Hook Cerliani - Types Of Brake Spring User Manual

Types of brake spring

Three different executions can exist for one single bobbin case:

• bobbin case without NBL spring;

• NBL – i.e. with no backlash spring;

• MF – i.e. with adjustable NBL spring (see following paragraph)

• Magnet –
The choice of the correct bobbin case depends on the usage.

NBL

No backlash spring bobbin case The NBL device prevents
excessive thread feeding off the bobbin also in case of lower
thread pulls during the sewing or during the automatic trimming
of the threads. This is very important for sewing machines
equipped with a trimming device. The NBL device consists of a
spring set (1) on the inside bottom of the bobbin case. The
spring presses the upper flange of the bobbin against the
bottom of the bobbin case holder (base), causing a breaking
effect. The shape of the setting spring depends upon the
different bobbin cases on which it is mounted.

MF

Adjustable no backlash spring bobbin case This patented
execution of the NBL device has the advantage, compared to the
prior system, to can adjust the pressure of the spring against
the bobbin. It is so possible to regulate the breaking of the
bobbin case according to the intensity of the pulling stress on
the thread during the trimming operation and of the inertial
force of the bobbin produced by the type of thread used. It is
thus possible to achieve a superior breaking for heavy threads
and a weaker breaking for light threads, without influencing
excessively the tension of the lower thread while sewing. This
tension must be in fact determined only by the tension spring on
the outside of the bobbin case. The adjustable NBL devise
consists of a sickle-shaped spring (1) fixed to the inside of the
bobbin case, which can be finely adjusted to apply light pressure
to the bobbin. The amount of pressure that can be applied to the
bobbin can adjusted by a screw (3). In order to avoid, during
sewing, the unscrewing of the adjusting screw by vibration,
CERLIANI has created a device to prevent this. It has been
accomplished by inserting a small plug of synthetic material (4)
underneath the pressure spring for the bobbin case latch (5)
into which the screw thread of the adjusted screw bites, holding
the screw firmly.