U.S. patent application number 10/700081 was filed with the patent office on 2005-05-05 for latching mechanism for combustion chamber plate of a fastener driving tool.
Invention is credited to Adams, Joseph S., Doherty, James E., Van Erden, Donald L..
Application Number | 20050091962 10/700081 |
Document ID | / |
Family ID | 34551111 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050091962 |
Kind Code |
A1 |
Van Erden, Donald L. ; et
al. |
May 5, 2005 |
LATCHING MECHANISM FOR COMBUSTION CHAMBER PLATE OF A FASTENER
DRIVING TOOL
Abstract
A combustion chamber assembly for use in a combustion tool
including a combustion chamber, at least one combustion chamber
plate disposed in the chamber, the at least one combustion chamber
plate and the chamber members being configured for relative
reciprocal movement, the combustion chamber assembly having at
least one latch member associated with control of movement of at
least one plate within the combustion chamber to divide the chamber
into multiple volumes. The combustion chamber assembly further has
a release for the latch member for permitting relative movement of
the at least one combustion chamber plate and the combustion
chamber.
Inventors: |
Van Erden, Donald L.;
(Wildwood, IL) ; Doherty, James E.; (Barrington,
IL) ; Adams, Joseph S.; (Salt Spring Island,
CA) |
Correspondence
Address: |
LISA M. SOLTIS
ILLINOIS TOOL WORKS INC.
3600 WEST LAKE AVENUE
GLENVIEW
IL
60025
US
|
Family ID: |
34551111 |
Appl. No.: |
10/700081 |
Filed: |
November 3, 2003 |
Current U.S.
Class: |
60/39.6 |
Current CPC
Class: |
B25C 1/08 20130101 |
Class at
Publication: |
060/039.6 |
International
Class: |
F02G 001/00; F01B
029/08 |
Claims
1. A combustion chamber assembly for use in a combustion tool
including a combustion chamber, at least one combustion chamber
plate disposed in said chamber, the at least one combustion chamber
plate and the chamber members being configured for relative
reciprocal movement, said combustion chamber assembly comprising:
at least one latch member is associated with control of movement of
at least one plate within the combustion chamber to divide said
chamber into multiple volumes; and a means for releasing said latch
member for permitting relative movement of the at least one
combustion chamber plate and the combustion chamber.
2. The combustion chamber assembly of claim 1 wherein the tool
includes a first combustion chamber plate and a second combustion
chamber plate in the combustion chamber and said latch member is
configured for releasably securing the first combustion chamber
plate relative to the second combustion chamber plate.
3. The combustion chamber assembly of claim 1 further including a
cylindrical rod associated with one of said plates and having a
shoulder wherein the latch member is on one of said shoulder and
said cylindrical rod.
4. The combustion chamber assembly of claim 1 wherein one of said
plates has a cylindrical portion sliding relative to said
cylindrical rod, said latch member is one of said cylindrical rod
and said cylindrical portion.
5. The combustion chamber assembly of claim 1 wherein the latch
member is configured to be biased towards the combustion chamber to
project laterally until a trigger is pulled.
6. The combustion chamber assembly of claim 1 wherein said latch
member pivotably engages the at least one combustion chamber
plate.
7. The combustion chamber assembly of claim 1 wherein said latch
member is relatively elongate and is pivotably secured to one of
the combustion chamber plates for movement between a first position
in relatively axial alignment with the combustion chamber and a
second position out of general axial alignment.
8. The combustion chamber assembly of claim 7 wherein said release
means includes a trigger connected to said latch member for causing
movement from said first position to said second position.
9. The combustion chamber assembly of claim 1 further including a
combustion chamber sleeve displaceable from at least one of the
combustion chamber members and wherein said at least one latch
member is disposed on the combustion chamber sleeve.
10. The combustion chamber assembly of claim 9 wherein the latch
member is configured to be biased towards the combustion chamber to
project laterally until a trigger is pulled.
11. In a combustion powered fastener driving tool, a combustion
chamber assembly, comprising: a combustion chamber; at least one
combustion chamber plate being displaceable in the longitudinal
direction of said combustion chamber; a latch member that
releasably holds the at least one combustion chamber plate for
common movement with a first combustion chamber member during
displacement of the at least one combustion chamber plate from a
second combustion chamber member; and means for releasing said
latch member.
