ROTARY MECHANISM

Abstract: A rotary mechanism for converting a reciprocal linear motion into a reciprocal rotary motion with increased torque at the end positions. Two pressurized air cylinders (1, 2) co-operate via links (14, 15) with a common lever arm (5) fastened to an output shaft. The cylinders provide an increased torque adjacent to each one of the end positions of the rotary motion.

Description: ROTARY MECHANISM The invention relates to a rotary mechanism for converting a reciprocal linear motion of an actuator, e.g.constituted by a piston-cylinder unit controlled by a pressurized fluid, into a reciprocal .rotary motion of an output shaft. In known rotary mechanismsof this kind, e.g. operating with rack and gear mean , a maximum torque is obtained between the positions of the r.otary motion, or a constant torque is develo during the entire stroke. However, such a characteristic is of disadvantegeous. In case, e.g.^the xotary mechanism is to be used for operating a valve between open and closed positions, a maximum torque is needed especially in these end positions. Thus, a primary object of the invention is to achieve a rotary mechanism which provides an increased torque at the end posi¬ tions and whichis-generally useful, e.g. as an actuator or a transport device. _ This object is achieved, according to the invention, by a rotary mechanism, the actuator of which comprises two co¬ operating, complementarily operating actuating units. , each such unit being link-connected to a lever arm fastened to the output shaft, said two actuating units operating non- uniformly in speed while being mutually motion controlled via the shaft in such a way that the two actuating units deliver an increased torque adjacent to each one of the end positions of the rotary motion. These end positions may have a desired re tive angular distance, which, e.g.,may be 90° or 180° in standard applications. These two acutating units, preferably in the form of pressurize fluid working cylinders^complement each other in such a way that one of the units provides an increased torque adjacent to one end position of the rotary motion (wherein the other unit contributes considerably less), whereas the otherunit produces an increased torque adjacent to the other end position of the rotary motion. A considerably increased torque will be obtained if the linear movement direction of each actuating unit is approximately transversal to a link, coupled between the lever arm of the shaft. and the actuating unit, in the particular end position. With such an arrangement, even a self-locking effect in the end positions is obtained, especially if the actuating units are linearly guided. If the stroke of the actuating unit is suitably dimensioned, an effective end positio damping effect of the rotary motion can possibly be achieved, wherein the kinetic energy is absorbed by the link mechanism and adjoining guiding means. According to a preferred embodiment, both actuating units are link-connected to a common lever arm, in particular a triangular lever arm, in which case the actuating units thus operate in the same plane as the motion plane of the lever arm, e.g.,in pa¬ rallel and adjacent to each other. Further suitable features are defined in claims 5-13 and will appear from the detailed description below. Thus, the invention will be further explained below with re¬ ference to the appended drawing, which illustrates two embodimen Fig. 1 shows schematically in perspective view a rotary mecha¬ nism according to the invention, wherein a portion of a sur¬ rounding casing is cut away for the purpose of illustration of the basic parts of the mechanism; Fig. 2 shows the rotary mechanism according to Fig. 1 in side view, partly in longitudinal section; Fig 3 shows, in a view corresponding to Fig. 2, another embodi¬ ment of the rotary mechanism according to the invention. The rotary- mechanism shown in Figs 1 and 2 comprises essentially two pneumatic cylinders 1,2 being arranged in parallel adjacent each other and serving as actuating units, and a guiding and linkin arrangement disposed in a casing 3, by means of which the line motion of the pneumatic cylinders is transformed into a rotary motion of an output shaft 4. According to the invention, the tσ_ pneumatic cylinders1,2co-ope while being mutually motion, controlled in that their piston rods 1a a 2a, respectively, are coupled via links to a common lever arm which is permanently fastened to the output shaft 4, from which the desired rotary motion is obtained. Both cylinders 1,2 are provided with pressurized air connections (not shown ) as well as a piston (hidden in the figures) , which is actuated by pressurized air and to which the piston rod 1a and 2a, respec- ri.vely, is connected. The end 1b, 2b of each piston rod is attached, in shown example by screwing , to the central part of a yoke 6 and 1 , respectively, which is oriented transver- sally relative to the respective piston rod and guided at both sides by means of guids in the form of steel rods 8,9 and.10,11 respectively, fixed to the casing, the steel rods fitting into corresponding through holes in the yoke. Hereby, it is secured that the piston rods 1a,1b will operate exactly linearly, even under the influence of great transversal forces caused by the link arrangement. Each yoke 6,7 has a through-going bolt 12 and 13, respectively, serving as a pivot pin for a pair of