Automatic sintering machine

Abstract

 Sintering machine for the automated production of sintered tips where the mold is permanently resident inside the machine and it is shifted between several stations where all the single operations necessary to accomplish the sintering cycle are carried out automatically. The machine comprises at least one sintering station (2) and one service station (3,4), one or more laterally opening molds (14,15) capable of sliding between said stations, means to accomplish the operations of loading, unloading and cleaning the molds, means to control the sequence of the operations, and means to provide pressure and heat.
Each mold comprises a plurality of elementary cells inside each one of them one tip is being sintered. Each cell is provided with an upper plunger and a lower plunger and can be opened horizontally as well as vertically.

Description

[0001] The present invention relates to a sintering machine for the sintering of metal diamond powders for diamond tool industry more in particular it refers to a sintering machine designed to operate in fully automatic cycle.

[0002] It is known that the cutting of rocks, marble, granites, as well as concretes or asphalt is usually carried out with diamond tools. Said tools are usually made of disks or steel blades provided of a plurality of diamond tips usually soldered via brazing or laser welded. These tips are made of diamond powders and metal powders and are industrially obtained through a sintering process.This process consists in subjecting the powders, finely mixed together, to a pressure in conjunction with heat. Among the different known sintering techniques one of the most common is the one of direct sintering, in other words the one that implies loading of the powders inside suitable molds which are later inserted in special presses capable of providing heat and pressure simultaneously.

[0003] Depending upon the physical characteristics required, and upon the final dimensions of the tip to be obtained, the powders are meticulously mixed and pre-weighed in many single doses, after that, each one of them is poured inside a suitable mold. The mold assembly usually comprises a central body for the side containment of the powders and two plungers, a lower one and an upper one, both capable of sliding inside a rectangular shaped cavity obtained inside said central body. The central body, in order to be disassembled to allow an easy tip extraction once the sintering process is finished, features an arrangement of different blocks held together by an external frame operating around them. The blocks are usually made of graphite, allowing a multiple setting in order to be able to sinter more tips within a single mold assemby.

[0004] The mold prepared in such way is then brought under a sintering machine where pressure and heat are applied to allow the process completion the process.

[0005] The preparation of the mold according to said procedure deeply affects the quality and especially the cost of each single sintered tip since it has the following disadvantages:
   it requires a skilled labor both for the preparation as well as the disassembling of the molds;
   the graphite's blocks, which the mold in made of, suffer oxidation at high temperature during the sintering cycle that leads to a dimensional alteration of shape and volume of the said blocks and consequently a short life of the molds and higher costs due to frequent replacement as well as a dimensional inconsistency of the tips produced during subsequent cycles of the same mold;
   In order to make the entire sintering process competitive, the mold is composed in such a way to allocate a high number of tips (50 or more). Consequently, even a minimum dimensional variation of one plunger versus another one causes a dimensional variation and/or an hardness variation in the tips implying higher manufacturing cost in the following productivity phases of the disks or blades;
   in order to start the production, it is necessary to equip each traditional sintering machine with several external frames to content said blocks;
   sintering of these kind of molds, due to their mass, requires a considerable amount of energy since the whole mold mass must be brought from room temperature to sintering temperature.

[0006] Great efforts have been done to ease the preparation of said molds and make the process more efficient, such as the automatic weighing of powders in single doses, eventually their cold prepressing in order to allow to load the mold with a solid tip instead of powders or the use of automatic means in charge to load and unload the molds inside the sintering machine. Such devices help, but don't solve the problems related to the mold manual preparation.

[0007] The present invention has the purpose of avoiding the use of the molds as above described and its manual preparation, proposing a fully automatic machine where in all single operations necessary to complete the sintering process of the diamond tips are carried out automatically.

