US3796251A

US3796251A - Machine for manufacturing shell moulds for lost-pattern precision casting

Info

Publication number: US3796251A
Application number: US00173866A
Authority: US
Inventors: P Jasson; P Chatourel
Original assignee: Peugeot & Renault
Priority date: 1970-09-15
Filing date: 1971-08-23
Publication date: 1974-03-12
Anticipated expiration: 1991-03-12
Also published as: DE2145929C3; SU419012A3; DE2145929A1; DE2145929B2; FR2104999A1; GB1353402A; FR2104999B1; JPS51148411U; JPS5320497Y2

Abstract

A machine for the manufacture of lost-pattern shell-moulds for precision casting, comprising a plurality of eliminable central pattern armatures or a group of eliminable patterns, each fixed on an operating head by means of which the pattern or cluster is successively dipped into immersion tanks of liquid refractory slurry and of refractory grains in fluidized suspension, in which the armature is rotatably mounted about three axes of rotation, the first being the vertical axis of a roundabout carrying operating heads on frames and bringing the heads by a discontinuous movement on rotation, successively above the various tanks located round the roundabout, the second axis of continuous rotation coinciding substantially with that of the armature and the third axis, perpendicular to the second, passing through the center of a circumference to which the second axis is tangential, the armature being external to the circumference while the roundabout, each armature and each operating head are respectively driven by first, second and third motors, the first and third motors being controlled automatically in such manner that the rotation of the armatures and their operating heads about their third axis is an angularly limited pivotal movement sufficient to dip the pattern or the cluster of patterns into each tank and to remove them from the tanks during the interruptions in the rotation of the roundabout.

Description

United States Patent [191 Jasson et al.

[ 1 MACHINE FOR MANUFACTURING SHELL MOULDS FOR LOST-PATTERN PRECISION CASTING [75] Inventors: Philippe Jasson; Pierre Chatourel,

both of Billancourt, France [73] Assignees: Regie Nationale Des Usines Renault Billancourt; Automobiles Peugeot, Paris, both of, France [22] Filed: Aug. 23, 1971 [21] Appl. No.: 173,866

[30] Foreign Application Priority Data Primary Examiner-J. Spencer Overholser Assistant Examiner-John E. Roethel Attorney, Agent, or Firm-Stevens, Davis, Miller & Mosher Mar. 12, 1974 [5 7] ABSTRACT A machine for the manufacture of lost-pattem'shellmoulds for precision casting, comprising a plurality of eliminable central pattern armatures or a group of eliminable patterns, each fixed on an operating head by means of which the pattern or cluster is successively dipped into immersion tanks of liquid refractory slurry and of refractory grains in fluidized suspension, in which the armature is rotatably mounted about three axes of rotation, the first being the vertical axis of a roundabout carrying operating heads on frames and bringing the heads by a discontinuous movement on rotation, successively above the various tanks located round the roundabout, the second axis of continuous rotation coinciding substantially with that of the armature and the third axis, perpendicular to the second, passing through the center of a circumference to which the second axis is tangential, the armature being external to the circumference while the roundabout, each armature and each operating head are respectively driven by first, second and third motors, the first and third motors being controlled automatically in such manner that the rotation of the armatures and their operating heads about their third axis is an angu- 19 Claims, 7 Drawing Figures PAIENTEBHAR 12 m4 3. 796' 251 SHEU 2 [IF 7 FIG) PATENTED "AB 1 2 I974 SHEET 3 0F 7 PATENIEBIARIZISM 3.796251 SHEET 6 [If 7 PATENTEUMAR 1 2 Ian 3; 796; 251

SHLEI 7 OF 7 MACHINE FOR MANUFACTURING SHELL MOULDS FOR LOST-PATTERN PRECISION CASTING The present invention relates to a machine for the manufacture of lost-pattern shell-moulds for precision casting, comprising a plurality of eliminable central pattern armatures or a cluster of eliminable patterns, each fixed on an operating head by means of which the pattern or the cluster is successively dipped into immersion tanks of liquid refractory slurry and refractory grains in fluidized suspension.

The succession of layers obtained by immersion in the slurry and sprinkling with refractory grains, combined with hardening of these layers by natural drying or chemical reaction forms round the patterns a shell of refractory material which, after elimination of the patterns, will constitute the mould.

