Title:
Method and apparatus for anchoring hardwood floor systems
Kind Code:
A1


Abstract:
A standoff sleeve/fastener assembly and a powered driver are provided for anchoring a subfloor component of a hard wood floor system to a concrete slab. The sleeve has a peripheral flange and a countersink at a first end. The fastener is disposed in the sleeve and has an enlarged head that is adjacent to but spaced from the first end of the sleeve. The driver has a nozzle with a striker bore sized to receive the head of the fastener and a recess sized to accommodate the peripheral flange of the sleeve. The subfloor component is anchored by (1) positioning the sleeve/fastener assembly in a hole in that component with the bottom end of the sleeve contacting the concrete slab, (2) positioning the driver nozzle so that the fastener head and the flange of the sleeve reside in its striker bore and recess respectively, and (3) operating the driver whereby its striker impels the fastener to (a) pierce and penetrate the concrete slab and (b) lock the sleeve between the concrete slab and the head of the fastener.



Inventors:
Haytayan, Harry M. (Nashua, NH, US)
Application Number:
10/301262
Publication Date:
05/27/2004
Filing Date:
11/21/2002
Primary Class:
International Classes:
B25C1/18; E04F15/22; F16B15/00; F16B19/14; (IPC1-7): E04H12/00
View Patent Images:
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Primary Examiner:
D ADAMO, STEPHEN D
Attorney, Agent or Firm:
Pandiscio & Pandiscio (470 Totten Pond Road, Waltham, MA, 02451, US)
Claims:

What is claimed is:



1. Method for anchoring to a concrete base an attachment assembly for a wood floor wherein said attachment assembly comprises an attachment member that has top and bottom surfaces and having at least two holes each with a counterbore extending down from said top surface, and at least two compressible pads each having a top side and a bottom side with said top side contacting said lower surface of said attachment member, said method comprising the following steps: (1) inserting (a) a sleeve having center bore, a distal end, a proximal end and a peripheral flange at said proximal end into each of said holes so that said peripheral flange resides in said counterbore and (b) a fastener having a distal end and a proximal end with an enlarged diameter head at said proximal end into each of said sleeves, with said distal end of said sleeve projecting below said attachment member by a predetermined amount so that it is substantially flush with the bottom side of said each compressible pad and with said head of said fastener extending above said proximal end of said sleeve; (2) providing a manually operable pneumatic driver having a nozzle with an end surface that is sized to fit in said counterbore, a striker mounted for axial movement in a striker bore in said nozzle with said striker bore having a diameter at least equal to the diameter of said head of said fastener, and means for reciprocally driving said striker through (a) a rapid drive stroke whereby said striker is moved from an at-rest position in which the striker is withdrawn into said bore to an extended fastener-driving position in which said striker projects beyond said end surface and (b) a rapid return stroke whereby the striker is withdrawn from said fastener-driving position back to said at-rest position; (3) positioning said driver so that said end surface of said nozzle resides within said counterbore and so that said fastener head resides in said bore; and (4) operating said driver so as to cause said striker to impact said fastener head with a force sufficient to drive said fastener into said base far enough to cause the head of said fastener to (a) drive said flange into tight engagement with said attachment member and (b) force said sleeve into tight engagement with said base.

2. Method according to claim 1 wherein in step (1) the head of said fastener extends above said attachment member.

3. Method according to claim 1 wherein in step (4) the depth of penetration of said fastener into said base is limited by said sleeve.

4. Method according to claim 1 wherein said distal end of said fastener is substantially flush with said distal end of said sleeve prior to step 3.

5. Method according to claim 1 wherein said sleeve has a tapered countersink for said bore at said proximal end, and said fastener head has a conical side surface.

6. Method according to claim 5 wherein the angle of taper of said fastener is greater than the angle of taper of said countersink.

7. Method according to claim 6 wherein said countersink has a taper angle of about 60° and said conical side surface has a taper angle of about 82°.

8. A fastener/standoff sleeve assembly for use in anchoring an attachment assembly for a wood floor to a concrete base, said assembly comprising: a fastener having a shank with a distal end and a proximal end, a pointed tip at said distal end, and an enlarged diameter head at said proximal end, with said head having a side surface that is tapered inwardly; and a sleeve for positioning said fastener in a hole in said attachment assembly, said sleeve having a distal end, a proximal end, a central bore that extends between said distal and proximal ends for accommodating the distal end of said shank, and a tapered countersink for said bore at said distal end of said sleeve, said countersink being shaped to accommodate said head of said fastener when said fastener is driven into said sleeve by an impact on said head while said sleeve is immobilized against axial movement.

