US1594371A

US1594371A - Adding and subtracting machine

Info

Publication number: US1594371A
Authority: US
Publication date: 1926-08-03
Anticipated expiration: 1943-08-03

Description

Aug. 3 1926.

W. W. LASKER ADDING AND SUBTRACTING MACHINE Filed April 1, 1924 3 Sheets-Sheet 1 INVENTOR William 14! [as/e1;

fiTORNE Y Aug. 3 1926.

' w. w. LASKER ADDING ANDMSUBTRACTING MACH NE Filed April 1. 1924 5 Sheets-Sheet 2 INVENTOR William (Lab-Ker; BY

' 1 fi TO'RNEY Aug. 3 1926.

; w. w. LASKER ADDING AND SUBTRACTING MACHINE Filed April 1, 1924 3 Sheets-Sheet 3 INVENTOR BY Wz'llz' am 14 Ana/2v:

I LTORNEY tion,

Patented. Aug. 3, 1926.

UNITED STATES .WILLIAM' W. LASKER, OF BROOKLYN, NEW

MACHINE CORPORATION, OF YORK,

YORK, Assmnon 'ro rownas ncooum'nre n. Y., a conronn'non or DELAWARE.

ADDING AND SUBTBAC'FING MACHINE.

Application filed April 1, 1924. Serial in. 703,474.

The present invention relates to computing machines which are arranged toperform addition and subtraction, and in connection with such machines the invention relates more particularly to improvements in the construction and operation of the carry tension mechanism.

Some of the objects of the present invention are to provide a computing'machine in which either steps of addition or subtraction can be performed, either being thrown into operation at will to change from one method of calculation to the other; to pro-' vide an improved carry tension mechanism for computing machines; to provide a carry tension mechanism which is positive and sure in operation and'in the use of which it is impossible for any carry rack to carry over more than one number unit; to provide a carry tension mechanism having a spring tension which is practically negligible in elfect upon the main operating lever of the machine; to provide a carry nism having a substantially uniform spring 'tension; to provide a simple and efieetivemeans for setting the carry racks to respond to the action of the carry at the proper time in the cycle of operation; to provide asimple and eflicient'means for changing the operation of the machine from an adding function to a subtracting func tion, or vice versa, as required; to provide an automatic means for changing the direction of the applied force upon the carry tension mechanism when a change is made from an adding function to a subtracting funcprovements as will hereinafter appear.

In the accompanying drawings, Fig. 1 represents an elevation of one side of a coinputing machine showing the mechanism embodying one formv of the present invention for causing actuation of the carry tension mechanism; Fig. 2 represents an elevation of the opposite side of themachine showing those partshaving relation to the operation of the carry tension mechanism; Fig. 3 represents a detail in plan of one of the carry racks and the numeral wheel operating adjuncts; Fig. 4 represents a detail in side elevation of one form of carry rack'control mechanism Fig. .5- represents a detail in side elevation of tension mechatension mechanism or vice ersa; and to provide other im:

' beheved unnecessary to describe it speclfias obviously the present invention only one of the carry tensionunits embodying one form of the present invention; Fig. 6 represents an edge elevation of the same.-

Referring to the drawings, one form of the present invention-is illustrated as applied to an adding and subtracting machine of the type operated by rotatable number or accumulator wheels 10,. which are arranged to be actuated by pinions 11 through engagement with index racks 12 at certain predetermined times. stood, by reference to Fig. 3, that in the present instance one unit only of the ma- It will be underchine is described, but inpractice there may beany number of these units with the accumulator wheels arranged side by side, each having numbers from naught to nine, so that the sequence of operation "is by way of the nine, members of the unit wheel, then a carry of one to the ten'wheel, and so on with a succession of carry numbers from one wheel to the other throughout the'succession, de-

pending upon how many accumulator wheels there arein a machine. It will be under-. stood that in this type-of machine one index rack 12 for each pinion, and that the racks are operated through the medium there is of a main operating machine arm 13, which in the present instance connects through a.

link 14 to a'main cam 15 on the main shaft 16, and from which motion is transmitted to the index racks to cause their actuation in accordance withthe respective set positions of these racks, as determined by the setting of the keys of the ke board of the machine. This construction f of the present invention, and it is therefore cally, requires the index racks to be actuated at the proper time and in the proper manner for the carrying out of the functions to which this invention relates.

