Abstract:
A tool for installing rivet nuts, the tool comprising a screw, a rotatable drive for rotating the screw and an anti-rotation device for preventing rotation of a rivet nut which has been screwed onto the screw.

Description:
RELATED APPLICATION DATA 
     This application claims priority to United Kingdom Patent Application No. 1002954.4 filed on Feb. 22, 2010, which is hereby incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention relates to a tool for installing rivet nuts. 
     BACKGROUND 
     A rivet nut is a blind nut comprising a flange and internally threaded body. Rivet nuts are installed by inserting them into a pre-drilled hole. The nut is then deformed by compressing it until the rivet nut is held tight in the hole and will not turn. 
     Rivet nuts may be installed using a hand tool. 
     Most hand tools currently being manufactured and sold throughout the world use a linear action to compress the rivet nut. Tools take the form of either a hand plier, where two handles are gripped and pulled together to directly compress the rivet nut, or a lever tool, where two handles are pulled together and the rivet nut is compressed using an action similar to that of a set of garden shears. 
     Both types of tool have many disadvantages in terms of quality, reliability, difficulty of access, the need to accurately set the stroke (or movement) of the tool to obtain the correct installation of the rivet nut, difficulty of use, and the requirement for two hands and a lot of strength to operate the tool. 
     A small number of hand tools use a rotary action to compress the rivet nut. These have the advantage that they require less force to be operated than the tools which use a linear action. However, the known tools are complicated and therefore expensive to manufacture. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to provide a tool for installing rivet nuts which uses a rotary action, but is simple, cheap to manufacture and of high quality. 
     Accordingly, the invention provides a tool for installing rivet nuts, the tool comprising a screw, a rotatable drive means for rotating the screw and means for preventing rotation of a rivet nut which has been screwed onto the screw. 
     As the tool includes means for preventing rotation of a rivet nut which has been screwed onto the screw, rotating the drive means will result in the rivet nut being compressed. 
     The screw may be a set screw or cap screw. In particular, it may be a conventional high tensile set screw or cap screw. Such screws are readily attainable from any hardware store. 
     The tool may be provided with a plurality of screws having different thread sizes. Usually it will be sufficient to provide screws having thread sizes from M4 to M8 inclusive as this will cover about 85 to 90% of market demand, but an M10 variant may also be provided. 
     The tool may comprise a body having an end face with a through hole for receiving the screw. 
     The outer surface of the end face may be roughened, for example by grit blasting. Roughening the end surface of the body means that it can provide a key to prevent rotation of a rivet nut which has been screwed onto the screw. 
     The body may be hollow and the drive means may be dimensioned to be a running fit with the bore of the body. The term “running fit” as used herein means that the drive means is free to rotate within the bore of the body. 
     The tool may comprise means to hold the drive means within the body. 
     The holding means may comprise a handle which comprises a projection. Alternatively, the holding means may comprise a first washer. The drive means may comprise a recess to receive the projection or first washer. 
     The bore of the body may comprise a recess around its circumference to receive the first washer. 
     The tool may further comprise a rotatable screw holder which comprises means for holding the screw and is dimensioned to be a running fit with the bore of the body. 
     The tool may further comprise means to hold the screw holder within the body. 
     The holding means may comprise a second washer. 
     The screw holder may comprise a recess around its outer circumference to receive the second washer. 
     The bore of the body may comprise a recess around its circumference to receive the second washer. 
     Alternatively, the holding means may comprise a retractable element which can be moved between a first position in which it does not hold the screw holder in place and a second position in which it does hold the screw holder in place. 
     The screw holder may comprise a recess to receive the retractable element. 
     The retractable element may be a screw located in an aperture in the body. 
     In use, the drive member may be engaged with the screw holder. 
     The screw holder and the drive member may be a push fit with one another. The screw may be held within the screw holder by a grommet. 
     The tool may further comprise means for facilitating rotation of the drive member and/or screw holder. 
     The rotation-facilitating means may comprise a bearing set. 
     The drive means may be rotatable by hand. 
     The invention further provides a kit of parts for assembling a tool according to the invention, the kit of parts comprising a plurality of elements each comprising a screw, each screw being of different thread size, and a drive means which can be used with any of the elements. 
