Apparatus for adjusting the track of rotor blades through remote control

An apparatus for adjusting the track of rotor blades through remote control, especially of a helicopter during flight. Each rotor blade has a two-part, lengthwise adjustable control rod with a servomotor which is associated with the supply unit for rotor blade control. A receiving/transmitting part is provided, and a control device (potentiometer) as well as a measuring device are installed in the control rod and are operatively connected with an operating station having an indicator or monitor. The receiving/transmitting part, and the energy source of the servomotor associated with the supply unit for rotor blade control, are integrated in the control rod and are combined with the servomotor to a structural unit and are accommodated in a common housing.

BACKGROUND OF THE INVENTION 
The present invention relates to an apparatus for adjusting or setting the 
track of rotor blades through remote control, especially for a helicopter 
during flight. Each rotor blade has a two-part, lengthwise adjustable 
control rod with a servomotor which is associated with the supply unit for 
rotor blade control. A receiving/transmitting device is provided, and in 
the control rod a control device (potentiometer) as well as a measuring 
device are installed which are operatively connected with an operating 
station which is provided with an indicator or monitor. 
Prior to mounting the rotor blades on the helicopter, the blades, which 
rotate with the rotor hub, are checked in a simulated hovering flight on a 
rigid test stand which is firmly located on the ground. In so doing, using 
a stroboscopic method, the blade track is measured, and each rotor blade 
is optimally adjusted by means of a lengthwise adjustable control rod in 
conformity with the test readings. 
However, during forward flight of the helicopter, aerodynamic forces act on 
the rotor blades and bring them out of track, as a result of which 
vibrations occur in the blade operating cycle which are transmitted to the 
entire helicopter. In order to stop these undesired vibrations, and to 
adjust the rotor blades to another track, the helicopter must be landed 
and when the rotor has stopped the control rod of one rotor blade at a 
time must manually be either lengthened or shortened. The helicopter can 
then resume flight. This process must be repeated until an optimum 
vibration behavior of the helicopter during flight is achieved; i.e. the 
length of all of the control rods of the rotor blades have been correctly 
adjusted. 
In an apparatus of the aforementioned general type (German Patent No. 27 57 
617), the supply unit for rotor blade control is arranged on the rotatable 
rotor hub. The source of energy, which is located in this unit and is a 
part of the drive system, is connected by means of lines, which extend 
externally of the control rod, with the servomotor which is accommodated 
in the control rod. The receiving/transmitting device for transmitting 
signals, such as control signals and measured values of the tensile and 
compressive forces which occur in the control rod, is also located on the 
rotatable rotor hub. Such an arrangement of the supply unit and of the 
receiving/transmitting device on the rotor hub cannot be utilized with all 
types of helicopters, because the possibility for mounting is not always 
present. Furthermore, the lines, which are located externally of the 
control rod between the servomotor and the supply unit, can be easily 
damaged or can produce an imbalance, thereby having an unfavorable effect 
on the adjustment operations. 
The main object of the present invention consists in substantially further 
developing an apparatus for adjusting the tracking of rotor blades of the 
aforementioned general type in such a way that the spatial separation of 
the receiving/transmitting device, the source of energy which is located 
in the supply unit and the servomotor, which is arranged externally of 
this unit, is eliminated and their connections are at the same time 
simplified.

