(12, UK Patent Application (19GB (“,2 141 063 A
`
`(43) Application published 12 Dec 1984
`
`
`(21) Application Nb 8311724
`(51) INT CL3
`
`821D 22/28
`
`(22) Date of filing 29 Apr 1983
`
`
`
`
`(71) Applicant
`
`Toyo Seikan Kaisha Limited (Japan).
`
`3—1 Uchisaiwaicho 1-chome, Chiyoda-ku, Tokyo,
`Japan
`
`
`
`
`
`
`
`
`
`(72) Inventors
`Hirotaka Nishikawa
`Yoshibumi Arai
`
`(74) Agent and/or Address for Service
`Brookes 8* Martin,
`High Holborn House, 52/54 High Holborn, London
`WCIV 68E
`
`
`
`(52) Domestic classification
`B3Q1B 2A3 2A5 2A6 2C1 2D 2F3A 2G 2K 2R
`F2A 300 D30
`U18 1809 B30 F2A
`
`(56) Documents cited
`None
`
`(58) Field of search
`B30.
`
`aratus
`
`54 Redrawin -ironin a
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`(57) In a redrawing-ironing
`apparatus provided with a punch 4
`fuixed on a ram 1, a die means
`including a redrawing die 12 and
`ironing dies 15, an annular piston
`26 for fastening the die means, a
`cup retainer pad 53 adapted to
`push the inner periphery of the
`bottom of a drawn cup placed on
`the redrawing die, and pins 39
`fixed on the annular piston and
`extending axially, the free end
`surface of the pin is engaged with
`the flange 533 of the cup retainer
`pad at the end of the redrawing. As
`a result, the caring portions of the
`drawn cup can be prevented from
`being thinned and broken into
`fragments at the redrawing. A
`hydrostatic bearing for the ram 1
`
`comprises three sets of oil pockets
`(Fig. 15(b))°.
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`GBZ141063A
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`SPECIFICATION
`
`Redrawing-ironing apparatus
`
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`This invention relates to a redrawing«ironing apparatus and, more particularly, to an improved -
`redrawing-ironing apparatus in which earing portions can be prevented from being extended too
`thin into fragments at the end of a redrawing process of a drawn cup.
`A drawn-ironed can body which is used extensively of late for carbonated beverage cans, beer
`cans and the like is usually formed by redrawing and then ironing in two or three steps a drawn
`cup formed from a metallic blank such as of aluminum alloy sheet or tinplate, on a redrawing—
`ironing apparatus. The diameter of the cup after redrawing becomes somewhat smaller (the
`inside diameter being equal to that of the drawn-ironed can body), and its height becomes
`somewhat larger by redrawing. So as to prevent wrinkles from arising on the bottom during the
`forming, the cup is redrawn while the inside periphery of its bottom is pushed under fluid
`pressure between a retainer pad and the surface of a redrawing die.
`At the end of the redrawing process, an excessively high pressure is exerted on'earing
`portions of the cup, which are formed usually at 4 to 6 portions circumferentially during the
`drawing process due to anisotropy of metallic sheets, and, therefore, the earing portion is
`extended thin and torn off the cup into fragments. Accordingly, the next coming cup is often
`redrawn with a tool having the fragments sticking thereon, and in such a case, the fragments
`are embedded in the sidewall portion of the redrawn cup, and the portion of the sidewall portion
`where the fragments are embedded becomes extremely thin in the process of ironing. Therefore,
`the sidewall portion tends to develop small holes therein, or completely rupture circumferentially
`due to tension incidental to the ironing.
`Further, the redrawing-ironing is carried out by means of a punch and a plurality of dies in a
`cooperative operation with the punch, and the punch is normally fixed on the nose of a ram
`reciprocating horizontally. The ram has its base fixed on a slide yoke and is supported by
`bearings, and is driven usually to a high-speed reciprocation by a crank mechanism through the
`slide yoke. In this case, it is preferable that a hydrostatic bearing device be employed for
`prevention of heat generation and wear on a sliding zone of the slide yoke and the ram.
`However, the hydrostatic bearing device proposed hitherto is not satisfactory, since it involves
`the problem that a deflection will result on the ram in case of high-speed reciprocation (200
`strokes per minute, for example).
