FR2598948A1 - Die assembly for forging metal caps for insulators - Google Patents

Abstract

The invention relates to a die assembly for forging metal caps for insulators, comprising an internal die 1, an external die 2, a first coupling-cavity forming die 3 and a second coupling-cavity forming die 4 composed of three disconnectable die elements comprising an orifice-forming die 5, a recess-forming die 6 connected to the orifice-forming die from which it is axially detachable, and a traction-separating die 7 connected in an extractable manner to the recess-forming die, and also coupling means 3c, 5c provided on the first coupling-cavity forming die 5 and on the orifice-forming die 5 and capable of engaging with each other with a view to moving the orifice-forming die away from a metal cap blank 14 during a displacement of the first coupling-cavity forming die with respect to the metal cap blank.

Description

Set of dies for forging metal covers for insulators
The present invention relates to a set of dies for forging metal covers for insulators, and in particular to a set of dies for forging metal covers comprising a coupling cavity intended to anchor a metal support, and a bell-shaped part intended enclose an isolator.

 In general, metal covers for power line insulators are made by molding malleable or ductile iron, and forged metal covers are used only for specific applications. The reason for this is that, although the forged metal covers have an inherently higher quality of reliability than the molded covers, the construction of the metal insulator cover, in particular its cavity portion, is not suitable forging. This construction requires expensive mechanical machining of the metal cover, so that, from an economic point of view, the forged metal covers are less advantageous than the molded covers.

 A method hitherto used to produce metal covers for ball-type suspension insulators has been described in the Japanese patent application published under No. 948/60 which uses a set of dies consisting of a die upper 51 and a lower die 52 shown in Figure 1. A metal cover blank 53 having a cylindrical coupling wall portion 53a provided with a bottom, and a bell portion 53b is pressed from upper directions and lower for bending inward the lower end of the part forming a coupling wall 53a, so as to form therein a hollow or a coupling cavity 53c which can be seen in the figure 2.

 However, the set of dies of the prior art only serves to bend the part forming a cylindrical coupling wall 53a, so that, in a subsequent step, it is necessary to cut by milling a lateral part of the wall forming part 53a to form an orifice 53d in order to introduce into the coupling cavity 53c, from one side, a metal insulator support. This additional method therefore reduces the productivity of insulators and poses another problem in that it decreases the resistance of the metal cover due to the fact that forged flow lines of the coupling wall portion 53a are cut during the formation of the orifice 53d. It is necessary, in particular during a subsequent process, to form by machining a recessed part in the coupling cavity 53c, at its internal upper surface formed by forging, so that forged flow lines from this inner top surface are cut where high strength is required.

This is a very important problem.

 In view of this problem, the present applicant has proposed a set of dies capable of forming a coupling cavity on an internal portion of the part forming the coupling wall, and a simultaneously orifice.

 However, the proposed array of matrices consisted of several separable matrix elements, so that the operation of separating the respective matrix elements was extremely complicated to the point of lowering the productivity of insulators.

 A main object of the present invention is to provide a set of dies for forging metal covers for insulators, which eliminates all the drawbacks of the prior art, which is capable of improving the productivity of metal covers while retaining a sufficient strength without cutting the forged flow lines, and which requires a simple operation to separate the dies from the blanks of metal covers.

 To achieve this goal, the set of dies for forging metal covers for insulators, according to the present invention, comprises an internal matrix intended to be applied against a bell-shaped part of a metal cover blank, an external matrix intended to be applied against an external part of the metal cover blank, a first coupling cavity forming matrix intended to be fitted, in the external matrix, axially with respect to the blank and having a forming surface oblique to bend inwardly a coupling wall portion of the blank by axially forcing its end against the oblique forming surface to form a coupling cavity, and a second coupling cavity forming matrix intended to be housed in a housing groove formed in the first coupling cavity forming matrix from its center to an outer side, in order to form an orifice in the coupling wall portion and shaping an internal portion of the coupling cavity, the second coupling cavity forming matrix being composed of three separable matrix elements comprising an orifice forming matrix, a matrix for forming a recess assembled to the orifice forming matrix from which it is axially detachable, and a matrix for separation by traction assembled in an extractable manner. if the recess fortification matrix, and also means for provided on the first coupling cavity forming matrix and on the orifice forming matrix of the second coupling cavity forming matrix and adapted to engage with one another for the purpose of spreading the orifice forming die of the metal cover blank during movement of the first coupling cavity forming die relative to the metal cover ltebauehe.

