US3314359A - Actuating mechanism for printing hammers - Google Patents

Description

April 18, 1967 v C, R. M. MARTIN ACTUATING MECHANISM FOR PRINTING HAMMERS Filed June 2l, 1965 4 Sheets-Sheet l FIG, FIG. v 1 B ibi 1 I all nul FIGB

FIGA

April 18, 1967 c. R. M. MARTIN ACTUATING MECHANISM FOR PRINTING HAMMERS Filed June 21, 1965 4 sheets-sheet 2 abn..

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April 18, 1967 c, R. M. MARTIN ACTUATING MECHANISM FOR PRINTING HAMMERS 4 Sheets-Sheet 5 Filed June 2l, 1965 April 18, 1967 c. R. M. MARTIN ACTUATING MECHANISM FOR PRINTING HAMMERS 4 Sheets-SheetI 4 Filed June 21, 1965 wm Nm United States Patent O 3,314,359 ACTUATING MECHANISM FOR PRINTING HAMMERS Claude Raymond Marie Martin, Paris, France, assignor to Socit Industrielle Bull-General Electric (Socit Anonyme), Paris, France Filed June 21, 1965, Ser. No. 465,567 Claims priority, application France, July 10, 1964, 981,399 1 Claim. (Cl. 101-93) ABSTRACT F THE DISCLOSURE An electro-mechanical module for actuating the striker hammers of a type drum printing machine is provided with positioning and centering means which afford the advantage that it can be rapidly and accurately positioned in the machine, or replaced by another one when it is worn.

'Ihe present invention relates to improvements in highspeed printing machines and more particularly in the electromechanical devices intended for the actuation of the striker hammers.

High-speed printing machines generally comprise a printing device consisting of a prin-ting drum bearing characters in relief on its periphery and continuously rotating at a relatively high speed, of the order of several hundreds of revolutions per minute. The characters are disposed in circular columns on the periphery olf the drum and each column contains, regularly spaced apart, all the characters of a complete series which may have to be printed.

` A row of striker hammers, comprising one hammer per column, is disposed along the drum, in parallel relationship to the axis of the latter, along a so-called printing line. web form) is moved past this printing line, between the hammers and the periphery of the drum, so that the characters on the drum then tra'vel past the paper sheet to be printed on. The actuation .of a hammer at the instant when a character of the corresponding column reaches -the printing line has the effect of applying the paper to the said character and thus causes the latter to be printed on the paper. Generally speaking, the inking is effected` by an interposed ribbon or carbon paper. It is also possible to ink the drum.

In high-speed printing machines, correct alignment of the characters printed on the paper requires absolute synchronism between the rotational movement of the drum and the movement of the striker hammers, in order that the latter may apply the paper to the drum at the precise instant when the characters chosen arrive opposite the printing line. The required precision is higher in proportion as the drum rotates at a higher speed. This result has been successfully achieved, on the one hand by limiting to a small value the length of the travel of the hammers, and on the other hand by using hammers of relatively small mass which, since they are in contact with an electromechanical actuating device when they are in the inoperative position, travel with an accelerated rectilinear movement under the action of the said actuating device, reach the paper and the drum as a result of the acquired speed, return rapidly to their inoperative position under the rebound eliect and are maintained in this position by means of a spring.

In addition, owing to the fact that the paper remains stationary at the time of the printing, While the drum rotates rapidly, it is necessary that the time for which the hammer applies the paper to the drum should be as A printing support (paper in sheet or 3,314,359 Patented Apr. 18, 1967 short as possible in order to ensure complete clarity of the printing. In order to achieve this result, a powerful mechanical impulse is required, which is capable of projecting the hammer towards the paper at a suicient speed. This impulse, which is imparted by the electromechanical actuating device, must be applied for a very short time, owing to the short length of travel of the hammer. Since the electromechanical device can have only a limited movement, owing to the fact that the hammer travels only a short distance, it is necessary to employ electromagnets of relatively large dimensions in order to obtain impulses of appropriate strength.

In known printing machines which are capable of printing up to 8 to l0 characters per inch on one line, it is relatively diiiicult to dispose the electromagnets correctly by reason of their size and the small amount of space remaining available owing to the small spacing existing between the hammers. For this purpose, it is known to dispose the electromagnets on either side of the printing line, along a section of a helix, each electromagnet being connected to a corresponding hammer by flexible Wires, bars, rods or levers. This arrangement is of complex construction and costly, requires delicate adjustments during the assembly of the parts and their positioning in the machine, and needs frequent maintenance.

