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(11) | EP 0 199 494 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Energy storage apparatus for a load tap selector |
| (57) An energy storage apparatus for a load tap selector has a rotating input frame 13
which is concentrically disposed with respect to a rotating output frame 12 to which
is connected an output shaft 13 which operates a load switching movable contact. The
input frame and the output frame each have a pair of flanges 14-17 which extend in
opposite radial directions and which overlap one another in the radial direction.
An energy storage spring 4 which is disposed between the flanges has engaging members
18, 19 secured to opposite ends which are capable of releasably engaging with recesses
formed in the flanges. When the input frame is rotated from a first position to a
second position while the output frame is restrained in the first position. one end
of the spring is restrained by engagement with the flanges on the output frame while
the other end of the spring is moved together with the input frame by engagement with
the flanges on the input frame. thereby stretching the spring and storing energy.
When the restraint of the output frame is released, the energy which was stored in
the spring is released and the output frame and the output shaft are rotated at a
high speed to operate the load switching movable contact. |
BACKGROUND OF THE INVENTION
[0001] This invention relates to an energy storage apparatus for a load tap selector. and particularly to a simple energy storage apparatus having improved drive performance.
[0002] One example of a conventional energy storage apparatus for a load tap selector is illustrated in Figures 1 through 3. In this conventional apparatus. a rotating input frame 1 and a rotating output frame 2 are concentrically disposed about the center of an output shaft 3. The input frame 1 is able to rotate independently of the output frame 2 when a rotational drive force is applied to it by unillustrated drive means. The output frame 2 is secured to the output shaft 3 so that when the output frame 2 is rotated. the output shaft 3 will rotate therewith and transmit a drive force to an unillustrated load switching movable contact. At a number of locations between the input frame 1 and the output frame 2 are provided radially-extending energy storage springs 4. The outer end 5 of each spring 4 is rotatably secured to the input frame I in a manner such that the spring 4 can rotate in the plane of the input frame 1 without a bending moment being applied thereto. and the inner end 6 of each spring is rotatably secured to the outer periphery of the output frame 2 in a similar manner. In the state shown in Figure 1 in which the energy storage springs 4 are aligned along radii of the input frame 1. they are in a relaxed state. and no energy is stored therein.
[0003] The operation of this conventional energy storage apparatus is as follows. The output frame 2 is first restrained in the position shown in Figure 1 in which the springs 4 extend radially outwards. This will be referred to as a first position. The input frame I is then rotated by an angle A. as shown in Figure 2. and then restrained in this rotated position. which will be referred to as a second position. This rotation causes the energy storage springs 4 to stretch and store energy. An unillustrated drive angle control mechanism then releases.the output frame 2 from the first position. and the torque exerted on it by the energy storage springs 4 causes it to rapidly rotate to the second position. as shown in Figure 3. The output shaft 3 is rotated together with the output frame 2. and the unillustrated load switching contact is operated.
[0004] From the symmetry of the structure. it can be easily seen that the output shaft 3 can be rotated in the opposite direction from that shown in the figures if the input frame 1 is rotated clockwise instead of counterclockwise. and thus reversible operation is provided by this apparatus.
[0005] The amount of energy which can be stored in each spring 4 is determined by the distance r of the inner end 6 of the spring 4 from the center of rotation of the input frame 1. the distance R of the outer end 5 of the spring 4 from this same center of rotation. the angle of rotation A of the input frame 1 with respect to the output frame 2. and the spring constant k of the spring 4. Given the values of these parameters. the extension of the spring 4 for a given angle of rotation A can be easily determined using the law of cosines. and once the extension is known the stored energy can be found.
[0006] Taking a simple example, if R = 2r and A = 30 degrees. then the energy stored in the spring is given by the following
[0007] This conventional energy storage apparatus has the drawback that a large amount of energy. as expressed by Equation (1). can not be stored in the springs 4 with a typical angle of rotation A unless the dimensions of the apparatus (in particular. the magnitude of r) are increased or unless the number of energy storage springs 4 is increased. in which case the apparatus becomes undesirably large or complicated.
SUMMARY OF THE INVENTION
[0008] It is an object of the present invention to overcome the above-described drawbacks and to provide an energy storage apparatus for a load tap selector which has a much greater energy storage capacity than a conventional energy storage apparatus of the same size.
[0009] It is another object of the present invention to provide an energy storage apparatus for a load tap selector which has a very simple structure.
[0010] It is another object of the present invention to provide an energy storage apparatus for a load tap selector which employs a smaller number of energy storage springs than a conventional energy storage apparatus while storing a larger amount of energy.
