Abstract:
An apparatus of diametrically expanding a desired portion of a metal shaft, including a driver section ( 5 ) which is rotatively driven by an electric motor with a workpiece held in a first sleeve thereof, a driven section ( 30 ) having a second sleeve located opposite to the first sleeve of the driver section ( 5 ), the driven section ( 30 ) being capable of relative movement to and from the driver section ( 5 ); a feeder unit ( 50 ) for effecting the relative movement of the driven section ( 30 ) to and from the driver section ( 5 ); a bias means ( 80 ) for causing the second sleeve to decline with respect to the axis of the first sleeve of the driver section ( 5 ); and a press unit ( 70 ) for pressing the driven section ( 30 ) toward the driver section ( 5 ).

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a metallurgical process apparatus, and more particularly to an apparatus of diametrically expanding a desired portion, such as a middle portion, of steel or any other metal shafts, so as to cut threads to form gears and cams in the expanded portion. 
     BACKGROUND ART 
     It is common practice to obtain a metal shaft having a partly increased diameter by machining a blank shaft of a relatively large diameter. However, this machining process takes time, and what is worse, wastes metal in the form of cutting chips. 
     In general, the mechanical power transmission shafts require components such as gears, cams, and sprockets whose diameter is larger than that of the shafts. In order to provide the metal shafts with these components, a mechanical method is not economical where the metal flesh of a shaft is machined to form gears as integral parts. An alternative way is to produce those component parts on a separate process, and then join them to the shafts by welding or bolting. This method is not efficient. Therefore, a metallurgical process was proposed for forcing a metal shaft to diametrically expand in a desired portion, and cutting gears or cams there. However, it has been considered to be impracticable to put the proposed metallurgical method in practice. 
     The inventor of the present application invented a method of expanding the diameter of a metal shaft in its middle portion through rotation, bending and compression, and has obtained Japanese Patent No. 1,993,956. This metallurgical method has overshadowed the conventional mechanical method, and made it possible to form gears or cams in the diametrically expanded portion of a metal shaft. 
     Nevertheless, the patented method is at the experimental stage, and is not fully developed for mass-production basis. The present invention has overcome the obstacles to practical use. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is an apparatus of expanding a diameter of a metal shaft in a desired portion, the apparatus including a driver section which is rotatively driven by an electric motor with a workpiece held in a first sleeve; a driven section having a second sleeve located opposite to the first sleeve of the driver section, the driven section being capable of relative movement to and from the driver section; a feeder unit for effecting the relative movement of the driven section to and from the driver section; a bias means for causing the second sleeve to decline with respect to the axis of the first sleeve of the driver section; and a press unit for pressing the driven section toward the driver section. 
     In performing the diametral expansion of a metal shaft, the driver section and the driven section are arranged such that the respective sleeves are axially aligned with a workpiece (blank shaft) held therebetween. Then, the driver section is driven to rotate the workpiece, and at the same time, the press unit is driven to compress it axially. At this stage, the bias means causes the portion of workpiece toward the driven section to decline with respect to the axis of the driver section. Preferably, the center of the bent is deviated outward from the center line of the blank shaft. Because of this deviation the bent portion is subjected to constant compression, and as a result, fracture due to fatigue is avoided; otherwise, fracture would be likely to occur the alternate application of compression and tension. In the course of rotation, bending and compression the workpiece is forced to diametrically expand in the portion between the holders of the driver section and the driven section. As the expansion proceeds, the driven section moves toward the driver section, during which compression is continued. 
     Upon completion of the expansion, the bias means is returned to its original position where the driver section and the driven section are axially aligned. Then the rotation and compression are stopped, and the finished shaft is released. 
     The press unit can be a fluid cylinder, a hydraulic jack, etc. The bias means can be an arrangement in which, for example, the sleeve of the driven section is pivoted rotatively around its own axis, and is declined by applying a force to it axially at right angle. 
