Vibration testing apparatus

Abstract

The invention relates to a vibration testing apparatus comprising a holder (2) for vibration test objects (3) connected to a vibrator (1) and to a frame (10), the principle of which is that the vibrator (1) is connected to at least two vibration test object (3) holders - carriages (2) movable on the frame (10), between which the vibrator (1) is positioned.

Description

[0001] Vibration Testing Apparatus

[0002] Technical Field

[0003] The invention relates to an apparatus for performing vibration tests, comprising a vibration test object holder connected to a vibrator and to a frame.

[0004] Prior Art

[0005] Vibration testing is challenging in many ways. Its implementation is energy intensive. Further demands concerning its design are the force requirements necessitating vibrators that provide sufficiently large forces. This means special requirements for the structures on which the vibration test objects are to be mounted. The criteria are that the structures must be strong and rigid. This is due to the need to provide a specified range of vibration excitation frequencies. A structure that is not sufficiently strong and rigid will start vibrating at its natural frequency as a result of excitation and thus add distortion to the vibration excitation range. The time demands of vibration testing are considerable, so any savings in power requirements, equipment size, etc. are helpful.

[0006] The disadvantage of existing vibration testing equipment is that the reaction forces from the vibrator acting on the test object affect the equipment frame by which they are absorbed. This results, on the one hand, in part of the energy of the vibrators remaining unused and, on the other, in not using part of the force coming from the vibrator, which necessitates using stronger vibrators than would be strictly necessary, which in turn requires using stronger and stiffer structures. A major disadvantage is the need of dimensioning the frame for the large forces involved and the relatively high energy consumption during the vibration testing.

[0007] It is an object of the present invention to provide an apparatus for vibration testing that also utilises for the purpose reaction forces, thereby easing all the above requirements for performing vibration testing.Summary of the Invention

[0008] The essence of the vibration testing apparatus comprising a vibration test object holder connected to a vibrator and to a frame according to the present invention is that the vibrator is connected to at least two vibration test object holders movable on the frame, comprised of carriages between which the vibrator is positioned. The carriages may be connected to a constant force source mounted on the frame and may consist of a pulley and a counterweight carried by a rope, or of a spring on a spring-loaded carriage connected via a non-linear gear to a rope. The object carriers on the carriages may be arranged at unequal heights above the frame and form an acute angle to the carriage travel path. The vibration test object is mounted on one of the carriages or the inserted pulse vibration test object is mounted on at least two carriages. Alternatively, the vibrator is coupled to at least three carriages and / or vibrators.

[0009] The advantage of the vibration testing apparatus is that it also utilises to perform the vibration tests the reaction forces of the vibrators, thus easing the requirements on the size and stiffness of the equipment and on power consumption.

[0010] Overview of Figures Included in the Drawings

[0011] The invention will be further elucidated by means of drawings, where the figures provided show:

[0012] Fig.l Existing design of vibration testing equipment

[0013] Fig.2 Schematic representation of the basic design of the vibration testing apparatus Fig. 3 Solution from Fig. 2, additionally equipped with a position adjusting drive

[0014] Fig.4 Schematic representation of an alternative solution of the vibration testing apparatus Fig. 5 Schematic representation of the simplest solution of the constant force source.

[0015] Fig. 6 Schematic representation of another solution of the constant force source.

[0016] Fig.7 Schematic representation of an alternative solution of the vibration testing apparatus for a case of need to consider at least partial involvement of gravitational forces Fig.8 Schematic representation of another alternative solution of the vibration testing apparatus that uses pulse force

[0017] Fig.9 Schematic representation of another alternative solution of the vibration testing apparatus to the solutions in Figs 2 and 8Fig.10 Schematic representation of another alternative solution of the apparatus Fig. 11 Arrangement with another vibrator included in serial arrangement next to the vibrator, allowing to modulate the vibration force on the carriages and vibration test objects attached thereto

[0018] for vibration testing, where the force of the vibrator is used to vibrate multiple carriages.

[0019] Fig. 12 Arrangement with inserted vibrators that can modulate other forces acting on different carriages and vibration test objects attached thereto

[0020] Fig.13 Schematic representation of another solution of the vibration testing apparatus using pulse force

[0021] Detailed Description of the Invention

[0022] Figure 1 shows schematically the existing design of the vibration testing equipment. The vibration test objects 3 are attached to the movable holder 2, which will be referred to hereafter as moving carriage. A vibrator 1 is included between the movable holder 2 and the frame 10. The vibrator 1 is a device that exerts force on the holder 2 causing the desired acceleration curve, i.e. the speed and divergence of the carriages 2 and the attached vibration test objects 3. The reaction force required for the vibrator 1 to act on the holder 2 and the vibration test objects 3 attached thereto is intercepted and absorbed by the frame 10. It is therefore unused.