9. A fastener/standoff sleeve assembly according to claim 8 wherein said fastener head has a conical side surface that has a taper angle greater than the angle of taper of said countersink.

10. A fastener/standoff sleeve assembly according to claim 8 wherein said fastener shank has a proximal relatively large diameter portion and a distal relatively small diameter portion, and said hole is sized to accommodate said distal relatively small diameter portion but not said proximal relatively large diameter portion.

11. Method for anchoring to a concrete base a floor attachment assembly that comprises a floor attachment member having top and bottom sides, at least two compressible pads attached to the bottom side of said floor attachment member, and two holes extending through said attachment member, said method comprising the following steps: (1) providing a fastener and sleeve assembly that includes a fastener having a shank with a leading end and a trailing end and a radially-projecting head at said trailing end, and a sleeve having an axial bore, a bottom end and a top end with a radially projecting flange at said top end, said leading end of said shank intruding into said axial bore; (2) inserting said fastener and sleeve assembly into said one of said holes with said bottom end of said sleeve projecting below the bottom side of said attachment member and with the head of said fastener disposed above and spaced from the top side of said attachment member; and (3) impacting said fastener head with a pneumatically-powered hammer with sufficient force to drive said fastener into said concrete base far enough to cause the head of said fastener to (a) force said flange into tight engagement with said attachment member and (b) anchor said attachment member to said base without compressing said pads.

12. Method according to claim 11 wherein in step (1) the head of said fastener extends above said attachment member.

13. Method according to claim 11 wherein in step (3) the depth of penetration of said fastener into said base is limited by said sleeve.

14. Method according to claim 11 wherein said sleeve has a tapered countersink for said axial bore at said proximal end, and said fastener head has a conical side surface.

15. A fastener/standoff sleeve assembly according to claim 8 wherein said sleeve has a peripheral flange at its said proximal end.

16. A fastener/standoff sleeve assembly according to claim 8 wherein said fastener has it shank inserted into said central bore of said sleeve, with said enlarged diameter head and the portion of said shank adjacent said head projecting from said proximal end of said sleeve.

17. A fastener/standoff sleeve assembly according to claim 16 wherein said fastener shank is gripped by said sleeve.

18. A fastener/standoff sleeve assembly according to claim 16 wherein said tip is substantially flush with said distal end of said sleeve.

19. A fastener/standoff sleeve assembly according to claim 18 wherein said sleeve has a peripheral flange at its said distal end and said enlarged diameter head of said fastener is spaced from said flange.

20. A fastener/standoff sleeve assembly according to claim 8 wherein said distal end of said sleeve has an end surface, said shank is stepped with a relatively large diameter portion extending distally from said head and a relatively small diameter portion extending between said tip and said relatively large diameter portion, and said relatively small diameter portion is disposed in said bore with said tip being substantially even with said end surface.

Description:

FIELD OF THE INVENTION

[0001] This invention relates to hardwood floor systems and more particularly to an improved method and apparatus for anchoring such systems to a base made of concrete or like material.

BACKGROUND OF THE INVENTION

[0002] Hardwood floor systems used for sports, such as basketball, require a significant degree of cushioning or impact absorption of the floor relative to the underlying base to which it is secured in order to reduce injuries. Accordingly a number of different floor systems have been designed to provide an appropriate amount of floor deflection and resiliency. Such floor systems include a plurality of hardwood floorboards, one or more subfloor layers supporting the floorboards, and a plurality of elastomeric pads attached to and underlying the subfloor layer(s) for supporting the floor system on a base in the form of a concrete or asphalt slab. In, some cases, the base may be a pre-existing wood floor. The floor system is anchored to the base by metal fasteners in such a way as not to precompress the elastomeric pads when the floor system is in an unloaded state, thereby leaving a gap of free space between the subfloor(s) and the base with the vertical dimension of that space being such as to allow downward deflection of the floor under impact, thereby providing shock absorption and resiliency or give, and reducing the amount of reaction force imparted by the floor system to the impacting person or object.

[0003] The free space provided between the subfloor layers and the base is also important with respect to reducing the effect of humidity changes on the dimensional stability of the wood components. Wood components are susceptible to absorption or expulsion of moisture, with a resultant expansion or contraction. The effect of humidity changes on the dimensional stability of the floor system is reduced by the free space since the latter limits moisture transfer between the base and the supported components.