The fragility of lost patterns, generally composed of hard-and fragile materials, has up to the present time been a major obstacleto the mechanization of these immersion and coating operations for moulds, together with the necessity of obtaining thicknesses of layers which are as uniform as possible, by manipulation of the moulds associated with a constant visual control of the distribution of the refractory products over their surface.

On the other hand, manual execution of these operations severely restricts the capacity of production and also the quality and the reproducibility of the work, in view of the importance of the human factor in its execution.

In addition, the clusters of patterns, taking into account their large weight, as soon as the first layers have been applied, are held suspended vertically by the operators when they are plunged into the tanks of slurry or the fluidized beds for adding the grains. This results in layers of liquid deposits which are thicker at the lower extremity than close to the operating handles and conversely, as a result of a larger erosion effect, layers of grains which are thinner at the extremities than close to the handles.

In spite of vertical overturning movements of the clusters and alternating rotation about their axis by a corresponding rotation of the handle, in order to make the thickness of the layers as uniform as possible, these layers remain heterogenous. In addition, these manipulations render the operation physically tiring,,in spite of the possible use of mechanical handling aids, such as balancers, which provide an additional source of irregularities in the composition of the moulds.

These irregularities in the composition of the moulds are a substantial cause of rejection, due to breaking of the mould during pouring or during their handling, or by casting defects in the parts due to variations of their conditions of solidification caused by variations in the thickness of the moulds.

The object of an application for a U.S. patent the present applicants, filed on June 15, 1971, Ser. No. 153,332 is a method which remedies these drawbacks by ensuring for the moulds, by entirely mechanical means, a combination of movements of rotation producing a plunging movement into the immersion tanks and in the fluidized beds.

According to this method, the armature is automatically rotated about three axes of rotation. The first is the vertical axis of a roundabout which, by a discontinuous movement of rotation, brings the operating head successively above the various tanks. The second axis of continuous rotation coincides substantially with that of the armature, and the third, perpendicular to the second, passes through the center of a circumference to which this second axis is tangential, the armature being external to the said circumference. The rotation about the third axis is an angularly limited pivotal movement which is however sufficient to dip the pattern or the cluster' of patterns into each tank and remove them from the tank during the interruption in rotation of the said roundabout.

The result of this combination of movements of rotation rotation of the mould about its axis, added to a rotation about a horizontal axis perpendicular to the axis of the mould and not passing through this axis, is that the mould passes into and is removed from the baths of slurry and the fluidized beds with a sweeping movement which is at the same time axial and rotary,

along the constantly variable inclinations of the mould,

which ensures a uniform distribution of the products over the whole surface. The. raised position of the mould corresponds to its draining and handling position between one tank to the other.

The pivotal movement is advantageously effected between the dipping position, during which the armature is orientated downwards, the second axis being then substantially vertical, and the drainage position during which the armature is obliquely orientated upwards, the angle swept out by the armature being less than 180.

According to this method, the patterns are fixed on the operating heads by fitting their tubular central armature on a fixing rod which locks the said armature in position by the inflation of deformable bearing surfaces which expand under the continuous action of elastic means, a compensation of these elastic means permitting the release of the expandable bearing surfaces and the removal of the moulds produced on the patterns.

The object of the present invention is a machine which enables the method described aboveto be carried into effect.

In addition to the great flexibility of adjustment of the various movements required for the. handling of fragile moulds, an important problem is that of the very difficult ambient conditions for a machine of this kind. The atmosphere of abrasive dust produced by the turbulence of the fluidized beds presents an operating problem of long duration for mechanical apparatus. The machine according to the invention has therefore also been designed with the object of resisting these conditions.

Of the same kind as that referred to in the beginning of the present description, the machine according to the invention is characterized by the fact that each armature is rotatably mounted around three axes of rotation, the first of which is the vertical axis of a roundabout carrying, through the intermediary of frames,

the operating heads'and bringing the latter by a disconthe roundabout, each armature and each operating head are respectively driven by a first, a second and a third motor, the first and the third of which are controlled automatically in such manner by control devices that the rotation of the armatures and their operating heads about their third axis is an angularly limited pivotal movement which is however sufficient to dip the pattern or the cluster of patterns into eachtank and to remove them from the said tank during the interruptions in the rotation of the said roundabout.

