US2744805A

US2744805A - Lift mechanism for extending a horizontal support

Info

Publication number: US2744805A
Application number: US322221A
Authority: US
Inventors: Mcmahan Walter Carl
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-11-24
Filing date: 1952-11-24
Publication date: 1956-05-08
Anticipated expiration: 1973-05-08

Description

May 8, 1956 LIFT MECHANISM FOR EXTENDING A HORIZONTAL SUPPORT Filed Nov. 24, 1952 W. C. MCMAHAN 2 Sheets-Sheet l 75e C. MoMA/4M IN V EN TOR.

TroRA/EY.

May 8, 1956 W C;- MCMAHAN 2,744,805

LIFT MECHANISM FOR EXTENDING A HORIZONTAL SUPPORT Filed NOV. 24, 1952 2 Sheets-Shea? 2 "431.752 C. McMA/MM INVENTOR.

United States vPatent CC man -Mt 1892.2

' VLm'r MECHANISM 'Fon EXTENDHSTG A f HORIZONTAL SUPPORT This invention relates to a liftrmechanism, such as is adapted to be incorporated in desks for mounting 4typewriters, or lin kitchen cabinets forzvmounting appliances and tliellike. j f :Such-,liftscommonly employ a shelf that may be vrnanua'lly.v moved from an inactive position below the'top of the vdesk or cabinet to an active position projecting laterally ofthe desk or cabinet, and adjacent the top. One suchmechanism is disclosed and claimed in a prior" ap# plication inthe name of Walter C. McMahan, Serial No. 212,535, filed` February 24, 1951, now Patent, No.' 2,676,- 077', issued April 20, 1954, and entitled` TypewriterLift Mechanism, of which the present application ,is a continuation-in-part.

It isl anobject of the present invention to improve, in general, such lift mechanisms.

Y kIt is another object of this invention to` provide a simple-.mechanism of this character whereby the plat- 2 anddash lines in Fig.-2. The platform may serve to support any `other device as, for example, a typewriter or the like beneath a desk top.

.The platform 10 is suspended by the aid of parallelogram'linkagevcomprising four

similararmsor links

12, 13, 14, 'and l15.I The lower ends of each of the links are mounted at

opposite sides

16 and 17 of the platform 10. For this purpose, a metal strip 18 is secured to the side 16 by the aid of wood or other appropriate screws 19 and 20. The strip 18 projects rearwardly beyond the rear surface 21of -the platform 10. The end of the link 12 is pivotally connected to the inside of the rearwardly projecting end 22 of the strip 18, as by theaid of a suitable pin 23. The end of the link 13 is` similarly pivotally mounted to .the outside of the .strip 18 by the. aid of-a pin 24. The

links

14 and 15 are similarly pivotally connected lto the 'platform 10 at the other side 17 thereof. For this purpose, a' strip or plate 25 is provided.

The upper ends of the

links

12, 13, 14, and 15 are mounted on a rigid stationary frame ystructure comprisin gba'rs 26 'and 27 that are, in turn, secured to the cabinet 2S in a manner to be hereinafter more fully described. For pivotally mounting the upper ends of the links 12 and-13 to the bar 26,=

pins

29 and 30 are provided.' Sim'- ilarly,

pins

31 and 32 pivotally mount the Yupper ends of links 14`and 15 to the bar 27. A brace 33 joins the form may be elevated to a position in which it is most accessible. I t is still another object of this invention to make it possible to fit the mechanism into cabinets of slightly different size. For this purpose, the supporting structure incorporates an adjustable element.

It lis stillanother object of this invention to provide a support of this character, which, whenwelevated, is positivelygand automatically restrained against inadvertent movement, all in animproved and simplified manner, andin which thefrestraint is easily manuallyy released.4 This yinvention possesses manyother advantages,and has other objects which may be made more clearlyapparent from a consideration of ,onelembodiment ofthe invention.A For this purpose, thereis shown a form in 4the .drawings accompanying and lforming part kof the present specification. The form willnow be described in detail, illustrating the general principles of the invention; but itis to be understood that this detailed descrip- .tion is not to be taken in a:limiting sense, since. the scope of t h,is invention .is best defined by the appendedclaims.

