US3023413A

US3023413A - Portable, air-operated, magazine-fed nailing machine

Info

Publication number: US3023413A
Application number: US37700A
Authority: US
Inventors: Howard R Fischer; James A Roberts
Original assignee: Chicago Pneumatic Tool Co LLC
Current assignee: Chicago Pneumatic Tool Co LLC
Priority date: 1960-06-21
Filing date: 1960-06-21
Publication date: 1962-03-06
Anticipated expiration: 1979-03-06

Description

3 Sheets-Sheet 1 H. R. FISCHER ETAL PORTABLE, AIR-OPERATED, MAGAZINE-FED NAILING MACHINE w NdHl l hhhhl l HHHHHu l H 2 FIL E m March 6, 1962 Filed June 21, 1960 INVENTORSI 661444190 A. HJCl/E/P (X40455 A. Foes/P219 y m ATTORNEY FIG. I

March 6, 1962 H. R. FISCHER ETAL 3,023,413

PORTABLE, AIR-0PERATED, MAGAZINE-FED NAILING MACHINE Filed June 21, 1960 3 Sheets-Sheet 5 United States Patent M ,023,4 3. PORTABLE, I -OPERATED, MAGAZINE-FED NAILING MACHINE Howard R. Fischer and James A. Roberts, Utica, N.Y., assignors to Chicago Pneumatic Tool Company, New York, a corporation of New Jersey FiledJune 21, 1960, Ser. No. 37,700 Claims. (Cl.- 1-44.4)

a driving blade assembly that strips the individual nail from the bonded nail strip, advances the nail to the surface of the work piece, has its hammering action automatically started thereupon and continues to be advanced as the nail is driven.

It is still another object of the invention to provide an air-operated, magazinefed, nailing machine that has an automatic control valve on the feed piston for controlling the operation of the hammer piston in response to the build up of air pressure against the feed piston when the nail point has engaged the workpiece.

It is still another object of the invention to provide a portable, air-operated, magazine-fed nailing machine in which a combined feed piston and hammer assembly is fully enclosed by. the machine body and themachine body serves as a connecting member for the support of the other component parts of the machine, whereby ofv the parts of the machine will be contained in one housing body.

It is a further object of the invention to provide in an air-operated, magazine-fed nailing machine in which the cycle. of operation of. the machine is started by a trigger-operated air valve, an adjustable cutoff valve that will automatically stop the machine when the nail has been driven to its full extent or to a predetermined distance into the work.

It is still a further, object of the invention to provide an air-operat d, magazine-fed nailing, machine in hen the anvil is slidably retained in a bushing within the feed piston structure and i s cushioned in its blow and returned against the sleeve. by rubber ring cushioning means fixed in the lower end of the feed piston structure.

Other objects of the invention are. to provide an airoperated, magazine-fed nailing machine, having the above objects in mind, which is of simple construction, has a minimum number of parts, is compact, light in weight, easy to load, maintain and handle, efficient and effective in use, and automatic in operation.

For a better understanding of the invention, reference m ybe had to the following detailed construction taken in connection withthe accompanying drawing, in which FIGURE 1 is a vertical sectional view taken through. the nailing machine of the present invention with the feed piston structure and the driving blade retracted,

FIG. 2 is an enlarged vertical sectional view of the top of the machine angled from the vertical section of F G- FIG. 3 is an enlarged fragmentary, vertical sectional view of the intermediate part of the nailing machine similar in section to FIG. 2, with the feeding piston advanced 3,023,413 Patented Mar. 6, 1962 to place the hammerinto operation and with the hammer resting upon the anvil,

FIG. 4 is an enlarged fragmentary vertical sectional View of the hammer exhaust control passage, similar in section to FIG. 3,

FIG. 5v is. a vertical sectional view of the nailer body and of the feed piston structure in full advanced to locate the. point of the nail upon the work surface, preparatory to the hammering action being effected,

