Abstract:
A method and apparatus for installing a hollow threaded insert into a hole in a substrate having first and second surfaces. The insert has a hollow shaft having a first end portion, a second end portion and an intermediate portion. The insert has a front flange at the first end portion for engaging the front surface of the substrate around the hole. The second end portion of the shaft has an internal thread and, the intermediate collapses to engage the second surface when a force is applied that pulls the second end portion toward the first end portion.

Description:
This is a continuation application of U.S. Ser. No. 09/707,113, filed Nov. 6, 2000 which is now U.S. Pat. No. 6,490,905. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to methods and apparatus for installing threaded inserts into a substrate. Such substrates, for example, include films, sheets or plates that may be curved or flat. The substrates may be made of materials such as metal, wood, glass, ceramic, cellulose, leather or plastic and may be completely solid, or partly porous, e.g. in the form of textiles or foam. More particularly, the invention concerns an insert that has a hollow shaft having first and second end portions and an intermediate portion between the end portions and a flange surrounding the first end portion. The insert is installed by passing the intermediate portion and second end portion through a hole in the substrate to preferably, but not essentially, pass through a rear surface of the substrate so that the flange of the insert contacts a front surface of the substrate. The second end portion is then pulled toward the first end portion to collapse the intermediate portion of the shaft upon the rear surface of the substrate (or upon the sidewalls defining the hole in the substrate) to form a gripping structure that secures the insert. 
     Inserts, as described above, are well known. They are for example readily purchased at local hardware stores for insertion into drywall substrates. Such inserts have more recently been used in production processes to provide threaded structures in substrates that may not be strong enough by themselves to support reliable threads or to reduce production time by eliminating the need to thread individual holes in the substrates with taps. 
     The use in production has, however, been hampered by the lack of processes and equipment to rapidly and reliably install such inserts. 
     The first, and still most common, way to install such inserts is by placing the shaft through a hole in the substrate, as above described, and turning a threaded rod with an end flange, e.g. a bolt having a bolt head or flanged threaded mandrel or screw head, into the threads in the second end of the insert thus pulling the second end toward the first end of the insert to collapse the intermediate portion of the insert, as previously described. 
     Such a method of installation has numerous disadvantages. For example, when the threaded rod with its end flange is turned to collapse the intermediate portion, significant torque is required. The high torque tends to turn the entire insert which can result in a bad installation by causing the formation of a defective gripping structure, or destroying or damaging the substrate or even more commonly, causing failure of threads within the insert. Great care must therefore be taken to assure that the insert does not spin. This often requires that a separate insert retaining means be employed that can withstand the required high torque. Even in such cases, the failure to obtain a good installation is more frequent than can be tolerated by many, if not most, production systems. 
     More recently, such inserts have been installed in production systems by threading a mandrel into the insert and longitudinally pulling the second end of the shaft of the insert toward the first end of the shaft of the insert, without applying a rotational torque. Nevertheless, the apparatus and processes for accomplishing that result have not been as reliable as desired. In particular, in existing apparatus, when the mandrel was pulled, it was necessary to move the entire drive assembly with the mandrel thus preventing secure attachment of the drive to a cylinder housing for the piston providing the pulling force. As a result, the drive (motor) tended to at least partially move rotationally when it was activated creating wear and misalignment and preventing smooth rotational operation. Further when the drive was activated to rotate the drive shaft, due to wear, as previously described, unacceptably high friction resulted between the drive shaft and piston through which the shaft passed, wearing both the drive shaft and the race or bore through the piston accommodating the drive shaft. As a further result, the turning of the drive shaft tended to also rotate the piston creating wear in the piston seals. The same increase in friction caused an increase in torque requirements to overcome friction losses. All of these problems resulted in significant down time and potentially unsatisfactory installation of the insert. As an even further disadvantage of such apparatus and methods, there was no good way to detect when the screw head (e.g. threaded mandrel) was withdrawn to permit positioning of an insert for loading onto the screw head. There was also no good way to detect where the screw head was screwed into the insert so that the nose retainer contacted the flange of the insert or where the shaft of the insert was inserted into the substrate so that the insert flange contacted the first surface of the substrate or where the screw head had been completely unscrewed from the insert. Accurate use of detectors would have been hampered in such devices due to motion of the drive relative to the cylinder housing and also due to lack of a secure attachment of the drive, the tendency of the piston to rotate and undesirable wear, as previously described. Attempts to stop the piston from rotating themselves give a further wear point as the misalignments due to the insecurely attached drive permit rotational forces to be applied to the piston to be at least partly successful in causing piston rotation due to wear as previously described. The devices further did not lend themselves to safe placement of detectors, i.e. there was no good way for internal detecting mechanisms and the required undesirable movements previously described caused vibration of any sensors used. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of an apparatus in accordance with a preferred embodiment of the present invention where the insert gun of the invention is mounted on a frame. 
