US 3425761 A
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Feb. 4, 1969 K. D. SCHREYER TYPEWRI'IER DESK MECHANISM Filed May 29, 1967 Sheet R .E WU E R T NC 0 m m H T E N N E K Feb. 4, 1969 K. o. SCHREYER 3,425,761
TYPEWRITER DESK MECHANISM Filed May 29, 1967 Sheet 2 of 2 KENNETH D.SCHH: R
BYdwf United States Patent 3,425,761 TYPEWRITER DESK MECHANISM Kenneth D. Schreyer, Doylestown, Pa., assignor to Standard Pressed Steel Co., Jenkintown, Pa., a corporation of Pennsylvania Filed May 29, 1967, Ser. No. 642,043 US. Cl. 312-28 Int. Cl. A47h 21/03 3 Claims ABSTRACT OF THE DISCLOSURE The present invention relates, in general, to office furniture and, in particular, to a typewriter desk mechanism which serves to move a typewriter into and out of a housing in a desk or similar piece of furniture.
Various mechanisms are presently available which serve to move a typewriter back and forth between a storage space within a desk and a position at which the typewriter may be used. One of'the more common arrangements employs a typewriter platform which undergoes horizontal and vertical movements from a lower position within the housing to an upper position at which the typewriter is used. Normally, the platform and the typewriter move horizontally from the housing to a prescribed point from which the two are moved vertically to the position at which the typewriter is used. The path is reversed when the typewriter is returned to the storage space.
Many typewriter desk mechanisms of this type suffer from one or more serious shortcomings. Some mechanisms are extremely difiicult to move back and forth between the two positions. As a result, the user of the typewriter leaves the typewriter at the position at which it is used during periods when not in actual use, for example overnight, instead of storing the typewriter. As a result, this typewriter desk mechanism is not serving its intended purpose.
Another shortcoming of many typewriter desk mechanisms which are presently available is that they employ an excessive number of component parts which contributes to the complexity of the mechanism. The complexity of these units often renders them unreliable and more costly than desirable.
Accordingly, it is an object of the present invention to provide a new and improved typewriter desk, mechanism.
It is another object of the present invention to provide a typewriter desk mechanism which is relatively simple in construction, easily manipulated, inexpensive to fabricate, and highly reliable in operation.
Briefly, a typewriter desk mechanism constructed in accordance with the present invention includes a platform upon which a typewriter may be placed and a carriage to which the platform is linked. The carriage is adapetd to move along a pair of tracks positioned, for example, along the inside walls of a housing within which the typewriter is stored when not in use. A stiff spring, connected between the carriage and the linkage, is arranged to employ an over-center concept. Prior to the application of a prescribed force, the spring alone 3,425,761 Patented Feb. 4, 1969 keeps the platform at a lower position. Once the necessary force is applied, the longitudinal axis of the spring passes over a balance or equilibrium point and the spring urges the platform to an upper position. In order to return the platform to the lower position, suflicient force must be applied to cause the longitudinal axis of the spring to pass back over the balance point with the result that the spring urges the platform to the lower position.
For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description, taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.
Referring to the drawings:
FIGURE 1 is a perspective view of a typewriter desk mechanism constructed in accordance with the present invention;
FIGURE 2 is a sectional view of the typewriter desk mechanism of the present invention with the typewriter platform in its retracted or lower position;
FIGURE 3 is a sectional view, similar to FIGURE 2, with the typewriter platform in its upper position;
FIGURE 4 is a horizontal section taken along line 4-4 of FIGURE 3; and
FIGURE 5 is a vertical section taken along line 5--5 of FIGURE 3.
Referring to the drawings, a typewriter desk mechanism constructed in accordance with the present invention includes a carriage 10 provided with means for longitudinal movement of the carriage along a pair of tracks 12 (only one of which is shown in FIGURES 2, 3, 4, and 5) positioned along the inside walls 13 of a housing in a desk. In particular, the carriage has a pair of vertical side panels 14a and 14b upon which two pairs of rollers 16a, 18a, and 16b, 18b, respectively, are individually mounted. The rollers are so arranged on the side panels that one roller on each panel is above its associated track, while the other roller is below the track. In this manner, the carriage may be moved along tracks 12. Lance formations 15a and 15b are provided on side panels 14a and 1412, respectively. These lance formations are arranged to abut against stops (not shown) on tracks 12 which limit the outward horizontal movement of the carriage, A transverse rod 19, extending between side panels 14a and 14b, provides transverse rigidity for the ,carriage.
