Abstract:
A tool pick assembly and a tool and block assembly are disclosed. A sleeve is positioned about the shank to allow rotation of the tool pick and also friction fit with the block. The sleeve is stepped in complement to the shape of the surface of the shank of the tool pick and the shape of the surface of the bore in the tool holder and extends substantially all of the length, optionally all of the length, of the stepped bore in the block to reduce or prevent dust and fines from entering and wearing the bore surface. When assembled, the stepped sleeve and complementarily shaped shank of the tool pick each do not extend past the rear surface of the bore to mitigate or prevent shank deformation from impact during use.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a §371 National Stage Application of PCT International Application No. PCT/SE2009/050786, filed Jun. 22, 2009, and claims priority under 35 U.S.C. §119 and/or §365 to U.S. Provisional Application No. 61/089,725 filed Aug. 18, 2008. 
    
    
     FIELD 
     The present disclosure relates to a sleeve for retaining a rotatable tool pick in a block. More particularly, the present disclosure relates to a retainer sleeve that fits about the shank of a rotatable tool pick to form a tool pick assembly and that is inserted into a bore of a block to form an assembly. 
     BACKGROUND 
     In the discussion of the background that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art. 
     Large trenching machines utilize large plates linked around a boom to form a cutting chain. Blocks to hold the tool picks are welded at the rear of these plates for optimal cutting.  FIGS. 1 and 2  show an example of such a plate  10  with a block  12  fixed to a surface  14  with a weld  16 . Located in the block  12  is a tool pick  18 . Conventional tool picks utilize rear retainers  20  where a portion of the shank of the tool pick  18  extends past the rearward surface  22  of the block  12 . 
     During operation as the chain of long plates travel around the boom to excavate material, the plates  10  pivot.  FIG. 3  illustrates a portion of the boom  30  indicating travel direction D of the plates  10 . During an excavating portion  32  of the travel cycle, the linked plates  10  are spaced apart due to friction with the material being excavated; during a return portion of the travel cycle, the linked plates  10  are slack and in some locations the plates  10  bend towards one another, reducing the clearance therebetween. In such a circumstance, the edge of the exposed end  24  of the shank of the tool pick  18  can be jammed against the following plate  10 , applying a force to the end  24  that can be high enough to deform the exposed shank and/or the rear retainer  20  of the tool pick  18 . Also, the contact point  26  on the plate  10  can itself be deformed (see  FIG. 2 ). The deformation can cause the edge of the exposed end  24  to misshapen, for example to spread out into a shape similar to a mushroom, or other portions of the tool pick  18  to misshapen. In such cases, removal of the tool pick  18  through the bore of the block  12  can be complicated and/or prevented. Where used, removal of a rear-retainer or employment of special tools for retainer removal or tool pick removal are likewise complicated and/or prevented by portions of the tool pick being misshapen. 
     Wear is detrimental to the lifetime performance of assemblies. For example, to encourage pick rotation, there is typically clearance between the pick and its sleeve. However, this clearance allows space for dust and fines to collect between the tool pick and the bore of the block. As rotatable elements of the assembly rotate, this material grinds the opposing elements, thereby enlarging the bore and allowing more fines to enter, accelerating the wear and reducing the life of the block. Similar wear problems can occur between the sleeve and one or more of the bore of the block or the shank of the tool pick if the clearance is too large and dust and fines collect therebetween. With regard to the use of an external retainer, a certain amount of clearance is required between the rear of the block and the groove in the pick shank to assemble the retainer. If too large, this clearance allows unnecessary freedom of movement between the pick and block, causing an unwarranted amount of slapping between the pick shoulder and face of the block. This slapping causes excessive wear in the bore and on the face of the block, reducing its life. 
     SUMMARY 
     The above limitations in the prior art are addressed, mitigated and/or eliminated by the presently disclosed step-shank sleeve retainer. 
     An exemplary tool pick assembly comprises a tool pick including a head portion and a shank portion projecting rearwardly from the head portion, and a sleeve positioned about the shank portion, wherein the sleeve includes a hollow cylindrical body having a first end, a second end and an axially continuous surface therebetween formed by a first surface portion joined to a second surface portion by a stepped portion, a first axially extending slit in the continuous surface extending from the first end to the second end, and a tool pick retaining feature, wherein the first surface portion of the sleeve has a larger diameter than the second surface portion of the sleeve and the stepped portion of the sleeve has an axially varying diameter, wherein the tool pick retaining feature projects radially inward from the second surface portion into a circumferential channel in the shank portion, wherein the shank portion has a first surface portion and a second surface portion, a diameter of the first surface portion being larger than a diameter of the second surface portion, and a stepped portion with an axially varying diameter, and wherein the first surface portion of the sleeve extends an entire axially distance of the first surface portion of the shank portion and the second surface portion of the sleeve extends at least a portion of the axial distance of the second surface portion of the shank portion. 
