US2884792A - Indexing apparatus - Google Patents

Description

O. R. NEMETH INDEXING APPARATUS May 5, 1959 2 Sheets-sneu 1 y Filed June 24, 1955 oTro RNEMETH INVENTOR BY Zbw wfw Arron EVS May 5, 1959 o. R. NEMETH 2,884,792

INDEXING APPARATUS Filed June 24, 1955 2 sheets-sheet 2 Q 37 Z u.

O MOVEMENT IG. 5 OTTO R. NEMETH INVENToR ATTORIVEKS'- United States INDEXING APPARATUS Application June 24, 1955, Serial No. 517,849

11 Claims. (Cl. 74--111) This invention relates to an indexing apparatus and more particularly to an electromagnetically operated pawl and indexing means in which uniformly precise, stepwise rotation of an index wheel may be achieved. A preferred application of the invention is for driving a mechanical type counter for totalizing or counting electrical pulses. In this instance, the shaft of the index wheel is used to drive the counter wheels of a conventional counter. Inasmuch as the mechanical counter or other device requiring uniform step-wise rotation constitutes no part of the present invention, the following speciiication will deal exclusively with the indexing apparatus.

In many conventional type escapement mechanisms ernploying a pawl and ratchet wheel for rotating a shaft in disc-rete steps, a pawl is caused to move between adjacent tooth elements spaced about the periphery of the ratchet fwheel and thereby exert a tangential force component to rotate the wheel through a given arc. Because of mechanical diculties encountered in uniformly moving the driving pawl the same distance each time the wheel is to be stepped, there is an element of uncertainty as to whether one step movement of the wheel will be exactly equal to any one of the preceding or subsequent step movements. It will be clear, of course, that a given number of pawl movements, equal to the number of teeth on the wheel, will eiect one complete rotation of the wheel, and that this number of movements will equal the number required for any subsequent complete rotation. There is no assurance as between individual pawl movements, however, that the wheel will be moved through precisely the same degrecs of arc each time.

One of the causes for uneven movement of the driving pawl can be attributed to wear and subsequent shifting ofthe moving parts. A further source of trouble is in the actuating means employed for moving the pawl. Where the pawl is used for indexing as well as driving the ratchet wheel, a stop means of some type must be used to limit the motion of the actuating means in order that the pawl cease moving the wheel after it has rotated through a desired arc. If such a stop means is used, there is the possibility that the pawl will shift out of proper alignment with the stop means so that movement of the pawl will be checked before the wheel has completed the predetermined arcuate movement. In this event, it is necessary to re-set or advance the stop means in accordance with the desired degree of arcuate movement of the ratchet wheel.

Further, in conventional pawl and ratchet wheel systems, the wheel can usually be moved in only one direction due to the nature of the ratchet wheel construction. There is generally no provision for dynamic balancing of the moving parts so that sudden shocks or vibrations may cause unintentional movements of the pawl and ratchet wheel.

In the case of prior art electromagnetically operated pawl means, the pawl and indexing roller, if any, are subject to high impacts during operation, since the magnetic field Strength generally increases as the pawl comes closer latent to engagement with the ratchet wheel. Further, the effectiveness of such magnetic devices oftentimes depends upon the shape and value of the current pulse actuating the mechanism. v

Bearing the above in mind, one object of the present invention is to provide a vastly improved indexing apparatus over conventional ratchet wheel and pawl arrangements, in which precise indexing of a wheel is assured notwithstanding wear in the moving parts of the system.

More particularly, an object of the invention is to provide an improved pawl and indexing means and animproved actuating means therefor, in which each individual step-wise arcuate movement of an index wheel may be made to equal each other individual step-wise movement thereof without the necessity of precise mechanical tolerances in the actuating means.

Another important object is to provide an indexing mechanism having an electrically and mechanically symmetrical construction whereby an index Wheel may be rotated in either direction.

Still another object is to provide an indexing apparatus of the above type in which all of the moving components are provided with inertia balancing with respect to their pivot points, whereby the structure will not be seriously affected by shocks and vibrations.

Another object is to provide a novel magnetic actuating means in which the magnetic eld strength decreases towards the end of the pawl stroke thereby decreasing the pawl impact on the index wheel and increasing the wearing life of the apparatus components.