FIG. 6 is a transverse sectional view of the nailing machine looking upon the top surface of the air distributing plate and as'viewed on line 6-6 of FIG. 1

FIG. 7 is an enlarged transverse sectional view of the nailing machine, taken just below the distributing plate and looking upon the laterally shiftable valve ring and into the air supply and exhaust passages of theffeed piston structure that serve to supply and exhaust air from the hammer piston chamber therewithin, and as viewed on line 7-7 of FIG. 1,

FIG. 8 is a transverse sectional view of the nailing machine at the upper end'thereof and taken through the feed piston andthe automatic valve for controlling the supply of air to the hammer piston cylinder, the view being taken on line 88 of FIG, 2,

FIG. 9 is a transverse sectional view of the nailing machine at the lower end thereof and taken through the driving blade and the automatic cutoff mechanism, and more particularly upon line 9 9 of FIG. 1, I

FIG. 10 is an enlarged fragmentary vertical sectional View looking upon: the trigger operated air supply valve within the handle and the cutoff valve mechanism, the cutoff valve being in its closed position, and

FIG. U is an enlarged fragmentary vertical sectional view similar to FIG. 10 butwith the cutoff valve mechanism having been operated by the feed piston, and the cutoff valve being in its open position.

Referring now to the figures, 15 represents a nailer body in which there is a cylindrical chamber 16 and extending laterally from the body is a valve handle 17. On the lower end of the nailer body 15 is a foot portion 18 to the underside of which there is fixed a nail magazine assembly 19. A driving blade guidejZ O; having 'a guide slot 21 is connected to the magazine by fastening

bolts

22 and 23. Nails N are T-shaped and are bonded together to provide nail strips that can be supported on a guideway 24 within the magazine 19. A nail strip follower 25 urges the nail strip toward the blade guide 20 so that the forwardmost nail is delivered to the guide slot '21. The nail follower 25 is forced forwardly by a long tension spring 27 that is connected to the follower and extended over a forward pulley 28 and anchored to a projection 29 at the rear end of the magazine.

To insert the nails into the magazine, the follower 25 is pulled rearwardly and held in its rearward position by raising a catch lock 30 into recess 31 in the magazine housing. A door 32 is provided on the top of the maganine and when it is opened a nail strip may be loaded into the magazine. These nails are vertically supported upon the guideway 24- by their heads and held against lateral displacement by side guide plates 33 and while being fed by the long tension spring 27 to the drive guide slot 21. When the door is closed,'the follower 25fis released and pushes the leading nail of the strip into slot 21 under a driving blade 34.

Upon the upper end of the mailer body 15 over the cylindrical chamber 16;, there is secured by means of screw bolts 37 a reduced diameter feed piston chamber extension cap 36 which serves as one hand grip for the machine. Slidable in the cylindrical chamber 1 6, is a feed piston structure 38 that has a small diameter upwardly-extending integral sleeve extension 39 that extends into a reduced diameter cylinder extension 41 provided by the cap 36. Sealing rings 40 are provided on the extension 39 to hold down air leakage to the main portion of the feed piston chamber 16. This piston sleeve extension 39 has a central passage 42 depending from its upper end into a valve chamber 43' which is closed from the depending passage 42 by an inverted cup-shaped automatic hammer control valve 44 supported in its closed position by a compression spring 45 resting upon an air distributor plate 47 that is restrained therewithin the feed piston structure 38 by a depending piston skirt 48 that is threaded tightly thereinto against the air distributor plate 47 to support the distributor plate therewithin.

The upper end of the piston skirt 48' is relieved at the opposite sides to provide an elliptical projection 49 that is surrounded by a ring valve 51 laterally shiftable within side spaces 52 afiorded by the elliptical shape of the projection 49. This ring valve mechanism has been described in detail in the Edward W. Stevens Patents 1,860,964 granted May 31, 1932 and 1,931,041 granted October 17, 1933 whereby a cutaway of the opposite sides provide an elliptical transverse shape of the projection 49, so that the ring valve 51 can move laterally first to close ports 53 in one side of the projection 49 and then ports 54 in the other side of the projection 49'.

