US3490673A

US3490673A - Fastener driving tool

Info

Publication number: US3490673A
Application number: US592771A
Authority: US
Inventors: Karl Diehl
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-11-09
Filing date: 1966-11-08
Publication date: 1970-01-20
Anticipated expiration: 1987-01-20
Also published as: FR1498215A; DE1478837A1; DE1478838B2; GB1169033A; DE1478839B2; DE1478837B2; CH453249A; DE1478838A1; DE1478839A1; US3465942A

Description

Jan. 20, 1970 K. DIEHL FASTENER DRIVING TOOL Filed Nov. 8. 1966 2 Sheets-Sheet l www m w MNA www

U.S. Cl. 227- 11 Claims ABSTRACT 0F THE DISCLOSURE An explosion-actuated fastener driving tool in which detent means cooperate with the driving piston of the tool to yieldably hold the piston in a retracted position and in which the detent means comprise retainer means radially movable supported in the barrel in which the piston is slidably guided and biasing means in form of a split ring for urging the retainer means against the piston.

The present invention relates to improvements in explosion-actuated tools or pistols for driving studs, bolts, nails or analogous fasteners into masonry walls, wooden boards and similar workpieces.

Presently known fastener driving tools normally cornprise a barrel which accommodates a reciprocable piston and has an open forward end adapted to receive a fastener. The piston is movable to and from a retracted position and leaves such retracted position in response to firing of an explosive cartridge. Detent means must be provided to yieldably hold the piston in retracted position, and it was found that conventional detent means are not entirely satisfactory. This is due to the fact that the space in a compact, lightweight fastener driving tool 1s limited and that the provision of detent means should not unduly weaken the piston and/or the barrel and should not contribute excessively to the bulk, weight and initial cost of the implement. If the detent means is to act upon the stem of the piston, it must extend considerably into the highly stressed front portion of the barrel. On the other hand, and if the detent means is provided on the so-called boss at the trailing end of the piston, its parts are exposed to hot products of combustion in the range of several hundred degrees C. and to pressures often exceeding 1,000 atmospheres. This excludes the utilization of parts which consist of rubber and also all readily availableand relatively cheap synthetic plastic substances. Furthermore, and if the detent means is installed in or on the stem of the piston, the latter is weakened and might not be able to withstand the aforementioned temperatures or pressures. Overdimensioning of the piston is not possible without undue increase in weight, maneuverabilily, bulk and cost of the tool.

As a rule, conventional fastener driving tools comprise detent means which are installed on the piston proper and act outwardly, i.e., in a direction toward the barrel of the tool. If is known to utilize rings which are recessed into the piston and slide along the internal surface of the barrel. Such rings weaken the piston, i.e., that element of the tool which is subjected to highest stresses, so that the life expectancy of the piston is very short Accordingly, it is an important Object of the present invention to provide a fastener driving tool or piston with novel and improved detent means for holding the piston in retracted position prior to firing of an explosive charge and to construct and assemble the detent means in such a way that its provision does not weaken or otherwise unfavorably affect the piston.

Another object of the invention is to provide novel detent means which can be readily incorporated in pres- 3,490,673 Patented Jan. 20, 1970 ently known fastener driving tools without necessitating extensive alterations in the design of such tools.

A further object of the instant invention is to provide very simple, long-lasting, compact and inexpensive detent means and to mount the detent means outside of the high-pressure and high-temperature zones in a fastener driving tool.

A concomitant object of the invention is to provide detent means whose components may be readily reached, inspected or replaced in response to mere partial dismantling of the fastener driving tool.

