US3823806A

US3823806A - Counterbalance touch control

Info

Publication number: US3823806A
Application number: US00321611A
Authority: US
Inventors: H Diamond
Original assignee: SCM Corp
Current assignee: Smith Corona Corp
Priority date: 1973-01-08
Filing date: 1973-01-08
Publication date: 1974-07-16
Anticipated expiration: 1991-07-16
Also published as: FR2213657A5; GB1426653A; IT999028B; CA1004198A

Abstract

The key depression touch of a key-actuated business machine is controlled by adjusting the position of a spring bail which simultaneously controls the tension of all the key lever springs. A manually positioned control member with attendant linkages positions the spring bail and simultaneously adjusts the tension of counterbalancing spring means to minimize the unbalanced spring forces acting on the spring bail and the entire touch control system at all touch settings of the touch control apparatus.

Description

United States Patent [191 Diamond [.11 3,823,806 7 [451 July 16,1974

[ COUNTERBALANCE TOUCH CONTROL [75] Inventor: Herrick R. Diamond, Homer, N.Y.

[73] I Assignee: SCM (Zorporation, New York, N.Y. [22] Filed: Jan. 8, 1973 [21] Appl. No.: 321,611

[52] US. Cl 197/33, 197/17 [51] Int. Cl B4lj 7/26 [58] Field of Search 197/33, 27, 17, 98

[56] References Cited UNITED STATES PATENTS 1,741,690 12/1929 Ely 197/33 2,098,285 11/1937 Gabrielson et al..... 197/33 2,148,690 2/1939 Going 197/33 2,148,877 2/1939 Rauscher 197/33 2,169,349 8/1939 Myers 197/33 2,226,924 12/1940 Dobson 197/33 2,567,943 9/1951 Kl0ski.....' 197/33 2,624,439 1/1953 Zeamer 197/33 2,660,285 11/1953 Kennedy, Jr 197/33 2,682,944 7/1954 Schremp 197/33 3,409,111 11/1968 Cappotto 197/33 Primary Examiner-Robert E. Pulfrey Assistant Examiner-E. H. Eickholt Attorney, Agent, or Firm-Kenneth W. Greb; Milton M. Wolson, Esq,

[ 5 7] ABSTRACT The key depression touch of a key-actuated business machine is controlled by adjusting the position of a spring bail which simultaneously controls the tension of all the key lever springs. A manually positioned control member with attendant linkages positions the spring bail and simultaneously adjusts the tension of counte'rbalancing spring means to minimize the unbalanced spring forces acting on the spring bail and the entire touch control systemat all touch settings of the touch control apparatus.

7 Claims, 5 Drawing Figures PATENTEB JUL 1 5 m4 SHEU 1 Hi2 COUNTERBALANCE TOUCH CONTROL BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to key actuated business machines and, more particularly, to apparatus for controlling the key depression touch of key-actuated business machines.

2. Description of the Prior Art Control of the effort, or touch, required to depress the key levers in key lever actuated business machines isvery important if operating personnel are to achieve maximum utilization of the machines. However, because most business machines have intricate key lever mechanisms, it is difficult to effectively control the key lever depression touch of these machines. For example, some business machines have'utilized spearately adjustable spring'devices connected to each key lever to adjust the depression touch for each individual key. Needless to say, though these individual spring adjustment mechanisms insured touch control for each individual key, they provide many problems, particularly with regard to uniformity of the depression touch between the various keys in the keyboard. In this type of machine, it was often necessary to adjust the touch control for a few keys in order to bring the depression touch of the keys into uniformity. Because of the numerous adjustments, the problems presented with maintenance of the machine were substantial.

A second approach of the control of the key depression touch of key-actuated business machines has been to connect each of the key levers to a spring bailby means of key lever springs and then adjust the position of the spring bail to simultaneously adjust the tension of all the key lever springs, thereby simultaneously adjusting the forces necessary to depress the individual keys. Although this approach appears simple, it has proved less than successful in many instances because of the substantial forces required to control the spring bail and thereby adjust and maintain the tension of all the key lever springs simultaneously.