. In the type of machine here illustrative of the invention, the accumulator wheels IO 'and pinions 11 are independently mounted shaftjl'l,

orms no part, however, I

project through opposite cable cam-slides 22 and 28,- which are, mount-. 5

I for free sliding movement relative to the plates 18. In the present instance, each of these slides 22 and 23 is provided with three of the cams 21, spaced a like distance apart for the purpose of simultaneously acting in pairs upon the pinion shaft designed to be controlledthereby. This provision of additional cams is made to take care of additional pinion shafts, each of which is pro- Vided with a set of pinions and accumulator wheels, as will be understood, so'that the machine can be equipped with one or more sets of adding and subtracting units. In normal or rest position of the machine, the cam slides 22'and 23 are in such a position that the cams 21 are directly beneath the rollers 20, and thereby hold the pinion shaft 17 in a position with the pinions 11 out of engagement with the index racks 12. In this connection, it will be understood that suitable spring mechanism is provided for holding the pinion shaft 17 in firm contact with the cam face of the slides 22 and 23. The function, therefore, of the cam slides 22 and 23 and cams 21 is first to maintain the accumulator pinions 11 normally out of engagement with the index racks 12 while determining in the operation of the machine, the time of shifting of the pinions into mesh with the index racks 12 to roll an adding or a subtracting operation, as the case may be. a

For the purpose of reciprocating the cam slides 22 and 23 at each adding or each subtracting stroke of the main operating arm 13, the cam slide 22 is provided at one end with a recess 24, which seats about a pin 25 on an arm 26, fast to a rock shaft 27, this last extending transversely of the machine to receive on its other end a second arm 28 carrying a pin 30, which seats in a recess 31 correspondingly located in the cam slide 23. Thus, movement imparted to the slide 22 will be translated to the slide 23 and the two operate in unison. To actuate the'slide 22 it is provided at one end with a trip lug 32 pivoted on a pin 33, fast to the slide 22, the said pin33 being intermediate the tripping end of the lug 32 and a stop pin 34, which in operating position of the In 32 is arranged to abut the edge of a shou der 35 formed on the slide 22. The opposite end of the s1ide22 carries a sim lar tri lug 36, pivoted on a pin 37 on the sli e 22 and also having a stop pin 38, to abut, in operating position of the lug, against the side face of a shoulder 40 on the cam slide. the

twolugs

32 and 36 are arran ed to be projected into operating position y-means of a common spring 41,.which has its ends connected respectively to the aforesaid lugs at a point to carry out the desired operation. Where the machine is set to carry out adding operations, one of these trip In this instance,

lugs will operate to shift the slides 22 and 23 from central position in the correct direction to cause an adding function, and when the machine is set for subtraction, the other of the lugs will be operated to cause the slides 22 and 23 to move from central position in the correct direction to carry out a subtracting function. In this instance, the lug 32 functions for the adding operation and the lug 36.for the subtracting operation, and selection of one lu or the other is made automatically, as will e explained. The mechanism which cooperates with the

trip lugs

32 and 36 consists, in the present instance, of two trip pins 42 fast to the face of the main so spaced apart and positioned as to come into the paths respectively of the two

trip lugs

32 and 36 at the proper time and in accordance with the operation tobe carried out. Thus, if the adding trip lug 32 is set so that it is in the path of the trip pin 42, the cam slides will be shifted to the right, whereas if the trip lug 36 is selected so that it is in the path of the trip pin 43, it will be operated, and the cam slides 22 and 23 moved to the left, as seen in Fig. 2.