`A final thickness of the sidewall portion of a redrawn and ironed can body is normally very
`thin such as to be about 0.10 to 0.15 mm, and, therefore, a dislocation of the alignment
`between the punch and the ironing dies due to a slight deflection of the ram may exert an
`excessive load locally on the sidewall portion of the can body, thereby to incur rupture of the
`sidewall portion.
`'
`Moreover, in a return step of the punch, there tends to arise a problem that the deflection
`allows the punch and the dies to come in contact with each other to damage the two, thus
`shortening their life. Further, the can body after ironing is pulled off the punch with a so-called
`stripper at the punch return step. In case where, however, the alignment between the punch
`and the stripper is lost by a slight deflection of the ram, an excessive load is applied locally on
`the open end portion of the can body and, the open end portion is damaged thereby, or the can
`body is fed as far as to the die means without being pulled off, thus breaking down the dies.
`This invention has been made in view of the problems of the prior art as mentioned above.
`According to the present invention there is provided a redrawing-ironing apparatus comprising
`a punch fixed on the nose of a ram; a die means including a redrawing die and a plurality or
`ironing dies for forming a can body from a drawn cup in a cooperative operation with the
`punch, a holding ring for the redrawing die and a plurality of holding rings for the ironing dies
`which are piled with a plurality of spacers therebetween; an annular piston for fastening the die
`means which is provided circumferentialiy to abut on the end surface of the redrawing die
`holding ring; a cup retainer pad adapted to push the inner periphery of the bottom of the drawn
`cup placed on the redrawing die; and a plurality and predetermined length of pins fixed on the
`annular piston and extending in the axial direction of die means.
`In the apparatus a free end surface of the pin is engaged with a flange of the cup retainer pad
`at the end of a redrawing process, thereby preventing a clearance between the redrawing die
`and the cup retainer pad from becoming less than a given value, so that earing portions of the
`drawn cup is prevented from being thinned and broken into fragments.
`The rarn in the apparatus reciprocates horizontally, the base thereof is fixed on a slide yoke for
`driving the ram, each sliding member of the slide yoke is provided with at least two sets of
`hydrostatic pressure sliding oil pockets in the longitudinal direction thereof, and the ram is
`supported by a hydrostatic pressure bearing having at least three sets of oil pockets in the
`longitudinal direction thereof which are spaced with bushings therebetween. Therefore, the
`deflection of the ram and the oscillation of the punch are small even at a high speed operation.
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`2
`GB 2141063A
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`The above and other objects, features and advantages of the invention will be apparent from
`the following description when the same is read in conjunction with the accompanying
`drawings.
`Figure 1 is a plan view, partly cut, of a main part of a redrawing-ironing apparatus which is
`given as an embodiment of this invention;
`Figure 2 is an inlet side view of a redrawing-ironing die means which is taken on line ll—ll of
`the apparatus of Fig. 1;
`Figure 3 is a vertical sectional view taken on the line Ill—Ill of Fig. 2, representing a die
`means and a retainer pad device;
`Figure 4 is a vertical sectional view representing a mounted state of the die means which is
`taken on line lV—IV of Fig. 2;
`Figure 5 is a vertical sectional view taken on line V—V of Fig. 3, representing the structure of
`an annular piston;
`Figure 6 is a transverse sectional view taken on line Vl—Vl of Fig. 2, representing a redrawing
`die and its vicinity;
`,
`Figure 7 is a vertical sectional view taken on line Vll—Vll of Fig. 1, representing a slide yoke
`and its sliding member;
`Figure 8 is a plan view of the slide yoke of the apparatus of Fig. 1;
`Figure 9 is a side View of the slide yoke of Fig. 8;
`Figure 10 is a vertical sectional view taken on line X—X of Fig. 8;
`Figure 11 is an explanatory vertical sectional view taken longitudinally of the sliding member
`of the slide yoke, wherein Fig. 1 1(a) and Fig.
`1 1(f) are drawings representing the cases of this
`invention, and Figs. 1 1(b), (0), (d) and (e) are drawings representing the cases of comparative
`examples;
`'
`Figure 12 is a vertical sectional View taken on line Xll—Xll of Fig. 1, representing a bearing
`system for the ram;
`Figure 13 is a vertical sectional View taken on line Xlll—Xlll of Fig. 1, representing similarly
`the bearing system;
`Figure 14 is a sectional view taken on line XIX—XIV of Fig. 13, representing oil pockets
`disposed longitudinally of the ram;
`Figure 15 is an explanatory sectional view of a main part of the ram running longitudinally of
`the bearing system, wherein Fig. 15(a) is a drawing representing the case of comparative
`example, and Fig. 15(b) is a drawing representing the case of this invention;
`Figure 16 is a block diagram of a deflection measuring apparatus for the ram.