[0008] More in particular the automatic sintering machine according to the present invention is comprising:

• two ore more identical multi-segment side mold assemblies, each one comprising a line of single cavities separated one from the other by divider means having a desired shape;
• one lower plunger plate assembly for each one of said side mold assembly comprising a plurality of single lower plungers mounted on a plate which allows minor individual horizontal movements of each plunger wherein a plunger for each cavity is provided and wherein each lower plunger is permanently engaged inside the corresponding cavity;
• one upper plunger plate assembly for each one of said sintering station wherein an upper plunger for each cavity is provided, said upper plunger assembly being permanently resident inside the sintering station and each upper plunger being aligned with the corresponding downstanding cavity of the side mold;
• at least one sintering station equipped with means to provide pressure and heat to the mold assemblies;
• at least one service station equipped with a plurality of automatic means to provide powder loading, cleaning and tip ejection for each cavity of said side mold assembly;
• shuttle means which supports in a fixed position all said side mold assemblies allowing to transfer each one of them from a service station to a sintering station and viceversa;
• lateral closing means for said side mold assembly to allow opening and closing of each cavity belonging to the mold asssembly;
• actuator means to move said shuttle means;

said shuttle means allowing both side mold assembly to be transferred back and forth from a service station , wherein each cavity of the mold assembly is opened, unloaded, cleaned, sprayed, re-closed and reloaded with powders doses, to a sintering station, wherein upper plungers are lowered until each upper plunger enter its own corresponding cavity and reaches the powder applying heat and pressure thereon, the machine operating in continuous cycle and allowing to obtain certified sintered tips from powder mix charge.

[0009] According to a characteristic of the present invention, the devices for the automatic loading of the powders inside the mold, comprises known weighing system for the single doses of powder evenly mixed and ready to be used directly, or it rather loads, inside each cavity of side mold assembly, a solid block obtained by pre-compacting the powders by previous cold-pressing cycle.

[0010] According to another characteristic of the present invention, the lower plungers feature one or more side wedges, capable of forcing minor side movements of each spacer of the mold assembly while they move upwards, during tip ejection from mold cavities.

[0011] According to another characteristic of the present invention, the device for the automatic unloading of the sintered tips includes known devices for the geometric and hardness measurements of each single sintered tip produced by the machine.

[0012] According to another characteristic of the present invention, the plungers and the spacer of the molds are made of a special conductive ceramic.

[0013] According to another characteristic of the present invention, the sintering machine can be equipped with an extra inspection station and/or with an automatic magazine wherein an automatic handling devices (robot) deposits the sintered tips in an organized manner and a computer maintains all position and inspection data in a data bank memory to allow tip sorting according to a desired criteria.

[0014] The present invention will now be further explained in details in relation to a preferred embodiment given only as an example and illustrated in the attached designs wherein:

Fig. 1 shows a machine top sectional view

Fig. 2 shows a vertical section along line AA of Fig. 1 and more in particular a sectional view of the sintering station.

Fig. 3 shows a vertical section along line BB of Fig. 1 and more in particular a sectional view of one of service station;

Fig. 4 shows a top view of one of the two linear molds assembly.

Figures 5A and 5B show, illustrated in cross section view, a mold cavity with its own plungers respectively in the sintering position and in the ejection position; and

Fig. 6 shows a side, a top and a prospectic view of a typical lower plunger.

[0015] As shown in Fig. 1 the sintering machine according with this invention comprises a main frame 1, a sintering station 2 and two service stations 3 and 4 aligned respectively one on the left hand side and one on the right hand side of station 2 and a sliding tray 14 equipped with two linear multi-segment molds assemblies 14 and 15 and provided with a closing cylinder 17.

[0016] The two service stations 3 and 4 are identical, and are equipped with an automatic powder loading unit for the molds 5 and 8, with molds cleaning unit 6 and 9, with automatic unloading unit 7 and 10 of the sintered tips, and with cylinders 19 an 20 for the tip ejection, each one of them provided with a plate 18.

[0017] Still in Fig. 1, inside the sintering station 2,are shown the four columns 13 and a toggle joint mechanism 11 for mold side closing equipped with the relevant cylinder 12. The sliding tray 14 which supports the mold assemblies, shifts horizontally on suitable guide 21.

