Note: Descriptions are shown in the official language in which they were submitted.
CA 02298865 2000-02-15
FIELD OF THE INVENTION
s The present invention relates to hand held air pressure operated fastener
driving tools, and more particularly to a tool which is held in one hand by a
handle secured
to the tool while applying an impact blow on an anvil of the tool by means of
a hammer held
by the other hand of the operator.
i o BACKGROUND OF THE INVENTION
United States patent No. 3,542,273 dated November 24, 1970, inventor
Granville R. Hedrick, discloses a nail driving device especially used for
driving nails into a
wooden flooring by means of a source of compressed air. The device of this
patent is
alternately operated by an external impact blow accomplished on the device
anvil while the
~ s operator's other hand holds a handle of the device; or by squeezing a
trigger accessible to the
hand holding the handle. The device in accordance with this prior patent thus
has a trigger
initiated operating system, which is used only as an alternative to the impact
blow initiating
system. One main disadvantage of the Hedrick nailer is that it does not
provide any reliable
security means for preventing the nails from being accidentally expelled from
the nailer.
2o United States patent No. 4,907,730 in 1990, inventor Jean-Paul Dion, shows
a pneumatic nailer which includes a feeler disc which must be applied against
the ground for
CA 02298865 2000-02-15
the nail driving operation to occur. Indeed, when the feeler disc is applied
against the
ground, a needle valve located inside the nailer main body closes an inner
channel for
allowing air to travel between chambers inside the nailer when the hammer is
impacted on
the anvil, and consequently for allowing the nail to be driven through the
floor boards. The
s Dion patent however does not include a reliable security device for
preventing the nails
from being accidentally expelled, since the feeler disc will be activated to
allow nail
expulsion whenever the nailer rests or abuts on a surface with its lower
surface.
OBJECTS OF THE INVENTION
It is therefore the main object of the present invention to provide fastener
driving tool including a safety device for the impact blow initiating system
such that it
disables the operation of the impact blow initiating system unless a trigger
on the handle is
squeezed during the hammer blow.
Another object of the present invention is to provide a tool of the character
i s described in which a trigger is squeezed during the fastener driving
operation such that the
operator's one hand must firmly hold the tool handle during the hammer blow
and thus a
possibility of the tool accomplishing an unintended displacement is decreased.
Another object of the present invention is to provide a tool of the character
described using the same source of fluid pressure to operate the trigger
initiated safety
2 o system as the source used to drive the main piston of the tool.
2
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SUMMARY OF THE INVENTION
The present invention relates to an air pressure actuated fastener driving
tool
comprising;
- a body having an upper end and a lower end;
- a work-piece engaging base secured to the lower end of said body and
defining a
passage for receiving a leading fastener from a supply of fasteners and for
guiding said
leading fastener into a work-piece underlying said base;
- a handle fixed relative to said body;
- a manually operated trigger operatively mounted to said handle so as to be
movable
between a rest position and an operating position;
- an air reservoir carried by said body with an inlet for connection to a
supply of
compressed air;
- an air operated cylinder and piston unit in said body, comprising a piston
movable in
a cylinder from an upper rest position to a lower fastener-driving position;
- a fastener driver secured to said piston and extending through said lower
end of said
body and into said base passage in said piston lower position for engaging and
driving said
leading fastener into the work-piece during downward operative stroke of said
piston from
its said upper position;
2 0 - a valve in said body including a valve seat carried by said body between
said air
reservoir and the cylinder of said unit and a valve member movable between a
closed
position seated on said valve seat and closing the communication between said
air reservoir
3
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and said cylinder, and an opened position communicating said air reservoir
with said
cylinder to cause said operative stroke of said piston;
- an impact blow receiving anvil protruding from and movably carried by said
upper
end of said body for movement between an upper and a lower position;
s - a lost motion system between said valve member and said anvil to prevent
said valve
member to move downwardly from said upper closed position when said anvil is
moved to
its lower position; and a lost motion disabling system connecting said trigger
to and
disabling said lost motion system when said trigger is in said operating
position whereby
said fastener driver can only drive said leading fastener if said trigger is
moved into said
i o operating position when a hammer blow is imparted on said anvil and moves
said anvil to
its lower position.
