US3830615A

US3830615A - Press, particularly for the manufacture of ceramic and refractory articles

Info

Publication number: US3830615A
Application number: US00285864A
Authority: US
Inventors: U Walchhuetter
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-09-02
Filing date: 1972-09-01
Publication date: 1974-08-20
Anticipated expiration: 1991-08-20
Also published as: DD99127A5; FR2152058A5; DE2240674A1; ES406212A1; GB1357986A; DE2240674B2; CH551264A

Abstract

A traverse is mounted above a mold for movement vertically toward and away from the same. It carries plungers which can enter into the mold, and a hydraulic unit which can be operated to press the traverse and plungers downwardly against the mold. A mobile abutment is mounted on a stationary support and travels with the traverse to provide a mobile reaction point for the hydraulic unit when the latter with the traverse has reached a lowered position in which the transmission of pressure from the unit to the traverse is required.

Description

United States Patent 1191 1111 3,830,615 Walchhuetter 1 1 Aug. 20, 1974 PRESS, PARTICULARLY FOR THE 3,115,676 12/1963 Quartullo 100/269 R x g gg ffgsgig ggs AND FOREIGN PATENTS OR APPLICATIONS 531,618 10/1921 France 100/269 R Inventor: Ulrico Walchhuetter, Quartlere Fiori 42,378 12/1965 Germany 100/269 R Edilnord, Brugherio, Italy 534,089 2/1941 Great Britain 100/269 R [22] Filed: Sept. 1, 1972 Primary Examiner-R. Spencer Annear [21] Appl- 285,864 Attorney, Agent, or FirmMichael S. Striker [30] Foreign Application Priority Data [57] ABSTRACT S .2, 1971 l l 1 3! 1972 :2 A traverse is mounted above a mold for movement vertically toward and away from the same. It carries [52] US Cl 425/344 72/453 72/454 plungers which can enter into the mold, and a hydrau- 00/269 41125/4157 425 he unit which can be operated to press the traverse 51 1m. 01 R2811 3/02 and plungers downwardly against the mold- A mobile [58 Field of Search 0 1'6 344 357 abutment is mounted on a stationary support and trav- 10(5/269R72/453 els with the traverse to provide a mobile reaction point for the hydraulic unit when the latter with the [56] References Cited traverse has reached a lowered position in which the transmission of pressure from the unit to the traverse UNITED STATES PATENTS is required 2,597,923 5/1952 Croston.. 100/269 R X 2,810,929 10/1957 W111i 425/443 X 16 Claims, 15 Drawing Figures PATENTEBMJBZOW 3.880.615

SIIEEI 10E 6 PATENTEB 19201974 sum 20? 6 PRESS, PARTICULY FOR THE MANUFACTURE OF CERAC AND REFRACTORY ARTHCLES This invention relates to a press, particularly a press 5 for the manufacture of ceramic and refractory articles, such as tiles for floors and facing, refractory bricks and tiles, and the like.

Ceramic or refractory objects are usually manufacvarious different compositions. It is known that a good compression of such powdered or granulated material depends upon two main factors, i.e., the working pressure and the de-aeration of powders, as carried out in i l the course of the compression cycle.

These two factors in turn vary from material to material, according to characteristics which are entirely independent one from the other. Accordingly, to be able to produce objects which perfectly hardened, and free from swells, deformations and other defects during the the baking, a press used for the production of such objects should be equipped in such a manner as to be capable to release the air from the material under different conditions, and moreover, to adjust the working pressure, both as to intensity and time, according to the characteristics of the material to be compressed.

The above requirements, however, are themselves formed by another consideration, namely that the out- -tured by compressing granular or powdered material of An object of this present invention is to provide a press of the type wherein a mobile traverse supporting plungers of a mold, is moved vertically by its own means along guide uprights, in order to be brought from an upper position wherein the plungers are spaced from the mold, to a lower position wherein the said plungers will impact against the mold. According to the invention, a hydraulic device is used as a compression member, and is mounted on the said mobile traverse and movable with the latter, a mobile abutment being provided for following the movements of the said hydraulic device, and forpresenting a reaction support during the steps of compression as carried out by the said hydraulic device, when the mobile traverse is 5 moved to the lower position.

put of the press, should be as high as possible so as to conditions, for the purpose of carrying out the nearly 5 complete de-aeration of the different types of powders treated. A mobile traverse supporting the upper plungers of a mold, according to this patent, is independent of the main compression member of the machine, and

submitted to the action of one or a plurality of pairs of hydraulic jacks which will cause the controlled lifting and lowering of the said traverse, in addition to permitting an adjustable pre-compression of the material to be carried out at the initial step of each compression cycle, and also to operate according to variable pressure on the material during the interval between subsequent and progressive compressions, as carried out by the main compression member.

" However, my prior patent does not solve the problem of controlling the value of pressures and the duration of the compression period of time. This is a disadvantage generally found in the case of screw and flywheel presses, which are largely used for the manufacture of ceramic articles owing to their high -and therefore low-costoutput.

