Push button assembly

The present invention relates to a push button assembly, comprising push button means, a switch actuator, and first spring means arranged to bias the switch actuator away from a switch actuating position.

As is well known to those skilled in the art, a push button is a device, which is provided on the control panels of various kinds of electrical devices to operate a switch installed inside a control panel so that the switch is turned on or off.

Figure 1 is a sectional view illustrating a conventional push button. Referring to Figure 1, the conventional push button 2 is installed in a seat depression 1a, which is disposed on a control panel 1. The push button 2 includes a cylindrical button unit 3, which is opened at its lower portion. A rod-shaped switch actuator (or push unit) 4 extends from the button unit 3, and passes through the seat depression 1a to push a switch 6, which is disposed at a predetermined position inside the control panel 1. A spring 5 elastically biases the button unit 3 in a direction away from a bottom of the seat depression 1a.

Thus, when an external force is applied to the button unit 3, the spring 5 is compressed by the external force, so that the button unit 3 and the switch actuator 4 are moved toward the switch 6. Due to the movement of the button unit 3 and the switch actuator 4, an end of the switch actuator 4 pushes the switch 6 so that the switch 6 is turned on or off. When the external force is released from the button unit 3, the spring 5 is returned to its original position, thus returning the button unit 3 and the switch actuator 4 to their original positions.

However, the conventional push button 2 has the problem that, when an excessive external force is applied to the button unit 3, the external force is transmitted through the switch actuator 4 to the switch 6 and a circuit board 7 to which the switch 6 is mounted, so the switch 6 and the circuit board 7 may be damaged or broken.

Furthermore, the conventional push button 2 has another problem that, when a user pushes the button unit 3 to press the switch 6 by the switch actuator 4, a reaction force opposite to the user's force is transmitted through the switch actuator 4 and the button unit 3 to the user, so the manipulation feeling is poor.

US 5,584,384 describes a push button with a moving member movably disposed inside a housing and moveable according to the operational state of the switch.

Accordingly, it is an aspect of the present invention to provide a push button, which is designed such that a switch or a circuit board is not damaged or broken even when an excessive external force is applied to the push button.

Another aspect of the present invention is to provide a push button having an excellent manipulation feeling.

A further aspect of the present invention is to provide an electrical device having the push button, which is designed such that a switch or a circuit board of the electrical device is not damaged or broken even when an excessive external force is applied to the push button.

According to the invention, there is provided a push button as defined in claim 1.

Other aspects of the invention are defined in the dependent claims.

Embodiments of the present invention will now be described, by way of example, with reference to Figures 2 to 6 of the accompanying drawings, in which:

• Figure 1 is a sectional view illustrating a conventional push button;
• Figure 2 is an exploded perspective view illustrating a push button according to the present invention;
• Figure 3 is a sectional view of the push button in Figure 2;
• Figure 4 is a sectional view of the push button in Figure 2, when a normal external force is applied to the push button;
• Figure 5 is a sectional view of the push button in Figure 2, when an excessive external force is applied to the push button; and
• Figure 6 is a sectional view illustrating another push button according to the present invention.

Referring to Figures 2 and 3, the push button 20 is disposed on a control panel 10 of various kinds of electrical devices, and is used to operate a switch 13, which is disposed inside the control panel 10.

A circuit board 12 is installed in the control panel 10 to control the operation of the electrical device. The switch 13 is mounted to the circuit board 12. A circular seat depression 11 is disposed on the control panel 10 in such a way as to be positioned above the switch 13. The push button 20 is mounted to the control panel 10 at the seat depression 11.

In an embodiment of the present invention, the push button 20 includes a button unit 21, a switch actuator (or push unit) 22, a first damping device, and a second damping device. The damping devices may be any of several known to those skilled in the art, such as springs or fluid damping pots. In this embodiment, the damping devices will hereafter be referred to as a first spring 23 and a second spring 24.

The button unit 21 is seated in the seat depression 11. The switch actuator 22 includes a disc (or support part) 22a and a finger (or push part) 22b. The disc 22a is disposed between the button unit 21 and the seat depression 11. The finger 22b extends from the disc 22a to pass through the seat depression 11. The first spring 23 is disposed between the button unit 21 and the disc 22a to absorb an excessive external force applied to the button unit 21 or a reaction force generated from the switch 13. The second spring 24 is disposed between the disc 22a and the seat depression 11 to elastically bias the switch actuator 22 in a direction away from the bottom of the seat depression 11.

The button unit 21 has a cylindrical shape, which is opened at its lower portion. Two locking hooks 21 a extend from a lower end of the button unit 21 so that the button unit 21 is seated in the seat depression 11 in such a way as to be movable by a predetermined distance. Furthermore, two locking holes 11a are disposed at the bottom of the seat depression 11 so that the locking hooks 21 a are movably locked to the locking holes 11a.

