AN ARRANGEMENT FOR A SWITCHBOARD DESK

Abstract: A switchboard desk is equipped with a desk-top which can be raised and lowered and at least two telescopic legs (5, 6). The desk comprises devices which effect the raising and lowering of the top, and devices which control the effective devices. The effective devices comprise at least two hydraulic cylinders each positioned in its respective telescopic leg and connected to a hydraulic pump (9). The latter is driven by means of an electric motor (E). The controlling devices comprise manually actuated devices (S2, S3) which switch on the electric motor to rotate in either direction according to the way they are actuated. A potentiometer (P) monitors the rotation of the electric motor and controls a digital voltmeter to make possible the indication of the position of the desk-top above a reference level.

Description: Title: An Arrangement for a Switchboard Desk Technical Field The present invention relates to an arrangement for a switchboard desk with a desk top which can be raised and lowered. The desk top is equipped with two or more telescopic legs. The arrangement comprises a device which effects the raising and lowering of the desk top and devices to control the said effective devices. State of the Art . It is already known to make desks with a desk-top- and a leg framework such that the desk-top can be raised and lowered in conjunction with manual influencing de¬ vices. It is also known to provide electric motors in the respective telescopic legs of a desk which can be raised and lowered,to effect the raising and lowering of the desk-top. The said electric motors are controlled by electrical circuits. Code plate devices are provided on the telescopic legs for monitoring the. actual position of the desk-top and in addition indicating devicds are provided to enable the desk-top height to be read off from the upper side. Description of the Invention The Technical Problem There is an overall aim with this kind of desk to obtain a technically simple and yet satisfactorily func-. tioning design for the various parts of the desk. One requirement in this connection is for few components in the control devices and in .the effective devices. To provide, for example, electric motors on at least two of the telescopic legs of the desk complicates the con¬ struction and is relatively expensive at the same time. The Solution The main object of the present invention is to pro¬ pose an arrangement which solves, amongst other things, the above-mentioned problems. It can be considered essentially characteristic of the new arrangement that, amongst other things, the effective devices comprise at least two hydraulic cylinders each positioned in its res¬ pective said telescopic leg and connected to at least one hydraulic pump which can be driven by means of an electric motor. It is a further characteristic of the subject of the invention that the controlling devices comprise manually actuated devices which switch on the electric " motor to rotate in either direction according to the way they are actuated, and that a device monitor¬ ing the rotation of the electric motor actuates indicat¬ ing devices which show the position of the desk-top above a reference level which may be formed by the floor on which, the desk is set up. Further developments of the principle of the inven¬ tion relate to more detailed information on how the various parts of the apparatus should be constructed. Thus, in a preferred embodiment the devices monitoring the rotation of the electric ' motor consist of potentio¬ meter devices which supply voltage to a digital volt- • meter, the outputs of which are connected or may be con¬ nected to the said indicating devices. The potentio- meter devices here can comprise at least one potentio¬ meter which is incorporated in a voltage divider, the central outlet of the- potentiometer being connected for voltage supply to the digital voltmeter. The electric motor is controlled by means of the manual influencing devices which control according to their actuation the voltage supply to relay devices or corresponding devices. The said relay devices or corres¬ ponding devices connect the power supply to the electric motor. In a first embodiment a first relay is employed for actuating the motor in a first direction of rotation, which may correspond to a downward movement of the desk¬ top. In a corresponding manner, a second relay connects the current to actuate the electric motor in a second direction of rotation, which thus corresponds to an up¬ wards movement of the desk-top. The apparatus is provided with limit switches for obtaining a maximum and minimum positio of the desk¬ top above the reference level, which thus means that the desk top may be operated only over a predetermined dis¬ tance. In a preferred embodiment the devices which monitor the rotation of the electric motor are designed so that a variation brought about by one of these devices of approximately 1 V in a supply voltage