The present invention has for its object to obviate thev detects of the prior art, by providing an electromechanical device for actuating the striker hammers, which is particularly characterised by great robustness, by virtue of which it has high resistance to wear and can hafve operating characteristics which remain substantially unchanged in the course of time. Moreover, owing to particular means ensuring its correct positioning within the machine, the said device affords the advantage that it can be rapidly positioned in the machine by any person even Without specialised training. Finally, there is provided in this device a self-lubricating pivotal connection which obviates all maintenance and which does not present the dangers of breakage of a joint consisting of a member of which the deformation is utilised.

The present invention concerns, ina printing machine comprising on the one hand a printing device comprising a character drum and striker hammers mounted in a frame, and on the other hand a series of actuating mechanisms grouped in modules, and in which each striker hammer receives a mechanical impulse supplied -by an actuating mechanism consisting of a lever actuated by means of an electromagnet, a module characterised in that it consists of a frame comprising a rigid partition which serves as a support for two groups of actuating mechanisms disposed symmetrically on either side of the said partition, each group of mechanisms consisting of two separate mechanisms, of which one comprises a straight lever pivotally mounted on a rst pivot pin secured perpendicularly to the plane of the said partition, the said straight lever being actuated by means of a iirst electromagnet supported by the said partition, and of which the other comprises a lever bent at an angle of about and pivotally mounted on a second pivot pin secured perpendicularly to the plane of the said partition and in parallel relationship to the first pivot pin, the said bent lever lbeing actuated by means of a second electromagnet supported by the said partition, the said electromagnets being disposed substantially at 90 to one another, the said frame also being provided with positioning and securing means by which the said module can be readily and accurately positioned, and also secured, within the said machine.

Further features and advantages of the invention Will become more clearly apparent in the course of the following description, given with reference to the accompanying drawings, in which:

FIGURES lA and 1B are two views in perspective, and partly in section, which show the relative positions of lthe modules in the printing mechanism of a printing machine;

FIGURE l illustrates how FIGURES 1A and 1B should be assembled;

FIGURE 2 is a view partly in section through the printing device of a printing machine, along a line corresponding to the line 2 2 of FIGURE 3;

FIGURE 3 is 'a View, in the direction of arrow 3 of FIGURE 2, of a number of neighboring modules showing the relative positions which they occupy in the printing machine;

FIGURE 4 is a view along a line corresponding to the line 4 4 of FIGURE 5, which shows the positions of two levers in relation to their pivot pins, and

FIGURE 5 is a view in section along a line corresponding to the line 5 5 of FIGURE 4, showing how the four levers are mounted in a module.

Referring now to FIGURES 1A and 2, which show a part of a. high-speed printing machine, partly in section, there will be seen a printing drum bearing on its periphery characters in relief which are disposed in circular columns, each column containing, regularly spaced apart, all the characters of a series which may have to be printed. Associated with each column is a striker hammer 11, so that the printing machine comprises as many striker hammers as there are character columns on the periphery of the drum. The striker hammers are disposed along the drum, in a row parallel to the axis of rotation of the drum. As may be seen from FIG-URE 2, each hammer, when in the inoperative position, is maintained at a distance from the periphery of the drum by a spring 12. Each hammer can move in a direction perpendicular to the axis of rotation of the drum to enable a paper sheet 13 (not shown in FIGURE 1A) to be applied to a chosen charac-ter in the column associated with the said hammer, whereby the said character is printed on the paper. FIGURE 2 shows that an inking ribbon 14 is disposed between the paper and the surface of the drum. The hammers are regularly spaced apart and their spacing varies from about two and a half millimeters to about three millimeters, depending upon the printing styles, so that from eight to ten characters can be printed per inch of line, depending upon the styles. In the inoperative position, each hammer is in contact, at its rear face, with an actuating device which will be described a little late-r. When the said device is actuated with the aid of means which will hereinafter be indicated, it propels the aforesaid hammer towards the paper. Owing to the speed reached, the hammer continues its movement and its rear face then ceases to be in contact with the actuating device. The hammer then strikes the paper by its forward face, rebounds and returns to the inoperative position, in which it is finally maintained by means of its spring.

According to the invention, the hammer actuating devices are so grouped as to constitute a number of units, called modules, each module being capable of being positioned in the printing machine andl replaced by another one when it is worn, so that it is unnecessary to change all the actuating devices when some of them are considered defective.