[0004] A number of different floor systems are known that are designed to provide some degree of impact absorption and are characterized by free space between the base and the subfloor layers. One of those systems is disclosed in U.S. Pat. No. RE37,615, issued Apr. 2, 2002 to Michael W. Niese for “Anchored/Resilient Hardwood Floor System”. The disclosure of that patent is incorporated here by reference.

[0005] In the construction disclosed and claimed in U.S. Pat. No. RE37,615, a plurality of mutually spaced sleepers in the form of elongated nailing members are used to form a subfloor layer for supporting a layer of hard wood floorboards that serve as the wear surface. One or more subfloor layers are interposed between the sleepers and the hardwood wear surface. The sleepers also include compressible supporting pads, e.g., pads made of a suitable elastomer. In the floor system disclosed in the aforesaid patent, a fastening arrangement is used to secure the sleepers directly to the base so that (a) the pads are not precompressed, i.e., the pads are not compressed beyond the compression that results solely from the weight of the flooring system components carried by the pads, and (b) the sleepers can deflect downwardly upon impact to the upper layer of the floor system but are restricted against upward movement beyond the initial static position of the pads. The fastening arrangement includes counterbored holes in the sleepers, floor-anchoring fasteners that extend through the counterbored holes into the base, and means for limiting the depth of penetration of the fasteners into the base so that the downward driving forces applied via the fasteners do not precompress the elastomer pads. Further details of such a system are presented hereinafter in connection with FIG. 1.

[0006] Floor systems similar to the type claimed of U.S. Pat. No. RE37,615 are in commercial use. The foregoing patent indicates that the floor system disclosed therein may be anchored by forcing fasteners into predrilled holes in the base or by driving fasteners into the base using a nail gun without any pre-drilled holes. However, as a practical matter prior to this invention it was not feasible or practical to anchor the sleepers to a concrete base without first predrilling holes for the fasteners in the concrete. Instead the usual practice has been to predrill holes in the concrete base and use fasteners that are characterized by a shoulder that function as a depth stop and an expansion curve adjacent their leading end for anchoring the fasteners in the concrete base, with the fasteners being surrounded by plastic lubricating sleeves that sit loosely in the counterbored holes and serve to reduce friction between the fasteners and the sleepers, as illustrated in FIG. 9 of U.S. Pat. No. RE37,615. Typically the lubricating sleeve has a peripheral flange at its top end and the flange portion has a counterbore to accommodate the head the fastener. The fasteners are driven into the predrilled holes by manually impacting them with a hammer.

[0007] Manually driving a fastener into dense concrete without predrilling a hole to accommodate the fastener cannot be done at all, or at least not without having to strike each fastener repeatedly. However, the holding power of a fastener driven into solid concrete by repeated blows is poor. If a fastener is impacted with sufficient force to penetrate a concrete substrate, a so-called “ball” is formed in the concrete around the leading end of the fastener. That ball is a densification of the concrete and it exerts a tight grip on the fastener. However, if thereafter the embedded fastener is impacted one or more times, the ball will be disrupted and even disintegrate, with the result that the concrete's grip on the fastener is weakened substantially. It is well known in the structural fastening field that the same phenomenon occurs when impact driving a fastener into a steel substrate. Therefore, to maximize the holding power, a fastener should not be hit more than once when impact driven into concrete or steel.

[0008] Heretofore powered impact-type drivers have been used for driving fasteners into concrete or other hard masonry substrates for the purpose of anchoring metal components to the substrates. However, prior to this invention use of power drivers for anchoring the sleepers disclosed U.S. Pat. No. RE37,615 was not feasible. The primary problem stems from -the counterbored holes in the sleepers. The counterbores are designed to accommodate the heads of the fasteners so they will not protrude above the sleepers where they can interfere with the underfloor members carried by the sleepers, particularly when the floor system is deflected downwardly under impact.

[0009] In the case where lubricating sleeves with peripheral flanges at their top ends are used with the fasteners, the counterbores also serve to provide a recessed seat for the flanges. However, the requirement that the heads of the fasteners (and also the flanges of the lubricating sleeves when used) be recessed in the counterbores has made it difficult to use a power driver. The need to recess the heads of the fasteners in the counterbores complicates attainment of the requirement that the striker or hammer of the power driver be able to drive the fasteners deep enough to assure a tight engagement of the fastener heads (or the flanges of the lubricating sleeves) with the bottoms of the counterbores, but not so deep as to preload the resilient pads. The counterbored holes also make it difficult to center the striker or hammer of the powered driver on the fastener head, which is an important consideration since optimum performance of the driver requires that its striker be readily centered on the fastener head and the driver be positioned to drive the fastener perpendicularly to the base. This centering problem is complicated by the fact that in actual practice the lubricating sleeves are sized to make a loose fit in the counterbored holes. Another factor discouraging against use of a power driver is the requirement that the action of the driver must not interfere with the use of fastener depth stop means designed to prevent compression of the resilient pads, as those disclosed in U.S. Pat. No. RE37,615.