; =Referring tothe drawings: Figure Jl is a top view Acfa device incorporating the presentjinvention, the-cabinet ,in which the device is iaccommodatedzbeing,shownin section; j

Fig. A2 is..,a vertical elevation of the apparatus -in the lowered position as illustrated-in Fig. 1, the cabinet also being shownin section; j a n Fig. 3 is a view similar to Fig. 2, the apparatusv'being shown in raised position, the'cabinet in whichy the device is accommodated being illustratedfas a fragmentary secl Fig.. 4 is an, enlarged fragmentary viewl of theglocking mechanism in the position of Fig. 3, the dotiand dash linesl illustrating the manner in which the mechanism is released; and 1 FignS, is a pictorial view ofthe complete' apparatus; 'illust'rated in lowered position. f -zA platform-10, of any suitable form, forms the base upon which-an appliance, or the like, mayf rest. An applianc'efsuch as an electric mixer 11, is illustrated in dot

parallel bars

26 and 27 and cooperates therewith to form a rigid construction. The ends of 'the `brace 'are secured, as by welding, tothe forward portion of the

bars

26 and 27. l j

The spacing between the

pins

23 and 24, mounting the lower ends of the

links

12 and 13, substantially precisely corresponds to the spacing between the

pins

29 and 30 mounting lthe upper ends .of the

links

12 and 13 to the bar 26. Similarly, the spacing between the pins mountingjthe'lower ends of the

links

14 and 15 corresponds to the spacingbetween the'pins 31 and 32vmounting the upper ends of Ithe links 14 and 15I to the frame member 27. The axes of the

pins

29, 30, 31, and 32 mounting the

links

12, 13,14, and 15 to the'frame 26, 27, and platform 10 respectively extend parallel to each other end. By virtue of these arrangements, a swinging parallelogram suspension for the platform 10 is provided, in which the platform 10 is optionally positionable in spaced parallel planes.v vThe platform 10 remainsv horizontal for all positions thereof upon proper initial orientation of the device. i For vmounting the

frame members

26 and 27 within kthe cabinet 2 8, supporting

members

34 and 35 are provided'. The supporting members v34 and 35y arerespectively kdisposed/immediately below the

frame members

26 and 27. The

frame members

26 and 27 andthe supporting members34 and 35 are respectively secured together, as'by the aid of appropriate welds 36 (Figs.v 4 and'5)'. The end`s'37` and`38 of the member 34 `are offset in a direction outwardly of the frame member A26 (see, also, Fig.Y 1). l An appropriate screw 39 passes throughf an appropriate aperture in the offset end 37 to secure that end 'of the supporting member toa cleat 99 immediately below the cabinet top. The other offset portion 38 of the 'supporting member 36 adjustably mounts a reversible bracket41 (Figs. 1 and 5). The bracket 41 has a ange 4 2y that may extend inwardly or outwardly, .depending upon the manner in which the structure is best adapted to be secured to the cabinet. In the present instance, the tlange42 abuts a vertical stud or brace 43 in thel rear corner of the cabinet 28.'v

The bracket 41 is also adjustable longitudinally of the supporting member 34 so that the supporting member 34 can conform rwithin limits to the size requirements of thecabinet in which it is installed. For this purpose, and

to provide for a reversal of the bracket 41, a strap 44 (see, also, Fig. 5) is carried by the bracket 41 and defines therewith a space receiving the offset end 38 and the bracket 41. The strap 44 may have its ends extending over the edges ofv the bracket 41 and welded thereto. Accordingly, the mounting bracket 41 is slidahly movable longitudinally of the offset end 38 and confined for such movement by the aid of the member 44. Furthermore, the bracket can be reversed in order to reorient the ange 42.

The left-hand supporting member 35 cooperates with the frame member 27 in a precisely symmetrical manner. This supporting member 35 has

offset ends

45 and 46, the rearward olset portion 46 adjustably mounting a bracket 47 similar to bracket 41. Appropriate screws 48, 49, and 50, together with the screw 39, properly mount the structure in the cabinet recess.

