Valve seat forming tool
BACKGROUND OF THE INVENTION 
     This invention relates to an improved valve seat forming tool and more particularly to a valve seat forming tool which may be used to accurately reform damaged or worn valve seats of an internal combustion engine. 
     Heretofore various mechanisms have been proposed to reform the valve seat of an internal combustion engine when that engine is being rebuilt. Reforming of the valve seat permits installation of new valve members or reground valves and constitutes an inexpensive way of reconditioning an engine thereby eliminating the necessity to secure a new engine or new engine block. 
     Among the various prior art references known to applicant which relate to tools for grinding or forming valve seats are the following: 
     
         ______________________________________                                    
Pat. No.                                                                  
        Inventor  Title            Issue Date                             
______________________________________                                    
1,325,278                                                                 
        Dexter    Facing Tool For  12/16/19                               
                  Dressing Valve Seats                                    
1,487,533                                                                 
        Bryan     Valve Seating Tool                                      
                                   3/18/24                                
1,790,378                                                                 
        Howser    Valve Tool       1/27/31                                
1,837,390                                                                 
        Albertson Valve Seat Recon-                                       
                                   12/22/31                               
                  struction Tool                                          
1,843,181                                                                 
        Stougaard Valve Reseating Tool                                    
                                   2/02/32                                
1,846,890                                                                 
        Miller    Valve Reseating Tool                                    
                                   2/23/32                                
1,899,169                                                                 
        Tyler     Tool Holder      2/28/33                                
1,902,207                                                                 
        Albertson Valve Seat Tool  3/21/33                                
1,904,941                                                                 
        Dunn      Valve Reseating  4/18/33                                
                  Tool Driver                                             
1,954,241                                                                 
        Hellyer   Milling Tool     4/10/34                                
1,962,273                                                                 
        Harris et al                                                      
                  Seat Facer       6/12/34                                
1,988,411                                                                 
        Beard     Valve Seat       1/13/35                                
                  Refacing Tool                                           
2,041,587                                                                 
        Beard     Refacing Tool    5/19/36                                
                  For Valve Seats                                         
2,082,461                                                                 
        Pardieck  Valve Seat Dresser                                      
                                   6/01/37                                
2,102,707                                                                 
        Holhut    Valve Seat Sur-  12/21/37                               
                  facing Tool                                             
2,126,789                                                                 
        Lindsey   Apparatus for Con-                                      
                                   8/16/38                                
                  ditioning Valves and                                    
                  Valve Seats                                             
2,209,021                                                                 
        Hawker    Bibb Seating Tool                                       
                                   7/23/40                                
2,217,772                                                                 
        Rottler   Pilot Stem       10/15/40                               
3,354,528                                                                 
        Appleby   Valve Seat Cutter                                       
                                   11/28/67                               
3,443,480                                                                 
        Wells     Means for Securing                                      
                                   5/13/69                                
                  Cutters to Tools                                        
3,516,329                                                                 
        Rendahl   Cutting Tool for 6/23/70                                
                  Valve Seats                                             
3,552,758                                                                 
        Minelli   Turning Head for Cutting                                
                                   8/04/70                                
        et al     Valve Seats of Internal-                                
                  Combustion Engines                                      
3,664,756                                                                 
        Wells     Tool Depth Control                                      
                                   5/23/72                                
                  Adjustment                                              
______________________________________                                    
 
    
     The references disclose various mechanisms for reforming, refinishing or grinding a valve seat. Included among the mechanisms are very expensive grinding machines which are attached to the engine block and fit over the seat which is to be resurfaced. Many of the prior art devices position the cutter blades over the valve seat by means of a cantilever support. Using a support of this nature renders alignment of the blades with respect to the valve seat difficult. 
     Other valve seat tools propose a pilot rod which cooperates with the valve stem opening in the engine block. A cutter assembly is then positioned on the pilot rod. 
     However, none of the prior art references teach an inexpensive tool which combines the necessary elements to align the cutter blades with respect to the valve seat in a precise and reproducible manner and to permit adjustment of the blades for proper sizing of the valve seat opening and proper inclination of surfaces forming the valve seat. It is believed that the present invention provides the necessary combination of elements in a new and unique manner. 
     SUMMARY OF THE INVENTION 
     Briefly, the present invention comprises a valve seat forming tool which includes a pilot rod for insertion in a valve rod opening of an engine block. A cutter assembly is rotatably positioned on the rod and includes an advance mechanism for translating the assembly longitudinally on the rod. The cutter assembly also includes a cutter blade subassembly positioned so that blades attached at the end of the blade subassembly may be adjusted radially from the axis of the pilot rod to reform a valve seat. 
