Abstract:
The tooth and adaptor for dredging machines object of the present invention relates to a tooth or wear member which, attached to an adaptor or adaptor member, creates an assembly the purpose of which is to deepen and clean the beds of ports, rivers, channels, etc., removing therefrom sludge, stones, sand, etc., the adaptors being attached to the blades of the propellers and thus forming the cutter head of the dredging machine. The constructive features of the coupling between the tooth and the tooth bar or adaptor allow making better use of the cutting material of the tooth and a simple and quick replacement thereof in the adaptor, between other advantages.

Description:
OBJECT OF THE INVENTION 
     The present invention, tooth and adaptor for dredging machines, relates to a tooth or wear member which, attached to an adaptor or adaptor member, creates an assembly the purpose of which is to deepen and clean the beds of ports, rivers, channels, etc., removing therefrom sludge, stones, sand, etc., the adaptors being attached to the blades of the propellers and thus forming the cutter head of the dredging machine. 
     The dredging machine, or dredger, allows excavating, transporting and depositing material that is located under the water, and they can be mechanical or hydraulic machines, the mechanical machines being used with cutting members, teeth or blades for their use on compact terrain. 
     The tooth and adaptor object of the present invention are preferably intended to be used in dredging machines having a suctioning cutter head of the type which while at the same time it excavates the terrain under the water, the loosened material is suctioned by a pump and transported through a pipe to somewhere else. 
     STATE OF THE ART 
     Systems of tooth and adaptor or adaptors are known in the state of the art for their application in dredging operations. The main objective of said operations is to remove material from marine or river beds, and to do this it is common to use dredge boats including a dredge or dredging machine on which the various teeth are arranged and in turn connected to tooth bars or adaptors. 
     The U.S. Pat. No. 3,349,548-B describes a tooth and adaptor system attached to one another by means of an elastic strap such that if such strap is poorly arranged, the entire system is altered as to its correct assembly. It also only has one contact area between the tooth and the adaptor, which negatively affects the distribution of stresses. 
     Another, also US, U.S. Pat. No. 4,642,920-B describes a tooth and adaptor system attached to one another by means of a retaining system formed by a pin, the area where the pin is housed being easily accessed by dirt, making the subsequent removal thereof difficult. This system presents difficulty in absorbing the torsional and bending stresses and loads, generating a strong lever reaction in the system. As with the preceding patent document, there are few contact surfaces between the tooth and the adaptor. 
     Spanish patent document number ES-2077412-A describes a tooth and adaptor assembly made up of three parts requiring the use of two fastening systems. The fact that it has three parts complicates the entire system because it requires a larger number of spare parts and three fastening systems, one of which requires the use of a hammer whereas the other two fastening systems are formed by welding, making the tasks for replacing them long and complex. 
     The solutions existing in the state of the art for dredging machines have, among others, the following drawbacks:
         The teeth are solid members such that the material of said members is not optimized for the functions for which it has been designed. Another drawback of using the solid teeth known in the state of the art is that they are more difficult to handle due to their weight.   The teeth used in the state of the art for the same application are larger, requiring more space for storage thereof.   The interlockings between tooth and adaptor known in the state of the art have a retaining member or vertical pin assuring the attachment between said tooth and the adaptor during operation thereof. When the tooth becomes worn it is necessary to replace it and to that end the cutter head is taken out of the water and usually has material from the aquatic bed where it is working adhered to the lower part of the teeth and adaptors. Said pin is usually removed by striking said pin at the upper part and re moving it through the lower part of the tooth-adaptor assembly, which often causes the pin to fall into the water (since the tooth is changed above the water) preventing recovery thereof. Likewise, the fact that there is material adhered to the lower part of the tooth-adaptor assembly makes it difficult to remove the mentioned pin because it prevents the pin from coming out of its housing. Furthermore it is common for the pin to be lost when it is inserted in the mass of material adhered to the assembly and subsequently falling into the water.   Due to the configuration of the interlockings existing in the state of the art, the teeth are excessively large, generating long interlockings, with less strength in the tooth, a larger occupied volume and an increase of the distance from the cutter head to the blade, which reduces the performance of the tooth and the assembly.   The adaptor likewise has no additional protection other than the protection provided by the tooth and is affected by the materials loosened due to the action of the tooth and striking against the adaptor, causing damage and wear thereof.       

