Abstract:
A method of forming a joint comprises the steps of: (a) at least filling a container with granular particles, the granular particles having a size of 0.25 mm to 1 mm; (b) inserting a component part into the container; and (c) at least partially filling the container containing this component part and the granular particles with a flowable, curable liquid, this liquid having curing time of less than 90 seconds. According to one embodiment of the present invention, the curable liquid has a gap fill of less than 0.25 mm and the curing time is less than about 5 seconds or less.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to a joint and method for producing a joint between two components and more particularly to a joint and method that uses micrograms and a fast curing adhesive to provide a fast alignment and joining of two components in precise relationship with one another.  
         BACKGROUND OF THE INVENTION  
         [0002]    It is known that stable joints can be formed by cementing two or more components in place. However, because the typical curing time for most cements is relatively long (i.e., 5 minutes to several hours or several days), the expensive fixturing equipment holding these components in precise alignment is tied up for a long time, making the equipment unavailable for producing more jointed parts and increasing queue time and assembly. Furthermore, during the long curing time the two component may be inadvertently moved out of alignment and then set in place in that position.  
           [0003]    Some methods of joining two or more components utilize a mixture of solid particles and a curable cementing compound to form such joints. For example, U.S. Pat. No. 4,836,967 describes a method for connecting a plurality of bars in a metal casting. This method includes the steps of pouring a granulated solid with grain size of 5 mm to 100 mm to into a metal casing having a centrally located aperture and a plurality of filling apertures, prestressing the solid by driving a mandrill through the filling apertures and injecting a hardening fluid such as a cement based grounding mortar through the central aperture. According to the summary of invention, prestressing the granulated solid results in a very stable joint. However, this step requires extra time during the joint assembly. Furthermore, making a casting with a special central aperture for accepting the hardening fluid and having to cover the central aperture after the hardening fluid is injected into the casing results in an expensive joint. Finally, this patent does not disclose how to achieve a precise alignment of the components relative to one another.  
           [0004]    U.S. Pat. No. 4,407,770 describes a method for anchoring cables inside a sleeve. This method includes the steps of partially filling the sleeve containing the cables with the curable liquid made of epoxy resin and mineral power, adding the aggregate particles and then, allowing the liquid mixture to cure to a solid mass. However, the epoxy resin/powder mixture takes relatively long time to cure.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the present invention to provide a method for accurately positioning two component with respect to one another and then rapidly joining them together while preserving this alignment, forming a solid joint.  
           [0006]    It is another object of the present invention to provide a stable joint comprised of two precisely aligned components. According to one aspect of the present invention, a method of forming a joint comprises the steps of: (a) at least filling a container with granular particles, the granular particles having a size of 0.25 mm to 1 mm; (b) inserting a component part into the container; (c) at least partially filling the container containing this component part and the granular particles with a flowable, curable liquid, this liquid having curing time of less than 90 seconds. According to one embodiment of the present invention, the curable liquid has a gap fill of less than 0.25 mm.  
           [0007]    According to another aspect of the present invention, a method of forming a joint by connecting at least one component part to a housing having a fill cavity, comprising the steps of: (i) introducing granular solid material having a grain size from 0.25 mm to 1 mm into the fill cavity; (ii) placing at least a portion of the component part into the fill cavity; (iii) applying a hardening fluid into the fill cavity over the granular solid material, wherein the hardening fluid has a gap fill of less than 0.25 mm.  
           [0008]    According to one embodiment of the invention, a method of forming a joint by connecting at least one component part to a housing having a fill cavity comprises the steps of: (i) introducing granular solid material having a grain size from 0.25 mm to 1 mm into said fill cavity; (ii) placing at least a portion of the component part into the fill cavity; (iii) aligning the component part with respect to the housing by moving the component part inside the cavity until a desired orientation is achieved; and (iii) applying a hardening fluid into the fill cavity, wherein the hardening fluid has a gap fill of less than 0.25 mm, to lock said component in said desired orientation.  