12. The combustion chamber assembly of claim 11 further including a
shoulder and a cylindrical rod wherein said latch member is on one
of the shoulder and the cylindrical rod.
13. The combustion chamber assembly of claim 11 further including a
first position and a second position of latch member motion,
wherein said release means includes a trigger connected to said
latch member for causing movement from said first position to said
second position.
14. A latching mechanism for use in a combustion tool including a
first combustion chamber plate and a second combustion chamber
plate, said combustion chamber plates being movable to a fastener
driving tool, comprising: a plurality of combustion chamber plates
movable relative to each other in the combustion chamber; and a
latch means including at least one a latch member having a first
position engaged with at least one of the plurality of combustion
chamber plates and a second position disengaged from said at least
one of the plurality of combustion chamber plates.
15. The latching mechanism of claim 14 wherein said latch member is
pivotably disengaged.
16. A combustion chamber assembly for a fastener driving tool,
comprising: a combustion chamber plate; a sleeve movable with
respect to said combustion chamber plate; a latch member associated
with said sleeve for positioning the combustion chamber plate
against said sleeve; and said sleeve and said combustion chamber
plate being displaceable relative to a tool housing.
17. The combustion chamber assembly of claim 16 wherein the latch
member reciprocates transversely relative to the movement of said
sleeve relative to said tool housing.
18. The combustion chamber assembly of claim 16 further including a
biasing element between the plate and the sleeve.
19. The combustion chamber assembly of claim 16 further including a
stop disposed in said chamber for restricting movement of the
plate.
20. The combustion chamber assembly of claim 16 wherein the stop
defines a reduced diameter sleeve to prevent plate movement.
21. A latching mechanism for a fastener driving tool having at
least one combustion chamber plate, comprising: a sleeve movable
with respect to at least one combustion chamber plate; and a
plurality of latches configured for retaining at least one
combustion chamber plate in a first position and a second
position.
22. The latching mechanism of claim 21 wherein said plurality of
latches have different circumferential angles such that at least
one of the combustion chamber plates is not aligned with at least
one of the plurality of latches in a first position and is aligned
with at least one of the plurality of latches in a second
position.
23. The latching mechanism of claim 21 further comprising a cam on
the housing for engaging at least one of a plurality of
latches.
24. The latching mechanism of claim 21 further including a spring
associated with the combustion chamber plate wherein the spring
biases the chamber plate against each of the plurality of
latches.
25. The latching mechanism of claim 18 wherein the latch engages a
cam for transversely moving the cam relative to the movement of
said sleeve.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a latching mechanism for a
simplified gas fastener-driving tool, in particular, a latching
mechanism for use in a combustion chamber of such a tool. Such
fastener-driving tools are available commercially from ITW-Paslode
(a division of Illinois Tool Works, Inc.) of Vernon Hills, Ill.
[0002] Combustion-powered tools, or combustion tools, are known in
the art, and one type of such tools, also known as IMPULSE.RTM.
brand tools for use in driving fasteners into workpieces, is
described in commonly assigned patents to Nikolich U.S. Pat. Re.
No. 32,452, and U.S. Pat. Nos. 4,522,162; 4,483,473; 4,483,474;
4,403,722, 5,197,646 and 5,263,439, all of which are incorporated
by reference herein. Similar combustion-powered nail and staple
driving tools are available commercially from ITW-Paslode of Vernon
Hills, Ill. under the IMPULSE.quadrature..quadrature. and
PASLODE.RTM. brands.
[0003] Fastener-driving tools are provided with a multitude of
components necessary for performing ancillary functions of the
tool. One particularly important ancillary function of the tool is
scavenging. There are two basic ways that residual combustion
products from a combustion chamber are scavenged: a) by dilution,
and b) by displacement. The dilution method consists of driving air
through the combustion chamber. Usually a fan drives this process.
Typically, 2.5 times the combustion chamber volume change is needed
to exchange the residual combustion gas with air, making it a
relatively inefficient method.
[0004] A more efficient process is displacement. The displacement
method consists of removing combustion products by reducing the
combustion volume to zero, hence displacing the combustion
products. Subsequently, when the volume is increased, air is drawn
into the volume.
[0005] One disadvantage of the current combustion-powered tools
used for fastening is that they have a multitude of components that
perform the ancillary functions needed to support the basic
function of the tool, such as the scavenging function. The use of
expensive electronic or electrical components, including batteries,
fan motors, control electronics and spark electronics for these
ancillary functions is known.
