US2679797A - Record controlled selective printing machine - Google Patents

Description

June 1, 1954 H, KEEN RECORD CONTROLLED SELECTIVE PRINTING MACHINE 6 Sheets-Sheet 1 Filed Aug. 30, 1951 Attorney H. H. KEEN RECORD CONTROLLED SELECTIVE PRINTING MACHINE June 1, 1954 6 Sheets-Sheet 2 Filed Aug. 30 1951 Attorney June 1, 1954 H. H. KEEN RECORD CONTROLLED SELECTIVE PRINTING MACHINE 6 SheetsSheet 3 Filed Aug. 50, 1951 .lnvenfor A a/wow H9 Kim,

June 1, 1954 KEEN 2,679,797

RECORD CONTROLLED SELECTIVE PRINTING MACHINE Filed Aug. 30, 1951 6 Sheets-Sheet 4 lnvenmr M92049 Hm: fife-EN June 1, 1954 H, KEEN 2,679,797

RECORD CONTROLLED SELECTIVE PRINTING MACHINE Filed Aug. 30, 1951 6 Sheets-Sheet 5 Inventor 1944/? 0.40 A6944 AEEA/ ANE; a. M

Attorney Patented June 1, 1954 RECORD CONTROLLED SELECTIVE PRINTING MACHINE Harold Hall Keen, Letchworth, England, assignor to The British Tabulating Machine Company Limited, London, England, a British company Application August 30, 1951, Serial No. 244,385

Claims priority, application Great Britain September 7, 1950 22 Claims.

This invention relates to printing mechanisms and more particularly to such mechanisms in which type selection is effected by one or more timed impulses.

This form of printing mechanism is particularly adapted for operation under control of data read from perforated record cards.

It is the object of the present invention to provide simplified means for controlling the selection of type and the resetting of the type member of a kind readily adaptable to multi-column printing mechanisms.

In accordance with the invention a printing mechanism for printing data represented by one or more timed electrical impulses, has a type wheel, a clutch through which the type wheel is driven, means for effecting engagement of said clutch under control of data impulses to drive the selected character on the type wheel towards printing position, means for effecting disengagement of said clutch at one or more predetermined times, the last disengagement so efiected positioning the selected character at the printing line, means for taking an impression from the character at the printing position, resetting means operative for the type wheel which has been selected for effecting a further engagement of said clutch within a predetermined period and further means operative to disengage the said clutch as the type Wheel reaches the normal reset position.

It is preferred to employ:

(1) A start and stop electromagnet to control the engagement and disengagement of the clutch so that control is wholly electrical permitting the ready adaptation of the mechanism to different data codes.

(2) A higher speed reset without requiring greater accuracy of clutch timing.

(3) Means for controlling automatic zero printing in a multi-column printing mechanism settable manually or by an impulse derived from a card or other source.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a sectional elevation of the printing mechanism.

Figure 2 is an enlarged elevation view of the parts pertaining to the selection and resetting means for one column of the printing mechanism.

Figure 3 is a diagrammatic view of the type selecting clutch.

Figures 4 and 4A taken together show the zero printing control and hammerlock mechanism.

Figure 5 is a plan view of the driving mechanism.

Figure 6 is a schematic elevation view of the driving mechanism.

Figure 7 is a timing diagram.

Figure 8 is a circuit diagram showing the control circuits for one type wheel.

The printing mechanism comprises a plurality of type wheels, each bearing both alphabet and digit type. The type selecting mechanism is basically the same for each wheel, although certain parts are arranged in staggered relationship to allow of the type wheels being closely spaced. This facilitates the construction of a printing mechanism of any required columnar size, eighty or one hundred columns being suitable for many purposes.

The type wheels are set to print the required characters under control of data sensed from the columns of punched record cards. Each column of such a card has provision for recording the digits from 1 to 9 and three so-called zone positions 0, X and Y. Selection of a digit type is effected by the sensing of a hole in one of the positions 1 to 9 and an alphabet type is selected by the sensing of a hole in the positions 1 to 9 together with a further hole in one of the three zone positions 0, X and Y. The cards may be sensed by any mechanism adapted for the electrical sensing of cards in motion, an example of such a mechanism being shown in United States Patent No. 2,438,071.

It will be apparent that various codings may be adopted for representing the letters of the alphabet and any additional symbols without affecting the construction of the type selection mechanism, the characters being arranged around the type wheel in an order appropriate to the coding. One coding which has been used previously for representing the alphabet is shown in United States Patent No. 2,438,071, the position R referred to in that patent corresponding to the Y zone position.

In the present mechanism, however, it is preferred to use a difierent coding which is set below:

Zone position Digit position 1 A B C 2 D E F 3 G H I 5 M N 0 6 P Q R 7 S T U 8 V W X From the table it will be seen that punching of and X, for example, represents the letter N, whilst a "5 punching alone represents the digit 5. Punching of the X or Y positions alone represents the values or 11 for use in the recording of pence.

The order in which the individualtypev are arranged around the type wheel follows'-from..the coding shown and the fact that the sensing of O, X and Y cause movements-of the type wheel of A, /2 and A; of the movement made by the type wheel in bringing two successive digits past the printing line. In the unselected positionthe type wheel has a 0 type opposite the printing line. If the type Wheel is now turned in the same direction as when a selection is taking place, the type will pass the printing line in the following. order: 11, 10, 0, 1, A, B, C, 2, D, E etc.

General construction The printing mechanism is assembled between two side plates which are held together by tie-bars to form a rigid frame. The general form of 'one of these side plates l is shown in Figure 1. Two type wheel drive shafts 2 and 3 (Figure '1) extend the length of the printing mechanism and are journalled at either end in bearings in the side plates. These two shafts run in-synchronism being driven from a common shaft in a manner to be explained.

On the shaft 2 are mounted a series oi clutches such as clutch 4 (Figure 1). The clutches are so spaced along the shaft 2 so that they serve to drive alternate type wheels. ,A'clutch 5 (Figures 1 and 2) is one of a similarseries of clutches which are mounted on the shaft 3 and are staggered in relation to the clutches on shaft 2 so that they drive the remaining type wheels. A gear 6 secured to the driven part of the clutch 4 drives a gear '2 which has secured to it a further gear which meshes with a gear 8. A type wheel 8 has gear gashes cut in the periphery, so that it can be driven by the gear 8.

