Abstract:
Unit cranes consist of three hinged arms ( 13-15 ), the middle arm ( 14 ) being in the form of a polygon comprising a number of units jointed together, the flexibility of the units being arranged by influencing the units internally. The object of the invention is to achieve improved traction curves and speed curves, and this is effected by influencing the movement of the units from the outside by means of a hydraulic mechanism ( 38 ).

Description:
FIELD OF THE INVENTION 
     The present invention is directed to a two arms system, and more specifically, toward an improved two arms system for a unit crane. 
     BACKGROUND OF THE INVENTION 
     There is a considerable call for a two-armed system for unit cranes, for instance. Such a crane consists of a rigid arm and thereafter an arm composed of a number of part-arms joined together which can be influenced hydraulically in such a manner that the part-arms form a polygon. This arm is in turn attached to a stand or to said stand via a supporting arm. The two arms in the system, together with a supporting arm if used, can thus be arranged to be situated one above the other and also so that all the arms are extended. Various units can be attached at the tip of the rigid arm, for use in clearing trees and bushes. Units functioning as excavators or loading means can also be attached, or even a concrete pump or concrete hose. In existing systems with two arms, the arm able to form a polygon is influenced by a hydraulic unit arranged between the arm parts so that, when the polygon is extended, the unit is located substantially in the middle of the polygon. Certain problems have been found to occur when operating such two-armed systems, as regards speed control of the top of the rigid arm, and problems also occur as regards the force exerted at said tip. Such a unit crane is suitable fitted on a caterpillar vehicle and this involves the problem of how to fold up the crane when it is not in operation. The arms will usually have a substantially vertical position, or they will be situated on the roof of the vehicle. There is also the problem of the actual joints of the unit arms being as stable as possible. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to solve the above-mentioned drawbacks and this is achieved by it being possible for both the arms in the system to be caused to lie one above the other, and possible also above a supporting arm so that, when the arm system is not in use the free end of the arm with several parts is attached either to a stand or to one end of a supporting arm, the other end of which is journalled in the stand. When folded up, therefore, the actual working tip or crane tip of the journalled package will be situated at the opposite part of the stand. To achieve suitable lifting power and suitable speed the crane tip is moved from a packaged position to the position is assumes when the tip is furthest away from the stand. The hydraulic mechanism influencing the arm with the many parts is arranged so that it influences two points situated outside two adjacent arm parts. 
     According to a preferred embodiment of the invention it is suitable to use a supporting arm which is in connection with a stand. In this case it is advisable to use two pairs of hydraulic cylinders. One pair of hydraulic cylinders is connected to the stand and to a point between the ends of the supporting arm. The supporting arm can be caused to move about its journalling point by means of one of the hydraulic cylinders. At the point between the two ends of the supporting arm it is suitable to arrange a bearing for a pair of hydraulic cylinders, one end of which is connected to said journalling point and the other end of which communicates with one end of the arm that can form a polygon. The first pair of hydraulic cylinders is used so that one hydraulic cylinder of the pair controls the movement of the supporting arm while the other hydraulic cylinder, together with the second pair of hydraulic cylinders, forms a closed hydraulic system, and since the second hydraulic cylinder in the first pair is parallel with the hydraulic cylinder infulencing the movement of the supporting arm, the second hydraulic cylinder in the first pair will automatically control the movement of the two hydraulic cylinders influencing the arm able to form a polygon. This arrangement of hydraulic cylinders provides smoother movements of the whole crane, as well as enabling savings in energy. 
     The stand to which the supporting arm is attached can be caused to moved in a number of different ways known per se. However, it has proved particularly advantageous if the stand is provided at its journalling end with one or more toothed wheel rims situated one above the other, each cooperating with a chain designed for cooperation with a toothed wheel, each chain being joined at its ends and the chains being influenced by a hydraulic system so that the chains are caused to move and influence the pin of the stand in order to effect movement of the stand. 
     The arrangement described above with toothed wheel and chain allows the crane to be moved as large an angle as possible in both direction. However, if the demand for a large turning angle is not so great, it is much simpler and less expensive to use two links joined together for each piston rod. 