[0006] A further disadvantage of these tools having complex
components is that the additional components make the tool more
susceptible to costly repairs.
[0007] Another approach to scavenging is taught by U.S. Pat. No.
4,712,379 to Adams, incorporated by reference herein, which
discloses a combustion chamber divided by a movable plate with
holes. The use of this approach accelerates the rate of combustion
so that the combustion pressure reaches a maximum early in the
drive stroke of the free piston. The acceleration in the rate of
combustion is due to the turbulence created in the combustion
chamber when the fuel-air mixture passes through the holes in the
movable plate.
[0008] An advantage of using the movable plates is that the piston
is shielded from the pressure increase in the first chamber where
the combustion is initiated. A further advantage is that the
combustion in the first chamber creates a flame that passes through
the holes in the movable plate, and ignites the second chamber
earlier in the piston's cycle. The earlier the pressure reaches its
maximum in the piston drive stroke, the more energy is delivered to
the fastener being driven, and ultimately, the work piece.
[0009] Another ancillary function of fastener-driving tools is to
establish the correct fuel-air mixture needed for efficient
combustion. This process is more difficult in the divided
combustion chamber approach. Known solutions to establishing the
correct fuel-air mixture include independently introducing the
correct amount of fuel to each chamber or premixing the fuel and
air in a pre-chamber before they are drawn into the divided
combustion chamber.
[0010] One disadvantage is that these approaches involve additional
components to support the mixing process. A further disadvantage is
that these known approaches often cannot accommodate the tool when
a rapid cycle is desired.
[0011] Thus, there is a need for a fastener-driving combustion tool
with movable plates that does not require electric or electronic
parts. There is also a need to provide a fastening tool combustion
chamber that achieves the correct fuel-air mixture. Another need is
to provide a fastening tool combustion chamber where the piston is
shielded from the pressure increase in the first chamber where the
combustion is initiated. There is also a need to provide the
turbulance to achieve rapid burn. A still further need is to
provide a fastening tool combustion chamber where the pressure is
delivered to the piston early in its drive stroke. Yet another need
is to provide a fastening tool combustion chamber that is less
expensive to manufacture. Still another need is to provide a
fastening tool combustion chamber that is less susceptible to
costly repair. A further need is to provide a fastening tool
combustion chamber that precisely controls the movement of the
plates in the combustion chamber.
SUMMARY OF THE INVENTION
[0012] The above-listed concerns are addressed by the present
combustion chamber assembly for a combustion-tool, which features a
combustion chamber, at least one movable plate and a latching
mechanism. The combustion chamber assembly provides a simplified
movable plate that can be selectively positioned for achieving the
desired fuel-air mixture. Movement of the plate is achieved by a
variety of latches that are less expensive to manufacture and
repair than the electric and electronic counterparts. Another
feature of the present combustion chamber assembly is that the
latch member also positions the movable plate in a specific
location where increased pressure can be delivered to the piston
early in the drive stroke. Shielding of the piston from pressure
increases is also accomplished by positioning the movable plate
between the regions where combustion is initiated and where the
piston is housed. Still another feature of the present invention is
the creation of the turbulance in the combustion chamber needed to
achieve a rapid burn of the fuel air mixture.
[0013] More specifically, the present invention provides a
combustion chamber assembly for use in a combustion tool including
a combustion chamber having at least one combustion chamber plate
disposed in the chamber and where the at least one combustion
chamber plate and the chamber members are configured for relative
reciprocal movement. The combustion chamber has at least one latch
member associated with at least one of the combustion chamber
members and the at least one combustion chamber plate for
releasably holding the relative position of the at least one
combustion chamber plate to the chamber during operation of the
tool. A release for the latch member is also provided which permits
relative movement of the at least one combustion chamber plate and
the combustion chamber.
[0014] In another embodiment, a combustion chamber assembly for a
combustion powered fastener driving tool has a combustion chamber;
at least one combustion chamber plate being displaceable in the
longitudinal direction of the combustion chamber, a latch member
that releasably holds the at least one combustion chamber plate to
a first combustion chamber member during displacement of the at
least one combustion chamber plate from a second combustion chamber
member, and a release for the latch member.
