GB2153463A - Vibration damper - Google Patents
Vibration damper Download PDFInfo
- Publication number
- GB2153463A GB2153463A GB08501815A GB8501815A GB2153463A GB 2153463 A GB2153463 A GB 2153463A GB 08501815 A GB08501815 A GB 08501815A GB 8501815 A GB8501815 A GB 8501815A GB 2153463 A GB2153463 A GB 2153463A
- Authority
- GB
- United Kingdom
- Prior art keywords
- friction
- friction plates
- plates
- plate
- ofthe
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04H—BUILDINGS OR LIKE STRUCTURES FOR PARTICULAR PURPOSES; SWIMMING OR SPLASH BATHS OR POOLS; MASTS; FENCING; TENTS OR CANOPIES, IN GENERAL
- E04H12/00—Towers; Masts or poles; Chimney stacks; Water-towers; Methods of erecting such structures
- E04H12/28—Chimney stacks, e.g. free-standing, or similar ducts
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04H—BUILDINGS OR LIKE STRUCTURES FOR PARTICULAR PURPOSES; SWIMMING OR SPLASH BATHS OR POOLS; MASTS; FENCING; TENTS OR CANOPIES, IN GENERAL
- E04H9/00—Buildings, groups of buildings or shelters adapted to withstand or provide protection against abnormal external influences, e.g. war-like action, earthquake or extreme climate
- E04H9/02—Buildings, groups of buildings or shelters adapted to withstand or provide protection against abnormal external influences, e.g. war-like action, earthquake or extreme climate withstanding earthquake or sinking of ground
- E04H9/021—Bearing, supporting or connecting constructions specially adapted for such buildings
- E04H9/0215—Bearing, supporting or connecting constructions specially adapted for such buildings involving active or passive dynamic mass damping systems
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/005—Damping of vibrations; Means for reducing wind-induced forces
Abstract
A device for damping the vibrations on tower-like structures, such as chimneys, transmitter masts has a pendulum 1 whose lower end 2 engages in a hollow space 3 formed by central holes in individual circular friction plates P1-P6 whose hole diameters become increasingly larger from top to bottom friction plates: depending on vibration amplitude successive plates are moved. All friction plates have the same plate thickness: with an assumed hole diameter d of the top friction plate the hole diameters of the friction plates located therebeneath increase according to the product i.d; with an assumed frictional force R1 by the top friction plate the outside diameter gradation of the friction plates result on account of the condition that all the other friction plates produce respectively double the frictional force of the top frictional plate. The specification contains a detailed mathematical discussion of the parameters involved. <IMAGE>
Description
SPECIFICATION
A device for damping vibrations
The invention relates to a device as described in the introductory part of Patent Claim 1. Such a device is the subject matter of German Offenlegungsschrift 32 15428. This is a friction vibration damper, on which an
additional mass fastened to a pendulum rod is throw into vibrations by the structure. The coupling ofthe
additional mass to the structure is effected via a friction weight which is moved by the pendulum rod. If thefriction weight consists of one piece, then the dissipation energy per vibration cycle corresponds to a rectangular area according to the formula
Wd = 4-R-x, wherein R is the frictional force and xis the vibration amplitude.According to this equation, the dissipation energy Wd increases in proportion to the vibration amplitude x. Such a vibration damper is described in
German Auslegeschrift 2616899. It has the disadvan tage that the pendulum swing can only set the friction weight in motion from a certain minimum swing of the structure, namely as soon as the inertial forces of the
pendulum mass exceed the frictional forces between the friction weight and a support.
By contrast, with a device according to the aforementioned German Offenlegungsschrift32 15 428, where the friction weight is divided into individual friction plates which are piled one upon the other and are displaceable relative to one another, is is possible to bring about a response ofthe damping device when very slight movements ofthe structure occur. As the amplitude of the pendulum movement increases, more and more friction plates are activated and the dissipated energy rises accordingly. With this known device, the expert encounters difficulties with the computational design of the contruction since there does not exist any theory which can be applied in practice.
The problem underlying the present invention isto improve the known device with stacked friction plates in such a way that its damping effect, related to a specific pendulum swing, is increased and its computational determination and consequently its design with respect to the respective structure is simplified.
According to the invention, for the solution ofthis
problem, a start is made from the aim to dimension on a friction vibration damper of the kind mentioned at the beginning the friction plates in such a way that there can be applied thereto the "den Hartog theory" ofthe double-mass vibrator with viscous damping.
With the attainment of this aim in the manner
described hereinafter it is possible for the first time to realise, in connection with a friction vibration damper,
a dependence of the dissipated energy on the square ofthevibration amplitude, as applies in known mannerto the viscous vibration damper. The dissipated energy thereof is calculated according to the equation
Wd = 7r-k w-x2, wherein k is a damping constant, w is the pulsatance ofthe vibration excitation and xis again the vibration amplitude. According to this equation, the dissipated energycorresponds to the area of an ellipse; it rises with the square ofthe vibration amplitude.
