Note: Descriptions are shown in the official language in which they were submitted.
< CA 02461515 2004-03-23
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'TITLE OF THE INVENTION: PNEUMATIC FASTENER DRIVING TOOL FOR
HARDWOOD FLOORING
FIELD OF THE INVENTION
The present invention relates to pneumatic fastener driving devices, and more
s particularly to a compressed air operated and impact blov~ triggered
fastener driving tool for
anchoring hardwood planks to a subfloor.
BACKGROUND OF THE INVF?NTION
Hardwood flooring generally consists of a number of elongated narrow tongue-
and-
groove planks individually fitted close to one another and then fastened in
position to a subjacent
i o subfloor. To fasten these hardwood planks to the subfloor of a room
composed for example of
plywood plates or floor joists, it is known to use pneumatic mallet-operated
fastener driving tools.
Such fastener driving tools generally comprise a main body with a floor-
engageable slider shoe
mounted to its bottom surface, upon which the tool rests against a hardwood
plank prior to
discharging a fastener in the latter, this shoe having a usually right-angle
step-shaped indentation
made thereon. These fastener driving tools also comprise a magazine holding
fasteners in the form
of metallic L- or T-shaped barbed cleats, and feeding them to a pneumatic
fastener discharge
mechanism, activated when a mallet strikes an impact-receiving member thereof.
The fastener
discharge mechanism comprises a number of pneumatically distinct chambers and
mobile parts, and
these mobile parts can be actuated upon occurrence of air pressure differences
between
corresponding chambers.
CA 02461515 2004-03-23
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To fasten a hardwood plank to the floor, a workman has to lay the fastener
driving
tool onto a hardwood plank, such that the 90° indentation made on its
shoe engages the angular edge
of the hardwood plank, and then uses a mallet to strike the impact-receiving
member of the fastener
discharge mechanism which causes the tool to discharge a cleat and forcibly
drive the latter
s transversely through the hardwood plank, and into the subfloo~°.
In prior art tools of this type, movement synchronisation between all mobile
parts
within the fastener discharge mechanism lacks optimization, which results in a
slower reload speed
of the tool. Furthermore, actual pneumatic flooring tools consume excessive
quantities of
compressed air. Also, the hammer striking head of the tool being usually
bolted to the tool main
o housing, access to internal parts is more time consuming.
OBJECTS OF THE INVENTION
An object of the invention is to improve upon US patent No. 4,907,730 issued
March
13, 1990.
An object of this invention is to facilitate access by the pneumatic tool to
floor areas
is close to vertical walls for driving fasteners adjacent thereto.
Another object of the invention is to improve upon reload speed of the
pneumatic
tool.
A further object of the invention is to reduce labour costs and reducing
maintenance
time by facilitating fast and easy access via the screwable impact receiving
member to the tool
o internal wear part components.
A general object of this invention is to provide a pneumatic miler of smaller
size, to
increase clearance in hard to reach places to be fastened.
CA 02461515 2004-03-23
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Another general object of the invention is to improve upon compressed air
supply
management during operation of the tool.
SUMMARY OF THE INVENTION
The present invention relates to a compressed fluid operated fastener driving
tool,
which can be selectively triggered for driving fasteners into an underlying
workpiece, said tool
comprising a frame, a fastener feeder for feeding fasteners to a fastener
discharge mechanism of said
driving tool, said fastener driving mechanism capable of shifting between a
rest and an operative
condition, said fastener discharge mechanism comprising:
- a housing; comprising:
o - a first chamber having a fluid inlet destined to be connected to a source
of
compressed fluid for keeping said first chamber pressurized,
- a second chamber, comprising first and second fluid inlet ports for
admitting
compressed fluid from said first chamber into said second chamber, said second
fluid
inlet port capable of being selectively opened and closed, said second chamber
being
1 s selectively depressurizable, said second chamber being pressurized when
said
fastener discharge mechanism is in said rest condition;
- a third chamber, comprising a piston slidably mounted therein, said piston
comprising a piston head and a plunger downwardly depending from said piston
head, wherein said piston is biased 1'~rom a first limit position towards a
second limit
2 o position when said third chamber is in fluid communication with said first
chamber,
said piston being in said first limit position when said fastener discharge
mechanism
is in said rest condition;
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- a valve controlling fluid communication between said first chamber and said
third chamber, said
valve being biased towards an. open limit position when said second chamber is
depressurized
where fluid communication is established between said first and said third
chamber, and said
valve being biased towards a closed limit position when said second chamber is
pressurized
s where fluid communication is interrupted between said first and said third
chamber;
wherein after said tool is triggered, said fastener discharge mechanism passes
from said rest
condition to said operative condition, and said second chamber is
depressurized to induce movement
in said valve towards said open position,
wherein when said valve is moved towards said open limit position, said second
chamber second
Zo fluid inlet port is closed, and fluid communication is established between
said first chamber and said
third chamber, thus urging said piston towards said second limit position for
allowing a fastener to
be struck by said plunger and thus discharged from said tool;
and wherein after said piston is moved towards said second limit position,
fluid flowing into said
second chamber through said first fluid inlet port pressurizes same and
initiates movement of said
1 s valve towards said closed limit position, and wherein after initiation of
movement of said valve
towards said closed limit position, said second fluid inlet port is opened to
accelerate pressurizing of
said second chamber and thus accelerate movement of said valve towards said
closed limit position.