The ring valve 51 alternatively shifts first to one side and then to the other depending upon the direction to which a hammer piston 56 is to be moved within a piston chamber 57. A key 59 holds the piston skirt 48 against being unthreaded from the piston structure 38 and the air distributor plate 47 in place. The piston skirt 48 has a long key Way 61 that receives a key 62 projected inwardly from the nailer body 15 to hold the piston structure 38 against rotation while being Worked. The feed piston is biased to its raised position by a return compression spring 63 that engages the underside of the piston structure 38. This spring 63 surrounds the piston skirt 48 and reacts between a shoulder 64 in the lower end of the nailer body 15 and a shoulder 65 on the piston skirt 48. The driving blade 34 is fixed to an enlarged lower end 66 of an anvil 67 that is slidably carried in a sleeve bushing 68 tightly fitted upwardly in the piston skirt 48 against an internal shoulder 69.

In the lower end of the piston skirt 48, FIGS. 1 and 3, there is provided cushioning means for the anvil 67 comprising a bottom retaining ring 71 fixed by two

pins

72 and 73 to the lower end of the piston skirt 48 that supports a rubber cushioning ring 74 and a metal wear ring 76 thereabove. The driving blade 34 extends downwardly from the enlarged end 66 of the anvil through these rings and between the

pins

72 and 73 and into the drive guide nail dispensing slot 21. The anvil 67 is bounced by the cushioning means after a hammer blow into the sleeve bushing 68 and limited in its upward movement by the engagement of the enlarged end 66 of the anvil with the lower end of the sleeve bushing 68.

In the valve handle 17 is a valve opening 77, FIG. 10. to which an air hose fitting 78 is threadedly connected. This hose fitting 78 has a valve compression spring 79 seated therein that normally holds a valve assembly 81 the closed position upon the end of the sleeve 82, FIG. 1, to prevent the passage of air through the valve bushing 82. The valve assembly 81 has a guide stem 83 that is slidable in the valve bushing 82 and is adapted to cover when the valve 81 is lifted from its seat, an exhaust port 84 in the sleeve 82, FIG. 10. This port 84 communicates with an exhaust passage 86 that exhausts air through the rear end of the handle to the atmosphere. The valve guide stem 83 has a reduced diameter portion 87. Upon the valve 81 being released forwardly into the closed position upon the end of the sleeve 82, FIG. 1, air from the machine can be returned through a port 91 on the upper side of the sleeve 82 along the reduced 4 diameter portion 87 of the valve stem, through the port 84 and be exhausted through the handle passage 86.

A trigger-operated arm 92 is pivoted Within a recess 93, extending upwardly from the underside of the valve handle 17, by a pivot pin 94 and engages the forward end of the valve guide stem 83 to open the valve 81 when a trigger plunger 96 is pulled upwardly by a finger while grasping the handle 17. The trigger plunger carries a rounded end 97 of the pivot arm 92. to pivot the same, and cause its nose end 97' to engage the end of the stem 83 and the valve 81 to be lifted from its seat against the action of the compression spring 79, FIG. 10. The exhaust port 84 in the sleeve 82 will be closed by the valve stem 83 and air entering the fitting 78 passes the valve 81, the sleeve port 91 and into an air supply passage 98 running through the full extent of the handle. The drillings for this passage 98 are closed by

plugs

99 and 101, one of these drillings leading from the valve sleeve port 91.

Within the inner part of the handle 17, is a verticallyextending opening 103 that has a vertically-extending valve bushing 104 tightly fitted therein. A cutofi. valve plunger 105 operates in the valve bushing 104 and is held down by along compression spring 106 reacting against a stop plug 107 secured in the upper end of the opening 103 by a sleeve pin 107 and against the upper end of a push rod 108. The push rod 108 extends downwardly through a depending reduced diameter extension 109 of the valve bushing 104 and is held in place against downward displacement by a stop pin 110 in the extension 109 and engaging the upper end of an elongated step recess 111 in the side of the push rod 108. The upward movement of push rod 108 is limited by the same stop pin 110 upon being engaged by the push rod at the lower end of the elongated recess 111.

