Mounting system for mounting a coil spring to a window frame in a sash counterbalance system

An anchoring system used to anchor a ribbon spring to a guide track. A mounting slot is formed in the guide track that provides access to the internal gap space. A counterbalance spring is provided having an offset tab section proximate a free end. A barb flap is formed by bending a segment of the counterbalance spring from the offset tab section. The offset tab section with barb flap are extended into the gap space through the mounting slot. As the counterbalance spring is unwound, a bias is created that engages both the offset tab section and the barb flap within the gap space. This locks the free end of the counterbalance spring in place without the need of any mechanical fastener.

BACKGROUND OF THE INVENTION

1. Field of the Invention

In general, the present invention relates to counterbalance systems for windows that prevent open window sashes from closing under the force of their own weight. More particularly, the present invention system relates to the structure of coil springs used in such counterbalance systems and the mechanism used to anchor the coil springs to the window frame.

2. Description of the Prior Art

There are many types of windows that are used in modern construction. Some windows are designed to open, some are not. Of the windows that are designed to open, some windows have sashes that open vertically and others have sashes that slide open laterally or rotate outwardly.

Windows that have vertically opening sashes are the most common window used in residential home construction. Vertically opening windows are either single-hung, having one sash that opens, or double-hung, having two sashes that open. In both single-hung and double-hung windows, a counterbalance system is used to hold a window sash in place once it is opened. If no counterbalance system is used, gravity will cause the sash of the window to close as soon as it is opened and released. Early window sash counterbalance systems were simply weights that were attached to the sash. The weights were attached to a sash by a rope or chain that passed over a pulley at the top of the window frame. Such counterbalance systems required window wells in which the weights moved. Accordingly, such windows were difficult to insulate. Additionally, the rough opening needed for the window had to be much larger than the window sashes. Additionally, window sashes attached to such counterbalance systems could not be tilted for cleaning or otherwise removed from the window frame.

Recognizing the many disadvantages of window well counterbalance systems, windows were manufactured with spring loaded counterbalance systems. Spring loaded counterbalance systems relied upon the pulling strength of a spring, rather than a hanging weight, in order to counterbalance the weight of a window sash. Accordingly, window wells for weights were no longer required.

Counterbalancing a window sash with a coil spring is a fairly simple matter. One end of the coil spring is attached to the window frame while the body of the coil spring is engaged by the sash. One of the simplest examples of a coil spring counterbalance system is shown in U.S. Pat. No. 2,732,594 to Adams, entitled Double Hung Window Sash.

In coil spring counterbalance systems, at least one coil spring is used on each side of a window sash. Multiple coil springs are used on windows with heavy sashes. The coil springs provide the counterbalance force to the window sashes needed to maintain the sashes in place. In order for the coil springs to resist the weight of a window sash, one end of the spring coil must be anchored to a stationary point along the window frame. In this manner, the coil spring winds and unwinds as a window sash is opened and closed. In the prior art, coil springs are typically anchored to the window frame using a screw or using an anchor block that is screwed in place. Both techniques have disadvantages. If a coil spring is attached to the window frame directly with a screw, the coil spring must be partially unwound in order to provide an accessible segment of the coil spring for attachment. This means that the coil spring must be physically manipulated while a screw is driven through the coil spring and into the window frame. Partially unwinding a strong coil spring while driving a screw through the coil spring is a complicated maneuver that can only be performed by hand. Consequently, the use of an anchor screw adds significantly to the labor and costs associated with the manufacture of the window. Furthermore, screw anchors tend to loosen over time. If the screw anchor loosens and protrudes, the screw can interfere with the movement of the window sashes. If the screw pulls loose, the coil spring is released and fails to function.

Anchor blocks are more reliable than anchor screws. However, anchor blocks protrude into the guide track of the window frame. Anchor blocks, therefore, present an obstruction in the window frame that may inhibit a window sash from fully opening.

In U.S. Pat. No. 8,181,396 to Kunz, an alternate anchoring system for a counterbalance spring is shown. In the Kunz system, a slot is formed in the wall of the window frame. The end of a counterbalance spring is bent into a certain configuration that enables the end of the spring to hook into the slot and mechanically engage the window frame. The system works well as long as the counterbalance spring is in tension. However, times do occur when there is little or no tension in the coil spring. These times occur during the manufacturing of the window and when a sash of the window is removed for cleaning, repair or replacement. Such a time also occurs when the window sash is opened with force, so that the speed of the opening window is greater than the speed at which the counterbalance spring can rewind. In such a scenario, it is possible for the counterbalance spring to experience compression. If this happens, the end of the coil spring can disengage from the slot in which it rests.

