Abstract:
The invention relates to a safety device for the manually operated soil compaction roller, comprising an operating lever and an adjusting element coupled to an actuator in order to drive said roller. In case of danger, a safety-control element travels in between the adjusting element and the operating lever and separates the positive coupling, whereupon the adjusting element swings into a neutral position and shuts down the machine. When the operating lever swings forwards, a command corresponding to a forward movement is transmitted to the drive mechanism of said roller via a second positive coupling.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a safety arrangement for a manually guided soil compaction roller. 
     2. Description of the Related Art 
     In such soil compaction rollers, in particular rollers which are run with an operator in attendance, the operator walks behind the roller and controls it via a handle, which is fastened to a pole and has a travel lever for setting the travel speed and direction. The roller is normally moved via a hydraulic unit in forward direction and reverse direction, that is toward the operator. 
     A safety arrangement, often also referred to as dead man&#39;s circuit, serves in such soil compaction rollers to switch off the propulsion of the roller if the roller moves backward, i.e. in the direction of the operator guiding the roller, and the operator himself can no longer move backward or cannot escape from the roller. This problem may occur, for example, if the operator walks backward with the roller into an obstacle, gets into a panic and consequently forgets to stop the roller or move it in the opposite direction. 
     An actuator which is able to register the fact that the roller runs against an obstacle, for example the operator, is therefore provided in known safety arrangements. To this end, the safety arrangements have an actuator which is displaceable between an operating position and a hazard position and, if the operator comes into contact with it, is displaceable out of the operating position into the hazard position and consequently stops the roller. 
     To this end, it is stipulated in standards that, after the response of the safety device, the stopping travel of the roller must be smaller than the remaining operating travel of the actuator after the roller is switched off in order to avoid squeezing the operator. 
     DE-A 41 29 915 A1 discloses a safety arrangement in which the travel speed and direction can be set via a travel lever. The roller is guided via an additional handle, which is vertically pivotable like a lever and can be pivoted from an upswung basic position down into a working position in which its free end is still clearly above the horizontal established by its pivot. The travel lever, otherwise held in neutral position by spring loading, is fixed in the desired deflected position in a positive-locking manner by swinging down the handle. When the handle is swung up, which is effected automatically, for example, if the handle comes into contact with an obstacle, the positive-locking connection is neutralized, as a result of which the travel lever moves into the neutral position in a spring-loaded manner and stops the roller. Movement of the roller in the opposite direction is possible by further actuation of the travel lever. 
     In such solutions, it is always possible to reach the neutral position or set the forward direction by actuation of the travel lever. In this case, it was assumed that the operator, upon coming into contact with an obstacle at the rear, releases the travel lever or that the holding force of the operator is less than the restoring force, initiated by the safety actuator, on the travel lever. However, it has been found that the holding force of the hand, in particular in a panic situation, can become enormous, so that the operator does not let go of the travel lever and, by further travel of the roller, a permitted maximum force of 230 newtons may be exceeded by the safety actuator in contact with the body of the operator. However, a higher loading than the admissible maximum force may alone result in considerable injuries to the operator. 
     In order to remove this problem, solutions in which, despite the force with which the operator takes a firm hold of the travel lever, a positive-locking connection between travel lever and the control line leading to the drive is unlocked by the safety actuator detecting the obstacle have been proposed. As a result, the spring-loaded control line jumps into the stop position. A disadvantage of this principle, however, is that the positive-locking connection between travel lever and control line can only be restored when the safety actuator displaced by the obstacle has again reached its initial or operating position, so that a coupling between travel lever and control line becomes possible again. Not until then is a movement of the roller in the opposite direction possible. To this end, however, the operator must have freed himself from his jammed position beforehand, since otherwise the safety actuator cannot be returned into the operating position. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The object of the invention is to specify a safety arrangement for a manually guided soil compaction roller, which safety arrangement, even if the operator frantically keeps a firm hold of the travel lever, permits reliable stopping of the roller and, on the other hand, permits forward travel of the roller away from the operator even if the safety arrangement has been triggered by travel of the roller against the operator. 
     According to the invention, the object is achieved by a safety arrangement having the features of patent claim 1. Advantageous developments of the invention can be gathered from the dependent claims. 