In one embodiment, said second fluid inlet port is closed by being obstructed
by said
valve when latter is in said open limit position, and said second fluid inlet
port is opened when it is
a o cleared by said valve after initiation of the movement of said valve from
said opened limit position
towards said closed limit position.
In another embodiment, said fastener discharge mechanism comprises an impact
receiving member, and said impact receiving member has to be struck to pass
said fastener discharge
mechanism from said rest condition to said operative condition.
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In another embodiment, said impact receiving member comprises a hollow head
member, comprising said second chamber therein.
In another embodiment, said head member comprises at least one air outlet
channel
s made therein, opening into said second chamber at a first end, and into an
atmospheric pressure fluid
volume at a second end, and said second chamber can be selectively
depressurized upon selective
establishment of fluid communication between said second chamber and said air
outlet channel
second end.
In another embodiment, a peripheral wall of said valve snugly and slidably
engages a
i a peripheral wall of said second chamber, said valve being slidable about
said second chamber, said
valve being slid away from said second chamber when said valve is in said
closed limit position, and
said valve being slid towards said second chamber when said valve is in said
open limit position.
In yet another embodiment of the invention, said second chamber first fluid
inlet port
is formed by at least one first inlet channel made in said valve, opening at a
f rst end into said main
s 5 chamber, and opening at another end into said second chamber, and said
second chamber second
fluid inlet port is formed by at least one second inlet channel made in said
head member, opening at
a first end into said main chamber, and opening at a second end into said
second chamber, and said
valve peripheral wall obstructs said second inlet channel second end when said
valve is in said open
limit position, and said second fluid inlet port is opened when. said valve is
not in said closed limit
2 o position.
In another embodiment, the fastener driving tool further comprises means fox
biasing
said piston towards said first limit position when said valve is in said
closed position.
In one embodiment, said third chamber is a cylinder.
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CA 02461515 2004-03-23
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In one embodiment, a shock absorbing cap is fitted on said head member.
The present invention also relates to a method for discharging a fastener out
of a
pneumatic fastener driving tool comprising a fastener feeder for feeding
fasteners to a fastener
discharge mechanism, which can be triggered to pass from a rest condition to
an operative condition,
and which comprises a housing having a pressurized first chamber, a
selectively depressurizable
second chamber comprising a fast fluid inlet port and a selectively closable
second fluid inlet port,
said second fluid inlet port being open and said second chamber being
pressurized when said tool is
in said rest condition, and a third chamber in which a piston having a plunger
is slidably mounted,
to said piston being movable between retracted and deployed limit positions
and being biased towards
said deployed limit position when .Fluid communication between said first and
said third chambers is
established, a valve being further nested within said housing and permitting
selective establishment
of fluid communication between said first and said third chamber, said method
comprising the steps
of:
i5 (a) triggering said fastener discharge mechanism to pass it in said
operative condition;
(b) depressurizing said second chamber and closing said second fluid inlet
port thereof;
(c) since said second chamber is depressurized, displacing said valve towards
said open position
to establish fluid communication between said first and said third chambers;
(d) displacing said piston towards said deployed limit position;
2 0 (e) striking a fastener with said plunger to discharge a fastener from
said tool;
(f) admitting compressed fluid into said second chamber from said first
chamber through said
first fluid inlet port to pressurize said second chamber and thus initiate
movement of said
valve towards said closed position; and
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(g) once movement of said valve is initiated, opening said second fluid inlet
port to further admit
compressed fluid into said second chamber, to further pressurize the latter
and accelerate
displacement of said valve towards said closed position.
In one embodiment, said method further comprises the step, after step (g), of
biasing
said piston towards said retracted limit position.
The present invention also relates to a pneumatic miler for use with floor
securing
cleats in working in hard to reach floor areas, said miler comprising a main
frame, a first air
chamber, a second air chamber, a piston member reciprocatingly° movable
through said second air
io chamber, said piston member defining a plunger having at a bottom end a
striker head for striking
and ejecting selected floor securing cleats in successive reciprocating cycles
with the cleats located
outwardly of said second air chamber, and at a top end a piston head, wherein
said second air
chamber forms an upper subchamber and a lower subchamber on opposite sides of
said piston head
in substantially airtight fashion relative to one another wherein said upper
subchamber and said
15 lower subchamber are of complementarily inversely variable volume, said
upper subchamber in
fluid communication with said first air chamber, a third air chamber in fluid
communication with
said lower subchamber, first valve means controlling air flow from said first
air chamber to said
upper subchamber, said first air chamber adapted to contain continuous over
atmospheric air
pressure level thereinto, unidirectional second valve means controlling air
flow from said lower
~o subchamber to said third air chamber, first channel means for through air
flow between said lower
subchamber and said third air chamber responsively to an air pressure
differential therebetween, and
trigger means for releasably moving said first valve means fiom a closed
condition to an opened
condition enabling air flow from said first air chamber to said upper
subchamber; wherein said first
CA 02461515 2004-03-23
g
valve means includes means to adjust the duration of each of said
reciprocating cycles of said piston
member.
