Abstract:
A power assisted combination shear used for forming structural louvers in the crimped seam of structural steel decking comprises a frame supporting a pair of jaws which are opened and closed by means of an operator-controlled pneumatic cylinder. One jaw terminates in a blade and the other jaw has a corresponding die member. The blade and die have undercut reliefs in the root portions, which permit the louver to be formed without breaking through to the edge of the seam. The louver comprises a sheared portion in the form of a bowed tab bridging a corresponding window formed in the seam by the shearing of the tab. The interference between the louver and window provides a substantial increase in the lateral resistance (shear strength) of the crimped seam, thereby obviating the need to additionally weld or screw the seam to provide the necessary shear strength for even the highest stress applications.

Description:
This application is a Divisional application of U.S. Patent application having application Ser. No. 09/356,540 filed on Jul. 19, 1999, now U.S. Pat. No. 6,212,932, by James R. Parker and titled “PNEUMATIC SHEAR FOR FORMING STRUCTURAL LOUVERS”. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to tools for forming features in the joints of structural steel decking and roofing commonly used in large commercial construction, for example, as subflooring for poured concrete floors or as roofing for large industrial buildings. Structural steel decking is typically manufactured in thicknesses ranging from 22 gauge to 16 gauge or more. The decking generally is supplied to the building site in panels ranging in size from 3 feet by 15 feet to about 3 feet by 35 feet. Longitudinal ribs, typically hat sections or flat-bottomed vee sections of from 1½ to 3 inches in depth are formed in the panels to increase the section modulus of the panels. The individual panels are typically provided with one edge having an exposed upward “male” lip. The opposite edge is provided with a female inverted “U” shaped lip. The individual panels are joined together by placing the female lip over the male lip and crimping the seam at periodic intervals. In many applications, the joints must secure the panels together so as not only to prevent one panel from lifting off the other, but also to prevent the panels from shifting laterally along the seam (along the y-axis as shown in FIG.  1 ). By holding the panels securely enough to prevent lateral shifting, the assembled decking adds considerable membrane strength to the finished building. Given the inherent weakness of crimped joints to lateral shifting, typically where high membrane strength is required, welding or screwing of the seam is necessary to meet the specified shear strength. 
     A prior art method for crimping steel decking comprises use of a hand-operated tool shown in FIG. 1, known as the 601 SEAM LOCKER, distributed by Miramar Specialties of Ventura, California The prior art apparatus comprises a compound-lever press in which the operator moves the handles apart to provide the force to crimp the panels together. An optional button punch is provided to upset a portion of the seam to provide some lateral stiffness. Since the apparatus comprises merely a compound lever arrangement, however, it provides a linear multiplication of the force exerted by the operator on the handles. As can be appreciated from the foregoing, hand crimping of thousands of seams is a laborious task and, given the inevitability of operator fatigue, an inherently unreliable method for providing seams having the uniformity necessary to achieve a high degree of lateral stiffness. 
     Various portable power tools have been developed for setting rivets, crimping sheet metal trusses, and for other applications. For example, U.S. Pat. No. 1,743,209 to Groehn discloses a fastener setting device comprising a toggle-actuated jaw and anvil adapted for setting rivets, particularly in the construction of automobile bodies. U.S. Pat. No. 3,877,280 to Cornell discloses a hand operated power assisted punch and die for crimping sheet metal studs and joists together to form a modular wall panel. U.S. Pat. No. 4,989,438 to Simon discloses a hand-operated power assisted punch and crimp for attaching comer bead to exterior comers in sheet rock or gypsum board walls. 
     Applicant&#39;s prior application Ser. No. 961,162, now U.S. Pat. No. 5,878,617 (incorporated herein by reference) disclosed a pneumatically operated decking crimper having multiple button punches arranged in a staggered configuration. The alternating offset upset portions of the flange formed by the multiple button punches substantially increased the lateral resistance of the crimped seam. However, the inclined walls of the upset portions will tend to pry the seam apart if sufficient side loading is applied. Accordingly, the lateral resistance of the seam thus formed may not be sufficient for some extremely high stress applications. Accordingly, what is needed is an apparatus for producing a crimped joint that has lateral resistance approaching the sheer strength of the roofing panel itself. 