With regard to the magnetic actuating means, another object is to provide an actuating mechanism which does not depend upon the value or shape of the exciting current pulse.

A more general object is to provide an indexing mechanism that meets the above objects and which is mechanically rugged and will give long and reliable service with minimum necessity of replacing worn parts.

These and further objects and advantages of this invention are attained by providing a rigid frame structure for mounting both an index wheel shaft and two symmetrically located pivot means for suitable support.- ing members. The rigid frame structure insures that the index wheel shaft will remain in a xed or constant spatial relationship with respect to the pivot means for the supporting members. Precise arcuate indexing of the index wheel in either direction is accomplished by indexiing means disposed at the ends of two arms rigidly extending from the pivoted supporting members respectively, on opposite sides of the index wheel. A pawl element, distinct from the indexing means is provided on each arm `and used as the driving pawl depending upon the desired direction of rotation of the index wheel. Each pawl is pivoted to its corresponding supporting arm for small arcuate movements with respect to the indexing means.

Pivoting or rocking movements of the supporting mem. bers is effected by a symmetrically arranged electromagf netic actuating means. Each pawl is arranged with re` spect to its associated indexing means and the index wheel to engage the wheel upon pivotal movement of the sup. porting member prior to engagement of the wheel by the indexing means. in this manner, the pawl will effect most of the movement of the index Wheel and the index, ing means will subsequently engage the wheel to index it to an exact desired position. Motion of the supporting member by the actuating means is checked by the index,- ing means itself. Therefore, any misalignment or wear in the pawl means or in the actuating means will not ,intro-Y duce any inaccuracies in the indexing of the index Wheel.

The supporting member for each arm is actuated by a separate electromagnetic eld established in such a manner that the magnetic forces effective in operating assmaa the supporting member, initially increase and then decrease with movement of the pawl and indexing means toward engagement with the index wheel. By this arrangement, the impact force of the indexing means with the wheel is minimized.

A better understanding of the various features of this .invention will be had by referring to the accompanying drawings, in which:

Figure 1 is a schematic perspective view of the indexing apparatus of this invention in normal rest position; Figure 2 is a view similar to Figure 1 showing one ofthe indexing means in operated position;

Figure 3 is a front elevational view of a modified embodiment of the invention;

Figure 4 is a plan view of the embodiment shown in Figure 3; and

`Figure 5 is a graph useful in explaining part of the operation of the invention.

. Referring to Figure 1, there is shown a frame structure rotatably supporting wheel means designed for angular step rotation in the form of an index wheel or ratchet wheel 11 keyed to a shaft 12. As shown, shaft 12 may be journalled in the frame and extend rearwardly therethrough to drive a mechanical counter 13 or any other device in which precise step-wise rotation in either direction is desired.

' The index wheel 11 is provided with a series of identical tooth elements 14 each having smoothly machined concave shaped exterior edges 1S. The edge of one tooth cooperates with the opposing edge of an adjacent tooth to dene a series of recesses in the index wheel periphery for receiving suitable pawl and indexing means to be described shortly. In Figure 1, there are shown ten teeth 14. This is the desired number when the index wheel shaft is to be used to drive a decade counter since ten movements of the pawl driving means will effect one complete rotation of the ratchet wheel to in turn eiect a complete rotation of a decade counter wheel. It will be understood of course, that any other number of teeth 14 may be used depending upon the particular mechanism to be driven by the system.

In the embodiment of the invention shown in Figure 1, the index wheel is arranged to be rotated through an arc of thirty-six degrees each time the mechanism is actuated.

The actuating mechanism comprises two identical structures arranged in mirror symmetry on either side of the index wheel 11 so that operation of one will turn the index wheel 11 in one direction and operation of the other will turn the wheel in the other direction. Since these structures are identical in operation, description of one will suice for both.

As shown in Figure 1 the structure to the left of wheel 11 includes an actuating means comprising an electromagnet coil 16 provided with pole pieces 17 and 17 extending from opposite ends of the coil in an upward direction to terminate in opposing spaced pole tips 18, 18'. Between the pole tips, there is positioned an elongated supporting core member 19 comprising a laminated magnetic core, Member 19 is pivoted to the frame 10 by a pivot means 20 disposed between the pole tips. With this arrangement opposite ends 21 and 21 of the core member 19 may swing into and out of alinement with the pole tips 18 and 18' respectively. In Figure 1, the supporting member 19 is shown in its normal inoperative position in which the tips 21 and 21 are arcuately displaced from the pole tips 18 and 18. The core member 19 is normally biased in this position against a stop 22 extending from the front wall of the frame 10, by a bias spring 23. The stop 22 may be secured to the pole piece 17 as at 24.

