Interchangeable coded key pad assemblies alternately attachable to a user definable keyboard to enable programmable keyboard functions

This invention relates to keyboards and, more particularly, to interchangeable key pad assemblies for providing at least a portion of a user keyboard. Specifically, one embodiment of the invention provides interchangeable key pad assemblies that are coded so that when they are alternately installed on a keyboard, one of a variety of programmable sets of keyboard functions is enabled for selection by user actuation of the keys.

One exemplary use of the invention is in association with molded rubber keyboards. Molded rubber keyboards have been used in combination with underlying printed circuit boards to provide a keyboard structure much less expensive than those where each key requires a separate push button member separately mounted in a frame. The term "rubber," as used in this specification and in the claims, refers not only to synthetic and natural rubbers, but also to other elastomeric materials.

Molded rubber keyboards usually comprise a rubber sheet integral with upwardly projecting rubber keys. Each rubber key is located above a recess in the sheet and its lower end includes such means as conductive rubber members for closing the switch contacts on the printed circuit board located directly below it. The recesses form a diaphragm which acts to space the conductive rubber members above the printed circuit board, except when a particular key is pressed.

Church, U.S. Patent No. 4,764,770, for example, discloses a keyboard assembly which has a printed circuit board providing a series of switch contacts and a molded rubber keyboard providing a rubber base sheet overlying the printed circuit board and having a series of rubber keys integral with the base sheet. Each key has contacts on its bottom surface for closing each of the switch contacts when its key is depressed. Stabilizing membranes prevent the keys from wobbling or binding. Although undesirable wobbling or binding is substantially eliminated, the keyboard is either a dedicated keyboard or one whose key functions are determined by the system to which the keyboard is mounted.

US-A-4 020 328 discloses an auxiliary keyboard apparatus that comprises a removable keyboard which has no structure for automatic configuration of the system. That is, this auxiliary keyboard apparatus is not coded. Therefore, this auxiliary keyboard apparatus requires manual data entry to an associated processor in order to identify different keyboards.

US-A-4 626 830 discloses a membrane keyboard in which there does exist a structure for keyboard coding. Specifically, the membrane keyboard comprises conductive traces between first and third pin positions and second and third pin positions, respectively, on the membrane. That is, the membrane keyboard disclosed in US-A-4 626 830 comprises a hard-wired coding structure integral with the membrane itself to effect direct electrical contact between the first and third pin positions and/or the second and third positions for keyboard coding.

DE-A-27 23 736 discloses a keyboard having an array of switches and an exchangeable cover plate. The cover plate extends over a part of the switches to prevent an actuation of those switches which are not required for a specific keyboard function.

Previously, overlays have been used to provide the user with identification of key functions for programmable or customizable key sets. Overlays are commonly used on computer keyboards and calculators. The typical overlay construction is a thin plastic sheet with screen-printed information. This material is not very durable and can be easily damaged.

Furthermore, these overlays typically are not securely attached to the computer keyboards and calculators. Consequently, they are easily dislodged and slide from the keyboard, frustrating the user. Also, the functions of the keys are dedicated or determined by the computer or calculator since the overlay does not operatively interact with the system.

Thus, the invention is based on the object of providing a custom key panel which allows the key functions to be tailored to a desired mode of operation.

This object is achieved by a custom key panel in accordance with claim 1.

Summary of the Invention

One embodiment of the present invention provides interchangeable key pad assemblies that are coded so that when they are alternately installed on a keyboard, one of a variety of programmable sets of keyboard functions is enabled for selection by user actuation of the keys. Each key pad assembly has a durable construction and is securely attachable to the remainder of the keyboard. Each key pad assembly is installed on the remainder of the keyboard and interfaces with the system with which the keyboard interacts, preferably a programmable system, to provide a custom key panel for the user so that key functions can be tailored to a desired selection of operations available to the user upon actuation of the keys.

The custom key panel in accordance with the invention is less prone to damage than an overlay, is securely attached, and imparts flexibility to the mechanical configuration of keys. The flexibility in configuration provides the user only the necessary function keys for the particular application. This provides a less cluttered panel for an improved human interface.

Brief Description of the Drawings

The above and other features of the invention and the concomitant advantages will be better understood and appreciated by persons skilled in the field to which the invention pertains in view of the following description given in conjunction with the accompanying drawings. In the drawings:

• Fig. 1 is an exploded view of one embodiment of a custom key panel in accordance with the invention;
• Fig. 2 is an electrical schematic drawing of the custom key panel shown in Fig. 1;
• Fig. 3 is a detailed drawing of a rubber keypad associated with the custom key panel shown in Fig. 1;
• Fig. 4 is a detailed drawing of a front panel of an interchangeable key pad assembly associated with the custom key panel shown in Fig. 1;
• Fig. 5 is a detailed drawing of a subpanel of an interchangeable key pad assembly associated with the custom key panel shown in Fig. 1;
• Fig. 6 is a detailed drawing of a spring retainer associated with the custom key panel shown in Fig. 1;
• Fig. 7 is a detailed drawing of a key adapter for allowing conventional keys to be incorporated into the custom key panel shown in Fig. 1; and
• Fig. 8 is a cross-sectional view of an interchangeable key pad assembly installed on the custom key panel shown in Fig. 1.