[0011] In an energy storage apparatus for a load tap selector according to the present invention. energy is stored in a tension spring whose ends are equidistant from the center of rotation of a rotating input frame and a rotating output frame. Means are provided for restraining one end of the spring on the output frame and for moving the other end of the spring with the input frame when the input frame is rotated from a first position to a second position. thereby stretching the spring and storing energy in it.
[0012] In a preferred embodiment. an input frame and an output frame each have a pair of flanges which extend in opposite radial directions and which overlap one another in the radial direction. An energy storage spring which is disposed between the flanges has engaging members secured to opposite ends which are capable of releasably engaging with recesses formed in the flanges. When the input frame is rotated from a first position to a second position while the output frame is restrained in the first position. one end of the spring is restrained by engagement with the flanges on the output frame while the other end of the spring is moved together with the input frame by engagement with the flanges on the'input frame. thereby stretching the spring and storing energy. When the restraint of the output frame is released. the energy which was stored in the spring is released and the output frame is rotated at a high speed.
[0013] Because the ends of the energy storage spring are maintained at the same distance from the center of rotation of the input frame. the energy which can be stored in the spring for a given angle of rotation is much larger than the amount which can be stored in a conventional apparatus of the same size in which each energy storage spring is radially disposed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014]
Figure l is a front view of a conventional energy storage apparatus for a load tap selector in an initial state prior to energy storage.
Figure 2 is a front view of the energy storage apparatus of Figure 1 in the state in which energy is stored in the springs.
Figure 3 is a front view of the energy storage apparatus of Figure 1 showing the state after the stored energy has been released.
Figure 4 is a front view of an embodiment of an energy storage apparatus for a load tap selector according to the present invention in an initial state prior to storing energy in the spring 4.
Figure 5 is a cross-sectional view taken along Line V-V of Figure 4.
Figure 6 is a front view of the embodiment of Figure 4 showin g the state in which energy is stored in the spring 4.
Figure 7 is a front view of the embodiment of Figure 4 showing the state after the stored energy has been released.
Figure 8 is a cross-sectional view taken along Line VIII-VIII of Figure 4.
Figure 9 is a cross-sectional view taken along Line IX-IX of Figure 6.
Figure 10 is a cross-sectional view taken along Line X-X of Figure 7.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] Hereinbelow. an embodiment of the present invention will be described while referring to Figures 4 through 10 of the accompanying drawings.
[0017] As shown in Figure 4. in this embodiment a rotating input frame 11 and a rotating output frame 12 are concentrically disposed with respect to a rotating output shaft 13. The input frame 11 is rotatably supported by the output shaft 13 so as to be able to freely rotate about the center of the output shaft 13. and the output frame 12 is secured to the output shaft 13 so that when the output frame 12 is rotated. the output shaft 13 will rotate with it. The output shaft 13 is connected to an unillustrated load switching movable contact which is operated by its rotation.
[0018] As best shown in Figure 5. which is a cross-sectional view taken along Line V-V of Figure 4. the input frame 11 has two parallel plate-shaped flanges 14 and 15 formed thereon which extend radially inwards towards the output shaft 13. Similarly. the output frame 12 has two parallel plate-shaped flanges 16 and 17 formed thereon which extend radially outwards from the output shaft 13 and which overlap the flanges 14 and 15 of the input frame 11 in the radial direction. The widths of all four flanges tthe distance from the left sides to the right sides of the flanges as seen in Figure 4) are identical. In this embodiment. the two flanges 16 and 17 of the output frame 12 are located on the outside of the flanges 14 and 15 of the input frame 11. but the opposite arrangement is possible with flanges 16 and 17 located between flanges 14 and 15.
[0019] In the left end of each of the flanges 14. 15. 16. and 17 is formed an arcuate hole. indicated by reference numerals 14a. 15a. 16a. and 17a. respectively, which opens onto the end surface of the member. In the right ends of the flanges. identical arcuate holes 14b. 15b. 16b. and 17b. respectively. are formed which open onto the end surfaces at the opposite ends of the flanges. The distance between the two holes in a given flange is the same for each of the four flanges 14. 15. 16. and 17.
[0020] The four holes 14a. 15a. 16a. and 17a at the left ends of the flanges are for the purpose of engaging with a first engaging member 18. and the other four.holes 14b. 15b. 16b. and 17b at the right ends of the flanges are for the purpose of engaging with a second engaging member 19. The first engaging member 18 comprises two coaxial. cylindrical flange engaging portions 18b and 18f having a shape complementary to the shapes of the holes in the left ends of the flanges. with which they engage. On the outside ends of the flange engaging portions 18b and 18f are formed two outside collars 18a and 18g. respectively. and on the inside ends of the flange engaging portions 18b and 18f are formed two inner collars 18c and 18e. respectively. These collars are coaxial with respect to the flange engaging portions 18b and 18f but have a larger diameter than the flange engaging portions 18b and 18f so as to prevent the movement of engaging member 18 in its axial direction. Between the inner collars 18c and 18e is secured an eccentric cylindrical portion 18d having a diameter larger than that of the inner collars 18c and 18e. The eccentric cylindrical portion 18d is disposed so that at least one part of its outer periphery is closer to the axial center of the inner collars 18c and 18e than are the outer peripheries of the inner collars 18c and 18e. In this manner. a recess 18h is formed between the two inner collars 18c and 18e.