Preferably, said lost motion disabling system is pneumatically operated from
the supply of compressed air in said reservoir.
1 5 Preferably, said tool further comprises:
- a sealed lost motion and lost motion disabling chamber formed in said main;
- a poppet member integrally linked to said valve member and having an
intermediate
portion in fluid-tight relationship with said chamber;
- an actuator, integrally attached to said anvil and in fluid-tight
relationship with said
2 o chamber and spaced from said poppet member intermediate portion, whereby
said lost
motion and lost motion disabling chamber is formed between said poppet member
4
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intermediate portion and said actuator;
- an air exhaust port connecting said chamber to the atmosphere when said
trigger is
in said rest position; and
- another valve connecting said chamber to said air reservoir and blocking
said
exhaust port when said trigger is in said operating position;
wherein when said trigger is in said rest position, a blow dealt on said anvil
will move said
actuator down into said chamber although short of said poppet intermediate
portion, said
chamber thus acting as said lost motion system since the air therein is
allowed to exhaust
through said exhaust port; and wherein when said trigger is in said operating
position, said
i o chamber communicates with said air reservoir for filling said chamber with
compressed air,
said chamber then acting as a lost motion disabling system since an air
cushion is created
between said actuator and said poppet member intermediate portion to transmit
the impact
of a blow dealt on said anvil from said actuator to said poppet member
intermediate portion,
and consequently to said valve member to move same into said opened position.
Preferably, said another valve is a three-way valve including a plunger
connected to said trigger and a valve body secured to said handle with an
inlet port
connected to said air reservoir, said air exhaust port and a third port
connected to said sealed
chamber, said another valve member connecting said air reservoir to said
sealed air space
and said sealed air space to atmospheric air through said exhaust port in the
operating and
2 o rest position of said trigger respectively.
Preferably, said tool further includes a lateral arm secured to said body and
5
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to said handle intermediate the same, said air reservoir formed in said arm.
Preferably, said handle is generally parallel to said base and higher than
said
anvil.
Preferably, said tool includes a lateral arm secured to said body and to said
handle intermediate the same, said air reservoir formed in said arm, the
handle generally
parallel to said base and higher than said anvil, and wherein said three-way
valve is mounted
close to said trigger and further including an air passage extending through
said arm
separate from said air reservoir and communicating said sealed air space to
said third port
through an air conduit made in said body.
i o Preferably, said tool further including a pneumatic return system to
return
said piston and said valve member to their upper and closed position
respectively, upon
completion of said operative stroke of said piston.
Preferably, said poppet member is tubular and carries said valve member at a
lower end thereof, said valve member also being tubular and having a generally
downwardly
~ 5 diverging conical shape and being provided with an annular groove therein,
said groove
having a truncated circular cross-section with converging outer edges, said
groove being
fitted with a resilient O-ring for sealing engagement thereof against said
seat in said closed
position of said valve member.
Preferably, said tool body includes a lower chamber in which said piston is
2o movable between said upper and lower positions, said piston upwardly
extending into said
tubular poppet member and protruding under said valve member, said piston
carrying a
6
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slider disc in fluid-tight relationship with said lower chamber and guiding
said piston in its
movements between said upper and lower position, said piston including a
tubular stem
having an inner channel linking said lower chamber above said slider disc to
the
atmospheric air; and wherein an annular channel closed at its lower end is
defined between
s said piston and said tubular poppet member surrounding said piston, said
piston being
provided at its upper end with a short sleeve fixedly attached to said piston
and sealingly
slidably engaging said poppet member, said poppet member annular chamber
having
channels therein linking same to said air reservoir, whereby compressed air is
continuously
present in said annular poppet member chamber for continuously biasing said
piston
i o towards said upper position by applying an upwardly oriented pressure on
said sleeve
member.
Preferably, said tubular piston opens into an upper chamber formed in said
body and including an exhaust channel to atmospheric pressure, and said body
further
including a dampening chamber located above said upper chamber in which said
piston
moving upwardly will be decelerated before reaching its upper position.