[0018] Fig. 2 shows that the sintering station comprises several upper plungers 32, and several lower plungers 38, a side mold assembly 33 equipped with side spacers 37 and 39. The upper plungers are fixed on the plate 31 which is equipped with cooling holes 47. Said plate is connected to an upper main plate 27 by means of fixing screws 48. Between the two plates 31 and 27 an insulating plate 30 is interposed, while between the plungers 32 and the plate 31 a copper laminar plate 28 is interposed; said copper plate is electrically connected to the main transformer omitted in the figure. The lower plungers 38 are mounted inside a suitable groove 49 located in the lower plunger plate 41 so that each plunger is free to make little longitudinal movements inside the groove itself. As the upper plunger plate 31, also the lower plunger plate 41 is equipped with cooling holes 50 and it is sliding on a main lower plate 42 which is fixed the lower main plate 44. Between plates 42 and 44 an insulating spacer 51 and a copper foil 43, electrically connected to the transformer is interposed.

[0019] Still in Fig. 2, is shown as the main lower plate 44, the upper cover plate 22 and the columns 23 are anchored to the frame 45; cooling holes 24 and relevant fittings 25 are provided inside columns 23.

[0020] The side mold 33 is mounted on a sliding tray 14 which slides on suitable carriage 52 supported by the guide 36 and free to shuttle upon the action of the cylinder 54.

[0021] Still in Fig. 2 it is shown the main pressing cylinder 46 that controls the movement of the main upper plate 27 which is driven vertically by means of suitable sleeves 29, which slide on columns 23. The plate receives the trust from cylinder 46 through the spherical joint 26.

[0022] Fig. 3 shows the cylinder 60 for sintered tips ejection , its shaft 58 and the lower plunger plate assembly vertical guide 62 with its wheels 61.

[0023] Fig. 3 also shows the upper plunger 32 disengaged from the cavities due to the main upper plate 27 being lifted. The same figure shows as well the wedge 57 existing in each lower plunger 38 inserted inside the two spacer 37 and 39 of the side mold 33.

[0024] In Fig. 4 can is shown the side mold assembly arrangement which comprises a line of elementary cells; inside each single cell a tip is sintered. Each cell has comprises a cavity 83, suitably shaped, the corresponding upper plunger 32 and lower plunger 38 moving vertically therein, a couple of spacer 82 (except for the first and last cell which instead have an ending spacer 81 instead of 82) and two side walls stripe shaped 37 and 39 common to all cells; all these pieces are kept together, by a containing frame 84 mounted on sliding tray 14. Still in Fig. 4 shows the main elements of the closing mechanism of the side mold composed of a cylinder 17 with relevant shoe 80 and operating along a direction parallel with the main machine axis 79, and a bracket 75 shifting along axis 78, perpendicular to axis 79, and operated by the cylinder 12 that by means of a shaft 77 activating a toggle joint leverism comprising a tris of double rods 70 and 71 having three fulcrums 86, 72,73. The fulcrums 73 are fixed to blocks 74 which are fixed to the frame 45 while fulcrums 72 are fixed to shaft 77 which moving in parallel direction to axis 79. The fulcrums 86 are instead fixed to bracket 75 moving in parallel direction to axis 78.

[0025] In Fig. 5A, and 5B is illustrated a cross section of a single elementary cell of the mold assembly. In the figures is shown the sintered tip 59, the upper plunger 32, the lower plunger 38, two out of the four elements composing the side mold 37 and 39, the sliding tray 33, the closing bracket 75 and spacer holding brackets 88 and 89. In the same figures is shown the sloping surfaces acting as wedges 90 and 90A, the insulating spacer 87, the brackets for anchoring the 85 and 91, and the relevant screws 86 and 92. Fig. 5b also shows the lower plunger plate 41.

[0026] In Fig. 6 is represented a typical lower plunger featuring upper surface 93, base 96 and with central body having double sloping surface 94 and 95.

