Patent Application
20050249554
This application claims priority to European Patent Application Serial No. 04011028.0 Filed on May 10, 2004.
The present invention relates to paving machines having screed assemblies and, more particularly, to screed assemblies having linearly extendable portions.
Paving machines are used for depositing, spreading, compacting, and smoothing paving material on a roadbed in such a manner that a uniform and drivable surface is produced. Screed assemblies are used to smooth and compact the paving material. The screed assembly is typically drawn behind the paving machine and is adjustable to establish both the thickness of the deposited layer of paving material and the width of the area over which the material is spread.
Modern screed assemblies typically include one or more base or fixed portions and one or more extendable portions that may be adjusted relative to the fixed portions to control the working width of the screed assembly. A common arrangement uses two base portions arranged end to end such that they may be independently tipped from horizontal to permit laying a paved mat having a desired cross-section, for example, a center crown. Each base portion commonly includes an extendable portion that may be moved inwardly to minimize the width of the screed assembly during transport and may be extended achieving a full doubling of screed width is difficult because of necessary structural overlaps in portions of the fixed and extendable screed elements. Because of this, the fully extended screed width is typically several centimeters less than double the fully retracted width.
One example of a screed assembly adapted to address this problem is found in U.S. Pat. No. 4,986,695, which describes an apparatus that uses a number of telescopic rods to permit elongation of the base screed portion in the extended position. However, this is a complex mechanical arrangement involving multiple components moving relative one to the other, and may not be suitable for screed assemblies where a high degree of rigidity is required and where simplicity of operation is necessary for trouble-free operation.
The present invention is directed to providing a double extending screed that overcomes one or more of the problems set forth above.
In one aspect of the present invention, a screed assembly for a paving machine includes a main screed portion having a fixed length frame and an extension screed portion having a variable length frame defined by an inner end wall and an outer end wall and having an intermediate wall. The inner end wall and intermediate walls are axially movable one relative to the other. A coupling portion is located between the inner and outer end walls and has a first coupling member connected to the inner end wall and extending through the intermediate wall toward the outer end wall and a second coupling member connected to the outer end wall and extending to the intermediate wall. The coupling members are coaxially slidable one within the other. An actuator is adapted to controllably move the extension screed portion longitudinally axially relative to the main screed portion between a fully retracted position at which the intermediate wall is urged toward the inner end wall and a fully extended position at which the intermediate wall is urged away from the inner end wall.
In a second aspect of the present invention, a method is disclosed for providing an extendable screed assembly for a paving machine. The screed assembly has a main screed portion having a fixed length frame and an extension screed portion extendable from the main screed portion. The extension screed portion has a variable length frame defined by an inner end wall and an outer end wall and has an intermediate wall. The inner end wall and intermediate walls are axially movable one relative to the other. A coupling portion is located between the inner and outer end walls and has a first coupling member connected to the inner end wall and extending through the intermediate wall to the outer end wall and a second coupling member connected to the outer end wall and extending to the intermediate wall. The first and second coupling members are coaxially slidable one within the other. An actuator is adapted to controllably move the extension screed portion longitudinally axially relative to the main screed portion between a fully retracted and a fully extended position. The method includes the steps of moving the variable length portion intermediate wall toward the inner end wall in response to the actuator moving the extension screed portion to the fully retracted position and moving the variable length portion intermediate wall away from the inner end wall in response to the actuator moving the extension screed portion to the fully extended position.
Referring generally to the figures, and in particular to
A coupling portion 42 is located between the variable length frame inner and outer end walls 30, 34. The coupling portion 42 has a first coupling member 46 connected to the inner end wall 30 and extending through the intermediate wall 38 toward the outer end wall 34, and a second coupling member 50 connected to the outer end wall 34 and extending to the intermediate wall 38. The first and second coupling members 46, 50 are coaxially slidable one within the other, and in a preferred embodiment cooperate to form an elongated cavity. Also in a preferred embodiment, the first and second coupling members 46, 50 are coaxially positioned cylinders 48, 52, one slidable within the other. However, the coupling members 46, 50 could be constructed of other configurations suitable for coaxial interaction such as triangular, rectangular, or other curved or polygonal structures.
An actuator 54 has a first end portion 58 connected to the main screed portion frame 18 and a second end portion 62 connected to the extension screed portion variable length frame outer end wall 34. In a preferred embodiment, the actuator 54 may be a linear operator such as a hydraulic cylinder, and may be at least partially located within the elongate cavity formed by the cooperation of the first and second coupling members 46, 50. The actuator 54 is adapted to controllably move the extension screed portion variable length frame 26 longitudinally axially relative to the main screed portion fixed length frame 18 between a fully retracted position at which the variable length portion intermediate wall 38 is urged toward the inner end wall 30 and a fully extended position at which the variable length portion intermediate wall 38 is urged away from the inner end wall 30.
As best seen in
In some applications of embodiments of the present invention, it may be desirable to increase the rigidity of the screed assembly 10 by preventing relative rotational movement between the coupling members 46, 50 while permitting relative linear movement.
To further enhance the rigidity of the screed assembly 10, the key 70 may be driven under power into or released under power from the keyway 74. This may be done in any of a number of conventional manners, including using a hydraulic or electrical actuator to move the key 70 relative to the keyway 74. The selected actuator may be bidirectional, or may be unidirectional with a resilient member such as a spring biasing the key in the non-powered direction. In the preferred embodiment illustrated in
In yet another embodiment of the present invention, as shown in
In yet another embodiment of the present invention, as shown in
For brevity and convenience of drafting, the foregoing description details the structure and operation of one extension screed portion 22 cooperating with a respective main screed portion 14. However, a typical screed assembly 10, as depicted in
In a typical application of a screed assembly 10 for a paving machine, it is desirable to adjust the working width of the screed assembly 10. During transport of the screed assembly 10 the outer extendable screed portions 22 may be retracted using the actuators 54 such that the variable length portion intermediate walls 38 are moved toward the inner end walls 30. In this position, the overall width of the screed assembly 10 is minimized. When preparing the screed assembly 10 for operation, the extendable screed portions 22 are extended using the actuators 54 to provide a desired total paving width.
The apparatus described above including the coupling portions 42 enables such extended width to accommodate structural overlaps such that the screed assembly 10 may be extended to fully double the retracted width. This occurs when the variable length portion intermediate wall 38 is moved away from the inner end wall 30 in response to the actuator 54 moving the extension screed portion variable length frame 26 logitudinally axially relative to the main screed portion fixed length frame 18 to the fully extended position. In this way, the paving machine screed assembly 10 may be readily adjusted from a minimum paving width up to a maximum paving width that is double the minimum width. According to specific design needs, selected ones of the disclosed embodiments of the present invention facilitate preventing rotational and/or linear movement between the first and second coupling members 46, 50.
Although the invention has been described with reference to various preferred embodiments, in light of the overall disclosure one skilled in the relevant arts may recognize or conceive modifications, variations, and alternative constructions not specifically addressed in detail above. For example, although several structures sufficient to enhance the rigidity of a screed assembly 10 and to prevent rotational and/or linear movement between the coupling members 46, 50 have been described, one skilled in the mechanical arts may well find other structures sufficient for this purpose. Such adaptations, and all other aspects, objects, and advantages of this invention as may be obtained from a study of the drawings, the disclosure, and the appended claims, are intended to be covered by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 04011028.0 | May 2004 | EP | regional |