     SUMMARY OF THE INVENTION 
     The present invention provides a power assisted combination shear and punch particularly suited to shearing and offsetting a portion of the crimped lip of structural steel decking and roofing panels thereby forming a structural louver in the seam. In a preferred embodiment, the invention comprises a frame supporting a pair of jaws which are opened and closed by means of a toggle linkage that is driven by an operator-controlled pneumatic cylinder. The input pivot of the toggle linkage is constrained to move linearly by means of a cross head formed in the frame which, in turn, causes the jaws to move in unison rather than one jaw moving against the other. One jaw terminates in a blade having an undercut relief in the root portion thereof, such that as the decking or roofing panel joint is sheared by the jaws, the undercut portion prevents the sheared section from breaking through to the edge of the seam. The other jaw has a corresponding die member which supports the seam as the sheared portion is sheared from the seam. The sheared portion forms a bowed tab or louver bridging the corresponding window formed in the seam. The interference between the louver and window provides a substantial increase in the lateral resistance (shear strength) of the crimped seam, thereby obviating the need to additionally weld or screw the seam to provide the necessary shear strength for even the highest stress applications. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The present invention will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying drawing figures in which like references designate like elements and in which: 
     FIG. 1 is a prior art crimping tool for use with steel decking and roofing; 
     FIG. 2 is a side plan view of an illustrative pneumatic shear apparatus incorporating features of the present invention; 
     FIG. 3 is a partial cross section view of the apparatus of FIG. 2 taken along line  3 — 3 ; 
     FIG. 4 is a cross section view of a bidirectional valve in accordance with the present invention; 
     FIG. 5 is a side elevation view of a jaw used in the illustrative pneumatic shear; 
     FIG. 6 is a side elevation view of the jaw assembly of the illustrative pneumatic shear; 
     FIG. 7 is an end view of the jaw assembly of FIG. 7; 
     FIG. 8 is a perspective view of a portion of decking having formed therein a structural louver in accordance with the present invention; and 
     FIG. 9 is a cross-sectional view of the decking of FIG. 8 taken along line  9 — 9 . 
    
    
     DETAILED DESCRIPTION 
     The drawing figures are intended to illustrate the general manner of construction and are not necessarily to scale. In the description and in the claims, the terms left, right, front and back and the like are used for descriptive purposes. However, it is understood that the embodiment of the invention described herein is capable of operation in other orientations than is shown and the terms so used are only for the purpose of describing relative positions and are interchangeable under appropriate circumstances. 
     The present invention relates to tools for forming features in the crimped joints of structural steel decking and roofing commonly used in large commercial construction, for example, decking used as subflooring for poured concrete floors or as roofing for large industrial buildings. As shown in FIG. 1, the individual decking or roofing panels are typically provided with one edge having an exposed upward “male” lip  4 . The opposite edge is provided with an inverted “U” shaped female lip  6 . The individual panels are typically joined together to form a seam  7  by placing the female lip  6  over the male lip  4  and crimping the seam at periodic intervals. A prior art method of crimping the seam comprises use of a crimping tool known as the 601 SEAM LOCKER in which the user positions the jaws of the tool over the joint and, by pulling the handles of the tool apart, exerts a crimping force on the seam. The jaws of the crimping tool close the seam  7  while the upset portion formed by the punch and die form an upset that adds some lateral resistance to the seam  7 . 
     Referring to FIGS. 2 and 3, an illustrative embodiment of the present invention comprises a tool  10  comprising a frame  12  having a handle  14  adapted to be grasped by a user at about waist level so that the lower extreme of tool  10  is at about foot level. The central section  16  of frame  12  comprises a rectangular frame constructed of hollow tubing which supports an upper extension  18  and a lower extension  20 . Upper extension  18  is constructed of a single piece of rectangular tubing welded to the upper surface  22  of central section  16  or, alternatively, upper extension  18  may be constructed of individual plates welded together to form a rectangular tube. Lower extension  20  is formed of two parallel plates welded to spacer  24  which, in turn, is welded to central section  16 . 
     Referring to FIG. 3, a pneumatic cylinder  30  is attached to the upper edge  28  of lower extension  20 . Pneumatic cylinder  30  may comprise a piston inside a bore or other conventional pneumatically actuated linear motor. Preferably, pneumatic cylinder  30  comprises a housing which is divided into upper and lower chambers  34 A and  34 B by a diaphragm  36 , which is crimped or otherwise sealed along the periphery of the housing. The center portion of diaphragm  36  is covered by a piston plate  38 , which acts as a rigid surface for the pressure in chamber  34 A to act upon. In the illustrative embodiment, pneumatic cylinder  30  exerts a force of 4,320 pounds at an inlet pressure of 100 psi with a maximum stroke of 2¾ inches, which corresponds to jaw movement of about {fraction (11/16)} inch for jaws having a 2¾ inch blade. Thus, when used in combination with the toggle linkage as described herein, the pneumatic cylinder  30  provides the force and displacement necessary to shear and then offset a louver (as described hereinafter) in virtually all standard structural steel decking in a single-pass operation. 