A need therefore exists for a counterbalance system that has an improved spring anchor mounting system that is reliable and is less likely to accidentally disengage when a counterbalance spring is not in tension. This need is met by the present invention as described and claimed below.

SUMMARY OF THE INVENTION

The present invention is the anchoring system used to anchor a ribbon spring to a guide track in a counterbalance system of window. The window has a window frame with a guide track. The guide track is defined in part by a first exterior wall. Due to its extruded construction, a second interior wall is disposed within the window frame. The interior wall and the exterior wall are separated by an internal gap space. A mounting slot is formed in the exterior wall that provides access to the internal gap space.

A counterbalance spring is provided that is wound into a coil. The counterbalance spring terminates with a free end. The counterbalance spring is bent into an anchor configuration proximate the free end. The anchor configuration includes a first bend in the counterbalance spring and a second bend in the counterbalance spring that defines a lateral section therebetween. The bends in the counterbalance spring also create an offset tab section of the counterbalance spring that extends from the second bend to the free end.

A barb flap is formed by bending a segment of the counterbalance spring from the offset tab section. The barb flap is angled so that it can easily pass through the mounting slot in only one direction. The offset tab section with barb flap are extended into the gap space through the mounting slot. The lateral section of the counterbalance spring remains in the mounting slot. As the counterbalance spring is unwound, a bias is created that engages both the offset tab section and the barb flap within the gap space. This locks the free end of the counterbalance spring in place without the need of any mechanical fastener.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring toFIG. 1, the counterbalance system10for a window sash12of a window assembly11is shown. The window sash12has a sash frame15that selectively engages a spring carriage16. In the shown embodiment, the spring carriage16holds a single counterbalance spring30. It will be understood that the spring carriage16can be configured to hold multiple counterbalance springs. A spring carriage16with a capacity of one spring coil30has been selected for the sake of clarity. It will also be understood that the spring carriage16can be any prior art spring carriage and/or brake shoe assembly that is designed to hold the coil of a counterbalance spring.

The spring carriage16rides in a guide track18that is formed in the window frame20on the sides of the window sash12. The guide track18often has an extruded plastic construction, and such a construction is shown. Mounting slots22are formed in the guide track18at the points where a counterbalance spring30is to be connected to the window frame20. The mounting slots22each have a width that is just slightly wider than the steel ribbon32used to create the coil spring30. Furthermore, each mounting slot22has a height that is slightly larger than the gauge of steel used in the steel ribbon32.

The counterbalance spring30is a wound ribbon spring that is biased into a coil34. Accordingly, the counterbalance spring30resists being unwound from the coil34. A counterbalance spring30is made from a steel ribbon32that has two ends35,36. When the steel ribbon32is wound into the shape of the counterbalance spring30, its first end35is located on the interior of the coil34. The second end36of the steel ribbon32terminates on the exterior of the coil34.

The steel ribbon32approaching the second end36is formed into an anchor configuration40. The anchor configuration40is specifically configured to mechanically engage a mounting slot22in the guide track18, as will later be explained in detail.

Referring toFIG. 2in conjunction withFIG. 1, it can be seen that the anchor configuration40begins when the steel ribbon32that extends from the coil34reaches a first bend42. At the first bend42, the direction of the steel ribbon32changes by a first angle, which is 90 degrees±15 degrees. Accordingly, after the first bend42, the steel ribbon32generally extends away from the center of the coil34.

The steel ribbon32extends through a short lateral section44as it progresses between the first bend42and a second bend46. The lateral section44has a length L1. At the second bend46, the direction of the steel ribbon32changes by a second angle, which is 90 degrees±15 degrees back into its original orientation. This creates an offset tab48that extends from the second bend46to the second end36of the steel ribbon32. The offset tab48has a length L2, the significance of which is later explained.

A barb flap38is formed at, or near, the center of the offset tab48. The barb flap38is created by a cut in the steel ribbon32that defines the profile of the barb flap38. However, the barb flap38has one fixed edge39that remains part of the steel ribbon32, therein retaining the barb flap38as part of the steel ribbon32. The fixed edge39is positioned on the barb flap38closest to the second end36of the steel ribbon32. The barb flap38is slightly bent along the fixed edge39. This causes the barb flap38to protrude as an angled barb from the offset tab48.

The angle of the barb flap38creates an opening41in the offset tab48. The opening41is positioned in the center of the offset tab48at a point equidistant from the two parallel side edges43of the steel ribbon32. The opening41in the offset tab48creates thinned sections45of the steel ribbon32on either side of the opening41. The thinned sections45extend from the opening41to the side edges43of the steel ribbon32. Being thinner than any other section of the steel ribbon32along the offset tab48, the thinned sections45create an area47along the offset tab48that is more flexible than the other areas of the offset tab48. It is, therefore, easier for the offset tab48to bend in the flexible area47than in any other area along the offset tab48.