The platform is swingable from the lowered position illustrated in Fig. 2 to the raised position illustrated in Fig. 3, the

links

12, 13, 14, and rotating about their upper pivotal mountings provided by

pins

29, 30, 31, and 32.

The configuration of each of the

links

12, 13, 14, 15 is such that in the elevated position of Fig. 3, maximum height of the platform 10 can be achieved. Thus, in this position, those

ends

12a, 13a, 14a, 15a of the links attached to platform 10 all extend slightly above the level of those ends 12b, 13b, 14b, 15b of the links attached to the

frame members

26 and 27. The platform 10 thus lies close to the top surface of the cabinet 28.

To permit this function, the

links

12, 13, 14, 15 are of a particular configuration, wherein they extend generally on one side of a straight line joining the pivotal mountings 23-29, 24-30, etc. of each link. In the present instance, the links are of angled configuration, the

ends

12a, 12b of link 12, for instance, forming an obtuse angle at an apex 12C. Optionally, the

links

12, 13, 14, 15 could be in the form of an arc. By virtue of this conguration, there is clearance between the links and the mechanism supported by the frame members 26. and 27 to permit the platform 10 to reach the elevated position of Fig. 3.

Provisions are made to permit the

ends

12a, 14a of

rear llinks

12 and 14 to pass the

forward links

13 and 15 respectively as these links move from the position of Fig. 2 to the yposition of Fig. 3. For this purpose, the distance between the outer surfaces of

ends

12a and 14a is substantially less than the distance between the inner surfaces of the

links

13 and 15, so that the

inner links

12 and 14 can extend between the outer links 13 and 15 (see Fig. 3).

These relative spacings are obtained because the ends 12a and 14a are mounted inwardly of the strips 18 and 25, while the

ends

13a and 15a are mounted exteriorly thereof.

A brace 76 connects the

rear links

12 and 14 together and also serve to maintain a rigid and slightly converging configuration between

links

12 and 14. This brace 76 is joined as by welding to the respective apices of the bends of the rear links.

In order to maintain the platform 10 in an elevated position, hook or catch

members

51 and 52 are provided. These catch members extend vertically from braces S3 and 54'. Brace 53 extends substantially parallel to the frame member 26 and the strip 18 and joins the

links

12 and 13 midway of their lengths and above the bends respectively. The brace S3 is pivoted to the link 12 by the aid of a pin 55, and is pivoted to the link 13 by the aid of a pin 56. The brace 54 is similarly secured.

As illustrated in Figs. 3 and 5, and by a comparison between them, the lower portion of the rear link 12 must also cross the brace 53 in reaching the elevated position. In order to permit this, the end 57 of the Vbrace that is secured to the rear link 12 is inwardly offset.

The hook or catch 51 is rigidly secured to the brace 53 in a suitable manner. Upon the platform 10 being moved to the elevated position, the catch 51 is moved into latching relationship with the lock bar 58. This lock bar 58 is carried by the

frame members

26 and 27. The ends of the bar 58 are mounted in parallel

elongate slots

59 and 60 in the ends of the

frame members

26 and 27 respectively. Collars 61 and 62 prevent the bar 58 from moving longitudinally. The bar 58 is thus movable in a direction transverse to its axis and in a plane extending longitudinally of both of

frame members

26 and 27.

A U-shaped handle 63 is mounted upon the lock bar 58 for manipulation thereof. For this purpose, the bar 58 extends through apertures in the arms of the handle respectively. Tension springs 64 and 65 are secured to the ends of the handle and the brace 33 as by suitable apertures receiving end turns of the springs. These

springs

64, 65, as viewed in Fig. 4, normally urge the handle and lock bar 58 toward the right in their guiding

slots

59 and 60. As the platform 10 reaches the elevated. position illustrated in Fig. 3, the latch or catch 51 engages the lock bar 58 near its end to move the lock bar against the force of the

springs

64 and 65 and toward the left, as viewed in Fig. 4. For this purpose, the catch 51 has an upper cam surface 66. A slot 67 in the catch 51 receives the lock bar 58 upon further movement of the catch 51 in an upward direction. This latching recess 67 adjoins the cam surface 66. The lock bar 58 is urged into the recess 67 by the operation of the tension springs 64 and 65 after the cam surface 66 is no longer effective.

