Vibration tamper

Abstract

The present invention relates to a vibration tamper, comprising a superstructure having a driving engine mounted on a machine frame and further having a guide bar, and further comprising a substructure having a compactor base driven by the driving engine and having a compactor plate and having a drive line, by means of which a drive connection between the driving engine and the compactor base is established such that the compactor base can move relatively to the superstructure along a compactor axis while executing at least one compacting amplitude. The driving engine of the vibration tamper is a liquid gas powered driving engine, wherein the superstructure and, more particularly, the guide bar on the superstructure, comprises a storage container for liquid gas, and wherein a gas supply line is provided to supply evaporated liquid gas to the driving engine.

Claims

1. A vibration tamper for ground compaction, comprising: a superstructure comprising a drive engine, which is mounted on a machine frame, and a guide bar; a substructure comprising a compactor base driven by the drive engine and a compactor plate; and a drive line, configured to establish a drive connection between said driving engine and said compactor base such that said compactor base can be moved relatively to the superstructure along a compactor axis (S) while executing at least one compacting amplitude, wherein the driving engine is a liquified petroleum gas powered driving engine, said superstructure comprises at least two storage containers for liquified petroleum gas, each of the at least two storage containers comprising a cartridge having a maximum filling capacity of not more than 1000 ml, and a gas supply line is provided through which evaporated liquified petroleum gas is supplied to said driving engine, wherein the at least two storage containers are replaceably disposed in a storage container holder disposed on said guide bar between two side beams of said guide bar, the storage container holder comprising a holding device for releasable fixation of each of said at least two storage containers in said storage container holder, and a lateral guard which at least partially shields each of said at least two storage containers in a respective side region thereof from the environment, and further wherein said at least two storage containers are connected in parallel to a piping system, including to said gas supply line, via a quick coupling system.

2. The vibration tamper according to claim 1, wherein the storage container holder comprises at least one of the following features: a) said storage container holder is vibration-cushioned relatively to vibration induced in the machine frame; b) said storage container holder is disposed on said guide bar in a vibration-cushioned manner; and c) said storage container holder is disposed on said guide bar between the guide bar mount on said machine frame and the rear grasping region on said guide bar, with respect to the main working direction.

3. The vibration tamper according to claim 1, wherein a protective cover is provided which is adapted to at least partially cover at least one storage container.

4. The vibration tamper according to claim 3, wherein said protective cover comprises at least one of the following features: a) said protective cover is mounted for rotation on said guide bar; b) said protective cover has a locking means for arresting said protective cover in a closed position; c) said protective cover has a holding device for fixation of at least one storage container in said storage container holder, wherein said holding device comprises: a resilient pressure applying element which is configured such that it exerts an effective contact pressure on said at least one storage container in said storage container holder in a closing direction of the protective cover, and/or a retaining and protective sleeve, which in its holding state, comes to bear, at least partially with its end marginal region, against at least one storage container.

5. The vibration tamper according to claim 1, wherein in said piping system there is provided, between a gas supply or at least one of said two storage containers and said driving engine, an evaporator adapted to ensure complete volatilization of the liquefied petroleum gas.

6. The vibration tamper according to claim 5, wherein said evaporator has a heat input port to which heat is supplied by way of at least cooling air warmed by the driving engine or by way of an oil circulation containing engine oil.

7. The vibration tamper according to claim 5, wherein said evaporator is mounted by a holder on the vibration tamper, wherein said holder is vibration-cushioned relatively to vibration induced in said machine frame.

8. The vibration tamper according to claim 7, wherein said holder comprises at least one of the following features: a) said holder is disposed on said guide bar of the vibration tamper by way of at least one vibration dampener; and/or b) said holder is part of said storage container holder in which the at least two storage containers are disposed.

9. The vibration tamper according to claim 1, wherein said vibration tamper comprises at least one the following features: a) an external oil cooler for the reduction of the engine oil temperature in said driving engine under working conditions; b) a tilt switching system, comprising a tilt sensor and/or an oil pressure sensor; and/or c) a piping system is at least partially disposed within said guide bar.