Engagement of the clutch is controlled by a clutch lever H. Energisation of a start magnet I6 moves the clutch lever l l to a position in which drive is transmitted by the clutch, from shaft 2 through the train of gearing to the type wheel 9.

By energising a stop magnet 12, the clutch lever I1 is moved into a position to effect disengagement of the clutch, to bring the type wheelto rest with a selected type at theprinting line.

The type wheel 8 is mountedforrotationon a stud i3 secured to a plate is which is pivotally mounted on a shaft l5 which also carries the gear 8. The plate it is urged clockwise by a spring I6, but is normally restrained by a cam i1 engaging the plate. t a fixed time in the printing cycle the cam i'l allows the plate M to move clockwise so that the type wheel 5 is impelled against a ribbon i 8 and paper 18 to print the required character. The paper i3 is fed round a platen 29 which forms part of a paper feeding mechanism 2| indicated in diagrammatic form. The paper feeding mechanism does not form part of the present invention and may be or" any convenient type which is capable of feeding sheets or continuous stationery at a suitable speed such as 80 or more lines per minute.

The clockwise movement of the'plate It takes place after the final selection ofthe type has. occurred land the type wheel is at rest; Each-type wheel is mounted on a separateplate M and the cam ii, which is inthe form of a-groovedshaft, extends the length of the print unit, to engage all the plates. Inthis .Way, all type wheelswhich are required for a particular printing operation are made to print at thesame moment.

Following the printing movement by the type wheel 9, it is reset by impulsing the start magnet ill, so engaging the drive from shaft 2 and then .impulsing the stop magnet I2 when the type wheel sponding to the gear 8 which is also mounted on the shaft 15. A clutch lever 24 controlling operationoi-the clutch 5 is positioned by a start magnet 26 and a stop magnet 25.

The type wheel next to the type Wheel 22 is driven through a clutch and gear train identical with that for the type wheel 9 from the shaft 2. The clutch for this wheel is controlled by a clutch lever 3| which is operated by a start magnet .21 and a stop magnet 28.

The next type wheel in the series is driven from the shaft 3 through a clutch and gear train identical with that for the type wheel 22. The clutch for this wheel is controlled by a clutch lever 32 (Figures 1 and 2) which is operated by a start magnet 29 and a stop magnet 50.

Thus the start and stop magnets are mounted so that a group controls four type wheels. The magnets l9, l2, 2'! and 28 related to the first and third type wheels of a group are mounted on crossbars 33, 35 and 35 which extend the length of the machine. The magnets 25, 25,29 and 30 related to the second and fourth type wheelsof a group are mounted on similar crossbars 34, 3! and 3B. The magnets controlling the other type wheels of the printing mechanism are similarly mounted in alternate fashion.

The crossbars are secured at either end of the printing mechanism to plates such as 39 and 40 which are attached to the side plates I by screws 4| passing through lugs 42 in the plates 33 and 40.

By removing the screws M, the plates 39 and la'may be removed, together with the Crossbars and the associated magnets, to allow easy adjustment or replacement of the magnet units.

Type wheel operating mechanism The construction and operation of a single type wheel operating mechanism will now be described in more detail with particular reference to the enlarged View of Figure 2.

The start and stop magnets 26 and 25 are mounted on a plate 43 which is attached to the crossbars 34 and 38 by screws 44. A magnet armature 45 is mounted at one end on a pivot 46 fixed in the plate 43,,so that the armature lics'between the pole pieces of the magnets 25 and 26. The free end of the armature 45 engages a slot 41 in a right angle projection of the clutch lever 24 which is also'pivotally mounted on the plate 43 by a stud 43.

The end of the clutch lever remote from the pivotpoint is V-shaped and is located in one of two complementarily shaped notches 49 and 50 in a lever 5! which is pivoted at 52. This lever ii is urged clockwise by a spring loaded pin 53 engaging the other end, so that the clutch lever 25 is always located positively in one or other of the notchesil, and 5D.

The clutch lever 24 is shown located in the slot 49 which is the position it assumes when the stop magnet 25 has been energised. A projection 54 on the clutch lever is then in a position to engage one of the teeth of a clutch plate 55 forming part of the clutch 5.

When the start magnet 26 is energised, the armature 5 is moved clockwise, so that the clutch lever 24 is moved anti-clockwise about the pivot 48 and the end moves from notch 49 to notch 55. In this position the projection 54 is clear of the teeth of the clutch plate 55 and the clutch is able to transmit the drive from shaft 3.

The arrangement described provides a mechanical latching effect so that the magnets need receive a short impulse only to effect setting of the clutch lever 2 which is then retained in position by the action of lever 5|.

The magnets 28 and as associated with the wheel next but one to wheel 22 are mounted on a plate 55 secured to the cross bars 34 and 37 to the rear of plate 43. These magnets operate the clutch lever 32, one end of which is visible in Figure 2, the remainder of the lever, together with the lever for latching it being hidden by the levers 24 and 5 l.

The clutch 5 has a driven gear 5'! (Figures 2 and 3) secured by rivets 58 to a locating plate 59. The gear and locating plate are rotatable on a flange 55 of the clutch plate 55. On the side of the clutch plate 55 not adjacent to the plate 59 is located a clutch dog 6|, which is pivotally secured to the plate 59 by a rivet 62 which also carries a spacing collar 63.

The clutch dog 6! has a projection 64 which may engage with the teeth of a ratchet 69 which is keyed to the drive shaft 3. The projection 64 is urged into engagement with the teeth of ratchet 59 by a spring H, one end of which engages the clutch dog 6! and the other end of which is held by a rivet El secured to the plate 59. The centre of the spring is engaged by a rivet 68 also secured to plate 59. Undue side play of the clutch dog 5! is prevented by the free end of it engagin a shouldered stud on plate 59.

The various rivets projecting from the plate 59 are so located with respect to the spokes of the clutch plate 55 that a limited degree of relative rotational movement can take place between the two plates. When this movement takes place in one direction, a pin 65 projecting from the free end of the dog 55 slides up a. shaped portion 66 of one of the spokes of the clutch plate 55. This causes the dog 55 to rotate about the pivot point 52 so that the projection at is disengaged from the ratchet 59. In the other direction of relative rotation the pin 55 moves down the spoke and the projection 5!. is allowed to engage the ratchet 69, thus transmitting the drive from shaft 3 to the locatin plate 59 and so to the driven gear 51.

The length of the flange 59 is such that when the clutches are assembled on the shaft 3, the outer edge of the flange abuts against the ratchet of an adjacent clutch, so that the correct spacin of all the clutches on the shaft is assured.