Briefly stated, one feature of my invention resides in the provision of a fastener driving tool which comprises a housing having a front end arranged to accommodate a stud, pin, nail or an analogous fastener and a rear end adjacent to a cartridge chamber or firing chamber, an elongated barrel received in the housing, a piston reciprocably received in the barrel and movable to and from a retracted position spaced from the fastener in the front end of the housing, and detent means for yieldably holding the piston in retracted position, The detent means comprises retainer means radially movably supported by the barrel and biasing means for urging the retainer means against the piston. Such retainer means may comprise one or more preferably spherical members reciprocable in radial aperture or apertures of the barrel and an annular member of springy material arranged to urge the retainer or retainers into frictional engagement with the peripheral surface of the piston. The annular member may be constituted by a split ring of spring steel or the like, and the retainer means may extend into the slot of such split ring to widen the slot in response to radially outward movement under the action of the piston when the latter leaves its retracted position. The peripheral surface of a portion of the piston may be congurated in such a way that the piston automatically shifts the retainer means radially outwardly whereby the thus deformed annular member bears against the adjoining portion of the housing and is propped or Supported against excessive radial expansion.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved fastener driving tool itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawings, in which:

FIG. 1 is an axial section through a fastener driving tool which is provided with a detent means embodying one rform of the present invention, the tool being shown in idle position;

FIG. -2 is a similar axial section through the barrel of the fastener driving tool which is shown in cocked position ready to drive a fastener pin into a hard workp1ece;

FIG. 3 shows the structure of FIG. 2 ready to drive a fastener pin into a relatively soft workpiece;

FIG. 4 is an enlarged fragmentary axial section through the housing of a second fastener driving tool which is provided with modified detent means; and

FIG. 5 is a transverse section as seen in the direction of arrows from the line V*V of FIG. 4.

Referring to the drawings in detail, and first to FIGS. 1 to 3, there is shown a fastener driving tool or pistol which comprises a composite housing including a tubular front portion 10 and a tubular rear portion 11. The front portion 10 is reciprocable, within limits, with reference to the rear portion 11 and its rear end is -telescoped into the front end of the rear portion. The volume of an annular compartment 12 in the front end of the rear portion 11 will increase or decrease, depending on the axial position of the front portion 10. This compartment 12 is constituted by a counterbore drilled into the front end of the rear portion 11. The means for guiding the front portion 1() during its axial movement comprises a split ring 15 extending into a circumferential groove 13 of the front portion 10 and into an elongated annular groove 14 machined into the internal surface of the rear portion 11. The axial length of the groove 14 exceeds the axial length of the split ring 15 so that the front portion can be shifted by a distance corresponding to the axial length of the unfilled portion of the groove 14. The ring simultaneously serves as a means for coupling the portions 10, 11 to each other. The axial length of the circumferential groove 13 equals or approximates that of the ring 15. It is clear that the groove 13 will be longer if the groove 14 receives the ring 15 without any or with minimal freedom of axial movement.

In order to permit separation of tubular portions 10 and 11, the depth of the groove 13 is suicient to accornmodate the entire split ring 15. To this end, the rear portion 11 is provided with one or more openings (not shown) which communicate with the groove 14 and enable the operator to force the ring 15 into the groove 13 by resorting to a rudimentary tool, whereupon the rear end of the front portion 10 is readily withdrawable from the compartment 12.

The firing mechanism is denoted by the numeral 26. The details of this firing mechanism are known from the art of conventional fastener driving tools and need not be described here. It is to be noted that other types of firing mechanisms can be employed in the tool of FIGS. 1 to 3 without departing from the spirit of the present invention. The front end of the casing 26a of the flring mechanism 26 is adjacent to the rear end of the tubular portion 11, and more particularly to a ring 16 which is affixed to and extends rearwardly from the tubular portion 11. In the illustrated embodiment, the ring 16 constitutes a further or rearmost tubular portion of the housing and is detachably coupled to the rear portion 11 by threads 17. Such detachability of the ring 16 is desirable in order to afford access to component parts which are installed in the interior of the barrel. In fully assembled position, the front end face of the ring 16 bears against an external annular shoulder of the rear portion 11.

