METHOD AND DEVICE FOR CUTTING GAS CONCRETE

Abstract: A method and a device for cutting gas concrete employing cutting wires (35), whereby, in order to decrease shocks and vibrations, and in order to cut blocks of gas concrete more rapidly and with a finer surface structure, said wires (35) are guided and driven separately from one another in such a way that they are guided in their lengthwise direction relative to a cutting frame (14) and that they are driven reciprocally relative to said frame (14), the average cutting speed (V) of the cutting wires (35) in their longitudinal direction being selected so as to be at least six times greater than the material-carrying speed (5, 70).

Description: The invention relates to a method for cutting gas concrete in a plastic state by means of a plurality of cutting wires driven reciprocally in their longitudinal direction. Such a method is known from DE-C-849976. The wires are arranged in a cutting frame, which together with these wires and their wire holders is reciprocated. The cutting process in gas concrete fabrication is costly because of the investment in an expensive cutting device and the personnel thereby required. It would be desirable to make the relative speed between the block of gas concrete for cutting and the cutter frame ― that is, the material carrying speed ― high to thus shorten the cutting time. This cutting speed is however limited, since when the cutting speed is too high there is great danger of the cutting wire breaking and/of since the then resulting cut surface is extremely uneven and/or extremely rough. The cutting forces which occur with excessive material carrying speeds lead to violent vibrations and shocks which are not acceptable either for the structure of the soft gas concrete or for the usually complicated and costly cutting device. The invention provides a new method with which a block of gas concrete can be cut more rapidly and/or with a finer surface structure and/or with less risks of cutting wire breaking and/or with less risks of gas concrete structure damage. To this aim the method according to the invention is characterised as indicated in claim 1. As a result the cutting wires can be driven with high frequency of preferably more than 10 Hz. and more preferably with a frequency in the order of magnitude of 50 Hz. without this leading to violent vibrations or jolts. With this high cutting wire speed the cutting speed can be considerably increased, while the surface structure obtained can be made so flat and smooth that even wallpaper can be adhered thereto without interposing of a plaster layer. It is noted that DE-A-2415594 discloses a cutting device for foam material having one cutting wire. It does not disclose a process of cutting gas concrete in plastic state. DE-A-3213900 relates to the cutting of foam bodies, particularly polystyrol and polyurethane. The frame together with wire end holders is reciprocated. GB-A-1080003 discloses a method of cutting gas concrete in a plastic state, in which two wires are moved in the same cutting plane, the one behind the other, which results in an at least approximately smooth cutting surface. The wires are bent during their reciprocating movements, due to which the lifetime thereof will be short. US-A-2115102 discloses a device for cutting cakes in which a plurality of wire-shaped saws is reciprocally driven relative to a cutting frame by means of a shaft having cranks distributed over its periphery. The invention also relates to and provides a device for performing the method according to the invention. This device is indicated in claim 5. Preferred embodiments of the method and the device according to the invention are indicated in the dependent claims. Mentioned and other features of the invention will be made apparent in the description following hereinafter of preferred embodiments of a device according to the invention. In the drawing in schematic form: Figure 1 shows a graph which provides an insight into the speed ratios during the cutting process. Figure 2 is a diagram of a cutting device according to the invention. Figure 3 is a perspective view of a preferred embodiment of a device according to the invention in practical operation. Figure 4 is a view along arrows IV-IV from figure 3. Figure 5 shows on a larger scale a perspective view of detail V from figure 3. Figure 6 shows on a larger scale a broken away view along arrows VI-VI from figure 4. Figure 7 shows on a larger scale a schematic view along arrows VII-VII from figure 6. Figure 8 is a section along lines VIII-VIII from figure 6. Figure 9 shows detail IX from figure 6 on a larger scale. Figures 10 and 11 each show a detail in each case of different cutting devices according to the invention. Figure 12 is a perspective, schematic view of detail XII from figure 11, and Figure 1 shows in a diagram the ratio between the average reciprocating cutting speed V of the cutting wire in its lengthwise direction in meters per minute during a forward stroke and a return stroke on the one side and the material carrying speed S in meters per minute on the other. The material carrying speed is the relative speed between the block of gas concrete for cutting and the cutter frame. In the known state of the art the cutting speed V is 4.5 m/min. It has been found in tests that if, with a cutting wire with a diameter of 0.7 mm, the ratio V/S is greater than the value indicated by the line a , a smooth surface is obtained. The lines b and c indicate the limits in the case of cutting wires of respectively 0.8 and 0.9 mm. Tests further show that when two cutting wires are disposed in the same cutting plane one behind the other the boundary line d runs less steeply than when only one cutting wire is used in the same cutting plane. It is now proposed to employ a considerably higher cutting speed V , preferably 9 m/min, so that the material carrying speed S can be markedly increased. In the preferred embodiment of the device 11 according to the invention, a block 12 of plastic gas concrete for cutting is supported by rods 16 which lie on grooved rolls 13 which are mounted for rotation both in front of and behind a cutting structure 14 (fig. 4) on a bearing frame 17 which can be moved up and down by means of hydrocylinders 15. One or more rolls 13 are driven to cause the block 12 to move during the cutting according to arrow 70 through the cutting structure 14 at a material carrying speed S . A block 12 for cutting is supplied by means of a grid 18a which has cross beams 19 with vertical pins 20, between which lie loose rods 16. Block 12 rests on these rods 16 when grid 18a arrives in figure 4 at the left hand side of cutting structure 14 while the grid rolls over freely rotating rolls 21 that are in a stationary disposition. In this position of grid 18a, while an empty grid 18b is likewise located on the right hand side of cutting structure 14, bearing frame 17 is raised, whereby block 12 is lifted together with rods 16 from the grid 18a and taken up by means of the grooved rolls 13. Cutting structure 14 is connected to fixed pillars 28 to which horizontal frame beams 23 and 24 are firmly attached at a level such that they do not impede the passage of block 12 and grids 18. Also firmly attached to pillars 28 are vertical guidings 12 which serve for vertical guiding of slides 25 of a cutting structure 14 that can be raised by means of hydrocylinders 26. This lifting is necessary to carry the empty grid 18a over rolls 21 to the position of grid 18b where it can pick up a cut block and be subsequently carried away. When cutting structure 14 is lowered it comes to rest on adjustable stops 29. Cutting structure 14 consists of a U-shaped upper frame 33 and a U-shaped underframe 32 which can be driven apart by means of hydrocylinders 34 for the purpose of tensioning cutting wires 35 and which can be fixed in position after tensioning by means of screw connections 36. Located in horizontal box girders 37 and 38 of upper frame 33 and under-frame 32 respectively are identical drive means 39 which co-operate with identical means 40 for holding cutting wires in position, so that only the box girder 38 with fittings is described with reference to figures 6-9. Accommodated in box girder 38 and attached thereto with flanges 43 and bolts 44 are vertical guide bushings 41, each with a guide lining 42. Guided therein is a guide pin 45 which is provided with a support disc 46 having a flat, horizontal support face 47. Located between flange 43 and support disc 46 is a spiral spring 48 which forces guide pin 45 downward. Arranged on the outer end of guide pin 45 is a sealing ring 49. The girder 38 has an oil chamber 50 in which a camshaft 51 is mounted for rotation. This camshaft 51 has exactly round eccentric cams 52 which are surrounded by roller or ball bearings 53. These bearings 53 each co-act with a support face 47. Two cams 52 at a time are arranged pair-wise in the same angular position 71-76 so that they can co-operate with a pair of guide pins 45 which follow behind each other and which bear a common wire end holder 55. The pairs of cams 52 are distributed evenly over the periphery so that the camshafts 51 are balanced, particularly with respect to the cutting reaction forces exercised thereon by the cutting wires 35. Each cutting wire holder 55 consists of a bridge piece which has slots 56 arranged at the same places on either side for accommodating two cutting wires 35 in each case (fig. 8). These slots 56 are chosen such that the cutting wires 35 can be positioned at the mutual pitch distances that occur. Each of both cutting wire ends 57 is accommodated in a metal plug 58 which supports via a compression spring 59 on the bottom 60 of a housing 61 provided with a passage 62 (fig. 9). Both camshafts 51 are connected to each other via cone drive gears 63 by means of a vertical shaft 64, the upper end of which takes the form of a spline shaft and can slide vertically relative to a bevel gear 66 and a drive wheel 67 which are each provided with a spline bore. Drive wheel 67 is driven by a motor 69 via tooth belt 68. When the upper frame 33 is moved downward relative to underframe 32 by means of hydrocylinders 34, cutting wires 35 can easily be fixed to the wire end holders 55. Cutting wires 35 are then tensioned by forcing apart of the frames 33 and 32. Both camshafts 51 remain continuously in the same position during their rotation, so that the distance between the both wire end holders 55 holding the same cutting wire 35 in position has a fixed value. In the cutting device 96 from fig. 10 wire ends 57 of cutting wires 35 are tensioned between two arms 97 mounted for pivoting on shafts 98, these arms being driven synchronously by two mutually coupled camshafts 94. In the cutting device 80 from fig. 11 and 12 each cutting wire 35 is tensioned between two wire end holders 81 which are attached via draw springs 82 to cutting structure 14. As a result of periodic synchronous actuation in opposing directions of two magnet coils 83 the cutting wire 35 is moved up and down with high frequency and at high cutting speed V . Figure 2 shows the principle of a cutting device 87, whereby in each case a cutting wire 35 is tensioned between two piston rods 88 of a pneumatic drive system. The tensioning of the cutting wire 35 is carried out by means of pneumatic chambers 95. The drive chambers 90 of the hydrocylinders 91 are fed by a liquid pump 92 via a rotary diverter valve 93 such that both piston rods 88 move up and down synchronously with a cutting speed V , while a block of gas concrete moves in a manner not illustrated through the cutting structure with a material carrying speed S .

