Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Background
This invention rela-tes to a hammer-activated powder-
actuated fastening tool. Powder-actuated fastening tools are
used for driving fasteners or studs into concrete and other
material. Such tools are conventionally of two types ~- high
velocity and low velocity. A low velocity tool includes a piston
which is driven by the explosive force of a fired cartridge
and drives the fastener into the workpiece, i.e., the material
into which the fastener is driven. A high velocity tool does
not include a piston, and the fastener is driv2n directly by
the explosive force of the cartridge.
Several low velocity stud drivers are available. One type
of low velocity tool is described in Patent No. 3,066,302 and in-
cludes a means for resetting the piston to its firing position at
the rear or breech end of the piston guide. This tool is a pistcl-
kype tool w~ich uses a trigger and sear to trip a spring-loaded
~iring pin. The firing pin is cocked by pushing the muz~le end of
the tool against the workpiece to move the piston guide rearwardly
within the tool housing and to compress the spring.
Pistol-type low velocity stud drivers are quite popular,
but they are relatively expensive. For this reason hammer-activated
stud drivers have been offered. Hammer-activated stud drivers are
conventionally operated by placing the muzzle end of the tool against
the workpiece and striking the rear end of the tool with a hammer to
fire the cartridge. Such tools do not need the trigger a~dsear
mechanisms and are less expensive than the pistol-type stud drivers.
However, the relative simplicity of the hammer-activated tools pro-
vides certain disadvantages. For example, the tool may be inadver-
tently drop-fired, i.e., the cartridge may be fired i~ the tool is
accidentally dropped on its rear end. Also, it is generally more
difficult to load and unload hammer-activated tools than pistol-type
tools. One type of hammer-activated tool is described in co-owned
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Patent No. 2,768,375, but this tool is a high velocity tool. To
the best of our knowledge, there is only one low velocity hammer-
driven powder-actuated stud driver on the market.
Summary of the Invention
The invention provides a low velocity hammer-activated
powder-actuated fastening tool which is inexpensive yet safe and
easy to operate. The tool is loaded merely by sliding the piston
; guide forwardly within the housing so that a cartridge can be
inserted through a breech opening in the housing into a cartridge
~older on the rear end of the piston guide. The tool is ready to
fire when the piston yuide is returned rearwardly to position
the cartridge adjacent the firing mechanism. The firing mechanism
includes a bolt which is spring-biased away from the cartridge,
and the rear end of the bolt i5 surrounded by a protectiv~ shroud
to prevent drop-firing and to protect the operator's hand from
improper directed hammer blows. A nut on the bolt can be position-
ed to provide a desired preset spring force. The tool is fired by
striking the bolt with sufficient force to overcome the force of
; the spring and to driye the bolt against the cartridge. The
explosive force of the cartridge drives the piston forwardly within
the pi~ton guide. The piston is returned to t~e rear of the piston
guide by moving the piston guide forwardly within the housing,
forward movement of the piston being prevented by an abutment in
the housing which extends through a slot in the piston guide.
A cartridge ejector pin on the rear end of the piston ejects the
spent cartridge from the cartridge holder when the piston is reset,
and the cartridge is free to fall from the housiny through the
breech opening. The piston is provided with a friction ring to
maintain the piston in a ready-to-fire position, but the piston
is free to move forward slightly from its cartridge-ejecting
position to permit a new cartridge to be inserted.
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Description of the Drawing
The invention will be explained in conjunction with an
illustrative embodiment shown in the accompanying drawing, in
which--
Fig. 1 is a longitudinal sectional view of a fasteningtool formed in accordance with the invention, the tool being
shown in a ready-to-fire position;
Fig. 2 is a view similar to Fig. 1 showing the tool
after it has been fired;
Pig. 3 is illustrating the piston guide moved forwardly
to reset the piston and to eject the cartridge;
Fig. 4 is a plan Yiew of the piston guide as would be
seen a,long the line 4-4 of,Fig. 3;
Fig. 5 is a sectional view taken along the line 5-5 of
Fig. 3;
Fig. 6 is an enlarged ~ragmentary view o~ the rear end
of the tool of Fig. 2; and
Fig. 7 is an enlarged plan Yiew o~ the abutmen~ spring.
Description of Specific Embodiment
Referring to Figs. 1-3, the numeral 10 designates gener-
ally a hammer-activated powder-actuated fastening tool which
includffs an outer cylindrical tubular housing ll, a cylindrical
tubular piston guide 12 which is reciprocable within the housing,
and a piston 13 which is reciprocable within the piston guide.