The typewriter desk mechanism of the present invention further includes a platform 20 upon which a typewriter 22 may be placed. Extending downward from the longitudinal edges of platform 20 is a pair of side panels 23a and 23b.
Platform 20 is connected to carriage 10 by means of a parallelogram linkage having two pairs of links 24a, 24b, and 26a, 26b, whereby the platform moves longitudinally with the carriage. In particular, links 24a and 26a are pivotally connected between side panels 14a and 23a, while links 24b and 26-12 are pivotally connected between side panels 14b and 23b. Corresponding pivot points of each pair of links 24a, 24b and 26a, 26b have a common horizontal axis. As a result, platform 20 may move in a vertical direction relative to carriage 10 when a force having a vertical component is applied to the leading transverse edge of platform 20. This vertical movement takes place after the platform is moved horizontally out of the housing from the position illustrated in FIGURE 2. Once platform 20' is clear of the opening of the housing and lance formations 15a and 15b hit against the stops on tracks 12, the platform may be moved from its lower position to the upper position illustrated in FIGURE 3.
Extending between carriage 10 and the parallelogram linkage is a stiff spring 30. One end of spring 30 is hooked onto transverse rod 19, while the other end of the spring is hooked onto a second transverse rod 28 extending between links 26a and 26b. Rod 28 provides additional transverse rigidity to the mechanism. The arrangement of spring 30 and links 26a and 26b is such that the common axis of the pivot points on side panels 14a and 14b of this pair of links (point 29a of link 26a) is located ahead of the longitudinal axis of the spring, as represented by a straight line 31a between the ends of the spring, with respect to the initiation of a movement of platform from its lower position in FIGURE 2 (after the platform has been moved horizontally out of the housing) to its upper position in FIGURE 3. This condition is made possible for the particular embodiment of the invention which is illustrated by the elbow shaped links 26a and 26b and the rod 28 being secured to these links at their bends. As platform 20 is moved from its lower position to its upper position, transverse rod 28 moves in the direction of arrow 32 in FIGURE 2. At some point after sufiicient force has been applied to plat form 20 to overcome the effect of spring 30, the longitudinal axis of the spring coincides with straight line 31b which passes through pivot point 2%. Prior to this condition, spring 30, being sufficiently stiff, tends to keep platform 20 at its lower position. Beyond this condition, the platform is urged upward by spring 30. At the completion of the movement of platform 20 from its lower position to its upper position, pivot point 2% is located behind the longitudinal axis of spring 30 as illustrated in FIGURE 3. In order to return platform 26) to its lower position, sufficient force must be applied to the platform to overcome the stiffness of spring 30 to cause the longitudinal axis of the spring to pass over pivot point 29a in a direction opposite to the one described previously.
Each of the side panels 14a and 14b is provided with a curved slot 32a and 32b, respectively, through which fingers a and 25b at the ends of links 24a and 241) respectively, project. These fingers bear against the upper edges of slots 32a and 32b to limit the downward movement of platform 20. In the absence of this engagement of fingers 25a and 2512 with slots 32a and 3212, spring would cause links 24a, 24b, 26a and 26b to turn counterclockwise about their pivot points on the carriage beyond the positions illustrated in FIGURE 2.
Fingers 25a and 251) also are adapted to engage obstructions on tracks 12 when the platform 20 is moved to its upper position to lock the carriage against longitudinal movements while the platform is in this position. When the platform is returned to its lower position, fingers 25a and 25b move clear of these obstructions to permit longitudinal movement of the carriage and the platform.
