A carriage adapted to be slidably mounted on a track

Abstract: A carriage adapted to be slideably mounted on a track comprises a main body having a pair of retaining elements adapted for lateral movement therein. Each turning element is biased inwardly to allow the carriage to be mounted on and removed from a channel formed in the track. A pivotally mounted knife element is adapted to engage each retaining element thereby moving said retaining element outwardly to a position in which they engage the side edges of the channel formed in the track, thereby securing the carriage to the track.

Description: THE PRESENT INVENTION relates to a carriage adapted to be slidably mounted on a track. Tracks are often provided in motor vehicles such as coaches or buses, trains or aircraft for mounting a large number of passenger seats. Typically an individual seat or a row of adjacent seats are secured via legs to a carriage which is then slidably mounted upon a length of track secured to the floor of the vehicle. In this way, a number of seats or rows of seats may be installed along a length of a vehicle such that the spaces between successive seats or rows of seats may be adjusted, thereby varying the "leg room" for passengers. When the seats have been located in their desired position, the carriage may be locked to the track, typically via a spring-biased plunger engaging a recess in the track. A significant problem with such installations, is that the locking mechanism uses relatively small plungers. This presents small engaging surfaces between the plungers and the track, resulting in extremely high local forces in the event that the carriage is urged along the track against the locking mechanism, for instance in an accident. These high local forces can cause damage to the track or carriage due to buckling or breakage. U.S. Patent 5,236,153 (corresponding to the preamble of claim 1) teaches of such an arrangement comprising a carriage slidably mounted on a track and two arms pivotally mounted on the carriage. A pivot pin is provided such that, when the pin is in one position, the arms are not engaged with the track and such that, when the pin is in a second position, the arms are forced outwardly into engagement with the track to prevent the carriage from moving relative to the track. Another common problem with such installations, is that different types of carriage each have an individual locking arrangement making it suitable for use with only a particular configuration of track. In the event of an accident, it is desirable to provide a locking mechanism which acts as an energy absorber allowing controlled movement of the carriage in relation to the track. This is particularly important when passengers in a vehicle are wearing seat belts, since sudden deceleration, causes each passenger to continue moving, due to inertia, relative to the seat belt which in turn applies considerable pressure to certain parts of the body, thereby increasing the risk of injury. It is therefore an object of the present invention to provide an improved carriage assembly. Accordingly, the present invention provides a carriage adapted to be slidably mounted on a track comprising an elongate upwardly open channel formed with at least one longitudinally extending lip, the carriage having a main body with at least one moveable retaining element adapted for lateral movement from a locating position in which the carriage may be freely mounted on and removed from said channel to a securing position in which the retaining element is adapted to engage the undersurface of said lip thereby securing the carriage to the track, and securing means characterised by a pivotally mounted knife element having a free end and adapted for movement from a first position to a second position in which the knife element engages part of the or each retaining element and moves said retaining element outwardly from said locating position towards said securing position. Preferably the or each retaining element is substantially elongate in form having a lower flange extending outwardly from below the main body of the carriage, said lower flange being adapted to engage the undersurface of said lip. Conveniently biasing means is provided to bias the or each retaining element inwardly towards said locating position. Conveniently said securing means is further adapted to move the or each retaining element outwardly from said locating position to an intermediate retaining position, said retaining position being partway between said locating position and said securing position such that the carriage may be retained upon said track and allowed to slide thereupon. Advantageously movement of said knife element from said first position to said second position results in outward movement of the or each retaining element from said locating position to said retaining position. Conveniently said securing means comprise means to depress the free end of said knife element when in said second position, thereby moving the or each retaining element outwardly from said retaining position to said securing position. Preferably the carriage is provided in combination with a track, the track comprising an elongate upwardly open channel formed with at least one longitudinally extending lip. In order that the present invention may be more readily understood, an embodiment thereof will be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a carriage having a section cut away, and showing part of the carriage, illustrated in phantom, in an alternative position; Figure 2 is a bottom view of the carriage illustrated in Figure 1; Figure 3 is a perspective view of a track suitable for use with the carriage illustrated in Figures 1 and 2. Figure 4 is a perspective view of another form of track suitable for use with the carriage illustrated in Figures 