CA1042603A - Pneumatic apparatus - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE:

An apparatus is described for driving fasteners or for other impacting applications. The apparatus comprises a cylinder, a piston slidably mounted in the cylinder, a hammer connected to the piston, an air reservoir, an air manifold or supply chamber connected to the air reservoir, a quick-acting poppet valve for rapidly admitting high pressure air on command to the upper end of the cylinder from the air reservoir, a trigger-operated control valve adapted (1) to transmit high pressure air to the poppet valve from the air manifold so as to cause the poppet valve to close off the upper end of the cylinder or (2) to exhaust high pressure air from the poppet valve so as to cause the poppet valve to open, and an exhaust control valve adap-ted to (1) transmit high pressure air from the air reservoir to the lower end of the cylinder so as to cause the piston to retract the hammer when the poppet valve is closed or (2) to exhaust air from the underside of the piston when the poppet valve is open and high pressure air from the air reservoir causes the piston to drive the hammer through its impact stroke. A
safety mechanism is provided to control operation of the exhaust control valve and, as an optional feature, a safety mechanism may be provided to releasably lock the trigger.

Description

iO4Z603 FIELD OF INVENTION
This invention pertains to pneumatic driving apparatus and more particularly to pneumatic fastener driving tools.

, BACKGROUND OF THE INVENTION
. Pneumatic nail-driving tools are old in the art and are exem-'plified by the devices disclosed in U.S. Patents 3498517, 3060441, 3035268, 3060440, 3595460 and 3711008.
Il Prior hand-held pneumatic driving devices known to the art ¦!have not been suitable for heavy-duty fastener-driving operations, e.g., operations requiring installation of nails or fasteners to high strength substrates such as prestressed concrete having 5,000 ¦
,to 10,000 psi compressive strength and structural steel plates with! -., ~
a thickness of 3/16th inch or greater. As a consequence, most . .
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104'~6~3 ! lleavy-duty fast~ner-driving operations ar~ carri~d out r~ith ', explosive-actuated devices which are time consuming and expensive ,'and dangerous to operate. Furthermore, eY.plosive-actuated ! fastener-driving means have substantial recoil and noise problems.
Prior attempts to provide pneumatic driving devices suitable for heavy-duty fastener-ariving operations have been generally unsuccessful due to the difficulty of generating the requirea 3 impact force to drive a nail or other fastener through high l~strength substrates such as concrete and steel plate. Because of , the problems of generating the required acceleration, prior pneu-¦~matic driving devices designed for heavy-duty fastener-driving , operations have been unduly complicated and have re~uired compli-¦Icated and large valving for feeding and exhausting the pneumatic jfluid so as to generate the desired acceleration and impact force.
I Furthermore, most prior designs have involved a mechanical spring for assisting the driving member on its return stroke. However, ,~the inclusion of spring means has had the unaesired effect of ; i,limiting the acceleration of the driving mem~er and the impact - ~'force exerted by such member on the fastener which is to be - ¦
idriven. Most hand-held prior art devices designed for pneumatical~
j~driving nails and similar fasteners have been low-energy ~evices, ~,i.e., devices that provide for little or no acceleration time jlbetween the commencement of the work or driving stroke of the ~
jidriving member and the impacting of the work by the fastener which 25 - ~is driven by the driving member. As a consequence, prior pneumati~
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104~6Q3 driving devices have had to be massive in order to generate sufficient energy to accomplish heavy-duty fastener driving operations. Unfortunately, such prior driving devices also tend to have severe recoil.
SUMMARY OP THE INVENTION
An ob;ective of the invention is to provide a pneumatic driving apparatus for heavy-duty fastener-driving operations which is simpler and capable of developing substan-tially more driving power per unit volume than prior apparatus intended for similar tasks, and which at the same time is reliable, easy to maintain and relatively inexpensive to manufacture.
A further ob~ective of the invention is to provide a pneumatic driving apparatus which is designed to permit precise control of the velocity of its driving piston, thereby controlling the energy output of the unit and making a maximum use of the available energy.

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Still another object is to provide a pneumatic driving apparatus which is designed so that the air power i8 utilized to substantially its full line pressure, and which further is characterized by a relatively small diameter, light-weight driving piston and unique valving for controlling flow of air.
Still another object is to provide a pneumatic driver that is adaptable for various impac~ing applications.
A further important object is to provide a pneumatic driver which utilizes relatively simple valving to achieve efficient operation.
Other objects of the invention are to provide a fluid operated driving device which utilizes a single piston for propelling the driving member, incorporates fail-safe features to prevent accidental firing and to render the unit inoperative in the event of tampering or breakdown, is incapable of firing successive shots accidentally, and operates with a minimum of : noise and recoil.
Still another object is to provide a heavy-duty pneumatic driving apparatus which can be hand carried and which does not rely or. any mechanical spring for its operation.
The foregoing objects, and other objects hereinafter disclosed or rendered obvious, are achieved by provision of ,~ , ~04Z603 apparatus for driving or impacting a fastener or other article comprising a cylinder, a hammer or impacting member, a fixed end means closing off one (the lower) end of the cylinder and defining an opening in which the hammer is slidably dis-posed, a piston connected to the hammer and reciprocally mounted within the cylinder for driving the hammer through a drive or impact stroke and a return stroke, an air reservoir, an air manifold or supply chamber connected to the air reservoir, a poppet valve for admitting high pressure air on command to the other (the upper) end of the cylinder from the air reservoir, the poppet valve including a movable poppet valve member adapted to engage and close off the upper end of the cylinder from the reservoir, a first control valve adapted (a) to ~ransmit high pressure air to the poppet valve from the air manifold so as to cause the poppet valve to close off the upper end of the cylinder or (b) to exhaust high pressure air from the poppet valve so as to cause the poppet valve to open, and a second control valve adapted to (a) transmit high pressure air from the air reservoir to the lower end of the cylinder so as to cause the piston to retract the hammer when the poppet valve is closed, or (b) to exhaust air from the lower end of the cylinder so that admittance of high pressure air to the upper end of the cylinder by opening the poppet valve will cause the piston to drive the hammer through its impact stroke, the second control valve being operable independently of the first control valve and the position of the piston within the cylinder.

`` 104Z6Q3 ILLUSTRATIVE EMBODIMENT OF THE INVENTION
In this application and the accompanying drawingc, there is described and shown a preferred embodiment of the invention and certain modifications thereof, but it i8 to be understood that these are merely exemplary and that other changes and modifications can be made within the scope of the invention.
THE DRAWINGS
Fig. 1 is a side view in elevation of a nail driver constituting a preferred embodiment of the invention;
Fig. 2 is an end view in elevation of the same device;
Fig. 3 is a sectional view taken along line 3-3 of Fig. 2 showing the device with its hammer in a retracted or ready position;
Figs. 3A and 3B are enlarged views of two portlons of Fig. 3;
Fig. 4 is a view like that of Fig. 3 showlng the same device with the hammer at the completion of its impact stroke;
Fig. 5, appearing on the same sheet as Fig. 3, is a cross-sectional view of the nail magazine taken along line 5~5 of Fig. 3;
Fig. 6 is a view like Fig. 3 of another embodiment of the invention in ready position;
Fig. 7 shows the device of Fig. 5 with the hammer at the completion of its impact stroke; and Figs. 8 and 9 are enlarged fragmentary ~ectional vlews in elevation of an auxiliary exhaust control valve that may be used in the devices of Figs. 3 and 6.