     Such a unit crane with its stand is suitable arranged on a platform provided with cab in such a way that the arm system in the form of a package does not come into contact with the cab in any way. The vehicle carrying the crane package may be part of a centrally controlled vehicle in which the engine is jointed to the supporting part for the crane package. By arranging the hydraulic unit outside the arm with the many part arms, the advantage is gained that the crane can be brought to be more or less horizontal with the various arms arranged one after the other and that it can be caused to assume a substantially downwardly-directed vertical position and upwardly-directed vertical position. The many joints in the arm system are subjected to considerable strain and it is therefore suitable for two arms to be combined so that one arm has two parallel shafts between which a pin located on the other arm is passed. The pin and the two arms together form a through-hole for a shaft journal. Each end of the shaft journal is provided with a tensioning ring having a conical surface and a tensioning cone, also having a conical surface, cooperating therewith. These two units with conical surfaces are brought into rigid contact with each other since the end cone is provided with a tightening bolt that can be screw into each end of the shaft journal. Reliable functioning of the shaft journal located at a point about which the two arms can be oscillated is thus achieved. 
     Additional characteristics of the present invention are revealed in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described in more detail with reference to the accompanying drawings in which 
     FIG. 1 shows a centrally controlled vehicle with a crane package in rest position, the vehicle being on its way to a work place, 
     FIG. 2 shows the vehicle at a work place where the unit crane is manipulating a tree, 
     FIG. 3 shows a unit crane and stand in partially extended position. 
     FIGS. 4-6 show various positions of a unit crane, 
     FIG. 7 shows an arrangement for retaining shaft journals at a joint, 
     FIG. 8 shows how the force in a crane tip varies between two possible positions of the crane tip, 
     FIG. 9 shows how the speed of the crane tip varies between its two outermost positions, 
     FIG. 10 shows a modification of the hydraulic system at the supporting arm according to FIG. 3, 
     FIG. 11 shows a flow chart for the hydraulics for the pistons according to FIG. 10, 
     FIG. 12 shows schematically a section of the turning device for the stand according to FIG. 3, 
     FIG. 13 shows a section along the line  22  in FIG. 1, 
     FIG. 14 shows a schematic section through a chain wheel, 
     FIG. 15 shows a detail according to the arrangement in FIG. 12, 
     FIG. 16 shows a modification of the arrangement according to FIG. 12, 
     FIG. 17 shows a modification of the pivoting arrangement utilizing links, 
     FIG. 18 shows an arrangement according to FIG. 17, seen from above, and 
     FIG. 19 shows only the links according to FIG.  17 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 11 designates a centrally controlled vehicle with a unit crane. The vehicle has an engine part arranged pivotably in relation to the support unit  3  for a crane unit. The engine part has a pair of front wheels and the support part  3  has bogie wheels  5 . A cab  6  is arranged on the support part. This cab may be pivotable depending on which direction the vehicle is to be driven in. Naturally the cab may also be stationary and control means may be arranged in the cab so that the operator need only turn his seat 180°. A stand is arranged on the supporting unit, said stand being pivotably arranged by means of bearings  11 , the movement of the stand being achieved with the aid of hydraulic cylinders  12 . The complete crane package consisting of three arms has been designated  8 . Considering now the centrally controlled vehicle  1  in FIG. 2, this is shown in operation and it can be clearly seen that the arm package has a two-armed system  9  and also a supporting arm  13 . The two-armed system is shown manipulating an object  10 , which in the present case is a tree, and the operation shown comprises the vehicle with the crane package attempting to exert pressure on the tree. 
     FIG. 3 shows the crane package with stand in partially extended position. It can be seen that the inner arm  14  in the two-armed system is journalled at one end to a rigid arm  15  with a crane tip  16 . The inner arm  14  is journalled at its inner end on a supporting arm  13  which is in turn journalled on the stand  7 . The inner arm  14  consists of a first arm  17 , a second arm  18 , a third arm  19  and a fourth arm  20 . All journalling points  22 - 34  joining the various parts of the arms together may be of the same type. One end of an arm part consists of two shaft parts and the connecting arm part consists of a studlike part which is placed between the two parts, the two parts and the stud part having holes that form a common hole for a shaft journal and this shaft journal is anchored in a special manner to be described in the following. The journalling points  22 - 34  thus constitute joint points for the units in the unit crane. The rear arm  14  in the crane has an arm  19   a  that is substantially solid and is provided at its end with two parallel arms with a part  19   b  forming a part of the actual rear arm, whereas the part  19   c  is completely protruding. The fourth arm also consists of two parallel parts spaced from each other, and has a part  20   a  included in the rear arm  14  and a part  20   b  that protrudes outside the rear arm  14 . Two intermediate arms are journalled at their free ends, between the middle of the second arm  18  and the upper end of the arm  19   a.  The lower end of the stand  7  comprises a plate, pivotable in relation to a substantially parallelepipedic part  35  which is turnable about a horizontal axis by means of hydraulic cylinders  12  shown in FIG.  1 . Above the pivotable plate  37  the stand  7  is provided with two flanges  36 . Between the two journalling points  28  and  30  are two hydraulic cylinders that influence the relative movement between the two arms in the two-armed system. At the middle of the supporting arm  13  is a flange arrangement with two journalling points  31  and  32 . A hydraulic arrangement  39  is situated between the journalling points  27  and  32 , and a hydraulic arrangement  40  is similarly arranged between the journalling points  31  and  33 . The relative position between the two arms  14  and  15  in the two-armed system is controlled by the hydraulic arrangement  38 . The two-armed system is in turn also influenced by the hydraulic cylinder arrangement  39  and the hydraulic cylinder arrangement  40  situated between the journalling points  31  and  33  controls the position of the supporting arm  13  which also has another influence, as already mentioned, namely that the position of the parallelepipedic unit  35  is influenced by the hydraulic arrangement  12 . 
     FIGS. 4,  5  and  6  demonstrate how the three arms in the crane package can be brought to three extreme outermost positions. FIG. 4 shows a purely horizontal position, FIG. 5 directed vertical downwards and FIG. 6 directed vertically upwards. 
     FIG. 7 shows how two arm ends can be joined together. In this case, one arm end must comprise two shafts or lugs  41  and  42  situated opposite each other and spaced apart. Each of the two shafts  41  and  42  is provided with a hole  43  and  44 . A solid stud  50  arranged at the end of the arm to be connected is inserted between the two shafts. This stud or journal is provided with a through-opening  49 . When the two arm ends are brought into engagement with each other, the openings  43 ,  44  and  49  will be situated opposite each other and a shaft journal  52  is inserted through them. A tensioning ring with an inner conical surface is applied at each end of the shaft journal and is placed in the holes  34  and  44 . A tensioning cone  46  with a bottom and a cylindrical wall, conical on the outside, is applied at each end of the shaft journal  52 . The conical surface of the tensioning cone  46  is brought into contact with the conical surface of the tensioning ring  45 . In the bottom of the tensioning cone is an opening for a tightening bolt, threaded for engagement with an opening, also with threading, in the shaft journal. The two conical surfaces can thus be brought into firm contact with each other so that the shaft journal is immovable in the two outer holes  43  and  44 . The shaft journal  52  may be provided with a grease cup  51  so that the bearing can be provided internally with lubricant. The bearing arrangement described can be used in all bearing arrangements in the unit crane or just in certain selected bearings, but it should be obvious that the bearing according to FIG. 7 is generally usable and may have applications entirely different from vehicles with unit cranes. 
     The crane tip in the unit crane has two outermost positions, one as shown in FIG.  1  and the other as shown in FIG.  4 . Between these two extreme positions the curves in FIG. 8 have been taken up for forces operating on the crane tip, the curve  54  showing how the force varies from the inner position in FIG. 1 to the outer position in FIG.  4 . Curve  55  also shows how the force varies in an inward movement. Curve  53  in FIG. 9, finally, shows the speed of the crane tip from the situation according to FIG. 1 to that according to FIG.  4  and curve  52  shows the equivalent speed during an inward movement. It is thus clear that the present invention has managed to produce a vehicle with a unit crane where, when not in use, the crane forms a convenient package, substantially horizontal, and is at a low level when the three arms are arranged one after the other, which is an advantage since the crane is then easy to service. It may then be suitable to bring the crane into the position shown in FIG.  4 . Another advantage is that the crane will on no account come into contact with the driver&#39;s cab  6 . No special vehicle is necessary as previously to transport the unit crane, and crane and vehicle provide an advantageous unit through the use of a centrally controlled vehicle. 
     It is clear that the speed and lifting capacity of the crane tip  16  vary depending on the hydraulic pressure used. 
     The embodiment shown in FIGS. 12-16 comprises a housing  71  in which a shaft  72  is pivotably journalled, the outward end  73  of which is designed for mounting of the tool or unit which the pivoting arrangement is designed to handle. In the example shown the shaft  72  is provided with two chain wheels  74  which are firmly secured to the shaft. 
     The housing  71  is also provided with a first cylinder  75  and a second cylinder  76 , the axes of these cylinders being parallel. A first piston rod  77  connected to a piston is displaceably arranged in a first cylinder  75  and a second piston rod  78  connected to a piston is displaceably arranged in the second cylinder  76 . The first piston rod  77  is provided at its free end with a first chain wheel  79  and the second piston rod  78  is provided with a second chain wheel  80 . The chain wheels  79  and  80  are freely pivotable in the ends of respective piston rods  77 ,  78  about shafts parallel to the shaft  72 . 
     The arrangement is symmetrical and the piston rods  77 ,  78  with chain wheels  79 ,  80  are identical. Only the piston rod  77  with chain wheel  79  will therefore be described in connection with FIG.  14 . The piston rod  77  is provided with a through-hole  81  in which a bearing sleeve  82  is journalled. In the example shown two chain wheels  79  are rotatably arranged on the bearing sleeve  82 , and the piston rod forms a spacer between the chain wheels  79 . On each side of the bearing sleeve  82  a lock and guide washer  83  is retained by its shaft  84  being inserted into the cavity in the bearing sleeve  82 . The side of the washer  83  facing the bearing sleeve and chain wheel is flat and holds the chain wheel in place axially, while the end of the washer  83  facing away from the sleeve  82  has a guiding protrusion  85 , semi-circular when seen in section, which has a certain axial extension as can be seen in FIG.  15 . In the example shown the guiding protrusion extends across the diameter of the washer  83  and runs in groove  86 , also semi-circular when seen in section, in the opposing walls  87  of the housing  71 . The washers  83 , bearing sleeve  82 , chain wheel  79  and end of the piston rod  77  are thus axially “locked” between the walls of the housing  71 . At the same time the grooves  86  and the guiding protrusions  85  running therein guide the end of the piston rod  77  linearly in the housing. As can be seen in FIG. 12, the piston connected to each piston rod  77 ,  78  has a partially spherical surface which cooperates with the cylinder  75 ,  76  and, in the example shown, is provided with a sealing ring  88 . The pistons can be displaced in the cylinders via hydraulic or pneumatic channels  89 . 
     Two long, flexible members for transmitting movement, e.g. in the form of two roller chains  90 , only one of which is visible in FIG. 12, are secured to the housing  71  by their ends  91 . Each chain passes 180° around the first chain wheel  79 , continues 180° around the chain wheel  74  and then 180° around the second chain wheel  80 . Chain guides  92  are provided at the attachment of the chain ends  91  to the housing  71  to guide and support the end portions of the chain. The first piston rod  77  with its piston and the second piston rod  78  with its piston are supplied with pressure fluid so that they move synchronously to and from but in opposite directions i.e. when the first piston rod  77  with its piston is in its uppermost position, as shown in FIG. 12, the second piston rod  78  with its piston is in its lowermost position. 
     It should be obvious that when the pistons and the piston rods  77  and  78  move synchronously in opposite directions, the chain running around the chain wheel  74  will move, thereby turning the shaft  72 . How far the chain wheel  74 , and thus the shaft  72 , can be turned depends naturally on the length of the chain and the stroke length of the piston rods. However, for normal requirements a turning angle of 180° is sufficient for the shaft  72 . 
     Since the pistons are constantly loaded with pressure fluid, the chains  90  remain taut and the arrangement is thus play-free. Since the chains encompass the chain wheel  74  along half of its circumference, as well as the first and second chain wheels  79  and  80 , the surface pressure on the wheels will be reduced when the shaft  72  is loaded. The arrangement can thus have small dimensions while still being able to take up considerable loads. 
