GB2025309A

GB2025309A - Moulding Presses

Info

Publication number: GB2025309A
Application number: GB7923860A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-07-13
Filing date: 1979-07-09
Publication date: 1980-01-23
Also published as: DE2830779A1; BE877553A; FR2430831A1; DE2830779C2; NL7905455A; GB2025309B; IT1125373B; IT7923920A0

Abstract

A press for constructional units such as bricks comprises upper and lower press tools (7), (5) which co- operate with a tubular mould (18). In order to obtain a greater uniformity in the density of the article being moulded, lower tool (5) is fixed, the mould assemblage (15) is hydraulically suspended during the moulding operation at the lower ends of the piston rods (19) of two positioning rams (20), and pressure limiting means (not shown) limits the pressure of hydraulic fluid in the cylinder spaces (24) whereby only the weight of the mould assemblage itself is balanced or supported and the mould is entrained by the moulding material to move downwardly relative to the tool (5) as the moulding material is compressed. The arrangement has the further advantage that the rams (20) can be operated to eject the moulded article from the mould. <IMAGE>

Description

SPECIFICATION Improvements in Moulding Presses The present invention relates to moulding presses for use in manufacturing artifical stones for example, constructional units and particularly lime-sand bricks.

In a known press of this kind, the mould is supported on springs so that it can be displaced downwardly against the action of the springs during a pressing and moulding operation. This displacement of the mould out of an upper initial pressing position is caused by the material being compressed and moulded in the mould cavity which exerts by friction during the pressing operation an entrainment action on the mould itself. Such a movement of the mould, against the action of the supporting springs, which have a predetermined spring constant, has an adverse effect on the distribution of the forces compressing the material being moulded, with the result that the density of the moulded article is non-uniform.

This effect is the greater, the heavier the mould for, depending upon the weight of the mould, the greater is the spring constant for the springs which have to be selected.

To eject the moulded articles after the pressing operation is terminated, ejectors are needed which work from the bottom upwards to move the moulded article out of the mould and into a position in which the moulded article can be grasped and carried away by suitable machinery.

Such a transposing device and a mould filling device form units which are fixedly mounted on the press.

A moulding press is also known wherein upper and lower press tools are each movable in opposite directions to compress material in the mould cavity, the mould being stationarily supported in the direction of its height. Such a construction of moulding press is very expensive because not only is a second drive needed for the lower press tool but also, the control of the drives for the press tools is complicated. Also, because of the difference in weight between the upper press tool and the lower press tool and the drive parts moved with these press tools, differences result in the pressures with which the upper and the lower press tools act on the material being moulded and these differences cannot be completely eliminated even with complicated controls.Also undesirable in such a construction is the positioning of drive means in the region below the mould where it becomes contaminated with stray moulding material which greatly encourages wear of its parts.

An object of the present invention is to provide a moulding press which can produce moulded articles of greater uniformity in density than hitherto, which is nevertheless relatively simple in its construction.

The present invention provides a moulding press comprising an upper press tool which is movable vertically, a lower, stationary press tool, a mould for receiving the press tool, the mould being supported for vertical movement and laterally bounding a mould cavity, the mould having an upper, filling aperture and a lower aperture, means for selectively positioning the mould vertically, and means for balancing the weight of the mould and any parts mounted upon it as the mould travels downwardly during a moulding operation.

A moulding press according to the present invention renders possible a movement of the mould during the pressing operation while eliminating the influence of the weight of the mould during its entrainment, so that the entrainment forces which have to be exerted by the material being moulded, on the mould, are extremely low. The reaction of the mould on the material being moulded is correspondingly low with the result that the moulded articles, pressed from above and below by the press tools, are exposed to more uniform pressure and have a high degree of uniformity in density.Also, as a result of the vertical positionability of the mould, ejector devices for moulded articles are eliminated because, after termination of the moulding operation, the mould can be lowered in relation to the stationary lower press tool to an extent such that the lower press tool itself acts directly as an ejector. Both the positioning of the mould before and after a moulding operation, and the release of the mould for entrainment movement during moulding, with balancing of the weight of the mould itself and any parts mounted upon it, require only simple drive means and controls, and the possibility is afforded also of constructing a filling device for the mould and a transposing device for the moulded articles each as a unit carried by the mould, so that these units follow the movements of the mould and always adopt the same position in relation to the mould.

In addition, the press offers the possibility of using it, in special cases, for onesided pressing operations, as a result of which the range of application of the press is considerably extended.

The cheapness of construction is accompanied by low wear because no movable components are needed in the region below the mould where they can become contaminated with moulding material.

A specific embodiment of the present invention will now be described by way of example and not by way of limitation, with reference to the accompanying drawings in which: Fig. 1 is a view of a press in accordance with the present invention in section on line I-I in Fig.

2; Fig. 2 is a view of the press in section on line Il-Il in Fig. 1; Fig. 3 is a diagrammatic circuit diagram showing the lifting device for the mould; and Figs. 4 to 9 are diagrammatic illustrations showing successive working operations of the press.

