FORCE COMPENSATOR

Abstract: The invention relates to a force compensator for supplying a substantially constant force in a substantially fixed direction at a random point of a bounded space, which force compensator comprises a frame, a parallelogram-shaped rod system (1, 2, 3, 4) arranged pivotally thereon and two force-providing elements (6, 7) arranged with an end on the rod system, wherein at least one of the force-providing elements (6) is arranged with the other end on the frame in order to compensate a constant force at the random point of the bounded space.

Description: FORCE COMPENSATOR The invention relates to a force compensator for supplying a substantially constant force in a substantially fixed direction at a random point of a bounded space . Known devices have the drawback that the compensating force can only be exerted on a path determined by the device. It is not therefore possible with this device to cause a force acting at a freely moving point in the space to be compensated by the device. There are a large number of occupations wherein activities must be carried out with practically outstretched arms. Back, shoulder and arm complaints can certainly occur through muscle strain when these operations are performed for a prolonged period. Such activities can for instance be medical operations or the wiring of a wiring cabinet . The invention has for its object to provide a device which obviates the above stated drawbacks . This objective is achieved by a force compensator for supplying a substantially constant force in a substantially fixed direction at a random point of a bounded space, which force compensator comprises a frame, a parallelogram-shaped rod system arranged pivotally thereon and two force-providing elements arranged with an end on the rod system. The advantage of the device according to the invention is that a constant force is exerted by the device at any point of the space bounded by the device. It is hereby possible to compensate a force, for instance a gravitational force, at any random point of the space bounded by the geometry of the device. According to a preferred embodiment an arm support is arranged on the device. By now mounting the device on 2 a seat or a table the user can allow his arms to be supported by the device, thus making it possible to perform work for long periods with practically outstretched arms. According to a specific embodiment of the invention the device is embodied such that two parallel arms are embodied as a tube and a rod running therein. This prevents objects or body parts being trapped between the two parallel arms during positioning. The invention will be further elucidated with reference to the annexed drawings. Fig. 1 shows a schematic view of the device according to the invention. Fig. 2 is a perspective view of a practical embodiment according to the invention. Fig. 3 shows a cross-section of a part of the preferred embodiment of fig. 2. Fig. 4 and 5 show a broken-away perspective view of a part of the device of fig. 2. Fig. 6 is a perspective view of an arm shell according to the invention. Fig. 1 shows the device according to the invention schematically. The device comprises a rod system consisting of an upper arm 1, a lower arm 2, a parallel rod 3 and a connecting rod 4. These parts are pivotally connected to each other such that they form a parallelogram-shaped rod system. This rod system is pivotally connected at pivot point 5 to a fixed component, for instance a seat or table. The device further comprises a first spring 6 and a second spring 7, which springs are arranged between a frame and upper arm 1 respectively connecting rod 4. Supposing that the force for compensating is applied to the outer end of lower arm 2, a force Fc„ and a moment c will then occur at pivot point 8 of the rod system as a result of the force. The force F ς is then compensated by spring 6 and upper arm 1. The moment M c is compensated independently of force F c by spring 7 and the rod system. With an appropriate choice of the spring constant and the points 3 of engagement a constant compensation force can be obtained at any point of the bounded space . A prerequisite for obtaining a constant compensation force is that the springs used provide a force = 0 at an effective length = 0. The effective length is herein the distance between both points of engagement of the spring It is a further prerequisite for obtaining a constant compensation force that the springs used are linear springs. A linear spring has a fixed spring constant . Fig. 2 shows an embodiment of the device according to the invention. The device 10 is arranged here behind a seat S. Arranged on the free end of lower arm 2 is an arm shell 11 in which a person can lay his arm such that preferably the weight of this arm is partially compensated. Fig. 3 shows a cross-section of a part of the device of fig. 2. in this embodiment the upper arm 1 is embodied as a tube through which runs parallel rod 3. Upper am 1 and parallel rod 3 are both pivotally connected to lower arm 2 by means of a locking pin 22. For protection purposes a cap 12 is arranged over both pivot points. Upper arm 1 and parallel rod 3 are arranged pivotally on their other end on a disc 13 respectively 14 (see figures 4 and 5) . Both discs are mounted on a main shaft 15. This main shaft 15 forms the pivot 5 of fig. 1. First spring 6 and second spring 7 are also arranged on the two discs. These springs 6,7 are further connected to the frame of the device via a spring shaft 16. Drum brakes 17 of the same type as arranged on a cycle are further arranged in the discs, whereby the movements of the device can be blocked. These drum brakes 17 are each energized by a pneumatic cylinder 18. The device is pivotally connected via a shaft 19 to a fixed component, for instance a seat or table. This 4 rotation can be blocked by means of the clamp 20 and pneumatic cylinder 21. Fig. 6 shows the arm shell 11 which is connected to lower arm 2 for pivoting in two directions by means of an L-shaped bracket 23. The pivot axes preferably both extend through the centre of gravity of the arm for supporting. The arm shell can hereby be pivoted easily and very lightly. The device according to the invention can also be applied in for instance a desk lamp. Hereby a very light, practically frictionless operation of the desk lamp is advantageously obtained, wherein the lamp likewise stands still in any desired position without the pivot points having to be fixed. As an alternative embodiment, one of the springs can be arranged between two arms of the rod system. It is further possible to apply active springs comprising for instance a pneumatic cylinder, a force and displacement sensor and a computing unit. These active springs take up a determined position subject to the force exerted on the cylinder. It is hereby possible to influence the characteristic of the compensating force. Instead of the four rods 1, 2, 3, 4 forming the parallelogram-shaped rod system, it is of course also possible to use for instance two chain wheels which are mounted on a rod and mutually connected by means of an endless chain. *****