     DESCRIPTION OF THE INVENTION 
     The invention describes a tooth with a front wear part and a rear projecting part or nose intended for being housed within a hollowing arranged in the body of an adaptor and an assembly formed by both for dredging machines, both members being attached to one another by means of a preferably hammerless, preferably vertical-type, retaining system, i.e. without needing to use hammers or without having to strike the pin attaching both members to one another. The adaptor is attached to the blade of the cutter head of the dredging machine at the end opposite to the hollowing by means of a coupling adapted for such purpose. 
     The object of the present invention is a tooth, an adaptor and the assembly formed by both, preferably applied to dredging machinery, allowing optimal wear of the material of the tip of the tooth and coupling between the tooth and the adaptor. These objects of the invention are achieved due to a particular construction of the contact surfaces between both members, allowing the self-tightening force to be produced close to the force (load), such that the horizontal component of the rearward reaction is larger and therefore the self-tightening force is also larger since the tooth pushes against the adaptor. 
     In dredging operations the tooth must be replaced on the actual dredge boat, i.e. at the worksite or the operations area, usually on the water and working directly on the cutter head carrying the adaptors, or tooth bar, and the teeth. Said operations are carried out by the employees on said boat, i.e. at the work site, far from maintenance shops with the suitable conveniences and tools for optimally performing these types of operations. For this reason all the mentioned components can be coupled with fastening members and pins so that the replacement operations are simple, without an excessive number of tools and preventing the use of complex equipment. 
     Another object of the present invention is to present in addition to the tooth-adaptor assembly, a tooth as well as an adaptor which, due to their configuration, allow a distribution of stresses that favors retaining the tooth in the adaptor and reducing the stresses to which the retaining system, and specifically the pin thereof, is subjected. The configuration of the tooth and of the adaptor can also be used outside of dredging operations, such that the adaptor or tooth bar can be connected to the bucket of an excavating machine or the like for on-shore works. 
     The tooth and adaptor object of the present invention have contact surfaces and constructive features allowing the coupling between both members to increase the performance of the coupling, particularly the efficiency of each tooth, thus improving the efficiency of the dredging machine. 
     The tooth is made up of two different parts, a first wear part, which is the part acting on the terrain and is subject to erosion due to the terrain, and a second part or nose, which is the part that is inserted in a housing arranged for such purpose in the adaptor, forming the interlocking of the system, and subjected to the reactions and stresses generated by the work of the tooth on the terrain. Said nose is formed by a lower base body and an appendage integrated in the upper surface of said lower base body, one of its ends being free and at the opposite end said nose is attached to the wear part. The gap between the wear part and the nose is determined by the upper surfaces of the appendage and by the lower surface of the lower base body which, after reaching a maximum height from the free end of the nose, converge towards the tip of the tooth, such that the union line of both surfaces is located on the side of the wear part of the tooth and in front of the line of maximum height of the nose. 
     The longitudinal vertical section of the nose varies along the length thereof, and has at the free end thereof a cross-section with rounded vertices. The area of the cross-section of the nose gradually increases as the nose approaches the end for being attached to the wear part of the tooth, specifically until a maximum height is reached between the lower side of the base body and the upper side of the appendage of the base body. After this point the area of the cross-section of the nose begins to decrease until the upper surface of the appendage intersects with the lower surface of the base body. 
     Said section can have different shapes, such as elliptical, trapezoidal or rectangular shapes, but having at least four sides. 
     The appendage located in the upper part of the nose, and the trapezoidal cross-section of which is narrower than the section of the base of the nose, is centered with respect to the latter. The height of said appendage is preferably nil in an area close to the free end of the nose (although it is possible for the appendage to have a certain height at said free end) and such height gradually increases until reaching said point of maximum height before decreasing again. The lateral sides of the successive cross-sections of the appendage and the upper side of the successive cross-sections of the base body of the nose of the tooth form an angle varying, due to manufacturing issues, between 45° and an angle of less than 180°, preferably between 45° and 135°. Even more preferably the angle is greater than 90°, such that the lower base of the appendage is larger than the upper base, although the opposite is also possible, i.e. the angle is less than 90° 
     The nose likewise has at least one first contact area with the inner surface of the housing of the adaptor, such contact area being formed by the two upper surfaces of the base of the nose that are located on both sides of the appendage of the nose of the tooth. The main feature of this first contact area is that it achieves the self-tightening of the tooth in the adaptor. 
