring 67 is located to the corresponding side of a hypothetical center line through the axis of hinge pin 25 and that of the coaxial lateral projections 75, 76 of toggle spring 67.

Upon movement of latch 45 to release door 20, the counterbalancing forces stored in

twisted torsion rods

52, 53 and expanded toggle springs 66, 67 rotate door clockwise (as shown in FIGS. 5 and 6) about hinge pins 25, 26 toward a first stable open position. As door 20 rotates, toggle springs 66, 67 contract to their normal configuration wherein the ends of the two arms of each coil of each spring are more closely spaced than shown in FIG. 5. Once having attained this stable configuration, loops 70, 77 of

springs

66, 67 merely ride along the inner surface of

apertures

71, 80 in depending arms 72, 78, respectively, and springs 66, 67 remain relaxed. During this portion of the cover 20 motion, springs 66, 67 contribute no appreciable force acting on cover 20, but cover 20 continues to be rotated by

torsion rods

52, 53.

As will be apparent to those skilled in the art, the angle of inclination of cover 20 at which relaxation of

springs

66, 67 occurs is a matter of choice, depending on the requirements of any particular application. In the preferred embodiment, this angle is substantially 5.

With continued rotation of cover 20, depending arms 72, 78 reach a position at which springs 66, 67 begin to be compressed by the force exerted on loops 70, 77 by the inner surface of

apertures

71, 80. Thereafter, further rotation is opposed by the compressive forces supplied by

springs

66, 67 which additionally pivot counterclockwise as shown in FIGS. 5 and 6 about their mounting ends (e.g., ends 68, 69 of spring 66). Depending on the parameters chosen in any given case, e.g., mass and size of cover 20, spring constant of

springs

66, 67 torsional forces supplied by

rods

52, 53 and desired angle of inclination of cover 20, a first stable configuration will ultimately be attained wherein the forces tending to raise cover 20, i.e., those supplied by

rods

52, 53, are balanced by those forces tending to lower cover 20, i.e., those supplied by

springs

66, 67 and the mass of cover 20. As will be apparent to those skilled in the art, the angle at which cover 20 achieves this first stable position may be selected over a wide range, depending on the requirements of any given application. In the preferred embodiment, angles in the range from l0-l5 are chosen, with best results being obtained at substantially 12.

If cover 20 is manually raised from this first stable position, a second, fully open stable position will be attained as follows. As cover 20 is rotated, depending arms 72, 73 further compress and counterrotate springs 66, 67. As

springs

66, 67 are further compressed, the spring forces increasingly oppose further rotation of cover 20 until the center position of each spring is exceeded. This center position may be visualized for spring 66 by drawing an imaginary line between end 69 and hinge pin 26 in F IGIS with the line passing through the geometrical center of both elements. As will be apparent to those skilled in the art, when loops 70, 77

pass over their respective center positions, the spring forces immediately act to assist rotation of cover 20 in the upward direction. As cover 20 is rotated the compression of

spring

66, 67 is relieved until a second stable configuration is attained wherein the forces tending to raise cover 20, i.e., those supplied by

spring

66, 67 are balanced by that force tending to lower cover 20, Le. that supplied by the mass of cover 20. As will be apparent to those skilled in the art, the angle at which cover 20 achieves this second stable position may also be selected over a wide range, depending on the requirements of any given application. In the preferred embodiment, this angle is substantially 85.

The action of

torsion rods

52, 53 and toggle springs 66, 67 during the lowering of cover 20 is substantially the reverse of that set forth above and for the sake of conciseness is not set forth in detail. Briefly described, when cover 20 is lowered from the second stable position (fully opened), toggle springs 66, 67 provide a force of increasing magnitude opposing further lowering until the springs pass over center, whereupon the spring forces assist further lowering of cover 20 until the first stable position is reached. If cover 20 is further lowered to the fully closed position,

torsion rods

52, 53 increasingly resist, while torsion springs 66, 67 decreasingly assist, further lowering of cover 20 until

springs

66, 67 are completely relaxed. There follows a range of movement wherein springs 66, 67 contribute no appreciable forces acting on cover 20, after which the expansion of

springs

66, 67 by depending members 72, 78 results in a spring force of increasing magnitude tending to oppose further lowering of cover 20 until this latter member is finally latched in the fully closed position.

It is important to not that the inner surfaces of

apertures

71, 80 provide a smooth camming action for spring loops 70, 77 at all times. This camming action enables the spring forces to be smoothly applied to cover 20, particularly when springs 66, 67 pass over center from either direction. This smooth application of spring forces greatly reduces the sudden acceleration ordinarily imparted to the cover member of known devices, thereby substantially reducing the problem of accidental breakage of the cover and cover mounting members.

It is also important to note that the additional forces supplied by

springs

66, 67 tending to oppose further closing of cover 20 when this member is approaching the fully closed position provide a braking effect which substantially reduces the possibility of cover 20 being slammed shut and correspondingly increases the useful life of the cover, cover mounting components and the latch mechanism. It is further noted that the forces provided by

springs

66, 67 when in the expanded state tending to raise cover 20, which assist

torsion rods

52, 53 in raising cover 20 during the initial movement of this member from the fully closed position, reduce the required initial load on

rods

52, 53, thereby enabling torsion rods of a correspondingly lighter construction to be employed.

As will now be apparent, the foregoing provides a full disclosure of a door opening and positioning mechanism which is compact, inexpensive to manufacture, and extremely reliable in operation. It is understood that various modifications, alternate constructions and equivalents may be employed without departing from the true spirit and scope of the invention. For example, toggle springs 66, 67 may each be formed in the shape of a single coil spring. Therefore, the above description and illustration should not be construed as limiting the scope of the invention, which is solely defined by the appended claims.

What is claimed is:

1. A support assembly for a closure member pivotally mounted on a fixed support for rotation between open and closed positions, comprising:

a framework for supporting said closure member,

a latch for retaining said closure member in a closed position,

a torsion rod having a longitudinally extending axis arranged substantially parallel to the pivotal axis of said closure member, a crank end of said torsion rod being connected to said closure member and the other end fixed in said framework,

said torsion rod being effective to bias said closure member to a partially open position upon release of said latch, and

an over-center means controlled by said closure member and having one stable position for yieldably retaining said-closure member in a fully open position, upon manually moving said closure member from said partially open position to said fully open position and another stable position intermediate said fully open and said closed position.

2. In a device of the character described in claim 1 wherein said over-center means comprises a torsion spring pivotally supported in said framework and having a linking connection with said closure member for movement over-center in response to the opening of said closure member to said fully open position.

3. In a device of the character described in claim 2 wherein said torsion spring is a double coil spring having its ends pivotally supported in said framework and an interconnecting loop between the two coils of said spring for linking said double coil spring to said closure member.

4. A support assembly for a closure member pivotally mounted on a fixed support for rotation between open and closed positions, comprising:

a framework including sidewalls,

a pair of substantially U-shaped brackets mounted in said framework, each one of said brackets positioned adjacent a different one of said sidewalls for hingedly supporting said closure member,

a latch means for releasably retaining said closure member in a closed position,

a pair of torsion rods having longitudinally extending axis arranged substantially parallel to the pivotal axis of said closure member, the crank end of each of said rods being connected to said closure member adjacent the respective ones of said brackets and the other end of each of said rods being secured to the opposite ones of said brackets,

a torsional means pivotally supported between the flanges of each of said brackets rockable overcenter in response to a manually controlled movement of said closure member between said partially open position and a fully open position for yieldably retaining said closure member in said fully open position, and

means associated with said closure member and engaging each of said torsional means for controlling the rocking of said torsional means upon movement of said closure member and for enabling the retension of said closure member in the fully open position,

said torsion rods and said torsional means storing energy upon the closing of said closure member to bias said closure member to a partially open position upon release of said latch.

5. In a device of the character described in claim 4 wherein said torsional means comprises a pair of toggle springs, each one disposed between the flanges of a different one of said brackets rockable over-center by said associated means.

6. In a device of the character described in claim 5 wherein each one of said pair of toggle springs comprises a double coil spring having its ends axially aligned for pivotal support in the respective flanges of the corresponding one of said brackets and an interconnecting loop in engagement with said associated means for rocking said double coil springs about said pivotal axes to an over-center position upon movement of said closure member to a fully open position following release of said latch and operation of said torsion rods, each of said double coil springs being adapted to yieldably retain said closure member in said fully open position. I

7. In a device of the character described in claim 6 wherein said associated means comprises a pair of angular brackets secured on said closure member for movement therewith, an arm of each of said angular brackets being disposed between the said flanges of the respective U-shaped brackets, each of said arms having an aperture therein for supporting the interconnecting loop of the corresponding double coil spring.

