Lid counterbalance mechanism

Abstract

A lid counterbalance mechanism featuring an arrangement for rendering spring counterbalance effects inactive upon opening movements of the lid through an intermediate opened position, while permitting friction brake counterbalance effects to be active during movements of the lid between the intermediate and fully open positions thereof.

Description

BACKGROUND OF THE INVENTION

In my prior U.S. Pat. No. 3,766,600, there is disclosed a counterbalance mechanism including a cabinet mounted stationary hinge part; a movable hinge part pivotally mounted on the stationary hinge part and connected for conjunctive vertical swinging movement with the cabinet lid; and a counterbalance assembly including an adjustable compression spring arranged to bear adjacent its opposite ends of the hinge parts for establishing a moment tending to essentially counterbalance torque effects of gravity on the lid throughout substantially the whole of the vertical swinging movements thereof. This prior construction features the utilization of the compression spring to maintain an end of a bolt seated relative to a rotary end bearing support; the spring bearing on a plate adjustably carried on an intermediate portion of the bolt for the purpose of varying compression of the spring.

SUMMARY OF THE INVENTION

The counterbalance mechanism of the present invention differs in mode of operation from that described in my above mentioned prior patent in that spring counterbalance effects are rendered inactive at a given intermediate open position of the lid, while friction counterbalance or lid motion braking effects remain operative throughout the range of lid movements between fully closed and open positions. This present mode of operation is permitted by mounting a compression spring bearing plate for free sliding movement lengthwise of one end of the bolt, which is coupled to the movable hinge part, and forming the stationary hinge part with stop tabs with which the bearing plate engages to limit expansion of the compression spring and thereby define the intermediate open position of the mechanism and lid.

In the preferred form of the present invention, the intermediate open position is tailored to essentially correspond to the point at which gravity induced lid torque changes direction relative to the axis of the hinge pin joining the movable and stationary hinge parts. However, the present mechanism also possesses utility in connection with installations wherein a lid has uni-directional torque characteristics.

DRAWINGS

The nature and mode of operation of the present invention will now be more fully described in the following detailed description taken with the accompanying drawings wherein:

FIG. 1 is a side elevational view of the lid counterbalance mechanism of the present invention;

FIG. 2 is a top plan view thereof;

FIG. 3a is a sectional view taken generally along the line 3--3 in FIG. 2 showing the mechanism in lid closed condition;

FIG. 3b is a view similar to FIG. 3a, but showing the condition of the lid in a lid intermediate open condition;

FIG. 3c is a view similar to FIGS. 3a and 3b, but showing the condition of the mechanism with the lid disposed in full open position; and

FIG. 4 is a graphic illustration of torque vs. lid angle for the present mechanism.

DETAILED DESCRIPTION

Reference is now made particularly to FIGS. 1 and 2, wherein the lid counterbalance mechanism of the present invention is generally designated as 10. Mechanism 10 includes a stationary or base hinge part 12, which is suitably affixed to a cabinet, not shown; a movable hinge part 14, which is suitably fixed to a lid, not shown; a counterbalance and motion snubbing assembly 16; and a hinge pin 18 for supporting hinge part 14 on hinge part 12 for vertical swinging movement about a pivot or hinge axis A between a lid closed condition, wherein the lid is essentially horizontally disposed and a lid open condition, wherein the lid is essentially vertically disposed. In the illustrated construction, the center of gravity of the lid passes over center relative to hinge pin 18 at an intermediate lid open position, such as that shown in FIG. 3b and designated as a lid angle of about 47.degree. in FIG. 4. Thus, the lid possesses bidirectional "LID-TORQUE" characteristics, wherein the effect of gravity is positive and tends to move the lid counterclockwise, as viewed in the drawings for lid angles below about 47.degree. and is negative and tends to move the lid clockwise, as viewed in the drawings for lid angles above about 47.degree..

One or more mechanisms 10 may be employed for any given installation depending upon the weight and/or dimensions of the lid to be counterbalanced. Also, it will be understood that mechanism 10 may be used solely for the purpose of counterbalancing the lid in which case the lid is supported for vertical swinging movement by separate hinge devices, not shown, in which case the movable hinge part may be fixed to the lid for relative movement therebetween or mechanism 10 may be employed to both counterbalance and support the lid, as in the case of more conventional mechanisms of this type. Thus, the term "fixed" as applied to the manner of attaching the hinge parts to the cabinet and/or lid is not meant to be limited to a "rigid" or "nonmovable" mode of attachment. Also, it will be appreciated that the orientation of hinge parts 12 and 14 relative to the horizontal when the mechanism is in lid closed condition, as well as the specific construction of these parts, will vary depending upon installation requirements.

By referring to FIGS. 2 and 3a, it will be understood that stationary hinge part 12 is of composite construction including an elongated, flat mounting plate portion 20 having one or more openings 22 through which fastener devices, not shown, may be passed for the purpose of securing hinge part 12 to a cabinet; and a generally U-shaped bracket portion 24 having essentially parallel leg portions 26a and 26b and a base portion 28. Leg portion 26b is welded or otherwise rigidly secured to plate portion 20. Leg portions 26a and 26b are formed with aligned apertures, not shown, to receive the ends of hinge pin 18 and are punched out to define aligned and inwardly facing stop tabs 30a and 30b. Base portion 28 is formed with a through opening or aperture 32 for supporting one end of the counterbalance and motion snubbing assembly 16.

