NL8004985A - Granular casting compaction method - applies dynamic load initially purely vibratory and finally forming cyclical load - Google Patents

Abstract

The method compacts castings of granular material such as concrete or breeze blocks, the material to be compacted being statically supported on one side. A dynamic load is applied to the other side, consisting purely of vibration in the first phase, and changing into cyclical loading in the last one. The vibration and dynamic load can be applied by a linear hydraulic motor (13,14,15) connected to a hydraulic control unit of the rotary type or servo valve type, generating a symmetrical or asymmetrical load.

Description

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Leonard Teerling Roden (Dr) - Netherlands

Device and method for compacting granular materials by both symmetrical and asymmetrical cyclic loads

The invention relates to a method for compacting moldings from granular materials such as concrete bricks and concrete clinkers, etc., by vibrating and applying cyclic loads to the moldings.

This effect is obtained with a device that can generate both a symmetrical and an asymmetrical vibration pattern.

In particular, being able to vibrate asymmetrically is essential in many compaction processes. Certain similarities exist with patent application 7906784, characterized in that in said patent application the molding of the molding is effected by lifting the molding with a specific frequency and dropping it on a separate shock device, while at the top of the molding there is a constant adjustable top load. This seems to be a good method for low-noise compaction of relatively 15 "dry concrete" for concrete tiles.

However, according to the present invention, the production of concrete bricks and clinker whose concrete mixture is slightly wetter can be carried out in an even quieter manner. The integration of the method into an installation is herein also easier to realize than in patent application 79067 & 4.

The current concrete block presses on the market deliver a noise level of more than 105 dBA. This noise level may be considered harmful to the health of the operating personnel. Although in general the quality of the concrete blocks produced may be called good, quality problems nevertheless arise with slight changes in the concrete mixture. Due to the very limited controllability, correction is a difficult process with often long downtimes. It should be noted that the high noise level is mainly due to impact noise, between the mold die and shim.

This is due to the axis offset between the direction of movement of the rotating eccentric masses and the directions of movement.

800 4 985 2% t t Λ of shim, molds, molding and top punch. For a high "impact force", a high rotation frequency is desired. However, the magnitude of the phase shift also increases with the frequency, and with it the noise level.

The aim of the invention is to provide an apparatus and method which obviates the aforementioned drawbacks and / or limitations. This objective is achieved with a hydraulic compaction system in which compaction is not effected by a kind of "shocking" vibration with rotary vibration motors, on which principle the compaction of, for example, concrete bricks is now achieved, but by applying cyclic loads on the molding whereby the load build-up is preferably asymmetrical. The water content, whereby the aforementioned concrete moldings are compacted, makes this method precisely possible. The concrete molding undergoes a kneading effect under cyclic loading, which is enhanced by the favorable water content or water-cement factor with which it is possible to work, as well as by the elastic behavior of the molding during this kneading process. As a result, the individual grains can move in the molding and thereby produce the most dense packing. Depending on the constructive design of the entire processing plant to be chosen, the cyclic load can be printed either from below or from above.

It will be clear to a person skilled in the art that, because the compaction mechanism acts directly on the molding and the contact between the punch and molding is maintained, there is little opportunity for the development of contact noise. According to the current state of the art, there are sufficient and simple means or measures to keep the noise level of the hydraulic installation itself below 75 to 0 dBA.

The invention, which relates both to the device 30 and the method of the device, will be explained in more detail with reference to drawings in which exemplary embodiments are presented.

Fig. 1 shows a hydraulic diagram with control device at a bottom drive.

Eig.2 shows a speed, acceleration and amplitude variation of the driven vibrating table.

Fig. 3 shows an exemplary embodiment of another possible embodiment of the control device.

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Fig. 4 shows a third exemplary embodiment of a possible embodiment of the control device.