~04z6u3 '~ DESCRIPTION OF THE INVENTION
Referring now to Figs. 1 and 2, the illustrated apparatus comprises a hoilow housing 2; a cap member 4; a nail recei~ing ;and positioning head 6; and a magazine 8 for holding a supply of :nails an2 feeding them to the nail receiving and positioning head !
.,6. Cap member 4 and head 6 are detachably secured to ~he upper ;and lower ends of the housing by means of screws 10 and 11 which ~'are screwed into tapped holes formed in the housing~ m e maga-'~zine is detachably secured to~the head 6 by means of screws 12. :
',~which pass through holes in thè head and are screwed into tappea , ~
¦~holes in.the adjacent end of the maga~ine. : , - .
¦~. Referring now to Figs. 3 and 4, the upper end of the housing. ,-'.,has an end wall 1~ which serves as a poppet valve housing. To . .
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;this end a cylindrical hore 15 is formed in the end wall.l4 and .

j.the upper end of bore 15 i5 counterbored as shown at 16.- -Slidably r mounted in bore 15 is a hollow'poppet valve that is identified .

,generally by numeral 17 and wh.ich comprises a,cylindrical wall 18 ,'sized to make a close sliding fit with bore 15,.a periphë~ral .: !; - , . . - -'.flange 19 at the u~per end of wall 18 sized to make a close slid---~ing fit in counterbore 16, and an upper end wall 20. The poppet -.

~valve also includes a centrally located boss 21 formed integral -. .~

Iwith end wall 20 and spaced from wall 18 so as to form an.inter-' ..:

,;nal annular cavity 22. The outer surfaces of wall 18 and flange ~19 are provided.with circumferentially-extending groove~ in whic~ .

',are disposed resilient sealing rings 23 that bear.against the ~' - - . , ' .
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' 104Z603 surrounding surfaces that define bore 15 and counteroore 16 an~ ~
serve to prevent lea~age of fluid while allowing the poppet valve ¦
to move axially. Ring seals 23 are pre~erably but not necessar- I
ily made of an elastomer material and may be in the form of O- ¦
rings. 'me upper end wall 14 of housing 2 is preferably provided with one or more passageways 24 that lead from counter~ore 16. to '/the atmosphere. Passageways 24 serve as bleeds to prevent a .pressure buildup in the space between the lower side of flange 19 ` ;~and the annular shoulder formed by the junction of bore ~5 an~
¦icounterbore 16. .
¦~ Thè bottom end of the poppet valve is ciosea off by a sub- -stantially xigid circular metal plate 25 and a circular resili~nt ~ sealing pad 26 bonded to plate 25. The latter eIements are formed .
- I.with central apertures to accommodate a hollow screw or threade~ - ¦
', bushing 27 which is screwed into the lower end of an axial bore 28' , formed in boss 21. Additionally, the poppet valve compxises-a cyll indrical axial extension 29 whlch is formed integral with end wall¦
20 ànd has an internal bore which forms an extension of~bore 28.
~ The cap member has a cavity 31 of circular cross-sec~ion to ~accG
~modate extension 29 and the upper end of the latter has a peripher j'al flange ox piston 32 that is sized to make a close sliding fit i ~icavity 31. The outer surface of flange 32 has a circumferentiallyl 'textending groove in which is position another sealing ring 34 ~sin~ .-j,ilar to ~ealing rings 23) that ~ears against the surrounding sur~ .
~ace of the cap member and serves to prevent leakage o~ flu~ while .

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,, i allowing extension 29 to move axl ~ ly in cavity 31. ~ resilient 'sealing pad 35 is secured in the upper end of cavity 31 for en-'gagement by the flat upper end surface of extension 29. Pad 35 acts as a valve seat for extension 29. Additionally, cap member j 4 includes one or more passageways or ports 36 that e~.tend from ,~cavity 31 to the atmosphere. The hollow extension 29, bore 28, 'cavity 31, pad 35, and passageways 36 together constitute a vent ~,valve for selectively discharging fl~id from the under~ide of the ~Ipoppet valve to the atmosphere. Preferably the axial dimensions ~of cavity 31, èxtension 29, bore 15, counterbore 16, flange 19 ana ¦¦wall 18 are set so that when the poppet valve is moved upwardly, a small gap exists between surfaces 37 and 38 when the flat upper ! end surface of extension 29 is seated tightly against pad 35 as ~ sho~n in Fig. 4. The effective area of the annular upper surface I,37 of poppet valve 17 is greater in area than the underside of pad 1~,26. ' ' ' . , ~ . .
I Pad 26 functions to provide a tight seal between the poppe~
', ,,,,,, ,li,valYe and the upper edge of a cylinder 40 when the poppet,valve .¦is in its down or closed position (Fig. 3). Cylinder 40 i5 ¦,formed with open top and bottom ends and its internal diametér lljis constant throughout its length. The botto,m end of cylinder -40 is secured in an opening ~ormed in the bottom end'wall 42 of,-, housing 2. Cylinder 40 may be secured to end wall 42 in various , ¦'ways, e.g., by a screw thread connection, a-shrink fit or by '~
- liwelding or brazing.' Preferably the bottom end of the cylinder '' ¦,has two circumferential grooves to accommodate xesilient sealing ' ,'rings 43 (like ring seals 23 and 34) which bear tightly against ¦! - -, .

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l l " ( lO~Z6Q3 "the surrounding surface of end wall 42. The bot-tom end o~ cylin-,'der 40 is closed off by a plug 44 which also ma~ be secured to the cylinder in various ways, e.g., by a screw thread connection, ~
~a shrink fit, or by ~elding or brazing. ~eakag~ of fluid between ¦
the outer surface of plug 44 and the inner surface of cylinder 4~
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;is prevented by another resilient sealing ring 45 seated in a J
circumferential groove in the,plug. The latter also ;s formed ,with a round axial bore 46 to slidably accommodate a hammer or ,driving member'47. The plug is formed with an internal'groove ~around bore 46 to accommodate a resilient sealing ring 48 that , ! surrounds and engages the outer sur~ace of hammer 47 wit~ just j~enoùgh force to prevent leakage of fluid therebetween while a~
iithe same time allowing the,hammer to move axially. The upper end I
'of hammer 47 is attached to a circular piston 49 that has flat ¦ ;
,upper and lower surfaces and is sized so that it makes a close-~'sliding fit with the inner surface of cylinder 40. Piston 49 has !
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~,a peripheral groove in which is disposed a resilient sealing ring l! . .
50 that bears against the smooth inner surface of the,cy~inder ' ~,and functions to prevent fluid from leaking between the piston' ~'and cylinder. An annular resilient cushion member 52 is attache~ ¦-to the inner surface of plug 44. Preferably the inner diameter ¦,of member 52 is sized so as to provide a subs~antial gap between ~,,it and hamm~ 47 in order to avoid any friction force that would ,~tend to impede ;movement of the hammer. Cushion member 52 is .!;preferably made of an elastomer such as a synthetic or natural rubber compound, but it also may be made of a resilient plastic ,'material. - ' ' "

