Window Counterbalance Brake Shoe Cam Locking Mechanism
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Solution Overview
Problem
Existing counterbalance systems for tilt-in double-hung windows, particularly those with vinyl frames, face issues with static locking mechanisms that can groove window tracks and interfere with the tilt action, leading to debris and performance problems.
Innovation Solution
A counterbalance system featuring a brake shoe with a dynamic locking mechanism, utilizing a flexible tab and cam mechanism that engages the guide track only when the window sash is tilted, preventing the ribbon spring from moving the sash and allowing free movement when closed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a static locking mechanism is used in the brake shoe, then the brake strength is sufficient to prevent sash movement, but the mechanism can groove the window track and create debris
Solution Approach 1:
The brake shoe incorporates a dynamic locking mechanism where a cam rotates to engage or disengage a locking surface from the guide track. This dynamic engagement allows the brake to provide strong locking force when needed while avoiding continuous contact that would cause grooving and debris generation.
Solution Approach 2:
The harmful static locking surface is replaced by a cam mechanism that extracts the locking function into a rotational element. The cam profile is designed to provide intermittent locking engagement, separating the locking action from continuous contact with the guide track.
2Reliability
If the brake shoe contains a strong brake mechanism to prevent ribbon spring movement, then the sash is secured when tilted, but the mechanism interferes with tilt action
Solution Approach 1:
The cam rotates automatically as the sash tilts, engaging the locking surface when the sash is in the tilted position and disengaging when closed. This dynamic response ensures the brake provides security only when needed, without interfering with the tilt operation.
Solution Approach 2:
The cam mechanism responds to the position of the sash through feedback from the tilt action itself. The rotation of the cam is driven by the movement of the sash, creating a self-regulating system that engages the brake based on the actual tilt condition.
3Reliability
If a cam mechanism is used to expand and lock the brake shoe, then the locking action is improved, but the structure becomes more complex
Solution Approach 1:
The cam mechanism is integrated directly into the brake shoe assembly, merging the locking function with the existing brake structure. The cam rotates within the brake shoe housing, combining multiple functions (braking, locking, and position sensing) into a single integrated component rather than separate elements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The dynamic locking mechanism effectively prevents the window sash from being moved by the ribbon spring when tilted, maintaining performance and preventing debris in the window track, while allowing uninhibited movement when closed.
Implementation Method 1
A cam is supported within the brake shoe. The brake shoe expands when the cam is turned.
Implementation Method 2
Ribbon springs are constant force springs and supply the counterbalance force needed to suspend the weight of the window sash.
Implementation Method 3
This causes the flexible tab to flex and extend away from the ribbon spring at an inclined angle.
Data Source
AI summary
A counterbalance system that is set into the guide track of a tilt-in window. The counterbalance system utilizes a brake shoe that is attached to a ribbon spring. The ribbon spring has a shaped head that is retained by the brake shoe. A flexible tab is formed in the ribbon spring near the shaped head. A protrusion extends from the brake shoe. The brake shoe has a receptacle that receives and retains the shaped head of the ribbon spring, therein interconnecting the ribbon spring to the brake shoe. A cam is supported within the brake shoe. The brake shoe expands when the cam is turned. This causes the protrusion on the brake shoe to be biased against the flexible tab in the ribbon spring. This, in turn, causes the flexible tab to flex and extend away from the ribbon spring at an inclined angle. Within the guide track of the tilt-in window, the extended flexible tab acts as a barb and engages the side wall of the guide track. This helps prevent the window sash from being moved when the window sash is tilted open.