     FIG. 2 is a side view of a preferred embodiment of an insert gun of the present invention. 
     FIG. 3 is a cross sectional view of the gun of FIG. 2 taken on line  3 — 3  of FIG.  2 . 
     FIG. 4 is an exploded isometric view of the gun of FIG.  3 . 
    
    
     BRIEF DESCRIPTION OF THE INVENTION 
     In accordance with the invention there is therefore provided a method and apparatus that overcome or minimize the disadvantages of the methods and apparatus discussed above in the Background of the Invention. Particularly, the apparatus and method of the invention permit reduced apparatus wear, better and more reproducible results, verification of crimp force to collapse the insert to form the grip, confirmation of the collapsed dimension of the insert, and the verification of the presence of proper threads in the installed insert. 
     As already discussed, the insert to be used in accordance with the invention is a hollow threaded insert for placement into a hole in a substrate where the substrate preferably, but not essentially, has front and rear surfaces. The insert has a shaft with a first end portion, a second end portion and an intermediate portion between the first end portion and second end portion. The insert has a front flange at the first end portion of the shaft for engaging the first (front) surface of the substrate around the hole. The second end portion of the shaft has an internal thread. The intermediate portion includes a gripping means that engages the rear surface of the substrate; or in the case where the shaft of the insert does not pass through the hole, the side walls of the hole; when a force is applied that pulls the second end portion toward the first end portion. 
     In particular, the method includes the steps of: 
     activating a rotatable drive having an attached drive shaft in turn having an attached externally threaded mandrel so that the threaded portion of the mandrel rotates into the hollow threaded portion of the insert through the flange until a nose retainer, through which the mandrel passes, contacts the flange of the insert; 
     moving the drive, drive shaft, mandrel and attached insert to place the shaft of the insert into the hole in the substrate so that the flange of the insert contacts the first surface of the substrate; 
     pulling the second end portion of the shaft of the insert toward the first end portion of the shaft of the insert by means of a pressure applied to a piston within a cylinder where the piston is connected to the drive shaft holding the mandrel so that the motion of the mandrel collapses the intermediate portion of the insert to grip the second (rear surface of the substrate, or the sidewalls of the hole), and so that the drive shaft moves in a compliant coupling toward the drive; 
     turning the drive in a reverse direction to disengage the mandrel from the threads in the insert; and 
     moving the mandrel, nose retainer, drive shaft and drive in a direction away from the flange of the installed insert. 
     The apparatus for installing a hollow threaded insert through a hole in a substrate includes a piston, a drive shaft, a cylinder, an externally threaded mandrel having threads that match the internal threads of the insert, a compliant coupling, a rotatable drive, and a nose retainer. 
     Structure is provided for moving the piston, drive shaft, cylinder, mandrel, compliant coupling, rotatable drive and nose retainer toward the flange of the insert so that the threads of the mandrel contact the threads of the insert and for moving the threads of the mandrel into the hollow portion of the insert through the flange so that the threads of the mandrel rotate into the threads within the hollow portion of the insert until the flange of the insert contacts the nose retainer. The structure for moving and rotating includes the drive shaft connected to the mandrel where the drive shaft is set into the compliant coupling to the rotatable drive. 
     Apparatus is provided for moving the mandrel with attached insert to place the insert shaft into a hole in the substrate so that the flange of the insert contacts the first (front) surface of the substrate and for pulling the second end portion of the insert toward the second (rear surface or hole sidewalls) surface of the substrate by applying pressure to the piston within the cylinder where the piston is connected to the drive shaft so that the intermediate portion of the insert collapses to grip the second) surface of the substrate and so that the drive shaft moves in the coupling toward the drive without moving the drive. 
