3. A fuel injector nozzle assembly as set forth in claim 2 including a nozzle tip portion in the nozzle housing, the damper plate being disposed in engagement with the nozzle tip portion; an opening in the nozzle tip portion defining in part the high pressure fuel delivery passage, the damper pin extending through the damper plate fuel flow passage with a calibrated clearance thereby defining a fuel flow leak path of fluid displaced from the accumulator chamber by the needle valve.

4. The fuel injector nozzle assembly of claim 3 wherein the first end of the needle valve is formed with a first seal area, the nozzle tip portion that is engaged by the one end of the needle valve having a second seal area that registers with the first seal area; the first and second seal areas closing the nozzle orifice when the needle valve first end engages the nozzle tip portion; the seal area on the needle valve first end being subjected to pressure in the high pressure fuel delivery passage when the needle valve is shifted toward the damper plate.

5. The fuel injector nozzle assembly set forth in claim 1 wherein the nozzle housing has a spring chamber adjacent the damper plate; the spring being located in the spring chamber; the spring having a force acting on the damper pin, the spring force being transferred to the needle valve second end through the damper pin.

STATEMENT UNDER ARTICLE 19 Applicant has made corrections to claims 1-5 to improve the form. Specifically, claim 1 has been amended to introduce a transitory phrase, i. e.,"the nozzle assembly comprising" between the first and second paragraphs. Claim 4 has been amended by changing the term"one" to--first--end.

Applicant has introduced into claim 1 some changes that emphasize the distinctions between the Hoffman et al device (the'738 patent) and the present invention. In the device of the '738 patent, the needle valve moves a distance"H,"during an initial injection pulse. At that time, the spring 33 becomes compressed. That injection pulse is followed by the main injection event as the second spring 49 becomes compressed.

Fuel injectors of this type operate at the maximum capacity of the pump with which the nozzle is used. The area on the needle valve shown at 21 in the'738 patent is the area that is pressurized during the initial pressure pulse as well as during the main injection event. Since the area for both of the stages is the same and since the pressure for both of the stages is at the same maximum value, it necessarily follows that the spring force for spring 33 at the start of the initial injection pulse would be less than the spring force for spring 49 at the start of the main injection event. It follows from this that there clearly would be a blending of the two injection phases. The initial injection pulse of the device of the'738 patent would not be terminated precisely at a calibrated time relative to the injection time during which the main injection event occurs. The needle valve actually is moving during both stages. It is moving during the main injection event through the distance H3 following the initial movement through distance Hl. There is no clear demarcation between the end of the initial injection pulse and the beginning of the main injection event. A similar blending was described by applicant in the description of the prior art fuel injection characteristic shown in Figure 9 of applicant's drawings.

It is the purpose of the teachings of the'738 patent to provide an additional dwell time following the initial injection pulse. This dwell time actually influences the initial injection pulse because it occurs during movement of the needle valve. There is no clear demarcation in the design of the'738 patent between the main injection event and the initial injection pulse.

One of the important results of this difference between applicants'teachings and the teachings of the'738 patent is an elongation of the injection time for the device of the'738 patent during the main injection event. The main injection event takes place as the second spring 49 becomes compressed. This makes it difficult to design an engine with a relatively constant combustion chamber volume.

Constant volume combustion is the result of the function achieved by applicant's structural limitations in the definition of the injection nozzle assembly of the present invention.

Applicant does not intend, of course, to the claim the constant volume combustion function.

Rather, they have defined structural limitations that make it possible to achieve the constant volume combustion function.

Of course, two springs do not necessary provide higher spring force. The spring force is determined by the effective spring constant. In the present case, however, the two springs do provide a higher spring force during the main ejection event relative to the spring force during the initial injection pulse because both springs 49 and 33 are compressed at that time against the opposing hydrostatic force acting on the annular area 21 of the'738 patent. The spring forces are additive. The spring 33 will yield, as explained previously, as the distance H, is traversed. This feature of the'738 patent is what causes a blending of the initial injection pulse with the main injection event. There is no clear demarcation in the case of the'738 device between the end of the initial injection pulse and the beginning of the main injection event. This is due to the fact, as explained previously, that the needle valve continues to move against the force of both springs until the stroking of the needle valve terminates as the intermediate disk 3 is contacted by annular projection 57.

Use of a secondary spring in the device of the'738 patent"teaches away"from the objective of achieving constant volume combustion. This is true because the secondary spring, which establishes a second stage injection, prolongs the duration of the main injection event as the secondary spring yields. A prolongation of the main injection event would result in variable volume combustion, not constant volume combustion.