Fastener-sleeve assembly and strip of collated fasteners

Abstract: A fastener assembly (10) comprises a fastener (20) having an elongate shank (22), which has a pointed end (24), and a head (26). The shank (22) of each fastener (20) defines an axis and has two portions of different diameters, namely a thicker portion (30) adjoining the head (26) and a thinner portion (32) adjoining the pointed end (24), and a shoulder (36) joining the thicker (30) and thinner (32) portions. The assembly (10) also includes a sleeve (40) associated with each fastener (20) by being disposed around the shank (22) of the associated fastener (20) and has an initial axial length, when disposed around the shank (22) of the fastener (20) but not compressed axially, and a critical axial length, at which the sleeve (40) splits when disposed around the shank (22) of the fastener (20) and compressed axially. The thicker portion (30) of the shank (22) of each fastener has an axial length between the initial and critical lengths of the associated sleeve (40). The fastener assemblies are typically provided as strips of collated fastener assemblies (70) with the sleeves (40) moulded integrally from polymeric material with frangible bridges (74) extending between adjacent sleeves (40).

Description: This invention pertains to a fastener assembly comprising a fastener and a polymeric sleeve, and to a strip of collated fasteners for a fastener driving tool, which may be pneumatically powered or combustion powered. The strip employs a polymeric carried providing a polymeric sleeve for each fastener. Fastener driving tools, which may be pneumatically powered or combustion powered, are used widely for driving fasteners of a type having an elongate shank with a pointed end and having a head. Typically, such fasteners are designed to be forcibly driven through a workpiece, into a substrate. Such fasteners include nails designed to be forcibly driven into wood and drive pins designed to be forcibly driven into concrete, masonry, or steel. An exemplary use of such drive pins is for attaching metal channels, which are used to mount plasterboard walls, to steel substrates. As exemplified in German Offenlegunsschrift No. 2,524,782, it is known for a fastener of the type noted above to have an elongate shank with two portions of different diameters, namely a thicker portion adjoining a head of the fastener and a thinner portion adjoining a pointed end of the elongate shank. In Ernst et al. U.S. Patent No. 5,069,340, and EP-A-0,502,667 a strip of collated fasteners of the type noted above is disclosed, which employs a carrier moulded of a polymeric material. As stated therein, polypropylene is a preferred material for the carrier. As illustrated and described therein, each fastener is a drive pin having an elongate shank of a uniform diameter except at a pointed end of the drive pin, and except at a flared portion where the elongate shank adjoins a head of the drive pin. Since the driving power of a combustion powered tool of a type exemplified in Nikolich U.S. Patents No. 4,403,722, No. 4,483,280 and Re-32,452, when driving the drive pins disclosed in Ernst et al U.S. Patent No. 5,069,340 is typically less than the driving power of a powder actuated tool employing a powder charge, it has been a practical necessity heretofore to employ a powder actuated tool employing a powder charge to drive such a steel pin through a steel workpiece into a substrate. This invention provides improvements over the pins and strip of collated fasteners illustrated and described in Ernst et al. U.S. Patent No. 5,069,340, especially in relation to the ability of pins associated with the strip to penetrate steel when driven by a combustion actuated tool of the type exemplified in the Nikolich patents noted above. According to a first aspect of this invention, a fastener assembly for attaching a workpiece to a substrate comprising: (a) a fastener having an elongate shank with a pointed end and having a head, the shank defining an axis, and (b) a polymeric sleeve disposed around the elongate shank of the fastener, the sleeve having an initial axially measured length, which the sleeve assumes when disposed around the shank but not compressed axially, the sleeve having a critical, axially measured length, at which the sleeve splits when disposed around the shank and compressed axially, is characterised in that the shank of the fastener has two portions of different diameter, namely a thicker portion adjoining the head and a thinner portion adjoining the pointed end, the shank having a shoulder joining the thicker and thinner portions, and in that the thicker portion of the shank has an axial length between the initial and critical lengths of the sleeve. This invention takes advantage of a characteristic of the fastener, namely the characteristic that the shoulder tends to arrest the fastener when the fastener is driven through a workpiece, into a substrate. Thus, the shoulder does not penetrate more than superficially into