US3687586A

US3687586A - Powder-forming press

Info

Publication number: US3687586A
Application number: US56835A
Authority: US
Inventors: Ei Hara; Tatsuichi Yokoyama
Original assignee: Mitsubishi Shindoh Co Ltd
Current assignee: Mitsubishi Shindoh Co Ltd
Priority date: 1970-04-22
Filing date: 1970-07-21
Publication date: 1972-08-29
Anticipated expiration: 1989-08-29
Also published as: DE2048856A1

Abstract

In a press for compacting and forming a powder material between a stationary lower punch, an upper punch driven by a cross bar, and an outer mold (die) driven by a cross shaft, a wedge retractably interposed between the cross bar and cross shaft is retracted by and progressively with the descent of the cross shaft by control means, with the resultant effect that the upper and lower punches press simultaneously on the powder material relative to the die. The action of the control means is adjustable to adjust the proportions of the pressing actions of the upper and lower punches.

Description

United States Patent Hara et al. Aug. 29, 1972 [54] POWDER-FORMING PRESS 3,048,893 8/1962 Choice 18/17 S [72] Inventors: Ei Ham, Tokyo; Tatsuichi 3,559,243 2/ 1971 Hermes ..18/ 16.5 Yokoyama, Urawa both of Japan 3,561,055 2/1971 Bnnkmann et a1. ..18/ 16.5 2,338,491 1/1944 Cutler ..l8/l6.5 [73] Assignee: Tamagawa Kikai Kinzoku 3,058,152 10/1962 Eldred et al. ..l8/17 S Kabushiki Kaisha, Tokyo-to, Japan Primary ExaminerJ. Howard Flint, Jr. [22] Flled' July 1970 Attorney-Robert E. Burns and Emmanuel J. Lobato [21] Appl. No.: 56,835

[57] ABSTRACT [30] Foreign Application Priority Data In a press for compacting and forming a powder material between a stationary lower punch, an upper April 22, 1970 Japan ..45/33817 punch driven by a cross bar and an outer mold (die) driven by a cross shaft, a wedge retractably interposed between the cross bar and cross shaft is retracted by [58] Fie'ld [16 R 16 l6 5 l6 7 and progressively with the descent of the cross shaft 18/17 17 w f by control means, with the resultant effect that the upper and lower punches press simultaneously on the v powder material relative to the die. The action of the [56] References Cited control means is adjustable to adjust the proportions of the pressing actions of the upper and lower UNITED STATES PATENTS P 3,172,182 3/1965 Assmann ..l8/l6.5 UX 3 Claims, 12 Drawing Figures PATENTEDAUFZQ I912 3.687 586 sumu m8 F I G. 5

SOL W PATENTEMpzsmn 3 15 5 sum 6 [IF 8 3 POWDER-FORMING PRESS BACKGROUND OF THE INVENTION I tion and the press tool is actuated in its retractive motion by a common main drive shaft rotating in synchronism with the driving part of the press ram, and separate motions which, while being intercoupled with the motion of this main drive shaft, are transmitted to the press tool in a separately controllable manner are produced, retractable wedge structure being interposed between a cross bar for driving an upper punch a cross shaft for driving an outer mold (die).

In a press of this type in which a powder material is placed in a die and is compressed or compacted and thereby formed by upper and lower punches, the first requirement is that the density of all parts of the formed article after compression, that is, the hardness thereof, be uniform. This uniformity of the formed article is greatly affected by factors such as the pressures exerted by the upper and lower punches of the press, the degree of compression, and the frictional resistance of the inner wall surface of the die.

In most of the known powder-forming presses in use at present, the actions of the upper and lower punches are not simultaneous. That is, after the powder material has been placed in the cavity of the die, the upper punch first thrusts into the die to press and compress the upper part of the material, and then, after the thrusting action of the upper punch has been stopped, the lower part is compressed by the lower punch thereby to complete the forming operation.

This non-simultaneous compression forming technique is disadvantageous in that it is diflicult to determine in a simple manner the ratio of the respective magnitudes of pressure application of the upper and lower punches. For the purpose of overcoming this drawback, there has been proposed a structural organization wherein a retractable wedge structure is provided between a cross bar for driving the upper punch and a cross shaft for driving the die, and the ratio of the magnitudes of pressure application of the upper and lower punches can be adjusted in a simple manner by adjusting the insertion and retraction of the wedge structure.

