US2993208A

US2993208A - Nailing apparatus and nail feeding mechanism therefor

Info

Publication number: US2993208A
Application number: US747251A
Authority: US
Inventors: Cast Adolf; Walliser Gustav
Original assignee: Karl M Reich Maschinenfabrik GmbH
Current assignee: Karl M Reich Maschinenfabrik GmbH
Priority date: 1957-06-14
Filing date: 1958-07-08
Publication date: 1961-07-25
Anticipated expiration: 1978-07-25
Also published as: US3011169A

Description

July 25, 1961 A. cAs-r ErAL 2,993,208

NAILING APPARATUS AND NAIL FEEDING MECHANISM THEREFOR Filed July 8, 1958 4 Sheets-Sheet 1 I 56 52 1/ 1' /5 m, 2M r/7' 5/ 'Q' Y /"Y 25 l 9 54 d o 25 /5 /4-/9 28 5 A9 l r ,l

l `4 L /Q7, n

July 25, 1961 Filed July 8, 1958 A. CAST El' AL NAILING APPARATUS AND NAIL FEEDING MECHANISM THEREFOR 4 Sheets-Sheet 2 67 7 l be @4 9 Q 175 X 5b l n( I E L l b9". 90 /V 98 92 Q- 70 75 7/ 72l L f es 71W/ l... l Q S6 54 SQL ,6g S5 e) 7e 8O 6b 84 y 82 3,5 74 as 40 77 78 .Im/anfora M6444( vudf/aeqy Wazaa, M, :2/@229% July 25, 1961 A. CAST mL 2,993,209

NAILING APPARATUS AND NAIL FEEDING MECHANISM THEREFOR Filed July 8, 1958 4 Sheets-Sheet i3 I C/Q. 40 5,9

July z5, 1961 NAILING Filed July 8, 1958 A, cAsT ErAL 2,993,208

APPARATUS AND NAIL. FEEDING MEcHANIsM THEREFOR 4 Sheets-Sheet 4 2,993,208 NAILING APPARATUS AND NAIL FEEDING MECHANISM THEREFOR Adolf Cast, Oberlenningen, and Gustav Walliser, Reutlingen-Betzingen, Germany, assignors to Firma Karl M.

Reich, Nurtingen, Wurttemherg, Germany Filed July 8, 1958, Ser. No. 747,251 Claims priority, application Germany Dec. 14, 1957 20 Claims. (Cl. 1-44.4)

The present invention relates to a pneumatically operated apparatus to a nail-feeding mechanism therefor, and more particularly to a nailing apparatus of the onestroke type as described in copending application, Serial No. 711,336, filed on January 27, 1958 in the names of Adolf Cast, Gustav Walliser and Willi Speidel, which is distinguished from the gradually hammering type in that the striker piston of the apparatus, upon being released by the manual operation of an actuating trigger or the like, is driven by compressed air to carry out a full stroke and to deliver an impact upon one of a series of nails or the like which are intermittently fed into the apparatus by compressed air in accordance with the individual strokes of the piston, so that ordinarily a single stroke of the piston will be sufficient to drive the nail to the desired depth into a wall, board, or other object.

`For insuring that only one nail at a time was fed to the apparatus in accordance with the individual strokes of the striker piston, the feeding mechanism of previous apparatus of this type usually included a spring loaded piston valve which was connected to the nail-feeding channel leading to the nailing apparatus and had a transverse bore through which the individual nails were passed. The wall of this piston valve 4also contained an annular groove which insured that, in the normal position of the valve, the portion of the nail channel between the cylinder of this piston valve and the nail-striking mechanism was in continuous communication through the annular groove with the compressed-air line terminating into the valve cylinder so that the compressed air would flow continuously through the nail channel.

The nails which were fed individually by the feeding device of this prior apparatus were passed into the transverse bore of the piston valve through an opening in the cylinder thereof. An impact of compressed air then shifted the piston valve to such an extent that its transverse bore would coincide with the end of the compressedair line terminating into the cylinder of the piston valve as well as uuth the nail channel so that the respective nail which was held ready within the transverse bore was then taken along by the air current then flowing through such bore and was thus fed to the nailing apparatus.

These prior nailing apparatuses had numerous serious disadvantages, one being that the constant passage of compressed feeding air through the nail channel required the head of the respective nails which were held ready within the nail-driving mechanism always to be smaller than the diameter of the nail channel so that a large portion of the air passing continuously through the channel escaped uselessly to the outside laterally of the nail head. If the apparatus was operated, for example, with an air pressure of 5 atmospheres, a channel with a cross-sectional area of 4 mm.2 allowed a flow of air of a volume of 750 liters per minute. Such a large consumption of compressed air is, however, hardly ever justified by the actual nailing operation.

It is one of the objects of the present invention to provide a nailing apparatus which avoids the above-mentioned disadvantage of similar apparatus of the prior art.

For attaining this object the invention provides a feeding mechanism which includes a slide valve which serves to control the feeding of the nails and also operates as a control member for regulating the supply of compressed air required for the nail-feeding operation. This slide valve is provided with a transverse bore which is disposed so that, when the valve is in a position in which the bore coincides with the nail-feeding conduit, such conduit will be free to admit a nail, while the supply of compressed air to such conduit will at such time be shut olf.

This new feature of the invention has the advantage that the nail-feeding conduit will be connected to the compressed-air line only for short periods, namely, only at such time when a nail is to be fed to the striking mechanism, while at all other times such feeding conduit will be open to the outer atmosphere so that a nail which is supplied by the nail dispenser can then pass into the nailfeeding conduit. This special control of the compressed air supply insures a relatively low air consumption which in an apparatus according to the invention of a size comparative to the known apparatus as above described only amounts to about to 200 liters per minute.

The known nailing apparatuses were also provided with special control elements, for example, an electromagnetic armature or an electromagnetic valve, which caused a flow of compressed air for shifting the mentioned slide valve of the feeding mechanism and were adapted to move the slide valve back and forth. Such control of the slide valve by means of elements which are operated independently of the nail-striking apparatus is easily subject to breakdowns and to an improper delivery of nails to the apparatus. It is therefore a further object of the present invention to provide means for controlling the movements of this piston valve directly in accordance with the sequence of the strokes of the striker piston so as to insure that the nail-feeding mechanism will be actuated at every full driving stroke of the striker piston.