     An exemplary tool and block assembly comprises a block including a body having a bore extending axially from a first side to a second side, a tool pick including a head portion and a shank portion projecting rearwardly from the head portion, and a sleeve positioned about the shank portion, wherein the sleeve includes a hollow cylindrical body having a first end, a second end and an axially continuous surface therebetween formed by a first surface portion joined to a second surface portion by a stepped portion, a first axially extending slit in the continuous surface extending from the first end to the second end, and a tool pick retaining feature, wherein the first surface portion of the sleeve has a larger diameter than the second surface portion of the sleeve and the stepped portion of the sleeve has an axially varying diameter, wherein the tool pick retaining feature projects radially inward from the second surface portion into a circumferential channel in the shank portion of the tool pick, wherein the shank portion has a first surface portion and a second surface portion, a diameter of the first surface portion being larger than a diameter of the second surface portion, and a stepped portion with an axially varying diameter, wherein the first surface portion of the sleeve extends an entire axially distance of the first surface portion of the shank portion and the second surface portion of the sleeve extends at least a portion of the axial distance of the second surface portion of the shank portion, wherein an inner diameter surface of the bore is complimentarily shaped to the axially continuous surface of the sleeve and forms a friction fit therewith, and wherein the tool pick is rotatable. 
     An exemplary excavating machine comprises a rotatable member and a tool and block assembly mounted thereon. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The following detailed description can be read in connection with the accompanying drawings in which like numerals designate like elements and in which: 
         FIG. 1  shows a prior art block attached to a plate of a cutting chain on a trenching machine. 
         FIG. 2  shows another view of the block and plate in  FIG. 1 . 
         FIG. 3  shows a schematic of the operation of a boom to excavate material. 
         FIG. 4  shows an exemplary embodiment of a tool pick assembly. 
         FIG. 5  shows an exemplary embodiment of a sleeve. 
         FIG. 6  is a schematic representation of a cut-away view of the tool pick assembly of  FIG. 4   
         FIG. 7  shows an exemplary embodiment of a tool and block assembly in cross-section. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 4  shows an exemplary embodiment of a tool pick assembly  100 . In the illustrated embodiment, the tool pick assembly  100  comprises a tool pick  102  and a sleeve  104 . 
     The tool pick  102  includes a head portion  106  and a shank portion  108 . The shank portion  108  projects rearwardly from the head portion  106  with an end  110  of the shank portion distal from the head portion  106 . The shank portion  108  includes a circumferential channel  112  or other depression that can be used for tool pick retention. The head portion  106  of the tool pick  102  can include any suitable features, including, for example, a shoulder region  114 , a tapered region  116  and a tip  118 . The tip  118  can be made from a hard material, such as tungsten carbide. 
     The sleeve  104  includes a hollow cylindrical-like body having a first end  122 , a second end  124 , and an axially continuous surface  126  therebetween. The axially continuous surface  126  is formed by a first surface portion  128  joined to a second surface portion  130  by a stepped portion  132 . The continuous surface  126  includes a first axially extending slit  134  extending from the first end  122  to the second end  124 . The axially extending slit  134  allows for circumferential compression of the sleeve  104  when installed in a bore of a block. 
     The first surface portion  128  of the sleeve  104  has a larger diameter D 1  than the diameter D 2  of the second surface portion  130  of the sleeve  104 . Connecting the first surface portion  128  and the second surface portion  130  is a stepped portion  132 . The stepped portion  132  has an axially varying diameter. In exemplary embodiments, the second surface portion  128  of the sleeve  104  is a rearwardmost portion (e.g., rearwardmost relative to the head portion of the tool pick when the sleeve is positioned about the shank).  FIG. 5  shows an exemplary embodiment of a sleeve  104  and illustrates the relationships between the first surface portion  128 , the second surface portion  130 , the respective diameters D 1  and D 2 , and the stepped portion  132 . 
     There may be various relationships between the surfaces and diameters in exemplary embodiments of sleeves. For example, the diameter D 1  of the first surface portion  128  of the sleeve  104  can be constant along the axial extent of the first surface portion  128  and the diameter D 2  of the second surface portion  130  of the sleeve  104  can also be constant along the axial extent of the second surface portion  130 . Also, for example, the diameter D 1  of the first surface portion  128  can be the largest diameter of the sleeve  104 . 
     The sleeve  104  is positioned about the shank portion  108  to allow rotation of the tool pick  102  about its axis  138 . Thus, the sleeve  104  is not in friction fit contact with the shank portion  108  of the tool pick  102 . However, the sleeve  104  is retained about the shank portion  108  to limit axial movement and includes a tool pick retaining feature. The tool pick retaining feature projects radially inward from the second surface portion  130  into a circumferential channel  112  in the shank portion  108 . An example of a tool pick retaining feature is shown in the figures as one or a plurality of tabs  140 . Other examples include one or a plurality of bumps or ridges or other projections. 