According to one form of embodiment of the invention, the roundabout comprises a circular platform mounted for free rotation about a fixed vertical column supported by a base, centered on the first axis and on the upper part of which are fixedly mounted the three motors, each connected to a driving element of a temporary coupling located in the horizontal circular path of engagement of the driven elements which are rigidly fixed to the operating heads by means of pivots centered on the third axes, while the platform is driven by a roller applied against-its external edge and con nected to the first motor.

The motors and control members of the machine will advantageously be hydraulic.

The great flexibility and facility of adjustment of the hydraulic control systems permit very sensitive operating adjustments to be made, compatible with the fragility of the moulds. Similarly, the speeds of rotation of the various movements may be easily regulated and can vary following an established program.

The complete automation of the moulding operations thus obtained together with the combination of the dipping and draining movements leads to a quality and a uniformityof the shells which cannot be achieved by manual methods, together with a production capacity compatible with the largest mass-production lines.

The invention further extends to the details of construction brought out in the description which follows below of one example of construction of the machine, this description being made with reference to the accompanying diagrammatic drawings, in which FIG. 1 is a general view in perspective of a machine with four stations, two for dipping and two for powdering by fluidized beds, arranged alternately on the circumference.

FIG. 2 is a plan view of the machine.

FIG. 3 shows a part of the machine seen in partial cross-section taken along the line IIIIII of FIG. 2.

FIG. 4 is a view in cross-section of an operating head pivot, of its driving device and its frame.

FIG. 5. shows a third motor, seen in cross-section, taken along the line VV of FIG. 3.

FIG. 6 shows an operating head provided witha cluster of patterns in course of production, seen in crosssection taken along the line VIVI of FIG. 4.

FIG. 7 is a plan view of the first motor and its driving roller.

As can be seen from the diagrammatic perspective view shown in FIG. 1, the machine according to the invention comprises essentially operating heads 1, four in number in the case of the example shown, mounted on a central roundabout, the platform 2 of which is surrounded by fluidized bed tanks 3 and immersion tanks 4, the assembly being mounted on a common base-plate 5. On the rotating platform 2 are mounted frames 6 supporting the operating heads 1. Driven by a first motor 15, this platform ensures, by successive rotations through about a first central vertical axis 7, the conveyance of the assemblies of clusters of patterns 8 and operating heads 1 from one work station to another, at which it is locked during the dipping operations of the clusters 8.

These clusters are mounted on the operating heads 1 by engaging their tubular central armatures 9 on the fixing rod 11, having clamping bearing surfaces expansible by compression of deformable surfaces 10 constituted for example by rubber rings kept continuously compressed in the state of rest (controls not operated) by elastic meanss 12 (not shown) located in the spindle of the head 1.

The operating heads 1 are each equipped with a second motor 16, ensuring for the moulds 8 in course of formation a continuous rotation about a second axis 13 which corresponds to their fixing axis, together with a partial rotation through an angle a about a third horizontal axis 14, perpendicular to the axis 13 and staggered with respect to this axis. This partial rotation, obtained by means of third motors 17, brings the mould 8 into the substantially vertical position shown at 8 (FIG. 6) at which it plunges fully into the immersion or powdering tanks, after having ensured its progressive penetration following a downward movement with rotation and a constant variation of inclination. The mould is then brought back, by reverse rotation through the angle a, into a reversed oblique lifting position 8 at whiclithe drainage of the excess liquid or of the excess grains is effected before the movement of a quarter-turn of the whole unit above the following tank (FIG. 6).

By varying the waiting time and the speed of movement, together with the number of sequences corre' sponding to the number of coatings applied, the method may be adapted to various types of moulds and there may be obtained in a repetitive manner for each of them the dipping program which corresponds to the best conditions.

The details of construction of the machine, the principle and operation of which have just been described in a very general manner, will now be described with reference to the example of construction shown in FIGS. 2 to 7.

The machine shown is essentially driven and controlled by hydraulic-elements which presents numerous advantages with respect to the flexibility of the movements and reliability of operation.