Fig. 5 shows a cross section of the control device according to the drawn cetop symbol in Fig. 1 and Fig. 3 · 5 Fig. 6 shows a cross section of the control device according to the drawn cetop symbol in Fig. 4 ·

Fig. 7 shows the deflection of the circumference of the rotor and the sleeve of the control device, in accordance with the drawn cetop symbol of both Fig. 1, Fig. 3 and Fig. 4. Fig. 9 to 12 schematically show possible methods

Fig. 13 shows the pressure build-up under cyclic loading.

In the hydraulic scheme (fig. 1) of the drive, the hydraulic pump 1, which is preferably pressure-controlled, sucks hydraulic fluid from the reservoir 2 and presses it via line 3 and the control device 4 to the linear hydraulic motor or vibration cylinder 5 ·

The vibration cylinder 5 drives a vibrating table 6, the latter being resiliently supported by the air bellows or air cylinders 7 and 8. In addition to air bellows, in some cases simple spring elements such as rubber and / or steel springs can also be used.

In the hydraulic scheme 9 is a so-called hydraulic accumulator for the purpose of absorbing pressure surges and accumulating hydraulic fluid at times when no fluid is supplied from line 3 via control device 4 to vibration cylinder 5 ·

The control device 4 is a so-called rotary control member in an embodiment in which it is possible to generate asymmetrical vibrations. Rotary controls, also known as hydraulic pulse or alternating current generators, are known in their basic form from the literature and from patent applications. However, to date it has not been possible to generate an asymmetrical vibration with the known embodiments. The hydraulic impulse generator 4 according to the invention comprises a rotating part 10 and an accumulator 11 which can be brought to a higher or lower pretension pressure via connection 12.

The operation of the impulse generator will be explained partly with reference to figure 2. During the trajectory t1, hydraulic fluid is supplied under pressure to the vibration cylinder 5, both to the space 13 and to the space 14. Due to the surface difference of the piston and the piston rod, the plunger 15 and the vibrating table 6 connected thereto move upwards. .

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Connection P is here connected to both A and B. When the plunger 15 has traveled the distance X1 and the plunger speed has become V1, high pressure hydraulic fluid is no longer supplied to the space 13, but only liquid under 5 pressure is in space 14, whereby the plunger 15 is delayed by a2 over the track t2. The speed V1 is reduced to zero when the amplitude becomes X2. B is connected to I and A to P. In this case, to prevent the underpressure t2 from forming underpressure in space 13, the generator is provided with a possibility of afterpressing hydraulic fluid under low pressure to space 13. This afterpressing takes place both. via channel 18 through the generator and line 19 to room 13, but is also possible via channel 16 through non-return valve 17 and line 20 to room 13 · This additional option is desirable if X2 ^> X1 at relatively low frequencies. After pressing, the hydraulic fluid is withdrawn from the accumulator 11. The size of the napers pressure can be adjusted by an adjustable throttle valve 22 placed in line 21. When traveling the path t3, the direction of movement of the plunger is downward. As with the path t2, B is connected to T and P to A. However, because the direction of movement of the plunger is now downwards, a back pressure (deceleration) is built up in space 13 by a throttle 23 built into the pulse generator. cross-section of the through-flow hole in this exchangeable throttle 23 results in a greater or lesser delay time t3 · The path X3 traveled in time t3 is thereby recorded. The connection P with both A and B is then established again.

The speed V3 is reduced to zero by the now upward acceleration a4e a1. The road X4 is taken here. The operating frequency can be varied by means of an adjustable drive 24.

The maximum occurring accelerating force is directly proportional to the prevailing system pressure. Because the system pressure is separate from the frequency, it is clear that a high "centrifugal force can be achieved even at a low frequency, unlike vibratory motors with eccentric rotating masses. Bigger or smaller. amplitudes can be achieved by varying the frequency, whether or not in combination with decreasing or increasing the system pressure and possibly the air pressure in bellows 7 and 8.

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It is clear that to obtain a desired amplitude profile, and in particular an asymmetrical amplitude profile, the "napers device" as well as the interchangeable throttle are essential.

