The invention relates to a device for sanding moulding trays which are pivotally mounted about their horizontal axis and carried by conveyor means mounted for stepwise movement along a number of sta¬ tions. Such devices are known. In general they make part of a plant, in which a supply of clay can be worked to mouldings adapted for firing so-called hand mould bricks. Usually a press is used of the type, which is capable of working the clay to lumps and depositing these lumps into moulding trays on the conveyor means mentioned herein befo- re, which passes stepwise under the press and displaces the moulding trays successively along a device for trimming the loaded moulding trays, a station where the loaded moulding trays are tilted, a station for reinαving the mouldings from the moulding trays on pallets, a devi¬ ce for washing and drying the empty moulding trays, and the device of the type indicated herein above for sanding the moulding trays to be moulded.

Such a plant is broadly disclosed in NIr-A-8601553. Here the end¬ less conveyor means is constituted by a conveyor of the belt conveyor type, the (multiple) moulding trays being positioned transversely to the direction of movement and being mutually pivotally connected so as to form the upper and lower run of the belt as well as the two roller- guided end sections of the belt. Other forms of such plants are known, with which the moulding trays are removably received in moulding tray carriers, which are swingably .suspended about the horizontal axes be- tween two endless chains guided in parallel vertical planes.

In these plants the sanding of the moulding trays is taking place along the lower, horizontal run of the path of the conveyor means. The sanding device is formed by a supply hopper, from which the sand is projected by blades towards a moulding tray in its tilted po- sition, i.e. with its moulding cavities turned downwards.

The sanding of the moulding trays prior to loading the same with clay lumps sanded in advance as well, is fontiing an important process step, when bricks having the characteristic hand-mould structure, have to be manufactured according to a mechanised way of processing. The sariding is indispensable not only for securing removal of the moul¬ dings from the moulding tray, but for obtaining the desired hand mould structure it is also essential, that the (after drying still somewhat moist) walls of the moulding cavities of the moulding tray are covered

with a uniform thin layer of sand. With the above well-known way of sanding, however, c___rtain areas of the walls to be sanded may be easi¬ ly missed, which results in unacceptable tracks at the surface of the ultimate "hand mould bricks". In tis connection it should be taken into consideration, that the moulding trays to be sanded are usually divided in a large number (e.g. sixteen or more) moulding cavities by means of partitions which must also be sanded on both sides. The use of more powerful projecting means to make sure that all parts of the surface of the individual moulding cavities are reached, often yields the opposite effect, because a thin layer of sand being applied and sticking in an initial stage, is coming off again under the influence of the sanding jet in a subsequent stage. Similar disadvan¬ tages are connected with a proposed alternative way of sanding by means of spraying with dry sand from a location over the moulding trays.

The present invention provides an effective solution for the drawbacks mentioned herein above, which is characterized in that a sand supply station is located laterally off a section of the path of said conveyor means, that leads upwardly along three stations which are positioned substantially vertically over one another, from which supply station a drawer-like sand receiving and passing member may be moved into a position right over a moulding tray in the second station and vice versa, means being provided along said path section, starting from a location at said second station upwards, which means cause the moulding trays - during displacement on said path section - to tilt through 180° from the filling position and to return into the filling position after passing the third station.

When using the sanding device acx_o__xiing to the invention the moulding trays are each time at the location, which herein above is called "second station" completely filled with sand and then, during the further displacement towards the "third station", tilted so as to discharge the aέcess of sand from the moulding tray. By first filling the moulding trays completely with sand, all of the walls of the indi¬ vidual moulding cavities will get into contact with sand with certain- ty. Furthermore tests have shown that upon tilting the initially fil¬ led moulding tray, an uninterrupted thin layer of sand keeps sticking to the cavity walls where desired. The excess of sand falling out of the tilting moulding tray, needs not to be discharged, but is cau t in and consequently is utilised for the partial filling of the next

moulding tray which has arrived at the second station. This partial filling is then supplemented by means of the drawer-like means, which has, while in its retracted position, during a displacement step of the conveyor means, received a supplementing amount of sand from the sand supply station and is transfering this amount to the moulding tray which has arrived at the second station.

The device according to the invention is particularly suitable for use in combination with a conveyor means formed by a drum which is rσtatable about a horizontal axis and of which the axial end walls are provided with bearings for the shafts of the rotatably suspended moul¬ ding trays or moulding tray carriers respectively, said bearings being positioned at the corners of a regular polygon. For, when viewing such an embodiment in a direction in which the drum is turning clockwise, it is particularly practical to integrate the sanding devi- ce into the last (four) quadrant of a complete cycle e.g. immediately preceding the loading of the (sanded) moulding trays with (fresh) clay lumps, which necessarily takes place in the upper angular area.