     Each of the elements may further comprise a body and a screw holder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be illustrated by way of example with reference to the following drawings (it is noted that some features shown some figures are omitted in other figures and some features shown in some figures are shown in greater detail in other figures) of which: 
         FIG. 1  shows a cross-sectional side view of a first embodiment of a tool according to the invention; 
         FIG. 2  shows a side view of the body of the tool shown in  FIG. 1 ; 
         FIG. 3  shows a side view of the drive member of the tool shown in  FIG. 1 ; 
         FIG. 4   a  shows a side view of the screw holder of the tool shown in  FIG. 1 ; 
         FIG. 4   b  shows an end view of the screw holder of the tool shown in  FIG. 1 ; 
         FIG. 5  shows a side view of the handle of the tool shown in  FIG. 1 ; 
         FIG. 6  shows a tool case containing a kit of parts for assembly into a tool according to the invention; 
         FIG. 7  shows a side cross-sectional view of two alternative screw holders; 
         FIG. 8  shows a cross-sectional side view of a second embodiment of a tool according to the invention; 
         FIG. 9  shows a side view of the body of the tool shown in  FIG. 8 ; and 
         FIG. 10  shows a side view of the screw holder of the tool shown in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     The tool shown in  FIG. 1  comprises a hollow cylindrical body  1  having an open end face  2  and a closed end face  3 , which is provided with a through hole  4 . The outer surface  5  of the closed end face  3  has been roughened by grit blasting and then case hardened. 
     The bore  6  of the body  1  is provided with a recessed groove  7  about its circumference, positioned towards the closed end face  3  of the body  1 . 
     The outer surface of the body  1  is provided with a threaded aperture  8  for receiving a removable handle  9 , positioned towards the open end face  2  of the body  1 . 
     Fitted within the bore  6  of the body  1 , adjacent to one another, starting with the member adjacent to the closed end face  3 , are a bearing set  10 , a screw holder  11  and a drive member  12 . 
     The bearing set  10  is cylindrical and is provided with a through hole  13 . The bearing set  10  which comprises one needle bearing sandwiched between two hardened thrust washers. 
     The screw holder  11  comprises a hollow cylindrical body  14  having an open end face  15  and a closed end face  16 , which is provided with a through hole  17 . The body  14  is dimensioned to be a running fit with the surface of the bore  6  of the body  1  of the tool. 
     The screw holder  11  includes a recessed groove  18  about its outer circumference. The screw holder  11  is retained within the body  1  of the tool by an “O” ring  19  which is fitted in the groove  18 . The screw holder may comprise a rubber grommet (not shown) located above the screw head to maintain that screw within the screw holder. 
     The drive member  12  comprises a cylindrical body  20  having a recessed and elongated groove  21  around its outer circumference. The body  20  is dimensioned to be a running fit with the surface of the bore  6  of the body  1  of the tool. The drive member  12  is retained within the body  1  of the tool by a nipple  22  located on the end of handle  9 , which is fitted within groove  21  on the drive member  12 . In an alternative embodiment (not shown), the drive member is retained within the body of the tool by an “O” ring, which is fitted within a recessed groove in the drive member. 
     A knurled knob  23  is removably attached to one end of the body  20  and a drive element  24  is provided at the other end of the body  20 . The drive element  24  comprises two sections  25 ,  26 , a first section  25  which comprises a hexagonal body of smaller cross section than the body of the drive member  12 , and a nipple  26 . The nipple  26  acts to locate the grommet above the screw head. The bore  27  of the body  14  of the screw holder  11  is dimensioned so that it is a push fit with the first section  25  of the drive element  24  of the drive member  12 . 
     The tool further comprises a set screw  28 , which has a hexagonal head (not shown) at one end. The set screw is a high tensile grade 8.8 or 10.9 strength set screw. 
     The through holes  4 ,  13 ,  17  in the body  6  of the tool, bearing set  10 , screw holder  11  and the drive element  24  are aligned with one another. The set screw  28  is positioned within the tool so that it passes through the aligned through holes  4 ,  13 ,  17  and the first section  25  of the drive element  24  is received in the end of screw holder  11 . 
