Abstract:
The invention relates to a cutting tooth for a ground working implement, particularly for a cutting wheel of a trench wall cutter, with a dedendum for reception in a holder of the ground working implement and at least one main cutting element for working the soil located at the top on the dedendum. For widening the working cross-section of the main cutting element at least one further reaming element is provided at the top on the dedendum and which, compared with the main cutting element, has a different cutting edge design.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a cutting tooth for a ground working implement, particularly for a cutting wheel of a trench wall cutter. Such a cutting tooth has a tooth root or dedendum for reception in a holder of the ground working implement and at least one main cutting element located on the top of the dedendum for working soil. 
   2. Related Art 
   Such cutting teeth are e.g. known from DE 297 20 261 U1 and DE 87 15 141 U1 and are used in underground working in trench wall cutters for producing trench walls. The cutting teeth can in particular be used in wheel cutters, where they are located on the circumferential surfaces of the cutting wheels. For producing a trench the cutting wheels are rotated and lowered into the ground. The cutting teeth break up and loosen the soil against the cutting wheels, so that it can e.g. be sucked off with the aid of a pump and/or can be processed to a suspension. 
   Ground working cutting wheels are frequently constructed in disk-like manner over a basic and in particular cylindrical wheel body, the disk axis coinciding with the cutting wheel rotation axis. The cutting teeth and optionally their holders are located in the disk areas of the cutting wheel. Between said disks fixed strippers placed on the cutting wheel frame can engage between the cutting teeth and optionally also their holders. During the cutting process the strippers form counterholders and give a firm resistance, so that on them it is also possible to break up harder rock material through the counterpressure of the moving cutting teeth. 
   The known cutting teeth have a shaft-like dedendum for reception in the cutting tooth holders. A carbide tip or cutting edge for cutting the soil is provided on an upper edge of the cutting tooth. 
   The width of the cutting tooth tip is more particularly chosen as a function of the ground to be worked. A narrower tip width is generally advantageous with harder rock material. By reducing the tip width and with an otherwise identical cutter design a higher superimposed load can be achieved, which increases the cutting progress, more particularly in hard rock. Thus, cutting teeth are known in which the cutting edge is narrower than the underlying front face of the dedendum. 
   In order in the case of such cutting teeth with a narrow tip width to prevent excessive wear to the comparatively wider tooth roots and optionally also the tooth holders, it is necessary to successively arrange several cutting teeth on a circumferential line of the cutting wheel in angularly adjusted manner. Thus, the tip-free dedendum sections and the holders are cut free by the circumferentially following cutting teeth. An alternating inclination of the cutting teeth by a few degrees to the side can also be necessary in order to cut free the stripper areas located between the cutting tooth-equipped disk areas. For the angular arrangement of the teeth the holders thereof can be laterally inclined on the cutting wheel circumference. 
   A laterally tilted arrangement of the individual cutting teeth on the cutting wheel makes it necessary to have different cutting tooth types on the same cutting wheel. Thus, each angular setting requires an individual cutting tooth type designed for said setting. Thus, with respect to the inclined holders it can be necessary for the carbide tip to be displaced to the right or left with respect to the cutting tooth centre, as a function of the tooth inclination, whereas with uninclined cutting teeth the tip is positioned centrally. 
   This makes it necessary to keep in stock a large number of cutting tooth designs on the building site in an uneconomic manner. The risk also exists that when replacing the cutting teeth a cutting tooth unsuitable for the given inclination is installed, which can lead to premature wear and increased costs for spares. 
   The object of the invention is to provide a particularly economically and universally usable cutting tooth, which is in particular suitable for harder rocks. 
   According to the invention the object is achieved by a cutting tooth characterized in that for widening the working cross-section of the main cutting element at least one further reaming element is provided on the dedendum at the top and which, compared with the main cutting element, has a different tip or cutting edge design. 
   It is a fundamental concept of the invention that the entire working width of the cutting tooth is not provided by a single cutting element and instead on the addendum several cutting elements are provided, which are mutually laterally displaced at right angles to the cutting direction. According to the invention several different cutting edge types are combined for removing soil over the entire working width. Tests have shown that with such a cutting edge design and when compared with known tooth types with a single cutting edge or tip, higher cutting speeds can be achieved in harder soils. 