     A calibration block is utilized to initially set the cutter blades at a desired diameter and angle for forming a valve seat. The tool is then removed from the calibration block and positioned upon an engine block to form a valve seat. Once set, the tool may be transported from valve seat to valve seat without recalibration. 
     Thus, it is an object of the present invention to provide an improved valve seat forming tool. 
     Still a further object of the present invention is to provide an improved valve seat forming tool which is manually operable and which is adjustable to form complex valve seat surfaces cooperative with multiangled valves. 
     Still a further object of the present invention is to provide a valve seat forming tool which is economical to manufacture, easy to maintain and store and which reliably provides valve seat assemblies. 
     These and other objects, advantages and features of the invention will be set forth in the detailed description which follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the detailed description which follows reference will be made to the drawing comprised of the following figures: 
     FIG. 1 is an assembly view of the improved tool of the present invention in combination with a calibration block; 
     FIG. 2 is a partial cross sectional view of a typical engine block wherein the tool of the present invention has been positioned for reforming a valve seat; 
     FIG. 3 is a cross sectional view of the cutter blade assembly taken substantially along the line 3--3 in FIG. 2; 
     FIG. 4 is a cross sectional view showing an adjustable cutter blade subassembly taken substantially along the line 4--4 in FIG. 2; 
     FIG. 5 is a cross sectional view of the advance mechanism associated with the tool taken substantially along the line 5--5 in FIG. 2; and 
     FIG. 6 is an enlarged cross sectional view of a cutter blade forming the surface of a valve seat for an engine block. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the detailed description which follows, reference will be made to FIGS. 1 and 2 for a description of the total assembly forming the valve seat forming tool of the present invention. FIG. 1 illustrates the tool as it is being calibrated. FIG. 2 illustrates the tool when actually in use. The remaining figures depict subassembly portions of the tool. 
     Referring therefore to the figures and particularly to FIGS. 1 and 2, the tool includes a pilot rod 10 defining a longitudinal axis 11. The pilot rod has a lower stem section 12 which is connected by means of a tapered section 14 to a larger diameter cutter mounting assembly section 16. Rod 10 terminates with a threaded end 18. The stem section 12 is split and includes cross slots 20. The slots 20 intersect with a threaded passage 22 which receives a bolt 24 having a head 26. Head 26 engages a wedge member 28 fitted over the bolt 24. When bolt 24 is turned it engages the wedge member 28 causing the segmented stem section 12 to spread thereby locking the pilot rod 10 firmly in position in a valve stem opening 30 of an engine block 32 as shown in FIG. 2. The cutter assembly and the attached components are then mounted on the rod 10 for translation in the direction of the longitudinal axis 11 along that rod 10. 
     A cutter advance assembly including subassemblies 68 and 70 is mounted on the rod 10. The cutter advance assembly comprises a body member 34 which is generally cylindrical in shape and includes an axial passage 36 which fits over the rod 10 so that the body member 34 may be rotated with respect to the rod 10. Projecting radially outwardly at the top of the body 34 are first and second handles 38 and 40. Handles 38 and 40 project in opposite radial directions. The handles 38 and 40 are threaded into threaded openings 42 and 44 respectively in the body member 34 and extend transversely to the axis 11. 
     Positioned above the handles 38 and 40 on top of the body member 34 is a cylindrical bearing member 46 which defines a top support surface 48. The bearing member 46 includes a downwardly projecting axial stem 47 which engages a bearing 52 so as to permit rotational movement of the bearing member 46 with respect to the bearing 52 member 34 while simultaneously maintaining the bearing member 46 and bearing 52 locked together for coincident longitudinal movement along axis 11. A lock washer or snap ring 50 fits in slot 51 defined in an axial counterbore 53 of body member 34 to secure the bearing member 46 and bearing 52 with the body member 34. 
     A split nut 56 includes internal threads 58 which cooperate with the threaded end 18 of rod 10. A manual adjustment knob 60 cooperates with the segments 62 and 64 forming the nut 56 to thereby engage or release threads 58 from threaded end 18. Segment 62 and 63 of the nut 56 are attached by means of cap screws 66 to bearing member 46 so as to slide on surface 48 to thereby insure coincident movement of the split nut 56 with the remainder of the cutter assembly. 
     Positioned at the opposite end of the body 34 are first and second cutter blade subassemblies 68 and 70. Each subassembly 68 and 70 is substantially identical except for the orientation with respect to the rod 10 reversed and end blades 90 and 110 may be distinct. Thus, in general, the description for one of the subassemblies 68 is considered applicable to both subassemblies 68 and 70. 