The individual key lever springs act together to exert a substantial force on the spring bail. Therefore, the

mechanism which positions the spring bail must provide forces sufficient to counteract the combined key lever spring forces. This has been done in the past by a manually positioned control member. However, because the combined spring lever forces acting on the spring bail are so much greater in settings which require heavy touch effort than in settings which require low touch effort, it is relatively difficult to position the control member in the settings for high touch effort. Further, touch control adjusting devices have a tendency to drift from heavy touch effort settings to light touch settings because of the combined unbalance force of the key lever springs.

In order to prevent this tendency to drift out of position, many of the touch control apparatuses use detent devices in which the control lever for selecting the touch control value is held in predetermined positions by means of detents to provide established touch control settings. These detent devices are not without disadvantages, and do not completely solve the problem of touch control selection. Most of the key-actuated business machines, such as typewriters or adding machines, are subject to vibration and impact laods which .tend to jar the detent device out of its setting. This is especially so in the newer electric typewriters and adding machines. Further, the detent device requires a separate notch for each settingof the control member, thereby limiting the number of settings usually provided. Also, because the unbalanced spring forces on the touch control device substantially increase as the touch setting is increased, it is more difficult to position the control member in the proper detent notch in the higher touch effort settings than in the lower touch effort settings.

Attempts have been made to overcome the problems of manually positioning the control member of the touch control apparatus by increasing the mechanical advantage of the manually positioned control member in relation to the spring bail. However, this approach usually involves apparatuses having relatively long linkages and levers such as that shown in US. Pat. No. 3,409,111 issued to D. Cappotto on Nov. 5, 1968 and in a Pat. No. 2,098,285 issued to C. Gabrielson et al. on Nov. 9, 1937, which cannot be conveniently positioned and actuated within the confines of existing business machine housings.

BRIEF SUMMARY OF THE INVENTION To overcome the problems inherent in the prior art,

the present invention sets forth apparatus to control the key depression touch of a key-actuated business machineby adjusting the position of a spring bail which simultaneously controls the tension of all the key lever springs. A manually actuated control member, with attendant linkages, positions the spring bail and simultaneously adjusts thetension of counterbalancing spring means, to minimize the unbalanced spring forces acting on the spring bail, and the entire keydepression touch control apparatus.

Accordingly, it is an object of the present invention to provide apparatus for controlling the key depression touch of key-actuated business machines which does not require application of large unbalanced spring forces in order to control the key depression touch.

Another object of the present invention is to provide apparatus for controlling the key depression touch of key-actuated business machines which can be adjusted from one touch setting to another without substantially changing the unbalanced forces acting on the touch control apparatus.

It is a further object of thepresent invention to pro-' vide apparatus for controlling the key depression touch of key-actuated business machines which does not require a variation of the forces exerted on the manually positioned control member when adjusting the key depression touch from one setting to another.

Still another object of the present invention is to provide apparatus for controlling the key depression touch of key-actuated business machines which does not tend to drift from one setting to another setting during operation of the business machine.

It is an additional object of the present invention to provide apparatus for controlling the key depression touch of key-actuated business machines which provides a counterbalance spring means having a spring which increases in pulling force as it slightly decreases in length.

Another object of the present invention is to provide apparatus for controlling the key depression touch of key-actuated business machines which is highly sensitive and provides an infinite number of touch settings.

A further object of the present invention is to provide apparatus for controlling the key depression touch of key-actuated business machines which adjusts all keys simultaneously and uniformly.

It is still another object of the present invention to provide apparatus for controlling the key depression touch of key-actuated business machines which provides a substantial mechanical advantage to allow easy manual positioning of the control member when adjusting the key depression touch setting.

An additional object of the present invention is to provide apparatus for controlling the key depression touch of key-actuated business machines which is relatively compact and easily mounted within the housing of normal business machines.

It is another object of the present invention to provide apparatus for controlling the key depression touch of key-actuated business machines which has relatively few parts, is relatively cheap to manufacture, and relatively durable in operation.

A further object of the present invention is to provide apparatus for controlling the key depression touch of key-actuated business machines which provides an extremely large mechanical advantage for the manually positioned control member so that unbalanced forces in the touch control system do not have a tendency to change the setting of the system.

