|Publication number||US3559272 A|
|Publication date||Feb 2, 1971|
|Filing date||Sep 16, 1968|
|Priority date||Sep 16, 1968|
|Also published as||DE1950091A1|
|Publication number||US 3559272 A, US 3559272A, US-A-3559272, US3559272 A, US3559272A|
|Inventors||Hsu Yung Shing|
|Original Assignee||Omark Industries Inc|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (14), Classifications (15)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Feb. 1971 YUNG SHING HSU DRIVING CAP FOR DRIVEPIN, AND TOOL AND METHOD THEREFOR 2 Sheets-Sheet 1 Filed Sept. 16. 1968 A TTOAZA/E Y YUNG SHING HSU Feb. 2, 1971 v DRIVING CAP DRIVEPIN, AND I'OOL AND METHOD THEREFOR Filed Sept. 16 1968 2 She'ts-Sheet 2 INVENTOE YLJNG s/-///-/c; A/SU United States Patent 3,559,272 DRIVING CAP FOR DRIVEPIN, AND TOOL AND METHOD THEREFOR Yung Shing Hsu, Milwaukie, Oreg., assignor to Omark Industries, Inc., Portland, Oreg. Filed Sept. 16, 1968, Ser. No. 759,855 Int. Cl. B23p 11/00 US. Cl. 29-432 6 Claims ABSTRACT OF THE DISCLOSURE HISTORY OF THE INVENTION This invention relates to a method and means for driving drivepins into a hard surface.
Manually driving fastening pins, studs, bolts, nuts and the like (hereafter collectively referred to as drivepins) such as for fastening metal fixtures to concrete flooring in the construction of large commercial buildings is slow and inadequate. Thus, there has been developed for the construction industry a variety of explosively actuated tools for driving such drivepins.
Explosively actuated driving tools have heretofore been comprised of two general types. One is referred to as the low-velocity driving tool and the other as the highvelocity driving tool. The low-velocity driving tool is adapted to receive a drivepin at the exit end of a cylindrical barrel with a piston located inwardly and spaced from the drivepin. An explosive charge located behind the piston, i.e., at the breech end of the barrel, is detonated by a firing mechanism which rapidly accelerates the piston toward the drivepin. See for example, the commonly assigned Kopf et a1. U.S. Pat. No. 2,239,121 issued on Mar. 8, 1966 on a Piston Powder Actuated Tool. The high-velocity tool is adapted to receive a drivepin at the breech end of the barrel. A charge is exploded directly against the head of the drivepin to rapidly accelerate the drivepin in free flight down the length'of the barrel and at the work surface. See for example the commonly assigned Kopf et a1. U.S. Pat. No. 3,221,966 issued on Dec. 7, 1965.
High-velocity tools have the disadvantage of high noise level, dangerous free fastener velocity, and high degree of spall and ricochet when the drivepin strikes the work surface. Low-velocity tools have the disadvantage of high noise level, power limitation, severe spall out in concrete, and high incidence of drivepin damage. The preferred embodiment of the present invention is thus adapted to provide an improved method and means for driving a drivepin which has the driving capacity of a high-velocity tool and the safety of the low-velocity tool as well as the unique characteristics of simplicity, low noise level and reduced drivepin and work damage.
SUMMARY OF THE INVENTION In general, the preferred embodiments of the invention comprises a drivepin with a driving cap attached to the head of the drivepin. The driving cap includes a propellant in the form of a power pill and a cushioning pad that functions as a silencer. The tool for driving the drivepin is adapted to receive the drivepin at the exit end of an open ended barrel. When the tool is placed against a work surface the pointed end of the pin is abutted against the work surface. A ramrod slidable within the barrel of the tool is adapted to be driven against the driving cap. The hard work surface provides a rigid resistance to the pin and upon driving the ramrod against the power pill of the driving cap from the opposite end, the impulse ignites the propellant. The energy of the propellant is transmitted to the head of the drivepin and propels the drivepin into the hard work surface. The cushioning pad being compressed against the drivepin expands or bulges within the barrel to form a gas tight seal.
