Fuel injector and method for making same
United States Patent [1 1 Roosa FUEL INJECTOR AND METHOD FOR MAKING SAME [76] Inventor: Vernon D. Roosa, 184 Wood Rd.,  
 West Hartford, Conn. 06190 [22] Filed: Nov. 29, 1972 [21] Appl No.1 310,570  
 [52] US. Cl 239/533; 137/509 [51] Int. Cl F02m 55/00 [58] Field of Search 137/509; 239/533 [56] References Cited UNITED STATES PATENTS 3.224.684 12/1965 Boosa 239/533 3,295,169 1/1967 Moslo 239/533 X FOREIGN PATENTS OR APPLICATIONS 1,453.616 8/1966 France 239/533 Primary Examiner-Harold W. Weakley Attorney, Agent, or Firm-Prutzman, Hayes. Kalb &amp; Chilton Apr. 8, 1975 [5 7] ABSTRACT A precision fuel injector having an inwardly opening pressure operated valve positioned in a bore forming a valve chamber and guided for reciprocal movement to open and close the valve wherein a threaded stepped cylindrical valve guide sleeve at the end of the valve chamber opposite the valve tip mounts the valve and cooperates with a mating portion of the bore to form an annulus filled with an initially flowable settable sealant. The sealant is pressurized during assembly of the guide sleeve and is forced into the clearance between the threads of the guide and the threads of the bore on both sides of the annulus to increase the length of the seal and to lock the guide sleeve in place. The blind end of the guide sleeve bottoms against a shoulder in the bore to establish a predetermined minimum cross-section of the annulus to minimize the possibility of fracture of the sealant ring therein due to differential expansion, and a pilot extending from the end of the guide sleeve and closely fitted within the surrounding bore protects the sealant against corrosion by the repetitive high impact hydraulic forces within the valve chamber.  
 5 Claims, 2 Drawing Figures Ill/454M? FUEL INJECTOR AND METHOD FOR MAKING SAME This invention relates to fuel injectors for internal combustion engines.  
  Fuel injectors of the type contemplated by this invention have a plunger or valve which is lifted from its seat by the pressure of fuel delivered to the injector by an associated high pressure pump in measured charges in timed relation with the associated engine.  
  It is an object of this invention to provide an improved arrangement for mounting a valve guide sleeve for such an injector.  
  Another object of this invention is to provide a novel method for using a sealant for securing a guide sleeve in the bore of a fuel injector and sealing and locking the same in position without escape of the sealant past the blind end of the insert.  
  Other objects will be in part obvious and in part pointed out more in detail hereinafter.  
  The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which is exemplified in the construction hereafter set forth, and the scope of the invention is indicated in the appended claims. In the drawing:  
  FIG. 1 is a fragmentary cross-sectional view of a fuel injector embodying the present invention; and  
  FIG. 2 is an enlarged fragmentary cross-sectional view showing the valve guide of FIG. 1. The exemplary injector shown in the drawing and embodying the present invention is of the pressure-operable type and includes an elongated tubular body having a discharge tip 12 rigidly positioned at one end thereof. The tubular body 10 further provides a central longitudinal bore extending throughout its length to form a valve chamber 14. Located within the valve chamber 14 is a rod-like plunger or valve 16 having a conical tip 18 which cooperatively engages a valve seat 20 to control the discharge of fuel from the valve chamber 14 through discharge orifices 22. A valve guide sleeve generally indicated at 24 is positioned within the bore of the tubular body 10 at one end of the valve chamber 14 to slidably mount and align the valve 16 with the valve seat 20 for rapid reciprocal movement under the influence of fuel pressure within the bore 14 acting against the bias of spring 26. The injector is provided with a fuel inlet 28 communicating with the valve chamber 14 for the delivery of discrete charges of high pressure fuel to the bore 14 from an associated high pressure charge pump, not shown.  
  As shown in FIG. 1, the upper end of the valve 16 engages a spring seat 30 which is in turn engaged by biasing spring 26. The other end of biasing spring 26 is similarly provided with a spring seat 32 to cause the spring to exert an axial force on the valve 16. An extension 42 of the spring seat 32 limits the lift of the valve 16 away from the valve seat 20.  
