EP2022613B1 - Impact device in a porous concrete cutting device - Google Patents

Abstract

The gear (4) has multiple vertically aligned lamella elements that are arranged on multiple vertical slots at lateral distance. Two vertical lamella packages have lamella elements arranged one above the other, where upper lamella package is horizontally arranged relative to a lower lamella package and is adjustably arranged in the gear. The lamella package is connected to a drive element, where the lamella package includes carrying elements that are connected to the drive element.

Description

The invention relates to a pusher device which is used as a frontal, mostly planar abutment for a still plastic porous concrete block, which is cut with a slitter in an aerated concrete cutting machine in its longitudinal direction with cutting wires in cuboid AAC.

For longitudinal cutting of aerated concrete blocks slitting devices are used in an autoclaved concrete cutting system having an upright cutting frame, between the horizontal crossbars at a certain lateral distance upright extending cutting wires are stretched like a gate. In addition, horizontally extending cutting wires can be arranged between the side rails of the cutting frame at a certain vertical distance.

Often, at least one horizontally arranged cutting wire and / or at least one horizontally arranged contour cutting element, for. Example, a contour cutting blade provided on the cutting frame, which separate a superficial, production-related uneven upper surface layer of a porous concrete block just before slitting or during the slitting process, so that a flat or contoured surface is formed.

For the longitudinal cutting of aerated concrete blocks, two different technologies are used. In one method, the aerated concrete block rests lying on a cutting bed and the cutting frame is moved in the longitudinal direction of the aerated concrete block, wherein the cutting wires penetrate the aerated concrete block. In the other method, the cutting frame is in a longitudinal cutting station of the cutting system arranged stationary and the aerated concrete block is pushed together with cutting bed through the cutting frame.

In both methods, pushers or counter-holding devices are used, which are attached to the end face of the porous concrete block and serve as an abutment against the cutting pressure. In the case of the stationary cutting frame, the aerated concrete block, pushed on a grid of movable longitudinal bars and usually front and rear pushed on impact devices through the cutting frame, usually at both ends a shock device is provided. By moving them together, the gaps formed by the vertical section are closed before the longitudinal section begins.

Thus, when emerging from the cutting pressure under tension cutting wires from the autoclaved aerated at the end of the cutting frontally no Porenbetonmaterialbrocken entrained by the cutting wires from the surface areas of the aerated concrete block, it is known that the impact device frontally with vertically aligned z. B. plate-shaped, arranged at a lateral distance lamellar elements, between which z. B. are formed due to the distance slots in which the cutting wires are located before cutting or in which the cutting wires can enter after leaving the aerated concrete body. For horizontal cutting wires and horizontal slots z. B. may be provided in the slats. By arranging these slots, it is possible for a cutting frame to extend beyond the front end of a cut aerated concrete block, with the cutting wires penetrating into the slots. Since the aerated concrete block is thereby supported by the lamellar elements of the impact device frontally, it is prevented that break out when moving out of the cutting wires from the autoclaved aerated concrete blocks, whereby rejects are avoided.

Out DE-PS 900 189 It has become known, a jumper device for stationary or movable arrangement in an autoclaved concrete cutting system according to the preamble of claim 1.

Autoclaved aerated blocks are often manufactured in a aerated concrete plant with different casting height. Optimal cuts but are usually only achieved when the cutting frame size, in particular the cutting frame height or the length and / or thickness of the cutting wires of the cutting system optimally z. B. on the aerated concrete block cross section and the aerated concrete material composition is turned off. The same applies to the dimensions of the pushers. For this reason, cutting systems are sometimes used in which the cutting frame is interchangeable. There is a problem with the impact device, which is not replaceable installed and may be oversized if smaller blocks of aerated concrete are to be cut. An oversized butt device would but abut the cutting frame, which is why although smaller bumpers can be used, but never larger.