Although the mechanism described above has a number of features which render it extremely worthwhile, two are of particular importance since they relate to the safety of an individual who may manipulate the platform and the freedom from damage of a typewriter placed on the platform. Spring 30 keeps platform 20 in its lower position so that a deliberate force is necessary to overcome the effect of the spring and move the platform to its upper position. Thus, an unloaded platform (one on which a typewriter has not yet been placed) will not spring upward. In contrast, some typewriter desk mechanisms which are presently available and which employ spring action require the load of a typewriter to prevent the platform from springing upward. As a result, in the absence of a typewriter, such a platform will spring upward to the surprise of a user and may cause him injury.
The action of stiff spring 30 also makes it practically impossible to move platform 20 upward until the platform has been pulled out of the housing to its outer limit. Until platform 20 reaches this position, the force applied to the leading transverse edge of the platform causes the platform to move outward more easily than upward. This is due to the fact that less horizontal force is required to draw the platform out of the housing than the vertical force which is required to overcome the stiffness of spring 30 to cause the spring to pass through the balance point. After the platform has been drawn to its outer limit and lance formations 15a and 15b abut against their respective stops, the platform is prevented from moving further outward so that the force applied to the leading transverse edge of the platform may overcome the effect of spring 30. As a result, a typewriter placed on platform 20 is not exposed to possible damage due to it being moved upward within the housing and hitting the ceiling of the housing. In order to raise the platform upward while it is still within the housing, a force quite different from the one normally applied in the usual usage of the mechanism must be employed.
While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.
What is claimed is:
1. A typewriter desk mechanism comprising:
a carriage having a pair of longitudinal edges and means for longitudinal movement of said carriage along a pair of tracks, said carriage also having a first transverse rod extending between said longitudinal edges of said carriage, one of said longitudinal edges of said carriage having a slot therein;
a platform upon which a typewriter may be placed, said platform having a pair of longitudinal edges;
a parallelogram linkage having two pairs of links pivotally connected between said longitudinal edges of said carriage and said longitudinal edges of said platform with corresponding pivot points of each pair of links having common axes, one pair of said links being elbow shaped and a second transverse rod extending between the bends of said elbow shaped links, whereby said platform moves longitudinally with said carriage and may move in a vertical direction relative to said carriage from a lower position to an upper position, one of said links having a finger which projects through said slot in said longitudinal edge of said carriage and is adapted to engage a stationary obstruction when said platform is moved to said upper position to lock said carriage against longitudinal mvoements;
and a stiff spring extending between said first and second transverse rods, the common axis of the pivot points on said carriage of one pair of said links located ahead of the longitudinal axis of said spring with respect to the initiation of a movement of said platform from said lower position to said upper position and located behind said longitudinal axis with respect to the completion of said movement of said platform from said lower position to said upper position.
2. A typewriter desk mechanism comprising:
a carriage having a pair of longitudinal edges and means for longitudinal movement of said carriage along a pair of tracks, one of said longitudinal edges of said carriage having a slot therein;
a platform upon which a typewriter may be placed;
a parallelogram linkage having two pairs of links pivotally connected between said carriage and said platform with corresponding pivot points of each pair of links having common axes, whereby said platform moves longitudinally with said carriage and may move in a vertical direction relative to said carriage from a lower position to an upper position, one of said links having a finger which projects through said slot in said longitudinal edge of said carriage and is adapted to bear against an edge of 5 6 said slot to limit movement of said carriage from position and said finger on said link bearing against said upper position to said lower position; said edge of said slot in said longitudinal edge of said means interconnecting one pair of said links; carriage. and a stiff spring having one end secured to said car- 3. A typewriter desk mechanism according to claim 1 riage and the other end secured to said interconnect- 5 wherein said carriage has a pair of vertical side panels ing means, the common axis of the pivot points on upon which two pairs of rollers are individually mounted said carriage of said one pair of links located ahead for said longitudinal movement of said carriage. of a straight line between said ends of said spring with respect to the initiation of a movement of said References Cited platform from said lower position to said upper 10 UNITED STATES P N position and located behind said straight line with 2,656,234 10/1953 Koch 312 28 respect to the completion of said movement of said platform from said lower position to said upper position, the stiffness of said spring alone being BOBBY GAY, Primw-y sufiicient, in the absence of any externally applied forces, to maintain said platform in said lower KOHNEN Asslsmnt Exammer' 3,003,838 10/1961 Chaft 312-28
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