When the projection 5 (Figure 2) on the clutch lever 24 is out of engagement with the teeth of the clutch plate 55, the clutch dog 5! is engaged with the ratchet es and the gear 5'? is driven. If now the stop magnet is impulsed the clutch lever 25 will move to the position shown in Figure 2, so that the projection 54 will engage one of the teeth of the plate 55 and arrest the movement of it. The gear 51 and the plate 59 will tend 6 to continue revolving due to the inertia of the driven mechanism. The shaft 3 rotates in an anti-clockwise direction as seen in Figure 2, so that continued rotation of the plate 59 causes the pin to slide up the portion 66 of the spoke of the plate 55, thus raising the clutch dog clear 2f the ratchet (-39 against the action of the spring One face of the crossbar 31 has a comb-like structure in which are pivoted a number of arms '12, one for each clutch on the shaft 3. One end of an arm 12 engages a spring loaded pin 13 and the other end is pressed lightly thereby against the periphery of the locating plate 59. When the plate 59 ceases to be driven arm 12 will drop into the next notch in plate 59 thus positively arresting the plate.

When the start magnet 26 is impulsed the clutch arm 24 moves into the slot 50 in the arm 5!. The clutch plate 55 is then free to move under the action of the spring H pressing the pin 55 of the clutch dog 6| a ainst the spoke of the plate 55, the plate 59 being held stationary by the arm 12. This relative movement between the plates allows the clutch dog Bl to engage the ratchet 68 so that the drive is again transmitted to the gear 51.

The gear 5'! meshes with the gear 23 which is free to rotate on a shaft 14. Secured to the gear 23 is a gear which meshes with a further gear it, which is free to revolve on the shaft [5 and which meshes with the type wheel 22. The type wheel 22 is driven from shaft 3 through this train of gearing, by selective energisation of the magnets 25 and 26 to bring the required type to the printing line at or before 216 of the cycle (Figure '7), in a manner to be described in more detail.

The plate It! on which is mounted the type wheel 22 has a nose Tl which is held in contact with the cam I! by the spring [5. i'he cam I! has a notch 18 into which the nose 'l'l may descend, so that the plate pivots clockwise about the shaft l5 and the type wheel is impelled against the ribbon I8, and paper I 9. The cam 11 is driven from a main driving shaft, makin one revolution for each cycle of the printing mechanism, and is so timed that printing due to plate I6 moving clockwise takes place at 225 in the cycle (Figure '7) after all selection has been effected.

An arm 19 is pivoted at on the plate Id. The free end of the arm is urged downwardly by a spring 83 also anchored to the plate [4. A stop 86 limits the downward movement of the arm 19. At an intermediate point on the arm 19 is pivoted a second arm 82 which is also joined to the arm 19 by a spring 8!. The upper end of the arm 82 abuts an adjustable stop screw 84 which normally holds a projection 81 on the lower end of the arm out of engagement with the type wheel 22.

When the plate i4 moves to effect printing the scissors action of the arms He and 82 causes the lower end of arm 82 to swing toward the type wheel to engage the projection 81 on the arm to engage one of the gashes in the wheel 22. This has the sheet of aligning the wheel at the moment of printing, so that any slight slackness or backlash of the gearing driving the wheel does not detrirnentally affect the alignment.

The type wheels are provided with a protective cover 88 which is slotted to allow the wheels to print and is also combed at the top to act as a lateral guide for'the plates carrying the Wheels.

;.Secured to the gear 16 is a disc 89 having a single notch 90' cutxtherein. One end of a lever 9| (Figures 1', 2 and 4), pivoted at '95 is held in contact with the periphery of the disc 89 by a spring 94. .When the type wheel has not been selected for printing a digit or a letter,'the (115089 is positioned so that the end of lever Si is restin in the notch 90. In this position a right angle pro- J'ection 92 on lever 9| is in thelower part of a slot .93cut in'the plate I4 (Figure 4) This prevents the plate is moving forward to printing position when the nose-TI reaches the notch I8 in the cam I "I.

As soon as the wheel is selected the gear I6 and the disc 89 begin to rotate. The lever 9| is then moved out of the notch 90 and the projection 92 is raised into the upper part of the slot. 93 (Figure 2) in which position it allows full movement of the plate I 4.

Zero printing control As already noted the type wheels are positioned with a type at the printing line unless a selection of a type is made. In addition,.the type wheel is normally prevented from printing by the lever SI unless a selection has been made. If a "0 selection is made, then the type wheel positionsthe third character at the printing line, that is the "0 type lying between the 10 and 1. type. However, the 0 t ps normally at the printing line is used for the automatic printing of zeros to the right of digits other than zero in a number such as 10400.

The manual control for zero printing comprisesaslide 96 (Figures 1 and 4) which may be set to any one of three positions. One of these slides is provided for each of the type wheels and they are mounted in a comb bar 9! extending between the side plates I. The comb bar is mounted at either end on brackets .99, of which one is shown in Figures 1 and 4, which are secured to a shaft I00 which may be rocked to move the comb barn. The comb bar0I is normally in the position shown in Figure 4.

For fully automatic printing of zeros to the right slide 95 is in the inner position where it is retained by a spring loaded pin 90 engaging with a' depression in the lower edge of the slide. The slide 99 is pivotally connected by astud IM to a further slide I02 also guided by the comb bar 9?. The end I of the slide I02 remote from the comb bar lies between the lever 9i relating to adjacent type wheels. Eaoh lever 9I has two right angle projections I03 and I 04 formed thereon. Thus the end I05 lies between the upper projection i03 of one lever 9i and the lower projection I04 of the next lever to the right.

.If .alever 9I is moved anti-clockwise due to the related type wheel having been selected, then its projection I03 will depress the end of a set slide 02, which being in contact with the projection I04 of the next lever 9| will move this lever anti-clockwise, so raising the projection 02 into the upper part of the slot 93. If no selection takes lace of the type wheel related to this latter lever, then the wheel will be free to move forward atthe printing time to print 0.

If a series of the slides 96 are set in the inner position, it will be apparent that all the corresponding levers 93 will be shifted if a selection takes place for a wheel on the immediate left of the set slides. Since the levers 9! do not control selection, the fact that a lever has been shifted by the zero control mechanism does not interfere with any subsequent selection which may occur.