The object of the invention is to provide a pusher device which can cooperate with different sized cutting frame and / or arranged in a cutting frame at different heights horizontally extending cutting wires and / or contour cutting elements together.

This object is solved by the characterizing part of claim 1. Advantageous developments of the invention are characterized in the subclaims.

The invention operates with a pusher device having at least two vertically stacked disk packs or lamella blocks each having its own lamellar elements, of which at least the upper disk pack relative to the lower disk pack horizontally back and again before or in the cutting direction and against the cutting direction of the cutting device of a cutting system slidably disposed in the jar. Moreover, the pusher device may be arranged to be displaceable or displaceable in an autoclaved concrete cutting system, either stationary or in the cutting direction and counter to the cutting direction.

Preferably, a plurality of stacked superposed, preferably each individually horizontally displaceable relative to each other slat packages are provided with at least a fixed disc pack arranged underneath are combined.

Conveniently, the disk packs are spaced apart at a vertical distance so as to form a horizontal gap into which a horizontal cutting wire of a cutting frame can engage.

Lamella elements according to the invention are in particular slats in the form of z. B. rectangular and elongated plates, for. B. metal, the upright standing laterally spaced from each other with their side surfaces parallel to each other, rearwardly mounted on support elements of the pusher are arranged so that a comb-like arrangement of the lamellar elements is formed. The thickness of the plates or lamellar elements may be the same or different and z. B. between 0.5 and 10 cm. The height of the web plates is z. B. between 4 and 20 cm and the length is z. B. 40 to 60 cm. The lateral distance between the web plates is z. B. 0.5 to 5 cm. The horizontal gap of the vertical distance between two disk packs has z. B. a wide of 2 to 4 cm.

Fig. 1

perspektivisch eine Porenbetonschneidanlage mit einer Stoßvorrichtung;

Fig. 2

eine Seitenansicht einer erfindungsgemäßen Stoßvorrichtung;

Fig. 3

die Seitenansicht nach Fig. 2 ohne Seitenführungswandung entlang der Linie III-III in Fig. 4 mit Blickrichtung in Pfeilrichtung;

Fig. 4

eine Draufsicht auf die Stoßvorrichtung nach Fig. 2;

Fig. 5

einen Querschnitt durch einen Teilbereich eines Lamellentragrahmens und einer Seitenführungswand entlang der Linie V-V in Fig. 3 mit Blickrichtung in Pfeilrichtung ;

Fig. 6

einen Querschnitt durch einen Teilbereich der Stoßvorrichtung entlang der Linie VI-VI in Fig. 2 mit Blickrichtung in Pfeilrichtung;

Fig. 7

den prinzipiellen Aufbau und die Arbeitsweise einer erfindungsgemäßen Stoßvorrichtung in einer schematischen Seitenansicht.

Fig. 8

schematisch eine Frontansicht eines erfindungsgemäßen höhenverstellbaren Schneidrahmens.

Reference to the drawing, the invention will be explained in more detail below by way of example. Show it:

Fig. 1

in perspective, an autoclaved concrete cutting plant with a pusher device;

Fig. 2

a side view of a shock device according to the invention;

Fig. 3

the side view after Fig. 2 without Seitenführungswandung along the line III-III in Fig. 4 looking in the direction of the arrow;

Fig. 4

a plan view of the pusher after Fig. 2 ;

Fig. 5

a cross section through a portion of a Lamellenträgagrahmens and a side guide wall along the line VV in Fig. 3 looking in the direction of the arrow;

Fig. 6

a cross section through a portion of the pusher along the line VI-VI in Fig. 2 looking in the direction of the arrow;

Fig. 7

the basic structure and operation of a shock device according to the invention in a schematic side view.

Fig. 8

schematically a front view of a height-adjustable cutting frame according to the invention.

In the Fig. 1 illustrated autoclaved concrete cutting 1 has a cross-cutting device 2, a fixed longitudinal cutting device 3 and a horizontally movable, butting jerking device 4 and a horizontally movable and upwardly pivotable, opposing pusher 5 and a cutting bed 6.

