With a MIGRA 1A constant force spring, the coiling diameter is almost the same over the entire strip length.
This produces an almost constant force over the entire working range.
The typical characteristics of a MIGRA 1A constant force spring are:
- Very small hysteresis
- Long extended length
- Force characteristic curve in the working range rises only slightly
- Service life depending on design up to 50,000 load cycles (typical applications require 5,000 – 20,000 cycles)
- Width 1.8 – 100 mm / thickness 0.05 – 1.0 mm (guide values)
Migra 1A constant force springs are ideal for applications with a linear movement, for example vehicle roof roller blinds.
In conjunction with a damper element, a relatively constant movement speed can be achieved,
as required for example in kinematic systems for cup holders, ashtrays or storage compartments in vehicles.
To achieve a higher spring force, two or
more MIGRA 1A constant force springs can be processed to form a multiple spring.
MIGRA 2A constant force springs constitute a special form.
The great advantage of the MIGRA 2A constant force spring is that relatively large spring forces are possible even in confined installation conditions. In addition, no special fixing of the spring ends is required.
The typical characteristics of a MIGRA 2A constant force spring are:
- Very small hysteresis
- Long extended length
- Force characteristic curve in the working range rises only slightly
- Width 1.4 – 10 mm / thickness 0.02 – 0.25 mm (guide values)
The MIGRA 2A constant force spring was specially developed for pressing carbon brushes with almost constant force on collectors of electric motors. MIGRA 2A constant force springs can most commonly be used where a constant extraction force is required in small installation conditions, for example in carbon brush holders, indicators and measuring devices, fuse switches for low-voltage technology, and also in ventilation valves for patients in hospitals.
With a POGRA 1A constant force spring, the coiling diameter in the working range is not constant,
and is instead unwound in such a way that the force characteristic curve increases according to demand.
The typical characteristics of a POGRA 1A constant force spring are:
- Very small hysteresis
- Long extended length
- Force characteristic curve in the working range rises in a straight line
- Width 1.8 – 100 mm / thickness 0.05 – 1.0 mm (guide values)
The POGRA 1A constant force springs are preferably used to push goods on shelves in department store and sales displays forward.
Because the issue of cost is often the main consideration, the outer ends of these types of springs are often fastened using
bolts or rivets, and inexpensive hole designs can be used.
Equally easy to use, and just as cost-effective, is the outer end with a separating cut, a spring end
in the shape of a “T”, or a step hook.
The inner end of the constant force spring does not need to be fixed. It is wound onto the supply roller and spring-actuated, and the spring length is defined to ensure that at least 1.5 coils remain on the roller during final extraction. A straight separating cut is therefore more than sufficient. If the springs are used without a supply roller and are only picked up at the circumference, a chamfer or radius at the edges can be advantageous. For designs that require fixing because an end stop is not otherwise possible, the inner spring end can be connected to the supply roller with screws or rivets. The advantage of this is to provide the supply roller with a step at the point where the connection is made. Alternatively, a step hook can also be used at the inner end which is hooked into a slotted roller for this purpose. It should however be noted that this can lead to an out-of-round run-out. In addition, the spring will also be kinked and become unusable if it is in fact pulled out to the stop.
