GB2183394A - Striker mechanism - Google Patents

Abstract

An intermittent striker mechanism comprises a movable striker 18 disposed adjacent an object 5 to be struck thereby; the striker being coupled with a movable armature 14 of a solenoid 2; means 4 to energise the solenoid intermittently and spring means 20 acting between the striker and a fixed stop 17 so that upon energisation of the solenoid the armature is moved in the sense to move the striker against the action of the spring means, away from the object characterised in that the means to energise the solenoid intermittently comprises an electronic circuit capable of producing pulses of predetermined width and spacing from a direct current source and in that the spring means is coupled with the striker so that between each pulse the striker is freely propelled by the spring means, without constraint thereby, to strike the object. The object 5 may be a gong. <IMAGE>

Description

SPECIFICATION Striker mechanism This invention relatestoastriker mechanism which is particularly, although not exclusively, concerned with electric bells.

Traditionally direct current electric bells are solenoid operated with a spring mounted clapper coupled with an armature forthe solenoid and also carrying one contact of a make and breakswitchto provide intermittent energisation of the solenoid.

More recently, spring controlled strikers coupled dir ectlywith a reciprocating solenoid armature have been employed.

With the previously known arrangements con siderablecare must be used during manufacture to adjustthe clapperor striker relativeto the bell gong in orderto obtain satisfactory operation. This adjustmenu can often be upset if the gong is removed and replaced.

According to the present invention there is provided an intermittent striker mechanism comprising a movable striker disposed adjacent an object to be struck thereby; the striker being coupled with a movable armature of a solenoid; meanstoenergisethe solenoid intermittently and spring means acting between the striker and a fixed stop so that upon energisation of the solenoid the armature is moved in the sense to move the striker against the action of the spring means, awayfrom the objectcharacterised in thatthe means to energise the solenoid intermittently comprises an electronic circuit capable of producing pulses of predetermined width and spacing from a direct current source and in that the spring means is coupled with the striker so that between each pulse the striker is freely propelled bythespr- ing means, without constraint thereby, to strike the object. Preferably the striker and the armature are formed as a single reciprocating unit. The spring means may be a coil compression spring embracing the striker and acting between a part on the striker and a fixed stop, the spring being secured onlyto eitherthe part orthe stop or leftto floatfree on the striker. Preferablythe striker is spaced from the objectwhen the spacing between the part and the fixed stop is equal to the relaxed length ofthe spring.

Three embodiments ofthe present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows, partly in section, an electric bell mechanism; and Figure2 shows a modified arrangement of solenoid and striker mechanism.

Figure3showsanotherarrangementofsolenoid and striker mechanism.

Referring to Figure 1 an electric bell comprises a base 1, a solenoid unit indicated generally at 2, a striker mechanism indicated generally at3, an elec troniccircuit4and a gong 5.

The solenoid 2 comprises a fixed armature frame 6 of magnetisable material mounted on the base 1 having a front pole piece 7 formed with an aperture8 and a rear pole piece 9 formed with a forwardly extending cylindrical part 10. A coil 11 mounted on a non-magnetisable bobbin 12 is disposed between the front and rear pole pieces with the bore 13 ofthe bobbin being a close fit overthe part 10.

The striker mechanism 3 is of magnetisable material and comprises an armature 14 extending with clearance through the aperture 8 and being a freely sliding fit within the bore 13. At its forward end 15the armature is extended as a reduced diameter rod 16 passing through an aperture (not shown) in a bracket 17 carried by the base 1. The rod 16 and the armature 14may be made from a single piece of material, or the rod could be a separate partfitted to the armature. The outer end 18 ofthe rod 16 constitutes a striker head forthe gong 5. A collar 19 is disposed on the rod 16 between its end 18 and the bracket 17 and a coil compression spring 20 extends between the collar and the bracket, embracing the rod.The spring 20may float freely on the rod or it may be secured eitherto the collar 19 orthe bracket 17 but it is importans that it should not be secured to both. In the "rest" position of the striker mechanism 3 with the distance between the collar 19 and the bracket 17 equal to the relaxed length of the spring 20 the end 18 is spaced from the gong 5 and the rear end 21 of the armature 14 is spaced from the part 10. Itwill be understood that the bore 13 and the aperture in the bracketl7constitutebearingsforthearmature 14/ rod 16, enabling this unit to reciprocate freely.

The electronic circuit4 is mounred on a board 22 carried by the base 1 and has input terminals 23. The output of the circuit4is connected to the coil 11 over wires 24.

The circuit3 which will not be described in detail is capable of producing from a direct current source, a pulsed output of predetermined pulse width and spacing.

The gong 5 is of conventional type and may be mounted on one or several supports (not shown) carried by the base 1.

