Olsson, Lars Jonas (Jonas Jonssons v�g 29, Hagfors, S-683 33, SE)
Lindholm, Morgan Oliver (�kerb�rsstigen 9, S-665-35 Kil, SE)
Olsson, Lars Jonas (Jonas Jonssons v�g 29, Hagfors, S-683 33, SE)
| 1. | Arrangement for releasably connecting a dummy block (10; 10\') to a press stem (12; 12\') of an extrusion press, characterized in that it comprises a first connec- ting element (20; 21\'), formed by an axially protruding rear portion of the dummy block (10; 10\'), and a second connecting element (21; 20\'), formed by an axially pro- trudi. ng front portion of a holder (11) for the dummy block (10; 10\'), mountable on or rigidly connected to the press stem (12; 12\'), wherein one of said two connecting elements consists of an axially protruding stud (20 ; 20\'), while the other connecting element con- sists of an axially protruding sleeve (21; 21\') that can be slipped on to said stud (20; 20\'), and wherein the arrangement also comprises a locking pin (24; 24\') which, when said sleeve (21; 21\') has been slipped on to said stud (20 ; 20\'), can be inserted in transversally exten- ding through bores (22,23; 22\', 23\') i. n the two connec- ting elements (20,21; 20\', 21\') in order to hold said two elements (20,21; 20\', 21\') releasably connected to each other. |
| 2. | Arrangement according to claim 1, characterized in that said stud (20; 20\') has an outer surface having a generally circular cross-section and that said sleeve (21; 21\') has an inner surface having a generally circu- lar cross-section. |
| 3. | Arrangement according to claim 1 or 2, characte- rized in that the locking pin (24; 24\') is arranged to be releasably held inserted in said bores (22,23; 22\', 23\') in the two connecting elements (20, 21; 20\', 21\') by snap-in means (25; Z5\') acting between the locking pin (24; 24\') and one connecting element (21; 21\'). |
| 4. | Arrangement according to any of the preceding claims, characterized in that the holder (11 ; 11\') is arranged to transmit only axial pulling forces to the dummy block (10; 10\') via the locking pin (24; 24\'), while it is arranged to transmit axial pushing forces to the dummy block (10; 10\') via special cooperating contact surfaces (28,29; 29\', 28\') of the holder (11; 11\') and the dummy block (10; 10\'), serving for the transmission of such forces. |
| 5. | Arrangement according to claim 4, characterized in that said contact surfaces are formed by an annular end surface (28; 28\') of said sleeve (21,21\'), provided at the free end of the sleeve, and a coopearating annu- lar surface (29; 29\'), extending in an approximately radial outward direction from said stud (20; 20\') at the inner end of the stud. |
| 6. | Arrangement according to claim 5, characterized in that said two annular surfaces consist of part-sphe- rical surfaces (28,29; 28\', 29\') having a large radius of curvature and that said stud (20; 20\') is arranged to be received with a small radial play in said sleeve (21; 21\'). |
| 7. | Arrangement according to any of the preceding claims, wherein the dummy block (10) consists of a gene- rally sleeve-shaped body (14) and a block core (15), formed by a separate element and comprising a generally frusto-conical front portion (16), whi. ch is arranged to be received in a central conical opening (18) in said body (14) at the front end of the body, and a rear shank (17), serving to hold the block core (15) to the body (14), characterized in that the shank (17) of the block core (15) comprises a portion, insertable into an axial passage (30) in said stud and provided with transversally extending through bores (31), into which said locking pin (24) can be inserted. |
As is well known, extrusion presses are utilized for the production of profile members of metal, especial- ly of aluminium or aluminium alloys. In this connection, a billet, heated to a high temperature, is placed in front of the dummy block in a cylindrical press chamber, whereupon, by means of the dummy block and the press stem located behind said block, it is forced under high pressure against an extrusion die, provided with a through opening, having a shape corresponding to the desired profile of the profile member.
As a consequence of the high temperature and the high pressure, during the operation of the press, the dummy block is subjected to a hard wear at its periphe- ral front portion. For this reason, the dummy block has to be replaced rather often, usually already after a usage time of only a few days. In order to facilitate the necessary replacement of the dummy block as soon as such a replacement is required, the dummy block has to be releasably connected to the press stem.
Previously, such a releasable connection between the dummy block and the press stem has been obtained by providing the dummy block with a central internally threaded bore at the rear end thereof in order hereby to permit the dummy block to be screwed on to a central threaded, stud, provided at the front end of the press stem. However, the use of such means for releasably connecting the dummy block to the press stem is unfavour- able above all due to the fact that, in practice, it is difficult and time-consuming to screw off the used dummy
block, while heated to a high temperature, from the threaded stud of the press stem and then to screw on a new dummy block on said stud.
