Safety device for a vehicle door actuated by a turnable shaft

A safety device for a vehicle door of the type actuated by a turnable shaft driven by a piston cylinder unit having a piston rod connected by a hinge bolt to a lever arm fixedly mounted on the turnable shaft. The safety device comprises a carrier coupled to the lever arm and slidably receiving the piston rod, a switch element on the carrier and a control element on the piston rod. When the door encounters an obstacle, the control element is brought into contact with the switch element to reverse the direction of movement of the door.

FIELD OF THE INVENTION 
The invention relates to a safety device (anti-clamping device) for a 
vehicle door actuated by a turnable shaft which is driven by a piston and 
cylinder unit, the piston rod of which is connected via a hinge bolt to a 
lever arm which is fixedly mounted on the turnable shaft. 
PRIOR ART 
As is known, an anti-clamping device for a vehicle door operates to reverse 
the direction of travel of the door leaf if in the range of movement of 
the door leaf an obstacle is encountered, for example, if a person enters 
when the door leaf is already moving towards closed position and the 
person could thus be clamped in the door. 
Anti-clamping devices are known which operate by pneumatic means. Thus, if 
an obstacle exerts a pressure upon the pneumatic system, a reversal of 
movement is effected, as a result of which the door leaf carries out a 
correspondingly reverse movement. 
Such anti-clamping devices operating on a pneumatic basis are, however, 
dependent on atmospheric conditions to a certain extent, because if the 
temperature rises or drops, the pressure in the pneumatic system also 
changes so that the response of the anti-clamping arrangement varies. Such 
arrangements are therefore not always functionally reliable. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide an anti-clamping device for a 
vehicle door, which is independent of temperature and which can be 
installed outside the finger-protecting strip of the door leaf. 
According to the invention, this is achieved in that a carrier for a switch 
element is associated with the piston rod of the piston-cylinder drive and 
the piston rod is movable relative to the carrier and carries the control 
element for the switch element. 
According to a preferred embodiment, the carrier comprises a sleeve 
concentric with the piston rod and supported on the hinge bolt. A spring 
is arranged concentrically on the piston rod and bears, on the one hand, 
on the piston rod and, on the other hand, on the sleeve, the switch 
element being provided on the sleeve. 
In a specific arrangement, the piston rod has an end with an elongated hole 
loosely receiving the hinge bolt to permit the relative movement; also, 
the sleeve body is provided with an elongated hole loosely receiving the 
control element. 
When the door leaf carries out the closing movement and in so doing 
encounters an obstacle, then the piston and cylinder drive has the 
tendency to continue to pull its piston rod in the pulling direction for 
the closure movement, while the lever arm, due to the obstacle, is not 
capable of performing any movement. As a result of this, the piston rod 
performs a movement relative to the carrier which is constructed as a 
sleeve. 
Since the control element is provided on the piston rod, the control 
element thus engages the switch element which is provided on the sleeve 
and effects the motion reversal. 
The location of the spring between the sleeve and the piston rod assures 
that the piston assumes the initial position with respect to the sleeve.

DETAILED DESCRIPTION 
FIG. 1 shows the door of a vehicle which comprises door leaves 1 and 2 
which are actuated in known manner by turnable shafts 3 and 4, 
respectively. 
The drive of each shaft is effected by a piston-cylinder drive 5 whose 
piston rod 6 is connected to the turnable shaft via a lever arm 7 which is 
fixedly mounted on the turnable shaft. A pivotable connection is made 
between the piston rod 6 and the lever arm 7 by a pivot or hinge bolt 13. 
An anti-clamping device 8 is associated with the piston rod and the lever 
arm and is illustrated in detail in FIG. 2. 
The anti-clamping device 8 comprises a carrier 9 slidably receiving the 
piston rod 6 and engaging the hinge bolt 13. Mounted on the piston rod 6 
is a control element 10 and mounted on the carrier 9 is a switch element 
11. 
The construction is such that the carrier 9 is formed as a sleeve 12 which 
is concentric with the piston rod 6. The sleeve 12 is supported on the 
hinge bolt 13 which connects the piston rod 6 with the lever arm 7 with 
play. More particularly, the end 6a of the piston rod is constituted as a 
forked head provided with elongated holes 17 permitting relative movement 
between bolt 13 and piston 6. 
A spring 14 is engaged at one end with the sleeve 12 and at the other end 
with the forked head 6a of the piston rod 6. An elongated hole 15 is 
provided in the sleeve 12 to loosely receive the control element 10 and 
permit relative movement between element 10 and carrier 9. 
During closing movement of the door leaf, the associated piston rod 
undergoes a movement in the direction of the arrow 16. 
If, during this movement, the door leaf encounters an obstacle, then the 
lever arm 7 can not participate in this movement, and it has the tendency 
to retain the piston rod. In this case, however, the piston rod can still 
undergo movement due to the elongated holes 17. During this movement, the 
control element 10 contacts the switch element 11 and controls a circuit 
which produces a direction reversal of the door leaf. 
For purposes of adjustability of the tension of the spring 14, the sleeve 
is composed of threaded sleeve sections 12a and 12b. The sleeve 12b, 
against which the spring 14 is engaged is threaded into the sleeve section 
12a and can be adjusted as regards its depth of threaded engagement to 
adjust the initial tension in the spring. A counter nut 18 serves to lock 
the two sleeve sections 12a and 12b. 
Not only can the spring tension be varied by the two sleeve sections 12a, 
12b, but it is also possible to compensate for friction of the bearings of 
the turnable shaft. 
As seen from the above, there is provided a safety device according to the 
invention which comprises a switch means actuable when the door encounters 
an obstacle and is prevented from closing whereby the door is driven in 
opposite direction. The switch means comprises the carrier 9 coupled to 
the lever arm 7 and slidably receiving the piston rod, switch element 11 
and control element 10 for operating the switch element. 
Although the invention has been disclosed in conjunction with a specific 
embodiment thereof, it will become evident to those skilled in the art 
that numerous modifications and variations can be undertaken within the 
scope and spirit of the invention as defined in the attached claims.