Patent Publication Number: US-3878746-A

Title: Burless blanking machine and process

Description:
O United States Patent 1 1 1111 3,878,746 Carmeli Apr. 22, 1975 [54] BURLESS BLANKING MACHINE AND 3.640.167 2/1972 Axtmann 83/623 x PROCESS 3.739.669 6/1973 56kt 83/623 x [75] Inventor: Werter Carmeli, Milan. ltaly Primary M. Meisler [73] Assignee: International Business Machines K Johnson Corporation, Armonk. NY. 122 Filed: 1161/. 23. 1973 [57] ABSTRACT In a tri le-action blankin press comprisin a frame. a Appl&#39; 4l8626 fixed die. a stripper, a cla mping plate, a pu nch, a drive slide driving the punch and actuating means. the strip- [30] Foreign Application Priority Data per can project from the die and an elastic member is DCC. 22. 1972 Italy 33436/72 interPd between P and drive slide- The machine adjustment is such that during a first part of 52 us. (:1. 831/126; 33/51; 83/1 37; the machine cycle the stripper acts as a Punch and the 83/582; 33/616; 33,623 clamping plate as a die so that the piece is partiall 1511 161. c1 B261 1/02 blanked its Punch side; during Said operation the [53] Field of Search H 83/7. 50 51 55 I37 elastic member is completely compressed and the con- 83/623 M6 389. 542. 543. 582. |26 nection between the drive slide and the punch becomes rigid; then the punch acts just as a punch and [56] Rderences and forces the piece into the die until it is completely UNITED STATES PATENTS blanked. The operation provides completely burless blanked pieces. 3.l78.975 4/l965 Gcorgcff 83/6l6 X 3.602.078 13/1971 Schindler 83/50 x 4 a s. 5 Drawing gu s PATENTEDIPRZZISIS SHEU 1 0F 4 FIG. 1  
 PATENTEDAPRZZIQIS arm a or 4 FIG. 4  
  1 BURLESS BLANKING MACHINE AND PROCESS BACKGROUND OF THE INVENTION This invention is directed to blanking apparatus and processes. more particularly to a line blanking apparatus and a process for blanking burless pieces with a fine blanking machine. In traditional blanking methods tool assemblies are used comprising essentially a die and a punch which are mounted on a single-action press. The pieces blanked according to said methods present major surfaces which are neither coplanar nor parallel to each other. and present lateral surfaces which are very rough and non perpendicular to the major surfaces and have cranks whose depth depends on the hardness of the material.  
  Said pieces. which can be suitable for coarse productions. cannot be used in fine works without undergoing several further processings. It is known in the art to obviate many of above-mentioned defects by using special tool assemblies on triple-action presses. according to a process usually known as fine blanking.&#34;  
  However. even the fine blanking cannot prevent burrs from forming on the punch side of the blanked pieces and that makes necessary to deburr the blanked pieces with suitable processings (e.g. sanding. tumbling. etc.). That does not represent a great disadvantage if the thickness of the blanked pieces is such to allow the cleaning operations without warping or anyhow damaging the pieces themselves. It is however impossible to tumble or sand very thin pieces. since said pieces are unavoidably warped by said operations. An alternative to mechanical deburring consists in chemical deburring. but it is so expensive to make the operation uneconomic.  
 SUMMARY OF THE INVENTION Accordingly it is a main object of the present invention to provide a blanking method for making high precision completely burless thin blanked pieces. Another object of the present invention is to provide blanked pieces which need no further cleaning operation.  
  A still further object of the present invention is to provide an improved triple-action press for blanking high precision smooth finish thin pieces. These and other objects will be readily perceived from the following description. claims and drawings.  
 BRIEF DESCRIPTION OF THE DRAWING FIG. I is a fragmentary cross sectional view of the triple-action press in accordance with the present invention.  
  FIG. 2 is a cross sectional view of the elastic member to be used in the press in accordance with the present invention.  