In this aerated concrete cutting 1 a cuboid porous concrete block (not shown) placed on the cutting bed 6 of the cross cutting device 2 and cross cut. Subsequently, the butt jointing device can be moved from one side of the cutting unit 1 in the direction of longitudinal cutting frame 3 against the one end face of the cross-cut aerated concrete block and the opposing pusher 5 from the other side of the cutting unit 1 also in the direction of cutting frame 3 against the other end face of the cross-cut porous concrete block wherein the resulting by the cross cutting air concrete body are pushed together so that the kerfs are closed. Thereafter, the pushers 4, 5 can transport the aerated concrete block through the slitter 3 in which the aerated concrete block is cut in its longitudinal direction.

At the beginning of slitting, there are the vertical slitting wires and, if present, the horizontal slits Wires of the cutting frame of the cutting device between the lamellar elements of the disk sets of the pusher 5. At the end of the cutting process drive the cutting wires in the lamella elements of the disk sets of the pusher. 4

The in the Fig. 2 to 6 as an example illustrated inventive impact device 4, 5 has frontally or to the cutting frame pointing one above the other several horizontal plate packs 10, 11, 12, 13, 14, 15, the front side in their initial position vertically aligned with each other. The upper three disc packs 10, 11, 12 are arranged in the double arrow 7 back and again in front of slidably and are each connected to a corresponding drive means in connection. The disk packs 13, 14, 15, however, are fixed or immovable in the pusher 4, 5 are arranged.

The lamellae packages 10 to 15 consist, as is known, of lamellar elements 8 in the form of upright side by side spaced lamella plates, between which vertical gaps or slots 9 are provided. Between the disk packs 10 to 15 horizontal gaps 16 are left free.

The number of disk packs is not critical. It is essential that at least the uppermost plate pack 10 is slidably disposed and that at least one further plate pack fixed or also displaceable is present underneath.

The lamellar plates 8 of the displaceable plate packs 10 to 12, the free front ends of which are located on the front side, are attached directly or indirectly via a crossbeam element on the back side to a horizontal support frame 17. Each supporting frame 17 usually has a front transverse strut 18, a rear transverse strut 19 and two lateral longitudinal struts 20, 21 and a central reinforcing longitudinal strut 22 (FIG. Fig. 4 ).

The longitudinal side struts 20, 21 have outside sliding or rolling guide elements 23, which is a horizontal sliding or rolling in correspondingly adapted guide elements 24 in or on vertically arranged side walls 25, 26 in the double arrow direction 7 ( Fig. 4 . 5 ). In this way, the displaceable plate packs 10 to 12 between the side walls 25, 26 are movably mounted and supported. The non-displaceable plate packs 13 to 15 store z. B. on frame racks 27 and between the side walls 25, 26 in a fixed arrangement.

The side walls 25, 26 are each secured to a horizontal support beam element 28, 29 of a frame construction of the impact device in the lower region, wherein the support beam elements 28, 29 at a short distance via supports 44 on parallel below arranged moving beam elements 30, 31 store. The mobile beam elements 30, 31 have rail wheels 32 which run on fundamentally supported rails 33 running in parallel to the beam elements 28, 29, 30, 31. On the rails 33, the pusher 4, 5 can be moved.

For the method, a drive device 34 is provided on both sides of the beam elements 28, 29, 30, 31, which can drive the pusher device 4, 5 via a pinion 35 and a rack 36 fixedly arranged on the rails 33 or in the rail region.

In the rear region, the support beams 28, 29 are connected to a transverse strut 40, on which vertical support columns 37, 38 are arranged, between which a cross member 39 is seated in the upper end region.

Between the cross member 39 and the transverse strut 40, a vertical support column 41 is arranged in the longitudinal center region.

between the rear cross member 19 of each support frame 17 and the support column 41 or the cross member 39 and the support column 41 of the frame structure of the pusher 4, 5 piston cylinder units 42 are arranged one above the other, the z. B. each with its own drive unit 43 are operable.