`Fig.
`1 represents a main part of a redrawing-ironing apparatus given as an embodiment of this
`invention: a ram 1 has its base fixed on a front end portion of a slide yoke 2. A numeral 3
`denotes a hydrostatic bearing system to bear the ram 1, and a redrawing-ironing punch 4 is
`installed on the nose of the ram 1. A numeral 5 denotes a redrawing-ironing die means, and 6
`denotes a stripper for pulling a redrawn and ironed can body 7 off the punch 4.
`As shown in Fig. 2 and Fig. 3, the die means 5 consists mainly of a holding ring 13 of a
`redrawing die 12, a first spacer 14, a holding ring 16 of a first ironing die 15, a second spacer
`17, a holding ring 19 of a second ironing die 18, a third spacer 20, and a holding ring 22 of a
`third ironing die 21. A numeral 23 denotes a nozzle for a cooling lubricant 24, and 25 denotes
`a discharge hole for the cooling lubricant injected through the nozzle 23.
`As shown in Fig. 4, the die means 5 is placed on two pieces'of rails 27 fixed on a housing 26
`and pushed by a leaf spring 29 fixed on a cover 28 which is installed hingedly on the housing
`26, thus being supported at three points. A base plate 30 which is fixed on the housing 26
`receives a stripper 6 having fingers (refer to Fig. 1).
`A cylinder plate 33 is fixed on the housing 26 with a bolt 34. There is formed an annular air
`cylinder 35 in the cylinder plate 33 along a’flange 13a of the redrawing die holding ring 13,
`and as shown in Fig. 3 and Fig. 5, an annular piston 36 with an O-ring 37 is enclosed in the air
`cylinder 35 so that it comes in contact with an end surface 138' of the flange 13a.
`A pressure air is supplied to the air cylinder 35 through a hole 38 and a piping (not
`illustrated). The holding rings 13, 16, 19, 22 and the spacers 14, 17, 20 are pushed and so
`fastened to the base plate 30 by the annular piston 36. Demounting or remounting of the ,
`holding rings or the spacers can be done far easily as compared with a conventional case
`wherein the fastening is done with bolts or the like, by opening the cover 28 and .depressurizing
`the air cylinder 35 to release the annular piston 36 from pushing and fastening.
`A given length and a plurality of pins 39 extending axially (3 pieces in case of the drawing)
`are fixed on the annular piston 36. The function of the pins 39 will be described later.
`A cup holder 41 is fixed on the cylinder plate 33 with bolts 45. As shown in Fig. 2 and Fig.
`6, the cup holder 41 is of a short cylindrical form with a feed side A open, and its inside
`diameter is specified to be almost equal to an outside diameter of the drawn cup 42 to be held
`therein and redrawn. A numeral 43 denotes a nozzle for injecting a cooling lubricant 44 onto
`the outside of the sidewall portion of the drawn cup 42.
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`GB2141063A 3
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`As will be apparent from Fig. 2 and Fig. 6, the outside 33a of the cylinder plate 33 on the
`feed side A of the drawn cup 42 is formed so as to be of the same plane as the outside 13b of
`the redrawing die holding ring 13 which is on the same plane as the outside 12a of the
`redrawing die 12. The drawn cup 42 can therefore be fed smoothly.
`In case the outside 12a of the redrawing die and the outside 13b of the redrawing die
`holding ring are aligned with the end surface 13a’ of the flange 13a so as to simplify the
`structure of the redrawing die holding ring 13, since the drawn cup 42 will be afloat axially
`when it comes near the redrawing die 12, the drawn cup 42 comes to bounce due to the
`pressures of the c00ling lubricant injected through the nozzle 43 and of air blown out of a hole
`52 of the punch 4 which will be described later, the center thereof is dislocated, and thus the
`drawn cup 42 tends to be crushed by a retainer pad 53 described later. However, such a
`trouble will not be caused in the case of this embodiment.