output corresponds to a raising or lowering of the desk-top bγ approximately .0 mm. The potentiometer may also be made to rotate through approximately 15° for each variation of 1mm regis¬ tered by the indicating devices. The said manual influencing devices for raising and lowering the desk-top are further preferably designed so that simultaneous actuation of the influencing de¬ vices cuts the supply to the electric motor and keeps it cut off. Advantages With the above proposals, conditions are provided for apparatus with relatively few components and tech¬ nically simple construction, taken as a whole. Moreover, considerable resolution in " the indication of the height of the desk-top is made possible. Furthermore, the proposed apparatus" can be made very insensitive to changes in the voltage supply. The indi¬ cation is also exceptionally insensitiveto variations in the voltage supply. Considerable advantages are also afforded by the subject of the invention which provides a simple, in¬ expensive and operationally reliable functioning of a desk which can be raised and lowered. Th.e system is ex- ceptionally insensitive to disturbance, and with thepro¬ posed construction only one electric motor is required, compared with previous proposals where there is an elec¬ tric motor for eachtelescopic leg. List of Figures A presently proposed embodiment of an arrangement with the characteristics which are significant to the invention is described below with reference to the ac- co panying drawings, on which Figure 1 is a perspective view looking at an angle from below and to the right, showing the construction of a desk incorporating the invention, Figure 2 is a basic diagram showing the position of various components in the desk shown in Figure 1, Figure 3 is a block diagram of a manipulating box comprised in the apparatus, Figure is a block diagram of a motor housing ap¬ pertaining to the apparatus, Figure 5 is a basic diagram of the construction of a manipulation card, Figure 6 is a basic diagram of the construction of an indication card, and Figure 7 shows schematically the electrical connec- tion of the electric motor used in the apparatus andthe manual actuating devices and relay devices for control- ling the electric motor in both its directions. Preferred Embodiment 5 In Figure 1 a desk, which may consist of a switch¬ board desk, is designated 1. The desk is formed by a desk-top 2 and a framework 3 which comprises a cross¬ bar 4-, to the ends of which two telescopic legs 5 and 6 are connected. The respective telescopic legs comprise 10 an outer part 5a and an inner part 5b. Towards the bot¬ tom the outer part a is provided with a base part 5c which extends in the depth direction of the desk. The base parts are equipped with adjustable feet 5d which are intended to co-act with a foundation on which the desk 15 can be set up. The desk-top 2 is fixed to the said inner parts 5b of the respective telescopic legs. The respective inner parts of the respective tele r ' scopic legs can be influenced by means of a hydraulic cy¬ linder arranged in the respective legs and not shown in 20 Figure 1. The hydraulic cylinders can be arranged in the respective telescopic legs in a manner which is known per se so that mutual displacement by means of the respective hydraulic cylinders can be effected by the leg parts 5a and 5b, and thus the raising and lowering of the desk- 25 top. Underneath the desk-top two bars 7 and 8 are pro¬ vided to which the said inner leg parts 5b are connected. The hydraulic cylinders in the telescopic legs are sup¬ plied in a known way by at least one pump 9, for example 30 a double pump of a known kind, which is positioned in a motor housing • Mot on the lower face of the desk-top. ' * The motor housing is positioned right underneath the desk¬ top and substantially in the central region thereof. The desk is also provided with a cable duct 10 and connecting 35. devices 11 for connecting an external electrical supply, for example for connecting to the conventional mains power - δ - supply. Ttte device 11 here is preferably formed as a plug which can be used in an electrical socket in the normal electricity mains supply circuit. In addition to the said pump 9 the motor housing contains an electric motor E which drives the hydraulic pump 9 via an output shaft. The hydraulic pump is in communication with the hydraulic cylinders in the tele¬ scopic legs via hydraulic pipelines 12 and 13. On the output shaft E 1 of the electric motor a potentiometer P and two limit switches e1 and e2 are provided. An el¬ ectrical cable to enable power to be taken of under the desk at is designated 13'. Th.e potentiometer is act¬ ed upon by the shaft via a helical thread and is of the ten-revolution type. On the underside of the desk-top 2, towards the back and right out to the right-hand side a manipulation box MAN is arranged. Manual actuating devices S1, S2 and S3 are provided at the rear end of the .manipulation box. In the manipulation box there