For the solution ofthe mentioned problem, the dimensioning ofthefriction plates p1 for = 1 ton has to be effected byobserving thefollowing rules:
a) All the friction plates pj have the same plate thickness t; the coefficient of friction L must be identical between the individual friction plates.
b) With an assumed hole diameter d of the top friction plate p1, the hole diameters from the top to the bottom friction plates increase in accordance with the product i-d; i = 1,2,3, , , n = consecutive number of the friction plates.
c) The progression of the outside diameterofthe friction plates results from the requirement that the energy dissipated per vibration cycle is to grow as the square of the pendulum swing id. This requirement is fulfilled if the friction plates pj for i = 2 ton are each designed to be double as heavy as the top friction plate p. There applies: Gi = 2 G1. Because ofthe assumed constant coefficient of friction between the individual friction plates, this condition may be formulated in such a way thatthere is to occur as from i = 2 a respective frictional force increase R = L. 2 G1 = 2 Rq R1 upon the activation of the friction plates.
Broughtto a short formula, with friction plates of identical thickness and with holes according to feature b), it is important that all friction plates with i 3 2 should produce the same frictional force, namely of double the magnitude as that ofthe top friction plate.
After having previously laid down the thickness of the friction plates, a uniform material for all friction plates and the outside diameter D1 of the top friction plate p1 as well as having laid down the hole diameter d1 thereof, a person skilled in the art can calculate the dimensions ofthe individual friction plates with the aid ofthe above shown connection between the weights ofthefriction plates. Since, as presupposed, the friction plates are to be circular discs with circular central holes, the weight thereof is determined according to the formula:
wherein
y = specific weight (Ntm3) t = friction plate thickness (m)
D = outside diameter (m)
d = hole diameter (m).
An expedient development ofthetopfriction plate p1 providesforthe outside diameter D, thereofto be between 4 and 12 times its hole diameter d1 and forthe hole diameter d, thereof to be only slightly largerthan the diameter ofthe pendulum rod in thezone of its lower end plunging into the hollow space formed by the friction plates p.
The result ofthe dependence of the dissipated energy Wd on the square ofthe vibration amplitude is that there is dissipated a specific mechanical vibratory energy, which is introduced into the structure, with substantially smaller pendulum swings "x" than is the case with friction dampers of a hitherto known construction with a linear connection between the dissipated energy and the vibration amplitude "x". As a result, it is possible, with the device according to the invention, to keep the dimensions in the direction of the pendulum swing correspondingly small. Therefore, the proposal according to the invention not only enables a particularly economic production ofthe vibration damping device; the smaller dimensions thereof are also very desirable because ofthe improved optical impression.
As already stated, the decisive advantage in favour of the device according to the invention lies in the particularly simple computational determination; this applies both with respect to the dimensioning of the constructional parts, and the friction plates in particular, and with respectto their adaptation to the conditions ofthe respective structure.
Hereinafter, a design examplefora friction weight with six friction plates will be calculated. For this purpose, reference is made to the accompanying diagrammatical representation of such a constructional form in the drawing.
The drawing shows a pendulum 1 in the position of rest. The friction weight consists of six friction plates p1 to p6 which are each designed in the shape of a circular dise of the thickness t. The lower end 2 of the pendulum 1 engages in a hollowspace3 which is formed by central circular holes in the individual friction plates. The friction weight rests on a base 4 of a housing not shown in detail. The base 4 may be flat, as shown, or may be domed in accordance with the pendulum motion.Its surface forms the friction surface for the friction weight which is composed of the plates p1 to p6 and which is displaced by the lower end 2 of the pendulum rod 7 during the movement of the pendulum 1, during which process, related to the position of rest shown in the drawing, there are moved first the top friction plate p1 and then, depending on the vibration amplitude, successively the friction plates p2to p6 until-with large swings ofthe structure-the friction weight is moved in its entirety.
The pendulum 1 is suspended on an indicated ball-and-socketjoint 5 the end of a bracket 6 which, as not shown in detail, is fixedly connected to a structure.
Suspended on the pendulum rod 7 is a bob 8 which weighs between 100 and 700 kg depending on the structure. By contrast, the friction weight composed of a pluralityoffriction plates p1 to p6 weights considerably less. Expressed in figures, it weighs less than 10% ofthe bob.
