INVERSE TAPED SHAFTS AND COMPLEMENTARY FOOT BLOCK DRILLS FOR CHILL ORDERS

Abstract

Chisel holder and foot block combination, including: a chisel holder (10; 50; 70) comprising an upper main section (14; 52; 73) and a hollow, cylindrical, slotted shaft (12; 51; 77) supported thereon, a first section (19; 64) of the shaft (12; 51; 77) adjoining a distal end (22; 65) of the shaft (12; 51; 77), comprising an outer surface of increasing diameter towards the distal end (22; 65) of the shaft (12; 51; 77), and a foot block (11) in which a bore (13) is included to receive the shaft (12; 51; 77), the bore (13) comprising an annular counterbore (35) adjacent to its upper mouth, a tapered upper bore section (36) immediately adjacent thereto providing an annular indentation (37) of the bore (13) at its lower end, and an inversely tapered bore section (38) adjacent to the indentation (37), wherein the inversely tapered bore section (38) in the hollow dimension corresponds to the first section (19; 64) of the shaft (12; 51; 77), at a similar position from a mouth of the bore (13) as the first shaft section (19; 64) from a bottom of the upper main part section (14; 52; 73), and wherein the inversely tapered bore section (38) is complementary to the first shaft section (19; 64) when the shaft (12; 51; 77) is inserted into the bore (13), wherein a widest part of the shaft (12; 51; 77), which, when inserted into the foot block bore (13) past an upper end of the inversely tapered bore section (38), is adapted to pre-tension the shaft (12; 51; 77) to fully insert it into the bore (13).

Description

[0001] This invention relates generally to bit assemblies for road milling, mining and trenching equipment, and more particularly to a complementary inversely tapered configuration for holding certain parts together in the assemblies.

[0002] US 2004 / 0174065 A1 discloses a drill bit assembly for road milling, mining, and trenching equipment with a streamlined tip assembly consisting of a combination of conical and cylindrical shapes and free of projections or annular recesses. The bit holder has a conical upper main body, followed by a cylindrical shank that is inserted into a bore in the base block.

[0003] US 8,622,482 B2 discloses a chisel holder with a shank that tapers from the conical main section to its distal end through two cones, with the largest diameter of the second cone being larger than the smallest diameter of the first cone, creating a step at the transition between the two cones. When the shank is driven into the bore in the base block, the shank is clamped in the bore at the transition point between the two cones.

[0004] From DE 20 2012 100 353 U1 a tool holder for mounting a chisel tool in a tool holder is known, which is characterized in that the chisel tool has a tool shank which can be inserted into the recess of the tool holder and which interacts with at least one clamping body via inclined or conical contact surfaces, wherein the tool shank is axially adjustable relative to the clamping body and can thereby be radially clamped in the recess. Background of the invention

[0005] In the world of heavy equipment, mining, trenching, and road milling equipment must be built to withstand the stress and wear of removing asphalt, concrete, rock, minerals, coal, and the like from the ground surface and underground.

[0006] Generally, some very hard materials, such as tungsten carbide and, more recently, industrially and artificially produced diamond materials, provide the cutting edge for such heavy equipment. In road milling, the surface removal equipment includes a rotating drum on which a plurality of bit assemblies, including the aforementioned tips made of very hard materials, are positioned very closely together and usually in a spiral or serrated pattern on the outside of a rotating drum.

[0007] Prior to Applicant's groundbreaking inventions in patents US 6,371,567 B1 and US 6,585,326 B2, the very hard points found in what are referred to herein as "bits" were pivotally mounted on bit holders, or on spacers, that were secured to foot blocks, which in turn were mounted on the outside of such drums, or on the outside of plates positioned on the outside of links for such heavy duty service. The spacers or bit holders were held to the foot blocks by bolting or by using other distal end retention means. Applicant's prior inventions eliminate the need for nuts on the rear end of the foot blocks by providing a bit holder having a hollow slotted shank which, when driven, has an enlarged overall super interference fit that securely engages the same against the foot block bore.

[0008] Particularly in road milling machines and other heavy-duty equipment having fixed configurations, the need for new and improved material removal arrangements where they come into contact with the material being removed has required that the equipment, even when improved, be largely interchangeably compatible.