10. The vibration tamper according to claim 1, wherein an automatic shutdown system is provided which is configured such that said automatic shutdown system permits liquified petroleum gas to flow through an evaporator only when there is an adequate negative pressure in the suction pipe of said driving engine, and further wherein said automatic shutdown system triggers, in a pressure governor, blocking and unblocking of the flow of fuel.

11. The vibration tamper according to claim 1, wherein a gas sensor is provided which is adapted to determine the liquified petroleum gas concentration in the external environment of said vibration tamper, and an emergency shutdown is provided which switches off said driving engine when said gas sensor detects a predetermined concentration level in the external environment of the vibration tamper.

12. The vibration tamper according to claim 1, wherein said cartridge comprises one of a screw valve type cartridge or a bayonet valve type cartridge.

13. The vibration tamper according to claim 1, wherein each of said at least two storage containers has a maximum filling capacity for liquified petroleum gas ranging from 400 ml to 1000 ml.

14. The vibration tamper according to claim 13, wherein said cartridge comprises one of a screw valve type cartridge or a bayonet valve type cartridge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is explained below with reference to the exemplary embodiments illustrated in the figures, in which:

(2) FIG. 1 is a side view of a generic vibration tamper;

(3) FIG. 2a is a perspective oblique view taken from the right to the front of a vibration tamper powered on liquid gas;

(4) FIG. 2b is a diagrammatic rear view of the vibration tamper shown in FIG. 2a;

(5) FIG. 3 is a perspective detailed diagrammatic view of the guide bar as shown in FIGS. 2a and 2b taken obliquely from the rear right;

(6) FIG. 4 is a detailed diagrammatic view of the attachment means as shown in FIG. 3;

(7) FIG. 5 is an elementary circuit diagram of an attachment means comprising a plurality of storage containers connected in parallel;

(8) FIG. 6 is an elementary circuit diagram of a heat input port to the evaporator fed with engine oil;

(9) FIG. 7 is an elementary circuit diagram of a vacuum switching system; and

(10) FIG. 8 is a diagrammatic drawing of a tilt switching system.

DETAILED DESCRIPTION OF THE INVENTION

(11) Like components are designated in the figures by like reference signs. Recurrent components are not necessarily individually denoted in each figure.

(12) FIG. 1a shows a vibration tamper 1 comprising a superstructure 2a, wherein the superstructure 2a comprises a driving engine 3 and a guide bar 4. There are additionally present a substructure 2b comprising a compactor base 5 including a base plate 9 and a transport handle 8. The substructure 2b is linked to the superstructure 2a via a bellows 6. The guide bar 4 and the driving engine 3 on the superstructure 2a are indirectly interconnected via a machine frame 10 or interconnecting console 10. Inside the bellows 6 there is disposed a power transmission system, for example, a connecting rod, which converts the rotational driving power of the driving engine 3 to a linear motion and transfers it to the compactor base 5. Between the driving engine 3 and the compactor base 5, there is thus present, in all, a driving transmission 11, which is not described in greater detail and is known per se and by means of which the driving energy of the driving engine 3 is transferred to the compactor base 5. In operation, the compactor base 5 tamps in an approximately vertical direction along the compactor axis S, for example, at a frequency of approximately 10 Hz, over the road subsurface U and compresses the subground material. Guidance of the vibration tamper 1 takes place manually by means of the guide bar 4, which is mounted via resilient damping bearings 7 on the machine frame of the superstructure 2a. The main working direction a is that direction of motion of the vibration tamper under working conditions, in which the compactor axis S is forwardly inclined in relation to the horizontal ground level and in which it automatically moves under working conditions.

(13) The vibration tamper 1 is classified as a so-called walk-behind machine, whose overriding common feature resides in the fact that during operation the machine operator is walking behind the machine while guiding the ground compacting machine. Correspondingly, the main working direction a is also the direction of advance counter to the region of the guide bar 4 protruding from the machine.

(14) One aspect of the present invention resides in the fact that the driving engine 3 is one powered by liquid gas. This is further illustrated in FIGS. 2a to 8 with reference to the vibration tamper 1.