[0010] Because of these problems there has been lacking a satisfactory and reliable way to secure the sleepers of the form disclosed in said patent to a concrete base without using pre-drilled holes for the fasteners. The need to predrill holes introduces a variety of limitations, the most significant of which is that installation of such systems is slow and costly due to the manual labor consumed in predrilling holes in the concrete and the need to precisely locate the holes to assure alignment with the counterbored holes in the sleepers, and the repeated hammering action required to seat the fastener.

OBJECTS AND SUMMARY OF THE INVENTION

[0011] The primary object of this invention is to provide a method and means for anchoring a hardwood floor system to a concrete base with fasteners without the need for predrilling holes for the fasteners.

[0012] A more specific object is to provide an improved method and means for anchoring floor system sleepers of the type that have counterbored holes to accommodate fasteners for anchoring the sleepers to a concrete base.

[0013] Another object is to provide a novel and improved fastener arrangement for anchoring hardwood floor systems.

[0014] Still another object is to provide a power driver that is adapted for driving fasteners to anchor sleepers that have counterbored holes for the fasteners.

[0015] A further object is to provide a novel and improved fastener arrangement comprising a fastener and a hard plastic standoff sleeve for the fastener that is adapted to withstand fracture by the fastener when the fastener is impacted by the striker of a power driver.

[0016] The foregoing and other objects of the invention are achieved by providing a standoff sleeve/fastener arrangement for anchoring a sleeper of the type described to a concrete base, and a power driver for driving the fastener into the concrete base. The standoff sleeves are sized to fit loosely (approximately {fraction (1/32)}″ to {fraction (1/16)}″ clearance in counterbored holes preformed in the sleeper. Each sleeve has a center bore for accommodating the shank of the fastener and a peripheral flange at its top end that is sized to fit within the counterbore. Also in relation to the associated fastener the sleeve has an effective length that enables it to function as a depth stop that prevents the fastener from pre-compressing the resilient pads of the sleeper. Each fastener has a radially projecting head at its top end, with the head having a tapered side surface and the sleeve having a countersink for accommodating the fastener head. In a preferred embodiment of the invention, the taper angles of the side surface of the fastener head and the countersink being are set so that when the head is driven into engagement with the top end of the sleeve, the impact force will be transmitted progressively to the sleeve from the fastener, with the radial and axial vectors of the impact force decreasing and increasing respectively with increasing penetration of the fastener. The fasteners are driven into the concrete base by means of a power driver that has a nozzle sized to fit within the counterbores of the holes in the sleeper and a striker bore that is sized to accept the head of a fastener disposed in one of the counterbored holes, whereby the striker of the driver will be aligned with the head of the fastener and the tool will be oriented perpendicularly to the sleeper, as required for optimum driving of the fastener into concrete. The standoff sleeves function as a depth stop to prevent or limit preloading of the resilient pads on the bottom of the sleeper by the driven fasteners. Preferably but not necessarily, the drive stroke of the driver's striker is limited so as to permit it to drive the fastener to a depth that is sufficient to secure the sleeper to the concrete base but not so far as to overload the resilient pads or damage the sleeve. Other features and advantages of the invention are set forth in or rendered obvious by the following detailed description which is to be considered together with the drawings.

THE DRAWINGS

[0017] FIG. 1 is a cross-sectional view in elevation of a sleeper-type flooring system;

[0018] FIG. 2 is a fragmentary side view in elevation of the same floor system;

[0019] FIG. 3 is a fragmentary plan view taken along line 3-3 of FIG. 1;

[0020] FIG. 4 is a an exploded view in elevation, partly in section, of a preferred form of fastener and sleeve provided according to the present invention;

[0021] FIG. 5 is a fragmentary sectional view illustrating a sleeve and fastener in ready position for a fastening operation;

[0022] FIG. 6 is a view similar to FIG. 5 showing a fastener near the end of its travel into a concrete base;

[0023] FIG. 7 is a side view in elevation of a powered driver modified for use in practicing the invention;

[0024] FIG. 8 is a fragmentary elevational view, partly in section, illustrating the nozzle portion of the powered driver of FIG. 7 in exploded relation to a fastener and sleeve used for anchoring a floor system according to the invention; and

[0025] FIG. 9 illustrates another type of floor system with which the invention may be used.

