Method for pressing groove section with bending angle smaller than or equal to 90 degrees

Abstract

A method and an apparatus or pressing groove section with a bending angle smaller than or equal to 90 degrees are provided. The apparatus comprises an upper convex die and a lower concave die are used for processing. The convex die comprises an expansion sleeve and an expansion core which are nested with each other. At least one of a central hole of the sleeve body and the core body is a wedge with a larger top and a smaller bottom, and a relative locking mechanism is arranged between the core body and the core body. The concave die comprises a multi-petal-shaped inner concave die and an external outer concave die which are in elastic connection.

We claim: 
     
         1 . An apparatus for pressing a groove section with a bending angle smaller than or equal to 90 degrees, comprising an upper die assembly and a lower die assembly which are coaxially arranged, wherein the upper die assembly comprises an expansion sleeve which is of a multi-petal-shaped structure in elastic connection and which has an outer part provided with a wedge die having a narrower top and a wider bottom, and an expansion core; in a central hole of the expansion sleeve, at least one of the central hole of the expansion sleeve and the expansion core is a wedge having a larger top and a smaller bottom; a height of a lowest point of the expansion core in a non-pressed initial state is greater than a height of a lowest point of the expansion sleeve; the expansion core is in clearance fit with the expansion sleeve, and a relative locking mechanism is arranged between the expansion core and the expansion sleeve; the relative locking mechanism is as follows: a transverse supporting rod is connected among petal bodies opposite to the expansion sleeve; the expansion core is of a structure with a longitudinal chute in a middle; an elastic part is arranged in the longitudinal chute; the transverse supporting rod penetrates through the longitudinal chute of the expansion core; and a bottom of the elastic part is pressed against the transverse supporting rod in the longitudinal chute of the expansion core; the lower die assembly comprises an inner concave die comprising a multi-petal-shaped structure in elastic connection, and an outer concave die; a groove of the inner concave die is a wedge-shaped groove matched with the expansion sleeve in an outer shape to enable the expansion sleeve to enter the groove of the inner concave die; a groove of the outer concave die is of a structure having a wider top and a narrower bottom; the inner concave die is arranged in the outer concave die; and an elastic body is arranged in the groove of the outer concave die and below the inner concave die. 
     
     
         2 . The apparatus according to  claim 1 , wherein the elastic connection is realized among the plurality of petal bodies of the expansion sleeve through a structure as follows: the petal bodies opposite to the expansion sleeve are connected through a transverse spring rod; the spring rod comprises the transverse supporting rod, and a spring: and a specific connecting relationship of the expansion sleeve and the spring rod is as follows: stepped holes having smaller interiors and larger exteriors are formed in inner walls of the petal bodies of the expansion sleeve; two ends of the transverse supporting rod respectively stretch into the stepped holes of the petal bodies on two sides; the spring is assembled at the end of the transverse supporting rod stretching into a larger hole of the stepped holes; limiting retainer rings are arranged at two ends of the spring at each end; and a size of a limiting retainer ring on an inner side is larger than a hole diameter of a smaller hole of the stepped holes. 
     
     
         3 . The apparatus according to  claim 1 , wherein the elastic connection is realized among the plurality of petal bodies of the expansion sleeve in a manner of peripheral series connection by elastic parts. 
     
     
         4 . The apparatus according to  claim 3 , wherein the relative locking mechanism further comprises an ascending stop auxiliary locking mechanism of the expansion core relative to the expansion sleeve; the ascending stop auxiliary locking mechanism is specifically as follows: an expanding cap larger than an upper size is arranged at the bottom of the expansion core, a flaring larger than an upper part is formed at the bottom of the central hole of the expansion sleeve, and the expanding cap is matched with the flaring. 
     
     
         5 . The apparatus according to  claim 4 , wherein a bottom of the expanding cap is a flat. 
     
     
         6 . The apparatus according to  claim 1 , wherein the central hole of the expansion sleeve and the expansion core are wedges each having a larger top and a smaller bottom. 
     
     
         7 . The apparatus according to  claim 1 , wherein an outer longitudinal section of the inner concave die is a trapezoid having a larger top and a smaller bottom, and inclination of an outer wall of the longitudinal section is matched with inclination of a groove wall of the groove of the outer concave die. 
     
     
         8 . The apparatus according to  claim 1 , wherein a positioning block is arranged at the bottom of the groove of the outer concave die and is a descending termination point of the inner concave die. 
     
     
         9 . The apparatus according to  claim 2 , wherein the outer concave die is of a multi-petal-shaped structure, and exteriors of the plurality of petals are supported through transverse adjustable supporting rods; and an external thread is arranged at the end of the transverse support connected with the multi-petal-shaped expansion sleeve; the external thread is arranged on an outer side of the limiting retainer rings and an adjusting nut is arranged and matched with the external thread of the transverse supporting rod. 
     
     
         10 . A method for pressing a groove section with a bending angle smaller than or equal to 90 degrees, comprising:
 1) assembling an upper die assembly on a stamping mechanism connected with an expansion core of the upper die assembly, and laying a flat-plate type workpiece to be processed at an upper port of the lower die assembly;   2) descending the stamping mechanism to drive an expansion sleeve and the expansion core of the upper die assembly to descend synchronously, wherein the expansion sleeve is contacted with the workpiece to be processed firstly during the descent; further descending the stamping mechanism, wherein the expansion core is further driven to descend while the expansion sleeve stops moving during the further descent since a stamping force of the stamping machine does not reach yield strength of the workpiece to be processed at this time, an elastic part in a chute of the expansion core is shrunk, and the workpiece is not bent; and expanding the expansion sleeve when the expansion core is descended to a bottom of the expansion sleeve, wherein the expansion core is contacted with the workpiece to be processed;   3) further descending the stamping mechanism wherein the stamping force of the stamping machine exceeds the yield strength of the workpiece to be processed, and the expansion sleeve and the expansion core bend the workpiece together to allow the workpiece to enter a groove of an inner concave die;   4) further descending the stamping mechanism, wherein the inner concave die is descended when the stamping force exceeds a resistance of an elastic body at a bottom of the inner concave die, the inner concave die is compressed inwards by an outer concave die along with descent of the inner concave die, and when the inner concave die is descended to a termination point at the bottom of the outer concave die, the workpiece is tightly extruded and hooped on an outer wall of the inner concave die to form a preset grooved part; and   5) the elastic body at the bottom of the inner concave die being subjected to elastic recovery to bounce the inner concave die upwards; meanwhile, the elastic part in the chute of the expansion core recovering deformation; and the expansion core and the expansion sleeve relatively moving to recover to initial states; wherein along with continuous ascent of the inner concave die, a groove width of the inner concave die is gradually enlarged, after the elastic body completely recovers the deformation, the inner concave die recovers to an initial position, the expansion sleeve and the expansion core are taken out of the groove of the inner concave die of a lower die assembly under a pull-up force of the stamping mechanism, and then the workpiece is taken out.   
     
     
         11 . The method according to  claim 10 , wherein in the step 5), an expanding cap of the expansion core provides the pull-up force for the expansion sleeve when the expansion sleeve and the expansion core recovering to the initial states are taken out of the groove of the inner concave die of the lower the assembly by the stamping mechanism. 
     
     
         12 . The method according to  claim 10 , wherein the stamping mechanism is a pressing machine.