Preferably, said trigger protrudes from said handle in said rest position of
said trigger, and wherein said trigger must be squeezed against said handle to
reach said
operating position.
z o DESCRIPTION OF THE DRAWINGS
In the annexed drawings:
CA 02298865 2000-02-15
Figure 1 is a vertical, sectional elevation of a pneumatic fastener driving
tool
according to the invention, in a rest position;
Figure 2 is an enlarged sectional view of the upper handle portion of the tool
of figure 1, more particularly showing the three-way valve and the trigger in
a rest position;
Figure 3 is similar to figure 2, but with the trigger being shown in a
squeezed
operating position;
Figure 4 is an enlarged sectional view of the three-way valve of figure 2;
Figure 5 is an enlarged sectional view of the three-way valve of figure 3.
Figure 6 is an inclined sectional view, at a larger scale, of the nail-driving
mechanism of the tool of figure 1, showing more particularly the upper and
intermediate
portions of the tool, with the valve member being shown in a closed position
and with the
piston being shown in an upper limit position;
Figure 7 is a view similar to figure 6, but showing a longer portion of the
tool main body, exclusive of the base portion, with the valve member being
shown in an
~ 5 opened position and with the piston being shown in a lower nail-driving
position;
Figure 8 is a view similar to figure 7, but with the valve member in a closed
position and with the piston being shown in an intermediate position; and
Figure 9 is an enlarged front elevation of the poppet member according to
the invention.
8
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1 shows a pneumatic fastener driving tool 10 according to the present
invention. Tool 10 comprises a hollow main body 12 having an upper end 12a and
a lower
end 12b and a work-piece engaging base 14 of known construction secured to the
lower end
s 12b of main body 12. Base 14 includes a passage 16 for receiving a leading
fastener (not
shown) from a supply of spring-loaded fasteners (not shown) fed from a
fastener magazine
18 of conventional construction. Passage 16 will also guide the leading
fastener as known in
the art into a work-piece underlying the base, e.g. through a floorboard, when
the leading
fastener is expelled as described hereinafter.
Tool 10 further includes a handle portion 19 integrally attached to and
forming part of body 12, handle portion 19 forming a lateral arm integrally
protruding from
main body 12 and including an inner air reservoir 20 which is in fluid
connection with an
intermediate portion of hollow main body 12, as detailed hereinafter. Handle
portion 19
integrally carries a handle 22 at its upper end. Reservoir portion 19 has an
inlet 24 for fluid
connection of reservoir 20 to a supply of compressed air. Thus, during use of
tool 10,
reservoir 20 is filled with compressed air. Reservoir 20 comprises inner
reinforcing ribs 26,
28, which are aerodynamically curved to favour air flow towards main body 12
in reservoir
20.
As shown in figures 1 and 2, handle portion 19 further comprises a U-shaped
2 o channel generally refer ed to with numeral 30, comprising three sections
30a, 30b, 30e.
First channel section 30a is in fluid communication with reservoir 20, and
leads to a three-
9
CA 02298865 2000-02-15
way valve chamber 32 which includes a three-way valve 34 of known
construction,
selectively activated by a trigger 36 pivotally attached under handle 22.
Three-way valve 34 is of known construction, and works generally as
follows. As shown in figures 4 and 5, three-way valve 34 comprises a main body
42 having
a lower passage 41, an intermediate chamber 44 and an upper passage 46. An
inlet port 41a
connects lower passage 41, through first channel section 30a, to air reservoir
20; an exhaust
port 46a connects upper passage 46 to the ambient air outside of tool 10; and
a third lateral
port in the form of several peripherally spaced-apart radial apertures 44a in
the valve body
42, connects intermediate chamber 44 to second and third channel sections 30b,
30c. A
i o plunger 38 is slidable inside lower passage 41 between a lower and an
upper position, with a
spring 39 continuously biasing plunger 38 towards its upper limit position
shown in figure
4. Plunger 38 comprises a lower annular shoulder 40 which serves as a seat for
spring 39
and which sealingly blocks lower passage 41 in the plunger upper limit
position. Air
passage through passage 41 is allowed when plunger 38 is in its lower limit
position.
i 5 A sleeve 48 is slidable in the upper passage 46 between an upper limit
position (figure 4) in which ambient air at the atmospheric pressure may pass
through radial
holes 50 in sleeve 48 to the intermediate chamber 44, and a lower limit
position (figure 5) in
which radial holes 50 register with and are sealingly blocked by the wall of
the upper
passage 46. A spring 49 continuously biases sleeve 48 towards its upper limit
position.
z o Valve 34 may be connected to the ambient air at atmospheric pressure since
exhaust port
46a is adjacent to and in fluid communication with a cavity 51 formed around
trigger 36 in
io
~
CA 02298865 2000-02-15
handle 22. Trigger 36 abuts against the upper tip portion 48a of sleeve 48 at
all times.
