Abstract:
Fastening system for anchoring wood floors to a base includes a fastener having a pointed distal end and a proximal head end, a sleeve for retaining structural members, the sleeve having a central bore therethrough, a countersink extending from a proximal end of the sleeve coaxially with the central bore, and an annular flange extending outwardly from the sleeve proximal end. The system further includes a driver for driving the fastener through the sleeve bore and into the base, the driver including a nozzle having a bore for receiving the fastener, the nozzle being adapted to enter the sleeve countersink. The driver further includes a hammer disposed in the nozzle and movable to engage the head of the fastener and to drive the fastener into locking engagement with the base, to fix the sleeve to the base, and thereby fix the structural members to the base.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This is a continuation-in-part of application Ser. No. 10/301,262, filed Nov. 21, 2002, in the name of Harry M. Haytayan, incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to the installation of wood floors and more particularly to an improved fastening system for anchoring such floors to a base made of concrete or like material.  
       BACKGROUND OF THE INVENTION  
       [0003]     Wood 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 of concrete or like material to which it is secured in order to reduce injuries. Accordingly, a number of different floor systems have been designed to provide appropriate floor deflection and resiliency. Such floor systems typically 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, usually 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 and 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.  
         [0004]     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 and expulsion of moisture, with a resultant expansion and contraction. The effect of humidity changes on the dimensional stability of the floor system is reduced by the free space inasmuch as the latter limits moisture transfer between the base and the supported components.  
         [0005]     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 herein by reference.  
         [0006]     In the construction disclosed and claimed in U.S. Pat. No. RE37,615, a plurality of mutually spaced sleepers  20  ( FIGS. 1 and 2 ) in the form of elongated nailing members are used with a subfloor layer  22  for supporting a layer of hardwood floorboards  24  that serve as a wear surface. One or more of the subfloor layers  22  are interposed between the sleepers  20  and the hardwood wear surface  24 . The sleepers  20  also include compressible supporting pads  26 , e.g., pads made of a suitable elastomer. In the floor system disclosed in the aforesaid patent, a fastening arrangement  30  is used to secure the sleepers  20  directly to a base  28  so that (a) the pads  26  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  20  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  30  includes holes  32  with counterbores  44  in the sleepers  20 , floor-anchoring fasteners  34  with heads  40  that extend through the counterbored holes  32  into the base  28 , and means  36  for limiting the depth of penetration of the fasteners  34  into the base  28  so that the downward driving forces applied via the fasteners do not precompress the elastomer pads  26 . As disclosed in U.S. Pat. No. RE37,615, cited supra, the means  36  comprises a cylindrical sleeve  36  which may but need not have an integral flange  42  (as shown in  FIG. 9  of the patent) or be used with a separately formed flange in the form of a circular washer ( FIG. 1 ). Counterbore  44  is sized to accommodate fastener head  40  and also flange  42 .  
         [0007]     Floor systems similar to the type shown and described in 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 the fasteners  34  into predrilled holes  38  in the base  28  or by driving the 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 functions as a depth stop and an expansion curve adjacent the 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 United States 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 of the fastener. The fasteners are driven into the predrilled holes by manually impacting them with a hammer.  
         [0008]     Manually driving a fastener into dense concrete without predrilling a hole to accommodate the fastener cannot be done, 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 unsatisfactory. When 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 which 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&#39;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.  
         [0009]     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 in U.S. Pat. No. RE37,615 was not feasible. The primary problem stems from the counterbored holes  32  in the sleepers  20 . The counterbored holes  32  are designed to accommodate heads  40  of the fasteners  34  so they will not protrude above the sleepers where they can interfere with the subfloor members  22  carried by the sleepers, particularly when the floor system is deflected downwardly under impact. The counterbores  44  serve to provide a recessed seat for the flanges  42 .  