In one embodiment, said pneumatic miler further includes a guide member,
mounted
to said main frame and opening into said lower subchamber of said second air
chamber, said guide
s member including a central slit slidably engaged by said plunger for guiding
motion of said plunger
during said reciprocating cycles thereof.
In one embodiment. said second air chamber defines a peripheral wall section
having
an inner wall, slidably engaged by said piston head, and an outer wall, a
first series of registering
access bores made into said wall section and opening into said third air
chamber, and said second
i o valve means consists of an elastic band applied against said second air
chamber outer wall in
releasable sealing register with said access bores of said wall section of
said second air chamber.
In one embodiment, the material nature of said guide ring member and the size
of
said guide ring member central slil: relative to the section of said plunger
slidably engaging through
said slit, are such that any ovetpressure inside said lower subchamber will be
allowed to outwardly
s 5 leak at a controlled rate through said slit toward ambient air.
In another embodiment, said trigger means includes an anvil member having an
outer
exposed section and an inner section, said anvil member movably mounted to
said main frame
between an extended position and a retracted position, a fourth air chamber in
fluid communication
with said first air chamber through a fluid passageway, and third valve means
opening said fluid
a o passageway at said extended position of said anvil member and closing said
fluid passageway at said
retracted position of said anvil member, and air outlet means providing air
outflow from said fourth
air chamber after said anvil member leaves said extended position thereof,
wherein said air outflow from said air outlet means provides the biasing means
that biases said first
valve means to move from its said closed condition to its said opened
condition.
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In another embodiment, said trigger means ands. said first valve means are
mounted in
a screwtube releasably screwable into a threaded access bore in said main
frame.
In another embodiment, said pneumatic naile~r further includes a combined
screw
mount assembly for releasably screwing said trigger means and said first valve
means to said main
frame, for facilitating manual access to said second air chamber and to said
piston head for
maintenance purposes.
In another embodiment, said pneumatic miler further includes a damper cover,
mounted to said exposed section of said anvil member, said damper cover made
from a shock
absorbing material.
Zo DESCRIPTION OF'fHE DRAWING
In the annexed drawings
Figure 1 is a front perspective view of a pneumatic tool according to the
present
invention;
Figure 2 is a bottom perspective view at a smaller scale of the tool of figure
l, with
the bottom slider shoe thereof being removed for clarity of the view;
Figure 3 shows an enlarged perspective partly broken view of the fastener
discharge
mechanism of the tool of figure 1, to show the inside content thereof;
Figure 4 shows an enlarged front cross-sectional view of the impact receiving
member of the tool taken along lines IV-IV in figure l;
2 o Figure 5 shows an enlarged perspective exploded view of the impact
receiving
member of the tool of figure 1; and
"o CA 02461515 2004-03-23
In
Figures 6 to 12 all show an enlarged front cross-sectional view of the
fastener
discharge mechanism taken along lines VI-VI in figure l, and sequentially show
the relative
displacement of internal parts of the fastener discharge mechanism during a
fastener discharge cycle
of the tool.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Figures 1-2 generally show a pneumatic mallet-operated fastener driving tool
20
according to the present invention, used for securing hardwood planks to a
subfloor.
Tool 20 comprise a G-shaped frame 22, made of a one-piece moulded metal for
example, defining a handle portion 22a integrally attached to one end of an
arm portion 22b, which
1 a integrally carries an elbowed baseplate 22c at its other end. Elbowed
baseplate 22c integrally carries
an attachment plate 22d. A fastener feeder in the form of an elongated
magazine 24 is affixed to one
side of frame arm 22b in a rearwardly upwardly sloped fashion, and is for
holding a supply of
fasteners, e.g. a strip of metallic L- or T-shaped barb-provided cleats
commonly used in floor
assembling duties. A launch plate 26 (concealed in figure l, but shown in
figure 2}, made from an
is assembly of two plates for ease of manufacture purposes, is affixed to the
bottom surface of elbowed
baseplate 22c perpendicularly to elongated magazine 24. Magazine 24 comprises
biasing means (not
shown) for biasing a strip of cleats loaded therein towards launch plate 26,
so that the first cleat of
the strip engages an elongated ejection-guiding groove 27 made in launch plate
26, from where this
cleat will be struck by a pneumatically driven plunger 28 (shown for example
in figure ~), to be
2 o ej ected from the tool and driven into a subj acent workpiece, as
described hereinafter.
As only shown in vgure l, an elongated shoe 29, made of plastic for example,
preferably engages the bottom surface of baseplate 22c, and forms the member
of tool 20 which will
CA 02461515 2004-03-23
rest on the subjacent workpiece prior to triggering a fastener discharge cycle
of the tool. Shoe 29 has
a step-shaped indentation 31 used for suitably positioning tool 20 relative
the workpiece it will be
used on, as described hereinafter.