     In order to install a rivet nut  29 , the rivet nut is screwed onto the set screw  28  and hand tightened until the head  30  of the rivet nut  29  is tight against the closed end face  3  of the body  1 . The knob  23  is then rotated clockwise. Because the end face  3  has been roughened it provides a key which prevents the rivet nut  29  from rotating when the knob  23  is rotated. This means that rotating the knob  23  causes the set screw  28  to rotate and compress the rivet nut  29 . Once the rivet nut has been installed, the knob  23  is rotated counter-clockwise to release the set screw  28  from the installed rivet nut. 
     For most rivet nuts  29 , it will be possible to turn the knob  23  by hand, but for larger sizes of steel or stainless steel rivet nuts, it may be necessary to use a ratchet spanner to turn the drive member  12 . 
     The tool of  FIG. 1  may be provided in the form of a kit of parts which may be used to install rivet nuts having a range of different thread sizes. The kit of parts shown in  FIG. 5  comprises a single handle  32  and drive member  33  and a number of elements  34  each comprising a body  35  together with a screw holder (not shown), bearing set (not shown) and set screw  36 , each of the set screws  36  having a different thread size. Usually it will be sufficient to provide set screws  36  having thread sizes from M4 to M8 inclusive as this will cover around 85 to 90% of market demand. 
       FIG. 6  shows two different types of screw holder  37 ,  38  for use in the kit of  FIG. 5 . Screw holder  37  is suitable for use with an M8 set screw and screw holder  38  is suitable for use with M4-M6 set screws, being drilled and broached to the appropriate size. 
     In order to assemble the tool, the desired set screw  36  is selected, and the handle  32  is screwed into the body  35  of the element  34  which contains that set screw  36 . The drive member  33  is then inserted into the open end of the body  35  and pushed into the body  35  until the first section of the drive member  33  is fully inserted in the recess of the screw holder. 
     The tool shown in  FIG. 8  is similar to the tool shown in  FIG. 1 , but there are two main differences. 
     The first main difference is that the hexagonal head set screw  28  has been replaced by a socket head cap screw  39 . Such cap screws are readily available as a standard product in grade 12.9 anywhere in the world in any quantity. This means that the tool shown in  FIG. 8  is suitable for use in any countries where it may be difficult to obtain hexagonal head set screws in the higher strength grades. 
     The second main difference is that the “O” ring  19  which holds the screw holder  11  in place in the body  1  has been replaced by a button head socket cap screw  40   a , thereby eliminating the need for the internal recessed groove in the body. The button head socket cap screw  40   a  has a dog point  40   b.    
     The body  41  of the tool of  FIG. 8  is shown in  FIG. 9 . It can be seen that, unlike the body  1  of  FIG. 2 , it does not include an internal recessed groove  7 . Instead, it includes a screw-threaded aperture  42 . The button head socket cap screw  40   a  is located in this screw-threaded aperture  42  so that it can be moved between a first position in which it does not hold the screw holder  43  in place and a second position in which it does hold the screw holder  43  in place. 
     The screw holder  43  of the tool of  FIG. 8  is shown in  FIG. 10 . The screw holder  43  is located within the body  41  by the support washer  44  shown in  FIG. 8 . It can be seen that the screw holder  43  comprises three adjoining cylindrical sections  45   a ,  45   b ,  45   c  of different cross-section, and two hexagonal bosses  46   a ,  46   b  of different cross-section, one at either end of the three sections  45   a - c.    
     The first hexagonal boss  46   a  is dimensioned so that it is a push fit in a recess  47  in one end of the socket head cap screw  39 . The second hexagonal boss  46   b  is dimensioned so that it is a push fit in a recess  48  in one end of the drive member  49 . The second section  45   b  has the largest cross-section of the three sections  45   a - c , and is dimensioned to be a running fit with the surface of the bore of the body  41  of the tool. The third section  45   c  is positioned between the second section  45   b  and the second hexagonal boss  46   b . When the tool is assembled, this section  45   c , having a smaller cross-section than the second section  45   b , acts to provide a recess  50  in which the button head socket cap screw  40   a  can locate, thereby holding the screw holder  43  in place. 
     The tool of  FIG. 8  may be provided in the form of a kit similar to that shown in  FIG. 5 . 
     The above embodiments are described to illustrate the invention, and are not intended to be limiting. The skilled person will be readily able to devise alternative embodiments without departing from the scope of the claims.