Another feature of the invention consists in the provision of a control piston which is actuated by compressed air only when the striker piston has arrived near the end of its driving stroke, and which, in turn, controls the operation of the mentioned slide valve in such a manner that the latter will admit the lfeeding air into the nail-feeding conduit only when the nail passages through the valve do not coincide with each other and lwhen the slide valve shuts off the nail-feeding conduit vfrom communication with the outer atmosphere. According to the invention, this control piston will be coupled only during its return stroke to a pressure control valve which is interposed in the feeding-air line, so

yas to open this valve and admit the feeding air into the cylinder of the slide valve lso that the latter will move therein, and its transverse bore will be shifted out of alignment with the nail-feeding conduit and the latter will thus be closed toward the atmosphere, whereupon the slide valve will free the opening into the nail-feeding conduit so that a blast of compressed air can then pass from the cylinder of the slide valve into the nail-feeding conduit to deliver a nail to the nailing apparatus.

A further object of the invention is to provide suitable rneans for adjusting the velocity of compressed feeding air which is kadmitted into the cylinder of the slide valve when the mentioned control valve is opened. It is thus possible to adjust the velocity of the feeding movement of the nails in accordance with the particular type of nails used, and also to control the movements of the slide valve.

The pneumatic one-stroke nailing apparatus of the prior art have the further disadvantage that a new nail is fed into the apparatus at each driving stroke of the striker piston. Although such apparatus may operate adequately if the material into which the nails are to be driven has always a uniform degree of hardness and always offers the same degree of resistance to the naildriving movement, it often occurs in actual practice that the degree of hardness of the material varies considerably. Thus, a nail may strike an unexpected harder portion in the material, `for example, a branch knot in a board to be nailed. Since the air pressure for driving the nails into such boards or other material has to be adjusted to a certain value, as otherwise the nail heads might be sunk too deeply into the material, the presence of such knots or harder points in the material would prevent the nail from being driven home completely by a single stroke of the striker piston, and several strokes would be required. If, however, a new nail would be supplied lto the apparatus at every one of these driving strokes as is true in the known apparatus, a plurality of nails might accumulate within the feed conduit or even within the nail channel of the apparatus, with the result that one or the other or both may be jammed full with nails and the apparatus would no longer operate and may even be seriously damaged.

It is therefore a further object of the present invention to provide a nailing apparatus of the type as described above as well as in the above mentioned copending application in which the actuating trigger may be repeatedly depressed and released to effect a plurality of strokes of the striker piston and to deliver repeated impacts thereof upon the nail within its guiding channel in the apparatus without danger that the feeding mechanism will be operated to deliver a new nail by air pressure into or through the feed conduit or into the apparatus before the previous nail has been completely ejected from the apparatus.

This may be attained according to the invention by the provision of a control element which is adapted to control the operation of the feeding mechanism and which is actuated by the striker piston near the end of its nail-driving stroke, that is, not until the nail has been p driven home completely.

Such control of the `feeding mechanism may be carried out either by mechanical, electrical, hydraulic, or pneumatic means. Thus, for example, since the striker piston of the nailing apparatus is driven within its cylinmechanism to feed a new nail to the apparatus. This valve may be interposed between the compressed-air line leading to the striker cylinder and a line leading from the nailing apparatus back to the cylinder containing the mentioned piston of the nail-feeding mechanism so that, when the valve is opened, the compressed air is branched off Within the apparatus and passed through the valve to the mentioned cylinder to operate the control piston therein and, through the latter, also the slide valve of the feeding mechanism, so that a new nail will then be delivered under air pressure through the nail-feeding conduit and the striker guide channel of the apparatus into the nail-guiding channel where, when the actuating trigger of the apparatus is next depressed by the operator, it will be hit by the striker piston and be driven into the wall, board, or other object upon which the nozzle end o-f the apparatus is placed.

The control element for operating the nail-feeding mechanism may also consist, for example, of an electric switch which is operated by the striker piston near the end of its driving stroke in a similar manner as above described with reference to the pressure valve. In this event, the mentioned control piston of the feeding mechanism may be replaced by an electromagnet with a recip- "rocating armature which is electrically connected to and controlled bythe mentioned switch. This switch may `be of a very simple type and may merely consist of a pair of electric contacts, one of whichis directly engaged by the striker piston near the end of its driving stroke so as either to open or close its connection with the other contact depending upon whether the electric circuit is of the open or closed-circuit type. The striker piston may -also function as a part of the switch itself by forming Va metallic connection between a pair of spaced electric contacts when the striker piston engages both contacts near the end of the drivin-g stroke.

If the control element within the nailing apparatus consists of a pressure valve as previously described, it may be advisable to provide an adjustable vent within the compressed-air line leading from Vthe valve to the nail-feeding mechanism. Such a vent will permit the feeding mechanism automatically to interrupt its operation as soon as a new nail has been delivered to the nailing apparatus. Such arrangement is advisable particularly if the device vfor controlling the operation of the feeding mechanism consists of -a spring-loaded piston which is operated by compressed air. The compressed air which is supplied to such control piston through the above-mentioned prcssurevalve while the latter is opened by the striker piston is then released to the outside within a certain period of time which may be varied by an adjustment of the size of the vent opening. As soon as the air pressure within the .line leading from the pressure valve of the nailing apparatus to the control piston o-f the feeding mechanism has thus been suiiciently decreased, the control piston will be returned by its spring to its original position.

The nailing apparatus according to the present invention is preferably further provided with a safety lever which, when the apparatus is not in operation, absolutely prevents any new nail from entering the apparatus, and which has to be manually released before a nail can be injected into the nail-guiding channel of the apparatus to be subsequently driven home by the striker piston. Thus, as long as this safetyV lever is not released, an accidental operationvof the feeding mechanism or of the actuating Vtrigger of the nailing apparatus will not result in the injection of a new nail into the apparatus itself but, although the nail will be fed toward the apparatus when the striker piston opens the above-mentioned pressure valve or engages the electric switch or similar means near the end of its power stroke, such nail will be arrested by the safety lever before entering the nail-guiding channel of the apparatus. Such safety lever may also be combined with other safety devices known in the art, for example, with one which also prevents the main actuating trigger of the apparatus from being depressed.

