Adjusting device for an airplane propulsion system

An adjusting device is provided for an airplane propulsion system using the reciprocating piston combustion engine and a propeller, which adjusting device simultaneously adjusts the throttle valve and the propeller pitch of the propellers. The adjusting device is formed with a connecting rod and a carrier rod connected thereto. The connecting rod is provided as an adjusting cable whereby the cable core is under spring pretensioning in lower rotational speeds of the motor.

BACKGROUND AND SUMMARY OF THE INVENTION 
The invention relates to an adjusting device for an airplane propulsion 
system of the type having a reciprocation piston combustion engine with an 
adjustable intake throttle valve and with a propeller pitch regulator. 
Such an adjusting device is described in German Unexamined Published Patent 
Application (DE-OS) 33 06 612. This device serves, with a single control 
lever, to adjust the throttle valve of a piston cylinder motor and 
therewith the motor operation as well as the blade pitch of the propellers 
driven by the motor, respectively the effective propulsion force at the 
airplane. It is there provided, through pivoting of the control lever to 
continually completely open the throttle valve already in the lower 
rotational speeds of the motor and through further pivoting of the control 
lever with the help of a propeller regulator for the propeller pitch 
reduce the same from larger to smaller pitch in order that the motor 
rotational speed is increased from the range of 2300 revolutions per 
minute to 5000 revolutions per minute. In this rotational speed range the 
motor power output which is absorbed entirely by the propeller is adjusted 
exclusively through the rotational input to the propeller regulator. The 
control lever effects or works on the throttle valve with this control 
arrangement via several linkage connections and intermediate levers 
whereby the adjustment because of the unavoidable linkage play or 
tolerances can be achieved only somewhat imprecisely. Furthermore, this 
linkage mechanism has the disadvantage that the throttle valve goes to the 
closing position upon breakage of an intermediate member causing 
consequent idle running of the motor and an acute danger that the airplane 
might crash. 
An objective of the invention is to provide an adjusting device of the 
above mentioned type with constructively simple means with the motor 
operation being precisely adjustable and also so that upon a breaking of 
an intermediate member the full motor operation and propulsion forces are 
provided to the airplane. 
This objective is achieved according to preferred embodiments of the 
invention by providing an adjusting apparatus which includes a movable 
connecting rod linked to the throttle valve and movably guided in a 
relatively fixed rod casing, a throttle valve spring continuously biasing 
the connecting rod toward an open throttle position, a manually releasable 
blocking device for selectively blocking movement of the connecting rod 
with respect to the rod casing, and a carrying rod connected to the 
connecting rod for movement therewith and also connected at a control 
member of the propeller pitch regulator via the interposition of a further 
pitch regulator spring member. 
When a connecting rod including a control knob operable by the airplane 
pilot is directly linked at a throttle valve lever and simultaneously a 
carrier rod is linked to the connecting rod for operating an adjusting 
lever for the propeller pitch of the propellers, there is permitted in a 
simple manner an exact and functionally certain adjustment of the motor 
operation and the torque of the propellers. Because an auxillary spring 
operates on the throttle lever in the opening direction, upon breaking of 
a member of the adjusting device, the throttle valve is fully opened and 
the motor performance is maintained. 
In especially preferred embodiments of the invention a commercially 
available adjusting cable is used for the connecting rod, including a 
cable casing or housing surrounding and guiding longitudinal movement of a 
metallic cable core whereby the control knob operated by the pilot is 
connected with the cable core. Such adjusting cable is provided centrally 
of the control knob with a blocking knob by means of which the blocking of 
the cable core with respect to longitudinal displacement may be 
selectively disconnected. 
In certain preferred embodiments, connecting pivot joints are arranged at 
the throttle valve lever and the adjusting lever for the propeller pitch 
so that the respective ends of the connecting rod and the carrier rod 
protrude through the respective connecting pivot joints. The ends of the 
cable core and the carrier rod are provided with abutment rings which are 
movable into abutment at the connecting pivot joints to effect respective 
pivotable movement of the adjusting lever and throttle valve lever.

