ENERGY ABSORBING CONNECTOR

Abstract: A first end (111) of a metal strip (110) is separated into first and second tabs (120, 130) which are connected in series between first and second members. At least one line of interruptions (117) extends along an intermediate portion (114) of the strip (110) from a point of separation between the tabs (120, 130) and a point proximate a second, opposite end (112) of the strip (110). The second end (112) of the strip (110) is coiled inside the intermediate portion (114) of the strip (110), so that tensile force applied to either of the members is absorbed both by tearing of the metal strip (110) and uncoiling of the metal strip (110).

Description: ENERGYABSORBINGCONNECTOR Field of the Invention The present invention relates to methods and apparatus for providing an energy absorbing connection between two members, such as a safety line and a support structure. Background of the Invention Energy absorbing connectors come in a variety of forms and are useful in a variety of applications. One type of energy absorbing connector is disclosed in U.S. Pat. No. 3,106,989 to Fuchs; U.S. Pat. No. 3,694,028 to Andres et al.; and U.S. Pat. No. 5,738,377 to Sugiki et al. These prior art arrangements connect a strip of metal between two members in a manner which causes the metal to tear when subject to force in excess of a threshold force. The shearing of the metal absorbs a significant amount of energy and reduces the likelihood of damage to the members and/or people in proximity to the members. This type of energy absorbing connector has been used on automobiles and in fall arrest systems. With regard to the latter application, various occupations place people in precarious positions at relatively dangerous heights, thereby creating a need for fall- arresting safety apparatus. Such apparatus typically require a reliable safety line and reliable connections to the support structure and the person working in proximity to the support structure. One type of known fall arrest system connects a horizontal line to a support structure to support individual worker safety lines and minimally interfere with the worker's movements. Examples of horizontal safety line systems are disclosed in U.S. Pat. No. 5,343,975 to Riches et al, U.S. Pat. No. 5,279,385 to Riches et al., U.S. Pat. No. 5,224,427 to Riches et al., and U.S. Pat. No. 4,790,410 to Sharp et al. An object of the present invention is to provide an improved energy absorbing connector for use at the ends of safety lines used in this type of system. Another object of the present invention is to provide an energy absorbing connector which strikes a good balance between energy absorbing capacity and cost effectiveness. Summary of the Invention The present invention provides methods and apparatus for absorbing energy at a point of connection between two members. On a preferred embodiment of the present invention, a first end of a metal strip is separated into first and second tabs. At least one tear line is provided along an intermediate portion of the strip, from a point of separation between the tabs to a point proximate an opposite, second end. The second end of the strip is coiled inside the intermediate portion of the strip. The resulting connector absorbs energy both by tearing along the tear line and by uncoiling. Additional features and/or advantages of the present invention may become more apparent from the detailed description which follows. Brief Description of the Drawing With reference to the Figures of the Drawing, wherein like numerals represent like parts and assemblies throughout the several views, Figure 1 is a top view of a metal strip configured according to the principles of the present invention and manipulable into an energy absorbing connector; Figure 2 is a side view of the strip of Figure 1 ; Figure 3 is a side view of an energy absorbing connector made from the strip of Figure 1; Figure 4 is a top view of the connector of Figure 3; and Figure 5 is a perspective view of a horizontal safety line system including the connector of Figure 3. Detailed Description of the Preferred Embodiment A preferred embodiment connector constructed according to the principles of the present invention is designated as 100 and 100' in Figures 1-5. The connector 100 is made from a metal strip 110, preferably stainless steel and approximately twenty-six inches long, three inches wide, and one-eighth of an inch thick. The strip 110 extends lengthwise between a first end 111 and a second end 112. Two lines of interruptions 117 extend parallel to one another along an intermediate portion 114 of the strip 110. The interruptions 117 divide the intermediate portion 114 of the strip 110 into an interior strip 137 disposed between opposite side strips 127. On the preferred embodiment 100, the interruptions are holes extending through the strip and having a diameter of one-eighth of an inch. Those skilled in the art will recognize that other interruptions, such as notches in one or both sides of the strip may be substituted for the holes without departing from the scope of the present invention. Each line of interruptions 117 starts at a point of separation between tabs 120 and 130 teπninates at a relative larger hole 119 at the second end 112 of the strip 110. On the preferred embodiment 100, each larger hole 119 has a diameter of one-half of an inch. A generally U-shaped cut 115 separates the first end 111 of the strip 110 into a first, outside tab 120, and a second, inside tab 130. A hole 121 extends through a central portion of the first tab 120 to receive a fastener, and a similar hole 131 extends through a central portion of the second tab 130 to similarly receive a fastener. The ends of the cut 115 are aligned with the lines of interruptions 117, and the middle of the cut 115 extends in arcuate fashion about the hole 131 at a radius equal to more than one-half the distance between the lines of interruptions 117. The strip 110 may be manipulated into the configuration shown in Figures 3-4. The second end 112 of the strip 110 and a proximate part of the intermediate portion 114 are coiled or rolled up inside the remainder of the intermediate portion 114. Tabs 120 and 130 are bent in opposite directions away from the intermediate portion 114 so that they extend perpendicular thereto and parallel to one another. Figure 4 shows the opening in the first tab 120 which is created by the removal of the second tab 130. The resulting connector 100' is suitable for connection in series between two other members. The rolled-up arrangement of the connector 100' is such that it occupies relatively little space while providing relative large energy absorption capacity. In particular, energy is consumed both by tearing of the metal strip 110 along the interruptions 117 and straightening of the metal strip 110 as the portions 127 and 137 tear away from one another. A preferred application for the present invention 100 may be described with reference to horizontal safety line systems of the type disclosed in U.S. Pat. No. 5,343,975 to Riches et al., U.S. Pat. No. 5,279,385 to Riches et al., U.S. Pat. No. 5,224,427 to Riches et al., and U.S. Pat. No. 4,790,410 to Sharp et al., which are incorporated herein by reference. As shown in Figure 5, the connector 100' is connected in series between a support structure 20 and the end of a horizontal safety line 40. The horizontal line 40 is also supported by intermediate brackets 90. A personal safety line 70 is interconnected between a worker's harness and a slotted coupling member 80 which moves along the horizontal line 40. In the event of significant impact on the line, such as during a fall arrest, the connector 100' absorbs some of the energy associated with the fall, and thereby reduces the likelihood of personal injury and/or damage to the most significant components of the system. A spent connector 100' may be readily replaced by means of bolts or other fasteners connected through the holes 121 and 131 in the tabs 120 and 130, respectively. Although the present invention has been described with reference to a preferred embodiment and a particular application, this disclosure will enable those skilled in the art to recognize additional embodiments and/or applications which fall within the scope of the present invention. For example, as suggested by the foregoing Background of the Invention, the present invention may be used in other environments, including automobiles. Thus, the scope of the present invention should be limited only to the extent of the following claims.