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¦ The outer surface o~ cylinder 40 is spaced ~rom t,he inner ,surface of housing 2 so as to provide a chamber 54,wnich serves as an air reservoir. Adaitionally, the outer di~meter of cylin-' der 40 is less than the outer diameter of the poppet valve by a ' selected amount so that a s~bstantial marginal portion of paa 26 , projects radially of the cylinder as shown in Fig. 3. '~referably ¦
I'but not necessarily, the upper end of the cylinder has an outside ~,'bevel 55 to m~ximize the amount of pad 26 which projects out be-¦~iyond the upper edge surface of cylinder 40.
j' Still referring to Figs. 3 and 4, the housing 2 is formed ¦Iwith a hollow lateral extension 57 which defines a manifol~ cham-~,lber S8 for supplying air or other pressurized fluid to reservoir ,chamber 54 and also to other portions of the device às herein-i~after described. Extension 57 has an inlet port 59 which is ~ithreaded for coupling to a flexible hose line (not shown~ leading j'to a regulated source of pressurized fluid,' e.g., an air compres-¦isor. Manifold chamber 58 communicates directly with reservoir .. ., . . .
Si,chamber 54 via a passageway 60. One portion of housing extension , 57 is formed with a relatively thick wall section 62 which is' ','provided with a bore 63 to accommodate a control valve 64.-- i! Referring now to Figs. 3 and 3A, control valve 64 comprises, a "control valve'housing 65 which is securea in-bore 63-by a aowel ,pin 61. As seen best in Fig. 3A, control valve housing 65 is ¦'closed off at one end by a bushing'66 that defines a port or --',,orifice 67 leading to passageway 60. An apertured pad 68, prçf''-.lerably maae of xesilient material, is secured to the inner end ~- ~-.~1i , . ' " ~: .
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!i 104Z603 ~ l l ' of bushing 66 and serv~s as a valve seat for a contxol valve mefn- ¦ ¦
, ber 69. Housing 65 also has a bore 70 at its other en~ to accom- i , modate a valve rod assembly 71 that is connected directly to valve member 69. At the inner end of bore 70, the valve housing 65 has a shoulder to which is secured another apertured pad 72 ~ .
.that is like pad 68 and also serves as a valve seat for valve , member 69. .Intermediate the two valve seats, housing 65 is pro- ¦
vided with a side port that connects directly with one end o~
. ¦~a passageway 73 formed in wall section 62. Connected to the llopposite end of passageway 73 is a tube 74 that.extends length~ise¦
¦!of chamber 54 and extends through and is secured in the upper .
jl end wall 14 of housing 2. The upper end of tube 74 communicates ,Idirectly with a passageway or cavity 75 in cap member 4 that . , ..
,.opens into counterbore 16 of the poppet valve housing. Referring 3jagain to the control valve, housing 65 has another port 76 that at one end communicates with bore 70 and at the other end is . :
ijopen to the atmosphere via a slot 77 formed in the side of hous- .
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ing 65. The valve rod assembly 71 includes a piston 79 that is 'sized to make-a sliding fit in bore 70. .
,' Control valve member 69 is shaped so that when it is moved up-~,against pad 68, it will close off port 67 and when it is mo~ed down against pad 72, it will close off the control valve chamber 1~ ' , ,' . ..... , - .

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- - ~ 10~2f~03 i.~fro~ bore 70. ~lot~7ever, in either position control valve member ', 69 is incapable of blocking off the side port leading to passag2-way 73. ~en the manifold inlet port 59 is connec.~ed ~o a source I
' of high pressure air, the air in manifold chamber 58 ~lill ac~ . ¦
via port 67 to force control valve mcmber 69 down agains~ pad 72, ,'whereby air will flow through the control valve housing 65 Lp .'into cavity 75 of cap member 74 via passageway 73 an.~l tube 74, an~
the resulting air pressure in cavity 75 will force poppe~ valve imember 17 down onto the upper end of cylinder 40.
. j The control valve member is shifted to its upper position by Imeans of a trigger 82 that is pivotally connected to housing 2.
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¦'For this purpose the bottom end wall 42 of housing 2 has a ver-tically extending cavity 83 and a side opening 84 that inter- `~
' sects cavity 83. The inner end of trigger 82 extends through !lopening 84 into cavity 83 and has a tongue that extends in~o a i,s1.ot 86 in the side wall of housing 2 and is pivotally attached - ¦Ito the housing by a pivot pin 87. The outer end~of trigger 82 ',',projects under the outer end of valve rod assembly 71. W~en the l! trigger is pulled up, i.e., pivoted counterclockwise as viewed 2U i,in Fig. 3, it will engage piston rod assembly 71 and force it ¦~upward so that valve member 69 will close off port 67 and allow !~ high pressure air in counterbore 16, cav~ity 75, tube 74 ana - ¦~.passageway 73 to be exhausted to the atmosphere via port.76 an~
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'' 104Z603 The bottom end wall 42 of housing 2 also is ~orrQed ~tit~ a .:circular bore to accommodate an exhaust or safety valve 88 ~thich is similar to control valve 64. As seen best in Fig. 3B, valve 8 ~ comprises an exhaust valve housing 89 ~,7hich is secured in the bore~

. in end wall 42 in any suitable manner, e~g. by a set screw 89~ or .

.'by a screw connection or a friction fit. 'Housing 8g is closed at '.one end by a threaded bushing 90 that defines a port or orifice 91. An apertured pad 92, preferably made of a resilient material, ,. . .
is secured to the inner end of bushing 90 and serves as a valve ~seat for an exhaust valve member 93 which is attached to a valve ! rod assembly 94. The other end of valve housing 89 has a bore 95 ,to accommodate valve rod assembly 94; At the upper end of bore 95 i!
~,'.the housing 89 has a shoulder to which is secured a,nother aper- ,-,',tured pad 96 which also serves as a seat for valve member 93; -J, The latter has a piston 97 that makes a sliding fit with bore 95. 1 j,Valve housing 89 has a lower side port 95A that connects bore 95 , -with an exhaust port 98 formed in the lower end wall 42-o~ housin~l;
~2, and an upper side port 95B that connects its interior space ,, ¦
!,through a h~le in the lower end of cylinder 40 with a passagewa~ -}.--I',99 in the lower end wall 42. Passageway 99 communicates with the ¦
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~linterior of cylinder 40 through an opening in pad 52. Valve' _ .

J'member 93 is adapted to close off port 91 when,it is moved upwar~

against pad 92 and to close off the upper end of bore 95 when it ~ is seated against pad 96. However,'in either position vaive , membex 93 i~ incapable of closing off the upper side 95B that -"

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,. 1042603 ~leads to pass~geway 9g. Hence, when valve me,~ber 93 is sea-ted .'against pad 96, a.ir can flow from air reservoix 54 into the lo~Jer .end of cylinder 40 via port 91 and passageway 99, and exhaust, '..port 98 is closed off. When valve me~er 93 is seated against pad 92, port 91 is closed off and aiL can be exhausted from the "lower end of cylinder 40 via passageway 99, bore 95 and exhaust .,port 98.
~, Movement of valve member 93 is controlled by a mechanical ¦,linkage that is carried by the head 6. The upper end of head jl6 has a cavity 102 and a boss 104 that extends up from its bot-' ¦Itom end wall 105 and preferably engages plug 44. Boss 104 has .
! an axial bore 106 that is aligned with and is sized to slidably ~jaccommodate hammer 47. Head 6 also has a lower axial extension .
~in the form of a foot 107 which has a bore that is an extension Il,of bore 106. The aforesaid mechanical linkage that controls ,movement of valve member 93 comprises a lever arm 108 that is dis~
' l'posed in cavity 102 and an actuating rod 109 that is'slidabl~, ,' ',positioned in a bore 110 in foot 107 that extends parallel-to . !,bore 106. One end of lever arm 108 is pivotally anchored to j~head 6 by means of a pivot pin 111. The other end of'arm 108 is ¦~pivotally attached to the upper end of rod 109 by,means of a pivotl.
¦ipin 113 that is carried by rod 109 and extends into an elongate ~slot 114 in arm 108. The latter is pivotally connected to valve ~imember 93 ~y means of a pivot pin 115 that is attached to the. , ,25 j,lower end of valve rod assembly 94 and extends into another j~elongate slot 116 formed in arm 108. '- .,-! -. .
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- j. 10~Z61~3 In the absence of any high pressure air in the device, the .weight of rod 109 and arm 108 is sufficient to hold valve m~m~er 93 down on pa~ 96 when the device is oriented vertically as shown i in Fig. 3. The length of rod 109 is such that it ~till pro~ect out . beyond the flat bottom surface 118 of foot 107 a short distance, e.g., 1/4-1/2 .inch, when valve member 93 is seated on pad 96 and will be flush with end surface 118 when valve member 93 is seated ¦
against pad 92. If high pressure air is supplied to the device, I
` valve member 93 will remain seated against pad 96 regardless o~
I,the orientation of the device until rod 109 is subjected to an upward force sufficient to overcome the downward force resulting ',from the influence of high pressure air in chamber 54 actiny on the upper side of valve member 93. . :
' Referring again to Figs. 3-5, the magazine 8 is hollow and ,.'defines an elongate channel 122 defined by opposite side walls 124, a bottom wall 126, and a top wall 128. Each side w~ll is "formed with a relatively shallow upper groove 130 and a relatively - - - 5I deep lower groove 131 separated by a rib 132. Grooves~130-act to .
I:receive and guide the fasteners to be driven. In this case the .
20 fasteners comprise nails 134 whose shanks are embedded or fric-i tionaily disposed in plastic sleeves 135 which are tied together .by connecting sections 136. Sleeves 135 and sections 136 are ,molaed as a continuous strip. Sleeves 135 are sized to exten~.
~into grooves 130 so that they are slidably supported by ribs 132~ .
1;Also, sleeves 135 are made equal to or slightly greater in diame-;.ter than the heads of nails 134 and further their diameters are .
~,sized so that they will make a close fit with bore 106. Also, ~,sleeves 135 have a length, preferably at least about 1~4"~ suffi- .
cient to keep the nail straight in bore 106 dbring the hammer's ., .