The most determining factors in the compaction process are the magnitude of the acceleration as well as the duration of the acceleration occurring. Increasing or decreasing the frequency increases or decreases this duration. The amplitude that occurs is a logical consequence of this situation (X = £ at2). This also means that the acceleration and duration parameters can be controlled from a direct amplitude control. For these reasons it is preferable to choose air springs or air cylinders as resilient elements, whereby by "playing" with differences in air pressure between bellows 7 and 8, without having to be regulated in the hydraulic system, directly both acceleration, speed if amplitude can be varied. This method is important if the compaction process is to be adjusted by either changes in the compaction mixture or the total mass to be vibrated changing. The mutual relationship t1, t2, t3 and t4 is determined by the opening time or the size of the openings in the rotor and housing of the impulse generator 10. In Figs. 3 and 4 other embodiments of the impulse generator are given in cetop symbols.

The control device 4 of figure 1 is shown in cross-section in figure 5, wherein in figure 5a the position of rotor 25 and bush 26 corresponds to the switching position for the section t4-t1 (of figure 2), figure 5b of section t2 and figure 5c of route t3.

In the drawn position of Fig. 5a, pressurized hydraulic fluid flows at P into the annular channel 27 and through channels 28 in the periphery of the sleeve 26 into the annular space 29. Depending on the number of pulses per revolution desired, hydraulic fluid through as many slotted channels 30 in the circumference of rotor 25 through openings 31 in the annular space 32 to connection B. In the switching position of fig. 5b the slots 33 have come for the openings 31 so that from space 34 under low pressure 35 hydraulic liquid can be squeezed. The hydraulic fluid is assisted for this purpose by a piston or diaphragm 35, under a low positive gas pressure in space 36. In the switching position of figure 5c, hydraulic fluid flows in the reverse direction again 800 4 985 * »6 through the annular space 32- the openings 31-channels 37, through the throttle 23 to the connection T.

The drawn outline of the circumference of the rotor and sleeve according to the figures resp. 7a and 7b are in accordance with the above.

It is noted that, although it is not preferred, it is also possible to cancel the switch position according to Fig. 5b and to allow only the low-pressure after-press to take place outside the generator. As shown in Figure 3. In this situation, the deflection of the circumference of the rotor and sleeve will be corresponding to Fig. 8a and Fig. 8b, respectively.

Another embodiment is shown in figure 6. This embodiment in fact combines the switching positions of figures 5a and 5b.

A "throttle check valve" 38 is placed in the rotor 25, which is pressed lightly by spring 39 on the seat 40. If under pressure 15 of the track t2 (fig. 2) underpressure threatens to arise in 32- 31- 37- 39 , due to the pressure difference between spaces 34 and 39, the check valve 38 will open and low pressure hydraulic fluid can be pressed. After passing through route t2, the "post-flow" comes to a standstill, the liquid pressure in spaces 34 and 39 becomes equal and the non-return valve closes again on seat 40. Then, when running through route t3, the hydraulic fluid flowing from B to I will flow through the narrow the flow-through opening of valve 38 undergoes a pressure drop, whereby the plunger 15 (fig. 1) returns with a delay.

I note that the outlined provisions for the traversing of paths t2 and t3 are especially necessary when working with lower frequencies. This applies to both symmetrical and asymmetrical vibrations. Impulse generators as described hitherto in patents and patent applications do not provide for this. When working with higher frequencies, in the order of 30 above 40 to 80 Hz, the napers provision is less critical. Above this frequency, "expansion" of the compressed hydraulic fluid in space 13 (FIG. 1) will be able to absorb the volume change that occurs when depositing the small 7 amplitude 12 occurring at higher frequencies. Likewise, the posterior provision will both 35 at high and low frequencies, are hardly necessary if the impulse generator is not used for reciprocating or moving up and down masses, but is used, for example, for picture fatigue devices where the hydraulic fluid pressure must vary and the mass forces are small.For the latter application, patents and patent applications exist in which the switching moments of pressure build-up are regulated, by placing the slots in the circumference of the rotor in a certain pattern relative to each other. then not in combination with an extra linear movement of the rotor, so impulse generators of this type are not very suitable for generating mass we went.