(15) FIGS. 2a to 4 illustrate further aspects concerned with the integration of the liquid gas powered driving engine 3 in the vibration tamper 1. In addition to the liquid gas powered driving engine 3 itself, elements on the superstructure 2a of the vibration tamper 1, particularly, the liquid gas supply system, are storage container holding means 14, such as a storage container holder, storage containers for liquid gas 15, an evaporator/pressure governor system 16, a piping system 17, an attachment means 18, and a protective cover 19.

(16) The liquid gas required for operation of the driving engine 3 is stored in the case of the vibration tamper 1 in the storage containers 15 on the vibration tamper 1 on the superstructure 2a itself. More specifically, in the case of the present exemplary embodiment as shown in FIGS. 2a to 4, the storage containers are two 0.425 kg gas cylinders, which are replaceably disposed in the storage container holding means 14 and directly stand on its base plate 26. As is visible, for example, in FIG. 3, the two gas cylinders 15 are in each case connected to the attachment means 18 via a quick coupler 20, which comprises, in addition to the end connectors 21 directed towards the quick coupler 20, a collecting block 22, the outlet side of which is connected to the piping system 17 leading to the driving engine 3. The two storage containers 15 are thus parallel to each other, so that liquid gas can be drawn from the storage containers 15 towards the piping system 17 simultaneously via the attachment means 18. The piping system 17 is thus functionally a gas supply line, through which the driving engine 3 can be effectively supplied with liquid gas. The piping system 17 can comprise for this purpose flexible and/or rigid piping, valve connections, etc.

(17) The liquid gas coming from the storage containers 15 is initially in a substantially liquid state. However, the driving engine 3 burns the liquid gas in the gaseous state. Between the driving engine 3 and the storage containers 15 there is disposed in the piping system 17 therefore an evaporator/pressure governor unit 16, to the inlet of which liquid liquefied gas is fed from the storage containers 15 and the outlet of which passes gaseous liquid gas on to the driving engine 3. The evaporator/pressure governor unit 16 is, in the present exemplary embodiment, a coherent component or a multifunctional module, in which an evaporator 23 and a pressure governor 24 are disposed, as described, for example, with reference to FIG. 6.

(18) FIGS. 2a to 3 illustrate, inter alia, the vibration-cushioned mounting of the storage container holding means 14 on the superstructure 2a relative to the machine frame 10 on the superstructure 2a. Due to the arrangement of the storage container holding means 14 on the guide bar 4, vibration attenuation of the machine frame 10 relative to the storage container holding means 14 is already achieved by the damping bearings 7 between the guide bar 4 and the machine frame 10. In the present exemplary embodiment, a further damping stage including the damping elements 25 is additionally provided between the guide bar 4 and the storage container holding means 14. The storage container holding means 14 is thus mounted an the guide bar 4 via the damping stage 25, although direct mounting of the storage container holding means 14 on the guide bar 4 is also possible and is included within the scope of the present invention. The storage container holding means 14 comprise substantially a trough shaped basic body having a base plate 26 and two side walls 27 disposed in the lateral marginal area of the base plate 26 and rising in the vertical direction. By means of said side walls 27, the trough-like storage container holding means 14 are articulated by means of the damping elements 25 to retaining lugs 28 rigidly attached to the guide bar 4. These retaining lugs 28 are connected to the side beams 29 of the guide bar 4. The storage container holding means 14 are in other words connected at two mutually opposing end regions to the guide bar 4 in a vibration-cushioned manner, so that vibration, including that induced in the guide bar 4, is transferred in a damped state to the storage container holding means 14. Particularly, FIG. 3 shows that the storage container holding means 14 are further set at a distance as far as possible from the damping bearings 7 in the direction of the grasping region 30 between the side beams 29 of the guide bar. By this means, the storage container holding means 14 can be implemented as a kind of vibration-balancing counterweight for the purpose of further reducing vibration in the guide bar.

(19) On the storage container holding means 14 there is further provided a lateral guard 31, which supplements the protective action of the heavy-duty and solid-faced side walls 27 towards the rear side of the vibration tamper 1 or towards the machine operator. More specifically, the lateral guard 31 is a transversal strut, which extends between the side walls 27 in the rear region of the storage container holding means 14.