The individual friction plates p1 top6 have central holes ofvarying size; the hole diameter ofthe plate p1 has been chosen to be such that it closely embraces the lower end 2 ofthe pendulum rod 7. The individual hole diameters have been chosen to be as follows:
Friction plate p1 :hole diameter d1 = d
Friction plate p2:holediameterd2= 2d Friction platep3:holediameterd3= 3d Friction plate p4: hole diameter d4 = 4d
Friction plate p6: hole diameter d5 = 5d Friction plate p6: hole diameter d6 = 6d
Forthe calculation ofthe outside diameter gradation of a concrete exemplified embodiment, a start is made from thafact thatthe top plate p1 has an outside diameter D1 which is six times the hole diameter d1; therefore, there applies: Dt = 6-d.
Furthermore, the following numerical values are assumed Specific weighty =
Holediameterd = 20 mm = 0.02 m;
Friction platethicknesst = 10 mm = 0.01 m.
According to the equation
there results with D1 = 6d, for the top friction plate
D1 = 6-0.02 - 0.12 m According to the rule claimed in Claim 2, the weight for all other friction plates Gi for i#2 is double that for the friction plate G1 if one presupposes the same coefficient offriction for each friction plate.
Therefore, G1 = 2.G1 = 17.58N for i#2.
If one inserts this value into the above equation (I)for the plate weight, then there results:
ForG1=2G1 = const = 17.58 and i = 2to Gthere result the following values forD1:-
D2 = 0.34 m.
The outside diameters of the other friction plates are calculated in the same way; the result for all friction plates is:
dim Dim GiN
p,: 0.02 0.120 8.79 p2: 0.04 0.172 17.58
p3: 0.06 0.178 17.58
p4: 0.08 0.185 17.58
p5: 0.10 0.195 17.58 p6: 0.12 0.206 17.58
Hereinafter, there will be shown the mathematical proof of the quadratic dependence of the dissipated energyonthevibration amplitudex = nd.
Starting out from the already explained rectangular hysteresis loop in friction damping, there result the following rectangular areas during the movement of 1,2,3 etc. to n friction plates: n=1:Wdl= 1.2.d.R1 n=2:Wd2= 1.2.d.R2 + 2.2.d.R1 n = 3: Wd3 = 1.2.d.R3 + 2-2-d-R2 + 3.2.d.R1 with the control variable i = 1 ton n 2: i.(2dRn+1-i) = Wd (il) 1=1 This equation takes into consideration the different displacement distances of the various friction plates.
Thetop orfirstfriction plate pX is always moved. Its hole diameter d is equated with the diameter ofthe pendulum end 2. The second friction plate P2 has a hole diameter2d, in otherwords a hole clearance d. If the pendulum end moves within this hole clearance, then only the first friction plate p1 is activated; here, the rectangularareaforafullvibrationcycle is Wdl = 2d.R1.Upon a further displacement, the friction plate p2 is activated with R2 and the additional vibration distanced istravelled. Onlywhen the pendulum swing islargerthan 2disthethirdfriction plate p3 activated, which plate, having a hole diameter of 3d, allows a pendulum play of 2d without being set in motion itself. These movement phases occur once in both vibration directions per vibration cycle, the friction plates being activated in the same succession.
According to Claim 1, there applies: Rj = 2R1 = const for i#2.
There thus results from the equation (II) for Wdn for n=1; i=1 :Wd1 = 2.d.R1.1
n=2; i=1,2 :Wd2=1.2d.R2 + 2.2d.R1 = 2.d.R1.4 n=3; i=1,2,3:Wd3= 1.2d.R3 + 2.2d.R2 + 3.2d.R1 = 2.d.R1 . 9
One readily discerns the dependence on n2; there thus applies the simple connection: Wdn = 2d-R1-n2 the relationship between the frictional force and the weight being given by R1 = ffG1
Claims (5)
1. A device for damping vibrations on tower-like structures, such as chimneys, transmitter masts or the like, which is provided with a pendulum (1)which is suspended on a bracket support (6) ofthe structure forthe performance of spatial oscillations and has a pendulum rod (7), whose lower end plunges loosely into a hollow space (3), which is open towards the top, of a friction weight which is composed of several unconnected circular-disc-shaped friction plates (pi) which are piled one upon the other and the lowest of which rests displaceably on a base (4) ofthe device, and the hollowspace (3) being formed by central holes in the friction plates (pi), whose hole diameters (di) become increasingly largerfrom the top to the bottom friction plates (pi), characterised in that the dimensioning ofthe friction plates (pi) for i= 1 ton is effected by observing the following rules:
a) All the friction plates (p=i) havethesame plate thickness (t);
b) with an assumed hole diameter (dl) of the top friction plate (p1), the hole diameters increase in accordance with the product i-d; c) with an assumed frictional force (R1) produced by the top friction plate (p1), there results the outside diameter gradation of the friction plates on account of the further condition that all the otherfriction plates (pi) produce for i = 2 ton respectively double the frictional force ofthetopfriction plate (p1) according totheformula
Ri = 2R1, for i = 2 to n.