     Ram  40  is attached to piston plate  38  in order to convert the pressure action on piston plate  38  and diaphragm  36  into a force for actuating the jaw mechanism as hereinafter described. A return spring  42  acts against the pressure in chamber  34 A to return the piston plate  38  to the upper limit of travel when the pressure in chamber  34 A is equal to the pressure in chamber  34 B. 
     The lower end of ram  40  terminates in a clevis  44  through which passes a clevis pin  46 . In addition to passing through clevis  44 , clevis pin  46  passes through the upper ends  56 ,  58  of the input links  50  and  52  of a toggle linkage  60 . The lower ends  62  and  64  of input links  50  and  52  are pivotally attached to the upper ends  66  and  68  of jaws  70  and  72 . Jaws  70  and  72  are pivotally attached to the lower end of lower extension  20  of frame  12  to open and close in response to the movement of toggle linkage  60 . As shown in FIG. 3, jaw  70  comprises a single blade while jaw  72  comprises a pair of blades  72 A and  72 B constrained by link pin  74  to move in unison. A cross-head slot  48  is provided in lower extension  20 . Cross-head slot  48  engages clevis pin  46  to constrain clevis pin  46 , which comprises the toggle input, to move linearly and, therefore, to constrain the jaws  70  and  72  to move in equal and opposite directions. 
     A conventional air valve  100  housed within upper extension  18  regulates a source of pressurized air admitted through fitting  104  and provides a pressurized output into hose  106  for admittance into pneumatic cylinder  30 . An external valve handle  102  is provided for controlling air valve  100  by the operator. Preferably, a bi-directional valve  120  is operatively disposed between air valve  100  and pneumatic cylinder  30  to admit pressurized air into pneumatic cylinder  30  when air valve  100  is open and to exhaust air from pneumatic cylinder  30  when air valve  100  is closed, thereby allowing pneumatic cylinder  30  to return to its upper limit of travel more rapidly, and thereby increasing the cycle rate of the apparatus. 
     As shown more fully in FIG. 4, a bidirectional valve  120  comprises a housing  122  having an inlet  124  which is threaded to receive a standard hose or tube fitting, an outlet  126  which is threaded to form an airtight seal with the inlet  128  (FIG. 2) of pneumatic cylinder  30 . Housing  122  further comprises an exhaust port  130 . Valve seat  132  is formed on the inner surface of exhaust port  130 . A flexible valve member  134  is constrained within chamber  136  of housing  122 . As can be seen from FIG. 4, as high pressure air from air valve  100  enters through inlet  124 , valve member  134  is forced against valve seat  132  to close off exhaust port  130  and direct the flow of air through outlet  126  into pneumatic cylinder  30 . Once air valve  100  is closed, air from pneumatic cylinder  30  begins to reverse direction and enter housing  122  through outlet  126 . The reversed flow of air through outlet  126  causes valve member  134  to seat against surface  138 , thereby opening exhaust portion  130  to permit relatively unobstructed exhaust of pressurized air from pneumatic cylinder  30 . 
     FIG. 5 is a side elevation view of jaw  70  of the apparatus of FIG.  2 . In the embodiment of FIG. 5, each of jaws  72 A and  72 B are mirror images of jaw  70  and therefore will not be discussed in detail. Jaw  70  comprises input arm  76 , output arm  78  and bearing journal  80  about which jaw  70  pivots under the urging of pneumatic cylinder  30 . Output arm  78  comprises a blade portion  82  having a rounded tip  83  and an undercut region  84  in the region of the root  86  of blade  82 . Preferably, the depth dimension “d,” of undercut region  84  at a minimum is equal to the stroke of blade  82  as urged by pneumatic cylinder  30  plus one-half the thickness of flange  7  such that the upper end of flange  7  is not sheared by blade  82 . The maximum depth “d” may be as large as desired to provide additional clearance, however, the undercut region  84  should not be so large as to reduce the strength of blade  82  below that necessary to effect the shearing action of flange  7  as described hereinafter. 
     As shown in FIGS. 6 and 7, jaw subassembly  88  comprises jaw  70  and jaw assembly  72  comprising jaw  72 A and jaw  72 B all pivoted about a common shaft  91 . As shown in FIG. 6, jaw  70  is displaced into the page from jaw  72 A and jaw  72 B is further displaced into the page from jaw  70 . Jaw  72 B is not visible in FIG. 6 because it is identical to and directly behind jaw  72 A. In the open position as depicted in FIG. 6, blade  82  is displaced from blades  82 ′ and  82 ″ of jaw  72 A and jaw  72 B, respectively, such that a flange  7  consisting of male lip  4  and female lip  6  can be inserted into the gap  92  defined between surface  90  of blade  82  and surface  90 ′,  90 ″ of blades  82 ′,  82 ″. 
