This application relates to piston-plus-crankshaft devices.
The following is a tabulation of some prior art that presently appears relevant:
The angled-cylinder or offset-crankshaft technique of designing internal and external combustion piston engines, piston pumps, and gas compressors is a technology that has been met with limited success. Designers of such devices have little guidance when employing this design technique to achieve results that produce a piston device that yields maximum performance gains, while requiring a minimum amount of modifications to traditional or existing engine, pump, or compressor designs.
Previous efforts to test and document the performance gains offered by the angled-cylinder or offset-crankshaft technology have employed tests that were conducted on internal combustion engines. Prototypes were constructed, and cylinder pressures, thermo-dynamics, and other characteristics of these engines were taken while in operation—for example discussion www.eng-tips.com/forum/thread7-201777, www.speedtalk.com/forum/offset bore & crank centerlines and U.S. Pat. No. 6,058,901 to Lee (2000). These tests mainly focused on some specific offset-crankshaft configuration targeted at some specific point in the combustion stroke. Additionally, new prototypes needed to be constructed to test configuration variables. This limited method of testing has produced misleading results.
Another method used to compare the performance between angled-cylinder or offset-crankshaft piston devices with conventionally configured piston devices focused on piston-to-sidewall frictions—for example “Reration between Crankshaft Offset and Piston Friction Loss. Amount of Offset and Engine Operating Condition”—Takiguchi Masaaki. Other efforts that have been employed are computer simulations and mathematical studies—for example www.camotruck.net/rollins/piston-offset, Theoretical Performance Comparison between Inline, Offset, and Twin Crankshaft Internal Combustion Engines—Taj Elssir Hasaan. These methods of determining performance gains have also produced misleading results.
The orientation of the cylinder in such devices is extremely critical to performance. Some of the prior art related to the angled-cylinder or offset-crankshaft suggest values that are ineffective—for example U.S. Pat. No. 6,745,746 B1 to Ishii (2004) and U.S. Pat. No. 4,664,077 to Kamimaru (1987). Others specify designs that are too impractical to be viable—for example U.S. Pat. No. 5,816,201 to Garvin (1998) and U.S. Pat. No. 6,827,057 to Dawson (2004). Still other prior art and patents are very indeterminate in defining this relationship. Such terms as “approximately” and “about” are typically used—for example U.S. Pat. No. 6,612,281 B1 to Martin (2003) and U.S. Pat. No. 5,076,220 to Evans et al (1991). Additionally, if values are expressed in prior art at all, they fail to take into consideration other critical factors such as connecting rod-to-stroke ratios, which would render any expressed value effectively meaningless—for example U.S. Pat. No. 4,708,096 to Mroz (1987).
Designers of piston devices wishing to employ the angled-cylinder or offset-crankshaft technology have also been confronted with mechanical interferences and clearance limitations between the cylinder, connecting rod, and piston. Prior art that has addressed this issue specify connecting rod designs that alter the connecting rod centerline, and therefore would be prone to early failure—for example U.S. Pat. No. 5,186,127 to Cuatico (1993) and US patent to Terzlev (1996). Manufacturers of piston devices would be reluctant to adopt such designs. Other prior art addressing this problem suggest integrating modifications to the block casting—for example U.S. Pat. No. 4,708,096 to Mroz. (1987). As the close proximity of the piston components with the bottom of the cylinder are critical in these devices, this approach would prove challenging in the manufacturing process.
Other concerns encountered when designing a piston device employing the angled-cylinder or offset-crankshaft technology have no known directly related prior art.
Accordingly designs and methods for providing designers of angled-cylinder piston devices with the ability to produce a device that benefits from the mechanical advantage inherent in the technology, while requiring as few modifications to existing or traditional designs as possible, thus making the angled-cylinder or offset-crankshaft technology viable.
If corrected for TDC, the angled-cylinder and the offset-crankshaft design techniques both produce a piston device with identical piston 23, cylinder 22, connecting rod 26, and throw 30 component relationships. The difference between these two design techniques involves which components of a traditional or existing design will be altered to achieve the desired result. Therefore, going forward, this design technique will be referred to as the angled-cylinder design, as when considering only the basic components involved, it is a more generic description.
As previously disclosed, the angled-cylinder technique can be applied to engines, gas compressors and liquid pumps.
1. Steam engines are typically built with open architecture lower ends. The crankshaft and connecting rod assemblies are not enclosed within a crankcase, and therefore they are exposed for easy experimentation.
2. The cylinder and piston assemblies of the steam engine used are constructed as individual components, and then mounted to a plate. The plate is then mounted to the lower assembly by means of machined posts. Adding a system of shims to these posts was a simple procedure, thus creating an assembly that could easily produce variable cylinder angles.
3. Steam engines are external combustion engines, and lend themselves to simple modifications that allow them to operate on controlled compressed air. This was critical, as my intention was to identify the performance gains offered by the angled-cylinder technique, without considerations of heat dissipation and accumulation, combustion gas expansion variations due to a multitude of factors, friction increases and decreases, and other variables related to combustion engines that could distort my observations. The modified steam engine allowed me to run tests that isolated the performance and torque gains inherent in the mechanical advantage of the angled-cylinder technique.
