TITLE: MAGNETIC VALVE CAP FOR THE VALVE STEM OF A PNEUMATIC TIRE

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims foreign priority from and the benefit of Canadian

Patent Application #2,545,839 "Magnetic Dust Cap" filed in the Canadian

Patent Office on May 1 , 2006.

BACKGROUND - Field of the Invention

The present invention relates to field of resilient tire and wheels and

more particularly to dust caps for inflating valves and stems and

specifically for a magnetic valve cap for the valve stem of a pneumatic

tire.

BACKGROUND - Description of the Prior Art

The prior art indicates that since the early 1920's there has been a great

effort in designing the ultimate dust cap for standard valves and tires and

the like. One common and popular design is the twist-on plastic dust

cap. The problem and frustration for most users of this product is that

they are not easily removed or put back on. They are easily fumbled,

dropped or misplaced while accessing the tire valve. Prior art valve caps

are illustrated in Figure 1 and Figure 2 herein and labeled "Prior Art".

There have been other designs of valve caps that involve either a tether

or hinge that allows the valve cap to remain attached to the valve

assembly. These designs are prone to failure and are cumbersome to

use. As well, valve stems are often located difficult to access areas within

a wheel rim making the turning motion to remove or replace them

difficult.

Therefore, there is a continuing need for a dust cap that is easy to use

placing on and off the valve stem.

SUMMARY OF THE INVENTION

In accordance with the present invention a magnetic dust cap comprises a

body, magnetic means and a washer. The washer is mounted over the

valve stem threaded portion to provide a ferrous contact surface for the

magnetic means. Magnetic means is placed within the body of the cap so

that when the cap is placed over the stem, the magnetic means adheres

to the washer and maintains the cap in place. The body completely covers

the valve stem threaded portion to provide a seal against moisture and

dirt. The present invention allows for quick and trouble free attachment

and removal of the cap because there is no twisting motion required on

the cap. The cap, once removed, can be adhered to an adjacent metallic

surface for easy location and retrieval. Once on the stem, the magnetic

valve cap seals the valve stem and prevents moisture and dirt from

entering the valve stem.

OBJECTS AND ADVANTAGES

One object of my invention is to overcome the deficiencies of the prior

art.

Another object of my invention is to provide a dust cap that magnetically

adheres to a valve stem without twisting motion.

Another object of my invention is to provide a kit comprising a dust cap

that magnetically adheres to a valve stem and a washer for placement on

the valve stem so that present valve stems can be retro-fitted.

Still another object of my invention is to provide an easily manufactured,

inexpensive solution to the problems noted above.

Still further objects and advantages of my invention will become apparent

from a consideration of the ensuing description and drawings.

DESCRIPTION OF THE FIGURES

Figure 1 illustrates a prior art dust cap on a valve stem.

Figure 2 illustrates other views of a prior art dust cap on a valve stem.

Figure 3 illustrates one embodiment of my invention on a valve stem.

Figure 4 illustrates another embodiment of my invention with the dust

cap shown in quarter-section.

Figure 5 illustrates yet another embodiment of my invention with the dust

cap, magnet and washer shown in assembly view and in cross-section.

Figure 6 illustrates the dust cap body of one embodiment of the invention

in cross-section.

DETAILED DESCRIPTION OF THE INVENTION

Prior Art

The most commonly available dust cap is the tried and true twist-on

plastic cap illustrated in Figures 1 and 2 as item (10). This type of cap is

cumbersome to work with and tends to fall off the stem when twisted off

and onto the ground. The result is that dirt and debris adhere to the cap

and once the cap is replaced onto the valve stem, the stem can become

dirty and clogged. Alternatively, the cap is lost and the average person

does not bother to replace the cap. The result is that the valve is subject

to the environment and prone to clogging and damage.

Figure 2 illustrates other shortcomings of the typical prior art valve cap.

Figure 2A and 2B and Figure show a typical cap (10) in quarter-section

and cross-section respectively mounted in a threaded engagement onto

the threaded portion (16) of a pneumatic tire valve stem (1 2). The

outside surface of the cap (10) includes a ferruled portion (1 8) for

gripping during the twist-off and twist-on operations. The cap includes

a domed portion (14) which leaves a space above the valve stem (1 2)

where dirt and debris can accumulate. Furthermore, the valve cover

includes a skirt (20) at the bottom thereof which is intended to protect

against ingress of water and dirt when the valve is fastened onto the

valve stem threaded portion. However, in many such installations, there

may be a gap (26) between the bottom surface of the cap (24) and the

top portion of the valve stem rubber portion (22). This permits the

ingress of dirt and water because the seal is not complete.

My invention

Referring to Figure 3 and Figure 4, my invention overcomes these

deficiencies by providing a new and inventive magnetic valve cap (30) for

a pneumatic tire comprising an external valve stem (32) having a

threaded top portion (34) which is located under the cap (30).

Referring to Figure 5, the valve stem top portion (34) is threaded and has

a width (36), a length (38), a top end (40) and a bottom end (42). The

valve stem has a rubberized bottom portion (32) also having a width (46)

and a top end (48).

Still referring to Figures 4 and 5, my invention, the magnetic valve cap

(30) comprises a body (50) for capping the valve stem threaded portion

(34). The body (50) comprises an outer surface (52), a closed top surface

(54), an open bottom end (56), an internal void (58) and an inside surface

(60). My magnetic valve cap further comprises magnetic means (62)

disposed within the body (50) as illustrated by arrows (64) and (66) and

further explained below. The magnetic means (62) is adapted to

removeably adhere to a washer (70) having threads (72) and adapted for

threaded engagement over the threaded top portion (34) of the valve

stem. The washer is installed onto the treaded portion of the valve stem

so that the washer has a final operating position abutting the top end

(48) of the rubberized bottom portion (32) where it meets the bottom end

(72) of the threaded top portion of the valve stem. In one embodiment of

the invention the body (50) is metallic. In another embodiment of the

invention the body (50) is non-metallic. In yet another embodiment of

the invention the body (50) is ferrous. In still another embodiment of the

invention the body (50) is non-ferrous.