The platform 2 is mounted on

bearings

18,19 and 20,

and rotates freely about a vertical fixed column 21 mounted on the base-plate 5. A central tubular element 22 surrounds the column, so that the

bearings

18 and 19 are protected by this element while the bearing 20 is protected by-the platform 2.

On the upper portion of the column 21 are fixed four supports 23 each carrying a third motor 17 connected to a driving element 24 of a temporary coupling, located in the horizontal circular path of engagement of the driven elements 25. These latter are rigidly fixed One of the coupling elements constitutes one of the arms 21 of a lever 30 mounted to oscillate on a shaft 31 perpendicular to the pivotal axis of the element in a driving sheath 32 rotatably mounted in a casing 33 fixed on the support 23. The other arm 34 of the lever 30 is provided with a counterweight 35 which compensates the weight of the jaws 27 which constitute the arm 29. A restoring member consisting of a magent 36 fixed in the sheath 32 and another opposite magnet 37 fixed on the extremity of the arm 34 urges the lever 30 into a coaxial position with respect to the sheath 32 (FIG. 4).

The third motors 17 are double-acting jacks, the piston rod 38 of which is rigidly fixed to a toothed rack 39 engaging with a toothed ring 40 rigidly fixed for rotation to the sheath 32 (see FIG. 5). i

For the purpose of braking the final pivotal movement of the operating heads 1, the pivots 26 of these latter, rotatably mounted in the frames 6, are provided with a braking pulley 31 connected by a cable 42 to the piston rod 43 of ajack 44 constituting a pneumatic spring fixed on the corresponding frame 6 (see FIG. 4) and supplied with fluid through the intermediary of a set of rotary joints 45 provided round the fixed column 21 (see FIG. 3).

Fixed on the pivot 26, the operating heads 1 are provided with second motors 16 (fluid-tight rotary) driving the fixing rods 11 for the central armatures 9 of the patterns or clusters of patterns. 8. The spindle of the operating head 1 comprises a compensating jack (not shown), the action of which is capable of opposing that of the elastic means which keep under compression the deformable bearing surfaces of the fixing rods 11.

The motors 16 and the compensating jacks are supplied with driving or control fluid by means of the set of rotary joints 45 (see FIG. 3), of another set of rotary joints 46 provided in the frame 6 round thepivot-26 (see FIG. 4), and of axial conduits 47 formed in the pivot 26 (see FIG. 6).

It will be noted that the joints 45 are protected by a skirt 48 formed by the supports 23 which surround the column 21 (see FIG. 3). Furthermore, the fixing rods 11 are provided at their base with a drainage collar 49 protecting the spindle of the operating heads 1 when they are lifted.

Distributors 50 (see FIG. 2) mounted on the platform 2 and controlled by sliding rods, the extremities of which are located in the path of a fixed cam (not shown), are intercalated in such manner in conduits coupling together the two sets of rotary joints 45 and 46 that they permit the supply of driving fluid. either to the compensating jacks of the operating heads 1 or to the second motors 16 of these heads.

The discontinuous rotation of the platform 2 is effected by a driving unit 51 capable of pivoting horizontally about a fixed vertical axis 52 rigidly fixed to the base 5.

This unit comprises a rotary fluid motor (first motor) driving by means of a gear (not shown) a roller 53 with a vertical axis capable of bein applied against a rolling track 54 provided on the outer edge of the platform 2 (see FIG. 7).

A hydraulic jack 55 is articulated by its cylinder on the base 5 and by the extremity of its piston rod on the driving unit 51, the position of the jack 55 with respect to the unit 51 and to the pivotal point of this latter being such that this jack enables the unit 51 to pivot so as to apply the roller 53 against the rolling track 54, or to move it away from this track.

When the patterns or clusters of patterns are dipped into the tanks 3 and 4, it is advantageous to lock the platform 2 in this manner so that it cannot accidentally make a movement of rotation.

To this end, a hydraulic jack 56 constituting a fifth motor, fixed on the base, actuates a locking device comprising an element capable of being engaged in a housing formed in another element. The element 57 connected to the piston rod of the jack 56 is arranged so as to slide radially with respect to the roundabout, and the other element 58 is provided at a number of peripheral points on the platform in such manner that the sliding element 57 is located facing a corresponding element 58 on the platform 2 as soon as the roller 53 has moved away from the edge of'the platform.