2. A device as claimed in Claim 1, characterised in that the coefficient of friction between each friction plate (pi) and the basis thereof is the same so that, related to the top friction plate (pal) with the weight G" there occurs upon the activation ofthefriction plates (pi) located therebeneath for i = 2 ton a respective increase ofthefrictional force ARj = 2,{t-Gl fori = 2to
3. A device as claimed in Claim 1 or 2, characte- rised in that the outside diameter (D1) ofthetop friction plate (pal) is between 4 and 12 times the hole diameter (dl) thereof, and in that the hole diameter (dl) thereof is only slightly largerthan the diameter (d) ofthe pendulum rod (7) in the zone of its lower end (2) which plunges into the hollow space (3) formed by the friction plates (pi).
4. A device as claimed in one of Claims 1 to 3 and whose energy which is dissipated by friction damping increases with the square ofthe pendulum swing or the number of the moved friction plates (pj).
5. Avibration damping device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3402449A DE3402449C2 (en) | 1984-01-25 | 1984-01-25 | Device for vibration damping on tower-like structures such as chimneys, transmitter masts or the like. |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8501815D0 GB8501815D0 (en) | 1985-02-27 |
| GB2153463A true GB2153463A (en) | 1985-08-21 |
| GB2153463B GB2153463B (en) | 1987-09-09 |
Family
ID=6225833
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08501815A Expired GB2153463B (en) | 1984-01-25 | 1985-01-24 | Vibration damper |
Country Status (4)
| Country | Link |
|---|---|
| AT (1) | AT385310B (en) |
| DE (1) | DE3402449C2 (en) |
| DK (1) | DK156256C (en) |
| GB (1) | GB2153463B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7928593B2 (en) | 2007-11-28 | 2011-04-19 | Vestas Wind Systems A/S | Method for damping oscillations in a wind turbine |
| US11078890B2 (en) | 2018-05-22 | 2021-08-03 | Engiso Aps | Oscillating damper for damping tower harmonics |
| EP3814628B1 (en) * | 2018-06-29 | 2023-08-02 | Vestas Wind Systems A/S | Damper unit for a tower structure |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3717460A1 (en) * | 1986-11-03 | 1988-05-19 | Teutsch Rudolf | DEVICE AND METHOD FOR VIBRATING ELEMENTS OF VIBRATION LABELED BODIES |
| DE4305132C1 (en) * | 1993-02-19 | 1994-04-21 | Uwe E Dr Dorka | Friction damper for securing support structure against dynamic effects - has superimposed friction plates contacting surfaces which are connected to friction damper connections |
| DE102012020851A1 (en) | 2012-10-24 | 2014-04-24 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | System for connecting a first component and a second component to form a rigid frame corner |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3215428A1 (en) * | 1982-04-24 | 1983-11-03 | Friedrich Maurer Söhne GmbH & Co KG, 8000 München | Device for damping vibrations in tower-like constructions such as chimneys, transmitting masts or the like |
-
1984
- 1984-01-25 DE DE3402449A patent/DE3402449C2/en not_active Expired
- 1984-12-20 DK DK613684A patent/DK156256C/en not_active IP Right Cessation
- 1984-12-21 AT AT0405584A patent/AT385310B/en not_active IP Right Cessation
-
1985
- 1985-01-24 GB GB08501815A patent/GB2153463B/en not_active Expired
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3215428A1 (en) * | 1982-04-24 | 1983-11-03 | Friedrich Maurer Söhne GmbH & Co KG, 8000 München | Device for damping vibrations in tower-like constructions such as chimneys, transmitting masts or the like |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7928593B2 (en) | 2007-11-28 | 2011-04-19 | Vestas Wind Systems A/S | Method for damping oscillations in a wind turbine |
| US11078890B2 (en) | 2018-05-22 | 2021-08-03 | Engiso Aps | Oscillating damper for damping tower harmonics |
| EP3814628B1 (en) * | 2018-06-29 | 2023-08-02 | Vestas Wind Systems A/S | Damper unit for a tower structure |
Also Published As
| Publication number | Publication date |
|---|---|
| AT385310B (en) | 1988-03-25 |
| DE3402449A1 (en) | 1985-08-01 |
| DK613684D0 (en) | 1984-12-20 |
| DE3402449C2 (en) | 1986-04-03 |
| DK156256C (en) | 1989-12-04 |
| GB2153463B (en) | 1987-09-09 |
| ATA405584A (en) | 1987-08-15 |
| GB8501815D0 (en) | 1985-02-27 |
| DK613684A (en) | 1985-07-26 |
| DK156256B (en) | 1989-07-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19950124 |