Thus, in a resting position of trigger 36 shown in figures 2 and 4, ambient
air
at atmospheric pressure may enter through three-way valve 34 and engage the
second and
third sections 30b, 30c of channel 30, while annular shoulder 40 blocks air
output from air
reservoir 20 through three-way valve 34. However, when trigger 36 is manually
forcibly
pivoted in its operating position in abutment over the sleeve tip portion 48a,
it downwardly
forces sleeve 48 against the bias of springs 39, 49 into its lower limit
position, sleeve 48
then engaging with its lower end 48b plunger 38 which is also consequently
lowered into its
lower limit position, thus allowing fluid connection through three-way valve
34 between
1 o first channel section 30a and second channel section 30b while blocking
ambient air from
flowing through three-way valve 34.
As shown in figures 6-8, the fastener driving tool main body 12 comprises
three distinct inner chambers, namely a lower chamber 52, an intermediate
chamber 54 and
an upper chamber 56. A first annular seat 58 integrally formed in the main
body inner wall
1 s separates the lower and intermediate chambers 52 and 54, while a second
annular seat 60
integrally formed in the main body inner wall separates the intermediate and
upper
chambers 54 and 56. A large opening 62 allows continuous fluid exchange
between air
reservoir 20 and intermediate chamber 54.
Main body 12 is fitted at its upper end 12a with a fixedly attached cover 63
2 o from which protrudes a slidable anvil member 64 through a top chimney
opening 65, anvil
member 64 being covered with a soft cap 66, as known in the art. Anvil 64 is
diametrally
11
~
CA 02298865 2000-02-15
slightly spaced from the inner wall of cover 63, so as to allow air
circulation therebetween.
Anvil member 64 is fixedly attached at its lower end inside body 12 to an
annular actuator
68, the lower diametrally larger end 68a of which being axially slidable in a
fluid-tight
fashion inside upper chamber 56, under cover 63, and guiding both actuator 68
and anvil 64
s in their sliding motion. Annular actuator 68 peripherally slidably and
sealingly engages the
outer surface of a hollow cylindrical poppet member 70 having an upper end 70a
and a
lower end 70b and which defines an inner channel 72. The poppet member lower
end 70b
includes a valve member 74 in the form of a diverging conical lower portion of
poppet
member 70. Valve member 74 comprises an annular sealing O-ring 76 fixedly
installed
1 o thereon, as described hereinafter. As shown in figures 6-8, valve member
74 is destined to
releasably and peripherally engage in fluid-tight fashion the chamfered lower
annular seat
58.
Poppet member 70 has an annular groove spacedly under and adjacent its
upper end 70a, securely engaged by a snap-ring 78, the latter forming a
peripheral abutment
1 s shoulder for actuator 68, for preventing actuator 68 from upwardly moving
beyond snap-
ring 78 relative to poppet member 70. Poppet member 70 also includes several
peripherally
spaced radial through-bores 80 (with two bores 80 being shown in the drawings)
spacedly
over and near valve member 74.
An annular stepped ring member 82 is fixedly and sealingly attached on the
2 o intermediate portion of poppet member 70, and more particularly between an
annular bulge
84 on poppet member 70 and a snap-ring 86 securely fitted in an annular groove
spacedly
12
CA 02298865 2000-02-15
above bulge 84. Stepped ring member 82 slidably and sealingly engages the
inner wall of
upper chamber 56, and is destined to releasably downwardly abut against the
upper surface
of upper seat 60, as described hereinafter.
