HAMPL, Jason (Starochodovska 66A, Prague 4, Prague, 14900, CZ)
Claims
1. A testing device for simulating impact on tested objects mounted on a sled (21) by acceleration of an impacter 1 controlled by a driving equipment associated with an energy source characterized in that it comprises at least one cam (4) driven by an impute shaft (5) associated with the energy source and having a transitory surface portion (42) and an active surface portion (41) for engagement with a roller (12) coupled to the impacter (1) whereby the active surface portion (41) of the cam (4) is formed into a shape, which, when followed by the roller (12) upon rotation of the cam (4) produces a predetermined course of acceleration of the impacter (1).
2. The testing device of claim 1 characterized in that at least one additional cam (4) with alternative shape of the active surface portion (41) to produce another predetermined course of acceleration of the impacter (1) is slidably mounted on the impute shaft (5) to engage the roller (12).
3. The testing device of claim 1 or 2 characterized in that the impute shaft (5) bears a rope winch (5) with a rope (6) attached thereto by one of its ends, the other end of the rope (6) being connected to the energy source.
4. The testing device of claim 3 characterized in that the energy source is a linear engine in the form of a elastic ropes bundle (7) attached by its one end to the rope (6) and fixed by its other end to the device structure.
5. 5. The testing device of claims 4 characterized in that the anchored end of the elastic ropes bundle (7) is adjustable relative to the direction of forces exerted by the elastic ropes bundle (7).
6. The testing device of any of claims 1 to 5 characterized in that the motion of the roller (12) off the active surface portion (41) is restrained by a shock absorbing assembly (8) positioned for engagement with a spring disc (14).
7. The testing device of any of claims 1 to 6 characterized in that the reversible motion of the linear engine (7) is restrained by a shock absorbing assembly (9) positioned for engagement with a side stop (54) provided on the rope winch (51). |
Description
Testing device for simulating impact on tested objects
Technical Field
[0001] The invention relates to a device for simulating impact on tested objects mounted on a sled by acceleration of an impacter controlled by a driving equipment associated with an energy source.
[0002]
Background Art
[0003] A usual method how to simulate the impact deceleration, i.e. a steep slowing down of a tested object, is a sharp stopping of a vehicle carrying a crash tested object such as a dummy with seat belts fastened. By this method, child restraint systems, seats for competition cars, partition walls separating passengers from the cargo space, etc. may be tested. The required deceleration rates may attain a value corresponding up to ten times the gravity acceleration and the tested object speed is expressed in tens of kilometers and the braking distance in decimeters.
[0004] A most conventional breaking system uses a resilient bush made of plastics with reversible deformation properties, inserted in a steel tube and provided with a hole the diameter of which is smaller than the diameter of a pin. The pin is connected to the tested object and is protruding into the bush during the impacting process. The kinetic energy of the moved object is thus absorbed by friction between the surface of the pin and the internal surface of the bush hole. The required rate and diagram of deceleration during the intrusion of the pin into the bush is achieved by providing variable diameters of the bush hole. Such breaking device is presumed to be used, for example, pursuant to UNECE Regulations No. 16 and 44 (although other methods with the same effect are not excluded).
[0005] Nevertheless, it may be understood that even upon maintenance of the prescribed bush temperature, the actual pin deceleration value will fluctuate due to the age and history of the bush exposed to tens of repeated tests. Therefore, the above-mentioned standards allow for relatively broad limits, in which the diagram of deceleration is defined,. For example, with UNECE Regulation No. 44, the limit for maximum
deceleration is 20 - 28 g. This may lead to disputable statements as to the compliance with the prescribed standards.
[0006] Concerning the physical effects, the impact deceleration may be substituted by impact acceleration exhibiting the same time behavior . To this effect, various devices called also catapults have been used. For example, UNECE Regulation No. 44, Series of Amendments No. 04 (§ 8.1.3.12.1.3.2 and Annex 7, Appendices 1 a 2) admits the use of a catapulting device.
[0007] US pat. No. 5,623,094 discloses a pneumatic catapult device, the general object of which is to accommodate the diagram of acceleration of an impacting member - impacter - simulating a barrier to the actual diagram of deceleration of the tested object during the collision taking into account all the deformation zones that may have influence on the course of deceleration. To this effect, in the principal embodiment the tested object is placed on a first carriage and the impact member on a second carriage slidably mounted on the first carriage carrying a pneumatic cylinder absorbing the kinetic energy of the second carriage. The carriages are thus accelerated at different rates. Nevertheless, the patent does not describe in example a system capable of performing an exact control of the course of acceleration.
[0008] Hydraulic driven catapults simulating the course of acceleration of an impacter by precise and prompt controlling the flow rate of a fluid moving at a high speed through the hydraulic system are also known from the prior art. Such systems may simulate various rates and diagrams of acceleration, which due to a feedback system may be maintained within relatively close limits. Such high flexible and sophistic systems are, however, very expensive and therefore more suitable for research and development purposes than for a routine practice of testing laboratories and shops.
[0009]
Disclosure of Invention
[0010] The primary object of the invention is to provide a simple and cost effective testing device for simulating impact by acceleration and designed to
practical impact testing and enabling to generate by simple means various acceleration rates and diagrams of an impacter dependent on the properties of the respective deformation zones of tested objects.
[0011] In carrying out the above object of invention a device for simulating impact on tested objects mounted on a sled by acceleration of an impacter controlled by a driving equipment associated with an energy source is provided. Substantially, the device comprises at least one cam driven by an impute shaft associated with the energy source and having a transitory surface portion and an active surface portion for engagement with a roller coupled to the impacter, whereby the active surface portion of the cam is formed into a shape, which, when followed by the roller upon rotation of the cam produces a predetermined course of acceleration of the impacter.
[0012] In an alternative embodiment, at least one additional cam with alternative shape of the active surface portion to produce another predetermined course of acceleration of the impacter is slidably mounted on the impute shaft to engage the roller.
[0013] In a more specific embodiment, the impute sharp bears a rope winch with a rope attached thereto by one its ends, the other end of the rope being connected to the energy source.
[0014] The energy source may be a linear engine in the form of a bundle of elastic ropes attached by its one end to the rope and fixed by its other end to the device structure.
[0015] In an alternative embodiment, in order to adjust the energy capacity of the energy source, and thus the final speed of the testing sled, the anchored end of the elastic ropes bundle is adjustable relative to the direction of forces exerted by the elastic ropes bundle.
[0016] In each of the embodiments, the motion of the roller off the active cam surface portion is restrained by a shock absorbing assembly positioned for engagement with a spring disc and the reversible motion of the linear engine is restrained by another shock absorbing assembly positioned for engagement with a side stop provided on the rope winch.
[0017] The device according to the invention shows minimum components, which may guarantee its maximum reliability and minimum trouble-causing
incidents. Its operation is simple and enables selection and performance of a desired or required course of acceleration consistent with the requirements of standards by selecting a suitable shape of the cam. As compared with a hydraulic controlled catapult, the production cost of the device is considerably lower which in turn may result in low operating costs.
[0018]
Brief Description of Drawings
[0019] Fig. 1 is a schematic view showing substantial parts of one embodiment of the testing device;
[0020] Fig. 2 illustrates acceleration diagrams and the limits defined by applicable standards.
[0021]
Best Mode for Carrying Out the Invention
[0022] As an example of preferred embodiment a testing device - catapult - for dynamic tests simulating the impact into a front part of a vehicle was elected. The tested object was a child-safety chair with a dummy situated in the direction of the simulated vehicle driving. This arrangement is consistent with Section 7.1.4.4.1.1. of EEC Regulation No. 44-04. The basic calculation was made in order to verify the feasibility of this embodiment according to the invention. More specifically, the calculation was made to determine the shape of the cam used for simulation of this type of impact.