           [0009]    According to yet another aspect of the present invention, a rigid joint comprises a plurality of components including: (i) a first component having an inner wall defining a fill cavity; (ii) a second component at least partially situated in the fill cavity of the first component; and (iii) a plurality of micrograms located between the inner wall and at least a part of the first component, the micrograms having a size of less than 1 mm. At least a portion of the micrograms is coated with a polymerizing liquid, such that the coated micrograms and the second component are fixably secured in place. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a cross-sectional view of a plurality of mechanical components positioned relative to one another.  
         [0011]    [0011]FIG. 2 is a cross-sectional view of the plurality of mechanical components of FIG. 1 after they have been joined to each other.  
         [0012]    [0012]FIG. 3 is a perspective view the plurality of mechanical components of FIG. 1 after they have been joined to each other.  
         [0013]    [0013]FIG. 4 is a cross sectional view of a frame and a frame base positioned relative to one another.  
         [0014]    [0014]FIG. 5 is a perspective view of the frame of FIG. 4.  
         [0015]    [0015]FIG. 6 is a perspective view of the frame base of FIG. 4.  
         [0016]    [0016]FIG. 7 is a cross sectional view of a portion of a frame base of FIG. 4 with a cavity containing micrograms and a side wall portion of the frame of FIG. 4.  
         [0017]    [0017]FIG. 8 is a perspective view of the frame and the frame base after they have been joined to each other. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    The present description will be directed in particular to elements forming part of, or in cooperation more directly with, the apparatus in accordance with the present invention. It is understood that elements not specifically shown or described may take various forms well known to those skilled in the art.  
         [0019]    Referring to FIGS. 1, 2 and  3 , a joint according to the first embodiment of the present invention comprises a first component  10  with a fill cavity  12  and a second component  13  at least partially situated in this fill cavity  12 . More specifically, according to the first embodiment of the invention, the second component  13  comprises a block  14  and a post  15 . The post  15  fits into the fill cavity  12  of the first component  10  and preferably has a textured outer surface  15 A. The fill cavity  12  may have any cross section suitable for receiving the required part (such as the post  15 , for example) of the second component  13 . The fill cavity  12  should be larger than the portion of the second component  13  that is being inserted into the fill cavity  12 . The walls  20  of the fill cavity are also preferably textured.  
         [0020]    A plurality of micrograms  16  are poured into the fill cavity  12  and fill the void  18  between the wall  20  of the cavity  12  and the inserted part (i.e., the post  15 ) of the second component  13 . The term “microgram” describes a solid particle that is not larger than 1 mm in its largest dimension. The width d of the void  18  needs to be a minimum of 3 micrograms. It is preferred that the width d be between 1 mm and 15 mm. In this embodiment, the void  18  has a width d of 2.5 mm to 3 mm (FIG. 2.) and the microgram size is about 0.3 mm.  
         [0021]    Alternatively, the micrograms  16  are poured into the fill cavity  12  first and then the second component  13 , or a part thereof, is pressed into the micrograms  16 , displacing the micrograms  16 . Either way, the micrograms  16  surround the part of the second component  13  that is situated inside the fill cavity. The micrograms  16  can be glass microspheres, metal microspheres, non spherical metal chips, table salt, sand or the like.  
         [0022]    The second component  13 , while its post  15  is surrounded by the micrograms  16 , is not yet locked in place and can be moved relatively to the first component in six degrees of freedom indicated by arrows  21 ,  22 ,  23 ,  24 ,  25 ,  26  (for example, up, down, sideways, and tilted around). Once the proper orientation of the second component  13  is achieved, a fast curing adhesive liquid  28  is applied from a container  29  to the upper surface  30  of the micrograms  16 . It is preferred that the liquid  28  is poured rather than dripped onto the top of micrograms  16 . This provides better (i.e., deeper) penetration through the micrograms  16  filling the inside of at least a portion of the fill cavity  12 . The liquid  28 , for example Super Glue, penetrates through at least the the top portion  32  (about 1 mm to 10 mm deep and, preferably, 3 mm to 6 mm deep) of the micrograms  16 , coats the micrograms  16 , fills the gaps between the micrograms, quickly hardens and locks the second component  13  in position. The curing time of the liquid  28  is less than 90 seconds and preferably less than 75 seconds and more preferably, no more than 30 seconds. It is most preferable that the curing time be no more than 20 seconds. In this specification the term “curing time” is defined as the time required for the liquid  28  to harden so that two components are prevented from further movement relative to one another, without the breakage of the joint.  