However, because of the non-simultaneous character of this operation, it is not possible to obtain a truly uniform density distribution throughout the formed article.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a powder-forming press in which a powdery or granular material can be compacted and formed into an article of ideally uniform density by simultaneous pressing action of upper and lower punches and by control of the pressing forces thus exerted simultaneously by the upper and lower punches.

According to the present invention, briefly summarized, there is provided a powder-forming press of the aforedescribed type provided therein and therewith control means for progressively retracting the wedge structure during the descent thereof in interposed contact with both the cross bar and the cross shaft to cause both the upper and lower punches to undergo simultaneous powder-compressing action relative to the outer mold (die), the control means being adjustable so as to adjust the proportions of the pressing actions of the upper and lower punches.

The nature, details, and utility of the invention will be more clearly apparent from the following detailed description with respect to a preferred embodiment of the invention and modifications thereof when read in conjunction with the accompanying drawings, in which like parts are designated by like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side elevation, in vertical section, showing the lower frame supporting and enclosing the main drive shaft and other drive mechanisms of a powderforrning press according to the invention and indicating the state at the completion of powder compression;

FIG. 2 is a front elevation, partly in vertical section, showing parts of the entire press, particularly mechanisms driven by toggle links to actuate upper and lower punches relative to the die;

FIG. 3 is a front elevation, in vertical section, showing a toggle mechanism and other drive mechanisms in the lower frame in the state at the completion of powder compression;

FIG. 4 is a front elevation, in vertical section, showing the tool holding device of the press;

FIG. 5 is a side elevation, partly in vertical section, showing a forced-retum device supported and enclosed within the lower frame for compulsorily returning a cross shaft coupled to an outer mold (die) of the press;

FIG. 6 is a section taken along a horizontal plane and showing mechanisms in the lower part of the lower frame;

FIG. 7 is a partial, front elevation showing the die and punch holding tool or die set in assembled state in the press;

FIG. 8 is a side elevation, partly in vertical section, showing a control mechanism for controlling a wedge structure retIactably inserted between a cross bar for driving the upper punch and a cross shaft for driving the die;

FIGS. 9 and 10 are partial side elevations, partly in vertical section and partly in schematic form, indicating the relationships between moving parts of the die assembly and their driving mechanisms within the lower frame, FIG. 9 showing the state at the time of preliminary pressing, and FIG. 9 showing the state at the completion of powder compression;

FIG. 11 is a side elevation showing a modification of the wedge structure control mechanism in which the slot in the control lever is curved; and

FIG. 12 is a side elevation showing still another example of the wedge control mechanism in which the angle of inclination of the control lever is adjusted through a rack and pinion mechanism.

DETAILED DESCRIPTION Referring to the drawings, the press illustrated therein and having a lower frame 1 is operated by power put out by an electric motor and transmitted through a speed-changer shaft (both not shown) to a worm 2 and thereby through a worm wheel 3 to rotate a transverse shaft 4 fixed to the worm wheel 3 in the clockwise direction as viewed in FIGS. 1 and 5.

This shaft 4 is fixed at its two ends to pinions 5, which are disposed symmetrically at opposed positions on respective lateral sides of the press and drive respective toggle mechanisms also symmetrically disposed on respective sides of the press. The pinion 5 on each side is meshed with a pair of upper and

lower spur gears

8 and 9 having offset crankpins 6 and 7, respectively, and adapted to rotate in synchronism in the arrow (counterclockwise) direction as shown in FIG. 1 to drive respective mechanisms described hereinbelow.

The crankpin 6 fixed to the spur gear 8 on each side of the press is rotatably connected to one end of a connecting rod 10, the other end of which is pin connected by pins 13 and 14 respectively to the distal or swinging ends of a pair of opposed toggle links 11 and 12, which are in vertical alignment when in their dead-center positions. The upper or proximal end of the upper toggle link 1 l is pivotally suspended from the upper part of the lower frame 1 by a pivot shaft 15, while the lower or proximal end of the lower toggle link 12 is pivotally connected to a cross bar 16 at a part near one end thereof.