When the slide is in the outer position, the end I05 of slide I02 is clear of the projection I03, so that the lever 93 to the right of this slide I02 is not operated by the zero printing mechanism, and there is no automatic zero printing to the right of this point. This enables the printing mechanism to be split into banks of any suitable size, each bank of wheels operating independently for printing zeros to the right.

With the slide 96 in the central position the slide I02 still lies between the projections I03 and I04 so that zero printing to the right still takes place. By rocking the shaft I00, however, the end I05 may be withdrawn to a position clear of projection I03, thus preventing automatic zero printing. Thus the central position of the slide provides optional zero printing governed by the position of shaft I00.

Secured to the shaft I00 is a lever I05 which is also pivotally attached at I I2 to a link I93. The link I0? (Figures 4 and 4A) is joined a lever I08 and a link I09, by a pivot II3. The other end of lever I08 moves about a fixed pivot I26, whilst the link I09 is connected to a further link IIO by a pivot H4. The other end of link H0 is connected to a lever III which moves about a fixed pivot IIB.

On a fixed pivot I I9 is a double lever H3, one arm of which may engage a notch in the free end of an armature I2! of amagnet I22. Part way along the other arm of lever II8 is a step I21 which may engage the free end of the lever III, whilst the end of this arm lies in the path of a cam I24 mounted on a shaft I25 wl'iich is an extension of the cam shaft I 7 (Figure 5). A spring II'I joining the levers III and H9 tends to turn the lever IIB clockwise.

With the magnet I22 unenergised, the armature I M engages the lever I I8 to prevent it being moved clockwise by the spring III. In this position the step I2? is clear of the end of lever I I I.

The high point on a cam I23, also secured to shaft I29 contacts the ends of links I00 and H0 connected by pivot I I I, tending to straighten the linkage. This causes the lever I I I to turn anticlockwise against the action of the spring I I1.

,Shortly after the high point of cam I23 has passed and the linkage has returned to the normal position, a high point, on the cam I24 engages one end of the lever I I8, turning it slightly anti-clockwise. This movement brings the other end of the lever free of the armature I2 I.

If the magnet I22 is energised at this time, the armature I2! will be attracted and when the high point of cam I20 passes, the lever H0 will rotate under the action of spring I I? so that the end normally engaged with the notch in the armature moves beyond it. The magnet I22 may now be de-energised without latching the lever H8.

When the cam I23 begins to depress the links I09 and IIO at approximately 216 (Figure 7) of the next cycle, the lever III will start moving anti-clockwise but immediately engages the step I2'I on the lever H3, thus preventing further movement. Continued rotation of the cam then causes the links I09 and E0! to shift to the left, which movement through the lever I08 causes rotation of shaft I00.

This rotation shifts the comb 97 to the left so that the end I05 of slide I02 is no longer between the projections I03 and I 04.

The'time for which cam I23 is operative covers the time when printing takes place (Figure 7), so that if the magnet I22 is energised in the following cycle any of the slides 96 which are in the central position will not be effective to cause printing of zeros to the right.

One example of the use of this optional zero printing will be given. In the printing of invoices under the control of record cards it may be desired to print at the top of the invoice in the centre the name and address of the consignee. In the body of the invoice, the quantity of each item and other numerical data may be listed down the centre.

It is desirable to have zero printing provided for when listing the numerical data, whereas it is not required when printing the address which will consist mostly of alphabetical characters. Accordingly, the address card or cards are punched with a special designation hole which is sensed at the first sens-ng station of the card sensing mechanism.

The sensing of the designation controls the energisation of a relay in known manner and the contacts of this relay permit a suitably timed cam impulse to energise the magnet I22. Thus each time an address card is sensed at the first station the magnet I22 will be energised and on the following cycle when the same card is being sensed at the second station to control printing the shaft I55 will be rocked to prevent automatic zero printing taking place wherever the slides 95 are in the central position.

When detail cards, which are not designated, are being sensed at the second station, the shaft I III) will not be rocked, so that the desired zero printing may be obtained.

It may be pointed out that if occurs in the address, as a street number, for example, then it will be punched in the card and a 0 will be printed by selecting the third character on the wheel and not by the zero printing control described.

A further feature of the zero printing control is the carrying over of the zeros to the right when a blank column occurs in the middle of a value. In printing sterling values, for example, it is usual to leave a blank column between the pounds and shillings and between the shillings and pence, but the zero printing to the right is required for the whole value.

The comb bar 97 has a series of extensions I28 (Figure i) each bearing a stud I30. A springy U- shaped clip I25 is provided with a slot enlarged at one end which enables it to be slipped over the head of the stud I39 and then slid forward on the shank of the stud so as to be retained thereby. The spacing of the two arms of the clip is such that one arm engages a stud I30 next but one to that engaged by the other arm.

A pin I3I is fitted to each arm of the clip and engages a slot in the outer end of a slide I02. Thus two of the slides Hi2 may be coupled to gether by the clips I29, the slide I02 in between these two slides being set by its slide 95 to the inoperative position.

In this way any movement of a slide I02 is transmitted to the slide next but one to the right if they are coupled by a clip I29 so that automatic zeros to the right control is carried across the intervening blank column, the slides m2 controlling the actual printing of zeros in the manner already described.

H ammerloclc control A magnet controlled linkage similar to that already described for optional zero printing control is used to provide optional hammerlock control whereby any required combination of wheels may be rendered inoperative when required. This linkage is mounted immediately behind that for zero printing control so that only certain parts are shown in Figures 4 and 4A. The timing of the operation of this linkage is the same as that of the one already decribed and it is operated by cams I32 and I33 (Figure 5).

The link corresponding to link I59 is connected to a link I34 and a lever I35 which is also pivoted at 125 (Figure 4A). The link IN is connected to a lever its (Figure 4) secured to a shaft I31. Also mounted on the shaft I31 is a comb bar I38 carrying a series of hammerlock levers I39 one for each type wheel. Each lever I39 may be manually set in one of two positions, in either of which it is retained by a spring loaded pin I 10.

The inner end of each lever I39 engages a stop arm II which is pivoted at I43 and is urged clockwise by a spring loaded pin I42 set in a cross bar I41. With the lever I35 in the position shown in Figure 4, the lower end of the stop arm MI is clear of a step I55 on the edge of the plate I I and therefore does not prevent the plate I4 being rocked to effect printing.

If the outer end of lever I39 is moved upwards, the stop arm I lI is forced to move counterclockwise and the lower end then engages the step I55, so preventing rocking of the related plate I4. The hammerlock lever is now in the effective position.

