IL35233A - Multimetal blind rivets and pulling stems - Google Patents

Description

gg This invention relates to blind The advantages of blind riveting or riveting from one side only of a structure by inserting a hollow rivet with a preformed head through a hole in the members to be riveted together and then forming a rivet head on the opposite side by means of a pulling stem is well known in the To be successful this type of rivet must be made of material which is sufficiently malleable so that the blind head may be readily formed by the pulling proces s and yet have sufficient strength in shear and tension to hold the riveted parts Aluminium alloy rivets have been used in the aircraft but in recent years the use of titanium alloys and other special alloys has found great favour where high strength and low weight are It is even more important where elevated temperatures are involved as in super sonic aircraft where certain titanium alloys are especially in great In the case of many alloys such as those of if an alloy having the required tensile and shear strength is used for the rivet there has been great risk of splitting the rivet shell in forming the blind It is an obj ect of this invention to provide a blind rivet which avoids this In accordance with this there is provided a blind rivet comprising a hollow rivet body having a tail section and a pulling stem for extension through the hollow rivet body to effect deformation of the tail section a the body including a head and shank section integral with the tail section at an the head and shank section being composed of a metal having relatively high shear and tensile and the tail being composed of a relatively ductile and formable The invention is more particularly described hereafter with reference to the accompanying Figure 1 is a sectional view illustrating a known type of blind rivet in an advanced step of installation by a pulling Figure 2 is a sectional view showing the installed rivet Figure 1 Figure 3 is a sectional view illustrating another embodiment of a known type of blind rivet of the bulbed head type at an advanced ste of installation by a pulling Figure 4 is a sectional view showing the installed rivet of Figure Figure 5 is a sectional view of an embodiment of a rivet according to the invention with a unimetallic pulling Figure 6 is a longitudinal view of a bimetallic pulling Figure 7 is a sectional view of another embodiment of the invention with a unimetallic pulling Figure 8 is a sectional view of the rivet of Figure 7 with a bimetallic pulling and Figure 9 is a sectional view of the rivet of Figures 7 and 8 with a trimetallic pulling Referring now particularly to Figure 1 and Figure 2 there is seen a conventional blind rivet having a preformed head 1 a body a rivet head 3 and a locking collar The pulling stem comprises a body section 5 which serves to hold a knurled or splined section 6 and an adapter section 7 for connection with a suitable pulling tool or A plug section 8 of the pulling stem is equipped with an enlarged tapered portion 9 and a portion 10 which respectively serve to form the blind head 3 and deform the rivet body 2 into holes provided in the member s being riveted together as shown in a manner more fully described in Patent Specification 931 After the stem is pulled to a predetermined position the locking collar 4 is set in place by means of a suitable tool as is well known to those skilled in the art and the stem body 5 fractures at a predetermined stress and which is predetermined by a usual breaking In Figure 3 and Figure 4 there is seen another type of blind rivet which is described more fully in Patent Specification In this embodiment the blind head 3 is formed in the shape of a bulbed or mushroom head as by means of the special constructions of plug section 9a which is de scribed as a bulb forming section in the above mentioned patent The present invention is concerned with rivets of either of the two type s de sc ribed above or of other type s known in the Referr ing now to Figure 5 there is seen the combination of a rivet according to the invention having a bimetallic body with a unimetallic pulling Here the pulling stem compr ise a body s ection a knurled or splined section and an adapter section as well as a plug The taper ed portion of the plug s ection 9 is also similar to that pr eviously de s cribed and performs a similar except for the combinations of special material as s et forth The head 1 and shank section 2b are compo sed of a high tensile and shear strength mater the shank section 2b being combined at interface 2a with a tail section 2c made of a metal or alloys having a high ductility and being readily Materials us ed for the head and shank s ection 2b have a shear strength of up to 000 pounds per square a tensile strength of up to 000 pounds per square inch at room temper ature and an acceptable strength at temperature s as high as 1000 degree s Materials us ed for the fail section be side s being ductile and readily for mable should be compatible with the material used for head forming as described herein and also capable of joining integrally with the head and tail section by means of friction welding or other integral forming process at interface Materials that may be combined to form the bimetal rivet of the invention are tabulated below in Table Table 1 Rivet Body Material Combinations Head and Shank Section Tail Section 2b 2c Pure Titantium Alloy Tantalum Alloy FS60 Zirconium Alloy Zirconium 2 Pure Vanadium Pure Molybdenum Same as above for all Same as above for all Same as above for all Stainless Steel Monel VascoMax 300 Stainless Steel Monel In the case of the pulling stem we require a material which tensile has a and is with the material used for the rivet sections as described To accomplish different combinations of materials may be employed for the pulling section 8b and th e plug