Again referring to FIGS. 2 and 3a, it will be seen that hinge part 14 is of generally U-shaped configuration including essentially parallel leg portions 34a and 34b and a base portion 36. Leg portion 34b may be formed with an offset upper portion 34b' having one or more apertures 37 adapted to receive suitable fastener devices for use in attaching hinge part 14 to the lid, whereas both of leg portions 34a and 34b are formed with aligned openings, not shown, for receiving hinge pin 18 and aligned apertures for receiving opposite ends of a second hinge pin 38, which defines a pivot axis B arranged essentially parallel to hinge pin pivot axis A.

Assembly 16 is best shown in FIG. 2 and FIGS. 3a-3c as including a coil type compression spring 40, which is arranged concentrically of a bolt 42 having its first or rearwardly disposed pg,6 end threadably or otherwise rigidly fixed within a connector 44 to prevent relative movement therebetween. The connector is in turn carried by second hinge pin 38 for vertical swinging or pivotal movements relative to movable hinge part 14, such that bolt 42 extends transversely of axes A and B. Spring 40 is arranged to bear adjacent its opposite ends on a spring bearing plate or disc 46, which is freely supported by bolt 42 for sliding movements lengthwise thereof and normally bears on connector 44; and on a retainer disc 48, which in turn bears on one end of a resiliently deformable, plastic brake shoe or snubber 50. Shoe 50 is arranged concentrically of and in frictional engagement with a second or forwardly disposed end portion of bolt 42 and has its forwardly facing end disposed in engagement with the converging inner or bearing walls 52 of a through bored, cupshaped member 54, which is in turn received within opening 32 of bracket base portion 28. Normally, the rim of member 54 would bear on a pair of ears 28a and 28a, which are punched formed in base portion 28 adjacent opposite sides of opening 32, whereby to permit pivot movements about axis C without friction engagement of member 54 with the walls of spring 32. The specific construction of brake shoe 50 and its immediately adjacent parts forms no part of the present invention, such shoe having been previously described for instance in commonly assigned U.S. Pat. Nos. 3,187,374 and 3,766,600. It is believed sufficient for the understanding of the present invention to note that the "snubbing" or friction braking action of shoe 50 on rod 42 serves to damp movements of the lid, as a function of the compression variations of spring 40 incident to lid positional changes, and the resultant "FRICTION TORQUE" is always opposite to the direction of movement of the lid. Thus, "FRICTION TORQUE" will either oppose or assist the "SPRING TORQUE" produced by spring 40 depending on the direction in which the lid is moved.

It will be appreciated that the front end of bolt 42 is constrained for axial sliding and vertical pivotal movements relative to hinge part 12 about pivot axis C by a first constraining means comprising the fitting of cup-shaped member 54 within opening 32 in engagement with ears 28a, whereas the opposite or rear end of bolt 42 is constrained for vertical tilting or pivotal movements relative to hinge part 14 about pivot axis B by a second constraining means comprising connector 44 and second hinge pin 38. Pivot axis C is disposed essentially parallel to axes A and B.

Reference is now made particularly to FIG. 3a, wherein mechanism 10 is shown as being in the condition it assumes when the lid is in full closed position, i.e. a lid angle of 0.degree.. In this condition of the mechanism, spring 40 is subjected to maximum compression, but since pivot axes A, B and C are disposed in alignment, the spring force acts directly through pivot axis A and no lid counterbalancing torque i.e. "SPRING TORQUE" or "FRICTION TORQUE," is created about such axis, as indicated in FIG. 4. Thus, the weight of the lid is effective to maintain same in fully closed position.

As the lid is lifted by an operator, second hinge pin 38 is forced to swing about hinge pin 18 in a clockwise direction, as viewed in FIGS. 1-3c, whereby to move connector 44 away from base portion 28 and permit spring 40 to expand and act through a moment arm to develop "SPRING TORQUE" tending to counterbalance "LID TORQUE." Incident to this relative movement of connector 44 and base portion 28 and the expansion of spring 40, bolt 42 is forced to slide relative to shoe 50 to develop "FRICTION TORQUE." The spring torque effects cooperate with friction torque or motion snubbing effects to define a lid counterbalance envelope, which is bounded by "SPRING TORQUE + FRICTION TORQUE" and "SPRING TORQUE - FRICTION TORQUE" and extends from between lid angles at about 0.degree. and 47.degree.. When the "LID TORQUE" lies within this envelope, for example for lid angles of between about 20.degree. and 38.degree., the lid is counterbalanced and will automatically come to rest when manually applied lid opening/closing forces are removed therefrom. When the "LID TORQUE" lies above this envelope, the lid will fall towards its closed position, whereas when it lies below this envelope, the mechanism will move the lid towards its intermediate open position.