The cross bar 16, which extends transversely from one side of the press to the other, is restricted in its movements to only a vertical movement by guides (guide grooves) 17 provided in the lower frame 1 on the two lateral sides thereof and slidably engaged with the ends of the cross bar 16 as shown in FIG. 6. Accordingly, when each spur gear 8 turns through one revolution, its crankpin 6 also revolves through one revolution, whereby the corresponding toggle links 11 and 12 undergo one cycle of toggle action to cause the cross bar 16 to undergo one cycle of vertical reciprocating motion.

Two columns (tie rods) 18 extend parallel and upwardly from the lower frame 1 on the laterally outer sides of the cross bar 16 and at their upper ends are fixed to end joined by a yoke or cross bridge 19. The cross bridge 19 at its middle is provided with a vertical screw rod (spindle) 20 connected with a cross head 21 and is further provided with a gear mechanism (not shown) for adjusting the vertical movement of the cross head 21 and a shaft 22 for connecting an adjusting handle.

The cross head 21 is provided at its lower part with slide members 23 slideably engaged with vertical guide grooves 25 supported on hollow fixed pillars 24 extending upward from and standing on the lower frame 1, whereby the cross head 21 can undergo only vertical movement. Below the sliding members 23, there is secured a downward-directed, tee-shaped mount 26 for tools which is adapted to be engaged by and support an upper punch holding tool as shown in FIG. 4 and described hereinafter.

The spur gear 9 disposed on each side of the press and driven by the pinion 5 has the same number of teeth as the spur gear 8 also meshed with the pinion 5,

whereby the two

spur gears

8 and 9 rotate in positive synchronism with the same speed and in the same direction. The motion of the outer mold (die) as described hereinafter caused by the initial setting of the timing to be always synchronously interrelated with that of the cross bar 16.

The crankpin 7 on the spur gear 9 on each side of the press is rotatably connected with one end of a connecting rod 27, the other end of which is pivotally connected to a pin 29 imbeddedly fixed to a sector arm 28, which is rotatably supported at its lower narrow end by a transverse pivot shaft 30, whereby the arm 28 can undergo swinging motion about the shaft 30.

On the surface of this sector arm 28 opposite that of the pin 29, a member 31 is attached by a pin. The lower surface of this member 31 is in the form of a concave arc, which is in surface contact with a projecting part 32 of a floating link 33, one end of which is rotatably connected to a transverse cross shaft 34. The other end of the floating link 33 is pin connected by a pin 36 to the lower end of a substantially vertical connecting rod 35. The upper end of this connecting rod 35 is coupled to a cross shaft 37 supported on a nut block with internal screw threads engaged with a vertical adjusting screw 41. The upper end of this screw is fixed to a bevel gear 40 meshed with a bevel gear 39 fixed to a horizontal adjusting-handle shaft 38.

Accordingly, by turning the adjusting handle (not shown) and its shaft 38, the adjusting screw 41 is rotated, by way of the

bevel gears

39 and 40, to adjust the vertical position of the cross shaft 37, whereby the position of the cross shaft 34 can be adjusted. A pair of vertical connecting rods 42, which extend outside of the lower frame 1, are fixed to the cross shaft 34 and fixedly connect the cross shaft 34 to a horizontal yoke 43 fixed to the upper ends of the connecting rods 42. A tee-shaped fitting 44 is screw fastened to the center of the upper part of the yoke 43 and is adapted to engage with the lower part of a die mounting tool as shown in FIG. 4.

The die mounting tool has a lower punch 45, which is supported on a mounting base 46 and held thereon by an attachment member 47 and is fixedly fastened thereto by

bolts

48 and 49. The outer mold (die) 50 is mounted centrally in a die plate 51, which is integrally connected by four columns 52 to a holding member 53 to engage with the above mentioned tee-shaped fitting 44. The die 50 coaxially surrounds the lower punch 45 and an upper punch 54 fixedly held by an upper holding member 56, which is slidably connected by vertical sliding rods 57 to the die plate 51 in a manner permitting relative movement between the member 56 and the die plate 51 only in a direction parallel to the rods 57. In the operation of the press, the powder 58 being compacted is placed in the space defined by the inner wall surface of the die 50 and the opposed working faces of the upper and

lower punches

54 and 45.