With the drivepin abutted against the work surface, the energy of the power pill is directly applied to force a penetration of the drivepin into the work surface. This is believed to be an important departure from prior art devices wherein an explosion first produces a rapid velocity in free flight on either a piston (low-velocity tool) or drivepin (high-velocity tool), with the kinetic energy of the rapid velocity producing the penetrating force. Also, the sealing effect of the cushioning pad renders the driving operation relatively noiseless. Other benefits and advan tages of the invention will become apparent by reference to the following detailed description and drawings wherein:
FIG. 1 is a perspective view with portions broken away illustrating the tool and operation of driving a drivepin into a concrete slab in accordance with the invention;
FIG. 2 is a cross sectional view of the tool used in the driving operation of FIG. 1;
FIG. 3 is a partially sectioned view of a drivepin having a driving cap attached thereto in accordance with the invention;
FIG. 4 is a partial view further illustrating the driving operation with the drivepin partially driven into the hard work surface;
FIG. 5 illustrates a modification to the drivepin; and
FIG. 6 illustrates a further modification to the drivepin.
DETAILED DESCRIPTION Referring to FIGS. 1 and 2 of the drawings, a driving tool 10 has an outer housing which serves as a handle 12, e.g. of molded plastic or the like. A tubular insert 14 in the handle 12 is constructed of a hard material, e.g. steel, and forms an open ended barrel 16 for the driving tool 10. The tubular insert 14 extends below the handle portion 12, and a guard fixture 18 is assembled to the handle portion 12, and is co-extensive with the extended end of the tubular insert 14. (As used hereafter, up and down, top and bottom, and similar directional terms are all with reference to the positioning of the tool as shown in FIG. 1. It is to be understood, however, that the tool may similarly be used on side walls, ceiling, etc.) The guard fixture 18 has a flared bottom portion which aids the user in positioning the tool squarely against a work surface 20 (see FIG. 1). A noiseproof lining 22 is molded to the inside of the flared portion of the guard fixture 18.
A ramrod 26 within the barrel 1-6 is generally circular in cross section with a lower portion 28 that is adapted to conform closely to the lower section of the barrel 16. A flange 30 above the lower portion 28 of the ramrod 26 is tapered so as to seat against a tapered entry 24 of the barrel 16 as shown in FIG. 2. A retaining cap 32 is threadedly engaged with the top of the tubular insert 14 land is adapted to permit sliding movement therethrough of the main portion of the ramrod 26 but not the flange 30. Thus the sliding movement of the ramrod 26 within the barrel 16 is limited in its upward movement by the flange 30 being abutted against the retaining cap 32, and is limited in its downward movement by the flange 30 being seated against the tapered entry 24 of the barrel 16. A knob 34 is afiixed to the top of the ramrod 26 and is adapted to be struck by a hammer 36 or the like as schematically illustrated in FIG. 1.
A drivepin 38 for the illustrated driving operation of FIG. 1 is shown in FIG. 3. The drivepin 38 is comprised of a shank with a point at one end and a head 40 at the other end. A driving cap 42 is attached to the head 40 of the drivepin 38. The driving cap 42 is comprised of a cylindrical pad 44 with an inset portion at one end adapted to fit over the head 40 of the drivepin 38 and an inset portion at the other end adapted to receive a power pill 46. A washer 41 of deformable material is attached to the shank of the drive pin adjacent the pointed end. The washer 41 provides a light frictional gripping action for holding the drivepin inside the barrel 16, and also in cooperation with the head 40 and driving cap 42 aligns the drive pin along the axis of the barrel 16 (see FIG. 1).
The drivepin 38 is formed from a hard metal such as steel.The material of the cushioning pad 44 is deformable under impact so as to expand or bulge against the wall of the barrel 16 to tightly seal against gas leakage (see FIG. 4). A suitable material for the cushioning pad is a soft grade of aluminum such as aluminum 1100. Other suitable materials include plastics such as Teflon, available from E. I. du Pont de Nemours Company. A lubricant 48 is coated on the outside of the aluminum cushioning pad 44 to minimize the friction between the aluminum pad 42 and the steel wall of the barrel 16. A suitable lubricant is the product known as Industrial Teflon Coating also available from E. I. du Pont de Nemours Company. It will be understood however that a plastic pad may be self lubricating.
