Air cooled engine screen and method

An air-cooled-engine screen (1) is sized and shaped to cover airflow entrances (2) to engines of engine-powered equipment and tools such as chain saws (4). Strands of the screen are designedly strong, fine and spaced apart to allow passage of sufficient air between them to cool the engines while preventing passage of fine particles and/or fibers that are gooey, gummy, resinous or sappy wet and would solidify or gum onto cooling fins and nearby engine parts such as spark-plug connections and cooling-air outlets when being used. Cleaning is facilitated by minimizing screen-surface obstruction. Select attachment means (8, 9, 10, 11 12) are provided for original equipment, for after-market add-on and for various long-term or temporary use conditions.

BACKGROUND OF THE INVENTION 
1. Field of the Invention. 
This invention relates to cooling of engines for powered equipment and 
tools such as chain saws and in particular to screens to prevent entry of 
gooey sawdust from palm trees and other sources from obstructing flow of 
cooling air over cooling fins of air-cooled engines on chain-saw engines 
and other powered equipment and tools. 
2. Relation To Prior Art 
Conventionally, chain-saw housings and housings for engines of other 
powered equipment have variously louvered or slatted covers over air 
entrances to cooling fins. Their purpose is to prevent entry of obstacles 
such as leaves and other debris from clogging cooling-air channels. 
Louvers, slats and fins, however, are inadequate protection against entry 
of fine particles that are gooey, gummy, resinous or sappy wet from 
entering and solidifying or gumming on cooling fins. Sawdust from trimming 
fronds of only a few palm-trees clogs up cooling fins of a chain saw. More 
time is required to keep a chain saw clean than to cut palm-tree fronds 
with it. One solution would be to use electrically powered equipment, were 
it not for distances from electrical outlets and difficulty of access to 
them by workers who trim palm trees and use other powered equipment. 
Improvement of entrances to air-cooled-engine equipment is needed to 
overcome this problem. 
SUMMARY OF THE INVENTION 
In light of need for improvement of cooling-air entrances to chain-saw 
engines and to engines of other powered equipment and tools, objects of 
this invention are to provide an air-cooled-engine screen which: 
Prevents entry of fine particles that are gooey, gummy, resinous or sappy 
wet from entering and solidifying or gumming onto cooling fins; 
Does not collect fine and gooey substances; 
Does not obstruct flow of cooling air; 
Can be wiped clean easily and conveniently whenever necessary; Is resistant 
to breakage and puncture; 
Can be attached easily as after-market add-on to existing engine-powered 
chain saws and other air-cooled-engine equipment; Can be made optionally 
to be removable and replaceable quickly and conveniently; and 
Can be produced inexpensively with original equipment. 
This invention accomplishes these and other objectives with an 
air-cooled-engine screen that is sized and shaped to cover airflow 
entrances to engines of engine-powered equipment and tools such as chain 
saws. Strands of the screen are designedly strong, fine and spaced apart 
to allow passage of sufficient air between them to cool the engines while 
preventing passage of fine particles and/or fibers that are gooey, gummy, 
resinous or sappy wet and would solidify or gum onto cooling fins and 
nearby engine parts such as spark-plug connections and cooling-air outlets 
when being used. Cleaning is facilitated by minimizing screen-surface 
obstruction. Select attachment means are provided for original equipment, 
for after-market add-on and for various long-term or temporary use 
conditions.