Other objects and advantages will be apparent from the following description of an embodiment of the inpointed out hereinafter in connection with the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS ratus shown in FIGS. 1 and 2.

FIG. 4 is a perspective view of the touch control apparatus shown in the minimum touch effort position.

FIG. 5 is a view of the touch control mechanism shown in the maximum touch effort position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the invention will hereinafter be described in connection with a' typewriter, it will be understood that the invention can be applied to a wide variety of key-actuated business machines other than typewriters.

Referring to FIG. 1, a typewriter, generally indicated at 10, has a frame 12, and a keyboard, generally indicated at 14, comprising a plurality of key buttons 16, each of which is connected to a key lever 18, which, through various linkages, actuates a typebar (not shown), as is well known in the typewriter art. As shown in FIGS. 2 through 5, each key lever 18 is connected by means of a key lever'spring 20 to a spring bail 22 fixed to a shaft 24 which is rotatably mounted to the left and

right walls

26 and 28 respectively of frame 12. At the left end of bail shaft 24, extending beyond left vention, and the novel features will be particularly wall 26, is fixedly positioned a spring lever 30 which rotates with shaft 24. A counterbalancing spring 34 is connected at one of its ends to a finger 32 on spring lever 30 and is connected at its other end to finger 36 extending 'from the left wall 26 of frame 12.

On the right end of bail shaft 24, extending beyond right wall 28 of frame 12, is fixedly connected a bell crank 38 which rotates with bail shaft 24. A second counterbalance spring 42 is connected at one of its ends to a finger 40 on bell crank 38 and is connected to a finger 44 extending from right wall 28 of frame 12. This assembly of spring 34 and spring 42 positions their respective lines of force substantially across the axis of shaft 24 as shown in FIGS. 2 through 4. This assembly also positions the spring 34 and the spring 42 in a sideby-side relationship with the row of springs 20 thus providing a compact and efficient counter-balance spring system. The bell crank 38 also includes an arm 46 to which is connected the swing arm 50 of a pivot member 52 by means of a translation link 48. Pivot member 52 is pivotally mounted ma leg 54.extending from the right wall'28 of frame 12 by means of a pivot pin 56 which extends through the upper and

lower arms

58 and 60 of pivot member 52. A cam pin 62 extends upwardly from upper arm 58 of pivotmember 52 to control the movement of the swing arm 50, as will now be described.

Pivot member 52 is controlled by manually positioning a control knob 64 rotatably mounted on the leg 54 of frame 12 A retaining pin 66 has a large cylindrical shank 68 extending through cylindrical passage 76 in the hub of the control knob and a smaller threaded end 70 which engages passage 72 in leg 54. The control knob 64 has'a cam groove 74 in the underside of the knob which spirals outwardly from the central cylindrical passage 76 of the knob, about which the knob rotates. Cam pin 62 fits within the cam groove 74 so that rotation of the control knob in the counterclockwise direction, shown by the arrow in FIG. 2, will tend to make cam pin 62 move away from the retaining pin 66, causing pivot member 52, including swing arm 50, to move in the clockwise direction, toward the position shown in'FIG. 4. Similarly,clockwise rotation of the control knob 64 will tend to move cam pin 62 closer to the retaining pin 66 and, therefore, urge the pivot member 52 with swing arm 50 around pivot pin 56 in the counterclockwise direction toward the position shown in FIG. 5.

A brake member 78 is placed between the leg 54 of frame 12 and the bottom of the control knob 64 to prevent random movement of the control knob. The brake member includes four contact feet 80 which are raised above and connected to the central position of the brake member by bent arms 81. The brake member is held fixed in place by the shoulder 69 of the retaining pin 66 formed between the shank 68 and the threaded end 70' of the retaining pin. Threaded end 70passes through the retaining pin passage 82 of the brake member. Additionally, an anchoring tab 84 extends from the central portion of brake member 78 and fits into an anchor slot 86 on leg 54 of the frame12. The contact feet 80 of the brake rub against the underside 88 of the control knob which forms a brake surface for the control knob, so that the control knob will not drift after it is set at a particular position.

OPERATION The effort required to depress a key lever is controlled by manually positioning the control knob which will position the spring bail to adjust the tension of the key lever springs which, in turn, determine the amount of force necessary to depress the key lever buttons.