When the cutoif valve plunger 105 is held down by its compression spring 106 it is supported upon the push rod 108 and air from the supply passage 98 passes through a port 112 in the valve bushing 104, about annular groove 113 in the plunger valve 105, a port 114 in the opposite side of the valve bushing 105 to a transverse passage 115 in the nailer body 15 and upwardly through a vertical passage 116 to the top thereof. This passage 116 communicates past a sealing ring 116' with a passage 117 in the extension cap 36 extending upwardly in continuation from the passage 116 and through a top port 118 into the feed piston chamber extension 41. The drillings providing the passage 117 and the port 118 are closed respectively by stop plugs 119 and 120 welded thereinto.

Air entering the the central passage 42 in the piston sleeve extension 39 exerts a downard pressure against the seated valve 44. This pressure is at this time insufiicent to overcome the resistance of the valve 45, so that the valve remains seated and the pressure of the air acting upon the valve 44 forces down the piston structure 38 to place the pointed end of the nail N in contact with the work piece, FIG. 5, and continues the downward movement of the feed piston 38 to maintain the hammering action of the hammer piston upon the nail until it is driven. Since the small hammer piston 56 is within the piston structure 38, both pistons are advanced. The downard movement of feed piston structure 38 is against the action of the return spring 63. The downward motion of the feed piston structure forces the driving blade 34 through the guide slot 21 and strips the first nail from the bonded strip of nails and pushes the nail downwardly into contact with the work piece. The nail is held in the vertical position in the guide slot 21 by the pressure from the succeeding nail of the bonded nail strip and the long magazine tension spring 27.

When the nail point contacts the work piece surface, however, greater resistance is encountered and the air pressure is built up in the cylindrical chamber 16 above the feed piston structure 38 and in the central piston passage 42 of the piston feed extension 39 to open the ham mer control valve 44 against the action of the compression spring 45 and allow the air to enter the valve chamber 43 (FIG. 3). The control valve chamber 43 has four radially-extending ports 122 from the outer ends of which the air passes downwardly through respective vertical passages 123 into an annular recess in the top of the air distributing plate 47. The air distributing plate 47, in turn has four radially-extending passages 126 leading outwardly into respective vertical notches 127 in the outer periphery of the distributing plate 47 whereby air will be distributed to the opposite sides of the piston structure 38 and into the spaces 52 at the opposite sides of the upstanding elliptical projection 49 on piston skirt 48 in which the ring valve 51 is shifted. The ring valve 51 moves laterally to alternately supply air to the opposite ends of the hammer piston chamber 57 and thereby causes the reciprocation of the hammer piston 56.

Air passes valve 51 and inwardly through ports 53 and downwardly through passages 128 at the one side of the piston skirt 48 and inwardly through the ports 129 into the hammer piston chamber 57 to lift the hammer piston 56. Vertical exhaust passages 132 have vertically spaced

ports

133 and 134 and an intermediate exhaust port 135 by which the exhaust air passes into the cylindrical chamber 16 of the nailer body 15 and outwardly through an exhaust port 136 thereof to the atmosphere.

The hammer piston 56 thus serves as its own valve to reverse the flow of air to the opposite sides of the hammer piston to obtain the reciprocation thereof. As the hammer piston 56 is lifted, the exhaust port 133 is closed by the piston itself and the lower exhaust port 134 is opened. The air above the hammer piston 56 is compressed sufiiciently to displace ring valve 51 from the ports 54 and allow the air then to pass from the ring space 52 through the ports 54 into the top of the hammer chamber 57 and reverse the movement of the hammer 56 so as to deliver a blow upon the anvil 67. The cycle of operation is automatically continued so that a series of blows are delivered to the anvil to drive the nail N. The hammer blows are transmitted from the anvil to the driving blade 34 and the entire piston structure advances downwardly as the nail is driven since pressure continues to be exerted on the top of the piston structure 38.

When the feed piston structure 38 is advanced downward to a point where the lower end of the piston skirt 48 contacts a cutoff valve actuator 141 lying in a slot 140 in the depending foot portion 18 of the nailer body 15, FIGS. 1, 5, and 11, the cutoff actuator 141 is pivoted on a pin 142 to the position shown in FIG. 11. On a threaded lower end 143 of the push rod 108 is an adjustable nut 144 with which the actuator engages. The downward movement of the feed piston 38 thus causes the opposite end of the actuator 141 to rise and engage with the adjustable nut 144 which in turn forces the push rod 108 and cutoff valve 105 upwardly against the action of the valve compression spring 106 until a passage 145 in the sleeve bushing 104 is exposed, FIG. 11. At this point air from the supply passage 98 enters the bushing 104 through the passage 145, takes over and forces the cutoif valve 105 up against a stop plate 146, O-ring 147 and the stop plug 107. Some of the air entering the sleeve bushing 104 beneath the cutoff valve 105 bleeds through a hole 149 in the valve 105 and outwardly through a hole 151 in the stop plug 107 to atmosphere. Since the passage 145 passes more air than the hole 149, the cutoff valve 105 remains in its raised position so long as the valve 81 is kept open by the trigger 96. In this position, the valve 105 closes the bushing port 11 4 to cutoff the flow of air to the feed piston chamber 16, air is then trapped in the

passages

115 and 116 in the nailer body 15, and in the feed piston chamber 16 and the hammer piston chamber 57. The hammer piston 56 delivers one or two more blows until enough air escapes through the

hammer exhaust ports

135 and 136 to lower the pressure in the central passage 42 sufliciently to permit the spring 45 to force the control valve 44 upwardly into engagement with its seat to close off the valve chamber 43 from the central passage 42 in the piston extension 39. At this point the hammer 56 ceases to operate. The piston structure 38 is returned by compression return spring 63 as the trapped air leaves through the exhaust passage 152 in the extension cap 36.

Due to the threaded connection between the adjusting nut 144 and the cutoff valve push rod 108, the point at which the cutoff valve is closed can be adjusted and the point of travel of the driving blade 34 at which the hammering stops and the blade ceases to be effective. Thus, by adjusting this nut 144 upon the push rod the nail heads can be driven flush with the work surface, countersunk from the work surface or left projected slightly above the work surface.

When the trigger 96 is manually released the valve 81 is closed by its spring 79 and the air is exhausted through the handle passage 86. The spring 106 forces the cutoff valve down until it contacts the push rod 108 which has been held in its raised position by the actuator 141. The feed piston 38 is raised and the actuator 141 then permits the push rod 108 to drop and the control valve 105 returned to its lowered position so that the nailing machine is made ready for the next cycle of operation.

It should be apparent that there has been provided an effective automatic control valve to control the operation of the hammer piston in response to the delivery of the nail to the work piece by the feed piston structure and an equally effective adjustable cutoff mechanism for automatically stopping the operation of the machine when the nail has been driven.

While various changes may be made in the detailed construction it shall be understood that such changes shall be within the spirit and scope of the present invention as defined by the appended claims.

What is claimed is:

1. In an air-operated, magazine-fed nailing machine, a nailer body having a feed piston chamber therein, air supply passages extending to the top of the feed piston chamber, a feed piston structure operable in said feed piston chamber, a return spring in the feed piston chamber for biasing the feed piston to its retracted position, said feed piston structure having a hammer piston chamber therein, a hammer piston operable in the hammer piston chamber, an anvil in the hammer piston chamber adapted to be actuated by the hammer piston, 21 driver blade depending from the anvil and the feed piston structure, valve mechanism for operating the hammer piston, a magazine for feeding nail strips, a driver blade guide connected to the magazine and having a guide slot for receiving the driver blade and the nail from the maga- Zine, an air-operated control valve on the feed piston structure operable in response to the resistance of the nail upon the work to supply the air to the hammer piston valve mechanism, whereby upon air being extended to the feed piston chamber the nail is advanced so that its point engages the work surface before the hammering action is effected by the opening of the control valve, and means responsive to a predetermined movement of the feed piston structure to shut off flow of air to the said air supply passages.

