US3430012A

US3430012A - Electric snap key switch assembly

Info

Publication number: US3430012A
Application number: US600969A
Authority: US
Inventors: Helmut Langenberger; Hans Kruse
Original assignee: Walther Bueromaschinen GmbH
Current assignee: Walther Bueromaschinen GmbH
Priority date: 1965-12-27
Filing date: 1966-12-12
Publication date: 1969-02-25
Anticipated expiration: 1986-02-25
Also published as: US3524975A; FR1509234A; SE346655B; DE1248132B; CH455001A; GB1098737A; SE333177B

Description

Feb. 25, 1969 LANGENBERGER ET AL 3,430,012

ELECTRIC SNAP KEY SWITCH ASSEMBLY Filed Dec. 12, 1966 Sheet of 2 Feb. 25, 1969 H LANGENBERGER ET AL 3,430,012

ELECTRIC SNAP KEY SWITCH ASSEMBLY Filed Dec. 12. 1966 Sheet 2 of 2 Fig. 4

IN VE N TOR:

f [ma may United States Patent W 40,597 US. Cl. 20067 Int. Cl. H01h 21/04 5 Claims ABSTRACT OF THE DISCLOSURE A spring switch key assembly for the keyboard of an electric calculating machine having a key shaft slidably mounted in an elongated housing. Contacts are disposed in the bottom of the housing. A snap spring mechanism is arranged to engage a contact arm with the contacts. An angular lever is pivotally mounted in the housing and connected to the lever and mechanism wherein depression of the key closes a circuit and the return of the key to its normal position closes a second circuit. In addition, there are cooperating notches and ribs on the switch key housing and keyboard opening for mounting of the housing in the keyboard.

The keyboard of an electric calculating machine contains a plurality of keys for the introduction of data into the calculating machine. Such keys are generally in the form of switches and each key comprises a housing having a contact therein connected to a source of electrical energy with the contact being engaged to complete the circuit when the key is depressed.

Numerous types of switch keys have been devised for introducing data into electric calculating machines upon the depression of the key. Such keys are generally spring switches or snap switches which, upon the depression of the key, will move a resilient switch contact into engagement with a stationary contact to close a circuit with the circuit being broken when the key is lifted or otherwise returned to its normal position. A major disadvantage of this type of a switch key is that it is difficult for the operator to ascertain with certainty whether or not the data which was supposed to have been entered by the depression of the key was actually entered. If the key was not sufi'lciently depressed by the operator the data will not have been entered since the circuit would not have been closed.

It had been proposed to correct this difliculty by delaying the breaking of the contact until after a short return movement of the key to its normal position. However, the problem then arose that in quickly striking one key there was danger of the operator accidentally depressing an adjacent key. The operator thus remained uncertain as to whether the data was actually entered. This uncertainty could be removed to some extent by some form of a visual indicator actuated when the key was completely depressed or by the operator noting the values recorded on the paper strip.

It is pointed out that the switch key to which the present invention relates is of the type which does not remain in its depressed position, but after its release the key will quickly return to its normal position. Thus, the keyboard does not present the operator a pattern of depressed keys which would quickly indicate to the operator whether or not the data was actually entered into the calculating machine.

It is therefore the principal object of the present invention to provide a novel and improved switch key assembly tor the keyboard of an electric calculating machine.

3,430,012 Patented Feb. 25, 1969 It is another object of the present invention to disclose an electric switch key assembly which will indicate to the operator both acoustically and by bearing pressure on the key that the data has been entered into the calculating machine.

It is a further object of the present invention to provide a simplified yet efiective arrangement for the mounting of a switch key assembly in the keyboard of an electric calculating machine.

The present invention essentially comprises a switch key assembly having a houosing in which there is a pair of fixed contacts. Also within the housing is a contact element having its inner end bent over the fixed contacts and a movable contact arm as one end mounted on the contact element bent portion for pivotal movement. The other end of the movable contact arm has contacts and is movable between the fixed contacts. Depression of the key actuates a key shaft which is slidably mounted within the housing and is operatively connected to one arm of an angular lever which is pivotally mounted within the housing. The other arm of the angular lever is connected by a spring to the movable contact arm. As a result of this construction, depression of the key to its lowermost or depressed position will pivot the angular lever and also snap the movable contact arm through the spring into contact with one of the fixed contacts. The key is then moved upwardly to be returned to its normal position under the action of a return spring. This upward movement of the key shaft will snap the movable contact arm back into engagement with the second fixed contact.

The clicking noise of the movable contact between the fixed contacts will indicate to the operator that the data has been entered by the depression of the key. In addition, the varying pressure exerted by the key will indicate to the operator whether or not the value has been entered.