A flanged gripping handie 14 is secured to the rear end of the
tool, and the tool is operated by grasping the tool around the
grip 14 with one hand and pressing the muzzle or forward end
15 of the- tool against a workpiece 16. In the illustration
given, the workpiece 16 is a piece o~ wood which is to be
,secured to a concrete support 17 by a nail or stud 18 which is
positioned within the muzzle end of the tool. A firing pin
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19 at the rear end of the tool is struck with a hammer to drive
the firing pin against a powder cartridge 20 with sufficient force
to fire the cartridge. The explosive force of the cartridge
propels the piston 13 forwardly to drive the fastener 18 into
the workpiece as illustrated in Fig. 2.
The piston guide 12 includes a cylindrical metal tube 22
which slides within the housing 11 and a muzzle tube 23 of smaller
diameter which is positioned within -the tube 2? and secured thereto
as by weld 24 or some other mechanical engagement, such as threads.
A generally cylindrical cartridge-mounting plug or holder 25 is
secured to the rear end of the guide tube 22 and is provided with a
central bore 26 lFig. 6~ for receiving the cartridge 20. The
cartridge holder includes an lnner portion 27 having an outside
diameter such that the inner portion is snugly received within the
guide tube 22 and an outer portion 28 having an outer diameter
approxlmatel~ the ~ame as the outer diameter o the tube 22. In
the embodiment illustrated the holder is secured to the tube 22 by
a weld 29 or some other mechanical engagement. The bore of the
cartridge holder includes three portions of different diameters
2Q which are sized to accommodate the different sized portions of the
cartridge. The bore includes a rim portion 30, a central portion
31 of slightly smaller diameter, and a forward portion 32 of
still smaller diameter which merges with a flared forward end 33.
The piston 13 is formed integrally from hardened metal and
includes an elongated forward portion 35 having a diameter substan-
tially the same as the inside diameter of the muzzle portion 23 of
the piston guide, a frusto-conical portion 36, and a rear portion
37 of slightly larger diameter than the forward portion 35. A pair
of axially spaced guide rings 38 and 39 extend radially outwardly
from the rear portion 37 and have an outer diameter subs-tantially
the same as the inside diameter of the guide tube 22. The rear ring
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39 has an axial dimension slightly greatex than the front ring 38
and is provided with an annular groove 40 which receives a
resilient split ring 41. The ring 41 has a normal outside diameter
greater than the inside diameter o~ the guide tube 22~ and when
the ring and piston are positioned within the guide tube 22, the
ring is compressed slightly by the tube. The separated ends of
the split ring move toward each other to accommodate this com-
pression. As will ~e described more fully hereinafterl the ring
4Q exerts a frictional force against the wall of the guide tube
22 to maintain the piston in a ready-to-fire position.
~ An abutment ring 43 is positioned within an annular recess
44 in the forward end of the outer housing 11 and includes a pair
of separated inwardly turned end portions 45 (see also Fig. 7~
which extend radially inwardly through an elongated axially extend-
ing slot 46 ~see Figs. 3 and 4) in the guide tube 22 of the piston
guide. The inwardly turned,ends 45 of the abutment ring extend
-
through the slot 46 a sufficient distance to engage the front
shoulder of the front riny 38 of the piston. The annular recess
44 in which the abutment ring is positioned secures the ring against
axial movement within the housing 11, and the inwardly turned
,ends 45 prevent'forwa,,rd movement of the ring 38 of the piston
beyond the abut~ent ring. The housing is indented inwardly at
lla between the end portions 45 of the abutment ring to prevent
rotation of the abutment ring and the piston guide within the
housing.
The piston and piston guide are shown in their retracted
or ready-to-fire positions in Fig. 1. The piston guide is retracted
within the housing against the firing mechanism designated generally
by the numeral 47, and the piston is retracted within the piston
3Q guide so that the rear ring 39 of the piston is adjacent the
cartridge holder 25. The tool is shown in Fig. 2 after it has
been fired. The piston guide 22 remains in its retracted position,
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but the pistoll has been driven ~orwardly by the cartridge to drive
the fastener 18 into the workpiece. The piston can thereafter be
returned to its ready-to-fire position within the piston guide by
causing thepiston guide to move axially forwardly within the ;
housing. This can be done by grasping the muzzle portion 23 of
the piston guide or by snapping the forward end of the tool with
a flick of the wrist while the tool is being held by the grip 14.