1 and 2. Figure 5 is a schematic cross-section through the carriage of Figure 1, along the line I-I, showing the carriage in connection with a track; Figure 6 is a side view of the carriage of Figure 1, with two parts in alternative positions; and Figure 7 is a schematic cross-section through the carriage of Figure 6, along line II-II, showing the carriage in connection with a track. Referring initially to Figure 1 and Figure 2, a carriage 1 is shown which is mountable on a track 2 or 3 as shown in Figures 3 and 4 respectively, the track being secured to the floor of a vehicle such as a motor vehicle, a train or an aircraft. The track 2, as shown in Figure 3, comprises a single elongate piece of extruded aluminium formed as an upwardly open channel of substantially C-shaped cross-section. The channel is defined by a base plate 4 and two upstanding elongate side walls 5, 6 which terminate at two inwardly facing and opposed lips 7, 8. Each side wall 5, 6 defines an edge of the open channel. Each lip 7, 8 has a respective undersurface 9, 10 and defines a respective linear edge portion 11, 12 which is parallel to the longitudinal axis of the track 2. The track 3, as shown in Figure 4, is of substantially similar configuration to that of track 2, the same reference numerals being used for like parts of the track. In this configuration, the lips 7, 8 are provided with a number of arcuate cut-away segments 13 at regular intervals along the length of the track 3. Each cutaway segment 13 on each lip 7, 8 is directly opposite a corresponding arcuate cutaway segment 13 on the opposite lip 8, 7. Each pair of opposing arcuate cutaway segments 13 define a nominal circle. Between neighbouring cutaway segments 13 on each lip 7, 8 there is formed a linear edge portion 14 which is parallel to the longitudinal axis of the track 3 and which links the ends of the neighbouring arcuate cutaway segments 13. The linear edge portions 14 of each lip 7, 8 are co-aligned, the linear portions of the two edges being parallel and spaced apart by a pre-determined distance. The carriage 1 comprises a substantially rectangular main body 15 having at each end a substantially cylindrical upwardly extending socket 16 adapted to receive the leg of a seat, and a downwardly depending registering lug 17 of substantially rectangular form. Within main body 15, there is provided an elongate central slot 18 therethrough within which there is received a pivotally mounted knife element 19, a lever 20 and a pair of opposing elongate retaining elements 21. Each retaining element 21 is of C-section having a vertical web 22, a horizontally outwardly extending upper flange 23 and a horizontally outwardly extending lower flange 24. Upper flange 23 is provided with an inwardly facing, inclined engaging surface 25 adapted to engage knife element 19. Each retaining element 21 is received within the main body 15 such that the upper flange 23 is slidably engaged upon an upwardly directed flat surface 26, and web 22 extends downwardly from main body 15 such that lower flange 24 may extend outwardly therefrom. A securing plate 27 is secured to the top of main body 15, thereby loosely retaining each retaining element 21 within the main body, such that each retaining element is capable of limited rotation about a longitudinal axis. Along the length of main body 15, there is provided a plurality of transverse apertures 28 therein. Within each aperture 28 is a helical spring 29 mounted upon a cylindrical pin 30, such that the outer end of spring 29 is secured to the outer end of pin 30 and the inner end of spring 29 engages web 22 of retaining element 21. In this way, the helical springs 29 serve as biasing means to bias each guide rail inwardly with respect to the main body 15. Knife element 19 is pivotally mounted upon a transverse shaft 31 at one end of slot 18. Knife element 19 is substantially elongate in form having a lower sharpened edge 32 for engagement with engaging surface 25 of each retaining element 21. Knife element 19 is provided with a knob 33 secured to its upper edge 34. Knife element 19 terminates at a free end 35 with a downwardly curving corner surface 36 and a flat undersurface 37. Also formed at free end 35 of knife element 19 there is an enlargened downwardly depending blade portion 38. Lever 20 is pivotally mounted about transverse shaft 39 at the opposite end of slot 18. Lever 20 is formed with an upwardly extending handle portion 40 secured thereto. The shank 41 of lever 20 is formed with an inwardly directed cam face 42 and an upwardly projecting protrusion 43 having a substantially arcuate profile. In operation, the carriage 1 is secured to the legs of a seat via sockets 16. The knife element 19 is then moved upwardly to a position substantially as shown in phantom in Figure 1, lever 20 also being moved to a substantially vertical position. In this condition, the biasing springs 29 bias the retaining elements 21 inwardly with respect to main body 15. The carriage 1 may then be lowered onto the track 2 or 3 such that registering lugs 17 are each received within the channel of the track. Knife element 19 may then be lowered to a position substantially as shown in bold in Figure 1. In this way, sharpened edge 32 engages the engaging surface 25 of each retaining element 21, and due to the downward motion of knife element 19, forces the retaining elements 21 apart with a limited degree of rotation relative to the main body 15. In this condition, the retaining elements are in a position similar to that illustrated schematically in Figure 5. The rotational motion is due to the fact that the inwardly biasing force due to springs 29 acts along a line below the point of application of the outward force due to knife element 19, thereby producing a lever effect which causes each retaining element to