Background Information Diaphragm pumps are used in pumping a wide variety of materials. They are particularly useful for abrasive or viscous liquids. They are useful for pumping slurries that might damage other pump designs, fluids with high purity requirements or fluids that are not robust. These pumps are often driven by incompressible hydraulic fluids. These pumps are extremely useful in applications where accuracy and precision are essential, such as for dispensing.

U. S. Patent Nos. 6,105, 829; 4,690, 621; 5,167, 837; 5,772, 899 and 5,262, 068 concern diaphragm pumps that dispense fluids with accuracy and precision. U. S. Patent No. 6,021, 925 provides an improved piston for driving incompressible fluids.

The RGENTM-01 dispense pump sold by Tokyo Electron Limited of Japan, incorporates the piston of U. S. Patent No. 6,021, 925 and it has proved to be a commercial success. In the commercial version of that pump provided in Figure 1, the piston, motor and hydraulic fluid housing are located directly behind the pump head dispense stage. The complete hydraulic fluid chamber opens up directly behind the dispense diaphragm and is one integral assembly, i. e. motor, piston, housing/fluid, and dispense diaphragm. For this configuration, the pump width is 118 mm.

The principal commercial uses for the RGEN-01 include photochemical dispense: photochemicals are dispensed onto silicon wafers as part of the semiconductor manufacturing process. The number of processes requiring pumps is growing, so more pumps are required on the tracks used to make semiconductors. This means real estate is at a premium. For other situations, such

as using diaphragm pumps to pump fuel into internal combustion engines, see U. S.

Patent No. 6,071, 089; real estate is also a premium.

What is needed are dispense pumps with foot prints that maximize the efficient use of real estate while providing improved performance.

SUMMARY OF THE INVENTION This invention provides a smaller pump with improved performance characteristics through the use of an improved hydraulic transmission system.

BRIEF DESCRIPTION OF THE DRAWING Figure 1 illustrates a prior art hydraulic transmission for a pump.

Figure 2 illustrates a hydraulic transmission for a pump of the present invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS The present invention provides a much smaller pump head than the RGEN- 01, it's immediate predecessor.

The prior art pump in Figure 1 provides a dispense diaphragm 10, part of the pump head 12, that is actuated by hydraulic fluid 20. The hydraulic fluid housing 14 is located directly behind the pump head 12 dispense stage. The hydraulic fluid is pressurized by the piston 24 that is actuated by the motor 26.

The customer needed us to shrink the size of it's dispense pumps dramatically. The customer requirement was to be able to fit up to 32 pumps per track for their new coater/developer equipment. Current coater/developer equipment using RGEN-01 could fit a maximum of 16 pumps per track. To force the issue, the customer constrained the width dimension of the pump to 60 mm maximum width-a pump half the width ofthe RGEN-01. Of course, performance could not be less than the RGEN-01.

Figure 2 provides Top and Side Views of the present invention. As Figure 2 provides, the piston 44 and cylinder 42 were relocated to the side of the pump

plates. As a result, the hydraulic fluid chamber holding/delivery area had to be split into two distinct sections, i. e. the"base plate"and"cylinder"sections.

This two-section design provides an oval shaped o-ring seal 40 to prevent hydraulic fluid from leaking at the connection interface of the two sections when assembled. Two internal 3mm ID channels 32 deliver the hydraulic fluid from the cylinder/piston section through the base plate to the dispense stage diaphragm.

This is indirect contrast to figure 1, where the channel to deliver hydraulic fluid from the piston to the dispense diaphragm is large.

The present invention provides a base plate 46 that has been designed with a ring channel 34 positioned at the dispense stage hydraulic fluid chamber 36. That ring channel 34 is connected to both of the 3mm fluid channels 32 in order to more uniformly distribute hydraulic fluid to the dispense diaphragm. The ring channel 34 also provides a plurality of perforations to allow the hydraulic to enter the hydraulic chamber 36 in an outwardly direction 38.

The pump of the present invention provides a dispense volume range of 0.1 - 4. 0 mL. The prior art RGEN-01 has a volume range of 0.5-10. 0 mL. This is a significant improvement in performance as the ratio of smallest to largest dispense volume, 1: 40 for the present invention and 1: 20 for the RGEN-01, has been doubled.

The main advantage of this design is that it allows for a smaller sized pump overall that also meets the customer design constraint of a 60mm width. This will allow the customer to install more dispense pumps per track-approximately double the amount versus RGEN-01.

Note that the size of the pump head of the current embodiment of the present invention is approximately the same overall size as the prior art RGEN-01.

This means that a higher capacity pump, in terms of dispense volume, can have the same overall size as the current RGEN-01, but have the look and footprint more aligned with a pump of the present invention. Thus, the hydraulic fluid transmission design of the present invention could be applied to a high volume pump like RGEN-01, and in general offers more flexibility for layout design of future diaphragm pumps.