Patent ID: 12224133

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG.1

FIG.1shows an electric power tool101, which, in this case is an electric drill. Electric power tool101is configured to be hand-held by an operative102and operated by an input device103which comprises a push button.

In use, the operative102operates electric power tool101by applying a force to input device103which enables the rotation of drill bit104.

In conventional applications input device103activates a switch which provides an on/off operation of the rotation of drill bit104. However, in the present invention, the input device103provides an improved control for the operative102of the rotation of drill104by means of input device103.

FIG.2

A schematic of electric power tool101in accordance with the present invention is illustrated inFIG.2.

In the embodiment, electrical power tool101comprises an electric circuit201which is connected to a pressure sensitive device202which is connected to the input device103.

Electric circuit201is further connected to the drill bit104of electric power tool101such that a signal can be transmitted to drill bit104to provide an indication of rotation.

In the embodiment, when operative102provides a force to input device103a pressure is applied to pressure sensitive device202which communicates with electric circuit201such that a signal may be transmitted from electric circuit201to provide an output such as the rotation of the drill bit104.

It is appreciated that the invention described herein relates to an electric power tool but is not specifically limited to an electric drill and rotation of drill bit. It is appreciated that the apparatus described herein and specifically the switch mechanism may therefore be utilized in alternative embodiments and alternative power tool and may further be utilized for alternative operations other than the rotation of a device.

For example, in alternative embodiments, the switch mechanism is incorporated into an electric screwdriver which outputs a rotation of the screwdriver in accordance with the invention. In a still further embodiment, the electric power tool may provide an output by means of the movement of a hammer.

FIG.3

An example pressure sensitive device202is shown in exploded schematic form inFIG.3.

In the embodiment, pressure sensing device202is a single point pressure sensor and, in this embodiment provides a resistive pressure sensor.

In the embodiment, pressure sensitive device202comprises a first conductive layer301, a second conductive layer302and a pressure sensitive resistive layer303.

In the embodiment, pressure sensitive resistive layer303comprises a quantum tunnelling material such as that available under the present applicant Peratech Holdco Limited.

Each of the conductive layers301and302comprise a conductive material which, in an embodiment, comprises a carbon ink and/or a silver-based ink.

When a force is applied in the direction of arrow304the force is transmitted from conductive layer301to conductive layer302via pressure sensitive resistive layer303.

Pressure sensitive resistive layer303is configured to exhibit a change in resistance in response to an applied force. In this way, by connecting pressure sensing device to an appropriate electric circuit and measuring the resistive output, a magnitude and/or position of force may be calculated from the output resistance.

FIG.4

An apparatus for providing a switch mechanism is shown in a perspective view with partial cutaway inFIG.4.

Apparatus401comprises a housing402and a pressure sensitive device403mounted to housing402. In the embodiment, pressure sensitive device403comprises a resistive pressure sensor which may be substantially similar to pressure sensitive device202described previously with respect toFIG.3.

In the embodiment, housing402is provided with a groove404which is configured to receive the pressure sensitive device403. This provides a means in manufacture for accurate placement pressure sensitive device403.

Apparatus401further comprises an actuator405which is movably connected to housing402. In the embodiment, actuator405is configured to move along an axis412towards and away from pressure sensitive device403.

Apparatus401further comprises a resilient member406which, in this embodiment, is a spring. Resilient member406comprises a first end407which is connected to actuator405and a second end408which is connected to pressure sensitive device403.

Actuator405is further connected to an input device409which comprises a push button substantially similar to conventional electric tool push buttons.

In an embodiment, apparatus401further comprises a guide rod410which is attached to housing402and fixed to actuator405. Guide rod410is positioned perpendicular to the pressure surface305of the pressure sensitive device403. A second resilient member411is sleeved over the guide rod410. In the embodiment, resilient member411again comprises a spring and is utilized to increase resilience upon application of a force to input device409.

In an embodiment, resilient member411is provided between the actuator405and housing402.

FIG.5

Apparatus401is shown in a cross-sectional diagrammatic view inFIG.5.

In the embodiment, when an operative applies a force501to the input device409, this force is transmitted to actuator405which can move along an axis in the direction of arrow502.

Apparatus401further comprises a positioning structure503which forms part of pressure sensitive device for403and which is attached thereto. Positioning structure503is configured to receive resilient number406at end408. In addition, actuator405comprises a positioning hole504at end407in which resilient member406is also positioned. This ensures that resilient member406is securely positioned to actuator405such that as actuator405moves in the direction of arrow502, resilient member406is substantially retained to actuator405and pressure sensitive device403.