The housing 10, 11, 16 accommodates a piston 18 which is reciprocable in an elongated cylindrical barrel 19, a composite resilient element 20, a cylindrical piston guide 36, and detent means 28 for the piston 18. The major part of the sleeve 19 is accommodated in the rear portion 11 and has a cylindrical bore 21 for the piston 18. The front end portion of the barrel 19 has radially extending ports 22 and its rear end portion extends into and rearwardly beyond the ring 16. The rear end of the bore 21 communicates with a forwardly flaring conical passage 23 located in front of a short cylindrical throat 24, the latter being provided in front of a cylindrical cartridge chamber or firing chamber 25. The throat 24 constitutes a combustion chamber.

The rear end portion of the barrel 19 which defines the passage 23, throat 24 and cartridge chamber 25 is provided with an external ange 27 which is tted into the ring 16. The flange 27 constitutes one element of means for limiting axial movements of the sleeve 19 and its end faces respectively cooperate With internal shoulder of the ring 16 to determine the rear end position and with the rear end face of the rear portion 11 to determine the front end position of the barrel. FIG. 1 shows the barrel 19 in its front end position in which the flange 27 abuts against the rear end face of the tubular portion 11. In FIGS. 2 and 3, the barrel 19 is shown in its rear end position in which the ange 27 abuts against the internal shoulder of the ring 16. Rearwardly of the ange 27, the external diameter of the barrel 19 de- 4 creases and such decrease is in part stepwise and in part gradual. Portions of the barrel 19 are slidably guided in the rear portion 11 and ring 16. The rear portion 11 is provided ywith one or more internal recesses 38 which surround an intermediate portion of the barrel 19.

The piston 18 comprises an elongated forward portion or stem 33 and a larger-diameter rearward portion or boss 29 which is adjacent to the passage 23. This boss 29 is slidably guided in the bore 21 of the sleeve 19. The stem 33 is slidably guided in parts lwhich are installed in the front portion 10. The detent ymeans 28 is installed in the sleeve 19 forwardly of the flange 27 and cooperates with the boss 29. The exact construction of detent means 28 will be described hereinafter.

The aforementioned resilient element 20 is installed in the rear region of the front portion 10. This resilient element 20 comprises a substantially cup-shaped member 39 whose bottom `wall is provided at its rear end, namely, at that end which is nearer to the firing mechanism 26. The bottom wall has an opening 40 whose diameter exceeds slightly the diameter of the boss 29 so that the latter can enter the bottom wall when the piston 18 is caused to perform a working stroke. In the region where the bottom wall meets the annular side wall of the cupshaped member 39, the latter comprises apertures or ducts 41 which communicate with the compartment 12.

The cup-shaped member 39 accommodates a short cylinder 42 of substantially U-shaped cross-sectional outline. The bottom wall of the cylinder 42 is adjacent to the bottom wall of the mem-ber 39 and has an opening 45 which receives, without clearance, the stem 33 of the piston 18. Thus, the bottom wall of the cylinder 42 serves as a means for guiding the stem 33 -when the piston reciprocates in the barrel 19. The external surface of the cylinder 42 tapers rearwardly toward the iiring mechanism 26 so that the cylinder 42 and the cup-shaped member 39 define between themselves an annular gap 54 of wedge-like cross-sectional outline. This enables the cylinder 42 to expand radially in response to the engagement of its bottom wall by the boss 29 of the piston 18. As clearly shown in FIG. 1, the rear surface of the bottom wall of the cylinder 42 is inclined forwardly toward the axis of the housing as indicated at 46.

