Sliding articulated extension-retraction mechanism

#1. Field of the Invention

#The present invention relates to a sliding, articulated, extension-retraction (SAER) mechanism which combines a four-bar parallelogram linkage with a crank-slider. The SAER mechanism can be employed in extensible and retractable structures, such as scaffolds, racks, camping tents, portable masts, folding posts, lifting structures, extendible arms, robotics, walls, and various other applications.

#2. Description of Related Art

#FIG. 1 is a diagrammatic view of a base unit of a sliding, articulated, extension-retraction mechanism according to the present invention.

#FIG. 2 is a diagrammatic view of an expanded base unit of a sliding, articulated, extension-retraction mechanism according to the present invention.

#FIG. 3 is a diagrammatic view of a sliding, articulated, extension-retraction mechanism according to the present invention.

#Similar reference characters denote corresponding features consistently throughout the attached drawings.

#The present invention is a sliding, articulated, extension-retraction (SAER) mechanism that combines a four-bar parallelogram linkage with a crank-slider. FIG. 1 diagrammatically shows a base unit 60 of the SAER mechanism, which has a parallelogram linkage formed by bars or links 62, 64, 66, and 68 which are joined at their ends by pivot pins 70. A connecting rod 72 has one end pivotally connected to crank 64 at a fixed position on the crank 64 by pivot pin 74, and a second end pivotally connected to slider block 76 by pivot pin 78, thereby combining a parallelogram linkage with a crank-slider 80 disposed on the interior of the parallelogram and extending between adjacent sides of the parallelogram. FIG. 2 diagrammatically shows an expansion of the base unit formed by adding a second crank-slider 82 to the diagonally opposite corner of the parallelogram opposite crank-slider 80. It will be apparent from inspection that as the crank 64 is rotated through angle α, slider 76 is displaced a distance 86 on link 62, while crank 68 will simultaneously be rotated through an angle β congruent to angle α, and slider 84 will be displaced a distance 88 on link 66 congruent to the distance 86.

#According to the present invention, the base units 60 can be stacked as shown diagrammatically in FIG. 3 to form the sliding, articulated, extension-retraction mechanism 100. The SAER mechanism 100 shown in FIG. 3 has three parallelogram linkages 102, 104, and 106 stacked vertically with a first crank-slider 108 attached between base link 110 and crank 112, and with first tandem crank-slider 114 between parallelogram linkages 102 and 104, and second tandem crank-slider 116 between parallelogram linkages 104 and 106. Each tandem crank-slider 114 and 116 has a similar structure, and will therefore be explained with reference to tandem crank-slider 114 only. Tandem crank-slider 114 has a pair of connecting rods 118 of equal length, each connecting rod 118 having a first end pivotally connected to the same slider block 120 at an equal distance from the common pivot pin 122. Each connecting rod 118 has a second end, one of the second ends being pivotally attached to crank 124 of parallelogram linkage 102 at pin 126, the other second end being pivotally attached to crank 128 of parallelogram linkage 104 at pivot pin 130, pins 126 and 130 being displaced from common pivot pin 122 by an equal distance. Hence, tandem crank-slider 114 defines two congruent triangles with a common side on level link 132, regardless of the position of slider block 120 on level link 132.