USRE42207E1 - Masonry anchor device - Google Patents

Abstract

An improved anchor device or fastening member which is particularly suited for use in the attachment of various fixtures and equipment to masonry, concrete, and other hard and/or friable substrates includes a head and a shank depending therefrom. The shank has a first threaded portion having a predetermined thread angle and a predetermined hardness, and a second threaded portion having a predetermined thread angle and a predetermined hardness. The first threaded portion is proximate to the head and the second threaded portion extends from the first threaded portion. The thread angle of the first threaded portion is different than the thread angle of the second threaded portion. In addition, the hardness of the first threaded portion is softer than the hardness of the second threaded portion. This provides for a more ductile anchorage when the fastening member is engaged with the substrate.

Description

BACKGROUND OF THE INVENTION

This invention is generally directed to a novel anchor device or fastening member which is particularly suited for use in the attachment of various fixtures and equipment to masonry, concrete, and other hard and/or friable substrates.

The prior art in one-piece, masonry tapping fasteners have uniform thread forms throughout the entire length of the fastener. They are typically heat treated to a case hardened metallurgical structure. These masonry tapping fasteners have failed for a variety of reasons, such as stripping out during the installation process, brittle failure while resisting the applied loads, and premature failure due to embrittlement and stress corrosion. As a result, users of these fasteners have been required to use other styles of fasteners that have exhibited better load versus displacement characteristics than that of a masonry tapping fasteners. These fasteners also back out of the substrate with relative ease in applications involving dynamic loads and system vibrations.

The present invention provides an anchor device or fastening member which overcomes the problems presented in the prior art and which provides additional advantages over the prior art, such advantages will become clear upon a reading of the attached specification in combination with a study of the drawings.

OBJECTS AND SUMMARY OF THE INVENTION

A general object of the present invention is to provide a novel fastening member which is particularly suited for use in the attachment of various fixtures and equipment to masonry, concrete, and other hard and/or friable substrates.

An object of the present invention is to provide a fastening member which produces a higher torque differential between the tapping torque of the thread and the strip-out torque of the fastening member, thereby resulting in a fastening member that has more inherent reliability, and the capability of being used in a wider variety of substrates versus the prior art.

Another object of the present invention is to provide a fastening member which has less overall axial movement per unit load, while resisting withdrawal forces.

Yet another object of the present invention to provide a fastening member which imparts higher radial loads on the substrate which results in large spall cones and generally higher pullout values in masonry.

A further object of the present invention is to provide a fastening member which provides a more uniform stress distribution at the surface and the upper regions of the substrate.

Yet a further object of the present invention is to provide a fastening member which has a higher resistance to dynamic loads, and system impacts and vibrations.

An even further object of the present invention is to provide a fastening member which provides an overall more ductile anchorage.

Briefly, and in accordance with the foregoing, the present invention discloses a fastening member which is particularly suited for use in the attachment of various fixtures and equipment to masonry, concrete, and other hard and/or friable substrates. The fastening member includes a head and a shank which depends therefrom. The shank has a first threaded portion having a predetermined thread angle and a predetermined hardness, and a second threaded portion having a predetermined thread angle and a predetermined hardness. The first threaded portion is proximate to the head and the second threaded portion extends from the first threaded portion. The thread angle of the first threaded portion is different than the thread angle of the second threaded portion. In addition, the hardness of the first threaded portion is softer than the hardness of the second threaded portion. This provides for a more ductile anchorage when the fastening member is engaged with the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The organization and manner of the structure and operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings, wherein like reference numerals identify like elements in which:

FIG. 1 is a side elevational view of a fastening member which incorporates the features of the invention;

FIG. 2 is a partial, enlarged side elevational view of the fastening member ofFIG. 1; and

FIG. 3 is a cross-sectional view of the fastening member alongline3—3 of FIG.1.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

While the invention may be susceptible to embodiment in different forms, there is shown in the drawings, and herein will be described in detail, a specific embodiment with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated and described herein.