         [0010]     However, the requirement that the heads  40  of the fasteners (and also the flanges  42  of the lubricating sleeves  36  when used) be recessed in the counterbored holes  32  has made it difficult to use a power driver. The need to recess the heads of the fasteners in the counterbored holes  32  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  26 . The counterbored holes  32  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  28 . This centering problem is complicated by the fact that in actual practice the lubricating sleeves  36  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 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.  
         [0011]     Because of these problems, there has been lacking a satisfactory and reliable way to secure the sleepers of the form disclosed in the aforesaid 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.  
         [0012]     One solution that has been advanced is described in my copending application Ser. No. 10/301,262, cited supra. The invention described in that application constitutes a substantial improvement over the prior art in that it facilitates use of a power driver. The present invention constitutes an improvement over the invention disclosed in my copending application Ser. No. 10/301,262.  
       OBJECTS AND SUMMARY OF THE INVENTION  
       [0013]     The primary object of this invention is to improve upon the invention disclosed in my copending application Ser. No. 10/301,262.  
         [0014]     Another object of this invention is to provide an improved fastening system and method for anchoring a wood floor to a concrete base with fasteners, without the need for predrilling holes for the fasteners.  
         [0015]     A more specific object is to provide an improved fastening system and method for anchoring to a concrete base floor assembly sleepers of the type that have counterbored holes to accommodate fasteners.  
         [0016]     Another object is to provide a novel and improved fastening system arrangement for anchoring hardwood floors.  
         [0017]     A further object is to provide a novel and improved fastener arrangement comprising a fastener and a hard plastic standoff sleeve for the fastener, the sleeve being adapted to withstand fracture by the fastener when the fastener is impacted by the hammer of a power driver.  
         [0018]     The foregoing and other objects of the invention are achieved by providing a fastening system including a sleeve and fastener arrangement for anchoring a sleeper of the type described hereinabove to a concrete base, and a power driver for driving the fastener into the concrete base. The sleeves are sized to fit loosely in counterbored holes preformed in the sleeper. Each sleeve has a center bore for accommodating the shank of the fastener, a larger bore for receiving a nozzle of a power driver, and a peripheral flange at its top end that is sized to fit within the sleeper counterbore. Also, in relation to the associated fastener, the sleeve has an effective length that enables the sleeve to function as a depth stop that prevents the fastener from pre-compressing resilient pads of the sleeper. Each fastener has a radially projecting head at its top end. The fasteners are driven into the concrete base by means of a power driver provided with a nozzle sized to fit within the larger bore in the sleeve and a hammer bore that is sized to accept the head of a fastener disposed in one of the sleeve center bores, whereby the hammer 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 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. The drive stroke of the driver&#39;s hammer may be limited so as to permit the hammer 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.  
         [0019]     In accordance with a further feature of the invention, there is provided a fastening system and method for anchoring wood floors to a supporting base. The system comprises a fastener having a shank, a pointed distal end, and a proximal head end having an enlarged diameter head with a flat proximal surface, a sleeve for retaining floor assembly structural members to the base, the sleeve having a central bore therethrough, a countersink extending from a proximal end of the sleeve coaxially with the central bore, and an annular flange extending outwardly from the sleeve proximal end. The system further comprises a driver for driving the fastener through the sleeve countersink and the sleeve bore into the supporting base. The driver comprises a nozzle having a bore for receiving the fastener, with the nozzle being adapted to enter the sleeve countersink. The driver further comprises a hammer movably disposed in the nozzle bore and movable to engage the flat surface of the head of the fastener and to drive the fastener into locking engagement with the base, whereby to fix the sleeve to the base, and thereby anchor the floor assembly structural members to the base.  
