Spiral Spring Counterbalance Unit

Abstract

A counterbalance unit, for lifting an overhead door, is provided. The unit includes a flat plate which can be mounted on the wall adjacent the door. A rigid, fixed, horizontal shaft extends forwardly from the plate. A pair of united cable drums is rotatably mounted on the shaft. A spiral spring is also mounted arund the shaft; the spring's inner end is connected to the drums and its outer end is connected to a housing. The spring functions to rotate the drums. The housing can be rotated around the shaft to tension the spring; however, usually it is locked in a fixed position. A cable is attached at its inner end to each drum; the cables extend over pulleys and are attached at their lower ends to the overhead door. In operation, the spring expands to rotate the drums, thereby winding up the cables and lifting the door.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation - in - part of my application for U.S. Pat. Ser. No. 870,273, filed Nov. 5, 1969, now abandoned.

Description

BACKGROUND OF THE INVENTION

This invention relates to a spiral spring counterbalance unit for raising an overhead door, such as a sectionalized garage door or the like.

At the present time, it is usual to counterbalance a sectionalized door with either an extension spring arrangement or a torsion spring arrangement.

If the door is light, the extension spring mechanism is used. This mechanism includes a pair of springs, one extending down beside each side edge of the door. Each spring is attached at its lower end to the bottom edge of the door and at its upper end to the garage wall. When the door is in the latched-down position, the springs are fully extended. When the door is unlatched, the springs contract to roll the door up along a pair of tracks.

In the case where the door is heavy, a torsion spring mechanism is normally used. This mechanism includes a long shaft which is rotatably mounted along the upper edge of the door. A pair of drums are mounted on the shaft, one at each end thereof. A torsion spring is threaded onto the shaft between the drums. One end of the spring is secured to a wall bracket and the other end is twisted, to tension the spring, and then secured to the shaft. The spring tends to unwind with consequent rotation of the shaft and drums. The drums are each connected to the upper end of a cable which is attached at its lower end to the bottom edge of the door. When the door is unlatched, the spring unwinds, thereby winding the cables onto the drums and lifting the door.

Both the extension spring and torsion spring arrangements have shortcomings. For example, in the case of the former, the extension springs must be balanced to pull on both sides of the door with the same force; otherwise the door will bind in its tracks. With use, the extension springs become unbalanced. In the case of the torsion spring mechanism, expensive, wide, grooved drums must be used. In addition, the torsion spring equipment is heavy and awkward to handle, thereby making it difficult to install and adjust.

SUMMARY OF THE INVENTION

With the foregoing remarks in mind, it is an object of this invention to provide a light, simple counterbalance unit having a pair of interconnected cable drums which are actuated simultaneously by a single spiral spring element whereby the drum cables apply equal lifting forces at each side of the door to be lifted.

It is another object to provide a unit of this type having means which permit of easy adjustment of the tension of the spring.

It is another object to provide a unit of this type which is capable of lifting the door through an extended distance, e.g. 7 feet.

Among other objects of the invention are that the unit should be adapted for use with either light or heavy doors, that the spring element should be easily replacable, and that the unit should be mechanically simple and easy to install.

In accordance with the invention, a number of known parts are combined in a novel arrangement to provide a single power mechanism adapted to raise a door through an extended travel. More particularly, the unit comprises a base having a flat plate, which is mounted on the garage wall, and a horizontal shaft which extends forwardly from the plate. A pair of interconnected cable drums are mounted on the shaft for simultaneous rotation about the shaft axis. A spiral spring is also mounted around the shaft. The inner end of the spring is attached to the drums and its outer end is secured to a normally stationary housing. In operation, the spring is in a tensioned condition when the door is in the closed position. When the door is unlatched, the spring expands and rotates the drums. As the drums rotate, they wind in their respective cables, which pass over pulleys and are connected to the bottom edge of the door; the door is therefore lifted with an even pull on both sides. In one feature of the device, the spiral spring has a diameter greater than the effective diameters of the drums; this ensures that sufficient mechanical advantage is available to enable the spring to raise the door throughout its vertical travel. In another feature of the device, the housing is rotatable about the shaft but can be locked in place for normal operations. As a result, the housing can be rotated to adjust the tension of the spiral spring and then locked when the desirable degree of tension has been obtained.