DESCRIPTION OF PREFERRED EMBODIMENT 
Reference is made first to FIGS. 1-4 in the drawings. At least one screen 1 
is sized and shaped to cover airflow entrances 2 to an air-cooled engine 
in an engine enclosure 3 for an engine-powered item such as a chain saw 4. 
Strands of the screen 1 have tensile strength, toughness, spaced-apart 
distances and strand-crossing distances to allow required airflow through 
the screen 1 while preventing passage of engine-gumming material through 
the screen 1. An example of screening material found to be suitable for 
use in cutting palm-tree fronds has plastic coated fiberglass strands and 
approximately sixteen openings per inch. 
Referring to FIGS. 1-4, 6, and 10-14, the screen 1 can be on an outside 
surface 5 of entrance material 6 as shown in FIGS. 1, 2, 6, 10 and 12-14 
or on an inside surface 7 of entrance material 6 as shown in FIGS. 3, 4, 9 
and 11. 
Referring to FIGS. 1-14, means for attachment of the screen to the 
enclosure 3 is preferably by bonding as depicted in FIGS. 1-4 and 10-11. 
Bonding can be accomplished with a high-bond adhesive 8 such as Crazy 
Glue.RTM. or various other types of known bonding agents and processes as 
illustrated in FIGS. 1-4 and 10-11. Alternative to high-bond adhesive 8 as 
means of attachment can be threaded fasteners 9 shown in FIGS. 6 and 9, 
two-pronged hooks 10 shown in FIG. 12, single-pronged hooks 11 shown in 
FIG. 13 and VELCRO.RTM. 12 shown in FIG. 14. For use of VELCRO.RTM. or 
other resilient-hook attachments, a first layer can be affixed to the 
screen 1 and a second layer can be attached to the entrance material 6 
and/or the engine enclosure 3 surrounding the airflow entrances 2. 
Screen-attachment apertures 13 in the screen 1 as shown in FIGS. 5-7 or in 
a screen border 14 as shown in FIG. 8 can be provided for insertion and 
containment of the threaded fasteners 9. 
The chain saw 4 with a chain blade 15 depicted in FIGS. 1-4 and a hedge 
trimmer 16 with a vibrator blade 17 depicted in FIGS. 6 and 9 are two of 
the more common powered items for which this invention is most 
advantageous. Other powered items needing this invention are foreseeable. 
Typically, they are hand-held items that require light weight and low cost 
of an air-cooled, two-stroke engine instead of higher efficiency and 
higher cost of other known engines. 
Some chain saws 4 and some hedge trimmers 16 have airflow entrances 2 in a 
generally elliptical patters as depicted in FIGS. 1 and 4. Others are more 
rectangular as depicted in FIGS. 6 and 9. The screens 1 for either can be 
shaped and formed accordingly as indicated by the rectangular form of 
screen 1 in FIG. 5 and the generally elliptical form of screen 1 in FIGS. 
7-8. 
Some chain saws 4 and fewer hedge trimmers 16 have airflow entrances 2 on 
top near a handle connection 18 or a surge pump. Air vents 19 on backs of 
engine enclosures 3 usually are not entrances but are exits which do not 
require covering. This invention is intended to cover all airflow 
entrances 2, no matter where they are positioned and regardless of how 
many there are. Covering groupings of airflow entrances 2 is preferable to 
covering single airflow entrances 2. 
Installing the screen 1 over the airflow entrances 2 on the engine 
enclosure 3 can be accomplished during manufacture or as after-market 
add-ons afterwards. The same installation factors with appropriate 
procedural adaptations apply for both. Inside-surface positioning may be 
preferable during manufacture for some manufacturers in order to achieve a 
desired appearance and to provide greater protection of the screen 1 
during use conditions. For inside-surface installation, it is important 
that the entrance material 6 be as thin as possible between the outside 
surface 5 and the inside surface 7 as described in relation to FIG. 11 in 
order to minimize debris crevices and to facilitate cleaning of the screen 
1. Also for inside-surface installation, arcuate outside surfaces of 
entrance material 6 is preferable for eliminating crevices. After-market 
add on with high-bond adhesive 8 is preferable for ease of cleaning and 
eliminating debris crevices. A cutaway section in the entrance material 6 
in FIG. 4 depicts inside-surface 7 positioning on preferably thin entrance 
material 6. 
As illustrated in FIGS. 1-4, 6 and 9, a patterned positioning of airflow 
entrances 2 on most engine enclosures 3 surrounds a plate for a starter 
wheel that is accessed by a starter line on a pull-start handle 20 for 
most conventional powered items. A new and useful air-cooled-engine screen 
having been described, all such foreseeable modifications, adaptations, 
substitutions of equivalents, mathematical possibilities of combinations 
of parts, pluralities of parts, applications and forms thereof as 
described by the following claims and not precluded by prior art are 
included in this invention.