     The drive is any suitable rotating drive, e.g. an electric or air motor that can be run in a reverse direction to disengage the screw head from the threads in the insert. Structure is also provided for moving the piston, drive shaft, cylinder, mandrel, slide coupling, rotatable drive and nose retainer away from the flange of the installed insert. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The inserts for use in accordance with the present invention are as previously described. Such inserts are usually made from a metallic material, e.g. aluminum, steel, copper, or bronze, but may be made from certain plastics that are both flexible and rigid enough to form a permanent grip when the second end of the insert is drawn toward the second surface of the substrate, and strong enough to maintain threads that can withstand the torque and retaining ability required for a particular application. The first end of the insert frequently has a length about equal to the thickness of the substrate or slightly less. The intermediate portion of the insert shaft, that forms the grip, usually begins at about the rear surface of the substrate and extends to the threads at the second end when the shaft of the insert passes through the substrate. 
     As already discussed, the substrate may be made of many types of materials and is usually of a thickness of from about 0.5 nm to about 15 cm. The thickness of the substrate is most commonly from about 1 mm to about 10 mm. It is nevertheless to be understood that the invention is not necessarily limited by substrate thickness. 
     The rotatable drive is usually a hydraulically operated motor, e.g. a pneumatic air motor, but may be any suitable source for application of a rotational force, e.g. an electric motor. 
     The drive shaft is usually a steel rod that may be provided with bosses or shoulders for seals or retention. A first end of the drive shaft is adapted to be fitted to a variable coupling, as described infra, and the second end of the drive shaft is usually formed to accept a threaded mandrel so that the mandrel, which is a wear part, can be quickly replaced without disassembly of the apparatus of the invention to remove the drive shaft. 
     An important aspect of the present invention is the variable (or compliant) coupling that permits the first end of the drive shaft to be connected to the spindle of the drive while at the same time allowing the drive shaft to move toward and away from the drive without causing drive movement. Such a coupling also allows for at least some misalignment of the spindle and drive shaft without creating significant wear. Examples of such variable or compliant couplings are slide couplings and spring loaded couplings. 
     The apparatus for pulling the second end of the shaft of the insert includes a piston within a cylinder. The piston is biased toward the nose of the insert gun, e.g. with a spring. When the piston is forced in a direction away from the insert, e.g. by application of pressurized hydraulic fluid to the face of the piston sealed within a cylinder, the piston engages the drive shaft, that passes through the piston, and forces the drive shaft away from the insert thus pulling the second end of the insert shaft toward the rear surface of the substrate to cause the intermediate portion of the shaft to form a grip against the rear surface of the substrate. “Hydraulic”, as used herein means the use of pressurized fluid to move a piston. The fluid may be either a liquid, e.g. an oil or a gas, e.g. air. 
     The entire gun assembly, i.e. cylinder, piston, drive, drive shaft, mandrel, variable coupling, and nose retainer, is moved in a slide on a frame using hydraulic, e.g. pneumatic, cylinders connected between the frame and a bracket holding the gun. 
     The invention may be better understood by reference to the drawings that show a preferred embodiment of the invention. 
     As seen in FIG. 1, insert gun  10  is mounted on bracket  12  that operates within a slide  14  on a frame  16 . In operation inserts  18  are forced through a blow tube  20  to an oriented position in an insert gripper  22 . The gripper  22  is then moved to a position beneath nose  24  by hydraulic cylinder  26  having its piston  28  interconnected to gripper  22 , so that the mandrel can be lowered to engage the threads of an insert  18 . The lowering of gun  10  is accomplished by hydraulic cylinder  30  connected between bracket  12  and frame  16 . 
     The gun  10 , whose component parts are best seen in FIGS. 3 and 4, includes a screw head (mandrel)  32  adapted to screw into the threaded second end  34  of the shaft  36  of the insert  18 . Insert  18  further has a first end  38  surrounded by a flange  40  and has intermediate collapsible portion  42 . 
     Mandrel  32  is readily replaceable and is held by chuck  44  attached to drive shaft  46 . Drive shaft  46  is in turn connected to slide coupling  48  that is connected to drive spindle  50 . Mandrel  32  is stabilized by nose  52  which also acts as a retainer against insert flange  40  when second end  34  is being pulled toward flange  40 . 
