US2649237A

US2649237A - Counterbalance and support means for ceiling-mounted folding stairways

Info

Publication number: US2649237A
Application number: US193422A
Authority: US
Inventors: Bjorklund Warren; Kartarik Henry
Original assignee: MINNESOTA WOOD SPECIALTIES Inc
Current assignee: MINNESOTA WOOD SPECIALTIES Inc
Priority date: 1950-11-01
Filing date: 1950-11-01
Publication date: 1953-08-18
Anticipated expiration: 1970-08-18

Description

1953 w. BJORKLUND ET AL 2,649,237

COUNTERBALANCE AND SUPPORT MEANS FOR CEILING-MOUNTED FOLDING STAIRWAYS Filed Nov. 1, 1950 2 Sheets-Sheet l I fizz/anion:

Aug. 18, 1953 w. BJORKLUND ETAL COUNTERBALANCE AND SUPPORT MEANS FOR CEILING-MOUNTED FOLDING STAIRWAYS 2 Sheets-Sheet 2 Filed Nov. 1, 1950 fivuwwiazs My Z aw Patented Aug. 18, 1953 UNITED STATS OFFICE COUNTERBALANCE AND SUPPORT MEANS FOR CEILING-MOUNTED FOLDING- STAIR- WAYS Application November 1, 1950, Serial No. 193,422

3 Claims. (01. 228-50) This invention relates to folding stairways or ladders adapted to be retracted when not in use within a ceiling opening, and particularly to mechanism adapted to facilitate the movement of such stairways to and from retracted position and for retaining them in selected positions.

It is an object of our invention to provide novel and efficient actuating mechanism whereby the lifting force exerted by a spring or equivalent device is controlled and made effective to substantially automatically return the stairway to fully retracted position when started toward such position by the application of slight external force, the lifting force being substantially nullified when the stairway is in either extended or retracted position.

A particular object is to provide novel connections between a spring and a folding stairway comprising a folding hanger having a lever projecting laterally therefrom and a link pivotally connected to the lever at one end and connected to. a spring at the other end whereby the force transmitted from the spring to the stairway increases rapidly from substantially zero when the stairway is fully extended to a value sufficiently high to lift and retract the stairway and such force is then reduced to the minimum required to hold the stairway in substantially horizontal retracted position.

A further object is to provide spring actuated mechanism of the class described which operates smoothly and efficiently to balance the stairway and facilitates its movement to and from its retracted position within a ceiling opening.

Other objects will appear and be more fully pointed out in the following specification and claims.

Referring to the accompanying drawings, which illustrate by way of example and not for the purpose of limitation, a preferred embodiment of ourinvention:

Figure 1 is a perspective view showing our improved mechanism with the stairway in fully extended position;

Fig. 2 is a similar view showing the lower portion of the stairway in partially retracted position; I

Fig. 3 is a perspective view showing the stairway and'operating mechanism in retracted position, as viewed from above;

Fig. 4 is a fragmentary side elevational view showing part of one of the springs and associated actuating mechanism in various positions;

Fig. 5 is a fragmentary sectional view taken on the line 5-5 of Fig.- 4 and with the spring removed to show-parts otherwise concealed;

Fig. 6 shows the mechanism of Fig. 4' as viewed in the direction indicated by the line 6-6 and with the spring removed, and

Fig. 7 is a perspective view of the lever member carried by one of the hanger members.

As shown, our invention is applied to a folding stairway composed of the

sections

8, 9 and 10 adapted to be folded one on another, as indicated in Fig. 2, hinges ll being provided to connect the sections 8 and 9 together and hinges l2 to connect the section 9 to the section Ill. The normally upper end, of the section i0 is hingedly joined to a supporting frame member I3 which constitutes one of the curbing members defining the ceiling opening where the stairway is to be used. Longitudinal frame members I extend from the member 13 to a fourth frame member if; to complete a rectangular ceiling receptacle into which the folding stair may be retracted when not in use. To close the ceiling opening and conceal the retracted stairway from below, a door panel [6 is mounted on the lower side of the stair section l0 and is preferably formed to extend flush with the ceiling when in closed position.