A further aspect of the invention comprises the mounting of the switch key housing in an opening in the keyboard by means of cooperating ribs and notches on the housing and keyboard opening respectively. Further, a resilient member is wedged between the housing and the keyboard opening to retain the housing in position and to form a tight closure in the keyboard opening.

Other objects and advantages of the present invention will be apparent upon reference to the accompanying specification when taken in conjunction with the following drawings wherein:

FIGURE 1 is a perspective view of a portion of the keyboard showing the keyboard openings with a switch key housing being mounted in one of said openings;

FIGURE 2 is an overall perspective view of the switch key housing;

FIGURE 3 is a perspective view of the resilient member utilized for mounting the housing in the keyboard as illustrated in FIGURE 1;

FIGURE 4 is a longitudinal sectional view through the switch key housing as illustrated in FIGURE 2 with the parts being shown in their normal or resting positions;

FIGURE 5 is a sectional view taken along the line 55 of FIGURE 4; and

FIGURE 6 is an overall perspective view of the switch ing mechanism within the housing.

Proceeding next to the drawings wherein like reference symbols indicate the same parts throughout the various views a specific embodiment of the present invention will be described in detail.

Referring to FIGURES 1-3 a switch key assembly according to the present invention is illustrated generally at 5. This assembly comprises a housing 6 having a substantially rectangular cross section as shown. The assembly 5 is mounted in a carrier plate 6 of the keyboard of the electric calculating machine. The carrier plate 7 is provided with an opening into which the housing 6 is inserted.

On the upper end of the housing 6 as may be seen in FIGURES l and 2 there are provided external retaining ribs 8 which engage the upper surface of carrier plate 7 when the housing 6 is in position as shown in FIGURE 1. Spaced below retaining ribs 8 are bosses 9. The distance of the bosses from their respective ribs 8 is equal to the thickness of the carrier plate 7.

The carrier plate opening 10 has a pair of notches 11 on opposed edges thereof as shown in FIGURE 1. It may be seen one notch of each pair is against the edge 13 of the carrier plate opening 10 whereas the other notches of the pair are spaced from edge 12 of the opening 10.

When the housing 6 is inserted into opening 10, the bosses 9 move through the corresponding notches 11 until they are positioned beneath the carrier plate 7. The housing 6 is then moved laterally against edge 12 of the opening. A resilient closure member 14 having tapered edges is then inserted between opening edge 13 and the housing 6. The closure member 14 has a external rib 14" which rests against the upper surface of carrier plates 7 when the closure member is fully inserted into the opening 10. This closure member not only retains the housing in position within carrier plate opening 10 but also provides a dust-proof closure for this opening so as to prevent the dust and other dirt from penetrating into the mechanism beneath the keyboard of the calculating machine.

The cover member 14 has retaining shoulders 14' which are sprung into position to engage the underside of carrier plate 7, thereby securing the closure member in position.

Proceeding next to FIGURES 4-6 the switching mechanism Within the housing 6 will be described in detail. The switching mechanism comprises an angular lever 15 whch is pivotally mounted on a pin 16 in the inner wall of the housing enclosure 17. The top or cover of the housing enclosure 17 is indicated at 18.

One arm 19 of the angular lever 15 has mounted on its end a tension spring 20. The other arm of the angular lever has a cylindrical enlargement 21 thereon and is seated in a recess 22 formed in key shaft 23. The key shaft 23 is mounted for vertical movement within the housing enclosure 17 and has a key 23' mounted on its upper end which projects outwardly of the housing. Thus, any vertical movement of key shaft 23 will cause a pivoting movement of angular lever 15.

Also within the housing enclosure 17 there is provided a movable contact spring member 24 having mounted on its lower end a double faced contact 25. The upper end of the contact spring member is bifurcated to form two ends 27 and 27' bent in the manner as illustrated in FIG- URES 4 and 6. The upper edges of the bifurcations 27 and 27' are indicated at 26 and are seated in recesses 28 formed in the undersides of a bent portion of a stationary contact element 29 mounted within the housing. With this arrangement the contact spring arm 24 is electrically connected to the contact element 29. The tension spring is positioned between the bifurcations and has its other end connected to the contact spring arm 24 as shown in FIGURES 4 and 6.

The connection of tension spring 20 to the angular lever 15 and the contact arm 24 is such that the tension force in the rest position as illustrated in FIGURE 4 is to the left of the bearing edge 26 of the movable contact arm 24.