The present invention provides a novel anchor device or fasteningmember20 which is particularly suited for use in the attachment of various fixtures and equipment to masonry, concrete, and other hard and/or friable substrates (not shown). The fasteningmember20 may be a screw.

The fasteningmember20 includes ahead22 which has ashank24 depending therefrom. Thehead22 may take a variety of forms and is dependant on the application. As shown inFIG. 1, theshank24 includes anunthreaded portion26 which extends from thehead22, a first threadedportion28 which extends from theunthreaded portion26, a second threadedportion30 which extends from the first threadedportion28, and acentering point32 which extends from the second threadedportion30. Thehead22, theunthreaded portion26 and the first threadedportion28 form afirst zone34 of thefastening member20. The second threadedportion30 and thecentering point32 form asecond zone36 of thefastening member20.

Thethreads40 of the first threadedportion28 and thethreads42 of the second threadedportion30 are helical and have a substantially constant major diameter, minor diameter and pitch. As shown inFIG. 2, thethreads42 of the second threadedportion30 have a smaller crest width than thethreads40 of the first threadedportion28. As shown, thethreads42 of the second threadedportion30 have a crest width of approximately two-thirds of the crest width of thethreads40 of the first threadedportion28. Thethreads42 of the second threadedportion30 have a smaller volume than thethreads40 of the first threadedportion28.

Eachthread40 of the first threadedportion28 has apredetermined thread angle44, and eachthread42 of the second threadedportion30 has apredetermined thread angle46 which is different than thethread angle44 of thethreads40 of the first threadedportion28. Thethread angle44 of thethreads40 of the first threadedportion28 is three to seven degrees less than thethread angle46 of thethreads42 of the second threadedportion30. The preferred difference is five degrees. The type of material used for the substrate dictate what thread angle is used.

As shown in the drawings, thethreads42 of the second threadedportion30 are at a relativelysharp thread angle46, indicated at forty-five degrees, and thethreads40 of the first threadedportion28 are at fortydegrees thread angle44. It is to be understood, however, thatother thread angles44,46 can be used. For example, a fifteendegree thread angle46 can be used in the second threadedportion30 and a tendegree thread angle44 can be used in the first threadedportion28; a thirty-sevendegree thread angle46 can be used in the second threadedportion30 and a thirtydegree thread angle44 can be used in the first threadedportion28; a sixty-fivedegree thread angle46 can be used in the second threadedportion30 and a sixty-twodegree thread angle44 can be used in the first threadedportion28, and the like. Thethread angles44,46 in the first and second threadedportions28,30 is adjusted based upon the type of substrate with which the fasteningmember20 is being engaged.

In addition, thehead22, theunthreaded portion26 and the first threadedportion28 which form thefirst zone34 of thefastening member20 have a predetermined hardness as measured on the Rockwell “C” scale, and the second threadedportion30 and thecentering point32 which form thesecond zone36 of thefastening member20 have a predetermined hardness as measured on the Rockwell “C” scale which is different than the hardness of thefirst zone34. In particular, thethreads40 of the first threadedportion28 have a hardness as measured on the Rockwell “C” scale which is different than the hardness as measured on the Rockwell “C” scale of thethreads42 of the second threadedportion30. The hardness as measured on the Rockwell “C” scale of the components of thefirst zone34 is softer than the hardness as measured on the Rockwell “C” scale of the components of thesecond zone36. The components of thesecond zone36 are selectively heat treated to provide the higher hardness level than the components of thefirst zone34. The arrangement increases the holding strength when the fasteningmember20 is engaged with the substrate. The components in thefirst zone34, and in particular thethreads40 of the first threadedportion28, are approximately twenty points softer as measured on the Rockwell “C” scale than the components of thesecond zone36, and in particular thethreads42 in second threadedportion30. For example, the components in thefirst zone34, and in particular thethreads40 of the first threadedportion28, can have a hardness of twenty-five as measured on the Rockwell “C” scale, while components of thesecond zone36, and in particular thethreads42 in second threadedportion30, have a hardness of forty-five as measured on the Rockwell “C” scale. For masonry and other like substrates, it is required that thethreads42 of the second threadedportion30 maintain at least a hardness of forty-five as measured on the Rockwell “C” scale. For other softer, yet friable substrates, this minimum hardness may not be required, and the minimum hardness differential may be different than forty-five as measured on the Rockwell “C” scale.