section These we join at interface by an integral forming process as in the case of the rivet itself described This is best seen in Figures 6 and The interface is sufficiently firm to apply pulling stress until the stem breaks at said breaking Superior results may be obtained insofar as the integral forming proces s is concerned by using the trimetallic embodiment shown on Figure An intermediate section 1 1 which forms interfaces 1 1 and l l with opposite parts of plug sections 11 c and l id said interfaces comprising integrally formed joints as described has been The material of section 1 1 is more readily joinable to the materials of sections 1 1 c and l i d respectively than would be these materials to each Materials that may be combined to form the stem of the invention are tabulated below in Table Table II Stem Material Combinations Pulling Section Hug Section Intermediate Sectio 8b 8c 1 1 Any one of the lV Inconel 750 Columbium Alloy l 3Al such as l 35N Same as above Tantalum Alloy suc as FS 60 Vasco Max 300 Same as Above Zirconium Alloy such as Zirconium AISI 4340 Same as above Molybdenum Alloy such as 5 Ti Pure Vanadium As used herein 35N is the designation used by Latrobe Steel for its alloy consisting of approximately 35 35 20 Chromium and 10 Vasco 300 designates Vanadium Alloys Steel s alloy consisting of approximately 18 9 1 aluminium and 02 The chemical composition of materials represented by the other material symbols used herein may be found in the publication DMIC Memorandum 232 dated February 1 entitled of Alloys for the Aerospace Industry and published by Defense Metals Information Battelle Memorial Ohio connection with rivet bodies where the individual sections are composed of materials having substantially different chemical for instance the combinations hereinabove the rivet body may be subjected to heat tr eatment after the sections are welded with the result that the head and shank material is hardened to a relatively high shear while the tail material remains or is made appreciably lower in shear strength and with sufficient ductility to be readily formed or upset without It was also dis covered that the required union can be accomplished if the head and shank section of the rivet body is subjected to heat treatment and the tail section of the rivet body also subjected to heat treatment separately prior to welding so that said head and shank section is treated to have a relatively high shear strength and said tail section is pretreated so as to have appreciably lower shear strength and sufficient ductility to be readily formed or upset without When the sections are heat treated separately prior to welding it is pos s ible to use materials of the same composition for both sections or of different substantially itions for the two Examples of materials where the same material is used for both sections of the rivet body and may be heat treated as aforesaid Beta III 1 5 and Beta C Examples where the sections of the rivet body are different materials and are treated before welding for the head and shank and Pure Beta III 5 or Beta C for the tail Further examples of materials of like or nearly like chemical composition heat treated to different conditions as separate parts prior to welding to form the rivet body are as follo 4 HEAD AND SHANK SECTION TAIL SECTION titanium solution treated 1625 titanium annealed 1325 1 hr 4 hrs 1 hr AC Beta III titanium composition Beta III titanium solution solution treated treated 5 Min 5 aged WQ aged 4hrs 4hrs AC 10 raised to 1175 AC titanium solution titanium hot o treated 1425 5 WQ straightened and ground aged 4 hrs AC Beta C titanium composition Beta C titanium solution 1500 cold teated 1500 15 drawn and aged 4 AC The above mentioned heat treated conditions would not be obtainable by heat treating the above metals after Additional examples of metals and their heat treatment before welding with a rivet body are as HEAD AND SHANK SECTION TAIL SECTION titanium solution treated 1625 Pure titanium 1 hr 4 hrs AC annealed 1300 1 hr AC Beta III titanium solution treated 5 WQ aged 4 hrs raised to AC titanium hot straightened and ground Beta C titanium solution o treated 1500 15 4 AC In the above AC stands for Air Cool WQ stands for Water Quench 10 is degree of vacuum expres sed in Torr In addition to use of friction welding to form the multimetal rivets and other forms of integral joining such as metallurgical bonding of the pres vacuum or diffusion type as well as fusion welding by use of electron or laser beams may be The adaptation of pulling stems to lockbolts is well known in the such lockbolt shown in Figure 1 of Patent Specification 017 granted on April The important feature is that the interface 8a or 1 1 be spaced from the breaking groove toward the adapter or pulling section 7 so that setting pull is exerted until after the plug or bolt section is locked with collar and thus sufficient resistance is created to break the stem at the breaking insufficientOCRQuality

Claims (1)

1. WHAT WE CLAIM In a blind rivet comprising pulling stem and body having a tail said pulling stem being through said hollow rivet body and having a thereon to enlarge tail section into a head pulled the improvement in rivet body a and shank section said tail section united end to said head and shank section comprising a metal having a high shear tensile said tail section comprising a ductile and readily said tail section and said head and shank section forming an interface therebe the material composing said head and shank section being of substa different chemical composition than the material comprising tail said interface comprising an integral head and shank section comprising an alloy from the group consistin of and said tail section comprising a metal selected the group consisting of molybdenum Tantalum FS 60 and The rivet of claim 1 in w a friction welded insufficientOCRQuality