2. In an air-operated, magazine-fed nailing machine, a nailer body having a feed piston chamber therein, air supply passages extending to the top of the feed piston chamber, a feed piston structure operable in said feed piston chamber, a return spring in the feed piston chamber for biasing the feed piston to its retracted position, said feed piston structure having a hammer piston chamber therein, a hammer piston operable in the hammer piston chamber, an anvil in the hammer piston chamber adapted to be engaged by the hammer piston, a driver blade depending from the anvil and the feed piston structure, valve mechanism for operating the hammer piston,

a magazine for feeding nail strips, a blade guide. connected to the magazine and having a guide slot for receiving the driver blade and the nail from the magazine, an air operated control valve on the feed piston structure operable in response to the resistance of the nail upon the work to supply the air to the hammer piston valve mechanism, said feed piston structure having a reduced diameter extension and said nailer body having a reduced diameter chamber extension for receiving the piston extension, said piston extension having a central passage depending from its upper end thereof to said hammer supply control valve so that the air that advances the feed piston has access to the control valve, a spring biasing said control valve upwardly into its closed position, whereby upon air being extended to the feed piston chamber the nail is advanced so that its point engages the work surface before the hammering action is effected by the opening of the control valve, and means responsive to a predetermined movement of the feed piston to shut off flow of air to the said air supply passages.

3. In an air-operated, magazine-fed nailing machine, a nailer body having a feed piston chamber therein and a laterally-extending handle portion, air supply passages extending from the handle portion to the top of the feed piston chamber, a feed piston structure operable in said feed piston chamber, a return spring in the feed piston chamber for biasing the feed piston to its retracted position, said feed piston structure having a hammer piston chamber therein, a hammer piston operable in the hammer piston chamber, an anvil in the hammer piston chamber adapted to be engaged by the hammer piston, a driver blade depending from the anvil and the feed piston structure, valve mechanism for operating the hammer piston, a magazine for feeding nail strips, a blade guide connected to the magazine and having a guide slot for receiving the driver blade and the nail from the magazine, an air-operated control valve on the feed piston structure operable in response to the resistance of the nail upon the work to supply the air to the hammer piston valve mechanism, a cutoff valve mechanism in the air supply passages of the handle portion, a depending push rod for operating said cutoff mechanism, and an actuator carried on the nailer body and engageable by said feed piston structure and engaging said push rod upon the nail having been driven a predetermined distance into the work piece, whereby upon air being extended to the feed piston chamber the nail is advanced so that its point engages the work surface before the hammering action is effected by the opening of the control valve and the machine automatically stopped when the nail has been driven.

4. In an air-operated, magazine-fed nailing machine, a nailer body having a feed piston chamber therein and a laterally-extending handle portion, air supply passages extending from the handle portion to the top of the feed piston chamber, a feed piston structure operable in said feed piston chamber, a return spring in the feed piston chamber for biasing the feed piston to its retracted position, said feed piston structure having a hammer piston chamber therein, a hammer piston operable in the hammer piston chamber, an anvil in the hammer piston chamber adapted to be engaged by the hammer piston, a driver blade depending from the anvil and the feed piston structure, valve mechanism for operating the hammer piston, a magazine for feeding nail strips, a blade guide connected to the magazine and having a guide slot for receiving the driver blade and the nail from the magazine, an air-operated control valve on the feed piston structure operable in response to the resistance of the nail upon the work to supply the air to the hammer piston valve mechanism, a cutoff valve mechanism in the air supply passages of handle portion, a depending push rod for operating said cutofi mechanism, and an actuator carried on the nailer body and engageable by said feed piston structure and engaging said push rod upon the nail 8 having been driven a predetermined distance into the Work piece, and said nailer body having a foot portion extending laterally therefrom, said foot portion having a slot therein leading from the body chamber, said actuator extending into the body chamber to be actuated by the feed piston and pivoted within said slot, and said push rod having an adjustable nut thereon and engageable by the outer end of said pivoted actuator, whereby upon air being extended to the feed piston chamber the nail is advanced so that its point engages the work surface before the hammering action is effected by the opening of the control valve and the machine automatically stopped when the nail has been driven.