A regulation of pressures, both as to mount and time, would be possible in the case of the traditional hydraulic presses. These, however, are not industrially acceptable, both because of their low rate of production and because of their high consumption of power necessitated by the required installation of high-power hydraulic equipment.

The present invention provides a press which permits a control of the pressures, and which, still making use of a hydraulic device as a main compression member, permits moreover a high production rate and the use of hydraulic equipment of only limited power.

The said hydraulic device, moving together with the mobile traverse, is compelled to execute a working stroke which is substantially equal to the reduction in thickness of the material during each single compression, thus requiring only a very limited volume of working fluid under pressure, and therefore a power which is also limited. Moreover, because the hydraulic device is moved with the mobile traverse, and because it is compelled to carry out only very short strokes, a high production rate can be maintained which is within the range of the production rate of modern screw and flywheel presses.

In particular, the mobile traverse may be moved vertically by means of a pair of hydraulic jacks. Other pairs of hydraulic jacks can be provided for carrying out the precompression and the intermediate compressions as necessary for a complete de-aeration of the material.

The mobile abutment which is provided so as to act as reaction member for the hydraulic device, can be of any suitable nature.

According to currently preferred embodiment of the present invention, the mobile abutment is in the form of a screw spindle threaded into a female thread provided on the upper fixed structure of the press, and arranged axially of the hydraulic device, being rotatable by a motor in a manner as to follow all the movements of the hydraulic device and to act as reaction means when the latter will expand.

According to a further embodiment, the mobile abutment may comprise two coaxial serrated members, fit-' ted with opposite toothing, one of which is secured to one of the elements of the hydraulic device, i.e., the piston or the cylinder thereof, and the other of which is engaged by the upper fixed structure of the press. One of these members is rotable in a manner as to displace its teeth from an angular position where the teeth of the two members can be moved to mesh, towards a position where the said teeth are opposite and prevented from meshing. The first position corresponds to the upper position of the mobile traverse, and wherein the second position corresponds to the lower position of said mobile traverse.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

FIG. 1 shows a front view of the novel press according to a first embodiment;

FIG. 2 is a side view of the press of FIG. 1;

FIG. 3 shows the circuit diagram of the hydraulic circuit of the press in FIG. 1;

FIGS. 4 to 7 show the successive steps of a compression cycle of the press of FIG. 1;

FIG. 8 is a front view of a press according to a second embodiment;

FIG. 9 is a plan view of a mobile abutment control mechanism;

FIG. is an exploded view of two serrated members of a mobile abutment;

FIGS. 11 to 14 show the different steps of a production cycle of the press of FIG. 8; and

FIG. shows the circuit diagram of the hydraulic circuit of the press in FIG. 8.

Referring now to FIGS. 1 and 2, the press of the present invention has a base 1 on a surface 2 of which a mold 3 of a type known in the art is supported, and which is used for the manufacture of ceramic tiles in particular.

Two vertical and parallel uprights 4 and 4' are arranged to extend upwardly of the base 1 at two sides of the mold; however, four uprights, aligned two by two can, be also provided, are at each side of the mold, or another rigid structure may be used. In any case, the uprights support at their upper ends an upper fixed structure 5. A mobile traverse 6 is joumaled at the ends of the uprights for sliding movement without play along the uprights. At its lower face the traverse 6 supports the upper plungers 7 for the mold 3, in a manner known in the art. The traverse stroke is usually limited between an upper position, indicated in FIG. 1, and a lower position wherein the plungers 7 are lowered onto the mold 3.

On each side of the base 1

brackets

8 and 8, respectively, project outwardly. At each end of the mobile traverse 6 two pairs of brackets are provided, i.e., a

first pair

9 and 9 of lower brackets, and a

second pair

10 and 10 of upper brackets. The brackets of each end are stiffened by means of vertical ribs, 11 and 11, respectively. Two

hydraulic jacks

12 and 12, resting vertically on the base brackets 8 and 8', bear with their rods against the brackets 9 and 9', respectively, of the mobile traverse 6. These jacks are generally of the single-acting type and are designed for raising and holding the mobile traverse 6, when they are supplied with fluid under pressure, and for lowering of the traverse 6 when fluid is discharged from them. The lowering occurs simply by gravity due to the weight of the traverse 6, or else as the result of a thrust exerted on the traverse in a manner which will be hereafter described.

A second hydraulic jack, l3 and 13 respectively, is juxtaposed with each hydraulic jack l2 and 12, the former also resting against the

respective bracket

8 and 8 but with its rod being out of engagement with the mobile traverse 6 when the latter is at its uppermost position. The free ends of the rods of the hydraulic jacks l3 and 13' are each provided with an adjustable member, 14 and 14', respectively, such as a threadable cap serving for changing the elevation of the said end for regulating the interference level among the brackets 9 and 9' and the

members

14 and 14 when the traverse is being lowered. The level of said caps is generally ar ranged in a manner that they will interfere with the respective bracket of the traverse 6 but after that the said traverse 6 is lowered onto the mold, and when the material is subject to a reduction in the thickness during the first compression step, wherein said reduction in the thickness will cause a further lowering of the mobile traverse. During this lowering movement, the interference among members 14 and 14' and the respective brackets 9 and 9' will occur.