the substrate, if the driving power of the fastener driving tool driving the fastener is not excessive for the task at hand. This invention also takes advantage of a characteristic of the sleeve, namely the characteristic that the sleeve has an initial, axially measured length, which the sleeve assumes when disposed around the shank of the fastener, and a critical, axially measured length, at which the sleeve splits when disposed around the shank of the fastener and compressed axially. This invention contemplates that the thicker portion of the shank has an axial length between the initial and critical lengths of the sleeve. Thus, the sleeve is compressed axially between the head of the fastener and the workpiece but does not split if the shoulder arrests the fastener when the fastener is driven through the workpiece, into the substrate. In a preferred embodiment, the sleeve includes an upper portion nearer to the head and a lower portion nearer to the pointed end and has a pair of diametrically opposed, outwardly opening, similarly curved, concave recesses between the upper and lower portions, each recess having an open window, from which a portion of the shank of the fastener is visible. This invention also provides a strip of collated fasteners. The strip comprises a plurality of fasteners, each being like the fastener described in the preceding summary, and a carrier moulded from a polymeric material. The carrier comprises a separate sleeve associated with each fastener and is frangible between the separate sleeves. Each separate sleeve is like the polymeric sleeve described in the preceding summary. Herein, such terms as "upper" and "lower" are used merely to refer to a fastener assembly or a strip of collated fasteners in a convenient orientation but not to limit the fastener assembly or the strip of collated fasteners to any particular orientation. A preferred embodiment of this invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a fragmentary, perspective view of a metal channel attached to a steel substrate by a plurality of similar fastener assemblies, each embodying this invention. Figure 2 is an enlarged, partially dis-assembled, perspective view of a strip of collated fasteners, the strip providing a plurality of the fastener assemblies and embodying this invention. Figure 2 shows one side of the strip, the opposite side being similar to the side shown. Figure 3 is a further enlarged, cross sectional view of one of the fastener assemblies, in which the fastener has been driven through the metal channel, into the steel substrate, by a driver blade of a fastener driving tool. The driver blade is shown fragmentarily and the fastener driving tool is not shown otherwise. As mentioned above, this invention provides improvements over the pins and strip of collated fasteners illustrated and described in Ernst et al. U.S. Patent No. 5,069,340. As shown in Figure 1, a plurality of similar fastener assemblies 10 are used to attach a workpiece 12, such as a mild galvanised steel, U-shaped channel or track, to a substrate 14, such as a harder steel beam. Such a channel is used to mount plasterboard walls (not shown) in a known manner. In many instances, such a channel or track has a nominal thickness of 24 gauge (0.024 inch or 0.6 mm). In some instances, such a channel or track has a nominal thickness of 16 gauge (0.060 inch (1.5 mm)). Most loading on such a channel or track tends to shear the channel or track. Each fastener assembly 10 comprises a fastener 20 having an elongate shank 22, which has a pointed end 24, and having a head 26. Moreover, the elongate shank 22 of each fastener 20 has two portions of different diameters, namely a thicker portion 30 having a larger diameter D 1 (preferably a diameter of about 0.112 inch (2.85 mm)) and an axial length of about 0.25 inch (6.4 mm)) and adjoining the head 26 of such fastener 20 and a thinner portion 32 having a smaller diameter D 2 (preferably a diameter of about 0.092 inch (2.35 mm)) and adjoining the pointed end 24 of such fastener 20, a flared portion 34 where the thicker portion 30 adjoins the head of such fastener 20, and a flared shoulder 36 joining the shank portions 30, 32. As shown, each fastener 20 is a drive pin, which is made from hardened steel. Preferably, each fastener 20 has its pointed end 24 re-shaped by barrel finishing such fastener 20 in a finishing medium for at least about ten hours. Each fastener assembly 10 further comprises a polymeric sleeve 40, which is associated with the fastener 20 of such fastener assembly 10, and which is disposed around the elongate shank 22 of the associated fastener 20. As shown in Figures 1 and 3, the polymeric sleeve 40 is compressed axially between the head 26 of the associated fastener 20 and the workpiece 12 when the associated fastener 20 is driven through the workpiece 12, into the substrate 14. As shown in Figure 3, each fastener 20 with the associated sleeve 40 disposed around the shank 22 of such fastener 20 is driven by a driver blade 