Airplane engine starter system and housing

A starting system for an internal combustion engine includes a starter motor and solenoid mounted within separate, angularly spaced receptacles of a reduction gear housing. The starter motor drives a reduction gear within a the gear housing, which, in turn, drives a pinion gear on a shaft. The solenoid controls a retractable rod which selectively pivots a cantilever arm within the housing. The pivoted cantilever arm pushes the pinion gear shaft against the action of a coil spring, which urges the pinion gear into engagement with the engine flywheel ring gear, turning the flywheel ring gear. The solenoid also acts as a switch for the starter motor. When the engine is started, power is removed from the solenoid, which causes the rod to extend, pivoting the cantilever arm in the opposite direction, and allowing the spring to withdraw the pinion gear from engagement with the flywheel ring gear. A plurality of strengthening ribs give the housing strength with a minimal weight addition. The starter system is particularly useful as a retrofit replacement for an existing Continental aircraft engine starter.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention is directed to a starter system for an internal combustion 
engine, and more particularly to a system including a starter motor and a 
solenoid driven pinion gear retraction system for use on existing aircraft 
engines. 
2. Description of the Related Art 
The development of internal combustion engines for airplanes has tracked 
somewhat with the development of automobile engines. Early examples of 
both had no separate electrical system, relying exclusively on magnetos 
for spark generation and hand cranks in the case of automobiles or hand 
"propping" for airplanes, for starting. Separate, battery operated 
starting systems for automobiles were developed in the early part of the 
century, including crankshaft driven distributors and coil and gap spark 
systems, but, for reasons of safety, reliability, and weight 
considerations, airplanes continued to use magnetos for spark generation 
and hand propping for starting. 
With the development of more powerful airplane engines and more efficient 
airframe designs, plus the need for more sophisticated, electrically 
driven instruments, separate electrical systems for airplanes were 
developed in the late 1920's and the 1930's. However, for most smaller 
general aviation airplanes, the addition of starters and generators still 
represented a weight penalty which could not be tolerated. This was 
especially true since the early iron core starter motors and generators 
with large copper windings were extremely heavy. 
After World War II was over, the flying public demanded electric starting 
systems for even the smallest airplanes and many engines, such as the 
venerable Continental 0-200, which were previously hand-propped, were 
retrofitted with electric starters. However, in the case of the 
Continental 0-200 and others, most such starters were either equipped with 
hand-operated cable pinion gear extenders, or with sprage clutches which 
were placed in line with the pinion gears and which merely disengage the 
pinion gears from the starter reduction gear, meaning that the pinion gear 
was constantly turning when the engine was running. The resulting constant 
wear and tear on the pinion gears was considerable, resulting in a 
shortened effective gear life and consequent frequent expense. 
With the recent veritable explosion in home-built and "kit" planes, 
interest in venerable engines such as the Continental 0-200 and others is 
very high. However, the archaic starter designs in such engines, including 
their excessive weight and the undue wear and tear resulting from constant 
gear engagement, has created a need for an improved starting system for 
existing Continental airplane engines. 
While improved starter systems have been developed for other airplane 
engines, including virtually all Lycoming direct drive piston engines, 
these prior starter systems have incorporated the starter motor and a 
solenoid pinion gear retractor with actuating lever in a single reduction 
gear housing chamber, with the solenoid placed outboard of and in line 
with the starter motor. Referring to FIG. 3, note the arrangement of a 
starter motor 6' and a solenoid pinion gear retractor 7' in a single 
receptacle 4' within a reduction gear housing 3'. This arrangement creates 
a number of problems. For instance, carbon dust from the brushes of the 
starter motor 6' tends to enter the solenoid 7' via the receptacle 4', 
shortening solenoid life and interfering with the lever action. Also, 
placement of the solenoid 7' outboard of and approximately aligned with 
the motor 6', a configuration designed to minimize the induction of carbon 
dust into the solenoid, necessitates a much longer cantilever lever arm 
from the solenoid 7' to a pinion gear (not shown) than would be otherwise 
required. Finally, the placement of the solenoid 7' and the starter motor 
6' in line with each other necessitates a bulkier, and therefor heavier 
reduction gear housing. 
Accordingly, it is clear that a need exists for an improved starter system 
for existing airplane engines, such as the Continental 0-200 and similar 
engines. Such a starter system should have a reduction gear housing with 
separate receptacles for a starter motor and a solenoid operated pinion 
gear extender, should be lighter than existing starters, and should space 
the starter motor and solenoid on the housing such that a lighter housing 
and a shorter pinion gear actuating lever are required. 