Since the nails are delivered into the nail receiving channel of the nailing apparatus at a considerable velocity, it is also necessary to provide suitable means for arresting the nail withinv the nozzle of the apparatus and for holding it in the proper position for being squarely hit by the striker after the nozzle lhas been pressed upon the object to be nailed and after a safety stop on the rear end of the nozzle has by such pressure been released from the trigger mechanism of the apparatus to permit the trigger to be actuated. After first gripping the nail tightly, these yarresting means must be capable of guiding the nail while the tip portion thereof is being driven into the object and of then being disengaged from theV nail Iduring the further driving movement of the striker permitting the nail head and the striker to pass to the forward end of ythe `nail-guiding channel in the nozzle.

These different objects may be attained by the provision of a new type of chuck having a plurality of radially extending gripping jaws, yonly the lower parts of which are adapted to exert a self-centering resilient `gripping action upon the nail shank, while their upper parts diverge gradually and preferably parabolically outwardly so as to permit the nail head and the striker to wedge the gripping jaws gradually apart whereby the friction upon the jaws will 4be reduced and their life be considerably increased. A' spring ring of a suitable material is -tted over the peripheral surfaces of the chuck so as to press resiliently upon the radially outer ends of the jaws.

Further objects, features, and advantages of the present invention 'will ibecofme apparent from the following detailed description thereof, particularly when read with reference to the accompanying drawings, in which- FIGURE 1 shows the nailing apparatus according to the invention in a vertical cross section taken along line I-I of FIGURE 8, with the striker piston illustrated in the retracted position;

FIGURE 2 shows Ia similar cross section lof the lower parts of the nailing yapparatus with the striker piston in the driving position but incapable of driving a nail cornpletely home;

FIGURE 3 shows a cross section similar to FIGURE 2, but with the striker piston in its most forward d-riving position;

FIGURE 4 shows a -front view, largely in cross section, of the nail-feeding mechanism `according to the invention in one position of its operation;

FIGURE 5 shows the feeding mechanism according to FIGURE 4 in another position of its operation;

FIGURE 6 shows the lower parts of the nailing apparatus in a vertical cross section taken along line VI-VI of FIGURE 8;

FIGURE 7 shows a cross section taken along line VII- VII of FIGURE 6;

FIGURE 8 shows a cross section taken along line VIII-VIII of FIGURES 1 and 6;

FIGURE 9 shows a cross section taken along line IX--IX of FIGURE 1;

FIGURE 10 shows a vertical cross section similar to FIG. 2 of a modification of the invention;

FIGURE 1l shows a cross section taken along line XI-XI of FIGURE 10;

FIGURE l2 shows a front View, partly in cross section of a modification of the feeding mechanism to be used in connection with the modification as illustrated in FIGURES 10 and 11;

FIGURE 13 is a top view of the detail of the nail supplying means; and

FIGURE 14 is a side view lof the nail supplying means.

Referring to the drawings, the nailing apparatus according to the present invention is basically similar to the one illustrated and described in the copending application, Serial No. 711,336, filed on January 27, 1958 as noted above, and entitled Nailing Apparatus. It consists of a central cylinder 1 with a striker piston 2 slideable therein. Cylinder 1 is surrounded by two

cylindrical walls

3 and 4 extending concentrically thereto and spaced from each other, thus forming a cylindrical storage chamber 5 and a cylindrical passage 6. All three

cylinders

1, 3, and 4, are combined into a solid unit by means of a cylinder foot 7 and a cylinder head S. Cylinder head 8 contains a pressure control valve 9 for admitting compressed air at the proper time through an inlet conduit 10 in foot 7 and passage 6 into the pressure chamber 11 above piston 2. Control valve 9 consists of a piston 9a and a rod 9b which latter when the control valve 9 is operated, projects into the hole 9 in contact with the packing ring 9 and thereby closes the hole. Cylinder head 8 further contains a resilient arresting device 12 for holding striker piston 2 in its retracted position. Cylindrical chamber 5 which communicates through a series of apertures 13 at its lower end with the central cylinder is adapted to receive the air which is expelled from cylinder 1 by piston 2 during the driving stroke thereof. After striker piston 2 has completed its driving stroke and the air pressure has been released from pressure chamber 11, the pressure of this stored-up air returns piston 2 to its retracted position, as shown in FIGURE l. Cylinder foot 7 contains a trigger mechanism consisting of a valve 14 with a pressure chamber 1S which communicates with inlet conduit 10 through an opening 16, and a smaller chamber 1'7 which communicates with control valve 9 through a conduit 18 and is adapted to be sealed off from pressure chamber 15 by a spring-loaded valve piston 19, the valve stem 20 of which has a transverse bore 21 and an axial bore 22 through which the inner chamber 17 of valve 14, and thus also pressure chamber 23 of control valve 9 through conduit 18 may communicate with the outer air when the nailing apparatus is in the position as illustrated in FIGURE l with striker piston 2 in the retracted position. If the nozzle 24 of the apparatus is pressed against the action of a spring 25 upon the object to be nailed, a projection 26 on its upper end will disengage from a projection 27 on the lower arm of a two-armed lever 28 permitting the latter to be pivoted by a trigger 29. The pressure of lever 28 is then transmitted through a sealing member 30 to the free end of valve stem 20, whereby the outer end of bore 22 will be closed so that pressure chamber 23 of control valve 9 will no longer communicate with the outer atmosphere. This pressure upon valve stem 20 will also open valve piston 19 so that the compressed air can flow from inlet conduit 10 through opening 16, valve 14, and conduit 18 to pressure chamber 23 of control valve 9, so that the latter will close, thereby shutting off the air vent 31 and opening the feed valve 32 to admit the air pressure from inlet conduit 10 through the cylindrical passage 6 and feed valve 32 to the pressure chamber 11 above striker piston 2 to drive the latter forwardly, so that the end of striker shaft 33 will hit a nail 34 in the nail-guiding channel 3S in nozzle 24 which extends coaxially to cylinder 1.

The ring 9 is a sealing ring which is resilient so that when the stem 9b projects into the ring 9 the latter will be forced to the side or laterally and thus the ring will slide against the stern 9b. Thus this will permit the stern 9b to be pushed through the bore 9' with the latter thus tightly closed. As soon as the stem 9b projects out through the bore 9' the rod or depending pin of valve 32 will contact and the valve opens.