Our improved actuating mechanism is preferably duplicated at opposite sides of the stairway and is operatively connected to the side rails of the section If). At each sidethe folding hanger comprises members IT and I8 pivotally connected together by a suitable hinge pin I9. The normally lower end of the hanger member I8 is joined to the section [0 by a pivot bolt or screw 20 and the normally upper end portion of the hanger member ll is pivotally supportedon one of the frame members 14 by a member 2| which constitutes a horizontal axis about which the hanger members may be oscillated from the extended position shown in Figs. 1 and 2 to a retracted position such as that shown in Fig. 3. The pivot member 2i passes through a perforation formed in the upper end portion of the hanger member ll.

Rigidly secured to the hanger member I-l near the pivot member 2| is a rigid lever member 22 which projects at one side of the member H, as best shown in Fig. 4. This lever member is formed with a flange 23 which projects perpendicularly to the inner face of the hanger member ll for engagement with a helical tension spring 24 and to support the spring in the angular position shown in full lines in Fig. 4 when the hanger member i is inthe fully extended position. Extending from the projecting end portion ofthe lever member 22 1s a link 25 which is joined to the member-22- by a pin 26' filling 3 in a perforation 2'! (Fig. 7) formed in the member 22. Oscillating movement of the link 25 relative to the lever member 22 in a counterclockwise direction (Fig. 4) is limited by a stop lug 28 carried by the member 22, so that the link functions as an extension of the lever when in engagement with the stop lug 28. One end of the spring 24 is connected to the otherwise free end of the link 25 and the other end of the spring is anchored on a member fixed on and projecting from one of the frame members I4. By this construction, the lever member 22 and link 25, together with the hanger members l1 and is may be caused to oscillate in planes which are parallel and adjacent to the inner face of the frame member l4 and the spring 24 is held under suitable tension and in a plane which is parallel to the inner face of the hanger member ll.

As indicated in Figs. 1, 2 and 4, the lever member 22 extends obliquely downward and laterally from the hanger member when the latter is in its fully extended position and the spring 24 extends in contact with the upper surface 1 of the flange 23 at an elevation slightly above the axis of the pivot bolt 2|, the spring being slightly bent by upward pressure exerted by the flange 23. By this arrangement, the pull of the spring is caused to bias the aligned hanger members in the proper direction for the subsequent retraction of the stairway.

Our stairway and actuating mechanism may be adapted for use with ceilings of various heights merely by changing the angle of incline of the stairway and effective lengths of the hangers. To this end we provide a multiplicity of perforations 32 in the adjoining and overlapping end portions of the hanger members I? and I8 so that the pivot pins [9 may be engaged in any selected pair of perforations to compensate for various angles of inclination of the stairway. To facilitate withdrawal of the stairway d wnward from retracted position, a cord 3| of suitable length is connected to the free end portion of the panel and depends therefrom within convenient reach of persons desiring to use the stairway.

In operation, assuming that the stairway and actuating mechanism are in the fully extended position shown in Fig. l, in which position the lower end of the section 8 rests on the floor, the springs 28 are under substantial tension but have only a slight tendency to raise the stairway because the force exerted by them is directed across and slightly above the extended axis of the pivot members 2!. By adjusting the effective length and/or angle of the hanger members [1 and i8 relative to the vertical, the direction of the force exerted by the springs may be adjusted so that more or less lifting force is applied to the hangers. With the mechanism in the fully extended position, the link 25 is firmly held against the lower side of the stop lug 28 by force exerted by the spring and the

members

22 and 25 remain in the same relative positions throughout the greater part of the arcuate movement to the fully retracted positions of the several members.

To retract the stairway, the section 9 is folded on the section it! and the section 8 is folded backward on the section 9, as indicated in Fig. 2. The operator then merely applies slight lifting force to the lower end portion of the door panel IE to move the hanger member I? in a clockwise direction as viewed in Figs. 1 and 2 and in a counter-clockwise direction as viewed in Fig. 4. Thereupon, the springs 28, acting through the system of levers comprising the members 22, links 25 and hanger members IT and I8, exert sufficient force to raise the stairway toward retracted position. The force thus exerted by the springs increases rapidly and reaches a maximum value sufficiently high to fully retract the stairway without substantial assistance from the operator. When the hangers are approximately in the position indicated in broken lines at A in Fig. 4 maximum lifting force is applied. This force is gradually reduced as the link 25 is drawn away from the stop lug 28 and thereafter further reduced, more rapidly, until the lever member 22 and link 25 reach their end positions indicated at B in Fig. 4, the corresponding position of the hanger member I! being substantially vertical. When in this position of rest the lifting force exerted on the stairway is just sufiicient to retain it in fully retracted position.