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` , 104Z603 drive stroke. The front end of ch~nnel 122 communicate~ with an : opening 138 in foot 107 which has a cross-sectional shape similar -to that of channel 122 except that it lacks grooves corresponaing .to grooves 131~ Thus, ~t each of its opposite sides opening 138 : has a rib 139 corresponding to rib 132 so as to provide a suppor~
.: i for sleeves 135. The series~of nails are urged forward ~0~7ar~ foo~
.107 by a pusher 140 which is disposed in channel 122 and has a t 'rib 142 at each side which slidably fits into the adjacent groove l,131. A tongue 146 on the lower side of pusher 140 is connected lQ l`to one end of a tension spring 143 which extends around a pulley j! 144 that is rotatably mQunted on a shaft secured in one of. the ! side walls 124. The other end of spring 143 is secured to a pin ~145 that also is anchored in a side wall 124. Spring 143-urges . the pusher toward foot 107. Upper wall 128 of the magazine ter- ~ .
~.,minates short of the rear end of the magazine so as to provide an 'end edge 147 that acts as a stop for a finger 148 on the upper end .of pusher 140, whereby to prevent the front end of the pusher from .
entering bore 106 and interfering with hammer 47 ~Jhen t~e last-. -nail has been discharged. The magazine 8 also is formed with a foot 150 whose bo~to~ end surface is flush with the bottom end - .
jsurface of foot 107. The two feet 107 and 150 cooperate to sta~i-- ,lize the fastening device and hold it perpendicular when it is .
plac~d against a su~strate into which a nail 134 is to be drlven.
j ~ The relative. sizes of orifices 67 and 91 ttogether wi~h the .amount by which the poppet valve pad 26 protrudes be~ond the ~pper .
edge of cylinder 40) are controlled so as to prevent do~nward .travel of hammer 47 and possibly accidental firing of-the de~ice ,'' ~ ' ~'' .

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,5 i )4Z6Q3 as it is connected to the high pressure,air supply an~ also so as ¦
, to assure rapid opening of the poppet valve, attain optimwm utili-zation of available air power and limit the force required to op- ~
,erate trigger valv2 64. In this connection it is to be note~'tha~¦
~,the volume of air reservoir 54 (which also should be considered `~to include the volume of passageway`60 and manifold chamber 58) is, relatively large in comparison to both the internal volume of '~,cylinder 40 and the combined volumes of the space above poppet ,'valve member 17 when it is in its down position (Fig. 3), i.e. - ¦
o !i counterbore 16, chamber 75, tube 74 and passageway 73. Hence sub-i~stantially more air is required to be moved to effect a,large l~change in the air pressure in air rèservoir 54 than is reyuired to be moved to effect a corresponding change in the air pressure ' above the poppet valve or the air pressure below piston 49. To ~ avoid any possibility of hammer 47 belng driven downward acciden- , j~tally as the high pressure air supply is connected to the device ~,~whereby the nail }ocated in bore 106 might be detached from the ~ . . .. .. . . .... .
¦~other nails and be driven down far enough to permit the next nail ~Jto be advanced into bore 106) it is essential to control the rela-~' j,tive rates of flow of air (a) between manifold 58 and counterbore ~
¦16 and cavity 75, and also (b) between reservoir 54 and the und,er- -,side of piston 4~. This objective is achieved by appropriately 'proportioning the smallest effective cross-sectional area of the passageways connecting manifold chamber 58 with countexbore ~6 ~' ~. ' ' .' . ,.
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,j , 10426(~3 of the poppet valve casing, i.e. the cross-sectional area of , orifice 67, and the smallest effective c~oss-sectional area of the passageways connecting manifold chamber 58 with reservoir 54 ~ and the interior of cylinder 40 below piston 49, i.e. the cross- ¦
~ sectional area of orifice 91. The first mentioned cross-sec~ional' area is made smaller than the second mentioned cross-sectional , area. The relative sizes of the two aforesaid smallest effective ¦
'~cross-sectional areas will depend upon the volumes of counterbore !
l~16 and cavity 75, reservoir 54 and cylinder 40~ the overlap o~ ~he~
l~poppet valve 17 with cylinder 40, the diameter of piston 49 ana ¦,the effective area of the upper surface 37 of poppet valve 17.
,However, in general b~st results are achieved when the second -',mentioned cross-sectional area i.e. orifice 91 is about four `times the first mentioned cross-sectional area, i.e. orifice -,t67. Typically, the diameters of orifices 67 and 91 are j about 1/8" and 1/4" respectively where piston 49 has a diameter of about 3.0 inch and the overlap of poppet valve 17 is about 1/8". The air supply iniet port 59 and passageway 60 I are substantially greater than orifices 67 and 91 as shown in - -IFigs. 3 and 4 (for convenience of illustration only, orificés i67 and 91 are represented as approximately equal in the "drawings). - --' ' ~ . : .
!i ~ , , . .. ., ., , .

I! -' - ' .
1. : " - '.' - - , - ' ! -. . .
" .. .

s . . .
i !
,, i . ~ o~z603 Operation of the device shown in Figs. 1-5 ~lill no~" be des- ~
cribed. Air under pressure, e.g. 125 psi, is suppliea to the f , manifold chamber 58 by connecting inlet port 59 to-a sultable ''supply oE pressurized air such as an air compressor ~not shown~. !
' This air passes tnrough the ori~ice 67 and acts on the va~ve 69 so that the latter closes off the opening in pad 72. T~e air passing through orifice 67 proceeds through passageway 73 and tu~e!
l,74 into the chamber 75 where it applies a force to the upper end " of the poppet valve 17, whereby the latter is urged to assume the ''position shown in Fig. 3 wherein the rubber disc 26 forms a tight ~seal with the upper edge of cylinder 40. Simultaneously, air is supplied by passageway 60 to the air reservoir chamber 54 and pro-ceeds through the orifice 91 of exhaust valve 88 to urge valve m~m .
,'ber 93 down against pad 96 to pxevent discharge of air from:exi~ ¦
''passagewa~ 98. The air entering the chamber of exhaust ~alve 8~ ¦, l~also passes through passageway 99 into the cylinder 40, thereb~
',providing a force on the underside of piston 49 which holds the ,~piston up against the sealing disc 26 as shown in Fig. 3. Any alr , trapped between the upper end of the piston and the disc 26 is -,~exhausted to the atmosphere via the passageway 28 and the ports 36. The device is now in its normal equilibrium position and -cannot be fired unless the push rod 109 is forced upwardly far -j~enough for valve member 93 to unblock the opening in val~e seat l,96. If the trigger is squeezed while operating rod 1~9 is in ~,the pos~ition shown in Fig. 3, the valve member 69 will change positions and the air pressure acting on the upper side of the . poppet valve 17 is released by discharge of air from chamber 75 vie tube 34, the internal chamber of valve 64, nd exit port 76.

.., i .