`Then, the drawn cup 42 is guided by a cage 46 (refer to Fig. 2) to descend on gravity in the
`direction indicated by an arrow B, and after reaching the position indicated in Fig. 2 and Fig. 6,
`it is fed in the direction indicated by an arrow C by a shuttie 47 and placed on the redrawing
`die 12.
`
`is reciprocated axially by a
`The punch 4 is fixed on the nose of the ram 1, and the ram 1
`crank mechanism (not illustrated), as described later, through the slide yoke 2. A hole 52 passes
`through the punch 4 and the ram 1, and pressure air is blown out of the punch nose at all times
`through the hole 52. The pressure air is so fed as to make the ironed can body easily come out
`of the punch 4 in the stripper 6.
`A hollow cylindrical retainer pad 53 functions to prevent wrinkles from arising on the drawn
`cup 42 during redrawing and is specified to have the inside diameter slightly larger than the
`outside diameter of the punch 4, and the outside diameter a little smaller than the inside
`diameter of the drawn cup 42. The retainer pad 53 is fixed on a sliding portion 54a of an
`annular air cylinder 54 via its flange 53a. A supporting portion 54b of the annular air cylinder
`54 is fixed on a support wing 55, and the sliding portion 543 is adapted to be slidable along a
`bushing 56 of the supporting part 54b. The pressure air is supplied into the annular air cylinder
`54 through a piping (not illustrated) by way of a hole 57. The support wing 55 is reciprocated
`axially at a given timing by a cam mechanism (not illustrated) driven by a crank mechanism (not
`illustrated) which drives the ram 1.
`The height of the pin 39 is specified so that the end surface 39a of the pin 39 will be
`engaged with the flange 53a of the retainer pad 53, when the clearance between the outside
`surface 12a of the redrawing die 12 and the nose surface 53b of the retainer pad 53 is kept
`preferably at about (0.5~O.9) X t (t being a thickness of the bottom of the drawn cup 42), thus
`leaving the above clearance not less than the above value. Therefore, at the end of the
`redrawing step, the earings 42a (Fig. 5) of the drawn cup 42 will never be thinner than the
`value (O.5~O.9) X t or so, and thus the fragments mentioned above can be prevented from
`generating. Further, with the height of the pin 39 as above, the above clearance will not
`develop greater than the thickness t of the bottom of the drawn cup 42 due to the engagement
`of the pin 39 with the flange 53a, and, therefore, the retainer pad 53 will be left powerful
`enough to suppress occurrence of the wrinkles.
`Redrawing-ironing and particularly redrawing are carried out on the above apparatus as
`follows:
`
`First, the drawn cup 42 which have descended on gravity by way of the cage 46 shown in
`Fig. 2 is placed on the redrawing die 12 by the shuttle 47. At this point of time, the punch 4
`and the nose of the retainer pad 53 are positioned rightward from the cup holder 41 so as not
`to prevent feeding of the drawn cup 42, as shown in Fig. 6. Subsequently, a support wing 55
`goes leftward, the nose surface 53b of the retainer pad 53 comes in contact with the inside of
`the drawn cup 42, and thus the inside is pushed under air pressure by the annular air cylinder
`54 (the state given in Fig. 3). At this point of time, there is left a clearance of about
`(0.1~O.5) X t between the pin 39 and the flange 533. The punch 52 then goes leftward to
`redraw, and at the point of time when the drawn cup (not illustrated) has passed the redrawing
`die 12, the end surface 39a of the pin 39 is engaged with the flange 533. The ironing process
`then ensues.
`
`The advantage that the pin 39 is fixed directly on the annular piston 36 is as follows: The die
`holding rings 13, 16, 19, 22 and the spacers 14, 17, 20 are often replaced owing to wear and
`failure of the dies. However, a dimensional accuracy of the thickness of each holding ring and
`spacer is about O~ + 0.02 mm. Therefore, a dispersion at about + 0.02 X 7 mm maximum (7
`being a total number of the holding rings and spacers) = + 0.14 mm will arise on overall
`thickness of the die means 5.
`
`In case the pin 39 is fixed on the annular piston 36, the dispersion will not affect the
`clearance between the outside surface 12a of the redrawing die and the nose surface 53b of the
`retainer pad when the pin 39 is engaged with the flange 53a. However,
`in case the pin 39 is
`fixed on the housing 26, or the cylinder plate 33, or the cup holder 41, the above dispersion
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`4.