[0021] The second engaging member 19 is identical in shape to the first engaging member 18. comprising outer collars 19a and 19b. cylindrical flange engaging portions 19b and 19f. inner collars 19c and 19e. and an eccentric cylindrical portion 19d which is displaced with respect to the axial centers of the inner collars 19c and 19e so that a recess 19h is formed therebetween.
[0022] The above-described holes 14a - 17a and 14b - 17b in the flanges 14 - 17 which engage with the flange engaging portions of the engaging members 18 and 19 are disposed such that when the engaging members 18 and 19 engage with any of the holes. the axial centers of the engaging members 18 and 19 will be equally distant from the center of rotation of the output shaft 13 by a distance Ra. In addition. the holes are shaped such that they can easily disengage from the engaging portions when the engaging members 18 and 19 are rotated away from the holes about the center of the input frame 11.
[0023] An energy storage spring 4 is disposed in a space between the flanges 14 and 15 of the input frame 11. the space being large enough so as not to obstruct the extension of the spring 4. The ends of the energy storage spring 4 are connected to the first engaging member 18 and the second engaging member 19 by connecting plates 20 and 21. respectively. Connecting plate 20 has an oval through hole 20a formed in its center. the through hole 20a being larger than eccentric cylindrical portion 18d but the end portions of the through hole 20a having a radius of curvature which is identical to the radius of the eccentric cylindrical portion 18d. The connecting plate 20 fits over the eccentrical cylindrical portion 18d inside recess 18h with the surface of its through hole 20a contacting eccentric cylindrical portion 18d. The radius of curvature of the end portions of through hole 20a is chosen to be the same as the radius of eccentric cylindrical portion 18d so as to reduce the maxiumum compressive stress acting on the surface of through hole 20a when it is being pressed against eccentric cylindrical portion 18d. Similarly. connecting plate 2: has an oval through hole 21a formed in its center which is larger than eccentric cylindrical portion 19d and whose end portions have a radius of curvature which is the same as the radius of eccentric cylindrical portion 19d. The opposite ends of the spring 4 are connected to the ends of the connecting plates 20 and 21. respectively.
[0024] The flanges 14 - 17 and the engaging members 18 and 19 together consitute means for restraining one end of the energy storage spring 4 on the output frame 12 and moving the other end of the spring 4 with the input frame 11 when the input frame is rotated. thereby stretching the spring 4 and storing energy in it.
[0025] The operation of this embodiment is as follows. Figure 4 and Figure 8 illustrate the embodiment when the input frame 11 and the output frame 12 are in a first position in which no energy is stored in the energy storage spring 4. An unillustrated restraining mechanism restrains the output frame 12 in the illustrated first position. and an unillustrated drive mechanism rotates the input frame 11 in the counterclockwise direction by an angle A to a second position. as shown in Figure 6. When the input frame 11 is so rotated. the holes 14b and 15b which engage with the flange engaging portions 19b and 19f. respectively. of the second engaging member 19 force the second engaging member 19 to move together with the input frame 11. and the second engaging member 19 is rotated clockwise about the center of the output shaft 13 and away from the first engaging member 18. The holes 16b and 17b in the right ends of flanges 16 and 17. respectively are shaped such that when the engaging member 19 is rotated about the center of the output shaft 13. the flange engaging portions 19b and 19f can easily disengage from the holes 16b and 17b. respectively. Similarly. the holes 14a and 15a in the left ends of flanges 14 and 15. respectively. can easily disengage from the flange engaging portions 18b and 18f of the first engaging member 18.
[0026] When the second engaging member 19 is rotated away from the first engaging member 18 by the rotation of the input member 11. a force is exerted on the first engaging member 18 through the energy storage spring 4 which tries to make it follow the movement of the second engaging member 19. However. as the flange engaging portions 18b and 18f are engaged with holes 16a and 17a of the flanges 16 and 17 of the output frame 12. and as the output frame 12 is restrained from rotating by the restraining mechanism. the first engaging member 18 remains stationary in the first position. As a result. the rotation of the second engaging member 19 stretches the energy storage spring 4 by an amount D as shown in Figure 9. and energy is stored in the spring 4.
