Patent Publication Number: US-6213694-B1

Title: Device for repairing metal-stamping dies

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to surface finishing tools and, more particularly, to a rotary power tool for refinishing the surface of metal stamping dies. 
     2. Discussion of the Related Art 
     Metal mold presses are used to stamp flat sheet metal into various desired shapes. For example, the automobile assembly operation uses metal mold presses to form automobile body parts. Metal mold presses include one or more stamping dies which are made of metal and have a predetermined shape to impart a desired shape to the sheet metal. The surfaces of the stamping dies are often chrome-plated such that they are quite hard. However, over time stamping dies can crack or dent, which causes the sheet metal stamped by the dies to have a corresponding flaw. Thus, the stamping dies must be repaired or replaced. Repairing the stamping dies is the preferred remedy, due to the costs involved. 
     In an effort to cut costs, some automobile manufacturers have using to use relatively thin sheet metal for their automobile parts. As a result, maintenance of the stamping dies is now even more important, as imperfections will cause readily visible surface irregularities in the formed parts. 
     One conventional method for repairing these dies is to use a compound oil which fills in the imperfections on the surface of the die. However, in the case of chrome-plated dies, this method is ineffective because the lubricity of chrome is incompatible with compound oil. Thus, such a method has only limited applicability, and is not a long-term solution to the problem in any event. 
     Another method is to fill in the holes or cracks by welding, and then grind the surface of the dies smooth to restore the original surface contour. The conventional method of doing this is to use a hand grinder or a file to remove the welding material until it is flush with the surrounding die material. It is critical that too much of the welding material is not removed, or else the surface will again be uneven, and the process will have to be repeated. Such a method is extremely tedious, difficult, and time-consuming, especially when done with the naked eye. Even an experienced worker requires a significant amount of time to properly repair a stamping die by this method, causing a depth production while the die is being repaired. 
     Others have proposed motorized surface abrading machines that include cylindrical cutters, grinders or abraders which are vertically adjustable relative to a work surface in order to control the amount of material removed. For example, see U.S. Pat. Nos. 915,746, 2,069,700, and 2,166,861. While such devices constitute an improvement over the prior art methods mentioned above, they do not provide an adjustable multi-point support capable of reliably controlling the placement of the cutter, grinder, or abrader relative to the work surface. 
     In particular, the device disclosed in U.S. Pat. No. 2,069,700 to Emmons has significant shortcomings for use in finishing stamping dies which have had a filler such as welding material applied to a crack or dent. For example, the device includes an adjustable stop positioned in front of the rotary cutter, and a roller directly behind the cutter. Thus, as the tool is advanced, the forwardly disposed stop slides over the raised segment defined by the welding material and raises the cutter up off of the work surface, such that the work surface is not properly finished. 
     Accordingly, it will be apparent that there continues to be a need for a metal mold repair tool for repairing metal stamping dies that includes an adjustable assembly for reliably positioning a finishing member relative to the work surface as the tool is advanced across the work surface. The present invention addresses this need. 
     SUMMARY OF THE INVENTION 
     Briefly, and in general terms, the present invention is directed to a metal mold repair tool for smoothing the work surface of stamping dies used in metal molds. The repair tool includes a pair of stops or guides disposed on opposite lateral sides of a rotary finisher to precisely position the finisher with respect to the work surface. The rotary finisher is preferably driven by a conventional drive motor. The finisher and guides are vertically displaceable relative to each other, such that the position of the finisher relative to the work surface can be adjusted as desired. 
     Thus, in one illustrative embodiment, the present invention is directed to an apparatus for repairing metal stamping dies comprising: a housing; a rotary finisher rotatably mounted on the housing; a drive assembly mounted on the housing, coupled to the rotary finisher, and operative to rotate the rotary finisher; and a pair of guides disposed on opposite lateral sides of the rotary finisher, wherein the guides and rotary finisher are displaceable relative to each other to alter the relative positions of the guides and rotary finisher. 