  In accordance with this invention, novel means are provided for locating and sealing the valve guide sleeve 24 in assembled position in the injector body. As shown in FIG. 2, the guide sleeve 24 is provided with a pair of axially spaced stepped cylindrical threaded portions 44, 46 with an intermediate annular recess 48 therebetween with the threads on portions 44, 46 being formed on the same helix but having different pitch diameters. Mating threaded cylindrical wal portions 50, 52 are provided within the bore of the injector. The shoulder 54 at the end of guide sleeve 24 bottoms on a mating shoulder 56 provided in the bore.  
  Prior to assembling the guide sleeve 24 in the injector body 10, a measured amount of an initially flowable settable sealant, for example, an epoxy resin, is applied to the threaded portion 46 of the guide sleeve 24. As the guide sleeve 24 is inserted axially into its assembled position, the threaded end portion 46 of the guide sleeve 24 threadably engages the mating threads 52 of the bore. During the initial axial movement of the guide sleeve, the threads 52 wipe the sealant from the end portion 46 into the annular recess groove 48 to completely fill the recess.  
  As the guide sleeve 24 is threaded to its final assembled position, the shoulder 54 is bottomed on the shoulder 56 and the sealant within the annulus 48 is pressurized to impart a hydraulic pressure on the sealant and force it into the clearances between the threads on both sides of the annulus. The amount of sealant utilized is sufficient to cause the sealant to be squeezed in between the mating threads 44, 50 and 46, 52, respectively, to lengthen the seal and lock the guide sleeve 24 in the injector body. The bottomed shoulders 54, 56 guard against the entry of sealant into the valve chamber 14. In this regard any excess sealant will be collected in the annulus 60 at the end of the threads.  
  The sealant thus positioned between the guide sleeve 24 and the injector body sets, or is treated so as to cause it to set, to provide a void free annular ring of sealant to permanently seal and lock the guide sleeve 24 in position. The bottoming of the shoulders 54, 56 establishes the cross-section of the sealant ring in annulus 48 at a predetermined minimum to minimize the tensile stress thereon, and the possibility of fracture. due to differential expansion.  
  The bottomed shoulders 54, 56, as well as pilot 62 which engages the surrounding annular surface 64 of the bore with a close fit, serve to isolate the sealant from the valve chamber 14. This construction which impedes or throttles the flow of fuel from valve chamber 14 to annulus 60, protects the sealant from corrosion by the repetitive high impact hydraulic forces occasioned by the delivery of the sequential measure of high pressure fuel delivered by the charge pump for injection to the engine.  
  From the foregoing, it will be apparent that this invention provides a novel arrangement and method for sealing and locking a guide sleeve within a bore or aperture of an injector body in a manner which assures a leak-proof seal therebetween while guarding against the escape of the sealant beyond the blind end of the guide sleeve and into the valve chamber.  
  As will be apparent to persons skilled in the art, various modifications and adaptations of the structure above-described will become readily apparent without departure from the spirit and scope of the invention, the scope of which is defined in the appended claims.  
 1 claim:  
  1. In a fuel injector, a tubular body having a valve chamber, a valve guide mounting a pressure operable valve disposed in the valve chamber and a spring biasing the valve toward a valve seat having a discharge orifice. the improvement wherein the valve guide is a generally cylindrical sleeve having an end portion and a pair of axially displaced cylindrically shaped threaded outer surface portions separated by a step, and the portion of the valve chamber remote from the valve seat is provided with a bore having a pair of stepped surface portions which cooperate with the stepped surface portions of said sleeve to form an annular therebetween when the end portion of the guide sleeve bottoms on a mating shoulder provided by the bore to guard against the entry of sealant into the valve chamber, each of said stepped surface portions of said tubular body being threaded and respectively engaging one of the stepped threaded portions of said sleeve, and an initially flowable settable sealant disposed in said annulus to be entrapped and compressed therein during assembly as the guide sleeve is assembled in the injector to form a voidfree ring of sealant filling the annulus and to force the sealant into the clearances between the threads in both directions from the annulus, the threads of the stepped surfaces of said valve guide and said tubular body being formed on the same helix but having different pitch diameters.  
  2. An injector as recited in claim l wherein a groove is provided between the stepped threaded outer surface portions of the guide sleeve to axially space said threads of different pitch diameters.  
  3. An injector as recited in claim 1 including throttling means for throttling the flow of fuel from said valve chamber toward said sealant to protect the sealant against corrosion.  
  4. An injector as recited in claim 3 wherein said throttling means comprises a pilot formed on the end portion of on said valve guide which is closely received in said bore.  
  5. The injector of claim 4 including an annulus between said pilot and the mating threads of said stepped surfaces.