[0015] The present invention further provides a latching mechanism
for use in a combustion tool including a first combustion chamber
plate and a second combustion chamber plate, the combustion chamber
plates being movable to a fastener driving tool, having a plurality
of combustion chamber plates wherein the combustion chamber plates
are movable relative to each other in the chamber, a latch release
for the latch member which releasably holds the plurality of
combustion chamber plates adjacent to one another; and a latch
including a latch member associated with one of the combustion
chamber plates in a first position engaged with at least one of the
plurality of combustion chamber plates and a second position
disengaged with at least one of the plurality of combustion chamber
plates.
[0016] In another embodiment, a combustion chamber assembly has a
combustion chamber plate and a sleeve movable with respect to the
combustion chamber plate. The combustion chamber assembly also has
a latch member associated with the sleeve for positioning the
combustion chamber plate against the sleeve, and the sleeve and the
combustion chamber plate are displaceable relative to a tool
housing.
[0017] In another embodiment, a latching mechanism for a fastener
driving tool having at least one combustion chamber plate has a
sleeve movable with respect to the combustion chamber plate, and a
plurality of latches configured for retaining at least one
combustion chamber plate in a first position and a second
position.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0018] FIG. 1 is a vertical cross-section of the present combustion
chamber assembly showing the tool off the work surface;
[0019] FIG. 2 is a vertical cross-section of the combustion chamber
assembly of FIG. 1 showing the tool in contact with the work piece
before the latch is released;
[0020] FIG. 3 is a vertical cross-section of the combustion chamber
assembly of FIG. 1 showing the latch released;
[0021] FIG. 4 is a vertical cross-section of an alternate
embodiment of the present combustion chamber assembly showing the
tool off the work surface;
[0022] FIG. 5 is a vertical cross-section of the combustion chamber
assembly of FIG. 4 showing the tool in contact with the work
surface before the latch is released;
[0023] FIG. 6 is a vertical cross-section of the combustion chamber
assembly of FIG. 4 showing the latch released;
[0024] FIG. 7 is a vertical cross-section of the combustion chamber
assembly of FIG. 4 showing the piston extended;
[0025] FIG. 8 is a vertical cross-section of another alternate
embodiment of the present combustion tool showing the tool off the
work surface;
[0026] FIG. 9 is a vertical cross-section of the combustion chamber
assembly of FIG. 8 showing the tool with a first latch engaged;
[0027] FIG. 10 is a vertical cross-section of the combustion
chamber assembly of FIG. 8 showing the second latch engaged;
and
[0028] FIG. 11 is a plan view of a divider plate of the tool of
FIG. 8.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0029] Referring now to FIG. 1, a combustion chamber assembly
suitable in use with combustion tools of the type discussed above,
and incorporating one embodiment of the present invention is
generally designated 10 and includes a combustion chamber 12 having
a generally cylindrical shape with a cylindrical wall 14. A
ring-shaped bottom 16 defines an opening 18 at which location a
guide cylinder 20 is secured, preferably by integral forming or
casting, however other known fastening technologies are
contemplated. The guide cylinder 20 has a bottom 22. A piston 24 is
located within the piston cylinder 20 and has a piston plate 26
abutting the combustion chamber 12 and a piston rod, or as most
commonly called, a driver blade 28 that extends from the piston
plate forming a general "T" shape in cross-section. The bottom 22
of the guide cylinder 20 has an opening 30 through which the driver
blade 28 protrudes.
[0030] In FIG. 1, the tool of the combustion chamber assembly 10 is
not in contact with the work surface and the piston 24 is in a
retracted position. The piston plate 26 is generally flush with the
ring-shaped bottom 16. Sealing rings or piston rings 32, 34 are
positioned in spaced relation on the piston plate 26 as is known,
and with the piston plate sealingly define a lower end of the
chamber 12, creating separate volumes on each side of the piston
plate 26. The driver blade 28 slightly protrudes from the opening
30 of the guide cylinder 20.
[0031] In the combustion chamber 12, one of two combustion chamber
plates includes a plate 36 having a generally cylindrical plate
base 38 with a tubular, generally cylindrical portion 40 extending
vertically from, and transverse to the base. The plate 36 is
configured to be reciprocally movable along the longitudinal axis
of the combustion chamber 12. A central opening 42 is defined by
the plate 36, extends up through the cylindrical portion 40 and is
generally perpendicular relative to the plate base 38.
