GB2370918A

GB2370918A - Mobile phone shield

Info

Publication number: GB2370918A
Application number: GB0100438A
Authority: GB
Inventors: Warren James Philbey
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-01-08
Filing date: 2001-01-08
Publication date: 2002-07-10
Also published as: GB0100438D0

Abstract

A shield device for use on the external antenna attached to a portion of a mobile phone 5 includes a rotatable casing 1 around the antenna, the casing 1 carrying a strip 7 of radiation-shielding material extending along its length and over an arc relative to the axis of the antenna in the range of 70 to 180{. The shield may be a rubber or resin sheet, covered with or containing particles of carbon, aluminium, beryllium, copper, iron, nickel, stainless steel, metal oxide or ferrite; alternatively it may be a wire mesh, knitted wire or perforated sheet. Other materials include cloth coated with nickel or metal-loaded tape. The shielding strip may extend over the top of the antenna, and may be glued onto the casing or encapsulated within it. The casing may be cylindrical or polygonal. A second shielding strip may be rotatable independently. A protrusion 6 acts as a marker to orient the shield.

Description

MOBILE PHONE SHIELD

This invention relates to a shield for a cellular mobile telephone, in particular to a guard device for use on an external antenna attached to the telephone. Cellular mobile telephones, also known as cell phones, employ microwave links to convey signals to and from base stations. There is a radio frequency link to a base station during the period when the phone is switched on, with not only a continuous signal while a call is in progress but also a link being maintained while the phone is on stand-by. Much public concern and much speculation has arisen over the risks posed by the signals to the health of the phone's users. Particular concern has arisen that the radiation emitted from the phone in the course of a call may cause disturbance to body cells, with possible associated health problems such as headaches, sickness, increased body temperature and memory loss. There have been suggestions that mobile phone use could lead to brain tumours, although this has not been proven.

Even with the phone on stand-by there is a perceived risk to sensitive body organs, for example to the kidneys when the phone is attached to a belt, or to the heart when the phone is kept in a breast pocket.

In general, the frequency range for radiation emitted by mobile phones is about 30 to 1,800 MHz, with corresponding wavelengths in the range of about 10 to 0.5 m.

Various suggestions have been made with a view to reducing the level of radiation to which the phone user is exposed. Previous proposals have included shielding the antenna with a material to absorb the radiation, but these have suffered from the drawback of reducing the signal strength, thereby reducing the useful range of the phone. Moreover most phones compensate for the resulting reduction in signal strength by correspondingly increasing the strength of the emitted signal. The net effect of such shields has therefore been to restore and even increase the amount of radiation reaching the user's body. Other proposals for protection units suffer from such drawbacks as not easily attaching to the phone, covering the body of the phone but not the antenna, and not using effective materials to block the emissions.

It is an objective of the present invention to provide a device for protecting a user against radiation from a mobile phone without making any significant reduction in the outward or inward transmitted signals.

According to the invention there is provided a shield device for use on an external antenna attached to a portion of a mobile telephone, characterised in that it comprises a rotatable casing around the antenna, which casing carries a strip of radiationshielding material extending along its length and over an arc relative to the axis of the antenna in the range 70 to 1800.

The invention extends to antennae and mobile telephones carrying a shield device as described and claimed herein.

The use of the defined shielding strip is effective and versatile in the direction and variability of protection for the body, while not blocking transmission between the phone and the base station. The user rotates the casing to a position in which the shielding strip is aligned with the part of the body to be protected. When on standby (switched on but not on a call) the phone is normally carried in a pocket, on a belt clip/pouch or carried by hand. At these times the user simply rotates the case of the device so that the shielding strip faces in the direction of the body. When a call is made or received the user rotates the case so that the shielding strip faces the head while the call is in progress. When the call is terminated the user simply rotates the device once again to offer the protection back towards the body. Alternatively the device can be left in position for calls, providing constant and instant protection.

The device can be made in a universal size to fit a wide range of antennae, or tailor made for individual makes and models. The shape of the casing is mainly dictated by the shape of the antenna, which commonly has a circular cross-section. The cross section of the device may therefore similarly be generally circular, but may alternatively be polygonal, for example five-, six-or seven-sided.

The choice of constructional material for the casing is not critical, provided that it does not absorb a significant proportion of the radiation, which could lead to an compensating increase in the emitted radiation. Many types of rubber and plastics are

suitable, including natural rubber, acrylic plastics, polycarbonate and polyacetals.. In one convenient embodiment the casing can be made of heat-shrink tubing, which can be applied to the antenna by alternate heating and cooling.