As such, thethreads42 of the second threadedportion30 are harder and much sharper than thethreads40 of the first threadedportion28. Therefore, thethreads42 of the second threadedportion30 will cut into the substrate, such as concrete which is brittle, and form a female thread form. Once thethreads40 of the first threadedportion28 are engaged with the thread form as cut with thethreads42 of the second threadedportion30, because thethreads40 of the first threadedportion28 are softer than thethreads42 of the second threadedportion30, thethreads40 of the first threadedportion28 compress against the substrate and the threads of the first threadedportion28 are compressed by the walls of the female thread form. Thethreads40 of the first threadedportion28 deform the substrate between the threads of the substrate thus, providing higher installation torque which provides a tactile feel during installation, and less tendency to fracture the substrate. In testing of this fasteningmember20 versus the prior art, a twenty-one percent increase in the pullout force from a concrete test block was found.

Because thethreads40 of the first threadedportion28 are heat treated to provide a more ductile, more malleable thread then thethreads42 of the second threadedportion30, and because the geometry (that is, wider crest width and higher volume thread) of thethreads40 of the first threadedportion28 provide a thread form that conforms more closely with the thread form that is tapped in the substrate by thethreads42 of the second threadedportion30, thethreads40 of the first threadedportion28 provide a more uniform stress distribution at the surface and the upper regions of the substrate and provide increased resistance to axial movement during withdrawal loads. This results because of the more intimate fit between the fasteningmember20 and the tapped thread form in the substrate throughout the entire length of thefastening member20.

Because of the friable nature of tapped threads in masonry, and because of the relatively high speed tapping that is typically employed in the installation of thefastening member20, it has been observed that the resultant threads tapped into the masonry substrate are not of a true or perfect form, especially near the surface and upper area of the anchorage, where the tapping threads make multiple rotations. These multiple rotations break down the initial thread form produced by the sharper crested, lower volume,harder threads42 provided in the second threadedportion30 of thefastening member20. Upon tapping the substrate, the tapped threads in an upper zone thereof spall and crush, and the resulting tapped thread is rough and less defined. The wider crested, higher volume, moremalleable threads40 provided in the first threadedportion28 of thefastening member20, tend to fill and conform to these more erratically shaped tapped threads found in the upper zone of the substrate.

By contrast, the bottommost thread in the tapped masonry is made in the last revolution of thefastening member20 and is therefore inherently more defined, and more representative of the thread of thefastening member20 in that zone. Thefastening member20 of the present invention produces an anchorage in masonry substrates and friable substrates that maintains a tighter, more intimate fit throughout the entire length of the threadedportion28,30 of thefastening member20 than the prior art fastening members. This tighter, more intimate fit throughout the entire length of the threadedportion28,30 of thefastening member20 improves a variety of performance characteristics over the prior art. Thisfastening member20 produces a higher torque differential between the tapping torque of thethread40,42 and the strip-out torque of thefastening member20, thereby resulting in afastening member20 that has more inherent reliability, and the capability of being used in a wider variety of substrates versus the prior art. This is especially important in those substrates that are both friable and soft, as in lightweight concrete and light weight masonry units, as well as those substrates that utilize very soft aggregates where fastening member strip-out is frequently encountered. Thefastening member20 has less overall axial movement per unit load, while resisting withdrawal forces. Thefastening member20 resists backing out, when subjected to dynamic loads, and system impacts and vibrations.