rotate due to its loose fit within the carriage 1. Each lower web 24 engages the undersurface 9 or 10 of track lips 7 or 8. In this condition, the carriage is retained upon track 2 or 3 such that the carriage is free to slide along the track. Once the desired position of the carriage is attained, lever 20 may be depressed such that cam surface 42 engages curved corner surface 36, thereby depressing knife element 19 into the position shown in Figure 6. This action forces enlargened blade portion 38 downwardly between respective guide rails 21, thereby pushing the guide rails further apart such that they straighten up and assume a position substantially as illustrated in Figure 7. In this condition the outer edges of lower flanges 24 engage a respective side edge of the channel formed in track 2 or 3 with considerable force, hence locking the carriage via friction, in the pre-determined position along the length of track. In this condition, due to the elongate form of retaining elements 21, any load then exerted on carriage 1 is spread over a substantial area of the rail 21. Thus the risk of the rail deforming is substantially reduced. However, in the event of the motor vehicle being involved in an accident, the retaining elements permit controlled forward movement of the carriage 1 relative to the track 2 or 3 in response to a predetermined force capable of overcoming the frictional force between each retaining element 21 and the track. Thus, if a substantial force is applied to the occupant of the seat the entire seat may move forward slightly, thus reducing the risk of injury being imparted to the occupant of the seat. In order to remove the carriage 1 from track 2 or 3, the first step is to lift lever 20 from the position illustrated in Figure 6 to that illustrated in Figure 1. This movement causes arcuate protrusion 43 to move upwardly thereby engaging flat undersurface 37 of knife element 19. The upward movement of lever 20 thus lifts the free end 35 of knife element 19, thereby raising enlargened blade portion 38 and permitting retaining elements 21 to assume the position illustrated in Figure 5, due to the biasing force of springs 29. In this condition, the carriage 1 is again allowed to slide along track 2 or 3 whilst being retained thereupon. To remove the carriage 1 completely from the track 2 or 3, the knife element 19 must then be lifted, using knob 33 for grip, such that sharpened portion 32 is removed from between respective retaining elements 21. Retaining elements 21 are then forced inwardly under the action of biasing springs 29, such that lower flanges 24 thereof no longer engage the undersurface 9, 10 of track lips 7, 8. The carriage 1 is now free to be lifted from track 2 or 3. Whilst the present invention has been described with reference to carriage 1 carrying sockets 16 for attachment to the legs of a seat, it is to be appreciated that alternative fixing means may be used. For instance, it is also envisaged that loops, rings or shackles may be secured to the carriage 1 to engage straps or ropes which can be used to lash and restrain heavy objects within a vehicle.

Claims: A carriage (1) adapted to be slidably mounted on a track (2,3) comprising an elongate upwardly open channel formed with at least one longitudinally extending lip (7), the carriage (1) having a main body (15) with at least one moveable retaining element (21) adapted for lateral movement from a locating position in which the carriage (1) may be freely mounted on and removed from said channel to a securing position in which the retaining element (21) is adapted to engage the undersurface of said lip (7) thereby securing the carriage (1) to the track (2,3), and securing means (19) characterised by a pivotally mounted knife element having a free end and adapted for movement from a first position to a second position in which the knife element engages part of the or each retaining element (21) and moves said retaining element outwardly from said locating position towards said securing position. A carriage according to Claim 1, wherein the or each retaining element (21) is substantially elongate in form having a lower flange (24) extending outwardly from below the main body of the carriage (1), said lower flange (24) being adapted to engage the undersurface of said lip (7). A carriage (1) according to Claim 1 or Claim 2, wherein biasing means (29) is provided to bias the or each retaining element (21) inwardly towards said locating position. A carriage (1) according to any one of the preceding claims, wherein said securing means (19) is further adapted to move the or each retaining element (21) outwardly from said locating position to an intermediate retaining position, said retaining position being partway between said locating position and said securing position such that the carriage (1) may be retained upon said track (2,3) and allowed to slide thereupon. A carriage according to Claim 4 wherein movement of said knife element (19) from said first position to said second position results in outward movement of the or each retaining element (21) from said locating position to said retaining position. A carriage (1) according to Claim 5, wherein said securing means (19) comprise means (33) to depress the free end (35) of said knife element (19) when in said second position, thereby moving the or each retaining element (21) outwardly from said retaining position to said securing position. A carriage (1) according to any one of the preceding claims in combination with a track (2,3) the track (2,3) comprising an elongate upwardly open channel formed with at least one longitudinally extending lip (7).

Inventors: SAWDY MICHAEL BARRY, SAWDY, MICHAEL BARRY
Applicants: NMI SAFETY SYSTEMS LTD, NMI SAFETY SYSTEMS LTD.
Application year: 1996
Main classification: B60N2
IPC codes: B60N2