 In a preferred embodiment, the recess forming die can be pulled and moved transversely after being moved away from the metal hood blank, when the cracking die is pulled and moved transversely.

 The oblique forming surface of the first mating cavity forming matrix is preferably in the form of a curved surface.

 The orifice forming matrix intended to eo: place the second mating cavity forming matrix preferably comprises, on a front edge, a curved forming surface in order to conform an internal peripheral surface of the following wall part an arc-shaped configuration.

 The set of dies for forging metal insulator covers makes it possible, during the manufacturing steps, to bend the part fc, forming a coupling wall of the metal cover blank. to form the coupling cavity in the wall-forming part, and to simultaneously form the orifice, in order to improve the productivity in metal covers. As the hole is formed using the orifice forming die without cutting out the forged portion or flow lines of the coupling wall portion, the strength of the coupling cavity of the metal cover is improved.

 Furthermore, in accordance with the invention, the hollowed out part is formed at the level of the internal upper part of the coupling cavity with the aid of the recess forming matrix during forming of the coupling cavity. When removing the dies during this step, once the pull-out separation matrix is removed from the blank, the recess forming matrix is moved away from the orifice forming matrix to be separated from the hollow part of the blank, and then extracted therefrom. In this way, the hollow part is formed exactly at the level of the internal upper part of the coupling cavity of the blank without any cutting or Milling by milling is necessary to form the hole and the hollowed out part, so that the resistance of the metal cover is improved because no forged line of it is cut.

 When the first coupling cavity forming matrix is removed, the orifice forming matrix of the second coupling cavity forming matrix is separated at the same time as the first of the cover blank, so that the removal of the dies is remarkably simplified, which considerably improves the productivity in metal covers.

To allow a better understanding of the present invention, several preferred embodiments thereof will be described in detail, by way of non-limiting example, with reference to the accompanying drawings in which
- Figure 1 is a sectional view of the matrices of the prior art used to form a metal cover
- Figure 2 is a sectional view showing a metal cover formed using the matrices of the prior art
- Figure 3 is a perspective view showing an embodiment of the set of dies for forging metal covers of the present invention
- Figure 4 is an exploded perspective view on an enlarged scale of the second mating cavity forming matrix of the set of matrices of Figure 3
- Figure 5 is a front elevational view of a piece for the production of a metal cover, before forging
- Figure 6 is a front elevational view of the piece of Figure 5, after forging in the form of a planar blank
- Figure 7 is a sectional view showing a step of forging the blank of the metal cover - - Figure 8 is a bottom plan view showing only the blank of Figure 7
- Figure 9 is a partial sectional view of the metal cover blank.

- Figure 10 is a sectional view showing a next step of forging the metal cover blank of Figure 7
- Figure 11 is a bottom plan view showing only the blank of Figure 10
- Figure 12 is a partial sectional view of the blank
- Figure 13 is a sectional view showing a forging step to form retaining ribs
- Figure 14 is a sectional view showing the first of the three steps for forming the coupling cavity and the hollowed out part at the coupling wall forming part of the metal cover blank
- Figure 15 is a sectional view showing the second of the three stages
- Figure 16 is a sectional view taken along the line
XVI-XVI of figure 15
- Figure 17-is a sectional view showing the third of the three stages
- Figure 18 is a plan view showing only a metal cover after forging; and
- Figure 19 is a sectional view showing the cover of forged metal using the array of dies according to the invention, used in insulators.

 Figure 3 shows in an exploded perspective view, a set of main dies represented upside down, used in three stages and, in particular, in the third stage. As will be described in more detail later, these three stages consist in bending a part forming a coupling wall 14b of a metal cover blank 14 to form a coupling cavity 14f, and in forming an orifice 14a. This set of dies comprises an internal die 1 intended to be applied against an internal upper surface of a bell-shaped portion 14c of the metal cover blank 14, and an external die2 which has a forming surface 2a intended to be applied against the outer circumferential surface of the metal cover blank 14 and consists of two die elements 2A and 2B.