FIGURES 1A and 1B, when assembled, show a series of identical modules, some of which have been diagrammatically illustrated and which have been positioned in a printing machine to show the manner in which these modules are disposed in relation to one another. One of the said modules has been shown in the withdrawn position in FIGURE 1B in order that the details of its construction may be more readily seen.

According to the invention, four electromechanical devices each consisting of a lever pivotally mounted on a pin and actuated by an electromagnet are combined in a module. Referring to FIGURE 1B, it will be seen that a module designed in accordance with the invention comprises a rigid trame 20 of appropriate moulded material, such as metal or plastic, the mass of which is suicient to damp substantially the vibrations produced by the shocks inherent in the operation. The frame is of such form that its interior constitutes mainly a rigid partition 21 which extends substantialiy through the plane of symmetry of the said module. Two groups of actuating mechanisms are symmetrically disposed on either side of the said partition. One of the said groups, which can be seen in FIGURE 1B, comprises a straight lever 22A mounted on a pivot pin 23A and adapted to be actuated by means of an electromagnet 24A, and a bent lever 25A mounted on another pivot pin 26A and adapted to be actuated by means of another electromagnet 27A. The electromagnets 24A and 27A are iixedly mounted on one face of the partition 21, while the two pins 23A and 26A are connected to a support 28A forming a bridge, which is in turn secured to the said face of the partition 21. Each lever is tlat and is terminated at one of its ends by a rounded portion intended to be brought into contact with the rear face of a hammer. The other end is provided with a member 29 which forms part of an armature intended to close the magnetic circuit of the electromagnet for the actuation'of the said lever. A second group of mechanisms, similar to the preceding one, is secured to the other face of the partition 2`1. This second group also comprises a straight lever 22B and a bent lever 25B, of which only the rounded portions can be seen in FIGURE 1B.

FIG. 5 shows how the four levers of one module are disposed in relation to the partition of the fra-me. It should be noted here that, in order to facilitate the understanding of the description, like parts have been denoted by the same references in the various figures. Thus, in FIGURE 5, there will `be seen the Support 28A, the levers 22A and 25A and the pivot pins `231A and 26A of FIGURE 1B, all the-se parts being disposed on the same face of the partition 21 and being partially shown, in FIGURE 5, in section along a plane extending through the pivot pins of the levers. FIGURE 5 shows that, on the other face of the lpartition 21, two pivot pins 23B and 26B serve for the pivotal connection of theV levers 22B and 25B respectively, these pins -being connected to a support 28B forming a bridge, which is in turn secured to the said other .face of the partition 21. Except for the levers, the parts whose references terminate in the letter A are symmetrically disposed, about the partition 21, with respect to the parts whose reference terminates in the letter B. On the other hand, the levers are mounted on their pins in such manner that one straight lever belonging to one of the groups of mechanisms and one bent lever belonging to the other group are disposed symmetrically about the partition 21. This arrangement, which has been adopted for the purpose of facilitating the assembly and reducing the diversity of the parts manufactured, makes it possibile to reduce the cost of production ot a module.

FIGURE 4 is a view along a line corresponding to the line 4 4 of FIGURE 5, showing the relative positions of the levers 22B and 25B and of their pivot pins 23B and 26B. Referring now to FIGURES 4 and 5, it will be seen that each of the levers is provided with a bearing surface 30 which enables it to be mounted on its pivot pin. This bearing surface extends entirely over that portion of the pin which is situated between the partition 21 and the internal face of the support connected to the said pin and its ends are machined to permit axial guiding of the lever on its pins. Each bearing surface is internally lined with a self-lubricating ring 3K1 of appropriate material, for example oil-impregnated sintered iron which ensures lifelong lubrication of each lever on its pin and thus considerably reduces the maintenance of the printing machine. FIGURES 4 and 5 further lshow that each of the straight levers 22A and 22B is formed with a circular hole 32 to permit the passa-ge of the bearing surface of the bent lever whose pivot pin is secured to the same support as the pin of the said straight lever. The diameter of the said hole is so adjusted that the said straight lever can pivot about its pin without being impeded, lbetween two predetermined operating limits. Thus, since each lever possesses its own pivot pin, the pivoting of each lever about its pin between these two limits can take place Without producing any mechanical interaction on another lever. Moreover, the .presence of the hole 32 makes available to each lever a great length of pin, which not only ensures'greater robustness of the lever, but also further improves its resistance to Wear. FIGURE 4 shows that the length of each bearing surface is greater than the distance between two like faces of two neighbouring levers and is slightly less than twice this distance.