With the respective drive unit 43, the associated piston-cylinder unit 42 is actuated, so that the thus about their support frame 17 in communication z. B. disk pack 10 can be pulled back and pushed forward again. Also, a mechanical displacement by means of spindles and z. As a self-locking gear are within the scope of the invention, as well as the mechanical locking of the disk packs at the load-receiving end point.

The Fig. 7a to 7c illustrate the principle of operation of a shock device according to the invention 4. Schematically represented is a longitudinal cutting frame 45 with longitudinal cutting wires 46, a cutting device 47 with horizontal cutting wires 48, a contour cutting device 49 with a Conturenschneidmesser 50, to be cut aerated concrete block 51, 51b, 51c and the movable plate packs 10 to 12 and the fixed plate packs 13 to 15.

To Fig. 7a If the uppermost layer 51a of the porous concrete block 51 is to be removed. For this purpose, the porous concrete block 51 and the pusher 4 are moved against the cutting devices 45, 47, 49 and the contour cutting blade 50 in the direction of arrow 52, wherein the contour cutting blade 50 can penetrate after ablation of the top layer 51a in the pusher 4 without the pusher bothers 4 , The contour cutting knife 50 has z. B. a horizontally lying flat blade 50a and vertical, on the side distance juxtaposed holding webs 50b; these elements can dip into a horizontal gap 16 and vertical slots 9. According to Fig. 7b a slightly smaller aerated concrete block 51b is to be cut. The cutting frame 45 has the same dimensions as in the case of Fig. 7a , The cutters 47 and 49 are set lower. The disk pack 10 is retracted so that the contour cutting knife 50 can freely penetrate into the pusher 4. The minimum aerated concrete block height is z. B. 40 cm.

In the device according to Fig. 7c a smaller cutting frame 45a is used because an even smaller block of aerated concrete 51c to be cut. For this reason, the disk packs 10 and 11 are retracted. The contour cutting device with the contour cutting knife 50 and the cutting device 47 with the horizontal cutting wires 48 are set even lower, so that in particular the contour knife 50 and an upper horizontal cutting wire 48 can penetrate into the pusher 4.

It is particularly expedient to combine the impact device according to the invention with a cutting frame whose height is variable, so that - as mentioned - the cutting frame is adjustable to different cross-sectional dimensions of aerated concrete blocks. The cutting wires are replaced by cutting wires according to different length and possibly other thickness, which is not a problem, because the cutting wires are usually mounted replaceable anyway in the cutting frame.

A variable in height cutting frame is z. B. from the DD 267 460 A1 . FIGS. 3 and 5 known. The known cutting frame consists of a U-shaped upper frame and a U-shaped subframe, the voltage of the cutting wires by means of hydraulic cylinders a few millimeters, z. B. to 10 mm, can be pressed apart, with screw fix after tightening the clamping state.

Based on this prior art, the present invention, which is applicable not only in combination with the impact device according to the invention, provides a cutting frame, which not only has a tensioning device for the wires, but also an adjustment for different lengths of cutting wire sets, so that the cutting frame dependent can be fitted with cutting wires of different lengths of the porous concrete block cross-section, with a respective assembly of course has the same length wires.

This invention is characterized in claim 22. Advantageous developments of the invention Cutting frames are specified in the subclaims dependent on this claim.

The invention is particularly useful for cutting frames in which according to DD 267 460 A1 the cutting wires can be moved up and down relative to the cutting frame and expediently also relative to each other by eg camshaft drives with a relatively high frequency.

Based on Fig. 8 the cutting frame according to the invention is explained in more detail by way of example.

The fixed longitudinal cutting device 3 includes a longitudinal cutting frame 45, which has a rectangular vertical support frame 55 which is mounted on a fundamentally fixed frame 56 with scaffold brackets 57. The storage can be unilateral, as shown, but it can also be provided on both sides.