It will be understood that suitable restoring mechanism is provided for returning theslides 22 and 23 to normal position after each operation; but as this mechanism forms a separate invention, it is believed unnecessary to'illustrate or describe these particular details.

For the purpose of making the selection above referred to, namely, of positioning the correct trip lug corresponding to the operation which is to be carried out in the ma chine, a rock bar 44 is provided, which is suitably pivoted at 45 to a fixed part, and is so arranged and located that rocking movement in a clockwise direction, as shown in Fig. 2, will cause one end of the bar 44 to contact with the stop pin 34, and by movement in a counter-clockwise direction will cause its other end to engage the stop pin 38, and whenever either end of the bar 44 picks up one of the stop pins it causes the trip lug of that stop pin to be shifted about its center to thereby remove its tripping end from the path of the corresponding trip pin on the cam 1.5, so that when the latter is rocked during an operation of the machine, it will fail to engage that particular trip lug. For convenience, the rock bar 44 will be considered as a subtraction lever 46 at one end and an addition lever 47 at the opposite end. The position of the rock bar 44 is, determined by an index arm 48 secured thereto and extending to a convenient location adjacent the position of the operator of the machine, so that it can be quick- 1y changed from one position to the other. This index arm 48 is provided with a later-- and 43, both. cam 15, and.

ally disposed locking ranged to be engage normally held in engagement by means of a spring 52, and having three

recesses

53, 54 and 55, one, 53,-of which serves to lock the index arm in adding position, another, 55, in subtracting position, and the intermediate one, 54, in total position.

In order to carry over an addition or a subtraction from one accumulator wheel to the next succeeding wheel, carry racks 56 are employed, each being operatively located with respect to the wheel pinion which it is to control. These carry rack 56 are supported and slidably guided by transversely dis osed guide strips 57, while across the atho movement ofthe respective ends of t e carry racks 56 are two movable resetting bars 58 which are arranged to be automatically operated in proper timed relation to not only reset the carry racks 56 after a carry operation but also to move out of the ath of the aforesaid carry racks 56 to al ow them to function. For thee-sake of clearness butone carry rack .56 with its parts comprisin one unit will behere described in detai as the several units are of duplicate construction. The carry rack 56 is provided on the edge toward the numeral pinion 11 with three rack teeth 60 which are located to mesh with the pinion with the pin .11 under normal conditions, and thus serve as a lock to prevent improper movement of the wheel 10 while also providing for the necessary carry movement to the adjacent wheel at the desired time, injeither direction.

. As a means for locking the carry rack 56 1n its normal position, it is provided with a slot 61 opening into a locking notch 62 to receive a tab or detent 63 of a latch 64 and provide a snugseating fit so that when the detent 63 is in the notch 62 the carry'rack 56 is locked against movement in both directions. The length of the slot 61 is such that'when the latch detent 63 is withdrawn from the notch 62 the stroke or carry movement of the rack is limited to a distance sufiicient only to move the pinion 11 one tooth on its pitch line, and this is true whether the rack 56 is shifted to carry an adding or a subtracting transfer.

Forv actuating the latch 64 so that the carry rack 56 is set for operation it is pivoted at 65 to a fixed strip 66 and is normally held by a spring 67 under tension to return and maintain the locking detent 63 seated in the notch 62.- The latch 64 is provided with atrip finger 68 projecting into the path of a trip 0 carried by the hub or pinion of the next preceding -accumulator wheel 10 and located thereon at the proper point to transfer the addition or subtraction from one wheel to the next. This trip 7 O has an enpin 50, which is ar-' by a pivoted latch 51 arm 80.

, with or passes through ment of the spring 84 with the hook 83, "so that when the bar 86 swings from an firing action to the sion bar 86 when a change is fromone form of calculatlon gaging face 71 on one side to actuate the latch 64 in one direction for addition carry, and another engaging face 72 on the opposite side to actuate the latch 64 in the opposite direction for subtraction carry.