In operation, during energisation ofthe coil 11 by each pulse, the armature 14 is attracted inwardly of the bore 13 against the action of the spring 20. The part 10 constitutes a positive stop for the rear end 21 ofthe armature and completes the magnetic circuit ofthe solenoid 2. Atthe cessation of each pulsethe energy stored in the spring 20 is released and because the spring is not secured to both the collar 19 and the bracket 17, the armature 14/rod 16 unit is propelledfreelyoutwardlyofthesolenoid2withoutany constraint bythe spring to cause the end 18to strike the gong 5.

Fora predetermined voltage inputattheterminals 23, the pulse frequency may be 30 cps with a pulse width of 10 ms. Conveniently the circuit may be arranged to vary the pulse width inversely with applied voltage changeto maintain optimum operation over a wide voltage range. Additionallythe circuit may also actto reduce the frequency of strike inver- selywith applied voltage in orderthatthe operational current may be generally constant overa wide voltage range.

The arrangement above described is relatively insensitive to pulse width. It is also insensitive to the precise location of the gong 5 so that adjustment during final assembly is not required to ensure sat isfactory operation.

Figure 2 shows a modified arrangement with the bracket 17 omitted in which the aperture 8 is increased in size and a flange 25 is provided attheend ofthe armature 14to overlap the pole piece7.The spring 20 is disposed overthe armature 14to act between the flange 25 and an end 26 ofthe bobbin 12.

This arrangement improves efficiency since it would never be possible to ensure thatthe armature is accurately concentric in the aperture 8 so the Figure 2 construction minimises magnetic side forces that would restrict movement of the armature and cause wear on the bearing face. Afurther modification would beto provide a tapered recess in the part 10 and a tapered end to the armature 14 as shown by dotted lines 27 and 28. Such arrangementwould in creasethesurface area of contact between these parts so improving the magnetic attraction between the poles. This arrangement also provides for an additional or alternative stop between flange 25 and face 7.

With the Figure 2 construction it will again be necessaryto ensurethatthe relaxed length ofthespring 20 is properly chosen. Furthermore with both constructions it may be possible to omit the bracket 17 and relyfor bearing support solely on the sliding action of the armature in the bobbin.

In a further modified construction (not shown) a spring 20 of non-magnetic material could be disposed between the part 10 and the rear end 21 ofthe armature. In this case it would be essential forthe relaxed length ofthe spring to be chosen to retain the free propulsion ofthe striker upon de-energisation of the coil.

Afurther modified construction is shown in Figure 3. In this arrangement the bore 13 is enlarged except at its forward end and a shoulder 13a separatesthese parts. The spring 20 is fitted inside the coil between the part 10 and a freely sliding collar 29. The thrust of the spring is transmitted bythe collar 29 to the arma- ture 14, until the collar 29 meetsthe shoulderl 3a when the armature continues to move withoutconstraint. The part 29 also acts to retain the spring within the assembly.

It will be understood thatthe part 10 has a reduced diameter end carried bythe pole piece 9 and the part 10 is a closefitwithin the bore 13. The arrangement of Figure 3 includes an armature whereby its centre of gravity is shifted so that wear on the bearing face 12 is reduced.

Although the above described arrangements 5, with the striker and the armature formed as a single reciprocating unit is preferred, itwill be understood thatthese parts could move along parallel paths.

Alternatively the striker could be pivoted to the armature and extend generally atrightanglesto it.

Claims (6)

1. An intermittent striker mechanism comprising a movable striker disposed adjacent an object to be struckthereby; the striker being coupled with a movable armature of a solenoid; meanstoenergisethe solenoid intermittently and spring means acting between the striker and a fixed stop so that upon energisation of the solenoid the armature is moved in the sense to move the striker against the action of the spring means, away from the object characterised in that the means to energisethe solenoid inter mittentlycomprisesan electronic circuit capable of producing pulses of predetermined width and spacing from a directcurrentsource and in that the spring means is coupled with the striker so that between each pulse the striker is freely propelled by the spring means, without constraint thereby, to strike the object.

2. A mechanism according to claim 1 in which the strikerandthe armature are formed as a single reciprocating unit.

3. A mechanism according to claim 1 or claim 2 in which the spring means is a coil compression spring embracing the striker/armature and acting between a part thereon and a fixed stop, the spring being secured only to eitherthe part orthe stop, or left to float free on the striker.

4. A mechanism according to claim 3 in which the striker is spaced from the object to be struckwhen the spacing between the part of the armature and the fixed stop is equal to the relaxed length ofthespring.

5. A mechanism according to any one of the preceding claims constituting a bell striker mechanism.

6. A mechanism substantially as herein described with reference to Figure 1 or Figure 2 or Figure3 of the accompanying drawings.