This nail-guiding channel 35 has a smaller diameter than the striker-guiding channel 36 which preferably forms an integral part of the foot 7, that is, a diameter substantially corresponding to the diameter of the lower reduced end of striker shaft 33 and that of the head of nail 34 which is to be driven into a board, wall, or other object 37. Cylinder foot 7 has a lateral extension 38 which serves as an operating handle of the apparatus. It contains the air inlet conduit 10 which is connected to a suitable source of air pressure, as well as a nail feed channel 39 which terminates into the upper part of the striker guiding channel 36, while its outer end may be connected to a flexible conduit 40 which leads to the nailfeeding mechanism shown in FIGURES 4 and 5. As illustrated in FIGURES 6 and 8, foot 7 of the apparatus also has a recessed portion 41 in which a safety lever 42 is pivotablymounted on a shaft 43 which carries at its outer end a handle 44. When the nailing apparatus is not in operation, handle 44 may be raised, whereby safety lever 42 will enter into the nail feed channel 39 to prevent any nail from entering into the nail-receiving and striker-guiding channel 36 of the apparatus. When handle 44 is depressed, safety lever 42 will be withdrawn from feed channel 39 and will then substantially close recess 41 so that, when the nail-feeding mechanism is then operated at a time when striker piston 2 is withdrawn from channel 36, it may deliver a nail by compressed air through

channels

39 and 36 into the reduced guide channel 35. As an additional safety feature, shaft 43 may be disposed so that, when handle 44 is raised and safety lever 42 engages into nail feed channel 39, shaft 43 locks trigger 29 in the released position, as shown in FIGURE l, while a recess 4S in shaft 43 allows trigger 29 to be actuated when handle 44 is depressed and safety lever 42 is withdrawn from feed channel 39, as illustrated in FIGURES 2 and 3.

In previous nailing apparatus of this type, the feeding mechanism was operated and a newA nail supplied to the apparatus in response to every driving stroke of the striker piston. Before the nailing operation was started, the air pressure which was supplied to the apparatus to drive the striker piston was adjusted to a strength which was sufficient to drive the nails completely home, but would not sink the nail heads too deeply into the material. Consequently, if the nail would encounter a portion of a toughness greater than the average for which the air pressure had been adjusted, for example a knot 46 in a board 37, the striker would not be able to drive the nail completely home by one stroke, as illustrated in FIG- URE 2. Usually, this would induce the operator of the apparatus to actuate the trigger at least once more to retract the striker piston and to exert another impact upon the nail head. However, since each stroke of the piston would also result in an operation of the nail feeding mechanism, this would mean that the nails would accumulate within and seriously jam the flexible feed conduit 40, and might even enter into the strike guiding channel 36 while the previous nail was still partly within the nail guide channel 35.

According to the present invention this may be avoided by providing a valve 47 or similar control device within the foot 7 of the apparatus. This valve may consist of a Valve disk 48 which is movable within a valve chamber 49 and is normally pressed by a spring 50 upon a valve seat 51. Valve chamber 49 is connected through a small channel 52 with the main air-inlet channel 10, while a small `chamber 53 at the other side of valve disk 48 is connected through a channel 54 and a tiexible conduit 55 to a cylinder 56 having a feed-control piston 57 slidably guided therein, as illustrated in FIGURES 4 and 5. Valve disk 43 has a stem 58 which is slightly inclined relative to the axis of cylinder l and the free end of which slightly projects into the lower end of cylinder 1. When striker piston 2 is retracted, this free end of stem Si; will be disposed slightly above the position which the lower side of piston 2 assumes when reaching the forward end of its driving stroke. When this occurs, piston 2 pushes valve stem 58 downwardly and thereby lifts valve disk 48 from its seat 51. The compressed air can then pass from the main inlet channel 10 through channel 52, Valve chambers 49 and 53, channel 54, and conduit 55 to cylinder 56 to drive control piston 57 therein forwardly.

Consequently, if in the operation of the nailing apparatus, a nail 34 is driven by striker 33 on piston 2 into a board 37 or the like, piston 2 will not engage valve stem 58 and lift valve disk 48 from its seat 51 until it reaches almost the end of its driving stroke and until striker 33 has driven nail 34 home almost completely. Thus, if the rst stroke of piston 2 is not sufficient to do this, trigger 29 may be released, thereby permitting valve piston 19 to close and the air in pressure chamber 23 of control valve 9 to escape through the freed end of bore 22, so that valve 9 can then retract under spring pressure and permit feed valve 32 to close and the air pressure from pressure chamber 11 to escape through vent 31. Simultaneously, the air compressed by piston 2 in the lower part of cylinder 1 and also stored up in the cylindrical chamber will drive piston 2 back to its fully retracted position where it will be retained by the arresting device 12. Since during its first driving stroke, piston 2 did not engage valve stem 5S and thus did not open valve 47, no compressed air was delivered to cylinder 56 to operate the feeding mechanism. Trigger 29 may then be pulled again to propel striker 33 forwardly, and

this may be repeated as often as may be necessary to drive nail 34 home completely without danger that during this time even a single nail will be delivered through feed conduit 40 or into the striker guide channel 36 of the apparatus. After piston 2 has thus in one or several driving strokes reached its most forward postion, as

illustrated in FIGURE 3, and has opened valve 47 and thereby actuated the nail-feeding mechanism in the man ner as will be subsequently described, the entire apparatus may be lifted from the board or other object 37 into which the nail was driven. Nozzle 24 will then be extended by spring 25, whereby the projection 26 on the nozzle will engage with projection 27 on lever 28 and return ythe latter as well as trigger 29 to the position shown in FIGURE 1. The pressure in chamber 11 then being released, fthe stored-up air from chamber 5 will return piston 2 to its retracted position. As soon as piston 2 has fully retreated from the striker guide channel 36, a new nail will be blown through feed conduit 40, feed channel 39, and striker guide channel 36 into nail guide channel 35 where it will be arrested by suitable means as subsequently described and held in fthe proper position to be struck squarely by striker 33 when nozzle 24 has been pressed upon the next place to be nailed and trigger 29 has thereupon been pulled.

