Abstract:
A telescoping bar includes a track pusher for adjusting and measuring the track on a motor vehicle&#39;s wheels. A pneumatic spring, housed within the telescoping bar, functions as an accumulator and applies expansion forces on either the two front wheels or two rear wheels of the vehicle.

Description:
FIELD OF THE INVENTION 
     The invention relates to an alignment device for motor vehicles. 
     SUMMARY OF THE INVENTION 
     The present invention is a system used for adjusting and measuring the track of a motor vehicle&#39;s wheels. The system includes a telescoping bar, which is adjustable in length and includes a spring that functions as a accumulator. The two opposing ends of the telescoping bar exert expansion forces on either the two front wheels or the two rear wheels of a vehicle. Such a system, also designated as a track pusher, exerts a specific initial stressing force, for example 100 N onto the vehicle&#39;s wheels. However, in known systems, a mechanical spring, in particular a compression spring, serves to produce the initial stressing force onto the wheels. In conventional systems where attempts have been made to measure several different vehicles that include different vehicle track widths, the strokes of the mechanical spring may produce imprecise and divergent expansion forces. 
     Thus, an objective of the invention is to create a system for adjusting the track on the wheels of a motor vehicle, in which a constant expansion force is supplied throughout the stroke. 
     One embodiment of the invention includes a pneumatic spring that serves as an accumulator. This embodiment includes a pneumatic spring housing and a piston rod telescoping axially out of the pneumatic spring housing with a certain force, e.g. 100 N. The pneumatic spring slidably attaches to the piston rod, which includes two attachment points that connect to a telescoping bar. Furthermore, during the stroke of the piston rod&#39;s as it moves out of the pneumatic spring housing, an axial guiding arrangement of the telescopically adjustable bar supports the piston rod radially. In this manner, the invention guarantees that forces acting on the relatively thinly-designed piston rod act only in the axial direction, in which the spring force is essentially transferred. 
     During operation, one end of the pneumatic spring housing may be pressed against one wheel of the motor vehicle, for example, the left front wheel. In this connection, the end of the housing forms one end of the telescoping bar. The free end of the piston rod may be attached and/or supported on the bar-shaped guiding arrangement designed, in particular, as a tube. The pneumatic spring housing may be guided axially by a certain stroke exerted, for example, by on one end of the guiding arrangement. The other end of the guiding arrangement, which forms the other end of the telescoping bar, may be pressed against the other wheel of the motor vehicle, for example, the right front wheel. 
     In addition, several embodiments of the invention are possible in which the pneumatic spring housing supports a pneumatic spring within a guiding arrangement. The guiding arrangement may be supported against one wheel of the motor vehicle with an end portion that forms an end of the telescoping bar. The piston rod connects to an end of the telescoping bar so that support against the other wheel may be achieved. For instance, the piston rod may connect directly with one end of the telescoping bar, whereby the piston rod may be supported radially against the guiding arrangement during its axial movement or so that the end of the telescoping bar has one or more guide parts that may slide axially on the guiding arrangement. 
     The guiding arrangement may be designed tubular, so that the guiding arrangement supports the pneumatic spring housing, which mounts inside the tubular guiding arrangement. 
     The embodiments of the invention ensure that a constant initial stressing force, for example of 100 N, is exerted over the entire range of track width. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is further described in the detailed description which follows, by reference to the noted drawings by way of non-limiting exemplary embodiments, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein: 
     FIG. 1 is a partial sectional view of a first embodiment according to the invention; 
     FIG. 2 illustrates an exemplary installation of the invention of FIG. 1 installed as a track pusher on two front wheels of a motor vehicle; 
     FIG. 3 is a sectional view of a second embodiment according to the invention; and 
     FIG. 4 is a sectional view of a third embodiment according to the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1-4 illustrate various embodiments according to the invention of systems that may be employed to adjust and align the track on the wheels of a motor vehicle. The exemplary embodiment of FIG. 1 illustrates a track pusher that includes a pneumatic spring  1 , which serves as an accumulator. The pneumatic spring  1  comprises a cylindrical, tubular pneumatic spring housing  2  and an axially sliding piston rod  3  that protrudes from one end of the pneumatic spring housing  2 . A certain initial stressing force, which may be produced in a known manner by a hydropneumatic arrangement arranged within the pneumatic spring housing  2 , acts on the sliding piston rod  3  during operation. This initial stressing force may be, for example, approximately 100 N. 
