Patent Publication Number: US-6705798-B2

Title: Cold planer

Description:
This application claims the benefit of priority based on European Patent Application No. 01115944.9, filed Jun. 29, 2001, which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates generally to work machines for the treatment of roadway surfaces, and more particularly to a cold planer for asphalt and concrete. 
     BACKGROUND ART 
     A prospectus entitled “Bitelli Volpe SF 100 T4M deep-cut cold planer for asphalt and concrete” describes a work machine comprising a frame which is supported by four wheels, a pair of oppositely arranged front wheels and a pair of oppositely arranged rear wheels. One of the rear wheels is adapted to raise and lower the frame relative to the respective rear wheel. Means are provided to allow for two operating positions of the one rear wheel. In a first operating position the rear wheel is mounted at the frame in what is called a projecting position, in a second operating position the rear wheel is mounted at the frame in a retracted position relative to the general outline of the frame. To allow for movement between the two operating positions a support arm is provided, which is, at its one end, pivotally connected to the frame and carries at its other end a wheel support comprising a lifting column. Typically, the rear wheel is driven by a hydraulic motor located in the hub of the rear wheel. Pressurized fluid is supplied to the hydraulic motor (and also any other hydraulic motors of other wheels which need to be driven) from an internal combustion engine mounted to the frame. To move the rear wheel from its projecting position into its retracted position the operator hydraulically lowers the frame with respect to the rear wheel. I.e. a hydraulic cylinder located inside the lifting column provides for this lowering movement. As soon as the frame or some other component fixedly mounted to the frame comes into engagement with the ground, the lifting column is lifted further by means of the hydraulic cylinder, so that the lower surface of the wheel is eventually spaced a certain distance from ground. Preferably, before the lifting of the wheel from ground has occurred, a pin locking the support arm at the frame is removed. After the wheel is spaced from the ground the operator pivots the support arm, and also simultaneously rotates the lifting column by about 120 degrees so that the running direction of the rear wheel is maintained for the two operating positions. 
     As is well known in the art, the possibility of positioning at least one of the rear wheels in the projecting position improves weight distribution during operation of the work machine, while the possibility of positioning the wheel in the retracted position allows the work machine to operate flush to a wall or curb. When the wheel is in the retracted position, easier movements of the work machine are possible. 
     However, the manual operation of displacing and locking or unlocking the pivotable wheel is somewhat uncomfortable for the operator, who is obliged to leave his seat and carry out the required operations manually. 
     EP 0 916 004 A1 discloses a work machine for the treatment of roadways having a rear support wheel which can be pivoted between an interior or retracted position and an exterior or projecting position by means of a guide rod gear consisting of a four-link mechanism with four vertical articulated axles and two guide rods pivotable in a horizontal plane connected to the rear support wheel. The guide rod gear pivots the rear wheel supported by a non-rotatingly locked lifting column from the exterior position to the retracted position such that the rear wheel turns in the retracted position and in the exterior position in the same direction. With this design the respective load of the work machine resting on the rear wheel is distributed to all four links of the four-link mechanism, which may result in a reduced stability and stiffness of the work machine. Also, precise couplings have to be provided which need to be inspected frequently so as to keep the wear, which might compromise good operation of the work machine, under control. 
     The present invention is directed to overcoming one or more of the problems or disadvantages associated with the prior art. 
     DISCLOSURE OF THE INVENTION 
     In accordance with one embodiment of the present invention there is provided a work machine, in which the automated movement to position a wheel assembly either projecting or retracted relative to the frame occurs with a greater stability in comparison with known machines, and which is less prone to wear, requires less maintenance, and is easier to manufacture than known machines. The change in position is accompanied by a corresponding rotation of the wheel assembly to keep the rotational direction of the wheel constant. This is accomplished by a work machine that includes a frame supported by a plurality of wheels or tracks, at least some of which are associated with respective lifting columns (also called inside column) adapted to raise and lower the frame relative to the respective wheels or tracks. Preferably, each of the wheels is associated with one respective lifting column. A work tool is supported by the frame, and a drive mechanism is adapted to rotate the work tool and at least one of the wheels or tracks. An articulation apparatus uses an actuator and a pivoting support arm to move one of the wheels or tracks between a projecting position and a retracted position relative to the frame, and includes a plurality of torque arms connected between the frame and the support arm to rotate the lifting column relative to the support arm in response to pivoting of the support arm. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of a work machine, i.e. a cold planer, in which the features of the present invention may be incorporated; 
     FIG. 2 is a top plan view—partially in section—of a detail of the cold planer of FIG. 1 with a rear support wheel arranged in a retracted position relative to the frame; 
     FIG. 3 shows the detail of FIG. 2 with the rear wheel arranged in a projecting position relative to the frame; 
     FIG. 4 is a longitudinal sectional view of the detail of FIG. 2; 
     FIG. 5 is an exploded view of the detail of FIG.  2 ; 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     FIG. 1 shows a work machine, i.e. a cold planer  1  for asphalt and concrete, also called a scarifier, which may incorporate the features of the present invention. The work machine  1  comprises a frame  2  supported by a pair of front wheels  4 , a pair of rear wheels  5 , and an operator seat  3  for an operator O. A work tool, e.g. a cutter or milling drum  6  for removing road surface material like asphalt or concrete is supported and rotatably connected to the frame  2 . A drive mechanism (not shown), for instance an internal combustion engine, is mounted inside of the work machine  1  on the frame  2  in a position behind the operator seat  3 . The drive mechanism supplies the power for rotating the work tool  6  and also for the front wheels  4  and/or the rear wheels  5  resting on the surface of the road paving to be worked on. In the work machine  1  shown in FIG. 1 one of the two rear wheels  5  is adapted to be moved between a projected position (shown) and a retracted position, and vice versa. Conceivably, more than one wheel  4 ,  5  could be designed to be movable between the two positions. 