OPERATION

[0027] The sintering machine according to the present invention works in fully automatic cycle. To assure this feature the machine is provided with mold assemblies that can either open and close vertically as well as open and close laterally. Vertical opening of the mold happens in the sintering station 2 by means the vertical lifting of the upper plungers 32 under action of the main cylinder 46; this allows loading and unloading of the sintered tips. Side opening of molds is instead achieved in two phases:

[0028] At first the pressure is released in the lateral closing cylinders 12 and 17 of the mold in the sintering station, secondly the lower plungers 38 are lifted by the ejector cylinders 60 in one of the two identical service stations 3 or 4; this to allow a further side opening of the mold due to lower plunger wedges imposing minor moments to side walls of the mold and consequently allowing the vertical ejection of the sintered tips from the mold without scratching the internal side walls of spacers 37,39,81,82 and 85.

[0029] The side mold assembly comprises a plurality of elementary cells each one presenting a cavity 83 wherein a pre-loaded dose of powders is placed between two plungers (a lower one and an upper one).

[0030] The cavities are separated the ones from the others by a line of spacers suitably shaped to impress to the tip the desired geometric shape. The whole assembly of said elements composing the side mold, are held laterally together by a containing frame 84, and vertically by little plates 88 and 89. The mold assembly usually feature more than ten cells aligned; to each single elementary cell in the mold, an upper plunger 32 and a lower plunger 38 are provided.

[0031] Two identical molds, made as above described, are mounted on a single sliding tray 33 and set inside the machine structure comprising a sintering station 2, located in a central position, and 2 identical service stations 3 and 4 set in line, one on the right and the other on the left side of the sintering station 2. Such an arrangement aims at having a mold constantly hot-pressed inside the sintering station 2, while the other mold, in hidden time, is prepared for the next sintering cycle; more in particular the other mold is opened, unload, cleaned, closed and loaded again and finally ready for the following sintering cycle, optimizing in such a way the production cycle time.

[0032] The operational cycle starts with the phase of loading the mold in one of the two service stations wherein one of the two linear multi-segment molds in temporarily resident I.e. mold 16 in Fig. 1 is empty, closed, laterally, open vertically and clean and ready to be loaded. With reference to Fig. 1, the operation of loading of the mold is completed by an automatic loading unit 8 that pours into every single cavity 83 of the mold 16 a dose of and premixed amount of powder at dust state or solid state, (in case each powders dose is pre-compacted by means of a previous cold pressing cycle). This loading cycle takes place in station 1 while the other twin mold 15 is being hot-pressed in the contiguous sintering station 2. Once the charging is completed, the mold 16 waits for the mold 15 to finish its hot-press cycle; when this it is finished, the side cylinders 14 and 12 release the side mold 15 and the upper plungers 32 of the sintering station 2 are lifted under command of the piston 21 that lift the plate 27 where the plungers are anchored thereon.

[0033] In the second phase takes place the shuttling of the sliding tray 33; the mold 15 moves from the sintering station 2 to the service station 3 while the pre-loaded mold 16 moves from service station 1 to sintering station 2. Said movement is operated by the cylinder 54 that pushes the tray 33 which is mounted on the saddle 52 sliding on guide ways 36. In such a way, the mold 16 previously loaded is now ready for the following sintering phase while simultaneously the mold 15, previously sintered, is ready for the following phase of unloading and loading again.