The shielding strip should preferably extend to the end of the casing remote from the phone so as to cover the end of the antenna. This end extension of the strip is beneficial in that a high proportion of the emitted radiation may emerge from the end of the antenna.

The position of the shielding strip on the casing should be clearly detectable by the phone user, so as to facilitate moving it into the required position. In one useful embodiment of the invention the casing includes a raised portion, for example one or more raised ribs or buttons, so that the position can be selected by touch without visual inspection.

The shielding strip can be mounted in or on the casing by a variety of methods. For example it can be attached to the casing by an adhesive, or moulded or extruded into the casing.

In a preferred embodiment of the invention the shielding strip is encapsulated in a protective layer to provide weather-and wear-resistance. This can be achieved by locating the shielding strip within the casing, such that the casing itself serves as the protective layer, or by placing a protective layer over the casing, with the shielding layer sandwiched between the casing and the layer. The use of heat-shrink tubing as the casing provides a convenient way of sandwiching the shielding strip between the antenna and the tubing.

The shielding strip is conveniently a sheet or tape material. This can be continuous, for example metal foil such as aluminium foil, or discontinuous, for example a sheet of rubber or resin embedded or coated with particles of carbon, metal such as aluminium, beryllium, copper, iron, nickel, silver or stainless steel, or a metal oxide, for example a ferrite. Alternatively, and also very conveniently, the strip is preferably in the form of a material with multiple small openings, for example wire mesh, knitted wire or perforated sheet, which may also be embedded in or attached to

rubber or resin. Epoxy resins, polyesters, polyurethane and silicones and paints based on such resins are all well suited as resin carriers for the embedded particles or material with openings. The polyurethane may conveniently be in the form of a foam.

Specific examples of suitable materials for the shielding strip include aluminium foil: cloth coated with nickel; paint loaded with silver; mesh formed of copper-clad steel wire or tin plated steel wire; polyester loaded with aluminium or copper, polyurethane loaded with carbon; silicone loaded with carbon, iron or iron oxide; tape loaded with aluminium or tin-plated copper; and stainless steel foil.

A wide range of thicknesses is possible for the shielding strip, depending on the particular application, from as little as 1 cm up to 2 mm. With optimum choice of material and thickness the radiation in the shielded direction is typically reduced by 85 to 95%.

The casing can incorporate means to secure it to the antenna, for example one or more 0-rings held within the casing. Alternatively the antenna can incorporate an attachment to receive a complementary portion of the casing. Preferably the casing is attached to the phone by a bearing located at the base of the antenna. Other attachment and rotating means may be adopted depending on the complexity, cost and durability required for manufacturing and marketing.

Disposition of the shielding strip over an arc in the range 70 to 180'gives a broad guard field for the user. For many purposes a smaller range is sufficient, typically 80 to 140 , offering a greater range through which the antenna has uninterrupted access to the base station. A guard field of approximately 1100 offers an optimum balance between protection and substantially unaffected signal strength.

In a further embodiment of the invention the guard device includes a second shielding strip disposed on a mounting which can similarly but independently rotate about the antenna. If desired the mounting for the second strip can be a casing of larger size than the first. By rotating the two strips independently they provide a convenient means of adjusting the strength and angle of protection so as to adjust the guard field.

If they overlay each other the field is at its narrowest but provides a double thickness barrier. Rotating them away from the overlaid position extends the angle of the field as a whole but with reduction of the overlapping portion.

The invention is further described by way of example with reference to the specific embodiment shown in the accompanying drawings, in which: Figure 1 is a perspective view of a shield device according to the invention.

Figure 2 is a perspective view of a second form of device according to the invention Figure 3 is a front view of a cellphone with a device according to the invention in position.

Figure 4a is a side view of the device of Figure 2.

Figure 4b is an end view from point X on Figure 4a of the device of Figure 2.

Figure 4c is a detailed sectional side view of part of the device of Figure 2.

The device shown in Figure 1 has a casing 1 made from transparent polycarbonate. At its lower end (the end to be attached to a phone 5-see figure 3) the casing carries attachment means 2 with an internal bearing 4 (see figure 4c) and a ribbed adjustment projection 6. A shielding strip 7 of carbon-loaded silicone and having a thickness of 50 um runs the length of the casing 1 and around its upper end to terminate at a point 8 at the centre of the end. The ribbed projection 6 is aligned with the strip 7.