As the piston guide moves forwardly within the housing, the
frictional force created by the split ring 41 on the piston will
cause the piston to move with the piston guide until the forward
ring 38 on the piston engages the inwardly turned ends 45 of the
abutment ring. Continued forward movemen-t of the piston relative
to the housing is thereaEter prevented, and continued ~orward
movement of the piston guide will move the cartridge holder 25 at
the rear end of the piston guide toward the piston. The rear end
of the piston is provided with a rearwardly extending ejector pin
48 (Fig. 2), and as the cartridge holder 25 approaches the piston,
the ejector pin 48 moves into the cartridge bore of the cartridge
holder to eject the cartridge as shown in Fig. 3. The housing 11
is provided with a breech opening 49 (see also Fig. 5) which is
closed by the piston guide when the tool is in the ready-to-fire
position of Fig. 1 but which exposes the rear or breecll end of
the cartridge holder when the piston guide is in the extended
position of Fig. 3. The ejected spent cartridge is therefore free
to fall through the breech opening 49 and out of -the tool.
The tool can be reloaded with a fresh cartridge when the
piston guide is in the position of Fig. 3 by inserting the cartridge`
.through the breech opening 49 into the cartridge holder. The for- -
ward end of the cartridge will push the ejector pin 4~3 on the
piston forwardly until the rim of the cartridge is seated in the
rim portion 30 of the cartridge bore. Relatively free forward
movement of the piston is permitted in order to minimize crushing
of the crimped end of -the cartridge by an enlarged anllular recess
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51 ~Fig. 6) in the bore of the guide tube adjacent the forward
end of the cartridge holder. This recess reduces the compressive
Eorce on the split ring ~1 carried by the piston and thereby
reduces the Erictional force exerted by the split ring. The
~orward end of the recess provides an inwardly extending shoulder
52 which is engageable with the split ring after the cartridge
has been inserted and which maintains the piston in -the ready-to-
fire position of Fig. 1. The shoulder 52 thus minimizes the
likelihood that the piston will be jarred out of its ready-to~fire
lO position by an improper hammer blow on the tool. ~lowever, when
-the cartridge is fired by a proper blow, the frictional force
exerted by the split ring will be easily overcome by the explosive
force of the cartrid~e.
The iriny mechan.ism ~7 includes an elonyated Eiriny pin
I9 which is mounted for axial sliding movement in a ~enerally
cylindrical guide tube 53. The particular firing pin illustrated
is a bolt which includes a head 54 and a shank 55 having a threaded
end which receives a nut 56. The bolt is biased rearwardly away
from the cartridge holder by a coil spring 57 wi-thin the guide
20 tube.
~s can be seen bes-t in Fig. 6, the yuide tube 53 includes
J a central portion 58 which has an outer diameter substantially the
same as the outer diameter of the housing 11, a forward externally
threaded end portion 59 of reduced diameter, and a rearward end
portion 60 of reduced diameter. The threaded forward end portion
59 is threadedly engaged with internal threads on the rearward end
of the housing 11. It will be understood, however, t~atthe mechan-
ical en~agement of components is not limited to threads.
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The firing pin extends through a central bore in the
guide tube, and the bore includes a rear end portion 61 which is
sized to accommodate the coil spring 57, a central portion 62 of
smaller diameter, and a radially enlarged forward portion 63 which
provides an abutment shoulder 64, The bolt head 54 engages the
shoulder 64 to limit rearward ~ovement of the bolt, and the
spring 57 is compressed between the nut 56 and the shoulder 65
between the rear and central bores 61 and 6~. The nut 56 can
be tightned on the bolt to compress the spring to provide a
desired preset force to minimize inadvertent firing of the
cartridge. The preset force must be overcome before the bolt
~ill move forwardl~ toward the cartridge.
A cylindrical spacer sleeve 66 surrounds the bolt shank
between the bolt head 54 and the nut 56 and provides an accurate
control on the preset spring force. The length of the spacer
~leeve is selected so that the nut can be tightened against the
rearward end of the spacer sleeve to provide the desired preset
spring force. If a greater preset force is desired, a shorter
spacer sleeve is used, and if a smaller preset force is desired
a longer spacer sleeve is used.
The spring preset can also be accomplished by the use
of a more expensive shoulder bolt which would function just
like a separate bolt and spacer.