By energising a hammerlock control magnet the shaft I31 may be rocked counterclockwise in the same way as for the shaft I00. The consequent movement of the comb bar I38 makes a set lever I39 ineffective to keep the end of arm I4! against the step I56, so that energisation of the control magnet renders the set hammerlock levers ineifective. This magnet may be energised when printing totals, for example, so providing a different arrangement of the wheels in banks to that which is operative when listing items.

A further series of hammerlock levers are provided which are manually set and not subject to magnet control. On the cross bar I41 are mounted a series of levers such as I44 (Figure 4) which may be held in one of two positions by a spring loaded pin I55. The lever I44 controls the position of the stop arm I II in the same way as lever I39, but provides an over-riding hammerlock control in that if it is set to be effective, the related type wheel will not print even if the shaft I3! is rocked.

Driving mechanism The means by which the printing mechanism is driven will now be described with particular reference to Figures 5 and 6. The driving metor (not shown) is coupled to a shaft I43 having a gear I59 secured thereto which drives a gear I50 secured to a shaft I5I. The shaft I5I also carries a gear I52 which meshes with a gear I53 secured to shaft I'M (Figure 6).

The gear I53 meshes with a further gear iE I secured to a shaft I55. On one end of the shaft I55 is a gear I56 which through a gear I5'I drives the shaft I25. As already described the shaft I25 carries the timing cams I23, I24, I32 and I33 for the zero printing and hammerlock controls and also extends through the side plate I to drive the cam shaft II' (Figures 1, 2 and 5).

The other end of shaft I55 has secured to it a bevel gear I59 forming part of a difierential which also includes a bevel gear I60 secured to a shaft I18 and two floating bevel gears 8L The shaft I18 has secured to it a gear I85 which meshes with a gear I84 on the end of the type wheel clutch shaft 2. (Figures 1, 2, 5 and 8). Through a gear 166, the other type wheel clutch shaftS is also driven from the gear I65.

The gear I85 is driven at constant speed during the selection and printing time from 0 to approximately 230 of the cycle of operation (Figure 7). This is considerably more than half the cycle but any type wheel may have to be reset after printing almost one complete revolution. Accordingly after the type wheel has started the resetting movement the gear I85 is accelerated, so that the type wheels may be reset in the shorter time available.

Also secured to theshaft H4 is a plate I 83, carrying two rollers I which drive a Geneva gear i8! secured to a shaft I89. Also secured to shaft IE9 is a gear I68 which meshes with a ring gear I62. This latter gear is fixed to a block I II which also carries the twobevel gears NH and acts as an additional bearing for the ends of the shafts I55 and I10.

The Geneva gear and the associated gears are so proportioned that between 248 and 342 of each cycle (Figured) the ring gear I82 is driven through the Geneva. mechanism. The gear- 82 carries the gears I6I of the differential round with it, so that during this portion of the cycle the shaft H0 will be accelerated and then decelerated to bring it back to the normal running speed.

Bearings for the various shafts of the driving mechanism are provided by the plates I12 and I13.

Type selection and resetting In order to illustrate the principles of operation of the printing mechanism some examples of type selection will now be described.

In Figure 8 isshown the electrical control circuit for the magnets and 28. A similar circuit is provided for the magnets of each type wheel.

A plug socket I98 (Figure 8) is connected by a plug wire (not shown) to the required columnar position of. the second sensing station, so that the data sensed from cards may control the startv magnet .26. p I

It is usual in record card controlled machines to arrange that the card feeding and sensing mechanism is run in synchronism with the printing mechanism, by driving them from the same motor for example. Thus, if a 3 hole is sensed in a card, the resulting impulse will. occur between 108 and 126 of the printing mechanism cycle which is the time at which an impulse is applied to a type wheel selection mechanism to cause selection of a 3 type. The timing of the index points in relation to the cycle is shown opposite the corresponding heading in Figure '7.

Let it be assumed that the column of the card being sensed has an 8 hole punched therein. Then at 8 time in the cycle (approximately 27) a circuit will be made in known manner from one power supply line I89, through the sensing mechanism and the connecting plug wire to the socket I98. The circuit is then completed through the contacts I99 and the start magnet 26 to the .other power supply line I88.

Energisation of the start magnet will disengage the clutch lever 24 (Figure 2) from the 12 clutchplate 55 so that the clutch engages and the type wheel is driven.

Thewheel continuesto be driven until approxi-. mately 171 of the cycle. At this time a circuit is made from the supply line I89 through. cam contacts I94, contacts I9I, stop magnet. 25. to line I88. 25 causes disengagement of the clutch 5 and the type wheel is brought to rest. The "8 type will now be at the printing line.

The contacts I 98..and I9I areoperatedby a bail (not shown) the .timing. of which is determined by the shaft I48 (Figure 5). These contacts are in the position shown in Figure 8 except during the period 224? to 360 of the cycle, when they are shifted to isolate the circuits operative during resetting from those operative during selection.

Several cam operated contacts, namely. I92, I93, I94, I95, I86 and I91 are used to set the timing of the control circuits. These contacts, with the exception of I93, are operated by cams (not shown) driven by the shaft I48 at constant speed. The cam (not shown) operating contacts I93 is driven by the shaft I18, so that this cam is subject to the acceleration imparted to the type wheels during resetting. The timing of the various contactsis shown in Figure 7.

Since the start magnet 26- is not impulsed again, the type wheel remains at rest and at approximately 225 of the cycle the cam I"! (Figure 2 allows the plate I4 to rock to print the digit 8 on the paper.

At 228 reset start cam contacts I92 close and a circuit is made from line I89, cam contacts i92, contacts 84 (shifted), contacts I9 (shifted), start magnet 26 to line I88.

The contacts I84 are operated in the following manner. Secured to the gear 23 forming part of the type wheel driving gear train is a cam disc I78 (Figure 2). The disc has a notch I81 and a high point I86.

A bar I78 acts as a comb bar for the clutches on shaft 3 and also as a support for a lever Ill. The upper end of this lever contacts the periphery of the disc I18 and is held against it by a spring loaded pin I79 which is housed in the bar I18.

The lowerend of the lever I'I'I carries a pin I88 which engages a slot in a slide I8I which is free to slide in a housing I82. The housing supports three pairs of mutually insulated contacts I83, I84 and I85. The contacts I84 and I are normally closed contacts, whilst contacts I 83 are normally open contacts. There are three projections on the slide IN to enable it to operate the contacts I83, I84 and I85.