The carry tension mechanism, whereby the carry rack ,56 is operated or fired when released by the latch 64, consists of a' bell crank. tension lever 76 mounted for rocking'movement on a rock'shaft fulcrum 77 and having a relatively long tension or firing arm 78 and a relatively short actuating The free end of the arm 78 seats between two lugs 81 and 82 fixed to the carry rack 56 and so spaced as to allow suf-. ficient clearance for the arm 78 to shift from the addition tension position to the subtraction tension position when the carry rack 56 is locked in its normal position. The armterminates ina hook 83 which receives one end of a tension 5 ring 84, the other end of which is held by a lhg 85 formed on a carry tension bar 86. This bar 86 extends transversely of the machine and is" supported at its ends by pivot pins 87, which are rotatably mounted respectively in parts of theirame 88. The pins 87 are respectively to space the tension "bar 86 at the proper distance from its axisof rotation and also to support the same therebetween. In this connection it should be noted'that the axis of rotation of this tension the point of attachadding position to a subtracting position there is no appreciable variation in the tension of the spring. The distance between the hook Y83 and the lug 85 is such as to place a tension upon the spring suflicient to effectively fire the carry rack 56 when the latter is releasedto be subjected to the action of the o erating arm 78. This arrangement, while supplying the desired spring carry racks, permits a minimum tension to be used, and through the coincident-axes of the spring and carry tension bar 86, there is no added spring tension transmitted to the operating lev' rs during the setting of these parts. It will be noted in Fig. 5 that the above described conbar 86 is coincident fixed to crank arms 90, which serve attachment point of the spring andthe carry rack endfof the arm 78.

For automatically shifting the carry tento the other,

to be made position by a change in the setting 0 the seposition. The trip the respective crank arms are provided with laterally extending pins 91, which seat respectively in end slots 92 of the levers 93, and are oscillated as the levers 93 are rocked by movement of the shaft 77 under the action of a link 94 which is fast to the shaft 77. This link 94 has a pin 95 seated in a bifurcated extension 96 at one side of a slide plate 97. That is to say, at one side of the machine thereis a slidably mounted plate 97 having a bifurcated extension 96 which straddles a in 95 on a link 94, so that when the plate is shifted in the cycle of operations it Will cause the link 94 to rock the shaft 77 and thereby transmit motion to the levers 93 so that the carry tension bar 86 with its associated parts is shifted from one position to another. In order to actuate the sliding plate 97 at the proper time to set the mechanism which it controls, it is supported in po-- sition upon the machine frame by stud bolts 98, which traverse respectively slots 100 in the aforesaid plate and permit the latter to have the required stroke in either direction.

otion is transmitted to the plate 97 by means of two trips 101 and 102, both being pivoted to the plate and arranged to be shifted from one position to another in accordance with whether or not the machine is to operate for an adding operation or for a subtracting operation. In the present instancethe two trips 101 and 102 are connected by a tension spring 103 acting to rock the trips inwardly out of their functioning 101 is arranged to control movement of the plate 97 for an adding operation while the trip 102 is similarly arranged to control movement of the plate 97 for a subtracting operation, and selection of one trip or the other is made by a selectin lever 104 having two oppositely disposed arms 105 and 106, one of which is arranged to engage a pin 107 on the trip 101 and the other arm 106 being arranged to engage a pin 108 on the trip 102. This lever 104 is pivoted at 109 to a fixed part and is connected at 110 to a link 111 which is connected by a crank 112 on a transverse shaft 113 running to the opposite side of the machine where acrank 114 connects by a link 115 with the selecting index arm 48. This select ing lever 104 is shown in position to release the subtraction trip 102 and the latter has therefore been thrown to operative position by the actlon of the spring 103, so that its lower extremity is in the path of movement of a trip pin 116 operatively located upon a rock cam 117. This cam 117 also carries a second trip pin'118, which is arranged to of the addition trip 101, so

travel in the path that when the latter is released to o erative this lecting lever 104, pin 118 will engage its trip 101' and cause the plate 97 to be shiftedto a new position. The rock cam 117 is fixed to the main shaft 16 and receives its motion in the cycle of operations during the operation of the main control arm or lever 13.