The use of a conventional bolt as the firing pin reduces
the cost of the firing pin and enables the preset force of the
spring to be adjusted as desired. However, other rod-like mem~ers
can be used. The use o~ a bolt and nut also provides two convenient
detents, one of which is engageable with the abutment surface 64 of
the firing pin guide to limit rearward movement of the firing pin
and the other of whic~ is engageable with the spring 57. Although
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the bolt is illustrated in the drawings with the bolt head 64
engaging the abutment surface 64 and in position to strike the
cartridge, the bolt could be reversed so that the nut 56 engaged
the abutment surface and the shank of the bolt was engageable
with the cartridge.
The coil spring 57 normally maintains the bolt head 54
against the abutment surface 64 of the guide tube. The forward
portion 59 of the guide tube extends forwardly beyond the bolt
;- head and spaces the cartridge holder 25 forwardly of the bolt
head to prevent inadvertent firing. The cartridge can be fired
only ii the rear end of the bolt is struck with suficient orce
to overcome the preset force of the spring and to dri.ve the bolt
forwardly to strike the cartridge with sufficient force to fire
the cartridge. In one specific embodiment of the invention,
the strength of the spring and the presçt force was such that
an impact of three ft. lbs. was required to fire the tool.
The grip 14 includes a knurled central gripping portion
68, an outwardly flared forward portion 69, and an outwardly
flared rearward portion 70 ~hich provides a protective shroud
surrounding the rear end of the firing pin. The shroud 70
terminates rearwardly of the firing pin and shields the firing
pin from impact if the tool is dropped and protects the operator's
hand from improperly directed hammer blows. The forward shroud
prevents the operator's hand from slipping down into the breech
area and enables the operator to hold the tool firmly against
the workpiece. The grip can be adhesively or otherwise suitably
secured to the outer surfaces of the firing pin guide 53 and
the housing 11, and the rear end of the grip extends inwardly
into engagement with the reduced diameter end portion 60 of the
firing pin guide to prevent the grip from moving downwardly
along the housing.
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As can be seen best in Figs. 3 and ~, the forward end of
the guide tube 22 of the piston guide is provided with an annular
recess 72 which is sized to accommodate the abu-tment spring 43. The
tool is assembled by inserting the piston into the breech end of
the piston guide before the cartridge holder 25 is secured to the
piston guide. The abutment ring can then be positioned within the
recess 72, and the diameter of the abutment ring can be reduced by
pressing the inwardly turned ends 45 together sufficiently to permit
the piston guide and abutment ring to be inserted into the forward
10 end of the housing 11. The piston guide is so inserted beEore the
firincJ mechanism 47 is secured to the rear end of t.he housing, and
the piston c~uide can he moved rearwardly w.ithin the housing
suf~iciently to alicJn the recess 72 in the piston guide with the
recess 44 in the forward end of the housing. When the recesses
are aligned, the abutment ring expands to position itself in the
recess 44, and the piston guide is moved forwardly to permit the
firing mechanism to be screwed into the rear end of the housing.
Thereafter, the forward end of the firing pin guide tube prevents
thepiston guide from moving rearwardly enough to align the recesses
20 4~ and 72. The i.ndentation lla in the housing prevents relative
rotation of the piston guide and the housing and prevents the gases
from the exploding cartridge from exhausting through the axial slot
in the piston guide directly into the breech opening.
After the tool is loaded with a cartridge as previously
described, the guide tube is moved rearwardly from the position
illustrated in Fig. 3 to the ready-to-fire position of Fig. 1. The
piston moves rearwardly with the guide tube by virtue of the
engagement between the split ring 41 on the piston and the shoulder
52 within the piston guide tube. The fastener 18 is then inserted
30 through the forward end of the muzzle portion 23 of the piston guide
and moved rearwardly until the point of the fasteller ls flushed with
the forward end as shown in Fic3. 1. An elonga-ted fastener of the
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type illustrated in Fig. 1 is conventionally equipped with a
cylindrical eyelet or washer 73 for centering the forward end of
the fastener within the muzzle and ~or frictionally retaining the
fastener within the rnuzzle until the tool is fired.
~J While in the foregoing specification a detailed descrip-
tion of a specific embodiment of the invention was set forth for
the purpose of illustration, it is to be understood that many of
the details herein given may be varied considerably by those skilled
in the art without departing from the spirit and scope of the
10 invention.