The inventor is aware that a so-called hydraulic servo valve can also be used as a control device for making the method of compacting possible. The vibration pattern is electronically controlled. This control device is not preferred for the present method because of both the much higher price, and because of the greater vulnerability when working in relatively dusty and dirty conditions.

When compacting concrete moldings, according to the method of the present invention (Figures 9 to 12), the initial phase of the compaction process will involve moving the mass to be compacted up and down (as outlined in Figure 1). and as the compaction process progresses, transition to a pure cyclic pressing process in which the concrete undergoes a varying pressing pressure as outlined in figure 13 · Even in the final phase of the compaction process it is possible to release the stamp from the molding so that at the bottom It is "shocked" with a small amplitude and hence with a still relatively low sound level. This extra option is important in the case of compacting fairly dry concrete, as is usual with concrete tiles. Fig. 9 shows the preferred embodiment of the device with the drive at the bottom (Fig. 1), the method of which is as follows. The molding 42 is enclosed by a bottom punch 6 and a top punch 43. The top punch 43 is connected to the plunger 44 of the hydraulic cylinder 45.

The plunger 44 exerts a small adjustable positive pressure on the molding 42 via punch 43. When driving plunger 15, the molding 42 will initially settle or compact under the influence of purely the vibrating movement, preferably asymmetrically, of the lower die . During settling, the upper punch will descend 43.

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The wedge on which the bagging is structurally arranged is not essential for the invention. For example, one can start from a hydraulic system for operating the upper cylinder 45, whereby provisions are made to discharge the hydraulic fluid in space 47 without pressure during the compacting process, via line 49 to the reservoir, while in space 46 there is an overpressure and hydraulic fluid is immediately pressed via line 48 as plunger 44 "drops". This settling under the influence of pure and only the vibration takes place within a time frame of about 1 to 2 seconds, whereby about 90 $ δ of the final compaction is reached. The compaction process by pure vibration then automatically switches to cyclic loading without the need for additional actions. This effect is caused by the fact that the plunger 15 speeds is hindered more in its movement because the valve 61 in line 48 prevents the hydraulic fluid from flowing back from space 46. Pressure is built up in space 46 to a level at which the reaction force in plunger 44 becomes the same as the maximum occurring force in plunger 15. The amplitude that plunger 15 then makes depends on the elasticity of molding 42, but more so on the compressibility of the hydraulic fluid in space 46. If additional "shocks" are required, as described in lines 23 to 27 of page 7, the installation of a tap in line 49 is necessary. When the required compaction of molding 42 is reached, the drive of cylinder 5, 25 stops, after which the lifting mold 60 either lowers or lifts with the aid of lifting cylinders 60 so that the molding 42 is released and can be removed from plunger 44 after lifting. One can also think of simultaneous lifting of mold 50 and molding 42. The molding 42 remains suspended in the molding mold 50 on adhesive, whether or not combined with a vacuum via top punch 43 · After supply of a supporting board, cylinder 45 is plungered 44 the molding 42 is pressed out of the molding die 50 onto this underlay board.

An alternative method shows Fig. 10 where the cyclic loading is imposed from above, with the difference that the hydraulic fluid in space 63 is pressureless and connected to the fluid reservoir. A hydraulic alternating pressure is only imposed in space 62. Here, too, the compaction under the influence of the vibration will initially be effected, to gradually progress to an 80 0 4 985 * * 9 cyclic load. In this method, the molding 42 is produced directly on the shim 64. In order to obtain the same compaction quality as in the method of fig. 9, a slightly damp concrete mix will generally be necessary.

The method according to Fig. 11 is practically similar to that of Fig. 10, with the difference that the shim is later supplied in accordance with the method of Fig. 9 and that a metal shim 65 is used which rests on a possibly slightly resilient surface 66 made of, for example, rubber or plastic.