[0009] Conventional toolholders generally have cylindrical shanks with a nominal diameter of 1-1 / 2 inches (the length notation inch, abbreviated to inch, means "inch" and is equal to 25.4 mm) and a nominal length of 2-1 / 2 inches to fit into existing base block bores, and Applicant's improved interference fit toolholders have shanks of similar diameters and lengths.

[0010] Given the rigorous nature of highway milling and material removal, it is highly desirable for both toolholders with removable tools mounted therein and tool / toolholder combination units containing either industrial diamonds or PCD materials at their tips to be driven into and retained within base blocks. In this regard, improved access to the rear of the base blocks for removing tool / holder combination units from their mounted position in the base block would be highly desirable.

[0011] A need has arisen for base blocks having shorter length bit holder bores and, consequently, for improved bit / holder combination units having shortened shanks thereon that snugly engage and are retained in such base block bores. Summary of the invention

[0012] The invention relates to a bit holder and foot block combination according to claim 1, wherein the bit holder has an upper main body portion and a hollow, slotted, generally cylindrical shank supported on the upper main body portion. Brief description of the drawings

[0013] The features of the present invention believed to be novel are set forth with particularity in the appended claims. The invention will best be understood from the following detailed description of presently preferred embodiments, taken in conjunction with the accompanying drawings, in which like reference characters indicate like parts: Fig. 1 is a side view of a bit holder and its corresponding foot block, with tapers exaggerated for clarity, constructed in accordance with the present invention; Fig. 2 is a cross-sectional view taken substantially along line 2-2 of Fig. 1, also showing an outline of the bit holder and foot block bore constructed in accordance with the present invention; Fig. 3 is a cross-sectional view similar to that in Fig. 2, showing the chisel holder mounted in the foot block bore; Fig. 4 is a front view of a bit / bit holder combination unit, with tapers exaggerated for clarity, constructed in accordance with the present invention, with a PCD-tipped insert; and Fig. Figure 5 is a front view of a combined bit / bit holder assembly having an enlarged diameter PCD insert integrally mounted on the top of the bit holder body. Detailed description of the preferred embodiment

[0014] With reference to Fig. 1 and Fig. 2 includes a chisel holder 10 and its corresponding base block 11 constructed according to the present invention, which are shown in an exploded view in Fig. 1, a shortened bit holder shank 12 and a complementary shortened base block bore 13. The bit holder includes a generally frusto-conical main portion 14 with a hollow central bore 15 therethrough, continuing through a generally hollow cylindrical slotted shank 12. In this preferred embodiment, the shank 12 has a reduced effective length of about 1-1 / 2 inches (overall length 1-3 / 4 inches) with a nominal diameter of 1-1 / 2 inches, the diameter varying along its length.A preferred embodiment of the shaft 12 includes a 1 / 4 inch long upper section 16 integrally connected to the bottom 17 of the generally frusto-conical (other shapes are possible) main body 14, a central reduced diameter section 18 of about 1 / 2 inch in axial length, and an inversely tapered section 19 of about 3 / 4 inch in length which widens as it descends from the reduced diameter section 18 to its terminus 22 adjacent a short (1 / 4 inch) distal end section 21.

[0015] The stem 12 of the present invention also includes an elongated slot 23 extending from the distal end 22 of the stem 12 through the inversely tapered section 19, through the reduced diameter section 18, and terminating adjacent the upper enlarged diameter section 16. The slot 23 has approximately the same percentage stem length ratio of about 1-1 / 2 inches to 1-3 / 4 inches of total stem length for the shortened stem as the slots used in the longer 2-1 / 2 inch stems. In this preferred embodiment, the slot 23 extends upwardly to the upper enlarged diameter section 16 of the stem 12 to allow radial deformation or compressibility of the upper section 16 of the stem 12.

[0016] In the preferred embodiment, the upper main body section 14 includes cutouts 24 (one of which is shown) ( Fig. 1) shown adjacent its top portion 25 for driving a chisel (not shown) from the top portion 25 of the bit holder 10 and from the top of the bit holder bore 15, and wedge-shaped undercuts 26 (one of which is shown) adjacent the rear annular flange 17 of the main portion 14 to allow forked tools to be inserted therein to assist in driving the bit holder 10 out of the base block 11. The distal end 22 of the shank 12 includes a largely solid annular wall, except for the slot 23 and the bit holder bore hole 15, which provides a substantially flat surface for receiving a suitable diameter drive pin, or other extractor, which can be used to drive the bit holder shank 12, or a chisel shank, out of the base block 11.

