Patent Publication Number: US-6701812-B1

Title: Screw catcher for power driven screwdrivers

Description:
BACKGROUND OF THE INVENTION 
     Customarily, when a screw is tightened by a power driver or an electric screwdriver, the screw is sometimes driven by the use of a magnet to hold a screw to a bit of an electric screwdriver. 
     However, since such screw tightening work attaches the head of a screw to the front end of an electric screwdriver, for example, a screw needs to be held by fingertips of an available hand. Or, if a screw is not screwed tightly, a screw needs to be supported by fingertips of an available hand. Such a supporting action occupies both hands of an operator, resulting in low work efficiency. Also, in a work environment with an unstable ground such as a construction site, it has always been inconvenient. 
     Since a screw that is driven by the front end of a driven screwdriver is not necessarily tight or not necessarily stable, a screw must be carefully tightened for small parts. As a result, an operator has to work hard and he or she tends to get more exhausted. 
     In order to solve the above problems with known technology, it is known to stabilize a screw at the driving end of an electric screwdriver by vacuuming the screw by the suction pressure of the air in Japanese Patent Application Hei 10-375218. 
     However, the above requires an air suction pressure generating apparatus. It causes a problem of requiring new equipment investment if the work place does not have such equipment. 
     Other screw capturing devices with manually positioned spring fingers mounted on a screwdriver are known or with automatic screw catchers of different types. 
     SUMMARY OF THE INVENTION 
     An object is to provide a screw capturing device for use with a power driver or an electric screwdriver that does not require vacuum, can be easily attached to or detached from a bit of an electric screwdriver, and does not interfere with, but makes easier, screw tightening work. 
     Furthermore, the invention can be made to correspond to several types of screws with different sizes, firmly capture the head of the screw, and can securely perform the screw tightening work. 
     Another object is to provide a screw capturing apparatus for a power driver or an electric screwdriver that enables visual confirmation that the head of the screw is captured and can perform the screw tightening work securely and safely. 
     And, another object is to provide a screw capturing apparatus for a power driver or an electric screwdriver that is light and small, and its components can be easily manufactured and assembled. 
     Because of the above construction, this apparatus can be adjusted to match the size of the screw. By operating the caliper adjustment means, the inner diameter of the opening part of the screw capturing device can be adjusted to match the diameter of the head of the screw to be tightened. When the front end of a power driver or an electric screwdriver is used with a screw supplier and the head of the screw is inserted into the opening between them, the elastic holding fingers hold the head of the screw. When the screwdriver that holds the screw is moved toward an object to place the screw in a screw hole of the object and the screwdriver is pushed toward the screw hole to turn the bit, the holding fingers receive the force in the opposite direction from the direction of a screw insertion as the screw enters into the screw hole. Since the holding fingers are pushed against the spring loaded means, it will not be a hindrance to screw tightening. When the screw is tightened and the screwdriver is detached from object, the holding fingers return to the initial position by the spring loaded means. 
     It is preferred that the screw capturing device is formed entirely of transparent materials or at least the holding fingers. If the holding fingers are transparent, the screw can be tightened securely and safely while visually confirming the status of screw capturing. 
    