The

jacks

13 and 13 are constantly fed at adjustable pressure with pressurized oil, in such a manner that they will be depressed during the first compression step, while offering an upward thrust of the mobile traverse, a thrust which can be adjustable from zero to a maximum level, so as to lighten the weight of the traverse on the material after the first compression step, or during the interval between a compression step and the subsequent one, to thereby permit the air compressed into the material to expand and to be released under established conditions which are dependent upon the material being treated.

As shown in FIGS. 1 and 2, the arrangement of the

jacks

12, 12' and 13, 13 is of the crossed-type in that,

while on the bracket 8 the jack 12 is arranged in front of the jack 13, in the case of bracket 8 the position of the jacks 12' and 13 is inverted, this with the purpose of preventing the application of eccentric forces on the mobile traverse 6.

Moreover, at the two sides of the upper fixed structure 5,

brackets

15 and 15 are provided which face the

upper brackets

10 and 10, respectively of the mobile traverse 6. The hydraulic jacks l6 and 16', respectively, will act at one side between the

brackets

10 and 15, and at the other side between the brackets 10' and 15, the function of the

jacks

16, 16 being that of pushing the mobile traverse 6 downwardly for accelerating the lowering or stroke or for supplying an established thrust onto the mobile traverse when the plungers 7 of the latter rest on the material in the mold 3, so as to produce a certain pre-compression of the material and therefore promote a first controlled de-aeration.

Laterally of the jacks l6 and 16 are provided singleacting hydraulic jacks 17 and 17'. These have rods which are directed towards the brackets 10 and 10'. The

jacks

17 and 17 are usually under pressure and the ends of their rods are provided with adjustable members, such as the

caps

18 and 18, which make it possible to adjust the level of the said ends, for forming a fixed abutment which will determine the upper position of the mobile traverse 6 in operation. The jacks 17, 17'

' can be discharged, in such a manner as to withdraw their rods, when the traverse is to be further raised for the purpose of replacing or cleaning the mold.

According to the present invention, the mobile traverse 6 is provided with a seat 20 in which a hydraulic device 21 is housed. The device 21 comprises a cylinder 22 of a large section and a double-acting piston 23, with a pressure chamber 19 being directed towards the mobile traverse and the free end of the piston 23 being directed towards the fixed structure, i.e., the stationary traverse 5. The hydraulic device 21 is perfectly coaxial with the vertical axis of the press.

The cylinder 22 (FIGS. 1 and 3), is fed at the lower end through a hole 24, which is supplied with oil under pressure through a line 25. The line 25 may receive fluid under at least two different pressures, i.e., at lower and at higher pressure. For this purpose, the supply to the cylinder is carried out via hydraulic equipment which is separated from the equipment of the other utilities of the press.

Such hydraulic equipment comprises a motor 26 driving two coaxial pumps 27 and 28, the first feeding fluid at relatively low pressure, the second feeding fluid at relatively high pressure. Pump 27 feeds an accumulator 29 from which the fluid under pressure can flow to the line through a piloted valve 30 which in a first position permits the quick flowing of the fluid to the line 25, in a second position connects the line 25 to discharge, and in a third position will close all passages. A safety valve 31 for. maximum pressure serves for regulating the feeding pressure of accumulator 29.

Similarly, the pump 28 feeds under high pressure to an accumulator 32, the pressure of which is controlled by a valve 33 of maximum pressure. The fluid under pressure is delivered to the line 25 through a piloted valve 34, which in a first position permits the passage of the fluid towards the line 25, in a second position connects the line 25 to discharge, and in a third position closes all passages.

The cylinder 22 is provided also with a lateral hole 35, at which terminates a line 36 (FIG. 3) for feeding an annular chamber 37 encircling the piston 23 and reserved for retracting said piston. Line 36 is fed through a line 38 departing from the hydraulic equipment of the press utilities, for instance for controlling the lower plungers of the mold and the hydraulic jacks of the mobile traverse, and the connection to the said line 36 is carried out in such a manner that the said chamber 37 is constantly fed with fluid, thus imparting to the piston a limited thrust downwardly due to the restricted area whereto the pressure of the fluid is imparted.

The line 38 (see FIG. 3), feeds via piloted valve 39, the

hydraulic jacks

17 and 17 and thus establishes the upper position of the traverse, when the valve 39 is dis-- charged, the plungers of the hydraulic jacks 17 and 17' can be retracted if the traverse is to be further lifted for replacing or cleaning the molds.