         [0020]     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  
       [0021]      FIG. 1  is a cross-sectional view of a known sleeper-type flooring system;  
         [0022]      FIG. 2  is an exploded perspective view of the same floor system;  
         [0023]      FIG. 3  is a partly sectional partly elevational view of a fastener and sleeve arrangement for use in the flooring system of  FIGS. 1 and 2 ;  
         [0024]      FIG. 4  is a an exploded view, partly in elevation and partly in section, of a preferred form of fastener and sleeve provided according to the present invention;  
         [0025]      FIG. 5  is a sectional view illustrating the sleeve and fastener of  FIG. 4  in ready position for a fastening operation;  
         [0026]      FIG. 6  is a side elevational, partly sectional view showing a known fastener driving tool;  
         [0027]      FIG. 7  is a side elevational, partly sectional, partly broken-away view of a modified form of the nozzle for the driving tool of  FIG. 6  as adapted for use in practicing the invention;  
         [0028]      FIG. 8  is a side elevational, partly sectional, partly broken-away view illustrating the nozzle of the driving tool of  FIG. 7 , a fastener and fastener-receiving sleeve in relation to a floor system that is to be anchored by the fastener and sleeve;  
         [0029]      FIG. 9  is a sectional view in elevation showing a sleeve and fastener after the fastener has been driven into a floor-supporting base;  
         [0030]      FIG. 10  is similar to  FIG. 9 , but illustrative of an alternative embodiment;  
         [0031]      FIG. 11  is a sectional view illustrating another known type of floor system with which the invention may be used; and  
         [0032]      FIG. 12  is similar to  FIG. 11 , but illustrative of the present invention applied to the floor system of  FIG. 11 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]      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 the wooden sleepers  20  having the resilient pads  26  on their bottom sides and supporting at least one subfloor layer  22  on their top sides. The subfloor layers are secured to the sleepers by nails or other fasteners  21 . The sleepers  20  are anchored to and supported by the base  28 , typically formed of concrete. Overlying the subfloor layer  22  is the wood floor  24  which usually is made up of interlocked tongue and groove maple floorboards that are anchored to the subfloors by fasteners  25 . The subfloor layer(s)  22  may take various forms, e.g., as disclosed in U.S. Pat. No. RE37,615 and the prior art listed therein. Typically, the subfloor layer  22  is formed of 4′×8′ plywood panels and has a uniform thickness of about ½inch. The sleepers  20  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.  
         [0034]     The pads  26  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 wood floorboards  24 . 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.  
         [0035]     Each of the sleeper members  20  is provided with at least one, and usually two or more of the through holes  32  to accommodate the fasteners  34  and standoff sleeves  36 . A counterbore  44  is coaxial with each hole  32  on the top side of the sleeper, so that each hole has a relatively small diameter bottom section  32  and a relatively large diameter top section  44 . The bottom end of each counter bore has a flat annular surface  46 .  
         [0036]     Referring to  FIGS. 4 and 5 , it will be seen that according to this invention, the fasteners  34  are essentially nails, being formed with a head  40  having a flat top surface and a shank  48  that has a pointed tip  50 . Preferably, the shank  48  is stepped so as to provide a relatively large diameter upper or trailing section  52  and a relatively small diameter lower or leading section  56 , with a short tapered transition section  54 . By way of example but not limitation, the fastener  34  may have an overall length of about 1⅜- 1 ½inch, a head diameter of about 1/2 inch and a head thickness of about 0.150 inch, a transition section  54  length of approximately ⅛ inch and diameters of 0.200 inch and 0.190 inch for shank sections  52  and  56  respectively. The larger diameter section  52  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, described hereinafter. The smaller diameter section  56  and its pointed tip  50  facilitate piercing of the dense concrete, and the tapered transition section  54  facilitates penetration of the concrete by the leading end of trailing shank section  52 . It is preferred, but not essential, that the shank section  56  have a plurality of shallow helical grooves (not shown herein, but shown in  FIG. 6  of my aforementioned application Ser. No. 10/301,262,) located rearwardly of the point tip  50 , 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.  