DETAILED DESCRIPTION OF THE INVENTION

[0026] FIGS. 1-3 illustrate a section of a floor system of the type disclosed in U.S. Pat. No. RE37,615. The floor system comprises a plurality of mutually spaced attachment members in the form of wooden sleepers 2 having resilient pads 4 on their bottom side and supporting at least one subfloor layer 6 on their top side. The sleepers are anchored to and supported by a base 8 formed of concrete. Overlying the subfloor layer 6 is a hard wood floor 10 which usually is made up of interlocked tongue and groove maple floorboards. The subfloor layer(s) may take various forms, e.g., as disclosed in U.S. Pat. No. RE37,615 and the prior art listed therein. Typically subfloor layer 6 is formed of 4′×8′ plywood panels and has a uniform thickness of about {fraction (1/2 inch)}. The sleepers 2 typically have a cross-sectional height of about 1.5 inch, and a width of about 2.5 inch, and a length of either 4 or 8 feet. The sleepers are usually spaced apart about 12 inches, although that spacing may vary depending upon their width. The foregoing dimensions are not critical, and hence sleepers having a different height, width, length and spacing may be used.

[0027] The pads 4 are molded from an elastomeric material in order to provide resiliency, vibration dampening and shock absorption for the floor system. The pads may take various shapes without affecting the invention. Thus, for example, the pads may be as illustrated in U.S. Pat. No. 5,388,380, issued Feb. 14, 1995 to Michael W. Niese and U.S. Pat. No. 6,367,217, issued Apr. 9, 2002 to Michael W. Niese et al. The pads may be solid or may be formed with hollow internal volumes or spaces to better permit the pads to deflect in the vertical direction immediately upon impact to the hard wood floorboards 8. The pads are sized to provide a space of predetermined minimum height between the sleepers and the supporting base, typically a height in the range of about 0.5 to about 0.75 inch, under the static weight of the floor system.

[0028] Each sleeper member is provided with at least one and preferably two through bores 14 to accommodate fasteners 16 and standoff sleeves 18 as hereinafter described. A counterbore 20 is coaxial with each bore on the top side of the sleeper, so that each bore has a relatively small diameter bottom section and a relatively large diameter top section. The bottom end of each counter bore has a flat annular surface 22 (FIG. 6).

[0029] According to this invention, the fasteners 16 are formed with a head 24 having a conical side surface and a flat top surface and a shank that has a pointed tip. Referring to FIGS. 4 and 6, preferably the shank is stepped so as to provide a relatively large diameter upper or trailing section 26A and a relatively small diameter lower or leading section 26B, with a short tapered transition section 26C. By way of example but not limitation, the fastener may have an overall length of 2.25 inch, a maximum head diameter of 0.5 inch, an overall shank length of 2 inches, a transition section (26C) length of {fraction (1/32)}-{fraction (1/16)} inch, and diameters of 0.200 inch and 0.190 inch for shank sections 26A and 26B respectively. The larger diameter section 26A serves to provide column strength to the fastener so that it will not buckle when it is impacted against the concrete base by the powered driver as described hereinafter. The smaller diameter section 26B and its pointed tip 27 facilitate piercing of the dense concrete; the tapered transition section facilitates penetration of the concrete by the leading end of shank section 26A. It is preferred, but not essential, that the shank section 26B have a plurality of shallow helical grooves located rearwardly of the point tip section, as indicated at 28 in FIG. 6, to facilitate penetration of the dense concrete under the impact force of a powered driver according to this invention. In order to assure penetration without bending, the fasteners are preferably made of an alloy or special high carbon steel and heat treated to HRc 53/56 hardness.

