MACHINE FOR EXTRUDING CONCRETE ELEMENTS

Abstract: A means of extruding machine for continuous moulding of prestressed hollow elements and slabs of concrete, of the kind comprising an extruding machine provided with wheels (2, 4) resting on a floor or steel bench (5). The machine comprises a front operational unit, a suitably vertical hopper (10) for supply of fresh concrete, and which lowermost opens into a horizontal, in direction rearwards directed moulding chamber (12). Through the moulding chamber extends a stationary, horizontally directed support shaft, which at the rear end supports a forming tube (20) for the concrete. On the support shaft is rotatably supported a feeding screw (16, 14) for feeding and compressing the concrete in rearward direction towards the forming tube (20), and a vibrator (44) situated in connection with the forming tube (40) and optionally vibrators situated elsewhere on the machine. In accordance with the invention, the forming tube (20) including the accenter (64) is connected to the rear end of the support shaft via an elastic damper member (50), such that the vibrator (54, 64) is mechanically separated from the remaining part of the extruding machine.

Description: Machine for extruding concrete elements. The present invention relates to a machine for extruding reinforced elements in concrete, particularly hollow reinforced concrete elements and slabs. Such extruding machines usually include a moveable frame or carriage which in front has an operational unit, thereafter an open feeding hopper unit for supply of fresh concrete which opens down into a horizontally backwardly extending feeding chamber for concrete, one through the feeding chamber stationary arranged support shaft for a rotating feeding screw which at the downstream end extends outwards into a forming tube in order to provide openings or voids in the extruded concrete element. The machine is furthermore provided with a number of vibrators, at least one of which is positioned on the top of the feeding chamber, and one inside each of the forming tubes. The machine is mounted on a casting floor or so called steel bench. In use the concrete mass is pressed from the feeding screws into and round the forming tube and from there out on the supporting base or stratum, simultaneously as the casting machine is pressed or moved forwards with suitable velocity, for instance one meter per minute. In order to accomplish a satisfactory production of hollow elements using a such machine it is, firstly, necessary to use fresh concrete with relatively law water content, usually so called «soil moisty» concrete without slump. Further one must utilize high feeding pressure on the screw, and high vibration during the compacting and feeding of the fresh or raw concrete, such that the concrete attains sufficient liquid state. The moulding or extruding machine usually includes a number of side by side arranged forming tubes with separate equipment for producing hollow elements with the required number of throughgoiπg openings. Known machines of this type make in general satisfactory products but exhibit still several shortcomings. A substantial shortcoming is that the vibrators produce high noise with a noise level above 100 decibels. Powerful vibration is however necessary in order to provide the necessary float in the concrete mass. The vibrators are usually driven with rotational speed of 10.-12,000 rpm. Not only causes such noise a large problem for the operators in the production premises, but subjects also the machine elements to large wear and necessitates frequent production shut-downs for maintenance and replacement of parts. The inventor has studied this problem and has realized that a substantial part of the noise originates from the fact that the vibrator means are positioned adjacent the forming tube such that the vibrations to all surrounding machine parts, through the compacted concrete, through the rigid support shaft and to the 5 remaining parts of the machine will all result in a very high noise level. A substantial part of these problems is solved through the present invention which is generally characterized in that the vibrator device positioned in connection with the forming tube is mounted in an elastic suspension which is mechanically separated from the forwardly positioned stationary shaft supporting o the rotating feeding screw. In a preferred embodiment of the invention the forming tube is together with the vibrator mounted on an elastic body which in front is fastened to the stationary shaft. Through this solution the forming tube is floating freely inside the concrete s mass and the vibration energy will migrate directly into the concrete mass and is not directly conveyed to the surrounding machine parts. Thereby the origin for vibratioπal noise is radically reduced, simultaneously as the need for vibration power may be reduced. The invention thus results both in reduced noise and less wear. o An embodiment of the invention shall be described further with reference to the