Pumps – Motor driven – Fluid motor
Reexamination Certificate
1999-05-10
2001-07-24
Thorpe, Timothy S. (Department: 3746)
Pumps
Motor driven
Fluid motor
C417S386000, C417S269000, C417S388000, C417S222200, C417S413300, C417S387000, C417S383000, C123S446000, C105S096100
Reexamination Certificate
active
06264437
ABSTRACT:
BACKGROUND
This invention relates to a pump intended for high pressure pumping and delivery of almost any liquid such as water, petrol, gas oil, oils, corrosive chemical liquids and sludge, but more particularly for the high pressure supply of fuel injectors for internal combustion engines.
Low pressure pumps are known for liquids of this type, and are generally centrifugal pumps, gear pumps, sometimes piston pumps or other types of pumps. With these known pumps, a high delivery pressure (in excess of 50 bars) either cannot be obtained or only with great difficulty and at great expense due to the fact that, once one starts using high pressures, the moving parts begin to seize and substantial leaking occurs due to the often very low viscosity of the liquids pumped.
To avoid such seizure or leakage, diaphragm pumps have been known to be used, in which case it becomes impossible to achieve high delivery pressure. In fact, the diaphragm is driven by a mechanical means (cam, lever or the like) on one side, and is subjected on the other side to the delivery pressure: it ensures that, once the pressure becomes high, the diaphragm deteriorates at the points where mechanical stress is applied.
Also known, to pump special liquids such as corrosive liquids, is the association of two pumps: a first pump which is a hydraulic pump that delivers and draws back a hydraulic liquid which, by way of reciprocating motion, drives the mobile elements of a second pump which draws in and pressurizes the liquid to be pumped. These mobile elements which ensure physical separation of the hydraulic liquid and the liquid to be pumped, though driven in reciprocating motion by the hydraulic liquid, are either deformable diaphragms or free-floating pistons.
The free-floating pistons are defective from the point of view of tightness, and this defect cannot be overcome when absolute tightness is required. If a seal is fitted between the free-floating piston and the cylinder in which it moves, perfect tightness cannot be obtained. If the seal is eliminated, either there will be a very thin film of oil between the friction surfaces and therefore micro-leakage, or the rubbing surfaces will heat up if there is no film of oil. In the particular case of high pressure fuel injection, no leakage, no matter how small, can be tolerated and, of course, heating is liable to cause an explosion.
The known free-floating piston-type devices, such as e.g., U.S. Pat. No. 4,443,160, must therefore be ruled out.
The invention thus relates to a pumping device in which the mobile elements—to which a reciprocating pumping motion is imparted by the hydraulic pump and which ensure a perfectly tight separation between the hydraulic “driving” liquid and the liquid to be pumped—are deformable diaphragms.
Generally, this type of deformable diaphragm pump has at least one of the following drawbacks and sometimes several simultaneously:
a—if the separating and pumping diaphragm is mechanically linked to the piston of the hydraulic pump, there is not equal pressure on both sides of the flexible diaphragm as a result of which the latter will not last over time, it will deteriorate;
b—if the diaphragm is completely free, i.e., unattached to any drive mechanism and driven solely by the hydraulic liquid delivered by the pump, there will be equality of pressure on the two sides of the diaphragm. However, due to inevitable leaks, even very minute ones, the volume of hydraulic liquid delivered increases with each cycle and ultimately exceeds the volume the diaphragm can deliver; this causes a hydraulic blocking which creates so much excess pressure that one or other of the pumps breaks. In the particular case of high pressure fuel injection, if the element that breaks is the element delivering the fuel, fire will inevitably break out,
c—in both eases, i.e., whether the diaphragm is attached to the piston or unattached, if the volume of hydraulic liquid continually being drawn in and delivered is constantly the same, the diaphragm will heat up as a result of the indefinitely repeated compression cycles, until it reaches a temperature such that the diaphragm(s) break.
U.S. Pat. No. 4,392,787 granted to Notta discloses a unit including a hydraulic slanted plant pump, each piston of the pump being associated at its end with a flexible diaphragm which is connected to a rod that slides inside the piston. This device has the drawbacks described above in “a” and “c”. The volume of liquid continually pressurized is always the same and will therefore heat up. Moreover, the inevitable little leaks are offset by the intake of additional oil via a non-return valve, but should a substantial leak accidentally occur, the piston will come into mechanical contact with the diaphragm thus destroying the latter.
U.S. Pat. No. 2,960,936 granted to Dean describes a pump in which a completely unattached diaphragm is cyclically pressed and released by a hydraulic volume displaced by a cam-driven piston. This device has drawbacks “b” and “c”. If, for any reason, the supply were to be stopped or slowed down, the diaphragm would not completely redeploy itself and a corresponding quantity of hydraulic liquid would be introduced at each cycle until the occurrence of breakage (drawback “b”). Furthermore, as the volume of hydraulic liquid compressed is always the same, heating will inevitably take place (drawback “c”).
German Patent No. 2,447,741 granted to Wanner discloses a diaphragm pump mechanically linked to a piston which slides inside a hydraulic pump piston. The drawbacks are the same as for above-mentioned U.S. Pat. No. 4,392,787.
SUMMARY OF THE INVENTION
To remedy these drawbacks, the invention provides a device in which each diaphragm is unattached and in which, at the end of each piston cycle, the “dead” chamber situated downstream of the top dead center of this piston (position of maximum compression), in which the liquid is in contact with the diaphragm, is made to communicate with the reserve of hydraulic liquid; as a result, the liquid situated in the chamber is forced back towards this reserve firstly by the expansion of the liquid and then by the forcing effect of the diaphragm which is held in countercheck by a spring.
We thus obtain, on the one hand, a continuously repeated heat exchange between the compressed liquid and the liquid that is not compressed, and, on the other hand, a return of the diaphragm to its initial position at each cycle or, in other words, a suppression of any increase in volume of the hydraulic liquid acting on the diaphragm, increase that is inevitably caused on an on-point basis by leaks; this is because it is not possible to manufacture a high pressure hydraulic pump with pistons, which does not heat up and which has a satisfactory, leak-free output.
According to a first object, the invention relates to a pump enabling any type of liquid to be pumped while imparting a very high delivery pressure thereto, of the type comprised by the association of two pumps: on the one hand, a hydraulic pump, and, on the other hand, a second pump in which the mobile means performing the suction and delivery of the liquid to be pumped, are flexible diaphragms to which reciprocating motion is imparted, first in one direction and then in the other, by the displacement of the hydraulic liquid pumped then drawn back by the first pump. The pistons of the first pump are tubular and passed through by the hydraulic liquid which, during the suction phase, passes through a crescent or groove hollowed out in the surface of the slanted plate or cam. The deformable diaphragms each are held in countercheck by a spring in such a way that, at the end of the compression stroke of each piston, communication is established between the chamber in which the hydraulic liquid finds itself forced against the diaphragm, and the suction chamber, this liquid being, on the one hand, sucked up by the motion of the piston and forced back by the diaphragm under the effect of its spring action, thus ensuring, on the one hand, an exchange between the hydraulic liquid heated by compre
Brown Steven
Hydro Rene Leduc
Nixon & Vanderhye P.C.
Thorpe Timothy S.
LandOfFree
High pressure pump for all liquids does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High pressure pump for all liquids, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High pressure pump for all liquids will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2443473