Referring further to FIG. 1, the free end of the piston 23 is provided with a counter-impact member 40 which serves as supporting means for an end impact member 41 of a screw spindle 42, the latter being coaxial to the hydraulic device 21. The screw spindle 42 is threaded into a female screw thread 43 provided in the upper fixed structure 5, and it projects above said upper fixed structure where it is coupled to an upper motor 44, preferably of the hydraulic type.

. The motor 44 (FIGS. 1 and 2) is supported by a mobile plate 45 which, through two pairs of end rollers 46 and 47, can slide along two

vertical uprights

48 and 49, respectively, which are arranged individually amongst the rollers of a pair, in such a manner that when the motor is energized, the latter is able to move vertically, following the screw spindle 42, while its stator cannot rotate due to the abutment imparted by the

uprights

48 and 49. The threads of the screw spindle 42 are of the self-locking type, i.e. the type which is not given to rotate under axial thrust.

The purpose of the screw spindle 42 is to provide a mobile abutment suitable to follow the movements of the hydraulic device 21, in a manner that when its impact member 41 rests against the counter impact member 40, during an expansion of said hydraulic device 21, the piston 23 is prevented from rising, so that therefore the cylinder 22 will be compelled to move downwardly. Thus, the screw spindle 42 has only the function of a mobile abutment; it does not supply or receive any forces suitable to supply the working pressure of the traverse. Therefore, the press object of this present invention can not be regarded as a screw press, as usually regarded in the art.

The hydraulic motor 44 is supplied through the line 38 by means of a control valve 50, which valve feeds the said motor via two

separate lines

51, and 52, respectively, for rotating the motor in one or the other direction at high speed, depending upon whether the screw spindle 42 is to move downward or upward, or for stopping the motor.

With reference to FIGS. 1, 4, 5, 6, and 7, it will be seen the different operations of the press can be carried out in one cycle of compression of tiles, including two steps of compression of the hydraulic device 21, the first step being carried out under a low pressure, and the second step being carried out under a high pressure.

According to the position shown in FIG. 1, at the early stage of operation or after the completion of a previous cycle, the

jacks

12 and 12 are under pressure, thus holding the mobile traverse at the upper position as established by the adjustable members 18 and 18' of

jacks

17 and 17, while the jacks l6 and 16', if not discharged, are retracted due to the higher thrust imparted by the

jacks

12 and 12.

Now, a loading carrier 53 (FIG. 2) of the type known in the art, is advanced on the mold in a known manner for withdrawing the compressed pieces located therein, and for filling the cavity of the mold with new material to be compressed; thereupon the carrier is retracted. The

jacks

12 and 12 are discharged, and if required, the jacks 16 and 16' are submitted to pressure; the traverse moves down and the plungers 7 are to rest against the material in the mold, carrying out a smooth precompression due to the weight of the traverse and of the device 21 with the possible addition of the thrust imparted by the jacks 16 and 16'. This pre-compression results in a major expulsion of the air trapped in the material, and a large reduction in the thickness of the material (FIG. 4).

The piston 23, following the downward motion of the mobile traverse, has been distanced from the end of the screw spindle 42, that is, the impact members 41 and 40 are distanced therebetween. Accordingly,'the motor 44 is actuated and the screw spindle 42 is rotated in such a manner that the impact member 41 will follow the downward motion of the impact member 40, stopping when it contacts the latter with a certain clamping effect.

The starting of motor 44, and therefore of the screw spindle 42, can be controlled by means of a suitable member actuated by the descending traverse. To stop the motor 44, preference is given to the use of a small generator (not shown), rotating with the screw spindle 42 and serving to stop the motor 44 when the screw spindle 42 is blocked against the piston 23.

Now (FIG. 4) the fluid under the lowest pressure is delivered through a valve 30 to the hydraulic device 21, for instance controlled by the generator, just when the screw stops. The hydraulic device 21 expands and, due to the abutment resulting from the screw 42, it will force the cylinder 22 to move downward, thus creating the first compression step, and thereby promoting a reduction in the thickness of the material together with a first hardening of the material itself. The period of time of the first compression step can be varied, according to the requirement of a given application,

through a timer means. The reduction in material thickness will cause the expansion stroke S of the cylinder 22 which, in turn, requires a limited amount of fluid for carrying out the compression. Due to the limited amount of fluid required, and also to the presence of the accumulator 29, the device 21 is put under pressure almost immediately, thus influencing importantly the press output while still using only limited power. Moreover, the pump 31 is allowed a complete cycle for recharging the accumulator 29.

When the first compression step is completed the conduit 25 discharges, and therefore the piston 23 urged by the oil entering through the hole 35 will descend further, thus separating from the impact member 11 of the screw spindle (FIG. 6) by an amount equal to the stroke S as performed by the cylinder 22.

It should be noted that during the compression step, and while the cylinder 22 and the traverse 6 are performing the descending stroke S, the brackets 9 and 9' of the traverse 6 will interfere with the caps 14- of the jacks 13 and 13' which, in turn, are depressed in opposition to the upwards thrust that they are imparting.