As further indicated in Fig. 3, the hanger members I! and i8 extend substantially vertically above the supporting bolts 2i when the stairway is fully retracted so that a low minimum spring tension is all that is required to retain the stairway in the retracted position. It will thus be evident that each hanger member I? and the lever member 22 carried thereby are oscillated through an angle somewhat in excess of degrees in passing from the fully extended to fully retracted positions of rest. Unusually smooth, quiet action and more efficient application of the spring tension is insured by our arrangement of the link 25 which forms an extension or elongation of the lever system during the portion of the arc of movement during which increased lifting force is desirable. During the remaining portion of the arc of movement the link 25 acts as a flexible extension of the spring.

The angles of the lever members 22 relative to the hanger members I"! and stop positions of the links 25 relative to the lever members 22 may be varied to meet varying conditions and to compensate for the weight, length and angles of inclination of particular stairways when extended.

Having described our invention, what we claim as new and desire to protect by Letters Patent 1s:

1. For a stairway having a hinge connection with a ceiling frame, said frame defining a ceiling opening into which the stairway may be retracted, improved actuating mechanism for the stairway comprising, a folding hanger adapted to oscillate in a substantially vertical plane and to be operatively connected to the stairway, means adapted to pivotally connect said hanger to said frame and defining a horizontal pivot axis, a lever member rigidly connected to and projecting laterally from said hanger near its pivot axis, said lever member extending crossways of said axis, a rigid link pivotally connected to said lever member and movable angularly relative to said lever member a stop projecting from said lever member anddisposed to so limit angular movement of said link relative to said lever member as to cause said link to prcject as a rigid extension of said lever member during a portion of the angular movement of the stairway to and from retracted position and a helical sprin operatively connected to said link to urge the stairway toward retracted position, the force exerted by said spring being reduced by angular movement of said link relative to said lever member when the stairway is in predetermined positions.

2. For a stairway having a hinge connection with a ceiling frame, said frame defining a ceiling opening into which the stairway may be retracted, improved actuating mechanism for the stairway comprising, a folding hanger adapted to oscillate in a substantially vertical plane and to be operatively connected to the stairway, means adapted to pivotally connect said hanger to said frame and defining a horizontal pivot axis, a lever member rigidly connected to said hanger and projecting laterally therefrom near its pivot axis, said lever member extending crossways of said axis, a rigid link pivotally connected at one end to said lever member, stop means limiting oscillating movement of said link relative to said lever member whereby said link is caused to project as a rigid extension of said lever member during a portion of the angular movement of the stairway to and from extended position and a helical spring operatively connected to said link to urge the stairway toward retracted position, the force exerted by said spring being reduced by angular movement of said link relative to said lever member when the stairway is in predetermined positions.

3. For a stairway having a hinge connection with a frame, said frame being mountable on a ceiling having an opening into which the stairway may be retracted, improved actuating mechanism for the stairway comprising, a foldable hanger composed of a pair of articulated members adapted to be operatively connected to said stairway and adapted to oscillate in a substantially vertical plane, means adapted to pivotally connect said hanger to said frame and defining a horizontal pivot axis from which said hanger members may be extended downward in substantial alignment one with the other and above which said hanger members may be extended in folded relation one to the other, a lever member fixed on and projecting laterally and obliquely downward from said hanger near its pivot axis, a rigid link pivotally connected to an end portion of said lever member, stop means projecting from said lever member and disposed to limit oscillating movement of said link relative to said lever member whereby said link is caused to project as a rigid extension of said lever member during a portion of the movement of the stairway to and from fully extended position, and resilient means operatively connected to the free end of said link for oscillating said lever member, link and hanger about said pivot axis, said resilient means being adapted to urge said hanger members and the stairway toward folded and retracted positions Within the ceiling opening, and the force exerted by said resilient means being reduced by the angular movement of said link relative to said lever member when the stairway approaches its fully retracted positions.

WARREN BJORKLUND. HENRY KARTARIK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 301,386 Newcomb July 1, 1884 1,091,602 Tompkins Mar. 31, 1914 1,934,456 Taylor Nov. 7. 1933 2,314,004 Marschke Mar. 16, 1943 2,506,380 Myers May 2, 1950 2,572,281 Pierce Oct. 23, 1951