accompanying drawings, wherein fig. 1 shows a longitudinal schematic section through an extruding machine of in per se known art and wherein the invention is included in the actual parts of the machine, more particularly in the forming tube, 5 fig, 2 shows two embodiments of hollow slabs of the kind produced with the machine, fig, 3 shows a longitudinal, schematic drawing, partly in section, illustrating the vital parts in a known machine, and which illustrates the usual way of mounting the vibrator in the forming tube, and o fig. 4 shows a somewhat enlarged corresponding longitudinal section and which further illustrates the solution in accordance with the invention. Fig. 1 shows a complete extruding machine comprising a driving unit 1 running on front wheels 2 and rear wheels 4 on a floor or so called steel bench 6, At the front of the driving unit is mounted a drive unit 8, at the rear end of which is mounted a container or open hopper 10, opening down into a horizontal feeding chamber 12, wherethrough is running a mandrel 14 which is supported on a stationary shaft 16 which further is supported in a bearing house 18. At the rear s end of the stationary shaft 16 is mounted a stationary forming tube 20 which envelopes the vibrator unit 22. On the top side of the feeding chamber above the forming tube is usually positioned a vibrator plate 24. It will be understood that all parts of the extruding machine which are in contact with the concrete are stationary, disregarding the rotating feeding screw 14, which is supported on the ιo support shaft 16. The machine is provided with a number of side by side situated feeding chambers with separate feeding screws for making hollow slabs as shown in fig. 2. In use fresh concrete is poured down into the container 10 from where it falls down into the feeding chamber 12 and is screwed backwards by means of ι$ the feeding screw 14, simultaneously as the concrete is compressed simultaneously as it is vibrated. At the rear end of the feeding screw the concrete is circumferentially distributed around the forming tube 20 subject to strong vibration, simultaneously as the entire extruding machine in result of the pressure from the feeding screw is being moved forward with desired velocity, 20 simultaneously as the extruded hollow element or slab is left behind on the substrate shown at the reference number 26 to the right side of fig. 1. On the top side is positioned finishing plate 27. The internal parts of the machine at a known extruder embodiment are shown in Fig. 4 in DE 20 59 760 C2 and is schematically illustrated on fig. 3. 5 Herein the feeding screw 30 is supported on a hollow support shaft 32. The feeding screw 30 is at the front end provided with gear drive 34 connected to a motor drive 35. The forming tube 36 comprises in this embodiment two parts, namely a rear part 36 which via an elastic coupling 38 is connected to a front part 40 of the forming tube, and which in the front side is mounted on a support disc o 42, attached to the rear end of the stationary shaft 32. Inside the front part 40 of the forming tube 38 is mounted a vibrator 44 on a longitudinal shaft 46 extending through the hollow stationary shaft 32 and which in front is connected to an electric motor 48. The construction shown in fig. 3 has proved to generate noise on a very high level since a substantial part of the vibrations will migrate to the support disc 42 at the rear end of the stationary shaft, and from there further to the machine parts. Simultaneously a correspondingly smaller part of the vibration energy will migrate radially outwards to the concrete mass which surrounds the forming tube 36, 40 such as illustrated in fig. 1. The reference number 7 in figs. 1 and 2 designates tension or stretching cables which are introduced on the bottom side of the slabs by means of not shown, known equipment. Fig. 4 shows a longitudinal view similar to fig. 3 through the internal parts of a machine in accordance with the invention. The section shown in fig. 4 constitutes substantially enlargements of the corresponding parts shown in fig. 1. and the same reference numbers are utilized on the same parts. The forming tube 20 is in accordance with the invention mounted on an elastic transition member 50, the front side of which is attached on a support disc 52 and which in accordance with the invention suitably is provided with a radial widening in direction rearwards, such that the circumference at this end runs flush with the outside of the elastic dampening member 50, which have the same outside : diameter as the forming tube 20 (shown stitched). The vibrator device in accordance with the invention consists suitably of an elongated body 22 which extends coaxially through the forming tube 20, and at the rear end is supported via a support pin 56 in the transverse wall 58 on the forming tube, and the foreend of which in similar manner is mounted on a transverse wall 60 on the forming tube via a support pin 62. The vibrator device itself includes an eccenter 64 positioned