A pair of supporting arms 25 and 26 are rigidly secured to the supporting member 19 and, as shown, extend upwardly to terminate respectively on either side of an indexing means in the form of an indexing roller 27. Extending transversely and intermediate the ends of the arms 25 and 26 there is provided a pivot pin 2S adapted to support pawl means including a pair of pawl arms 29 and 30 terminating on either side of a pawl roller 31.

As shown more clearly in the corresponding structure to the right of the index wheel 11, a coil spring 32 is secured to and wound about the pivot pin an-d has its ends terminating on the pawl arm as at 33 to bias these arms back against a cross bar stop 34. With this arrangement, each pawl may pivot about its pivot pin in a direction towards the index wheel but is limited against rotation in the other direction by the stop 34. The pawl roller 31 is normally positioned ahead of the indexing roller 27 with respect to the index wheel 11, so that upon rocking movement of the supporting member 19, the pawl roller will engage the wheel prior to the indexing roller.

It will be noted from Figure 1, that the frame structure 10 serves to hold the pivot means 20 for the supporting member 19 in fixed spatial relationship with respect to the index wheel shaft 12. The indexing roller supporting arms 25 and 26 extends upwardly adjacent the periphery of the index wheel in a direction transverse to the line connecting the pivot means 20 and the shaft 12 so that rocking movement of the supporting member 19 will cause the indexing roller to move generally towards and away from the index Wheel. The radius arm between the indexing roller 27 and lthe pivot means 20 is designated R-l in Figure 1 and is made of suiiicient length or extent such that when added to the radius R-Z of the index wheel to the points of contact on ,the teeth surfaces 15, the sum will always be greater 'than the distance D between the index wheel shaft 12 and the pivot means 20. By this construction, the indexing roller 27 will be checked in its movement towards the index wheel by the wheel itself. In other words, there is no way in which the indexing roller can swing pastor through the index wheel.

This checking or stopping of the movement of the indexing roller 27 by the index wheel is an important feature of the present invention and is illustrated more clearly in Figure 2 which shows the indexing roller 27 pushed against one of the recesses in the index wheel 11. Note that the radial distances R-1, R-2, and the distance D between the shaft 12 and pivot means 20, form a triangle, the sum of the distances R-1 and R-Z always being greater than the distance D.

The operation of the indexing apparatus will =be clear from the above description. When the electro-magnet coil 16 is energized by a pulse of electrical energy applied to the terminals of coil 16, the supporting member 19 is magnetically pulled towards a position `of alinement with the pole tips 18 and 18 by the generated magnetic field. Movement of the supporting member about the pivot means 2G causes the supporting arms 25 land 26 to swing to the right or towards the index wheel periphery as viewed in Figures l and 2. The pawl roller 31 will rst engage the outer end of the inner concave edge 15 defining a recess between adjacent tooth elements 14 of the index wheel, and roll along this inner edge, simultaneously exerting a downward or tangential force component causing the index wheel to rotate. The pawl is free to follow the peripheral movement of the wheel and remain in complete engagement with the recess throughout such movement because of its pivotal mounting to the arms 25 and 26. Thus, as the index wheel rotates through the designated arc, the pawl support arms 29 and 30 will pivot in a clock-wise direction with respect to the indexing means support arms 25 and 26 to accommodate this movement of the index wheel.

Following the movement of the pawl roller 31, the indexing roller 27 is positioned to engage the index wheel recess immediately above the recess engaged by the pawl roller. It will be noted from Figures l and 2 that the indexing roller 27 is positioned for combined tangential and radial movement towards the index wheel 11. Movement of the indexing roller 27 is stopped or checked by 'the index wheel itself, since the sum of the radial lengths R41 and R-Z is greater than the separation distance D between the index wheel shaft `and pivot means 20, as previously described. Because of the smoothly machined recess edges and the rounded indexing roller, the rachet wheel will always be stopped in its periphenal movement at exactly the same corresponding positions, It will be *evident that so long as the radial distances R-I and R-Z 'and the distance D remain fixed, the index wheel necessarily must be indexed to exactly corresponding positions each time the mechanism is actuated. The constant spatial relationship of these distances is assured in View of the structural frame 1i? itself serving as the mounting means, `'and 'the rigidity of the supporting `arms 25 and v26.