The invention has for its purpose to provide an arrangement of the kind initially specified which makes it possible to perform a replacement of the dummy block in a considerably more simple and rapid manner than pre- viously possible.
The arrangement, according to the invention pro- posed for said purpose, is primarily characterized in that it comprises a first connecting element, formed by an axially protruding rear portion of the dummy block, and a second connecting element, formed by an axially protruding front portion of a holder for the dummy block, mountable on or rigidly connected to the press stem, wherein one of said two connecting elements consists of an axially protruding stud, while the other connecting element consists of an axially protruding sleeve that can be slipped on to said stud, and wherein the arrange- ment also comprises a locking pin which, when said sleeve has been slipped on to said stud, can be inserted in transversally extending through bores in the two con- necting elements in order to hold said elements releasab- ly connected to each other.
The arrangement above described results in that the dummy block can be mounted on the press stem and removed therefrom in a very simple and rapid manner.
The only steps that need to be taken when the dummy block is to be mounted on the press stem consist in slipping the connecting element having the shape of a sleeve on to the connecting element having the shape of a stud and then inserting the locking pi. n through the transversally extending bores in the two connecting ele- ments. In corresponding manner, when the dummy block is to be removed, this can be effected simply by removing
the locking pin by means of a suitable mandrel, where- upon the dummy block unobstructedly can be slipped off from the press stem.
The two connecting elements may have any suitable cross-sectional shapes adapted to each other. However, said stud may preferably have an outer surface having a generally circular cross-section and sai. d sleeve an inner surface having a generally circular cross-section.
Furthermore, the locking pin may suitably be arran- ged to be releasably held inserted in said bores in the two connecting elements by snap-in means acting between the locking pin and one connecting element.
Since the axial forces that have to be transmitted from the press stem to the dummy block during a working stroke of the press are very high and constitute a mul- tiple of the axial forces required to provide the return movement of the dummy block, the holder may preferably be arranged to transmit only axial pulling forces to the dummy block via the locking pin, while i. t is arranged to transmit axial pushing forces to the dummy block via speci. al cooperating contact surfaces of the holder and the dummy block, serving for the transmission of such forces.
Sai. d ccntact surfaces may suitably be formed by an annular end surface of said sleeve, provided at the free end of the sleeve, and a cooperating annular surface, ex- tending in a generally radial outward direction from said stud at the inner end of the stud, In order to reduce the requirements for accuracy in respect of the axial alignment of the dummy block in relation to the holder, said two annular contact sur- faces may consist of part-spherical surfaces having a large radius of curvature and said stud may be arranged to be received with a small radial play in said sleeve.
The dummy block may consist of a member formed in
one single piece. However, in known manner, it may com- prise a generally sleeve-shaped body and a block core, formed by a separate element and comprising a generally frusto-conical front portion, which is arranged to be received in a central conical opening in said body at the front end of the body, and a rear shank, serving to hold the block core to said body. Said shank may in known manner be secured to the body of the dummy block by means of a nut mounted on a rear threaded portion of said shank. However, the invention makes it possible in- stead to obtain the required connection between the block core and the body of the dummy block by means of the locking pin utilized for connecting the two above- mentioned connecting elements releasably to each other.
For this purpose, the shank of the block core may com- prise a portion insertable into an axial passage in the above-mentioned stud and provided with a transversally extending through bore, into which said locking pin can be inserted.
Below the invention is described in further detail with reference to the accompanying drawings, in which:- Figure 1 shows a longitudinal section through an arrangement according to a first embodiment of the in- vention, selected by way of example only, Figure 2 shows a corresponding view of an arrange- ment according to a second embodiment of the invention, also selected by way of example only, and Figure 3 shows a corresponding view of an arrange- ment according to a third embodiment of the invention.
In Figure 1, reference numeral 10 generally desig- nates a dummy block of an extrusion press and reference numeral 11 generally designates a holder for the dummy block that may be rigidly or releasably connected to a press stem 12, which has been indicated in dash-dotted lines and by means of which the dummy block may be moved
axially backwards and forwards within a press chamber 13, indicated in dash-dotted lines. In the illustrated case, holder 11 has been assumed to be provided with a central threaded bore in which a central threaded stud of press stem 12 is received.
The press is intended to be used for the produc- tion of profile members of metal. These members are formed from a billet, heated to a high temperature and placed in press chamber 13 in front of dummy block 10.
During the working stroke of the dummy block, i. e. when the dummy block is moved successively to the right ac- cording to Figure 1, the billet is forced under high pressure against a press di. e (not shown) which is pro- vided with a through opening having a shape corresponding to the desired profile of the profile members.