     Due to the proximity of these surfaces with the tip of the tooth, i.e. the point of application of the force produced during the work of the tooth on the terrain, causes the reactions on said surfaces to be greater and therefore the self-tightening forces (components of said reactions} are also greater. 
     The nose has a second contact area with the adaptor, this contact area being located on the lower surface of the base of the nose, in the area close to the free end thereof. 
     The adaptor is also made up of two parts: at one end it has a configuration that can vary depending on the type of machinery to which it is connected, i.e. either a cutter head of a dredging machine, or to the bucket of an excavating machine, whereas at the opposite end it has a hollowing, housing or cavity intended to receive the nose of the tooth. The inner configuration of the surfaces of the hollowing or housing of the adaptor for receiving the tooth are complementary to that of the nose of the tooth, thus assuring a perfect coupling between both members. 
     For the coupling between the tooth and the adaptor, both parts preferably have a hole or through borehole from the upper part of the adaptor, traversing the nose of the tooth, and to the lower part of the adaptor. A pin preferably with surfaces of revolution and with a preferably hammerless retaining system (which does not require striking with a hammer or mallet for being inserted or removed) aiding in changing teeth in the adaptor will be inserted in said housing. 
     The coupling of the rear part or nose of the tooth in the hollowing or housing of the adaptor is due to the conjunction of the planes defining the described locking surfaces. A tightening or crushing effect between the tooth and the adaptor is furthermore achieved by means of said planes when a stress is applied perpendicular to the wear tip of the tooth and upwardly, this being the normal working situation of the teeth in a cutter head of a dredging machine. 
     Due to this interlocking system, the pin is subjected to fewer stresses than in conventional interlocking systems since the to oth-adaptor system tightens itself when it is subjected to upward vertical loads in the tip of the tooth, releasing stresses into the retaining system and its pin, and therefore allowing designing pins of the retaining system with a smaller size and section since they are subjected to fewer stresses, thus reducing deterioration or mattage of the pin and allowing it to be reused. 
     With the described configuration of the coupling the contact surfaces between the tooth and the adaptor are closer to the working tip of the tooth than in known couplings. This reduces the lever effect created between the tooth and the adaptor, and therefore the stresses to which the assembly is subjected, including the fastening or retaining system, are also reduced, thus reducing deterioration or mattage. Reducing lever stresses in the tooth allows reducing the dimensions of the nose of said tooth. And furthermore, due to its geometry, the resistant section of the rear projection or nose decreases towards the free end thereof, such that the bending moments in said area, caused by the load at the tip of the tooth, decrease and therefore the larger moments are located at the point where the resistant section is larger. Reducing the total dimensions of the system also allows therefore reducing the height of the interlocking, thus achieving a more deeply penetrating system. 
     The tooth object of the invention together with the adaptor allows optimizing the wear material, i.e. the use of the material arranged in the front wear part of the tooth, which is the part that directly acts on the terrain, is optimized. Said optimization is achieved by reducing the material of the tip of the tooth that is not going to be used to a minimum. The material forming part of the tip of the tooth, or wear tip, and which is then not worn, is material that has been paid for but then not used for its purpose. The material of the tip of the tooth is optimized because the tip has been designed according to the inclination of the upper surface of the appendage of the nose, which is parallel to the line of wear of the tooth, thus making use of the largest possible amount of material at the tip of the tooth before being replaced with a new tooth. 
     Due to this configuration of the tooth-adaptor coupling, and taking into account that dredging operations are done “blindly” for the user, the tip of the tooth must be completely worn, the unused wear material being minimal, before the tooth bar begins to become worn, since if this occurs it causes a serious drawback both in terms of time and financial resources, since not only the tooth but also the adaptor has to be replaced. It is necessary to take into account that the wear time of the teeth further depends on the revolutions at which the cutter head works, of the material it is working on, it being difficult to predict the life of the teeth. It also so happens that once the tooth is worn, and before the tooth bar begins to be worn due to the direction action on the terrain, the user perceives increased vibrations, notifying him or her that the tip of the tooth has already been consumed. Said vibration is due to the fact that as the tooth gradually wears, the section thereof gradually increases, the section of attack of the tooth on the terrain therefore being increasingly larger, causing the mentioned vibration since the optimal section for penetration has been consumed, such that when the entire section of the tip of attack has been consumed and the tooth bar is reached, said vibration is very large notifying the operators that it is necessary to replace the tooth. 