[0023] Figure 2 shows schematically the basic design of the vibration testing apparatus according to the present invention. The vibration test objects 3 are attached to two carriages 2 travelling along a track on the frame 10. The carriages 2 function as holders of the vibration test objects 3. The two carriages 2 are interconnected by a vibrator 1. The vibrator 1 is a device that exerts force on the two carriages 2 causing the desired acceleration curve, i.e. the speed and divergence of the carriages 2 and the attached vibration test objects 3. In the present setup, the force exerted by the vibrator 1 and the resulting reaction force both act on both the carriages 2, causing the desired vibrations. In this case, the vibration forces are assumed to be much larger than the gravitational forces, which thus need not be considered. Consequently, it is possible to increase the number of vibration test objects 3 to twice as much, thus reducing the general power and time requirements. Since the vibration test objects 3 can be distributedamong more carriages 2, it is possible to make the carriages 2 smaller, resulting in better stiffness and lower weight, as both deteriorate with size.

[0024] In Figure 3, the solution from Figure 2 is additionally provided with a position adjusting drive 9, which ensures that the vibrating carriages 2 remain permanently in the travel area and that, for example, undue friction and vibrations do not push the vibrating carriages 2 from the guiding track. The position adjusting drive 9 is typically a very weak actuator with an integrating controller component between the frame 10 and one of the vibrating carriages 2. Instead of the position adjusting drive 9, a spring, even including a very weak one, can be used between the frame 10 and one of the vibrating carriages 2. In the other figures, the position adjusting drive 9 will not be shown.

[0025] Figure 4 shows schematically an alternative design of the vibration testing apparatus according to the present invention. If gravitational forces need to be considered, i.e., the vibration forces are smaller than or comparable to the gravitational forces, then the movement of the holder 2 must be vertical in the direction of gravity. In this case, the carriages 2 are provided with a source of constant force 4 equal to the weight of the object consisting of the carriage 2 itself and all the vibration test objects 3 attached to it. This source of constant force 4, connected via a rope 7 to the corresponding carriage 2, causes it to levitate. The vibrator j_ then here as well distributes the force, and with it the reaction force of equal magnitude, between the two carriages 2. The constant force sources 4 may also be mounted on the bottom from the side of the frame 10.

[0026] Figure 5 shows schematically the simplest solution of the constant force source 4, consisting of a pulley 6, a rope 7 and a counterweight 8. The limiting factor to this solution is that it only works for force magnitudes of the vibrator 1 that are smaller than the gravitational force of the carriage 2 and the vibration test objects 3 attached to it. If they were larger, the counterweight would not be able to follow the movement of the holder 2 during the vibration test.

[0027] Figure 6 shows schematically another design of the constant force source 4, consisting of a spring 11 connected at one end to the frame 10 and at the other end via a spring-loaded carriage 12 and a non-linear gear 13 to a rope 7. The spring 11 is factory tensioned to a gravity value G represented by the weight of the attached carriage 2 and all vibration test objects 3 mounted to it. When the spring-loaded carriage 12 moves downwards, thedeformation of the spring 11 and thus the force it exerts increases. However, the non- linear gear 13 reduces its gearing so that a constant force equal to the gravity G is still applied to the rope 7. Conversely, when the spring-loaded carriage 12 moves upwards, the deformation of the spring 11 and hence the force it exerts decreases. However, the non-linear gear 13 increases its gearing so that a constant force equal to the gravity G is still applied to the rope 7. A suitable non-linear gear is the Archimedean spiral.

[0028] Apart from a spiral, for example a four-joint mechanism or a cam can also serve as non-linear gear.

[0029] Figure 7 shows a schematic representation of an alternative design of the vibration testing apparatus in case it is necessary to consider at least partially the involvement of gravitational forces. The carriages 2 are arranged obliquely relative to the travel direction on the frame 10, where the angle, or sine of the angle of this oblique arrangement corresponds to the partial involvement of gravitational forces.

[0030] Figure 8 shows schematically another alternative design of the vibration testing apparatus that uses pulse force. Pulse force is a force of varying magnitude acting directly on different parts of the inserted object 5 subjected to the vibration test pulse force that is not caused by an inertial effect from acceleration. The inserted vibration test object 5 subjected to pulse force is mounted between the two moving carriages 2, which form the holder of the vibration test objects 5 subjected to the pulse vibration test. The vibrator 1 here also exerts force and a corresponding reaction force on the two moving carriages 2. Thus, the inserted vibration test object 5 exposed to pulse force is subjected to the required vibration force.

[0031] The apparatus from Figure 8 can also be arranged vertically as in Figure 4 or obliquely as in Figure 7.

[0032] Figure 9 shows schematically another alternative design of the vibration testing apparatus to those shown in Figs 2 and 8. The left-hand carriage 2 functions as both the vibration test object holder 3 and pulse vibration test object holder 5. The right-hand carriage 2 in Figure 9 only functions as pulse vibration test object holder 5. Between the two carriages 2, both the vibrator 1 and the pulse vibration test object 5 are located. The right-hand carriage 2 may also function as vibration test object holder 3.

[0033] Figure 10 shows schematically another alternative design of the vibration testing apparatus.The vibrator 1. force is used to vibrate multiple carriages 2..