The arc of protection provided by the strip 7 is 750 measured with reference to the centre line CL of the casing (see Figures 4a and 4b).

When making or taking a call the user turns the shielding strip 7 towards the head, with the aid of the projection 6, leaving a clear path away from the head for substantially uninterrupted transmission of signals through the casing 1, while shielding the head by means of the strip 7. The shield device shown in Figures 2, 4a, 4b and 4c is generally similar to that of Figure 1, with equivalent portions using the same reference numbers as Figure 1. This device however further includes an outer

casing 11 which is rotatable about the first casing 1 by means of an interlocking tongue 12 and groove 13 at the base. The casing 11 carries a second shielding strip 17. The casing 11 and strip 17 are made of the same materials as casing 1 and strip 7. The arc of protection provided by the strip 17 is also 750 measured with reference to the centre line CL of the casings, giving an adjustable field of protection from 75 to 1500 boy rotation of the casing 11.

Shield devices according to the invention offer many advantages. They provide a significant field of protection against radiation emitted from the phone. The field of protection can be adjusted according to the disposition of the phone to direct the field of protection to the most beneficial direction for the user or even to extend the amount of protection. The device is inexpensive; it is simple to attach to the phone; and it is lightweight and non obstructive in use. Its use requires no specialist knowledge and it requires no maintenance.

Claims

Claims 1. A shield device for use on an external antenna attached to a portion of a mobile telephone, characterised in that it comprises a rotatable casing around the antenna, which casing carries a strip of radiation-shielding material extending along its length and over an arc relative to the axis of the antenna in the range 70 to 180 .
2. A device as claimed in claim 1, in which the casing has a circular crosssection.
3. A device as claimed in claim 1, in which the casing has a polygonal crosssection.
4. A device as claimed in any preceding claim, in which the material of the casing is selected from natural rubber, acrylic plastics, polycarbonate and polyacetals.
5. A device as claimed in any preceding claim, in which the casing is made from heat-shrink tubing.
6. A device as claimed in any preceding claim, in which the shielding strip extends to the end of the casing remote from the phone so as to cover the end of the antenna.
7. A device as claimed in any preceding claim, in which the casing includes a raised portion so that its position can be selected by touch without visual inspection.
8. A device as claimed in any preceding claim, in which the shielding strip is attached to the casing by an adhesive, or moulded or extruded into the casing.
9. A device as claimed in any preceding claim, in which the shielding strip is encapsulated in a protective layer to provide weather-and wear-resistance.
10. A device as claimed in claim 9, in which the shielding strip is located within the casing, such that the casing itself serves as the protective layer.
11. A device as claimed in claim 9, in which the shielding strip is sandwiched between the casing and the layer.
12. A device as claimed in any preceding claim, in which the shielding strip is a sheet or tape material.
13. A device as claimed in any preceding claim, in which the shielding strip material is a sheet of rubber or resin embedded or coated with particles of carbon, metal such as aluminium, beryllium, copper, iron, nickel, silver or stainless steel, or a metal oxide, for example a ferrite.
14. A device as claimed in any of claims 1 to 11, in which the shielding strip is in the form of a material with multiple small openings.
15. A device as claimed in claim 14, in which the shielding strip incorporates wire mesh, knitted wire or perforated sheet.
16. A device as claimed in claim 15, in which the wire mesh, knitted wire or perforated sheet is embedded in or attached to rubber or resin.
17. A device as claimed in any of claims 1 to 11, in which the material of the shielding strip is selected from aluminium foil : cloth coated with nickel ; paint loaded with silver ; mesh formed of copper-clad steel wire or tin plated steel wire ; polyester loaded with aluminium or copper, polyurethane loaded with carbon ; silicone loaded with carbon, iron or iron oxide ; tape loaded with aluminium or tin-plated copper ; and stainless steel foil.
18. A device as claimed in any preceding claim, in which the shielding strip has a thickness in the range 1 pm to 2 mm.
19. A device as claimed in any preceding claim, in which the casing is secured to the phone by a bearing located at the base of the antenna.
20. A device as claimed in any preceding claim, in which the arc covered by the shielding strip is in the range 80 to 1400.
21. A device as claimed in any preceding claim, which includes a second shielding strip disposed on a mounting which can similarly but independently rotate about the antenna.
22. An antenna carrying a shield device as claimed in any preceding claim.
23. A mobile phone having an antenna as claimed in claim 22.