The unit is characterized by a flat structure which can be mounted over the wall opening and does not interfere with the movement of the door. It is powered by a single spring which, through a cable and pulley arrangement, applies equal lifting forces at each side of the door. The spring's tension can be varied so that the unit can be used with doors of different weights. The unit is simple, light, and easy to install and adjust.

Broadly stated, the unit comprises: a base, adapted to be mounted on the wall, including a horizontal shaft adapted to extend forwardly from the wall; a pair of interconnected drums mounted on the shaft for simultaneous rotation therearound; spring-end fixing means associated with the base and adapted to be rotated around the shaft independent of the movement of the drums; means, associated with the base and operatively connected with the spring-end fixing means, for disengagably locking the spring-end fixing means to prevent rotational movement thereof; and a spiral spring, disposed around the shaft, having one end secured to the normally stationary spring-end fixing means and the other end operatively connected to the drums for rotation thereof, said spring having an outer diameter substantially greater than the effective diameter of the drums.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the unit;

FIG. 2 is a side section view of the unit;

FIG. 3 is a front plan view of the unit;

FIG. 4 is a perspective view of the unit in combination with pulleys, as it would appear in use;

FIG. 5 shows another version of the assembly shown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now to FIGS. 1 - 3, the unit includes a base comprising a vertical, flat plate 1 and a horizontal shaft 3. The plate 1 is secured to the garage wall adjacent the door 20 (see FIGS. 4-5). The shaft 3 is rigidly fixed to the plate 1 and extends forwardly from it.

A spring housing 5 is rotatably mounted on the shaft 3. The housing 5 consists of a central, cylindrical sleeve 5c, which slidably fits on the shaft 3, a radially extending back member 5a, and a forwardly extending rim 5b. The parts 5a, 5b, 5c are integrally joined together to form a single assembly.

A locking mechanism 6 is associated with the base and operatively connected with the housing 5. This mechanism 6 functions to normally lock the housing 5 so that it cannot rotate about the shaft 3; it can be disengaged, when required, to permit the housing 5 to be rotated. In greater detail, the mechanism 6 includes the spaced lugs 6a which are attached to the exterior surface of the rim 5b. A catch element 7 is pivotally attached to the plate 1 and is urged toward the rim 5b by spring 8. When biased by the spring 8, the catch element 7 engages the lug 6a and prevents counter-clockwise rotation of the housing 5. To disengage the catch element 7, one pivots it to the left so that the lug 6a can pass beneath it.

A cable drum structure 9 is rotatably mounted on the shaft 3. The structure 9 comprises rotatable drum-supporting means, such as the hub 10, and a pair of cable drums 11 associated with the said means. The hub 10 includes a pair of bearing races 10a, which are mounted on the sleeve 5c, and a web 10c which is carried by the races 10a and is held in place by the race shoulders 10b. It will be noted that the hub 10 is adapted to rotate freely about the shaft 3 and that the hub 10 and housing 5 rotate independently of one another. Turning now to the cable drums 11, they are integral with the web 10c for simultaneous rotation about the axis of the shaft 3. The drums 11 are thin, whereby their cables 12a, 12b are wound thereon in a single width coil. The races 10a are held in place by the washer 15. The bolt 14, threaded into the bore 4 of shaft 3, holds the washer 15 in place.

A spiral spring 17 is provided within the housing 5. The outer end of the spring 17 is secured to the housing 5. As shown, this may be done by providing a slot 18 in the rim 5b; a short piece of the spring 17 is bent backwards to catch on the edge wall of the slot 18. The inner end of the spring 17 is attached to the cable drum structure 9. This may conveniently be done by cutting a slot in the hub web 10c and bending the end of the spring 17 back over its edge.

From the foregoing, it is seen that the housing 5 provides a normally stationary, spring-end fixing means which is associated with the base. When the hub 10 is stationary -- as in the case where the door 20 is in the latched position -- the housing locking mechanism 6 can be disengaged and the housing 5 rotated around the shaft 3 to tension the spring 17.