[0030] The standoff sleeves 18 may be made of various materials. Preferably they are made of a high density plastic such as Delrin® or a high impact plastic such as a high density polyethylene. The sleeves have a cylindrical shape and are characterized by a center bore 30, and a peripheral flange 32 at one end, hereafter caller the top end. Additionally the top end of each sleeve has a conical countersink 34 for bore 30. The height of flange 32, i.e., its dimension measured longitudinally of the, sleeve, is less than the depth of the counterbores 20. The overall length L1 of the sleeve is set so as to be less than the distance between the bottom surface 36 (FIG. 1) of subfloor 6 and the upper surface of base 8 after the floor system has been anchored to the base without precompressing pads 4. Also the length of the portion of each sleeve between flange 32 and its bottom end surface, represented as L2 in FIG. 6, is equal to the combined vertical distance between the annular surface 22 of counterbore 20 and the upper surface 9 of base 8 after the floor has been anchored to the base without precompressing pads 4. Sleeves 18 are formed with the diameter of center bore 30 equal to the diameter of shank portion 26B, so that when the fastener is inserted into the sleeve, it will be held up by shank section 24A being gripped by surface-to-surface contact with the sleeve in bore 30 or by an interference fit between bore 30 and shank transition section 26C, with the result that the head of the fastener will be in a raised or upwardly projecting position relative to the top end of the sleeve. Preferably the sleeve and fastener are sized so that when the sleeve 18 is inserted in a hole 14 with its flange resting on the bottom surface 22 of counterbore 20, and a fastener is inserted in the sleeve, the head and a substantial portion of the shank portion 26A of the fastener will project above the upper surface of the sleeper, as shown in FIG. 5. As a minimum, at least the head of the fastener should project above the head of the sleeper in order to facilitate alignment of the powered driver used to propel the fastener into a concrete base. Preferably also fastener 16 and sleeve 18 are sized so that when the fastener is inserted into sleeve its pointed tip 27 is even with, or just short of being even with, the bottom end surface of the sleeve.

[0031] A suitable form of powered driver is disclosed in U.S. Pat. No. 5,645,208, issued Jul. 8, 1997 to Harry M. Haytayan for “Pneumatic Fastening Tool With Safety Interlock”. The disclosure of that patent is incorporated herein by reference. With reference to the drawings of that patent, the driver illustrated therein includes a nozzle member 6 that is provided with (1) an axially-extending bore 112 that accommodates a hammer 68 (also identified by persons skilled in the art as the “striker”), (2) a side entry port for fasteners carried in strip form by a magazine 8 that is attached to the nozzle member, and (3) a second axially-extending bore 118 that accommodates a spring-biased valve-actuating safety rod 120. Such a device is capable of driving fasteners into concrete with a single impact without any predrilling, with the fasteners having a holding power in the concrete in excess of 1000 lbs., partly as a result of the ball phenomenon described above. Pneumatic drivers embodying the design disclosed in U.S. Pat. No. 5,645,208 are available commercially from Pneutek, Inc. of Hudson, N.H. One such driver is Pneutek Model PT 1100.

[0032] FIG. 7 illustrates a pneumatic driver 40 of the type disclosed in U.S. Pat. No. 5,645,208 and exemplified by Pneutek Model PT 1100, but modified to incorporate a nozzle according to the requirements of the present invention. For the purposes of this invention, a fastener-carrying magazine is not required. Consequently the nozzle does not have a side entry port for fasteners. The bottom end of nozzle 42 has a circular configuration with an outside diameter that is smaller than the diameter of the counterbores 20. Preferably the o.d. of the bottom end of the nozzle is about 0.19 inch less than the diameter of counterbores 20. Referring to FIG. 8, the nozzle has an axial bore 44 for the striker or hammer (not shown) of the driver. Bore 44 is coaxial with the center point of the nozzle's circular end face 46 and has a diameter that exceeds the maximum diameter of fastener head 24 by a small amount, preferably by about {fraction (1/32)} to about {fraction (1/16)} inch. The nozzle has another axially extending bore 48 that accommodates the safety rod 50 of the driver. Bore 48 is eccentric to the center point of end face 46, being formed in a portion of the wall of the nozzle that surrounds bore 44. Rod 50 is biased downwardly by a spring 52 so that normally it projects beyond the end face 46 as shown in FIGS. 7 and 8. Rod 50 is equivalent to and serves the same function as the safety rod 120 disclosed in the aforesaid patent.