Upon cessation of the electrical pulse to the magnetic coil '16, the magnetic field will 'collapse fand the biasing spring23 will pull vthe supporting member i9 in a counter- 'clockwise direction until it engages the stop 22. The pawl and indexing rollers will then resume the position shown in Figure l. Release of the pawl from the recess is accommodated by its pivotal mounting to the arms 25 'and 26 whereby it may swing further in a clockwise direction to disengage itself from the upper portion of the recess. After disengagement, the spring 32 will return the pawl arms to their normal position against the stop 34. In order to hold the index wheel 11 in its indexed po-sition as the pawl roller 31 is being withdrawn, a spring biased -arm 35 supports a roller 36 which is adapted to be seated in a recess of the index wheel as shown in Figures l and 2. Roller 36 merely rides along the inner concave surfaces 15 of the wheel during step-wise operation of the wheel.

insofar fas the actuating means is concerned,'it will be noted that by arranging the pole piece tips 18 and 18 at a radial distance from 'the pivot means 20 greater than v the radial distance of the ends 21 and 21 in the manner shown, there is never :any physical contact between the Supporting member core ends and these pole tips. Further, 'there is no stop means or other checking mechanism necessary in the actuating system since the indexing roller serves entirely as the means to check rocking movement of the supporting member 19. Close tolerances in the actuating means is therefore not necessary. It will be noted from an inspection of Figure 2, that if the indexing roller did not stop the movement of the supporting .member 19, it would still tend to rotate in a clockwise direction upon energization of the magnetic pole tips, since the member is not fully in alinement with the pole tips. There is thus a relatively large margin of tolerance available in the actuating means.

By arranging the magnetic pole tips with respect 'to the supporting member core 19 as shown, 'the magnetic force tending to aline the core member with the pole tips 13 and 1S' will initially increase with rocking movement of the core until the core tips 21 and 21 'are juxtaposed the edge portions of the tips 18 and 1S', after which the force will decrease tending towards zerowhen the member is in perfect alinement.

This magnetic characteristic is graphically illustrated in Figure 5 in which curve 37 shows the variation of the magnetic force with changes in the position of the core member 19 as it rotates in a c'lockewise direction. Note that as the core member approaches alinement with the pole tips, the magnetic force tending to rotate it, drops off. Thus, there is not as .large an impact of the indexing roller against the index wheel recesses as is the case in conventional magnetically operated systems, and wear on the indexing roller is diminished. Because of the fact that the complete stepping of the index wheel is effected by a single magnetic attraction, the duration or shape of the current pulse applied to coil 16 is immaterial provided that it is above a given minimum value and duration. In other words, no further current pulses are necessary -to return the pawl and indexing roller. Thus a full cycle of operation is 'effected by a single pulse of current fed to the coil 116.

It will further be noted that precise tolerance in the driving pawl 'means is not necessary. lt is only necessary that the pawl roller 31 move the index wheel a suicient arcuate distance s-uch that the indexing roller 27 will engage the recess immediately following the recess engaged by the pawl. The indexing roller 27 itself will then elfect the inal' movements for accurately indexing 'the index wheel. Thus, wear 'of the pawl roller and other pawl parts will not aiect the acuracy of the indexing.

The supporting core member 19 is made slightly asymmetrical with respect to its pivot point 20 in order to dynamically balance the indexing and pawl means with respect to this pivot point. By such inertial balancing, sudden jars or vibrations will set up equal and opposite force moments about the pivot point 'thereby canceling themselves out and there is 'thus no chance of inadvertent `pivotal movement of the member in the absence of a current pulse.

Similarly, the pawl arms 29 and 30 terminate iat their rear ends in a counter weight 38 to dynamically balance the pawl with respect to its pivot point 28, and the rear portion of the index retaining arm 35 is, in like manner, provided with a mass for proper inertial balancing.

The index wheel itself is perfectly symmetrical in contradistinction to the conventional ratchet wheels, and thus its dynamic balancing is assured.