     In another illustrative embodiment, the present invention is directed to a repair tool for stamping dies, including: a housing; a rotary finisher rotatably and adjustably mounted on the housing; a drive assembly mounted on the housing, coupled to the rotary finisher, and operative to rotate the rotary finisher; and a pair of guides disposed on opposite lateral sides of the rotary finisher 
     Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the features of the present invention. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a metal mold repair tool depicting one illustrative embodiment of the present invention; 
     FIG. 2 is an exploded perspective view of the metal mold repair tool of FIG. 1; 
     FIG. 3 is a perspective view, in enlarged scale and in partial phantom, of the metal mold repair tool of FIG. 1; 
     FIG. 4 is a fragmented, perspective view of components included in the metal mold repair tool of FIG. 1; 
     FIG. 5 is a cross-sectional front view of the metal mold repair tool of FIG. 1 showing a rotary finisher in a lowered position with respect to a work surface; 
     FIG. 6 is a cross-sectional front view similar to FIG.  5  and showing the rotary finisher in a raised position with respect to the work surface; and 
     FIG. 7 is a cross-sectional front view similar to FIG.  5  and showing another illustrative embodiment of the metal mold repair tool of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following detailed description, like reference numerals will be used to refer to like or corresponding elements in the different figures of the drawings. Referring now to FIGS. 1 and 3, there is shown a metal mold repair tool  10  according to one illustrative embodiment of the present invention. The tool  10  comprises, generally, a housing  12 , a rotary finisher  14  rotatably mounted on the housing adjacent the front end thereof, an adjustment assembly  16  mounted on the housing  12  and engaged to the rotary finisher for altering the position of the rotary finisher relative to the housing, and a drive assembly  18  connected to the housing, engaged with the rotary finisher, and operative to rotate the finisher (FIG.  3 ). The tool may be used to finish surfaces of metal stamping dies, with the height of the rotary finisher  14  being adjustable relative to the housing  12  to accurately and reliably control the amount of material that is removed from a surface of a metal stamping die  19 . 
     The housing  12  is elongated to define a hand-held housing with a forward longitudinal end  20  and a rear longitudinal end  22 . The housing further defines an interior chamber  24  which houses a portion of the drive assembly  18  therein. The housing defines, at the forward end  20 , a pair of opposing, forwardly projecting arms  26  and  28 . The respective arms include lateral through bores  30  and  32  to receive a portion of the adjustment assembly  16 , as described in greater detail below. The bottom ends of the respective arms extend below the bottom of the housing to define a pair of elongated stops or guides  34  and  36 . With the tool  10  laid flat against a work surface  19 , it will be apparent that the guides contact the work surface and the remainder of the housing is elevated above the work surface (FIGS.  5  and  6 ). 
     The rotary finisher  14  is rotatably mounted on the housing  12  adjacent the forward end  20  thereof, with the respective arms  26  and  28  flanking it on either side. The rotary finisher is preferably cylindrical, and can take many different forms, such as a cutter, grinder, abrader, and the like, each of which will have a suitable surface for performing a particular function. The finisher may also assume other shapes to create complementary contoured surfaces in the work surface, as is described in greater detail below in connection with FIG. 7. A pair of drive shafts  15  and  17  extend outwardly from the opposite longitudinal ends of the finisher for engagement with the adjustment assembly  16 . 
     The drive assembly  18  includes an electric drive motor  38  and drive shaft  40  (FIG.  3 ), a first pulley  42  engaged to the drive shaft for rotation therewith and located outside of the housing  12 , and a second pulley  44  disposed adjacent the forward end  20  of the housing alongside one of the arms  26 . The drive shaft  40  extends through an opening  41  formed in the side wall of the housing  12  and is press fit into a central opening formed in the first pulley  42 . The drive motor is powered by an electric cord  45  which terminates in a conventional plug (not shown) for insertion in an electrical outlet. A drive belt  46  runs over the first and second pulleys to transmit rotation of the first pulley to the second pulley. The drive motor is connected to the housing  12  and is housed in the interior chamber  24 . Thus, the drive motor, drive shaft, and the first pulley are disposed at fixed locations relative to the housing  12 . The second pulley, however, is not directly mounted to the housing, and therefore may be displaced relative to the housing  12  as a result of influence from the adjustment assembly  16 , as described in greater detail below. The pulleys are preferably housed in a suitable cover  47  (FIG. 1) that is releasably connected to the housing  12 . Alternatively, the cover may be integral with the housing. 
     While in the illustrative embodiment the tool  10  comprises an electrically powered drive motor  38 , it will be apparent that the tool can be powered by pressurized air or by any other well-known means. Thus, the illustrative embodiment is merely an example of one illustrative embodiment of the present invention. 
     The adjustment assembly  16  is provided to allow a user of the tool  10  to adjust the position of the rotary finisher  14  relative to the housing  12  and thus to the guides  34  and  36 . The adjustment assembly comprises a pair of eccentric drives  50  disposed on either side of the rotary finisher  14 . The respective eccentric drives are generally cylindrical and include eccentrically disposed through bores  52  through which the respective rotary finisher drive shafts  15  and  17  extend. The eccentric drives also include bearings  54  sized for press fitting insertion into the respective through bores  52 , the bearings including inner races sized to engage the respective drive shafts  15  and  17 . Thus, the drive shafts are journaled in the eccentric drives, such that the rotary finisher  14  may rotate with respect to the eccentric drives  50 . One of the drive shafts  15  passes through the respective bearing and is press fit into a central opening formed in the second pulley  44 . Thus, the second pulley is carried by the drive shaft  15 . That drive shaft is preferably made longer than the other drive shaft  17  for extension through the pulley  44  in addition to the eccentric drive  50 . 
