Valve base roughening process

The thorough bonding required between the base or flange of a molded rubber sleeve for a valve, and a tire tube of rubber or the like, is realized by simulating the roughened effect normally produced through abrasion. Such effect is achieved by specially configuring the surface of the base in the molding process; that is to say, the surface normally resulting from abrasion is equivalently produced by forming the contacting surface of the critical mold portion (such as a plunger or the like) in a cross-hatched or knurled pattern, whereby a desired cross-hatched pattern is formed in the particular surface of the base.

BACKGROUND, OBJECTS AND SUMMARY OF THE INVENTION 
The present invention pertains to the manufacture of valves and like 
devices, and particularly to a process of efficiently producing valve 
stems surrounded by rubber or the like so as to form an assembly that is 
easily attachable to rubber tubes adapted for use in tires. 
In order to provide complete background information so that the objectives 
and purposes of the present invention may be thoroughly appreciated, 
reference may be made to a number of U.S. Pat. Nos. 583,437; 1,931,649; 
1,938,816; 2,014,129; 2,499,565; 2,600,942; 2,724,423; 3,474,498. In 
particular, U.S. Pat. No. 583,437 relates to a method of molding, around a 
valve stem, a rubber sleeve, the base of which is formed with depressions 
or corrugations; such construction is for the purpose of preventing 
shearing strain from being exerted on the base due to the normal creeping 
of the tire tube on the wheel rim with which the valve stem is associated. 
U.S. Pat. No. 1,938,816 discloses a general notion of roughening the 
surface of a sectional mold which is designed to vulcanize or otherwise 
unite a valve stem base member to a tire tube. However, the purpose of the 
method of this latter patent is to insure that the roughening provided in 
the resultant product spans the seam between the edges of the base member 
and the tire tube; accordingly, the roughening of the base member is 
produced on a surface not extensively in contact with the tube. As will be 
made clear hereinafter, the purposes and objects of the present invention 
differ substantially from the aforecited art. 
It has long been known to fabricate valve stem assemblies in which 
processes a conventional valve stem is surrounded by a sleeve of rubber 
material which is so shaped or formed as to have a broad base or flange 
member suitable for attaching the entire assembly to a rubber tube. The 
attachment or joinder is generally accomplished by a vulcanization or 
similar step; however, in performing same it has been necessary, in order 
to insure proper bonding, to provide that the outer surface of the base or 
flange of the rubber sleeve be suitably roughened. The roughening is 
conventionally accomplished by abrading the aforenoted molded surface, 
generally by mounting the valve assemblies with respect to dials in a 
buffing machine which is indexed on successive wire wheel brushes. 
It will be understood that the roughening or abrading process is a 
time-consuming operation; accordingly, it is a primary object of the 
present invention to eliminate this abrading or roughening step while 
enabling the same satisfactory bonding in the subsequent vulcanization 
procedure. 
Another object is to reduce substantially the cost of the bonding process 
by completely eliminating the roughening step. 
A primary feature of the present invention resides in the fulfillment of 
the above objects by providing that the mold plunger or similar portion of 
the mold apparatus be so configured that the outer surface of the base or 
flange will simulate the normally roughened surface. This is achieved by a 
configuration of fine cross-hatching or knurling, by which is meant that 
the surface of the mold portion preferably has a series of intersecting 
ridge lines with grooves defined therebetween, the particular pattern 
generally being diamond or V-shaped and with very close spacing between 
the ridge lines. The configuration for the mold portion is realized by 
well-known machining processes to produce the requisite pattern. 
Considered in its method aspects, the present invention achieves, in a 
subsequent vulcanization step, effective bonding between the base or 
flange of a molded rubber valve device and a tire tube of rubber or the 
like, involving appropriate configuring or patterning of the surface of 
said base which contacts the tube surface, by the improvement which 
comprises simulating the required base surface normally resulting from 
abrasion by forming the surface of the contacting mold portion in a 
cross-hatched pattern. 
The resulting product of the present invention is a valve or valve stem 
device which is surrounded by a rubber sleeve or the like having a base or 
flange member whose outer surface is configured as already described; that 
is, whose surface is cross-hatched due to contact with a cross-hatched 
mold portion. 
Other and further objects, advantages and features of the present invention 
will be understood by reference to the following specification in 
conjunction with the annexed drawing, wherein like parts have been given 
like numbers.