The test engine was assembled with the above mentioned modifications. The output shaft was fitted with a cogged-belt pulley that allowed coupling to an electric generator, also fitted with a cogged pulley, and joined with a cogged belt. The engine's pulley was also marked to allow engine revolutions-per-minute (RPM) readings to be made with an optical tachometer. Extensive tests were conducted, and the results were consistent.
Measuring the amount of modification in terms of cylinder angle became futile, as the small adjustments necessary became too difficult to gauge accurately when measured as cylinder angle. Therefore, I developed the more precise technique of measuring this configuration in terms of the intersection between the cylinder's centerline 37 with the length of throw's centerline 36, 38
What these tests allowed me to conclude are as follows:
1. The configuration of the cylinder centerline with the length of throw centerline intersect 45 is extremely critical. Very minute changes to the cylinder angle produces measurable changes in torque and performance.
2. The performance and torque gains that can be gleaned from the angled-cylinder technique are not linear. During testing, as the cylinder's centerlines 37 were oriented away from the crankshaft main axis 34 and towards the crankpin center axis position held at 90° of a clockwise rotation 32, the gains were rather small until I approached a cylinder centerline to throw centerline intersect 45 of 30%. The gains then increased exponentially until reaching a throw centerline intersect 45 of 45%, and then began to decrease. Gains in performance rapidly decreased after reaching a cylinder centerline to throw centerline intersect 45 of 49%. It is within the range of a cylinder centerline to throw centerline intersect 45 of 30% to 49% that performance increases of 15% or more can be realized, and this range of cylinder 22 orientation is within the scope of the present embodiment.
CLASS 1—This class determines a specific cylinder centerline to length of throw intersect 45. A piston device with a connecting rod/stroke ratio of less than 1.5/1 respectively presents a greater amount of interference and increased frictions, and therefore permits a lower amount of cylinder angle. Accordingly, a cylinder centerline to length of throw centerline intersect 45 of 33% is determined. In the case of a compressor or pump, a tolerance of +/- 3% of length of throw 38 is determined, and in the case of an engine or motor, a tolerance of +/- 2.5% of length of throw 38 is determined.
CLASS 2—This class also determines a specific cylinder centerline to length of throw intersect. A piston device with a connecting rod/stroke ratio of greater than 1.9/1 respectively presents a lesser amount of interference and friction increases, and therefore permits a greater amount of cylinder angle. Accordingly, a cylinder centerline to length of throw centerline in-tersect 45 of 46% is determined. In the case of a compressor or pump, a tolerance of +/- 3% of length of throw 38 is determined, and in the case of an engine or motor, a tolerance of +/- 2.5% of length of throw 38 is determined. Piston engines or motors with connecting rod/stroke ratios greater than 4/1 are outside the scope of this embodiment.
CLASS 3—This class determines a sliding amount of cylinder centerline to throw centerline intersect 45. Piston devices with connecting rod/stroke ratios between 1.5/1 to 1.9/1 would have the cylinder centerline to length of throw centerline intersect 45 determined proportionally from 33% to 46% respectively, including the above stated tolerances.
The tolerances are to allow for other device characteristics such as connecting rod 26 width, or piston 23 diameter, and in the case of an engine or motor, expansion of components due to higher operating temperatures is considered.
This selection process provides the optimum amount of cylinder centerline to length of throw centerline intersect 45 as a function of the connecting rod/stroke ratio.
This method of determining optimum cylinder centerline 37 orientation is within the scope of the present embodiment.
Another concern when designing an angled-cylinder piston device is the interference between the connecting rod 26 and the piston's 23 base, also known as the piston skirt 75, as shown in
Another concern when designing an angled-cylinder piston device is the interference between the connecting rod 26 and the cylinder's 22 base, as shown in
A designer of an angled-cylinder piston device wishing to avoid re-designing as many peripheral components as possible may take the approach of angling the cylinder 22 about the piston pivot 24 location at TDC in the original design. This design technique would avoid having to re-design the cylinder heads 21, but would create a condition of excess cylinder volume 57 when the piston 23 is positioned at TDC, as shown in
Another concern when designing an angled-cylinder piston device is the increase in friction between the piston 23 and the cylinder 22 wall as shown in
Thus the scope of the embodiments should be determined by the appended claims, and their legal equivalents, rather than by the examples given.
This application claims the benefit of provisional patent applications filed by the present inventor: Application No. 61/217,858, filed 2009 Jun. 6, Confirmation No. 5343Application No. 61/271,522, filed 2009 Jul. 22, Confirmation No. 3572Application No. 61/271,523, filed 2009 Jul. 22, Confirmation No. 3755Application No. 61/273,363, filed 2009 Aug. 3, Confirmation No. 7705Application No. 61/340,083, filed 2010 Mar. 12, Confirmation No. 3185
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