Moreover, tool 20 comprises a fastener discharge mechanism 30. As seen in
figures
s 2-3, fastener discharge mechanism 30 comprises a housing 32, made of two
parts for ease of
manufacture i.e. a hollow body and a head baseplate, the bottom surface of
housing 32 being
secured to a guide plate 23 comprising a circular guide hole 25 made therein,
guide plate 23 being in
turn secured to attachment plate 22d of frame 22. Guide hole 25 registers with
plunger 28, and
plunger 28 reciprocates within guide hole 25 during nailing cycles of the
tool. A compressed air
to intake port 36 is made in housing 32. A flexible hose (not shown),
connected at one end to a
compressed air source such as an air compressor or a compressed air cylinder
(not shown), can be
connected at the other end to air intake port 36, for feeding compressed air
to fastener discharge
mechanism 30. Air intake port 36 opens into a first or main chamber 38 of
fastener discharge
mechanism 30.
m A metallic impact receiving member or anvil 46 is threadingly fitted in a
circular
threaded opening made transversely across the top surface of housing 32. The
engagement of impact
receiving member 46 to housing 32 is kept airtight by an annular seal 43
(shown in isolation in
figure 4 and in sealing compressed engagement therewith in figure 8). Impact
receiving member 46
forms the anvil member that a workman will strike with a mallet for example,
to set off tool 20 and
2o drive a cleat in a subjacent workpiece, as described hereinafter. Impact
receiving member 46
comprises a hollow head member 48 with external screw threads 47a (figure 5)
defining a central
axis 47, on top of which is releasably snap-fitted a cap 50 made for example
of rubber or plastic; cap
50 comprises perforations thereon, to allow fluid circulation between both
sides thereof. Cap 50 is
sized to almost fully enclose the upper end portion of head member 48, thus
protecting the latter
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CA 02461515 2004-03-23
12
against accidental impact on walls or floors. Sound dampening properties are
also achieved with cap
50 during nailing stroke cycles. Cap 50 will also prevent accidental spatters
of lubricant outwardly
from head 48, which may happen when the tool is excessively lubricated.
However, even without
protective cap ~0, trigger 54 is fully operational and the hammer can strike
directly on impact
s receiving member 54. Head member 48 is made for example of a lathed metal
block, and comprises
a cavity therein forming a head cavity 51. The threads 47a of head member 48
screwingly releasably
engage complementary threads 32a of housing 32. A number of air outlet
channels 49 are radially
inwardly downwardly bored in head member 48, and open t~o head cavity 51. In
one embodiment
(not shown in the figures), there are four regularly spaced-apart air outlet
channels 49 made in head
io member 48. Additionally, head member 48 is provided with a. number of air
inlet channels 68; only
two air inlet channels 68 are shown in figure 4, but more or Less of such air
inlet channels could be
provided in alternate embodiments of the invention. Air inlet channels 68 open
transversely onto
head cavity 51 at one elbowed inner end portion G8b, and onto main chamber 38
at the other outer
end 68a. Preferably, end portion 68b make a large acute angle with the main
body of elbowed
i5 channel68.
A transverse trigger-accommodating opening 52 is made through the upper end
portion of head member 48, coaxially with central axis 47, and opens into head
cavity 51. A trigger
54 is mounted in trigger-accommodating opening 52, and comprises a discoid
upper impact-
receiving portion 54a and a lower sliding portion 54b. Sliding portion 54b
slidably engages the inner
2o peripheral wall of opening 52, allowing trigger 54 to be slidab~ly movable
between a rest position as
shown for example in figure 4, where impact-receiving portion 54b is spaced-
apart from the upper
surface of head member 48, and an operative position as shown in figure 7 for
example, where the
bottom surface of impact-receiving portion 54a comes to engage with and is
pressed against the
upper surface of head member 48. Impact-receiving portion 's4a is the member
towards ~~hich the
. CA 02461515 2004-03-23
13
mallet blow of a workman will be directed in order to move trigger 54 from its
rest position towards
its operative position, which will result in tool 20 discharging a cleat.
Hence, to limit vibrations
arising from the mallet blow, a toroidal ring 55 (called O-rang 55 hereafter),
made of a resilient
shock-absorbing material such as rubber, is preferably nested. in a
complementary toroidal channel
s 54c made on the bottom surface of impact receiving portion 54a, for comfort
of the user.
A cylindroid elongated air evacuation member 56 is nested within head cavity
51,
coaxially with central axis 47. The top surface 56a of air evacuation member
56 is centrally bored at
56b, and the corner rim portion 56c of member 56 engages a peripheral
indentation made in the
lo~~er free end portion of trigger sliding portion 54b. A toroidal wear ring
61 nested in a
1 o complementary annular channel 56d made radially in the outer surface of
air evacuation member 56.
