1. Field of the Invention
The present invention relates to grinding tools (see DEFINITIONS section), more particularly to outdoor grinding tools (see DEFINITIONS section), and also more particularly to bit assemblies (including a bit-securing and bit-shielding sub-assembly(ies) for grinding tools.
2. Description of the Related Art
Stump cutting tools conventionally include a rotating disc assembly that includes a rotating disc and multiple bit sub-assemblies located at regular angular intervals the peripheral edge of the rotating. FIGS. 1 and 2 show a simplified conventional rotating disc assembly 100 including disc 102; and bit sub-assembly 104. Bit sub-assembly includes: bit holder 108; and bit 112. Conventional bit holder 108 provides a substantially rigid mechanical connection (see DEFINITIONS section) between the bit sub-assembly and the rotating disc so that there is substantially no relative motion between the bit sub-assembly and the rotating disc. Angular direction R shows the direction of rotation of the disc in operation.
In FIG. 1, the bit sub-assembly 104 and its pocket 106 are centered at a twelve o'clock position over the center 107 of the disc. FIG. 2, at dotted area 112a, shows the view taken tangent to the top of the disc when the disc is in this twelve o'clock position of FIG. 1. It is this view that defines the “footprint” of the bit. This concept of a “footprint” will be important for understanding certain aspects of the present invention. In the example of FIG. 1 and FIG. 2, the front face of the bit is substantially perpendicular to the viewing vector that defines the foot print of bit 112, but this is not necessarily always true in the prior art, or in the present invention. Both the angular length (that is, angular length in direction R) of the bit sub-assembly and/or a non-orthogonal geometry for the bit itself can cause the front face of the bit to be non-perpendicular to the foot-print defining viewing vector. When the footprint of the bit is substantially perpendicular to the viewing vector, its footprint area will generally be at least approximately equal to the surface area of the front face of the bit. However, when the front face of the bit is not perpendicular to the viewing vector, then its footprint area will be less than the surface area of the front face of the bit.
In conventional usage, this idea of inclining the front face of the bit, forward or backward or not at all, relative to the footprint-defining viewing vector is called a “rake angle.” Conventionally, rake angle is adjusted by the grinder designer depending on factors such as soil type and/or rotational speed.
For present purposes, the important thing to note is that the footprint of the bit—that is, dotted area 112a taken perpendicular to the viewing vector—is entirely exposed as the disc rotates in direction R during operation of the grinder. More specifically: (i) no portion of disc 102 is interposed in front of the footprint when viewed from the viewing vector; and (ii) no portion of bit holder 108 is interposed in front of the footprint of the bit as its footprint is viewed from the viewing vector.
U.S. Pat. No. 5,555,652 (“Ashby”) discloses a land clearing apparatus that includes a rotating rasp used to shred trees, brush and debris. More specifically, rasp 20 includes drum 22, guard 26, removable impact structures 34 and adaptors 48. As shown in FIG. 2 of Ashby, the removable impact structures and respectively associated are located at regular angular intervals around the rotating drum.
U.S. Pat. No. 5,996,657 (“Riesselman”) discloses a stump cutter including a rotatable disk having multiple cutting tool holders. The cutting tool holders each have a cutting tool bit cantilevered therefrom to engage a stump brought into contact with the cutting tool. The cutting tool holder/bit sub-assemblies alternate in the angular direction with sub-assemblies that Riesselman refers to as non-cutting protectors. As shown in FIG. 1 of Riesselman, each bit extend in the radial direction beyond the outermost radial edge of the protectors by a distance of L1. With respect to its protectors and bits Riesselman discloses the following: “In the embodiment shown, the protector 20 is spaced sufficiently far out so that cutting tool bites into an object only to the depth L1 of the hardened cutting tip 16. With traditional stump cutters, no leading protector is provided and the cutter wheel could inadvertently overbite and cause wheel hang-up. I have found that with use of a protector with a massive non-cutting leading edge which is placed ahead of the lead cutting tool a distance denoted by P1, the problem of broken cutting tools is substantially eliminated. That is, the non-cutting leading edge of the protector can be spaced rotationally ahead of the cutting tool to provide protection to the cutting tool. I have found that even with P1 distances of six or seven inches I can still provide protection for the first stage cutter and holder located behind the protector . . . . By having a massive protector that has a greater mass than the cutting tool and is not cantilevered outward as the cutting tool is, the protector can absorb shocks and impacts through gradual abrasion of the protector while the first stage cutting teeth of a row of cutting teeth can be protected.” Riesselman does not seem to disclose how large its dimension L1 is supposed to be.
U.S. Pat. No. 6,138,725 (“Leonardi 1”) discloses various operating angles and/or angles between components associated with a stump grinding tool rotating disc.
U.S. Pat. No. 6,176,445 (“Shinn”) discloses a cutter tooth located on the outer peripheral surface of a rotatable cutter adapted for clearing, mulching and grinding trees.
Description Of the Related Art Section Disclaimer: To the extent that specific publications are discussed above in this Description of the Related Art Section, these discussions should not be taken as an admission that the discussed publications (for example, published patents) are prior art for patent law purposes. For example, some or all of the discussed publications may not be sufficiently early in time, may not reflect subject matter developed early enough in time and/or may not be sufficiently enabling so as to amount to prior art for patent law purposes. To the extent that specific publications are discussed above in this Description of the Related Art Section, they are all hereby incorporated by reference into this document in their respective entirety(ies).