Abrading – Machine – Rotary tool
Reexamination Certificate
2001-07-24
2002-06-25
Rose, Robert A. (Department: 3723)
Abrading
Machine
Rotary tool
C451S359000
Reexamination Certificate
active
06409584
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a pneumatic tool and more particularly, to a speed adjusting device of a pneumatic grinder and which stabilizes the rotational speed of the grinder and makes sure that the speed will not be fluctuated by changes of the pressure, and the speed adjusting device will not malfunctioned
BACKGROUND OF THE INVENTION
A conventional pneumatic grinding tool such as grinders or polishers is designated by reference
10
in
FIG. 1. A
rotator
14
is installed in a cylinder
13
in a casing
12
and the rotator
14
has a grinding plate
16
on the axle
15
thereof. A speed adjusting device
20
is installed in the chamber
17
in the casing
12
and the speed adjusting device
20
is co-rotated with the rotator
14
. After the high pressure air is introduced in the pneumatic tool, the air pressure enters in the chamber
17
via an inlet
18
and then enters in the cylinder
13
via several holes
19
to drive the rotator
14
. By the rotation of the rotator
14
to grind objects by the grinding plate
16
.
Due to many factors affect the air pressure so that the air pressure for the pneumatic tool is not constant. When the air pressure raised, the rotational speed of the rotator
14
increases. On the contrary, the speed reduces when the air pressure drops. Because the grinding plate
16
has a pre-determined speed limit, it could be broken when the speed is higher than the pre-determined speed limit. Therefore, a speed adjusting device
20
is required to prevent the situation mentioned above.
As shown in
FIGS. 2
,
3
and
4
, a conventional speed adjusting device
20
has an axle
22
and an adjusting rod
24
which is a straight rod and fixed to the axle
22
and rotatable with the axle
22
. A stop
26
is slidably mounted to an end of the adjusting rod
24
. The stop
26
is biased by a spring
27
. Two adjusting members
28
are respectively engaged with the recesses
241
in two ends of the adjusting rod
24
. Each adjusting member
28
has a tip end
281
at its pivot able end. The axle
22
is fixed to the rotator
14
at its front end and is rotatable with the rotator. The stop
26
is located in front of the inlet
18
as shown in FIG.
1
.
When the rotator
14
is not rotated, the stop
26
is pushed by the spring
27
and maintained to slide forward, and the two adjusting members
28
are not open outward as shown in FIG.
2
. When the rotator
14
is rotated, the speed adjusting device
20
is rotated and the two adjusting members
28
are moved outward because of the centrifugal force as shown in FIG.
4
. The stop
26
is pushed backward by the tip end
281
of the speed adjusting members
28
so that the distance between the stop
26
and the inlet
18
is changed. The outward movements of the two adjusting members
28
are increased when the air pressure and the speed of the rotator
14
are high. This will move the stop
26
toward the inlet
18
to reduce the volume of the air coming in to prevent the rotator
14
from over-speed.
There are some inherent shortcomings:
1. As shown in
FIG. 3
, the speed adjusting device
20
is an elongated shape so that there are cut points “b” on the outside of the two longitudinal sides “A”. The cut points “b” generate turbulent air flow and make the speed adjusting device to be in an idle status which makes the tool shaking.
2. In the situation in
FIG. 4
, the tip end
281
of the adjusting members
28
pushes the stop
26
due to the centrifugal force, and the direction of the stop
26
is parallel with the direction of the air flow. The inlet air directly affects the stop
26
so that the adjusting members
28
bear the inlet pressure. The tip end
281
is then worn out and becomes too short to move the stop
26
such that the function of adjusting the speed of the rotator
14
is loosened. The adjusting members
28
may also shift abnormally as shown in FIG.
5
and jammed with the stop
26
. This could mis-function the tool.
3. The adjusting rod
24
is a long rod and the two recesses
241
on two ends of the rod
24
makes the adjusting rod
24
to be a hollow rod which tends to be deformed when the rod is proceeded with heat treatment. The two ends of the rod are symmetrically deformed and result shaking when the rod is rotated. Similarly, the stop
26
is a thin member which is deformed after being heat-treated so that the stop
26
could have interference friction with the axle
22
.
4. The speed adjusting device
20
bears the air pressure directly so that the parts of the device tend to be worn out by the air pressure.
5. Because the stop
26
is affected by the high pressure air flow, it is difficult to move back when the pressure increased and the adjusting member
28
are difficult to open outward. When the inlet pressure is higher than 90 psi as shown in
FIG. 6
, the function of the speed adjusting device reduced and the speed of the rotator increases so that the conventional speed adjusting device cannot control the speed of the rotator.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a speed adjusting device for a pneumatic grinding tool and which effectively controls the speed of the rotator of the pneumatic grinding tool.
Another object of the present invention provides a speed adjusting device for a pneumatic grinding tool wherein the pressure that the speed adjusting device bears can be reduced.
The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention.
REFERENCES:
patent: 3930764 (1976-01-01), Curtiss
patent: 4729436 (1988-03-01), Amador et al.
patent: 0779036 (1980-11-01), None
Gison Machinery Co., Ltd.
Rose Robert A.
Troxell Law Office PLLC
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