The power pill 46 is selected to have the properties of high energy output preferably in the range of about 40 to 300 foot/pounds. The preferred propellant material is one that can be contained in a small volume, will ignite by a high impulse, e.g. one pound second, and is sufliciently stable so as not to be ignited at a lower impulse or by friction such as might be encountered in mishandling of the pins or a loaded tool. Also these conditions should remain constant for a substantial shelf life period. A suitable propellant for the power pill is composed of compacted nitrocellulose fibres having a density of about 1 gram per cubic centimeter.
OPERATION In operation, the fastening pin 38 with the driving cap 42 attached thereto, is inserted into the exit end of the barrel 16 of the driving tool 10, as shown in FIG. 1 of the drawings. The driving tool 10 is positioned against the work surface 20 with the guard fixture 18 aiding in the proper alignment of the barrel with the work surface 20. The ramrod 26 is then moved against the driving cap 42 to push the drivepin 38 tightly against the work surface 20. The hammer 36 is used to strike the knob 34 of the ramrod 26 which strikes the power pill 46 in the driving cap 42 which creates the suflicient impulse to release the energy of the propellant. Reliable ignition will be achieved from a 2 pound hammer swing at a rate of 10l5 feet/second thereby producing an appropriate pound/second value. The energy of the propellant is transmitted to the drivepin 38 through the pad 44 to drive the drivepin into the work surface 20.
Although we do not wish to be bound by this theory, it is believed that an important feature for igniting the relatively stable propellant material of the power pill is the protrusion 29 on the end of the ramrod 28. This protrusion initially causes a shearing force on the center area of the pill and because the following peripherial area 29-c'ontains the material being sheared and prevents it from flowing away from the protrusion, frictional heat is generated to cause the desired ignition. The protrusion 45 of the cushioning pad 44 is believed to provide a similar shearing function as the pill is forced against the deformable material at the peripherial area 45'.
The penetration of the drivepin into the work surface 20 is illustrated in FIG. 4 of the drawings. As shown, the propellant forces axial compression of the pad 44 with a resulting lateral expansion or bulging. This bulging of the pad 44 forms a gas tight seal around the driving cap 42. This sealing off of the gasses renders the tool substantially noiseless. The driving cap breaks away from the head of the drivepin at the end of the power stroke and remains solidly expanded within the barrel of the tool. The lubricant coating on the exterior of the driving cap allows it to be ejected from the barrel by driving the ramrod against the driving cap with the hammer.
A significant safety factor is believed to be achieved by the invention. The propellant requires a substantial impulse before it will detonate, and it is inert to static compression. Thus until the tool is positioned so as to abut the drivepin against a hard work surface, the ramrod cannot ignite the propellant. Ramming the propellant of the fastening pin without the rigid resistance of the work surface will only result in a manual driving of the drive pin (with propellant intact) out of the barrel. Also, with the drivepin abutted against the work surface, the propellant drives the drivepin directly into the work surface and the velocity of the drivepin as it is driven into the work surface is substantially less than the velocity of a drivepin or piston in free flight as in the prior devices. For safety purposes this can be important in instances where excessively hard objects, such as pieces of metal or stone that are embedded in a concrete slab, lie in the path of the drivepin. If the pin strikes at a very high velocity, as in the prior devices, the ricocheting of the pin from such hard objects can be dangerous.
A further advantage is believed realized in the attainment of much greater efiiciency of the driving force. First because the propellant energy is applied directly to the driving of the drivepin, and second because the ramrod, after igniting the power pill 46, follows the drivepin down the barrel 16. The moving ramrod inhibits the gas expansion within the chamber resulting in increased energy being applied to the drivepin.