[0033] Still referring to FIGS. 7 and 8, the bottom end of the nozzle is provided with a circular recess 56 that is coaxial with bore 44. Recess 56 functions as a counterbore for bore 44. The annular surface 58 that forms the inner end of recess 56 is flat. Recess 56 has a diameter that is slightly greater than the o.d. of flange 32 of sleeves 18, preferably about {fraction (1/32)} to about {fraction (1/16)} inch greater. Preferably the depth of recess 56, i.e., the dimension measured parallel to bore 44, is the same as that of flange 32, but it may differ therefrom by a small amount, e.g., plus or minus {fraction (1/32)} to {fraction (1/16)} inch. As noted above, the diameter of striker bore 44 must be large enough to readily accommodate the fastener head 24 but not so large as to introduce a degree of lateral play that make its difficult to locate the nozzle in a counterbore 20 or will locate the striker axis off center with respect to the fastener head. The length of the striker (not shown) is set so that when the driver is fired, i.e., operated, the striker will move through its downward stroke far enough to cause the end of the striker to be flush with or protrude beyond annular surface 58 of nozzle recess 56 by approximately {fraction (1/32)} inch, whereby to cause the head of the fastener to be seated in countersink 34 and to force the sleeve into tight engagement with base 8.

[0034] With the foregoing apparatus, anchoring of floor systems of the type described in U.S. Pat. No. RE37,615 is greatly facilitated. To anchor a sleeper as herein described and illustrated, a sleeve 18 and a fastener 16 are inserted in one of the holes 14 (FIG. 5). Holes 14 and sleeves 18 are sized so that holes 14 are approximately {fraction (1/32)}″ to approximately {fraction (1/16)}″ larger than the o.d. of the sleeves. The sleeve may be inserted first, followed by the fastener; alternatively and preferably, a fastener 16 and a sleeve 18 are assembled together as shown in FIG. 5 and then inserted into a hole 14. In either case, the bottom end of the sleeve will touch the upper surface 9 of base 8 and the bottom side of flange 32 will engage or nearly engage the surface 22 of the sleeper. Then nozzle 42 of driver 40 is placed over the sleeper so that the head of the fastener extends up into striker bore 44 and flange 32 of sleeve 18 resides in recess 56. When the bottom surface 46 of the nozzle engages the upper surface of flange 32, safety rod 50 will be depressed, activating the driver for operation by the user. With the driver connected to a source of pressurized air, the driver is fired by squeezing its trigger 60. When the driver is fired, the striker of the driver will impact the head of the fastener at a high velocity and with a great downward force, causing the fastener to penetrate concrete base 8. The striker of the driver forces the fastener into the concrete far enough (approximately 1″ to 1½″) to cause its head 24 to be seated in countersink 34 and to lock sleeve 18 tight against the base 8. However, because of the depth-limiting action of the sleeve on the fastener, the fastener is not driven into the concrete so far as to precompress the resilient pads. Further assurance that the fasteners are driven into the concrete the correct amount is provided by the fact that the stroke of the striker is limited as described above. The limited stroke of the striker also eliminates any possibility that the striker will crush the sleeve.

[0035] FIG. 6 also illustrates a preferred relationship of fastener head 24 and counterbore 34. Although satisfactory results are obtained when the angle of taper of the side surface of the fastener head 24 is the same as that of countersink 34 of sleeve 18, it is preferred that the taper angle of the countersink be less than that of the fastener head measured relative to the center axes of the sleeve and fastener. Preferably the countersink has a taper angle of about 60° and the side surface of the fastener has a taper angle of about 82°, as indicated in FIG. 4. The advantage of that arrangement is explained with reference to FIG. 6 which illustrates the position of the fastener as its head first engages the sleeve under the driving force of the striker of driver 40. The first contact between fastener head 24 and the countersink surface 34 is limited, consisting essentially of a circumferential line contact with the force of the fastener head comprising both radial and axial vectors. As the fastener is driven further down into the sleeve, its head deforms the countersink portion of the sleeve radially so as to permit the entire inclined side surface of the head to contact the countersink surface. Essentially the area of contact between the fastener head and the sleeve increases with increasing penetration of the fastener. The difference in taper angle limits the initial contact area and also allows the fastener to move down vertically relative to the sleeve at the beginning of the stroke, thereby limiting the magnitude of the initial shock of impact experienced by the sleeve and consequently reducing the possibility of the sleeve being shattered by the initial impact. This is an important consideration in the case of hard plastic sleeves, since fracture of the sleeve will frustrate the requirement that the compressible pads not be preloaded.