  FIGS. 3. 4 and 5 show three different moments of the blanking cycle in accordance with the present invention.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT While the invention will be described in connection with a preferred embodiment it will be understood that the invention is not limited to that embodiment. Referring now to FIG. I, the mount I is supported by the machine frame 2 and in turn supports the die 3. The die 3 has a substantially flat outer surface 4 and is provided with a die aperture 5. The number 6 generally indicates the stripper. which consists of a stripper body 7. a flange 8 and a worksurface 9. The stripper body 7. which has a cross section complementary to the die aperture S, is partially nested in said die aperture and is slid-ably guided by the walls which define it. The flange 8 is slidably guided by the walls defining the chamber 10 in the mount 1 and. since the diameter of the chamber 10 is greater than the diameter of the die aperture 5. said flange limits the downward movement of said stripper. The stripper 6 projects. in the position shown. from the outer surface 4 of the die 3. The stripper 6 is actuated by the hydraulic cylinder 11 through the ram 12.  
  The mount 13 of the clamping plate is supported by the base l4 and in turn supports the clamping plate 15. The clamping plate 15 has a substantially flat outer surface 16 and is provided with an aperture [7 which has the same cross section as the die aperture 5 and is aligned therewith.  
  The base 14, slidably guided by means not shown. is vertically movable under the action of the hydraulic cylinder 18.  
  The number 19 generally indicates the punch. which consists of a punch body 20. a head portion 21 and a work surface 22. The punch body 20 has a cross section complementary to the clamping plate aperture l7. in which it is partially nested. and is slidably guided by the walls defining said aperture.  
  The work surface 22 of the punch is. in the position shown. flush with the outer surface of the clamping plate. The head portion 21 of the punch I9 has a circu lar section and is slid-ably guided by the walls defining the chamber 23 in the mount l3. The plate 25 is fastened to the lower end of the punch head portion and engages an elastic element connecting said plate 25 to the plate 26, which in turn is secured to the drive slide 24 vertically movable under the action of the main motor (not shown).  
  A cross section of the elastic member connecting the punch to the drive slide is shown in FIG. 2.  
  Said elastic member comprises an upper plate 25 to be fastened to the punch. a lower plate 26 to be secured to the drive slide. a cup spring 27, bushes 28, screws 29 and washers 30. The upper plate 25 comprises a central body 31, a flange 32 provided with holes 33, and a member 34 disposed on the upper side of the central body 31 which is apt to engage a recess in the punch. An annular recess 35 opens in the lower surface 36 of the upper plate 25 and is coaxial with the plate itself.  
  The lower plate 26 is provided with threaded holes 37, in which screws 29 engage, said holes being coaxial with the holes 33 in the flange 32. and further provided with the central threaded hole 40 which is able to engage a suitable member of the drive slide 24.  
  The cup spring 27 is nested in the annular recess 35 and engages both the bottom surface 38 of said recess and the upper surface 39 of the lower plate 26. The bushes 28 are inserted into the holes 33 of the flange 32 and the screws 29 with the washers 30 fasten said bushes to the lower plate 26. so that the upper plate 25 is reciprocably movable with respect to the lower plate 26., said upper plate 25 being slidably guided by the bushes 28.  
  The maximum spacing between the lower plate and the upper plate is determined by the length of the bushes 28. The working process for making burless thin blanked pieces by a press according to the present invention will be described with reference to FIGS. 3. 4 and 5.  
  As previously stated. the burless fine blanking process requires a triple action press. The three machine actions actuate respectively the stripper 6a. the clamping plate 150 and the punch 19a and their magnitude and phase must be adjusted so that the following condi tions are attained:  
 l. The action (the force on the stripper 60 must be sufficient to overcome the strain strength of the material to be blanked plus the force exerted by the cup spring 27a.  