Air evacuation member 56 is hollow and defines an evacuation airway 58
therein. Moreover, an
annular cross-sectionally semi-circular recess 59 is made ;peripherally in the
outer wall of air
evacuation member 56, beneath wear ring 61. A number of through-holes 60 are
made radially in air
evacuation member ~6, in register with this recess 59; in one; embodiment, air
evacuation member
n56 is provided with four peripherally spaced through-holes 60. Through-holes
60 are meant to keep
evacuation airway 58 in fluid communication with air outlet channels 49 and
thus with the
atmosphere. Moreover, a toroidal, cross-sectionally U-shaped seal 63 (called U-
cup 63 hereinafter),
is nested in a complementary annular channel 56f made in the outer wall of air
evacuation member
56, beneath recess 59.
a o Notches 62 are made in air evacuation member 56, at the bottom free end
portion
thereof (as best shown in figure 5). An annular discoid closure plate 70,
comprising an annular seal
in the form of a U-cup 73 nested in a dedicated annular recess 70a made in its
peripheral wall, is
pressed against the bottom extremity of air evacuation member 56. An elongated
bolt 72 coaxial
with central axis 47 extends through the hollow of annular closure plate 70,
through airway 58, and
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CA 02461515 2004-03-23
14
into a threaded bore 54e made centrically in trigger 54, to which it is
screwed; closure plate 70, air
evacuation member 56 and trigger 54 are thereby fastened together, and will
move as one during
operation of the tool.
Accordingly, as sequentially shown by figures 4 and 7, downward movement of
s trigger member 54 from its rest position towards its operative position
results in similar downward
movement of air evacuation member 56 and closure plate 70 from a rest position
(as shown in figure
4) towards an operative position (as shown in figure 7). In the rest position,
U-cup 63 of air
evacuation member 56 peripherally and snugly engages the peripheral wall of
head cavity 51; when
the latter is in its operative position, U-cup 63 clears the wall of head
cavity 51.
Zo A two-tiered valve 64 is coupled to the assembly of closure plate 70 and
air
evacuation member 56, and can slide inwardly or outwardly of head cavity 51,
coaxially with axis
47, between a closed and an open position. Preferably, the shape of valve 64
relative to that of the
peripheral wall of head cavity 51 is such that self guiding properties are
imparted to valve 64 when
moving between its open and closed positions. The portion of head cavity 51
delimited by the upper
m surface of a valve upper portion 64a and U-cup 63 installed peripherally on
air evacuation chamber
56 will be further referred to as closure chamber 53; of course, since valve
64 is slidable within head
cavity 51, closure chamber 53 is of variable inner volumf;. Air pressure
acting within closure
chamber 53 will control opening and closure of valve 64, as described
hereinafter. Upper portion
64a has a central hole 65 on its top surface 64c chamfered at 64d and opening
downwardly into a
2o valve inner cavity 74, and a lower portion 64b. Air evacuation member 56
extends through valve
access hole 65, with closure plate 70 being nested in valve inner cavity 74,
and the outer wall of
evacuation member 56 snugly yet slidably engages valve 64 at valve hole 65, in
an airtight fashion
due to the presence of a U-cup 66 attached to valve upper portion 64a. Valve
inner cavity 74
comprises a broad upper portion 74a, and a narrowed lower portion 74b, the
latter'having a diameter
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CA 02461515 2004-03-23
substantially equal to the external diameter of closure plate 70. When air
evacuation member 56 is in
its rest position and valve 64 is in its closed position (as shown in figure 6
for example), closure
plate 70 is located above and doer not engage the narrowed portion of valve
inner cavity 70 thus
allowing fluid communication between valve inner cavity 74 and the air volume
located beneath
5 closure plate 70, but otherwise closure plate 70 engages the narrowed
portion 74b of valve inner
cavity 74 in an airtight fashion; thus cutting off fluid communication between
valve inner cavity 74
and the air volume located beneath closure plate 70. It is to be noted that
valve inner cavity 74 is in
fluid communication with airway a8 through notches 62 regardless of the
relative position of valve
64 and air evacuation member 56 during nailing cycles.
so Still in figure 4, a number of elbowed air feed closure channels 80 are
drilled in valve
upper portion 64a (with only one closure channel 80 being shown in the
figures); an inner end 80a
of closure channel 80 opens into closure chamber 53 of head cavity 51, and its
outer radial end 80b
opens into main chamber 38.
The outer peripheral wall of valve upper portion 64a is fitted, in annular
recesses
is made expressly therefor, with two complementary annular seals, an O-ring 76
and a U-cup 78
positioned below O-ring 76. Regardless of the position of valve 64 within head
cavity 51:
- U-cup 78 engages the peripheral wall of head cavity 51; preventing fluid
leaks through the
engagement of valve 64 with the wall of head cavity 51; and
- fluid communication between the main chamber 38 and closure chamber 53 is
established
2c through elbowed closure channels 80.
In addition, when valve 64 is in its open position, the peripheral wall of
valve upper
portion 64b is pressed against and obstructs end 68a of air inlet channel 68,
and residual fluid flow,
which may leak out of air inlet channel end 68a even though it is obstructed,
is prevented from
infiltrating closure chamber ~3 by O-ring 76, as shown in figure 8 for
example.
CA 02461515 2004-03-23
16
Valve lower portion 64b, on the other hand, generally comprises a cylindroid
wall in
which a series of horizontal elongated apertures 67 axe made (as best shown in
figure 5). Valve
lower portion 64b depends into main chamber 38, and is snugly slidably fitted
around an upper rim
s portion 82a of a cylinder 82, as shown in figures 3 and 6-12. ~~uch snug and
slidable engagement of
valve lower end portion 64b and cylinder upper rim portion 82 also impart a
self guiding capability
to valve 64 when the latter moves axially along axis 47 between its closed and
open positions.