Channel 54 leading from valve 47 to cylinder 56 of the feeding mechanism may also communicate to some extent with the outer atmosphere through a vent bore 59. The outer portion 60 of vent 59 is enlarged and has inner screw threads into which a setscrew 61 is screwed which has a conical tip 62. The outer enlarged portion 60 of vent 59 communicates with the outer air through a bore 63. When setscrew 61 is screwed into Vbore 60, an annular slot will be formed between the conical tip 62 and the wall of bore 60. By providing setscrew 61 with tine screw threads, it will be possible to adjust the cross-sectional area of this annular slot Very accurately and thus to control the speed at which the compressed air may escape from channel 54 through vent 59 as soon as piston 2 has started its return movement and allowed valve 47 again to close. This, in turn, will gradually relieve the air pressure in cylinder 56, permitting piston 57 to return to its original position so that, when the next nail is to be driven home, piston 57 can again be actuated for its next feeding operation.

The nail feeding mechanism according to the present invention, as illustrated in FIGURES 4 and 5, comprises the mentioned cylinder 56, one end of which is connected to the flexible conduit 55 leading to valve 47, so that when the latter is opened kby striker piston 2, the compressed air will act upon one side of piston 57 and move the same toward the left. At its other side, piston 57 carries a rod 64, the end portion of which is provided with a suitable recess 65 which, when piston 57 is moved fully to the left, is adapted to pick up a nail 34 from the end of feed rails 66 as seen in FIG. 13 when the rod 64 is moved to the left, a nail 34 will be retained in the recess 65 and will be pulled to the right whereby the nail will fall into the hopper 68 by gravity. When striker piston 2 begins its return movement and releases valve 47, and the air pressure in cylinder 56 and conduit 55 decreases by gradually escaping through vent 59, a spring 67 returns piston 57 to its original position. Rod 64 thereby draws nail 34 into a hopper 63 through a slot 69v in the wall thereof, and, as soon as the nail head has disengaged from rail 66, nail 34 will drop by gravity into hopper 68.

Hopper 68 is connected to a cylinder 701 with diametrically opposite transverse passages 71 in its Walls which are coaxial with hopper 68. Cylinder 76` contains a slide valve 72 which, by the action of a return spring 73, is normally held in one end position in engagement with a stop pin 74. In this position, a transverse bore 75 in slide valve 72 coincides with passages 71 in cylinder so that at such time nail conduit 40 will communicate through hopper 68 with the outer atmosphere and will be capable of receiving a nail 34 which is dropped into hopper 68 by the operation of rod 64. In addition to spring 73, cylinder 70 may be provided with a cushion 76 of resilient material which will soften the impact of slide valve 72 upon the end Wall of cylinder 70, and which also has the advantage that it will take over a substantial part of the cushioning action of spring 73. Therefore, spring 73 does not have to be made of any greater strength than necessary to insure the proper return of slide valve 72 against stop pin 74 when the air pressure acting upon the valve is relieved, so that undue knocking of the valve will be avoided and the wear upon the valve will be reduced.

Cylinder 70 is directly connected to nail conduit 40 by a conduit 77. The opening 78 of this conduit in cylinder '70 is disposed in such a position that, on the one hand, when slide valve 72 engages against stop pin 74 and bore 75 coincides with passages 71, this opening 78 will be closed by the slide valve, and that, on the other hand, opening 78 will be uncovered by slide valve 72 and free to admit a blast of compressed air into nail conduit 40 when valve 72 is pushed toward the left against the action of spring 73 and cushion 76 and has almost reached the end of its stroke, and when bore 75 is shifted entirely out of communication with passages 71, and the solid part of the valve has shut off nail conduit 40 entirely from the outer atmosphere.

The side of cylinder 70 containing its pressure chamber 7.9 is connected through a channel 80 with a pressure control valve 81 which consists of a cylinder 82 which is adapted to be connected through a conduit 83 to a source of compressed air and contains a valve disk 84 which normally is pressed by a spring 85 against the Valve seat 86 to maintain this valve in the closed position. Valve disk 84 is secured to a valve stem 87 which is slidably guided within the upper wall of the housing of control valve 81 and projects to the outside thereof.

For opening valve 81 at the proper time so as to admit a blast of compressed air from conduit 83 into pressure chamber 79 to act upon slide valve 72 and, subsequently, to pass through conduit 77 into nail conduit 40, a bell crank 90 is pivotably mounted on a bracket 91 so that its shorter lower arm 92 normally rests upon the upper end of valve stem 87, while its longer arm 93 extends toward feed control cylinder 56 and through an aperture 94 in the wall of this cylinder toward the inside thereof. At its upper end, arm 93 terminates into a detent 95 which has an inclined upper surface. Piston rod 64 has a ilat portion within cylinder 56 on which a pawl 96 with an inclined lower surface is eccentrically pivotable to an extent limited by a stop pin 97.

When the striker piston 2. of the nailing apparatus opens valve 47 near the end of its driving stroke, a blast of compressed air is passed through conduit 55 into cylinder 56 and drives piston 57 against the action of spring 67 toward the left, whereby at the end of this stroke, groove 65 in rod -64 picks up a nail 34 from the end of rails 66. During this forward movement of rod 64 the lower inclined surface of pawl 96 slides loosely over the upper inclined surface of detent 95 on arm 92 of bell crank 90. As soon as striker piston 2 of the nailing apparatus retracts and valve 47 is closed so that the pressure in cylinder 56 will be gradually released through vent 59, piston 57 and rod 64 thereon will retract under the action of spring 67. Since near the end of the forward movement of rod 64, pawl 96, after passing over detent 95, has dropped by gravity back to its normal position in engagement with stop pin 97, it will, during the following return movement of rod 64 engage with detent 95 and take the latter along and thereby pivot bell crank 90 in a clockwise direction. The short arm 91 of bell crank 90 will then press upon valve stem 87 and will thereby lift valve disk 84 from its seat 86 so that a blast of compressed air can pass through valve 81 into pressure chamber 79 where it will act upon the face of slide valve 72., pressing the same toward the left and thereby first shutting oi nail conduit 40 from the atmosphere and then passing a blast of compressed air through conduit 77 into the nail conduit, whereby the nail which has previously been dropped into the conduit will be 10 conveyed to the nailing apparatus and into guide channel 35 thereof.