 2. The action on the clamping plate 150 must be greater than the action on the stripper 6a.  
 3. The action on the punch 19a must be sufficient to overcome the blanking stress of the material to be blanked plus the actions on the clamping plate a and on the stripper 6a.  
 OPERATION The machine cycle can be divided into three main subcycles which we shall name first stroke.&#34; second stroke&#34; and ejection and reset.&#34; Said three machine subcycles will be first briefly defined and then described in details. The subcycle defined first stroke begins as the machine starts; the machine is shown in its rest position in FIG. 3. During the first stroke the stripper 60 acts as a punch and the clamping plate 150 acts as a die. while the punch 19a acts as a blank holder (and follows closely the piece to be blanked): this is a blanking stroke opposed to the usual one and the partial blanking depth on the punch side is equal to the initial distance between the two plates 25 and 26.  
  The second subcycle defined second stroke begins when the punch 19b has compressed the spring 271) of the elastic member at its maximum and a rigid connection between the punch 19b and the drive slide 24!; has been achieved.  
  Through the rigid connection the drive slide 24b actuates directly the punch l9h which penetrates into the material to be blanked overcoming the opposite actions on the stripper 6b and on the clamping plate 15b.- this is the actual blanking stroke during which the material is forced to enter the die 3b and is completely blanked. The third subcycle. that we have defined ejection and reset. begins when the punch 19b and the drive slide 24h reverse their motion. During said subcycle the blanked piece is ejected and the machine reset.  
  We shall now give a detailed description of the three subcycles previously defined. The machine is shown in its rest position in FIG. 3. The punch work surface 22a is substantially flush with the clamping plate outer surface 16a. The elastic member spring 270 has the maximum extension compatible with the elastic member adjustment; said adjustment determines the depth of the partial blanking on the punch side. Thus the connection between the drive slide 24a and 19a is of elastic kind. The hydraulic cylinder 11a actuates the stripper 6a through the ram 12a. Said action is sufficient to overcome the strain strength of the material to be blanked, plus the force exerted by the spring 270 on the punch 19a. The pressure in the hydraulic cylinder 18a is sufficient to bear the weight of the base 14a. of the mount 13a and of the clamping plate 15a.  
  Starting the machine. the drive slide 24a begins moving upwards driven by the main motor through a double toggle mechanism (not shown in the figures). Since the pressure in the cylinder 18a is sufficient to bear the weight of the base and of the assembly it supports. the base 140. the mount 13a and the clamping plate will follow the movement of the drive slide 24a. Likewise. since the elastic element 27a is able to bear the weight of the punch 19a. the punch 190 will follow the upward movement of the drive slide. As a result. the drive slide 240, the clamping plate 150 and the punch 190 will move upwards, maintaining the same position with respect to one another as in the rest position. When the clamping plate outer surface 16a meets the material to be blanked. the action of the drive slide is transmitted to said material. which in consequence is pushed upwardly toward the outer surface 40 of the die 3a and towards the work surface 9a of the stripper 6a. which projects out of the die 30. As the upper surface of the material to be blanked meets the work surface 9a of the stripper 6a the action of the hydraulic cylinder 18a on the base 14a and therefore on the clamping plate 15a is sufficient to overcome the action on the stripper 6a. The action exerted by the elastic element 270 on the punch 19a is not sufficient to overcome the action on the stripper 60. As a consequence the clamping plate 15a continues its upward motion pushing that part of the material to be blanked which does not face the work surface 9a of the stripper 60, while that part of the material which faces the work surface 90 is stopped and forced to penetrate into the aperture of the clamping plate 15a. Under the action ofthe stripper 60. which forces the material into the aperture 170 of the clamping plate 15a, the punch [90 recedes with respect to the clamping plate 150 and follows under pressure the material. while it is partially blanked. preventing the material from bending and in so doing altering the real dimensions of the perimeter so impressed. Since the drive slide 24a continues moving upwards and the punch 19a stands still. the elastic member spring 27a is compressed.  