5. In an air-operated magazine-fed nailing machine as defined in claim 3, said cutoff valve being vertically movable and normally spring biased toward said push rod, an air passage leading from the one of said air supply passages and normally closed by the cutoff valve, said push rod when lifted by the actuator adapted to lift the cutoff valve above the air passage to let air entering the valve opening complete the lifting of the cutoff valve, and air exhaust passages leading through the cutoff valve and the handle portion to the atmosphere, said cutoff valve air passage passing more air than the cutoff valve exhaust passages whereby to sustain the cutoff valve in its lifted position until air supply is shut off.

6. In an air-operated, magazine-fed nailing machine, a nailer body having a feed piston chamber therein, air supply passages extending to the top of the feed piston chamber, a feed piston structure operable in said feed piston chamber, a return spring in the feed piston chamber for biasing the feed piston to its retracted position, said feed piston structure having a hammer piston chamber therein, a hammer piston operable in the hammer piston chamber, an anvil in the hammer piston chamber adapted to be actuated by the hammer piston, a driver blade depending from the anvil and the feed piston structure, the piston structure, hammer piston, anvil, and driver blade having a common longitudinal axis, valve mechanism for operating the hammer piston, a magazine for feeding nail strips, a driver blade guide connected to the magazine and having a guide slot for receiving the driver blade and the nail from the magazine, and an air-operated control valve on the feed piston structure operable in response to the resistance of the nail upon the work to supply the air to the hammer piston valve mechanism, and hammer valve mechanism on the piston structure including an air distributor plate and a piston skirt retained within the piston structure, said piston skirt having a projection providing spaces at the opposite sides thereof, a laterally shiftable ring valve shiftable upon the projection, and supply ports running through the piston skirt to feed air to the upper and lower sides of the hammer piston chamber, and exhaust port means in the piston skirt and operable by said hammer piston and in cooperation with the ring valve to effect the reciprocation of the hammer piston, whereby upon air being extended to the feed piston chamber the nail is advanced so that its point engages the work surface before the hamering action is effected by the opening of the control valve.

7. In an air-operated, magazine-fed nailing machine, a nailer body having a feed piston chamber and a laterally-extending handle portion, air supply passages extending from the handle portion to the top of the feed piston chamber, a feed piston structure operable in said feed piston chamber, a return spring in the feed piston chamber for biasing the feed piston to its retracted position, said feed piston structure having a hammer piston chamber therein, a hammer piston operable in the hammer piston chamber, an anvil in the hammer piston chamber adapted to be engaged by the hammer piston, a driver blade depending from the anvil and the feed piston structure, valve mechanism for operating the hammer piston, a magazine for feeding nail strips, a

blade guide connected to the magazine and having a guide slot for receiving the driver blade and the nail from the magazine, and an air operated control valve on the feed piston structure operable in response to the resistance of the nail upon the work to supply the air to the hammer piston valve mechanism, said feed piston structure having a reduced diameter extension and said nailer body having a reduced diameter chamber extension for receiving the piston extension, said piston extension having a central passage depending from its upper end thereof to said hammer supply control valve so that the air that advances the feed piston has access to the control valve, and a spring biasing said control valve upwardly into its closed position, said air supply passages extending through the handle portion, the mailer body and the reduced-diameter chamber extension, a control valve in the handle air passage, a trigger means for operating the air control valve provided on the handle portion and cut on valve means in said handle passage and operable by the feed piston structure when the nail has been driven a predetermined distance, whereby upon air being extended to the feed piston chamber the nail is advanced so that its point engages the work surface before the hammering action is effected by the opening of the control valve.

