The device of the present invention is applicable, although not exclusively, to the field relating to the lubrication of mechanical components of reciprocating compressors and of small-sized internal combustion engines. In order to supply the necessary amount of liquid lubricant in the above machines, lubrication systems are required that are capable of handling even very modest lubricant flow rates and to supply them to the required points; moreover, said systems should have a simple mechanics, be realizable at low cost, and be able to utilise the motion provided by the machine on which they are mounted, without resorting to unduly complicated mechanisms (like additional small shafts, power takeoffs, etc.).
At present, lubrication in small-sized piston engines and in reciprocating compressors is performed substantially either by splash lubrication, in case this method is considered satisfactory, or by employing gear pumps, in case the needs of a good lubrication are more pressing. Recently, mechanically actuated (usually by a cam), small-sized, positive displacement pumps have also been developed, as well as electromagnetically controlled valves, specifically for small internal combustion motors of motorcycles or scooters.
Splash lubrication, which relies on the splashing and agitation caused by the very components to be lubricated (which are wetted by the oil generally contained inside an oil sump), has the advantage to be extremely economical and simple, provided it is able to insure a sufficient lubrication. Nevertheless, it has considerable drawbacks, like the need to maintain a constant lubricant level inside the oil sump in order to avoid seizure, the fact that the lubricant is not accurately supplied only to the points were it is really needed, the fact that it is impossible to supply the lubricant under pressure, the impossibility of using this kind of system in two-stroke engines with dry sump oil pumps, since in these applications the sump oil pump must work under dry conditions. Lubrication under pressure has become the mostly used system because of its undoubted advantages linked to its utilisation, these advantages being, among others, the increase of the performance of the kinematical couples lubricated under pressure as compared with that obtainable without the contribution of the feed pressure. In particular, the lubrication relying on gear pumps has the advantage of putting under pressure the lubrication circuit and of allowing to accurately reach the various points or areas to be lubricated, with the required oil flow rate and the correct (prescribed) pressure value.
In this case, the lubricant also has the not negligible task of cooling the surfaces which are in mutual contact. Also the use of cam-actuated positive displacement pumps has quickly become widespread, besides that of electromagnetic pumps, in the field of small-sized internal combustion engines and in the technical field of compressors, due to the possibility of feeding the lubricant under pressure, by controlling the flow rates, and therefore, taking advantage of the possibility of cooling down the various lubricated kinematical couples. However, the inconvenience of the utilisation of gear pumps lies in the increased costs involved in the production of high-quality mechanical components, like gearwheels for instance, and in the need to provide an adequate power takeoff (drive), so that the machine to be lubricated is more difficult to manufacture. On the other hand, the drawbacks of utilising cam-actuated pumps, in their commonly used version, are the requirement of their assembling in the vicinity of the driving shaft and the need of having available an adequate oil level in the oil sump in order to permit the priming (pump starting). Moreover, the disadvantages of using electromagnetically controlled pumps are generally the increased production cost, the electric power absorption, and the necessity of providing a control unit.
The invention will now be described for illustrative purposes only having regard to three of its possible embodiments, which are neither limitative nor binding, and which are depicted in the annexed drawings, in which:
a and 2b are two orthogonal views of the second embodiment of the needle-shaped positive displacement pump according to the present invention;
a and 3b are two orthogonal views of the third embodiment of needle shaped positive displacement pump according to the present invention.
The present invention suggests a valid alternative to conventionally used arrangements in the field of lubrication systems for small-sized, internal combustion motors, and for positive displacement compressors. In substance, it consists of a piston pump whose structure, however, is such as to permit to put under pressure the lubricant taken from the oil sump, wherein, the free, upper surface of the oil level may also be located far away from the rotating members of the machine. This holds in particular in an application concerning air compressors of the reciprocating kind, which generally have an oil sump located somewhat distant from the driving shaft from which it is possible to draw the motion for the actuation of the pump.
The operation of this system—called “A-version”—, shown in
In
In
The operation of the system illustrated in
The crank 7′, while rotating around its axis, brings about a relative motion between the piston 2′ (hinged on the eccentric bore 9′ of the crank; X-axis) and the cylinder body 1′, the latter being hinged (at 15′) to the oil sump (not shown). The resulting motion is a classical reciprocating motion of a conventional crank mechanism whose stroke is twice the distance existing between the axis of the crank 7′ and the axis X of the eccentric bore 9′ of the crank 7′. Starting from the BDC, the piston 2′, in the course of its upward motion, generates a negative pressure inside the cylinder 1′ which is due to the fact that there is no fluid communication to the outside because the suction inlet (analogous to 10 of
This system may be equipped with a pressure-relief valve 8′.
In the “C-version” corresponding to the third embodiment according to
The operation of the system named “C-version” (third embodiment) is identical with the device named “B-version” (second embodiment) except that the lubricant arrives at the delivery zone by passing through an additional, rigid duct 4″. In this version, the problem of connecting together the pumping zone with the delivery zone, which are in relative motion to each other, is solved by using a cylindrical rigid element 4″ (rigid duct) that slides within the piston-bearing body 14″. In this case too, the system may be equipped with a pressure-relief valve 8″.
Obviously, also in the third embodiment of
Number | Date | Country | Kind |
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NA2006A000068 | May 2006 | IT | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IT07/00368 | 5/28/2007 | WO | 00 | 11/26/2008 |