On the cross shaft 34 there is further provided a substantially horizontal link 63 disposed perpendicularly thereto. The link 63 has at its end remote from the cross shaft 34 a rectangular slot 62 slidably accommodating a block 61 which is free to slide horizontally in the slot 62 relative to the link 63 and is held by a pin 60 fixed to the lower frame 1.

To a part of the link 63 intermediate between its ends, the lower end of a link 65 is pin connected by a pin 64. The upper end of this link 65 is pin connected by a pin 67 to a cylinder 66, within which is disposed a piston having an external piston rod 68 fixed to the lower frame 1. This piston is actuated by compressed air supplied from a compressed air source (not shown) to the cylinder 66 through a pressure-reducing valve 94 and a control valve 93.

The upper punch 54 and the die 50 are driven respectively by the cross bar 16 and the cross shaft 34. Between the lower surface of the cross bar 16 and the upper surface of the cross shaft 34 and at the middle parts thereof, there is interposed a wedge structure 70 for effecting a preliminary press stroke in the powder compressing stroke and for controlling the magnitudes of the pressures applied simultaneously by the upper and

lower punches

54 and 45.

The wedge structure 70 is slidably fitted in a groove 71 disposed transversely on the upper surface of the cross shaft 34 at the middle part thereof and having a depth which is approximately one-half of the height of the wedge structure, which is thereby free to slide along the groove 71 perpendicularly to the axes of the cross bar 16 and cross shaft 34. The cross bar 16 is provided on its lower surface at a part thereof confronting the groove 71 with a groove 72 having an inclined surface for engagement with the inclined surface of the wedge structure 70.

The geometric dimensions and shapes of these grooves and the wedge structure are so designed that, when the cross bar 16 descends and contacts the wedge structure 70, an appropriate gap a is formed between the cross bar 16 and the cross shaft 34 in accordance with the horizontal position of the wedge structure 70.

A pin 73 is provided on a bracket extending outward from the large end of the wedge structure 70 and is slidably engaged with a slot 77 formed in a control lever 76. The control lever 76 is fixed at its lower end to a shaft 75 rotatably supported by a bearing 74 fixed to the lower frame 1 and is therefore capable of undergoing swinging movement. The control lever 76 at its upper part has a pin 78 by which it is pin connected to one end of a link 79, the other end of which is pin connected by a pin 80 to one end of an adjusting lever 81.

The adjusting lever 81 at its middle part is hinged on one end of an adjusting screw rod 82 and at its other end has a pin 84 slidably engaged with a vertical slot 83 formed in a part of the lower frame 1, whereby the pin 84 and the corresponding end of the adjusting lever 81 can slidably move somewhat in the vertical direction. The other end of the adjusting screw rod 82 is coaxially disposed within a gear 85 and engaged with the internal screw threads thereof. The gear 85 is meshed with a gear 86 which can be turned by an adjusting handle (not shown).

Thus, the adjusting screw rod 82 can be freely adjusted toward and away from the wedge structure 70 by turning the adjusting handle to rotate the gears 86 and 85. Consequently, the adjusting lever 81 also swings about the pin 84, whereby the angle of inclination of the adjusting lever 76 can be adjusted through the link 79. Accordingly, it is possible to adjust the position of the wedge structure 70 relative to the cross bar 16 and the cross shaft 34 and vary the gap a therebetween due to this position and to adjust the degree of preliminary pressing.

Furthermore, below the aforementioned link 63, there is provided a stop lever 87 which is capable of rotating about pivot shaft 30 together with the sector arm 28, and which constitutes a support structure for the link 63 and a driving member for the return of the link 63. In addition, a vertical rod 88 for forced return is suspended by a flange 89 at an upper part thereof from the lower frame 1 at a position above the cross bar 16, being held in a manner permitting only its vertical movement. This rod 88 has a hollow interior with internal threads engaged with the upper part of an adjusting screw rod 90 fixed at its lower end to a lower flange 91. By means of a suitable gear mechanism 92 coupled to the lower flange 91, the vertical distance between the upper flange 89 and the lower flange 91 can be adjusted.