   This observation is substantiated by the fact that the individual cutting elements do not break away the soil independently of one another. Thus, a main cutting element advancing in the cutting direction can weaken and therefore preloosen the rock structure also outside its geometrical cross-section. For the complete working of this preloosened rock by the reamers it is only necessary to have a comparatively low cutting capacity, which can be applied by the simply designed cutting elements. 
   Thus, according to the invention, it is e.g. possible to provide a cutting tooth with a narrower main cutting element relative to the holder and/or dedendum in order to be able to also work harder soils and achieve an adequate cutting progress. The main cutting element can e.g. be frontally and centrally fitted to the dedendum. In order to ensure the free cutting function of the tooth, according to the invention additional reamers are provided, which are in particular positioned symmetrically to the main cutting element. These reamers widen the total working cross-section of the cutting tooth. Thus, in the case of a small main cutting element and therefore good cutting progress a total cutting width can be achieved which exceeds the width of the dedendum and/or the holder thereof. Thus, with the inventive cutting teeth the holders and the stripper areas located between the cutting wheel disks can be reliably cut free with a good cutting progress without an inclination of the cutting teeth being required for this purpose. 
   Thus, the invention makes it possible for a considerable proportion of the tooth positions on the cutting wheel to provide only a single cutting tooth type, which greatly minimizes the spares storage costs and significantly reduces the risk of erroneous tooth installation. With one tooth the invention makes it possible to cover virtually the entire cutting disk. 
   For a particularly good cutting progress in the most varied soil geologies it is advantageous for the main cutting element to have at least one wedge-shaped cutting edge or tip. The cutting edge of the main cutting element then has a longitudinal extension and can be referred to as a linear cutting edge. A wedge-shaped cutting edge is very suitable for cutting in particular hard soils. 
   It is also advantageous for the reaming element to have at least one pin-type cutting edge. Such a pin-type cutting edge can in particular be conical, the cone e.g. having a round or oval base surface. A pin-type cutting edge is particularly suitable for the finished cutting of the soil already preloosened by the main cutting element. As a result of its small standing surface the provision of an additional pin-type cutting edge only slightly reduces the total contact pressure of the trench wall cutter, so that there is only a slight change to the cutting progress of the main cutting element. Furthermore pin-type cutting edges are comparatively inexpensive and require a comparatively small soldering area on the tooth root. The pin-type cutting edge can also be called a point cutting edge. It is generally advantageous for a good cutting progress for the main cutting element to have a more aggressive cutting edge compared with the reaming element. 
   Appropriately the two cutting elements are made from tungsten carbide and a less hard material can be used for the dedendum for economic reasons. In particular together with receptacles for the cutting elements, the dedendum is advantageously made from cast metal. 
   A particularly cost-effective and at the same time more efficient cutting tooth is obtained when the reaming element has a round shaft bit. Such a round shaft bit typically has a shaft and a larger cross-section head located thereon and on the end of which is provided a carbide pin. The round shaft bit can be constructed as a simple cutting pin. 
   According to a preferred embodiment of the invention it is advantageous to provide on the dedendum at least one reception sleeve, particularly with a circular or elliptical internal cross-section and in which is in preferably replaceable manner provided at least one reaming element. This leads to a particularly simply designed and universally usable cutting tooth. 
   According to the invention the main cutting element is oriented in a main cutting direction on the dedendum for soil removal purposes. The main cutting direction can also be called the cutting direction and is in particular that in which the cutting tooth moves tangentially as a result of the purely rotary movement of the cutting wheel. The cutting tooth advance direction, which particularly corresponds to the cutting wheel radial direction is perpendicular to the cutting direction. Appropriately the dedendum longitudinal axis is at least approximately parallel to the advance direction. 
   A particularly good cutting progress can be brought about in that the main cutting element is placed in leading manner on the dedendum compared with the reaming element in the main cutting direction. Advantageously the main cutting element is provided frontally on the dedendum on the face facing the soil. It can in particular at least zonally project in the main cutting direction over the end face of the dedendum. Appropriately the main cutting element is positioned upstream of a cutting edge support area located at the top on the dedendum and on which in turn are provided the reaming element and optionally its receptacle. 