     With reference in particular to FIGS. 2,  3 ,  6  and  8 , in operation of the tool  10  in accordance with the present invention, a user positions jaws  70  and  72  over flange  7  and depresses the valve lever. High pressure air entering pneumatic cylinder  30  causes ram  40  to be forced downward, exerting a force on clevis  44 . Toggle linkage  60  actuated by the force on clevis  44  begins its motion from a first position as shown in FIGS. 2 and 3 and in which the force multiplication of the toggle linkage is minimum. Toggle linkage  60  is then urged by ram  40  to a second position (not shown) in which the longitudinal axis of links  50  and  42  are collinear and the force multiplication of the toggle linkage theoretically approaches infinity. 
     The force input from links  50  and  52  cause jaws  70  and  72  to rotate in the directions indicated by the arrows “R” in FIG.  6 . This in turn causes surface  90  of blade  82  to pass between surfaces  90 ′,  90 ″ of blades  82 ′,  82 ″. The edges of blades  82 ,  82 ′, and  82 ″ are held substantially square and the clearance between blade  82  and blades  82 ′ and  82 ″ is held sufficiently narrow that blades  82 ′ and  82 ″ cooperate to act as a die against which blade  82  works to shear the lateral edges  156 ,  158  of a rectangular tab or louver  160  (FIG. 8) while leaving the orthogonal edges  162  and  164  of seam  7  intact. The action of blades  82 ,  82 ′,  82 ″ then cooperate to deform the tab  160  into a bow-shape supported at the orthogonal ends  162  and  164 , which bridges the window  166  that is formed in flange  7  by the shearing of tab  160 . The action of blades  82 ′ and  82 ″ on supporting seam  7  also deforms seam  7  slightly to form bulges  163 ,  165  extending in a direction opposite the deformation of tab  160 . 
     As shown in FIG. 8, the displaced tab  160  comprising crimped portions of lip  4  and “U” shaped lip  6  is displaced in a direction opposite the reveal portion  168  of window  166 . If seam  7  is subjected to a shear loading in the “y” direction shown in FIG. 1, the displaced tab  160  will bear against the reveal portion  168  of window  166  in the regions indicated at  170  and  172 . The bearing in these regions  170  and  172  is substantially normal to the contacting surfaces, therefore, no mechanical advantage is generated that would tend to pry on tab  160  or otherwise restore displaced tab  160  to its original configuration. Accordingly, in order for the seam to shift laterally, tab  160  would need to be sheared in the “y” direction by reveal  168  of window  166 . Accordingly, the shear strength of a seam  7  sheared and upset using tool  10  has a lateral stiffness that approaches the shear strength of the decking material itself. By providing a mechanical feature in seam  7  that produces such extremely high shear strength, the need to screw the seam  7  together (a laborious task with substantial additional material costs) or weld the seam  7  (which releases toxic fumes when used on galvanized decking) is obviated. 
     The force multiplication of a toggle linkage such as is used in the present invention is highly sensitive to the beginning and ending gap of the jaws  70  and  72 . As pivots wear through use, the toggle linkage may begin to go over center before the louvering operation is complete or, particularly where lighter gauge metal is used, the louvering may be complete before the linkage approaches its maximum force multiplication, thereby reducing the efficiency of the stroke. Accordingly, means are provided to permit both the input stroke to clevis  44  to be adjusted as well as the linkage ratio of the toggle linkage itself The input stroke is adjustable by means of a threaded engagement  140  (FIG. 3) between ram  40  and clevis  44 . Similarly, the linkage ratio of the toggle linkage  60  (FIG. 2) is adjustable by means of a threaded engagement  142  between an upper half  144  and a lower half  146  of link  52 . Manipulation of the aforementioned adjustments permits the input stroke to be regulated to prevent the toggle linkage  60  from going over center, which could lead to the mechanism becoming jammed, and permits the linkage ratio of the toggle linkage  60  to be adjusted to provide a predetermined displacement of tab  160  when the toggle linkage  60  is in the on-center position with the axis of links  50  and  52  collinear. The predetermined gap can be adjusted to accommodate the specified shear strength necessary to support a wide range of standard structural steel decking and roofing panels. 
     Although certain preferred embodiments and methods have been disclosed herein, it will be apparent from the foregoing disclosure to those skilled in the art that variations and modifications of such embodiments and methods may be made without departing from the spirit and scope of the invention. For example, in the illustrative embodiment the “die” formed by jaw assembly  72  is made from two identical jaws  72 A and  72 B that are identical mirror images of jaw  70 , however, jaw assembly  72  could be made as a one-piece die without departing from the scope of the invention. Accordingly, it is intended that the invention shall be limited only to the extent required by the appended claims and the rules and principles of applicable law.