     After the diameter of the shaft is partly expanded, it must be taken out. However, it often happens that it is difficult to release it from the sleeves because of the remainder of the force applied in the process. In order to overcome this difficulty, an extra remover can be employed, which is provided with a device engageable with the expanded portion of the workpiece. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional side view of a first embodiment of the present invention; 
     FIG. 2 is a plan view of the first embodiment; 
     FIG. 3 is a vertical cross-section of a main portion of the first embodiment to illustrate the operation of diametral expansion; 
     FIG. 4 is a cross-sectional side view of a second embodiment; 
     FIG. 5 is a plan view of the second embodiment; 
     FIG. 6 is a vertical cross-section of a main portion of the second embodiment to illustrate the operation of diametral expansion; 
     FIG. 7 is a cross-section of a main portion of the second embodiment; 
     FIG. 8 is a schematic view exemplifying a third embodiment; 
     FIG. 9 is a plan view of an expanding unit employed in the third embodiment; 
     FIG. 10 is a side view of the expanding unit of FIG. 9; 
     FIG. 11 is a front view of the expanding unit of FIG. 9; 
     FIG. 12 is a perspective view showing a remover whereby, subsequent to the diametral expansion, a finished workpiece is released; 
     FIG. 13 is a side view of the apparatus using the remover to release a finished workpiece; 
     FIG. 14 is a plan view of the situation shown in FIG. 13; 
     FIG. 15 is a cross-section of a chuck sleeve employed in a different embodiment; 
     FIG. 16 is a cross-section of an example of a chuck sleeve; 
     FIG. 17 is a schematic view of a diametrically expanded metal shaft; 
     FIG. 18 is a cross-section of another type of chuck sleeve; and 
     FIG. 19 is a cross-section of a finished metal shaft processed by use of the chuck sleeve of FIG.  18 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, a first preferred embodiment of the invention will be described: 
     The diametrically expanding apparatus (hereinafter “apparatus”)  1  is provided with a pair of side plates  3  erected on a base  2  anchored in a floor (not shown). A rectangular framework  4  is provided on the side plates  3 , and is provided with a driver section  5  in its left-hand end portion. Herein, the “drive” includes “rotate”. The driver section  5  includes a holder sleeve  10  rotatively carried on a main sleeve  6  secured to members  4   a  on the framework  4 , and the holder sleeve  10  is provided with a driven gear  12  at its end. The holder sleeve  10  houses a chuck sleeve  15  fitted therein so as to hold a workpiece (metal blank shaft). The chuck sleeve  15  includes a bore  16  in its core through which the workpiece fits. The bore  16  includes a female thread section  16   a  at one end with which an extruding screw  17  is engaged through a through-hole  10   a  produced at an end of the holder sleeve  10 . 
     Under the main sleeve  6  is provided a driving motor  20  whose output shaft carries a driving gear  21  which is engaged with the driven gear  12 . 
     A driven section  30  is provided opposed to the driver section  5  which is provided with a slide  35  slidable along a rail  31  provided on the framework  4 . The slide  35  is provided with a ring-shaped rotary frame  37  carried by a shaft  36  at one end. The rotary frame  37  has a main sleeve  38  on the driven side, and the main sleeve  38  rotatively houses a holder sleeve  40 . The holder sleeve  40  houses a chuck sleeve  45  for holding a workpiece, the chuck sleeve  45  corresponding to the chuck sleeve  5  of the driver section  5 . The chuck sleeve  45  includes a bore  46  in its core. The bore  46  includes a female thread section  46   a  at one end with which an extruding screw  47  is engaged through a through-hole  40   a  produced at an end of the holder sleeve  40 . 
     A feeder unit  50  is provided behind the slide  35  so as to move the driven section  30  to and from the driver section  5 . The slide  35  is provided with a bracket  52  at its rear end which carries a bearing  53 . The framework  4  has a cross-bar  4   b  at its rear end in which a bore  54  is produced, and is provided with a stationary sleeve  55  ahead of the bore  54 . The sleeve  55  has a slit  56  extending along its length. The slit  56  houses a slide  57  having a threaded hole  57   a , the slide  57  having a projection  57   a  projecting through the slit  56 . The slide  57  can reciprocally move with its projection  57   a  kept projecting through the slit  56 . 