         [0023]    As stated above, it is preferred that the wall  20  defining the fill cavity  12  and the outer surface  15 A of the component  13  that fits inside the fill cavity  12  be textured; for example threaded, or sand blasted. This would provide a better gripping surface for the adhesive to bind with. The micrograms  16  have a size of 1 mm or less and preferably less than 0.5 mm. It is most preferable that the size of the micrograms  16  be between 0.25 mm and 0.5 mm. The small grain size (0.25 mm and 0.5 mm) produces more surface area and thus more bonding area, resulting in higher strength joint. Furthermore, smaller micrograms result in smaller gap areas between the micrograms. This, in turn, results in faster cure times. The fast curing adhesive liquids used with smaller size micrograms  16  should be less viscous in order to fill the smaller sized gaps between the micrograms  16 . However, because all adhesive liquids have some viscosity, if the size of the micrograms is less than 0.25 mm the gap area between the micrograms becomes very small, making it hard for the liquid  28  to penetrate into the gaps. This results in weaker joints.  
         [0024]    Preferable curing liquids are polymerizing liquids, for example, liquids that undergo anionic polymerization. An example of such liquid is cyanoacrylate adhesive such as a fast curing, single component cyanoacrylate instant adhesive available under the trade name of LOCTITE® PRISM™ 401 from Loctite Corp. of Newington, Conn. Typical curing or fixturing times for adhering to various materials for one of these fast curing liquids are provided below in Table 1. The data for other suitable materials is provided in Table 2. I have used LOCTITE® PRISM™ 401 and the Loctite product number 420 with glass microspheres of about 0.3 mm diameter and achieved a curing time, and thus a stable bond between two steel components  10  and  13 , in about 5 seconds or less. Thus, two components can be secured in position quickly, maintaining the required alignment between the two components without disturbing their relative positions.  
                                           TABLE 1                           Performance of LOCTITE ® PRISM ™ 401 on metallic and non-metallic       substrates:                Material   Typical Fixturing Time (seconds)                            G-10 epoxy glass:   10           Steel (degreased):   13           Aluminum (etched):   6           Zinc dichromate:   60           Neoprene rubber:   5           Nitrile rubber:   5           ABS:   6           PVC:   6           Polycarbonate:   23           Phenolic materials:   10                      
 
         [0025]    [0025]                                           TABLE 2                       Loctite                                   Product       Number   404   409   414   415   416   420   422                   Typical   Rubber   General   Plastic   Gap   Gap   Wicking   Gap       Use   “O” Ring   Purpose   Bonder   Filling   Filling   Type   Filling           Bonder   Gel       Metal   Plastic   Plastic   Plastic               Adhesive       Bonder   Bonder   Bonder   Bonder       Color   Clear   Clear   Clear   Clear   Clear   Clear   Clear       Gap Fill   .005″   .010″   .006″   .008″   .008″   .002″   .008″       Resin Base   Ethyl   Ethyl   Ethyl   Methyl   Ethyl   Ethyl   Ethyl       Viscosity cP   80   Gel   110   1500   1500   2   2500       Strength psi   3,500   3,200   3,200   3,600   3,200   2,900   3,200       Tensile       Shear       Temperature   −65° F. to   −65° F. to   −65° F. to   −65° F. to   −65° F. to   −65° F. to   −65° F. to       Range   180° F.   180° F.   180° F.   180° F.   180° F.   180° F.   180° F.       Cure Speed*   30 sec.   75 sec.   20 sec.   30 sec.   30 sec.   20 sec.   30 sec.       (Fixture)       Full cure**   24 hrs.   24 hrs.   24 hrs.   24 hrs.   24 hrs.   24 hrs.   24 hrs.       Specific   1.09   1.10   1.05   1.09   1.05   1.05   1.09       Gravity       Technical   404   409   414   415   416   420   422       Data Sheet                                    