FIGURES 4 and 5 further show that the armature secured to the end of each lever compnises not only the member 29, but also the web of the lever and another member 33, the members 29 and 33 being disposed on either side of each lever. It will fur-ther -be noted that the mem- bers 29 and 33 have different thicknesses and that they are differently disposed, depending upon whether the lever on which they are mounted is close to or distant from the partition 21. This arrangement enables the corresponding actuating electromagnet to be olset in relation to the web of the lever. Owing to this offset, the electromagnets which are secured to the same face of the partition 21 are situated substantially in a common plane and are so positioned that, when the module of which they form part is positioned in or extracted from the machine, they a-re not likely to strike against any of t-he members of a neighbouring module. Consequently, the modules need not be engaged one within the other when they are posig tioned in the machine.-

Referring now to FIGURES 2 and 4, it -Will be noted that each lever can take either one of the following two states by pivoting about its pin between its two limits. In a rst state, the armature of each lever, attracted by the corresponding electromagnet, comes into contact with the pole pieces 34 of the said electromagnet. In a second state, or inoperative state, the armature ris removed from the pole pieces 34 under the action of a return spring 35 disposed between these pole pieces and then comes into contact with a rest abutment 36. Referring to FIGURE 2, which shows the levers in the inoperative state, it is also to be noted that the pivot pins otf the levers are preferably situated in a plane perpendicular to the direction of movement of t-he hammers and extending through the mean position of the path-of the point of contact of a lever with its hammer, and un-t der theseconditions the friction between the said lever and the said hammer is minimised. In FIGURE 2, this plane is represented -by a dash-dotted line bearing the reference letter A. By the aforesaid arrangement of the pivot pins, rapid wear on the levers and the hammers is thus avoided.

It is also to be noted that, in order to enable the mechanisms of a module to retain substantially constant operating characteristics in the course of time, the .pole pieces 34 of each electromagnet are coated with an anti- -remanence element 37 (also shown in FIGURE 4), which consists of a strip of non-magnetic material. For this purpose there may with advantage be employed a flexible plastic material known under the trade name Mylan It will further be noted from FIGURE 2 that, owing to the fact that a straight lever and a ben-t lever lbelonging to the same groulp of mechanisms each possess a separate pivot pin, the |lever arms of these levers are difierent. In order that the operating time may be the same for these two levers, it is necessary that the rest abut ments 36 of each of the levers be correctly and carefully adjusted and that their adjustment should not cal strength which, in addition, affords sufficient stabili-l ty and Ihardness to satisfy the necessary conditions. By way of example, a plastic material such as an acetal resin known under the trade name Delrin may be employed.

FIGURES 1A, 1B and 2 show that the two electromagnets for the Aactuation of the levers of one mechanism, such as the electromagnets 24A and 27A, -for example, 'are disposed lsubstantially at 90 to one another and in a common plane. `of each electromagnet are so designed that magnetic saturation is reached even with an -open air gap, so that the influence of the uctuations of the control volt-age and of the electrical resistance of the winding of each electromagnet on the response time of those electroma-gnets can be reduced. In addition, in order to avoid disturbing effects due to magnetic ux leakages, each electromagnet is covered with a magnetic shielding 38, which may also be seen in FIGURE 4.

FIGURES 1A, 1B and 2 furthermore show that etten module is -provided with a guide comb 39 which serves as a guide for each of the levers of this module, so as to ensure correct positioning of each of them in relation to the hammer which it is to actuate.

FIGURE 3 is a view in the direction 3 of FIGURE 2, but illustrating only the modules, and showing the relative position occupied =by the latter in the printing machine. =FIGURE 3 shows that, in each module, the levers are so positioned that two levers constituting one of the two groups of mechanisms of a module are separated from the two levers of the other group of mechanisms of this same module by a space which is sufficiently large to receive two levers of -a group of mechanisms of another module, these two modules being staggered in relation to one another and disposed on either side of the printing line, while the points of contact of the various levers with their respective hammers are disposed substantially on a common line. In this way, each module has one of its two groups of levers disposed between two groups of levers belonging -to an opposed module, and the other group of 'levers disposed between two groups of levers belonging to two contiguous modules and opposed to the aforesaid module. It is possible by means of this arrangement to give the partition 21 of each module a relatively great thickness, which assists in further increasing the rigidity of a module and thus makes it possible to obtain high stability `of the adjustments of the mechanisms offa module, regardless of the number of times that they are positioned in and extracted from the machine.