; (i ( . Hence, due to the pressure in reservoir 54, the poppet valve 17 will move up and thereby allo~7 pressurized air to act on the upper end of piston 49. However, no movement of the piston ~;ill occur because an equilibrium force condition exists as a result of the opposi.ng force of the pressurized air acting on the bottom i . surface of piston 49 and additional static frictional forces due to engagement of O-ring seal 50 with the cylinder 40 and the.
rod 47 with seal 48 (for this purpose, the seals 48 and 50 are i~
jlarranged so that with commonly accepted mating tolerances the~ wil " develop a total static frictional force which is at least subs~an-¦
! tially e~ual to the downward force exerted on the piston resuiting 3ifrom the area differential between its upper and lower surfaces;
,.it is to be noted also that if the diame3-er of rod 47 were to be made so large that the force resulting ~rom the area differential ' is substantially greater than the static frictional forces exer~e~l.
by the seals, all that will occur is that the piston 49 will me~el~
crawl. toward the lower end of the cylinder when the poppet valve is opened). If trigger 82 is repeatedly released and squeezed, the poppet.valve will repeatedly move toward ana away . from cylinder 40 but piston 49 will remain stationary. In order . to fire the unit, the safety mechanism actuator rod lQ9 must be .~.
' pushed up far enough so that the valve member.9~ now blocks ori-fice 91. When this occurs, the air pressure acting on the under-.side of.piston 49 is rapidly exhausted to atmosphere-by outflow of 2~ . air via passagèway 99, valve casing 89, bore 95 and port 98 I~ .
thereafter the trigger 82 is squeezed so as to move the valve mem-ber 69 up far enough to close off orifice 67, poppet val~e 17-wlll .
move up rapidly toward chamber 75 and the full line pressure in reser~oir 54 will act on the upper end of piston 49 so as to cause .' , .
-2~

the latter to move rapidly through its normal firing stroke.
The piston 49 will not return to its normal starting position , until the actuator rod 109 is released and trigger ~2 is also j released.
The advantages of controlling th~^ relative sizes of orifices , 67 and 91 of the control and eY~haust valves will now be describe~.
~en inlet 59 is connected to a source of high pressure air, ,pressure builds up on both sides of poppet valve 17. If a rapia ~build-up of pressure were to occur in reservoir 54, poppet valve ~17 might open and piston 49 might be driven downwardly a substan-tial amount by the air pressure acting on its upper side. However making orifice 91 relatively large allows the air pressure in the bottom end of cylinder 40 to build-up ~uite fast, whereb~
I;piston 49 is placed almost immediately in an equilibrium condition li Where piston 49 is about 3.0 inches in diameter, the poppet ¦
¦,valve stroke typically is about 3/8" and with a line pressure of jjabout 125 psi, the poppet valve will open fully within about 3 ,milliseconds. The speed at which the poppet valve will o~pen is I,influenced by the size of the vent opening in bushing 27 (as well ~as by the amount of overlap of the poppet valve relative to cylin-~der 40, and the 5mallest effective cross-sectional area of the -¦
passageways leading from cavity 75 to the atmosphere via valve 64 The smaller the opening in bushing 27, the faster poppet valve-17 ~
-~,will open. However, if the opening is too small, it will restrict~ -llthe rate of upward movement of piston 49; also a whistling noise ¦'may be produced when piston 49 undergoes its return stroke.

j~, ' ,. ' . ,.
i', , ' , '~

1~''' .
, l . .
,, ' ` i `` ; 104Z603 'l~ypically where piston 49 is about 3.0" in diameter, the opening in bushing 27 is about 1/8 inch for op-timum operat~on of the pop- ¦
pet valve.
It has abeen determined that certain design criteria mus~ b~
observed in order to promote optimum operation of the device.
In this connection it is to be apprecia-tea that in order for the air power to be utilized to its full line pressure, it is essen-tial that the poppet valve provide a relatively wide mouth for ~ rapidly applying high pressure air from reservoir 54 to the up-!'per end of cylinder 40. By way of exàmple, with piston 49 having i ¦!a diameter of about 3.00", the maximum poppet valve opening (i.e.
¦,the maximum gap between the poppet vàlve and cylinder 40) is -!i , . .
~preferably between 0.3 and 0.5 inch. Secondly, in order ~o allo.q ; the nammer to reach its maximum velocity under the applied pneu-,'matis power, the length of the hammer ~7 is set so that the hammer ~,e~periences a predetermined amount of travel prior to driving thi~ ¦
nail into the work-piece. This pretravel will vary accoraing ~o ~the nature of the work-piece or substrate into which the nail is- ¦ -to be driven, hut preferably it is at least about t~Jo inches.
jIn its at-rest position, the hammer may b~ close to the nail posi-~tioned in bore 106, but preferably it is spaced from the nail a ,substantial distance. -~ -. Figs. 6 and 7 disclose a modification of the nvention incor- -.porating a trigger lock mechanism. This modification is p~e- ~ ~
.. , . . -ferred for larger diameter ham=ers. In this connection it~is~to ,, - ', ' , .-:, ,. , .

, ' ' -.
, "
,, - " 104Z603 .~be recalled that when the trigger oE the embodiment of ~igs. 3 andi 4 is operated without pushing safety rod 109 up far enough to ~lock orifice 91, the poppet valve will open but no motion of h~m--: mer 47 will occur because an equilibrium force condition exists because of rrictional forces on piston ring seal 50 and ha~er ! -.seal 48. However, if the hammer diameter and/or the line air pressure is increased, the force acting on the upper side of p.iston 49 ma~ be so great relative to the force acting on the ~,lower side of the piston as to cause the hammer to move toward the `linail in bore 106 when the trigger is squeezed even though rod lOg ¦! is not pushed up far enough to close off orifice 91 of the exhaust valve. Hence, it ma~ be desirable in certain cases to provide a .
''trigger safety mechanism to prevent movement of hammer 47 except - j.when safety rod 109 is depressed far enough to operate the 15 '.exhaust valve. As a practical matter it has beeh found that the , ~esired equilibrium force condition is easily attained w.here . . . - .
! the hammer diameter is not larger than about 3/411 and does no~
:..".exceed about ~0~ of the diameter of piston 49, and the air :
.pressure in reservoir 54 does not.exceed-about 175 psig, ' Referring now to Figs. 6 and 7, the head 6 is providea with a ¦
I,second axially extending bore 160 in which is disposed a second 'ioperating rod 162. The upper end of rod 162 is pivotally connec- ¦
ited to one end.of a link 163 which is pivotall~ attached to head 1~6 by a pivot pin 164. The other end of link 163 is pivotally ..25 . j-connected to a crank 165 which is pivotally connected to: head 6 - ~ .
.-!

: , -, .
-',S' , .. . . . .

104Z603 ~ I
,by means of a pivot pin 166. The upper end of the crank exten~s !' into a notch formed at the inner end of trigger 82 and a si~e abutment 167 on the crank engages the inner surface of the housing~
2 to limit pivotal movernent of the crank arm in a clockwis~
direction. A compression spring 169 acts between a por~ion o' the head 6 and the bo~tom end of cranX arm 165 to urge the crank arm to the position shown in Fig. 6, whereby the bottom end of operating rod 162 protrudes slightly below the bottom surface 118 of foot107. Crank 165, link 163, and rod 162 form a trigger ~latch mechanism. So long as actuating rod 162 is not force~ up-i!wardly in the foot 107, the spring 169 maintains the crank in the ! position shown in Fig. 6 whereby the upper end o the crank locks "trigger 82 so that it cannot be squeezed to operate control valve . .
64. If, however, the device is held down on à substrate into Iwhich a nail is to be driven so that the reaction forae of the isubstrate forces actuating rod 162 upwardly and thereby causes - ,link 163 to pivot crank 165 counterclockwise (Fig. 7) far enough~
: `i for its upper end to become disengaged from trigg-er 82, the trig-- i! - . . . ' ger will be free to fire the device. Spring 169 will urge crank ,165 back to the position shown in Fig. 6 when the force urging - 'rod 162 upwardly is removed. If trigger 82 is released after ro~
~162 has returned to the position shown in Fig. 6, crank arm 165 will move clockwise under the influence of the notched end o~
,triggex 82 fax enough to allow the trigger to return to its locked - 25 tposition.- As~is apparent, actuating rod io~- and--i62~are-locatea-- --- . --- - :.......... . . .. .