(20) Further protection of the storage container 15 disposed in the storage container holding means 14 is afforded by the protective cover 19. The protective cover 19 is, more specifically, a protective cover pivotally disposed on a transverse spar 32 of the guide bar, which protective cover is capable of being pivoted down on to the storage containers 15 under working conditions, as shown in FIGS. 2a and 2b and, for example, is capable of being pivoted up for the purpose of replacing the storage container 15, as shown in FIG. 3. In the pivoted up state, the protective cover 19 thus uncovers the storage containers 15 such that they can be easily and simply removed from the storage container holding means 14 or replaced therein. In the pivoted down state, the protective cover 19 prevents damage occurring to the storage container 15 from above and thus also to the regions of the attachment means 18 and of the conduit system 17 that are covered by the protective cover 19. The protective cover 19 also comprises a locking screw 37, by rotation of which the protective cover 19 can be locked in the closed position, as shown in FIGS. 2a and 2b. The locking screw 37 engages for this purpose in a mating counterpart 38 on the storage container holding means 14. This prevents the protective cover 19 from jumping up in an uncontrolled manner under working conditions.

(21) In addition to the substantially solid-faced protective hood, the protective cover 19 further comprises two protective tubes 33, which are disposed on the interior surface of the protective cover 19 and protrude in the direction of the storage container 15. The protective tubes 33 are configured such that, in the pivoted down state of the protective cover 19, they at least partially cover the connecting regions of the valves on the attachment means 18 directed towards the storage containers 15 and surround the sides thereof, so that in this way there is obtained additional protection of this highly sensitive region in terms of safety. For this purpose, a slotted recess is provided in each of the protective tubes, through which recess the connecting means are guided for the purpose of connecting the storage container 15 to the attachment means 18.

(22) Another feature of the vibration tamper 1 is the arrangement of the evaporator/pressure governor unit 16 on the guide bar 4 in a likewise vibration-cushioned manner with regard to the machine frame 10 and with regard to the guide bar. Between the evaporator/pressure governor unit 16 (that is, the relevant holding device 36 that serves to hold the evaporator/pressure governor module 16) and the retaining lug 34 on the guide bar 4, there is, thus likewise, present a damping element 35, so that vibration of the guide bars is transferred in a damped manner to the evaporator/pressure governor unit 16.

(23) FIG. 4 illustrates the basic function of the quick couplers 20. These comprise the end connectors 21 disposed on the flexible pipe ends of the attachment means 18. On the storage containers 15 there are provided appropriate coupling counterparts 39 adapted to establish a gastight transfer connection between the storage container 15 and the piping system 17 for the accommodation of the connectors 21. More specifically, the quick coupler 20 is adapted such that a valve will only be opened when a gastight fluid communication route has been established, and the quick coupler 20 will only be released after the relevant valves have been closed. The quick couplers 20 can be coupled and uncoupled by carrying out purely manual pushing and turning movements on the connectors 21 relatively to the coupling counterparts 39, so that no specific tool is necessary for replacing the storage container 15, for example.

(24) FIG. 5 is an elementary circuit diagram and illustrates, in an alternative embodiment to that shown in FIGS. 2a to 4, the parallel arrangement of more than two storage containers 15 in the storage container holding means 14. The storage containers 15 shown in FIG. 5 are, for example, cartridges having a maximum capacity of 1000 ml. The cartridges 15 are connected to the attachment means 18 by means of quick couplers 20 as described above. Each pipe connection between a cartridge 15 and the attachment means 18 is also provided with a stopcock 40 and a check valve 41 mounted down-stream, as regarded in the outflow direction. The check valve 41 substantially serves the purpose of automatically closing the attachment means 18 with respect to the environment when a storage container 15 has been removed from the closing device 18, for example, for the purpose of replacement. Thus, the check valve 41 automatically ensures that the liquid gas present in the other storage containers will not flow out through that connecting arm from which the storage container 15 had been removed. Between the attachment means 18 and the remaining piping system 17 leading to the driving engine 3, there is also provided a central stopcock 42, by means of which the transfer of liquid gas from the storage containers 15 to the driving engine 3 can thus be centrally blocked or unblocked. It goes without saying that the diagram shown in FIG. 5 can be almost arbitrarily extended or reduced to accommodate different numbers of storage containers 15.