When the type wheel is in the unselected position, one end of the lever I'IT rests in the notch I8'I in the cam disc I86. This moves the slide I8I to the extreme left and the projections thereon open the contacts I84 and I85. As soon as the type wheel starts to move to a selected position the lever is shifted out of the notch. This shifts the slide I8I to the right and allows contacts I84 and I85 to close. V

When the wheel is nearing the normal rest positionduring resetting the lever I'II is engaged by the high portion I88 of the disc which shifts the slide I8I a further step to the right, causing the closure of contacts I83.

With the start magnet re-energised, the clutch 5 is again engaged and the type wheel is now driven towards the normal rest position, the direction of movement being the same as when selecting. As already explained, the wheel is ac- Theenergisationof the stop magnet 13 c'elerated during resetting to compensate for the shorter time allowed.

When the wheel is nearing the rest position the contacts R83 are closed to make a circuit from line E89, cam contacts Hi3, contacts I83 (shifted), contacts it! (shifted), stop magnet 25 to line I88. This causes disengagement of the clutch 5 and the type wheel is brought to rest in the normal position.

The cam contacts we close once during each 18 of the cycle when the mechanism is running at constant speed. The cycle timing is expressed with relation to the rotation of shaft Hi5, consequently when the type wheel is accelerated the contacts E93 close more frequently, the actual timing being determined by the speed of shaft l'lil (Figure 5) at any particular moment. This change in timing is indicated by the dotted line in Figure '7. However, since the contacts and the type wheel are controlled by the same shaft, the closure of contacts 595 will occur in the same relation to the position of the type wheel independently of the actual speed of rotation.

Since the contacts 536 must be closed for a reset start impulse to reach the start magnet any wheel which has not been selected will not be reset, since the corresponding lever ill will be holding the contacts its open.

Suppose now that a card is sensed bearing the punching 5 and in one column, representing the letter N. The wheel will be started when the 5 impulse occurs and stopped by the digit stop impulse through cam contacts H35 in the manner just described. The 5 type will now be at the printing line.

At 189 of the cycle a second impulse, due to the sensing of the will be applied to the start magnet to start the wheel rotating again. Just after 198 of the cycle the X stop cam contacts use will close to energise the stop magnet 25 in the manner as the contacts i9 5.

Thus the wheel has been driven during approximately 9 of the cycle in addition to the original movement due to digit selection. This additional zoning selection movement will bring the N type to the printing line. The time between the start and stop impulse is not exactly 9 or one half of the time allowed for a movement between adjacent digits due to the time required for operating the clutch. The result, however, is to select the type next but one to the 5 type.

Printing will be effected as before and the reset start impulse will then energise the start magnet. The ratchet $9 of the clutch has only one quarter of the number of teeth of the clutch plate 55, so that the ratchet 69 may have to move part or" a revolution after the clutch plate ha been released before the dog 6! can drop in and commence driving. This delay automatically corrects for the difference in relative position that may have occurred between type wheels due to some being selected by a digit only and some by a digit and a zone. Thus, after all the Wheels have been started on their resetting movement they will have been brought back into synchronism, in the sense that all will have digit type passing the printing line at the same time, although the actual digit type will be determined by the selection which have been effected. This feature simplifies the reset stopping arrangements in that no account need be taken of any zoning selection which may have been effected.

-If a is sensed from the card, then no digit selection will take place. When the 0 impulse occurs, the start magnet will be operated and approximately 13 later, the 0 stop cam contacts I95 will close to operate the stop magnet, so that the type wheel will have been moved three quarters of the distance between adjacent digit type.

It will be seen that the digit stop impulse is produced at a time slightly after a 0 impulse, so that the start magnet is already energised when the digit stop impulse occurs and this latter impulse is therefore ineffective.

Ihe Y stop: impulse produced by the cam contacts I9! is timed to allow one quarter of a digit movement by the wheel if a Y hole is sensed.

Use with a. counter Various counters for use with record card controlled machines are known which provide a readout of the registered value as a timed impulse in each denomination. It will be apparent that such a readout may be used to control the selection of type wheels in the same manner a timed impulses derived from a card.

In order to register negative decimal numbers, it is usual to employ complements. Thus the number 27 would be registered on a four denomination counter as 9972. It is often required that when the number is printed that it should be printed in the true form with a sign indication rather than in the complemental form. This conversion may be readily cheated by the printing mechanism described.

In any column where conversion is required the plug socket I98 for the start magnet is connected to a cam controlled contact which closesat 9 time. The impulse from the counter is directed to the stop magnet 25. Thus the type wheel is started by the cam timed impulse and stopped by the counter impulse which is the reverse of the normal procedure.

In the case of a 2 impulse from the counter, the wheel will have moved seven digit positions before it is stopped so that the '7 type will be at the printing position. Similarly, the '7 impulse from the counter will bring the 2 type to the printin position.

It is arranged that the duration of the 9 timed start impulse is such that the 9 counter impulse starts before it and finishes after it, so that if a 9 counter impulse occurs the clutch is not engaged at all. This is the converse case to that which happens with a 0 card impulse When selecting in the normal manner.

The contacts I (Figure 2) are closed as Soon as the type wheel is selected, so that the closure of this contact occurs at a time in the cycle representative of the digit selected. Accordingly, the contacts 585 may be used to control entry to a counter which is designed to be set by an im pulse occurring at a corresponding time in the cycle, to ensure that the value entered into the counter is the same as that printed by the printing mechanism.

What I claim is:

l. A printing mechanism for printing datarepresented by timed electrical impulses comprising a type wheel having a plurality of printing characters thereon, a driven member, a clutch engageable for driving said type wheel from said driven member means for effecting engagement of said clutch, mean responsive to said timed impulses for actuating said engaging means, means for efiecting disengagement of minedtime; means for'takingat a predetermined time an impression fromthe character brought to theprintingline, impulseoperated resetting means for actuating said clutch engaging, means and means for actuating said disengaging means as the type wheel reaches thenormal-reset position;

2.'A printing mechanism for printing data represented by timed electrical impulses comprising a type wheel having a plurality of printingcharacters thereon, a driven member, a clutch engageable for driving said type wheel fromsaid driven member; electrical impulse operated means for engaging said clutch, electrical impulse operated means for disengaging said clutch, means for applying-to said clutch engaging means said data representing impulses, means for applying at a fixed time an impulse to said clutch disengaging means for stopping said type wheel after said clutch engagement, means for taking at a predetermined time an impression from the character brought to the printing line, means for applying a further impulse to said clutch engaging means after printing for returning. said type wheel to reset positionand further means for applying an impulse to said clutch disengaging means for causing disengagement of said clutch as said type wheel reaches said rest position.