     Gun  10  is further provided with a cylinder  54  and a piston  56  contained within the cylinder  54 . Cylinder  54  includes spring retainer sleeve  58  for holding a spring  60  that biases piston  56  toward a cylinder front end cap  62 . Piston  56  is provided with a through bore  64  permitting passage of shaft  46 . Shaft  46  is free to rotate within bore  64  but is keyed to piston  56  so that longitudinal movement of piston  56  also longitudinally moves shaft  46 . Preferably a thrust bearing  65  is provided to reduce friction with piston  56  when shaft  46  is rotated with respect to piston  56 . This is especially true when a longitudinal force, e.g. the weight of drive  66 , is applied to shaft  46  that increases friction with piston  56 . 
     A drive  66  is provided that rotates spindle  50  when the drive is activated. Drive  66  is preferably an air motor operated by means of valve  96  controlling flow from air supply  98  but may also be another type of rotating drive such as an electric motor. The drive is securely attached to cylinder  54  by threading the front of drive housing  93  into sleeve  58 . The housing of drive  66  does not move relative to cylinder  54 . The slide coupling  48  permits longitudinal movement of drive shaft  46  relative to spindle  50  so that there is also no longitudinal movement of spindle  50  relative to cylinder  54  even when shaft  46  itself move longitudinally with respect to cylinder  54 . 
     As previously discussed piston  56  has a central bore  64 , and also has piston front surface  68  facing the screw head  32 . The drive shaft  46  passes through and is retained by central bore  64  so that longitudinal movement of the piston  56  moves drive shaft  46  while permitting drive shaft  46  to rotate within bore  64 . 
     Cylinder  54  housing piston  56  is rigidly connected to the drive  66  and slidably connected to frame  16  by slide  14  so that cylinder  54  can slide relative to frame  16  but cannot rotate relative frame  16 . 
     The nose  52  is rigidly connected to cylinder  54 . Nose  52  engages flange  40  of insert  18  to hold it against first surface  68  of substrate  70  when the second end of the insert shaft is pulled toward the first end of the insert shaft to form a grip  72  against second surface  74  of substrate  70 . 
     A fluid inlet including port  76  in cylinder  54  is provided for permitting fluid under pressure to enter cylinder  54  and contact the front face  68  of piston  56  to push piston  56  and retained drive shaft  46  in a direction toward drive  66  and to cause drive shaft  46  to slide within coupling  48 . 
     A fluid outlet is also provided to permit fluid to be released from cylinder  54  which may use the same port  76  as the fluid inlet. The direction of flow through port  76  is controlled by an external valve. 
     A control  78  is provided for controlling the operation of the apparatus in response to input from sensors  80 ,  82 ,  84 ,  86 , and  88  forming part of control  78 . Control  78  activates drive  66  for causing screw head  32  to screw into threaded portion  34  of insert  18 . Control  78  then stops drive  18  and causes cylinder  54  to move in slide  14  relative to frame  16  along with gun  10  and the insert  18  held on the screw head  32  to insert the shaft  36  of the insert into the hole in substrate  70 . The control  78  closes valve  92  permitting outlet from port  76  and causes fluid under pressure from reservoir  94  to enter cylinder  54  through port  76  to force screw head  32  attached to drive shaft  46  by coupling  44  toward drive  66  to cause the grip  72  of the insert  18  to engage second surface  74  of substrate  70 . Control  78  stops fluid inlet into cylinder  54  and opens the outlet to relieve pressure in cylinder  54 . Control  78  then causes drive  66  to activate in reverse to unscrew screw head  32  from now installed insert  18 . Unscrewing from the insert verifies that the threads in the insert are undamaged. Control  78  then causes gun  10  to move relative to the frame in a direction away from the installed insert. 
     The sensors of the control  78  includes a piston position sensor  80  that may be a magnet moving with the piston and a magnetic field detector attached to the cylinder or may be a feeler switch. Other sensors are: sensor  82  for detecting when cylinder  54  is positioned relative to the frame in a positions where gun  10  (attached to bracket  12  by cylinder  54 ) is withdrawn to permit positioning of an insert for loading onto screw head  32 ; sensor  84  for detecting where the screw head  32  is screwed into the insert so that nose retainer  52  contacts flange  40  of the insert; sensor  88  for detecting where the shaft  18  of the insert is inserted into substrate  70  so that insert flange  40  contacts the first surface  68  of substrate  70  and sensor  86  for detecting where the screw head  32  has been unscrewed from the insert. Control  78  handles signals from the sensors and provides commands to operate pistons, inlet and outlet valve  90  and drive  66  using a programmed logic chip within control  78 .