SUMMARY OF THE INVENTION 
In the practice of the present invention, a starter for an internal 
combustion engine includes a basically circular reduction gear housing 
with a pair of angularly spaced and physically separate receptacles for 
accommodating a starter motor and a solenoid pinion gear extender, 
respectively. The pinion gear is adapted to turn with the reduction gear 
and is equipped with a spring which automatically retracts it when 
solenoid electrical power is removed. The starter motor is a modern, high 
efficiency, high RPM motor connected to drive the reduction gear. The 
housing incorporates a number of spoke-like strengthening ribs for added 
strength. The resulting starter system represents a considerable weight 
savings over conventional starter systems while providing greater torque 
and a reliable pinion gear retraction system with no migration of carbon 
dust from the starter motor to the solenoid. The angular displacement of 
the starter motor relative to the solenoid permits the use of a shorter 
lever arm for extending the pinion gear. 
OBJECTS AND ADVANTAGES OF THE INVENTION 
The principle objects and advantages of the present invention include: to 
provide an improved starter system for an aircraft internal combustion 
engine; to provide such a starter system with a reliable pinion gear 
equipped with a cantilevered solenoid driven extender and a spring 
retractor; to provide such a starter system with a modern, high 
efficiency, high RPM, yet light-weight motor; to provide such a system 
with a reduction gear housing which incorporates two angularly spaced, 
physically separate receptacles for the starter motor and the solenoid 
pinion gear extender; to provide such a system in which the housing is 
provided with strengthening ribs for additional strength; to provide such 
a starter system which represents a substantial improvement in performance 
over existing starters, while weighing substantially less; and to provide 
such a starter system which is particularly well suited for its intended 
purpose. 
Other objects and advantages of this invention will become apparent from 
the following description taken in conjunction with the accompanying 
drawings wherein are set forth, by way of illustration and example, 
certain embodiments of this invention. 
The drawings constitute a part of this specification and include exemplary 
embodiments of the present invention and illustrate various objects and 
features thereof.

DETAILED DESCRIPTION OF THE INVENTION 
I. Introduction and Environment 
As required, detailed embodiments of the present invention are disclosed 
herein; however, it is to be understood that the disclosed embodiments are 
merely exemplary of the invention, which may be embodied in various forms. 
Therefore, specific structural and functional details disclosed herein are 
not to be interpreted as limiting, but merely as a basis for the claims 
and as a representative basis for teaching one skilled in the art to 
variously employ the present invention in virtually any appropriately 
detailed structure. 
Certain terminology will be used in the following description for 
convenience in reference only and will not be limiting. For example, the 
words "upwardly", "downwardly", "rightwardly" and "leftwardly" will refer 
to directions in the drawings to which reference is made. The words 
"inwardly" and "outwardly" will refer to directions toward and away from, 
respectively, the geometric center of the embodiment being described and 
designated parts thereof. Said terminology will include the words 
specifically mentioned, derivatives thereof and words of a similar import. 
Referring to the drawings in more detail the reference numeral 1 in FIGS. 1 
and 2 generally designates a starter system in accordance with the present 
invention, shown mounted on the top rear of an aircraft engine 2. As shown 
more clearly in FIGS. 4-6, the system 1 comprises a circular reduction 
gear housing 3, with a pair of angularly spaced and physically separate 
receptacles 4 and 5. A starter motor 6 and a solenoid 7 are mounted within 
the receptacles 4 and 5, respectively. 
II. Starter Motor and Reduction and Pinion Gears 
Referring more particularly to FIG. 6, the gear housing 3 houses a small 
gear wheel 10 which abuts a reduction gear 11 within a central chamber 12. 
A pair of ball bearings 13 and 14 are spaced on either side of the 
reduction gear 11. The bearing 13 can be press fit into a recess 15 in the 
housing 11. The bearings 13 and 14 support a pinion gear shaft 16 which is 
adapted to turn with the reduction gear 11. A coil spring 21 extends 
between the press fit bearing 13 and a spring keeper 22 which surrounds 
the pinion gear shaft 16 near one end 23 thereof. A pinion gear 24 is 
attached to the shaft 16 at the opposite end and a twisted spline 25 is 
formed on the shaft 16 behind the pinion gear 23. In a well-known fashion, 
the twisted spline 25 turns the pinion gear shaft 16 as the shaft 16 is 
engaged, insuring that the gear teeth 26 on the pinion gear 24 will mesh 
with corresponding ring gear teeth 27 on an engine flywheel 28 (FIG. 7). 