After the completion of the compression step, and when the plunger 22 is lowered as illustrated in FIG. 6, thus separating from the screw spindle, such as a separation will remove the abutment to the traverse which is free to lift upwardly due to the expansion of the air compressed into the material, and eventually aided by the upward thrust of the hydraulic jacks l3 and 13, a thrust which can be varied according to the type of material which is treated. Accordingly, the material is free to expand, and the residual air therein can be exhausted.

The duration of the expansion and intermediate compression of material can be regulated via a timer (not shown), serving also for the second downward motion of the screw spindle 42.

When the screw spindle is lowered, controlled by the generator associated therewith, pressure is applied to the hole 24 through the conduit 25, but this time making use of the high-pressure fluid of the accumulator 32, controlled by the valve 34. The cylinder 22 will now carry out (FIG. 7) a second compression step, which is considerably stronger than the first one. As a result, the material is subjected to a further reduction in thickness, and the cylinder 22 carries out a stroke S which is usually shorter than the previous stroke S, thus further increasing the hardening of the material.

Generally, two compressions will be sufficient for obtaining the final hardening of the pieces, principally since the pressures of the first and of the second compressions can be adjusted both as regards the value and the duration of each compression; therefore, subsequent compressions can be avoided, as are otherwise often required for some types of materials. However, the novel press can carry out subsequent compressions if desired, i.e. compressions after the second one, if it is provided with a suitable hydraulic circuit as shown in FIG. 3.

, After the second compression (assuming that no others are required), oil is discharged through the hole 24, the screw spindle 42 executes an upward motion, the hydraulic jacks 12 and 12' are pressurized, and therefore the traverse 6 will move upward, overcoming the thrust imparted by jacks l6 and 16 and stopping against the members 18, thus becoming positioned again as shown in FIG. 1. The compression cycle is now complete and the press is available for a subsequent cycle.

According to the embodiment of FIG. 8 the hydraulic device 21, also comprising the cylinder 22 mounted on the traverse 6, and the plunger 22, is of the singleacting type. The piston 23 has a counter impact member 54 with a ball-shaped seat, on which an impact member 55 with a ball-convex head rests, and which is retained in piston 23 by a plate 55'. The impact member 55 is supported by a traverse 56 to which it is secured by means of screws 57, and therefore said traverse can restraint the impact member 55 and also the piston 23, through the plate 55 screwed to said piston 23.

The small traverse 56 projects with two end portions transversely of the axis of piston 23, and at the ends of these two end portions two vertical pins 58 and 58' are mounted, being secured by means of

nuts

59 and 59, respectively. The upper ends of the

pins

58 and 58 are fitted with enlarged heads 59 and 59', respectively, and accommodated in

chambers

60 and 60, respectively, which are provided on the fixed traverse 5 of the press. The pins 58 and 58' are guided by

sleeves

61 and 62, respectively, which are housed into through-holes which respectively communicate the

chambers

60 and 60 with the lower face of the fixed traverse 5. The sleeves 61 and 61' serve to guide the

pins

58 and 58 for perfectly axial movement, so that they have no freedom of play.

The height of the heads 59 and 59', relative to the bottom of

chambers

60 and 60, when the mobile traverse 5 is at its upper position, is equal to the distance of the lower face of the upper plungers 7 from the surface of the matrix 62 of the mold 3. Therefore, when the mobile 6 is lowered, the

heads

59 and 59 will rest against the bottom walls of the

chambers

60 and 60, respectively, at the same time at which the plungers 7 will reach or nearly reach the level of the matrix surface 62 (compare FIG. 14).

Accordingly, the rest position of

heads

59 and 59 defines a stopping position for the small traverse 56 and therefore of the plunger 23; however, the cylinder 22 and the mobile traverse 6 are free to continue their downward movement, in a manner which will be explained further hereinafter.

The small traverse 56, as illustrated in FIGS. 8 and 10, is provided with a first serrated lower member 63a comprising a plate portion 63 and modular teeth 63 projecting therefrom, the teeth being of round sector section and having side walls which are perfectly plane and vertical with respect to the base plate 63.

An upper serrated member 64a, also having a plate portion 64 and modular teeth 64' which are directed downwards, is provided opposite the lower member 63a, the teeth 63 and 64' being so configurated that they can mesh. The teeth 63 surround an internal space into which acylindrical portion 65 can enter. The latter is provided on the upper member 64a and the internal flanks of the teeth 64 terminate at the portion 65.

The upper serrated member 64a has a coaxial collar 66 engaged by a vertical rod 67 and terminating above the fixed traverse 5. A member 68 (FIGS. 8 and 9) is keyed to rod 67 and has two

teeth

69 and 70 angularly separated by an angle d. The member 68 can be moved angularly by means of a hydraulic jack 71 of the double-acting type, in a manner such that it is brought towards two opposite angular positions, which correspond to the interference of the

teeth

69 and 78, and of an intermediate abutment 72.