A hollow piston or plunger 88 having an upper end 88a and a lower end 88b
s is axially slidable inside the poppet member channel 72, with piston 88
being guided by
means of a short upper sleeve 90 which slidably and sealingly engages the
inner wall of
poppet member 70 at the piston upper end 88a, and by a slider disc 92 which is
threadingly
and sealingly attached at the piston lower end 88b and which slidingly and
sealingly
engages the main body 12 inner wall in lower chamber 52. Slider disc 92
presents a cross-
1 o sectionally upwardly convergent annular trough 92a.
A central channel 94 is defined longitudinally inside piston 88, being opened
at piston upper end 88a. Since piston 88 comprises several peripherally spaced-
apart
through bores 96 (with a single bore 96 being shown in the drawings) near its
lower end 88b
although spacedly over disc 92, there is continuous fluid communication
through piston
1 s channel 94 between:
a) the portion of upper chamber 56 located above actuator 68 and poppet member
channel 72 above short sleeve 90 when piston 88 is at least partly lowered;
and
b) the portion of lower chamber 52 located above slider disc 92.
Several peripherally spaced-apart exhaust holes 98 are made between the
20 lower edge of anvil 64 and the upper portion of actuator 68, where both
loosely fit inside
cover 63. Several other peripherally spaced-apart exhaust holes 100, generally
registering
13
CA 02298865 2000-02-15
with holes 98, are made in cover 63. A single hole 98 and a single hole 100
are shown in
the drawings. Holes 100 lead outside of cover 63, to the ambient air.
A channel 101 in main body 12 links the U-channel third section 30c with
the main body upper chamber 56, between actuator 68 and stepped disc 82.
s The lower end 88b of piston 88 carries a fastener driver in the form of a
driver blade 102 which is fixedly attached to the piston lower end 88b under
disc 92 and
which downwardly extends through base 14 in channel 16. An annular pad 103 is
located at
the bottom end portion of lower chamber 52, to receive and absorb the impact
of the
downwardly propelled disc 92.
1 o Figure 9 shows poppet member 70. It can be seen that the valve portion 74
of poppet member 70 includes an annular groove 104 which has a truncated
circular cross-
section having converging outer edges 106, 108. Thus, O-ring seal 76 (not
shown in figure
9) can be resiliently forced into groove 104 to be installed therein, without
any glue or other
adhesive being required to securely fix O-ring 76 into groove 104. This is an
important
1 s improvement over the prior art devices, such as the Hedrick patent
discussed in the
Background of the Disclosure section of the present specification, in which
the groove was
cross-sectionally L-shaped and consequently included divergent outer edges,
and in which a
glue or other adhesive, or a metal bonding method, was used to secure the O-
ring seal to the
valve member. The consequence of this in prior art devices, was that over time
the O-ring
2 o was often accidentally released due to the glue or metal bonding becoming
less efficient,
which rendered the miler less efficient or dysfunctional. Also, the metal
bonding or glue
14
CA 02298865 2000-02-15
used to fix the O-ring to the valve member, often prevents another O-ring from
being
installed at the position of the old, deficient O-ring. Thus, the whole valve
member must be
replaced even if only the O-ring becomes wom, the latter being very likely to
occur at least
once during the lifetime of a pneumatic fastener driving tool such as tool 10.
It is
s understood that the price difference between a resilient O-ring and the
whole valve member
is quite important, and thus having to replace the whole valve member because
of a worn O-
ring is highly undesirable. The O-ring of the present invention, resiliently
forced into the
annular channel having convergent outer edges, allows an easy installation and
replacement
of the O-ring 76 when it becomes worn, thus effectively reducing the
manufacturing cost
1 o and the maintenance labour costs of the tool.
It is noted that lower and upper chambers 52, 56 are fitted with rigid
cylindrical sheets 110, 112 having smooth inner surfaces, to provide a smooth
sliding
engagement thereon of slider disc 92 in lower chamber 52 and of stepped ring
member 82
and actuator 68 in upper chamber 56. As known in the art, sheets 110, 112 are
provided
15 since the inner walls of main body 12 have been machined with a rougher
inner surface.
As also known in the art, anvil 64 is formed with a diametrally smaller upper
chamber 114 at its upper end, which acts as a shock absorber to dampen the
upward
movement of piston 88 when it is biased upwardly after a fastener has been
driven by the
action of the air pressure on the short sleeve 90. Indeed, once the upper end
of sleeve 90
2 o and piston 88 extend into chamber 114, the air therein will act as a
dampening cushion to
help prevent eventual fatigue failure of tool 10 under the repeated impacts of
the piston
CA 02298865 2000-02-15
slider disc 92 against lower seat 58.