An alternative embodiment of the drivepin and driving cap is illustrated in FIG. 5 of the drawings. The power pill 46 is placed adjacent to the head 40 of the drivepin 38 and a suitable wrapping 50 secures the power pill to the drivepin. Whereas a similar driving force is achieved as compared to the driving cap having a cushioning pad, the benefits of noiselessness may be sacrificed. Another embodiment is shown in FIG. 6 where a drivepin 52 is provided with a head 54 having an inset provided therein for receiving a power pill 46.
Other alternatives and modifications will be apparent to those skilled in the art without departing from the scope of the invention. Thus the above described embodiments of the invention are intended to set forth preferred examples of the invention and are not intended to limit the scope thereof which is defined in the following claims.
What is claimed is:
1. A driving cap comprising a deformable cylindrically shaped cushioning pad adapted to be placed on the head of a drivable member, a power pill embedded in the cushioning pad opposite the drivable member, said power pill being ignited at no less than one pound second impulse.
2. A driving cap comprising a deformable cylindrically shaped cushioning pad adapted to be placed on the head of a drivable member, a power pill embedded in the cushioning pad, and means between the power pill and cushioning pad to assist the ignition of the power pill.
3. A driving cap as defined in claim 2 wherein a cavity is formed in the end of the cushioning pad, said ignition assistance means comprising a protrusion in the bottom of the cavity, said power pill being in the cavity abutted against the protrusion and spaced from the boltom of the cavity.
4. A driving cap as defined in claim 3 whereby said power pill has a level of ignition no less than one pound second impulse.
5. A driving cap as defined in claim 2 wherein the power pill is composed of compacted nitrocellulose fibres having a density of about one gram per cubic centimeter.
6. A method of driving a drivepin into a hard work surface which includes placing a driving cap including an expandable pad and power pill on the head of a drive pin with the expandable pad between the head of the drivepin and the pill, confining the drivepin with driving cap in the barrel of a tool, abutting the drivepin against a solid work surface and striking the power pill with a ramrod to create sufiicient impulse for axially compressing the pad to cause peripheral expansion for sealing off gasses and then igniting the power pill to thereby drive the drivepin into the work surface While continuing the axial compression of the pad.
References Cited UNITED STATES PATENTS 6/ 1909 Gehne 227147 1/ 1921 Temple 227-9 11/ 1951 Temple 227-9 4/1957 Henning et a1 22711 1/1960 DeCaro 10238 7/1963 Turner 10239 6/ 1964 Rosenberg, Jr 8510 6/ 1967 Hilti 29432 3/ 1968 Kvavle 227 9UX 8/1968 Kvavle 22710 8/ 1968 Kvalve 102--3 8X US. Cl. X.R.
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US3688964 *||Sep 1, 1970||Sep 5, 1972||Speed Fastener Inc||Fastener drive tool for caseless loads|
|US3952398 *||Aug 12, 1974||Apr 27, 1976||Haytayan Harry M||Process for pneumatically impelling a hammer to drive a nail into a substrate|
|US4830254 *||Jan 28, 1988||May 16, 1989||Hsu Yung Shing||Two-stage power driving system for powder actuated tools|
|US5497929 *||May 26, 1995||Mar 12, 1996||Innovative Quality Prod Corp||Self-powered fastener system|
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|US20120321413 *||Aug 6, 2012||Dec 20, 2012||Fernando Masas||Apparatus for installing fasteners and explosive loads for use therewith|
|WO1995012476A1 *||Nov 4, 1994||May 11, 1995||Innovative Quality Products Corporation||Self-powered fastener system|
|WO1999024777A1 *||Nov 10, 1998||May 20, 1999||Joe Lin||Solid propellant charge unit for fasteners|
|U.S. Classification||29/432, 227/10|
|International Classification||B25C1/00, B25C1/18, B25C1/16, B25C1/12, B25C1/08|
|Cooperative Classification||B25C1/126, B25C1/188, B25C1/087, B25C1/16|
|European Classification||B25C1/16, B25C1/08B3, B25C1/12C, B25C1/18C|