The operation of the machine is as follows:

For adding, the index lever 48 is swung counter-clockwise from the position, shown in Fig. 2, to a position where the locking pin 50 is seated in the recess 53 and locked by the spring controlled latch 51. This movement of the index lever 48 is transmitted directly to'the subtraction arm 46 and the addition arm 47, and indirectly, through the link 115, crank 114, shaft 113, crank 112, link 111, to the selecting lever 104. The action of the selecting rock bar 44 and the lecting lever 104 is the same and is carried out in unison; thus the subtracting arm engages the pin 38 so that its continued movement swings the trip 36 about its pivot 37 out of the path of the trip pin 43, while the addition arm 47 moves away from the pin 34 and allows the trip 32 to be swung by the s ring 41 into the path of the trip pin 42. i imultaneously on the opposite side of the machine the selecting lever 104 brings its arm 106 into engagement with the pin 108 to turn the trip 102 out of the path of the trip pin 11.6 and release the trip 101 so that it will be engaged by the trip pin 118 on the return stroke of the operating arm of the machine. \Vith the setting of the machine for adding, the operator then punches the keys for the'numbers to be added and follows this by pulling the main operating arm 13 forwardly. In consequence, the cam 15 is rocked in the same direction, its trip 43 passing the trip 36 and its trip pin 42 swinging the tri 32 out of the way to take a position to the left of trip 32 at the end of the forward stroke of the main arm 13. The same operationis taking place at the opposite side of the machine because the main shaft 16 transmits motion to the cam 117 and causes the trip pin 118 to take a position to the right of the trip 101. Upon the return stroke of the main arm 13 the respective pins 42 and 118 engage the addition trips 32 and 101 and since these trips are prevented from turning by reason of their pins 34 and 107 respectively abutting the edges of the cam slide 22 and the plate 97, the return rocking movement of the cam 117 causes the slide 22 and the plate .97 to move in the required direction. The movement of the cam slide 22 slide 23.so that these two slides 22 and 23 operate together and cause the pinion shaft 17 to ride 'down the right hand face of the cam 21 tobring the pinionsll into mesh with the indexracks 12 t'o'roll in an adding accumulation at the proper time in the return stroke of lever 13. The movement of the slide plate 97 is transmitted by the bifurcated extension 96 to the pin 95 on the consequentl racks is released and the firin next succeeding number of the site direction to whichthey did on the 'tion operation. By reference to 1, it

link 94 so that the latter is rocked to trans mit this motion to the rock shaft 77 which through the levers 93 swings the carry tension bar 86 to the adding position. This shiftin of the bar 86 changes the direction of pulf of the carr tension spring 84 and trans ers the pressure of the firing arm 8 from the lug 81 to the lug 82 so that when the carry rack 56 is released it will be fired in the required direction to erform a carry operation. The foregoing adding operation takes place on the return stroke of the main lever 13, during the first part of which the pinions 11 roll in an adding accumulation and tripping such carry racks, as are to be set, by a fractional amount and before the return stroke is completed the resetting mechanism for control ing the carry arm 78 fires the set carry racks to allow ful carry to take place. When this happens, the cam slides 22 and 23 have been returned to their normal position with the earns 21 raising the pinions 11 out of mesh with the index racks 12 and in mesh with the teeth 60 of the carryracks 56 so that the motion of the fired carry racks turns the accumulator pinions a distance equal to one tooth and thus brings the required accumulator wheel into indicating ositio'n. In this connection it should be note that it is impossible for the firing movement of the carry rack to overthrow because it has a positive lock stopthrough engagement with the carry pawl tab 63. This prevents a carry of more than one unit at each carry operation.