   A particularly high contact pressure and therefore a particularly good cutting progress can be achieved in that the cutting width of the main cutting element is smaller than the dedendum width. The cutting width of the main cutting element can also vary over its height. The cutting width can in particular be understood to mean the size of the removal cross-section of the main cutting element perpendicular to the main cutting direction and perpendicular to the cutting tooth advance direction. 
   A further advantageous embodiment of the inventive cutting tooth is characterized in that, when considered in the main cutting direction, the reaming element projects laterally over the main cutting element and in particular over the dedendum. Preferably the reaming element projects on either side over the main cutting element or dedendum and for this purpose at least two reaming elements can be provided. Such an arrangement ensures a reliable free cutting of the dedendum and optionally gaps for stripper elements on the cutting wheel. The concept of lateral projection more particularly means a projection at right angles to the advance direction and/or the longitudinal axis of the dedendum. 
   A cutting tooth with a particularly reliable free cutting function is also obtained through the provision of at least two reaming elements. When considered in the main cutting direction, a reaming element is provided on either side of the main cutting element in each case. A cutting tooth particularly suitable for taking up the operating forces and which is therefore robust can be obtained in that the main cutting element, the reaming elements and in particular the dedendum are built up in mirror symmetrical manner. The symmetry plane is appropriately in the main cutting direction. 
   The cutting progress can be further improved in that the main cutting element has a longitudinal cutting edge running at right angles to the main cutting direction. Appropriately in V-shaped manner, two secondary cutting edges are connected to the longitudinal cutting edge. Whereas the longitudinal cutting edge appropriately runs roughly in the advance direction, the secondary cutting edges appropriately run at right angles to the advance direction from the cutting tooth centre to the longitudinal sides of the dedendum. Preferably two or more longitudinal cutting edges are provided in parallel. 
   The inventive cutting tooth can also be used as a hinged tooth which, as a function of the cutting wheel rotation angle, is tilted in order to cut free axially displaced soil areas. If the cutting tooth is to be used as a hinged tooth, it is advantageous for at least one reaming element, considered in the main cutting direction, to be located solely on one side of the main cutting element. Advantageously the reaming element is positioned in such a way that when the hinged tooth is tilted, i.e. when the longitudinal axis of the tooth diverges from the radial direction of the cutting wheel, it works the soil built up under said cutting wheel. 
   An inventive cutting tooth can also be used as a so-called sizing tooth, which is located on the axially outer disks of the cutting wheel, in order to cut free the outer area of the cutting wheel, i.e. its end faces. Here again the reaming element is preferably only located on one side with respect to the main cutting element. If the cutting tooth is to be used as a sizing tooth, appropriately at least one further cutting element is located on the dedendum on the cutting tooth side where the reaming element is also located. The further cutting element is preferably identical to the reaming element and in particular has a pin-type cutting edge. Appropriately the further cutting element is located on the dedendum below the reaming element. There are preferably several cutting elements in the dedendum longitudinal direction, which improves the cutting action in the outer area of the cutting wheel. 
   Particularly when used as a hinged tooth or sizing tooth, it is advantageous to laterally displace the longitudinal cutting edge with respect to a median plane of the dedendum, when considered in the main cutting direction. In the case of a sizing tooth the longitudinal cutting edge is appropriately displaced towards the reaming element and in the case of a hinged tooth away from said reaming element. Preferably in the case of a sizing tooth the longitudinal cutting edge is displaced towards the outer area of the cutting wheel. 
   Apart from the reaming element not provided there, the cutting wheels can be fundamentally constructed in the manner described in DE 297 20 261 U1 and DE 87 15 141 U1 and can be inserted into a cutting tooth holder as described in DE 87 15 141 U1. Apart from being usable on a wheel cutter, the inventive cutting teeth can also be used on a chain cutter. A trench wall cutter constructed for use of the inventive cutting teeth advantageously has two cutting wheel pairs, which are axially parallel on the underside of a frame. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in greater detail hereinafter relative to preferred embodiments and the attached diagrammatic drawings, wherein show: 
       FIG. 1  A perspective view of a first embodiment of an inventive cutting tooth. 
       FIG. 2  A side view of the cutting tooth of  FIG. 1 . 