    
     Other objects and advantages of the invention will become apparent from consideration of the drawings forming part of this application. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of an example of the invention; and 
     FIG. 2 is a partially sectional view of the example of the invention when it is installed on a power driven screwdriver. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As seen in the drawings, A indicates the screw capturing apparatus of this invention, and B indicates a bit of a power driver or an electric screwdriver sold in retail stores and referred to hereinafter simply as a screwdriver. 
     The screw capturing apparatus A has an attachment means  10  to attach the device A to the screwdriver bit B. The attachment means  10  is composed of a bushing  11  and an attachment nut  12  that attaches the bushing  11  to the bit B. The bushing  11  is formed generally cylindrical and has flanges  111  and  112  in the front end and the mid-section. Several slots  113  are formed longitudinally from the flange  112  in the mid-section to the rear end of the bushing  11 . A screw thread  114  is cut on the outer circumference of the rear end of the bushing  11 . 
     The bit B of the electric screwdriver can be inserted into a hole  115  internal to the bushing  11  in the direction of its axis. In the example shown, screw thread  121  is cut on the inner circumference of the attachment nut  12 . For example, a roughened surface  122  is cut on the outer circumference of the attachment nut  12  to be easily rotated by fingertips. 
     Therefore, after moving the bushing  11  with the bit B in its hole  115  to the place where the front end of the bit B extends through the front end of the bushing  11 , the screw thread  121  of the nut  12  can be screwed to the screw thread  114  and is tightened by turning the nut  12  to attach the bushing  11  to an appropriate location close to the front end of the bit B. 
     Another device to attach the bushing  11  to the bit B is, for example, a set screw or the like. 
     The screw capturing means A has the screwchuck-like device  20  to capture the head of a screw C at the front end of the bit B. The screwchuck  20  has a circular portion  21  in the center, an elastic circular portion  22  having slots  23  to add elasticity to the inner end, and screw holding means  24  at the outer end. A screw thread  25  is cut on the outer circumference of the circular potion  21  and the elastic circular portion  23 . Also, the screw holding means  24  is extended outwardly from the circular portion  21  and has elastic holding fingers  24   a ,  24   a , and  24   a  spaced circumferentially. The front end of each holding finger is located about the circumference and forms an opening  24   b  that can receive the head of the screw C. Also, each holding finger  24   a  is bent or formed to create a cam on the outer side of each holding finger  24   a . The outer diameter of the screw holding part  24 , therefore, significantly increases in size from its inner end to the middle and reduces in size from the middle to the front end. 
     Preferably, the entire screwchuck  20  or at least the screw holding portion  24  is formed by elastic materials such as plastic or metal. 
     The screw capturing device A has a spring loaded means  30  to always move the screwchuck  20  forward from the bushing  11 . In the example shown in the drawings, the spring loaded device  30  is composed of a sleeve  31  that is slideably mounted on the outer circumference of the forward portion of the bushing  11  between the flanges  111  and  112  slideable in the direction of the axis of the bushing  11  and coil spring  32  that is located between the sleeve  31  and the rear flange  112 . 
     By inserting the bushing  11  into the screwchuck  20  and pushing the sleeve  31  into the inner circumference of the circular portion  21  of the screwchuck  20 , the screwchuck  20  and the sleeve  31  are frictionally connected. Furthermore, in the preferred embodiment of the present invention, the screw capturing device A has an adjustment ring  40  as a caliper adjustment means to adjust the inner diameter of the chuck fingers  24   a  of the screw holding means  24  of the screwchuck  20 . A screw thread  41  on the inner circumference of the adjustment ring  40  matches with the screw thread  25  on the outer circumference of the circular potion  21  and the elastic circular portion  22  of the screwchuck  20 . Also, for example, a roughened surface  42  is made on the outer circumference of the adjustment ring  40  to be easily rotated by finger tips. 
     When the adjustment ring  40  is turned in the specified direction by matching the male screw thread  25  of the screwchuck  20  frictionally engaged with the sleeve  31  and the screw thread  41  of the adjustment ring  40 , the adjustment ring  40  moves forward in the direction of the axis of the screwchuck  20 . During this process, it tightens the elastic circular portion  22  of the screwchuck  20  and further tightens the screwchuck  20  and the sleeve  31 . And, when the adjustment ring  40  is turned in the opposite direction, it moves backward. 
     Since the screw holding means  24  of the screwchuck  20  significantly increases the size of the outer diameter from the base end to the middle, the caliper of the opening  24   b  is gradually reduced when the adjustment ring  40  is moved further forward when the adjustment ring  40  is turned in one direction. On the contrary, when the adjustment ring  40  is turned in the other direction and moved backward, the caliper of the opening  24   b  will be enlarged by the elastic recovery force of the fingers  24   a.    
     Therefore, without replacing the screwchuck  20  for each size of the head of the screw used for tightening, several types of screws C can be tightened by using one screwchuck by operating the adjustment ring  40  to change the caliper of the opening  24   b  to be an appropriate size. 
     When using the screw capturing apparatus A of the above construction, as shown in FIG. 2, the head  50  of the screw C (that is being held in the aforementioned screw supplier not indicated in the drawings) is pushed into the opening  24   b  of the screw holding part  24  and is captured. Since the holding fingers  24   a  are elastic, the head  50  of the screw C can be engaged by pushing the opening  24   b  of the screw holding means  24  open to capture the screw C. Therefore, the screw C can be securely captured. 
     When the captured screw C is screwed to an object, the threads  51  of the screw C are entered into the screw hole in the object and the front ends of the holding fingers  24   a  touch the object. The holding fingers  24   a  receive a force in the opposite direction from the direction in which the screw C is being screwed and that force is transmitted to the sleeve  31  through the screwchuck  20  to pressurize the coil spring  32 . Therefore, the screw holding means  24  is retrieved as the screw C is screwed tighter. That is, the screw holding means  24  firmly supports the head of the screw C until the screw C is completely tightened. When the screw is completely screwed and the screwdriver is detached from the screw, the screw holding means  24  is returned to the initial position by the coil spring  32 . 
     Since most of the said attachment means  10 , the said spring loaded means  30 , the said screw capturing means  20 , and the said caliper adjustment means  40  are formed almost cylindrical and hollow inside, the screw capturing apparatus can be small and light. Therefore, without affecting load torque of the screwdriver, this apparatus can be assembled and dissembled easily. Besides, it will not be a hindrance to a screw tightening work and enables a secure screw tightening. 
     Furthermore, when the screwchuck  20  or at least the holding fingers  24   a  use transparent material, the screw C can be tightened while confirming the captured condition of the screw C. The screw tightening work becomes more efficient and reliable. 
     The screw capturing apparatus of this invention can be applied to the aforementioned various bits and screws. 
     As explained above, this apparatus can be easily attached to or detached from the bit of, say, an electric screwdriver. Therefore, it can be used with screws sold in retail stores. Also, since this apparatus can be used by installing to the front part of the bit of the screwdriver, it does not require new equipment like a suction pressure generating apparatus and can automatically capture a screw. Since the screw capturing device is allowed to move forward or backward by the spring loaded device, it can securely hold a screw from the beginning of the screw capturing to the completion of the screw tightening. It improves the efficiency and accuracy of the screw tightening work. Furthermore, since the screw holding part of the screw capturing device and the caliper of the opening are elastic and this apparatus has a caliper adjustment device, it can be used to tighten several types of screws of different sizes. 
     When the above screw capturing device is made of a transparent material, the screw capturing conditions can be confirmed and the screw can be securely and safely tightened. 
     The invention enables minimization, manufacturing, assembly, and installation to a bit easily. It also does not make the screw capturing apparatus a hindrance to the screw tightening work.