       FIG. 6  is a schematic representation of a cut-away view of the tool pick assembly of  FIG. 4 .  FIG. 6  illustrates an example of interaction between the sleeve  104  and tool pick  102  in the tool pick assembly  100 . In an exemplary embodiment, the shape of the shank portion  108  is approximately the same as the inner diameter surface of the sleeve  104 , allowing for relative rotation and the tool pick retaining feature. For example, the shank portion  108  has a first surface portion  142  and a second surface portion  144 , where a diameter d 1  of the first surface portion  142  is larger than a diameter d 2  of the second surface portion  144  and a stepped portion  146  with an axially varying diameter connects the first surface portion  142  and the second surface portion  144 . To allow relative rotation, diameter d 1  is less than diameter D 1  and/or diameter d 2  is less than diameter d 2 . Also, for example, the first surface portion  128  of the sleeve  104  extends an entire axially distance of the first surface portion  142  of the shank portion  108  and the second surface portion  130  of the sleeve  104  extends at least a portion of the axial distance of the second surface portion  144  of the shank portion  108 . In alternative embodiments, the sleeve  104  extends the entire length of the axial distance of the second surface portion  144  of the shank portion  108 , e.g., the end  110  of the shank portion  108  distal from the head portion  106  is axially coterminous with the second end  124  of the sleeve  104 . 
       FIG. 7  shows an exemplary embodiment of a tool and block assembly  200  in cross-section. The exemplary embodiment of a tool and block assembly  200  comprises a block  260  including a body  262  having a bore  264  extending axially from a first side  266  to a second side  268 . A tool pick assembly is positioned in the bore  264  of the block  260 . The tool pick assembly comprises a tool pick  202  and a sleeve  204 . The tool pick  202  includes a head portion  206  and a shank portion  208  projecting rearwardly from the head portion  206 . The sleeve  204  is positioned about the shank portion  208 . The tool pick  202  and sleeve  204  in the tool and block assembly  200  are substantially the same and have substantially the same features as those disclosed and described herein in connection with the tool pick and sleeve of  FIGS. 4-6 . 
     As shown in  FIG. 7 , the tool pick assembly is positioned in the bore  264  of the block  260 . The tool pick  202  is rotatable relative to the sleeve  204  about axis  238 . An inner diameter surface of the bore  264  is complimentarily shaped to the axially continuous surface of the sleeve  204  and at least portions of the axially continuous surface form a friction fit with the inner diameter surface of the bore  264 . For example, the bore  264  has two portions  270 ,  272  with different diameters with a stepped portion  274  therebetween with an axially varying diameter. In the free- or static-state, the diameters of at least one of the first surface portion  228  and the second surface portion  230  of the sleeve  204 , optionally the diameters of both of the first surface portion  228  and the second surface portion  230  of the sleeve  204 , are larger than the diameters of the corresponding portions  270 ,  272  of the bore  264 . Because the sleeve  204  is circumferentially compressible, the sleeve  204  compresses to fit inside the bore  264  and the elastic properties of the sleeve  204  provide for friction retention of the sleeve  204  in the bore  264 . In this compressed, friction-retention state, the relationship of the sizes of the diameters of the sleeve surface portions  228 ,  230  relative to the shank portion  208  remains such that the tool pick  202  is rotatable relative to the sleeve  204 , which is itself substantially stationary, if not stationary, relative to the block  260  by operation of the friction fit. 
     Installation of the tool and pick assembly into the block can be by any suitable means. In an exemplary embodiment, an operator can use a standard dead-blow hammer to knock the tool and pick assembly into the block. When installed, the sleeve is positioned tightly against the bore and seals out dust and fines from grinding into the bore wall. Fines that do approach the holder enter between the shank of the tool pick and the sleeve. However, this is generally acceptable since the tool pick and the sleeve are replaced with new parts during every pick change. 
     It is noted that the retention method disclosed herein can be used with various blocks. For example, internally grooved bores are not needed for the disclosed sleeve, although internally grooved bores will not diminish the performance of the tool pick nor diminish the retention from that of a smooth bore. 
     The disclosed tool and block assembly  200  can be incorporated into an excavating machine, such as Tesmec model TRS-900 and Trencor model 1660HDE. In an exemplary embodiment, the excavating machine comprises a rotatable member with the tool and block assembly mounted thereon. An example rotatable member is the chain of long plates travelling around a boom to excavate material. 
     Although described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without department from the spirit and scope of the invention as defined in the appended claims. 
     The disclosures in the U.S. provisional patent application No. 61/089,725 from which this application claims priority, are incorporated herein by reference.