[0017] The Fig. The foot block 11 shown in Figure 1 includes a generally flat or partially hollow circular segment shape at its mounting end 27, which is adapted to be mounted either on the cylindrical surface of a drum (as shown) or on a plate mounted over the outer surface of the drum or heavy-duty links (not shown). The mounting portion 28 of the foot block 11 further includes a serrated upper portion 30 stepping back on each side from a central spine 31, thereby providing a path for the loosened pavement material to move efficiently around the foot block 11.

[0018] Outward of the mounting portion 28 is a generally annular bit holder receiving portion 32 having a substantially flat, annular top surface 33 and a shortened axial body depth of approximately 1-1 / 2 inches in height. In this preferred embodiment, the bit holder block mounting portion 32 includes a multi-segment bit holder block bore 13, shown by a dotted line. The shortened body height has an L-shaped bottom surface 34 underlying it, which can be considered a cutout from the previous foot blocks having the bit holder block bore 2-3 / 8 inches in length.

[0019] The preferred embodiment of the bit holder block bore 13, as shown in Fig. 1 and Fig. 2, includes a generally annular counterbore 35 adjacent its tip, a 1 degree per side tapered upper segment 36 immediately below the upper counterbore, which provides at its base a generally annular throat 37 which is the narrowest portion of the bore 13, and an inverse taper or generally widening taper 38 extending below the throat to the L-shaped cutout portion 34.

[0020] The counterbore 35 and the tapered top surface are preferably machined surfaces. The tapered bore surface is preferably machined from the constriction 37 across the horizontal side 39 of the L-shaped lower section to the edge 34 of the machined section.

[0021] An arcuate cutout segment below line 34 with its innermost boundary shown at 40 extends to the bottom of the foot block attachment portion 28 and does not need to be machined.

[0022] While the slot 23 in the bit holder shank 12 can have a number of widths, depending upon the precise configuration of the sidewall thickness (approximately 3 / 8 inch), the angle of the reverse taper of the reverse tapered portion 19 of the shank 12, and the hardness and compressive strength of the specific steel used for the bit holder 10, the width of the slot 23 shown is approximately 5 / 8 inch.

[0023] While the upper taper portion 36 of the bit holder block bore shown in the preferred embodiment includes a 1-degree taper portion, it may also be a straight, hollow, cylindrical configuration or a continuous inverse taper portion through the base block 11 within the scope of the present invention. The inverse taper portion 38 in this preferred embodiment may vary between approximately 0.001 to 15 degrees per side of inverse taper.

[0024] The respective inverse taper sections of the stem 19 and the base block bore 36 need not be identical inverse tapers. Applicant currently operates within the limits of approximately 0.001 degrees to approximately 2 degrees per side. Furthermore, various inverse tapers were discussed in Applicant's prior co-pending applications (Ser. No. 14 / 959,551), which also provide sufficient radial retention forces.

[0025] In operation, the compressibility of the sidewall 12a of the bit holder shank 12 constructed according to the present invention allows the shank to be driven into the base block bore 13 by compressing the outer circumferential periphery of the shank 12 into the bore 38 of the reverse-tapered portion 19 of the shank. As the reverse-tapered portion 19 of the shank 12 reaches the reverse-tapered portion 38 of the base block bore 13, the shank 12 is more easily driven into the base block bore 38 as it expands until the reverse-tapered portion 19 is generally fully positioned within the base block 11. The shank 12 is then almost complementary to the inversely tapered portion 38 of the foot block bore 13, with the rear annular flange 17 of the bit holder main body 14 sitting on the upper annular portion 33 of the foot block bit holder attachment portion 32.

[0026] It should be noted that, within the scope of the present invention, the inverse tapered section in this embodiment, with variable degrees of inverse taper per side, in the inverse taper 19 will be similar to the angle of the inverse tapered section 38 of the bottom of the base block bore 13. It need not be identical, and variations may be utilized. The objective of the present invention is to provide an inverse tapered section 19 of the bit holder that, by its configuration, typically sits in the base block bore 38 and is reluctant to exit the base block bore 13 unless forced out by an extractor.

