Description

Technical Field

This invention relates to stands for supporting and manipulating heavy machinery during fabrication, repair, and maintenance.

Background of the Invention It is difficult to repair and maintain heavy machinery, such as vehicle engines and transmissions, without supporting the machine on a stand. Shops dedicated to repair of engines and transmissions generally employ a fixed engine stand, which is bolted onto the floor or otherwise reinforced to prevent movement. Such stands typically comprise a base to elevate the engine to a convenient working height, and a transverse shaft to which the engine or transmission is bolted, which provides for manual rotation of the workpiece to enable the worker access to all sides of the engine.

Some stands, such as that disclosed in Pacheco, U.S. Pat. No. 4,932,628, are mobile, and provide supports upon which the engine rests during testing or maintenance. However, these stands do not provide convenient access to the underside of the engine, and may fail to provide sufficient stability to permit safe work on workpieces larger than the average automobile engine.

The traditional fixed engine stand provides a rotatable shaft, to which the engine is bolted. The shaft is typically fitted with stops and cogs, to permit one to position the engine in one of four rotational positions, separated by 90°. This allows access to all sides of the engine, although not always at a convenient angle. Positioning the engine can be quite strenuous, especially where the engine is not balanced about the axis of rotation. Even where the engine is reasonably balanced, many procedures require removing components from the engine, destroying the balance. Further, even when balanced, the inertia of a large

engine or transmission is a considerable impediment to easy rotation. The strain of rotating an engine or transmission by hand on such a stand is a constant source of strained muscles and backs, and leads to worker injury and absence. Recent improvements, such as "The Revolver ^® " (Marathon) begin to address the problem by providing a hand-operated crank to rotationally position the engine. Unfortunately, the crank operates at a ratio of 96: 1 , and thus is likely to replace the strain injuries with repetitive motion injuries.

Disclosure of the Invention

I have now invented a fixed stand having a transverse rotatable shaft powered by a precisely controllable motor. The motor permits the worker to rotate the workpiece to any angle desired, without strain on the operator.

Brief Description of the Drawings

Figure 1 depicts a perspective view of a stand of the invention. Figure 2 illustrates an embodiment of a shaft for use in a stand of the invention.

Figure 3 is an exploded view of an adaptor plate for use with the stand of the invention.

Modes of Carrying Out the Invention A. General Methods

The stand of the invention is generally assembled by welding the components. The material selected for the components will be strong and hard enough to support the con¬ siderable weight of the workpieces for which the stand is designed, without significant deviation from true. The components will preferably be high grade steel (such as A36 mild) or other strong alloy (such as 4130 chrome/molly). The stand should be capable of supporting engines and transmissions weighing between 400 and 3,000 pounds. Referring now to Figure 1 , the base (1) provides the platform upon which the rest of the stand is supported. The base is preferably anchored directly into the floor of the shop where it will be used, as a permanent fixture. This provides the greatest degree of stability and safety, and permits one to work on off-center or lop-sided workpieces without danger of tipping the stand over. The base may be provided with additional flanges or extension, extending laterally and/or downwardly from the base to increase the stability of the stand. The base is

typically bolted or welded to a floor of appropriate composition. Alternatively, the base may be mounted in the floor by forming a hole in the floor, placing the stand within the hole, and filling the space around the base with cement or concrete. The base is provided with a width and length sufficient to provide a stable platform for the rest of the stand, and an adequate anchor to the floor, for example about 27" long by about 15" wide. It may be fabricated from heavy steel plate, e.g. , 1" steel plate. The sides of the base may be beveled inward to reduce the risk of injury to the operator's toes. The bottom surface of the base is preferably flat, while the upper surface may optionally be provided with a buttress (10) to provide additional support to the column (2). The base may be provided with a plurality of mounting holes (11) to receive bolts or reinforcing rods (e.g. , "rebar"). Alternatively, the stand may be mounted on a mobile platform, which may ride on rails or conventional wheels. The mobile platform should have lateral dimensions sufficient to insure that the stand cannot tip over, even when fully loaded. If wheel-mounted, the wheels must be equipped with brakes to prevent motion while a workpiece is being rotated. The column elevates the shaft (6) to a height convenient for work by a standing operator. The column may be vertical, but is preferably inclined at an angle of 10° from vertical to aid in balancing the stand when loaded with a workpiece. The column preferably elevates the shaft (6) to a height of about 3 feet above the floor. The shaft may be mounted on a platform (3) welded to the top of column (2), or may be mounted directly atop the column. The column top may alternatively provide sufficient horizontal surface to serve as a platform, whether by sheer cross-sectional area of the column, or by flaring or broadening the column at the top. The column and buttress (10) may be each constructed from commer¬ cially available 3/4" steel box tube or channel form.

The column supports the shaft supporting means (4). In general, the shaft supporting means will comprise bearings or other supporting surfaces sufficient to support the shaft and workpiece without significant sideways motion during rotation. Thus, the shaft supporting means should also function to retain the shaft and maintain it in position (e.g. , during rapid rotation of an unbalanced or off-center workpiece). Preferably the shaft supporting means comprises three heavy bearings or pillow blocks (e.g., 3" roller bearings). The shaft supporting means are affixed to the platform or upper surface of the column by standard means, such as bolt or weld. In a presently preferred embodiment, the pillow blocks are

spaced about 6" apart atop the platform, beginning about 9" from the attachment end of the shaft.