     Preferably, the through bores  52  in the eccentric drives  50  are formed at predetermined locations thereon such that the rotary finisher  14  can only be lowered to a position in which its lower end is aligned with the bottom ends of the guides  34  and  36 . Therefore, the finisher can not be lowered to a position below that of the guides, and thus can not remove material below the plane of the work surface. 
     The bearings  54  may take many different forms, and preferably comprise ball bearing assemblies with inner and outer races and plural balls which ride in a track defined between the respective races. Other bearings, such as roller bearings, may also be used. 
     The eccentric drives  50  include first and second cylindrical portions  55  which flank respective annular arrays of teeth  56  formed generally centrally thereon, the teeth defining a central gear portion of the eccentric drives and which are engaged by respective pinions  58  mounted on a rotatable adjustment shaft  60 . The adjustment shaft extends through an opening in the side wall of the housing  12  and terminates in a knurled adjustment knob  62  disposed outside of the housing. Thus, rotation of the adjustment knob causes the adjustment shaft, pinions, and the eccentric drives to rotate. Because the drive shafts  15  and  17  of the rotary finisher  14  pass through the eccentric drives at a location offset from the center of those drives, rotation of the eccentric drives causes the rotary finisher to be displaced vertically relative to the housing  12 . Thus, the adjustment assembly is operative to adjust the position of the rotary finisher relative to the housing. Because the drive shaft  15  carries the second pulley  44 , vertical displacement of the rotary finisher results in vertical displacement of the second pulley as well. 
     The through bores  30  and  32  each include reduced-diameter segments  70  and enlarged segments  72 , with the segments  70  receiving the first cylindrical portions  55  of the eccentric drives  50 , and the segments  72  receiving the enlarged gear portions  56  and second cylindrical portions of the eccentric drives  50 . Respective recesses  74  lead rearwardly and upwardly from the enlarged segments  72  to receive the respective pinions  58  which mesh with the respective gear portions  56  of the eccentric drives  50 . 
     Because the eccentric drives  50  must be able to rotate relative to the housing  12 , the through bore segments  70  and  72  are sized to loosely receive the respective cylindrical portions  55  of the eccentric drives. 
     The tool  10  may also include additional guides formed generally centrally on the bottom of the housing  12  at a location rearward of the rotary finisher  14 . The additional guides extend downwardly to the same extent as the first and second guides  34  and  36 , to provide a stable multi-point contact with the working surface  19 . 
     In addition, while the bottom of the finisher  14  and the guides  34  and  36  are shown in the illustrative embodiment as being flat for finishing a flat stamping die, it will be apparent that the bottom of the finisher and of the guides can assume a different contour to match that of the surface being finished. For example, as shown in FIG. 7, the finisher  14  can be formed with a concave surface, such that the guides and finisher define a generally semi-circular contour to complement a curved work surface. 
     In use, a worker may hold the tool  10  in his or her hand and connect the tool to an appropriate power source, such as an electrical outlet or source of pressurized air. In the illustrative embodiment, the tool includes the drive motor  38 , and actuation of the drive motor, for example by flipping a switch (not shown) mounted on the housing, causes the drive motor to rotate the shaft  40 , which translates into rotation of the first and second pulleys  42  and  44 . This causes the rotary finisher  14  to rotate, and the tool can then be placed against a work surface of a stamping die  19 , with the guides  34  and  36  abutting the work surface and the rotary finisher  14  disposed at a selected height relative to the work surface as dictated by the adjustment assembly  16  and guides  34  and  36 . The tool is then advanced across the work surface, with the finisher smoothing the work surface. 
     If the height of the rotary finisher  14  requires adjustment, the user may simply rotate the adjustment knob  62  to control the adjustment assembly  16  and thereby selectively raise and lower the finisher relative to the housing  12  and guides  34  and  36 . It will be understood that rotating the knob in one direction causes the finisher to initially be lowered, and that if the user continues to rotate the knob in the same direction, the finisher is raised relative to the housing due to the eccentric drives  50 . Once the rotary finisher  14  is adjusted to the proper height relative to the guides  34  and  36 , the tool may be placed on the work surface and advanced across the surface to grind away a portion of the surface as dictated by the height of the finisher. 
     From the foregoing, it will be apparent that the metal mold repair tool  10  of the present invention provides an efficient, reliable, and adjustable tool for smoothing a working surface of a stamping die or the like. 
     While forms of the present invention have been illustrated and described, it will be apparent to those of ordinary skill in the art that various modifications and improvements can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.