Cable drive for motor-vehicle sliding door

A cable drive for a motor-vehicle sliding door has a pair of cable sections of predetermined diameter and each having one end attached to the vehicle and an opposite end, a pin fixed on the vehicle, defining an axis, and having a screwthread of a pitch at least equal to the cable diameter, and a gear having a core threaded onto the pin. A pair of coaxial drums having smooth outer surfaces are axially coupled to but rotatable on the core and are each connected to a respective one of the opposite ends of the cable sections. A spring is engaged between and urges the drums rotationally oppositely to tension the cable sections. Interengaging formations on the gear and on the drums rotationally couple the drums to the gear and a reversible drive motor coupled to the gear simultaneously rotates the gear about the axis, axially displaces the gear on the pin, winds up one of the cable sections on the surface of the respective drum, and unwinds the other of the cable sections from the surface of the respective drum.

FIELD OF THE INVENTION 
The present invention relates to a motor-vehicle sliding door. More 
particularly this invention concerns a cable drive for opening and closing 
such a door. 
BACKGROUND OF THE INVENTION 
A standard motor-vehicle sliding door moves on tracks between a closed 
position and an open position. It is now standard to provide a drive for 
power-assisted and even remote operation of this door, which under the 
best of circumstances can be difficult to manipulate. 
In a standard arrangement a pair of cable sections, which may be separate 
or parts of a common cable, each have one end anchored on the door and an 
opposite end anchored on a respective drum. The drums are coaxially 
mounted on a common drive pin and are biased in angularly opposite 
directions by a spring connected between them to keep the cable sections 
taut. A drive gear rotated by a reversible electrical motor can engage one 
or the other of the coaxial drums, depending on whether the door is to be 
opened or closed, to rotate the two drums, paying the cable off one of 
them and winding it up on the other. 
To preserve the cable each of the drums is formed with a helical groove 
intended to receive the respective cable section when it is wound thereon. 
It is important that the cable wind up smoothly, without turns one atop 
the other, so that the cable itself does not chafe and in order to 
maintain the assembly as compact as possible. 
The problem with this arrangement is that the drums are fairly expensive to 
manufacture, mainly due to formation of the helical cable-seat groove. In 
addition the cable is pulled at an angle at least toward the end of a 
windup operation, so it is fairly common for the cable to jump out of its 
groove and ride up on previously laid turns, causing a chafing problem and 
possibly leading to binding of the drum due to its increased diameter. 
OBJECTS OF THE INVENTION 
It is therefore an object of the present invention to provide an improved 
cable drive for a motor-vehicle sliding door. 
Another object is the provision of such an improved cable drive for a 
motor-vehicle sliding door which overcomes the above-given disadvantages, 
that is which ensures that the cable will be wound up in a single layer of 
turns on the drums. 
SUMMARY OF THE INVENTION 
A cable drive for a motor-vehicle sliding door has according to the 
invention a pair of cable sections of predetermined diameter and each 
either having one end attached to the vehicle or a common center portion 
connected to the door and an opposite end, a pin fixed on the vehicle, 
defining an axis, and having a screwthread of a pitch at least equal to 
the cable diameter, and a main gear having a core threaded onto the pin. A 
pair of coaxial drums having smooth outer surfaces are axially coupled to 
but rotatable on the core and are each connected to a respective one of 
the opposite ends of the cable sections. A spring is engaged between and 
urges the drums rotationally oppositely to tension the cable sections. 
Interengaging formations on the gear and on the drums rotationally couple 
the drums to the gear and a reversible drive motor coupled to the gear 
simultaneously rotates the gear about the axis, axially displaces the gear 
on the pin, winds up one of the cable sections on the surface of the 
respective drum, and unwinds the other of the cable sections from the 
surface of the respective drum. 
With this system, therefore, the drums travel axially as they rotate, 
automatically forming neatly aligned adjacent turns of the cable section 
being wound up and smoothly paying out the cable being unwound. In fact 
the point at which the cables tangent the respective drums will not move 
at all during the winding and unwinding operations so that the cable 
sections can be accommodated easily in a very narrow guide. 
The cable sections in accordance with the invention can be separate with 
their one ends fixed at separate respective locations to the vehicle. In 
this case respective rollers are provided on the door over which the cable 
sections pass. Alternately the cable sections are parts of a single cable 
having a central part constituting the one ends and connected to the door. 
The axis of the threaded pin according to the invention is vertical and the 
gear is underneath the drums. A spring can be provided for urging the 
drums axially down against the gear. In addition or alternately a snap 
ring seated in the core above the drums serves an upper abutment for the 
drums which therefore are captured axially on the core between the gear 
and the snap ring. 
Both outer surfaces in accordance with the invention are cylindrical and of 
substantially the same diameter. One of the drums is formed of an inner 
sleeve extending along the core inside the other of the drums and an outer 
sleeve defining the respective outer surface and forming with the inner 
sleeve an annular compartment open toward the other drum. The spring is a 
torsion spring set in the compartment and having one end seated in the one 
drum and another end seated in the other drum. 
The inner sleeve extending along the core inside the other of the drums and 
the other drum are formed with radially alignable and radially 
throughgoing notches and the core is formed with an outwardly projecting 
lug received with angular play in the notches. The lug and notches 
constitute the formations. 
Outer ends of the drums are formed with radially outwardly projecting 
flanges. In addition according to the invention the drive motor is 
provided with an axially elongated drive gear meshing with the main gear 
that can have end flanges limiting axial travel of the drums and the main 
gear. Position detecting switches engageable with and operable by the 
drums or gear in end positions thereof are connected to a controller that 
operates the motor on detection of travel of the drums or gear into their 
end positions.