The dual zone heat treatment provides for an overall more ductile anchorage. Thethreads40 of the first threadedportion28 typically endure more abuse during the installation process, and more stress and movement once installed, but because thethreads40 of the first threadedportion28 are more ductile, thefastening member20 bears these more handily than the prior art. In addition, ductility is a requirement of structural fastenings, and in applications that tend to embrittle the fastening member and/or applications where stress corrosion cracking is of concern.

Thelarger thread angle46 of thethreads42 of the second threadedportion30, i.e. larger than thethread angle44 of thethreads40 of the first threadedportion28, produces higher radial loads in the substrate than thethreads40 of the first threadedportion28. The increased radial load manifests itself as higher compressive forces imparted into the substrate during the act of withdrawing thefastening member20. Higher compressive forces generated in the second threadedportion30 of thefastening member20 in masonry has shown to produce large spall cones and higher withdrawal resistance. A five degree differential in thethread angle44,46 has been calculated to impart a fourteen percent increase in radial loading. Thefastening member20 biases the higher radial loads in the second threadedportion30 of thefastening member20, and lesser radial loads in the upper zones of the substrate, where in many cases, the surface of the substrate is unsupported and prone to premature spalling.

A plurality ofnotches48 are provided in thethreads42 of the second threadedportion30. As shown, three equidistantly spacednotches48 are provided in eachthread42 of the second threadedportion30. As shown inFIG. 3, eachnotch48 is “V” shaped, however it is to be understood that other shapes, such as a “U” shape can be used. In addition, while three equidistantly spacednotches48 are shown, it is to be understood that more or less than three notches can be provided and the notches do not need to be equidistantly spaced. The shape, amount and spacing of thenotches48 is dependant upon the type of substrate used. Thenotches48 are used to cut the friable substrate during tapping of the female thread in the substrate.

While the transition of thethread angle44,46 from thethreads42 in the second threadedportion30 to thethreads40 in the first threadedportion28 is shown as an abrupt change, it is to be understood that this change can be formed by blending the thread angle down along a plurality of thethreads40 in the first threadedportion28.

While the unthreadedportion26 is shown in the drawings, it is to be understood that the unthreadedportion26 can be eliminated and instead, the first threadedportion28 can extend to thehead22 of thefastener member20.

While a preferred embodiment of the present invention is shown and described, it is envisioned that those skilled in the art may devise various modifications of the present invention without departing from the spirit and scope of the appended claims.

Claims (33)

1. A fastening member comprising:

a head; and

a shank depending from said head, said shank having threads forming a first threaded portion having a predetermined thread angle and which is proximate to said head, and threads forming a second threaded portion having a predetermined thread angle and extending from said first threaded portion, said thread angle of said first threaded portion being different less than said thread angle of said second threaded portion, said threads in said first threaded portion and said threads in said second threaded portion have a substantially constant minor diameter and said threads in said first threaded portion have a constant major diameter and said threads in said second threaded portion have a constant major diameter, said constant major diameters being equal to each other.

2. A fastening member as defined inclaim 1, further including a centering point provided on said second threaded portion.

3. A fastening member as defined inclaim 1, wherein said threads in said first threaded portion and said threads in said second threaded portion have a substantially constant major diameter and pitch.

4. A fastening member as defined inclaim 1, wherein said threads in said first threaded portion are helical and said threads in said second threaded portion are helical.

5. A fastening member as defined inclaim 1, wherein each said thread in said second threaded portion has at least one notch provided therein.

6. A fastening member as defined inclaim 5, wherein each said notch is “V” shaped.

7. A fastening member as defined inclaim 1, wherein said thread angle of said first threaded portion is three to seven degrees different than said thread angle of said second threaded portion.

8. A fastening member comprising:

a head; and

a shank depending from said head, said shank having threads forming a first threaded portion having a predetermined thread angle and which is proximate to said head, and threads forming a second threaded portion having a predetermined thread angle and extending from said first threaded portion, said thread angle of said first threaded portion is three to seven degrees different less than said thread angle of said second threaded portion, said threads in said first threaded portion have a constant major diameter and said threads in said second threaded portion have a constant major diameter, said constant major diameters being equal to each other.