3. A printing mechanism for printing characters represented by at most two timed electrical impulse according to a code, the first said impulse selecting a group of characters and the second said impulse selecting a particular character from the selected group, comprising a type wheel having thereon a'plurality of said characters arranged in said groups, a driven member, a clutch engageable for driving said type Wheel from said driven member, impulse-operated means for engaging said clutch, electrical impulse-operated I means for disengaging said clutch, means for applying to said clutch engaging means said character represent ng pulses, means for applying at a predetermined time an impulse to said clutch disengaging means after the first data-representing impulse, to bring said type Wheel tov rest with the first character of the selected. group at the printing line, means for applying at a predetermined time a second irnpulse to said clutch disengaging means after thesecond data-representing impulse, if any, to bring said type Wheel to rest with the selected character of said group at the printing line, means for taking thereafter and while said type Wheel is at rest an impression from said selected character at a predetermined time, means for applying a further impulse to said clutch engaging means after printing for returning said type wheel to reset position and further means for applying an impulse to said clutch disengaging me'ansfor causing disengagement of said clutch as'said type wheel reaches said reset position.

A multi column printing mechanism comprising a plurality of type-wheels, each having thereon a plurality of printing characters arranged in groups; for each said type-wheel, a clutch for driving said type Wheel, i1 ipulse-operated clutch engaging, impulse-operated clutch disengaging means, and means for applying to said impulse-operated clutch engaging means at a selected group of characters, and the second, representing a selected character in a group; means for applying to all said clutch disengaging means at a fixed time an' impulse to bring each said type'wheel to rest, with the first character of said selected group at the printing line; means for applying to said clutch disengaging means at predetermined times and after the application of the second data representing impulses, if any; impulses for bringing the selected characters of said selected groups to the printing line; means for taking thereafter and While said type wheels are at rest impressions from said selected characters at a predetermined time; means for applying a further impulse to all said clutch-engaging means after printing for re turning said type wheels to reset position; and further means for applying an impulse to all said clutch disengaging means for causing disengagement of said clutches as said type wheels reach reset position.

5. A printing mechanism comprising a type wheel having thereon a plurality of printing characters arranged in groups, a clutch for driving said type wheel when engaged, impulse-operated clutch engaging means, impulse-operated clutch disengaging means, means for applying to said clutch engaging means at most two timed impulses in accordance with a character-representing code the time of the first said impulse represented a selected group of characters and the second representing a selected character in a group, cam-operated means for generating and applying at fixed times electrical impulses to said clutch disengaging means for bringing said type wheel to rest firstly when the first character of the selected group reaches the printing line and secondly when the selected character of said selected group reaches the printing line, means for taking thereafter and while said type Wheel is at rest an impression from the selected character at a predetermined time, and further camoperated means for applying to said clutch engaging means after printing and at a further predetermined time an impulse for returning said type Wheel to reset position, and for applying an impulse to said clutch disengaging means for causing disengagement of said clutch as said type wheel reaches reset position.

6. A printing mechanism according to claim 5 comprising also means for suppressing printing if said type wheel is at the reset position at printing time.

7. A printing mechanism according to claim 5 comprising also a printing character at the print line when said type Wheel is at reset position and manually settable means for controlling printing from said character.

8. A multi-column printing mechanism comprising a plurality of type wheels, each having thereon a plurality of printing characters arranged in groups and including numerals and alphabetic letters; for each said type wheel, a clutch fordriving said type wheel, impulseoperated clutch engaging means, impulse-operated disengaging means, and means for applying to said clutch engaging means at most two timed data-representing impulses in accordance with a character-representing code, the timing of the first said impulse representing a selected group of characters and the timing of the second representing a selected character in'a group; means-for applying to all said clutch engaging means at a fixed time an impulse to bring eachsaid-type wheel-to rest'with the first 17 character of said selected group at the printing line; means for applying to said clutch disengaging means and after the application of the second data-representing impulses, if any, impulses for bringing the selected characters of said selected groups to the printing line; means for taking thereafter and while said type wheels are at rest impressions from said selected characters at a predetermined time; means for applying a further impulse at a further predetermined time to all said clutch-engaging means after printing for returning said type wheels to reset position; further means for applying an impulse to all said clutch disengaging means for causing disengagement of said clutches as said type wheels reach reset position; and for each type wheel, manually settable control means and means controlled by an adjacent type wheel for jointly controlling printing of that type wheel when in the reset position at printing time.

9. A multi-column printing mechanism according to claim 8 comprising also a pivoted mounting plate for each said type wheels, means for pivoting each said plate for printing, and a lever for each type wheel having a first position when said type wheel is in reset position and a second position when said type wheel is -moved from reset position, said lever when in said first and second positions preventing and allowing respectively pivoting of said plate for printing.

10. A multi-column printing mechanism according to claim 9 comprising also two oppositely facing projections on each said lever, an interposer settable by said manually settable control means for effectively connecting projections of levers of adjacent type wheels, whereby movement of one lever is communi cated to an adjacent lever.

11. A multi-column printing mechanism comprising a plurality of type wheels, each having thereon a plurality of printing characters arranged in groups; for each type wheel, a pivotted mounting plate, a clutch for driving said type wheel, impulse-operated clutch engaging means, impulse-operated clutch disengaging means, and means for applying to said impulseoperated clutch engaging means at most two timed data-representing impulses in accordance with a character-representing code, the timing of the first said impulse representing a selected group of characters and the second, representing a selected character in a group; means for applying to all said clutch disengaging means at a fixed time an impulse to bring each said type wheel to rest with the first character of said selected group at the printing line; means for applying to said clutch disengaging means at predetermined times and after the application of the second data representing impulses, of any, impulses for bringing the selected characters of said selected groups to the printing line; means for rocking at a later predetermined time all said plates while said type wheels are at reset for printing from said selected characters; means operative during rocking of said plates for aligning said selected characters on said type wheels; means for applying a further impulse to all said clutch-engaging means after printing for returning said type wheels to reset position; and further means for applying an impulse to all said clutch disengaging means for causing disengagement of said clutches as said type wheels reach reset position.