With reference to the accompanying drawings, a two-stage press has a fixed lower portion 1 resting on the ground a fixed press head 3 supported with spacing above the lower portion 1 on vertical supporting and guide columns 2, a lower press die 4 with pressing tool 5, supported stationarily on the lower portion 1, an upper press die 6 with pressing tool 7, a carrier 8 for the upper press die 6 and a double acting hydraulic ram 9 for the upper press die, which comprises a pressure medium cylinder 10 with a vertical longitudinal axis, a pressure piston 11 displaceable in the cylinder 10 and a piston rod 12 which connects the pressure piston 11 to the carrier 8.The pressure piston 11 can be acted upon in the cylinder compartment 13 by hydraulic working fluid to execute a downwardly directed pressing stroke, and in the cylinder compartment 14 situated below the pressure piston 11 to perform an upwardly directed return stroke.

The press further comprises a mould 1 5 comprising a supporting frame 1 6 and a mould lining 1 7. The mould lining, which is interchangeably mounted in the supporting frame 1 6 for reasons of wear, laterally bounds a mould cavity 18 presenting an upper filling aperture and a lower aperture, which closely receive the upper press tool 7 and the lower press tool 5 respectively, for a pressing operation. The supporting frame 16 of the mould 1 5 is guided for parallel displacement on the vertical guide columns 2 of the press and is suspended at the lower ends of the vertically guided piston rods 1 9, of a group of for example, two double acting hydraulic rams 20.Each of the rams 20 consists in detail of a hydraulic cylinder 21, having a vertical longitudinal axis, and a piston 22 which is displaceable vertically therein and the under side of which is connected to its piston rod 1 9. Both the cylinder compartment 23 situated above the piston 22 and the cylinder compartment 24 below the piston 22 can be pressurized by hydraulic working fluid through hydraulic fluid lines, as explained below.For double sided pressing, the pressing tools 5 and 7 have an external contour coinciding closely with the internal cross-sectional configuration of the mould cavity 1 8. When the mould is changed, the tools 5 and 7 can be changed accordingly.The lower pressing tool 5 or the upper pressing tool 7 can also be exchanged for a pressure plate which is not constructed to engage in the corresponding aperture in the mould cavity but is sized to close the aperture in the mould cavity by covering it, the plate engaging under or over the cavity. With such a construction, the two stage press being described can also work as a simple acting press, having a single press tool acting at one side, either from above or from below.

Although a mould cavity and an upper and a lower press tool are referred to above, nevertheless, it is understood that the mould 1 5 may also comprise a plurality of mould cavities for the simultaneous pressing of a plurality of moulded articles, in which case both the upper and lower press tools have a corresponding matching, multiple construction.

As can be seen from Fig. 2, the mould 15, which offers a table at the top, has mounted upon it a filling device 25 consisting of a filling box 26 and a hydraulic ram 27 by means of which the filling box is displaceable out of its first position below a storage container 28 for material to be pressed, horizontally inwards into a second position above the mould cavity 1 8 and back into its first position, illustrated. Thus, the filling device forms a unit which moves vertically up and down with the mould. Associated with the press, substantially at the height of the top of the lower pressing tool 5, is a conveyor belt 29 by means of which finished pressed moulded articles can be carried away, for example to stacking pallets.Also mounted on the mould 1 5 is a transposing device 30 which comprises transposing grippers 31 and a hydraulic ram 32. The transposing device 30 can be moved by means of the ram 32 out of a first position illustrated in Fig. 2 in which the grippers 31 lie above the mould cavity 18, to grasp a finished, pressed moulded article standing ready in the plane of the top of the mould and after grasping the moulded article, transfer this to the conveyor 29 after the mould 1 5 has been lowered to an end position seen in Fig. 8. This transposing device 30 is also a unit which moves vertically with the mould 1 5.

The circuit diagram in Fig. 3 illustrates the control of the rams 20 for the mould 1 5. The cylinder compartments 23 are connected to a common main line 33 and the cylinder compartments 24 are connected to a common main line 34, which originate from a common three position valve 35. Leading to the three position valve 35 is a pressure line 36 from a hydraulic pump 37 which is in communication with a reservoir or tank 38 at the input side.