It will also be seen from FIGURE 3 that all the component parts of each module are so disposed as to form ra at unit, the overall thickness of whichis substantially equal to seven times the distance between two like faces of two neighboring levers. The modules may therefore be disposed in the machine as indicated in FIGURE 1A and extracted without any of their par-ts touching the parts of the neighboring modules. This feature renders possible the positioning or extraction of a module without any necessity for touching the other modules.

Referring now -to FIGURES 1A, 1B, 2 and 3, it will be seen that the frame 20 of each module is provided in its lower part with an engagement and orientation member 40 consisting, for example, of a tongue which serves for orienting this module when it is positioned in the machine. The said tongue is adapted 4to engage between two slideways G of the machine asy shown in FIGURE 1B. on its forward face two positioning studs or bosses 41 which serve to position this module perfectly in the machine, so that the point of contact of each of the levers of the said module with a corresponding hammer is exactly situated, when in the inoperative position, :at a predetermined appropriate distance from the surface of the drum for obtaining a correct impression. When a module is The winding and the magnetic circuit' In addition, the frame of each module comprises thus positioned in the machine, its positioning 'bosses 41 'bear against two perfectly plane bearing surfaces S machined in the frame of the machine, as shown in FIG- URES 1A and 2. These two perfectly trued bearing surfaces define a plane, called the reference plane and represented in FIGURE 2 by a dash-dotted line bearing the reference B, against which the positioning bosses bear in order to position the Amodule appropriately. Each module is thus positioned in the machine in relation to the said plane. In addition, each module is provided with a spring-loaded centering point 42 situated as close as possible to the point of Contact of the levers and of the hammers and co-operating with the engagement and orientation member 40 Iso as to ensure, by means of its conical tip, the correct positioning of the module in the said plane, so that the ends `of the levers of this module, which are in contact with the hammers, are situated exactly opposite to the hammers .which they are to actuate. It will be noted from FIGURE 2 that, in order to enable a module to be accurately centered by means of its centering point 42, the printing machine is provided with a centering hole 43 in which there engages the conical tip of the centering point, and which is so disposed as to ensure correct positioning of the module in relation to the frame of the machine. FIGURE 2 further shows that the attachment of a module in the machine is effected by means of Ia single securing screw 44 Situated between the two positioning bosses 41 and accessible from the forward face of the machine when the paper sheet 13 has been withdrawn. It will furthe-r be noted that the centering hole 43 is completed by a retaining device which, in the described example, consists of a lresilient clip 45 engaging in a groove 46 in the centering point. The said retaining device is intended to prevent the module from falling when the screw 44 is withdrawn in the positioning of the said module in the machine or its extraction therefrom. In order that one of the modules disposed in the machine may be extracted, it is necessary to exert a sufficient grip, especially as the resilient clip 45 engaged in the groove 46 in the centering point exerts a strong retaining action on the said module. In order to facilitate the extraction, engagement means are provided at the rear of the module and close to the axis of the centering point. For this purpose, a projection 47 may be provided on the frame of the module, close to the axis of the point 42, .which projection may be engaged by any appropriate means, such as a hook, for example, in order to effect the extraction. FIGURES 1A, 1B and 2 further show that the electromagnets of a module are electrically fed by means of conductors 48 which may be connected to current supply cables 49 by -means of a connecting plug 50. There is provided at therear of each module a securing device 51 which has the object of maintaining each connecting plug assembled with the corresponding module and which thus prevents it from hanging d own when the said module is withdrawn from the machine. The said securing device 51 may be of the mortise type as shown in the accompanying figures, and may then .be employed, not only to secure the said connecting plug, but also, when a module is positioned in the machine, to engage any suitable means for extracting the said module from the machine.