[0027] This is an important feature of the applicant's invention that is not present in previous embodiments of a super-interference-sized slotted shank capable of being driven into a base block bore. Super-interference is defined as an interference greater than that found in the most extreme fit tables in design manuals for solid shaft diameters. The slot and hollow shank allow resilient radial compression of the shank through the constriction of the base block bore, thereby providing increased compression holding force between the shank and the corresponding portion of the base block bore when the shank is fully inserted therein.

[0028] With reference to Fig. 3 shows what it looks like when the bit holder 10 is fully driven into the base block bore 13 so that the rear annular flange 17 of the bit holder body 14 sits on the upper annular wall 33 of the bit holder receiving portion 32 of the base block 11 and the shank 12 is fully driven into the base block bore 13. At the bottom of the upper quarter-inch of the flared diameter segment 16 of the shank 12, the lower edge 16a of this portion provides a near annular interference fit with the one-degree tapered upper segment 36 of the base block bore 13.Because of the slot 23 extending to this upper quarter-inch segment 16, the generally annular force or shrink fit of 0.001-0.003 inches for a 1-1 / 2-inch diameter shank can be increased to substantially ring contact rather than matched interference contact, providing a contact surface that may have a height of approximately 1 / 8 inch. This generally force or shrink fit, in combination with the annular insert groove 43 in the bit holder body 14 between the shank 12 and the rear annular flange 17 of the upper body section, reduces the stress between the shank 12 and the bit holder body 14 when the shank is driven into the foot block bore 13.

[0029] The reduced diameter section 18 of about 1 / 2 inch in axial length is smaller in diameter by about 0.020 inch per side than the upper part 16 and the inversely tapered sections 19 of the shaft 12. As most clearly shown in Fig. 3, when the shank 12 is fully driven into the base block bore 13, the inversely tapered portion 19 of the shank 12 and the inverse taper of the base block bore 38 mate in a generally complementary manner. This provides a structure that reduces the ability of the shank to withdraw itself from the base block bore during the extreme forces exerted on the bit holder 10 or its corresponding bit (not shown) in operation. Yet, the wedge-shaped undercuts 26 and the angled slotted rear surface 40 of the base block bore 13, along with the shortened length of the base block bore 36-38, provide additional clearance for accepting variously shaped extraction tools that can be used to drive the bit holder 10 from the base block bore 13 when desired.

[0030] With reference to Fig. 4, a bit / bit holder unit 50 is shown constructed in accordance with the present invention and includes a shank 51 and a main body portion 52 having a generally axially extending, annular cup-like portion 53 with a recess 54 therein. This recess matingly receives a transition member 55, which may be cylindrical or slightly tapered, as shown in Fig. 4. This transition element 55 may be made of steel, tungsten carbide, or the like, as desired, and includes at its top a generally cylindrical recess 56 into which a diamond or PCD layer or coating on its tip, or a thermally stable polycrystalline element, is applied, generally by brazing.

[0031] As in Fig. 4, the diamond-coated tip may be flat 57, oval 58, conical 60, or the like. In this embodiment, the transition element 55 is preferably made of tungsten carbide. Outward of the annular, uppermost extending cup-like portion 53 of the main body is an annular tungsten carbide ring or shroud 61, which provides additional support and wear resistance to withstand material flowing around the outside of the bit / bit holder 50. The transition element 55 shown in Fig. The diamond tip elements 57, 58, 60 shown in Figure 4 have a diameter of 0.500 inch to about 0.565 inch at the base and can be obtained commercially from a number of sources. The shaft 51 of the diamond tip elements shown in Figure 4 Fig. The embodiment shown in Figure 4 is similar to that shown in Fig. 1, Fig. 2 and Fig. 3, which has a 1 / 4 inch enlarged diameter upper portion 62 of the main body, a reduced diameter middle portion 63, and an inversely tapered portion 64 of about 3 / 4 inch in axial length terminating in a distal end portion 65 of about 1 / 8 to 1 / 4 inch in axial length.

[0032] The slot 66 in the shaft 51 is Fig. 3, it has a width of approximately 5 / 8 inch and extends upwardly from the distal end 65 to the enlarged diameter upper portion 62. While the slot 66 shown here has parallel sides, it should be understood that the slot may have various configurations, including a wider slot resulting in an even more compressible shaft 51.