For subtraction, the index, lever 48 is swung clockwise to the position, shown in Fig. 2, where the pin 50 is seated in the recess 55 and locked bythe spring control latch 51. This movement of the index lever 48 is transmittpd directly to the arms 46 and 47, and indirectly, by way of link 115 and shaft 113 to the "link 111 of the selecting lever 104. The resulting movement of the lever 48 is to cause the addition tri 32 to be raised and held out of the path of the .pin 42 on the return stroke of the latter, and-to drop the trip 36 into the "ath of thepin 43 on the forward stroke of the latter. Therefore, as the cam 15 moves counter-clockwise on the fonwardstroke of the mainoperating lever 13 the pin 43 will engage the trip 36 and transmit motion to the connec'tgd cam slides 22 and 23 to cause them to mo in the oppoaddiwill be seen by this'o peration that t e cam slide 23 moves downwardly to the rlght, and

' thus allows the accumulator shaft 17 to ride down the upper-side of the cams 21 so that "the index racks 12 engage the pinions 11 to roll in a subtracting operation on the forward stroke.

Following this rolling out of the subtraction operation the continued forward pull of the main operating lever 13 will cause the cam 117 to reach the position where the pin 116 engages the trip 102 and therefore transmits its -motion to the slide plate 97 and move the latter downwardly to the right,

as shown in Fig. 1, thus actu tension mechanism, including the link 94, rock shaft 77,

ating the carry pin 95, so that the carry tension bar 86 is swung counter-clockwise to substraction position. During this swinging of the tension bar 86 the the tension spring 84 direction of pull of will be changed and result in shiftingthe firing arm 78 away 80 from lug 82 and into 81, and places the carry me a to carry in the o it bid for the dition enga ement with lug under tension posite direction from which carry. On the return stroke of the main lever 13 the cam slides 22 and 23 are automatically returned to their normal position, and ion shaft cams 21 and brings 17 rides back to the trap consequently the pinof the the aforesai pinions again into mesh with the carry racks 56.

When the main operating lever 13 has reached a oint just return stro e, the their control latch ation are released by before the end of its carry racks which have es set for a carrying opera fractional amount,

which insures the latches against return to the locking notches prior to the carry operation, and

a continuation of the return movement finally releases the resetting mechanism controlling these carry racks so that the said racks are subtraction, are fired tion from which they ing carry operation free to be fired by the tension or firing arms 78. These, of course,

for the in the opposite direcwere during the add- It will be noted that 10;

upon this return stroke of the operating lever 13 the cams 15 and 117 carry their pins 42 and 118 respectively past the addi- -tion trips 32 and 101, because these latter are held out of the way through'the positioning of the selecting arms '44 an Thus, for a subtracting 43 and 116 are the ones the respective parts 6. 104. operation, cam ins functioning to s ift controlled thereby,

while upon an adding operation the pins 42 and 118 become the 0 moving the respective direction.

It will now be app unitary carr tension racks of ad ing and perating pins for parts in the opposite arent that a complete mechanism for carry 120 subtracting machines has been devised, wherein the heretofore complex mechanism been greatly simplifie for this purpose has (1 and the number of parts very materially reduced. This simpli- 12 fication of the carry tension mechanism 'results also in raising the percentage of durabilit and certainty pare to carr fore used WhlOl'l emp tension mechanisms of operation, as comhereto-. loy a multiplicity of connected to the other ng machines comprisin parts, ;;incl uding pawls, springs, detents, and the like. In the present invention all such trains of mechanisms have been eliminated with the result that defects due to the presence of the elements of such mechanisms are done awa with. It should also be noted that the simplified carry tension mechanism of the present invention is common to both addition and subtraction carry operations and has therefore disposed of all parts which have been commonly brought into use for a subtraction carry in place of other parts employed during addition carry. Thus the present invention does away with expensive, complicated and burdensome parts which havc been in long use and which the industry to which this invention pertains has found heretofore no method of dispensing with.

Although but one form is shown in which this invention maybe embodied, it is to be.

understood that the invention is not limited to any specific construction, but might be applied in various forms without departing from the spirit of the invention or the scope of the appended claims.