     A feed rod  60  is supported by the bearing  53  of the bracket  52  and the crossbar  4   b  such that it can rotate around its own axis. The feed rod  60  has male threads  60   a  with which the slide  57  is engaged. The feed rod  60  is prevented by a ring  61  from detaching from the side plate  3 , and can be manually rotated by a handle  62 . 
     Under the driven section  30  is provided a press unit  70 , which presses the driven section  30  toward the driver section  5 , and a hydraulic jack  71  is provided on the base  2 . A cam  75  is provided adjacent to the jack  71  such that it can rotate on a cam shaft  73  clockwise or anticlockwise. The cam  75  includes an abutment  75   a  in its front portion which is engageable with a rear portion of the rotary frame  37  of the driven section  30 . The cam  75  is provided with a receiving portion  75   b  designed to come into abutment with a piston rod  71   a  of the jack  71  during the rotation of the cam  75  and receive a lifting force from the jack  71 . 
     When the jack  71  is operated, the piston rod  71   a  extends to lift the cam  75 . As a result, the cam  75  rotates around the shaft  73  anticlockwise in FIG. 1, and causes the driven section  30  to advance toward the driver section  5 . The hydraulic jack  71  can be substituted by a hand-operated jack of a type which is commonly used for lifting a motor car when a tyre is replaced in puncture. Instead of oil, air or any other liquid can be used. An alternative tool can be a known screw jack. Instead of a hand-operated jack, a power jack can be used. 
     The driven section  30  is provided with a bias means  80  for rotating it clockwise or anticlockwise. The bias means  80  includes a nut  82  secured to the main sleeve  38 , and a screw bar  85  engageable with the nut  82 . A lower end of the screw bar  85  is in abutment with the slide  35 , and is provided with a handle  86  in its upper end. By rotating the handle  86 , the screw bar  85  is rotated and allows the nut  82  to move up or down together with the main sleeve  38 . In this way the driven section  30  rotates around the shaft  36  clockwise or anticlockwise. 
     In operating the apparatus  1  the ends of a workpiece (normally a steel shaft) W are insertedly held in the chuck sleeve  15  of the driver section  5  and the chuck sleeve  45  of the driven section  30 . The threading amount (length) of the extruding screw  17  is adjusted so as to obtain an optimum extrusion allowance d (FIG.  2 ). Then the workpiece W is inserted until its end comes into abutment with the end of the extruding shaft  17 . The extruding screw  47  of the driven section  30  is adjusted and brought into abutment with the rear end of the workpiece W. 
     Then the distance between the driver section  5  and the driven section  30  is adjusted by the feeder unit  50  to be a desired distance D. This distance D is a distance required for obtaining a desired expanded diameter in the workpiece W, and it is desirable to ascertain it through a test beforehand. The adjustment is made by advancing the slide  57  (a preliminary movement) by the handle  62  until its projection  57   b  comes into abutment with rear end of the slit  56 , and continuing to operate the handle  62  to gradually advance the rod  60 . Since the top of the feed rod  60  is integral with the slide  35  of the driven section  30 , the driven section  30  is caused to advance along the framework  4 . At this stage the workpiece W is loosely held by the chuck sleeves  15  and  45 , so that it does not move because its end is kept in abutment with the extruding screw  17 . 
     The workpiece W is axially pressed by the press unit  70 , and the driven section  30  is declined by the bias means  80  as shown in FIG.  3 . Specifically, the press is performed by the jack  71  so as to rotate the cam  75  in the arrow X direction. With the press unit  70  and the bias means  80  kept in operation, the motor  20  is turned on to cause the workpiece W to rotate and become bent under pressure provided by the press unit  70 . The rotations per minute can be a few or a few tens, and the bent angle can be at least 3 to 7 degrees. The center P around which the workpiece W is bent is deviated outward from the center line CL of the pre-bent workpiece W. The pressure depends upon the thickness of the workpiece W and any other factor. It is reported that a pressure of 20 to 30% of a uni-axial compressive yield stress in a metal shaft is enough to expand the diameter of a metal shaft (“Study on Diametral Expansion of Round Bars (I)” Volume  34 , by Ni&#39;ihama Technical College). 