 The matrix assembly also comprises a first coupling cavity forming matrix 3 intended to be fitted vertically in a movable manner in an insertion opening 2b formed in the part of matrix 2B contiguous to the lower part of the surface 2a for forming the external matrix 2. The first coupling cavity forming matrix 3 comprises, at one of its ends, an oblique forming surface 3a which is substantially in the form of a curved surface intended to be forced against one end of the coupling wall portion 14b of the metal cover blank 14, in a vertical direction, to bend this coupling wall portion 14b inwardly, in order to form the coupling cavity 14f shown in FIG. 18. The first coupling cavity forming matrix 3 further comprises a housing groove 3b which passes through it vertically and extends from its central part ale to its outer lateral surface, which groove 3b is intended to accommodate a second coupling cavity forming matrix 4 described below.

 The second coupling cayity forming matrix 4 is adapted to be housed in an insertion groove 2c formed in one face of the external matrix 2 and of the housing groove 3b of the first coupling cavity forming matrix 3. The second coupling cavity forming matrix 4 is made up of three separable elements represented in FIG. 4 and intended to form the orifice 14a of the coupling wall 14b, on one of the faces thereof, and a hollow part 14g of the coupling cavity 14f, at the level of the internal upper surface of the latter. It comprises an orifice forming matrix 5 having a core portion 5a which comprises, along its edge, a curved forming surface 5b intended to conform an internal peripheral surface of the coupling wall portion 14b according to a configuration in an arc (of a circle).

 The orifice forming matrix 5 comprises, at its other end, stepped coupling projections 5c defining anchoring means with stepped coupling notches 3c formed in the housing groove 3b of the first forming matrix coupling cavity 3. When the latter is moved upward to be distant from the metal cover blank 14 of FIG. 18, the stepped coupling notches 3c and the projections 5c come into engagement with each other to move the orifice forming die 5 away from the metal cover blank 14 at the same time as the first coupling cavity forming die 3.

 A recess forming die 6 is assembled to the orifice forming die 5 and is detachable, from the bottom, from the lower surface of the latter (from the top, from the upper surface of the die 5, according to the views of Figures 3 and 8 which represent these matrices upside down). The recess forming die 6 comprises, in its main portion, a coupling groove 6a which extends longitudinally and, at one of its ends, a core-shaped part 6b which is fully domed and disc-like, which corr-espo; id a the forming surface 5b of the orifice forming matrix 5. The recess forming matrix 6 also comprises, on a side dc a part forming noffat 6b, a coupling part 6c adapted for come into contact with a lateral edge of the orifice forming matrix 5 in order to prevent its transverse removal.

 A traction separation matrix 7 is assembled with the recess forming matrix 6 and can be separated from it transversely at its lower surface (upper surface according to the views of FIGS. 3 and 4). The traction separation matrix 7 is provided, on its upper surface, with a coupling pin 7a adapted to slide in the coupling groove 6 ce the recess forming matrix 6 and, at the 'one of its ends, of a core part 7b which corresponds to the core part 5b of the recess forming matrix 6.When the separation matrix by tr - etion 7 is extracted from the assembly by or, as seen in FIG. 16, is moved to the left by a predetermined distance, the recess forming die 6 falls on a lower part 7c of the pull separation matrix 7, so that it s moves away from the recessed portion 14 g of the metal cover blank 14 by lowering. Then, the coupling pin 7a engages in the left end of the coupling groove 6a, which has the effect that the recess forming die 6 is pulled or moved in cooperation with the separation die by pull 7 to the left, as seen in Figure 16.

 A method of forming a metal cover 43 by forging using dies 1 to 7 constructed according to the description above, and dies prepared separately will now be explained with reference to FIGS. 5 to 18.

 First, a long circular bar is cut in the form of metal pieces 8 in the form of a column of circular section and of predetermined length, as illustrated in FIG. 5.