DESCRIPTION OF PREFERRED EMBODIMENT 
Referring now to the drawing figures, there will be seen in FIG. 4 a mold 
apparatus comprising an upper part 10 and a lower part 12 shown together 
at a parting line 14 when the mold is closed. The upper part 10 includes a 
top plate 16 to which is mounted a plunger 18; fitted within the plunger 
18 is a mold pin 19 for purposes which will become apparent. The lower 
part 12 includes a mold plate 20, defining a mold cavity 22, and a bushing 
24. Retained within the mold cavity 22 is the required valve stem 30 
around which rubber or the like is to be molded to form a sleeve 34. The 
valve stem 30 protrudes into the bushing 24, such that the portion 31 of 
the valve stem will not be surrounded by the rubber sleeve. 
It will be appreciated that in the process of molding the rubber sleeve, 
the rubber material is prevented from entering the interior of the valve 
stem 30 by reason of the positioning of the mold pin 19 which thereby also 
serves to define a suitable aperture 32 in the rubber material 
constituting the sleeve 34. The sleeve 34 includes a cylindrically molded 
portion 36, as will be apparent, and in which there is included at the 
upper end a series of spaced, axially extending, grooves 37 at the outer 
periphery of the sleeve. These grooves are for the purpose of permitting 
escape of air from between an inner tube and tire when same are mounted on 
a rim. To produce such grooves the inner periphery of the mold plate 20 
includes protrusions or ridges 38. As will be seen in FIG. 1, the sleeve 
34 flares out into a base or flange member 40, which is shown as having 
been formed at the upper end of the mold cavity 22. 
The primary feature in accordance with the present invention may be 
understood by particular reference to FIG. 2 in which the outer surface 42 
of the base or flange member 40 is clearly illustrated as being configured 
in a very special manner. This configuration involves a plurality of very 
finely formed depressions 44 (FIG. 3), in a triangular or diamond shape 
and defined by intersecting ridge lines 45. This pattern, which will be 
referred to as a cross-hatched pattern, results from the configuration of 
the corresponding plunger face 46 (FIG. 5) which is constructed to have 
just the negative of the configuration seen in FIGS. 2 and 3. Thus FIG. 5 
shows a series of raised diamond-shaped mesas 48, which are produced by 
machining closely spaced intersecting grooves 49 into the particular 
surface 46 of the plunger 18. The acute angles of the mesas 48 are 
approximately 60.degree. and the spacing between the individual mesas is 
preferably about ten to thirty thousandths of an inch. By this finely 
produced cross-hatched pattern, the required roughened effect normally 
produced by abrasion is simulated in the outer surface 42 of the base or 
flange 40 of the sleeve 34. 
Accordingly it will be understood that the technique or method of the 
present invention results in a valve stem assembly which can be more 
economically produced inasmuch as the abrasion step has been eliminated. 
It will be appreciated that except for the machining required in producing 
the necessary configured surface 46, the mold apparatus illustrated in 
FIG. 4 is entirely conventional. Thus once this machining has been 
accomplished, a tremendous number of the suitably molded valve stem 
assemblies can be manufactured, meeting all the criteria for efficient 
attachment of the molded assembly to a tire tube or the like by reason of 
the required textured or roughened configuration for the appropriate 
surface 42 of the base or flange of sleeve 34. 
It will be understood that subsequent to the molding operation as 
described, any surface mold skin which may adhere can be removed by 
passing each valve under a pumice spray and thereafter each is subjected 
to a lukewarm water spray to remove the pumice. 
While there has been shown and described what is considered at present to 
be the preferred embodiment of the present invention, it will be 
appreciated by those skilled in the art that modifications of such 
embodiment may be made. It is therefore desired that the invention not be 
limited to this embodiment, and it is intended to cover in the appended 
claims all such modifications as fall within the true spirit and scope of 
the invention.