The cylinder 42 is installed immediately behind an annular shock absorber or cushion 43 which consists of rubber or other highly elastic material. The cushion 43 is separated from the stem 33 by a cylindrical liner 44 whose rear end vface is normally separated from the bottom wall of the cylinder 42 by an annular clearance 52. This cushion 43 is installed in the annular wall of the cup-shaped member 39 but is normally separated therefrom by a narrow annular clearance 53. 'The latter will disappear in response to axial compression and resulting radial expansion of the cushion 43 when the boss 29 of the piston 18 strikes against the inclined rear end face 46 of the cylinder 42. The cushion 43 abuts against the front end face of the cylinder 42 and against the rear end face of the cylindrical guide 36 for the stem 33, the guide 36 having a bore 50 which can receive the stern 33 and is coaxial with the bore of the liner 44. The front end face of the cushion -43 also abuts against a circumferential shoulder of the liner 44. Such shoulder is formed at the point where the smaller-diameter rear portion of the liner 44 meets its larger-diameter front portion. The front portion of the liner 44 is received in a counterbore 47 of the guide 36. A washer 48 of rubber or other suitable elastomeric material is installed between an external shoulder of the guide 36 and an internal shoulder of the front portion 10.

As stated before, FIG. 1 shows the fastener driving tool in idle position in which the ange 27 of the barrel 19 abuts against the rear end face of the rear portion 11. FIG. 2 illustrates the tool in cocked position with a short fastener pin 49 inserted into the front end of the front portion 10. The shaft of the fastener pin 49 carries a collar 51 which abuts against the front end face of the guide 36. The larger-diameter rear portion of the pin 49 is received with little or no clearance in the front part of the bore 50. The front end face of the front portion has a concentric undercut recess 56 which receives a ring 55 consisting of highly heat-resistant elastomeric material. The tip of the pin 49 abuts against a relatively hard workpiece W, e.g., a masonry wall made of concrete or the like. This workpiece does not yield to manually applied pressure so that, when the operator exerts pressure against the housing 10, 11, 16, the guide 36 yields and moves rearwardly by pushing the cupshaped member 39 and cushion 43 toward the liring mechanism. In FIG. 3, the front end face of the front portion 10 is pressed against a relatively soft workpiece W', e.g., a board made of soft wood, whereby the tip of the fastener pin 49 penetrates into the workpiece W I and the rearward axial displacement of the guide 36 is shorter than in FIG. 2. In other words, the exact axial position of the fastener pin 49 prior to tiring of a cartridge in the chamber 25 depends on the hardness of the workpiece into which the pin is to be driven in response to actuation of the firing mechanism 26. Irrespective of the starting position of the fastener pin 49, the tool of FIG. 2 or 3 is ready for firing when the barrel 19 is shifted rearwardly through a predetermined minimal distance and the piston 18 assumes its retracted position in which the stem 33 is spaced from the fastener pin 49.

The detent means 28 of FIGS. l to 3 is constructed and installed for the purpose of yieldably holding or retaining the piston 18 in the retracted position shown in FIG. 2 or 3, namely, in a position in which the front end of the stem 33 is spaced from the fastener pin 49. This detent means comprises a spherical retainer 31 and an elastically deformable annular biasing member here shown as a split elastic ring 30. The retainer 31 is reciprocable in a radial aperture 32 of the barrel 19 and this aperture is dimensioned in such a way that a portion of the retainer can extend into the bore 21 to engage the peripheral surface of the boss 29. Another portion of the retainer 31 extends radially outwardly beyond the aperture 32 and is biased by the ring 30 which latter tends to urge the retainer against the peripheral surface of the boss. Such bias suffices to yieldably hold the piston 18 in retracted position so that the stem 33 is spaced from the fastener pin 49.

The rear porton 11 is provided with an internal annular groove 37 (see FIG. 2 or 3) which receives `the ring 30 when the barrel 19 is held in its front end position shown in FIG. 1. The rear portion of the barrel formed with a peripheral groove 35 which can receive at least a portion of the ring 30 so that the latter is thereby held against axial displacement with reference to the barrel.

It will be seen that the provision of the detent means 28 does not in any way weaken the piston 18 and that the major part of this detent means is loca-ted outside of the path of hot combustion products and is not subjected to excessive pressures. The holding action of the spherical retainer 31 is very reliable but this retainer will immediately release vthe boss 29 when a cartridge in the chamber 25 is fired in response to actuation of the firing mechanism 26. The piston 18 is then propelled forwardly and its stem 33 drives the fastener pin 49l into the workpiece W or W.