Claims: 1. Method for cutting gas concrete in a plastic state by means of a plurality of cutting wires (35) driven by means of drive means reciprocally in their longitudinal direction, characterised by holding the wire ends (57) of said cutting wires (35) in position by means of wire end holders (55) which are guided in the lengthwise direction of said wires (35) relative to a cutting frame (14) by and reciprocally by driving said wire end holders (55) relative to each other and to said cutting frame (14) by means of said drive means without leading to violent vibrations or jolts. 2. Method as claimed in claim 1, characterized by the wire end holders (55) being driven with a frequency of more than 10 Hz. 3. Method as claimed in claim 2, characterized by the wire end holders (55) being driven with a frequency of more than 25 Hz, and more preferably with a frequency of approximately 50 Hz. 4. Method as claimed in any of the foregoing claims, characterized by the wire ends (57) of in each case at least two cutting wires (35) disposed one behind the other in the same cutting plane being fixed to a common wire end holder (55). 5. Device (11) for cutting gas concrete in a plastic state according to the method as claimed in claim 1, comprising at teast a carrier accommodating a block of gas concrete for cutting, a cutting frame (14), drive means for driving of a relative material carrying movement S between said carrier (16) and said cutting frame (14), a plurality of cutting wires (35) arranged in said cutting frame (14), the wire ends (57) of which are held in place on said cutting frame (14) by means of wire end holders (55), and drive means (51) for reciprocal driving of said cutting wires (35) in their longitudinal direction, characterized in that wire end holders (55) are mounted for movement in said cutting frame (14) in lengthwise direction of said wires (35) relative to said cutting frame (14) and that said drive means (39) drive said cutting wires (35) reciprocally relative to each other and to said cutting frame (14) without leading to violent vibrations or jolts. 6. Device (11) as claimed in claim 5, characterized in that each cutting wire (35) of a series of cutting wires (35) is held in position between to wire end holders (55) which are both synchronously driven reciprocally by the drive means (39), that preferably both the wire end holders (55) holding in position at least the same cutting wire (35) are driven mechanically by two sets of drive means (51) coupled to each other by means of a cone drive gear (63, 64). 7. Device (11) as claimed in any of the claims 5 and 6, characterized in that at least one and preferably two series of wire end holders (55) is or are driven by a campshaft (51), said camshaft (51) being provided close to at least one round, eccentric cam (52) with a bearing ring (53) mounted thereon, said bearing ring (53) co-operating with a substantially flat support face (47) of a slidably guided wire end holder (55). 8. Device (11) as claimed in any of the claims 5-7, characterized in that cams (52) for driving of wire end holders (55) are distributed uniformly over a camshaft periphery. 9. Cutting device (11) as claimed in claim 7 or 8, characterized in that a wire end holder (55) is guided for sliding in wire direction in a slide bearing (41) accomodated in a lubricating oil chamber (50) in which is also disposed a camshaft (51) driven for rotation which co-operates with a support face (47) of said wire end holder (55) which is forced by means of a spring (48) in the direction towards said camshaft (51). 10. Cutting device (11) as claimed in claim 8 or 9, characterized in that the cutting wire holder (55) extends over some distance in the plane of the cutting frame (14) transversely of the cutting wire direction and has in this transverse direction a series of attachment location for a wire end (57), that said wire end holder (55) is guided for sliding in said cutting frame (14) in lengthwise direction of the cutting wire (35) by means of two slide bearings (41) disposed adjacent to each other, in which a holder part (45) is slidably accommodated, whereby each of both holder parts (45) co-operates with a cam (52) of a camshaft (51).

Inventors: SCHREUDERS, WILLEM JOHANNES
Applicants: DUROX GASBETON B.V.
Application year: 1988
Main classification: B28B11
IPC codes: B26D1, B23D57, B28B11, B26D5