IL28793A - Automatic starter switch for preheating and ignition of fluorescent lamps having heated cathodes - Google Patents

Description

PATENT ATTORNEYS PATENTS AND DESIGNS ORDINANCE SPECIFICATION Automatic starter switch for preheating and ignition of fluorescent lamps having heated cathodes ELE St a Body organized under the laws of of Switzerland do hereby declare the nature of this inTention and in what manner the same is to be to particularly described and ascertained in and by the following e invention relates to starters or ignition switches of the type having tapped choke coil or ballast and a normal off contact operated the expansion and a hot wire preheating and igniting fluorescent lamps having heated In conventional starters of this when tion does not the attempt of effecting ignition is automatically repeated upon retarded opening of the normal off bu the ratio o the opening period to the closing period of the contact unfavourable to such a degree that the temperature of the cathodes to a value which is insufficient for obtaining a correct so that ignition is rendered difficult and sometimes Flickering of the occur over long periods resulting in increased wear of the contacts and in shortening the lifetime of the object of the present invention is to operate the normal off contacts i such a manner that upon repeated switching the temperature of the cathodes does not decrease to a below that required for According to the present invention there is provided an automatic starter device for igniting luminescent tubes with a preheating circuit with contact in series with a choke and with the cathodes of the whereby a hot wire circuit is connected to some winding of the choke and the hot wire is connected to a control lever and perates this control lever after a which control engaging the normal off which is as a action snap controlling the opening and closin of the preheating circuit in such a manner as to prevent a temperature decrease of the during repeated switching a value quired for the emission In the accompanying Figure 1 is a diagram representing the ture curve the cathodes as a function of time in a conventional fluorescent Figure 2 illustrates one form of of an ignition switch and its associated circuit diagram according to present Figure 3 represents ication of the switch Figure represents a diagram of temperature curve for the tube according to Referring to Figure the cathodes of a tional uorescent tube preheated to a temperature of about 800 to whereafter the normal off contact is opened at point When the discharge lamp does not temperature of the cathodes decreases to the point at which the normal off contact closes the cathode temperature then slightly The sure as is substantially shorter than opening so that the cathode perature does not rise above a minimum C of about required for emission of but nuously decreases Figure 2 represents an ignition switch according to the A switch housing is provided with four minals 9a and In the housing a hot wire 11 has the other end is secured the hub of a control lever 15 mounted in the housing pi The 2 of the hot wire is connected to terminal and end 3 to terminal The terminal 9a connected to the movable contact 9 of an inductance Coi or choke having its 10 connected to the terminal Thus hot 1 is connected in circuit a selective number of windings of coil normal off contact comprises a contact S carried by a resilient contact and a fixed contact One end of resilient contact arm is to the housing 31 a point and connected terminal 5a of the The contact arm 23 further carries a ferromagnetic a 21 which is associated with a permanent A tension spring 22 fixed with one end to the hous ng acts upon the voting control lever 15 fo tensioning the ho wire 11 by urging lever to turn in the direction of The opening movement of the is a 28 carried by the and coacting abutment on to the ferromagnetic being attracted by the permanent magnet the silient contact arm 23 is flexed and a sufficiently strong contact pressure is exerted on off contact pair 6 The electric diagram represented housing 31 is of conventional When the supply rant is switched in between the conductors 7 and a heating current flows the conductor 7 through the coil the electrode 2 of cathode tube terminal off contacts terminal electrode 3 of the cathode tube to the conductor At the tim a control current the coil through contact 9a hot wire terminal 10a to the end 10 of the coil Due this current the hot wire 11 is dually heated and expands The control lever can pivot in counterclockwise direction owing to the action of the spring 22 and acts upon the contact arm 23 at a point 25 intermediate the permanent magnet 20 and the place of attachment of the At the moment when the pressure exerted by the end of control lever due to the action of spring 22 exceeds force of tion of permanent magnet contacts suddenly in manner of a snap switch and interrupt the preheating circuit of the cathode while producing in the an induced electromotive force which mally effects a flicker free ignition of the tube the contacts open at such an instant which is unfavorable with respect the momentary value of the or when the voltage of the net 8 is too or the ambient temperature very it may happen that the tube 1 does not ignite and the normal off contacts close again switching is repeated once or several Such a case is represented in the diagram according to Figure It is seen from this that the normal off contacts have substantially identical opening periods A2 A3 closing periods 332 A3 so that the cathodes each closure of the contacts heated with a sufficient margin of safety above the minimum value and safe ignition occurs after the first or second petition of the switching provided that the lamp is The closing periods Bl B2 can be modified by varying the number of windings of the coil so that they can be made substantially equal to the opening periods A2 A3 The stop member 26 relieves the hot wire 11 from mechanical stress and limits the opening gap between the contacts to a minimum value as determined by In the modification according to Figure 3 a contact strip 29 is secured to the contact arm 23 and is provided with an offset armatur finger 27 acting with a permanent magnet The control arm 15a acts upon the contact arm 23 at the place where the strip 29 is secured to the The circuit diagram of this modified switch is the same as that shown in Figure 2 and operation of the switch is identical with the operation as explained in relation with Figure In both examples according to Figures 2 and 3 the normal off contacts due to the permanent magnet associated with the resilient contact arm operates as a magnetic q ick action or snap of a magnetically operated quick action s tch the same effect can be by a mechanical quick action switch in which the movable contact is provided on a biased contact spring requires adjustment and causes switching insufficientOCRQuality

Claims (1)

1. CLAIMS automatic starter for igniting luminescent tubes preheating circuit with normal contact in series with a chok and with the cathodes of the whereby hot wire circuit is connected to some windin th choke and the hot wire is connected to a control lever and operates this control lever after which control lever engaging the normal o f which is formed as a quick action snap controlling the opening and closing of the preheating circuit in such manner as t prevent a temperature decrease of the cathodes of the luminescent tube at the moment of ignition during a repeated switching action to below a value required for emission of An ignition switch as claimed in Claim in whic the contact of said normal contact is associated with a permanent magne fo producing snapping An ignition switch as claimed in Claim in which stop means are provided for limiting the opening movement of said movable contac and mechanically relievin from said hot wire upon opening of the normal off An ignitio switch as claimed in Claim in which the movable contact membe of normal off contact is provided with a ferromagnetic strip having an armature portion offset with respect to the contact membe and coacting with said permanent ignition switch as claimed in Claim wherein the movable contac of said normal off contact is carried by a contact means being provided acting on said to a biasing o operate quick snap An automatic starter switch claimed in claim in said preheating circuit comprises a hot a pivotally mounted control lever operative y nected to one end of said wire to be actuated upon dilatation of the hot and a choke coil having a movable tapping contact electrically connected to the other end of said hot one end of the choke coil being electrically connected to said first named end of the hot whereby said hot wire is selectively connected in circuit with variable number of windings of the choke so that by var ng the number of windings of the choke coil in circuit with the hot substantially identical opening and closing periods of the normal off may be obtained upon repeated Dated this 17th October 1967 insufficientOCRQuality