.
.
~, .' ., .

. .

"

., ., ..... ,........................ . 1, i04Z603 close enough to each other so that when foot 107 is passed down onto a substrate or work-piece, both rods will be depressed at the same time. Preferably rod 109 projects out further from foot 107 than daes rod 162, so as to assure that the latter will not be depressed without the former being depressed. More preferably, rod 109 projects further than rod 162 such that trigger 82 remains locked until rod 109 has moved up enough to cause valve member 93 to block or~fice 91.
In practice the air pressure acting on valve member 93 o exhaust valve 88 bbiases rod 109 do~nward ~ith a force that is sufficient to co~ply wit~ statutory requirements. Typically, ~safety la~s for powde~-actuated devices prescribe that a force of atleast about 35 pounds be re~uired to operate a safety ~ech~nis~ like rod lOq, and this requirement is easily satis-~ied by the pneumatlc force acting on valve member 93. How-eyer, if desired, the farce required to depress rod 109 may be increased or decreased by merely changing the diameter of valye ~e~ber q3, or by regulating the air pressure in 2~ ~esexyoir 54, or by spring biasing the rod. Thus, as shown in Fi~s. 6 and 7, a tension spring 170 may be connected between link 108 and head 6 so as to oppose upward movement of rod 109 and valye assembly 71.
Figs. 8 and 9 illustrate operation of an auxiliary exhaust control valve that may be incorporated in the devices shown in Figs. 3 and 6 for the purpose of further controlling the velocity of piston 49 dur~ng the drive stroke so as to maximize the energy output of hammer 47. As is obvious to a person skilled in the art, the velocity achieved by the 3Q hammer during its drive stroke affects the energy output o the device Because the deyice does not incorporate any spring for a~ ting piston 49 to execute its return CD/ ,~ - 27 -stroke, the velocity at which hammer 47 is driven do~nward when the device is fired depends upon the rapidity with which the poppet valve fully opens to apply the full line air pressure to the upper end of piston 49 and the rate at which the air pressure on the underside of the piston is relieved ~the effect of friction on hammer 47 and piston 49 is almost negligible during the wor~ stroke~. In the development of this inyention, it has been determined that for certain cases if the passageway provided for exhausting air from the bottom end of cylinder 40 in advance of piston 4~ offered no impedence to such air flow, the energy output of hammer 47 would be di~inished. This result is believed to be due to a dissipation of air power because of movement of the piston at the beginning of the work stroke which prevents the hammer fro~ achieving maximum acceleration.
Howeyer, passageway ~9-, valYe 88 and exhaust port 98 do offer a measurable impedence to air flow and by appropriately controlling the size of the foregoing, the velocity of the hammer is controllable, with the result that a very high impact force is generated by the hammer on the nail in bore lQ6. By way of example, where piston 49 has a three inch diameter, the minimum opening provided by passageway 99, exhaust port q8 and the opening in valve seat 96 is about 1/4", lin practice passageway 99, exhaust port 98 and the opening in valve seat 96 may but need not be made with equal diameters). Nevertheless, it has been determined that if the minimum effective cross-sectional area of the exhaust path provided for the bottom end of cylinder 40 is variable the energy output of the unit may be further improved. There-fore, as shown in Figs. 8 and 9, the exhaust port 98 isreplaced by a tapered bore 172 which serves as a valve seat ana a lar~e ~ounterbore 173. The latter is threaded to cb/ ~ - 28 -receive a valve body 174 which only partly fills the same so as to leave a flow chamber 175. Valve body 174 has one or more by-pass discharge passageways 176 and a main passage-way 177 in which is slidably mounted a valve member 178 having a tapered valve head 1~9 sized to seat in bore 172. A com-pressIon spring 180 urges yalve head 179 against seat 172.
Valve mem~er 178 has a through bore 182 whose diameter is relatively small compared to exhaust valve opening 95A, bore 172 and passageways 176.
This auxiliary valve functions as follows. During the initial part of the drive stroke of hammer 47, air is exhausted through bore 182. Bore 182 is sized so that during the initial part of the hammer's drive stroke air is exhausted at a first rate whic~ allows the hammer to accelerate without any dissipation of air po~er. As the hammer continues its ~ork stroke, air pressure builds up on the underside of piston 49 until finally enough pneumatic force is exerted on the flat end surface 184 of valve head 179 to overcome the force of spring 180, whereupon valve member 17a rapidly 2~ moves away from valve seat 182 and tnereby permits air to be exhausted to the atmosphere at a muchgreater rate via passageways 176. In practice it is preferred that the auxiliary exhaust control valve be designed so as to open when hammer 47 has mo~ed through about 40-80~ of its work stroke.
The invention herein described offers a number of advantages. For one thing, it provides a device which is capable of developing more power per unit volume than prior known devices of similar intent. By way of example, devices made in accordance with this invention and connected to an 3Q air supply of 125 psi are capable o~ driving nails with a length ~f Z" and a shank diameter of 0.153" through 1"
thick pine into 800Q psi pre-stressed concrete. Secondly, cb/~ 29 -it has safety features whic.h prevent it from firing acciden-tally. Thirdly, it cannot be fired in a so-called automatic or repeat mode; successive shots cannot be fired without first releasing safet~ rod lO~ and trigger 82 so that the unit can be recharged. Fourth, the drive piston 49 is ~si~ple and can haye a small weight and size due to the unitls operating efficiency, with the result that the over-all size of the device ~s substantially smaller than other known deyices of similar power output. Fifthly, the poppet Yalye is entirely ~neumatically operated and when open, proyide~s a relatiyely large opening for applying air to pi$ton 49 from air reservoir 54. Also, the poppet valve ~as a low weight due to its hollow design. This not only ~lso reduces the overall weight of the device but also con-tributes to the poppet valve's extremely fast operating speed.
Seventhly, optimum efficiency is achieved with relatively -simple and reliable valving. Still another advantage is that the device may ~e used to drive different types of fasteners or for other impacting operations, e.g., punching 2Q holes in a plate. Further~ore, the device may be designed to accept a ~re-filled disposable magazine in place of the refillable magazine 8. Also, the device is relatively quiet ~hen operated. Still another advantag~ resides from the fact tA~t the upper end of the device may be provided with a knob or handle as shown for pressing it down onto a sub-~strate with enoug~ force to depress rod lO9 (and also rod 162~
A further significant advantage with respect to extending the life of the tool is derived from the fact that the hammer 47 is made long enough so tnat its outer end will protrude from tAe end surface 118 of foot 107 as the piston 49 reaches cushion 52 at the end o~ its work stroke (see Figs.

c~ - 30 -.......