         [0037]     Still referring to  FIGS. 4 and 5 , the sleeves  36  may be made of various materials. Preferably, they are made of a high density plastic such as Delrin® a high impact plastic such as a high density polyethylene. The sleeves  36  are of a cylindrical shape and are characterized by a center bore  60 , and a peripheral flange  62  at one end  64 , herein referred to as the top end. Additionally, each sleeve  36  has a counterbore  66  for bore  60  at its top end  64  to serve as a countersink for the top end of the fastener. The height of the flange  62 , i.e., its dimension measured longitudinally of the sleeve, is less than the depth of the sleeper counterbore  44 . The length of the sleeve  36  is such that the sleeve projects through the sleeper  20  and into engagement with the concrete base  28 , while the sleeve flange  62  engages the upper surface  72  of the base  28 .  
         [0038]     More specifically the overall length L 1  of the sleeve  36  is less than the distance between a bottom surface  70  ( FIG. 1 ) of the subfloor  22  and an upper surface  72  of the base  28  after the floor system has been anchored to the base without precompressing the pads  26 . Also, the length of the portion of each sleeve between flange  62  and its bottom end surface  68 , represented as L 2  in  FIG. 4 , is equal to the combined vertical distance between the annular bottom surface  46  of sleeper counterbore  44  and the upper surface  72  of base  28  after the floor has been anchored to the base without precompressing the pads  26 . The outside diameters of each sleeve  36  and its flange  62  are sized so as to provide a clearance with the sleeper holes  32  and its counterbore  44  respectively. Such clearance is desired to allow the sleepers and the supported flooring members to move vertically under changing loads and also to avoid squeaking due to friction when the flooring members move vertically. Preferably the clearances are between about 0.040 and about 0.060 inch.  
         [0039]     According to the preferred mode of practicing the invention (hereinafter the “automatic mode”), only the sleeves are pre-positioned in the sleeper holes  32  and the nails are fed from a magazine attached to the powered driver that is used to drive the fastener into the underlying base, as described hereinafter However, it is contemplated that the sleeves  36  and the fasteners  34  may be pre-positioned manually in the counterbored sleeper holes  32 , with the powered driver then being used to drive the fasteners into the underlying base (hereinafter the “manual mode”).  
         [0040]     In the manual mode, the fasteners  34  may be pre-assembled to the sleeves  36  before the sleeves are inserted into sleeper holes  32  or each fastener may be inserted into a sleeve after the sleeve has been inserted into a sleeper hole. If the invention is practiced in the manual mode, the driver may but need not have a fastener-carrying magazine, in which case the nozzle  82  does not have the side entry port  88  for fasteners. In view of the manual mode option, the sleeves  36  may be formed with the diameter of center bore  60  equal to the diameter of shank portion  56 . With this size arrangement (which is suitable for the automatic as well as the manual mode of operation), when the fastener  34  is pre-positioned within the sleeve  36  as required for the manual mode, its shank section  56  will be gripped by surface-to-surface contact with the sleeve in bore  60 , with the result that the fastener will be held straight (i.e. coaxial with the sleeve) in the manner illustrated in  FIGS. 5 and 8 , thereby facilitating driving of the fastener by the powered driver.  
         [0041]     Further with respect to the manual mode of operation, the sleeve and fastener are sized so that when the sleeve  36  is inserted in a sleeper hole  32  with its flange  62  resting on the bottom surface  46  of sleeper counterbore  44 , and a fastener is inserted in the sleeve, the head  40  and a substantial portion of the shank portion  52  of the fastener project above the upper surface of the sleeper, in the manner shown in  FIGS. 5 and 8 , thereby facilitating alignment of the driver nozzle with sleeve and fastener. As a minimum, at least the head  40  of the fastener should project above the upper surface  74  of the sleeper  20  in order to facilitate alignment of the powered driver used to propel the fastener into the concrete base  28 . It also is preferred that the fastener  34  and sleeve  36  be sized so that when the fastener is inserted into and gripped by the sleeve, the pointed tip  50  of the fastener is even with, or just short of being even with, the bottom end surface  68  of the sleeve.  