[0033] With reference to Fig. 5 is a chisel / chisel holder 70 constructed in accordance with the present invention, substantially identical to that shown at 50 in Fig. 4, except that an enlarged tip or tip insert 71, having a root diameter of approximately 3 / 4 inch, is fitted into the generally annular, axially extending flange 72 at the top of the bit / bit holder body portion 73. This insert 71 is fitted into a substantially cylindrical recess at the top of the bit / bit holder body portion 73. This recess may also have a slight taper therein, depending on the configuration of the root of the insert 71, which is coated with a TSP diamond or PCD diamond layer.

[0034] Like the Fig. The embodiment shown in Figure 4 also includes the embodiment of Fig. 5 an annular tungsten carbide ring 75 positioned outwardly therefrom and preferably brazed into an annular recess 76 externally adjacent the bottom of the annular axially extending flange.

[0035] As in Fig. 4 and Fig. 5, the hollow portion 50a or 70a of the shaft 77 preferably extends upwardly to the rear annular flange 52a or 78 of the body, and in these embodiments extends upwardly past the top of the collar portion 52a or 79 of the body, where it terminates, leaving the remainder of the upper tapered portion of the body as a solid structure.

[0036] The Fig. 1, Fig. 2 and Fig. The embodiment shown in Figure 3 is that of a chisel holder in which a chisel can be inserted into the upper hole of the chisel holder. Fig. 4 and Fig. The embodiments shown in Figure 5, which include PCD diamond tipped or TSP diamond inserts, are formed integrally with the main body of each embodiment and do not rotate thereon, as does a chisel in the first embodiment shown in Fig. 1-3. These diamond-tipped and TSP diamond inserts should provide significantly extended service life compared to tungsten carbide bits, so rotating their tips is not necessary to achieve a significant extension in service life. Of course, a rotating diamond-tipped bit could provide even longer service life on a rotating bit.

Claims

[1] Chisel holder and foot block combination, comprising: a chisel holder (10; 50; 70) having an upper main body portion (14; 52; 73) and a hollow, cylindrical, slotted shank (12; 51; 77) supported thereon, a first portion (19; 64) of the shaft (12; 51; 77) adjacent to a distal end (22; 65) of the shaft (12; 51; 77) and comprising an outer surface of increasing diameter towards the distal end (22; 65) of the shaft (12; 51; 77), and a base block (11) in which a bore (13) is contained to receive the shaft (12; 51; 77), the bore (13) comprising an annular counterbore (35) adjacent to its upper mouth, immediately adjacent thereto a tapered upper bore portion (36) providing an annular indentation (37) of the bore (13) at its lower end, and an inversely tapered bore portion (38) adjacent to the indentation (37), wherein the inversely tapered bore portion (38) corresponds in hollow dimension to the first portion (19; 64) of the shaft (12; 51; 77), at a similar position from an opening of the bore (13) as the first shaft portion (19; 64) from a bottom of the upper main body portion (14; 52; 73), and wherein the inversely tapered bore portion (38) is complementary to the first shaft portion (19; 64) when the shaft (12; 51; 77) is inserted into the bore (13), wherein a widest part of the shaft (12; 51; 77), when inserted into the base block bore (13) past an upper end of the inversely tapered bore portion (38), is adapted to bias the shaft (12; 51; 77) to insert it fully into the bore (13). [2] Combination according to claim 1, wherein a circular segment of the bore (13) extends beyond the inversely tapered bore portion (38) of the base block (11) to a lower part of a fastening portion (28) thereof. [3] A combination according to claim 2, wherein the circular segment extends from the inversely tapered bore portion (38) of the base block (11) at an angle to an axis of the bore (13) which is smaller than that of the bore (13) below the constriction (37) thereof. [4] Combination according to claim 1, wherein the shaft (12) includes: a section (18) of reduced diameter adjacent to an upper part of the first section (19), and the slot (23) extending axially from the distal end (22) of the shaft (12) through the first portion (19) and through the reduced diameter portion (18). [5] The combination according to claim 4, wherein the shaft (12) further comprises: an upper portion (16) adjacent a top of the reduced diameter portion (18), the upper portion (16) being dimensioned to form an interference fit with the tapered upper bore portion (36) of the base block bore (13) when the stem (12) is fully inserted therein. [6] Combination according to claim 1, wherein: the widest part of the shaft (12) has a super interference fit with the inversely tapered bore section (38).

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