A child resistant lighter may be considered to be a lighter which cannot be operated by a child of age less than five years of age. A child resistant lighter may be considered to be a lighter embodying a mechanism intended to make it difficult to operate by a child.

A gas lighter generally comprises a reservoir for liquified hydrocarbon gas or other fuel, a valve on the reservoir for controlling release of the fuel, an actuating system for opening and closing the valve and an ignition system. A conventional ignition system comprises a pyrophoric flint cooperating with a spark wheel. The spark wheel is mounted on axis between two thumb wheels. The spark wheel may be cylindrical in shape and the thumb wheels usually have a slightly greater diameter than the spark wheel. The rims of the thumb wheels are usually roughened or may have teeth so that they may be rotated easily by a user's finger or thumb. When the spark wheel is rotated with sufficient force and speed against the flint a spray of sparks is created.

Previous attempts to make child resistant lighters have involved mechanisms which are complex to operate and which require a higher operating force or are not very efficient. The protection afforded by such lighters may be uncertain leading to a risk of product recalls and difficulties in meeting the criteria for regulatory approval.

Other lighters are not acceptable because they are too difficult to operate.

According to the present invention a gas lighter having a security ignition system comprises a reservoir containing combustible fuel: a valve to control release of gas from the reservoir; a mechanism for opening the valve; and an ignition arrangement comprising a flint cooperating with the spark wheel, the spark wheel being operable by at least one thumb wheel mounted

coaxially with the spark wheel and arranged so that rotation of the thumb wheel causes rotation of the spark wheel to ignite gas released from the valve; wherein the thumb wheel is connected to the spark wheel by a resilient coupling means so that the spark wheel is not caused to rotate during initial rotation of the thumb wheel through a first angle, but wherein further rotation of the thumb wheel (or when the torque applied exceeds a predetermined value) the coupling means to engages the spark wheel rotating the spark wheel against the flint.

In a first preferred embodiment the first angle is in the range about 30-120° preferably about 60-100°, more preferably about 90°.

Rotation of the spark wheel is impeded by friction with the pyrophoric flint so that the spark wheel needs to be rotated with sufficient torque to overcome the frictional force in order to generate a spark.

When an adult actuates a lighter the thumb wheel may be rotated through an angle of 135-270°. However, a child's thumb is smaller so that pressure and rotation can only be applied for a shorter duration, so that the thumb wheel can only be rotated through a smaller angle than the first angle, insufficient to cause ignition on the lighter of our invention. Similarly a child using a finger tip may not be able to rotate the thumb wheel through a sufficient angle to cause ignition on the lighter of the present invention.

In a first embodiment of the invention at least one thumb wheel is coupled to the spark wheel. Alternatively, both thumb wheels may be coupled to the spark wheel.

Preferably the torque required to rotate the thumb wheel during the first rotation is about 0.06N. m, that is less than the torque required to produce the spark.

In preferred embodiments when the thumb is removed from the thumb wheel or wheels after ignition the resilient coupling means causes the thumb wheel or wheels to rotate backwards to the original position. This resets the ignition mechanism for re- use.

The resilient coupling means preferably includes or comprises an elastic element connecting at least one of the two thumb wheels to the spark wheel.

In a first preferred embodiment the resilient coupling means is a spring, preferably a helical spring, the first end of which is connected to the thumb wheel and a second end of which is connected to the spark wheel.

Preferably the thumb wheel includes a circumferential slot with abutments at each end, a first end of the spring being received in the slot so that the spring may rotate freely between the abutments as the wheel is rotated though the first angle. The angular distance through which the wheel may rotate between the abutments is preferably equal to the said first angle. In this way the thumb wheel can rotate freely before engagement of the spring. Alternatively, the angular distance may be less than the first angle so that the spring may be tensioned before the spark wheel is engaged.

The spring may comprise a cylindrical helical coil having first and second ends, the first end extending longitudinally to engage the second thumb wheel and the second end extending radially to engage the spark wheel.

In a preferred embodiment the spring is received on an axial shaft connected to the second thumb wheel, the first end of the spring being engaged in an aperture or abutment of the first thumb wheel. The arrangement of the slot or abutment permits free rotation of the thumb wheel through the first angle while the coils of the spring are tightened. The rotation and tensioning of the spring by further rotation of the thumb wheel causes the coils of the spring to contract radially so that the coils grip the shaft so that the spring is held firmly. In this embodiment the outer surface of the spring may be roughened or toothed to form a spark wheel for engagement with the flint as disclosed in US-A-4509916; the disclosure of which is incorporated herein by reference.

The coupling between the thumb wheel and the spark wheel may comprise an elastomeric member having a first portion secured to the thumb wheel and a second portion secured to the spark wheel and arranged so that rotation of the thumb wheel causes the resilient member to distort creating a restoring force resisting further

rotation of the thumb wheel. The restoring force preferably urges rotation of the thumb wheel back to the starting position and also that the thumb wheel returns to the starting position when a user's thumb is released.

The second thumb wheel may have a formation adapted to engage a complimentary formation of the spark wheel to permit free rotation of the thumb wheel through the said first angle but to cause the spark wheel to be engaged and rotated against the frictional force of the flint by further rotation of the thumb wheel.

Preferably a projection extending from the second thumb wheel is received in a circumferential slot in the spark wheel, the angle of the circumferential slot being selected so that the spark wheel is engaged following rotation of the thumb wheel through the first angle.

The elastomeric member may be composed of rubber or similar resilient material capable of withstanding repeated twisting forces.