     Another object of the invention consist of the tooth being able to have between the front wear part and the nose for coupling to the adaptor, according to the previously defined inclined planes, a perimetral projection or flange or collar, the main purpose of which is to protect the contact area between the tooth and the adaptor from the material loosened during its dredging operation. Said collar also carries out three functions in the coupling:
         Protecting the adaptor from wear through the deflectors in the upper and lower areas and which have been designed to redirect the flow of loosened material, preventing such material from rubbing or striking against the adaptor and therefore preventing the wear thereof,   Preventing the loosened material from entering into the interlocking, acting as a plug and also reducing the entrance of material in the fastening or retaining system, and   Making contact with the adaptor after prolonged wear through stoppers located in the upper and lower areas, said stoppers being thicker to resist the larger stresses to which it is subjected when contact with the adaptor is made, determining a third contact area between the tooth and the adaptor.       

     Said collar can have variable thicknesses along its length depending on the stresses to which it is subjected during the work of the coupling. Specifically, said collar has the thickest areas in its upper and lower area such that when contact is made, the reactions of the tooth bar on the collar exert a component directly opposing the applied force (Fc). In addition the middle area of the collar has a curve towards the tip of the tooth that adapts to the shape of the interlocking, according to the parallelism to planes S and I and allowing the contact areas to be closer to the tip of the tooth, this area being where the main contact areas, located close to said tip to also reduce the lever effect, are located. Said central areas have less thickness than in the upper and lower areas. 
     Another object of the invention is a tooth the nose of which is hollow, such that the amount of material that is worn out is reduced. 
    
    
     
       DETAILED DESCRIPTION OF THE DRAWINGS 
       To complement the description being made and for the purpose of aiding to better understand the features of the invention, according to a preferred practical embodiment thereof, a set of drawings is attached as an integral part of said description which show the following with an illustrative and non-limiting character: 
         FIG. 1  depicts a perspective view of a collarless tooth and an adaptor prior to their coupling. 
         FIG. 2  depicts a side elevational view of a collarless tooth and an adaptor prior to their coupling. 
         FIG. 3  depicts a perspective view of a collarless tooth. 
         FIG. 4  depicts the rear elevational view of a collarless tooth. 
         FIG. 5  depicts a side elevational view of a collarless tooth. 
         FIG. 6  depicts a plan view of a collarless tooth. 
         FIG. 7  depicts a side elevational view of a collarless tooth showing the inclined planes S and I. 
         FIG. 8  depicts a side elevational view of a tooth with a collar. 
         FIG. 9  depicts a front elevational view of a tooth with a collar. 
         FIG. 10  depicts a plan view of a tooth with a collar. 
         FIG. 11  depicts a cross-section of a solid tooth with a collar. 
         FIG. 12  depicts a cross-sectional view of a hollow collarless tooth. 
         FIG. 13  depicts a side elevational view of a collarless tooth. 
         FIG. 14  depicts a section, according to Y-Y, of the hollow collarless tooth of  FIG. 13 . 
         FIG. 15  depicts a section, according to Z-Z, of the hollow collarless tooth of  FIG. 13 . 
         FIG. 16  depicts a section, according to AC-AC, of the hollow collarless tooth of  FIG. 13 . 
         FIG. 17  depicts a section, according to AA-AA, of the hollow collarless tooth of  FIG. 13 . 
         FIG. 18  depicts a section, according to AB-AB, of the hollow collarless tooth of  FIG. 13 . 
         FIG. 19  depicts a section, according to AE-AE, of the hollow collarless tooth of  FIG. 13 . 
         FIG. 20  depicts a perspective view of an adaptor. 
         FIG. 21  depicts a view of an adaptor. 
         FIG. 22  depicts a rear view of an adaptor. 
         FIG. 23  depicts a section, according to AB-AB, of the adaptor of  FIG. 22 , showing the inclined planes SA and IA. 
         FIG. 24  depicts a view of a collarless tooth and an adaptor coupled together. 
         FIG. 25  depicts a section, according to AE-AE, of the coupling between a collarless solid tooth and an adaptor shown in the  FIG. 24 . 
         FIG. 26  depicts a collarless tooth and an adaptor coupled together showing the forces to which the assembly may be subjected and its reactions. 
         FIG. 27  depicts a collarless tooth in which the appendage of the nose of said tooth has a certain height along its entire length. 