         [0042]     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.  FIG. 6  disclosed a driver  80  as disclosed in the patent. That driver includes a bottom member  81  that comprises a nozzle  82  having an axially-extending bore  84  that accommodates a hammer  86  (see  FIG. 7 ), which also is identified by persons skilled in the art as a “striker”), (2) a side entry port  88  for fasteners  34  carried in strip form by a magazine (see magazine  90  in  FIG. 7 ) that is attached to the nozzle member, and (3) a second axially-extending bore  92  that accommodates a spring-biased valve-actuating safety rod  94 . The bore  92  is formed in a portion of the wall of nozzle  82  that surrounds and defines bore  84 . Bore  92  extends through and in non-concentric relation with the bottom end face  100  of the nozzle. As shown in  FIG. 6 , safety rod  94  normally projects out of the bottom end face  100  of nozzle  82 . Such a driver 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 a well-known ball phenomenon described in my copending application Ser. No. 10/301,262, cited supra. 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.  
         [0043]     Referring to  FIGS. 7 and 8 , for the purposes of this invention the powered driver, e.g., a Pneutek Model PT 1100, is provided with a modified form of bottom member  81  wherein the nozzle  82  has a bottom end section  96  characterized by a cylindrical outer surface terminating in an annular end face  100 . The cylindrical section  96  has an outside diameter that is smaller than the diameter of the countersinks  66  of sleeves  34 , so as to permit it to be inserted into those countersinks. However, the outside diameter of bottom end section  96  is not so large as to introduce a degree of lateral play that makes it difficult to center the nozzle in countersinks  66 , since in the manual mode an off-center nozzle may result in the hammer  86  striking the head of the pre-positioned fastener off center; and in the automatic mode an off-center nozzle may result in the fastener being misaligned with the sleeve center hole  60 , both situations being undesirable for obvious reasons. Preferably, the outside diameter of the bottom end section  96  of the nozzle  82  is about 0.015 to 0.036 inch less than the diameter of the countersinks  66 . The driver nozzle bore  84  is coaxial with the center axis  98  of the nozzle&#39;s circular and annular end face  100  and has a diameter that exceeds the diameter of the fastener head by a small amount, so as to readily accommodate the fastener head  40 . Preferably the bore  84  diameter exceeds the maximum diameter of the fastener head  40  by about 0.015 to 0.021 inch.  
         [0044]     A bore  92  for safety rod  94  is formed in the upper section of nozzle  82  eccentric to the bottom end section  96 , so that the safety rod extends down along side of and close to the cylindrical outer surface of nozzle bottom section  96 , whereby the outer or bottom end of the rod can engage the flange  62  of a sleeve  34  into which the nozzle is inserted. Rod  94  is biased outwardly by a spring  102 . In its normal at-rest (extended) position under the influence of spring  102 , the outer or bottom end of rod  94  does not project beyond the end face  100 , but instead it is located short of that end face so that nozzle end section  96  may be inserted into countersink  66  of a pre-positioned sleeve  34  before the safety rod can engage the flange  62  of that sleeve. Additionally the relationship between the end face  100  of the nozzle and the end of safety rod  94  is such that when the rod engages flange  62 , the end face  100  will be spaced from the bottom end wall  59  of the countersink  66  by a distance substantially equal to or less than the distance that the safety rod needs to be retracted in order to place the driver in condition for firing. By way of example but not limitation, if the depth of countersink  66  is 0.88 inch and the safety rod needs to be retracted 0.25 inch in order to place the driver in condition for firing, in its normal at rest position the outer end of safety rod  94  may be 0.50 inch behind end face  100 .  
         [0045]     In the automatic mode, the sleeves are pre-positioned in the holes  32  of a sleeper, and the driver has a magazine  90  ( FIG. 7 ) that carries a strip of fasteners  34 . The driver is then inserted into a pre-positioned sleeve and then fired, whereupon a fastener is driven through the sleeve hole  60  into the substrate or base  28 , with the fastener and sleeve being in the anchored relationship shown in  FIG. 9 . In the manual mode of operation, each sleeve is pre-positioned with a fastener inserted therein, in the manner shown in  FIG. 5 , and then the driver nozzle is inserted into the sleeve counter bore  66  with the fastener extending up into the hammer bore  84 , after which the driver is fired to cause the fastener to be driven into the base  28  as shown in  FIG. 9 .  