are two cards which are described below and are designated I and M . The base parts 5c of the respective telescopic legs are made with the same profile as the bars 7 and 8, but the base parts 5c are made longer. The bar profile is of the type which has an open, substantially rectangular or square cross-section, the open part of the profile being directed downwards in the case of the base part 5c and upwards in the case of the bars 7. In the arrange- • - ent shown the height-adjustment devices 5d are access¬ ible from above with a screw-driver, hexagonal key or the like, which considerably facilitates the horizontal ad¬ justment of -the desk. The said manipulating box MAN also contains indicating devices which are visible from the upper side of the desk, which is not shown in Figure 1. In Figure 2 the devices with which the raising and lowering of the desk-top is effected are shown in a basic diagram, together with the " devices which control these - "" " - 7 - devices. Moreover, the hydraulic cylinders arranged in the respective legs of the desk are indicated by H and H' . The hydraulic pump 9 and the said cylinders are of a kind which is known per se and which is available on the open market. The raising and lowering devices may be regarded as comprising the said hydraulic system 9 ι H, H 1 and the said electric motor. The controlling de¬ vices comprise the equipment assembled in the manipula¬ tion box MAN and the monitoring devices P, e1 and e2. Display units are indicated by the letter D in Figure 2. With regard to the manual actuating devices, S1 is a manipulating device for switching a 220 V mains supply on and off. The manual actuating device S2 is used for manoeuvring the desk in the upwards direction and the device S3 for manoeuvring the desk in a downwards direc¬ tion. The said actuating devices 51, S2 and S3 can be of a kind which is known per se. The electric motor Ξ drives the hydraulic pump .in a manner which is knwn per se and the potentiometer P applied to the transmission between the electric motor and the pump monitors the rotation of the electric motor. The potentiometer again can be of a kind which is known per se and can be arranged in a manner which is known per se. The same applies to the limit switches e1 and e2 provided on the transmission between the motor and the pump. The construction of the manipulation box Man is shown in more detail in Figure 3. In the " box there are an indication card I and a manipulation card M . In addition, the earthed plug 11 * for connecting the equip¬ ment to a 220 V, 50 Hz electricity supply is also com- • prised therein, The positioning of the switch S1 is shown, as is the connecting up of the manual actuating devices S2, S3. The various parts are connected by leads in a manner which is known per se. The lead to the switch S1 is inserted in a shrink-fitted sheath 6. An earth screw is indicated by 17. The leads are provided with stress-relieving devices in a known way. The leads between S2, S3 and the indicating card are shown schema¬ tically by 18 and the leads between the indicating card and the manipulation card by 19. In Figure 3 contact breakers P1 and P2 are also shown, and as far as these contact breakers are concerned reference is made to Fig¬ ure 5 described below. The parts contained in the motor housing Mot are shown in Figure 4. The electric motor. Ξ is of the ORIENTAL BKEA 60101 type, which consists of a single- phase non-synchronous motor (see also Figure 7). A junc¬ tion box to which the electric motor connections are made is designated 20. The supply is effected via the lead 21 which is introduced via a through-bore 22 in the box. The physical positioning of the potentiometer P and the limit switches e1 and- e2 is also shown. The connecting leads ' are indicated here by 23 and these leads are intro¬ duced via a through-bore 24. Conventional stress-relieving devices 25 and 26 relieve the loading of outer forces on the said leads. The limit switch e1 defines the highest position of the desk-top above the reference level, while the limit switch e2 defines the lowest position above the said reference level. Figure 5 shows the manipulation card which in this case comprises the connections a- and b to the limit switches, the connection c to the potentiometer, the connection d to the electric motor, and the connection e to the power supply. The connections a , b and c are located in the said connecting device P1. The con¬ necting device P2 is provided for connecting the mani¬ pulation card. There is also a power transformer Tr, two relays Re1 and Re2, and two anti-interference units St81 and Stδ2. A condenser MK appertaining to an elec- trie motor is also arranged on the manipulation card. Figure 6 shows the indication card I which bears, amongst other things, a digital voltmeter DV with inte¬ gral operating circuits for the display unit which com¬ prises the three elements D', D" and D ,t l . Furthermore, there is a DC transformer which is designated DCO. The said potentiometer P (see Figure 4) appertains to a voltage divider with resistances R1, R2 and R3. The connections Pa and Pb are connected respectively to the resistance R1 and to the resistance R2 which in turn is series-connected to the resistance R3. The resistance R1 is connected to the output of the DC transformer. The central output Pk on the potentiometer is connected to the digital voltmeter via the lead 27. A voltage trans¬ forming circuit AN applies a negative voltage to the digital voltmeter DV. The equipment is connected via a contact device P3 to the above-mentioned contact device P2 on the manipulation card. The equipment shown in Fig¬ ures 5 and 6 can-consist of components which are known per se, and they are therefore not described in more de¬ tail. Figure 7 shows the basic connection of the electric motor Ξ , its associated condenser MK, the anti-interfer¬ ence circuits Stfll, St82, and the connections of the manual actuating devices and the said relays Re1 andRe2 to the electric motor for the control thereof in its two rotary directions. The connection to the electricity power supply is indicated by 28. As far as the remain¬ ing designations are concerned, reference is made to the various drawings described above. The manipulation volt¬ age which is used is approximately 11 V. Since the xunc- tioning of the motor is-known per se it will not be des¬ cribed in detail here. The apparatus listed above functions substantially as follows: The relays R1 and R2 can be controlled by the mani- pulation devices S2 and S3 and are intended to operate the electric motor Ξ in one direction or the other, according to the operation of the said devices. The mutual relationship between the said relays, the actuat¬ ing devices S2 and S3, the limit switches e1 and e2 can be seen in Figure 7 t amongst other places. The said switches S2 and S3 are designed in such a way that when they are actuated simultaneously they cause the power supply to the motor to be cut off and to remain cut off for as long as there is simultaneous actuation. The anti- interference devices eliminate interference transients. Furthermore, the manipulation card shown in Figure 5 is designed to transmit the power supply to the indicating card shown in Figure 6, preferably consisting of 11 V smoothed direct current. The shaft of the electric motor is designed so that is operates the movable micro-contact Pk on the potentiometer P . According to the position of the movable contact Pk the potentiometer then supplies various voltages to the digital voltmeter DV. In a pre¬ ferred embodiment a change of 1 mV in the voltage corres¬ ponds to approximately 1 mm change in the height of the desk-top above the reference level. The said digital voltmeter DV actuates the display unit with its component display elements D', D' 1 and D* 1 ' according to the volt¬ age changes occasioned by the potentiometer. In the pro¬ posed system the potentiometer contact Pk "will be rotated through approximately 14° before a change of 1 mm occurs on the display unit. The resolution of the reading is i 1 mm. As mentioned above, the digital voltmeter is of a kind which is known per se and operates on the known "dual slope" principle. The advantages of the system described above are, amongst others, that a reliable, technically simple sy¬ stem is obtained, with few components and high indicat¬ ing resolution. The construction of the said manipula¬ tion box may be extremely simple so that it contains relatively few components. The components on the mani¬ pulation card may be on a card with printed circuitry which is preferably arranged on one side of the card. As for the indicating card I , this comprises a card with printed circuitry on both sides. Moreover, the proposed apparatus is very insensitive to variations in the power supply. When the voltage of the power supply changes, then the voltage from the potentiometer to the digital voltmeter also changes. However, this does not bring about any change in the display unit since a reference voltage to the digital voltmeter is changed to a corres- ponding extent. The quotient between -the voltage from the potentiometer and the reference voltage thus always remains constant with respect to changes in the voltage of the power supply. For obvious reasons, however, the supply voltage should not continuously exceed certain limit values, since the electronic circuits require a specific voltage range in order, to function. The indica¬ tion is thus exceptionally insensitive to changes in the voltage ,of the power supply. The advantages of the above-described apparatus for a switchboard desk are therefore that the system is sim¬ ple, inexpensive and operationally reliable. Moreover, the. arrangement is exceptionally insensitve to distur¬ bance. Furthermore, in the present case only one elect- rice motor is used. The invention is not limited to the embodiment shown above by way of example, by may be modified within the framework of the following Patent Claims.