SPECIFIC DESCRIPTION 
As seen in FIGS. 1 through 3, a motor vehicle 1 is provided with a sliding 
door 2 operated by a drive shown generally at 3. The door 2 has a central 
arm 4 received in a guide rail 28 of the type described in commonly owned 
patent application Ser. No. 08/831,981. The drive 3 pays out and winds 
back a pair of cable sections 8a and 8b having ends 9a and 9b anchored on 
the vehicle 1 and opposite ends anchored on coaxial drums 5a and 5b 
coupled together by a torsion spring 7 and rotated by a motor 6 about a 
vertical axis A. The cable section 8b passes around an idler roller 18 
mounted on the vehicle 1 and both sections 8a and 8b pass around wheels 
10a and 10b mounted on the arm 4. In FIG. 6 a single cable 8 is provided 
both of whose ends are anchored on the arm 4. 
The drums 5a and 5b according to the invention have radially outwardly 
projecting end flanges 27 and are coaxial to the vertical axis A defined 
by a threaded pin 16 fixed on the motor-vehicle body 1 and extending 
substantially perpendicular to the cable sections 8a and 8b. The drum 5a 
has a cylindrically tubular inner sleeve 20 that rides on a tubularly 
cylindrical core 12 of a large-diameter gear 13 having a threaded bore 15 
screwed onto the pin 16. The drum 5b in turn rides on the center sleeve 20 
and the drum 5a has an outer sleeve 21 defining with its inner sleeve 20 
an annular compartment 22 holding the torsion spring 7 whose one end is 
seated in the drum 5a and whose other end is seated in the drum 5b. The 
drums 5a and 5b have identical smooth cylindrical outer surfaces 11a and 
11b on which the respective cable sections 8a and 8b can wind up. A snap 
ring 19 holds the drums 5a and 5b on the core 12 against axial movement 
relative thereto. In addition or alternately a spring such as shown 
schematically at 29 may urge the upper drum 5a down against the lower drum 
5b and urge it down against the gear 13. 
The gear 13 is formed with a radially projecting entrainment lug 17 and the 
drum 5b and the inner sleeve 20 are formed with radially open notches 23 
and 24 having end faces 25 and 26 that can angularly engage this lug 17 as 
shown in FIG. 5. The tension in the spring 7 is such that normally the lug 
17 only engages one of the surface 25 or one of the surfaces 26. 
The gear 13 meshes with an axially long gear 14 carried by the motor 6. In 
addition the pitch of the screwthread of the pin 16 is generally least 
equal to the diameter of the cable forming the sections 8a and 8b. Thus as 
the motor 6 rotates the gear 14 which in turn rotates the gear 13 and both 
the drums 5a and 5b, the entire drum assembly formed by both the drums 5a 
and 5b and by the gear 13 will move axially through a stroke L which is 
substantially shorter than the length of the gear 14. The gear 14 may be 
formed with end flanges such as shown at 14' to limit the axial travel of 
the gear 13. The cable sections 8a and 8b will therefore wind up on the 
surfaces 11a and 11b in adjacent turns in a single layer. 
End switches such as shown schematically at 30 may be operated by the gear 
13 and are connected to a controller 31 that stops the drive motor 6 when 
the gear 13 reaches end positions. The axial or vertical position of the 
gear 13 is directly related to the horizontal position of the door 2, so 
that these switches 29 can indicate the open or closed position of the 
door 2.