  When the clamping plate 150 has clamped the material external to the figure to be blanked against the outer surface 40 ofthe die 30. the first subcycle. i.e. the first stroke is completed. That part of the material which faces the work surface of the stripper has been forced into the clamping plate aperture for a depth essentially equal to the initial distance between the plates 25 and 26 of the elastic member. Since said distance is less than the thickness of the material to be blanked. the material has been partially blanked on the punch side and the edges of the partially blanked figure are rounded off. As shown in FIG. 4 the elastic member spring 27b is completely compressed and the plates 25b and 26b of the elastic member are in contact. The punch 19b and the drive slide 24b are now rigidly connected and the second subcycle. i.e. the second stroke begins.  
  Since the drive slide 24b continues its movement upwards. the punch 19b is pushed upwards and since the clamping plate stands still. the punch slides through and out the clamping plate aperture 17b. The action on the stripper 6b is not sufficient to bear the action of the drive slide 24b, so that the punch 19b pushes the partially blanked part out of the clamping plate aperture 17b and, against the action of the stripper 6b. forces it into the aperture 5b of the die 3b blanking now the piece on the die side. The machine is so preset that the piece is completely blanked before the punch 19b penetrates into the aperture 5b of the die 31). so that when the work surface 22b of the punch 19b is flush with the outer surface 4b of the die 3b the motions of the punch 19b and of the drive slide 24b reverse and the return stroke begins.  
  In order to facilitate the separation of the material from the outer surface 4c of the die 3c. the pressure in the cylinder 11c. acting on the stripper 6c and the pressure in the cylinder 18c acting on the clamping plate lSc are momentarily interrupted. The punch 19(- moves downward and the pressure on the clamping plate c is reset. the punch 19c continues moving downward and comes out of the blanked material. Before the punch 19c reaches the return stroke end also the pressure acting on the stripper 6c is reset. The material is caused to advance to another work position and air blasts blow away the blanked piece. When the punch reaches the return stroke end, the machine cycle is over and an identical cycle is ready to start.  
  While the invention has been particularly shown and described with reference to a preferred embodiment thereof. it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.  
 What is claimed is:  
 l. A blanking press comprising:  
 a frame;  
 a die. having a die aperture. said die being rigidly secured to said frame;  
 a stripper disposed within said die aperture and slidably guided by said die aperture, said stripper projecting from the outer surface of said die during one predetermined period of the machine cycle;  
 a clam ping plate opposed to said outer surface of said die for clamping the material to be blanked against said outer surface of said die, said clamping plate being provided with an aperture. said aperture having essentially the same section of and being essen- 6 tially aligned with said die aperture:  
 a punch disposed within said aperture of said clamping plate. said punch being slidably guided by said aperture;  
 a drive slide;  
 means for connecting said punch and said drive slide. said means being able to maintain the work surface of said punch substantially flush with the work surface of said clamping plate during another predetermined period of the machine cycle. said means being further able to allow said punch to recede into said aperture of said clamping plate a predetermined distance after which said means supply a direct transmission of the motion of said drive slide to said punch;  
 means for actuating said stripper;  
 means for actuating said clamping plate; and  
 means for actuating said drive slide.  
  2. A blanking press according to claim I, wherein said means for connecting said punch and said drive slide comprise essentially a first plate secured to said punch. a second plate secured to said drive slide and a spring at least partially nested between said plates within a suitable cavity formed in said plates. so that said punch and said drive slide can approach compressing said spring until said plates meet and form a rigid transmission of the motion from said drive slide to said punch.  
  3. A blanking press according to claim 1, wherein said means for actuating said stripper is hydraulic means. said means for actuating said clamping plate is hydraulic means and said means for actuating said drive slide is mechanical means.  
  4. A blanking press according to claim 1, wherein said stripper projects from the outer surface of said die an amount which is less than the thickness of the material to be blanked.