Referring toFIG. 3in conjunction withFIG. 1andFIG. 2, it can be seen that the guide track18is preferably an extruded component. When a guide track18of a window frame is manufactured, the guide track18is typically extruded with a series of parallel walls that are separated by gap spaces. This maximizes the strength of the guide track18while simultaneously minimizing the amount of material needed to form the guide track18. The result is that the guide track18has an exterior wall24that faces the window sash12, and an interior wall26that is parallel to the exterior wall24. The exterior wall24and the interior wall26are separated by a gap space28having a width W1. The mounting slot22is formed in the exterior wall24of the guide track18, therein providing access to the gap space28between the exterior wall24and the interior wall26.

Referring toFIG. 3,FIG. 4, andFIG. 5, it can be seen that the length L1of the offset tab48is at least twenty-five percent longer than the width W1of the gap space28between the exterior wall24and the interior wall26of the guide track18. The offset tab48is inserted into the mounting slot22. The barb flap38extending from the offset tab48is angled away from the second end36to the steel ribbon32. As such, the barb flap38is oriented to pass through the mounting slot22without binding on the exterior wall24during the insertion process. The flexible areas47on the sides of the barb flap38also enable the offset tab48to flex during the insertion process. The flexing helps the barb flap38to pass through the mounting slot22and prevent the second end36of the steel ribbon32from binding against the interior wall26. Since the length of the offset tab48is longer than the width of the gap space28, the offset tab48contacts the interior wall26at the opposite side of the gap space28during the insertion process. The offset tab48flexes as it is deflected by the interior wall26. This enables the offset tab48to continue to pass into the gap space28until the lateral section44of the anchor configuration40reaches the mounting slot22.

As the lateral section44of the anchor configuration40reaches the mounting slot22, the lateral section44passes into the mounting slot22. The mounting slot22is formed through the exterior wall24of the guide track18. The exterior wall24of the guide track18is made from extruded plastic and has a thickness that is typically about ⅛thof an inch. The lateral section44of the anchor configuration40has a length that is just slightly larger than the thickness of the exterior wall24of the guide track18. As a consequence, the lateral section44of the anchor configuration40in the mounting slot22serves as a pivot fulcrum. Within the gap space28, the offset tab48pivots until the offset tab48contacts the interior wall26and the barb flap38contacts the exterior wall24. The offset tab48is caused to bend by the narrowness of the gap space28. This bend biases the barb flap38against the exterior wall24. In this orientation, the presence of the barb flap38and the dual contact points prevents the offset tab48from exiting the mounting slot22. The anchor configuration40is, therefore, mechanically interlocked with the mounting slot22and cannot be unintentionally withdrawn.

As the counterbalance spring30is pulled downward by the movement of the window sash, the counterbalance spring30begins to unwind along the outside surface of the exterior wall24. The sections of the counterbalance spring30that unwind from the coil34are biased against the outside surface of the exterior wall24of the guide track18. The steel ribbon32, therefore, remains pressed against the guide track18and out of sight as the counterbalance spring30moves up and down while winding and unwinding.

The anchor configuration40can be inserted into the mounting slot22by a simple manipulation of the counterbalance spring30. This manipulation can be easily automated for manufacture. Furthermore, the counterbalance spring30need not be partially unwound in order to connect the counterbalance spring30to the guide track18. Lastly, the mechanical interconnection between the anchor configuration40and the mounting slot22does not require the use of mechanical fasteners, such as screws or locking pins. It will therefore be understood that the anchor configuration40of the counterbalance spring30can be connected to a guide track18in a window frame in a highly cost effective and labor efficient manner.

Referring toFIG. 6, an alternate embodiment of a counterbalance spring60is shown. In this embodiment, the counterbalance spring60has the same configuration as the counterbalance spring previously shown, except that the offset tab62is bent in the opposite direction at the second bend64. As a result, the slot anchor configuration66is provided with a hooked shape.

When inserted into a mounting slot22, it will be understood that the offset tab62of the slot anchor configuration66will pass through the mounting slot22. The offset tab62then extends downwardly and presses against the interior wall26of the guide track18.

It will be understood that the embodiments of the present invention are merely exemplary and that a person skilled in the art can make many variations to those embodiments. For instance, the length of the offset tab can be varied and the curvature of the offset tab can be varied. The first and second bends can be more or less than ninety degrees. All such variations, modifications, and alternate embodiments are intended to be included within the scope of the present invention as defined by the claims.