Claims: P a t e n t C l a i m s 1. An arrangement for a desk with a desk-top (2) which can be raised and lowered and at least two tele¬ scopic legs (5 ? 6) and comprising devices which effect the raising and lowering of the desk-top and devices to control the effective devices, characterised in that the effective devices comprise at least two hydraulic cylin¬ ders (H, H') » each positioned in its respective said telescopic leg and connected to a hydraulic pump (9) which can be driven by means of " an electric motor (E), that the controlling devices comprise manually actuated devices which switch on the electric motor to rotate in either direction according to the way they are actuated, and that a device monitoring the rotation of the elect¬ ric motor actuates an indicating device (DV, D) which shows the position of the desk-top above a reference level, 5 for example a floor on which the desk has been set up. 2. An arrangement according to Patent Claim 1, characterised in that the device monitoring the rotation of the electric motor consists of a potentiometer device which supplies voltage to a digital voltmeter (DV) which o is connected to or comprises the said indicating device (D). 3. An arrangement according to Patent Claim 2, characterised in that the potentiometer device comprises a potentiometer (P) which appertains to a voltage divider (R1/R2, R3) and the central output (PL) of which is con- 5 nected to the digital voltmeter (DV). 4. An arrangement according to any of the preceding Patent Claims, characterised in that theelectric motor (E) can be connected to a power supply source (28), for example an alternating current source, via relay devices 0 (Re1, Re2) or corresponding devices which can be connect¬ ed in by means of the manual actuating devices (52, 53). 5. An arrangement according to Patent Claim 4, characterised in. that a first relay (Re1) connects τhe current to actuate the electric motor (E) in a first direction of rotation corresponding to a downwards move¬ ment of the desk-top, and that a second relay connects the current to actuate the electric motor in a second direction of rotation corresponding to an upwards move- ent of the desk-top. 6. An arrangement according to any of the preceding Patent Claims, characterised in that limit switches (e1,e2) are provided to define the maximum and minimum positions of the desk-top above the reference level. 7- An arrangement according to any of the preceding Patent Claims, characterised in that a change of approxi¬ mately 1 mV in an output voltage, occasioned by the de¬ vice monitoring the rotation of the electric motor, corresponds to a raising or lowering of the desk-top oj approximately 1 mm. έ. An arrangement according to any of Patent Claims 3-7, characterised in that the potentiometer (P) is rotated through approximately 14° for each variation of approximately 1 mm which the indicating device (D) regis- ters. 9.. An arrangement according to any of the preceding Patent Claims, characterised in that the manual actuating devices (S2, S3)- are designed so that when they are actuated simultaneously the supply to the electric motor is cut .and remains cut.

Inventors: JOHANSSON LARS AOKE, LUNDSTROEM KURT ALBERT, SVENSSON AOKE PEDER, WALLIN PER OLOV THOMAS, WARELL BENGT HUGO, JOHANSSON, LARS, AOKE, LUNDSTROEM, KURT, ALBERT, SVENSSON, AOKE, PEDER, WALLIN, PER, OLOV, THOMAS, WARELL, BENGT, HUGO
Applicants: TELEVERKET
Application year: 1985
Main classification: A47B9
IPC codes: A47B9, A47B17