[0023] In the embodiment shown in Fig. 1 , the child-safety chair 3 with a child dummy is placed on a sled 21. The sled 21 is slidably mounted on rails 2, which may be equipped with wheels for moving in the testing area in order to reduce friction. This part of the device, i.e. the sled system, is shown only for better understanding of the purpose of the invention and is demonstrated on a smaller scale. To simulate an impact initiated by swift pushing the sled 21 against the tested object an impacter 1 is provided for contact with the tested object at one end and fitted with a roller 12 with antifriction bearing at the other end. The impacter 1 is urged by a spring 13 over a spring disc 14 to engage by its roller 12 a cam 4. The cam 4 is
mounted on a fluted shaft 5 and its outer periphery is composed of an active surface portion 41 and a transitory surface portion 42. The active surface portion 41 is formed to such a shape that upon rotation of the cam
4 the required and predetermined course of acceleration of the impacter 1 derived from rolling the roller 12 along the active surface 41 of the cam 4 is achieved. For various types of acceleration diagrams a number of cams 4 with appropriately shaped active surfaces corresponding to desired acceleration diagrams types may be slidably mounted on the fluted shaft 4 and thus adjustable into the position in contact with the roller 12. The shaft
5 further bears a rope winch 51 to which a pull rope 6 is firmly attached. The opposite end of the pull rope 6 is attached to an energy source - in this embodiment to a linear engine in the form of an elastic ropes bundle 7. To stop the impacter 1 at the end of its movement before the roller 12 reaches the transitory surface portion 42 of the cam 4 a first shock absorber assembly 8 is mounted on the immovable part of the testing device structure. To stop the delayed rotation of the rope winch 51 and that of the cam 4 before the roller 12 engages the opposite end of the transitory surface portion 42, the rope winch 51 is provided with a side stop 54 for engagement with a second shock absorber assembly 9 also mounted on the immovable part of the testing device structure. The shaft 5 bearing the rope winch 51 is driven through a clutch 10, pinion 52, and crown gear 53 assembly by an external motor 101. By winding up the pull rope 6 on the rope winch 51 , the elastic rope bundle 7 is stretched and linear motor loaded by energy. The anchored end of the elastic ropes bundle 7 is mounted for longitudinal motion on the immobile testing device structure in the direction of the pull rope 6, more specifically in the direction of the force exerted by the elastic ropes bundle 7. This arrangement enables to set the maximum extension of the elastic ropes bundle 7 by election of the corresponding position of the anchored end of the bundle and thus to adjust the energy capacity of the linear motor and finally the speed of the sled 21. Fig 2 illustrates the limits of admissible acceleration diagrams expressed as gravity acceleration (g) - time (milliseconds /ms/) relationship pursuant
to the respective EEC Regulation No. 44. Curves L1 and L2 define the limits of the testing field and curve K characterizes the predetermined acceleration diagram, from which the shape of the active surface portion 41 of the cam 4 is derived and calculated..
[0025] The energy source for driving the testing device is the elastic ropes bundle 7 wherein the character of the tensile force exerted thereby is subject to a minor non-linearity dependent on the rate of contraction. This force is maximal at the time the impacter 1 and the sled 21 begin to accelerate and subsequently declines by a step by step process Nevertheless, the required acceleration of the sled 21 and the necessary acceleration force shall exhibit a different behavior. They should grow from the zero point or almost the zero point to a maximum and then to turn back to the zero point. The differences in such a behavior and the growth of kinetic energy of the sled 21 require that the transmission realized by the cam 4 fixed on the common fluted shaft 5 along with the rope winch 51 and the steel wire rope 6 attached to the elastic ropes bundle 7 is variable. At the beginning of the catapulting process, when the required acceleration of the sled 21 is low, or even zero, the energy of elastic ropes is absorbed mostly by acceleration of the rope winch 51 and the cam 4. Their kinetic energy is later added to the energy of elastic ropes upon the acceleration of the sled 21..
[0026] As elastic ropes, rubber ropes of 20 mm in diameter were used. The relationship between the rubber rope force and its extension was approximately linear with a minor progression in the area of 60 to 80 percent of its extension. The force required for the extension of the rope was higher than the rope releasing force due to a hysteresis effect. The total force exerted by the elastic ropes bundle 7 prepared for catapulting was 29.6 kN. This force was transmitted to the rope winch 51 by a steel wire rope 6 of 12.5 mm in diameter and having the load capacity of 93 kN. The coefficient of safety was 3.14. The additional bending stress of the rope 6 was very low as the diameter of the rope winch 51 was almost 70 times higher than the diameter of the rope 6. The maximum inertia force of the sled 21 amounted 84 kN by this test.
[0027] After completion of the simulated impact, both the impacter 1 and the sled 21 moved through the testing device at a speed slightly exceeding 50 km per hour. The sled 21 was stopped by friction breaks applied to the rail 2, on which the sled 21 moved. The breaks are not shown in Fig. 1.
[0028] The elastic ropes bundle 7 was installed below the stopping track of the sled 21 and therefore a distance of about 4.8 m was available for this track. The corresponding required deceleration rate amounted to about 2 g and lasted approximately 0.7 sec.
[0029] After completion of the acceleration process, the motion of the impacter 1 was stopped at a much shorter distance by the effect of the return spring 13 and the shock absorption assembly 8.
[0030]
Industrial Applicability
[0031] The device according to the invention may be used by testing shops performing dynamic tests of safety systems to satisfy the regulatory authorities. It may be used as well by testing laboratories of manufacturers producing safety systems to control their current production and subject to minor modification to the device, even for research and development purposes.
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