Patent Publication Number: US-H2266-H

Title: Glue jig to position adhesive-applied specimens

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described was made in the performance of official duties by one or more employees of the Department of the Navy, and thus, the invention herein may be manufactured, used or licensed by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 
    
    
     BACKGROUND 
     The invention relates generally to a glue jig for setting specimens or coupons to be adhesively bonded. In particular, the glue jig enables several specimens to be arranged for concurrent joint arranging and curing. 
     Specimens or coupons can be attached together for material response testing to measure strength and shear modulus of the bond. The lap joint represents one such configuration, and this can be achieved for select materials by chemical adhesive or glue. 
     SUMMARY 
     Conventional glue jigs yield disadvantages addressed by various exemplary embodiments of the present invention. In particular, various exemplary embodiments provide expansion in number of joints to be produced concurrently. Improved repeatability and scalability in establishing such joints over an extended curing interval represents an objective for the embodiments described in this disclosure. 
     Various exemplary embodiments provide a jig for setting and gluing pairs of specimens along their joining faces to cure into a lap joint. The jig includes a platform with a setting surface flanked by first and second upright walls, first and second plates and fasteners. The platform positions the pairs of specimens for lap joint arrangement. The setting surface has a plurality of orifices disposed along the pairs of specimens. 
     The orifices are disposed along a longitudinal non-joining face, a lateral non-joining face, or a corner of adjacent specimens. The first and second plates are fastened respectively adjacent said first and second upright walls opposite the setting surface with the fasteners to tighten the plates to the upright walls. The pins are inserted into corresponding orifices to retain the pair of specimens along their non-joining faces from translation along the setting surface. 
     The plurality of pins includes retainer pins along said longitudinal non- joining face, alignment pins along said lateral non-joining face, and stop pins at said corners of adjacent pairs of specimens. The plates include threaded orifices through which to insert the fasteners. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and various other features and aspects of various exemplary embodiments will be readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, in which like or similar numbers are used throughout, and in which: 
         FIG. 1  is a plan schematic view of a glue jig; 
         FIG. 2  is a perspective view of the glue jig with adhered components; and 
         FIG. 3  is a plan view of a glue joint fusing two specimens. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized, and logical, mechanical, and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
       FIG. 1  shows a plan schematic view  100  of a glue jig. The jig restrains specimens for fusing together using adhesive, such as glue. The exemplary configuration described corresponds to a single lap joint, although artisans of ordinary skill will recognize other configurations can be contemplated without departing from the scope of the invention. 
     The glue jig includes an upper side plate  110  and a lower side plate  115  to constrain a jig box  120 . Both plates  110 ,  115  are removable upon complete curing of the adhesive. A set of thumb nuts  130  secures the plates  110 ,  115  to the box  120  to inhibit lateral movement. The plates  110 ,  115  include holes passing therethrough, with screw threads extending half-way through the thickness from outward to inward. Tightening the nuts  130  enables the plates  110 ,  115  to hold the box  120  in compression. The box includes a setting platform on which the specimens are positioned for gluing together, and bounded by upright walls. Some specimens can be disposed to abut either wall. 
     The box  120  uses retaining pins  140  for specimen disposition along their longitudinal axes as well as glue alignment pins  145  for specimen disposition along their lateral axes. Stop pins  150  restrict the specimens at their corners, for example where specimens abut each other The pins  140 ,  145 ,  150  are secured to the box  120  by orifices drilled through its bottom face and are disposed upright therein. These orifices correspond to the same diameter as their respective pins. 
     The schematic view  100  shows four specimens: first  160 , second  165 , third  170  and fourth  175 . The initial alignment pins  140  restrain the specimens from lateral translation, whereas the glue alignment pins  145  restrict longitudinal sliding. The specimens  160 ,  165 ,  170 ,  175  are disposed with one edge (or wall) facing the jig box. Adhesive regions  180 , identified by dash ovals, correspond to the interfacing surfaces of the specimens to be glued together. 
     As shown, upper and lower lap joints provide an example configuration, although the box  120  is not limited thereto. The third sample  170 , adjacent the upper plate  110 , adheres to the first sample  160 . The fourth sample  175  adheres to the second sample  165  adjacent the lower plate  115 . 
     The glue jig is designed for Tensile-Lap Adhesive Specimen Preparation for reproducible production of tensile-lap thick specimens to measure strength and shear modulus of non-rigid adhesives. This preparation conforms to ASTM D3983-98, Standard Test Method for Measuring Strength and Shear Modulus of Non-rigid Adhesives by the Thick-Adherend Tensile-Lap Specimen. 
     Exemplary embodiments of the glue jig were developed due to restraints imposed by 1) specimen specific preparation requirements and 2) available testing equipment. The glue jig, for the configuration described, can hold two pairs of specimens in place for corresponding pairs of lap joints during cure interval. However, this depicted arrangement is not limiting being extendible to additional specimens, and/or alternate types of joints. Removable side plates  110 ,  115  and retaining pins  140 ,  145 ,  150  facilitate use of the jig. The metal frame is readily oiled with spray to inhibit undesired sticking if any glue is spilled on parts not intended to form the glue joint. 
       FIG. 2  shows a perspective view  200  of the jig box  120  with a pair of single lap joints adhering pairs of specimens. Excess glue  210  escapes from the joint regions  180  after squeezing the specimens together for desired separation. 
       FIG. 3  shows a plan view  300  of a glue joint fusing two specimens. Removal of the excess glue shows a single lap joint  310  (within the joint region  180 ) to securely attach the first and third specimens  160 ,  170  together 
     Procedures for use can be generalized as follows: First, place the first and second specimens  160 ,  165  as metal test parts with dimensions 2″×0.25″×0.300″ into the center of the box  120  of the glue jig so that one end of each specimen rests against the stop pins  150 . 
     Second, for the upper half, deposit appropriate amount of glue on the first specimen  160  as well as the third specimen  170  against the alignment pin  140 . Third, gently tighten the side plate thumb screws  130 . This tightens the first specimen  160  to the third specimen  170 , thereby leaving a glue line thickness of 0.060″ by 0.750″ length. 
     Fourth, repeat this process for the lower half of the Glue Jig with the second and fourth specimens  165 ,  175 . After a suitable post-cure period, remove the pins  140 ,  145 ,  150  from the glue jig box  120  and gently remove the test specimens  160 ,  165 ,  170 ,  175  and trim the excess glue  210  from the edges and ends with an appropriate knife. 
     The development of this glue jig provides several advantages over the glue jig in the ASTM standard. For a single lap joint, two or more specimens can be cured in the same jig. The joints can be reproducible for preparing and comparing multiple sets of specimens. Removable retaining pins  140 ,  145 ,  150  facilitate removal of test specimen  160 ,  165 ,  170 ,  175  without prying, preventing damage to the glue joint  310 . Metal parts to be adhered in this manner can tolerate heat loads during adhesive cure multiple times and are thus less vulnerable to warp or other distortion. This type of jig can be manufactured in any size to fit a wide variety of applications. 
     While certain features of the embodiments of the invention have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments.