US3412932A - Punch interposer arrangement and associated selection means - Google Patents

Description

Nov. 26, 1968 E. E. MASTERSON ET AL PUNCH INTERPOSER ARRANGEMENT AND ASSOCIATED SELECTION MEANS 5 Sheets-Sheet 1 Filed July 14, 1966 INVENTORS DAV/D w. BERNARD EARL E. MASTERSON v CHE/VG-HUA WANG 8) MICHAEL s. smsamvow WRTQZZZ NOV. 26, 1968 E, E, MASTERSQN ET AL 3,412,932

PUNCH INTERPOSER ARRANGEMENT AND ASSOCIATED SELECTION MEANS Filed July 14, 1966 5 Sheets-Sheet 5 INVENTORS DAV/D W. BERNARD EARL E. MASTERSO/V CHE/VG-HUA WANG MICHAEL S. SHEBANOW Nov. 26, 1968 E. E. MASTERSON ET AL 3,412,932

PUNCH INTERPOSER ARRANGEMENT AND ASSOCIATED SELECTION MEANS 5 Sheets-Sheet 4 Filed July 14, 1966 Fig. 7

Nov. 26, 1968 E. E. MASTERSON ET AL 3,412,932

PUNCH INTERPOSER ARRANGEMENT AND ASSOCIATED SELECTION MEANS 5 Sheets-Sheet 5 Filed July 14, 1966 lNVE/VTORS DAVID W. BERNARD EARL E. MASTERSO/V CHENG-HUA WANG MICHAEL S. SHEBAIVOW United States Patent PUNCH INTERPOSER ARRANGEMENT AND ASSOCIATED SELECTIGN MEANS Earl E. Masterson, Newtonville, David W. Bernard, Sherhorn, Cheng-hua Wang, Newton (Ienter, and Michael S. Shebanow, Medfield, Mass., assignors to Honeywell Inc-, Minneapolis, Minn., a corporation of Delaware Filed July 14, 1966, Ser. No. 565,251

18 Claims. (Cl. 234-115) ABSTRACT OF THE DISCLOSURE For an actuator arrangement including a flexible-strip interposer, improved magnetic features for thrusting the interposer into, and out of, actuating condition magnetically, including such features as: opposed fiux generating means (permanent versus solenoidal, in certain cases) with a ferromagnetic interposer flexure; a nonmagnetic guide sheet intercepting the working gap; individual pole pieces for each flexure; a common permanent magnet for each aligned set of such pole pieces; and an adjustable flux-shunt between the common magnet and the pole pieces.

This invention relates to mechanisms for perforating computer record media selectively; more particularly it relates to a high-speed computer punch arrangement including an improved flexure interposer arrangement and an improved simplified magnetic selection arrangement associated therewith for providing faster, more reliable, punching operation, as well as simplified construction and maintenance characteristics.

Electronic data processing apparatus has placed a great emphasis upon operating associated terminal (input/output) mechanisms, such as a high-speed punch, with everincreasing speeds, yet with no sacrifice in reliability. The commercial environment of data processing mechanisms has further complicated the design constraints of such terminal equipment by requiring that it be relatively simple and inexpensive to produce, and especially that it be relatively maintenance-free. This is particularly true in view of the very expensive down time costs that result when any mechanical component fails so as to interrupt the operation of the high-speed electronic data processing system, whose hourly operating costs are extremely expensive. Therefore, a primary object of the invention is to provide a high-speed computer punch mechanism capable of operating at very high speeds, yet with reliability over a reasonably long life. A related object is to provide such a punching mechanism employing deflected flexure strips, as interposer means for selectively applying punching thrust to associated punches and to provide improved magnetic means therefor. A further related object is to provide improved magnetic selection means and associated magnetic means to actuate such fiexure-interposers for control of selective punching thereby.

Another object is to provide, for such an array of interposers and associated punches, a magnetic selection means comprising a pair of pole pieces for directing permanent magnetic flux operatively through each such interposer, in combination with a single common permanent magnet therefor. A related object is to provide adjustable magnetic shunt means between such pole pieces and such a permanent magnet for adjusting the strength of the field passing therebetween.

Still another object is to provide such an array of pole pieces and associated interposers and to include compensating pole and related means to reduce magnetic edge effects, fringing fields and the like for the outboard interposer arrangements. Another object is to provide with such an array, bidirectional interposer actuation means including opposed retain/release means. Still another object is to provide such an array of pole pieces in combination with bucking solenoid means adapted to oppose such permanent magnetic flux. A further object is to provide such solenoid means arranged to selectively activate interposers to an on position, otherwise permitting them to be held fail-safe by said permanent magnetic flux.

A still further object is to provide such an array of pole pieces and associated flexure interposers with integral sheet guide means along a linear set thereof. Another object is to provide such an arrangement including nonmagnetic punch construction to prevent erroneous punch translation.

According to a preferred embodiment of the invention, a high-speed serial card punch mechanism is provided to include two rows of aligned punches; a continually oscillating bail structure; two rows of flexure-interposer means mounted on the bail, each flexure array controllably actuated into driving registry with respective ones of said punches by a linear array of magnetic selection elements, each element actuating a respective flexure and comprising a pair of pole pieces operatively confronting the flexureinterposer and adapted to continually direct permanent magnetic flux therethrough for maintaining the flexure biased (deflected) to a normally off condition, being also provided with bucking solenoid means for selectively releasing the flexure into on condition by opposing this flux. In addition, a permanent magnet is provided to so energize such a set of pole pieces and magnetic shunt means is also provided therebetween to adjust the effective strength of the permanent magnet field at the flexures. Also a plurality of magnetic field directing and compensating means is provided adjacent the operative magnetic select elements and interposer/punch elements.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of the preferred embodiment of the invention as illustrated in the accompanying drawings, wherein like reference numerals denote like elements:

FIGURE 1 is an idealized perspective showing of high speed card punch embodiment of the present invention, some parts being omitted and some simplified for clarity;

FIGURE 2 is an enlarged sectional view of the arrangement in FIGURE 1 in the up, or nonpunching, phase;

FIGURE 3 is an isometric exploded view of one of the interposer assemblies of FIGURE 1 together with associated strippers, punches and magnetic select means, the interposer guide means therein being slightly modified;

FIGURE 4 is a front elevation of the magnetic shunt portion of one of the selection assemblies in FIGURE 1;

FIGURE 5 is a simplified sectional view of operating punch and interposer elements as in FIGURE 2, however, indicating the Down, or punching, phase;

FIGURE 6 is a fragmentary sectional view, much enlarged, of one of the preforms in FIGURE 3; and

FIGURE 7 is a very schematic idealized sectional front view of the pole pieces in one of the selection assemblies in FIGURE 1.

In general With reference now to the drawings, the invention Will be explained by way of an embodiment which implements an interposer arrangement for a two column (12 punches per column) high speed serial punch apparatus. This arrangement, as best seen in FIGURE 1, is a combined interposer-actuator unit A, shown in operative relation with a pair of associated multipunch magnetic selection arrays ML, MR. Unit A includes a pair of like multipunch interposer assemblies IL, IR, each being arranged to drivingly connect a driving means, in the form of a punch bail (bail frame H being shown) with selected punches in an associated aligned set of punches P, P (FIGURE 3). These elements, generally, implement the high speed serial punch, the functions of which are known and more particularly described in copending application Ser. No. 402,412 (now issued as U.S. Patent No. 3,279,- 690), commonly assigned. In essence, an eccentric drive shaft (not shown here) is arranged to rotate at high speeds (for instance, about 5,000 rpm.) so as to constantly reciprocate the bail (frame H) in a nearly-linear punching motion, as understood in the art. This bail is preferably flexure-coupled to the drive shaft and also is preferably flexure-suspended from a mounting support, as indicated in the aforementioned application. Bail frame H includes a shaft-coupling header portion HF. According to a feature of the invention, frame H is arranged to be integral with a set of projecting, subtended multipunchpair stripper means comprising stripper array ST (FIG- URES 1, 3).

Paired interposer assemblies IR, IL are mounted on bail H to be relatively symmetrical about stripper array ST. Assemblies IR, IL are identical, each including a multifingered interposer fiexure sheet 30, 30 respectively (only 30 is shown in FIGURES 1, 3), each finger 3, 3' thereof being arranged to be selectively positioned to drive an associated one of punches P, P respectively when the latter is selected. In the illustrated punch unit, two columns or sets P, P of 12 punches each, are shown, being understood as act-uable for selectively punching associated rows and columns in a passing computer record such as.

a punched card. It will be understood that the record medium is to be moved in a conventional manner below the lower punch ends, as is well understood in the art.

Thus, actuator unit A, being operatively arranged between left and right magnetic assemblies ML, MR, respectively, comprises a bail frame H, a stripper assembly ST projecting integral therebelow and a pair of left and right interposer assemblies IL, IR, respectively, the latter being attached to H to be symmetrical about stripper assembly ST. Assembly ML is shown exploded laterally away from unit A only for illustration purposes. Thus, the left columnar row (set) of punches P1 through P12 is disposed so that each punch may be selectively engaged for punching actuation by an associated one of interposer flexure fingers 31 through 312 respectively (only a portion being shown in FIGURE 3) of associated interposer flexure sheet 30 in left interposer assembly IL. Similarly, for companion set of punches P1 through P'12, which are disposed in operative relation with respective fingers 3-1 through 3-12 (not shown) of interposer flexure sheet 30 in right interposer assembly IR.

As seen in FIGURES 1 through 3, the stripper array ST projects integrally from frame H to comprise a central body portion of actuator unit A and includes a plurality of stripper extensions ST1 through ST13, each terminating in an enlarged head portion sh. Adjacent pairs of heads sh are adapted to engage opposite sides of respective paired punches, as seen hereinbelow. Stripper extensions ST1 through ST13 are separated by prescribed cutout slots SC-l through SC-12, fashioned to be just about wide enough to admit an associated pair of punches therealong, such as paired punches P1, P1 in slot SC-l. Stripper heads sh are engaged along associated slots pg formed along opposite sides of each punch. Slots pg are arranged so that heads sh may travel therealong and may engage the upper limit thereof just after punching is completed, i.e. when bail H has bottomed in its downward thrust, the unselected punches being held up (by retainer meanssee below) while heads sh begin to return the selected punches as bail H returns upwardly. Thus, a surrounding pair of confronting heads sh will engage a punch after it has bottomed to retract it (strip it) and return to to the unactuated (or UP position shown in FIGURE 2), being thus automatically returned upward with bail H.

Punches As is somewhat conventional in the art, punches P are aligned in prescribed lateral positions by guiding bores in a die means D, so as to be drivenly engaged by respective ones of flexure fingers 31 etc. Punches P are also arranged to be maintained in the aforementioned UP, or rest, position when not selected, being so maintained by retainer means (SP, FIGURE 2) engaged therewith. More particularly, as FIGURE 2 shows, a retainer flexure spring SP is provided in a slot ps in each punch P, for instance, spring SP-l being provided for punch P-l, spring SP1 for companion punch P1, etc. Slots ps have their upper limits offset between paired punches (those in punches P offset from those in punches P) to allow associated retainer springs SP, SP to be similarly offset, and non-interfering, while projecting from a common base. The upward thrust of these retainer springs may be stoplimited to establish a prescribed up-plane RR (FIG- URES 2, 5) for the tops thereof, just below the driving interposer flexures 3, and out of engagement therewith. A simple stop means as indicated at stop bar SX (FIG- URE 2) projects from the rigid frame to effect this, being stoppingly engaged by the lower end of stop grooves ps of paired punches along a common plane. Thus, slots ps will be of difierent lengths to accommodate the different engaging position for retainer springs SP, SP, yet terminated along a common plane by stop SX. As those skilled in the art will appreciate, other equivalent retainer and stop means may be provided.

Each punch is also provided with a magnet MG for punch verification purposes. Magnets MG comprise permanently magnetized material carried by the punches and adapted to be brought operatively adjacent an associated verification detector PCM when the punch is properly driven to its maximum bottoming excursion (down position). Thus, by sensing the presence of the magnets, each detector PCM provides a verifying indication that its associated punch has perforated the record.

Punches P are comprised of tool steel or other tough metal. Preferably, the top portions PT of punches P are separately fabricated to comprise a high durability, wearresistant, non-magnetic material, such as Stellite (trade name), and are atfixed, such as by welding or the like, to the main shank portion of the punch. This provides a durable, impact-resistant tip for driven engagement with the associated fiexure interposer finger. This tip material is also specified as non-magnetic to prevent false punch-translations (explained below), i.e. not to be carried downward to activate detector PCM when bail H descends if the punch is not selected. Such may occur if a punch becomes magnetized and is magnetically attracted to follow a moving magnetized part. For instance, stripper heads sh may become magnetized by the adjacent fields from the magnetic assemblies MR, ML, etc., and, in turn, might attract an adjacent punch tip to follow them toward the down position. It will be appreciated by those skilled in the art that such false translations of a nonselected punch P are intolerable; for instance, they interfere with the transport of a passing record and also can induce a false punch echo (punch verification signal) from detector PCM. In this connection, it will also be appreciated that stripper projection ST, including stripper arms ST-l through ST-13 and associated heads sh, is preferably comprised of a nonmagnetic, preferably demagnetized, tool steel or the like so as to be tough and strong, and yet retain no magnetization such as might falsely translate one of the punches, as aforesaid.

Magnetic selection FIGURES 1 and 3 show the environment in which interposer assemblies IL, IR are arranged, being clamped on bail H to be symmetrical about stripper assembly ST, and also to be symmetrically surrounded by the left and right magnetic assemblies (ML, MR, respectively). Leftward magnetic assembly ML includes an elongate, strongly magnetized, permanent bar magnet 23 enclosed in a nonmagnetic (preferably aluminum) casing 21 to which upper and lower sets of pole pieces, 27, 29 respectively, are attached. Magnet 23 comprises a strongly ferromagnetic material and includes a pair of opposite polarity, upper and lower projecting poles 23-P, 23-PP, respectively. Upper and lower sets of pole pieces 27, 29, respectively, comprise a number of vertically paired, lowreluctance, flux-conducting members mounted on casing 21 so as to be in operative flux-conducting relation with upper and lower magnet poles 23-P, 23-PP, respectively. Lower pole pieces 29 comprise fourteen spaced, relatively identical, projections 29-0through 29-13 (a portion being shown in FIGURE 3 as well), all cantilevered out relatively orthogonal from lower magnet pole 23-PP to be relatively orthogonal to the vertical bail (driving) axis V. Similarly, upper pole pieces 27 comprise a set of fourteen projections 27-0 through 27-13, all cantilevered out from upper magnet pole 23-P at the same oblique angle, being also oblique to axis V. Casing 21, preferably aluminum, is adapted to direct the flux from magnet 23 to pole pieces 27, 29f

Upper pole pieces 27 thus extend downwardly toward a corresponding one of the lower pole pieces 29 to be vertically registered therewith, thus forming fourteen identical pole pairs. Each of the twelve inboard pole pairs 27-1/ 29-1 through 27-12/ 29-12 are thus disposed so that each pair may project a permanent magnet flux somewhat normally toward the respective one of the twelve magnetic interposer flexure fingers 3-1 through 3-12 with which it is operatively associated, being spaced therefrom in opposing flux-coupled relation. Thus, each such pole pair can attract (and repel) a corresponding flexure toward (and away from) themselves, out of (and into) the thrust-transmitting, ON position (and the OFF, or no-punch, position). These ON/OFF positions are indicated for flexures 3-2/3'-3, respectively, in FIGURE 4 and 3-1/3-1 in FIGURE 5. The two outboard pole pairs in assembly ML, namely pole pairs 27-0/29-0 and 27-13/29-13 (FIGURE 3) are not operatively associated with any interposer flexure, but are provided (as detailed below) to help balance the magnetic field for the outboard fiexures, 3-1, 3-12, respectively, in cooperation with the outboard strippers ST-l, ST-13. As shown, all the pole pairs (27-0/2 9-0 through 27-13/29-13) are normally set to apply flux from permanent magnet 23 to pull flexure fingers 3-1 through 3-12 toward themselves, i.e., to be set normally OFF.

The twelve inboard, interposer-actuating, pole pairs are also each provided with a bucking solenoid winding about each (upper and lower) pole piece. These winding pairs, when current-pulsed, are each adapted, as seen below, to substantially cancel out the aforementioned flexure-attracting permanent magnet flux from their re spective pair of poles to selectively translate the associated flexure finger to ON (punching) position. Thus, a bucking solenoid winding is provided on each of upper pole pieces 27-1 through 27-12, namely windings 27-31 through 27-312, respectively; while, similarly, on lower pole pieces 29-1 through 29-12, windings 29-31 through 29-312, respectively, are provided, as is best seen in FIG- URE 3. Select means (not shown) will be understood as provided to apply sufiicient select current to each such pair of pole windings at times when the associated flexure interposers are selected, i.e., to be released to ON for punching a selected associated punch. The field generated by this current thus bucks, and cancels out, the corresponding permanent magnetic flux, releasing the preflexed, pre biased flexure finger to be returned by its natural internal resilience to the ON or punch position. Punch position is where the flexure engages the associated inner (punching) preform 5 so as to be stiffened thereby while thrusting the associated punch through the record when carried down by bail H.

Thus, for example, when bail H is in UP (START) position of the punching cycle thereof (i.e., at its upward extreme and ready to start downward in a new punching cycle), if the record were to be punched at the position thereon under punch P'-2, a punch-current (Select) signal would then be applied through associated bucking coils 29-32/27-32 to oppose the permanent magnetic flux emanating from associated pole pieces 29'-2/27-2 and holding associated interposer finger 3'-2 in OFF position, i.e. engaged against outer preform 1. In this OFF position, interposer 32 is flexed a maximum and is biased to snap back against inner preform 5' when released, thus bridging slot C-2 therein. Application of the aforesaid select-current signal so releases interposer 3'-2 to assume this ON position so that when bail H next descends the free tip 1T of the interposer, as stiffened by preform 5, will engage the head PP'-2 of punch P-2 to drive it down for punching that (selected) position in the record. When bail H, thereafter, ascends to complete this punching cycle, the associated pair of stripper heads sir-2, sir-3, engaged about head PP-2 (in slots pg therein) will, of course, return P'-2 toward UP position for beginning the next punch cycle. Punch P'-2 may be similarly selected in the next cycle; or it may be not selected, in which latter case the permanent magnet field from poles 292/27-2 will be allowed to retain flexure interposer 3'-2 back in OFF position as indicated for interposer 3-1 in FIGURE 5.

Magnet 23 is comprised of a high retentivity, permanently magnetized ferromagnetic (high mu) material, while projecting pole pieces 27, 29 are comprised of a low retentivity easily magnetizable material. According to a feature of the invention, magnetic assembly ML is also provided with a flux-shunt 25, (FIGURE 4) movably clamped between upper pole piece set 27 and upper magnet pole 23-P to be adjustably positionable between poles 23-P, 23-PP to assume various flux-shunting positions therebetween and establish a variable shunt-gay dy (shown full-open in FIGURE 1 and partly closed in FIGURE 2). Thus, shunt 25 is a high permeability, lowreluctance material mounted fiux-couplingly between pole 23-P and pole piece set 27 while being set to return a variable portion of the magnetic flux from pole 23-P to magnet 23, this portion varying inversely with the length of gap dy. Such shunted flux is prevented from passing through, and between, paired ones of pole pieces 27, 29. Shunt 25 thus adjusts the permanent magnet strength of the field emanating from pole pieces 27, 29 and may control the force exerted thereby to pull associated flexure fingers 3 into the OFF (no punch) position. Slots 25-S are provided in shunt 25 to accommodate clamp means for allowing this variable shunt positioning. As recognized by those skilled in the art, such an adjustable shunt is an extremely convenient means for adjusting the net magnetic force upon the interposer fiexures and thus is convenient 'for standardizing the pull of the magnetic assemblies (MR, ML) either during fabrication or in the field. This makes the manufacturing tolerances and positioning tolerances less critical, both for assemblies ML, MR and for the overall actuator unit A.

It will be appreciated that magnetic shunt 25 (25' similar) may comprise a magnetic flux conducting, low reluctance material being affixed to casing 21 to be adjustably positionable, i.e., to be moved up and down to create a variable shunting gap dy between the poles 23-P and 23-PP of permanent magnet 23. Shunt 25 is shown in FIGURE 1 as fully-open, thus recirculating or returning a minimum amount of (substantially no) magnetic flux to permanent magnet 23; while being shown in FIGURE 2 as having reduced gap dy so as to return a greater portion of the magnetic flux, thus preventing it from circulating through pole pieces 27, 29. It will be appreciated by those skilled in the art that such an adjustable shunt has advantageous uses especially in association with a flexure-interposer actuator unit, such as assembly A, where simplicity and ease of fabrication and maintenance are salient features. For instance, here, the

spacing between flexures 3 and interposer poles 27, 29 somewhat critically affects the resultant magnetic field applied thereto, and may be shuntadjusted. That is, provision of shunt will allow adjustment, both at the factory and in the field, in the strength of the permanent magnet field emanating from poles 27, 29 to thus compensate for variations in the characteristics of affecting parts, from unit to unit. For instance, in the manufacture, the heat treating and the handling of permanent magnet 23, magnetic characteristics may be introduced that vary from unit to unit. Similarly, if pole arrays 27, 29 are manufactured by different people at different times, their dimensions, metallurgy, etc., may vary somewhat, as may their mounting position relative to fiexures 3. Such variances in manufacturing tolerances can be compensated for by varying shunt position to normalize the emanent field. For example, shunt gap dy may be set to a prescribed (e.g., one-half) gap until final assembly when it may be adjusted up or down to normalize the emanant field when the net effect of manufacturing variations has made the field a little too strong or a little too weak, respectively. Similarly, linear variations in characteristics along one set of pole pieces can also be compensated for by this shunt; for instance, skewing it longitudinally so that gap dy is greater at one end of magnetic array ML than at the other. Alternatively, individual shunts may be provided for each set of pole pieces 27-1/29-1, etc.

It is quite apparent, of course, that such individual shunts act to couple the permanent magnet and solenoid pole pieces in a characteristic manner. Such a shunt, being freely adjustable, may be disposed to bridge all, or a portion, of the interpole-piece gap (dy). For example, a shunt piece 25 may be permanently fixed to bridge the entire base-gap between pole pieces 27-1, 291 and thus, inherently, form a flux-return path (since it will inherently provide a lower reluctance path than the outside air). Thus, in certain cases the shunt 25 will comprise a sheet of metal bridging both the permanent magnet pole faces and the pole pieces to provide a flux path for both entirely along its length (rather than being adjustable as illustrated). It should be realized that, besides shunting a portion of perman nt magnet flux as aforementioned, the additional shunt function of solenoid flux return is quite advantageous. For instance, it has been noticed that this greatly alleviates the common problem of cross talk" (between adjacent magnets-often a vexing problem, as workers in the art well know). It will, of course, be apparent that such cross talk leakage can act to undesirably couple adjacent magnets so that they affect, and degrade, one anothers operation. This is undesirable because it makes it impossible to normalize the flux condition of a magnet assembly since, being influenced by its neighbor magnet, one cannot predict whether that neighbor will be on or off (the inductive coupling between the two being different in either case) and hence cannot reference upon a single normal environment.

Of course, other magnetic means may be provided to perform these interposer-positioning functions of magnetic assembly ML. For instance, magnetic means might be mounted adjacent each fiexure 3, on the bail, to translate it to OFF position selectively, in advantageous relation with the light, self-restoring flexure. It will also be understood that magnetic assembly MR, arranged symmetrically on the opposite side of actuator unit A and having similar parts (with same numerals, but primed) is arranged identical to comparison assembly ML described above, MR being adapted to control the ON, OFF (punch, no-punch) positioning of associated interposer flexures 3' in the corresponding interposer assembly IR.

FIGURE 7 will summarize the features and operation of this magnetic selection assembly, illustrating, in front elevation, the paired pole pieces thereof in relation with one another and with associated fiexure interposer means (in phantom). Here a set of fourteen pairs of pole pieces comprising magnetic assembly ML (assembly MR is similar, of course) appears, with associated magnetic shunt 25 being exploded away for clarity. FIGURE 7 thus shows frontally only the pole tips of the fourteen pairs of poles 2743/2941 through 2713/2913 of magnetic selection assembly IL, indicated in FIGURES l and 3 especially. The flexure strips 3 associated with the inboard pole pairs 27I/29-1 through 2712/2912 are indicated fragmentarily and in phantom, as 31 through 3-12, respectively. FIGURE 7, though not necessarily to scale, thus illustrates a representative relationship of the pole pairs to one another and to these fiexure strips. It will be apparent that the indicated magnetic select means, besides being convenient to implement and very clean in operation, long-lived, etc, is readily controlled. For instance, with inboard pole pairs 1-12 thus regularly disposed and so uniformly arranged along the array of flexures, it is easy to arrange for equal-strength selection/ release fields therealong. Moreover, so sizing and spacing these pole pieces and overlapping them with their associated flexures gives a highly efficient operation.

Another feature of the invention is the provision of two dummy coilless outboard pole pairs, 27- /29-0 and 27-13/29-13 confronting no fiexures, as indicated. Those in the art will recognize that this helps greatly to normalize the magnetic forces on the outboard fiexures (e.g., especially 3-1 and 3-12) to be operated like the other fiexures. Provision of the outboard stripper head units, sh1 and sh-13, also facilitates this. Where necessary, a pair of dummy outboard fiexures and associated solenoid units may also be added to optimize this effect, according to the invention.

In summary, workers in the art will recognize the advantages in so actuating the interposers between off and on positions without the use of mechanical parts, but merely by the selective application of a solenoid current pulse. This eliminates the conventional and troublesome mechanical linkage used for this purpose, such as sliding interposer thrust means; restore cam means; associated alignment and guide means for the interposer and the linkage therefor, as well as synchronization means to synchronize these mechanical parts with the punch bail; to synchronize the restore cam with the interposer actuator, etc. It will be appreciated that this eliminates many parts and a good deal of expense, both in fabrication and in adjustment needs. It also improves reliability greatly, since these mechanical parts are fussy and troublesome to make and to maintain, being prone to a good deal of abrading Wear, for instance, being apt to drop out of synchronism, etc. It will also be appreciated that such selection means advantageously coact with the novel stripper arrangement whereby the stripper engaging means is hung centrally from the constantly reciprocating bail, leaving a good deal of room for access of the aforementioned magnetic selection means. It will be appreciated that making the fiexures magnetic is a simple yet attractive way of making them responsive to such magnetic selection means; especially when they are made part magnetic and part structural.

I rzterposer Only one of the interposer assemblies IL will be particularly described, it being understood that the companion assembly IR is similarly constructed and arranged. Interposer assembly IL will first be generally described with respect to FIGURES l, 2 and 3, there being seen to comprise a thin, resilient, multifingered, interposer fiexure sheet 30 surrounded by a pair of spaced inner and outer guide sheets 5, 1, respectively. A spacer 13 separates outer sheet 1 from flexure sheet 30. According to a feature of the invention sheets 1, 30, 5 are clamped together and conjunctively flexed (deflected) inwardly against stripper ST between a pair of inner and outer clamp bars 7, 15, respectively. Bar 15 is attached to bail H, as indicated more particularly in FIGURE 2. It will be generally understood that interposer sheet 30 comprises 12 interposer flexure fingers 3-1 through 3-12 and is so disposed upon bail H that each of these fingers 3 may be engaged punchingly with an associated one of the punches (Pl through P12 respectively) when carried by bail H into the downward punching phase of the punch cycle.

According to another feature, outer, nonpunching preform sheet 1 (sheet 1' similar) comprises a flexible, nonmagnetizable metal sheet adapted to be deflected by clamp bars in a prescribed manner so the free end thereof is engaged guidedly along one side of all the stripper heads sh as indicated in FIGURES 1 and 2. It is found that the magnetic flux from the pairs of pole pieces 27/29 is able to pass relatively unaffected through the cross-section of such a sheet to attract associated ones of fingers 3 theretoward. Preform 1 thus serves as a guiding stop for the set of interposer flexures 3-1 through 31-12 which, in the nonpunching (OFF) positions thereof are held somewhat conformingly thereagainst and out of driving engagement with the associated (nonselected) punch when bail H is depressed. Preform 1' is similarly related to associated flex-ures 31 through 3'12. This conforming contact is indicated in FIGURE 5 for nonpunching flexure 3-1, the latter being pulled by the permanent magnetic flux from associated poles 29-1/271 to curve against preform 1. Such conformed flexing of sheet 1 allows it to contact a flexure finger 3 very smoothly and evenly along its vertical length without distorting it, stressing it, shearing it, or vibrating it (no bounce). Sheet 1 thus acts as a stop-limiting member.

So forming the outer preform of a single integral sheet for guiding a set of interposer flexure fingers is obviously convenient. Moreover, the solid sheet was found surprisingly effective in transmitting magnetic flux from magnet assembly ML to the fingers, where it had been supposed previously that flux-notches in the sheet were required for this. Avoiding such notching of preform 1 obviously strengthens it, as well as simplifying its fabrication. However, one or several holes, such as hole 1h in sheet 1 (FIGURE 3) may be provided to view the tips of adjacent interposer fingers (e.-g. 3-1) for alignment thereof relative the tops of associated punches.

Similarly, inner punch preform 5 may be comprised of a flexible, nonmagnetizable metal sheet adapted to be deflected between clamps 7, against the side stripper ST with flexure sheet 30 bendingly engaged relatively coplanar and conformingly thereagainst, thus establishing a pre-flexed static condition thereof. Flexure fingers 3 are thus spring-biased to be urged into the ON position. The free end of preform 5 may be slightly beveled for flatter, low pressure engagement against the stripper. Punch preform 5 is believed to function as a preformed deflected beam curved to provide a prescribed stiffening reinforcement of associated interposer fingers 3, extending coextensive therewith almost to their tip so as to prevent them from buckling when thrust against an associated punch. However, with sheet 5 so disposed just above the tops of associated punches P1 through P12, it becomes necessary to provide for clearing such punches when they are nonselected since sheet 5 is carried down therepast with bail H during punching phase (FIG- URE 5). Thus, a set of 12 clearance cutouts C1 through C-12 (FIGURE 3) are provided at this free end of sheet 5, each being disposed and dimensioned to clear an associated punch. Thus, cutouts C-l, etc., are slightly wider than the enlarged punch heads PP and are cut deeply enough to admit heads PP when bail H, with attached interposer assembly IL, descends to its bottommost (Down) position. Punch phase (or Down position) is indicated in FIGURE 5 where nonselected punch P-1 (head PP-l thereof) is indicated as having entered a corresponding cutout C-l in punch preform 5. Sheet 5 may thus be stamped out to include cutouts C.

related to flexures 3'1 through 3'12.

Preferably, the flexure fiingers are arranged to be sufficiently wide to bridge associated ones of cutouts C (but little wider), being dimensioned to overlap successive ones of the lands therebetween and thus be guided on both sides. Thus, the fingers will be somewhat wider than associated punch beads which must fit within the cutouts.

Thus, according to a feature of the invention, a set of flexure interposers associated with a row of punches, as well as the associated inner and outer preforms therefor, are each formed from a single flexible metal sheet, the sheets being mounted in common upon the punch bail and being clamped there to be preflexed in common (biased) in common integral bending arrangement. The outer preforms (1, 1) may be formed to comprise a sheet about 3.125 by 2.359 inches with a thickness of 18-20 mils found satisfactory for this embodiment. Both pairs of preforms (1, 1', 5, 5) are formed from a nonmagnetic material having a high degree of flatness (at least adjacent the interposer sheets 30, including fingers 3, 3' which are also very flat) being about twice the thickness of sheets 30, 30". For instance, a flatness in the neighborhood of 0.003 TIR has been found acceptable. It is preferred in this embodiment to make inner preforms 5, 5' about 25 mils thick and outer preforms 1, 1 about 19 mils thick, Evidently, the preforms (1', 1, 5', 5) must be somewhat thicker than the interposer sheets 30, 30 to exhibit somewhat more stiffness. Sheets 30, 30 will be magnetizable, light and highly resilient. For instance, it may preferably be about 10 mils thick, with spacers 15, 15 about the same. Sheets 30, 30' may comprise 10-10 cold-rolled steel or blue spring (1095) high-carbon steel, or other hard nonmagnetic steel and will also include ferromagnetic material, inserted therein or clad thereon, as indicated below.

Workers in the art will appreciate many advantages from mounting the interposer assemblies IR, IL on the bail H. One such advantage is that the stripper ST may project from bail H to guide interposer elements, yet with no rubbing between these members at any time. Moreover, the stripper heads sh and the surface of the stripper body may also act to position the preform guides.

Flexure characteristics FIGURES 2 and 5 will be seen to supplement FIG- URES 1 through 3, showing a section through both interposer assemblies IR, IL in illustrative operating relation with associated portions of stripper ST and respective punches. It will be assumed in FIGURE 2 that the entire assembly is in Bail-up phase where the punches and flexure interposer fingers are all disengaged. Thus, those punches that punched in the preceding cycle will be understood as having just been returned to Up position by the stripper. The punches are all understood as being retained Up, offset above stripper heads sh a prescribed clearance (e.g., about 4 mils) by the retainer means (e.g. springs sp) as aforesaid. The punches thus present their top surfaces aligned along a prescribed Up-plane RR (FIGURE 2) by stop means SX (above). Plane R-R is arranged to be spaced below the engaging tips of the interposer flexures 3, 3' a prescribed amount (gap d here about 10 mils). With this arrangement, there will be no appreciable impact between an interposer flexure and the associated punch head when the two are engaged since engagement will occur very close to the top of the bail stroke where relative velocity (along V axis) is close to zero. Thus, a gentle, smooth engagement of interposer with punch is achieved, something very desirable in the art. For illustration purposes, it will also be understood that, in FIG- URE 5, one of the interposer flexures (3-1), is nonselected, i.e. has been pulled out of punch position and into no punch position (from ON to OFF position, as indicated by the arrow) where it may clear (not engage) associated punch P1 when the bail/stripper mount supporting it is so depressed in this punch phase. On the other hand, fleXure 31 is seen selected, i.e., allowed to snap to ON position by select-current fields and is thrusting punch P'l. As aforesaid, punches P, P are indicated as having separately formed heads PT of a high durability, nonmagnetic material welded thereon.

According to the invention, a modification of the interposer flexure structure may be effected whereby flexures 3, 3 are fabricated in a compound structure having a tough, durable, resilient structural portion I-A (e.g. of a hard spring steel) and a high mu, ferromagnetic (e.g. soft iron) portion I-B, bonded intimately to portion IA. For instance, it has been found that cold-rolling such a sheet of soft iron onto a sheet of (high carbon) blue spring steel under high pressure can molecularly bond the two together into a satisfactory compound interposer fiexure. These layers must be very intimately bonded so that, when flexed, they deflect as a substantially integralbeam element, without experiencing any appreciable internal stresses, such as different shear stresses which might tend to part the layers, especially at the clamping point. In an alternate form, the fiexures may comprise a three-part sandwich having a pair of outer spring steel sheaves molecularlybonded to an intermediate ferromagnetic iron layer. It has been found that the mechanical strength and durability of compound flexures so fabricated is improved without sacrificing any needed magnetic-attraction characteristics. Workers in the art will visualize other equivalent ways of providing these two different materials in such a composite interposer flexure.

According to another feature which may be used either instead of, or together with, the aforementioned multilayer construction of flexures 3, 3' is the provision of a wear tip IT on the free end of the fiexure fingers to be engaged with the top of a respective punch. More particularly, it has been found that welding a relatively thin layer of wear material, such as Stellite, onto the tips of interposers 3, 3 and thereafter machining, or otherwise forming, these tips to conform to the desired precise dimensions, squareness, etc., reduces the likelihood of abrading wear thereof by the punch. Such wear is especially troublesome in tending to make the tips nonsquare so that they engage the top of a respective punch unevenly. Such oblique engagement can quickly lead to misaligned punching actuation and also accelerate the further wear of the two parts, e.g., by gouging out of the top of the punch because of the reduced en- Y gaging area, etc.

Interposer operation FIGURE 5 is somewhat similar to FIGURE 2 showing roughly the same cross-sectional area, but at a different phase in the punch cycle, that is, at the punching (or Baildown) phase of the cycle, where FIGURE 2 illustrates res phase (Bail-up). FIGURE 5 illustrates selected and non-selected interposers and punches. Thus, interposer 31 is seen in the selected (interposed, punch-thrusting) condition, as is associated punch P1. Conversely, companion interposer 31 is seen in the non-selected (noninterposed) condition, and associated punch P-l is non-selected and non-punching.

The interposer assemblies are seen here arranged symmetrically about central bail H and stripper frame ST projecting therefrom, as in FIGURES 1-3 above. Initial stripper head sit-1 is shown engaged with outer preforms 1, 1 to space and flex them properly. Inner preform 5 is seen as guiding interposer 3'1 to thrust associated punch P'-1 downward sufiicient to effect punching, bail H and stripper ST having bottomed at the punching phase in this driving cycle. Selected" flexure interposer 3'1 is thus understood to be in conformed, guiding, stiffening engagement against preform 5. The magnetic interposer-select means is fragmentarily indicated by lower pole pieces 29, 29 and their associated solenoids 29-31, 2931 respectively. It will be understood that selection of flexure 3'1 was effected by effectively nullifying the pull of the permanent magnet flux from associated pole pieces 271, 291, thus preventing these from pulling flexure 3'1 into nonselected (OFF) position against outer preform 1'. As aforesaid, this is done by applying a select current pulse through coils 2'31, 27'31. The resultant bucking (select) field thus releases flexure 31 to return itself into engagement against inner preform 5'. The preflexing of the interposer flexures assures this self-return action. On the other hand, companion flexure 3-1 will be seen as pulled outwardly against associated outer preform 1 by the permanent mag net flux from associated pole pieces 271, 291, there evidently being no bucking (select) field from associated solenoids 29-31, 27-31. Thus, flexure 3-1 is kept clear of punch head PP-l of associated punch P-l when it is depressed with the bail assembly, as shown in this punching phase. Head PP-l avoids contact with inner preform 5 by riding up into the associated slot C-l therein provided for this, as indicated. It will further be appreciated that non-selected punch P-1 will be maintained in this UP condition (by retainer spring sp), being ready, when the bail assembly has returned upwardly, to begin the next punching cycle. However, selected punch P'1 will be therewhile engaged in stripper grooves pg, by associated surrounding stripper heads sh-I, sIz-Z (sliding along these grooves) and will be returned to the UP position for beginning the next cycle. It will be recognized that it is thus a feature of the invention that the magnetic interposer selecting means are relatively fail-safe, in that, being held normallyoff, they are less likely to produce erroneous punching, e.g., as might occur if no punch pulses were required to clear the interposers and failed to occur.