     Referring now to FIGS. 2 to  5  there is shown a portion of a work machine of the type shown in FIG. 1 which incorporates the features of the present invention therein. The work machine of the invention includes an articulation apparatus  15  (FIGS. 2 and 5) adapted to pivotally move one of the rear wheels  5  between the projecting position  60  (in FIG. 3) and the retracted position  70  (see FIG. 3) relative to a frame  2 . 
     The articulation apparatus  15  is arranged between the frame  2  and a rear wheel support of the rear wheel  5 . 
     As is shown in FIG. 4 the rear wheel  5  is supported by the rear wheel support comprising a U-shaped bracket  35  and, fixedly mounted thereto, a vertical lifting column (also called inner or inside column)  32 . The inside column  32  is slideably mounted inside a support column (also called outside column)  30 . The wheel  5  is rotatably mounted by a bearing  35   a  on the bracket  35 . Preferably, as will be described below, the articulation apparatus  15  extends between the frame  2  and the inside column  32  of the rear wheel support. 
     The articulation apparatus  15  comprises: 
     a support arm  11  pivotally mounted at the frame  2 ; 
     an actuator  55  for rotating the support arm  11 ; 
     a torque arm system  4013  (FIG. 3) connected between the frame  2  and the support arm  11  in a manner sufficient to maintain the rotational direction Y of the one wheel  5  by causing the lifting column  32  to rotate relative to the support arm  11  in response to the actuator  55  pivoting the support arm  11  relative to the frame  2 . 
     The torque arm system  4013  comprises torque arms  40  and a coupling member that, in a preferred embodiment, is in the form of a ring  13 . The ring  13  is pivotally connected to one of the torque arms  40  and is further coupled to the inside column  32  thus coupling the torque arms  40  and consequently the torque arm system  4013  to the inside column  32 . As is shown in FIG. 4 the support arm  11  is provided with a housing  28  forming a cavity adapted to receive the ring  13 . 
     It is noted that the support arm  11  is the only support for connecting the rear wheel support and its inside column  32  to the frame  2 . The torque arm system  4013  has no load support function. The torque arm system  4013  is only used for rotating the inside column  32  and consequently the rear wheel support so as to maintain the direction of rotation of the rear wheel the same regardless whether the rear wheel  5  is in the projected or retracted position. 
     As to the support arm  11 , one can see particularly in FIGS. 3 to  5 , that this support arm  11  has a fork-shaped end  11   a  defining the housing  28  receiving the ring  13 . The support arm  11  is provided with a first hole  21  for pivotally mounting the support arm  11  to the frame  2  by means of a pin  12 . 
     The fork-shaped end  11   a  and the ring  13  are provided with a through-hole  11   b  and  13   a , respectively. The through-hole  11   b  and the through-hole  13   a  are mutually coaxial. Through-hole  11   b  receives an outside column  30  that ends at the upper wall of the housing  28 . The inside column  32  extends through the through-hole  13   a.    
     As shown in FIG. 4, the outside column  30  comprises a first sleeve  31 , which is coaxially fixed, for instance by means of welding within the hole  11   b . Inside the outer column  30  is, coaxially arranged to the outer column  30  the inner column  32 , which passes through the through-hole  13   a.    
     A longitudinal groove  32   a  is provided in the outside of the inside column  32 . The groove  32  has a certain length defining the desirable extent of movement between the inside column  32  and the outside column  30 . A key  33  is fixedly mounted at an inner surface of the ring  13  and is in slideable engagement with the groove  32   a . The key  33  and the groove  32   a  allow longitudinal relative sliding motion along a vertical axis Z between the inside column  32  and the outside column  30 . 
     Inside the inside column  32  there is a hydraulic jack  34 , the body  34   a  of which is connected to the outside column  30 , while the end of a stem  34   b  of the hydraulic jack  34  is connected to the bracket  35  supporting the wheel  5 . More particularly, the bracket  35  has a pair of coaxial and oppositely located holes  35   a  supporting the ends  5   a  of a pin supporting the wheel  5 . The hydraulic jack  34  allows lifting and lowering, respectively, the wheel  5  in the direction Z. Thus, the height of the support arm  11  relative to the ground or pavement to be worked on can be adjusted. 