Cylinder 82 defines an enclosure that is usually at atmospheric pressure
except during nailing stroke
cycles. It is to be noted that when valve 64 is pushed downwardly in its
closed position, apertures 67
io are covered by the outer wall of cylinder upper rim portion 82a, valve 64
airtightly engages upper
rim portion 82a owing to the presence of an annular seal 79, and fluid
communication between the
inside of cylinder 82 and main chamber 38 is blocked. However, when valve 64
is pushed up in its
open position, apertures 67 are partly uncovered by the outer wall of upper
rim portion 82a, and
fluid communication is established between main chamber 38 and the inner
chamber of cylinder 82.
15 Cylinder 82 is coaxially aligned with central axis 47, and comprises a
cylinder body
82b below upper rim portion 82a. 'The lower end of cylinder body 8Zb is fitted
in a registering hole
made in the bottom surface of housing 32, and its lower rim abuts against
guide plate 23. A partition
88, integral to housing 32, surrounds the entire length of cylinder body 82b
spacedly therefrom, and
a collar 89 snugly surrounds the upper portion of cylinder body 82b. An
enclosure in the form of
2o auxiliary chamber 90 is formed between the outer wall of either cylinder
body 82b or collar 89 and
partition 88.
Furthermore, a number of peripherally spaced small escape holes 84 are made in
cylinder body 82b, in the lower portion thereof. A narrow elastic band 86 is
stretched radially
around the outer face of cylinder 82, and covers holes 84, so as to only
permit unidirectional radially
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CA 02461515 2004-03-23
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outward fluid flow from the inside of cylinder 82 to auxiliary chamber 90
through escape holes 84,
but not radially inwardly from auxiliary chamber 90 to the inside of cylinder
82. Another set of
larger holes 85 are made in cylinder main body 82b, adjacent the lowermost
extremity of cylinder
82.
A piston 92, comprising a piston head 94 and a cross-sectionally rectangular
plunger
28 (introduced above) is slidably installed within cylinder 82 coaxially
therewith. Plunger 28
registers with notch 27 made in launch plate 26. A peripheral flange (figure
6) depends downwardly
from the upper surface of piston head 94, and the outer surface of flange 95
slidably yet snugly
engages the inner wall of cylinder 82 and in an airtight fashion.
1 o Plunger 28 extends through a guiding ring 9fi bearing against guide plate
23 and
centered relative to guide hole 25. Guide ring 96 is composed of two ring
halves 96b and 96c, as
illustrated in figures 3 and 12, fitted together and biased towards one
another and towards plunger
28 by a resilient toroidal O-ring 96d. The axial slit through which plunger 28
extends in guide ring
96, defined centrically thereon at the interconnection between halves 96b and
96c, is labelled 96a in
the figures, and is wider than plunger 28. O-ring 96d maintains the two rings
halves 96b, 96c biased
against the main wider faces of plunger 28. A differential air pressure
between upstream and
downstream ends of ring 96 is insufficient to bias halves 96b, 96c away from
plunger 28, and
therefore, no air leakage is ever produced along the face of plunger 28.
However, since slit 96a is
wider than plunger 28, the two gaps formed between the opposite two narrower
side edges of
2o plunger 28 and corresponding registering sections of ring halves 96b, 96c
respectively, form air
passageways constituting an air leakage zone to compensate for any
differential air pressure between
upstream and downstream ends of ring 96, such leakage being shown by arrows K
in figure 12. It is
to be noted that such controlled leakage is properly achieved during the
entire life cycle of tool 20.
Indeed, O-ring 96d will continuously bias ring halves 96b and 96c towards the
wider face of plunger
~;~~.
CA 02461515 2004-03-23
18
28, with very little effect from wear occurring upon repetitive sliding motion
of plunger 28 against
ring halves 96b and 96c during repeated nailing cycles of tool 20. Therefore,
guiding ring 96
provides a continuous yet controlled air leakage outflow which will vary very
little even considering
frictional wear of its components.
A discharge damper 98 diametrically larger than ring 96, made of a shock-
absorbing
material such as rubber is installed within and at the bottom end of cylinder
82, and bears against
guide plate 23, in order for guide ring 96 to be interposed be ween damper 98
and guide plate 23.
Discharge damper 98 is shaped such that its top surface matches the shape of
the undersurface of
piston head 94.
i o Piston 92 can slide within cylinder 82 between a retracted limit position,
as shown in
figure 6 for example, where the top surface of piston head 94 comes in
register with the upper rim of
cylinder 82, and a deployed limit position as shown in figure 10 for example,
where the
undersurface of piston head 94 snugly engages discharge damper 98 and plunger
28 is extracted out
of cylinder 92 through the aperture made in guide ring 96 and guide hole 2~.