The manner in which the piston 18 can be moved back to retracted position and in which a cartridge can be introduced into the chamber 25 is known from the art and need not be described here.

Referring now to FIGS. 4 and 5, there is shown a moditied detent means 28' which may be used as a substitute for the detent means 28 of FIGS. l to 3. This detent means 28 again comprises a spherical retainer 31 and a modified elastic biasing ring 30. The ring 30 is slotted (i.e., it is constituted by a split ring), the slot being shown at 34 and receiving a portion of the retainer 31. The barrel 19 has a peripheral groove 35 which receives a portion of the ring 30' so that the latter is compelled to share all axial movements of the barrel. The piston 18 of the tool shown in FIGS. 4 and 5 has a frustoconical rearward portion or boss 29' which tapers forwardly toward the stem 33. This leaves an annular gap 57 of wedge-like cross-sectional outline whose width increases forwardly (see FIG. 4). The bias of the ring 30' is sufficient to urge the inner portion of the retainer 31 against the conical peripheral surface of the boss 29 whereby the piston 18 is held in retracted position. When a cartridge which has been inserted into the chamber 25 is red in response to actuation of the tiring mechanism (not shown in FIGS. 4 and 5), the pressure of gases in the throat 24 overcomes the bias of the ring 30 whereby the conical boss 29 pushes the retainer 31 radially outwardly and the piston 18 is propelled into engagement with the fastener. The bias of the ring 30 need not be strong, as long as it suices to retain the piston 18' in retracted position. The force exerted by combustion products upon the rear end face of the boss 29 exceeds many times the bias of the ring 30. Such combustion products will cause the retainer 31 to expand the ring 30 whereby at least a portion of the external surface of the ring comes in actual abutment with and is supported or propped lby the internal surface of the ring 16. The same holds true for the

rings

16, 30 of the embodiment shown in FIGS. 1 to 3. The component parts of the detent means 28 or 28 preferably consist of metallic material.

An important advantage of the detent means 28 or 28 is seen to reside in that the retainer 31 and/or the

ring

30 or 30 need not be mounted on the piston 18 or 18'. The retainer 31 merely bears against the strongest portion of the piston, namely, against the boss 29 or 29' so that the provision of such detent means does not shorten the useful life of the piston. As stated before, the retaining action of the biasing means 28 or 28 need not be very strong, as long as the

piston

18 or 18 is safely held in retracted position prior to liring of a cartridge. The detent means remains effective for long periods of use because the

ring

30 or 30 is not directly exposed to elevated temperatures and/or pressures so that its elasticity remains intact. In addition, the inertia of the detent means is negligible so that the retainer responds immediately, either to engage and hold the piston or to` release the piston in response to buildup of pressure in the throat 24. No plastic deformation of the detent means takes place during tiring and its operation is not affected by combustion products.

Due to the fact that the external surface of the

elastic ring

30 or 30 can be moved into actual engagement with the internal surface of the adjoining portion of the barrel, the ring is subjected to negligible tangential stresses despite the fact that its expansion is practically instantaneous. The clearance between the external surface of the

ring

30 or 30 and the adjoining portion of the housing is preferably small so that such external surface is propped in response to relatively small radial expansion of the ring.

That portion of the

ring

30 or 30 which is subjected to strongest bending stresses is located diametrically opposite the retainer 31. This is of advantage because the propagation of Ibending stresses from the region of corttact with the retainer 31 to the portion which undergoes maximal bending stresses must take place along one-half of the circumferential length of the

ring

30 or 30 whereby the latter absorbs a substantial part of such stresses and remains intact for long periods of actual use.