       FIG. 3  A rear view of the cutting tooth of  FIG. 1 . 
       FIG. 4  A plan view of the cutting tooth of  FIG. 1 . 
       FIG. 5  Another embodiment of an inventive cutting tooth, constructed as a hinged tooth, in a perspective view. 
       FIG. 6  A side view of the cutting tooth of  FIG. 5 . 
       FIG. 7  A front view of the cutting tooth of  FIG. 5 . 
       FIG. 8  A plan view of the cutting tooth of  FIG. 5 . 
       FIG. 9  Another embodiment of an inventive cutting tooth, constructed as a sizing tooth, in a perspective view. 
       FIG. 10  A side view of the cutting tooth of  FIG. 9 . 
       FIG. 11  A rear view of the cutting tooth of  FIG. 9 . 
       FIG. 12  A plan view of the cutting tooth of  FIG. 9 . 
   

   Similarly acting elements are given the same reference numerals in all embodiments. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 to 4  show a first embodiment of a cutting tooth according to the invention. On its lower side, the cutting tooth has a dedendum  10  for reception in a cutting tooth holder. In the side view of  FIG. 2  the dedendum  10  is U-shaped with two parallel front edges and a rounded base portion. On the two front faces of the cutting tooth, which are roughly radial when placed on the cutting wheel, as well as in the base area of the dedendum  10  is provided a longitudinal groove  16  with a substantially V-shaped cross-section. The longitudinal groove  16  forms part of a positive connection by means of which the cutting tooth is releasably fixed in the not shown cutting tooth holder. 
   The dedendum  10  also has a crosshole  17 , which intersects both the longitudinal groove  16  and also the adjacent, solid part of dedendum  10 . Crosshole  17  receives a shear pin in order to secure the cutting tooth  10  in the holder. On dedendum  10  is provided a further crosshole  18 , which can be used for inserting a tool on extracting the cutting tooth from the holder. 
   For cutting operation the cutting tooth is inserted by means of its dedendum  10  in the cutting tooth holder on a cutting wheel. The cutting wheel is rotated about its cutting wheel axis, so that the cutting tooth is moved tangentially in a main cutting direction  60 . Simultaneously the cutting wheel is introduced linearly into the ground, so that a cutting tooth movement takes place in the advance direction  65  perpendicular to the main cutting direction  60 . 
   On the top of the dedendum  10  a main cutting element  20  made of carbide or hardened metal is provided. The main cutting element has a polyhedron-like construction and a wedge-shaped longitudinal cutting edge  22  extending perpendicular to the main cutting direction  60  roughly parallel to advance direction  65  and to the longitudinal axis of dedendum  10  upwards and away from the latter. 
   The main cutting element  20  is located frontally on the cutting tooth, the longitudinal cutting edge  22  projecting over the underlying end face of dedendum  10 . On the top of the main cutting element  20  are provided two secondary cutting edges  23 ,  23 ′, which branch off in V-shaped manner from the longitudinal cutting edge  22 . The secondary cutting edges  23 ,  23 ′ run outwards at right angles to the main cutting direction  60 . On its rear side remote from the longitudinal cutting edge  22 , the main cutting element  20  is supported by a cutting edge support area  14 , whose height decreases with increasing spacing from the main cutting element  20 . 
   Behind the frontally positioned main cutting element  20 , two reaming elements  30 ,  30 ′ are provided on the top on dedendum  10 . As shown in  FIGS. 1 and 4  relative to the reaming element  30 , reaming elements  30 ,  30 ′ in each case have a round shaft bit  33  with a conical tip area. A conical, carbide pin-type cutting edge  32  is provided on the tip of the round shaft bit  33 . 