The structure to the yright of the index wheel 11 in .Figures l and 2 is a mirror image of the above described mechanism and operates in an identical manner when a pulse of current is applied to the coil 40. Since the index wheel is symmetrical, the engagement of the pawl and indexing means is effective in turning and indexing the wheel in the same manner as pawl roller 31 and indexing 'roller 27, except that the wheel `is stepped in a clock-wise direction. When the mechanism is used to operate a mechanical counter, pulses applied to the coil 16 may be added while pulses applied to the coil '40 may be subtracted so that the final indication on the counter wheels 13 would represent the total number of pulses applied to coil 16 less the total number applied to coil 4i?.

Referring now to Figures 3 and 4, there is shown in front and plan view, respectively, a modified embodiment of the present invention in which three 'coupled wheel elements are employed for angular step rotation. In this embodiment, the index wheel 41 is similar to the index wheel 11 of Figures l and 2, but is provided with two ratchet wheels 42 and 43 'coaxially disposed on 'ope posite sides of the wheel 41 and keyed to the wheel shaft 44. The actuating magnetic means and supporting core members, such as core member `45, are also similar to the magnetic means 16, 17, 17 and the supporting core member 19 of Figures l and 2 and are energized and operated in the same manner.

In Figure 3 however, the pawl `means 46 for the left hand structure is off-set behind the indexing means 47 in a manner to engage the ratchet wheel 43 as clearly shown in Figure 4. Similarly the pawl means 48 for the right hand structure is off-set lin front of the indexing means 49 in a manner to engage the ratchet wheel 42. By this arrangement, the index wheel 41 is initially stepped in either direction depending upon which kpawl and indexing means is energized, the indexing means 47 or 49 functioning to index the wheel to exactly the sa'me position in the same manner as described in connection with Figures l and 2. In Figure 3, a retaining roller 50 on a spring biased arm 51 may be used to hold the index wheel 41 in its stepped position as the pawl means is being retracted from one or the other of the ratchet wheels. This roller will ride in and out of the recesses of the wheel in the same manner as the roller -36 on arm 35v of Figure l.

By using ratchet wheels into which the pawl means may be moved, a more linear or constant torque during the stepping of the mechanism may be realized. This torque characteristic is attained by proper shaping of the recesses in the ratchet wheels and proper dimensioning of their diameters in order that the pawl will be moving substantially tangentially to the wheel when it initially engages the recess. As shown clearly by the arcuate arrow 52 in Figure 3, the pawl 48 will engage the recess in ratchet wheel 42 when it is moving substantially tangentially to the wheel. Only a small percentage of the entire arcuate stroke of the pawl is utilized in moving the wheel and thus this movement is substantially linear in the direction of a tangent, and the resulting driving torque on the wheel will therefore be substantially constant.

The rear ratchet wheel 43 is identical to the ratchet wheel 42 but yis mounted on the shaft 44 in an opposite sense so that its specially designed recesses may cooperate with the pawl 46 in the same manner when the wheel is to be stepped in the other direction.

It is thus seen that both embodiments of the present invention provide a greatly improved indexing mechanism over conventional ratchet and pawl systems. The symmetrical configurations enable accurate operation and indexing of an index wheel in either direction, with small inertia and high speed. Further, dynamic inertial balancing in all of the pivoted components of both embodiments result in a rugged and reliable mechanism notA appreciably affected by shocks and vibrations. In

addition, the novel arrangement of the magnetic actuating means with magnetic force characteristics as depicted in Figure 5, insure long life and minimum wear on the moving parts. v

Many modifications of the disclosed embodiments falling within the scope and spirit of the present invention will occur to those skilled in the art. The indexing apparatus is, therefore, not to be though of as limited to the specific embodiments set forth for purposes of illustration.

What is claimed is:

l, An indexing apparatus comprising, -in combination: a frame; wheel means designed for equal angular step Irotation and having a shaft rotatably mounted on said frame; pivotable support means symmetrically mounted on said frame on either side of said wheel means; indexing means secured to each of said support means for movement into engagement with and also away from the periphery of said wheel means, said indexing means being positioned `relative to said support means and said wheel means so as to exert a combined radial and tangential force on said periphery of said wheel means upon engagement therewith; pawl means coupled to each of said indexing means and positioned to move towards and into engagement with said wheel means ahead of said indexing means, whereby each indexing means and its coupled pawl means on either side of said wheel means is adapted to separately effect said angular step rotation of said wheel; and, symmetrically disposed actuating means for pivoting said indexing means and coupled pawl means toward said shaft for said wheel means.

