Abrasive throwing wheel and abrasive throwing blade

Details Abrasive throwing wheel and abrasive throwing blade Abrasive throwing wheel and abrasive throwing blade

2001-03-08

2002-09-10

Rose, Robert A. (Department: 3723)

Abrading

Machine

Sandblast

C451S098000

Reexamination Certificate

active

06447378

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a rotatable abrading device, and more particularly, to a mechanical device for propelling abrasive materials at abrading velocities against a surface to be treated. Such devices are commonly known as abrasive throwing wheels or centrifugal blasting machines. This invention also relates to an abrasive throwing blade and to an assembly comprised of the blade in position on the abrasive throwing wheel.
Centrifugal blasting machines comprising rotors or wheels having a plurality of blades installed thereon have been known in the art for many years. When the wheel is rotated at very high speeds, the blades propel an abrasive material against a work surface. The blades are sometimes referred to as abrasive throwing blades or simply throwing blades. Due to the action of the abrasive material on the throwing blades, the blades exhibit considerable wear over a period of time. Attempts have been made to fabricate the throwing blades from abrasion resistant alloys. In other cases, special blade configurations have been employed to minimize the effects of the abrasive material on the blades.
Notwithstanding these attempts to minimize wear and extend the life of the throwing blades, periodic blade removal and replacement cannot be avoided. This results in a loss of valuable operating time. Furthermore, while the blades must be removable, they must also be held securely in place such that they resist the tremendous centrifugal and other forces exerted on them when the abrasive throwing wheel is rotated at high speeds.
Several methods have been proposed for securing the throwing blades in a removable manner to the throwing wheel. One method involves securing the blades to the front side of a wheel disk, usually by means of a bolt or by means of radial grooves in the wheel, frequently of a dove tail shape. Another method employs two wheel disks that are maintained in spaced-apart relation. Longitudinal narrow edges of the throwing blades are generally inserted into radial grooves arranged in opposing surfaces of the two disks. Auxiliary means, such as bolts, pivotal locking means, eccentrics, set screws, etc. can be employed to secure the blades against radial displacement. Examples of these devices can be found in U.S. Pat. Nos. 2,819,562, 3,352,064, and 3,654,736. Blade replacement in these designs is not always easy because a number of parts must be disassembled to access the blade or because the blades may “freeze” or become jammed in the grooves in the wheel.
A number of other designs have been proposed. For example, U.S. Pat. No. 2,696,364 describes a turbine mounted on a shaft and a plurality of buckets mounted between an inner plate and an outer plate. The buckets are held between the plates by machine bolts, which pass completely through the wheel perpendicular to the plane of the wheel. The bolts clamp the plates and grip the turbine buckets between teeth formed on roots of the buckets and on peripheral marginal faces of the plates.
U.S. Pat. No. 2,955,799 describes a rotor including a hub and a plurality of blades circumferentially spaced about the hub. Interengaging means mount the blades in the hub with axial play therebetween. The blades have roots, and the interengaging means include a single pin support connecting the root of each blade to the rotor.
U.S. Pat. No. 2,970,809 relates to a rotor structure having a rim portion with a recess that receives a radially extending blade. The blade has a root portion of less thickness than the width of the recess. Thus, the blade is loosely received in the recess. A pin is provided for insertion in the rim and through the root portion for supporting the blade.
U.S. Pat. No.3,165,294 relates to a rotor drum provided with a plurality of axially spaced, circumferentially extending slots of dovetail shape. A loading recess is provided in the radially inward wall of the dovetail slot. A radially extending threaded or tapped hole is provided adjacent the loading recess, a threaded member of plug being received therein. The head of the threaded plug is provided with a recess for receiving a tool, such as an Allen wrench, for screwing the threaded plug into and out of the tapped hole.
U.S. Pat. No. 3,287,858 describes a blasting wheel, which supports in vane channels a vane secured to a steel backing plate, which is, in turn, anchored to a channel in the wheel by bolts in a block that is integral with the plate or secured thereto. A positioning pin is used to position the backing plate in the vane channel. The vane face also is connected with the backing plate by a pin that seats in an opening in the backing plate. The pin serves as a positioning element and a reinforcement against centrifugal force developed during operation of the wheel. The pin connection prevents the plate and vane from sliding axially following development of centrifugal force.
U.S. Pat. No. 3,368,308 relates to a throwing wheel and a shaft rotatably mounted on suitable journals and carrying a runner head upon which throwing blades are mounted. The blades are equally spaced around the runner head and can be held in any suitable manner, such as by use of an enlarged dove tailed edge on one side of the blade engaging a corresponding dove tailed slot in the face of the runner head.
U.S. Pat. No. 3,867,791 describes a throwing blade that is secured to a wheel by means of a blade block, which is mounted on the wheel. The blade block has a first groove near an inner end of the block and a second groove near an outer end. The blade includes lugs for insertion in the grooves. A centrally disposed impeller restricts movement of the blades, particularly in a radial direction. The blades are thus maintained in a fixed position on the blade blocks. While commercial success has been achieved with this device, the rear of the blade must generally be machined in the area where it contacts the impeller. This adds to the cost of the blade. Additionally, it is rather difficult to cast a blade of the type disclosed in the patent because of its large cross-sectional area.
Another arrangement is shown in U.S. Pat. No. 3,894,360. In this design, the blades are mounted on brackets having an angular cross-section, and the brackets, in turn, are mounted on the throwing wheel. The rear of each blade is provided with a cast-in insert stud, which is adapted for insertion through an opening in the angular bracket. The stud is provided with a slot adapted to receive a clip, which holds the blade in position on the angular bracket. The only securing means in this arrangement is comprised of the stud and the spring clip. Should either the stud or spring clip fail, such as by wear around the area of the stud, the blade may fly off the wheel.
U.S. Pat. No. 4,249,350 provides, in combination, a blade block adapted for mounting on an abrasive throwing wheel and a blade supported by and detachably connected to the blade block. The blade has an inner end, an outer end, a forward surface and a rear surface. Cooperating engagement means are provided on the blade block and the blade for permitting inward movement of the blade while preventing substantial outward movement thereof relative to the blade block. An abutment means on the blade block acts as a bearing or driving surface for the blade. The abutment surface is located outwardly of the engagement means and usually contacts the rear surface of the blade. The abutment means substantially prevents rearward movement of the blade without obstructing its forward movement. Locking means substantially prevents inward movement of the blade relative to the blade block in order to prevent disengagement of the cooperating engagement means.
U.S. Pat. No. 4,649,673 describes a shot blasting wheel having a base plate with angularly spaced, elongated grooves that engage complementary tongue formations on throwing blades. A rearwardly directed lug is provided on each blade, which is engaged by a bolt or stud, which is parallel to the surface of the blade and enters the wheel normal to the plane of the wheel. The lug inc

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