     
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT 
     As observed in  FIG. 1 , the invention object of the present application, tooth and adaptor for dredging, is formed by an interchangeable tooth  10 , an adaptor  20  coupled to a blade of a cutter head of a dredging machine, and a retaining member  30  responsible for assuring the connection between the tooth and the adaptor. 
     As can be observed in  FIG. 3  and  FIG. 20 , the tooth  10  consists of a front wear part  11  or tip of the tooth responsible for the task of eroding the terrain, in contact with the ground and stones, and in its rear part it has a projection or nose  12  intended for being housed in a housing or hollowing  24  arranged in the adaptor  20 . 
       FIG. 4  shows how the nose  12  of the tooth is formed by a lower base body  16  and an appendage  15  integrated in its upper surface, with a free end  14  attached at the end opposite to the front wear part, said nose  12  being separated from the wear part by the intersection of the upper surfaces of the appendage and the lower surface of the base body. More specifically, the gap between the wear part  11  and the nose  12  is determined by the two inclined planes S, I determined by said upper surfaces of the appendage and lower surface of the base body, such that the imaginary horizontal intersection line of both planes  1   1  is located in front of the vertical line (h max1 -h max2 ) determining the maximum height of the tooth  10 , located in the side opposite to that of the free end of the nose  14 . Said maximum height of the tooth H 3  is formed by the maximum height of the base body H 1  combined with the maximum height of the appendage H 2 . 
     According to a first vertical plane XY varying along the horizontal axis x, the base body of the nose,  FIG. 13  to  FIG. 19 , has a cross-section at the free end x 0 , according to a second vertical plane YZ, with a rectangular shape with rounded vertices such that the area of the cross-section, along the horizontal axis x, of the nose  12  gradually increases as the nose approaches the end for being attached to the wear part of the tooth, inclined planes S, I, specifically until the lower surface of the nose intersects the lower inclined plane I, after the point where the area of the cross-section along the horizontal axis x of the nose begins to decrease again until the intersection x 1  of the inclined upper S and lower I planes. 
     In addition, the section of the appendage  15  of the nose  12  of the tooth  10  has a trapezoidal cross-section, its lower base being narrower than the upper surface of the base body of the nose  16  and centered with respect to said base body  16 , such that the height of said appendage is nil in an area close to the free end  14  of the nose x 0 , and its height gradually increases until reaching a maximum height H 2 , at which point the upper surface of said appendage  15  and therefore of the nose  12  intersects the upper inclined plane S of separation with the wear part of the tooth  11 , the height of the appendage decreasing after this point until reaching the intersection x 1  of the upper S and lower I inclined planes. Said appendage  15  could also not have nil height at the free end of the nose  14  (see  FIG. 27 ), or not be centered with respect to the base of the nose  16 . 
     The lateral sides  151 ,  152  of the successive cross-sections of the appendage  15  and the upper side  121 ,  122  of the successive cross-sections of the base of the nose  16  of the tooth  10  form an angle varying between 45° and 180°, preferably between 45° and 135°, and even more preferably greater than 90°. 
     According to the foregoing, the description provides that the nose of the tooth  10  has a lower base body  16 , with a section of at least four sides (a, b, c, d) with rounded vertices and with an upper surface  120  and a lower surface  123 . On said lower base body  16  there is an upper appendage  15  with an upper surface  153  and a lower surface  154 , and with a trapezoidal section the lower base  154  of which is larger than the upper base  153  and the lower base  154  is in turn narrower than the upper surface  120  of the lower base body  16  and is centered with respect to the upper surface  120  of the lower base body  16 . The nose also has a free end  14 , opposite to the front wear part or tip  11 , and an end opposite to the mentioned free end and attached to the tip  11  of the tooth  10 . 