         [0046]     When a sleeve  36  is inserted into a hole  32  in a sleeper  20  or other member of like purpose, the bottom end of the sleeve will engage or be in near engagement with the base  28 . When subsequently the bottom end section  96  of driver nozzle  82  is inserted into the sleeve countersink  66 , the spring-biased safety rod  94  will engage the sleeve flange  62 . The spring  102  acts on rod  94  to resist intrusion of the nozzle into the sleeve. Preferably the stiffness of spring  102  is such that the driver needs to be pushed down against the plastic sleeve flange  62  with moderate manual force in order to depress the safety rod  94  far enough to place the driver in condition for firing.  
         [0047]     In both the automatic and manual modes of operation, the sleeves are pre-positioned in the sleeper holes  32 . It is preferred that when a sleeve is inserted into a sleeper hole  32 , the bottom end  68  of the sleeve  36  will touch the upper surface  72  of the base  28  and the bottom side of the sleeve flange  62  will engage, or nearly engage, the surface  46  of the sleeper center bore  44 . In both modes the driver nozzle is inserted into the countersink  68  of a pre-positioned sleeve and the safety rod engages the flange  62  of that pre-positioned sleeve. In the manual mode the head  40  of the fastener extends up into the nozzle bore  84 . In the automatic mode, a fastener  34  fed from the magazine  90  is pre-positioned in hammer bore  84 , and when the driver is fired its hammer  86  impacts that pre-positioned fastener and drives it down along bore  84  into the pre-positioned sleeve.  
         [0048]     In both modes, when the driver is fired, the hammer  86  of the driver impacts the head  40  of the fastener at a high velocity and with great force, causing the fastener to penetrate the underlying hard and dense base  28 , whereby the fastener and the surrounding sleeve serve to position and anchor the sleeper to the base. The hammer  86  of the driver forces the fastener  34  into the concrete base  28  far enough to cause the fastener head  40  to be seated against the bottom wall  59  of countersink  66  and to lock the sleeve  36  tight against the base  28 . However, because of the depth-limiting action of the sleeve  36  with respect to the sleeper, the fastener  34  cannot be driven into the concrete so far as to precompress the resilient pads  26 . Further assurance that the fasteners are driven into the concrete the correct amount is provided by the fact that the stroke of the hammer  86  is limited. The limited stroke of the hammer also substantially eliminates any possibility that the hammer will crush the sleeve.  
         [0049]     With the foregoing apparatus, anchoring of floor systems of the type described in U.S. Pat. No. RE37,615 is greatly facilitated. The automatic mode using a magazine type driver is preferred over the manual mode not only because of time saving and convenience, but because the manual mode requires a higher air pressure supply for the driver tool than does the magazine type. That is because In the magazine type the mass of the fastener (pre-positioned in the hammer bore by action of the magazine) is effectively added to the mass of the hammer during the driving action, providing a more forceful impact for a given air pressure supply.  
         [0050]     Referring to  FIG. 10 , it will be seen that the fastener may be provided with a smaller head  40  and a washer  58  placed inside the countersink  66  of the plastic sleeve  36  and in engagement with a bottom end wall  59 . The washer  58  is engaged by the fastener head  40  when the fastener  34  is driven into the base  28 . The washer  58  effectively increases the diameter of the fastener head  40 , assuring adequate bearing area for locking the sleeve  36  to the base  28 .  