According to a further feature of the invention the drawer-like means is adapted to be moved in a direction transversely to the longi- tudinal direction of the moulding tray, into the second station, said means being - when taking its retracted position - locates between an outlet opening of a fixed supply hopper positioned there above and forrtiing the supply station, and a seini-stationary bottom plate under¬ neath, the drawer-like means being, at its side turned away from the second station - extended by a bottom portion movable along with said means, said bottom portion being adapted to close the outlet opening of the supply hopper during displacement of said drawer-like means into said second station.

In a preferred embodiment embodiment the longitudinal edge of the semi-stationary bottom plate facing the second station, is normal¬ ly i.e. with the conveyor means moving, slightly spaced relative to the passing moulding trays, but is adapted to be displaced until con¬ tacting the outer wall of the moulding tray when stationary in the second station of the still standing conveyor means. In a practical en±jcxiiment the drawer-like means is attached to the ends of two substantially vertically positioned levers, which are adapted to perform a swinging motion about an axis which is parallel to the axes of the moulding trays.

The invention will be hereinafter further explained by way of

example with reference to the drawing.

Fig. 1 is j±Lagramatic perspective view of the device of the in¬ vention and . fig. 2 is.an elevational view of the device, in which the means for guiding the moulding trays are illustrated.

With reference to the drawing four moulding trays 1, 2, 3 and 4 with horizontal axes la - 4a are shown, which may be displaced step¬ wise in the arrow direction (vide fig. 1) according to a circular path. For this purpose the moulding trays are mounted for rotation about their axes la - 4a to the ci___r_uπ_fe____c_e of a d_-_m-shaped convey¬ or member, adapted for step-wise rotation about a horizontal axis (not shown in the drawing. The drum end walls of this conveyor member com¬ prise support bearings lb - 4b for the moulding tray shafts, said bea¬ rings being located in the corners of a regular polygon. The moulding trays have an ejpngated form and are longitudinally divided by parti¬ tions into a number (for example 16) moulding cavities, the size of which corresponds with that of a hand mould brick. The moulding trays may be removably provided in moulding tray carriers which are mounted to the conveyor member. The conveyor member carries a total number of e.g. twenty πpulding trays, which are uniformly (±Lstributed over its circumferεnce, so that the four moulding trays shown in fig. 1 to¬ gether cover an arc of 3 x 18 = 54°. The four moulding trays 1 - 4 are shown in fig. 1 in four successive positions or stations I - IV, in which they halt for a while, each time after a displacement step (of 18° in this example) being carried out by the conveyor meπiber. Station H is on the level of the axis of rotation (not shown) of the conveyor member, so that the moulding trays in stations I and III are positio¬ ned vertically one over the other, while the moulding tray in station IV is taking a position which is slightly off-set to the outside with respect to those in stations I and III.

The moulding tray II which has arrived at station II is comple¬ tely filled by sand and will be turned upside down during the next displacement step towards station III. A partial filling is taking place already, when the moulding tray 2 is still on its way to station II, due to an amount of sand falling out of a foregoing tilting moul¬ ding tray 3, which was filled in an earlier stage. Any sand falling along the outer side of the inner longitudinal wall of the moulding tray 2 will be caught by the moulding tray 1 approaching station I.

At the moment the moulding tray 2 - partially filled with spil-

ling sand - has came to a standstill in station II, suppletion is ta¬ king place from a supply hopper 6, which is fixedly πounted beyond the carrying drum circumference and close to the outer longitudinal wall of the moulding tray 2 in station II (7 designates a part of the fixed framework, to which the supply hopper 6 is attached) . The supply hop¬ per 6 has a drawer-like bottom portion 8, which is generally formed as a rectangular frame, the length and width of which substantially cor¬ respond with those of a moulding tray and of a corre_por*____ng rectan¬ gular outlet opening of the supply hcpper 6. In the position shown in the drawing the rectangular frame of the bottom 8 fits - with a slight clearance - to the lower edges of the outlet opening of the hopper 6, while under the drawer-like member there is a semi-stationary bottom plate 9. The space surrounded by the frame of the member 8 is divided into a number of longitudinal secti- ons by means of upright longitudinal partitions 10. The member 8 is fastened to the upper ends of two parallel levers 12, which are moun¬ ted for a swinging motion about an axis 11 and may be driven by a me- chanis e which is diagramatically indicated at 13. The member 8 is extended in a direction turned away from the station II, by a plate portion 14, extending along a part of a cylindrical surface around the axis 11.