The coil spring 21 acts to push the keeper 22 rightwardly in FIG. 6, thus 
insuring that the pinion gear 24 will be retracted away from the flywheel 
28 in the event that electrical power is lost or shut off from the 
solenoid 7 while the pinion gear 24 and the flywheel 28 are engaged. The 
starter motor 6 spins a shaft 29 to which is attached a gear 30, which 
drives the reduction gear 11. A pair of ball bearings, of which only 
bearing 31 is shown, surround and support the motor shaft 29 at either 
end. 
III. Solenoid and Cantilever Lever Arm and Spring 
Referring to FIGS. 8 and 9, the action of the solenoid 7 will now be 
described. The solenoid 7 is both a linear actuator for the pinion gear 
and a switch for the starter motor. The solenoid 7 comprises a movable 
plunger 33, shown in phantom lines. A blade terminal 34 is internally 
connected to terminal 35 via a coil (not shown) which energizes the 
plunger 33. The application of electrical power to terminal 35 thus 
energizes the blade terminal 34 which causes the plunger 33 to be 
retracted. This causes an armature-connected rod 41 to be retracted as 
well. The rod 41 has an elongate bore 42 near the exposed end thereof, 
through which one end 44 of a cantilever arm 43 is inserted. The 
cantilever arm 43 comprises a raised pivot surface 45 on one side thereof, 
which pivot surface 45 engages a pivot recess 46 in the housing 3. A 
spring engaging recess 51 on the opposite side of the cantilever arm 43 
engages a center portion 52 of a spirally wound spring 53. Two ends of the 
spring 53, of which only one end 54 is shown in FIGS. 8 and 9, are 
received within a corresponding pair of bores 55, of which one is shown in 
phantom lines in FIG. 9. An opposite end 61 of the cantilever arm 43 
extends into a recess 62 in the housing 3 and is positioned to engage the 
top end 23 of the pinion shaft 16. The cantilever arm 43 extends from the 
solenoid rod 41 to the pinion gear shaft end 23 through an elongate 
chamber 63 in the housing 3. 
Once the plunger 33 is fully retracted, it also urges a washer (not shown) 
into shorting relationship between terminals 35 and 36. Terminal 36 is 
permanently connected to a positive lead 37 of the starter motor 6. Thus, 
the solenoid 7 also acts as a switch for the motor 6, only switching on 
the motor 6 after the pinion gear 24 is fully engaged with the flywheel 
28. 
To provide additional strength to the housing 3 with minimal additional 
weight, the housing 3 is constructed with a plurality of spoke-like ribs 
64 extending from a center portion 65 of the housing 3 to a like plurality 
of attachment appendages 66. 
IV. Operation 
The operation of the starter system will now be described with reference to 
FIGS. 1, 2 and 4-9. When the engine 2 is to be started, a starter switch 
(not shown), which can be integrated into a magneto switch or can 
constitute a separate switch, is turned on, supplying power to the 
solenoid terminal 35. The solenoid 7 retracts the plunger 33 against the 
action of the spring 53, which causes the cantilever arm 43 to pivot about 
the recess 51 in the housing 3. The pivoting cantilever arm 43 thus urges 
the pinion gear shaft 16 to the left in FIGS. 7-9, pushing the turning 
pinion gear 24 into engagement with the flywheel 28. As the pinion gear 
shaft 16 is extended, the twisted spline 25 insures that the gear teeth 26 
on the pinion gear 24 will mesh with the ring gear teeth 27 on the 
flywheel 28. The solenoid then internally shorts contacts 34 and 35 to 
provide power to the starter motor terminal 37. The starter motor 6 spins 
the shaft 29 and gear 30 and thus the reduction gear 11 which turns the 
pinion gear shaft 16. Once the engine 2 has started, the starter switch is 
released and the solenoid 7 extends the rod 41. This action, coupled with 
the spring action of the spring 53, causes the cantilever arm 43 to pivot 
in the opposite direction, and permits the spring 21 to retract the pinion 
gear shaft 16, thus retracting the pinion gear 24 from engagement with the 
flywheel ring gear 26. At the same time, power is removed from the starter 
terminal 37 by opening the connection between solenoid terminals 35 and 
36. 
The resulting starter system 1 is an improved, lighter weight, and more 
reliable starter than was previously available for the Continental 0-200 
and similar engines. A number of innovative features are incorporated, 
including separate housing receptacles for the starter motor 6 and the 
solenoid 7 within a generally circular housing 3, the resulting shortened 
cantilever arm 43, and the use of strengthening ribs 64 for added strength 
with a minimal weight penalty. 
It is to be understood that while certain forms of the present invention 
have been illustrated and described herein, it is not to be limited to the 
specific forms or arrangement of parts described and shown.