The disc 22a of the switch actuator 22 supports a lower end of the first spring 23 and an upper end of the second spring 24 at upper and lower surfaces of the disc 22a, respectively. The disc 22a is designed to be movable in a vertical direction in response to an external force and the interaction between the two springs 23, 24.

The finger 22b of the switch actuator 22 downwardly extends from a centre of the disc 22a, and sequentially passes the centre of the second spring 24 and the bottom of the seat depression 11b. In this case, the finger 22b is installed in such a way that its lower end is spaced apart from the switch 13 by a predetermined distance in a normal state. Thus, when the button unit 21 is pushed by an external force, the external force is transmitted to the disc 22a through the first spring 23. At this time, the switch actuator 22 is downwardly moved to operate the switch 13 so that the switch 13 is turned on or off. In order to allow the finger 22b to pass through the seat depression 11, the seat depression 11 is provided with a through hole 11b at the bottom.

The first and second springs 23, 24 are disposed between the button unit 21 and the seat depression 11 to elastically bias the button unit 21 and the disc 22a. When a normal external force is applied to the button unit 21, only the second spring 24 is elastically compressed to move the switch actuator 22 to the switch 13, so that the switch 13 is turned on or off. However, when an excessive external force is applied to the button unit 21, the first and second springs 23, 24 are elastically compressed, so that the first spring 23 absorbs the excessive external force and the second spring 24 moves the switch actuator 22 to operate the switch 13. For such operations of the springs 23, 24, the first spring 23 has a relatively larger spring constant than the second spring 24.

For a clear description of the drawings, upper and lower positions are designated herein. However, the arrangement of the push button according to the present invention is not limited to these positions.

The operation and effect of the push button according to the present invention will now be described.

Referring to Figure 4, when a normal external force is applied to the button unit 21, the second spring 24, having a smaller spring constant in comparison with the first spring 23, is elastically compressed. At this time, the button unit 21 and the switch actuator 22 are downwardly moved, so the lower end of the finger 22b pushes the switch 13. The switch 13 is thus turned on or off.

Subsequently, when the external force is released from the button unit 21, the button unit 21 and the switch actuator 22 are returned to their original positions by a restoring force of the second spring 24.

When an excessive external force is applied to the button unit 21, the second spring 24, having a smaller spring constant than the first spring 23, is primarily and elastically compressed, in the same manner as when the normal external force is applied to the button unit 21. At this time, the button unit 21 and the switch actuator 22 are downwardly moved, so the lower end of the finger 22b pushes the switch 13 so that the switch 13 is turned on or off.

However, since the external force applied to the button unit 21 in this state exceeds the compression limit of the second spring 24, the excessive external force is not completely absorbed by the second spring 24.

Thus, after the second spring 24 is elastically deformed, the first spring 23 is elastically compressed, as illustrated in Figure 5. When the first spring 23 is elastically deformed as described above, the switch actuator 22 does not move and only the button unit 21 moves downwards, thus effectively absorbing the excessive force applied to the button unit 21.

That is, the excessive force applied to the push button 20 is absorbed by the first spring 23, so the force is not transmitted to the switch 13 or the circuit board 12 to which the switch 13 is mounted.

Furthermore, when a user pushes the button unit 21, a reaction force acting between the switch actuator 22 and the switch 13 is absorbed by the first spring 23, thus providing an excellent manipulation feeling to the user.

Referring to Figure 6, in a second embodiment of the present invention, the push button 20' includes a button unit 21', a switch actuator 22', a first spring 23', and a second spring 24'. During an operation of the push button 20', an external force is applied to the button unit 21'. The switch actuator 22' integrally extends from the button unit 21', and moves along with the button unit 21' to push the switch 13 so that the switch 13 is turned on or off. The first and second springs 23', 24' having different spring constants are integrated into a single structure.

When an external force is applied to the button unit 21', one of the two springs 23', 24', that is, the first spring 23' or the second spring 24' having a relatively smaller spring constant, is primarily and elastically compressed so that the switch actuator 22' operates the switch 13. In such a state, when the external force is further applied to the button unit 21', the other spring 23' or 24' having a relatively larger spring constant is secondarily and elastically compressed, thus absorbing the external force.

As is apparent from the above description, the present invention provides a push button, which is provided with a first spring having a larger spring constant between a button unit and a disc of a switch actuator, thus allowing an excessive external force to be absorbed even when the excessive external force is applied to the button unit, therefore preventing the excessive external force from being transmitted to a switch or a circuit board disposed below the push button.

Furthermore, the push button of the present invention allows a reaction force, acting between the switch actuator and the switch when the switch actuator pushes the switch, to be absorbed by the first spring having a larger spring constant, thus providing an excellent manipulation feeling.