The timing of the driving of t_ιe drum-shaped conveyor member on one hand and that of the levers 12 with the drawer member 8 on the other hand is such, that as soon as the conveyor member with the moul- ding trays has come to a standstill, the mechanism 13 will enter into operation to displace the member 8 from the position shown in fig. 1 to a position vertically over the moulding tray 2 in .station II. Du¬ ring this movement the plate-like extension 14 is taken along to close the outlet opening of the supply hcpper 6 and stop a further outflow of sand.

It will be clear that in this manner the member 8 will take with it an amount of "suppletion sand", the volume of which is equal to the surface of the outlet opening of the supply hopper (= surface of the opening in the member 8) multiplied by the height of that member. As soon as the member 8, on its way towards station II has passed the near longitudinal edge of the semi-stationary bottom 9, the amount of suppletion sand is allowed to fall through the member 8 into the moul¬ ding tray 2. The longitudinal partitions 10 of the member 8 promote a uniform distribution of this amount of sand in the width direction of

the moulding tray. In station II the member 8 is located with its lo¬ wer side just free from the upper surface of the moulding tray 2. An excess of suppletion sand, if any, will thus be taken back when the member 8 is subsequently returning to its starting position shown in the drawing, while smoothly striking the completely filled moulding tray 2. upon retraction of the member 8 the conveyor member is perfor¬ ming a next displacement step, whereby a next, empty moulding tray 1 is displaced to station II, the filled moulding tray 2 is moved into position m and s_bπultaneously turned through 180°, while the iπver- ted, sanded moulding tray 3 is moved from station III to station IV, and is thereby simultaneously performing the first 90'-stage of its tilting back movement.

Herein above the bottom plate 9 is indicated as a "semi-statio¬ nary bottom plate" The reason of this is, that the bottom plate 9 can make a short reciprocating movement relative to a moulding tray 2 in station II. The timing of this reciprocating movement (according to arrow x) with respect to the movement of the conveyor member is such, that the bottom plate 9 is taking a retracted position away from the station II, as long as the conveyor member is moving. During that time there is a slit between the outer longitudinal walls of the moulding trays and the longitudinal edge 15 of the bottom plate 9, which slit secures free passing of the moulding trays. As soon as the moulding tray 2 in station II has come to a standstill, however, and the mecha¬ nism 13 is entering into operation, the bottom plate 9 will be moved with its edge 15 -towards the moulding tray, so that the slit is closed so as to prevent suppletion sand to fall through.

In the example shown a conveyor belt 16, mounted for moving in the arrow direction, is provided under the member 8, so as to catch any spilling sand and to discharge this sand to the moulding tray 1 in position I.

Finally, the guide means required for controlling the positions of the moulding trays in the various stations are described with refe¬ rence to fig. _

The moulding trays or moulding tray carriers 1 - 4 are each pro- vided with two guide rollers 17 and 18, i.e. one roller at each moul¬ ding tray end. All of the guider rollers 17, which are located on one side of the conveyor member, e.g. to the front in fig. 2, are each mounted to the end of a carrying arm 19. This carrying arm is fixedly connected to the respective moulding tray (carrier) shaft 20 and is

extending perpendicularly from the bottom surface of the respective moulding tray.

The guide rollers 18 located on the other side of the conveyor member are mounted for rotation about an axis which substantially coincides with one of the longitudinal bottom edges of the respective moulding trays or moulding tray carriers. Each group of guiding rol¬ lers located on the same side is cooperating with an associated guide way on that side. Thus the guide rollers 17 cooperate with the guide way 21 shown at the front in fig. 1. 25 shows a small portion only of the guide way for the rollers 18 on the other side, said portion being the portion which precedes station I. During the displacement step to station I and subsequently to station II a guide way for the rollers 18 could be omitted, because on that trajectory the moulding trays get their stability from the rollers 17. For tilting the moulding trays on the trajectory from sta¬ tion II to station III, however, the guide rollers 18 are playing an essential role. It will be understood, that, in order to have the moulding tray 2 tilt clockwise when moving to station III, it will be necessary for the guide way on the other side of the conveyor member to block the upgoing movement of the roller 18 of that moulding tray and urge said roller to follow an inwardly curved path. For this pur¬ pose the roller 17 must be permitted to swerve from the shown position in fig. II to the left, so that the guide way 21 will have to be in¬ terrupted at that location. In a similar way the roller 18 will - when moulding tray 3 is moveing from station III to station IV - have to be blocked in its upgoing movement and be forced to move laterally (to the right as seen in the drawing) . At the same time the roller 17 in station III will have to move out (towards the left as seen in the drawing) from the guide way 21 and subsequently to re-enter into said guide way 21 just before reaching the 90"-position in station IV.