In use, the fastener driving tool 10 is in a resting position as shown in
figures
1, 2, 4 and 6. Compressed air is continuously fed into air reservoir 20
through inlet 24. In
this position, U-channel second and third sections 30b, 30c communicate with
the ambient
s air through three-way valve 34, and thus atmospheric pressure exists in the
annular area of
main body upper chamber 56 between actuator 68 and stepped ring member 82.
Also,
through exhaust holes 100 and 98, and through upper chamber 56 (above actuator
68) and
piston channel 94, atmospheric pressure exists in the small area of lower
chamber 52
between the poppet valve member 74 and the piston slider disc 92. Through the
opened
1 o base 14, ambient air is allowed in lower chamber 52 under slider disc 92
and piston 88, and
lower chamber 52 is thus at atmospheric pressure. However, intermediate
chamber 54, being
in continuous communication with air reservoir 20, is filled with compressed
air. Since the
lower face of the integrally-linked poppet radial bulge 84 and stepped disc 82
has a greater
surface than the horizontal surface value of the upper conical face of valve
member 74, the
15 overall pressure differential on the poppet member 70 is upwardly oriented,
and
consequently valve member 74 is upwardly biased in an upper limit position,
sealingly
engaging the chamfered under face of lower seat 58. Compressed air is also
allowed
through bores 80 into poppet channel 72 under sleeve 90, to upwardly bias
sleeve 90 and
consequently to upwardly bias piston 88 in an upper limit position.
2 o In this resting position of tool 10, if a blow is dealt onto anvil 64,
actuator 68
will be consequently downwardly biased in upper chamber 56, forcing part of
the air therein
16
CA 02298865 2000-02-15
out through U-channel second and third sections 30b, 30c and out of tool 10
through three-
way valve 34. The air initially at atmospheric pressure which remains in the
annular area
between actuator 68 and stepped ring member 82 may be slightly compressed, but
the
calibrated sizes of the inner components of tool 10 are such that the slight
additional
s pressure on the upper face of stepped ring member 82 will not be sufficient
to counteract the
pressure of compressed air thereunder. Thus, stepped ring member 82 and
consequently
poppet valve member 74 remain motionless. Due to cap 66 being diametrally
larger than
the cover opening 65, the downward stroke of anvil 64 is limited to a maximum
value which
is less than the distance required by actuator 68 to reach stepped ring member
82.
1 o Consequently, if trigger 36 is not squeezed, dealing a blow on anvil 64
will not result in a
fastener being expelled from tool 10, since no action results from actuator 68
being
downwardly biased in this condition of tool 10.
To drive the leading fastener with blade 102, two things have to be
accomplished: firstly, trigger 36 must be squeezed, and secondly while trigger
36 remains
1 s squeezed, a blow must be dealt on anvil 64.
When trigger 36 is squeezed, as shown in figures 3 and 5 and as discussed
hereinabove, ambient air is no more allowed into U-channel 30. Instead, three-
way valve 34
allows compressed air from air reservoir 20 to fill U-channel 30 and to enter
the annular area
in tool main body upper chamber 56 between actuator 68 and stepped ring member
82, to
2o form a compressed air cushion therein. Actuator 68 is upwardly driven, by
the underlying
compressed air cushion, to an upper limit position shown in figure 6, in which
actuator 68
17
CA 02298865 2000-02-15
upwardly abuts against snap-ring 78. In this condition of tool 10, the
equilibrium of poppet
member 70 is not compromised, since the upwardly oriented air pressure on the
lower
surface of actuator 68 is equal to the downwardly oriented air pressure on the
upper surface
of stepped ring 82, since their horizontal surfaces are of equal value. Thus,
poppet member
s 70 remains in its upper limit position, with valve member 74 still sealingly
closing the
passage between lower and intermediate chambers 52, 54.