The shaft (6) should be rigid, and capable of supporting a load in excess of 2,000 pounds without significant bending over its length. In a preferred embodiment, the shaft is about 2-3" in diameter by about 29" in length. If the stand is intended only for smaller engines (for example, less than 700 lbs), a 2" diameter shaft is sufficient. The drive end of the shaft may be modified to accept a coupling (7) to the drive motor (5). Such modification may be by turning the shaft down to a diameter of 1.75" at the last 4", to accept coupling (7). The coupling preferably provides a positive engagement between the motor (5) and the shaft (6), and permits the motor to rotate the shaft. The coupling also permits one to remove the shaft and/or motor (e.g. , for service), and helps isolate the motor from impact and jarring vibration which may occur when mounting an engine or transmission to the shaft. A Lovejoy coupling is presently preferred.

The motor (5) must provide sufficient torque to rotate the shaft when fully loaded with a large engine or transmission. Ideally, the motor should provide at least about 2000 to about 4500 inch/pounds of torque. The motor should be able to rotate the shaft at a reasonable rate, so that the operator need not wait an unduly long period of time to rotate the workpiece. Preferably, the motor is capable of rotating a heavy load 360° in less than 60 seconds, more preferably in about 12 seconds. Additionally, the motor should comprise a brake or be capable of functioning as a brake, so that the motor can maintain the angular position of the shaft even when power is not applied. Ideally, the brake should function automatically in the event that power to the motor is interrupted, so that rotation of the workpiece is quickly halted. The brake should be capable of maintaining the angular position even against the torque applied to the shaft by an unbalanced engine (e.g. , as where the engine has been partially disassembled). The motor's gearing may be sufficient to provide substantial resistance or braking action. The motor should also be provided with controls (9) to start and stop, and to change direction. The controls may comprise momentary contact switches for clockwise and counterclockwise rotation. Alternatively, the controls may consist of a momentary contact rocker switch, connected so that the center (spring-loaded) position is "OFF", while rocking the switch to either direction activates the motor in forward or reverse. Momentary contact switches are preferred for safety reasons,

so that the motor ceases rotation immediately if the operator removes his or her hand from the controls.

The attachment end of the shaft (8) is adapted to receive a mounting plate, and/or to receive tooling, such as that manufactured by the Detroit Diesel-Allison division of General Motors). The mounting plate (400) (see Figure 3) generally comprises a shaft receiving portion (430) and a workpiece-gripping portion (410). The attachment end of the shaft should include some means for insuring that the shaft's rotation is completely and positively transmitted to the workpiece or mounting plate. This means may take the form of a slot or flat machined into the attachment end, and/or holes drilled into the side of the shaft at the mounting end. Additionally, a hole may be drilled into the end of the shaft along its long axis, to receive mounting rods provided by the manufacturer for manipulation of the workpiece. In one embodiment of the invention (depicted in Figure 2), a hole (201) is drilled in the end of shaft (6) 5" deep by 1-3/8" diameter. Bolt holes (5/8") (202) are provided perpendicular to hole (201) to allow one to secure the workpiece with set screws or the like. Alternatively, the shift may be equipped with a flat (203) or slot capable of engaging a mating piece on the workpiece or mounting plate, for example, a woodruff key.

Figure 3 is an exploded view of a suitable mounting plate (400) for use with the stand of the invention. The mounting plate comprises a body portion (401) having an aperture (430) for receiving the shaft. The aperture preferably has the same cross-sectional shape as the shaft, within close tolerances. The mounting plate may be equipped with flange (410), having mounting holes (420) to facilitate bolting the workpiece onto the mounting plate. The mounting holes (420) are spaced to match the bolt positions provided on the workpiece, and thus may vary from engine to engine and transmission to transmission. A number of mounting plates may be prepared to accommodate the workpieces to be mounted. The mounting plate also includes means for fixing the mounting plate to the shaft and for locking rotation of the mounting plate to the shaft. Both functions may be performed by the same device. For example, the fixing/rotation locking means may comprise a woodruff key (430) as depicted in Figure 3. The woodruff key is retained in slot 440 and engages a flattened side or groove in the attachment end of the shaft. Preferably, the woodruff key is equipped with one or more bearings (460), preferably two or more bearings, which are permanently mounted in the upper surface of the woodruff key. The bearings receive mounting bolts (480), the ends of which press-fit into the bearings after passing through securing holes 470.

Thus rotation of the mounting bolts serves to raise the woodruff key, or to urge it against the shaft surface. Alternatively, the fixing/rotation locking means may comprise bolts or pins which pass through securing holes 470 and then through holes provided in the shaft, perpendicular to the shaft axis. Such bolts or pins must be capable of withstanding the shearing forces inherent in such an application. Alternatively, the rotation locking means may be provided by using a shaft and matching aperture 450 which are non-cylindrical, e.g. , wherein the cross-sections of the aperture and shaft are hexagonal or square at the attachment end.

The above description is not intended to limit the scope of the invention in any way: the scope of the invention is defined by the claims appended hereto. Other variations may occur to one of ordinary skill in the art, and are to be considered as falling within the scope of my invention if they otherwise meet the limitations of the appended claims.