In figure 12, every time the alternating pressure in space 62 is minimal, the springs 77 will lift the molding 42 by a stroke or amplitude which depends on the minimum set pressure in space 62.

In the downward movement, base plate 65 strikes an anvil 66, which can optionally be made somewhat resilient. This method is suitable for the somewhat drier concrete mixtures.

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Claims (13)

Method for compacting moldings from granular materials such as concrete bricks and concrete pavers, characterized in that the material to be compacted is statically supported on one side, while on the other side a dynamic load is exerted which emerges in the first sealing phase. pure vibration exists and in the final phase changes into a cyclical load. 2. Method according to claim 1, characterized in that the dynamic loads and vibrations are imposed on the material to be compacted by means of at least one linear hydraulic motor connected to at least one hydraulic control device of the rotation type (impulse generator) or of the type servo valve which generates a symmetrical or an asymmetrical load. 3. Method as claimed in claims 1-2, characterized in that when the dynamic loads are imposed on the underside of the molding, the lower punch is resiliently supported by preferably linear air motors (air bellows, air cylinders) as outlined in figure 1, with which the compaction system can be influenced or adjusted by varying the air pressure in the counteracting linear air motors. 20 Method according to claims 1-3, characterized in that the mold itself does not undergo dynamic loads and therefore does not belong to the co-accelerated or co-loaded mass. 5. Method according to claims 1-4, characterized in that such provisions are arranged and such a working sequence is followed that the moldings can be easily removed after compaction, as described in lines 23 to 32 of page 8. . 6. Method as claimed in claims 1-5, characterized in that a shock proof 30 can be applied as the last sealing phase after cyclic loading, by releasing the lower stamp from the molding in the situation of dynamic loading at the bottom and in the situation of dynamic loading at the top, the molding at the bottom being lifted by the spring support and then impacting on a sub-anvil on the downstroke. 80 0 4 985 1 -m Method for the method as claimed in claims 1-6 for generating symmetrical or asymmetrical vibrations, characterized in that this hydraulic control device is preferably a rotary control valve (impulse generator), with at least one napers-5 provision for negative pressure in the linear hydraulic motor to be driven and contains provisions for making the stroke of the linear hydraulic motor in heath directions of movement of unequal duration 8. Device as claimed in claim 7, characterized in that the napping device (s), the main elements of which consist of a piston-diaphragm or bellows-type accumulator with a series-connected check valve, preferably integral with the remainder of the impulse generator but possibly also in the hydraulic system outside the generator. 9. Device according to claims 7-8, characterized in that two annular spaces which are in constant communication with each other are recessed in order to obtain a short and low-loss path of the hydraulic fluid in the impulse generator, in the rotor and the sleeve. and where the connections P (press), A (conn. piston rod side) and ka (conn. press accumulator) terminate. 10. Device as claimed in claims 7-9, characterized in that the hydraulic fluid to be supplied to connection B (conn. Piston side) flows from the annular space in the rotor through at least one, preferably slot-shaped, channel in the circumference from the rotor via as many openings in the sleeve to an annular space on which at least one connection B opens. 11. Device according to claims 7-10, characterized in that the hydraulic fluid flowing from connection B to connection T is not discharged along the circumference of the rotor as when feeding, but via centrally drilled channels in the rotor and subsequently in the longitudinal direction through the rotor to the front side. 12. Device according to claims 7-11, characterized in that in order to enable afterpressing of hydraulic fluid under low pressure from connection T to B, through the impulse generator 35, provisions are made for this, which consist of at least one post slot in the circumference of the rotor between I and B, or a non-return valve, placed in the central drain in the center of the rotor. 800 4 985 tr *. V 13. Device as claimed in claims 7-12, characterized in that in order to obtain the desired delay time t3, a constriction is arranged in the central discharge channel in the rotor, either in the non-return valve as claimed in claim 12 or in an exchange-5. edible throttle plate in the center drain in the center of the rotor. 80 0 4 985