The features of the above-described improved interposer arrangements may be summarized as follows, with particular reference to FIGURES 2 and 5. As aforesaid, a feature of the invention is that the interposer flexures do double duty, serving both as the armature of the selecting solenoid means and as the mechanical interposer linkage. Furthermore, this linkage function is provided without any abradng parts and with a small, compact, lowmass unit. Each row of interposers may be considered as being clamped between a pair of relatively stiff (preform) guide means, the overall assembly being mounted on the stripper-bail frame so that these guide means are preformed into a prescribed flexed curvature and carry the interposer flexure with them to be similarly pre-flexed. Thus, in the nonpunching position an interposer will be held aganst the outer preform so that it cannot engage the top of the associated punch. When bail-stripper ST is in UP phase, starting a punch driving cycle, selected interposer flexures are released to snap into engagement with the inner preform where as the downstroke of the bail begins, they may engage the top of the associated punch as to thrust them punchingly. As the punching load is applied and stripper ST thrusts downwardly, toward the die D and the perforable record therebeneath, the thin selected interposers transmit this thrust to respective punches smoothly and firmly, being reinforced and stiffened by the inner preform. The deflected, guided flexu-res thus react like a rigid column to transmit the required punching force without buckling. Since both the preforms and the flexures have a common point of attachment (to bail H) there can be no relative sliding motion or resultant abrasion, etc. between them and therefore no relative wear. 1

The deflected beam preforms 1, 5 are a feature of the invention that provides convenience as Well as efliciency since they avoid the fussy manufacturing problems that would be inherent in providing the bail frame with contoured guide surfaces. That is by deflecting preforms 1,

13 in common with their associated intermediate flexure interposer, a pair of guiding, conformingly contoured surfaces is automatically provided.

Since the interposer assemblies IL, IR are carried by reciprocating bail assembly and since selection is performed magnetically, the relative motion and abrasion which normally exists in prior art machines between the reciprocating and fixed members is eliminated, as is any resultant wear. The interposers, being held in a normally non-punching position by a permanent magnet field, move to punch position in a snap-flexing action because of their inital flexing preload, doing so, of course, when the (bucking) releasing field is applied from associated solenoid coils. Translation of the interposer from non-punching to punching position will be understood to occur at the top of the up-down stroke of the bail when a clearance is established between the punch and the interposer, for instance, when the punches are in the condition shown in FIGURES 2 and 7. Thus, the punch selecting interposer system of the invention has only one moving part, and that part a simple flexure means which has no sliding, abrasive pivoting or impacting motions. No prior art interposer system is known which can claim these highly desirable characteristics.

Equivalent magnetic interposer translating arrange ments may be provided according to the invention for other actuator arrangements where the selectable actuation of driven members is accomplished by selectable coupling thereof with a driving flexure member. Such systems may be provided for the actuation of print hammers in a high speed computer printer apparatus, other record marking appartus, or the like. Equivalent interposer means and selection means will occur to those skilled in the art.

While in accordance with the provisions of the patent laws, the above has illustrated and described preferred forms of the invention and their modes of operation, it will be apparent to those skilled in the art that changes may be made in the apparatus described without depart ing from the spirit and scope of the invention as set forth in the appended claims, and that, in some cases, certain features of the invention may be used to advantage without a corresponding use of other features and certain features may be changed or substituted for, equivalently, as appreciated by those skilled in the art.

Having now described the invention what is claimed as new and desired to be secured by Letters Patent is:

1. Apparatus for selectively actuating driven means comprising bending guide means; elongate flexible interposer means disposed in flexed engagement with said guide means, said guide means being adapted to so engage said interposer means as to bias it flexingly into a prescribed driving condition along a prescribed driving path along which said interposer means may drivingly actuate said driven means; drive means arranged to periodically thrust said interposer and guide means together along said path; and coupling control means for selectively displacing said interposer into and out of said path, and thus out of said driving relation with said driven means; continuous nonmagnetic limit means interposed between said interposer means and said control means so as to intercept the working flux gap and being adapted for limiting the said displacement of said interposer means out of said path; said interposer means comprising a ferromagnetic strip; each said control means comprising an opposed first and second flux-generating means adapted and disposed to urge said associated ferromagnetic strip into and out of said driving condition.

2. The combination as recited in claim 1 wherein said driven means comprise at least one set of aligned reciprocable marking elements; wherein said interposer means comprises a set of ferromagnetic preflexed flexure strips aligned with each said set of elements, each strip being disposed to engage a respective one of said marking ele- 'ments when assuming said driving condition, said first magnetic flux generating means including a plurality of magnetic pole means, one thereof being disposed in fluxcoupled relation with each of said strips for selectively controlling said urging relative said driving condition.

3. The combination as recited in claim 2 wherein said control means comprises one set of aligned pairs of pole pieces for each set of interposer strips, each pair of pole pieces being operatively disposed adjacent the nondriving position of a deflectible portion of a respective strip and including solenoid energizing means for selectively enabling the deflection of said associated strip portion into said driving condition; said set of pole piece pairs being operatively associated with a common permanent magnet means for energization thereof to normally urge said associated strip portions into said non-driving position except when opposed by said associated solenoid energizing means.

4. The combination as recited in claim 3 wherein adjustable flux-shunt means is provided coupling each said set of pole pairs with said associated magnet means, being disposed in adjustable flux-shunting relation across the poles thereof.

5. The combination as recited in claim 4 wherein each said solenoid means includes a solenoid winding about each pole piece in said respective pair and is adapted to be selectively energized for providing solenoid flux arranged to cancel the permanent magnet fluxemanating from sa d respective pole pieces to thereby release said associated prebiased strip to flex itself returningly to said driving condition.