         [0051]     The invention is not limited in its application to floor systems of the type wherein the floor attachment members are in the form of nailing strips, or sleepers, that carry the resilient pads. For example, the invention also is applicable to a wood 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. 11  illustrates that system. In this case, the system comprises an upper floor wear surface in the form of a plurality of interlocked floorboards  110  supported in spaced relation to the dense supporting base  112  by spaced rows of substructure assemblies  114 . Each substructure assembly  114  comprises an elongated panel  116 , a pair of spaced rows of compressible pads  118  attached to the bottom surface  120  of the panel  116  adjacent its opposite edges, and a corresponding pair of rows of nailing strips  122  secured to the top surface  124  of the panel  116  above the rows of pads  118 . The floorboards  110  are nailed to the substructure assemblies  114  and the latter are secured to the base  112  by fasteners  126  that pass through holes  128  in the panels  116  and are secured in holes  130  in base  112 . Each fastener  126  is provided with a shoulder  132  intermediate its opposite ends that functions as a depth stop to limit the depth of fastener penetration into the base  112 , and thereby prevents precompression of the pads  118  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  136  is disposed in each of the holes  128  in the panel  46  in surrounding relation to a fastener and has a flange  138  that overlies the panel  116 . A head  134  of the fastener  126  is seated against the flange  138 . The sleeves  136  project down through the panel  116  only a limited distance and do not contact the base  112  when the fastener is driven into the base to the extent allowed by depth stop  132 . The nailing strips  122  provide an air space  140  between the upper surface  124  of the panel  116  and a lower surface  142  of floorboards  110 .  
         [0052]     Since substructure assemblies  114  of the type shown in U.S. Pat. No. 6,367,217 are installed first before the floorboards  110  are nailed in place, the present invention makes it possible to anchor the substructure assemblies  114  to the hard concrete base  112  without any need for predrilling holes in the base. Referring to  FIG. 12 , this is accomplished by replacing fasteners  126  and lubrication sleeves  136  with the fasteners  34  and sleeves  36  illustrated in  FIGS. 4, 5  and  12 , with the lengths of the fasteners and sleeves being adjusted to allow the sleeves  36  to function as depth stops and the fasteners to penetrate the base  112  to a depth sufficient to assure that the heads  40  of the fasteners force the sleeves into tight engagement with the base without precompressing the resilient pads  112 . As with the application of the invention to the sleeper type construction shown in  FIG. 1 , the sleeves  36  and the holes  128  in each panel  116  ( FIG. 12 ) are sized so as to provide a clearance of approximately 0.040 to 0.060 inch. 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. The holes  128  may be provided with countersinks as shown in  FIG. 12  to accommodate the flanges of sleeves  34 . Alternatively, the holes need not have countersinks, in which case the flanges may extend over and engage the upper surface of the panels  116  in the manner shown in  FIG. 3  of U.S. Pat. No. 6,367,217, cited supra.  
         [0053]     Although it is preferred to use fasteners with step-down shanks  48  as shown in  FIGS. 4 and 5 , the invention may be practiced with fasteners that have straight shanks, e.g., a shank having a substantially constant diameter except for the pointed tip  50 , as shown in  FIG. 12 . In such case, it is preferred that at least for the manual mode of operation, the shank diameter be the same as that of bore  60  so that the shank makes a tight fit in and is gripped by the sleeve and that its length of the fastener be such that its head protrudes above the flange  64 , in the manner shown in  FIG. 5 . Further with respect to the embodiment of  FIG. 12 , in the manual mode, when the fastener and sleeve are pre-assembled, it is preferred that the pointed tip of the fastener be substantially even with the bottom end of the sleeve. Of course, the shank diameter may be slightly smaller than sleeve bore  60 , in which case the sleeve  36  may be inserted in the sleeper hole  32  first, and then the fastener may be inserted into the sleeve bore  60  with the tip  50  thereof engaging the underlying base  28  or  112 .  
         [0054]     As used herein in relation to the resilient support pads  26 ,  118 , 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 consequence 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  26  and  118  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”.  
         [0055]     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 the nozzle  82 , as shown in  FIGS. 6-8 , is capable of withstanding 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.