GB2179588A

GB2179588A - Production of mouldings

Info

Publication number: GB2179588A
Application number: GB8620680A
Authority: GB
Inventors: Gunter Becker; Karl Schermuly
Original assignee: Passavant Werke AG and Co KG; Passavant Werke Michelbacher Hutte
Current assignee: Aqseptence Group GmbH
Priority date: 1985-08-28
Filing date: 1986-08-27
Publication date: 1987-03-11
Also published as: DE3530681C2; DE3530681A1; BE905339A; GB8620680D0; GB2179588B; FR2586610A1; NL8602108A

Abstract

The production of mouldings, for example concrete blocks, with uniform bulk density and accurate dimensions is achieved by measuring the block height and weight of the demoulded mouldings and by calculating the bulk density from these two values. If variations from the desired values occur, the filling level is immediately altered. Both measurements are carried out outside the vibration area so that precision measuring instruments can be used. To eliminate the influence of different board heights, the board upper side and the block surface is sensed and the difference determined. The procedure for determining block weight is such that the board with the blocks thereon is weighed and the known board weight is subtracted as the constant.

Description

SPECIFICATION Method and apparatus for producing mouldings The invention relates to a method and apparatus for producing mouldings, in particular concrete blocks, of uniform bulk density and size.

In the production of concrete blocks with accurate dimensions and predetermined minimum bulk density it is importantforthese two values to be con tinuouslymonitored so that the desired values can be maintained as accurately as possible by varying the filling level ofthe mould and/orthevibrationtimes.

In a known device for measuring block height (DE PS 1 759 927) an adjustable limit switch is connected to load pressure elements, which can be lowered into the mould cavities, and shuts off the vibration when the block height is reached. Since the limit switch has its fixed point on the machine frame, differences in the thickness of the carrying boards are nottaken into account because the mould then occupies different vertical positions. Moreover, accurate measuring instruments with digital displays cannot be used within the vibration area. Finally, adjustment to a constant block height does not indicate anything in respect of bulk density which is critical for the compressive strength of the finished blocks.

The problem thus arises of accurately maintaining bulk density and block heightand, in the eventof variations, of readjusting the production parameters tothepredeterminedvalueswith minimum timing delay. This problem is solved in accordance with the present invention by successively measuring the block height and weight of the demoulded mouldings, and by calculating the bulk density from these values. Since the measurements are now taken outside the vibration area it is possible to use precision measuring instruments. The board with the demoulded layer of blocks can likewise be readily weighed outside the moulding area so that a computer can be used to calculate very rapidly any variatins in bulk density and corrections in the filling level can be carried out.Since height measurement and weighing take up only one working cycle in each case, it is possibleforthe correction to be effected during the second, succeeding cycle.

In orderto eliminate differences in board height during height measurement, in a preferred development of the invention the upper side of the board and upper surface of the block are sensed. The difference then gives the exact block height. The procedure for determining bulk density is preferably such that the entire carrying board with the layer of blocks situated thereon is weighed, the board weight is subtracted therefrom, as the known constant, and the net weight of the layer of blocks is then divided by the known volume ofthe layerofblocks. The average bulkdensityofa moulding is calculated by dividing theweight of a moulding, resulting from the weight of the layer of blocksandthe numberof mouldings perlayerof blocks, by the volume resulting from the measured block height and the known cross-sectional area of a moulding. It is not necessary to take into account differences in the weight of the carrying board, since they are negligibly small in relation to the weight of layer of blocks.

A preferred apparatus for carrying out the method according to the invention comprises, disposed adjoining the demoulding station, a height sensing de viceforthecarrying board and block upper side, a liftingtablewith load cellsfortheweighing operation, and a computer, connected to the height sensing device and the load cells, for determining block height, bulk density and the actual variation from the desired block height and bulk density. The height sensing device preferably comprises two independently coupled roller sensors beneath which the board and layer of blocks pass. The roller sensorfor the carrying board entrains with it the roller sensorfor the blocks, the coupling designed as a stop member being set to the lowest anticipated block height.The roller sensorforthe carrying board may also be provided with a lower stop member which is so adjusted that the roller sensor can only carry out a shorttravel.

Further details ofthe apparatus according to the invention are evident from the embodiment described below, by way of example, with reference to the accompanying drawings, wherein: Figure lisa side view showing two measuring devices in a conveying device provided downstream of a block manufacturing machine; and Figure2 shows a section along the line ll-ll in Figure 1 through the height sensing device.

Referring to the drawings, the conveying device for the mouldings 2 demoulded onto carrying boards 1 is in the form of a roller conveyor 3 which may be driven or has an additional tow drive. Afirst measuring point 4for block height is disposed at a small distance behind the demoulding station which, in conventional manner, coincides with the block-moulding station.