links 14,15 and 16,17, respectively, disposed symmetrically relative to the common motion plane (the sectional plane to the left in Fig. 2) , these links being fitted with play into corresponding recesses in each yoke and, with their opposite ends, being pivotably connected to the common lever arm 5 by means of a pivot pin 18 and 19, respectively. The device described above operates in the following manner: Starting from the position shown in Fig. 2, the left cylinder chamber of the cylinder 1 and the right cylinder chamber of the cylinder 2 are pressurized, whereby the cylinder 1 pulls the piston rod 1a to the right and the cylinder 2 pushes the piston rod 2a to the left. These linear movements are mutually controlled by means of the linking arrangement 14,15, 5,16,17. In the beginning, the piston rod 1a is pushed rather fast to the right, causing the pair of links 14,15 to pivot clock-wise and, owing to the linear guides 8,9, to excert an upwardly directed force on the pivot pin 18. This force is rather great and provides a corresponding great torque on the output shaft. At the ' same time, the piston rod 2a moves rather slowly and contributes considerably less to the torque output. The total torque is, however, very great adjacent to this end position, which can be explained by the fact that the link pair 14,15 is oriented at right angle to the piston rod 1a and to the recti¬ linear guides 8,9 so as to provide a manifold force amplificat During continued movement the speed of the piston rod 1a will decrease, as will the the contribution of the cylinder 1 to th total torque on the shaft 4, whereas the speed of the piston rod 2a and its contribution to the torque will increase. In the other end position shown in Fig. 1 , i.e. upon a rotary movement of 90 of the shaft 4, reverse conditions prevail, i.e. the cylinder 2 provides the major part of the torque, whereas the contribution of the cylinder 1 is practically negl gible. All in all, the torque will be substantially increased in each end position of the rotary motion, and the torque is minimal half way between the end positions (where each cylinde provides as great a contribution) .As mentioned above, such a characteristic is advantageous when the rotary mechanism serve as an actuating device so as to provide a rotary motion which in each end position requires a particularly great torque for overcoming friction and/or mass inertia. It will be understood that the illustrated mechanism is self- locking in the end positions. Thus, if a torque is excerted on the shaft 4 in the position shown in Fig. 2, the pair of links 14,15 will be subjected to a force transversally to the recti. linear guides 8,9, which force has no component- in the directi of the piston rod 1a and, consequently, will not cause any movement. In certain cases it is desired to dampen the move¬ ment at the end of a stroke. Such damping can be achieved by means of the guiding and linking mechanism itself, namely if the stroke of the cylinder pistons is somewhat longer than the stroke defined by the end postions of the linking mechanism shown in Figs 1 and 2. Thus, the necessary damping energy will b absorbed by the links and the guides in the casing 3 , whereas t cylinders can be dimensioned rather small even for this reason (apart from the fact that the desired tσrlque increase will be obtained by way of the design of the link mechanism) . The whole device can therefore be made small and compact, i.e. with minor cylinders and a sturdy but non-voluminous., guiding and linking arrangement. In Fig. 3, there is shown a rotary mechanism similar to that of Figs. 1 and 2, the major difference being such a dimensioning of the various parts that the rotary motion is effected between end positions located at an angular distance of 180 . Correspond parts are given the same reference numerals, though provided with prime characters. In this case, the difference between the contributions of the two cylinders 1 ' ,2* to the torque of the shaft 4 ' at the end positions is even greater than that of the previous embodiment, since the momentarily "weaker"cylinder (2 1 in Fig. 3) has its adjoining link 16' oriented radially towards the center axis of the shaft 4 ' . It should be noted that several modifications can be made by the skilled- man within the scope of claim 1. By adjusting the transversal distance between the cylinders and the relative lengths of the various links as well as the angular distance between the pivot pins 18,19 relative to the shaft 4 , any desired angular distance between the end positions of the rotary motion can be obtained, namely between 0 and 180 . Further¬ more, the cylinders can operate in different planes and each be coupled to a separate lever arm on the shaft. Nor need they be arranged in parallel to each other, but may be located mutually at an angle (though in movement planes transversal to the shaft 5) . Moreover, it is preferred to make the rotary mechanism in certain standard sizes with a possibility to connect several units in parallel to a common rotary shaft. In principle, the pressurized air cylinders may be replaced by otherlinearly operating actuators, such as linear induction motors or the like. The important feature is that the two actuating units co-operat complementarily while being mutually controlled in such a way that a torque characteristic with increased end position values is obtained.

