push button box

Abstract: Procedure for the generation of control signals in a push button box designed e.g. for the control of a crane and comprising at least one push button element, and a push button box implementing the procedure. For the generation of control signals, signals representing the position of the push button element (4) are transferred by non-contacting means from the push button element to a signal generating unit (7a,7b, 21-26) which produces control signals proportional to the position of the push button element (4).

Description: The present invention relates to a push button box the generation of signals. For generating two-step, multi-step or stepless control signals, there is currently no light-weight push button box of absolutely air-and-watertight construction that would also be suited for one-hand control. Such a control box is needed e.g. for an overhead travelling crane provided with a hanging push button box for stepless or stepwise motion control. In certain push button boxes in current use, two-step or multi-step control is based on the utilization of the time differences between the contact actions of contact elements located at different levels in the direction of deperession. In such a solution, contact elements located at different levels produce an output signal at different instants depending on the depth of depression of the button. There are also control boxes that use a handle mounted on a shaft passing through the box and, when the handle is turned, actuating a contact element with several contacts in the box in a stepwise manner, functioning much like a camshaft. The shaft may also be used to drive a signal source, such as a potentiometer, which supplies a stepless or a stepwise signal that is dependent on the angle of displacement of the control handle. In special environments, e.g. wet spaces or spaces containing explosive substances, where the push button box has to be well sealed, the sealing increases the cost because every hole made in the box shell for the control gear has to be separately sealed in accordance with the environmental classification of the locality in question. The motion required for the depression of single-step push buttons can nowadays be transmitted through a membrane or a flexible covering on the contact elements, thus rendering the enclosure of the push button box sufficiently tight and obviating the need for making and sealing a hole. There are also push buttons which use the Hall effect to produce 0-1 signals. Employing this principle makes it possible to achieve a good tightness of the box enclosure, because the push button incorporates no moving parts. Further, DE-A-3008561 proposes a push button construction based on the bistable nature of a magnetic field. However, these principles cannot be reasonably applied to construct push buttons with multi-step or stepless control signal functions for use in enclosed control boxes. A normal requirement concerning a push button used for stepless or stepwise control of crane movements is that it should give the user a good feel of the position of the operating arm employed. This feature is difficult to implement with currently used push button constructions because the feel of position in these constructions depends on several factors, e.g. possible bearing suspension of the operating arm and of the shaft going through the control box, counter forces presented by the contact elements, etc. In the control box constructions currently used, the relatively large size of the contact elements for stepwise control or of the signal transducer for stepless control, the shafts going through the box enclosure and the sealing arrangements needed to ensure a tightness corresponding to the environmental conditions, and the devices needed to produce the required feel of step are all factors increasing the weight of the control box. Besides being heavy, such a control box is ill adapted for one-hand operation. US-4,366,463 discloses a push button box according to the preamble of claim 1 wherein several push buttons are mounted in a box-type cut-out which is to be mounted at the enclosure of a signal generating means. The box shaped cut-out may be environmentally sealed to the enclosure. In the box shaped cut-out the push bottoms are Hall effect switches which communicate with signal generating units located under the box shaped cut-out. GB-A-2 010 588 discloses a handheld push button box wherein several push buttons are mounted in a longitudinal cut-out so that the upper side of each push button is essentially in line with the outer circumference of the enclosure of the push button box. The object of the present invention is to eliminate the drawbacks referred to above and to achieve a push button control box construction that provides an improved tightness of enclosure and a better feel of operating arm position and is also light enough to enable the control box to be used without difficulty with one hand only. The push button box according to the invention is characterised in claim 1. Preferred embodiments of the invention are presented in the subclaims. The invention provides the following advantages : Improved tightness of the control box construction, resulting from the fact that no actuating elements penetrating the box enclosure are used. Long functional life, resulting from the fact that the control box of the invention employs no movable electrical actuating elements. Therefore, the durability of the device of the invention is determined by the durability of the rocker arm of the push button, typically of the order of 20.10⁶ operations. Light weight, resulting from the absence of contact elements and the use of a small-size card-mounted electronic component for detecting the push button position. Excellent feel of position of the push button element, resulting from the fact that the equipment determining the feel, such as counter springs and the rasters needed for stepwise control, can now be manufactured considering only the requirements dictated by the desired feel of position. Thus, the construction of the invention is free of the frictional forces, counter forces of contact elements etc. affecting the feel of position in existing constructions. Good ergonomic properties of the push button box, resulting from the fact that the box construction lends itself to effective utilization of the wrist and thumb motions suited for actuating a lever resembling a rocker arm. In the following, the invention is described by the aid of an example, reference being made to the drawings attached, wherein: Figures 1a and 1b illustrate the construction of the push button box of the invention as applied for the control of three crane movements. Figures 2a and 2b illustrate the construction of a single push button in the push button box of the invention. Figure 3 illustrates the signal processing in the push button box of the invention. Fig. 1a is a front view and Fig. 1b a lateral view of the push button box 1, the enclosure 2 of which is provided with cup-shaped cut-outs 3 in which the push buttons 4 are mounted. The rear side of the enclosure 2 of the push button box 1 is provided with finger stoppers 5 designed to help the user get a firm and correct grip of the control box. Inside the control box 1 is a circuit card 6 which accommodates four position sensing elements 7a and 7b for each button. These sensor elements perceive the position of the button 4 through the enclosure 2 of the control box 1. The circuit card also accommodates a signal processing circuit 21 - 26 which takes care of further processing of the signal provided by the position sensors 7a,7b. The push button box 1 can be equipped as a wireless control box, in which case it is provided with a radio transmitter 9 with an atenna either inside or outside the box. For crane control, the signals can be transmitted to the crane - preferably in serial form - through a cable 19, the box enclosure being provided with a cable gland 18. Instead of a radio transmitter 9, it is also possible to use other types of wireless transmitter, e.g. an infrared transmitter or an induction transmitter. Fig. 2a shows a lateral view of a push button 4 placed in a cup-shaped cut-out 3 in the enclosure 2 of the control box 1, and Fig. 2b a section along the line A-A. The push button 4 comprises a rocker arm 10 mounted on a shaft 11 supported by bearings in bearing housings 12 in the box enclosure. Attached to the rocker arm 10 are two magnets 13 which, when either end of the rocker arm is depressed, move orbitally about the shaft 11, resulting in a change in their distance from the circuit card 6 and the four sensor elements 7a,7b measuring the magnetic field. The use of two magnets 13 and four sensors 7a,7b measuring the magnetic field ensures that the magnitude and direction of the change of the field are correctly interpreted by the signal processing circuit 21-26, although in principle one magnet and two field measuring elements would suffice. The push button 4 is also provided with a spring return device 14 to return the rocker arm to the mid-position and to produce a feel of step. The spring return device consists of a spring 15 and its mounting accessories 16 and 17. One end of the spring return device is attached to the rocker arm 10 and the other end to the cup-shaped cut-out 3 in the box enclosure. The device returns the rocker arm 10 to its mid-position when the user looses his hold of the arm. A stepping button output signal can be generated by the circuit card 6, so that it is not strictly necessary to use a rocker arm construction providing a feel of step. The push button 4 can easily be provided with a mechanism producing a feel of step. However, such mechanisms are already known in the art and are therefore outside the scope of the present invention. Fig. 3 illustrates the signal processing in the push button box 1. The equipment needed for crane control are the signal processing devices 7a and 7b and 21 - 26 in the push button box, a signal transmission line 27 and a signal receiver along with its actuators in the electrical control cabinet of the crane. Attached to the push button 10, which is of the rocker-arm type, is a magnet 13. Mounted on the circuit card under the push button are two sensor elements 7a and 7b, e.g. Hall elements, sensitive to the strength of the magnetic field. The sensors 7a and 7b are so placed on the circuit card 6 that, when the push button 10 is in its rest position, the magnet 13 is located symmetrically relative to the sensors 7a and 7b, and that the sensors 7a and 7b are located in the direction of the path of the magnet 13 when it is deviated from the rest position. In the symmetric position (rest position) of the magnet 13, the signals generated by the sensors 7a and 7b are about equal. When the push button 10 is depressed, the magnet 13 attached to it is also deviated from its symmetric position relative to the sensors 7a and 7b. This results in an increase in the strength of the signal generated by that sensor (e.g. 7a) which is now closer to the magnet. Correspondingly, the signal of the other sensor (e.g. 7b) becomes weaker because the distance to the magnet has increased. The signals produced by the sensors 7a and 7b are fed into an amplifier 21 to facilitate further processing of the signals. For reasons of safety, each control signal needed for the control of a crane is generated in duplicate by providing each push button with two magnets, each of which has its own path and its own pair of sensor elements on the circuit card. Thus, a complete push button comprises two magnets and, correspondingly, four sensor elements on the circuit card. The assembly of one magnet, the two sensor elements provided for it and the amplifier unit required