 Then, the column-shaped block 8 is crushed in axial directions using upper and lower forging dies (not shown) to forge by forming a planar blank similar to a disc 9 having a projection 9a in the center of its lower surface and shown in Figure 6.

 Then, the planar blank 9 is forged using a set of forging dies composed of an upper die 10, a lower die 11, an orifice forming die 12 and a push rod ejection 13 shown in FIGS. 7 to 9, in order to shape a blank 14 for the metal cover 43 described later and forged in a cavity of this set of dies. The blank 14 thus formed comprises, formed integrally, at its lower end, a portion forming a coupling wall 14b having, on one side, an orifice which has the configuration of a horseshoe or a U, visible in FIG. 8, at the level of its upper end, a cylindrical bell portion 14c and, at its intermediate portion between the coupling wall portion 14b and the bell portion 14c, a partition 14d shown in FIG. 7.

 The blank 14 thus formed is then forged using another set of forging dies composed of an upper die 15, a lower die 16, an orifice forming die 17 and an ejection rod 18, in a cavity of this set of dies, so that the part forming a coupling wall 14b is elongated in an axial direction of the blank 14, that the part forming a bell 14e has, on its circumference, an annular stepped part 14e which widens inwards and has an L-shaped cross section, and that in addition the partition 14d becomes thinner, as shown in FIGS. 10 and 12.

 Then, as can be seen in FIG. 13, the upper surface S of the annular stepped part 14e of the blank 14 is pushed inward using a lower die 41 fixed to a mounting member 40 of an upper die 42 comprising at least one internal recess which abuts against an external portion of the end of the bell-shaped portion 14c, in order to bend the annular stepped portion 14e inwards near its lower portion E, thus define two ribs 14i superimposed on each other on the inner circumferential surface of the end of the bell portion 14c in order to prevent the disassembly of the metal cover 43 when it is applied to an insulator shown in the figure 19.

 Then, the set of dies according to the invention is used to carry out three steps which consist in bending inward the end of the part forming a coupling wall 14b of the metal cover blank 14, form the coupling cavity 14f on the internal portion of this part forming the coupling wall 14b and to form the recessed part 14g on the internal upper surface of the coupling cavity 14f, as illustrated in FIGS. 14, 15 and 17.

 During the first step, as can be seen in FIG. 14, different dies are used, such as the inner die 1 mounted on a mounting member 21, the die element 2A of the outer die 2, two dies forming 3X and 3Y of a construction similar to that of the first coupling cavity forming matrix 3, the orifice forming matrix 5, the recess forming matrix 6, the traction separation matrix 7 and similar elements mounted between the mounting members 21 and 22. The blank of the metal cover 14 equipped with the internal matrix t and supported by it is clamped by the matrix elements 2A which surround it and move in its direction and then is still tightened and fixed with the aid of fixing members 23. The recess forming matrix 6 and the traction separation matrix 7 are then inserted into the hollow formed in the wall forming part of horseshoe or U-shaped coupling 14 b of the metal cover blank 14 from the side thereof. Then, the orifice forming matrix 5 is lowered as far as the recess forming matrix 6, and, successively, the two forming matrices 3X and 3Y as far as the metal cover blank 14 to form the cavity d coupling 14f and the recessed part 14g in the U-shaped coupling wall 14b.

 After this forming operation, the mounting member 22 is raised and the fixing members 23 are lifted as well as the two forming dies 3X and 3Y to move them away from the part forming the coupling wall 14b of the cover blank. made of metal 14. In this state, the rough cover of metal 14 is, according to the view in FIG. 14, moved to the right at the same time as the mounting member 21, the internal die 1, the element of matrix 2A of the external matrix 2, the recess forming matrix 6 and the traction separation matrix 7, and is ready for the second step illustrated in FIG. 15.

 In the second step, a single forming matrix 3Z is used as the first mating cavity forming matrix in place of the two forming matrices 3X and 3Y. In the same way as during the first step, the fixing members 23 are lowered to clamp and fix the matrix element 2A from the outside. In this state, the orifice forming die 5 is lowered onto the recess forming die 6, and then the forming die 3Z is lowered to conform the coupling wall portion 14b of the hood blank metal in a configuration close to its predetermined configuration. During the second step, in addition, a movable cam body (25 is lowered to force a tear forming matrix 24 to move towards the coupling wall 14b from the opposite side to the recess forming matrix 6 and to the traction separation matrix 7, in order to define a tear forming part 14h on an external surface of the coupling wall 14b.