A module similar to that just described may be readily and rapidly positioned in the machine -by any, even unskilled, person adopting the following procedure. When the connecting plug is disengaged from its securing device, the orientation tongue of `the module is then engaged between two slideways G in the printing machine, and the module is then pushed towards the striker hammers, in the directi-on indicated -by the arrow F in FIGURE 1B, so as to bring the centering point 42 as close as possible to the corresponding centering hole in the printing machine. The module is then advanced until the centering point comes into contact with the resilient clip at the said centering hole. At this instant, pressure is exerted on the rea-r of the module Yuntil the -said resilient clip engages in the groove 46 in the centering point and thus suih-ciently maintains the module to enable it to be released without danger of falling. In Ithis position, th-e module is positioned almost correctly in th-e machine and its positioning bosses 41 are then c-lose to the bearing surfaces S of the frame of the machine. At the same time, owing to the fact that the module is transversely positioned by means of its centering point and its tongue guided by its slide- Ways, the levers of the module are situated substantially opposite to their respective hammers. It is then sufficient, in order to effect the final positioning and attachment of the module, to screw in the securing screw 44. In the course of this operation, the positioning bosses 41 bear against -their bearing surfacesS, While the point 42, which is already centered on its centering hole 43, compresses its spring. At lthe same time, the points of contactv of the levers and of the hammers move in the direction of the drum and are finally positioned at a predetermined distance from Vthe surface of the drum which is considered appropriate for vobtaining a correct striking.

In order to withdraw a module from the printing machine, the paper sheet 13 is first removed to obtain access to the screw 44 and to unscrew it. In the course of the unscrewing, the spring of the centering point partially expands, which has the effect of forcing the module-tothe rear and substantially removing the positioning bosses from their bearing surfaces. However, it will be noted that the resilient clip 45 remains engaged in the groove in the centering point, so that the module is retained both by its point .and by its tongue vand is not likely to fall. The module can then fbe extracted fby exerting a simple pul-l on it and using the projection 47 or the securing device 51 to enable the module to l:be more readily disengaged from the resilient clip.

It will .be noted that, owing to the fact that the modules are not engaged one within the other, the positioning or extraction of fa module can be rapidly effected by an unskilled person without any necessity for -any subsequent delicate readjustment` It will yalso be noted that the positioning of a module in the machine or its extraction therefrom takes place from that side of the frame of the machine which is further from the paper. This feature ensures that the module is substantially completely protected from the penetration of paper dust. Moreover, it renders possibley separate dismantling of the set of striker hammers without the modules having to be moved.

The characteristic features of the invention will be more clearly apparent from the following claim.

I claim:

In a printing machine which comprises on the one' hand a printing device comprising a movable character support and striker hammers mounted in .a frame, and on the other hand a series of hammer actuating mechanisms, an actuating module comprising:

a frame with a single' rigid partition extending substantially through a plane of symmetry, the said frame comprising two plane positioning bosses trued to bear against two bea-ring surfaces of the printing machine to permit positioning of the said frame, perpendicul-arly to a reference plane defined by the said bearing surfaces,

a rst set of hammer actuating mechanisms disposed on one of the two faces of the said partition and comprising a straight lever pivotally mounted on a rst pivot pin secured perpendicularly to the said partition, a lever bent lat an angle of about and pivotally mounted `on a second pivot pin secured perpendicularly to the said partition, each of the said levers consisting of a thin web assembly with a relatively long hub by which it is pivotally mounted on its respective pivot pin, the said straight lever being formed with an Iaperture for the passage of one end of the hub of the bent lever to permit oscillatory motion of the said straight lever, each of the said levers having one of its tvvo ends proled to constitute a surface of contact with `a corresponding striker hammer, the said first set of mechanism comprising in addition a rst electromagnet secured to the said partition and having pole pieces opposite to the other end of the said straight lever to attract filed ends of the `leve-rs and perpendicularly to a plane extending through the said positioning bosses so as to be engaged in a centering hole in the frame of the machine to enable the said levers to be positioned exactly opposite -to the corresponding striker hammers.

References Cited by the Eixaminer the said other end of the straight lever, when the UNITED STATES PATENTS said first electromagnet is energised, and a second 10 2,940,385 6/1960 House lOl-93 electromagnet secured to trie said -partition and hav- 3 144 821 8/1964 Dre-za 101 93 bent lever lto attract the said other end of the bent 3177803 4/1965 AntOnugC-i 101 93 lever when the second electromagnet is energised,

. 3,200,739 S/1965 Antonucci lOl-93 a second set of hammer actuating mechanism-s similar lo 3 233 540 2/1966 Gomup 101 93 to the rst `set of mechanisms and disposed on the 266,418 8/1966 Russo 101 93 other face of the said partition, and

a retractable centering point disposed close to the pro- WILLIAM B. PENN Primary Examineh

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