An outer roller sensor 7 is mounted vertically dis placeably on a support frame, in the form of a gibbet 5, and in front of which is a blast nozzle 6 which can operate with compressed air; itsubstantiallycomprises a lift rod 10which is guided in plain bearings 8, 9 and the weight of which is forthe most part equalised by a tension spring 11. The lift rod 10, which is provided at the bottom with a fork 12 for a sensing roller 13, has abovethe lower plain bearing 8an adjustable stop member 14 which enables the sensing roller 13to be set a few millimetres belowthe thinnest board 1 expected. The second adjustable stop member 15 serves to adjustthe roller sensor 16 for block height to slightly below the lowest block height.This second roller sensor 16 also has on the lift rod 19a lowerfork17formounting asensing roller 18. The lift rod 19 is guided by means oftwo plain bearings 21,21 on the lift rod 10 of the other roller sensor. The entire measuring device 4 can be rendered inoperative by means of a lifting cylinder 22 which is mounted on a bracket 23 of the support frame 5. The height indicator, which is represented here as an analogue scale 24, is preferably in the form of a digital display and transmitting system.

An immediately adjacent measuring station 25for block weight comprises an underframe 26, a set of pneumatic bellows 27, an intermediate frame 28 and a roller lifting table 30 carried by load cells 29, the rollers of which table engage the board 1 through the conveyor roilers 3.

The block height can be measured while in motion or after stopping and raising the board. The reading is fed to the computer and any deviation from the desired value is calcuiated. In the weighing station, the board is briefly halted and raised from the conveyor rollers by the pneumatic cylinders. The weighing result is likewise fed to the computer, after subtraction of the board weight. The computerthen calculates the bulkdensityfromthetwo measured values and, in the event of any variation from the desired value, adjusts vibration and filling level. The measurement of block height and the weighing procedure may also be combined in one station.

The device can be calibrated before each operation and setto the finished block height. The rollersensor for block height can be displaced transversely so that measurement can also be effected at other representative locations. It is also possible to provide two roller sensors at different locations and to produce a mean value from both measurements.

Claims

1. A method for the production of mouldings, for example concrete blocks, of uniform bulk density and size, comprising successively measuring the block height and weight of the demoulded mouldings, and calculating the bulk density from these values.

2. A method as claimed in Claim 1, wherein the block height is determined by sensing the carrying board and upper surface of the block.

3. A method as claimed in Claim 1 or Claim 2, wherein the bulk density of the layer of blocks is determined by weighing the loaded board, subtract- ing the board weight and dividing the weight of the mouldings bythevolume calculated from the area and height of the mouldings.

4. A method as claimed in any one of the preced ing claims, wherein the average bulk density of a moulding is determined by dividing the weight of a moulding by the volume of a moulding calculated from the average block height and the known cross sectional area ofa moulding.

5. Apparatusforcarrying outthe method accord ing to any one of the preceding claims, comprising a demoulding station for layers of blocks placed on carrying boards and adjoining a conveyor device, a height sensing device, disposed downstream ofthe demoulding station,forthe carrying board and block upper side, a lifting table with load cellsforthe weighing operation, and a computer, connected to the height sensing device and the load cells, for deter- mining block height, bulk density and the actual varia tion from the desired block height and bulk density.

6. Apparatus as claimed in Claim 5, wherein the height sensing device comprisestwo independently coupled roller sensors, one of which senses the car rying board nearthe layer of blocks and the other senses the block upper side.

7. Apparatus as claimed in Claim 6, wherein the roller sensorforthe block upper side is displaceable transverselyto the conveying direction.

8. Apparatus as claimed in Claim 6 or Claim 7, wherein the rollersensorforthe carrying board is provided with a lower stop member at orjust below the level ofthethinnest board expected.

9. Apparatus according to any one of Claims 5 to 8, wherein the height sensing device has a spring for weight equalisation.

10. Apparatus as claimed in any one of Claims 5 to 9,whereinthe height sensing device hasa lifting cylinder to effect disengagement from the sensing position.

11. Apparatus as claimed in any one of Claims Sto 10, wherein a blast nozzle for cleaning purposes is disposed upstream of the sensing rollerforthe car- rying board.

12. Apparatus as claimed in any one of Claims 5 to 1 1,wherein the lifting tablefortheweighing operation comprises a set of rollers which can be raised through the rollers of the conveyor track.

13. Apparatus as claimed in Claim 12, wherein pneumatic cylinders or bellows are provided as lifting means.

14. Apparatus as claimed in Claim 12 or Claim 13, wherein the lifting means carry an intermediate frame on which the load cells are supported.

14. Amethodforthe production of mouldings of uniform bulk density and size substantially as hereinbefore described with reference to the accompanying drawings.

16. Apparatus for carrying out the method of Claim 1 substantially as hereinbefore described with reference to and as shown in the accompanying drawings.