The powder forming press of the above described organization according to the invention operates in the following manner. When a specific quantity of the powder to be compacted is placed in die 50 the power from the motor is transmitted through worm 2, worm wheel 3, shaft 4, pinion 5, gear 8, and other subsequent mechanism to actuate the toggle mechanism, whereby cross bar 16 begins to descend from its uppermost position as indicated in FIG. 8.

As a result, the powder 58 within die 50 is compacted to a suitable degree by upper punch 54. Then, when the inclined surface of groove 72 of cross bar 16 contacts the inclined surface of wedge structure as indicated in FIG. 9, the direction of the compressed air operating in cylinder 66 is changed by control valve 93, whereby cross shaft 34 is caused to descend, and die 50 is also actively caused to descend under the control action of cylinder 66.

On one hand, since pin 73 fixed to the large end of wedge structure 70 is engaged in a freely slidable state in slot 77 of control lever 76, wedge structure 70 shifts toward its retracted position (left position as viewed in FIGS. 8, 9, and 10) as pin 73 slides along slot 77, and the gap between cross bar 16 and cross shaft 34 progressively decreases. Then, when cross bar 16 and cross shaft 34 contact each other, the compacting action is completed.

FIGS. 9 and 10 are views interconnected by imaginary lines for the purpose of clarifying the relationship between the die, punches, and driving mechanisms within the lower frame. FIG. 9 indicates the state after upper punch 54 has thrust into die 50 a distance of c and has thereby effected a preliminary compression, while FIG. 10 indicates the state at the completion of the compacting of the powder.

The time instant indicated in FIG. 9 is that at which cross bar 16 has descended and has just contacted wedge structure 70, and a gap a due to wedge structure 70 exists between cross bar 16 and cross shaft 34. Then, as the compression proceeds from this state to the compression-completed state indicated in FIG. 10, the powder is compacted and formed from a filled height H to a height h. During this operation step, die 50 descends through a distance designated by b in FIG. 10. Accordingly, the amount of compression by lower punch 45 corresponds to this distance b.

On one hand, during this operation step from the state of FIG. 9 to that of FIG. 10, wedge structure 70 retracts, and, consequently, the gap between cross bar 16 and cross shaft 34 decreases from a to zero. During this operation, upper punch 54 is thrust further into die 50 by an additional distance a, whereby the amount of compression due to upper punch 54 becomes a +c.

Of this compression amount a c due to the upper punch, distance c corresponds to the initial preliminary compression, while distance a corresponds to the amount of compression accomplished by the retraction of wedge structure 70 due to the sliding of pin 73 along slot 77 of control lever 76 in the operation up to the completion of compression. Accordingly, this compression is accomplished in proportion to the descent of cross shaft 34, and the resulting action, therefore, is a simultaneous compressing and forming action of the upper and lower punches relative to the die.

When the compression step ends, cross bar 16 begins a rising movement. At this time, since air cylinder 66 is applying a downward force on link 63 and, therefore, die 50, the rising of die 50 is suppressed during the application of this downward force. Accordingly development of cracks in the compacted product or breakage thereof is prevented. In presses known heretofore there have been instances wherein, when the force applied by the upper punch is removed, and the stress which was being applied to the lower punch, die, and other parts no longer exists, the die rises because of mechanical play such as play in parts such as links, whereby cracks develop in the formed product or breakage thereof occurs.

At the instant when the final compression step is completed, member 31 of sector arm 28 is disposed on projecting part 32 of arcuate shape provided on floating link 33 as indicated in FIG. 1 because of the action of the connecting rod 27. Then, a sector arm 28 rotates further in the counterclockwise direction, stop lever 87 also rotates simultaneously in the counterclockwise direction until it disengages from link 63. Consequently, floating link 33 is pressed downward by member 31 sliding on projecting part 32, thereby rotating in the clockwise direction about pin 36 at the lower part of connecting rod 35 and causing cross shaft 34 and, therefore, die 50 to descend. The press is then in the state wherein punch out has been completed and the compacted powder formed article can be taken out.

Thereafter, control valve 93 is switched to cause cylinder 66 to operate and stop lever 87 to rotate in the clockwise direction, whereby link 63 is caused to rotate upward about pin 60, and cross shaft 34 is caused to rise.