Downward movement of the platform 10 is then prevented by engagement of the lock bar 58 with the hook 51. Further upward movement from the elevated position is similarly limited. The latch 52 operates in an entirely symmetrical manner and simultaneously with the catch 51. The

catches

51 and 52 pass inwardly of the olfset ends 37 and 45 of the supporting

members

34 and 35 respectively upon the platform reaching the elevated position.

In order to release the mechanism so that it may be moved to the lowered position, the handle 63 is moved outwardly. This handle is conveniently located, as shown most clearly in Fig. l, and is readily available for manipulation by the user. To release the mechanism, the handle 63 is moved outwardly in the direction of the arrow 68, illustrated in Fig. 4, to the dotted line position therein illustrated. The lock bary 58, mounting the handle 63, is similarly moved outwardly to the dotted line position, where it is freed from engagement with the upper Wall of the slot 67. Accordingly, the

catches

51 and 52 can pass downwardly with respect to the latch member 58, and theV entire mechanism can be retracted.

In order to maintain stable positioning of the mechanism and to assistl in lowering and raising the platform 10, an eccentric spring constructionv is provided. For this purpose, heavytension springs 69 and 70 are provided. These

springs

69, 70 have ends secured to a U-shaped bracket 71 of ytwisted'configuration. This bracket 71 also cooperates with the brace 33 to maintain a rigid configuration with the frame members 26 and. 27. The other ends of the

springs

69 and 70 are secured to the brace 33. Conveniently, the springs 69= and 70 may pass through those

apertures

72 and 73 of the brace 33 that also mount the tension springs 64 and 65 respectively.

The

arms

74 and 75 of the U-shaped bracket are secured to the

rear links

12 and 14 respectively at a place spaced from, but close to, the pivoted pins 29 and 31. Accordingly, the bracket 71` is arcuately movable along with the

links

12 and 14. V

In the position illustrated in Fig. 2, the spring 69, for instance, extends on one side of the pivot pin 29 about which one end of the spring 69 is arcuately movable.v In this position, the spring 69 urges the construction in a counterclockwise direction. The spring 70 operates similarly. This corresponds to maintaining the apparatus in the loweredposition. As the device is rotated,however,

the place of attachment of the ends of the

springs

69 and 70 moves with respect to the pivot pin 29 and the place of attachment of the other ends of the

springs

69 and 70. After an initial movement corresponding to further tensioning of the

springs

69 and 70, the

springs

69 and 70 pass the pivot pins 29 and 31 respectively and then extend on the opposite side of the

pins

29 and 31 about which the ends of the

springs

69 and 70 are arcuately movable. Accordingly, the

springs

69 and 70 now urge the mechanism in a clockwise direction corresponding to elevated position of the mechanism. The tension springs 69 and 70 thus assist in moving the mechanism and also to maintain it in stable position.

The inventor claims:

l. In a lift mechanism: a pair of frame members; a pair of rear links pivoted on a common axis by said frame members respectively; a pair of forward links pivoted on a common axis spaced from said first axis and by said frame members respectively; a support; means pivotally connecting the links to the support; those ends of the links attached to the support being forwardly inclined so that when said support is elevated to the level approximating that of said frame members, clearance is provided between said rear links and the forward ends of said frame members; said frame members having longitudinally extending slots at their forward ends; a latch bar extending between said frame members and guidingly received in said slots; a handle carried by the bar substantially centrally thereof; resilient means urging said bar rearwardly of said frame members; and a hook member engaging said bar upon movement of said support to an elevated position, said hook member being carried by said links.