     FIGS. 2 and 5 show that the support arm  11  has also a second hole  23  adapted to receive therein a pin  14  so as to provide a pivot connection between the actuator  55  and the support arm  11 . The actuator  55  consists of a hydraulic cylinder having the body  55   a  pivotally connected to the frame  2  and a shaft  55  pivotally connected to the second hole  23 . 
     As shown in FIG. 5 the support arm  11  and the ring  13  are provided with a third hole and a hole  13   b , respectively, for a pivotal connection to the torque arms  40 . 
     More particularly, the torque arms  40  comprise a first connecting rod  41  pivoted to the frame  2  and a second connecting rod  42  pivoted to the ring  13 . The connecting rods  41 ,  42  are pivoted to a third connecting rod  43 , which in turn is pivoted to the support arm  11 . 
     The first connecting rod  41  has a first hole  41   a  adapted to receive a pin  19  pivoted to the frame  2 , and a second hole  41   b  receiving a pin  17  pivoted to the third connecting rod  43 ; the second connecting rod  42  is provided with a first hole  42   a  receiving a pin  20  pivoted to the ring  13 , and a second hole  42   b  receiving a pin  18  pivoted to the third connecting rod  43 ; the third connecting rod  43  has a first hole  43   a  receiving the pin  17  pivoted to the first connecting rod  41 . A second hole  43   b  receiving the pin  18  is pivoted to the second connecting rod  42 , and finally the third connecting rod  43  has a third hole  43   c  receiving a pin  16  pivoted to the support arm  11 . 
     Turning again to the support arm  11 FIG. 4 shows that this arm  11  is provided also with a housing or cavity  50  within which an actuator  51  is located, which is used for blocking a rotary movement of the support arm  11  with respect to the frame  2 . Indeed, a body  51   a  of the actuator  51  is coupled preferably fixedly mounted in the housing  50  provided in the support arm  11 . A stem  51   b  of the actuator  51  can be inserted into holes  52 ,  53  provided in the frame  2  so as to block or lock the articulation apparatus  15 . Blocking or locking the articulation apparatus  15  will also lock or block the wheel  5  supported by the inner column  32  in the retracted position  70  or projecting position  60  relative to the frame  2 , respectively. 
     INDUSTRIAL APPLICABILITY 
     In operation, starting from the configuration shown in FIG. 2 in which the wheel  5  is arranged in the retracted position  70 , retracted relative to the frame  2 , pressurized oil is introduced into the actuator  55  and thus stem  55   b  is retracted, with the consequence that the support arm  11  can be rotated clockwise as shown by arrow V, until the configuration shown in FIG. 3 is reached with the wheel  5  being in its projecting position  60 . The rotation of the support arm  11  is effected by the actuator  55 . 
     In order to move from one configuration to the other, i.e. from the retracted position  70  to the projecting position  60  and vice versa, the action of the torque arm system  4013  is required to keep, during rotation of the support arm  11 , the direction Y of advancement of the wheel  5  always the same and preferably parallel to the advancement direction Y 1  (see FIG. 3) of the work machine  1 . 
     When the wheel reaches the projecting position  60 , fully projecting from the frame  2  as shown in FIG. 3, the stem  51   b  of the actuator  51  is inserted into the hole  52  provided in the frame  2  so as to block the wheel  5  in the external projecting position  60 . 
     If it is desired to move the wheel  5  from the projected position  60  of FIG. 3 into the retracted position  70  of FIG. 2 it is sufficient to actuate the actuator  55  in the opposite direction so as to extend the stem  55   b . Stability of the wheel  5  in the retracted position  70  is provided by the stem  51   b , which is then inserted into the hole  53  provided in the frame  2 . 
     In view of the above it is clear that the articulation apparatus  15  of the invention provides for enhanced operational reliability compared with prior art work machines. According to the present invention, the only weight or load bearing element of the articulation apparatus  15  is the support arm  11 . The support arm  11  requires only one pivot point  21  at the frame  2  so as to allow a play-free or rigid rotational movement of the wheel  5  between the projecting and retracting positions, respectively. Thus, a more stable motion, less vibrations and less wear are obtained with the work machine of the invention. 
     It should be understood that through the use of a rotating inner column  32  together with a single support arm  11  of an articulation apparatus  15 , that rotates the inner column  32  and the wheel  5  by 120 degrees as the wheel shifts from the retracted position  70  to the projecting position  60 , or vice versa, a swinging motion for the wheel assembly is obtained. 
     Both the articulation apparatus  15  and also its torque arm system can be of any suitable design as long as the desired rotation of the inner column  32  is obtained. For instance the torque arm system could be replaced by a system not using any torque arms but sensing the angular position of the support arm  11  and accordingly rotating the support arm  11  so as to maintain the running direction of the wheel. 
     Also, the ring  13  could be replaced by a half ring or any other suitable coupling member. 
     Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, disclosures, and the appended claims.