Auxiliary reservoirs or tanks in the circuit are designated by 38' in each case and illustrated separately for the sake of simplicity, although these auxiliary reservoirs 38' may be identical with the main reservoir 38. Interposed in the pressure line 36 is an adjustable pressure limiting valve 39. Interposed in the main line 33 between the three position valve 35 and the branches to the cylinder compartments 23 is a relief valve 40 which can be blocked by a two-way valve 41, as illustrated, or be released so as to be free to act as a relief valve. Before the branch of the main line 34 to the cylinder compartments 24, and connected to the main line 34, is an excesspressure safety valve 42 and a branch line 43 in which there is interposed an adjustable pressure limiting valve 44 followed by a two-way valve 45 through which the branch line 43 to an auxiliary reservoir 38 can be freed or blocked after switching over.If the two-way valve 45 is transferred from its position illustrated into the blocking position, the action of the rams 20 during their downward travel is controlled exclusively by the three-way valve 35 which, in its first position displaced towards the right out of its illustrated position, causes a down stroke of the mould 15, in its second position displaced towards the left out of its illustrated position causes an up stroke of the mould 15 and in its mid position illustrated stops the lifting drives 20 hydraulically.If, in the mid position of the three position valve 35 illustrated, the two-way valve 45 is transferred into the valve position illustrated, with an adjustment of the pressure limiting valve 44 which takes into consideration the weight of the mould and the components connected thereto, the mould is held floating in equilibrium, motionless in position, until, during a pressing operation, a downwardly directed entrainment force acts on the mould 1 5. This entrainment force is distributed to the pistons 22 with the result that the pressure of hydraulic fluid in the cylinder compartments 24 tends to increase and is releived via the pressure limiting valve 44, by displacing the hydraulic medium through the valve 45 into the reservoir 38'.

Accordingly, the mould executes a downward movement, independent of its weight and its loading, and depending only on the entrainment force exerted upon it by the moulding material during the pressing operation. The upper cylinder compartments 23, during a downward movement of the pistons 22, are supplied with hydraulic fluid through the relief valve 40, from the reservoir 38'.

If, at the end of an entrainment movement of the mould 1 5 by the pressing operation, after termination of the pressing operation, the mould 1 5 is to be moved further down, namely, out of its position shown in Fig. 7 into the position of Fig. 8, then the two-way valve 45 is switched over and the three-way valve 35 is moved into its left end position. As soon as the pressure pistons 22 in the cylinders 21 have reached their end position, through admission of hydraulic fluid to the cylinder compartments 23, the three position valve 35 is switched into its mid position as shown.On the other hand, if the three position valve 35 is set in its right hand end position to raise the mould into an initial pressing position and if, at the same time, the two-way valve 41 is operated, as a result of which the valve 40 relieves the pressure of hydraulic fluid in line 33 to the reservoir 38', then the pistons 22 travel upwards as a result of the admission of hydraulic working fluid to the cylinder compartments 24, until they have reached their required end position in the working cylinders 21. As soon as this has happened, the threeway valve 35 is displaced into its mid position shown so that the upward movement is terminated.

Fig. 4 illustrates diagrammatically, the initial position of the components of the press before the mould cavity 1 8 is filled with moulding preparation, which is carried out as shown in Fig.

5 by moving in the filling box 26 over the mould cavity 18. After the filling box has returned to its position under the storage container 17, the upper press die is moved into an initial position for the pressing operation, which is illustrated in Fig. 6. Then follows the pressing operation by further downward movement of the upper press die, the mould 1 5 being entrained downwards during the pressing operation by the entrainment action of the moulding preparation being compressed. Fig. 7 illustrates the position of the components of the press on termination of the pressing operation. Then the upper press die is moved upwards again and the mould 1 5 is lowered further until the top of the mould 1 5 and the top of the pressing tool 5 of the lower press die 4 lie in alignment in one plane as shown in Fig. 8. In this position, as likewise illustrated in Fig. 8, the transposing device is moved inwards to grasp the finished moulded article lying free for a transfer operation and then outwards to transfer it to the conveyor 29. This final position of the parts is illustrated in Fig. 9, after which the parts of the press are again transferred into the initial position as shown in Fig. 4.

Claims

1. A moulding press comprising an upper press tool which is movable vertically, a lower, stationary press tool, a mould for receiving the press tools, the mould being supported for vertical movement and laterally bounding a mould cavity, the mould having an upper, filling aperture and a lower aperture, means for selectively positioning the mould vertically, and means for balancing the weight of the mould and any parts mounted upon it as the mould travels downwardly during a moulding operation.

2. A press as claimed in claim 1 in which the means for selectively positioning the mould is hydraulically operated and the balancing means comprises pressure limiting means for limiting the pressure of working fluid supporting the mould against downward travel during a moulding operation.

3. A press as claimed in claim 2 in which the mould is suspended at the lower ends of vertically guided piston rods of two or more double acting hydraulic rams operable to selectively, vertically position the mould.

4. A press as claimed in claim 2 in which the piston rods form vertical guides for a carrier carrying the upper press tool.

5. A press as claimed in any preceding claim in which the mould is guided for movement along vertical guide columns of the press.

6. A press as claimed in any preceding claim in which the upper or lower press tool is exchangeable for a pressure plate which engages over the filling aperture or under the lower aperture of the mould cavity to close the aperture.

7. A press as claimed in any preceding claim further comprising a filling device for the mould cavity and a transporting device for moulded articles, said devices being mounted on the mould so as to be movable up and down with the mould.

8. A moulding press substantially as hereinbefore described with reference to the accompanying drawings.