As shown in FIG. 4, when the control knob 64 is rotated counterclockwise, the cam pin 62 will move in helical cam groove 74 of the control knob away from retaining pin 66 of the control knob so that the swing arm 50 of pivot member 52 will rotate clockwise, thereby pulling translation link 48 to the left to cause bell crank 38 to rotate counterclockwise. The counterclockwise rotation of bell crank 38 will cause the bell of spring bail 22 to move upward toward key levers 18, thereby allowing each key lever spring 20 to contract to a lower stressed condition. Thus, the key lever springs will exert a relatively light force on the key levers so that the amount of force or touch required to depress the key buttons on the key lever will be at a minimum.

When the spring bail 22 is in the raised position, the finger 40 of bell crank 38 is positioned with respect to finger 44 of right wall 28 of frame 12, so that counterbalance spring 42 connecting fingers-40 and 44 is ex tended to a maximum position and substantially crosses the axis of shaft 24. Similarly, finger 32 of spring lever on the left end of bail shaft 24 is positioned so that the counterbalance spring 34 connecting spring lever finger 32 with finger 36 of left wall 26 of the frame is also at the maximum extension and substantially crosses the axis of shaft 24. Accordingly, the forces of both counterbalance springs 34 and 42 exert torques on spring bail shaft 24 which oppose the torques exerted on the spring bail shaft 24 by the key lever springs 20.

To move the touch control system from a setting requiring light depression pressure to one requiring heavier pressure, the control knob 64 is rotated in the clockwise direction (opposite the arrow in FIG. 2), so that the cam pin 62 will follow the helical cam groove 74 ofthe control knob 64 toward the center of the control knob, thereby moving pivot member 52 counterclockwise and swing arm 50 toward the right, which motion is, in turn, translated through translation link 48 to arm 46 of hell crank 38 to rotate the bell crank 38 in the clockwise direction. If control knob 64 were turned the full range of travel clockwise, arm 46 of bell crank 38 would move upward to the vertical position shown in FIG. 5, and fingers 32 of

spring lever

30 and 40 of bell crank 38 would move closer to the frame to slightly shorten counterbalance springs 34 and 42. Having one end of spring 34 connected to finger 32 of spring lever 30 and one end of spring 42 connected to finger 40 of bellcrank 38, the pulling force of the

spring

34 and 42 increases as the ends of the

springs

34 and 42 are carried away from the axis of shaft 24 thereby compensating for the decreasing pulling force as the

springs

34 and 42 slightly shorten. ln the position shown in FIG. 5, the spring ball 22 has been moved to a nearly vertical position extending the key lever springs 20, increasing the tension of the springs, and, therefore, increasing the force required to depress the key levers. While the extended key lever springs 20 exert a counterclockwise torque on the bail shaft 24,

the left and right counterbalance springs 34 and 42, though shortened, still exerted a counterbalancing clockwise torque on the bail shaft 24, which balances the torque exerted by the key lever springs 20. Accordingly, it can be seen that no matter what positions the spring bail 22 is placed in or being moved to by the control knob, there will be counterbalancing forces exerted on the bail shaft 24, so that the unbalanced force exerted on the bail shaft 24 will be of a relatively small nature.

The counterbalance apparatus of the invention possesses many advantages. For example, the apparatus provides great sensitivity of adjustment because the helical cam in the control knob requires a large displacement to adjust the touch control over its full range.

Similarly, the use of a helical cam groove in the rotatable control knob offers an extremely high mechanical advantage in positioning the spring bail, so that a minimum of force is necessary on the part of the operator of the machine to adjust the control knob. Additionally, because of the high mechanical advantage involved, the net forces which are fed back from the spring bail shaft to the control knob through the touch control apparatus are relatively small and can easily be handled by the brake mechanism described without the necessity for detents or other fixed stops in the control range. Therefore, the system will not have a tendency to drift from one position to another, but will tend to be more stable and not require continuous adjustment, as has heretofore been the case with many touch control systems. Since no detents are necessary to hold the control knob, an infinite number of settings for the control knob will be available to the operator. a

It should also be noted that the apparatus has relatively few moving parts which require a minimum of adjustment to insure proper operation. Therefore, the apparatus should be relatively inexpensive to manufacture and be highly durable in service. v

It will be understood that various changes in the details, materials and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art within the principle and scope of the invention, as expressed in the appended claims.