As can be seen, the first motor 15 driving the roundabout, the third motors 17 causing the pivotal movement of the operating heads 1, the fourth motor 55 controllingthe pivotal movement of the driving unit 51 and the fifth motor 56 ensuring the locking action, do not rotate with the platform 2 and are directly connected to fluid conduits outside the roundabout. Only the second motors 16 driving the patterns or clusters of patterns in rotation, the compensating jacks in the spindles of the operating heads 1 and the jacks 44 constituting the pneumatic spring aresupplied through the intermediary of the sets of rotary joints 45 communicating with the external source or sources of fluid by axial passages provided in the fixed vertical column 21.

As in any modern automatic installation, and irrespective of the nature of the source of energy employed, the motors providing the movements of the various mobile elements of the machine are controlled, with a view to obtaining an automatic cycle of operation comprising a number of successive operations, by mean of detectors mounted in such manner, known per se, in the path of the moving elements carrying out the operations, that they initiate the next following operation from a pre-determined position of these mobile elements. In the case of the example of construction shown, there are provided, among others, electronic proximity detectors. Such a detector 59 fixed on the casing 33, reacting in the presence of a moving metallic blade 60 rigidly fixed to the pivoting sheath 32, and co-operating with the control of a third motor 17, has been shown by way of example in FIG. 4.

Finally, with a view to increasing advantageously the flexibility of operation of the machine, the platform 2 and the driving coupling element 27 are rigidly fixed for rotation with cams co-operating with rods controlling deceleration members interposed in the supply circuits respectively of the first and

third motors

15 and 17. A cam of this kind 61, rigidly fixed to the sheath 33 acting through the intermediary of a rod 62 pro vided with a roller 63 on a deceleration member 64,

constituted by a throttling device inserted in the supply conduit of the jack 17, has been shown in FIG. 4.

In addition, the machine according to the invention may be associated with a fluid-tight electronic control cubicle receiving for example the signals emitted by the electronic proximity detectors and supplying the impulses controlling the operation of the various motors. It is clear that a cubicle of this kind permits programmed automatic working of the machine.

Furthermore, while considering that the use of hydraulic or pneumatic motors offers optimum reliability and flexibility of operation, electric motors or jacks for example could be employed.

What we claim is:

1. A machine for manufacturing lost-pattern shell moulds, comprising a plurality of eliminable central pattern armatures or a cluster of eliminable patterns, each fixed on an operating head for successively dipping each pattern or cluster into immersion tanks of liquid refractory slurry and of refractory grains in a fluidized suspension, each armature being rotatably mounted about three axes of rotation, the first of which is the vertical axis of a roundabout to which said operating heads are attached by frames, said roundabout comprising a circular platform mounted for free rotation about a fixed vertical column supported by a base plate for bringing said operating-heads by a discontinuous movement of rotation successively above a plurality of tanks which are located around said roundabout, the second of said three axes being an axis of continuous rotation coinciding substantially with that of the armature, said machine being characterized in that the third of said three axes is perpendicular to the second and passes through the center of a circle to which said second axis is tangential, being on said second axis at a point beyond the point of tangency to said circle, first, second and third motors for driving each armature and each operating head, said third motors fixedly mounted on the upper part of said roundabout and each connected to a'driving element of a temporary coupling located in the horizontal circular path of engagement of the driven elements which are rigidly fixed to the operating heads by means of pivots centered on the third axes, a roller applied against the outer edge of the circular platform and connected to the first motor for driving said platform, and control devices for automatically controlling each first and third motor for rotating said armatures and operating heads about their third axis through an are limited to less than 180 and including a position wherein the second axis is substantially vertical, for dipping each pattern or cluster of patterns into each tank and for removing same from each tank during the interruptions in the rotation of said .roundabout about said first axis.

2. A machine in accordance with claim 1, characterized by the fact that the platform comprises a central tubular element surrounding the said column and that it is mounted on bearings protected by'the said platform and the tubular element.

3. A machine in accordance with claim 1 characterized by the fact that one of the driving elements of the couplings is a pair ofjaws, the opening of which is horizontal during the rotation of the roundabout, while the other driving element comprises two horizontally aligned rollers, one alongside the other during this rotation for engaging said jaws in said position.