[0034] The third phase foresees closing of the mold assembly 16 first laterally then vertically inside the sintering station 2 and, simultaneously, the ejection of the sintered tips 59 from mold 15 from station 3. The closing of the mold 16 in station 2 is caused by the side cylinders 12 and 14 while the following lowering of the upper plungers 32 is operated by the main pressing cylinder 46; said plungers reach the mold 16 and each one of them fits its correspondent cavity 83 until it reaches the previously loaded powder mix and apply a predetermined pressure. Simultaneously, the ejection of the sintered tips 59 from mold 15 performed in service station 3 is accomplished by means of the cylinder 60 which forces the progressive insertion of the lower plungers 38 inside the cavity 83 of the side mold until each sintered tip appears out and flush to surface the upper of the mold 15. During the progressive insertion of the lower plungers 38 inside the cavity 83, the insertion of the wedge leaned surface located on each lower plunger, forces a unidirectional side opening movement of the spacers 82,81,85 and 37 to allow a scratch free tip ejection from the molds cavities.
The considerable trust generated therein causes the lateral closing of mold 16 along axis 78 and reaches a suitable "V" shaped support withstanding the reaction force which has low friction surfaces 55 and 56 to allow a free tray shuttling.
During the third phase, the lower plunger 38 stays still and withstands the pressure force provided by the cylinder 45 throughout the upper plungers 32.
The forth phase foresees the sintering cycle of mold 16 inside station 2 and the ejection of the sintering tips 59 from mold 15 inside service station 3. Sintering process requires heating of the mold up to a predetermined value of temperature and for a predetermined amount of time. Heat is provided by means of Joule effect from electric current supplied by a transformer laterally mounted to the machines, which is electrically connected to the copper plates 28 and 43 shown in figure 1.
Throughout the entire heating cycle, the powders inside the cavities 86 are maintained compressed by the cylinder 46. Each single mechanical machine component is heat isolated by means of built in cooling system which is activated throughout the entire heating cycle. Mold 16 unloading takes place automatically by means of a manipulator 7, suitable to travel parallel to mold 16 and capable to reach and pickup each sintered tip 59 emerging from mold 15. Manipulator means can be provided with Jaws featuring built-in sensors capable to provide output signals related to the external dimensions of the tips as well as its hardness. Recording these data it is consequently possible to obtain and inspection certificate for each sintered tip manufactured by the machine
The fifth and last phase foresees cleaning of mold 16 inside service station 3 by means of an automatic cleaning device 6 while inside sintering station 2, sintering of mold 15 is taking place. Usually sintering process takes much longer time than all the service operations such as unloading, cleaning, and loading of the molds inside the service stations 3 or 4. Cleaning requires brushing of the inner wall of every single cavity 83 of the mold. During this phase a vacuum system collects all particles removed from mold. Mold preparation requires anti-adhesive to be applied preferably by means of a nozzle spraying a special solution and a lateral closing of the mold prior starting mold loading. When mold 15 is closed and cleaned inside service station 4 and mold 16 is under sintering inside station 2, a situation like the first one is repeated. The cycle is completed and ready to restart.

[0035] From what above explained it is easy to understand that the sintering machine according to the present invention features several advantages which are not attainable from the regular sintering machine, more precisely:

• It allows to eliminate extensive labor assistance.
• It allows to avoid to require an expensive set of mold to equip the machines;
• It allows a full inspection of the manufactured tips;
• It allows to use plungers manufactured in advanced ceramic which implies a better mold life and better tip quality.

It is to be understood that the invention here described is susceptible to variations and modifications and substitutions of equivalents without departing from the spirit and scope of the invention which is not intended to be limited by the foregoing except as may appear in the following appended claims.
In particular the mold could be mounted on a turning table rotating inside the machine wherein the stations are arranged in a circle rather than linearly, without departing the limit of protection of the present invention.

[0036] Furthermore, upper plungers could be mounted on an upper plate, which can translate with a mold slide instead of remaining stationary inside the sintering station, without departing the limit protection of the present invention.the limit protection of the present invention.

[0037] Also the spacers 81 , 82, and 85 could be kept together simply by means of grove-and-tongue or dove tail coupling means which couple them to the side walls 39 and 36 rather than by means of brackets 88 and 89, without departing the limit protection of the present invention.