42 of a fastener driving tool, which may be pneumatically powered or combustion powered. The driver blade 42 is similar to the driver blade illustrated and described in the Ernst et al patent referenced above. Reference may be had to the Ernst et al patent referenced above for further details of the driver blade and associated components of the fastener driving tool and for further information relating to such pneumatically powered and combustion powered tools, which are well known. Each polymeric sleeve 40 includes a lower, annular portion 50 and an upper, general hexagonal portion 52, which is integral with the upper, annular portion 50. Each polymeric sleeve 40 grips the elongate shank 22 of the associated fastener 20 with the lower portion 50 nearer to the pointed end 24 of the gripped shank 22 and with the upper portion 52 nearer to the head 26 of the associated fastener 20. Each polymeric sleeve 40 has a pair of diametrically opposed, similarly curved, concave recesses 60, one of which is shown in each polymeric sleeve 40 in Figure 2. In one embodiment, the total length of the polymeric sleeve 40 is about 0.375 inch (9.5 mm). Each such recess 60 has an open window 62, from which a portion of the elongate shank 22 of the associated fastener 20 is visible. As shown in Figure 2, the plurality of the fastener assemblies 10 are provided in a strip 70 of collated fasteners 20. Along with the fasteners 20, the strip 70 comprises a carrier 72, which is moulded from the polymeric material noted above. The carrier 72 comprises a separate, polymeric sleeve 40 for each fastener 20 and is frangible between the respective sleeves 40. The carrier 72 is similar to the carrier illustrated and described in the Ernst et al patent referenced above, to which reference may be had for further details not illustrated or described herein. When the fastener 20 is driven through a workpiece, such as the workpiece 12, into a substrate, such as the substrate 14, it is a characteristic of the fastener 20 that the flared shoulder 36 tends to arrest the fastener. Thus, the flared shoulder 36 does not penetrate more than superficially into the substrate, if the driving power of the fastener driving tool driving the fastener 20 is not excessive for the task at hand. Whether or not the shoulder arrests the fastener 20 can be empirically determined and depends upon such factors as the dimensions of the fastener 20, the surface roughness at the pointed end 24 and elsewhere on the fastener 20, the characteristics of the workpiece and of the substrate, and the driving power of the fastener driving tool. Preferably, as mentioned above, the pointed end 24 is re-shaped by barrel finishing the fastener 20 in a finishing medium for about ten hours. Furthermore, it is a characteristic of the polymeric sleeve 40 that the polymeric sleeve 40 has an initial, axially measured length, which is about 0.375 inch (9.5 mm) in one embodiment and which the polymeric sleeve 40 assumes when disposed around the shank 22 of the associated fastener 20, and a critical, axially measured length, at which the polymeric sleeve 40 splits (in a manner illustrated and described in the Ernst et al patent referenced above) when disposed around the shank 22 of the associated fastener 20 and compressed axially between the head 26 of the associated fastener 20 and a workpiece, such as the workpiece 12. The initial and critical lengths of a given sleeve disposed around the shank of a given fastener can be empirically determined. This invention contemplates that the thicker portion 30 of the shank 22 of each fastener 20 has an axial length between the initial and critical lengths of the associated sleeve 40. In other words, the axial length of the thicker portion 30 is more than the critical length of the associated sleeve 40 but less than the initial length of the associated sleeve 40. Thus, when the fastener 20 is driven through a workpiece, such as the workpiece 12, into a substrate, such as the substrate 14, the associated sleeve 40 is compressed axially and bulges outwardly between the head 26 of the fastener 20 and the workpiece but does not split if the flared shoulder 36 arrests the fastener 20. As an example, if the initial length of the polymeric sleeve 40 is about 0.375 inch (9.5 mm), if the axial length of the thicker portion 30 of the associated fastener 20 is about 0.25 inch (6.4 mm), if the nominal thickness of the workpiece 14 is about 0.024 inch (0.6 mm), and if the flared shoulder 36 arrests the associated fastener 20 when the flared shoulder 36 has passed through the work-piece 14, the polymeric sleeve 40 can be thus compressed to a resulting length of about 0.225 inch (5.7 mm). Consequently, the associated sleeve 40 compressed axially and bulging outwardly between the head 26 of the fastener 20 and the workpiece provides a compressible washer, which helps to resist tearing of the workpiece from the substrate, particularly when the workpiece is subjected to loading that tends to shear the workpiece.