4. A machine in accordance with claim 3, characterized by the fact that one of the coupling elements constitutes one of the arms of a lever mounted to oscillate about an axis perpendicular to the pivotal axis of the element in a driving sheath driven by a third motor, the other arm being provided with a counter-weight, and

a restoring member interposed between this latter arm the armature and the said sheath for urging the lever into a coaxial position with respect to thesheath;

5. A machine in accordance with claim 4, characterized by the fact that the said restoring member comprises two opposite magnets, one of which is fixedon the sheath and the other on the extremity of the free arm of the said lever.

6. A machine in accordance with claim 1 characterized by the fact that the pivots of the operating heads are provided with a braking pulley coupled to a pneumatic spring controlled and fixed on the corresponding frame.

7, A machine in accordance with claim 1, characterized by the fact that in order to produce the discontinuous drive of the said platform, the first motor and the roller are pivotally mounted on the base in a horizontal plane, afourth motor being adapted to cause them to pivot to a limited extent in one direction for the purpose of applying the roller against the outer edge of the platform, and in the other direction for moving the said roller away from this edge.

8. A machine in accordance with claim 7 characterized by the fact that a fifth motor is fixed on the baseplate for actuating a locking device comprising an element for engagement in a housing formed in another element, one of the elements coupled to the fifth motor being radially slidable with respect to the roundabout, and the other provided at a number of peripheral points on the platform, so that the slidable element is located facing a corresponding element on the 'platform as soon as the roller has moved away from the edge of the platform.

9. A machine in-accordance with claim 8 characterized by the fact that the said motors are fluid motors.

10. A machine in accordance with claim 7 characterized by the fact that the first and second motors are rotary. motors.

'1 l. A machine in accordance with claim 8 characterized by the fact that the third, fourth and fifth motors are jacks, the moving part of the third motors being coupled to a toothed rack engaging with a toothed wheel rigidly fixed for rotation with the driving element of the coupling.

12. A machine in accordance with claim 11, characterized by the fact that the first, third, fourth and fifth motors are directly connected to driving fluid conduits outside said roundabout, the second motors and the pneumatic springs being coupled to driving fluid conduits rotating with the roundabout and supplied through the intermediary of rotary joints provided on the fixed vertical column.

13. A machine accordance with claim 12, characterized by the fact that the third motors are secured to the fixed column by means of a support constituting a skirt surrounding and protecting the rotary joints.

14. A machine in accordance with claim 1 characterized by the fact that the motors for ensuring the movements of the various movingelements of the machine are controlled, for the purpose of obtaining an automatic operating cycle comprising a plurality .of successive operations, by means of detectors mounted in such manner in the path of the moving elements which carry out the operations, that they initiate the next following operation from a predetermined position of the said moving elements.

15. A machine in accordance with claim 14, characterized by the fact that the detectors are selected from the group of apparatus consisting of electronic proximity detectors and earns.

16. A machine in accordance with claim 15, characterized by the fact that the platform and the driving coupling member are rigidly fixed for rotation with cams co-operating with rods for controlling deceleration members interposed in the supply circuits respectively of the first and third motors.

17. A machine in accordance with claim 16, characterized by the fact that it is associated with a fluidtight electronic control cubicle located in proximity to the machine and co-operating therewith for ensuring the automatic cycle of operation.

18. A machine in accordance with claim 1, characterized by the fact that the operating heads comprise fixing rods of central armatures, the said rods having deformable bearing surfaces expansible under the continuous action of elastic means, while a compensating jack is mounted in the operating heads acting in opposition to the said elastic means, in order to permit the liberation of the corresponding central armature.

19. A machine in accordance with claim 9, characterized by the fact that distributors mounted on the said platform, controlled by sliding rods the extremities of which are located in the path of a fixed cam, and supplied with driving fluid through the intermediary of rotary joints provided on the fixed central column, are coupled in such manner to the compensating jacks and to the second motors that they permit the alternative supply either to the compensating jacks or to the second motors.