     Therefore, referring to FIGS. 2 and 4, the subassembly 68 includes a threaded pin 72 which projects radially and at an acute angle with the axis 11 from the body 34. The threaded pin 72 includes a cylindrical head 74 which is calibrated for cooperation with a micrometer sleeve 76 attached by a set screw 77 to a barrel 78. Barrel 78 is threaded on the pin 72. Thus, the barrel 78 may be rotated on the pin 72 to provide for a translation of the barrel 78 with respect to the pin 72. 
     The barrel 78 includes a circumferential slot 80 which co-acts with a U-shaped blade holder 82 and more particularly, the leg 81 of holder 82. Blade holder 82 also includes a longitudinally projecting arm 84 which fits within a guide slot 86 defined in the body member 34. Slot 86 is parallel with the pin 72. The arm 84 connects with a blade positioning section leg 88 which grips a cutting blade 90. 
     The cutting blade 90 as shown in FIG. 6 includes cutting blade surfaces 92 and 94 which are defined at angles of 30° and 45° respectively from the horizontal. Note that the blade edges 92 and 94 lie in a plane which passes through the axis 11. 
     To adjust the radial distance of the edges 92 and 94 from the axis 11, the barrel 78 is rotated about the stem or pin 72. The indicia on the head 74 associated with the micrometer 76 are calibrated to indicate the radial movement of the blade 90 and edges 92, 94 from or with respect to the axis 11. In the manner, it is possible to accurately control the radial dimension of a valve seat which is formed by the blade 90. In other words, the calibration on the head 74 is dependent upon the angle which the stem or pin 72 makes with the axis 11. 
     A vertical gib 96 mounted in a slot 98 in body 34 impinges against the arm 84. The gib 96 is retained against the arm 84 by a cutter locking screw 100 threaded into the body 34 so that the end of screw 100 thereof will engage the gib 96. Thus, the screw 100 may be loosened so that the barrel 78 may be rotated to appropriately adjust the position of the blade 90. Upon adjustment of the position of the blade 90, the screw 100 is tightened against gib 96 which, in turn, locks against arm 84 so that the subassembly 68 remains in a substantially fixed position. 
     To initially calibrate the position of the cutter blade 90, a calibration block 102 is adapted to receive the pilot rod 10 as shown in FIG. 1. The gib 96 is released and the blade 90 is then set against a calibration surface 104 of block 102 by rotating the barrel 78. A set screw 77 then may be released to permit rotation of the micrometer head 74 with respect to the barrel 78 so that the head setting may be adjusted to a &#34;zero&#34; setting. Adjustments from this initial setting then will precisely define the radius of the valve seat cut by the blade 90. 
     The subassembly 70 is fashioned in a similar manner to the subassembly 68 through a blade 110 associated with subassembly 70 projects in exactly the opposite direction from blade 90. Blades 110 and 90 are adjusted to equal radial distances. Blade 110 is also adjusted to cut at 60° from the horizontal. Thus, blade 90 referring to FIG. 6 cuts valve surfaces 112 and 114. Blade 110 cuts valve surface 116. 
     In operation the tool is calibrated as depicted in FIG. 1. Calibration block 102 and cooperative calibration surface 104 serve to calibrate blades of one configuration such as blades 90. At the opposite end of the calibration block 102 a second calibration surface 105 serves to calibrate a different type of blade such as blade 110. 
     Subsequent to calibration, the device is inserted in an engine block 29 by inserting the rod 10 into the valve stem opening 30. The split nut 56 is tightened down so as to bring the blades 90 and 110 into contact with valve surfaces 112, 114 and 116. The handles 38 and 40 are then used to rotate the body 34 and attached subassemblies 68 and 70. This, in turn, causes the blades 90 and 110 to cut the surfaces 112, 114 and 116 to the desired shape. The cut of the valve seat surface may be accurately controlled by means of the micrometers associated with the subassemblies 68 and 70. The split nut 56 may be advanced downwardly in order to cut the surfaces 112, 114 and 116 more deeply. Upon completion of resurfacing of a valve seat in the engine block 32, the device may be removed and repositioned in another valve stem opening. Recalibration is not necessary. Reproducibility of the seat forming operation is good. 
     While there has been set forth a preferred embodiment of the invention, it is to be understood that the tool may be altered while still providing the benefits and advantages associated with the invention. Therefore, the invention is to be limited only by the following claims and their equivalents.