The angular travel permitted by the abutment 72 is similar to that of the teeth 64' of the upper serrated member 64a, extending from a position wherein the teeth 64' are located opposite and coaxial to the teeth 63' of the lower serrated member 63a, to a position wherein the teeth of the two members are offset in such a manner that they can mesh to thereby allow the two

members

63a, 64a to get quite close.

When the mobile traverse 6 is in upper position similar to that shown in FIG. 1 the

teeth

63 and 64 are in mesh. The length of the teeth 63, or at least of that portion of them which enters the spaces between the teeth 64' with the traverse 6 in upper position, is equal to the distance between the upper plungers 7 and the surface of the matrix 62, and thus, when the mobile traverse 6 is lowered to a point where the upper plungers 7 are in line with the matrix 62, the teeth 63' will be entirely withdrawn from teeth 64' and the upper serrated member 64a is thus free to rotate, bringing the teeth 64' opposite the teeth 63'.

The upper serrated member 64a is supported by the rod 67, and is mounted on the fixed traverse via a bushing 73, thus relieving the compression stresses as transmitted to the traverse 5 by the hydraulic device 21.

FIG. illustrates the hydraulic circuit which feeds the hydraulic device 21. There is provided an electric motor 74 driving two

pumps

75 and 76. The pump 75 is suitable for supplying oil under low pressure, while pump 76 is suitable for supplying oil under high pressure. A conduit 77 communicates with the pump 75 and supplies pressurized fluid to an accumulator 79 via a one-way valve 78', a piloted non-return valve 80 is interposed in conduit 77 whose operation is controlled by an electric valve 81. A second one-way valve 82 has the purpose of preventing the pressurized oil fed by the pump 76, from entering the pump 75. The conduit 77 communicates with a conduit 83, which latter feeds the hydraulic device 21.

The supply conduit 84 from the high-pressure pump 76 has interposed in it a first one-way valve 85 and a piloted second one-way valve 86; the operation of the latter is controlled by an electric valve 87. A pressure compensating unit 88 is also fed through conduit 84. The conduit 84, after the valve 86, connects with the conduit 77 for feeding the conduit 83. The

conduits

77 and 84 are moreover provided with

over-pressure safety valves

77 and 84, respectively- The conduit 83, via a check valve 89 piloted (i.e., controlled) by an electric valve 90, communicates with a free-surface fluid tank 91 which in turn is connected to the common discharge post of the apparatus. The electric valves 81 87 and 90 are connected to a conduit 92 which in addition supplies the hydraulic jack 71, via an electric valve 93. The conduit 92 is fed with fluid by the low-pressure pump 75, through a transversal conduit 94 which connects the conduit 77 to the conduit 92.

The tank 91 (FIG. 1) is generally arranged at the uppermost part of the press, and it serves for delivering oil into the hydraulic device 21, when a suction is generated within the chamber of said hydraulic device (in a manner which will be explained further hereinafter).

The operation of the press above described will be better understood with reference to FIGS. 8, 11, 12, 13, 14.

In operation, the pairs of hydraulic jacks 12 12, 16 16, 13 13', 17 17' will operate exactly as described with reference to FIGS. 1 to 7, and therefore no description need here be given about the action of these jacks concerning the mobile traverse 6.

Now considering FIG. 8, at the start of each single compression cycle the mobile traverse 6 descends, and the hydraulic device 21, the small traverse 56, the pins 58 and the lower serrated member 63a will move downwards. At the moment on which the upper plungers 7 are just in line with matrix 62 (FIG. 11), the

heads

59 and 59 of the

pins

58 and 58, respectively, will contact the bottom walls of the

chambers

60 and 60, respectively, thus stopping the downward motion of the small traverse 56, of the impact member 55 and of the plunger 23. At the same instant, the lower serrated member 63a has disengaged its teeth 63 entirely from the teeth 64- of the upper serrated member 64a. However, stopping of the movement of piston 23 does not cause stopping of the mobile traverse 6 and of cylinder 22, which are still free to continue their downward stroke, thus permitting the plungers 7 (FIG. 12) to enter the cavity of matrix 62 and to compress the material arranged therein, until the reaction of the compressed material is sufficient for stopping further downward movement of the mobile traverse 6 and the cylinder 22. During this first compression step, as illustrated in FIG. 11, the volume of chamber 19 of the hydraulic device will expand to a value 111 (see FIG. 12), thus generating a suction which in turn will cause an aspiration of oil from the tank 91 through the one-way valve 89. At this moment, as illustrated in FIG. 12, the hydraulic jack 71 is actuated so as to make the serrated member 64a rotate, and thus the teeth 64 are brought opposite the teeth 63, thus preventing meshing or engagement thereof.