[0032] A separation plate 44 is located between the plate 36 and
the ring-shaped bottom 16. The separation plate 44 has an outer
diameter corresponding to the inner diameter of the cylindrical
wall 14. A movable rod 48 projects through the central opening 42
of the plate 36 and is attached to the separation plate 44. The rod
48 is generally cylindrical and has a length that exceeds the
length of the cylindrical portion 40. The rod 48 has an outer
diameter generally corresponding to the diameter of the central
opening 42 for relative slidably movement and extends transversely
from the separation plate 44. A shoulder 50 is located at a free
end of the rod 48, has a diameter that exceeds the inner diameter
of the central opening 42 and is configured for impeding motion of
the rod 48 in the longitudinal direction with respect to the plate
36. Both the cylindrical portion 40 and the rod 48 project through
an opening 51 in an upper end of the chamber 12.
[0033] Drive rods 52 are fixedly connected to the plate 36 and
extend outside of a cylindrical wall 54 of the guide cylinder 20 in
a direction generally parallel to the axis of the combustion
chamber 12. The drive rods 52 each extend through an upper rod
opening 56 formed in the separation plate 44 and a lower rod
opening 58 formed in the ring-shaped bottom 16 of the combustion
chamber 12. A drive ring 60 is concentrically placed around the
cylindrical wall 54 of the guide cylinder 20 and is secured to a
lower end of each of the drive rods 52, as seen in FIG. 1. A
compression spring 62 is associated with each of the drive rods 52
and extends between the drive ring 60 and the ring-shaped bottom 16
of the combustion chamber 12. When the tool incorporating the
combustion chamber assembly 10 is off the work surface, the
compression springs 62 bias the plate 36, and in turn, the
separation plate 44 toward the ring-shaped bottom 16.
[0034] A latching mechanism including a latch member 64 is fixedly
and pivotably attached to the shoulder 50 of the cylindrical rod 48
at a pivot point 66, which is disposed generally transversely to
the longitudinal axis of the combustion chamber 12. In the present
embodiment, the latch member 64, the pivot point 66, the rod 48,
the shoulder 50, and the cylindrical portion 40 are considered to
be parts of the latching mechanism. In the preferred embodiment,
the latch member 64 is attached to the cylindrical rod 48. However,
it is also contemplated that the latch member 64 could be pivotably
attached to the cylindrical portion 40, as long as the plates 36
and 40 can move in uniform in a first direction, and can be
separated for movement in a second direction. Other latching
mechanisms contemplated include but are not limited to, a latch
member 64 as shown, or any other latch member, a pivot point 66 as
shown, or any other pivotable action where a latch member is
engaged with a combustion chamber plate 36 and 40. When the latch
member 64 is in a vertical orientation (FIG. 1), the plate 36 is
engaged at a location 68. When engaged, the contact between the
latch 64 and the cylindrical portion 40 prevents the cylindrical
rod 48 from moving relative to the cylinder portion 40 and the
plate 36. The latch 64 locks the cylindrical rod 48, and in turn,
the separation plate 44 in an adjacent and static position relative
to the plate 36.
[0035] For providing flow out from the combustion chamber 12, a
check valve 70 is provided on the ring-shaped bottom 16. In
operation, an actuation member 72 is provided on the drive ring 60
opposite the check valve 70. When the drive rods 52 move to
increase the distance between the plate 36 and the ring-shaped
bottom 16, the actuation member 72 moves in the direction of the
check valve 70. When the distance between the plate 36 and the
ring-shaped bottom 16 is at its maximum distance, the actuation
member 72 and the check valve 70 engage, blocking the check valve
and preventing gas flow out from the combustion chamber 12 (as
shown in FIG. 2).
[0036] A plurality of holes 74 are provided on the separation plate
44. The holes 74 are generally uniformly arranged on the separation
plate 44 to allow the flow of gases between a forechamber section
76 and a main chamber section 78, shown in FIG. 3.
[0037] A plurality of outlet openings 80 for air and exhaust gas
flow out of the guide cylinder 20 is provided at a location closer
to the bottom of the cylinder 22. The piston 24 actuates the flow
of air and gases out of the outlet openings 80 as the piston passes
the outlet openings moving in a direction towards the bottom
22.