8. In a device of the character described in claim 7, wherein said aperture in each of said arms is substantially circular in form for loosely supporting said interconnecting loops and is adapted to enable relaxation of the corresponding ones of said toggle springs during a portion of the angular movement of said closure member and to thereafter cam said toggle springs overcenter for the retention of said closure member in the fully open position.

9. A support assembly for a closure member pivotally mounted on a fixed support for movement between open and closed positions, comprising:

a framework for hingedly supporting said closure member,

a bracket mounted on said closure member and having an arm disposed in a plane parallel to the direction of movement of said member, said arm including a substantially circular aperture therein, and

a toggle spring having one extension pivotally sup ported in said framework and the other extension loosely supported in said aperture,

said aperture being of a size sufficient to enable relaxation of said toggle spring during a portion of the angular movement of said closure member between closed and open positions and the surface of said aperture being adapted to thereafter cam said toggle spring over-center whereby the torsional force of said toggle spring yieldably retains said closure member in the fully open position,

Claims

1. A support assembly for a closure member pivotally mounted on a fixed support for rotation between open and closed positions, comprising: a framework for supporting said closure member, a latch for retaining said closure member in a closed position, a torsion rod having a longitudinally extending axis arranged substantially parallel to the pivotal axis of said closure member, a crank end of said torsion rod being connected to said closure member and the other end fixed in said framework, said torsion rod being effective to bias said closure member to a partially open position upon release of said latch, and an over-center means controlled by said closure member and having one stable position for yieldably retaining said closure member in a fully open position, upon manually moving said closure member from said partially open position to said fully open position and another stable position intermediate said fully open and said closed position.

4. A support assembly for a closure member pivotally mounted on a fixed support for rotation between open and closed positions, comprising: a framework including sidewalls, a pair of substantially U-shaped brackets mounted in said framework, each one of said brackets positioned adjacent a different one of said sidewalls for hingedly supporting said closure member, a latch means for releasably retaining said closure member in a closed position, a pair of torsion rods having longitudinally extending axis arranged substantially parallel to the pivotal axis of said closure member, the crank end of each of said rods being connected to said closure member adjacent the respective ones of said brackets and the other end of each of said rods being secured to the opposite ones of said brackets, a torsional means pivotally supported between the flanges of each of said brackets rockable over-center in response to a manually controlled movement of said closure member between said partially open position anD a fully open position for yieldably retaining said closure member in said fully open position, and means associated with said closure member and engaging each of said torsional means for controlling the rocking of said torsional means upon movement of said closure member and for enabling the retension of said closure member in the fully open position, said torsion rods and said torsional means storing energy upon the closing of said closure member to bias said closure member to a partially open position upon release of said latch.

6. In a device of the character described in claim 5 wherein each one of said pair of toggle springs comprises a double coil spring having its ends axially aligned for pivotal support in the respective flanges of the corresponding one of said brackets and an interconnecting loop in engagement with said associated means for rocking said double coil springs about said pivotal axes to an over-center position upon movement of said closure member to a fully open position following release of said latch and operation of said torsion rods, each of said double coil springs being adapted to yieldably retain said closure member in said fully open position.

8. In a device of the character described in claim 7, wherein said aperture in each of said arms is substantially circular in form for loosely supporting said interconnecting loops and is adapted to enable relaxation of the corresponding ones of said toggle springs during a portion of the angular movement of said closure member and to thereafter cam said toggle springs over-center for the retention of said closure member in the fully open position.

9. A support assembly for a closure member pivotally mounted on a fixed support for movement between open and closed positions, comprising: a framework for hingedly supporting said closure member, a bracket mounted on said closure member and having an arm disposed in a plane parallel to the direction of movement of said member, said arm including a substantially circular aperture therein, and a toggle spring having one extension pivotally supported in said framework and the other extension loosely supported in said aperture, said aperture being of a size sufficient to enable relaxation of said toggle spring during a portion of the angular movement of said closure member between closed and open positions and the surface of said aperture being adapted to thereafter cam said toggle spring over-center whereby the torsional force of said toggle spring yieldably retains said closure member in the fully open position, said aperture additionally dimensioned to enable said surface to expand said toggle spring when said closure member is adjacent said closed position so that said toggle spring supplies a braking force tending to oppose further motion in the direction of said closed position.