Claims

1. A machine for manufacturing lost-pattern shell moulds, comprising a plurality of eliminable central pattern armatures or a cluster of eliminable patterns, each fixed on an operating head for successively dipping each pattern or cluster into immersion tanks of liquid refractory slurry and of refractory grains in a fluidized suspension, each armature being rotatably mounted about three axes of rotation, the first of which is the vertical axis of a roundabout to which said operating heads are attached by frames, said roundabout comprising a circular platform mounted for free rotation about a fixed vertical column supported by a base plate for bringing said operating heads by a discontinuous movement of rotation successively above a plurality of tanks which are located around said roundabout, the second of said three axes being an axis of continuous rotation coinciding substantially with that of the armature, said machine being characterized in that the third of said three axes is perpendicular to the second and passes through the center of a circle to which said second axis is tangential, the armature being on said second axis at a point beyond the point of tangency to said circle, first, second and third motors for driving each armature and each operating head, said third motors fixedly mounted on the upper part of said roundabout and each connected to a driving element of a temporary coupling located in the horizontal circular path of engagement of the driven elements which are rigidly fixed to the operating heads by means of pivots centered on the third axes, a roller applied against the outer edge of the circular platform and connected to the first motor for driving said platform, and control devices for automatically controlling each first and third motor for rotating said armatures and operating heads about their third axis through an arc limited to less than 180* and including a position wherein the second axis is substantially vertical, for dipping each pattern or cluster of patterns into each tank and for removing same from each tank during the interruptions in the rotation of said roundabout about said first axis.

2. A machine in accordance with claim 1, characterized by the fact that the platform comprises a central tubular element surrounding the said column and that it is mounted on bearings protected by the said platform and the tubular element.

3. A machine in accordance with claim 1 characterized by the fact that one of the driving elements of the couplings is a pair of jaws, the opening of which is horizontal during the rotation of the roundabout, while the other driving element comprises two horizontally aligned rollers, one alongside the other during this rotation for engaging said jaws in said position.

4. A machine in accordance with claim 3, characterized by the fact that one of the coupling elements constitutes one of the arms of a lever mounted to oscillate about an axis perpendicular to the pivotal axis of the element in a driving sheath driven by a third motor, the other arm being provided with a counter-weight, and a restoring member interposed between this latter arm and the said sheath for urging the lever into a coaxial position with respect to the sheath.

5. A machine in accordance with claim 4, characterized by the fact that the said restoring member comprises two opposite magnets, one of which is fixed on the sheath and the other on the extremity of the free arm of the said lever.

7. A machine in accordance with claim 1, characterized by the fact that in order to produce the discontinuous drive of the said platform, the first motor and the roller are pivotally mounted on the base in a horizontal plane, a fourth motor being adapted to cause them to pivot to a limited extent in one direction for the purpose of applying the roller against the outer edge of the platform, and in the other direction for moving the said roller away from this edge.

8. A machine in accordance with claim 7 characterized by the fact that a fifth motor is fixed on the base-plate for actuating a locking device comprising an element for engagement in a housing formed in another element, one of the elements coupled to the fifth motor being radially slidable with respect to the roundabout, and the other provided at a number of peripheral points on the platform, so that the slidable element is located facing a corresponding element on the platform as soon as the roller has moved away from the edge of the platform.

9. A machine in accordance with claim 8 characterized by the fact that the said motors are fluid motors.

10. A machine in accordance with claim 7 characterized by the fact that the first and second motors are rotary motors.

11. A machine in accordance with claim 8 characterized by the fact that the third, fourth and fifth motors are jacks, the moving part of the third motors being coupled to a toothed rack engaging with a toothed wheel rigidly fixed for rotation with the driving element of the coupling.

13. A machine in accordance with claim 12, characterized by the fact that the third motors are secured to the fixed column by means of a support constituting a skirt surrounding and protecting the rotary joints.

14. A machine in accordance with claim 1 characterized by the fact that the motors for ensuring the movements of the various moving elements of the machine are controlled, for the purpose of obtaining an automatic operating cycle comprising a plurality of successive operations, by means of detectors mounted in such manner in the path of the moving elements which carry out the operations, that they initiate the next following operation from a predetermined position of the said moving elements.

15. A machine in accordance with claim 14, characterized by the fact that the detectors are selected from the group of apparatus consisting of electronic proximity detectors and cams.