Abstract: A hydraulic tensioner is provided with a no-return device and with an anti-rotation device capable of being disabled having a pin, integral with the cylinder of the tensioner, which slides in a first longitudinal slot formed on the outer wall of the piston and a means able to disable the anti-rotation device. The disabling means includes a second slot, at right angles with respect to the first longitudinal slot to which it is connected, situated at the end of the first longitudinal slot nearer to the bottom of the cylinder. The second slot may also be a throat connected to the first longitudinal slot to which it is perpendicular, and which extends for the whole circumference of the piston. The second slot is preferably shaped as a ramp to join the bottom of the first longitudinal slot to the outer surface of the piston.

Abstract: A cartridge tensioner (10) for drive transmission belts and chains comprises a cylinder (12) with a cylinder bore, a piston (14) slidably received in the cylinder bore and provided with a piston bore (40), a vent device (16) housed in the piston bore and comprising an end part and a stem integral with each other, a pressure spring (18) acting between a shoulder of the cylinder and the vent device, and a retaining device (20), accessible from the outside of the cylinder. The retaining device, in a position engaged with the stem of the vent device, retains the vent device preventing the action of the spring on the piston, and, in a position of disengagement from the stem of the vent device, allows the spring to bias the device against the piston and to act consequently on the piston.

Abstract: A hydraulic tensioner is provided with a no-return device and with an anti-rotation device capable of being disabled having a pin, integral with the cylinder of the tensioner, which slides in a first longitudinal slot formed on the outer wall of the piston and a means able to disable the anti-rotation device. The disabling means includes a second slot, at right angles with respect to the first longitudinal slot to which it is connected, situated at the end of the first longitudinal slot nearer to the bottom of the cylinder. The second slot may also be a throat connected to the first longitudinal slot to which it is perpendicular, and which extends for the whole circumference of the piston. The second slot is preferably shaped as a ramp to join the bottom of the first longitudinal slot to the outer surface of the piston.

Abstract: A cartridge tensioner (10) for drive transmission belts and chains comprises a cylinder (12) with a cylinder bore, a piston (14) slidably received in the cylinder bore and provided with a piston bore (40), a vent device (16) housed in the piston bore and comprising an end part and a stem integral with each other, a pressure spring (18) acting between a shoulder of the cylinder and the vent device, and a retaining device (20), accessible from the outside of the cylinder. The retaining device, in a position engaged with the stem of the vent device, retains the vent device preventing the action of the spring on the piston, and, in a position of disengagement from the stem of the vent device, allows the spring to bias the device against the piston and to act consequently on the piston.

Abstract: The monitoring method includes the steps of: acquiring a signal from an acceleration sensor; calculating a transform in the frequency domain of the signal to obtain a sequence of samples; acquiring a sample in the sequence of samples; calculating an actual amplitude value of the acquired sample; calculating a relative deviation between the actual amplitude value of the acquired sample and a reference amplitude value; and comparing the relative deviation with at least one predetermined threshold to immediately detect any irregularity in, and so prevent in-flight failure of, the helicopter transmission assembly.

Abstract: The monitoring method includes the steps of: acquiring a signal from an acceleration sensor associated with an epicyclic assembly; sampling the signal at a predetermined sampling frequency to obtain an initial sequence of samples; dividing the samples in the initial sequence into groups, each defined by a predetermined number of samples; acquiring predetermined groups of samples; filtering the acquired groups of samples to obtain an intermediate sequence of samples; processing the intermediate sequence of samples to obtain a final sequence of samples; calculating a sixth-order moment of the final sequence of samples; and comparing the sixth-order moment with at least one predetermined threshold to detect any vibrational irregularity in the epicyclic assembly of the helicopter.

Abstract: The method includes the steps of: acquiring a signal from an acceleration sensor; calculating the Fourier transform in the frequency domain of the signal to obtain a sequence of samples; acquiring from the sequence of samples a set of samples including samples at the meshing frequency of the gears monitored by the sensor, and samples at the harmonic frequencies of the meshing frequency; calculating the energies associated with the set of samples and the signal; calculating a noise energy parameter correlated to the ratio between the energy of the set of samples and the energy of the signal; comparing the noise energy parameter with at least one predetermined threshold; and generating an alarm signal in the event the noise energy parameter exceeds the threshold value.

Abstract: The method includes the steps of: acquiring a signal from an acceleration sensor; calculating the Hilbert transform of the signal filtered and sampled beforehand; defining a complex signal having the filtered and sampled signal as the real part and the Hilbert transform of the filtered and sampled signal as the imaginary part; calculating a phase signal given by the difference between the phase of the complex signal and a reference phase; calculating the variance of the phase signal; comparing the variance with at least one predetermined threshold; and generating an alarm signal if the variance exceeds the threshold value.

Abstract: The monitoring method includes the steps of: acquiring a first signal from an acceleration sensor; calculating a transform in the frequency domain of the first signal to obtain an initial sequence of samples, each of the samples having a respective amplitude and a respective frequency; processing the initial sequence of samples to obtain a final sequence of samples; calculating a sixth-order moment of the final sequence of samples; and comparing the sixth-order moment with at least one predetermined threshold to detect any vibrational irregularity in the helicopter transmission assembly.