     In this way the diametral expansion is performed in a portion of the workpiece W that is located between the chuck sleeves  15  and  45  through compression the the sequence of rotation, bending and pressing. As the diametral expansion continues, the distance between the chuck sleeves  15  and  45  becomes short, and finally both the ends of the expanded portion of the workpiece W come into contact with the end faces of the chuck sleeves  15  and  45 . After the desired diametral expansion is achieved, the rotation and pressing are continued, and the bias means  80  is returned to its original state, thereby returning the workpiece W to its original straight position. In this way a straight metal shaft having an expanded diameter is obtained. The rotation and pressing are stopped, and the workpiece W is released from the chuck sleeves  15  and  45 . 
     At first, the workpiece W is loosely held by the chuck sleeves  15  and  45  so that the diametral expansion does not extend to an undesired portion of the workpiece. However, it often happens that since the workpiece W becomes too tightly held by the chuck sleeves during the rotation, bending and pressing, it is difficult to remove from the chucks. In this case, the extruding screw  17  is inserted and pushes the workpiece W on the end thereof so that it is pushed by the distanced to allow a gap corresponding to the allowance d between the ends of the expanded diameter and the end faces of the chuck sleeves. A remover  90  shown in FIG. 12 is used by fitting a recess  91  of the remover  90  into the gap d, thereby enabling the remover  90  to come into engagement with the diametrically expanded portion G. Then the workpiece W can be drawn in the right-hand direction in FIG.  1 . The remover  90  is provided with a semi-circular recess  92  complementary with the contour of the main sleeve  6 , and with an engaging side  93  which is engageable with the back of the rotary frame  37 . When the workpiece W is to be drawn, the engaging side  93  is kept in engagement with the rotary frame  37 , and the feeder unit  50  is reversely rotated. 
     By referring to FIGS. 4 to  6 , a second preferred embodiment will be described: 
     This embodiment is different from the first version in that the press unit  100  is a double hydraulic cylinder type  101  (hereinafter, “double cylinder”) instead of the hydraulic jack  71  and the cam  75  used in the first embodiment. More specifically, the slide  35  of the driven section  30  is slidably mounted on a second slide  102  which slides on the framework  4 . The feeder rod  60  of the feed unit  50  is connected to the second slide  102 , and moves the driven section  30  together with  30  forward and backward. The double cylinder  101  is located between the rear frame  103  of the second slide  102  and the slide  35 , and pushes the slide  35  forward. The other components are the same, and function in the same manner, so that like reference numerals designate like elements and components in the first embodiment. 
     An advantage of the second embodiment is that since the driven section  30  is directly pushed by the double cylinder  101  without the use of the hydraulic jack  71  and the cam  75 , the overall structure can be simple and a high efficiency is achieved in the power transmission. The double cylinder  101  is convenient in that it can be used for drawing the workpiece after the diametral expansion is finished. FIGS. 13 and 14 illustrate a manner of drawing the workpiece subsequently to the diametral expansion. The extruding screw  17  is driven until the workpiece is slightly extrude from the chuck sleeves  15  and the recess  91  of the remover  90  (FIG. 12) is engaged with the diametrically expanded portion G. Then the engaging side  93  of the remover  90  is placed face to face with the rotary frame  37 . In this situation the feeder unit  50  is reversely operated to move the driven section  30  backward, and cause the remover  90  to draw the workpiece out of the chuck sleeve  15  of the driver section  5 . The other end of the workpiece is easily drawn out of the chuck sleeve  45  of the driven section  30  by hand. 
     Referring to FIGS. 8 to  11 , a third preferred embodiment will be described: 
     This embodiment is characteristic in that the apparatus  110  is incorporated in a conventional lathe; the illustrated lathe  111  is a known NC (numerical control) lathe having a tailstock  105 . More specifically, the expanding unit  120  is incorporated in the tailstock  105 . The apparatus  110  includes a chuck  112  which also functions as a driver section, and a tool holder  113 . 