[0038] Referring to now to FIG. 2, the position of the plate 36 and
the separation plate 44 at the top of the combustion chamber 12
correspond to a completely expanded main chamber section 78. When
the tool 10 contacts the work piece, the workpiece contact element
(not shown) compresses the spring 62 moving the drive ring 60
towards the bottom 16 of the chamber 12, which displaces the plate
36 by the drive rods 52 toward the top of the combustion chamber
12. Since the latch member 64 defaults to a vertical position, the
plate 36 lifts the separation plate 44 through engagement between
the latch and the cylindrical portion 40. In a vertical
orientation, the latch member 64 prevents the cylindrical rod 48,
and in turn, the separation plate 44 to which the cylindrical rod
is attached, from moving apart from the plate 36 until a trigger 79
(shown schematically) is pulled. A spring 55 is connected to the
separation plate 44 and the plate 36 and is located in a recess 57
of the plate 36. The actuation member 72 mounted on the drive ring
60 blocks further movement of the drive ring by contacting the
closed check valve 70.
[0039] Located on the cylindrical wall 14 of the combustion chamber
12 is at least one radial opening 82. Relatively smaller diameter
feed channels 84 communicate with a metering head 86 which delivers
fuel to the radial openings 82. As the cylindrical portion 40 moves
upward relative to the combustion chamber 12, a stirrup 88 that is
pivotally supported on the cylindrical wall 14 by a pivot point 90,
and is slidably engaged by the cylindrical portion 40 at a roller
89, moves the metering head 86 towards the feed channel 84. When a
metering valve 99 is opened by the metering head 86, fuel is
injected into the main chamber section 78.
[0040] As the plate 36 and the separation plate 44 are moved to the
top of the combustion chamber 12, fuel is mixed with air and the
fuel-air mixture is displaced into a main chamber section 78
through ports 37 and holes 74.
[0041] A dampening device 92 such as a resilient bumper is located
at the bottom 22 for damping the movement of the piston 24. The
dampening device 92 may be of rubber or any similar known
material.
[0042] Referring now to FIG. 3, the tool incorporating the
combustion chamber assembly 10 is depicted after the trigger 79 has
been pulled. The trigger 79 releases the latch member 64 by moving
the latch member to an inclined or non-vertical position, allowing
the separation plate 44 to move away from the plate 36, which
remains positioned adjacent to the top of the combustion chamber
12. The spring 55, which is disposed in recess 57 when the plates
36 and 44 are together, actuates the movement of separation plate
44. Alternatively, a spring could be located outside of the
chamber, such as between the shoulder 50 and the top of plate 36 or
any other configuration that would bias the plates 36 and 44 apart.
This movement of the separation plate 44 defines a volume between
the plate 36 and the separation plate referred to as a forechamber
section 76. Fuel is displaced through the holes 74 on the
separation plate 44 between the main chamber 78 and the forechamber
section 76 as the separation plate moves relative to the plate
36.
[0043] An ignition device 94 such as a spark plug is provided for
generating an electrical spark for igniting the fuel mixture and is
preferably located at the end of the cylindrical rod 48. The
ignition device 94 initiates combustion in the forechamber section
76 as the separation plate 44 moves away from the plate 36.
[0044] Many variations on the illustrated embodiment are also
possible, including different ignition systems, chamber shapes,
fuel injectors, and valving and sealing arrangements. Whatever the
specific configuration, the operation of the fastener-driving tool
incorporating the combustion chamber assembly will be described in
detail with reference to FIGS. 1-3.
[0045] In operation, the holes 74 of the separation plate 44 enable
the displacement of the fuel-air mixture from the main chamber
section 78 to the forechamber section 76 so that both chambers have
fuel. The flow through the holes 74 in the separation plate 44
causes turbulence in the forechamber section 76. Soon after the
trigger 79 is pulled, a spark from the ignition device 94 ignites
the turbulent fuel-air mixture in forechamber section 76, resulting
in increased flame speed results in the forechamber section. The
flame then flows through the holes 74 from the forechamber section
76 to the main chamber section 78. Combustion gases impact the
piston 24 and drive the piston down through the guide cylinder 20.
The increased flame speeds in the main chamber section 78 result in
combustion occurring sooner in the piston stroke such that the
piston 24 has more inertia as it is driven down through the guide
cylinder 20.