4 and 7). Preferably, the hammer is made long enough so that it will project at least about l/16th inch and more (prefer-ably 3/16th inch~ beyond the end surface 118 of the foot 107 before the piston 49 commences to compress the cushion 52.
In driying a nail into a rigid substrate, e.g., a metal plate oyerlying a concrete floor, the end surface 118 engages the work, and the nail driving stroke is completed ~hen the end of the hammer is flush with t~e end surface 118. However, the pneumatic force driving the hammer will urge it to keep moving down and, since it is long enoug~ to do so, the ~ammer will move beyond the end surface 118 before the cushion 52 begins to exert a decelerating force on piston 49. This move-ment of t~e hammer beyond surface 118 causes the tool to recoil up away from the work. This upward recoil of the tool allows the yalve member 93 of exhaust valve 88 to move away from its valve seat ~2 ~due to the differential between the ^ relatively high pressure in cham~er 54 and the near atmos-pheric pressure in valve body 8~ just enough to let high pressure air pass from chamber 54 through the interior of valve body 8~ into cylinder 4~ on the underside of piston 49.
In this connection it is to be noted that since valve member ~3 makes a sliding fit with the valve body 89 (typically a dia~etral clearance of between Q.OQl and 0.005 inch is provid-edL, air from chamber 54 can leak past the valve member 93 as soon as it is moved off of its valve seat 92, or its valve seat 96 ~the yalve mem~er 69 of control valve 64 makes a comparable sliding fit in its valve body 65). As a consequence of the exhaust valve 88 opening enough to allow air to pass from chamber 54 into the bottom end of cylinder 40, a pneumatic force or air cushion is provided on the underside of tne piston which tends to decelerate the piston rapidly so that the piston compresse3 the cushion 52 only slightly or stops just c~ 31 short of it. As a consequence, the piston does not strike t;~e cushion 52 hard enoug~ to put a large tensile stress on the bolts 11 whic~ hold the nail receiving or positioning head 6 to the housing 2. Without this decelerating action at the terminal portion of the driving stroke of the hammer, t~e force exerted by the piston on the end wall member 44, and thus on the head 6, might overload the screws 11 and thus ~ig~t tend to damage the tool or cause its breakdown after a s~ort period of use. The deceleration of the hammer ~s yery ~ast and occurs almost instantaneously after the bottom end of the Rammer has moved flush with the end surface 118 of foot 107. This same feature prevents damage to the tool in the event it is held against a work surface and fired after the supply of nails has been ex}lausted. In suc~ event, tlle hammer will strike the work surface before t~e piston reaches cushion 52 and the recoil of the tool `- will cause Yalve 88 to open enough to decelerate the piston and t~ereby prevent the piston from destructively impacting the cus~ion as previously described. It is to be noted 2Q t~at the ~light openin~ of exhaust valve 88 which occurs on the upward recoil movement of the tool does not cause the piston 4~ to move upward again, for the simple reason that t~s poppet yalve 1~ will still be open. Piston 49 can move up.again only after the operator has released trigger 82.
~ final.adyantage is that the device is capable of a number of modifications obvious to persons skilled in the art ~Tthout detracting from the advantages already noted.

c~ 32 -

Claims (36)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Apparatus for driving or impacting a fastener or other article comprising a cylinder, a hammer or impacting member, a fixed end means closing off one (the lower) end of the cylinder and defining an opening in which the hammer is slidably disposed, a piston connected to the hammer and reciprocally mounted within the cylinder for driving the hammer through a drive or impact stroke and a return stroke, an air reservoir, an air manifold or supply chamber connected to the air reservoir, a poppet valve for admitting high pressure air on command to the other (the upper) end of the cylinder from the air reservoir, said poppet valve in-cluding a movable poppet valve member adapted to engage and close off the upper end of the cylinder from the reservoir, a first control valve adapted (a) to transmit high pressure air to the poppet valve from the air manifold so as to cause the poppet valve to close off the upper end of the cylinder or (b) to exhaust high pressure-air from the poppet valve so as to cause the poppet valve to open, and a second control valve adapted to (a) transmit high pressure air from the air reservoir to the lower end of the cyl-inder so as to cause the piston to retract the hammer when the poppet valve is closed, or (b) to exhaust air from the lower end of the cylinder so that admittance of high pressure air to the upper end of the cylinder by opening of the poppet valve will cause the piston to drive the hammer through its impact stroke, said second control valve being operable independently of said first con trol valve and the position of said piston within said cylinder.

2. Apparatus according to claim 1 including sealing means surrounding said hammer for preventing leakage of air from the low-er end of the cylinder via said opening while allowing said hammer to move through its drive or impact stroke and its return stroke.

3. Apparatus according to claims 1 or 2 wherein the return stroke of the piston and hammer is arranged to be produced without the assistance of springs or like energy-storing devices that require transfer of energy thereto during the drive stroke, whereby substantially all the available energy applied to the piston during the drive stroke is utilized to drive or impact a fastener or other workpiece.

4. Apparatus according to claims 1 or 2 for driving a fastener wherein the valving is arranged so that when the poppet valve is opened with the second control valve in exhaust position, the hammer will be caused to accelerated progres-sively over a substantial portion of its drive stroke and to reach its maximum velocity as the piston nears the lower end of the cylinder.

5. Apparatus according to claims 1 or 2 comprising means for positioning a fastener so that it is engaged and propel-led by the hammer as the latter is driven through its impact stroke.

6. Apparatus according to claims l or 2 further including a trigger for operating said first control valve.

7. Apparatus according to claims 1 or 2 further including a trigger for operating said first control valve and means for releasably locking said trigger.

8. Apparatus according to claim 1 or 2 further including a trigger for operating said first control valve, means for releasably locking said trigger, and means for releasing said locking means.

9. Apparatus according to claim 1 or 2 further including a trigger for operating said first control valve, means for releasably locking said trigger, and means for causing said locking means to be released when the apparatus is engaged with workpiece.

10. Apparatus according to claim 1 or 2 further including a trigger for operating said control valve and spring means opposing unlocking of said trigger.

11. Apparatus according to claim 1 or 2 further including an end means closing off the bottom end of the cylinder and defining an opening communicating with the interior of said cylinder through which the hammer or impacting member is movable lengthwise, said end means also comprising an end wall with a cushion member in the path of said piston.

12. Apparatus according to claim 1 or 2 further including an end means closing off the bottom end of the cylinder and defining first and second openings communicating with the interior of said cylinder, and further wherein said hammer or impacting member is movable lengthwise through said first opening and said second control valve is connected to said second opening.

13. Apparatus according to claim 1 or 2 wherein said second control valve comprises a first port leading to said air reservoir, a second port leading to the bottom end of said cylinder, and a third port leading to the atmosphere, and a control valve member movable so as to selectively close off said first or third ports.

14. Apparatus according to claim 1 or 2 wherein said second control valve comprises a first port leading to said air reservoir a second port leading to the bottom end of said cylinder, and a third port leading to the atmosphere, and a control valve member movable so as to selectively close off said first or third ports, and further wherein said second control valve is arranged so that the air pressure in said air reservoir biases its control valve member in a direction to close off said third port.

15. Apparatus according to claim 1 or 2 wherein said second control valve comprises a first port leading to said air reservoir, a second port leading to the bottom end of said cyl-inder, and a third port leading to the atmosphere, and a control valve member movable so as to selectively close off said first or third ports,and further including means for shifting the control valve member of the second control valve in a direction to close off its first port.

16. Apparatus according to claim 1 or 2 wherein said second control valve includes a hollow valve casing having a first port leading to said air reservoir, a second port leading to the bottom end of said cylinder, and a third port leading to the atmosphere, and a control valve member movable so as to selectively close off said first or third ports, and means including a mechanical member located outside of said valve casing for shifting the control valve member of the second control valve in a direction to close off its first port.

17. Apparatus according to claim 1 or 2 further includ-ing an end means closing off the bottom end of the cylinder and defining an opening communicating with the interior of said cylinder, a passageway connecting said second control valve to said opening, and an auxiliary exhaust control valve for controlling flow of air from said second control valve to the atmosphere, said auxiliary control means comprising means for increasing and decreasing the rate of discharge of air to the atmosphere in accordance with increasing and de-creasing air pressure in said passageway.

18. Apparatus according to claim 1 or 2 wherein said second control valve comprises a first port leading to said air reservoir, a second port leading to the bottom end of said cylinder, and a third port leading to the atmosphere, and a control valve member movable so as to selectively close off said first or third ports, said control valve member of said second control valve being incapable of closing off the second port of said second control valve.

19. Apparatus according to claim 1 or 2 wherein said poppet valve includes a hollow poppet valve casing and said poppet valve member comprises piston means slidably mounted in said poppet valve casing for reciprocal movement between a first position wherein said poppet valve member is spaced from said cylinder and the upper end of said cylinder is open to said reser-voir and a second position wherein said poppet valve member engages the upper end of the cylinder and closes it off from said reservoir.