DETAILED DESCRIPTION OF THE DRAWINGS 
A commercially available adjusting cable is provided as a connecting rod 1 
and includes a two part cable housing or casing 2 and a metallic cable 
core 3 longitudinally guided in the cable housing 2. The cable housing 2 
is held at fixedly disposed attachment plates 4 and 5 by means of 
counter-nuts at respective opposite sides of said plates. At one end of 
the cable core 3 a control knob 6 is fastened, in which knob 6 a blocking 
knob 7 is centrally arranged. The other end of the cable core 3 protrudes 
through a connecting pivot joint 8 that is arranged at a one-armed 
throttle valve lever 9 and is provided with an abutment ring 10 which in 
the FIG. 1 illustrated position of the adjusting device abuts at the 
facing surface 11 of the connecting pivot joint 8. The connecting pivot 
joint 8 is formed with a guiding casing 12 having an outwardly protruding 
pin 13 engageable in a bore of the throttle valve lever 9. At its other 
end the throttle valve lever 9 is fastened at the shaft of a throttle 
valve 14 which is bearingly supported in the suction or intake pipe 15 of 
a reciprocating piston combustion motor. The pivotable movement of the 
throttle valve lever 9 is limited by means of a right-hand disposed 
abutment 16 and a left-hand adjustable abutment 17. Between the guiding 
housing or casing 12 of the connecting pivot joint 8 and the facing 
surface of the cable casing 2 there is disposed a helical spring 18 under 
pretensioning. 
Approximately in the middle of its longitudinal extension, a connecting 
piece 19 is fixedly clamped to the cable core 3, at which connecting piece 
19 a carrier rod 20 is connected and disposed to extend at a sharp angle. 
The carrier rod 20 exhibits a pin 20 which is provided in its forward 
region with an abutment ring 23 and which protrudes through the connecting 
pivot joint 26 arranged at the adjusting lever 24 of a propeller regulator 
25. The pivotable movement of the adjusting lever 24 is limited by means 
of a right-hand abutment 27 and a left-hand abutment 28. A prestressed 
spiral spring 29 is disposed between the carrier rod 20 and the push 
rotation linkage 26 of the adjusting lever 24. 
When the blocking knob or button 7 is pushed into the control knob 6, the 
blocking device 30 is disconnected. A now freely movable cable core 3 will 
be moved toward the right by means of the supporting helical spring 18 
acting at the fixedly disposed cable casing 2 as well as by means of the 
strength of the helical spring 29. The maximum pushing movement, 
respectively the angular path "al", of the throttle valve lever 9 is 
limited by means of the right-hand abutment 16 of this throttle valve 
lever 9. When in this position, the throttle valve 14 is fully opened and 
the motor rotational speed is approximately 2300 revolutions per minute. 
The abutment ring 23 of the carrier rod 20 abuts at the connecting pivot 
joint 26 of the adjusting lever 24. Both spiral springs 18 and 29 have 
been substantially unstressed during this first shoving movement "al". 
Upon further forward or rightward pushing of the control knob 6 only 
friction forces at the junction of the cable core and joint 12 occur 
without anymore effective movement of lever 9. 
If the pushing knob 6 is pushed further toward the right along the path 
"a2", the adjusting lever 24 is pivoted by corresponding angular movement 
until it comes to abutment on the right-hand abutment. During this 
pivotable movement the propeller pitch of the propellers are adjusted by 
means of the propeller controller 25 hydraulically from maximal to minimal 
pitch. The thereby increasing torque of the propellers correspondingly 
increases the motor operation and its rotational speed increases to 
approximately 5000 revolutions per minute. 
Shortly before reaching the right-hand abutment 27 an end switch 22 is 
closed by the connecting piece 19 by means of which an injection device of 
the motor is switch toward increased fuel enrichment. The motor operation 
thereby increases to its highest value which is approximately with a motor 
speed of 5300 revolutions per minute. 
The FIG. 4 enlarged illustration of the adjusting cable shows a 
disconnected blocking device 30 in the position shown. A guide tube 32 is 
conformed to and provided in the inside of the fixedly disposed cable 
casing 2 and the control knob 6 is threadably attached to this guide tube 
32. A blocking knob 7 is longitudinally guided against the strength of a 
spring 33 centrally in the switching knob 6 (here shown in the pushed-in 
position) and is secured against falling out. A blocking rod 34 is 
threadably connected to the blocking knob 7, which blocking rod 34 
conforms to and is disposed inside of the guide tube 32 and includes a 
sloped receptable opening for receipt of a blocking ball 36 which is 
biased by a leaf spring 35. When one releases the blocking knob 7, the 
blocking ball 36 will be shoved against the sloped surface 37 of the 
receptable through a breakthrough of the guide tube 32 in a winding of a 
threadpath of the cumferential windings 38 of the cable casing 2. Thereby 
the guide tube 32 and the cable core 3 fixingly connected thereto are 
blocked against longitudinal sliding movement. It is furthermore possible 
to utilize a rotational movement of the switching knob 6 for fine 
adjustment of the cable core 3 and the activating members connected 
thereto. 
Although the present invention has been described and illustrated in 
detail, it is to be clearly understood that the same is by way of 
illustration and example only, and is not to be taken by way of 
limitation. The spirit and scope of the present invention are to be 
limited only by the terms of the appended claims.