         [0026]    [0026]FIG. 4 illustrates a second embodiment of the present invention. A frame  40  comprising three side walls  42  (FIG. 5) needs to be aligned with the frame base  46  and rigidly attached thereto. According to this embodiment of the present invention, the frame base  46  includes a long and narrow fill cavity  48  formed by the walls  50  (FIG. 6). This fill cavity  48  is filled with the micrograms  16 . The side walls  42  of the frame  40  are pressed into the fill cavity  48  and the micrograms  16  are displaced to fill the void between the walls  42  and the walls  50  (FIG. 7). Alternatively, the side walls  42  are inserted into the fill cavity and the micrograms  16  are used to fill the void between the walls  50  and the walls  42 . The frame  40  is moved (translated and rotated) until it has the correct orientation relative to the frame base  46 . The frame  40  is held in this position by a holding fixture (not shown) and a fast curving liquid  28 , for example, LOCTITE® PRISM™ 420, is then poured into the fill cavity  48  on both sides of walls  42 . The fast curing liquid  28  seeps at least into the top layer  32  of the micrograms  16 , undergoes polymerization, quickly hardens and rigidly secures the frame walls  42  inside the cavity  48  of the frame base  46 . The hardening of the fast curing liquid  28  secures quickly the frame  40  in precise orientation with respect to the frame base  40  (FIG. 8). I have achieved a rigid connection between the frame and the frame base in about 5 seconds or less. This is much faster than 5 minutes to several days time required for hardening cementing components typical of the prior art.  
         [0027]    It is an advantage of the method of the present invention that it provides an improved method for assembling components that require sizeable movements and precision when positioning and aligning by providing these components with unrestricted movement (six degrees of freedom). The improved process is non-destructive to the alignment because the fast curing fluid  28  does not displace the two components relative to one another. It is also an advantage of the improved method that the components are rapidly and fixably secured to one another without introducing distortion, creep, or other non-desirable changes in position of these components.  
         [0028]    Existing technologies that could be replaced with the above described method of the present invention are, for example, complicated and time-consuming mechanical screw adjustments. Although such mechanical screw adjustments could accomplish precision alignments, the cost in parts and labor is very high. The improved method of the present invention can also be used instead of the prior art methods that require filling the void between two components (that have been aligned) with an adhesive that needs to be cured by the ultraviolet light or with long-time curing adhesive such as epoxy resin.  
         [0029]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.  
       PARTS LIST  
       [0030]    [0030] 10  First component  
         [0031]    [0031] 12  Fill cavity  
         [0032]    [0032] 13  Second component  
         [0033]    [0033] 14  Block  
         [0034]    [0034] 15  Post  
         [0035]    [0035] 15 A Outer surface  
         [0036]    [0036] 16  Micrograins  
         [0037]    [0037] 20  Inner wall  
         [0038]    [0038] 21 ,  22 ,  23 ,  24 ,  25   26  Directional arrows  
         [0039]    [0039] 28  Liquid  
         [0040]    [0040] 29  Liquid container  
         [0041]    [0041] 30  Upper surface  
         [0042]    [0042] 32  Top portion  
         [0043]    [0043] 40  Frame  
         [0044]    [0044] 42  Frame walls  
         [0045]    [0045] 46  Frame base  
         [0046]    [0046] 48  Fill cavity  
         [0047]    [0047] 50  Walls of the frame base