The support frame 55 has an upper horizontal cross member 58 and a lower horizontal cross member 59 and a first vertical side strut 60 and a second vertical side strut 61.

In the region of the lower transverse strut 59 sits on each side strut 60, 61, a guide element or guide box 62, 63, between which a lower cutting frame crossbar 64 is fixed or immovable to the guide elements and / or struts. In this case, a transmission means is provided at least in a guide element.

In the region of the upper transverse strut 58 and at a vertical distance above the lower fixed cutting frame crossbar 64, an upper cutting frame cross bar 65 is arranged, which is movable with sliding guide elements 66 in the direction of arrow 67 on the side struts 60, 61 movable up and down.

Between the lower and the upper cutting frame cross member 64, 65 is in the range of side struts 60, 61 each have a z. B. automatically operable piston cylinder assembly 68, which engages the cutting frame crossbars 64, 65 and / or the Gleitführungselementen 66.

According to the invention, each piston-cylinder arrangement is of double-piston design in that a piston 69 is guided into an upper region of the cylinder 71 of the piston cylinder assembly and a piston 70 in the lower region, a cylinder bottom 72 being provided between the two pistons and the upper piston 69 being provided on the upper cutting frame transverse member 65 and the lower piston 70 acts on the lower cutter frame transverse spar 64.

The upper cylinder space receiving the upper piston 69 is shorter than the lower cylinder space accommodating the lower piston. The length of the cylinder chambers can also be reversed, d. that is, the lower one may be shorter than the upper cylinder space. The upper piston 69 is movable in the double arrow direction 73 and the lower piston 70 in the double arrow direction 74, wherein the two pistons can be operated independently of each other movable.

The stroke of the upper piston is suitably between 200 and 600 mm and the stroke of the lower piston 70 expediently between 5 and 20 mm.

Between the upper and the lower clamping frame cross member 65, 64 are wire-like cutting wires 75 stretched, of which only three are shown, so as not to disturb the clarity of the drawing.

According to an advantageous embodiment of the invention, the wire ends of the cutting wires according to DD 267 460 A1 held in the crossbars 64, 65 by means of wire end holders, which are mounted relative to the respective cross member 64, 65 in the longitudinal direction of the cutting wires 75, said drive means, the wire end holder relative to the cross bars 64, 65 move up and down.

To ensure such a drive in the cutting frame 45 according to the invention sits on one side - in the example shown on the side of the first side strut 60th - At the upper cross member 65, a motor 76 which drives via gear means an upper, disposed in the cross member 65 drive means, for. As a horizontally mounted camshaft and a vertical tooth webs and tooth spaces exhibiting toothed rod 77 which engages in the lower guide box 62, and on the gear means provided therein, a lower in the cross member 64 arranged drive means, for. B. also drives a horizontally mounted camshaft. In this case, the toothed rod 77 is so in communication with the transmission means that it can slide up and down by the transmission means. Thus, when the crossbars 64, 65 are driven apart or toward each other with the piston cylinder assemblies 68, the rack linkage 77 can freely slide through the gear means without being separated from the gear means or losing the drive contact.

The cutting wires 75 sit in a conventional manner interchangeable in the wire end holders or the wire end holder sit interchangeable in the cross bars 64, 65, so that the cutting wires can be replaced. Accordingly, they can be completely exchanged for shorter or longer cutting wires. This is made possible by the variability of the distance between the upper and the lower cross member 64, 65. For replacement, after removing the one set of cutting wires of predetermined length, the cross members 64, 65 are moved with the piston cylinder assemblies 68 in positions in which the new wire lengths between the cross beams This is done with the operation of the lower piston 70. After the new cutting wires have been inserted, a tensioning of the wires by the operation of the piston 69 in a conventional manner, because for clamping only a small stroke is required.