by these can be called a signal channel of the push button. In crane applications, two such channels are needed for each button. The signals of all sensor elements 7a,7b are amplified by the amplifier unit 21, whereupon a multiplexer unit 22 selects one of these signals in rapid succession for input to an A/D converter. The data processing unit typically uses a microprocessor, e.g. Intel 80535. The function of the processor is to take care of saving the data as required and to check that the signals obtained from the sensor elements 7a and 7b are acceptable. The signals are checked in two ways: 1. The signals provided by the two sensor elements in one signal channel of a push button must be equal in magnitude - with a predetermined accuracy - but opposite in sign. 2. The information provided by each channel of a push button must be in agreement with the information provided by the other channel. In addition, the processor checks that the signals are within the allowed signal range. Checking the signals for correctness and acceptability as explained above makes it possible to identify e.g. an extraneous ferromagnetic particle causing interference when it gets into the magnetic field measured by the sensor elements 7a and 7b. This improves the operational safety of the push button box in the control of a crane. The momentary button position data produced by the data processing unit 24 are then applied to a parallel-serial converter 25, which converts the position data into serial form. The data processing unit 24 also adds supplementary information to the control signals, to enable the receiver to verify that the information was correctly transmitted and to enable the control signals to be directed to the appropriate drives. As the transmission line to the crane is generally quite long, the serial signal is amplified by a line amplifier 26 before it is passed to the signal bus 27. The signal bus 27 may be an electrical or an optical data transmission cable 19, a radio transmitter 9 or some other type of wireless transmitter, e.g. an infrared or an induction transmitter. A receiver unit 28 incorporated in the crane processes the signal obtained from the signal bus 27 to give it the form required for the control of the crane movements. A serial-parallel converter 29 arranges the serial data so as to produce distinct control signals that can be applied to the various crane motor drives. The converter also identifies the signals used for verifying whether the data transfer was successful or not. If this verification indicates that an error has occurred in the transmission, suitable means are employed to prevent the use of erroneous signals in the control of the crane. Such means may include e.g. triggering a signal relay 31 to open the main switch of the crane. The signals needed for the control of the crane movements are converted to an analog form by a D/A-converter and then directed as control signals to the appropriate crane motor drives. Besides stepless motion control, the signal transmission procedure described above can also be applied in the transmission of single-step ch data or multswitch data or multi-step control signals from the push button box to the crane. These signals can be passed directly to the parallel-serial converter 25. At the receiving end they are available as relay signals 31 controlled by the outputs of the serial-parallel converter 29. The invention is also applicable in the case of fixedly mounted push button boxes.

Claims: Push button box for the generation of signals, said push button box comprising a plurality of push button elements (4) located outside of an enclosure of the push botton box in at least one cut-out (3), and a signal generating unit (7a,7b,21-26) located inside of the enclosure (2) adjacent the cut-out for the generation of control signals, which unit receives the signals representing the position of the push button element by non-contacting means and generates control signals proportional to the position of the push button element (4), that a partition between the push button element (4) and the signal generating unit (7a,7b,-21-26) is formed by the enclosure (2) of the push botton box, characterized in that each push button element (4) is located in an own corresponding accommodated cup-shaped cut-out (3) at the outside of the enclosure (2) of the push button box, and that the depth of the cut-out (3) corresponds essentially to the heights of the push button element (4). Push button box according to claim 1, characterized in that the partition is essentially rigid and unmovable. Push button box according to one of the preceding claims, characterized in that each push button element (7) has two movable ferromagnetic parts (13) located in the cut-out (3), whereas the signal generating unit (7a, 7b, 21-26) comprises four elements (7a, 7b) for measuring the magnetic fields inside the enclosure (2). Push button box according to one of the preceding claims, characterized in that the push button element (4) consists of a rocker arm (10) mounted on a shaft (11) supported by bearings in bearing housings (12) in its cut-out (3) of the push button box. Push button box according to claim 4, characterized in that the push button element (4) is provided with a spring return device (14) to return the rocker arm (10) to its middle position. Push button box according to any one of the preceding claims, characterized in that the push button box is so designed that each push button element (4) is placed in a box section which is at a certain angle to at least one other box section, and that each box section is provided with a protrusion (5) in the box enclosure (2) to help the user get a correct handgrip of the box.

Inventors: JUSSILA OLAVI, SEITSONEN JUHA, JUSSILA, OLAVI, SEITSONEN, JUHA
Applicants: KONE OY
Application year: 1989
Main classification: H01H9
IPC codes: H01H9, B66C13