Rosette Anti-Twist Mechanism Using Third Fastening Point
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rectangular rosettes for door locks tend to twist over time due to torque from friction and loose screws, causing alignment errors that are noticeable to the human eye, especially in modern facilities with mechatronic or electronic components where larger rosettes are used.
Innovation Solution
The rosette is secured with two screws and internally threaded bolts on both sides at a standard distance, and an additional screw or centering pin is used 21.5 mm below the square pin, utilizing the pre-drilled hole for a short backplate to provide a form-fitting third fastening point, preventing twisting by creating two fixed points: the centering pin and the square pin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two screws are used to fasten the rosette on both sides of the square spindle, then the rosette can be securely attached, but the rosette twists over time due to torque from friction and loose screws
Solution Approach 1:
The patent adds a third fastening point below the square spindle, transitioning from a two-point attachment system to a three-point system. This dimensional addition creates a triangular stabilization pattern that prevents rotational twisting while maintaining secure attachment. The third point is positioned 21.5 mm below the spindle axis, forming a stable triangle with the two upper fastening points.
Solution Approach 2:
The patent utilizes the pre-drilled hole for a short backplate (which is already present in the door assembly) as the third fastening point. This preliminary preparation of the mounting hole allows the additional fastening element to be installed without requiring extra drilling, thereby preventing rosette twisting while maintaining ease of installation.
2Ease of manufacture
If the hole for the additional fastening element is pre-drilled by door manufacturers, then installation is easier, but the hole diameter is too large allowing rosettes to twist when screws loosen
Solution Approach 1:
The patent applies different drilling requirements to different locations: the two upper holes for standard screw attachment are pre-drilled with standard diameters for ease of installation, while the lower hole for the additional fastening element is drilled with a precise diameter matching the fastening element. This localized differentiation ensures both ease of installation and precise fit where needed.
Solution Approach 2:
The patent introduces a centering pin as an intermediary element that fits into the precisely drilled lower hole. This centering pin serves as a mediator between the rosette and the door, providing a stable reference point that prevents twisting while allowing for easy installation. The centering pin compensates for any dimensional variations in the pre-drilled hole.
3Manufacturing precision
If a centering pin is used to prevent twisting, then alignment is improved, but the device complexity increases
Solution Approach 1:
The patent makes the additional fastening element serve multiple functions: it acts as both a structural fastener to secure the rosette and as a centering pin to prevent twisting. By positioning the fastening element 21.5 mm below the spindle axis, it simultaneously provides mechanical attachment and rotational stabilization, eliminating the need for separate centering pins or alignment features.
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
In a rosette (21, 21a) in which a lever handle (22) or a rotary knob is guided, the latter having a square spindle for engaging the door lock, a screw (17'), a bolt with an internal thread, a centering pin (24), or an opening for a screw or a centering pin (24) is provided 21.5 mm below the square spindle, according to the invention. This reliably prevents rotation of rectangular rosettes. Preferably, a centering pin (24) with a collar (25) is used, or the centering pin (24) is attached to a plate which is received in the rosette (21a). These measures are particularly useful when the rosette (21a) provides space for mechatronics and/or electronics, since such a rosette is particularly large and angular errors are therefore more noticeable.