[0027] When the input frame 11 has reached the second position. an unillustrated rotational angle control mechanism causes the restraining mechanism to release the restraint of the output frame 12. When the restraint is released. the first engaging member 18 is drawn towards the second engaging member 19 by the tensile force of the energy storage spring 4. the engagement between the first engaging member 18 and the flanges 16 and 17 of the output frame 12 produces a torque on the output frame 12. and the output frame 12 is rapidly rotated clockwise towards the second Position. as shown in Figures 7 and 10. The rapid rotation of the output frame 12 causes the output shaft 13 to which it is secured to rapidly rotate and operate the unillustrated load switching movable contact. When the output frame 12 reaches the second position. holes 14a and 15a once again engage with engaging portions 18b and 18f of the first engaging member 18. and holes 16b and 17b again engage with the engaging portions 19b and 19f of the second engaging member 19.
[0028] Due to the symmetry of the structure. rotation of the output shaft 13 in the clockwise direction can be performed by the same series of operations described above except that the input frame 11 is rotated in the clockwise direction.
[0029] The energy stored in the spring 4 by rotation of the input frame 11 can be found given the angle of rotation A. the initial separation L between the centers of the engaging members 18 and 19. the distance Ra of the centers of the engaging member 18 and 19 from the center of the output shaft 13. and the spring constant k of the energy storage spring 4. For example. if Ra = 1.3r (wherein r has the same value as in Figure 2). L = r x √2. and A = 30 degrees. then the stored energy E is expressed by the following equation:
It can be seen that if k has the same value as for the conventional apparatus illustrated in Figure t. the stored energy is about 5 times as large as the amount expressed by Equation (1) for the same angle of rotation A.
characterised in that the spring extends generally transversely to a radius extending from the axis of rotation to the spring.
a rotating output frame (12) which is connected to a load switching movable contact so as to operate said load switching movable contact when said output frame rotates:
a rotating input frame (13) which is coaxially disposed with respect to said output frame and which can rotate with respect to said output frame in a plane which is parallel to the plane of rotation of said output frame;
an energy storage spring disposed in a plane which is parallel to the planes of rotation of said input frame and said output frame: and
means(14-19) for restraining one end of said energy storage spring when said output frame is restrained by a restraining mechanism and for moving the other end of said energy storage spring with said input frame in the direction of rotation of said input frame when said input frame is rotated in any direction while maintaining the ends of sa-id spring at a constant distance from the center of rotation of said input frame. whereby energy is stored in said spring.
a first pair of flanges which extend radially outwards from the rotational center of said input frame and a second pair of flanges which extend radially inwards towards the rotational center of said input frame. one of said pairs of flanges being secured to said input frame so as to rotate therewith and the other pair being secured to said output frame so as to rotate therewith. said first and second pair of flanges overlapping in the radial direction with both flanges of one of said pairs of flanges being disposed between the flanges of said other pair of flanges with a space between said first and second pairs. there being a gap between the inner pair of said pairs which is at least as large as the diameter of said energy storage spring. each of said flanges having end surfaces formed on its opposite ends which face in the directions of rotation of said input frame and in each of which is formed a hole which opens onto said end surface. each of said holes being equidistant from the rotational center of said input frame. the distance between the holes in each flange being the same for all of said flanges: and
a first engaging member and a second engaging member which are connected to opposite ends of said energy storage spring and which are disposed at opposite ends of said flanges and extend perperpendicular to the plane of rotation of said input frame. each of said engaging members having engaging portions which can releasably engage with said holes in said flanges.
two of said engaging portions: and
two outer collars formed on its ends outside of said engaging portions and two inner collars formed inside of said engaging portions with respect to the lengthwise centers of said engaging members. each of said collars having a larger diameter than said engaging portions, said outer collars being disposed outside of the outer pair of said flanges and said inner collars being disposed inside of inner pair of said flanges with respect to the lengthwise centers of said engaging members when said engaging portions engage with any of said holes in said flanges.
an eccentric cylindrical portion which is formed in each of said engaging members between said inner collars and which is eccentric with respect to said inner collars so that a recess is formed between said inner collars of each of said engaging members; and
a first and a second connecting plate secured to opposite ends of said energy storage spring. each of said connecting plates having a through hole formed therein which is larger than said eccentric cylindrical portions but whose radius of curvature for a portion of its circumference is the same as the radius of each of said eccentric cylindrical portions. said first and second connecting plates being disposed in the recesses of said first and second engaging members. respectively. with said through holes surrounding said eccentric cylindrical portions and with the portions of the surfaces of said through holes having the same radius of curvature as said eccentric cylindrical portions contacting said eccentric cylindrical portions of said first and second engaging members. respectively.