On one hand, cross bar 16 which has finished its compression operation is caused to rise by the toggle mechanism, and when cross bar 16 contacts lower flange 91 of forced-return rod 88, it rises as it lifts this rod 88. Then, when upper flange 89 contacts yoke 43, cross bar 16 acts through forced-return rod 88 to raise yoke 43. Consequently, cross shaft 34 is raised further, and die 50 also is raised and caused to assume a state wherein it can be filled with a charge of powder.

In the above described example, a slot 77 of straightline shape is formed in the control lever 76. When a curved slot as shown in FIG. 11 is formed for this purpose, the movement of the wedge structure 70 becomes large as the point of the compression completion is approached, and the upper punch is thmst rapidly into the 'die, whereby the upper compression becomes greater, and the powder in the region near the upper surface thereof can be made hard. Furthermore, as a mechanism for regulating the swinging motion of the control lever 76, a rack and pinion as indicated in FIG. 12 can also be used.

Since the retraction movement of the wedge structure in the press of the invention is controlled mechanically as described above, the wedge structure is continually in a stable state irrespective of the magnitude of the compressing force, and the process step of compacting a powder or granular substance can be carried out positively and accurately. Furthermore, since the retraction of the wedge structure is controlled by the control lever 76, it is possible to cause this retraction of the wedge structure to be carried out interrelatedly with the descent of the die and to accomplish simultaneous compressing and forming of the powder or granular substance, thereby forming an article with uniform density.

In addition, by adjusting the inclination angle of the control lever 76, the amount of insertion of the wedge structure between the cross bar 16 and the cross shaft 34 can be varied, and the magnitudes of simultaneous force application can be regulated. Moreover, in the case where the retraction of the wedge structure is carried out in linear proportion to the descent of the die, the control lever can be set vertically, thereby to make possible compressing and forming in a state wherein no action whatsoever of the wedge structure is produced, that is, non-simultaneous compressing and forming in two steps.

We claim 1 In a powder-forming press of the type having a stationary lower punch, an upper punch driven by a cross bar to move vertically in synchronism therewith, a die disposed floatingly and slidably around said upper and lower punches and driven by a cross shaft to move vertically in synchronism therewith, said die and punches defining a space of variable volume for accomodating and compressing a powder material therein, the cross bar and cross shaft being guided to move along substantially the same vertical line of action, a wedge structure interposed between the cross bar and and cross shaft and being movable in a horizontal direction of insertion and retraction thereof, and means for controlling the horizontal movement of said wedge structure relative to said cross bar and cross shaft, the improvement wherein said control means comprises means for effecting a gradual retraction of said wedge structure during descent thereof in interposed contact with both said cross bars and cross shaft, thereby to cause both the upper and lower punches to undergo simultaneous powder-compressing action relative to said die.

2. The combination as defined in claim 1 in which said control means comprises a control lever pivotally supported at one end thereof on a stationary part of the press and having a guide slot, a pin connected to the wedge structure to move therewith and engaged slidably with said guide slot, and adjusting means for adjusting the angle of inclination of the guide slot relative to said vertical line of action, the guide slot in inclined state thereby functioning as a cam surface to cause said pin and, therefore, the wedge structure to retract progressively during descent thereof.

3. The combination as defined in claim 2 in which said guide slot is of a shape whereby said pin is guided in a path other than a straight-line path. 5

Claims

1. In a powder-forming press of the type having a stationary lower punch, an upper punch driven by a cross bar to move vertically in synchronism therewith, a die disposed floatingly and slidably around said upper and lower punches and driven by a cross shaft to move vertically in synchronism therewith, said die and punches defining a space of variable volume for accomodating and compressing a powder material therein, the cross bar and cross shaft being guided to move along substantially the same vertical line of action, a wedge structure interposed between the cross bar and and cross shaft and being movable in a horizontal direction of insertion and retraction thereof, and means for controlling the horizontal movement of said wedge structure relative to said cross bar and cross shaft, the improvement wherein said control means comprises means for effecting a gradual retraction of said wedge structure during descent thereof in interposed contact with both said cross bars and cross shaft, thereby to cause both the upper and lower punches to undergo simultaneous powder-compressing action relative to said die.

3. The combination as defined in claim 2 in which said guide slot is of a shape whereby said pin is guided in a path other than a straight-line path.