Claims: A fastener assembly (10) for attaching a workpiece (12) to a substrate (14) comprising: (a) a fastener (20) having an elongate shank (22) with a pointed end (24) and having a head (26), the shank defining an axis, and (b) a polymeric sleeve (40) disposed around the elongate shank (22) of the fastener, the sleeve having an initial axially measured length, which the sleeve (40) assumes when disposed around the shank (22) but not compressed axially, the sleeve (40) having a critical, axially measured length, at which the sleeve splits when disposed around the shank (22) and compressed axially, characterised in that the shank (22) of the fastener (20) has two portions (30, 32) of different diameter, namely a thicker portion (30) adjoining the head and a thinner portion (32) adjoining the pointed end, the shank (22) having a shoulder (36) joining the thicker and thinner portions (30, 32), and in that the thicker portion (30) of the shank (22) has an axial length between the initial and critical lengths of the sleeve (40). A fastener assembly of claim 1, wherein the sleeve (40) includes an upper portion nearer to the head (26) of the fastener (20) and a lower portion nearer to the pointed end (24) of the fastener (20) and has an outwardly opening, curved, concave recess (60) between the upper and lower portions, when uncompressed. A fastener assembly of claim 2, wherein said recess (60) is one of a pair of diametrically opposed, similarly curved, concave recesses (40). A fastener assembly of claim 2 or 3, wherein each recess (60) or each of said recesses (60) has an open window (62) through which a portion of the shank (22) is visible. A strip (70) of collated fasteners, the strip comprising a plurality of fastener assemblies, which are formed integrally as a carrier and are frangible between the individual sleeves (40) of the fastener assemblies, characterised in that the fastener assemblies are in accordance with any one of the preceding claims. An assemblage comprising a steel substrate (14), a steel workpiece (12) disposed against the substrate (14), and a fastener assembly, the fastener of the fastener assembly being driven through the workpiece (12), into the substrate (14), so that the sleeve (40) of the fastener assembly is compressed axially and bulges outwardly between the head (26) of the fastener and the workpiece (12), characterised in that the fastener assembly is according to any one of claims 1 to 4, the fastener being driven through the workpiece (12), into the substrate (14), so that the shoulder (36) of the fastener is disposed approximately where the workpiece (12) is disposed against the substrate (14). An assemblage according to claim 6, in which the workpiece (12) is thin having a nominal thickness between 0.6 and 1.5 mm and the sleeve (40) acts as a compressible washer which resists shearing of the workpiece (12).

Inventors: GUPTA HARISH C, GUPTA, HARISH C.
Applicants: ILLINOIS TOOL WORKS, ILLINOIS TOOL WORKS INC.
Application year: 1995
Main classification: F16B15
IPC codes: F16B15, F16B43, F16B19