12. A multi-column printing mechanism comprising a plurality of type-wheels, each having thereon a plurality of printing characters arranged ingroups and including alphabetic and numeric characters; for each said type wheel a pivoted mounting plate therefor; a drive shaft; for each type wheel a clutch engageable for said driving type wheel from said shaft; a constant speed main shaft; coupling means for driving said drive shaft from said main shaft at a constant first speed and at an accelerated second speed; for each type wheel, impulse-operated clutch engaging means, impulse-operated clutch disengaging means, and means for applying to said clutch engaging means at most two timed data-representing impulses in accordance with a character-representing code, the timing of the first said impulse representing a selected group of characters and that of the second a selected character in a group; means for applying to all said clutch disengaging means at a fixed time an impulse to bring each said type wheel to rest with the first character of said selected group at the printing line; means for applying to said clutch disengaging means at predetermined times and after the application of the second data-representing impulses, if any, impulses for bringing the selected characters of said selected groups to the printing line, means for rocking at a later predetermined time all said plates w-hile said type wheels are at rest for printing from said selected characters; means operative during rocking of said plates for aligning said selected characters on said type wheels; means for applying a further impulse to all said clutch-engaging means after printing for returning said retype wheels to reset position; further means for applying an impulse to all said clutch disengaging means for causing disengagement of said clutches as said type wheels reach reset position; and means controlling said coupling means for driving said drive shaft at said constant first speed for bringing said selected characters to said printing line and at said accelerated second speed during at least part of the resetting of said type wheels.

13. A multi-column printing mechanism comprising a, plurality of type wheels, each having thereon a plurality of printing characters arranged in groups and including alphabetic and numeric characters; for each said type wheel a pivoted mounting plate thereof; spring means biasing each said plate towards printing position; a first drive shaft; 21. second drive shaft; for each type wheel a clutch engageable for driving said type wheels from said shafts, alternate type wheels being driven by said shafts; a constant speed main shaft; coupling means for driving said drive shafts from said main shaft at a constant first speed and at an accelerated second speed; for each type wheel, impulse-operated clutch engaging means, impulse-operated clutch disengaging means, and means for applying to said clutch engaging means at most two timed data-representing impulses in accordance with a character-representing code, the timing of the first said impulse representing a. selected group of characters and that of the second a selected character in a group; means for applying to all said clutch disengaging means at a fixed time an impulse to bring each said type wheel to rest with the first character of said selected group at the printing line; means for applying to said clutch 19 disengaging means at predetermined times and after the application of the second data-representing impulses, if any, impulses for bringing the selected characters of said selected groups to the printing line; a cam normally holding said plates away from the printing position but permitting at a later predetermined time while said type wheels are at rest rocking of said plates under the action of said spring means for printing from said selected characters; means operative during rocking of said plates for aligning said selected characters on said type wheels; means for applying a further impulse to all said clutch-engaging means after printing for returning said retype wheels to reset position; further means for applying an impulse to all said clutch disengaging means for causing disengagement of said clutches as said type wheels reach reset position; and

means controlling said coupling means for driving said drive shafts at said constant first speed for bringing said selected characters to said printing line and at said accelerated second speed during at least part of the resetting of said type wheels.

14. A multi-column printing mechanism as claimed in claim 10, in which the said slide is manually set to bring the interposer to a first position in which the interposer is effective, to a second position in which the interposer is effective, and to a third position in which the interposer is not between two projections and is inefiective to communicate movement between adjacent levers, and having electromagnetically controlled means for moving the interposer from the second position to the third position.

15. A multi-column printing mechanism as claimed in claim 14, comprising also means for coupling a first interposer with a second interposer next but one adjacent to it whereby any movement of said first interposer is communicated to said second interposer.

16. A printing mechanism as claimed in claim 15, in which the character 0 is at the printing position when the type wheel is at the reset position.

17. A multi-column printing mechanism as claimed in claim 12 in which said coupling means comprise a differential gear having an input gear, an output gear and floating gears, the input gear of the differential being driven by the main shaft and the output gear driving said driving shaft, a Geneva gear mechanism driven by the main shaft, and a ring gear attached to the floating gears of the differential, the ring gear being driven intermittently by the Geneva gear mechanism, whereby said drive shaft is driven at constant speed during the period of character selection and is accelerated during at least part of the subsequent period.

18. A multi-column printing mechanism as claimed in claim 12 in which each said clutch comprises a gear secured to a locating plate, a clutch pawl pivotally secured to the locating plate, and engaged by a clutch plate, and a drive ratchet secured to the clutch driving shaft, the clutch pawl being moved into and out of engagement with the drive ratchet by relative rotational movement of the locating plate and the clutch plate which are free to revolve on the said driving shaft whereby the locating plate is not driven when the clutch plate is held stationary and. is driven from the said shat when the clutch plate is free to move.

19. A. multi-column printing mechanism as claimed in claim 18 in which the clutch plate has a number of teeth on the periphery thereof equal to four times the number of teeth on the drive ratchet.

20. A multi-column printing mechanism as claimed in claim 19 having a clutch lever movable to a first position to engage a tooth of the clutch plate and to a second position in which it frees the clutch plate, a magnet armature engaging said lever, said clutch disengaging means comprising a stop electromagnet for moving the armature so that the clutch lever is in the said first position, and said clutch engaging means comprising a start electromagnet for moving the armature so that the lever is in the said second position and detent means for positively locating and retaining the clutch lever in either said first or said second position when neither magnet is energised.

21. A multi-column printing mechanism as claimed in claim 20 comprising also means for rendering ineffective said stop magnet during a time when the start magnet is energised.

22. A multi-column printing mechanism as claimed in claim 20 having a cam rotated in synchronism with the type wheel, a first pair of normally closed electrical contacts which are opened under control of said cam when the type wheel is at the reset position and a second pair of normally open contacts which are closed under control of said cam as the type wheel approaches the reset position during the resetting movement, said first contacts controlling the application of reset impulses to the start magnet and said second contacts controlling the application of impulses to the stop magnet to bring the type wheel to rest at the reset position.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,909,550 Pierce May 16, 1933 2,030,427 Buhler Feb. 11, 1936 2,157,035 Torkelson May 2, 1939 2,199,561 Fuller May 7, 1940 2,386,422 Beattie Oct. 9, 1945 2,438,071 Page Mar. 16, 1945 2,566,944 Last Sept. 4, 1951

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