Since the outer end of the spring 17 is normally fixed, expansion of the coil spring results in rotation of the hubs 10; the drums 11 correspondingly turn and wind in the cables 12a, 12b, thereby lifting the door 20. It will be noted that the spring 17 has an outside diameter which is substantially greater than the effective diameter of the drums 11 (by "effective diameter" is meant the outer diameter of the cable coils when fully wound on the drums). The use of a spring having such a large diameter ensures that sufficient leverage is provided to lift the door through its full travel.

The unit is mounted on the wall adjacent the door. One of the advantages of the mechanism is that it can be mounted at any position on the wall; its cables 12a, 12b can be lead through an arrangement of pulleys to bring them to the pulleys 19 located adjacent the upper corners of the door 20.

To counterbalance the unit, the door 20 is locked in the down position. At this point, the cable drums 11 are locked so that they cannot rotate. The locking mechanism 6 is then unlatched. Housing 5 is free to rotate, and a wrench can be used to turn sleeve 5c. Housing 5 is rotated with the result that spring 17 is tensioned. When it is felt that the proper tension has been reached, the locking mechanism 6 is actuated to lock housing 5. The door 20 is then unlatched. If the tension is properly set, the door 20 will just begin to move and will slowly slide upwardly.

Those skilled in the art will comprehend equivalents to the housing 5 and locking mechanism 6. For example, a framework of interconnecting rods could be used in place of the solid housing. The spring end could be welded to a forwardly projecting lug extending from the framework. The function of the housing 5 is to provide means for fixing one end of the spiral spring 17, when required. The means can be rotated when needed to wind up the spring. In place of the locking mechanism 6 which is described, one could, for example, secure a tab to the rim 5b. The tab would have a central opening adapted to line up with one of a group of spaced, threaded holes formed in plate 1. A threaded screw could be inserted through the tab and into one of the holes to lock the housing 5 to the plate 1. It will be understood that minor changes in the size, form and construction of the various parts of the improved counterbalance unit may be made and substituted for those herein shown and described, without departing from the spirit of the invention, the scope of which is set forth in the appended claims.

Claims

What is claimed is:

1. A counterbalance unit for an overhead door which closes an opening in a wall which comprises:

a base, adapted to be mounted on the wall, including a horizontal shaft adapted to extend forwardly from the wall;

a pair of interconnected drums mounted on the shaft for simultaneous rotation therearound;

spring-end fixing means associated with the base and adapted to be rotated around the shaft independent of the movement of the drums;

means, associated with the base and operatively connected with the spring-end fixing means, for disengagably locking the spring-end fixing means to prevent rotational movement thereof; and

a spiral spring, disposed around the shaft; having one end secured to the normally stationary spring-end fixing means and the other end operatively connected to the drums for rotation thereof.

2. A counterbalance unit as set forth in claim 1 wherein:

the spring has an outer diameter substantially greater than the effective diameter of the drums.

3. A counterbalance unit for an overhead door which closes an opening in a wall which comprises:

a base comprising a vertical, flat plate to be mounted on the wall and a horizontal shaft extending forwardly from the plate;

a hub mounted rotatably and coaxially on the shaft;

a pair of drums rigidly secured to the hub whereby the drums may be rotated simultaneously around the shaft;

spring-end fixing means associated with the base and adapted to be rotated around the shaft independent of the movement of the hub;

means, associated with the base and operatively connected with the spring-end fixing means to prevent rotational movement thereof; and

a spiral spring, disposed around the shaft having its outer end secured to the normally stationary spring-end fixing means and its inner end secured to the hub for rotation thereof, said spring having an outer diameter substantially greater than the effective diameter of the drums.

4. The counterbalance unit as set forth in claim 3 wherein:

the spring-end fixing means comprises a sleeve, rotatably mounted on the shaft beneath the hub, and a back member connected with the sleeve and extending radially therefrom, said back member having a forwardly extending rim at its outer end, the spring having its outer end secured to the rim.

5. The counterbalance unit as set forth in claim 4 wherein:

the locking means comprises a lug on the rim and a spring-actuated member carried by the plate, said spring-actuated member being adapted to contact the lug to prevent further movement of the spring-end fixing means in at least one direction.