Claims (30)

1. An impact apparatus (4 and/or 5) for stationary or displaceable arrangement in a porous concrete cutting plant (1), wherein the impact apparatus (4 and/or 5) has lamella elements (8) which are arranged so as to form vertical slots (9) at a lateral distance and orientated vertically on the end face, characterized by at least two stacks of lamellae (10, 11, 12, 13, 14, 15) arranged vertically one above the other which have their own lamella elements (8) in each case and at least the upper stack of lamellae (10) of which is arranged in the impact apparatus (4 and/or 5) so as to be displaceable horizontally forwards and back again relative to the lower stack of lamellae.
2. An impact apparatus according to Claim 1, characterized in that for displacement purposes each displaceable stack of lamellae (10, 11, 12) is connected in each case to a driving means (42, 43) arranged in the impact apparatus and permitting displacement.
3. An impact apparatus according to Claim 1 and/or 2, characterized in that at least one lower stack of lamellae (13, 14, 15) is arranged in a stationary manner.
4. An impact apparatus according to one or more of Claims 1 to 3, characterized in that a plurality of stacks of lamellae (10, 11, 12) arranged one above the other and displaceable relative to one another are provided.
5. An impact apparatus according to one or more of Claims 1 to 4, characterized in that a plurality of stationary stacks of lamellae (13, 14, 15) arranged one above the other are provided.
6. An impact apparatus according to one or more of Claims 1 to 5, characterized in that at least the uppermost stack of lamellae (10) [is] arranged at a vertical distance from the stack of lamellae arranged below it, so that a horizontal gap (16) is formed.
7. An impact apparatus according to one or more of Claims 1 to 6, characterized in that the lamella elements (8) have lamellae in the form of plates which are arranged standing on edge at a lateral distance and designed in the manner of a comb.
8. An impact apparatus according to Claim 7, characterized in that the lamella elements (8) of each stack of lamellae (10, 11, 12, 13, 14, 15) are arranged fastened to support elements at the rear.
9. An impact apparatus according to Claim 8, characterized in that the support elements of the displaceable stacks of lamellae (10, 11, 12) are connected in each case to a driving means (42, 43).
10. An impact apparatus according to Claim 9, characterized in that the support elements have in each case a horizontal, substantially rectangular support frame (17) which is connected to the respective driving means (42, 43).
11. An impact apparatus according to Claim 10, characterized in that the support frame (17) has a front cross member (18), a rear cross member (19) and two lateral longitudinal members (20, 21), wherein the rear cross member (19) is connected to the driving means (42, 43).
12. An impact apparatus according to Claim 11, characterized by a central reinforcing longitudinal member between the cross members (18, 19).
13. An impact apparatus according to Claim 11 and/or 12, characterized in that the longitudinal lateral members (20, 21) have horizontal sliding elements (23) on the outside which are guided in corresponding horizontal sliding guide elements (24) arranged in a fixed manner in the impact apparatus.
14. An impact apparatus according to Claim 13, characterized in that the horizontal sliding guide elements (24) are arranged on vertical lateral walls (25, 26) arranged in the impact apparatus.
15. An impact apparatus according to Claim 14, characterized in that the non-displaceable stacks of lamellae (13 to 15) are mounted in a fixed manner on or between the lateral walls (25, 26).
16. An impact apparatus according to Claim 14 and/or 15, characterized in that the lateral walls (25, 26) are fastened in each case in the underside region on a horizontal support-beam element (28, 29) of a frame structure of the impact apparatus, wherein the support-beam elements (28, 29) are mounted at a slight distance above supports (44) on travelling-beam elements (30, 31) which are arranged parallel below the latter and which have rail wheels (32) which run on rails (33) running parallel to the beam elements (28, 29, 30, 31) and carried on or supported by the ground.
17. An impact apparatus according to Claim 16, characterized in that the impact apparatus (4, 5) is movable on the rails (33), wherein a driving apparatus (34) is provided preferably on both sides of the beam elements (28, 29, 30, 31) for the moving.