Claims

1. Machine for automatic sintering of metal and diamond powders comprising.

- two ore more identical multi-segment side mold assemblies (14,15), each one comprising a line of single cavities separated one from the other by divider means (81,82,84,85,37,39) having a desired shape;

- one lower plunger plate assembly (41) for each one of said side mold assembly comprising a plurality of single lower plungers (38) mounted on a plate (41) which allows minor individual horizontal movements of the plungers wherein a plunger (38) for each cavity is provided and wherein each lower plunger (38) is permanently engaged inside the corresponding cavity (83) ;

- one upper plunger plate assembly (31) for each one of said sintering station (2) wherein an upper plunger (32) for each cavity (83) is provided, said upper plunger plate assembly (31) being permanently resident inside the sintering station (2) and each upper plunger (32) being aligned with the corresponding downstanding cavity (83) of the side mold assembly ;

- at least one sintering station (2) equipped with means to provide pressure and heat to the mold assembly (14 or 15) ;

- at least one service station (3,4) equipped with a plurality of automatic means to provide powder loading (5,8), cavity cleaning (6,9) and tip ejection (7,10) for each cavity of said side mold assembly,

- shuttle means (14) which supports in line and in a fixed position all said side mold assembly (14,15) allowing to transfer each one of them from a service station (3,4) to a sintering station (2) and viceversa ;

- lateral closing means (12,17) for said side mold assembly to allow opening and closing of each cavity (83) belonging to the mold assembly (14,15) ;

- actuator means (54) to move said shuttle means ;

said shuttle means (14) allowing both side mold assembly (14,15) to be transferred back and forth from a service station (14 or 15), wherein each cavity of the mold assembly is opened, unloaded, cleaned, sprayed, re-closed and reloaded with powders doses, to a sintering station (2), wherein upper plungers (32) are lowered until each upper plunger enter its own corresponding cavity (83) and reaches the powder (59) applying heat and pressure thereon, the machine operating in continuous cycle and allowing to obtain certified sintered tips from powder mix charge.

2. Sintering machine according to claim 1 wherein said lateral closing means for side mold assembly comprises:

- a multiple toggle-joint leverism , operating along a first horizontal axis of the mold (78), wherein a plurality of double rod levers (70,71) are shifted back and forth from a bent position to a straight position by means of a linear translation of a single driving rod (77) activated by a cylinder (12) ;

- a cylinder (17) operating along a second horizontal axis (79) of the mold perpendicular to the first one.

3. Sintering machine according to claim 1 wherein said means to provide powder loading (5,8) inside a service station (3 of 4) comprises automatic weighing means to weigh each single dose of powder mix.

4. Sintering machine according to claim 1, wherein said means to provide powder loading (5 and 8) inside a service station (3 or 4) comprises gripper means suitable to handle powders supplied in a solid status, the powders being previously pre-compacted by means of a cold-pressing cycle to ease material handling.

5. Sintering station according to claim 1 wherein said means for cleaning (6 and 9) each cavity (83) of the mold assembly comprises brush and nozzle means to spray anti-adhesive solution inside said cavities.

6. Sintering machine according to claim 1, wherein said means for unload (7 and 10) sintered tips (59) from side mold assembly comprises inspection means capable to provide tip dimensions as well as tip hardness, said inspection means being built-in inside the gripper means of the automatic unloading device.

7. Sintering machine according to claim 1, wherein said spacers (81,82,84) and said plungers (32,38) are shaped as arcs having desired curvature to be able to impress to the tips a predetermined shape.

8. Sintering machine according to claim 1 wherein said plungers (32,38) are made of a special ceramic material capable of conducting electricity.

9. Sintering machine according to claim 1 wherein said lower plungers (38) are provided with one ore more little side wedges (94,95) capable of forcing minor horizontal movements of the spacers inside the side mold assembly opening during the sintered tip ejection from the mold, said movements allowing side opening of each cavity (83) for a scratch free tip (59) ejection from mold assembly.

10. Sintering machine according to one of the preceding claims, wherein the shuttle means (14) is shaped as a circle and rotates like a turning table, the sintering (2) and the service stations (3,4) being arranged in a circle to allow side mold assembly transfer from station to station by means of a rotation of the shuttle means instead of a linear translation.

11. Sintering machine according to claim 6, wherein a robot and a computer means are provided to allow organized storage of each single tip (59) produced by the machine, the computer means keeping in its memory data bank position and inspection data of each tip and allowing subsequent tip sorting according to a desired criteria.

Drawing