Having thus described my invention, I claim: I

1. A mechanism for adding and subtracting machines comprising a reciprocal carry rack, an accumulator wheel arranged to be moved to mesh with said rack, a tension spring, a firing member connected to one end of said spring and arranged to hold said car ry rack under tension, a fulcrum for said member located between said sprin connection and the carry rack end of sai mem: her, ,and means connected to the other end of said spring for changing the direction of the applied tension'of said spring whereby the direction of carry of said carry rack can be reversed.

2. A mechanism for adding and subtrafzting machines comprising a reciprocal carry rack, an accumulator w eel arranged to be moved to mesh with said rack, a tension spring, a firing member-connected to one end of said 5 ring and arranged to hold said carry rac under firin tension, afulcrum or said member located between said spring connection: and the-rack end of said firing member, and means including a pivoted arm end of said spring for changing the direction of the appliedtension of said spring whereby the firing direction of said member isreversed to change from one form of carry tothe other.

3. A mechanism for adding and subtracta reciprocal carry rack, an accumulator w eel arranged to be moved to mesh with said rack a tension spring, a firing member connected to one end of said spring and arranged to. hold said carry rac under firin tension, a fulcrum for said member located spring connected to shift said between said spring connection and the rack end of said firing member, and means including an arm pivoted on an axis coincident with the member end of said spring for changing the direc tion of the applied tension of said spring, whereby the firing direction of said member is reversed to change from one form of carry to the other.

4. A carry tension mechanism for adding and subtracting machines comprising a carry rack mounted to move in a direction for addition carry and in a direction for subtraction carry, a firing member arranged to cooperate with said carry rack, a tension spring connected to said'member, means holding said spring under constant tension, means for swinging said spring and holding means about the spring connection with said member as an axis to change the direction of the applied tension, a selecting device for setting said swinging means for a prede termined carry operation, means actuated. at a predetermined timein said machine for causing said swinging means to function, and means for locking said selecting device in set position to retain the operation ofing all the selected operation.

5. A carry tension mechanism for adding and subtracting machines comprising a carry rack mounted to move in a direction for addition carry and in a direction for subtraction carry, a firing member arranged to cooperate with said carry rack, a tension to said member, means holding said spring under constant tension, means for swinging said spring and holding means about the spring connection with said member as-an axisto change the direction of the applied tension, a selecting device for setting said swinging means for an addition carry, and means actuated at a predetermined time in the addition stroke of said machine for causing said swinging means tofunction to shift said spring and holding means from subtracting carry position to carry position. carry tension mechanism for adding and subtracting machines comprising a carry rack mounted to move in a direction in a direction for for addition carry and subtraction carry, a firing member arranged to cooperate with said carry rack, a tension spring connected to 'said member, means holding said spring under constant tension, means for swinging said spring and holding means about the spring connection with said member as an axis to change the direction of the applied tension, a selecting device for setting said swinging means for an addition carry, means actuated at a predetermined time in the addition stroke of said machine for causing said swinging means to function spring and holding means from subtracting carry position to adding. carry position, and means for locking said tension spring means for all successive addition operations.

7. In an adding and subtracting machine, the combination of accumulator wheels, a common mechanism for controlling addition and subtraction, a carry rack, a latch arranged to lock said carry rack in a central position, means to automatically release said latch, a pivoted carry tension means for firing said carry rack, means to intially release I said carry rack to set said carry rack for a the combination of accumulaton wheels, a

common mechanism for controlling addition and subtraction, a carry rack, a latch arranged to lock said carry rack in a central osition, means to automatically release said atch, a pivoted carry tension means for firing said carry rack, means to initially release said carry rack to for a carry operation, means operating at the same side of the fulcrum of said carry tension for; reversing the action of said carry tenslon upon sa d carry rack, and means for maintaining a substantially constant tension set said carry rack v on said carry tension means when shifting said tension means from one form of carry to the other.

Signed at Philadelphia, county delphia, State of Pennsylvania, day of March, 1924.

this 18th WILLIAM W. LASKERQ of Phila-