Measuring and testing – Specimen stress or strain – or testing by stress or strain... – Specimen clamp – holder – or support
Reexamination Certificate
2000-08-29
2002-04-30
Noori, Max (Department: 2855)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
Specimen clamp, holder, or support
C177S21000R
Reexamination Certificate
active
06378379
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a force-reduction mechanism with a plurality of levers for a force-measuring device. The levers follow each other in a functional sequence where the force to be reduced is transmitted from one lever to the next by way of coupling elements. The force is introduced by way of a first coupling element into a first lever that is rotatably supported by a fulcrum on a stationary support. Mechanisms of the kind that the invention relates to have at least one additional lever beyond the first lever. The additional lever is connected by a coupling element to a preceding lever within the functional sequence of levers. Furthermore, in the kinds of mechanisms envisaged by the invention, the stationary support, coupling elements and levers are configured at least in part as portions of a monolithic material block.
Force-reduction mechanisms for a force-measuring device are known from EP 0 518 202 B1, where a force is reduced by means of at least one lever that is rotatably supported on a stationary support, the force being introduced into the lever by way of a coupling element. The stationary support, coupling elements and levers are configured as separate portions of a monolithic material block. In order to achieve large reduction ratios, embodiments are described which have two or three serially arranged levers connected by coupling elements. The levers are designed for a degree of structural strength commensurate with the load that each of them is exposed to, and they are essentially disposed at vertical positions immediately above one another. The fulcrum or pivotal axis of each lever, i.e., the resting point of the lever, is designed as a slender, flexible portion through which each lever is connected to the stationary support. If the input force into the mechanism is large, the fulcrum reactions of the levers will be of a corresponding magnitude. Consequently, the stationary support will have to be designed for adequate rigidity in the areas between its mounting portion and all of the fulcra. Thus, to meet a given minimum of structural rigidity, the stationary support needs to have the appropriate geometric dimensions. Accordingly, a certain predetermined portion of the monolithic material block has to be set aside for the stationary support. The customary dimensions of material blocks used in this application allow for two or possibly three levers and a stationary support of appropriate dimensions, together with a parallelogram linkage surrounding the force-reduction mechanism with two parallel-guiding members extending from a fixed leg to a movable leg of the parallelogram.
As mentioned in EP 0 518 202 B1, if a larger number of levers are provided in order to achieve larger reduction ratios, it will be necessary to either use a larger material block or to reduce the dimensions of the stationary support to allow for the additional lever volume. Each additional lever has to be supported by an adequately rigid portion of the stationary support. The levers following each other in sequence are arranged essentially parallel to each other, meaning that an imaginary longitudinal line defined by the fulcrum and the coupling pivots of each lever runs essentially parallel with the corresponding imaginary lines of the other levers. This imposes design limitations on the possible spatial arrangements for the levers, the stationary support, the fulcra and the coupling elements. The fulcra of sequentially adjacent levers are in alternating positions near opposite ends of their respective levers. Accordingly, the middle portion of the stationary support between the fulcra at opposite sides is weakened because of the material taken up by the levers. Thus, with a material block of customary size, it is impossible to increase the number of levers without a loss of structural rigidity. However, the use of a larger material block is undesirable, because the force-transmitting mechanism needs to be designed as a component fitting into an overall force-measuring system. If this one component were redimensioned, other components including standardized parts shared with other systems would likewise have to be changed.
OBJECT OF THE INVENTION
It is therefore the object of the present invention, to provide a force-reduction mechanism in which large reduction ratios can be achieved in a compact space.
SUMMARY OF THE INVENTION
In accordance with the present invention, the foregoing objective can be met by a force-reduction mechanism with a plurality of levers following each other in a functional sequence. The force to be reduced is passed from one lever to the next by way of coupling elements. The force is introduced through of a first coupling element into a first lever that is rotatably supported by a fulcrum on a stationary support. Beyond the first lever, the mechanism according to the invention has at least one additional lever. The additional lever is connected by an additional coupling element to a lever that precedes the additional lever in the functional sequence of levers. The stationary support, coupling elements and levers are configured at least in part as distinct portions of a monolithic material block. In the force-reduction mechanism proposed by the invention, at least one of the additional levers has a fulcrum axis that is movable in relation to the stationary support.
The present invention is based on the observation that the use of only spatially fixed fulcra or pivotal supports for the levers represents a severe limitation on the possible layouts for additional levers and the possible reduction ratios. Given that the coupling elements connecting the levers can transmit tensile forces only, the connection from the second to the third lever at the latest will require a space-consuming reach-around portion to be added to one of the levers. For example in
FIGS. 5 and 7
of EP 0 518 202 B1, already the first lever reaches laterally around the second lever. A reach-around portion of this kind needs to have a lever portion designed for a compressive load and a coupling element designed for a tensile load. The compressive lever portion reaches laterally from one lever around the other and thereby unnecessarily reduces the possible length of the lever that lies inside the reach-around portion. This represents an undesirable design limitation, given that in any event the levers have to be progressively shorter in order to allow each of the levers to rest on a fixed fulcrum on the stationary support.
It has been found that the force-reduction potential, i.e., the attainable reduction ratio in relation to the volume or to the largest side surface of the material block, can be increased by using at least one additional lever with a fulcrum axis that is movable in relation to the stationary support. In an advantageous embodiment of the invention, the movable fulcrum of a lever is located on a preceding lever. As is obvious in this embodiment as well as in general, a lever fulcrum that is fixed on a preceding lever participates in the movement of the preceding lever.
A preferred embodiment of the invention has a first, second and third lever arranged in a functional sequence. The respective fulcra of the first and second lever are located on the stationary support, while the fulcrum of the third lever is located on the first lever and thus shares the movement of the first lever.
A further developed embodiment of the inventive concept has four levers in a functional sequence. The respective fulcra of the first and second lever are located on the stationary support. The fulcrum of the third lever is located on the first lever and thus shares the movement of the first lever, while the fulcrum of the fourth lever is located on the second lever and thus shares the movement of the second lever.
The advantage of a movable fulcrum is that is requires no space on the stationary support. Also, the concept of a movable fulcrum provides more freedom in the design of force-reduction mechanisms. In particular, it eliminates the need for reach-around portion
Emery Jean-Christophe
Iseli Marc
Köppel Thomas
Kueffner Friedrich
Mettler-Toledo GmbH
Noori Max
LandOfFree
Force-reduction mechanism for a force-measuring device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Force-reduction mechanism for a force-measuring device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Force-reduction mechanism for a force-measuring device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2894104