18. An impact apparatus according to Claim 17, characterized in that the driving apparatus (34) drives the impact apparatus (4, 5) by way of a pinion (35) and a toothed rack (36) arranged on the rails (33) or a toothed rack (36) arranged in a fixed manner in the region of the rails.
19. An impact apparatus according to one or more of Claims 16 to 18, characterized in that the support beams (28, 29) in the rear region are connected to a cross member (40) on which are arranged vertical support columns (37, 38) between which a transverse support (39) is mounted in the upper end region.
20. An impact apparatus according to Claim 19, characterized in that a vertical support column (41) is arranged between the transverse support (39) and the cross member (40) in their longitudinal central region.
21. An impact apparatus according to one or more of Claims 11 to 20, characterized in that piston-cylinder units (42), which are capable of being operated for example by their own driving unit (43) in each case, are arranged one above the other between the rear cross member (19) of each support frame (17) and the support column (41) or the transverse support (39) and the support (41) of the frame structure of the impact apparatus (4, 5), wherein the associated piston-cylinder units (42) are capable of being actuated by the respective driving unit (43) so that in this way the stacks of lamellae (10 to 12) connected by way of their support frames (17) can be pulled backwards and pushed forwards again.
22. An impact apparatus according to Claim 21, characterized in that spindles with a self-locking gear mechanism are provided instead of the piston-cylinder units (42), wherein mechanical locking means for the stacks of lamellae are advantageously additionally provided at the loading-bearing end point.
23. An impact apparatus according to one or more of Claims 1 to 22, combined with a vertical longitudinal cutting frame (45), the vertically extending cutting wires (75) of which are stretched in an interchangeable manner and the suspension height of the cutting wires of which is variable, so that sets of cutting wires of different length can be interchanged.
24. An impact apparatus according to Claim 23, characterized in that the cutting frame (45) has an upper crosshead (65) and a lower crosshead (64), at least one of which is arranged and guided in such a way that the distance of the crossheads (64, 65) from each other is variable in two steps.
25. An impact apparatus according to Claim 24, characterized in that the degree of variability in a first suspension step amounts to up to 600 mm, in particular between 100 and 300 mm, and in a second suspension step it amounts to up to 20 mm, in particular between 8 and 15 mm.
26. An impact apparatus according to Claim 24 and/or 25, characterized in that at least one double-piston piston-cylinder arrangement (68), which has two pistons (69, 70) capable of being operated independently of each other and one piston (70) of which provides with its stroke the suspension step and the other piston (69) of which provides with its stroke the tension step, is arranged between the crossheads (64, 65) for the variability in two stages.
27. An impact apparatus according to one or more of Claims 23 to 26, characterized in that the crossheads (64, 65) are arranged on a fixed support frame (55), wherein the lower crosshead (64) is connected in a fixed manner to the support frame (55) and the upper crosshead (65) is arranged on the support frame (55) so as to be capable of being moved up and down by way of guiding elements (66).
28. An impact apparatus according to one or more of Claims 23 to 27, characterized in that the interchangeable cutting wires (75) are situated in a manner known per se in the crossheads (64, 65) in wire-end retaining means which are movable up and down relative to the crossheads and relative to one another by means of driving means, for example camshafts.
29. An impact apparatus according to Claim 28, characterized in that the driving means are connected by way of transmission means to a motor arranged on the upper crosshead (65), wherein a vertical toothed rack (77) extends from the motor as far as the transmission means arranged on the lower crosshead (64), and the toothed rack (77) is connected to the transmission means in such a way that when the distance between the upper crosshead (65) and the lower crosshead (64) is altered the toothed rack (77) can slide through the transmission means without losing driving contact with the transmission means.
30. A porous concrete cutting plant (1) having at least one impact apparatus arranged so as to be stationary or displaceable, characterized by an impact apparatus (4, 5) according to one or more of the preceding Claims.

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