     In the safety arrangement according to the invention, in addition to the first coupling known per se, often designed as a jaw clutch, between a travel lever and an adjusting element connected to a control line, a second coupling is provided. The first coupling can be released by displacement of a safety actuator from an operating position into a hazard position. The second coupling, however, is retained even in this case, but can only transmit forces of the travel lever to the adjusting element if the travel lever is moved in the forward direction. This has the advantage that, if the roller runs into an obstacle and the safety actuator is actuated by the obstacle, e.g. the body of the operator, the first coupling is neutralized, as a result of which the adjusting element moves into neutral position in a spring-loaded manner and stops the roller. So that the operator can free himself from his emergency situation, he can put the travel lever, which at first is still in the reverse travel position, into the forward position. The movement of the travel lever in the forward direction is transmitted via the second coupling to the adjusting element and thus via the control line to the drive of the roller, so that the latter moves in the forward direction away from the operator and releases the latter. 
     The second coupling likewise preferably has a positive-locking clutch in which the adjusting element carries a driver, against which a stop provided on the travel lever can run. This ensures that forces can be transmitted only in one direction, namely the forward direction of the roller. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and further advantages and features of the invention are explained in more detail below with the aid of the attached figures, in which: 
     FIG. 1 shows a perspective view of a handle for a soil compaction roller with the safety arrangement according to the invention in the operating position; 
     FIG. 2 shows the handle from FIG. 1 with the safety arrangement in hazard position; 
     FIG. 3 shows a front view of the safety arrangement according to the invention in accordance with the position of FIG. 1; 
     FIG. 4 shows a front view of the safety arrangement in accordance with the position of FIG.  2 : 
     FIG. 5 shows a side view of the handle with the safety arrangement according to the invention and a travel lever in forward position; 
     FIG. 6 shows a side view of FIG. 1 with the travel lever in reverse position; 
     FIG. 7 shows a side view of FIG. 2 with travel lever in reverse position and safety actuator in hazard position; 
     FIG. 8 shows a side view of the handle with travel lever in forward position and safety actuator in hazard position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The figures essentially show the same arrangement, but with different positioning of the elements. Therefore the construction of the safety arrangement according to the invention will first of all be described with reference to FIGS. 1 and 3. A description of the mode of operation then follows with reference to the further figures. 
     A handle  2  is fastened to a retaining plate  1  fastened to a pole (not shown) of a soil compaction roller, via which handle  2  the soil compaction roller can be guided in a conventional manner. In the arch of the handle  2 , a travel lever  3  is arranged so as to be pivotable on a pivot  4 . For ergonomical reasons, the travel lever  3  has an extension  5 , which is designed in such a way that it can be grasped by the operator at the same time as the operator keeps a firm hold of the handle  2 . The travel lever  3  is pivotable in the forward or reverse direction, a fact which is identified by arrows V and R. 
     The movement of the travel lever  3  can be transmitted to an adjusting element  7  via a jaw clutch  6 , which can be seen in particular in FIG.  3  and serves as first coupling. The adjusting element  7  is likewise arranged so as to be pivotable on the pivot  4  and is pivotably coupled at one lever end  8  to the end of an actuating device  9  serving as control line. A drive (not shown) for the roller can be activated via the actuating device  9 , which is designed, for example, as a Bowden cable. The drive is normally a hydraulic pump, the pumping capacity of which can be adjusted by means of the actuating device  9 . Instead of a Bowden cable, a control linkage, for example, may also be used for the actuating device  9 . 
     The adjusting device  7  is provided on one side with the jaw clutch  6  and is loaded on the other side by a spring  10 , which is supported against a step  11  on the pivot  4 . 
     As a result, the jaw clutch  6  is kept closed by spring loading, and the manual force, acting on the travel lever  3 , of the operator is transmitted in a positive manner to the adjusting element  7  and the actuating device  9 . 
     Furthermore, a safety actuator, which essentially comprises an impact pot  12 , a plunger  13  and a guide  14 , is arranged on the retaining plate  1 . The impact pot  12  is firmly connected to the plunger  13  and, by means of a spring  15  supported against the guide  14 , is held in an operating position, in which the control is not affected by the safety actuator. However, the plunger  13  is held in the guide  14  in an axially movable manner, so that the plunger  13  can be displaced with the impact pot  12  out of the operating position into a hazard position against the action of the spring  15  if the impact pot  12  runs, for example, into the body of the operator or another obstacle. 