20. Apparatus according to claim 1 or 2 wherein said poppet valve includes a hollow poppet valve casing and said poppet valve member comprises piston means slidably mounted in said pop-pet valve casing for reciprocal movement between a first position wherein said poppet valve member is spaced from said cylinder and the upper end of said cylinder is open to said reservoir and a second position wherein said poppet valve member engages the upper end of the cylinder and closes it off from said reservoir, and further including at least one vent passageway in said poppet valve member which communicates at one end with the upper end of the cylinder, at least one vent port leading to the atmosphere exterior of the apparatus and communicating with the opposite end of the vent passageway(s), and a vent valve for controlling flow of air between the vent passageway(s) and the vent port(s), said vent valve comprising a vent valve member movable with the poppet valve member for interrupting flow of air between the vent port(s) and the vent passageway(s) when the poppet valve member is moved to its first position and for restoring such flow of air when the poppet valve member is moved out of its first position.

21. Apparatus according to claim 1 or 2 wherein said first control valve comprises a hollow valve casing having a first port leading to said air manifold, a second port leading to the poppet valve, a third port leading to the atmosphere, and a control valve member movable so as to selectively close off said first port or said third port.

22. Apparatus according to claim 1 or 2 wherein said first control valve comprises a hollow valve casing having a first port leading to said air manifold, a second port leading to the poppet valve, a third port leading to the atmosphere, and a control valve member moable so as to selectively close off said first port or said third port, and further wherein air pressure in the air manifold biases the control valve member of the first control valve in a direction to close off said third port.

23. Apparatus according to claim 1 or 2 wherein said first control valve comprises a hollow valve casing having a first port leading to said air manifold, a second port leading to the poppet valve, a third port leading to the atmosphere, and a control valve member movable so as to selectively close off said first port or said third port, and further wherein air pressure in the air manifold biases the control valve member of the first control valve in a direction to close off said third port, and the control valve member of said first control valve is incapable of closing off the second port of said first control valve.

24. Apparatus according to claim 1 or 2 wherein said first and second control valves have orifices communicating with said air manifold and air reservoir respectively which are characterized by the fact that the orifice of the second control valve has a larger effective cross-sectional area than the orifice of the first control valve.

25. Apparatus according to claim 1 or 2 wherein said first and second control valves have orifices communicating with said air manifold and air reservoir respectively which are characterized by the fact that the effective cross-sectional areas of the first and second control valve orifices are in a ratio of about 1:4.

26. Apparatus according to claim 1 or 2 further in-cluding a magazine for holding a plurality of fasteners which are disposed in single file and extend parallel to the path of movement of said hammer, means defining a guideway for said hammer, a fastener delivery aperture through which fasteners may be delivered one by one into said guideway for engagement by said hammer as said hammer is moved through its drive or impact stroke, and means for delivering fasteners into the guideway via said fastener delivery aperture.

27. Apparatus according to claim 1 or 2 further including a hollow housing with said cylinder disposed within and subdividing the interior of said housing into a first chamber located between the housing and the cylinder and a second chamber within the cylinder, and further wherein said first chamber forms said air reservoir.

28. Apparatus according to claim 1 or 2 further in-cluding a hollow housing with said cylinder disposed within and subdividing the interior of said housing into a first chamber located between the housing and the cylinder and a second chamber within the cylinder, and further wherein said first chamber forms said air reservoir, said housing has an exhaust port, and said second control valve is disposed so as to selectively connect the lower end of said second chamber with said first chamber or said exhaust port.

29. Apparatus according to claims 1 or 2 comprising a housing containing said cylinder and air reservoir and further wherein said second control valve comprises a hollow valve casing which is attached to said housing and has first, second and third ports which lead respectively to the air reservoir, the bottom end of the cylinder and the atmosphere exterior of said housing,and a control valve member which is movably disposed within its valve casing so as to selectively close off said first or third ports.

30. Apparatus according to claim 1 or 2 comprising a housing containing said cylinder and air reservoir and further wherein said second control valve comprises a hollow valve casing which is attached to said housing and has first, second and third ports which lead respectively to the air reservoir, the bottom end of the cylinder and the atmosphere exterior of said housing,and a control valve member which is movably dis-posed within it valve casing so as to selectively close off said first or third ports, and further including a first

CLAIM 30 CONTINUED:
activating member mounted to and projecting from said housing ]
and means connecting said first activating member and the control valve member of said second control valve for shifting said control valve member in a direction to close off the said first port of said second control valve when said first activating member is forced inwardly of said housing.

31. Apparatus according to claim 1 or 2 comprising a housing containing said cylinder and air reservoir and further wherein said second control valve comprises a hollow valve casing which is attached to said housing and has first, second and third ports which lead respectively to the air reservoir, the bottom end of the cylinder and the atmosphere exterior of said housing and a control valve member which is movably dis-posed within its valve casing so as to selectively close off said first or third ports, and further including a first activating member mounted to and projecting from said housing and means connecting said first activating member and the control valve member of said second control valve for shifting said control valve member in a direction to close off the said first port of said second control valve when said first activating member is forced inwardly of said housing, a trigger for operating said first control valve, means for releasably locking said trigger, and means for releasing said locking means including a second activating member mounted to and projecting from said housing for operating said releasing means, said second activating member and said releasing means being connected so that the trigger is unlocked when the second activating member is moved inwardly of the housing.

32. Apparatus according to claim 1 or 2 comprising a housing containing said cylinder and air reservoir and further wherein said second control valve comprises a hollow valve casing which is attached to said housing and has first, second and third ports which lead respectively to the air reservoir, the bottom end of the cylinder and the atmosphere exterior of said housing,and a control valve member which is movably disposed within its valve casing so as to selectively close off said first or third ports, and further including a first activating member mounted to and projecting from said housing, means connecting said first activating member and the control valve member of said second control valve for shifting said control valve member in a direction to close off the said first port of said second control valve when said first activating member is forced inwardly of said housing, a trigger for operating said first control valve, means for releasably locking said trigger, and means for releasing said locking means including a second activating member mounted to and projecting from said housing for operating said releasing means, said second activating member and said releasing means being connected so that the trigger is unlocked when the second activating member is moved inwardly of the housing, and an extension at an end of said housing defining a guideway for said hammer, and further wherein said first and second activating members are rods slidably disposed in and projecting from said extension.

33. Apparatus according to claim 1 or 2 comprising a guideway for said hammer, an aperture opening into said guideway for intro-ducing a fastener into said guideway in position to be driven by said hammer, and a fastener discharge opening at the end of said

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guideway remote from said cylinder; and further wherein said hammer is retracted in a first position at the end of its return stroke and is extended in a second position at the end of its drive stroke and said hammer has a length such that it protrudes from said fastener discharge opening when it is in its second position.

34. Apparatus according to claim 1 or 2 further including a hollow housing with said cylinder subdividing the interior of said housing into a first chamber located between the housing and cylinder and a second chamber within the cylinder, with said first chamber forming said air reservoir, and further comprising an extension of one end of said housing defining a guideway for said hammer, and an aperture opening into said guideway for introducing a fastener into said guideway in position to be driven by said hammer, said aperture being located so that said hammer must travel a predetermined distance in moving from its first retracted position to its second extended position before engaging a fastener disposed in said guideway in alignment with said aperture.

35. Apparatus according to claim 1 or 2 wherein said poppet valve comprises a poppet valve member having a hollow body of circular cross-section with a first outside diameter at one end ant a second smaller outside diameter at the other end;
an integral wall closing off said one end of said hollow body;
an extension formed integral with one side of said wall, said extension being coaxial with and extending away from said hollow body;

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a boss formed integral with the opposite side of said wall, said boss being located within and extending coaxially of said hollow body;
a plate attached to said boss and closing off the other end of said hollow body, said plate having a smaller diameter than the outside diameter of said one end of said hollow body; and a passageway extending through said extension, said wall, said boss and said plate for conducting air through said valve member.

36. Apparatus according to claim 1 or 2 including a first foot section in which said hammer is slidably mounted and a second foot section spaced from said first foot section for assisting in stabilizing said apparatus with respect to a workpiece.