 After this forming operation, the mounting member 22 is raised to force the fixing members 23 and the forming matrix 3Z acting as the first coupling cavity forming matrix to move away from the wall forming part of coupling 14b of the metal hood blank by moving upwards. In this case, the forming die 3Z being raised, the coupling notches 3c are brought into engagement with the coupling projections 5c to force the orifice forming die 5 to stand up moving away from the metal cover blank 14 at the same time as the forming die 3Z. During the raising of the mounting member 22, the movable cam body 25 visible in FIG. 16 is also raised to retract outward the tear forming matrix 24. In this state, the blank of the metal cover 14 is, according to the view of Figure 16, moved to the right at the same time as the mounting member 21, the inner die 1, the closing die 2A of the outer die 2, the recess forming die 6 and the pull-out separation matrix 7 so that the metal cover blank 14 is ready for the third step illustrated in FIG. 17.

 During this third step, the formers dies shown in FIGS. 3 and 4 are used. As during the first and second steps above, the fixing members 23 are lowered to wander and fix the formers or 2A matrix elements from the outside. In this state, the orifice forming die 5 is lowered down to the recess forming die 6, and then the die elements 2B composing the outer die 2, and the first die cavity die. coupling 3 are lowered successively to 1: metal hood cover 14 to form and finish the part forming a coupling wall 14b according to the predetermined configuration. This last cor-door consequently, in its internal portion, the cavity coupling 14f provided, on one side, with the orifice 14a, which coupling cavity 14f comprises, in its internal upper surface, the recessed part 14g shown in FIG. 18.

 After this closing operation, the mounting member 22 being raised, the fixing members 23 are lifted, the first coupling cavity forming matrix 3 and the matrix elements 2B to move them away from the wall forming part of coupling 14b of the metal bonnet blank 14. In this case, moreover, since the first mating structure for mating cavity 3 is lifted, the mating notches 3c engage with the projections coupling 5 to force the orifice forming material 5 to rise away from the metal cover blank 14 at the same time as the first coupling cavity forming matrix 3.

 In addition, at the end of the third forming step, a positioning member 26 visible in FIG. 16 is lifted under the effect of the upward movement of the mounting member 22 to open the outer portion of the separation matrix by traction 7. In this state, a traction member 27 is moved transversely to force the separation matrix by traction 7 to move to the left, as seen in FIG. 16, using a coupling pin 27a and a coupling orifice 7d. When the traction separation matrix has moved over a predetermined distance, the recess forming matrix 6 falls down to the cavity or the lower portion 7c of the traction separation die 7, so that the core portion 6b of the recess forming die 6 is lowered and away from the recessed portion 14g.

Then, the coupling pin 7a engages with the left end of the coupling groove 6a, so that the recess forming die 6 is pulled or, as seen in Figure 16, moved toward the left together with the traction separation matrix 7.

 In addition, once the metal cover has been extracted from the dies, an orifice 14j is shown, shown in FIG. 18 and intended to allow a support to extend there, by drilling in the lower portion of the teardrop portion. 14h of the part forming the coupling wall 14b.

 In the above steps, the metal cover 43 is completely fabricated. The metal cover 43 thus obtained is adjusted and fixed, for example, on a head 44a of a suspension insulator 44 using a cement 45, as illustrated in FIG. 19. On the other hand, the the lower end of a metal support 46 fixed to another insulator is engaged in the coupling cavity 14f formed at the level of the upper end of the metal cover 43.

 The present invention can, moreover, be carried out in the following manner.

 In the previous embodiment, the hole 14 is formed when the coupling wall portion 14b is formed. This orifice 14a can, on the contrary, be formed during the forging steps using the first and second mating cavity forming dies 3 and 4. In this case, it is preferable that the portion of the wall-forming part coupling intended to include the orifice 14a is previously designed thinner.