Claims: CLAIMS 1. Force compensator for supplying a substantially constant force in a substantially fixed direction at a random point of a bounded space, which force compensator comprises a frame, a parallelogram-shaped rod system arranged pivotally thereon and two force-providing elements arranged with an end on the rod system, wherein at least one of the force-providing elements is arranged with the other end on the frame. 2. Force compensator as claimed in claim 1, wherein the rod system comprises a first pair of substantially parallel rods and a second pair of substantially parallel rods, which rods are mutually connected by means of pivots for pivoting in one plane, wherein the rods are bounded by the pivots, the first force- providing element is connected to a first rod, connected pivotally to the frame, of the first pair and the second force-providing element is connected to a first rod, connected pivotally to the frame, of the second pair. 3. Force compensator as claimed in claim 2, wherein at least the second rod of the second pair extends beyond the rods of the first pair. 4. Force compensator as claimed in claim 1, wherein a support, for instance an arm shell, is arranged on the rod system. 5. Force compensator as claimed in claims 3 and 4, wherein the support is arranged pivotally on the outer end of the second rod of the second pair. 6. Force compensator as claimed in claim 4 or 5, wherein the pivoting lines of the arm support substantially intersect the centre of gravity of the arm supported by the arm support . 7. Force compensator as claimed in claim 1, wherein at an effective length equal to zero the force-providing elements supply a force equal to zero. 6 8. Force compensator as claimed in claim 1, wherein the force-providing elements are linear springs with a spring constant greater than zero. 9. Force compensator as claimed in claim 1, wherein the force-providing elements are active springs. 10. Force compensator as claimed in claim 1, which comprises blocking means for fixing in a position. 11. Force compensator as claimed in claim 10, wherein the blocking means are pneumatically controllable brakes. 12. Force compensator as claimed in claim 1, wherein the parallelogram-shaped rod system comprises two chain wheels mounted on a rod and an endless chain running over the chain wheels. 13. Support construction comprising a force compensator as claimed in claim 4. 14. Seat comprising at least one support construction as claimed in claim 13, for instance for supporting an arm of a user. 15. Table comprising at least one support construction as claimed in claim 13, for instance for supporting an arm of a user. *****

Inventors: BOUHUIJS MENNO CORNELIS, BOUHUIJS, MENNO, CORNELIS
Applicants: BOUHUIJS MENNO CORNELIS, DEMCON PRODUCT DEV ENGINEERING, BOUHUIJS, MENNO, CORNELIS, DEMCON PRODUCT DEVELOPMENT ENGINEERING
Application year: 1999
Main classification: A47C9
IPC codes: A47C7