(25) To achieve perfect functioning of the liquid gas powered driving engine 3, it is important that the liquid gas be supplied in the gaseous state. In order to make it possible to achieve virtually quantitative volatilization of the liquefied gas, there is disposed between the attachment means 18 and the driving engine 3 in the piping system 17 the said evaporator/pressure governor unit 16 comprising the evaporator 23 and the pressure governor 24. The pressure governor 24 is connected down-stream of the evaporator 23, as regarded in the direction of fluid effluent flow towards the driving engine 3. The essential objective of the pressure governor 24 is to ensure a constant pressure of the gas supplied to the driving engine 3. The pressure governor 24 is an automatically effective pressure governor, which automatically executes the relevant pressure control. The evaporator 23 is intended, on the other hand, to effect complete volatilization of the liquefied gas issuing from the storage containers 15. In the present exemplary embodiment there is thus provided, for this purpose, means for heating the evaporator 23, in that warmed engine oil is fed to the evaporator 23. For this purpose, there is provided, in the exemplary embodiment illustrated in FIG. 6, an oil pump 43 driven by the driving engine 3, which oil pump pumps warmed engine oil from the engine oil sump 44 towards the evaporator 23 and recycles the same from the evaporator 23 back to the engine oil sump 44. In this evaporator oil circuit 45 there is further disposed a pressure relief valve 46.

(26) FIG. 7 illustrates by way of example the basic modus operandi of an automatic shutdown system for the vibration tamper 1. The automatic shutdown system causes the gas supply to the driving engine 3 to be blocked when the driving engine 3 demands no fuel, or when the driving engine 3 is switched off. The basic principle of the automatic shutdown system illustrated in FIG. 7 involves the fact that an adequate negative pressure predominates in the suction pipe 46 between the carburetor 47 and the driving engine 3 only when a negative pressure is produced in the suction pipe 46 of the driving engine 3 by the rotary movement of the driving engine 3 and the concomitant motion of the piston. For this reason, provision is made for a feedback to be present between the negative pressure in the suction pipe 46 leading to the evaporator/pressure governor unit 16, which feedback permits the transfer of liquid gas through the evaporator/pressure governor unit 16 only when an adequate negative pressure predominates in the suction pipe 46. For this purpose, a pressure signal line 48 is provided between the suction pipe 46 and the evaporator/pressure governor unit 16, by means of which signal line a suitable cut-off device in the evaporator/pressure governor unit 16 is controlled such that an outflow of liquid gas from the evaporator/pressure governor unit 16 to the driving engine 3 is only possible when there is adequate negative pressure in the suction pipe 46.

(27) FIG. 8 finally illustrates the operating principle of a tilt switching system. The essential element of the tilt switching system is a sensor 49, by means of which it is possible to detect at least when a predetermined maximum degree of tilt of the vibration tamper 1 in relation to the horizontal ground level of the road subsurface U has been exceeded. The degree of inclination describes the tilt angle of the compactor axis S of the vibration tamper 1 in relation to a reference perpendicular standing on the ground horizontal. The data ascertained by the sensor 49 are transferred to a control unit 50. When the control unit 50 ascertains that the limit of tilt has been exceeded, it stops the engine. This can take place, for example, by disconnecting the triggering current supply 51 or by comparable measures. Additionally or alternatively, for example, also shutoff valves or similar measures can be triggered by the control unit 50 in this case, in order to prevent an uncontrolled outflow of liquid gas from a toppled vibration tamper 1.

(28) While the present invention has been illustrated by description of various embodiments and while those embodiments have been described in considerable detail, it is not the intention of Applicants to restrict or in any way limit the scope of the appended claims to such details. Additional advantages and modifications will readily appear to those skilled in the art. The present invention in its broader aspects is therefore not limited to the specific details and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of Applicants' invention.