Detailed Description of the Preferred Embodiments

The custom key panel in accordance with the invention is an assembly of parts that preferably allows an interchangeable key pad assembly to be associated with system keyboard means to provide one of a variety of sets of key functions available to the user. The custom key panel provides direct execution of commands that typically are most frequently selected by the user.

In one embodiment, the custom key panel does not make an electrical connection when plugged in. It mechanically actuates switches for addressing a processor in the system with a unique identification code for each interchangeable assembly. This provides a very reliable system.

One embodiment of the custom key panel in accordance with the invention is generally indicated by the numeral 10, as shown in Fig. 1. The custom key panel 10 preferably comprises switch means 12 in the form of user selectable key means 14 and actuable key decoding means 16.

The custom key panel 10 also preferably comprises key means 18 selectively mountable in relation to the switch means 12 for actuating the switch means. The key means 18 preferably comprises mechanical switch actuating means comprising at least one key 20 which is selectively actuable by the user. The key means 18 also comprises key encoding means 22 which actuates the key decoding means 16 when the key means is mounted in relation to the switch means 12 for identifying the function selectable by the user when at least one key 20 is actuated by the user.

The switches 14 and 16 are preferably conductive rubber members 24 or pellets compression molded into a sheet 26 of non-conductive rubber, forming the keypad or matrix of switches. The conductive members 24 are held above traces 28 on a printed circuit board 30 by the non-conductive rubber sheet 26. When a switch 14 or 16 is depressed, the conductive member 24 shorts the traces for that location and is acknowledged by the processor as a closed switch.

There are preferably six binary address switches, which allow 64 possible custom key panel key function options. The six address switches are arranged in the same matrix as hole locations on a subpanel 32 of the custom key panel assembly. The subpanel 32 can hold down an address switch 16 (ensuring closure) when there is no hole.

The configuration of each address switch 16 allows overtravel or compression of the rubber actuator without exerting excessive force on the assembly. This ensures switch closure under worst case tolerance stack-up and bowing of the subpanel 32 and the keyboard. The address switches 16 preferably have a small travel of 0.5 mm to closure, then a large overtravel of 3.0 mm. The travel of standard key switches is typically 1.7 mm with no overtravel.

The custom key panel 10 preferably allows an interchangeable key pad assembly 18 to be plugged into a front bezel 40 of an electronic instrument, such as the HP 70004A modular measurement system display/mainframe, to provide one of a variety of sets of key functions available to the user. The key pad assembly 18 is preferably retained in the bezel 40 by a mechanical spring 42. The spring 42 is installed from the backside of the bezel 40 and is retained by the key pad. The spring 42 latches over the edge of the subpanel 32 to retain the right side of the assembly. The left side is sandwiched around a shelf 44 in the bezel 40.

The key pad assembly 18 is installed by aligning the left side to the shelf 44 on the bezel 40, then rotating the assembly around the shelf like a hinge until the spring 42 latches. The operation is similar to closing a door.

To remove the key pad assembly 18, an opening 46 is provided in the front panel to insert a tool, such as a screwdriver blade. As the screwdriver is pushed into the opening 46, the spring 42 is forced away from the subpanel 32, which disengages the key pad assembly 18. The key pad assembly 18 is then forced away from the key pad by another portion of the spring, and any residual force from the depressed address switches 16. The key pad assembly 18 comes to rest at a sufficient distance away from the bezel 40 to provide finger clearance to grab the key pad assembly 18 for removal.

The key pad assembly 18 preferably utilizes conventional keycaps 50. The keycaps 50 are typically double shot injection molded keys with nomenclature integral to the keycap. Each keycap presses onto an adapter 52 allowing the keycap to function in the key pad assembly 18. Designers of custom key panels can modify these tools to create unique keycaps for each application.

This affords a great amount of flexibility to the design of future key panels. There can be, for example, fifteen separate keys. These can be either half wide keycaps or quarter wide keycaps. Or there can be as many as three double wide keycaps used in the far left column (major user keys) with the remaining nine locations either half or quarter keys. The front panel can be screen-printed to provide any required identification of the key functions.

When the custom key panel is removed from the instrument, the keycaps are preferably captivated and can not fall out. This is accomplished by providing the subpanel 32 with apertures 60 into which the keycaps 50 connected to the adapters 52 are deposited. A front panel 62 having apertures 64 is then placed over the subpanel 32 and the keycaps 50 so that the apertures 64 align with the keycaps. The front panel 62 also includes welded studs 66 in which are fitted spacers 68. The studs 66 extend through holes 70 in the subpanel 32, and nuts 72 are threaded on the studs to hold the key pad assembly 18 together. The key pad assembly is rugged and durable enough to withstand damage during abusive handling outside of the instrument.

This invention has many advantages beyond what overlays can offer. Where flexibility, reliability, durability, and optimized human interface are desired, this invention is an ideal solution. There are numerous applications that can benefit from using a custom key panel in accordance with the present invention.

The foregoing description is offered primarily for purposes of illustration. One modification is to mold the entire key pad assembly 18 from a plastic material. In another contemplated embodiment, the address switches can be replaced by electrical address coding means, such as a diode matrix or read only memory.