It should be noted, (see FIG. 12), that when the teeth 64. are brought opposite the teeth 63' the piston 23 is blocked to the fixed traverse 5, that is, it cannot be further lowered or lifted up, and therefore the different compressions steps are carried out through the movement of cylinder 22 only.

Once the operations illustrated in FIG. 12 are completed, the first compressions step is carried out, by delivering to chamber 19 the low pressure oil supplied by the pump 75; for this purpose the valve is opened by means of the electric valve 81. During the first step, the volume of chamber 19 (FIG. 13) will expand again to a value I12 with a very quick pressurization, this being due to the assistance given by accumulator 79, and to the fact that the chamber 19 was still filled with the fluid aspirated during the step of FIG. 12.

When the first compression step is completed, the piloted valve 89 is opened just for an instant, thus discharging a very small amount of oil to the tank 91, just sufficient to drop the pressure in the chamber 19 which still maintaining the chamber filled with fluid.

The second compression step is then carried out (FIG. 14), by delivering to the cylinder pressurized oil supplied by the pump 76 through one-way valve and as a result of opening the piloted valve 86 by means of the electric valve 87. In this instance also, the pressurization of the chamber 19 is prompt, since said chamber is still filled with oil, and further delivery of oil is facilitated by the accumulator 88. Thus a further in crease in the volume of chamber 19 takes place, up to a maximum value of I133.

The second compression step is now completed.

It should be observed that the values hl, I22 and 113 of the chamber 19 correspond to the respective reductions in the thickness of the materials being compressed.

When the second compression step, or eventual further compression steps, are completed, the compression cycle is ended and therefore the oil in chamber 19 is discharged entirely, or partially, by opening the oneway valve 89 via the electric valve 90, while the upper serrated member 64a is made to rotate in direction opposite to its previous rotation, thus offsetting the teeth 64 with respect to the teeth .63. The hydraulic jacks l2 and 12 are pressurized and thus the mobile traverse 6 is lifted to the upper position. During this movement, the piston 23 will move within the cylinder 22 for decreasing the volume of the chamber 19, thus forcing the fluid from the latter and into the tank 91, reinstating the assembly to the starting condition as illustrated in H6. 8.

Of course, the invention may be realized in other forms; in fact, both in the case of FIG. 1 and in the case of FIG. 8 the hydraulic device 21 can also be arranged on the mobile traverse in a position in which it is turned l 80 from the illustrated positions, so that the piston 23 will influence the traverse while the cylinder is directed to the fixed traverse. Also the molds used with the press need not be of the type when plungers enter the mold cavity; instead, they could be of the type wherein the upper plungers are larger than the mold cavity and carry out the compression by forcing the matrix downward, in a manner known in the art of molds for the manufacturing of ceramic articles.

I claim:

1. A press, particularly for making ceramic articles, comprising a support structure; a mold on said support structure; a mobile traverse mounted on said support structure above said mold for vertical movement toward and away from the latter; plungers on said traverse and positioned to enter into said mold in response to movement of said traverse toward said mold; a hydraulic unit carried by said traverse and operative for exerting pressure via the same on said plungers when the latter are in said mold; and adjustable abutment means mounted on said support structure in engagement with said hydraulic unit, said abutment means being movable with said traverse relative to said support structure to a plurality of positions in each of which it is stationary with reference to said support structure and constitutes a mobile reaction point for said hydraulic unit when said hydraulic unit exerts pressure on said plungers via said traverse.

2. A press as defined in claim 1; further comprising hydraulic means operatively associated with said hydraulic unit for initially supplying to the same hydraulic fluid at a lower pressure and for thereupon supplying to said hydraulic unit hydraulic fluid at a higher pressure.

3. A press as defined in claim 1, wherein said hydraulic unit comprises a double-acting cylinder-and-piston device.

4. A press as defined in claim 1, wherein said hydraulic unit comprises a single-acting cylinder-and-piston device.

5. A press as defined in claim 1; and further comprising hydraulic jacks engaging said traverse and operative for lowering and raising the same towards and away from said mold, respectively.

6. A press, particularly for making ceramic articles, comprising a support structure; a mold on said support structure; a mobile traverse on said support structure above said mold and mounted for vertical movement toward and away from the latter; plungers on said traverse and positioned to enter into said mold in response to movement of said traverse toward said mold; a hydraulic unit carried by said traverse and operative for exerting pressure via the same on said plungers when the latter are in said mold; abutment means mounted on said support structure for movement in unison with said traverse and for engaging said hydraulic unit so as to provide'a mobile reaction point for the latter when said hydraulic unit exerts pressure on said plungers via said traverse; hydraulic jacks engaging said traverse and operative for lowering and raising the same towards and away from said mold, respectively; first additional hydraulic jacks operable for exerting downward pressure on said traverse in direction towards said mold; and variable-pressure second additional hydraulic jacks operable for exerting a lesser upward pressure on said traverse in opposition to said downward pressure.

