Spring washers are specifically designed to provide a compensating spring force and sustain a load or absorb a shock. Many design variations have evolved to best serve one or the other of these two basic functions or to optimize both functions in a single part within specific I.D./O.D. limits. Two principle factors are at work that continually increase the requirement for spring washers:
The continuing effort to down-size many end products, relative to both weight and cost, creates a need for small, multi-functioning assembly components,such as washers that support a load,span a hole,or both,while providing a compensating spring force.
Automated assembly requires some "play" or tolerance in the "fit" of components. Spring tension is needed to compensate for these tolerances. Recognizing these two broad areas of influence,it can be stated that the more common applications for spring washers are:
- To take up "play" in assemblies due to cumulative commercial tolerances.
- To compensate for small dimensional changes in assembled components.
- To eliminate end play or rattles.
- To maintain fastener tension or "tightness".
- To compensate for expansion and contraction or cold flow of material.
- To absorb intermittent shock loads and function as working springs capable of providing controlled reaction under dynamic loads.
A. Single Wave Washers
These washers are designed for applications involving low loads and requiring high deflection. The Load/Deflection (L/D)curve for this type of washer is virtually linear. Applications include the take up of large tolerance variations,eliminating end play in electric motors,minimizing rattles and cushioning light loads.
- Apply greater bolt tension per unit of applied torque.
- Provide hardened bearing surfaces to create more uniform torque control.
- Provide more uniform load distribution through controlled radii (section) cutoff.
- Provide protection against looseness resulting from vibration and corrosion.
- Optimum locking device for use in applications with hardened faying or bearing surfaces.
A split washer or a spring lock washer is a ring split at one point and bent into a helical shape. This causes the washer to exert a spring force between the fastener's head and the substrate, which maintains the washer hard against the substrate and the bolt thread hard against the nut or substrate thread, creating more friction and resistance to rotation.
Spring washers are a left hand helix and allow the thread to be tightened in a right hand direction only, i.e. a clockwise direction. When a left hand turning motion is applied, the raised edge bites into the underside of the bolt or nut and the part that it is bolted to, thus resisting turning. Therefore spring washers are ineffective on left hand threads and hardened surfaces. Also, they are not to be used in conjunction with a flat washer under the spring washer, as this isolates the spring washer from biting into the component that it is fastening.
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