Expansion of spring 40 continues until bearing plate 46 moves into engagement with stop tabs 30a and 30b at the intermediate lid open position shown in FIG. 3b (corresponds to the 47.degree. lid angle position shown in FIG. 4), whereby to render the spring inactive or ineffective with regard to the development of "SPRING TORQUE," during continued opening movements of the lid. As will be apparent from viewing FIGS. 3b and 3c, connector 44 moves away from bearing engagement with plate 46 and thus spring 40 after the plate has become engaged with stop tabs 30a and 30b.

Although spring 40 is ineffective with respect to the production of "SPRING TORQUE" for lid angles above about 47.degree., since plate 46 no longer bears on connector 44, it does however continue to exert uniform force on brake shoe 50, as bolt 42 is "pulled" or "pushed" therethrough by connector 44, during opening and closing movements of the lid. As a result, there is produced counterbalance envelope bounded by "+ FRICTION TORQUE" and "- FRICTION TORQUE" for lid angles between about 47.degree. and 85.degree.. The slight curvature of these torque curves shown in FIG. 4, is due to the slight change in moment arm produced by movement of hinge pin 38 about hinge pin 18.

When "LID TORQUE" lies within this friction defined envelope, e.g. for lid angles between about 47.degree. and 56.degree., the lid is effectively counterbalanced, whereas the lid is permitted to "fall" towards its fully open position for lid angles of from between about 56.degree. and 85.degree.. Thus, with the present mechanism, the effects of gravity serve to maintain the lid in either of its fully open or fully closed positions, whereas the lid is essentially counterbalanced for a substantial portion of its swinging movements intermediate these positions with the mechanism tending to move the lid towards its intermediate position, as this position is approached during opening movements of the lid.

While not specifically illustrated, it is contemplated that an obvious variation of the present mechanism would involve reversal of hinge parts such that connector 44 may be pivotally connected to the stationary hinge part in which case the stop tabs would be carried on the movable hinge part. It is also contemplated that the present mechanism possesses utility in installations, wherein the lid has "uni-directional," as opposed to "bi-directional," torque characteristics. In this latter case, "SPRING TORQUE" would become inactive at an intermediate open position, which is disposed closely adjacent the fully open position of the lid, in order to prevent the mechanism from biasing the lid into its fully open position, which might otherwise result in jolting of the lid or damage to stop devices defining such fully open position; the envelope defined by "FRICTION TORQUE" being relied upon to retain the lid in fully open position into which it may be moved by manual pressure.

Claims

I claim:

1. A mechanism for use in counterbalancing the weight of a lid supported on a cabinet for vertical swinging movement between closed and open positions, said mechanism comprising:

a stationary hinge part adapted to be fixed to said cabinet;

a movable hinge part adapted to be fixed to said lid;

hinge pin means for pivotally connecting said movable hinge part to said stationary hinge part for vertical swinging movements relative to said cabinet about an essentially horizontally disposed hinge axis;

first and second constraining means supported for vertical pivotal movements on said stationary hinge part and said movable hinge part, respectively;

a bolt carried by said first and second constraining means to extend essentially transversely of said hinge axis, one of said first and second constraining means providing a slide support for one end of said bolt and defining a bearing surface, an opposite end of said bolt being rigidly fixed to an other of of said first and second constraining means;

friction means arranged for frictional engagement with said bolt, said friction means having one end thereof arranged in engagement with said bearing surface;

plate means supported for free sliding movement lengthwise of said bolt adjacent said opposite end thereof;

compression spring means arranged to bear adjacent opposite ends thereof on said plate means and an opposite end of said friction means whereby said plate is normally biased into engagement with said other of said first and second constraining means and whereby said friction means is biased into engagement with said bearing surface and directed thereby into frictional braking surface engagement with said bolt, said constraining means being supported on said hinge parts for relative separating movement upon movement of said lid from said closed towards said opened position whereby to permit said spring means to expand for purposes of establishing a lid counterbalancing torque about said hinge axis;

stop means carried by one of said stationary end movable hinge parts with which said one of said first and second constraining means is associated, said stop means being positioned for engagement by said plate means upon movement of said lid into an intermediate open position, whereby to effect separation of said plate means from said other of said first and second constraining means and prevent further expansion of said spring means during lid opening movements between said intermediate open position and said opened position.

2. A mechanism according to claim 1, wherein said other of said first and second constraining means comprises a connector member to which said opposite end of said bolt is rigidly attached, and said connector member is supported for pivotal movement to its associated one of said stationary and movable hinge parts by a second hinge pin having its axis arranged essentially parallel to said hinge axis.

3. A mechanism according to claim 2, wherein said connector member is pivotally connected to said movable hinge part and said stop means is carried by said stationary hinge part.

4. A mechanism according to claim 3, wherein said stationary hinge part includes a generally U-shaped bracket having essentially parallel leg portions apertured to receive opposite ends of said hinge pin and a base portion, said stop means is in the form of a pair of stop tabs punched from said leg portions, said first constraining means includes an opening formed in said base portion and a through bored cup-shaped member received within said base portion opening concentrically of said one end of said bolt, and said cup-shaped member pivotally bearing on said base portion adjacent said opening and defining said bearing surface.