`GB 2141063A
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`will be influential directly to the above clearance.
`Since the thickness t of the bottom of the drawn cup 42 is usually about 0.3~O.4 mm, if the
`above clearance is set at 0.3 mm X 0.5 = 0.15 mm to a specific die means 5 when the
`thickness t is 0.3 mm, then a replacement of the die means may cause the above clearance to
`be 0.15 mm — 0.14 mm = 0.01 mm owing to the above dispersion. When the clearance is
`such small as above, there may arise the trouble that the earings 428 of the drawn cup 42 are
`extended thin and broken into fragments.
`As described above, in case the die means is fastened by the annular piston, the die holding
`rings and spacers can be replaced very easily. Further, in case the pin for preventing the
`clearance between the redrawing die and the retainer pad from being less than a given value is
`fixed on the annular piston, the above earings trouble will not be incurred from a fluctuation of
`an overall thickness of the die means due to the above replacement.
`Next, a description will be given of a support means of the ram which is capable of preventing
`a deflection of the ram reciprocating horizontally at high speed.
`As illustrated in Fig. 1, the slide yoke 2 on whose front end portion a base portion of the ram
`is fixed, has one pair of sliding members 59 adapted to slide along upper and lower
`1
`hydrostatic pressure sliding surfaces 60a of slide rails 60, by a crank mechanism (not illustrated)
`including a connecting rod 58, thus reciprocating horizontally (Fig. 7). The slide rails 60 are
`fixed on a frame 61.
`
`As shown in Fig. 8, Fig. 9 and Fig. 10, there are provided two sets of slender hydrostatic
`pressure sliding oil pockets 62 in the longitudinal direction, that is, the direction in which the
`ram 1 moves, one set thereof being provided at positions opposite each other on the upper
`surface 59a and the lower surface 59b of each sliding member 59.
`A primary pressure oil kept at a predetermined hydrostatic pressure (for example, a hydrostatic
`pressure oil at 100 kg/cmz) is led to the oil pocket 62 from a pressure oil source (not
`illustrated) by way of a primary conduit hole 63a, an orifice 63b and a secondary conduit hole
`63c, decreases in pressure when passing the orifice 63b, so that the oil pressure (secondary
`pressure) in the oil pocket 62 becomes, for example 50 kg/cm2 (Fig. 10). As shown in Fig.
`1 1(3), a thin pressure oil film layer 64 (0.04 mm thick, for example) is formed between the
`upper surface 59a and the lower surface 59b, and the hydrostatic pressure sliding surface 60a
`opposite to each of them, and the sliding member 59 slides to reciprocate in the direction
`indicated by the arrow along the slide rail 60 with the oil film layer 64 therebetween. Therefore,
`the sliding member 59 and the slide rail 60 will be prevented from heating and wearing.
`It is necessary to provide at least two sets of the oil pockets 62 in the longitudinal direction of
`each sliding member 59, so as to prevent the sliding member 59 from inclining, that is,
`ascending leftward and descending leftward, and thus the punch 4 from oscillating vertically.
`Namely, as shown in Figs.
`1 1(b) and (d),
`in case where one set of oil pockets 62’ are
`provided on each sliding member 59', since upper and lower pressure oil film layers 64'a and
`64'b corresponding to the upper and lower oil pockets 62' are equal in average thickness,
`pressures exerting on both pressure oil film layers 64’a and 64’b are also equal (when thought
`excepting a pressure according to gravity working on the sliding member 59'), and thus
`restoring force for the inclination of each sliding member 59' as shown in Figs. 6(b) and (d)
`scarcely functions.
`Further, when the sliding member 59' moves at high speed in the direction indicated by
`arrow A as kept slanting higher leftward, as shown in Fig.
`1 1(b‘), the oil in the clearance
`between the upper surface 59’a of the sliding member and a slide rail 60a flows relatively in the
`direction indicated by arrow Va shown in Fig.
`1 1(b). In this case the clearance formed by the
`upper surface 59'a of the sliding member and the slide rail 60a becomes gradually wider in the
`oil flowing direction, and, therefore, a pressure working on the pressure oil film layer 64’a on
`the upper surface of the sliding member slightly drops to P'a.
`On the other hand, the oil in the clearance between the lower surface 59'b of the sliding
`member and a slide rail 60b flows relatively in the direction indicated by arrow Vb shown in Fig.