[0046] Downward movement of a piston 24 actuates the flow of air
and gases out of the one way flow outlet openings 80. After the
piston 24 reaches the end of its stroke, it is brought back to its
initial position by a vacuum caused by thermal feedback produced by
the cooling of the fuel gases. The combustion chamber remains
sealed until the piston 24 returns to its initial position.
[0047] Referring now to FIGS. 4-7, a second embodiment of a
combustion chamber assembly having a latching mechanism for a
combustion chamber plate of a fastener-driving tool is shown and
generally designated 100. A feature of the embodiment 100 is that
the latching mechanism uses a simple spring biased latch member and
stop configuration. In FIG. 4, the combustion tool of the
combustion chamber assembly 100 is similar to the tool of the
combustion chamber assembly 10, in which the combustion chamber 10
is mounted, is off the work surface, and a workpiece contact
element 104 protrudes from a housing 106 (not shown). A sleeve 108
is collapsed over a piston cylinder 110 and a spring 112 biases the
sleeve against the piston cylinder. A divider plate 114 is nested
between the piston cylinder 110 and the sleeve 108 preferably near
a top of the sleeve (FIG. 4). In addition, the divider plate 114 is
dimensioned for slidable movement relative to the sleeve 108. When
a laterally reciprocating latch member 116 is engaged, the divider
plate 114 is positioned against an inner end surface 117 of the
sleeve 108. In the engaged position (FIGS. 4-7), an end 116a of the
latch member 116 projects into the interior of the sleeve 108. As
best seen in FIG. 5, the end 116a is preferably inclined, however
other configurations are contemplated. Further, the latch member
116 is preferably spring biased to the engaged position by a spring
116b.
[0048] A piston 118 is located within the piston cylinder 110 for
reciprocal movement similar to the piston 24. A piston plate 120 is
generally flush with the top of the piston cylinder 110 and a
driver blade 122 depends from the piston plate 120 and through an
opening 123 in the bottom of the piston cylinder.
[0049] Referring now to FIG. 5, the workpiece contact element 104
of the tool is in contact with the work surface and the tool has
been depressed against the work piece prior to firing as is known
in the art. As the tool is depressed, the workpiece contact element
104 pushes the sleeve 108 into a top position displaced from the
piston cylinder 110, thus creating a sleeve volume 126. With the
latch member 116 laterally projecting from a wall 128 of the sleeve
108, the latch causes the divider plate 114 to move upward with the
sleeve, adjacent the sleeve end wall. Simultaneously, air is drawn
into the sleeve volume 126 past a sleeve seal 130. When the sleeve
108 reaches the sleeve top position (FIG. 5), fuel is injected
into, (FIGS. 1-4) and sealed in the sleeve volume 126 by the seal
130.
[0050] Referring now to FIG. 6, the embodiment 100 is depicted when
the latch member 116 is released, or is moved laterally generally
outward, after the trigger 79 is fully depressed, causing ignition.
A second spring 132 is attached to the sleeve 108 and drives the
divider plate 114 downward until a stop 134 disposed on an inner
wall 135 of the sleeve 108 engages the divider plate. A first flow
volume 136 and a second flow volume 138 are defined in the sleeve
volume 126 by the downward displacement of the divider plate 114.
The fuel-air mixture flows through holes 140 in the divider plate
114 from the second flow volume 138 to the first flow volume 136.
Turbulence is thus created in the first flow volume 136 which is
used to produce a faster flame speed.
[0051] Referring now to FIG. 7, combustion occurs in the first flow
volume 136 by igniting the fuel air mixture when the divider plate
114 reaches the stop 134. In the preferred embodiment, ignition
occurs via a spark plug as is shown in the art. While the
combustion starts in the first flow volume 136 under turbulent
conditions, the flame propagates through the holes 140 in the
divider plate 136, igniting the second flow volume 138. The rapid
expansion of combustion gases drives the piston 118 down in the
piston cylinder 110 to impact a fastener. Venting of the combustion
gases occurs when the piston 118 passes check valves 146 at the end
of the stroke. The piston 118 returns to the initial position (FIG.
4) in the piston cylinder 110 by the vacuum caused by the cooling
of the combustion gases.