Since at the end of the forward stroke of piston 57, the grooved part 65 of piston rod 64 has picked up a new nail 34 from feed rails 66, such nail will, during the return stroke of piston 57, be drawn into hopper 68 and be dropped therein. However, the different parts of the nailfeed control mechanism are dimensioned and adjusted relative to each other so that the rst jaction occurring during the return stroke of piston 57 will be the pivotal movement of bell crank by the engagement of detent by pawl 96 so that the valve 81 will be opened and slide Valve '72 be moved toward the left to shut off the passages '71 and to deliver a short blast of compressed air through opening 78 and conduit 77 into nail conduit 40 to convey the nail which Was previously deposited therein to the nailing apparatus. During the further course of the return stroke of piston 57, that is, within a period of fractions of a second, pawl 96 will slip over the edge of detent 95 and thus disengage from bell crank 90, permitting valve 81 to close under the action of its spring 35, whereby bell crank 90 will also be pivoted back to its original position. The compressed air remaining in chamber 'I9 ywill then be released through conduit 77, nail conduit 40, and recess 41 in the handle portion of the nailing apparatus, permitting Vslide valve 72 to return under the action of spring 73 toward stop pin 74 and thereby shutting off the opening 78 of conduit 77 and bringing bore 75 into coincidence with passages 7l. During this interval, the new nail 34 has been drawn on rod 64 suiciently into hopper 68 to disengage of its own accord therefrom and to drop into and through the hopper and through the new coinciding

passages

71 and 75 into nail conduit 40 where it will lie until striker piston 2 again opens valve 47 and will start the new cycle of events as above described. As previously stated, the speed at which the feed control piston 57 retracts, as well as the length of time during which the pressure control valve 81 will remain open, and thus also the time during which the compressed air will pass into nail conduit 40 and act upon the nail therein, may be very accurately adjusted by setscrew 61 in vent 59 of the nailing apparatus.

A further control of the operation of the ifeeding mechanism may be attained according to the invention by an adjustment of the velocity of flow of the compressed air supplied into the nail conduit 40, and thus of the speed at which the nails are blown through conduit 40 and into the nailing apparatus. For this purpose, a setscrew 98 may be disposed in the wall of channel 80 which connects valve 81 with pressure chamber 79. By adjusting this setscrew, it is possible to vary the crosssectional area of the flow of compressed air passing through channel 8@ into pressure chamber 79, and through the latter `and conduit 77 into nail conduit 40. Thus, the velocity of the compressed air may be adjusted in accordance with the particular type and shape of the nails used. Such adjustability of the ow of compressed air into pressure chamber 79 has the further advantage that it is thereby also possible to regulate the movements of slide valve 72.

Since the nails are thus `delivered into the striker guide channel 36 of the apparatus and then into the nail guide channel 35 at a `considerable velocity, it will be necessary to provide suitable means which are capable of arresting each nail as it is being propelled into the guide channel 35 so that it will not be driven into the board or other object to be nailed by the velocity of the Ifeeding movement since there would then be very little or no control of the position of the nail within guide channel 35, and the striker 33 might then not hit the nail head squarely but at a slight angle with the result that the nail would be bent. According to the present invention, this nail arresting and holding device consists of a chuck 99, the body part 100 of which is mounted on or integral 11 with nozzle 24 and'has a plurality ofrradial guide slots therein, in which jaws 101 are mounted so as to be slidable in radial directions. The central outer part of each jaw 101 is provided with a wide recess in which a resilient layer 102 is embedded. The flanges 1133 forming the recess are outwardly extended to retain a spring ring 104 of a suitable material, preferably made of a special rubber composition known under the trade name Vulkollan This spring ring 104 is fitted tightly over the peripheral surfaces of the body part 15?@ and over the resilient layers 192 on jaws 1M so to press the latter radially toward the central axis of guide channel 35. The lower parts 105 of the inner gripping surfaces of jaws 101 preferably extend parallel to each other and at equal distances from the central axis of guide channel 35 so that, when a nail 34 is inserted into the chuck, jaws 101 will grip the shank of the nail and hold the same exactly coaxially with striker 33 so that the latter will hit the nail head squarely. The upper parts 1Go of the inner gripping surfaces flare outwardly, and are preferably of a substantially parabolical shape, so that the nail head when driven by striker 33, will gradually and uniformly separate the jaws, pivoting the latter at first slightly relative to each other about their lower inner edges soV that the gripping engagement of the nail shank by jaws lul will continue until the nail head and the striker 33 have entered between the lower parts 105 of jaws 101. Such gradually flaring and preferably parabolical shape of the upper parts of jaws 101 has the advantage that a sudden impact of the nail head upon the jaws will be avoided since such 4force will be converted into a gradual sliding movement. Consequently, the ylife of the chuck will be considerably extended.

Instead of operating feed control piston 57 by means of compressed air whenever striker piston 2 reaches the forward end of its driving stroke, such operation may also'be carried out by other means. Thus, for example, as illustrated in FIGURES l and ll, the air-pressure control valve 47 in the foot 7 of the nailing apparatus according to FIGURES l to 3 may be replaced by a pair of electrical contacts 197 which may be closed by being connected by the lower surface of piston 2 near the end of its driving stroke. The two contacts may also be disposed above each other, and may either be separated from each other or connected to each other by the engagement of one of them by piston 2, depending upon Whether a closed or open-circuit arrangement is used. As illustrated in FIGURE l2, the control cylinder 55 and control piston 57 may then be replaced by an electromagnet 163 which is mounted in a stationary position and connected by a cable 109 to a source of electric current and contacts 107, respectively. Rod 11%, taking the place of rod 6ftof the embodiment shown in FIG-

URES

4 and 5 is slidably mounted and carries an armature 111 which, when striker piston 2 engages the electrical Contact or contacts 107 so that electromagnet 108 will be energized, will be attracted by the latter against the action of a spring 112. It Will thus be seen that, except for the fact that the propelling force for moving rod 109 forwardly is electric rather than pneumatic, the function of the feed control mechanism remains the same as described with reference to FIGURES 4 and 5.

Although our invention has been illustrated and described with reference to the preferred embodiments thereof, we wish to have it understood that it is in no way limited to the details of such embodiments, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed our invention, what we claim is:

l. In combination with an apparatus operated by compressed air for driving nails or the like into walls or other objects and having a cylinder, means on said cylinder for receiving and holding a nail or the like, a striker piston having a striker shaft thereon slidable longitudinally within said cylinder, mechanical means for arresting said piston in a retracted position within said cylinder, means for directing compressed air on one side of said piston for propelling said piston forwardly from said retracted position so as to carry out a driving stroke and exert a single impact upon said nail, feeding means for supplying nails to Vsaid receiving means, and control means adapted to be acted upon by said piston at a certain point of its driving stroke for controlling the operation of said feeding means in accordance with the length of said driving stroke.

