Metal deforming – With indication of condition or position of work – product,... – Trueness
Reexamination Certificate
2001-02-23
2002-06-25
Tolan, Ed (Department: 3725)
Metal deforming
With indication of condition or position of work, product,...
Trueness
C072S031020, C029S888080
Reexamination Certificate
active
06408663
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for truing crankshafts and, more particularly, to a method and apparatus for the fast and cost effective truing of crankshafts during the manufacture or reassembling of pressed-together multi-cylinder engine crankshafts. Specifically, the invention relates to a novel technique and tool for truing the crankshafts used in personal watercraft and snowmobile engines, as well as certain outboard engines and other multi-cylinder two-stroke engines.
BACKGROUND OF THE INVENTION
Crankshafts for precision machines must be accurately manufactured, or reassembled, to properly drive the engine components of the machines of which they are part. Methods and tools used in the manufacture of crankshafts are described in U. S. Pat. Nos. 4,979,335, 5,625,945 and 5,984,599. A most important aspect of such accurate manufacturing, or reassembling, is the truing of the crankshafts. A crankshaft is often comprised of multiple crankshaft sections, and each of these sections usually consists of two “journals”, connected by a center pin, and one or more associated bearings. A “journal” is an annular disc, or “web”, with a peripheral pin transversely attached to it. A “connecting rod”, attached to the peripheral pin, connects the crankshaft to the corresponding piston of the engine of which the crankshaft is part. When a crankshaft is comprised of multiple crankshaft sections, “truing” refers to the straightening of the crankshaft, whose sections are out of alignment with respect to the crankshaft's axis of rotation, by pinching, hammering, wedging or otherwise applying a force or forces on the components of the sections so as to realign the components until the distortion of the crankshaft is minimized or eliminated. Uncorrected distortions will tend to cause misalignment of the main bearings, crankpins and other components of the crankshaft sections and result in a distorted crankshaft, that is, one that wobbles. These deviations from the true running of the crankshaft sections, with respect to the axis of rotation of the crankshaft, are remedied by the truing, or straightening, operation. Proper truing of the crankshafts is particularly critical when the crankshafts are “pressed-together crankshafts”, that is, crankshafts used in multi-cylinder engines where the connecting center pins of at least some of the sections are press fit to one or both of the journals to which they are connected. Press fitting is the assembling of any two machined pieces by creating a bond between them as a result of the fact that one of them has been inserted within the other, so as to be properly in place, by the use of force. For example, a round connecting center pin may be press fit to a journal by providing, in the journal, an orifice with a diameter between 0.0002 and 0.004 inches smaller than the diameter of the pin, and forcing the pin into the orifice by mechanical exertion. Pressed-together crankshafts for multi-cylinder engines are built and reassembled by manufacturers and rebuilders such as Kawasaki, Polaris, Yamaha and others for combustion engines with several cylinders and, in particular, for combustion engines for personal motorized watercrafts, snowmobiles and similar vehicles. In contrast to pressed-together crankshafts, “single-piece crankshafts” are designed so that the journals and connecting center pins form one solid single piece, and, since the crankshafts themselves are forged in one piece, the connecting rods and the bearings are designed so that they may be replaced and/or serviced while the crankshaft remains in one piece. As a result, single-piece crankshafts cannot be disassembled and reassembled, and, consequently, the crankshaft truing techniques for single-piece crankshafts are different from the crankshaft truing techniques for pressed-together crankshafts, and normally involve bending and compressing the one-piece crankshaft until it runs true on one axis of rotation. Pressed-together crankshafts, on the other hand, must be disassembled and reassembled whenever their bearings fail, or when their connecting rods wear or break due to extended use. Otherwise, the engines do not operate properly, or simply stop running, unless the crankshafts are taken apart and reassembled, aligned and trued. Also, pressed-together crankshafts often have to be taken apart to replace defective bearings and to perform repairs or maintenance. When taken apart, these crankshafts always fall out of tolerance and have to be re-aligned and re-trued.
Techniques for truing, or straightening, workpieces such as crankshafts are described in U.S. Pat. Nos. 4,517,717, 4,860,566, 5,001,917, 5,235,838 and 5,333,480. Most of these techniques are concerned with single-piece crankshafts, and they involve bending, flexing, hard rolling and the like, by themselves or in combination; but such techniques do not allow an operator to determine the degree of distortion and perform the necessary straightening correction on a pressed-together multi-cylinder-engine crankshaft without having to remove the crankshaft from the work station. Removing a pressed-together multi-cylinder-engine crankshaft from the work station is time consuming, adds an extra step, in which the probability of human and/or machine error increases, and contributes additional and unnecessary cost to the truing operation. Conventional crankshaft truing techniques can be cumbersome and time-consuming, and add substantial costs to the building and reassembling of crankshafts, particularly when the crankshafts are pressed-together crankshafts. It is apparent, then, that a need exists to provide a technique and a tool for properly and quickly truing crankshafts, and, in particular, for properly and quickly truing pressed-together multi-cylinder-engine crankshafts in minimum time and with minimum expense.
SUMMARY OF THE INVENTION
An object of this invention is to provide a technique and a tool for accurately truing crankshafts. An object of the instant invention is also to provide a method and an apparatus for accurately and rapidly truing pressed-together crankshafts, which method and apparatus may be used on practically all kinds of pressed-together crankshafts regardless of their make or origin. Another object of the invention is to provide an inexpensive method and apparatus for properly truing the pressed-together crankshafts normally found in the multiple-cylinder combustion engines used in personal watercrafts and snowmobiles, as well as in other multiple-cylinder outboard engines.
A further object of this invention is to provide a method and a tool for the accurate, rapid and inexpensive truing of said crankshafts that can be used and operated by essentially one operator with minimum amount of training and which allows the operator to detect and measure the degree of distortion and perform the required correction while the crankshafts remain on the work station, that is, without having to remove the crankshafts from the work station. These and other objects of the invention will become apparent from the disclosure that follows.
The above objects are achieved by the truing tool and method of the instant invention. When used properly and in accordance with the method disclosed herein, the truing tool, or apparatus, of this invention allows one single operator to accurately determine the existence, location and degree of distortion and then proceed to straighten and assemble pressed-together crankshafts in minimum time and with minimum expense.
The truing tool, or apparatus, of this invention comprises a supporting base, a set of lockable holding means, a movable shelf, a cam-operated lever, sliding position detection means, and a top-mounted clamp. When assembled in the manner provided herein, the apparatus provides the means for holding the crankshaft to be trued in a “measuring position”, that is, in a position with respect to the work or assembly station where an operator may detect, locate and measure the degree of distortion and decide if, where and how much force to apply t
Fonte Raúl V.
Short Block Technologies, Inc.
Tolan Ed
LandOfFree
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