[0052] Referring now to FIGS. 8-11, another alternative combustion
chamber assembly incorporating a latching mechanism is generally
designated 150. Components which are shared with the latching
mechanism 100 have been designated with identical reference
numbers. A distinctive feature of the embodiment 150 is that the
latching mechanism uses at least one spring biased latch member and
a cam to engage at least one of the latch members. Another feature
of the mechanism is that it increases the flow of air and fuel
through openings in the divider plate 114, which maximizes the
firing response time of the tool. The latching mechanisms of the
combustion chamber assembly 10, 100 use a hole size in the divider
plate, 44, 114 that optimizes the drive force of the piston. In
some applications, the optimal hole size may be too small to allow
the divider plate to snap back into the upward position after the
tool has been triggered. This affects the rate at which the tool
can be repeatedly fired. In the latching mechanism of the
combustion chamber assembly 150, an important distinguishing
feature is that the shape of a divider plate 152 is modified to
achieve large openings when the plate is in the upward motion, yet
is occluded by the latching mechanism to maximize the piston
drive.
[0053] Referring now to FIG. 8, the latching mechanism of the
combustion chamber assembly 150 is shown in the ready position,
wherein the workpiece contact element 104 is shown attached to a
sleeve 154 in a rest position. The sleeve 154 is collapsed against
the divider plate 152 which is, itself, collapsed against the
piston 118. A housing 156 is attached to the piston cylinder 110.
The sleeve 154 is collapsed over the piston cylinder 110 and a
spring 158 biases the divider plate 152 against the piston
cylinder. The divider plate 152 is nested between the piston
cylinder 110 and the sleeve 154. A first latch member or latch tab
160 and a second vertically displaced latch member or latch tab 162
are biased by springs 163 to project laterally outwardly from the
sleeve 154. In addition, the tabs 160, 162 are laterally
reciprocable relative to the sleeve 154. The first latch tab 160 is
located near a top of the sleeve 154 and the second latch tab 162
is located near the bottom of the sleeve.
[0054] Referring now to FIG. 9, the workpiece contact element 104
is placed against the work piece, displacing the sleeve 154 upward
and creating the sleeve volume 126. Fuel is injected and mixed with
air at the start of sleeve displacement. The second latch tab 162
is slidingly engaged by the trigger 79 and keeps the divider plate
152 against the piston 118. A cam 164 on the housing 156 slidingly
engages the first latch tab 160 prior to firing to protrude into
the sleeve volume 126. The first latch tab 160 and the second latch
tab 162 are formed at different circumferential angles such that
scallops 166 (best seen in FIG. 11), are not aligned with the
second latch tab 162 but are aligned with the first latch tab
160.
[0055] Upon full depression, the trigger 79 releases the second
latch tab 162 which slidingly disengages the divider plate 152.
Next, the divider plate 152 moves upward against the first latch
tab 160 due to a biasing force generated by the spring 158. In this
manner, sleeve volumes 156, 138 are defined on either side of
divider plate 152. The first latch tab 160 is shaped to occlude the
scallops 166 in the divider plate 152. When combustion is initiated
in the first flow volume 136, the flame must pass through the
divider plate 114 at the holes 168 and are blocked from passing
through the divider plate at the scallops 166. The combustion of
the gases in the second flow volume 138 causes the piston 118 to be
driven down the cylinder 110 for impacting a fastener.
[0056] This configuration allows the divider plate 152 to move more
easily against the hydraulic friction in the motion upward. This
advantage is due to the increased surface area of the total holes
168 in the divider plate 152 when the scallops 166 are not
occluded. More air transfer between the first flow volume 136 and
the second flow volume 138 can occur as a result of the scallops
166. When there is less hydraulic friction, the divider plate 152
can move upward towards the first latch tab 160 at an increased
rate which, in turn, makes the firing cycle shorter.
[0057] Accordingly, the latching mechanism of the embodiments
discussed above provides a latch member which serves to position at
least one movable plate within a combustion chamber of a combustion
powered tool. A latching mechanism using spring biasing on at least
one latch member was also provided. A feature of the embodiments
discussed above is that a simplified mechanism for precisely
controlling at least one movable plate for achieving the correct
fuel-air mixture in the combustion chamber is provided. The present
invention also provides a low cost and easy to repair alternative
to electronic or electrical parts.
[0058] While particular embodiments of the latching mechanism for a
combustion chamber plate of a fastener driving tool has been shown
and described, it will be appreciated by those skilled in the art
that changes and modifications may be made thereto without
departing from the invention in its broader aspects and as set
forth in the following claims.
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