8. In an air-operated, magazine-fed nailing machine, a mailer body having a feed piston chamber therein, air supply passages extending to the top of the feed piston chamber, a feed piston structure operable in said feed piston chamber, a return spring in the feed piston chamber for biasing the feed piston to its retracted position, said feed piston structure having a hammer piston chamber therein, a hammer piston operable in the hammer piston chamber, an anvil in the hammer piston chamber adapted to be engaged by the hammer piston, a driver blade depending from the anvil and the feed piston structure, valve mechanism for operating the hammer piston, a magazine for feeding nail strips, a blade guide connected to the magazine and having a guide slot for receiving the driver blade and the nail from the magazine, an air-operated control valve on the feed piston structure operable in response to the resistance of the nail upon the work to supply the air to the hammer piston valve mechanism, said piston structure including a depending skirt, a vertically-extending bushing retained in said piston skirt against upward displacement, said anvil being vertically slidable in said bushing, said anvil having an enlarged bottom head and engageable with the lower end of said bushing to limit its upward movement, said driver blade depending from the enlarged bottom head of the anvil, an annular retaining ring fixed within the lower end of the depending piston skirt, cushioning ring means supported by said retaining ring and engageable by the enlarged bottom head of the anvil to cushion the blow and return the anvil preparatory to the next blow, whereby upon air being extended to the feed piston chamber the nail is advanced so that its point engages the work surface before the hammering action is effected by the opening of the control valve, and air out off means in the air supply passages actuable by the skirt of the piston structure to shut off flow of air through said passages upon the piston structure moving a predetermined distance in the direction of the nail.

9. In a fluid powered nailing machine including a housing having a main piston chamber, a main piston operable in this chamber and carrying a nail driver element for engagement with a nail that is to be driven into a workpiece, a return spring biasing the main piston to a returned initial position, a piston cylinder defined within the main piston, the driver element having an upper portion thereof in the lower end of the piston cylinder, a hammer piston reciprocable in the piston cylinder for pounding the said upper portion of the driver element, and valve mechanism for alternately applying operating pressure fluid to opposite ends of the piston cylinder to reciprocate the hammer piston; control means initially causing pressure fluid to be applied to the main piston to move the latter against the spring so as to carry the driver element against the nail to be driven, and for subsequently causing in response to a predetermined resistance of the nail to the driven ele-' ment pressure fluid to be applied simultaneously to the main piston to press the driver element continuously against the nail and to be applied to the valve means to effect reciprocation of the hammer piston, and air shut ofl? means responsive to a predetermined movement of the driver element subsequent to its engagement with the nail to cut off the flow of pressure fluid to the machine.

10. In a fluid powered machine for driving a rigid linear element into an object, including a main piston carrying a driving member for driving the rigid element, the main piston being movable to carry the driving member linearly into abutment with the rigid element, a reciprocable hammer piston for pounding the driving member; means for initially causing pressure fluid to be applied to the main piston to carry the driving member into abutment with the rigid element, and for subsequently acting in response to a predetermined resistance of the rigid element to the driving member to cause operating pressure fluid to be applied to the main piston to hold the driving member in pressed abutment with the rigid element and simultaneously with the latter application to cause pressure fluid to be applied alternately to opposite ends of the hammer piston to reciprocate the latter; and means responsive to a predetermined linear movement of the driving member subsequent to its abutment with the rigid element to shut off flow of pressure fluid to the machine.

References Cited in the file of this patent UNITED STATES PATENTS 963,924 McSherry July 12, 1910 2,546,354 Bacon Mar. 27, 1951 2,648,841 Smith Aug. 18, 1953 2,857,596 Allen Oct. 28, 1958