Claims: C L A I M S 1. A rotary mechanism for converting a reciprocal linear motion of an actuating device into a reciprocal rotary motion of an output shaft. (4), c h a r a c t e r i z e d in that the actuating device comprises two co-operating, complementarily ope rating actuating units (1,2), each such unit being link-connecte (14,15,16,17) to a lever arm (5) fastened to the output shaft (4) , said two actuating units operating non-uniformly in speed while being mutually motion controlled via the shaft in such a way that the two actuating units deliver an increased torque adj cent to each one of the end positions of the rotary motion. 2. A rotary mechanism as defined in claim ^ c h a r a c t e ¬ r i z e d in that each actuating unit (1) is arranged so that i linear movement direction (8,9) is approximately transversal to a link (14,15) , coupled between the lever arm (5) and the actuating unit (1a) , in the particular end position (fig.2) . where this actuating unit (1) provides an increased torque. 3. A rotary mechanism as defined in claim 1 or 2, c h a r a c ¬ t e r i z e d in that the two actuating units (1,2) are arrange in parallel to each other. 4. A rotary mechanism as defined in anyone of claims 1-3, c h a r a c t e r i z e d in that the two actuating units (1,2) are link-connected (14,15,16,17) to a common lever arm (5) . 5. A rotary mechanism as defined in claim 4, c .h a r a c - t e r i z e d in that said common lever arm (5) is substantially triangular. 6. A rotary mechanism as defined in anyone of claims 1-6, c h a r a c t e r i z e d in that each actuating unit is constituted by a piston-cylinder unit (1,2) operating with pressurized fluid. 7. A rotary mechanism as defined in claim 6, c h a r a c¬ t e r i z e d in that a piston rod (1a,1b) of each piston- cylinder unit is link-connected to said lever arm (5) . 8. A rotary mechanism as defined in claim 7, c h a r a c ¬ t e r i z e d in that the end (1b,2b) of each piston rod is guided along a rectilinear guide (8,9 and 10,11) . 9. A rotary mechanism as defined in claim 8, c h a r a c ¬ t e r i z e d in that said rectilinear guide comprises two parallel guides (8,9 and 10,11) located ' on each side of the piston rod. 10. A rotary mechanism as defined in claim 9, c h a r a c - t e r i z e d in that the end (1b, 2b) of the piston rod is connected to a yoke (6,7) guided by said two guides (8,9 and 10,11) , said yoke being link connected (14,15 and 16,17) to said lever arm (5) . ' 11. A rotary mechanism as defined in claim 10, c h a r a c ¬ t e r i z e d in that said yoke (6,7) is connected to said leve arm (5) by means of at least to parallel flat links (14,15 and 16,17) located on each side of the piston rod (1a,1b) . 12. A rotary mechanism,as defined in claim 11, c h a r a c ¬ t e r i z e d in that said flat links (14,15 and 16,17) are connected to said yoke (6,7) by means of a transversal bolt (12,13) serving as a pivot pin. 13. An rotary mechanism as defined in anyone of claims 1-12, c h a r a c t e r i z e d in that two or more actuating unit pairs are arranged so as to co-operatively rotate the output sha

Inventors: BERGSTRAND GUNNAR, BERGSTRAND, GUNNAR
Applicants: MOVECO SYSTEM AB
Application year: 1985
Main classification: F16H21
IPC codes: F15B15, F16H21