 As can be seen from the description above, the set of dies for forging metal covers according to the present invention is capable, during the manufacturing steps, of forming the coupling cavity by bending the part forming coupling wall, and simultaneously the orifice, and also to form with great precision the orifice and the hollowed out part in the riveta 'of the part forming the coupling wall by forging using the second matrix of forming the coupling cavity, without requiring any special machining, such as cutting, which improves the resistance of the coupling cavity and does not cut the forged flow lines of the wall part coupling. In addition, when the first coupling cavity forming die is moved away from the metal cover blank, the orifice forming die of the second coupling cavity forming die can be moved at the same time as the first, which remarkably simplifies the operation which consists in separating the dies from the blank, in order to improve the productivity in metal covers for insulators.

 It is also clear to a person skilled in the art that the preceding description relates to a preferred embodiment of the present invention and that various changes and modifications can be made without departing from the scope of the invention.

Claims (9)

 1. Set of dies for forging metal hoods for  insulators, characterized in that it comprises an internal matrix (1)  intended to be applied against a bell-shaped part (14c) of a  metal cover blank (14), an outer die (2) intended to be  applied against an external part of the metal cover blank, a  first coupling cavity forming die (3) intended to be  embossed in the outer die, axially with respect to the blank, and  having an oblique forming surface (3a) for bending inward  térieur a part forming a coupling wall (14b) of the blank in for  tearing its end against the oblique forming surface to form a  coupling cavity (14f), and a second cavity forming die  coupling (4) intended to be housed in a housing groove (3b) formed in the first coupling cavity forming matrix (3) of  then its center to an outer side, in order to form an orifice (14a)  in the part forming the coupling wall and shaping a portion in  dull mating cavity, the second cavity forming matrix  coupling (4) consisting of three separable matrix elements  comprising an orifice forming matrix (5), an electrical forming matrix  drain (6) assembled to the orifice forming die (5) from which  it is axially detachable, and a separation matrix by traction  (7) assembled in an extractable manner to the recess forming matrix,  and also coupling means provided on the first matrix of  coupling cavity forming (3) and on the orifice forming die  (5) of the second coupling cavity forming die (4) and suitable  to engage with each other in order to dismiss the forum matrix  orifice mage (5) of the metal cover blank (14) during movement  of the first coupling cavity forming die (3) relative to  to the blank metal hood.  2. Set of dies according to claim 1, characterized in  that the oblique forming surface (3a) of the first forming matrix of  coupling cavity (3) is in the form of a curved surface.  3. Set of dies according to claim 1, characterized in that  that the orifice forming die (5) has coupling projections  stepped (5c) and the first coupling cavity forming matrix (3) has, in its housing groove (3b), stepped coupling notches (3c), which projections and notches constitute the coupling means.  4. Matrix assembly according to claim 1, characterized in that the orifice forming matrix (5) comprises, on its front edge, a curved forming surface (5b) intended to conform an internal peripheral surface of the part forming a coupling wall (14b) in an arc configuration.  5. Matrix assembly according to claim 4 characterized in that the recess forming matrix (6) comprises, on one of its ends, a part forming a core (6b) fully curved and similar to a disc, which corresponds to the curved forming surface (5b) of the orifice forming matrix (5).  6. set of dies according to claim 5, caracterlse an that the recess forming matrix (6) comprises, on one side of as part forming a curved core (6b), an accocpicm-cnt part (6e) intended coming into abutment against a lateral edge of the orifice forming matrix (5), in order to prevent its transverse disassembly.  7. Set of dies according to claim 1, 3 characterized in that the recess forming die (6) can, once spaced from the metal cover blank (14), be pulled and moved tra-avarsalemant when the traction separation matrix (7) is pulled and moved transversely.  8. Matrix assembly according to claim 1, characterized in that the recess forming matrix (6) comprises, in its main portion, a coupling groove (6a) which extends longitudinally and the separation matrix by traction (7) has on its surface a coupling pin (7a) capable of sliding to engage in the coupling groove (6a) of the recess forming matrix.  9. Matrix assembly according to claim 1, characterized in that the traction separation matrix (7) comprises at one of its ends, a core part (7bi which corresponds to the core part (6b) of the recess forming matrix (6).