2. The combination as defined in claim l, wherein said feeding means are at least partly operated by cornpressed air, means for controlling the supply of compressed air to said feeding means, said rst control means being at least partly disposed within said cylinder and adapted to be engaged by said piston near the end of its full driving stroke so as to control the operation of said second control means to supply compressed air to said feeding means and thereby to deliver a nail to said receiving means only if said piston has substantially completed its full driving stroke.

3. The combination as defined in claim l, wherein said means for directing compressed air on one side of said piston includes an actuating trigger adapted to be manually engaged for propelling said piston forwardly from said retracted position, storage means for air compressed by the forward movement of said piston for re'- turning said piston at the end of each driving stroke to said retracted position, said control means being disposed in a position so as to be acted upon by said piston near the end of its full driving stroke, so that said feeding means will be operated to supply a nail to said receiving means only if said piston has substantially completed its full driving stroke, even though said actuating trigger has to be repeatedly engaged and said piston has to carry out a plurality of partial driving and return strokes until it can complete said full driving stroke.

4. The combination as defined in claim l, wherein said control means comprise a valve connected to kand interposed between a source of compressed air and said feeding means, said valve having a valve stem normally partly extending into said cylinder near the forward end thereof and adapted to be engaged and depressed by said piston to actuate said valve to deliver a blast of compressed air to said feeding means to operate the same only if said piston has substantially completed its full stroke.

5. The combination as dened in claim l, wherein said nail receiving means on said cylinder comprise a nozzle having a channel therein coaxial with said cylinder for receiving and guiding said striker shaft during the driving and retracting movements thereof, a nail feed channel extending at an angle to said nozzle channel and gradually leading into the same, said nail feed channel being adapted to be connected to said feeding means, said feed channel having a slot therein, a safety lever pivotably mounted for movement from the outside of said feed channel into the latter for preventing the passage of a nail into saidnozzle channel when said apparatus is not to be used, and a handle connected to said lever and accessible from the outside for operating said lever.

6. The combination as defined in claim l, wherein said means for directing compressed air on one side of said piston includes an actuating trigger adapted to be manually engaged for propelling said piston forwardly from said retracted position, storage means for air compressed by the forward movement of said piston for returning said piston at the end of each stroke to said retracted position, said nail receiving means on said cylinder comprising a nozzle, having a channel therein coaxial with said cylinder for receiving and guiding said striker shaft during the driving and retracting movements thereof, a handle portion mounted on the forward end of said cylinder, a nail feed channel within said handle portion extending at an angle to said nozzle channel and gradually leading into the same, said nail feed channel being adapted to be connected to said feeding means, said feed channel having a slot therein, a shaft rotatably mounted Within said handle portion, a safety lever secured to said shaft and adapted to be pivoted from the outside of said feed channel into the latter for preventing the passage of a nail into said nozzle channel when said apparatus is not to be used, and a handle on said shaft and Iaccessible from the outside for operating said lever, said shaft having a portion thereon adapted to engage with said actuating trigger and lock the same against any movement thereof when said vlever is pivoted into said feed channel.

7. The combination as defined in claim 1, further comprising storage means for air compressed by the forward movement of said piston for returning said striker piston at the end of each driving stroke to said retracted position, said control storage means for air compressed by the forward movement of said piston comprising a pair of electric contacts, at least one of said contacts being adapted to be engaged by said striker piston near the end of its full driving stroke, said feeding means comprising nail supplying means, a slidably mounted shaft, electro-magnetic means connected to said contacts and to a source of electric current for moving said shaft from a first position to a second position, a nail feeding conduit connected to said receiving means on said cylinder, and means on said shaft for picking up a nail from said supplying means during the movement of said shaft by said electromagnet when said striker piston has engaged at least one of said contacts and for then inserting said nail into said nail-feeding conduit during the return movement of said shaft after said striker piston has disengaged from said contacts to return to said retracted position.

8. The combination as defined in claim 7, further comprising a valve body having coaxial transverse passages extending through its walls, one of said passages connected to the end of said nail conduit, and the other passage adapted to receive said nail from said pickup means, a conduit connecting said valve body with said nail conduit and having an end opening in said valve body laterally spaced from said passages, a slide mem' ber within said valve body adapted to reciprocate between a first and second position, and in the first position adapted to close said opening into said connecting conduit and to free said coaxial passages to permit said nail to fall through said passages into said nail conduit, and in the second position adapted to free said opening into said connecting conduit and to close said passages and also to seal said nail conduit toward the atmosphere, a control valve connected to a source of compressed air for admitting said air into said valve body for moving said slide member from said first position to said second position after said nail has been dropped into said nail conduit, and, when said slide member is in said second position, for passing said compressed air through said connecting conduit into said nail conduit and upon said dropped nail therein to convey the same to` said receiving v means on said cylinder, and means connected to s'aid control valve and adapted to be connected to and to be driven by said shaft carrying said pickup means at least during a part of the movement thereof for opening said control valve to permit the compressed air to act upon said slide member and pass into said nail conduit after said nail has been dropped into said nail conduit, and to be released by said shaft for then shutting off said cornpressed air to allow said slide member to return to said first position after said nail has been conveyed to said receiving means, and resilient means for returning said slide member to said first position.

9. The combination as defined in claim l, wherein said control means comprise a valve connected to and nterposed between a source of compressed air and said feeding means, and disposed near the forward end of said cylinder and adapted to be engaged and actuated by said piston to deliver a blast of compressed air to said feeding means to operate the same only if said piston has substantially completed its full stroke.