2. An indexing apparatus according to claim l in which said wheel means includes an index wheel with a plurality of teeth defining symmetrical recesses about its periphery, said recesses being adapted to receive either one of said indexing means, and in which said indexing means and coupled pawl means on either side of said index wheel is responsive to a single pivoting of said support means to eiect a single angular step rotation of said wheel.

3. An indexing apparatus according to claim 2 in which said pawl means are olf-set in a forward and rearward relationship with respect to the corresponding indexing means to which they are coupled, and in which said wheel means also includes ratchet wheels co-axially disposed on said -shaft to the front and rear of said index wheel, respectively, said ratchet wheels being adapted to receive said pawl means, respectively, upon movements towards and away from said shaft, whereby said index wheel and shaft may be turned in either direction.

4. An indexing apparatus according to claim 2 in which each of said pawl means are adapted to engage said index wheel recesses on respective sides upon movements towards said index wheel, whereby said wheel may be turned in either direction.

5. An indexing apparatus according to claim l, in which each of said symmetrically disposed actuating means includes an electromagnet positioned to magnetically attract said support means upon energization to pivot said support means towards alignment with the force eld of said electromagnet, whereby the magnetic force tending to move said support means and associated indexing means and pawl means, initially increases as the pawl means engages said wheel and decreases as the indexing means engages said wheel.

6. An indexing apparatus according to claim l in which said indexing means, said support means, and said pawl means include counter balancing integral masses, respectively, in said indexing means, said support means, and said pawl means to provide dynamic balancing with respect to the pivot points of said indexing means, support means, and pawl means.

7. An indexing apparatus comprising, in combination: a frame; an index wheel; a shaft rotatably mounting said index wheel to said frame; a supporting member; pivot means pivoting said supporting member to said frame for rocking movement with respect to said frame, said `frame maintaining said shaft for said index wheel and said pivot means in iixed spatial relationship with respect to each other; an arm rigidly secured to said supporting member and extending from said supporting member to a position adjacent said index wheel, said arm terminating 'in an indexing member; a pawl means pivotally mounted on said arm for pivotal movement with respect to said indexing member; stop means on said arm positioned to check pivotal movement of said pawl means; bias means normally holding said pawl means against said stop means, whereby said pawl means is normally positioned closer to said index wheel than said indexing means; and actuating means for pivoting said supporting member whereby said pawl is moved to en-gage said index wheel to rotate the same and said indexing member is moved to subsequently engage and index said index wheel.

8. An indexing apparatus according to claim 7 in which the radial distance between said indexing member and said pivot means added to the radius of said index wheel is greater than the distance between said pivot means and said shaft for said index wheel, and in which said indexing member is positioned for combined tangential and radial movement towards said index wheel, whereby further pivotable rocking movement of said support means is checked by said index wheel.

9. An indexing apparatus according to claim 8, in which said supporting member is made of magnetic material and said actuating means includes an electromagnet positioned to magnetically attract said supporting member upon energization to pivot said supporting member.

10. An indexing apparatus according to claim 9, in which said electromagnet is positioned from said pivot means a radial distance greater than the radial dimension of said supporting member, whereby said supporting member is actuated to move towards an aligned position with respect to said electromagnet without physical contact therewith, and whereby the magnetic force tending to move said supporting member initially increases as the pawl means engages said wheel and decreases as the indexing member engages said wheel.

l1. An indexing apparatus according to claim 9, in which said supporting member, said arm and indexing member, and said pawl means include counter balancing integral masses, respectively, in said supporting member, said arm and indexing member, and said pawl means to provide dynamic balancing with respect to the pivot points of said supporting member, said arm and indexing member, and said pawl means.

References Cited in the le of this patent UNITED STATES PATENTS 274,325 Himmer Mar. 20, 1883 10 o Winslow Jan. 8, 1889 Landon Sept. 17, 1918 Franca Mar. 23, 1926 Richter Dec. 19, 1933 Barth. Feb. 10, 1942 Smith June 5, 1945 Lonnqvist Apr. 10, 1956

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