9. A fastening member as defined inclaim 8, further including a centering point provided on said second threaded portion.

10. A fastening member as defined inclaim 8, wherein said threads in said first threaded portion and said threads in said second threaded portion have a substantially constant major diameter, minor diameter and pitch.

11. A fastening member as defined inclaim 8, wherein said threads in said first threaded portion are helical and said threads in said second threaded portion are helical.

12. A fastening member as defined inclaim 8, wherein each said thread in said second threaded portion has at least one notch provided therein.

13. A fastening member as defined inclaim 12, wherein each said notch is “V” shaped.

14. A fastening member comprising:

a head; and

a shank depending from said head, said shank having a first, hardened threaded portion having a predetermined hardness and which is proximate to said head, and a second, hardened threaded portion having a predetermined hardness and extending from said first threaded portion, said hardness of said first threaded portion being softer than said hardness of said second threaded portion.

15. A fastening member as defined inclaim 14, wherein said hardness of said threads in said second threaded portion is at least twenty points harder than said threads of the first threaded portion as measured on the Rockwell “C” scale.

16. A fastening member as defined inclaim 14, wherein said hardness of said threads in said second threaded portion is at least forty-five as measured on the Rockwell “C” scale.

17. A fastening member as defined inclaim 14, further including a centering point provided on said second threaded portion.

18. A fastening member as defined inclaim 14, wherein said threads in said first threaded portion and said threads in said second threaded portion have a substantially constant major diameter, minor diameter and pitch.

19. A fastening member as defined inclaim 14, wherein said threads in said first threaded portion are helical and said threads in said second threaded portion are helical.

20. A fastening member as defined inclaim 14, wherein each said thread in said second threaded portion has at least one notch provided therein.

21. A fastening member as defined inclaim 20, wherein each said notch is “V” shaped.

22. A fastening member comprising:

a head; and

a shank depending from said head, said shank having threads forming a first threaded portion having a predetermined thread angle and a predetermined hardness, said first threaded portion being proximate to said head, and threads forming a second threaded portion having a predetermined thread angle and a predetermined hardness, said second threaded portion extending from said first threaded portion, said thread angle of said first threaded portion being different less than said thread angle of said second threaded portion and said hardness of said first threaded portion being softer than said hardness of said second threaded portion, said threads in said first threaded portion have a constant major diameter and said threads in said second threaded portion have a constant major diameter, said constant major diameters being equal to each other.

23. A fastening member as defined inclaim 22, wherein said thread angle of said first threaded portion is three to seven degrees different than said thread angle of said second threaded portion.

24. A fastening member as defined inclaim 22, wherein said hardness of said threads in said second threaded portion is at least twenty points harder than said threads of the first threaded portion as measured on the Rockwell “C” scale.

25. A fastening member as defined inclaim 22, wherein said hardness of said threads in said second threaded portion is at least forty-five as measured on the Rockwell “C” scale.

26. A fastening member as defined inclaim 22, further including a centering point provided on said second threaded portion.

27. A fastening member as defined inclaim 22, wherein said threads in said first threaded portion and said threads in said second threaded portion have a substantially constant major diameter, minor diameter and pitch.

28. A fastening member as defined inclaim 22, wherein said threads in said first threaded portion are helical and said threads in said second threaded portion are helical.

29. A fastening member as defined inclaim 22, wherein each said thread in said second threaded portion has at least one notch provided therein.

30. A fastening member as defined inclaim 29, wherein each said notch is “V” shaped.

31. A fastening member as defined inclaim 1, wherein said threads in said first threaded portion and said threads in said second threaded portion are truncated along the major diameters thereof.

32. A fastening member as defined inclaim 8, wherein said threads in said first threaded portion and said threads in said second threaded portion are truncated along the major diameters thereof.

33. A fastening member as defined inclaim 22, wherein said threads in said first threaded portion and said threads in said second threaded portion are truncated along the major diameters thereof.

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