     The nose of the tooth and its section, as well as that of the area of attachment with the front part of the tooth or tip of the tooth, is determined by the progressive gap of the upper  120  and lower  123  surfaces of the lower base body  16  starting from a point close to the free end  14  of the nose  12  and therefore increasing the section of said base body  16  in the direction of the tip of the tooth  11 , until defining a maximum gap H 1  corresponding with the maximum height H 1 ) of the lower base body  16 . The upper  153  and lower  154  surfaces of the appendage  15  also progressively separate from one another from a point close to the free end  14  of the nose  12 , thus increasing the section of said appendage  15  in the direction of the tip of the tooth  11 , until determining a maximum gap H 2  defining the maximum height H 2  of the appendage  15 . The union of the maximum heights H 1 , H 2  of the lower base body  16  and of the appendage  15 , determine a line of maximum height H 3  of the nose of the tooth  12 , such that after said line of maximum height H 3  the upper surface  153  of the appendage  15  and the lower surface  123  of the lower base body  16  begin to converge towards the tip  11  of the tooth  10  until the union of both surfaces  153 ,  123 , the union line of both surfaces  11  being located on the side of the wear part of the tooth  11  and in front of the line of maximum height H 3 . Said maximum height is located at a balance point between good penetration of the system, which as mentioned depends on the total height of the nose, and of the resistance of the system, which depends on the stresses to which it is subjected. 
     The adaptor,  FIG. 20 , is formed by a body having a coupling  21  at one end to be attached to a blade of the cutter head of a dredging machine and at the opposite end it has a hollowing or housing  24  for receiving the rear projecting part or nose  12  of a tooth  10 , which is inserted in said housing  24 . The inner surfaces,  FIG. 22 , of said housing  24  of the adaptor  20  are complementary to the surfaces of the nose  12  of the tooth  10 . In other words, said housing  24  is formed by a lower base hollow  22  and an inverted T-shaped appendage in its upper surface  25  in the opening  28  of the housing  24  coinciding with the free end thereof. The shape of said free end or opening  28  is defined by two inclined planes, an upper plane SA and another lower plane IA, which correspond with the upper surface of the hollow appendage and with the lower surface of the base hollow of the nose, intersecting at their intersection line (or point)  12  formed by the infinite points x 3  of the intersection of the planes, such that the intersection line  1   2  of both planes is in front of the line (h max1 -h max2 ) determining the maximum height A 3  of the hollowing  24 , as shown in  FIG. 23 . 
     As previously described, the inner surfaces are complementary to that of the nose of the tooth, therefore the infinite sections of said housing are complementary to the infinite sections of the nose of the tooth such that according to a first vertical plane XY, which varies along the horizontal axis x, the hollowing has at the bottom  26  of the hollowing  24 , opposite to the opening  28 , a cross-section, according to a second vertical plane YZ, with rectangular shape with rounded vertices, such that the area of the cross-section of the hollowing  24  gradually increases as it approaches the opening  28  of the hollowing  24  (planes SA, IA), specifically until the lower side of the hollowing  24  intersects with the lower inclined plane IA, such that after this point the area of the cross-section of the hollowing  24  begins to decrease again until the intersection x 3  of the inclined upper SA and lower IA planes. 
     Likewise the section of the upper appendage  25  of the hollowing  24  has a trapezoidal cross-section, narrower than the base of the hollowing  22 , and centered with respect to same  22 , such that the height of said appendage is nil in an area close to the bottom of the hollowing  26 , and its height gradually increases until the upper surface of said appendage  25  intersects with the upper inclined plane SA of separation, the height of the appendage  25  decreasing after this point until reaching the intersection x 3  of the inclined upper SA and lower IA planes. Likewise, the upper appendage  25  may not end in its area close to the bottom of the hollowing  26  with nil height, but rather with certain height, and it could also not be centered with respect to the base of the hollowing  22 . 
     Obviously as in the nose  12  of the tooth  10 , the lateral sides  251 ,  252  of the successive cross-sections of the appendage  25  and the upper side  221 ,  222  of the successive cross-sections of the base of the hollowing  22  forms an angle with one another varying between 45° and 180°, preferably between 45° and 135°. Even more preferably said angle is greater than 90°. 