When a blow is dealt on the anvil 64, e.g. with a hammer, the air cushion
between actuator 68 and stepped ring member 82 acts to transfer the impact of
this blow to
stepped ring member 82 in the form of an added downward pressure thereon, thus
1 o effectively downwardly biasing poppet member 70, as shown in figure 7. Of
course, the
force of the blow dealt on anvil 64 must be sufficient to counteract the
pressure differential
resulting from the surface differential between the stepped ring 82 and the
valve member 74.
Once poppet member is downwardly biased, the compressed air is allowed to flow
around
valve member 74, into lower chamber 52 above slider disc 92. Since atmospheric
pressure
1 s exists under disc 92, the latter is suddenly downwardly driven by the
incoming compressed
air, to downwardly drive blade 102 and consequently forcefully expel a
fastener from tool
10. Since the horizontal component of the downwardly biased upper face of disc
92 is much
greater than the counter-acting horizontal annular under face of the upwardly
biased short
sleeve 90 located at the upper end of piston 88, the resistance exerted by
short sleeve 90 to
2 o the downward movement of piston 88 is not significant. Once piston 88 hits
annular pad
103, it reaches its lowermost position.
18
CA 02298865 2000-02-15
Independently of whether trigger 36 is released or not, poppet valve 74
automatically retrieves its resting position after the hammer blow is dealt,
due to the greater
pressure applied by the compressed air on stepped ring 82 than on poppet valve
74 as
described hereinabove. Indeed, the hammer blow on anvil 64 only temporarily
shifts the
s pressure balance in the tool main body 12, which will rapidly return to its
initial condition
after the hammer blow has been dealt. Thus, as shown in figure 8, poppet valve
member 74
sealingly engages lower annular seat 58 once again under the bias of the
upwardly moving
stepped ring 82. The compressed air in the lower chamber 52 above slider disc
92 then
flows through holes 96 into piston channel 94, through poppet channel 72
(above sleeve 90)
1 o and out of tool 10 through exhaust holes 98 and 100.
Once the pressure in lower chamber 52 above disc 92 nears the atmospheric
pressure, the upward pressure applied by the compressed air against sleeve 90
upwardlly
biases piston 88 in poppet channel 72 as shown in figure 8, back to its
initial upper limit
position as shown in figure 6. Thus, tool 10 retrieves its initial resting
condition. As already
1 s explained and as known in the art, the upward movement of piston 88 is
dampened when it
nears its upper limit position, by the presence of an air cushion at
atmospheric pressure in
dampening chamber 114.
It can be seen that according to the present invention, the combination of the
annular
space in the main body upper chamber 56 located between actuator 68 and
stepped ring 82,
z o together with three-way valve 34, plays two roles:
a) it is a lost motion system when said annular space is filled with air at
atmospheric
19
CA 02298865 2000-02-15
pressure which is allowed to exhaust through three-way valve 34 outside of
tool 10, since
any blow dealt on anvil 64 does not have any repercussion over actuator 68;
and
b) it is a lost motion disabling system when said annular space is filled with
compressed air, since the pressure of any blow dealt on anvil 64 is then
transmitted to
actuator 68.
The nailer according to the present invention is a safe tool, since it
requires
two actions to take place concurrently to expel a nail: squeezing the trigger
36 and dealing a
blow on anvil 64. It is important to note that having to deal a blow on top of
anvil 64 is not
a drawback relative to the existing devices which only require a trigger to be
activated for
i o the nail to be expelled. Indeed, the blow dealt on the upper portion of
the tool 10, and more
particularly on anvil 64, is axially aligned with the direction in which the
fastener is to be
expelled. As know by the person skilled in the art of the present invention,
this directed
axial blow is desirable, since it helps to maintain the work-piece engaging
base 14 firmly
against the work-piece being nailed, e.g. the flooring. The tool has a natural
tendency to be
lifted slightly over the flooring when a fastener is expelled due to the
outcoming fastener
hitting the hard floor, which may result in the fastener not being properly
driven through the
floor. The blow dealt on the anvil helps to prevent the tool from this slight
upward reaction
movement, since it drives the tool towards the floor.
It is understood that although compressed air is the favoured and effectively
2 o the most used fluid for fastener driving tools, any other suitable
compressible fluid could be
used without departing from the scope of the present invention.
CA 02298865 2000-02-15
Any further modification, which does not deviate from the present invention,
is considered to be included therein.
21