     FIG. 16 shows a modified form of the invention, the cylinders  75  and  76  having been mounted at 90° to each other. The function is the same as described with reference to the embodiment shown in FIGS. 12-15. In the embodiment according to FIG. 16 the chain will encompass an angle of 270° of the chain wheel  74  by the shaft  72 , thereby further distributing the load on the toothed wheel  74 . For reasons of clarity the grooves  86  mentioned in connection with the description of FIGS. 12-16 have been omitted but may of course be included in this embodiment also. The grooves will then cross each other which does not, however, affect the function of the pistons and guide protrusions  15 , the latter having elongate form as mentioned. 
     It is implicit that the wheels  79  and  80  do not necessarily have to be provided with teeth but may have some other peripheral surface depending on the type of chain. Cogged belts are also possible. 
     The arrangement described above for turning the stand with the aid of toothed wheel and chain is suitable if large turning angles are required for the unit crane. However, if such large turning angles are not necessary then it is both cheaper and simpler to use a link system instead of toothed wheel and chain. FIGS. 17 and 18 show in perspective and seen from above a turning arrangement which is simple and inexpensive to manufacture and which uses links instead of the chains and toothed wheels mentioned above. In most cases at least one or two piston rods are required to achieve turning in both directions, and in the present case the actual housing, designated  94 , for the turning arrangement is shown. The pin or unit to effect turning of the stand is then designated  13  and is in the form of a substantially cylindrical unit journalled at its ends in some suitable manner. The link and piston arrangement of the cylindrical pin is arranged in a plane perpendicular to the central axis of the pin. A radially outwardly directed flange  100  is arranged in some way on the envelope surface of the cylindrical unit. On said flange are two journalling pints for two groups of links and piston rods. Obviously only one piston rod and two links are required to achieve turning movement in both directions but it is more advantageous to have two groups of links and pistons, the groups directed in different directions around the periphery of the unit. One group is connected at the flange  100  and a link  97  is provided here which is pivotable connected by one end  104  to the outwardly directed flange  100 . The other end  98  is connected to the piston rod  95 . A link  101 , moveable via its end  102 , is arranged between the two ends of the link  97 . The other end  103  of the link  101  is journalled at a fixed point in the housing, arranged at a unit  104 . It is thus only the end  103  that is moveable around a stationary point. The moveable parts are thus the link arms, piston rods and unit  93 . Relatively large turning angles can be achieved in both directions thanks to the links being arc shaped. It has proved advisable to have two levels of identical links with a spacer between these levels arranged at one end  98  of the link  97  and corresponding ends for the other group with links and piston rods. It is advantageous to have two similar types of link systems arranged one above the outer as this enables a better point of application with the piston rods at the links in the different levels. 
     FIG. 10 shows a variation of the supporting arm  13  in FIG. 3 where the hydraulic pistons  39  and  40  have been replaced with a first pair of hydraulic pistons  57  and  56  and a second pair of hydraulic pistons  58  and  59 . The hydraulic pistons  56  and  57  replace the hydraulic piston  39  in FIG.  3  and these hydraulic pistons are journalled at their ends in the same way as the hydraulic piston  39 . The hydraulic piston  40  according to FIG. 3 has been replaced in FIG. 10 with the hydraulic pistons  58  and  59 . The hydraulic pistons in each pair are always located parallel to each other. The hydraulic pistons  56 ,  57  and  59  are hydraulically connected together in a closed system, whereas the hydraulic piston  58  is controlled by a control unit  71 . The control unit  71  is connected hydraulically to the hydraulic cylinder  58  by the tubes  61  and  62 , forming a closed hydraulic system, and controls the piston between its two ends, thereby raising and lowering the supporting arm  13  in relation to the post  60 . Since the two pistons  58  and  59  are parallel to each other, the piston  59  will always follow the movement of the piston  58 . The pistons  59 ,  56  and  57  are connected by tubes  63 - 70  to form a closed hydraulic system which means that when the piston  58  is caused to move by the control unit, the piston  59  will automatically move the pistons  56  and  57 . Allowing the arm system to be influenced via the supporting arm  13  by two hydraulically closed system reduces the total kinetic energy required for the unit crane.