What is claimed is:

1. An apparatus for adjusting the depression touch effort of key levers in a key lever actuated business machine, comprising:

a spring bail chine; key lever spring means operatively connected to each key lever and to said spring bail effecting the depression. touch effort of the key lever and urging said spring bail to move in a given direction; counterbalance spring means operatively connected to said spring bail for urging said spring bail to.

move in a direction opposite to said given direction of said key lever spring means, said counterbalance spring means includes a shaft, a member extending substantially radially from said shaft, and a spring connected to said member, said spring being operable by said member for moving said spring from a position substantially crossing the axis of said shaft to a position away from the axis of said shaft to increase the pulling force of said spring'as said spring decreases in length; and

movably mounted in the business macontrol means operatively connected to said spring bail and to said counterbalance spring means for adjusting said k'ey lever spring means thereby effecting the depression touch effort of the key levers and for simultaneously adjusting said counterbalance spring means to minimize variations of the spring forces acting on said control means.

2. The apparatus as defined in claim 1 wherein said control means includes a linkage connected to said counterbalance spring means for moving said spring bail to adjust the depression touch effort of the key levers through said counterbalance spring means.

3. The apparatus as defined in claim 1 wherein said spring bail is rigidly connected to said shaft of said counterbalance spring means and said spring bail is moved by said shaft for adjusting the depression touch effort of the key levers.

4. The apparatus as defined in claim 1 wherein said spring bail is rigidly connected to said shaft of said counterbalance spring means, said member of said counterbalance spring means is rigidly connected to said shaft and said control means includes a linkage connected to said member and operable to move said pr'ession touch effort of the key levers.

5. The apparatus as defined in claim 1 wherein said control means includes a brake means to resist movement of said control means, said counterbalance spring means and said spring bail from any adjusted position of said control means.

6. The apparatus as defined in claim 5 wherein said.

control means includes a control knob and said brake means includes a brake member contacting said control knob to prevent said control knob from drifting from adjusted positions.

7. The apparatus as defined in claim 1 wherein said control means includes:

a control knob rotatably mounted in the business machine; a cam surface in said control knob; and pivot means in contact with said cam surface and operatively connected to said spring bail to position said spring bail in response to manual positioning of said control knob to adjust the depression touch effort of the key levers.

Claims

1. An apparatus for adjusting the depression touch effort of key levers in a key lever actuated business machine, comprising: a spring bail movably mounted in the business machine; key lever spring means operatively connected to each key lever and to said spring bail effecting the depression touch effort of the key lever and urging said spring bail to move in a given direction; counterbalance spring means operatively connected to said spring bail for urging said spring bail to move in a direction opposite to said given direction of said key lever spring means, said counterbalance spring means includes a shaft, a member extending substantially radially from said shaft, and a spring connected to said member, said spring being operable by said member for moving said spring from a position substantially crossing the axis of said shaft to a position away from the axis of said shaft to increase the pulling force of said spring as said spring decreases in length; and control means operatively connected to said spring bail and to said counterbalance spring means for adjusting said key lever spring means thereby effecting the depression touch effort of the key levers and for simultaneously adjusting said counterbalance spring means to minimize variations of the spring forces acting on said control means.

4. The apparatus as defined in claim 1 wherein said spring bail is rigidly connected to said shaft of said counterbalance spring means, said member of said counterbalance spring means is rigidly connected to said shaft and said control means includes a linkage connected to said member and operable to move said member for moving said spring bail to adjust the depression touch effort of the key levers.

6. The apparatus as defined in claim 5 wherein said control means includes a control knob and said brake means includes a brake member contacting said control knob to prevent said control knob from drifting from adjusted positions.

7. The apparatus as defined in claim 1 wherein said control means includes: a control knob rotatably mounted in the business machine; a cam surface in said control knob; and pivot means in contact with said cam surface and operatively connected to said spring bail to position said spring bail in response to manual positioning of said control knob to adjust the depression touch effort of the key levers.