`1 1(b). In this case, since the clearance formed by the lower surface 59'b of the sliding member
`and the slide rail 60b becomes gradually narrower in the oil flowing direction, a pressure
`exerting on the pressure oil film layer 64'b on the lower surface of the sliding member slightly
`rises to P’b.
`
`Where the pressures exerting on the pressure oil film layer 64'a on the upper surface of the
`sliding member and also exerting on the pressure oil film layer 64’b on the lower surface of the
`sliding member come to a state P'a<P'b, the sliding member 59’ moves upward so that the
`pressures on the pressure oil film layers 64'a and 64'b come to a state P’ = P'b.
`Then, in Fig.
`1 1(0) where the sliding member 59' moves at high speed in the direction
`indicated by the arrow B, the pressure exerting on the pressure oil film layer 64’a on the upper
`surface of the sliding member slightly rises to P”a, and the pressure exerting on the pressure oil
`film layer 64'b slightly drops to P”b. Therefore, the pressure exerting on both pressure oil film
`layers on the upper and lower surfaces of the sliding member become P"a>P"b, and thus the
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`GBZ141063A
`
`sliding member 59' moves downward so that the pressures come to a state P"a = P"b.
`As shown in Fig.
`1 1(d), a similar phenomenon will result in case where the inclination of the
`sliding member 59' is reversed such that it inclines higher rightward; when the sliding member
`59’ goes at high speed in the direction indicated by the arrow A, the sliding member 59' moves-
`downward and as shownIn Fig.
`1 1(e), on the other hand, when it goes in the direction
`indicated by the arrow B, the sliding member 59' moves upward. Such behavior of the sliding
`member 59’ is due to a so-called wedge effect, which gets larger as the sliding speed increases.
`In case where two oil pockets 62 are provided in the longitudinal direction of each sliding
`member 59, when the inclination becomes higher leftward, for example, as shown in Fig.
`1 1(f),
`the thickness of the pressure oil film layer 64a corresponding to the left side upper oil pocket
`62a becomes thinner than that of the pressure oil film layer 64b corresponding to the left side
`lower oil pocket 62b.
`Then, since the pressure of a primary pressure oil is constant, the pressure Pa exerting on the
`upper pressure oil film layer 64a becomes higher than the pressure Pb exerting on the lower
`pressure oil film layer 64b, and thus a force working downward is exerted on the left end
`portion of the sliding member 59. Similarly a force working upward is exerted on the right end
`portion of the sliding member 59, and a restoring force to the inclination operates. As a result,
`as shown in Fig.
`1 1(a), the upper. surface 593 and the lower surface 59b of the sliding member
`59 slide in substantial parallel with the hydrostatic pressure sliding surface 60a.
`Fig. 12, Fig. 13 and Fig. 14 represent the hydrostatic pressure bearing system 3 which bears
`the ram 1. The hydrostatic pressure bearing system 3 is provided with a cylindrical sleeve 65.
`bushings 66 and oil pockets 67. As shown in Fig. 12 and Fig. 13, one set of the oil pockets 67
`consists of 4 pockets, each two pockets being disposed opposite to each other vertically and
`horizontally, and each oil pocket 67 is spaced with the bushing 66.
`As shown in Fig. 14, the oil pockets 67 are provided in three sets in the longitudinal direction
`(or in the direction in which the ram 1 moves). A primary pressure oil (a hydrostatic pressure oil
`at, for example, 100 kg/cmz) kept at a predetermined hydrostatic pressure is led to each oil
`pocket 67 from a pressure oil source (not illustrated) by way of a piping 68a, an orifice 68c
`(refer to Fig. 10) in a head 71, a piping 68b and a conduit hole 69, and the oil pressure
`(secondary pressure) in the oil pocket 67 works, for example, at 50 kg/cmz.
`There is formed a pressure oil film layer 70 (0.04 mm thick, for example; refer to Fig. 15)
`between the bushing 66 and the ram 1. Thus the ram 1 and the bushing 66 are prevented from
`heating and wearing. An inner surface 66a of each bushing 66 is so formed as to position
`substantially on the same phantom cylindrical surface by a simultaneous grinding. As a result,
`the inner surface 66a is formed so as to have a radial deviation between each set of about 5 pm,
`or below. It is not desirable that the above deviation exceeds about 5 pm, since a wedge effect
`becomes too large to impede a deflection of the ram 1. The pressure oil in the oil pocket 67
`flows out by way of oil reservoirs 72, and conduit holes 73a, 73b.