[0034] In Figure 11, another vibrator 1 is mounted in serial arrangement next to the vibrator 1 to modulate the vibration force on the carriages 2 and the vibration test objects 3 attached thereto. The serially connected vibrators 1 ensure superposition and modulation of the vibration forces. The benefit of this setup is that one vibrator 1_ provides one part of the vibration spectrum, typically with a larger amplitude and lower frequency, on which the other vibrator 1 superimposes a second part of the vibration spectrum, typically with a smaller amplitude and higher frequency.

[0035] Figure 12 shows mounted vibrators 1 that can modulate different forces on each of the carriages 2 and vibration test objects 3 attached thereto. The magnitude of the forces in each branch of the connection of the vibrators 1 depends on the ratio of the weights of the carriages 2 with the attached objects 3 thereto and the weight of the vibrators L The serially connected vibrators 1 ensure superposition and modulation of the vibration forces. The vibrators j_ connected in parallel provide identical vibration forces on all connected carriages or other vibrators. The connection of the vibrators 1 may be serial, parallel or combined serial and parallel and variously hierarchically branched.

[0036] Figure 13 shows schematically another design of the vibration testing apparatus that uses pulse force. The inserted object 5 exposed to pulse force is fixed in multiple points, here totalling three, to multiple moving carriages 2, here totalling three.

[0037] All the described variants can be mutually combined. The variants are shown schematically. The connection of the vibrators to the carriages or the attachment of the inserted objects to the carriages, -shown schematically, is executed as rigid, usually by rods. Ropes can be replaced by belts, straps, chains, or drawbars. Vibrators are usually implemented as electromagnetic vibrators or hydraulic vibrators. Vibrators can also be spring-loaded with an additional drive to counter resistance losses. Spring-loaded vibrators can store and release energy during movement.

[0038] The vibrators are controlled by computer.

[0039] The principal advantage is the use of the otherwise absorbed reaction force of the vibrator for the vibration testing. This will have a positive effect in terms of smaller required size of thevibrators and less stringent requirements on the design of the holders - here the moving carriages and frames, and on energy consumption.

[0040] Another advantage is the possibility of partial modulation of the vibration forces without the need to always use the vibrators strictly separately.

[0041] Industrial Applicability

[0042] The vibration testing apparatus according to the present invention can be used for all vibration tests of a variety of products and also for determining the fatigue limits of materials.

[0043] Vibration tests are used to test a wide range of products that must withstand mechanical vibrations, shocks or other dynamic forces in real life conditions including in transport, and to verify reliability of products against vibrations. Some of the main product categories for which vibration testing is carried out include the automotive industry (e.g. shock absorbers, locks, chassis components, plastic parts, but also complete vehicles), aerospace (e.g. engines, fuel tanks, components, electronics), the space industry (e.g. satellites, rockets, instruments; in these applications vibration testing is mandatory for flight clearance), electronic and telecommunications equipment (e.g. mobile phones, tablets, computers and other electronic devices, circuit boards, connectors, batteries, consumer electronics), machine engineering (e.g. engines, pumps, compressors and other heavy machinery as well as machinery, equipment and other mechanical systems subject to vibrations), packaging materials to verify that the packaging will protect the products from mechanical damage during transport and handling, and other products.PATENT CLAIMS

[0044] 1. Vibration testing apparatus comprising a vibration test object holder connected to a vibrator and to a frame, characterized in that the vibrator (1) is connected to at least two carriages (2) moving on the frame (10), between which the vibrator (1) is positioned, wherein the carriages (2) function as holders for vibration test objects (3) and / or pulse vibration test objects (5), in which the objects (5) subjected to pulse force are positioned between the carriages (2).

[0045] 2. Vibration testing apparatus according to claim 1, characterized in that the carriages (2) are connected to a constant force source (4) mounted on the frame (10).

[0046] 3. Vibration testing apparatus according to claim 2, characterized in that the constant force source (4) comprises a pulley (6) and a counterweight (8) carried by a rope (7).

[0047] 4. Vibration testing apparatus according to claim 2, characterized in that the constant force source (4) comprises a spring (11) on a spring-loaded carriage (12) connected via a non-linear gear (13) to a rope (7).

[0048] 5. Vibration testing apparatus according to claim 1, characterized in that the object carriers (3) on the carriages (2) are arranged at a non-uniform height above the frame (10) and form an acute angle to the carriage travel path (2).

[0049] 6. Vibration testing apparatus according to claim 1, characterized in that the vibration test object (3) is mounted on one of the carriages (2) or the pulse vibration test object (5) is mounted on at least two carriages (2).

[0050] 7. Vibration testing apparatus according to claim 1, characterized in that the vibrator (1) is coupled to at least three carriages (2) and / or vibrators (1).

Claims

List of Reference Symbols1 vibrator2 movable holder - carriage3 vibration test object4 source of constant force5 object subjected to pulse force 6 pulley7 rope8 counterweight9 position adjusting drive10 frame11 spring12 spring-loaded carriage13 non-linear gear

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