Referring now to Figure 6, the internal void (58) comprises a top

cylindrical portion (80), a middle disc-shaped portion (82) and a bottom

wafer-shaped portion (84). The top cylindrical portion (80) of the void

comprises a generally rectangular cross-section having a height (86) and

a width (88) substantially equal. The void top cylindrical portion (80) is

adapted to accommodate the entire length and width of the threaded top

portion of the valve stem so that when the cap is placed over the valve

stem the bottom surface of the cap (56) rests below the top surface (63)

of the threaded washer (70) in its installed position on the threaded

portion of the valve stem. The bottom of the cap forms a tight

compressive seal around the diameter of the washer and prevents

moisture and dirt from getting into the void of the cap body. The middle

disc-shaped portion (82) of the void has a rectangular cross-section, a

height (90) and a width (92) that is substantially longer than its height.

The bottom wafer portion (84) is shaped like a thin truncated cone having

a top surface (94) and a bottom surface (96) and a first (98) and second

(100) inwardly inclined sides. The top surface is shorter than the bottom

surface and the bottom surface (96) of the bottom wafer portion (84) has

the same length (92) as the bottom surface of the middle disc-shaped

portion (82) of the void so that a lip (102) is formed around the perimeter

of the lower surface of the disc-shaped portion.

Referring to Figure 5, the magnet means (62) comprises a permanent

magnet. In one embodiment of the invention the permanent magnet

comprises a rare earth magnet. In another embodiment of the invention

the permanent magnet is an earth magnet made from neodymium-iron-

boron (NdFeB). In yet another embodiment of the invention the rare earth

magnet is made from samarium-cobalt (SmCo). In a preferred

embodiment of the invention the rare earth magnet is at least N42 grade.

The rare earth magnetic (62) is shaped in the form of a ring having an

annulus (1 10) having a diameter (1 12) permitting passage of the top

portion of the valve stem without frictional contact. The magnet has a

thickness (1 14) equal to the height (90) of the middle disc-shaped

portion of the void (82) so it may be fitted entirely within the middle

disc-shaped portion of the void. Once the rare earth magnet is inserted

into the disc-shaped portion of the void the Mp (102) acts to support the

bottom surface of the magnetic and retain it within the disc-shaped

portion of the void. In another embodiment of the invention the magnet

is adhesively secured within the disc-shaped portion of the void.

Still referring to Figure 5 the washer (70) is adapted for threaded

engagement with the top portion of the valve stem so that the washer

may be placed on the top portion of the valve stem and threaded down

the valve stem until it is in permanent and compressive contact with the

top (48) of the rubber portion (32) of the valve stem. When the cap is

placed over the valve stem as shown in Figure 3, the rare earth magnet

comes into contact with the top surface of the washer and adheres

magnetically thereto thereby maintaining the cap body in a secure and

removeably fixed position. When the cap is removed from the valve

stem, the rare earth magnetic will removable fix the cap to an adjacent

metallic body, such as a vehicle fender, thereby preventing loss of the

cap.

Referring to Figure 7, there is shown another embodiment of the valve

cap body (1 30) wherein a circular dependent flange (1 32) is adapted to

enter the threaded portion of valve stem and further seal the valve stem

against the ingress of water and dirt when the valve cap is placed over

the threaded portion of the valve stem.

Referring to Figure 8, there is shown another embodiment of the valve

cap body (1 36) incorporation cilia or brushes within the inside wall of the

void in order to provide additional sealing against the ingress of water

and dirt once the valve cap is installed over the threaded valve stem.

Referring to Figure 9, there is shown another embodiment of the cap

body (140) wherein a rubber o-ring is incorporated within the top

cylindrical portion of the void to provide for sealing of the valve once the

cap is placed on the valve stem.

Referring to Figure 10, there is shown another embodiment of my

invention wherein the bottom surface of the ring magnet (146) is coated

with a gelatinous sealing substance (148) such as silicon in order to

further seal the valve stem against water and dirt.

Referring to Figure 1 1 , there is shown another embodiment of my

invention wherein the washer (1 50) is permanently fixed to the valve stem

(1 52). This can take place during the manufacturing of the valve stem or

after market at a tire shop. In this embodiment, the valve stem upper

portion (1 54) may or may not be threaded. In this configuration, no

threads are necessary on the top metallic portion of the valve stem and

this will save the valve stem manufacturer money. The valve body (1 56)

is placed over the top portion of the valve stem and is magnetically

adhered to the washer.

Referring to Figure 12, there are shown three embodiments of valve

stems (A, B and Q. There is a different thickness of the gap (160, 162,

164) between the top of the rubber portion of each valve stem and the

bottom of the metallic portion of each valve stem. To accommodate this

gap, my invention will be supplied with a variety of washer thicknesses

(166, 168).

Referring to Figure 1 3, there are shown various ornamental aspects of my

invention wherein the valve cap body may take the shape of a skull (1 70

side view, 1 72 top view) or a dome (1 74 side view, 1 76 top view).

Referring to Figure 14, there are shown more ornamental aspects of my

invention wherein the cap body is in the shape of an eight-ball (1 80 side

view, 182 top view) or a die (1 84 side view, 1 86 top view).

Although the description above contains much specificity, these should

not be construed as limiting the scope of the invention but merely

providing illustration of some of the presently preferred embodiments of

this invention. Thus the scope of the invention should be determined by

the appended claims and their legal equivalents.