at the front end in the vibrator body so close to the foreend of the forming tube 20 as possible. The vibrator is preferably electrically driven and is receiving electric power through a cable 66 which is passed through the hollow support shaft 16. By positioning the vibrator with eccenter as close to the elastic dampening member 50 as possible, optimal vibration is provided on the concrete mass positioned outside the forming tube. The forming tube will in this fashion obtain a floating suspension inside the rearward ly directed extrusion chamber, a fact which is also rather favourable with the aim to obtain even compression or compacting of the concrete mass. The arrows 70 in fig. 4 illustrates the vibration pattern, namely such that optimal vibration will be situated at the fore end of the forming tube behind the dampening member 50 and with gradually reduced vibrations to a zero towards the rear end of the forming tube, a fact which is very desirable in order to avoid sink in the concrete mass which otherwise may cause deformed hollow openings through the hollow element or slab. An extruding machine in accordance with the invention has proved to result in a reduction of the noise level from 100-110 decibel down to a noise level of 80- SO decibel or lower. This implies in reality that the practical noise level with a machine in accordance with the invention only is a fraction of the noise level experienced with known machines. It can be informed that the maximum permitted noise level in production premises in Norway with the use of hearing protection means is stipulated just at 80-90 decibel while a noise level of or above 100 usually is not permitted on premises staffed with operators in close vicinity of the machine. Tryouts have furthermore shown that with existing machines operating with satisfactory vibration the vibrators must be driven with a speed up to 12000 rpm. while a machine in accordance with the invention may utilize vibrators with vibration velocity down to 6000 rpm with correspondingly further reduction of the noise level and wear on the machine. With known machine today the vibrators cause rather large wear on the machine parts such that for instance the bearings must be replaced frequently.

Claims: PATENT CLAIMS 1. Means on extruder for continuous moulding of prestressed hollow elements or slabs of concrete, of the kind comprising an extruding machine provided with s wheels (2, 4) resting on a casting floor or steel bench (5), which machine comprises a forward operational unit, one suitably vertical hopper (10) for supply of fresh concrete, which lowermost opens into a horizontal, rearwardly directed forming chamber (12), one through the forming chamber stationary, horizontally directed support shaft, which shaft rearmost supports a forming tube (20) for the o concrete, one on the stationary support shaft (32) rotatably supported feeding screw (16, 14) for feeding and compressing the concrete in direction rearwards towards the forming tube (20), and a vibrator (44) situated in connection with the forming tube (40) and optionally vibrators in other positions on the machine. characterized in that the forming tube (20) including the eccenter (64) is s supported at the rear of the stationary support shaft via an elastic damper means (50), such that the vibrator (54,64) is mechanically separated from the remaining part of the extruding machine. 2. Means in accordance with claim 1 , characterized in that the damper means (50) consists of a rubber member or the like, preferably having the same diameter as the forming tube. 3. Means in accordance with claim 1 , characterized in that the vibrator device (22) in the forming tube (20) includes an electrical unit with an eccenter (64) mounted in the front at a short distance from the damper means (50) for the forming tube (20). 4. Means in accordance with claim 2 or 3. characterized in that the vibrator device (22) receives electrical power via a cable (66) carried through a central opening through the support shaft to the drive unit (8). 5. Means in accordance with any of the preceding claims, characterized in that the vibrator member (22) is supported in front of the forming tube (20) and at the rear end on a transverse wall in the forming tube (20). s 6. Means in accordance with any of the preceding claims, characterized in that at the rear end of the stationary support shaft is provided a disc (52) for supporting the damper member (50), which disc at the rear end is given substantially the same diameter as the damper member (50) and also the forming tube (20). 0 7. Means in accordance with claim 6, characterized in that the disc (52) has a curved or conically shaped circumference with increasing diameter in direction rearwards, and is serving as a guiding disc for the concrete which is being pressed in direction rearwards to the s forming tube.

Inventors: THORESEN BJOERN O, THORESEN, BJOERN, O.
Applicants: THORESEN BJOERN O, THORESEN, BJOERN, O.
Application year: 1998
Main classification: B28B3
IPC codes: B28B1