On depression of key 23', the key shaft 23 will move downwardly within the housing enclosure 17 and will pivot the angular lever 15 in the clockwise direction as viewed in FIGURE 4. As the tension force exerted by spring 20 becomes positioned to the right of the bearing surface 26, the movable contact arm 24 will snap to the right to engage a fixed contact 30 mounted on contact element 31 which extends outwardly of the housing enclosure.

When the operator releases his finger from key 23', a compression spring 32 will return the key shaft 23 to its normal position and accordingly pivot angular lever 15 in a counter clockwise direction. As the force exerted by spring 20 passes to the left of bearing edge 26 the contact arm 24 will be returned to its resting position as viewed in FIGURE 4 with contact 25 being in engagement with fixed contact 23. Fixed contact 23 is similarly mounted on contact element 31 which extends outward- 1y of the housing enclosure.

In order to minimize the possibility of the bearing edges 26 of the movable contact arm from coming out of recesses 28, the

bifurcations

27 and 27 may be provided with lugs which extend into recesses 34 and 35 formed in the walls of the housing enclosure 17. These recesses would have such a diameter so as to enable the bifurcations to pivot freely therein but not sufficient so as to enable the bearing edges 26 to become removed permanently from the recesses 28.

In order to limit the range of vertical movement of key shaft 23, the key shaft is provided with a shoulder 36 which moves in a groove formed in an inner wall of the housing enclosure and indicated at 37. Thus, the key shaft is detained in its resting position by the shoulder 36 engaging the upper end of the groove 37 as shown in FIGURE 5. The downward movement of the key shaft is limited by a felt pad 38 positioned on the top wall 18 of the housing enclosure 17 as illustrated in FIGURES 4-6.

The

contact elements

29, 31, and 31' all of which extend outwardly of the housing enclosure 17 are electrically connected to the circuitry within the calculating machine. The dead center arrangement of the angular lever, and the tension spring connecting the angular lever to the movable contact arm assure proper making and breaking of the data introducing circuits upon the depression and release of the keys on the keyboard.

Thus it can be seen that the present invention provides a switch key assembly which gives an audible signal to the operator upon the introduction of data into the machine when the key is depressed. In addition, the bearing pressure on the key resulting from the dead center arrangement indicates to the operator whether or not the data has been entered. The mounting of the switch key assembly in the keyboard of a calculating machine is extremely effective yet enables the switch key assembly to be removed for maintenance or other purposes. At the same time a dust free closure is provided between the switch key assembly and the opening in the keyboard.

It is understood that this invention is susceptible to modifications in order to adapt it to different usages and conditions, and accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the claims.

What is claimed is:

1. An electric snap switch for the key board of an electric calculating machine, and comprising an elongated housing having a bottom wall and normally disposed in a vertical position, a pair of spaced fixed contacts in said housing bottom wall, a contact element within said housing with its inner end being bent to extend over said fixed contacts, there being a recess on the under-side of said bent portion, a rigid movable contact arm having one end seated in said recess for pivotal movement therein and contacts on its other end movable between said fixed contacts, a key shaft with a slot therein slidably mounted for limited axial movement in said housing towards said bottom wall, a first spring between said key shaft and housing bottom wall urging said key shaft outwardly of said housing to its normal unactuated position, an angular lever pivotally mounted in said housing and having first and second arms radially extending from the pivot point, said arms being directed away from the housing bottom wall, the end of said first arm being operatively connected to said key shaft slot, and a second spring connecting said second arm of said angular lever and said movable contact arm so that the depression of said key shaft against the force of said first spring would move said movable contact arm against one fixed contact and return of said key shaft to its normal position will move said movable contact arm against the other fixed contact.

2. In a switch key assembly as claimed in claim 1 wherein said bent portion of the contact element is bifurcated with recesses on the underside of each bifurcation, the end of said movable contact arm engaging said contact element being bifurcated, said first spring being positioned between said contact element and movable contact arm bifurcations.

3. In a switch key assembly as claimed in claim 1 with there being recesses in the inner wall of said housing, and lugs on said movable contact arm adjacent said pivot end seated in said housing recesses to retain said movable contact arm in engagement with said contact element.

4. In a switch key assembly as claimed in claim 1 with said key board having a carrier plate with an opening therein into which said housing is positioned.

5. In a switch key assembly as claimed in claim 1 with said housing having a rectangular cross section, said key shaft being positioned longitudinally of said housing, said angular lever being pivotally mounted above said contact element bent portion.

References Cited UNITED STATES PATENTS 2,779,835 1/ 1957 Russell. 3,056,002 9/1962 Ball. 3,244,847 4/1966 Erpel 200172 X 3,270,157 8/ 1966 Johnson.

ROBERT K. SCHAEFER, Primary Examiner.

D. SMITH, In, Assistant Examiner.