Patent Application
20050263912
The present invention relates, generally, to smaller, internal combustion engines that have carburetors, and particularly relates to carburetors that are adjustable, e.g., via rotational adjustment of at least one flow metering valve.
A portable power tool, such as a chain saw, a hedge trimmer, an edger, or a blower, is often powered by a gasoline engine. Typically, a carburetor is associated with such a smaller engine.
A small engine carburetor has one or more adjustable components, often referred to as needle valves, which control fuel flow. To calibrate fuel flow, each valve is rotationally adjusted to axially extend or retract a valve control surface within a fuel passage in the carburetor until optimum fuel flow through the passage is achieved. Adjustment within the carburetor is commonly done by “metering” during no load or idle engine operation by a first “idle” needle valve and during part or full load operation by a second “main” needle valve. Pre-calibration of the carburetor on a flow test bench may be performed prior to being assembled to an engine. After assembly of the carburetor to an engine, it is customary to adjust the metering valves, if needed, to fine tune fuel flow to the actual demand of the operating engine. Such calibration is first done at an assembly facility, and may subsequently be done by a qualified technician.
Recently, in response to federal and state “clean air” regulations, there has developed an increasing need to prevent gross misadjustment, especially by non-qualified people. Such prevention of gross misadjustment is directed to the prevention of excessive emission of carbon monoxide and unburned hydrocarbons from an internal combustion engine. Thus, subsequent over adjustment of fuel flow is to be prevented/discouraged.
In accordance with one aspect, the present invention provides a device for a power tool that includes an internal combustion engine and a carburetor for supplying an air and fuel mixture to the engine. The carburetor includes at least one externally adjustable component. The device includes an air filter arrangement for in-taking air, filtering the air, and directing the filtered air to the carburetor. The arrangement includes a housing. The device includes a tamper resisting portion extending from the air filter arrangement housing and extending adjacent to the location of the at least one adjustable component. The tamper resisting portion includes a segment that permits access to the at least one adjustable component along a first direction and limits access to the at least one adjustable component off of the first direction.
In accordance with another aspect, the present invention provides a device for a power tool that includes an internal combustion engine and a carburetor for supplying an air and fuel mixture to the engine. The carburetor includes at least one externally adjustable component. The device includes a housing portion of an air filter arrangement that is for in-taking air, filtering the air, and directing the filtered air to the carburetor. The housing portion is configured to at least partially enclose an air filter of the air filter arrangement. A tamper-resisting portion extends from the housing portion and extends adjacent to the location of the at least one adjustable component. The tamper resisting portion includes a segment that permits access to the at least one adjustable component along a first direction and limits access to the at least one adjustable component off of the first direction.
The foregoing and other features and advantages of the present invention will be apparent from the description below with reference to the drawings wherein:
An example chain saw 10 that has an example air filter arrangement 12 for helping to prevent carburetor tampering in accordance with the present invention is shown in
In general, the structures at the area of the invention include an ignition system switch lever 18, a choke system mechanism lever 20, a carburetor 22 (schematically shown in
The levers 18 and 20 are provided to enable the operator of the chain saw 10 to readily manipulate an ignition switch and a choke mechanism, respectively, and both levers are positioned near a handle 26 (see
The air filter arrangement 12 is best described with reference to
The filter housing base 34 includes a base floor 40 and a perimeter wall 42. The base floor 40 includes ports 46 and 48 that are in fluid communication with inlet ports in the carburetor 22 (see
The base floor 40 also is provided with several openings 52 into which threaded portions of fasteners 59 extend. The fasteners 59 are screwed into complementary threaded holes (not visible) in the carburetor 22, and this arrangement constitutes the means by which the filter housing base 34 is attached to the carburetor.
The perimeter wall 42 is integral with the base floor 40 and extends, generally, perpendicularly from the perimeter of the housing base floor in the direction of the cover 36. As is best seen in
The perimeter wall 42 includes an anterior section 56, a posterior section 58, a first lateral section 60, and a second lateral section 62. The first lateral section 60 joins one terminus of the anterior section 56 to one terminus of the posterior section 58, and the second lateral section 62 joins the other terminus of the anterior section to the other terminus of the posterior section. Consequently, when installed in the chain saw 10, the anterior section 56 is nearest the front of the chain saw, the posterior section 58 is nearest the rear of the chain saw and the first and second lateral sections 60, 62 are disposed toward opposite sides of the chain saw.
In the embodiment shown in the drawings, a portion 64 of the first lateral section 60 of the perimeter wall 42 that is adjacent the posterior section 58 of the perimeter wall is recessed inwardly toward the housing base interior. Integral with the first lateral section 60 of the perimeter wall 42 is an augmentation, or extension, 66 that extends in a direction perpendicular to the extent of the base floor 40. Further, the augmentation 66 and the recessed portion 64 of the first lateral section of the housing base perimeter wall are located in substantially the same plane as can best be seen in
The air filter arrangement 12 additionally includes first and second opposed support legs (only one visible, 70) that are positioned on the housing base 34. The first support leg 70, as shown in
In accordance with the present invention, the shown example has a pair of openings 78 that extend through the first support leg 70 and the augmentation 66 with which the leg is integral. The openings 78 are aligned with carburetor adjustment needles 80 and, thus, provide access holes to the needles for the purpose of adjusting the carburetor. However, it is to be appreciated that the access is somewhat limited. Specifically, access is only permitted along the axis of each opening 78 (i.e., a first direction). As such, the first support leg 70 with the openings 78 inhibits access to each adjustment needle 80 along directions other than the respective axial direction (i.e., off of the first direction). As such, a level of difficulty is provided against an unauthorized person that tries to engage the adjustment needles with some other type of tool, such as pliers. Also, in one example, each of the adjustment needles 80 includes an engagement portion (i.e., a head, visible in
It is to be appreciated that the filter housing 30 may be otherwise utilized, configured, etc., without effect to provision of the present invention. Within the shown example, the filter housing base 34 also includes a mounting element 84 on which the ignition system switch lever 18 is mounted. In the shown example, the ignition system switch lever is mounted for pivotal movement. As such, the mounting element is a cylindrical projection that mates with an opening on the ignition system switch lever 18. In the shown example, the mounting element 84 is located on the recessed portion 64 of the first lateral section 60 of the perimeter wall 42. Specifically, the mounting element 84 is integral with the outside surface of the first lateral section 60 of the perimeter wall 42. A hole may extend into the mounting element 84 in order to receive a member (e.g., a screw accompanied by a washer) that retains the ignition system switch lever 18 on the mounting element.
Further within the shown example, to assist in preventing the ignition system switch lever 18 from proceeding in its pivotal movement beyond an “ON” position, a stop lug 86 is provided on the filter housing base 34 at a location adjacent to the mounting element 84. The filter housing base 34 also includes a guide lug 88 at a location that is adjacent to the stop lug 86 for providing a guiding surface for the choke system mechanism lever 20. The person of ordinary skill will appreciate that the choke system mechanism lever 20 interacts with addition structure (e.g., a valve lever that has an arm, as shown in
Also included on the filter housing is a pair of positioning elements 90 located, generally, adjacent the mounting element 84. In the shown example, the positioning elements are integral with the augmentation 66 and are located forwardly of the mounting element 84. The positioning elements 90 provide a mounting location for an S-shaped leaf spring 92 of an ignition circuit (partially shown, see electrical leads within
While an example embodiment of the invention has been shown and described herein, it is to be understood that the invention is not so limited but covers and includes any and all modifications and variations that are encompassed by the following claims.