     Referring to FIG. 11, the expanding unit  120  includes a base  125  having a dovetail mortise  123 , and a rotor  127  on which a tailstock  130  and the expanding unit  120  are arranged side by side. By turning the rotor  127  at 180° the expanding unit  120  or the tailstock  130  is caused to face the chuck  112 . 
     The expanding unit  120  includes a pair of slides  137  slidably mounted on the upright sides of a frame  135 , each slide  137  having a block  138  secured thereto. The block  138  has a threaded hole axially produced, and a screw bar  139  therethrough with the respective threads being in engagement. The screw bar  139  is part of the feeder unit  150 , and is provided with a driven gear  140  at one end. The frame  135  houses a feeder motor  143  whose shaft carries a driver gear  145  in engagement with the driven gear  140 . The rotation of the motor  143  clockwise or anticlockwise causes the rotor  138  to move forward and backward together with the second slide  137  along the screw bar  139 . Instead of the power-driving feed, a manually-operated feeder can be employed. 
     The second slide  137  is equally provided with the driven section  30 . More specifically, the slide  35  of the driven section  30  is slidably mounted on the second slide  137  to which the rotary frame  38  is joined by means of the shaft  36 . The other components of the driven section are the same as those described above. 
     The bias means  80  is the same as those used in the first and second embodiment; it is provided with the nut  82 , and the screw bar  85  mating with the nut  82 . The screw bar  85  is in abutment with the slide  85  at its lower end, and is provided with a handle  86  at its upper end. By turning the handle  86 , the screw bar  85  is rotated but does not ascend or descend. Because of the joint between the lower end of the screw bar and the slide  35 , the nut  82  moves up or down together with the main sleeve  38 . In this way the driven section  30  rotates clockwise or anticlockwise together with the shaft  36 . 
     The press unit  100  composed of a hydraulic cylinder  101  can be used, as in the second embodiment. The hydraulic cylinder  101  is in abutment with the frame of the second slide  137 , and its piston rod is intended to push the slide  35 . 
     In expanding the diameter of the metal shaft by means of the expanding unit  120 , one end of the metal shaft is held by the chuck mounted on the head of the lathe, and the other end of it by the chuck sleeve  45  of the driven section  35 . 
     The driven section  35  is moved by the motor  143  of the feeder unit  150 . In this way the rotation, bending and compression are performed to diametrically expand the metal shaft in the same manner as the first and second embodiments. 
     This expanding apparatus  100  is incorporated in a known lathe, and the rotation provided by the head of the lathe can be used in place of the the driver section described above. By substituting the lathe for the driver section, the structure of the apparatus is simplified only with the provision of the other components, thereby reducing the cost and size of the apparatus. In the illustrated example the expanding unit  120  is associated with a tailstock, which is indispensable to the lathe. By turning the rotor  127  clockwise or anticlockwise, the tailstock or the expanding unit can be switched over. It is also possible to use the expanding unit as an ancillary tool where it is not associated with the tailstock. 
     In the embodiments referred to above the chuck sleeve has a bore of an equal diameter but its shape is not limited to a particular shape or size. The driven section shown in FIG. 15 has a chuck sleeve which can be easily replaced. 
     This is the same with the driver section (not shown). The chuck sleeve shown in FIG. 16 can produce a diametrically expanded portion G shown in FIG.  17 . The diametrically expanded shaft shown in FIG. 18 has steps at G 1 , G 2 , and G 3 . When chuck sleeves having different inside diameters are prepared regardless of their same outside diameter, they can be selectively applied to various metal shafts having different diameters. It is possible to employ an conventional chuck instead of the chuck sleeves described above. 
     Industrial Applicability of the Invention 
     The diametrically expanding apparatus of the invention easily obtains metal shaft having a diametrically expanded portion, and facilitates the formation of gears, cams and sprockets there without welding or bolting. The processed metal shafts can be immediately used as power transmission shafts and the like.