7. A press as defined in claim 6, said support structure comprising adjustable means for adjusting the maximum vertical distance of said traverse from said mold.

8. A press as defined in claim 7, wherein said adjustable means comprises normally extended retractable auxiliary hydraulic jacks.

9. A press, particularly for making ceramic articles, comprising a support structure; a mold on said support structure; a mobile traverse on said support structure above said mold and mounted for vertical movement toward and away from the latter; plungers on said traverse and positioned to enter into said mold in response to movement of said traverse toward said mold; a hydraulic unit carried by said traverse and operative for exerting pressure via the same on said plungers when the latter are in said mold; and abutment means mounted on said support structure for movement in unison with said traverse and for engaging said hydraulic unit so as to provide a mobile reaction point for the latter when said hydraulic unit exerts pressure on said plungers via said traverse, said abutment means comprising a tapped element above said traverse, and a threaded spindle with self-locking threads threaded into said tapped element to extend vertically and coaxially with reference to said hydraulic unit and having a lower end portion for engaging the latter.

10. A press as defined in claim 9, said abutment means further comprising motor means operatively associated with said spindle for turning the same in a sense advancing or retracting said lower end portion with reference to said hydraulic unit.

11. A press as defined in claim 10, said hydraulic device including a cylinder and a piston slidable in said cylinder, said piston having an upwardly directed enface positioned for engagement by said spindle.

12. A press as defined in claim 10, said hydraulic device including a cylinder and a piston slidable in said cylinder, said cylinder having an upwardly directed exposed endface positioned for engagement by said spindle.

13. A press, particularly for making ceramic articles, comprising a support structure; a mold on said support structure; a mobile traverse on said support structure above said mold and mounted for vertical movement toward and away from the latter; plungers on said traverse and positioned to enter into said mold in response to movement of said traverse toward said mold; a hy draulic unit carried by said traverse and operative for exerting pressure via the same on said plungers when the latter are in said mold, said hydraulic unit including a cylinder element and a piston element slidable in said cylinder element; abutment means mounted on said support structure for movement in unison with said traverse and for engaging said hydraulic unit so as to provide a mobile reaction point for the latter when said hydraulic unit exerts pressure on said plungers via said traverse; and additional abutment means for terminating the movement of one of said elements with said traverse towards said mold in response to said plungers reaching a predetermined position relative to said 16. A press as defined in claim 15, said abutment means comprising two serrated coaxial members having facing teeth, one of said members being rotatably journalled on said support structure, and the other of said members being located on said hydraulic device, said members together providing said mobile reaction point when the teeth of said members are in opposed relationship and are thus prevented from meshing.

Claims

6. A press, particularly for making ceramic articles, comprising a support structure; a mold on said support structure; a mobile traverse on said support structure above said mold and mounted for vertical movement toward and away from the latter; plungers on said traverse and positioned to enter into said mold in response to movement of said traverse toward said mold; a hydraulic unit carried by said traverse and operative for exerting pressurE via the same on said plungers when the latter are in said mold; abutment means mounted on said support structure for movement in unison with said traverse and for engaging said hydraulic unit so as to provide a mobile reaction point for the latter when said hydraulic unit exerts pressure on said plungers via said traverse; hydraulic jacks engaging said traverse and operative for lowering and raising the same towards and away from said mold, respectively; first additional hydraulic jacks operable for exerting downward pressure on said traverse in direction towards said mold; and variable-pressure second additional hydraulic jacks operable for exerting a lesser upward pressure on said traverse in opposition to said downward pressure.

13. A press, particularly for making ceramic articles, comprising a support structure; a mold on said support structure; a mobile traverse on said support structure above said mold and mounted for vertical movement toward and away from the latter; plungers on said traverse and positioned to enter into said mold in response to movement of said traverse toward said mold; a hydraulic unit carried by said traverse and operative for exerting pressure via the same on said plungers when the latter are in said mold, said hydraulic unit including a cylinder element and a piston element slidable in said cylinder element; abutment means mounted on said support structure for movement in unison with said traverse and for engaging said hydraulic unit so as to provide a mobile reaction point for the latter when said hydraulic unit exerts pressure on said plungers via said traverse; and additional abutment means for terminating the movement of one of said elements with said traverse towards said mold in response to said plungers reaching a predetermined position relative to said mold, while permitting continued movement of the other element.

14. A press as defined in claim 13, wherein said piston element and said cylinder element define with onE another an internal chamber whose volume changes in response to relative movement of said elements; and further comprising a fluid-containing tank communicating with said internal chamber.

15. A press as defined in claim 14, said additional abutment means comprising a pair of parallel vertical pins arranged to cooperate with said one element and with a stationary component of said support structure.

16. A press as defined in claim 15, said abutment means comprising two serrated coaxial members having facing teeth, one of said members being rotatably journalled on said support structure, and the other of said members being located on said hydraulic device, said members together providing said mobile reaction point when the teeth of said members are in opposed relationship and are thus prevented from meshing.