6. The combination as recited in claim 5 wherein is also provided two pairs of outboard pole pieces each being arranged to normalize the magnetic effects upon a respective adjacent outboard strip and thus assure uniform magnetic flux distribution across said set of strips without edge effects.

7. The combination as recited in claim 6 wherein is also provided for each said set of strips an integral, relatively continuous nonmagnetic outer guide sheet disposed adjacent and between said associated pole pieces and said strips as disposed in said nondriving position for conformed stop-limiting engagement with said strips there, being mounted to be reciprocated in common therewith.

8. The combination as recited in claim 7 wherein said driving means comprises a constantly oscillating punch bail; wherein said marking elements each comprise a punch, each of said punches being provided with a nonmagnetic wear tip adapted to prevent the magnetically induced translation thereof.

9. The combination as recited in claim 8 wherein said apparatus comprises a high-speed punch assembly for selectively and encodingly perforating data processing records in response to prescribed character-encoded punch signals, said punch assembly comprising a periodically reciprocating bail member; at least one array of aligned punches, each being arranged to be selectively displaced along an associated punch path in response to occurrence of associated ones of said character signals; said bail member also including stripper means projecting therefrom to be periodically reciprocated in synchronism therewith, said stripper means comprising a plurality of punchretractor heads disposed in alignment to be in retracting engagement with associated ones of associated punches; an array of flexure means operatively associated with each said punch array and mounted on said bail member to be reciprocated therewith, said array comprising a plurality of aligned flexures each being associated couplingly with a respective one of said punches and comprising an elongate planar spring member predeflected to normally assume a first condition adapted for coupling engagement with said associated one of said punches also being adapted to be selectively flexed and translated out of said first condition into a second noncoupling condition; each said flexure array also including a guiding sheet member associated deflectingly with said flexures, being clamped in common therewith against said bail member to deflect them together, conformingly and stilfeningly; and interposer translate means comprising said set of pole piece pairs associated with each said array of flexure means, each pole pair thereof being disposed in operative relation with one of said flexures for selective translation thereof into said first condition responsive to occurrence of a prescribed one of said punch signals.

10. The combination as recited in claim 2 wherein each said plurality of pole means is operatively associated with a respective said set of strips and also includes permanent magnet flux-generating means coupled in common therewith.

11. A marking arrangement for marking data processing records comprising:

record marking means selectably movable along a prescribed marking path between a marking and a nonmarking position; driving means continually oscillating along a prescribed drive path spaced from said marking path; interposer means disposed between said driving means and said marking means for selective coupling thereof, said interposer means comprising at least one elongate flexible cantilevered ferromagnetic strip and a guide means engaged with each said interposing strip for flexing thereof so that the free tip is normally disposed in a driving condition along a coupling path between said drive and marking paths for driving engagement with said driven marking means; and bidirectional magnetic control means disposed in flux-coupling relation adjacent said interposer strip and adapted to selectively actuate said tip thereof into said driving condition and out of said driving condition to a nondriving condition, to thus control actuation of said marking means from said nonmarking to said marking position; continuous limit means disposed in working-gap flux-intersecting relation between each said strip and said associated control means for defining said nondriving condition, said control means including first magnetic means for urging said tip in one of said conditions and second, selectible magnetic means for urging said tip oppositely into the other of said conditions.

12. The combination as recited in claim 11 wherein said marking means comprises at least one set of individually, selectably actuable marking elements reciprocable between respective marking and nonrnarking positions; wherein said interposer means comprises a set of prefiexed magnetic spring members for each said set of marking elements, said members being deflectable in substantially one resilient axis only, one said spring memher being arranged for engagement with each one of said marking elements; and wherein said magnetic control means comprises a set of pairs of magnet pole pieces for each said spring member set, one pair of pole pieces being disposed operatively adjacent each of said spring members along said resilient axis for selective translation thereof into said conditions to thus control said selective marking.

13. The combination as recited in claim 12 wherein each said set of pole piece pairs is operatively disposed with a common permanent magnet to provide said first magnetic means; wherein each said pair of pole pieces is provided with selectively energizable solenoid means to provide said second magnetic means.

14. The combination as recited in claim 13 wherein adjustable flux shunt means is provided intermediate each said permanent magnet and associated ones of said pole piece pairs for controlling said urging thereof.

15. Apparatus for selectively actuating driven means comprising bending guide means; elongate flexible interposer means disposed in flexed engagement with said guide means, said guide means being adapted to so engage said interposer means as to bias it flexingly into a prescribed drivingcondition along a prescribed driving path along which said interposer means may drivingly actuate said driven means; drive means arranged to periodically thrust said interposer and guide means together along said path; and coupling control means for selectively displacing said interposer into and out of said path, and thus, selectively, out of said driving relation with said driven means; said interposer means comprising a ferromagnetic strip; each said control means comprising a pair of solenoid pole pieces arranged to project from a prescribed base plane into operative adjacency with a respective interposer strip so as to be capable of electromagnetically translating the strip, these pieces being separated along this plane by a prescribed base-gap; permanent magnet means adapted to be coupled to both said pole pieces across said base-gap so as to project a prescribed permanent-magnet flux therethrough for operate coaction with said respective strip; and shunt-return means arranged between said magnet means and said pole pieces so as to bridge at least a portion of said base-gap relatively along said plane and to thereby provide a shunt for returning a prescribed portion of said permanent magnet flux to said magnet means as well as also providing a prescribed low-reluctance return path between said pole pieces along said base plane and thereby eliminating cross-talk leakage to adjacent control means; said shunt-return means comprising material of prescribed reluctance extending across at least a portion of said base-gap.

16. The combination as recited in claim 15 wherein said shunt return means material extends completely across said base-gap.

17. The combination as recited in claim 16 wherein said solenoid pole pieces are adapted to selectively pull said strip out of said driving condition and wherein said permanent magnet flux is adapted to hold the strip so pulled.

18. The combination as recited in claim 17 wherein there is also provided a continuous non-magnetic limit means interposed between said interposer means and said control means for limiting the said displacement of said interposer means out of said driving path.

References Cited UNITED STATES PATENTS 3,104,053 9/1963 Rabinow 234119 X 3,232,525 2/1966 MacNeill et a1 234-33 3,279,690 10/ 1966 Masterson 234--115 3,307,781 3/1967 Jones 234- X WILLIAM S. LAWSON, Primary Examiner.

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