In preparation for operation of tool 20, a hose, connected at one end to a
compressed
air source, is connected at the other end to compressed air intake port 36,
and magazine 24 is loaded
with a strip of cleats. When the tool is at rest, as shown in figure 6, piston
92 is in its upper limit
position, and closure chamber ~3 is pressurized. Air pressure within closure
chamber 53 is
substantially equal to that of main chamber 38, but since the surface area of
valve 64 exposed to
2o closure chamber 53 is greater than that exposed to main chamber 38, the
pressure-borne force acting
on valve 64 from within said closure chamber 53 is greater than that acting
thereon from within
main chamber 38, and hence a net downward force is applied on valve 64, thus
urging it
downwardly towards its closed position and thus towards the upper rim of
cylinder 82.
CA 02461515 2004-03-23
19
To use the tool, and trigger a fastener discharge cycle thereof, a workman
grabs it by
handle 22a, and places it on top of a workpiece such as a hardwood plank which
has been previously
been placed at a desired anchoring location on the subfloor. Tool 20 has to be
positioned relative to
the plank such that indentation 3 2 made in shoe 29 bears against an upper
edge of the plank. A
s substantial force is required to push trigger 54 down, e.g. a 35 pound
force; a safety feature
preventing accidental release of the trigger by simple manual push. Therefore,
once the tool is
properly positioned, the workman strikes the obliquely orientf;d impact
receiving member 46 with a
mallet or a hammer, and directs his blow coaxially with axis 47 and towards
trigger member 54.
When trigger 54 is struck, it is pushed against the bias of compressed air
pressurizing closure
io chamber 53, from its rest position (figure 6) to its operative position
(figure 7). Concomitantly, air
evacuation member 56, which moves as one with trigger 54, will be moved from
its rest position
towards its operative position, and closure plate 70 is pushed down to become
airtightly engaged on
the wall of the narrowed portion 74b of valve inner cavity 74~. In this
operative position, U-cup 63
does not engage the wall of head cavity 51, and closure chamber 53 is in fluid
communication with
i5 the atmosphere through air outlet channels 49. Consequently. closure
chamber 53 is depressurized
through the depressurizing port formed by air outlet channels 49, as suggested
by arrow A in figure
7, and the air pressure within closure chamber 53 instantly drops. As a
consequence, since closure
chamber 53 is depressurized while main chamber 38 is pressurized, a
differential air pressure is
generated so that a net upward force is applied on valve 64 urging it towards
its open position, as
ao shown in figure 8. In such a position, the outer wall of valve 64 covers
and obstructs end 68a of each
air inlet channel 68, inter alia air channelled through air inlet channel 68
from main chamber 38 to
closure chamber 53 to escape from air outlet channels 49, to substantially
prevent undesirable waste
of pressurized air. Consequently, since valve 64 is open, compressed air from
main chamber 38
applies a very high downward force on piston head 94 which urges piston 92
downwardly from its
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CA 02461515 2004-03-23
2~
retracted limit position towards its deployed limit position, and thus a
massive amount of
compressed air fills the inner chamber of cylinder 82 above piston head 94, as
suggested by arrows
B in figure 9. When piston 92 is being forcibly and rapidly urged towards its
deployed limit
position, air located beneath piston head 94 will be forced outside of
cylinder 82 through holes 84
s and 85, to accumulate into annular auxiliary chamber 90 as suggested by
arrows C and D in figure 9.
The compressed air into annular chamber 90 will serve to return piston 92 to
its initial, upper
position, as later described.
This downward motion of piston 92 causes plunger 28 to shoot out of housing
32,
through guide ring 96 and guide hole 2~, and sweep notch 27 of launch plate
26, in which is nested
l o one cleat from the cleat strip loaded in magazine 24. This sweeping of
notch 27 causes the cleat
nested therein to be discharged from tool 20, driven through the hardwood
plank subjacent to the
shoe 29 and into the subfloor being worked on.
When piston 92 is in its deployed limit position, piston head 94 is positioned
beneath
escape holes 84, compressed air coming from main chamber 38 and filling the
inner chamber of
15 cylinder 82 infiltrates holes 84 in order to further pressurize auxiliary
chamber 90, as suggested by
arrows F in figure 10.
Compressed air located within main chamber 38 and inside cylinder 82 apply an
upward force on closure plate 70, as suggested by arrows E in figure 10, which
results is urging the
closure plate 70 - air evacuation member 56 - trigger 64 assembly upwardly
towards its rest
2o position.
When air evacuation member 56 reaches its rest position, fluid communication
between closure chamber 53 and the atmosphere through air outlet channels 49
is interrupted, and
closure chamber 53 starts to fill up with air flowing in through closure
channels 80 from main
chamber 38. Valve 64 consequently starts to move downwardl:y towards its
closed position. As soon
CA 02461515 2004-03-23
2l
as valve 64 starts to move, end 68b of each air inlet channels 68b hecomes
uncovered by the side
wall of valve upper portion 64a, thus re-establishing fluid communication
between main chamber 38
and closure chamber 53. Therefore, compressed air starts to flow into closure
chamber 53 also
through air inlet channels 68, thus accelerating the re-pressurizing of
closure chamber 53 and
thereby accelerating displacement of valve 64 towards its closf:d position.