[0036] The invention is not limited in its application to floor systems of the type wherein the floor attachment members are in the form or nailing strips or sleepers that carry the resilient pads. Thus, for example, the invention also is applicable to a hardwood floor system of the type disclosed in U.S. Pat. No. 6,367,217, issued Apr. 9, 2002 to Michael W. Niese et al. for “Sleeper Assembly For Resilient Hardwood Floor System”. FIG. 9 illustrates that system. In this case the system comprises an upper floor wear surface in the form of a plurality of interlocked floorboards 60 supported in spaced relation to the dense supporting base 62 by spaced rows of substructure assemblies 64. Each substructure assembly comprises an elongated panel 66, a pair of spaced rows of compressible pads 68 attached to the bottom surface 70 of the panel adjacent its opposite edges, and corresponding pair of rows of nailing strips 72 secured to the top surface 74 of the panel above the rows of pads. The floorboards are nailed to the substructure assemblies and the latter are secured to the base by fasteners 76 that pass through holes in the panels and are secured in holes in base 62. Each fastener is provided with a shoulder 78 intermediate its opposite ends that functions as a depth stop to limit the depth of fastener penetration into the base and thereby prevents precompression of pads 68 by the downward driving forces applied by the fasteners as they are driven into the base, with pre-drilled holes being required in the case of a concrete base. A lubricating sleeve 80 is disposed in each of the holes in panel 66 in surrounding relation to the fasteners and has a flange 82 that overlies panel 66. The head 84 of fastener 76 is seated against flange 82. The sleeves project down through panel 66 only a limited distance and do not contact the base when the fastener is driven into the base to the extent allowed by depth stop 78. The nailing strips 72 provide an air space 86 between the upper surface 74 of panel 66 and the lower surface 88 of floorboards 60.

[0037] Since substructure assemblies of the type shown in U.S. Pat. No. 6,367,217 are installed first before the floorboards 60 are nailed in place, the present invention makes it possible to anchor them to a hard concrete base without any need for predrilling holes in the base. This is accomplished by replacing fasteners 76 and lubrication sleeves 80 with fasteners 16 and sleeves 18 as illustrated in FIGS. 1 to 6, with the lengths of the fasteners 16 and 18 being adjusted to allow the sleeves to function as depth stops and the fasteners to penetrate the base to a depth sufficient to assure that the heads of the fasteners will force the sleeves into tight engagement with the base without precompressing the resilient pads. As with the sleeper type construction shown in FIG. 1, the sleeves 18 and the holes in each panel 66 are sized so as to provide a clearance of approximately {fraction (1/32)}″ to {fraction (1/16)}″. In both types of floor constructions, the reason for such clearance is to prevent floor squeaking as the floor is subjected to loading and unloading forces.

[0038] Although it is preferred to use fasteners with step-down shanks as shown in FIGS. 4-6, the invention may be practiced with fasteners that have straight shanks, e.g., a shank having a substantially constant diameter except for a pointed leading end. In such case it is preferred that the shank diameter be the same as that of bore 30 so that the shank makes a tight fit in and is gripped by the sleeve. Also, it is preferred that the fastener and sleeve be pre-assembled with the pointed tip of the fastener substantially even with the bottom end of the sleeve. Alternatively, the shank diameter may be slightly smaller than bore 30, in which case the sleeve 18 may be inserted in hole 14 first, and then the fastener may be inserted into bore 30 with its tip engaging the underlying base 8.

[0039] As used herein in relation to resilient support pads 4, the terms “precompressing” and “precompression” are synonymous with “preloading” and are intended to embrace the situation where the pads are essentially not compressed at all by the fasteners, and also the situation where the pads are compressed somewhat as a consequent of the fastening operation but are still capable of further compression to the extent required to allow the floor system to deflect downwardly when impacted within the operating limits contemplated by the parameters of the system. In this context it is recognized that the support pads 4 and 68 are compressed by the weight of the floor components, and such compression is not to be construed as coming within the scope of the term “precompression”.

[0040] The advantages of the invention are obvious and significant. No predrilling of the concrete base is required in order to anchor floor systems with fasteners. Furthermore the invention eliminates the need to use fasteners characterized by a shoulder that functions as a depth stop and fasteners having expansion curves for locking them in pre-drilled holes in a concrete base. The driving of the fasteners is rapid, with the manual labor limited to inserting the sleeves and fasteners in holes in the wooden attachment strips, and positioning and firing the driver. Additionally pneumatic drivers of the type described herein are reliable and easy to use, and a nozzle as shown in FIG. 8 is capable of withstanding the wear and tear encountered in the field. Overall the invention provides a tremendous saving of cost and time while providing anchor strengths far in excess of what has been achieved heretofore in the installation of hardwood floor systems on concrete slabs. Still other advantages will be evident to persons skilled in the art. Moreover, those skilled in the art will readily comprehend the various modifications to which the invention is susceptible.