Positioning structure503is provided on pressure surface305of pressure sensitive device403.

The embodiment ofFIG.5further illustrates the guide rod410which is positioned perpendicular to pressure surface305and pressure sensitive device403. As shown, guide rod403is fixed to actuator405at end505. At end506of guide rod410pressure sensitive device403comprises an opening507into which guide rod410is received. In this way, guide rod410does not affect the resistive output from pressure sensitive device403.

In the embodiment shown inFIG.5apparatus401is shown in a rest position in which resilient member406and actuator405are resiliently biased away from pressure sensitive device403by means of resilient member406. Resilient member411, provided between actuator405and the housing of apparatus401also works to bias actuator405away from pressure sensitive device403.

Thus, in this rest position, force501is not transmitted to pressure sensitive device403and the output from pressure sensitive device403does not activate the electric power tool by means of its electric circuit. When force501is applied, an output from pressure sensitive device can be made as will be described further with respect toFIG.6.

FIG.6

A substantially similar view of apparatus401is shown inFIG.6in which force501has been applied by means of input device409to actuator405. The force applied to actuator405has led to resilient members406and411being compressed as illustrated thereby transmitting force501to pressure sensitive device403.

In this way, a change in the electrical signal from pressure sensitive device403can be recorded by means of electrical circuit201which can be utilized to activate the electric power tool, for example, by indicating a rotational speed of drill bit104.

FIG.7

A method of operating an electric power tool incorporating apparatus401described previously is shown inFIG.7.

At step701, a force such as force501is applied to actuator405. In practice, operative102applies a force to input device409which is transmitted to actuator405.

At step702actuator405moves along axis412in the direction of arrow502towards pressure sensitive device403. This compresses resilient member403such that, at step703a force is transmitted to pressure sensitive device403.

At step704, a change in electrical signal from pressure sensitive device403is determined by electric circuit201by utilizing the change in resistance recorded from pressure sensitive device403.

At step705, the output from the electric power tool is altered in response to the change in the electrical signal.

In this way, the pressure sensitive device permits a change in applied pressure to affect the speed, rotation or other parameter in regards to the output from electric power tool.

FIG.8

A further embodiment in accordance with the invention is shown inFIG.8.

Apparatus801provides a switch mechanism suitable for an electrical power tool. In the embodiment, apparatus801comprises a housing802and a pressure sensitive device803which is mounted to housing802. In the embodiment, pressure sensitive device803comprises a resistive pressure sensor and, in this embodiment is a dual-point sensor. This means that pressure sensitive device records an applied pressure at two points of the sensing device.

Apparatus801comprises a first actuator804which is moveably connected to housing802such that actuator804can move along an axis towards and away from pressure sensitive device803in a substantially similar manner to the embodiment of apparatus401.

Apparatus801further comprises a first resilient member805which is substantially similar to resilient member406described previously. Thus, resilient member805is connected at a first end to actuator804and to pressure sensitive device803at a second end.

In a substantially similar manner, housing802comprises a groove806which is configured to receive pressure sensitive device803. Groove806is provided on an inner wall of housing802.

In the embodiment, apparatus801comprises a guide rod807which is attached to housing802and is positioned perpendicular to the pressure surface of pressure sensitive device803. Guide rod807is fixed to actuator804at one end and housing802at the opposite end. Resilient member808is sleeved on guide rod807. Actuator804is resiliently biased away from pressure sensitive device803by means of resilient member805and resilient member808.

In this embodiment, apparatus801further comprises a further resilient member809which is positioned between actuator804and pressure sensitive device803.

A second actuator810is also provided and is connected to an input device811at one end with the opposite end of actuator810abutting against pressure sensitive device803.

Thus, in this way, apparatus801comprises first and second input devices811and812which can be operated by operative102.

In this embodiment, when a force is applied to input device812resilient members805,808and809are compressed to activate separate points on the pressure sensitive device803simultaneously. This provides increased control from the input device812for operative102.

When operative102applies force to input device811, pressure is exerted on pressure sensitive device803in region813thereby providing an alternative response. This therefore gives apparatus801two separate modes which provide an increased range. When applying force to input device811, the lack of resilient members included reduces the effort required by operative102. However, for increased sensitivity input device812may be utilized to provide increased control.