10. The combination as defined in claim 9, further comprising storage means for air compressed by the forward movement of said piston for returning said striker piston at the end of each driving stroke to said retracted position, a conduit connecting said valve with said feeding means, and adjustable means for releasing the air pressure from said conduit after said piston has conipleted a full driving stroke and has disengaged from said valve to return to said retracted position.

l1. The combination as defined in claim 9, further comprising storage means for air compresed -by the forward movement of said piston for returning said striker piston at the end of each driving stroke to said retracted position, said feeding means comprising a cylinder, a conduit connecting said cylinder to said valve, a pisto-n slidable within said cylinder, nail-supplying means, means connected to said last piston for picking up a nail from said supplying means when said last piston is driven by said blast of compressed air, a nail-feeding conduit connected to said receiving means on said cylinder, and resilient means for returning said last piston after said striker piston has completed a full driving stroke and has disengaged from said valve to return to said retracted position and by such disengagement has caused actuation of said valve to discontinue said blast of compressed air, said pickup means being adapted to insert said nail into said nail-feeding conduit during `a part of the movement of said last piston.

l2. The combination as defined in claim ll, further comprising a valve body having coaxial transverse passages extending through its walls, one of said passages connected to the end of said nail conduit, and the other passage adapted to receive said nail from said pickup means, a conduit connecting said valve body with said nail conduit and having an end opening in said valve body laterally spaced from said passages, a slide member within said valve body adapted to reciprocate between a first and second position and in the first position adapted to close said opening into said connecting conduit and to free said coaxial passages to permit said nail to fall through said passages into said nail conduit, and in the second position adapted to free said opening into said connecting conduit and to close said passages and also to seal said nail conduit toward the atmosphere, control means for controlling the conduit between a source of compressed air and said valve body for moving said slide member from said rst position to said second position after said nail has been dropped into said nail conduit, and, when said slide is in said second position, for passing said compressed air through said connecting conduit into said nail conduit and upon said dropped nail therein toI convey the same to said receiving means on said cylinder, and means for operating said control means for controlling the conduit between a source of compressed air and said valve body to shut off said compressed air and allow said slide member to return to s'aid first position after said nail has been conveyed to said receiving means, and resilient means for returning said slide member to said first position.

13. The combination as' defined in claim l2, wherein said control means for admitting said compressed air into said valve body and for shutting it off therefrom comprise `a control valve interposed between a source of compressed air and said valve body, and means connected to said control valve and adapted to be connected to and to be driven by said pickup means at least during a part of the movement thereof for opening and closing said control valve.

14. A nail feeding mechanism for a nailing apparatus 15 comprising a nail conduit having one end adapted to be connected to said apparatus, nail supplying means, means movable from one point in one direction by a force derived yfrom an operation of said nailing machine for picking up a nail from said supplying means, resilient means for returning said pickup means to said point when said force ceases, said pickup means being adapted during a part of its movement to release and drop said nail, a valve body having upper and lower coaxial passages extending through its walls, one of said passages adapted to receive said dropped nail, the lower passage being connected to the other end of said nail conduit, a conduit connecting said valve body with said nail conduit and having an end opening in said valve body spacedV from said coaxial passages, a slide member adapted to reciprocate within said valve body between a first and second position, and in the rst postition adapted to close said opening into said connecting vconduit and to free said coaxial passages so that said dropped nail can fall through said passages into said nail conduit, and in the second position adapted to free said opening into said connecting conduit and to close said passages and also to seal said nail conduit toward the atmosphere, control means for admitting compressed air into said valve body for moving said slide member from said first position to said second position after said nail has been dropped into said nail conduit, and, when said slide is in said second position, for passing said compressed air through said connecting conduit into said nail conduit and upon said dropped nail therein to convey the same toward the end which is adapted to be connected to said nailing apparatus, means for operating said control means to shut off said compressed air and to allow said slide member to return to said first position after said nail has arrived at said end of said nail conduit, and resilient means for returning said slide member to said iirst position.

15. A nail feeding mechanism as defined in claim 14, wherein said slide member has a transverse passage adapted in said first position to coincide with said coaxial passages in said valve body, and adapted in said second position to be shifted laterally from said coaxial passages to close the end of said nail conduit, said resilient means for returning said slide member to said first position comprising a spring acting upon said slide member, and a resilient cushion adapted to take up the yimpact of said slide member when moving to said second position.

16. A nail Afeeding mechanism as defined in claim 14, further comprising a nail receiving hopper connected to said upper passage, said pickup means comprising a cylinder, a piston movable in one direction Within said cylinder until the force of a short blast of compressed air sup plied by said nailing apparatus, a piston rod on said piston extending from said cylinder and having a recess near its free end adapted to pick up said nail from said supplying means and, at the termination of said blast and during the following return of said piston under the action of said resilient means adapted to release said nail and drop the same into said hopper.

17. A nail feeding mechanism as defined in claim 14,

wherein said control means for admitting compressed air into said valve body and for shutting it off therefrom comprise a control valve interposed between a source of compressed air and said valve body, and means connected to said control valve and adapted to be connected to and to be driven by said pickup means at least during a part of the movement thereof for opening and closing said control valve.

18. A nail feeding mechanism as defined in claim 17, further comprising a passage connecting said control valve with said valve body, and means for adjusting the cross-sectional area of said passage for regulating the velocity and pressure of said compressed air passing into said valve body when said control valve is open.

19. A .nail feeding mechanism as defined in claim 17, wherein said last connecting means comprise a bell crank having one arm adapted to act upon said control valve, a pawl pivotably mounted on said pickup means adapted to slide freely over the free end of the other arm of said bell crank when moving with said pickup means in one direction, and adapted to engage with said free end of said other arm at least during a part of the movement thereof with said pickup means in the other direction, and then to press said rst arm upon said control valve to open the same to admit a blast of compressed air into said valve body and upon said slide member to close said nail conduit toward the atmosphere and to pass said blast into said nail conduit, said pawl being adapted to disengage from said free end of said other arm before completing the movement in said other direction for then allowing said control valve to close under spring pressure.

20. A nail feeding mechanism as defined in claim 19, further comprising a nail receiving hopper connected to said upper passage, said pickup means comprising a shaft having a groove near its free end adapted to pick up a nail from said supplying means, means for slidably mounting said shaft, electromagnetic means adapted to be connected to a source of electric current and to electric contacts in said nailing apparatus, at least one of which is adapted to be engaged by a striker piston of said apparatus at a certain point of its stroke, said electromagnetic means being associated with said shaft for moving the same from a rst position to a second position for picking up said nail when said striker piston has engaged at least one of said contacts and for then moving said nail into said hopper and dropping it through said hopper and said passages into said nail conduit during the return movement of said shaft to said first position after said striker piston has disengaged from said contacts, and resilient means for returning said shaft to said lirst position.

References Cited in the tile of this patent UNITED STATES PATENTS 536,427 Hayes Mar. 26, 1895 2,416,312 -Harkeem Feb. 25, 1947 2,732,554 Knott e Ian. 31, 1956