SUMMARY OF THE INVENTION 
The apparatus of the present invention is characterized primarily in that 
the parts of the supply unit for rotor blade control, namely the source of 
energy of the servomotor, and the receiving/transmitting part, are 
integrated in the control rod and are combined with the servomotor into a 
structural unit and are accommodated in a common housing. 
The advantages obtained with the present invention are based in particular 
on the fact that the control rod with the integrated structural components 
is functional by itself and can be subsequently installed into any 
helicopter without significant modification. 
Pursuant to a particularly preferred embodiment of the present invention, 
the source of energy and the receiving/transmitting part can be mounted on 
the support plate for the servomotor; this support plate can be axialy 
displaced, and closes off one end of the housing. 
Utilization of the inventive apparatus on a helicopter allows adjustment of 
the rotor blade by the copilot from the cockpit or control room by means 
of the controls at the control unit independent of the actual control of 
the flight. The adjustment of the rotor blades is effected from a zero 
setting on the control unit. This adjusting can be optimally carried out 
not only based on acoustic or optical signals at the control unit, but 
also based on vibrations of the helicopter felt by the pilot. The 
inventive control rod with the integrated structural components used for 
adjusting the track can, after conclusion of the adjustment process, i.e. 
after achieving the optimum flight behavior, either remain on the 
helicopter or be removed and replaced by another simple pitch change link, 
for example one inherent to the helicopter. The length of this pitch 
change link which is to be installed must, however, prior to its 
installation be set in conformity to the length of the control rod which 
was removed. 
DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring now to the drawing in detail, for the remote control for 
adjusting or setting the track of the rotor blade 1, a control unit 2 
which has non-illustrated operating and control devices is shown in the 
cockpit or control room of the helicopter. Each rotor blade 1 is provided 
with a two-part control rod 3 which can be adjusted with regard to its 
length, and which is mounted in a known manner. A plurality of structural 
components which are part of the supply unit for rotor blade control is 
arranged in the control rod 3. The adjustment of the length of the control 
rod 3 mounted on the helicopter, and the control of the control forces, is 
effected from or at the control unit 2 in the cockpit of the helicopter. 
As shown in FIGS. 2 and 3, each lengthwise-adjustable, two-part control rod 
3 has its own drive system, which essentially comprises a source of energy 
4, which can be electrical, hydraulic, or pneumatic, a servomotor 5, and a 
receiving/transmitting part 6. One end of the portions of the control rod 
which face one another is provided with a rotatable, fixed threaded 
spindle 7 which cooperates with a non-rotatable spindle nut 8 at the other 
end of the portion of the control rod. A housing 10 having a support plate 
11 at the front end serves to accommodate the rod end connection of 
threaded spindle 7 and spindle nut 8 in a protected manner. The support 
plate 11 can be axially displaced in the housing 10. The source of energy 
4, the servomotor 5, and the receiving/transmitting part 6 can also be 
disposed in a protected manner on that side of the support plate 11 which 
faces the housing 10. A potentiometer (not illustrated) is also mounted in 
the housing 10. The threaded spindle 7 is mounted in an extension 19 of 
the support plate 11 by means of a roller bearing 9, and is operatively 
connected by means of a pair of spur gears 13 with the servomotor, which 
is disposed in the housing 10 and in the illustrated embodiment, is an 
electromotor 12. A mounting eye (not referred to in greater detail) of the 
control rod 3 is connected to the extension 19 of the support plate 11. 
The rotary motion necessary for adjusting the length of the control rod 3 
is transmitted from the electromotor 12 via the pair of spur gears 13 to 
the threaded spindle 7. By means of a pair of forked arms 14 and 14', and 
a pair of guide pins 15 and 15', which at the same time serve as a 
limitation of the adjusting path, the spindle nut 8 is arranged in the 
housing 10 in such a way that it is non-rotatable yet can be axially 
displaced. Externally of the housing 10, the spindle nut 8 has a part 16 
on which is disposed the other mounting eye for the control rod 3. A 
signal coil is designated with the reference numeral 17. The tensile and 
compressive forces which occur in the lengthwise adjustable control rod 3 
during the adjustment of a rotor blade in conformity with the movement or 
turbulence of the rising or returning rotor blade 1 are detected by a 
measuring device 18, which is equipped, for example, with an extensible 
bar, is converted into an electrical signal, and is transmitted to the 
control unit 2 in the control room of the helicopter, where it is 
indicated as a signal in the control device. 
The present invention is, of course, in no way restricted to the specific 
disclosure of the specification and drawing, but also encompasses any 
modifications within the scope of the appended claims.