2. In a lift mechanism: a pair of frame members; a pair of rear links pivoted on a common axis by said frame members respectively; a pair of forward links pivoted on a common axis spaced from said first axis and by said frame members respectively; a support; means pivotally connecting the links to the support; those ends of the links attached to the support being forwardly inclined so that when said support is elevated to the level approximating that of said frame members, clearance is provided between said rear links and the forward ends of said frame members; said frame members having longitudinally extending slots at their forward ends; a latch bar extending between said frame members and guidingly received in said slots; a handle having an aperture through which said bar extends; resilient means engaging an end of the handle for urging said bar rearwardly of said frame members and for angularly orienting said handle; and a hook member engaging said bar upon movement of said support to an elevated position, said hook member being carried by said links.

3. In a lift mechanism a: support; a pair of strips adapted to be secured to opposite sides of the support; said strips being adapted to project rearwardly beyond said support; a rst pair of arms pivotally secured at one end to the rearwardly projecting portions of said strips respectively; a second pair of arms pivotally secured at one end to said strips respectively and forward of said rearwardly projecting portions; said arms all being of similar angled configuration between their ends; a pair of frame members pivotally securing the other ends of said arms; said arms providing a parallelogram suspension for said support for movement of said support from a lowered position to an elevated position with respect to said frame members; a bar extending between said frame members, said frame members having slots guidingly receiving the ends of said bar for translation of said bar in a direction longitudinally of said frame members; and at pair of hook members carried by said arms and engageable with the ends of said bar upon movement of said arms to elevate said support; the angled configuration of said first pair of arms providing clearance between said arms and said bar.

4. In a lift mechanism: a support; a pair of parallel ner sides of said strips; a second pair of arms, each arm being pivotally secured at one end to said strips respectively and forward of said rearwardly projecting portions, said pivotally secured ends of said second pair of arms being disposed on the outside of said strips; a pair of substantially parallel frame members, one of said frame members pivotally securing the other end of one of said first pair of arms and the other end of one of said second pair of arms on one side of said one frame member, the other of said frame members pivotally securing the other end of the other of said first pair lof arms and the other end of the other of said second pair of arms on one side of said other frame member; said first pair of arms having anangled configuration; said arms providing a parallelogram suspension for said support for movement of said support from a lowered position to an elevated position with respect to said frame members; and a releasable latch for holding said support in an elevated position, and carried by said frame members, the configuration of said first pair of arms providing clearance between said first pair of arms and said releasable latch, and the mounting of said pairs of arms on said strips providing clearance between the first pair of arms and the second pair of arms,

5. In a lift mechanism: a pair of parallel spaced frame ogram suspension for a platform or the like; a pair of supporting members extending in juxtaposed relationship with respect to said frame elements respectively, each of said pair of supporting members having an offset end; a pair of bracket members for said ends respectively having a flange for attachment to a cabinet or the like; and a pair of loops for removably and slidably mounting said brackets with respect to said offset ends respectively, said brackets being reversible on said ends for reorienting said anges.

6. In a lift mechanism a: pair of substantially parallel frame members, each of said frame members having a slot at one end thereof for receiving a latch bar; a latch bar having ends accommodated in said slots and guided for translation in a direction substantially longitudinally thereof by said slots; resilient means urging said bar in one direction in said slots; a rst pair of arms pivotally mounted at one end on said frame members respectively, said rst pair of arms being of angled configuration; a second pair of arms pivotally mounted at one end on said frame members respectively and spaced from said rst pair of arms; a platform pivotally mounting the other ends of said arms, said arms providing a parallelogram suspension for said platform; the distance between the other ends of said first pair of arms being less than the distance between the other ends of said other pair of arms; and a catch carried by said arms for engagement with said bar upon movement of said platform to an elevated position.

References Cited in the le of this patent UNITED STATES PATENTS 1,035,664 Vaaler Aug. 13, 1912 1,606,975 Tobey Nov. 16, 1926 2,322,648 Lundstrom June 22, 1943 2,428,211 Fox Sept. 30, 1947 2,561,505 Fox July 24, 1951 2,585,566 Lundstrom Feb. 12, 1952 2,676,077 McMahan Apr. 20, 1954 FOREIGN PATENTS 99,489 Switzerland June 1, 1923