Once valve 64 is closed, the relative position of closure plate 70 and valve
inner
cavity 74 is such that U-cup 73 no longer provides airtight engagement
therebetween, and the
compressed air located in cylinder 82 above piston 92 is evacuated into the
atmosphere through
notches 62, air evacuation chamber 58, and out of air outlet channels 49, as
suggested by arrows I in
io figure 11. The pressure above piston head 94 having thereby dropped, no
resistance will longer stop
the compressed air previously forced into auxiliary chamber 90 to relax and
spread throughout
cylinder 82, by being injected through holes 85 beneath piston head 94, as
suggested by arrows J in
both figures 11 and 12. Therefore, this depressurizing of auxiliary chamber 90
will thus allow for
piston 92 to spring back to its initial, retracted limit position, as
illustrated in figure 12.
15 Thereafter, once piston 92 has returned to its retracted limit position,
residual
pressurized air located in cylinder 92 beneath piston head 94 leaks out in
controlled fashion through
the interstice between plunger 28 and guide ring 96 (as illustrated by arrows
K is figure 12) and the
inner chamber of cylinder 92 returns progressively to atmospheric pressure,
whereas air chamber 53
is once again brought to the same overpressure level than main chamber 38.
Tool 20 is then ready
2 o for a new nailing cycle.
An important feature of the tool of the present invention -is the fact that
the closing
movement of valve 64, i.e. when a pressure difference on both sides thereof
urges it from its open
position towards its closed position, is not constant and is achieved in two
parts. Firstly, when the
valve 64 is in its open position and just after air evacuation member 56 has
moved back to its initial
CA 02461515 2004-03-23
22
rest position so as to pneumatically isolate closure chamber 53 from the
atmosphere, compressed air
is admitted in closure chamber 53, to initiate movement of valve 64 towards
its closed position,
from main chamber 38 exclusively through closure channels 80 since air inlet
channels 68 are
obstructed by the peripheral wall of the valve. Secondly, as valve 64 starts
to move towards its
closed position, its peripheral wall progressively clears each air inlet
channel end 68b, and
compressed air starts to flow towards closure chamber 53 through air inlet
channels 68 as well,
which will allow closure chamber 53 to become pressurized faster, thus
permitting prompt
displacement of valve 64 towards its closed position. With such variable speed
displacement of
valve 64, the time before piston 92 can return to its initial position is
reduced, and so is the reload
1 o speed of tool 20.
By modifying the amount of closure channels 80 made in valve 64, and/or their
shape, and/or other characteristics thereof, the rate of the initiation of the
movement of valve 64
from its open towards its closed position can be adjusted. Hence,
modifications only have to be done
to these channels to modify the closure speed of valve 64 and t:he reload
speed of the taol.
i5 Accordingly, 30 to 50% less compressed air supply volume is required for
proper
operation of tool 20, thus reducing operation costs of the tool 20 in both
overhead (size of
compressed air pump) and variable costs (electricity for operating the
compression pump).
In the embodiment shown in the figures, the optional O-ring 76 aids in
preventing air
flow towards closure chamber 53 through air inlet channels 68 when valve 64 is
open. Still another
2 c alternate functional embodiments of tool 20 could be envisioned where
valve 64 is deprived from
such an O-ring 76, since the peripheral wall of valve upper portion 64a has a
transverse projection
276 (figure 4) which may be sized and shaped to snugly penetrate and sealingly
engage and obstruct
inlet channel end 80a sufficiently so as to substantially prevent air to flow
therethrough towards
CA 02461515 2004-03-23
23
closure chamber 53 when valve 64 is open; however, with this latter
embodiment, reinforcing
tolerances must be tight.
In the embodiment of the invention, U-cup 78 establishes airtight engagement
of the
peripheral wall of valve 64 to the peripheral wall of head caviay 51. In
another embodiment, impact
s receiving member 46 is deprived from such a U-cup, and head member 48 is
deprived from air inlet
channels 68. In this embodiment, the re-pressurizing of closure chamber 53,
necessary to bias valve
64 towards its closed position after a nailing stroke, is accomplished as
compressed air permeates
towards closure chamber 53 from main chamber 38 through the interstice formed
between the
peripheral wall of valve 64 and the peripheral wall of head cavity 51, instead
of passing through air
1o inlet channels 68. In yet another embodiment where head member 48 comprises
air inlet channels 68
and impact receiving member is deprived from a U-cup such as U-cup 78,
compressed air could
permeate both through air inlet channels 68 and the interstice formed between
the peripheral wall of
valve 64 and the peripheral wall of head cavity 51 to re-pressurize closure
chamber 53.
It is to be noted that although the present tool is described for use with a
conventional
15 continuous air supply, it could be adapted for use with lever actuated
manual release controlled air
supply types of pneumatic nailing tools.
Impact receiving member 46 screwable onto and detachable from main housing 32
is
the preferred embodiment. However, adapting the present invf°ntion to a
standard fixed head such as
one disclosed in US patent 4,907,730 should be considered within the scope of
the present
2 o invention.
Main use of the present invention is directed toward installation of hardwood
flooring. However, other applications are deemed within the scope of this
invention, in particular,
nailing softwood (e.g. pine tree) floorings of the tongue-and-groove
interconnection type, or
~~
CA 02461515 2004-03-23
24
installation of panelling elements or of outdoor decking. Therefore, the
present invention is directed
to any pneumatic tool triggered by a hammer blow.