     The hazard position is shown in FIG.  2 . In this case, it can be seen that the impact pot  12  with the plunger  13  has been displaced in the forward direction V of the roller, i.e. in the direction of the jaw clutch  6 . By the penetration of a conical point  16 , formed on the plunger  13 , between the two halves of the jaw clutch  6 , i.e. between the adjusting element  7  and the travel lever  3 , the adjusting element  7  is displaced axially against the action of the spring  10 , whereupon the jaw clutch  6  is disengaged. As a result, the force flow between the travel lever  3  and the adjusting element  7  is neutralized. The adjusting element  7  is loaded by a spring device (not shown) in such a way that, when it is not loaded by the travel lever  3 , it pivots automatically into neutral position, which corresonds to a stoppage of the roller. If the jaw clutch  6  is therefore disengaged, the adjusting element  7  automatically pivots into its neutral position and stops the travel of the roller via the actuating device  9 . The disengaged clutch  6  is also shown in FIG. 4, from which it can clearly be seen that the plunger  13  lifts the adjusting element  7  from the travel lever  3 . 
     However, the problem that the operator may already be jammed between the impact pot  12  and an obstacle is still not solved with the stoppage of the roller. In order to free himself, the operator, according to the invention, can therefore pivot the travel lever  3  in forward direction V. When the neutral position of the adjusting element  7  is reached, a positive-locking clutch serving as second coupling comes into engagement, this positive-locking clutch being formed by a pin  17  fastened to the travel lever  3  and a driver  18  formed on the adjusting element  7 . The pin  17  extending in the axial direction of the pivot  4  is so long that it can reach the driver  18  even if the adjusting element  7  is disengaged by the plunger  13 . 
     During forward movement of the travel lever  3 , the pin  17  therefore presses against the surface of the driver  18  and pivots the adjusting element  7  in the forward direction. The movement of the adjusting element  7  is accordingly transmitted via the actuating device  9  to the drive of the roller, as a result of which the roller moves away from the jammed-in operator in the forward direction. 
     Instead of the arrangement of the second coupling shown in FIG. 1, it is of course also possible for the adjusting element  7  to carry a pin, against which the travel lever  3  runs during forward movement. In normal operation, it is in addition expedient for no contact to take place between the pin  17  and the driver  18  when the jaw clutch  6  is engaged. Instead of a pin  17  inserted into the travel lever  3  as shown in FIGS. 3 and 4, another stop may of course also be formed on the travel lever  3 . 
     For better understanding, the abovedescribed mode of operation of the safety arrangement is explained below with reference to the side views shown in FIGS. 5 to  8 . 
     FIG. 5 shows the travel lever  3  in the forward position and the safety actuator with the impact pot  12  in the operating position. Accordingly, FIG. 6 shows the travel lever  3  in reverse position. The position of the travel lever  3  is transmitted via the respectively engaged jaw clutch  6  to the adjusting element  7  and the actuating device  9 , so that a reliable control of the roller drive is possible. 
     FIG. 7 shows a state in which the roller was first of all in reverse travel due to the travel lever  3  located in reverse position and then an obstacle was detected via the impact pot  12 . The plunger  13  has been pushed against the jaw clutch  6  and has released the latter. Accordingly, the spring-preloaded adjusting element  7  has pivoted into neutral position and stopped the drive via the actuating device  9 . The machine is stopped in the state shown in FIG.  7 . 
     In the state shown in FIG. 8, the operator has pivoted the travel lever  3  in the forward direction V, so that the pin  17  has been able to run against the driver  18  of the adjusting element  7 . By further movement of the travel lever  3  in forward direction V, the appropriate control command is transmitted via the actuating device  9  to the drive of the roller and the latter is driven in forward direction. By moving the roller away from the body of the operator, the impact pot  12  can return into its original operating position, whereupon the plunger  13  is displaced out of the jaw clutch  6  and the jaw clutch  6  can engage again. The original operating state is thus restored. 
     Apart from being used in rollers, the safety arrangement may of course also be used in other machines which are run with an operator in attendance.