     A first free end  5  of the piston rod  3  attaches at a point of attachment  11  on a bar-shaped guiding arrangement  6  so that the pneumatic spring housing  2  and the piston rod  3  are guided axially within the guiding arrangement  6 . The point of attachment  11  may include two diametrically opposite points of attachment  11  for supporting and securely attaching the first free end  5  of the piston rod  3  to the guiding arrangement  6 . Attachment of the point of attachment  11  to the guiding arrangement  6  may be established, for example, by a transverse pin  12 . The distance of the point of attachment  11  from a first end  4  of the guiding arrangement  6  corresponds to at least the stroke H by which the piston rod  3  may telescope out of the pneumatic spring housing  2 . When the piston rod  3  fully extends so that it is completely telescoped, a first end  13  of the pneumatic spring housing  2  remains retained within the first end  4  of the guiding arrangement  6 . In the exemplary embodiment of FIG. 1, the first end  4  of the guiding arrangement  6  guides telescopically the pneumatic spring housing  2 . The guiding arrangement  6  bar-shaped design may be designed as a tube having various configurations, e.g., a slit tube  6 , a fully encased tube or a tubular jacket. The guiding arrangement  6  comprises a cavity in which the piston rod extends axially. The pneumatic spring housing  2  may also be pushed into the cavity of the guiding arrangement  6  by the force of the stroke H exerted against the initial stressing force of the pneumatic spring  1  accumulator. 
     As depicted in FIGS. 1 and 2, the second free end  8  of the pneumatic spring housing  2  may be equipped with a pressure cap  18  made from materials such as plastic, hard rubber or other similar flexible but durable substances. As illustrated in FIG. 2, the second free end  8  of the pneumatic spring housing  12  may press against a front wheel  9 , e.g. the left front wheel, of a motor vehicle. In this manner, the second free end  8  serves as a bar end  8  of the telescoping bar. Pressing against the other front wheel, a second end  7  of the of the guiding arrangement  6 , provided with a pressure cap  19 , also fictions as a bar end. In this configuration, the pressure caps  18  and  19  press against the inner surfaces of the tires of the two wheels  9  and  10 , respectively, as FIG. 2 shows. The accumulator of the pneumatic spring  1  exerts an expanding action via the two ends  7  and  8  of the telescoping bar on the two wheels. Since the initial stressing force of the pneumatic spring  1  supplies a constant force over the range of the width of the vehicle&#39;s track, the track pusher according to the invention achieves a high degree of precision in measuring track adjustments and alignments. 
     FIGS. 3 and 4 illustrate further examples of executing exemplary embodiments according to the invention. In the examples of FIGS. 3 and 4, the pneumatic spring  1  mounts inside the guiding arrangement  6  (tubular guide). The guiding arrangement  6  supports the pneumatic spring  1  by way of attachment at the point of attachment  11  of the guiding arrangement  6 . In this embodiment, the second end  7  of the guiding arrangement  6  presses against the wheels of a motor vehicle during expansion. Meanwhile in FIG. 3, an attachment mechanism  14  connects to the piston rod  3 , which can be moved telescopically out of the pneumatic spring housing  2  essentially with a constant force exerted by a certain stroke. In the example of execution shown in FIG. 3, the piston rod  3  connects with end  8  of the telescoping bar via an attachment mechanism  14 , which may be a tappet, that is guided axially on the guiding arrangement  6  via two support points. In comparison to FIG. 3, the piston rod  3  of FIG. 4 connects directly with the axially sliding end  8  of the telescoping bar. The ends  7  and  8  of the bar in the examples of FIGS. 3 and 4 may also be designed in the form of plastic caps or the like. 
     In FIG. 3, the two support points, supported radially on the guiding arrangement  6 , provide the axial guiding for the tappet  14 . In FIG. 3, the two support points forms a piston-like widening  16  that attaches at the end of the tappet  14  which connects to the piston rod  3 . The piston-like widening  16  rests slidably within the inner wall of the tubular guiding arrangement  6 . As a further axial support point, a guiding bore  17 , provided within the sealing cap at end  4  of the guiding arrangement  6 , radially supports the tappet  14 , as the tappet  14  slides within the bore. In this manner, the telescoping bar provides simultaneous radial support of the piston rod  3 , as well as axial support. The spring force of the pneumatic spring  1  transfers essentially in the axial direction onto the end  8  of the telescoping bar via the piston rod  3 . 
     In FIG. 4, a guiding part  15  rigidly connects with end  8  of the telescoping bar. The guiding part  15  mounts form-fittingly onto and slides axially on the guiding arrangement  6 . At the same time, the guiding part  15  ensures radial support of end  8  of the telescoping bar on the guiding arrangement  6 . Thus, the embodiment of FIG. 4 provides simultaneous radial and axial support for the piston rod  3  on the guiding arrangement  6 , so that the spring force exerted by the pneumatic spring  1  transfers essentially in the axial direction onto the end  8  of the bar. In FIG. 4, the tubular design of the guiding part  15  rests against the outside of the tubular guiding arrangement  6 . However, it is also possible for the guiding arrangement  6  as well as the guiding part  15  to include slitted guide tubes that interlock at their guide fingers.