Of course, the improved fastener driving tool is susceptible of many additional modifications without departing from the spirit of the present invention. For example, the detent means 28 or 28 may be replaced by other types of analogous detent means, or such detent means may be multiplied. Also, the spherical retainer 31 may be replaced by a pinor stud-shaped retainer lwith a preferably spherical or semispherical head which is reciprocable radially of the barrel 19 so that its head can bear against the piston. Moreover, each of the detent means may comprise a single elastic ring and two or more retainers 31. The

ring

30 or 30 may `be replaced by other types of resilient biasing means capable of urging the retainer or retainers 31 (or analogous retainers) into satisfactory holding engagement with the

piston

18 or 18.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims:

What is claimed as new and desired to be protected by Letters Patent is:

1. An explosion-actuated fastener driving tool cornprising a housing having a front end arranged to accommodate a fastener and a rear end adjacent to a firing chamber; an elongated barrel received in said housing; a piston reciprocably received in said barrel and movable to and from a retracted position spaced from said front end of said housing; and detent means cooperating with said piston for yieldably holding the latter in said retracted position, said detent means comprising retainer means radially movably supported by said barrel and biasing means for urging said retainer means against said piston and comprising a split ring having a slot into which a portion of said retainer means extends, said piston cooperating with said retainer means to move the latter rnomentarily in radially outward direction during movement of said piston away from said retracted position to thus move an increasing portion of said retainer means into said slot to thereby radially expand said split ring.

2. A fastener driving tool as defined in claim 1, wherein said retainer means is reciprocable in a radial aperture of said barrel and comprises portions extending inwardly and outwardly from said aperture, at least that portion of said retainer means which extends inwardly of said barrel being of spherical shape.

3. A fastener driving tool as defined in claim 1, wherein said piston has a conical peripheral surface which tapers forwardly and is engaged by said retainer means in the retracted position of said piston so that said peripheral surface displaces the retainer means radially outwardly in response to movement of said piston from retrated position on firing of a cartridge in said firing chamber.

4. A fastener driving tool as defined in claim 1, wherein said barrel has a radially extending aperture accommodating said retainer means and a peripheral groove communicating with said aperture, at least a portion of said split ring being normally received in said peripheral groove.

5. A fastener driving tool as defined in claim 1, wherein said barrel is reciprocable, within predetermined limits, in the interior of said housing and wherein said housing comprises a series of coaxial tubular portions.`

6. A fastener driving tool as defined in claim 1, Wherein said piston comprises a smaller-diameter forward portion and a larger-diameter rearward portion, said detent means being arranged to engage with said rearward portion `which latter is slidable in said barrel, and further comprising guide means provided in said housing for the forward portion of said piston.

7. A fastener driving tool as defined in claim 1, wherein said barrel is reciprocable in said housing and is shiftable rearwardly in response to axial stresses transmitted thereto by a fastener which is introduced into the front end of said housing.

8. A fastener driving tool as defined in 'claim 1, wherein said retainer means comprises a ball of metallic material and said split ring consisting of metallic material and being recessed into a peripheral groove of said barrel.

9. A fastener driving tool as defined in claim 1, wherein said piston comprises a portion arranged to displace said retainer means radially outwardly against the opposition of said biasing means in response to movement of said piston from retracted position.

10. A fastener driving tool as defined in claim 1, wherein said piston has at a rear end portion thereof a surface portion engaging said retainer means and constructed to momentarily move said retainer means in radially outward direction during movement of said piston away from said retracted position.

A11. A fastener driving tool as defined in claim 10, wherein said retainer means is a ball reciprocable in a radial opening in said barrel, and wherein said housing has a rigid portion surrounding said ring with small clearance to limit radial expansion of said ring.

References Cited UNITED STATES PATENTS 1,726,012 8/1929 Bilz 227-147 2,839,754 6/1958 Pfafrr 227-147 2,973,520 3/1961 Bell 227--147 3,055,008 9/1962 Bell et al. 227-10 3,172,119 3/1965 Siddons 227-10 XR 3,255,942 6/1966 Bell et al. 227-8 3,348,751 10/1967 Henning 227-8 GRANVILLE Y. CUSTER, IR., Primary Examiner