In an alternative embodiment the distance between adjacent coils when the spring is relaxed is selected so that the coils are brought into contact when the free end of the spring is rotated through said first angle, preventing further tightening of the spring so that the second end rotates with the further rotation of the first end.

The invention is further described by means of example but not in any limitative sense with reference to the accompanying drawings, of which: Figure 1 is a cross-section view of a thumb wheel and striker wheel assembly in accordance with this invention.

Figures 3 and 4 illustrate the thumb wheels of the arrangement shown in Figures 1 and 2. Figure 5 illustrates the striker wheel of the arrangement shown in Figures 1 and 2.

Figure 6 illustrates the spring shown in Figures 1 and 2.

Figure 7 illustrates an alternative thumb wheel and striker assembly in accordance with this invention.

Figure 8 illustrates the components of the assembly shown in Figure 7.

Figure 9 is a prospective view of the resilient member shown in Figures 7 and 8.

Figures 10 and 11-as exploded views of the assembly shown in Figure 7 are cross- section views of a further embodiment of the invention.

Figures 14 and 15-illustrates the tensioning of the spring in the embodiment shown in Figures 12 and 13.

Figures 1 to 6 show the thumb wheels and spark wheel arrangement of a first lighter in accordance with this invention.

A first thumb wheel (1) comprises a shaft (2) and a cylindrical wheel (3) having a roughened or knurled periphery (4). A helical spring (5) having a longitudinally extending first end (6) and a radially extending second end (7) is located on the shaft (2). The spark wheel (11) has a roughened or toothed circumference. (12) to generate sparks when rotated against a pyrophoric flint (not shown) in conventional manner.

A second thumb wheel (13) has a knurled or roughened periphery (14) and includes a socket or bore (15) arranged to receive a first end (6) of the spring so that the first end of the spring and second thumb wheel are constrained to rotate together.

The second end of the spring (7) is received in a radial slot (16) in the spark wheel so that the second end of the spring is constrained to rotate with the spark wheel.

A circumferential slot (17) is arranged to receive a lug or projection (9) extending towards the spark wheel from the first thumb wheel. The circumferential slot (17) allows free rotation of the first thumb wheel through a first angle of about 30-120°, preferably about 60-100° more preferably about 90° before it engages the lug or projection and causes the spare wheel and thumb wheel to rotate together.

In use of the lighter the user rotates the thumb wheels with his thumb. During the initial rotation through the first angle, the torque applied to the spark wheel by the spring is insufficient to generate sparks. However at the end of the first rotation the lug (9) engages the abutment at the end of the circumferential slot forcing the spark wheel to rotate with a higher torque to generate sparks to ignite the gas flow.

When the thumb wheels are released the tension in the spring drives the thumb wheel back to their original location relative to the spark wheel resetting the mechanism for further use.

Rotation through a small angle less than the first angle for example by a child does not cause generation of sparks and consequently reduces the risk of injury.

Figures 7 to 11 show a second embodiment of the invention. The first thumb wheel (20) has an axial shaft (21) which engages second thumb wheel (22 when rotated by the action of a user's thumb on roughened circumferential portion (23) and (24). A spark wheel (25) mounted for rotation on shaft (21) has a toothed periphery (26) for engagement with a pyrophoric flint (not shown) in a conventional manner. A lug (31) extends inwardly from the second thumb wheel (22) to engage within a circumferential slot (30) in the side of the spark wheel. The spark wheel can rotate until lug (31) abuts a corresponding end of the slot (30) following rotation through a first angle. Further rotation of the thumb wheel urges rotation of the spark wheel causing generation of sparks and ignition of the lighter. Thus the angle of the circumferential slot (30) is equal to the first angle.

A resilient member (27) composed of rubber or other elastomeric material has outer teeth (29) for engagement within the inner face of the first thumb wheel (20). Four inwardly projecting lugs (28) extend towards the strike wheel and engage in slots between outwardly facing lugs (32) on the adjacent face of the spark wheel. The angular rotation of the thumb wheel generates an insufficient force through the tensioning of the resilient member (27) to cause the spark wheel to rotate against the friction caused by the pyrophoric flint. When the thumb wheels have rotated through the first angle the abutment between the lug (31) and the end of the circumferential slot (30) forces the spark wheel to rotate generating sparks. Release of tension

between a users thumb and the thumb wheels allows the resilient member to rotate the thumb wheels in a reverse direction resetting the striking mechanism. Thus a person requires sufficient strength to rotate the thumb wheels through the first angle and to continue the rotation to generate sparks. A child having a smaller finger or thumb will have difficulty in maintaining the necessary prolonged rotation of the thumb wheel.

Figures 12 to 15 show a third embodiment of the invention. A first thumb wheel (40) has an axial shaft (43) received in a socket (44) of the second thumb wheel (41). A spring (42) having a roughened or toothed outer surface provides a strike wheel for engagement with a flint (46). A first end (45) of the spring is received in an aperture (47) of the first thumb wheel, the angular location of the slot being selected so that the thumb wheels may rotate freely through the first angle without causing ignition of the lighter. Further rotation of the thumb wheels causes the end (45) of the spring to abut against an abutment at the end of slot (47) tensioning the spring. During this tensioning the spring contracts radially as shown in figure (13) so that the core (44) of the second thumb wheel is gripped causing the spring (42) to rotate generating a spark and igniting the lighter. Release of the thumb wheels allows the first thumb wheel to rotate backwards to reset the lighter for further use.

A lighter in accordance with this invention may be arranged to generate a spark when the torque applied to the thumb wheel (s) exceeds a predetermined value, without need for engagement of the resilient member, particularly a spring, with a lug or abutment of the thumb wheel.