     In other words, the adaptor  20  has at the end opposite to that of the coupling  21  a hollowing or housing  24  for receiving the rear projecting part or nose  12  of a tooth  10 , which is completely inserted in said housing  24 . Said housing  24  is formed by a lower base hollow or hollowing  22  having a section of at least four sides with rounded vertices, an upper surface  220  and a lower surface  223 , arranging on said upper surface a hollow upper appendage  25  forming the housing  24  of the nose  12  of the tooth  10 . Said hollow appendage  25  is formed by an upper surface  253  and a lower surface  254 , and it also has a trapezoidal section the lower base  254  of which is larger than the upper base  253  and such lower base  254  is in turn narrower than the upper surface  220  of the lower base hollow  22 , said hollow appendage  25  being centered with respect to the upper surface  220  of the lower base body  22 . The housing  24  has an opening  28  at the end opposite to the end for coupling the adaptor to the, and an end opposite to that of the opening  28  forming the bottom  26  of the housing  24 , and therefore located close to the coupling to the blade. The housing  24  of the adaptor  20  is also determined by the upper  220  and lower  223  surfaces of the lower base hollowing  22  which progressively separate from one another from a point close to the bottom of the hollowing  26  of the adaptor  20 , such that the section of said base hollowing  22  gradually increases in the direction of the opening  28  of the adaptor  20  until a maximum gap A 1  is defined, corresponding with the maximum height A 1  of the lower base hollowing  22 . The upper  253  and lower  254  surfaces of the hollow upper appendage  25  progressively separate from one another from a point close to the bottom of the hollowing  26  of the adaptor  20 , the section of said hollow appendage  25  thus increasing in the direction of the opening  28  of the adaptor  20 , until determining a maximum gap A 2  defining the maximum height A 2  of the hollow appendage  25 . The union of both heights A 1 , A 2  of the lower base hollowing  22  and of the hollow appendage  25  determine a line of maximum height A 3  of the opening  24  of the housing  24  of the adaptor  20 . After said line of maximum height A 3  the upper surface  253  of the hollow appendage  25  and the lower surface  223  of the lower base hollowing  22  begin to converge in the direction opposite to that of the bottom of the hollowing  26  until the union of both surfaces  253 ,  223 , the union line of both surfaces  12  being located on the opposite side of the bottom of the hollowing  26  and in front of the line of maximum height A 3  of the opening  28  of the hollowing  24  of the adaptor  20 . 
     As shown in  FIG. 24  and  FIG. 25 , both members are coupled together by inserting the nose  12  of the tooth  10  into the housing  24  of the adaptor  20 , the different complementary surfaces of the nose  12  and of the housing  24  coming into contact with one another. 
     At the same time the adaptor  20  has been installed through its coupling  21  in the blade or propeller of the cutter head of the dredging machine, the tooth  10  is installed, using for that purpose a preferably hammerless retaining member  30 , i.e. a member that does not require the action of a mallet or hammer for removing it from or inserting it in the housings intended for such purpose in the tooth and in the adaptor. The retaining system is vertical, being inserted and removed through the upper part of the tooth and of the adaptor, traversing the nose  12  of the tooth  10  and the body of the adaptor  20  through respective through holes  13 ,  23 . 
     Once the assembly is put together and during the working operations, the tooth  10  is subjected at its tip  11  to an upward perpendicular force (Fc) in the lower side of the tip of the tooth  11 , less commonly being able to be subjected to a force normal Fs to the tip of the tooth due to the swell of the boat, causing a series of stresses and reactions in the coupling between the tooth  10  and the adaptor, specifically in the contact surfaces between both. 
     The first contact area between both is formed by the two surfaces, both in the tooth and the adaptor, coming into contact with one another, specifically those which are located on both sides of the appendage  15  of the nose  12  of the tooth  10  or of the appendage  25  of the hollowing  24  of the adaptor  20 , i.e. surfaces  121 ,  122  in the tooth  10  and surfaces  221 ,  222  in the adaptor  20 . This first contact area, which is very close to the tip of the tooth  11 , generates self-tightening reaction Rx 2  preventing the tooth  10  from being ejected from the adaptor  20  due to the stresses to which it is subjected. It is also possible that there is only one first contact surface between the tooth  10  and the adaptor  20 , for example in the case in which the appendage  15  of the nose  12  of the tooth  10  is not centered with respect to the base of the nose  16  of the tooth  10 . 
     A constructive alternative in the tooth  10  consists of arranging a collar or flange  40  therein (see  FIG. 8  to  FIG. 11 ), located on the perimeter of the tooth and coinciding with the gap previously defined between the front part of the tooth or tip  11  thereof and the beginning of the nose  12  of the tooth  10 . The thickness or width of said collar  40  varies depending on the area of the tooth it surrounds depending on the stresses to which said area is subjected. 
     Another feature of the tooth  10  object of the present invention is that the nose  12  of the tooth  10  has a hollowing or cavity  50  to reduce the weight of the tooth without affecting its mechanical features (see  FIG. 12 ). 
     It should be mentioned that the adaptor has at least one groove  27  in its contact area with the tooth for inserting a tool and aiding in removing the tooth once the retaining member arranged between both has been removed.