`An oil groove 74 formed on an outside bushing 66a communicates with the oil reservoir 72
`through a conduit hole 74a. The oil groove 74, for example, that on the left side of the
`drawing, feeds oil to the clearance between an inner surface 6631 of the left side bushing 66a
`and the ram 1, and thus prevents deterioration of a bearing function due to cavitation which
`tends to occur as an oil film gets thinner, and also roughening of the inner surface 661, thereby
`ensuring a long life of the bushing.
`ItIs necessary that the oil pockets 67 are provided in at least 3 sets in the longitudinal
`direction of the sleeve 65 so as to prevent the ram 1 from deflecting, and the punch 4 from
`oscillating, particularly during high—speed movement.
`The reason is deemed as follows. In case oil pockets 67' are provided in two sets and
`consequently metal bushings 66’ in two sets, a maximum linear speed of the ram 1 during
`high-speed movement (200 strokes per minute, for example) will be caused about at the middle
`of the strokes and becomes 8.2 m/sec, for example.
`In this case, the ram 1 will be curved upward on its own weight, as shown in Fig. 15(a), in
`the middle of a right side oil pocket 67'a and a left side oil pocket 67’b, and the portion of the
`ram 1 positioned at the above middle will be slightly higher (upward in Fig. 15(a)) than the
`portions thereof positioned along each oil pockets.
`Further, the portion of the ram 1 along the right side oil pocket 67’a is inclined slightly lower
`rightward, and the portion along the left side oil pocket 67'b is inclined slightly to lower
`leftward. As in the case of the sliding member 59 of the slide yoke, the ram 1 moves slightly
`downward at the position of the right side oil pocket 67'a at its forward stroke (that is, a stroke
`moving leftward of the drawing), and slightly upward at the position of the left side oil pocket
`67’b at the same stroke. As a result, the left side nose portion of the ram 1 on which the punch
`is mounted moves upward.
`On the other hand, in a return stroke (that is, a stroke moving leftward of the drawing), the
`ram 1 moves slightly upward at a position of the right side oil pocket 67’a, and also moves
`slightly downward at a position of the left side oil pocket 67‘b.
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`6
`GBZ141063A
`
`The left side nose portion of the ram 1 moves downward consequently. Thus the position
`where the ram is supported at the bearing system is different vertically between at the forward
`and return strokes of the ramr1, and the difference is enlarged at the nose portion of the ram 1,
`and, therefore, the punch 4 mounted on the nose of the ram 1 will be subjected to large vertical
`oscillations.
`
`In an apparatus like redrawing-ironing can body forming machine, wherein a slender ram is
`supported with its one end fixed on a slide yoke and reciprocated horizontally by a crank
`mechanism through a connecting rod, the ram itself vibrates in accordance with the vibration of
`the apparatus. In the prior art therefore, the deflection of the ram consists of a deflection due to
`vibrations of the apparatus and a deflection due to the above-mentioned wedge effect, thus
`developing to a big deflection from duplication of both the two deflections.
`Under such circumstances, the deflection of the ram usually can be minimized by enlarging
`the outside diameter of the ram and increasing its rigidity against the deflection of the ram.
`However, in the redrawing-ironing can body forming machine the outside diameter of the ram 1
`must be smaller than that of the punch 4, namely the outside diameter of the ram is restricted
`to cope with the size if the sidewall portion of the can body to be formed.
`However, the oscillation of the punch 4' can be minimized without enlarging the ram outside
`diameter under the above condition, by suppressing the vertical movement of the ram due to
`the above-mentioned wedge effect by the following arrangement wherein, as shown in Fig.
`15(b). at least 3 sets of the bushings 66 are provided close to each other in the hydrostatic
`pressure oil bearing, namely, a bushing of the hydrostatic pressure oil bearing is provided
`additionally in the middle of two bushings 66’ of the hydrostatic pressure oil bearing in the prior
`art shown in Fig. 1 5(a).
`As described above, in case of two bushings, the ram 1 is curved upward due to flexure from
`its own weight in the middle of the two bushings of the hydrostatic pressure oil bearing, as
`shown in Fig. 15(a), and the center portion of the ram comes hig