   Two reception sleeves  37 ,  37 ′ are provided in the rear portion of the cutting edge support area  14  on the top of dedendum  10  for holding the reaming elements  30 ,  30 ′. The round shaft bits  33  of the reaming elements  30 ,  30 ′ are inserted in the reception sleeves  37 ,  37 ′, which can in particular have a round or elliptical internal cross-section. The reaming elements  30 ,  30 ′ are positioned in such a way that their pin-type cutting edges  32 , considered in the main cutting direction  60 , project laterally over the main cutting element  20 , i.e. at right angles to advance direction  65 , so that the entire removal cross-section of the cutting tooth is wider than the geometrical width of the main cutting element  20  and its secondary cutting edges  23 ,  23 ′. As can in particular be gathered from  FIGS. 3 and 4 , pin-type cutting edges  32  also project laterally over the dedendum  10 , so that the reaming elements  30 ,  30 ′ cut the entire width of the tooth free. In the advance direction  65  the pin-type cutting edge  32  and the upper end of longitudinal cutting edge  22 , from which the secondary cutting edges  23 ,  23 ′ emanate, are positioned roughly at the same level. 
   Reaming elements  30 ,  30 ′ are positioned behind the main cutting element  20 , i.e. the cutting edges  22 ,  23 ,  23 ′ of main cutting element  20  are in advance of the pin-type cutting edges  32  of reaming elements  30 ,  30 ′ in the main cutting direction  60 . 
   The longitudinal axes of the round shaft bit  33  of the two reaming elements  30 ,  30 ′ are roughly positioned in V-shaped manner relative to one another. The longitudinal axes are tilted with respect to advance direction  65  both in the main cutting direction  60  and also to the sides of the cutting tooth. 
   As can in particular be gathered from  FIGS. 3 and 4 , the main cutting element  20  is positioned centrally on the tooth face, the longitudinal cutting edge  22  being in the centre of the front face. The entire cutting tooth, including the main cutting element  20  and reaming elements  30 ,  30 ′, is constructed in mirror symmetrical manner, the longitudinal cutting edge  22  of main cutting element  20  being in the plane of symmetry. 
   A further embodiment of an inventive cutting tooth, which can in particular be used as a hinged tooth, is shown in  FIGS. 5 to 8 . Dedendum  10  of said cutting tooth essentially corresponds to the tooth dedendum of  FIGS. 1 to 4  and will not therefore be described again. 
   The cutting tooth shown in  FIGS. 5 to 8  differs from the previously described cutting tooth essentially in that the main cutting element  20  is positioned in laterally displaced instead of central manner on the cutting tooth face. Unlike in the previously described cutting tooth, in the embodiment of  FIGS. 5 to 8  a reaming element  30  is only provided on one side of the main cutting element  20 . The reaming element  30  is positioned on that side of dedendum  10  from which the main cutting element  20  is displaced away from the tooth centre. 
   Admittedly, in itself the main cutting element  20  has mirror symmetry, but as a result of the displacement of the main cutting element  20  and the solely unilateral arrangement of the reaming element  30 , the overall cutting tooth is not mirror symmetrical. 
   A further embodiment of an inventive cutting tooth, which can in particular be used as a sizing tooth, is shown in  FIGS. 9 to 12 . Dedendum  10  of said tooth once again essentially corresponds to the cutting tooth dedendum  10  of  FIGS. 1 to 4  and will not be described again. 
   Unlike in the previously described cutting teeth, the main cutting element  20  of the embodiment of  FIGS. 9 to 12  has a width at right angles to the main cutting direction  60  which exceeds the width of dedendum  10 , i.e. the main cutting element  20  unilaterally projects laterally over the dedendum  10 . The longitudinal cutting edge  22  is arranged in eccentrically displaced manner in the direction of the lateral projection on main cutting element  20 . 
   In the embodiment of  FIGS. 9 to 12 , once again there is only a single reaming element  30  which, considered in the main cutting direction  60 , is on the side of the cutting tooth where the main cutting element  20  projects over the dedendum  10 . 
   Relative to the advance direction  65 , the pin-type cutting edge  32  of reaming element  30  is roughly at the same height as main cutting element  20 . Below the reaming element  30  and laterally on dedendum  10  there are two further cutting elements  77 ,  78 , which once again have round shaft bits. The longitudinal axes of the round shaft bits of the further cutting elements  77 ,  78  are roughly parallel to the longitudinal axis of the round shaft bit of reaming element  30 , but can also be mutually displaced in the main cutting direction  60 . 
   The main cutting elements  20  of the embodiments of  FIGS. 5 to 12  in each case terminate roughly flush with the underlying flanks of the tooth roots  10  on their longitudinal sides remote from the reaming elements  30 .