In the case illustrated in Fi. gure 1, dummy block 10 consists of a generally sleeve-shaped body 14 and a separate block core 15, comprising a generally frusto- conical front portion 16 and a shank 17 extending in a rearward direction from said front portion. By means of a nut 19, mounted on a rear threaded portion of shank 17, block core 15 is held to body 14 i. n a position in which it has its portion 16 received in a central coni- cal front opening 18 in body 14. Portion 16 of block core 15 and opening 18 in body 14 may in practice have more complicated shapes than those for the sake of simplicity shown in the drawing.
In order to make it possible to connect dummy. block 10 releasably to holder 11 and hence also to press stem 12, body 14 is provided with a first connecting element, formed by a rear axially protruding tubular stud 20, while holder 11 is provided with a second connec- ting element, formed by an axially protruding front sleeve 21 which can be slipped on to stud 20. Stud 20 and sleeve 21, which both may have a circular cross-section, are
provided with transversally extending through bores 22 and 23, respectively. These bores 22 and 23 serve to make it possible, after an insertion of stud 20 into sleeve 21 or slipping said sleeve on to said stud, res- pectively, to provide a releasable connection between the two connecting elements by means of a locking pin 24, insertable into bores 22 and 23.
The connecting-elements, formed by stud 20 and sleeve 21, and the locking pin 24, cooperating with said elements, makes it possible, when required, to replace the dummy block in a very simple and rapid manner.
In order to make it possible to have locking pin 24 releasably held in a position inserted i. n bores 22 and 23, there is provided a resilient locking ring 25, which acts as a snap-in means and i. s placed in a groove 26 in the wall of one of the two bores 23, provided in socket 21, and which can be brought into engagement with a groove 27 in locking pin 24.
By means of holder 11, axial pulling forces can be transmitted from press stem 12 to dummy block 10 via locking pin 24. Axial pushing forces on the other hand are not transmitted via the locking pin but instead via special cooperating contact surfaces of holder 11 and dummy block body 14, serving for the transmission of such forces. These contact surfaces are formed by an annular end surface 28 of sleeve 21 at the free end of said sleeve and a cooperating annular surface 29 of the body of the dummy block, extending in an approximately radial outward direction from stud 20 at the inner end of said stud. In order to make sure that only axial pulling forces will be transmitted from the press stem to the dummy block via locking pin 24, the locking pin is re- ceived with a small play in bores 22 in stud 20.
In order to avoid that the body of the dummy block will be subjected to all too high bending stress and
in order to permit a reduction of the requirements for accuracy in respect of the axial alignment of dummy block 10 in relation to holder 11, surfaces 28 and 29 may suitably consist of part-spherical surfaces having a comparatively large radius of curvature R, and stud 20 may be arranged to be received with a small radial play in sleeve 21.
The embodiment according to Figure 2 differs from the embodiment according to Figure 1 substantially only in respect of the shape of shank 17 of block core 15 and the manner for holding the block core to body 14 of dummy block 10.
While, in the embodiment according to Figure 1, block core 15 is secured to body 14 by means of a nut 19, in the embodiment according to Figure 2, it is instead secured to body 14 by means of locking pin 24. In this case, shank 17 comprises a portion insertable in an axial passage 30 in stud 20 and provided with a trans- versally extending through bore 31, into which locking pin 24 can be inserted.
In Figure 3, elements corresponding to various ele- ments of the arrangement shown in Figure 1 have been pro- vided with the same reference numerals as those used in Figure 1, however with the addition of a prime mark.
It may be noted that the more precise shape of block core 15\'and opening 18\'in body 14\'of dummy block 10\'deviates from the shape of corresponding ele- ments of the arrangement according to Figure 1 and that, instead of a central threaded bore, holder 11\'has a threaded stud which extends from the rear side of the holder and by means of which the holder can be releasab- ly connected to press stem 12\'.
However, the essential difference between the embodiment according to Figure 3 and the arrangement according to Figure 1 consists in the design of the
means serving for releasably connecting body 14\'of dummy block 10\'to holder 11\'. In the embodiment accor- ding to Figure 3, these connecting elements consist of a stud 20\', protruding in an axial direction from holder 11\', and a sleeve 21\', protruding in an axial direction from body 14\'and adapted to be slipped on to stud 20\'.
Stud 20\'and sleeve 21\'are provided with transversally extending through bores 22\'and 23\', respectively, which permit the two connecting elements to be releasably held connected to each other by means of a locking pin 24\'inserted into bores 22\'and 23\'.
The contact surfaces serving to transmit pushing forces from holder 11\'to dummy block 10\'are formed by an annular end surface 28\'of sleeve 21\'and a coope- rating annular surface 29\'of holder 11\'. Both surfaces 28\'and 29\'consist of part-spherical surfaces having a relatively large radius of. curvature R\'.
The invention is not restricted to the embodiments above described and shown in the drawings. Instead, many other embodiments are feasible within the scope of the invention as defined in the following claims.
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