Claims: WHAT IS CLAIMED IS: 1. An energy absorbing connector, comprising: a metal strip having a first end, a second end, and an intermediate portion disposed therebetween, wherein a generally U-shaped cut in the first end separates the first end into a first tab and a second tab, and the first tab and the second tab are arranged to extend in opposite directions away from one another, and a separate hole is formed through each said tab, and a separate line of discontinuities in the strip extends from each end of the U-shaped cut to a respective position proximate the second end of the strip, and the second end of the strip and most of the intermediate portion of the strip are rolled up in spiral fashion inside a remainder of the intermediate portion of the strip. 2. The connector of claim 1, wherein the discontinuities are intermittently spaced, circular holes extending through the strip. 3. The connector of claim 2, wherein each said line of discontinuities terminates in a respective, relatively larger hole extending through the strip proximate the second end. 4. The connector of claim 3, wherein the circular holes are approximately one-eighth of an inch in diameter, and each said larger hole is approximately one-half inch in diameter. 5. The connector of claim 4, wherein the strip is made of stainless steel approximately one-eighth of an inch thick. 6. A method of making an energy absorbing connector from a strip of metal, comprising the steps of: separating a first end of the strip into a first tab and a second tab; forming at least one line of intermittent interruptions in an intermediate portion of the strip, from a point of separation between the first tab and the second tab to a point proximate a second, opposite end of the strip; forming an opening through the strip and about the point, wherein the interruptions have a first width, measured perpendicular to the at least one line, and the opening has a second, relatively greater width, measured perpendicular to the at least one line; and rolling the strip about itself from the second end to a point proximate the first end. 7. The method of claim 6, wherein the separating step involves making a U- shaped cut in the first end. 8. The method of claim 7, wherein the separating step further involves bending the first tab and the second tab to extend away from one another in co-planar fashion. 9. The method of claim 6, wherein the forming step involves making intermittently spaced holes through the intermediate portion of the strip to provide the line of interruptions. 10. The method of claim 6, further comprising the step of making a hole through each said tab. 11. An energy absorbing connector, comprising: a metal strip having a first end, a second end, and an intermediate portion disposed therebetween, wherein the first end is separated into a first accessible, anchoring tab and a second accessible, anchoring tab, and the intermediate portion is provided with at least one tear line which aligns with a line of separation between the first tab and the second tab, and the second end is coiled in spiral fashion inside more than a full revolution of the intermediate portion and thereby rendered inaccessible, whereby when the first tab and the second tab are pulled in opposite directions with sufficient force, the intermediate portion uncoils to absorb energy, and tears to absorb energy. 12. The connector of claim 11, wherein the second tab is cut from an interior portion of the first tab. 13. The connector of claim 11 , wherein a bolt hole extends through each said tab. 14. The connector of claim 11 , wherein each said tear line includes a plurality of intermittently spaced holes through the strip. 15. The connector of claim 14, wherein each said tear line terminates in a relatively larger hole proximate the second end. 16. The connector of claim 2, wherein the holes distributed along one line of discontinuities are staggered longitudinally relative to the holes distributed along the other line of discontinuities. 17. The connector of claim 16, wherein each said line of discontinuities terminates in a respective larger opening extending through the strip, and a line extends diametrically through each said larger opening. 18. The connector of claim 1 , wherein the strip is rolled at least three full revolutions about the second end. 19. The connector of claim 1 , wherein a fastening hole extends through each said tab. 20. The connector of claim 19, wherein the rolled portion of the strip is disposed between a column of space extending axially through the hole in the first tab and a column of space extending axially through the hole in the second tab. 21. The connector of claim 11 , wherein a U-shaped cut separates the first tab and the second tab, and the at least one tear line includes first and second lines of intermittent holes extending through the strip, and each of the lines aligns with a respective end of the cut. 22. The connector of claim 21, wherein the holes in the first of the lines are staggered longitudinally relative to the holes in the second of the lines, whereby transversely spaced segments of the intermediate portion alternatively tear longitudinally to absorb energy.

Inventors: CASEBOLT SCOTT C, CASEBOLT, SCOTT, C.
Applicants: CASEBOLT SCOTT C, DB IND INC, CASEBOLT, SCOTT, C., D B INDUSTRIES, INC.
Application year: 1999
Main classification: A62B35
IPC codes: A62B35