[0001] This invention relates to a turntable assembly, particularly a turntable ladder of
a fire-fighting vehicle, having a ladder assembly and flexible guide ropes disposed
substantially one above another and laid to the top of the ladder, which guide ropes
are passed over deflection units attached to the end faces of ladder diagonals.
[0002] In a turntable assembly of the above-mentioned type, a double deflection of two guide
ropes disposed one above the other is known, wherein two comparatively large single
pulleys are seated one behind the other in a support bracket, which in turn is attached
to the ladder diagonals. The single pulley facing the attachment point has a slightly
larger diameter than the other, more remote single pulley, so that both guide ropes
are situated comparatively closely one above the other but without contact. The large
overall length of the deflection unit, which is determined by the two single pulleys
disposed one behind the other, is a disadvantage. The known deflection unit is not
suitable for use in a turntable assembly where space is very restricted. If, as in
another constructional variant, both deflection pulleys are disposed not one behind
the other but side by side in parallel, the space requirement increases in width.
However, for turntable assemblies a narrow type of construction is exactly what matters,
since the deflection units are situated in the region of the ladder diagonals of the
ladder assemblies between the upper and lower beams and are also slightly inclined.
[0003] The object of the present invention is to create a turntable assembly of the type
cited initially in which the deflection unit is constructed in a very space-saving
manner.
[0004] The object forming the basis of the invention is achieved by the means cited in the
characterising clause of claim 1.
[0005] The subject of the invention is advantageously developed further by the features
of subsidiary claims 2 to 13.
[0006] The essence of the invention is that at least one deflection unit is provided with
a row of rollers disposed substantially in a semicircle, via which a guide rope is
guided along the semicircular arc which determines the radius of deflection of the
guide rope, the rollers having a radius which is very small compared with the radius
of deflection.
[0007] It is particularly advantageous if the small rollers are of substantially identical
construction, wherein in an advantageous further development of the subject of the
invention a profiled roller may be provided at each end of the semicircular arc, the
radius of which profiled rollers corresponds to that of the other small rollers.
[0008] All the rollers may be spaced apart at the same distance from each other. The rollers
are preferably situated closely one behind another in a row on the semicircular arc,
but without mutual contact between them.
[0009] The rollers have axes of rotation which run parallel to each other.
[0010] It is also advantageous for a roller according to the invention if the deflection
unit additionally comprises a single central deflection pulley, which is large compared
with the rollers, for the deflection of another guide rope. In this respect the profiled
rollers are situated in close proximity to the large central deflection pulley or
to the other guide rope guided on this large deflection pulley without contacting
the latter.
[0011] The small rollers preferably consist of self-lubricating plastic material, and the
bearing pins of the small rollers have tubular stainless steel elements, which are
advantageously distance bushes which are disposed between the side cheeks of the support
bracket of a deflection unit. The distance bushes are screwed down to fixed bearing
bolts between the side cheeks of the support bracket.
[0012] If more than two guide ropes are to be deflected on a single deflection unit, an
additional row of rollers of the above-mentioned type may be provided for a third,
outer guide rope.
[0013] Therefore, by means of the invention at least one of the two flexible ropes to be
deflected in the same region is not passed over a single pulley, the radius of which
corresponds to the radius of deflection, but is passed over a row of rollers disposed
in a circle, which results in an extremely space-saving arrangement. The centres of
the radii of deflection are thereby displaced in parallel in order to permit the maximum
radii of deflection for a given overall height of the deflection unit. Due to the
extremely space-saving mode of construction, a plurality of flexible ropes can be
accommodated using a single deflection unit.
[0014] The invention is described in more detail below in terms of an example of an embodiment
and with reference to the accompanying drawings, where:
- Figure 1
- is a schematic vertical section through a deflection unit with two flexible guide
ropes to he deflected;
- Figure 2
- is a section through the deflection unit shown in Figure 1 along the line A-A;
- Figure 3
- is a section along line B-B of Figure 1;
- Figure 4
- is a section C-C from Figure 1;
- Figure 5
- is a schematic vertical section through the right half of a five-piece ladder assembly,
illustrating the installation of double deflection units in the region of the ladder
diagonals at the side; and
- Figure 6
- illustrates a prior art deflection unit similar to that of Figure 1.
[0015] As shown in Figures 1 to 5, a turntable assembly (1) is provided in the form of a
turntable ladder of a fire-fighting vehicle, the ladder assembly having five individual
ladder parts (2 to 6) as can be seen in particular from Figure 5. Each ladder part
has horizontal rungs (18), a lower beam (19), an upper beam (20) and ladder diagonals
(7) between the lower and upper beam. So that the individual ladder parts can be extended
or telescopically retracted, the flexible (electrical and/or hydraulic) guide ropes,
which are installed in the ladder assembly and which run from the lowest (largest)
ladder part (6) to the uppermost (smallest) ladder part (2), have to be passed over
deflection units (10) which are located in the region of the ladder diagonals (7).
In particular, front and rear deflection units (10) for two guide ropes (8, 9) disposed
one above the other are provided in each case on the second and fourth ladder parts
(3 and 5). In this respect the front deflection units are inclined slightly to the
left in relation to the vertical, and the rear deflection units (10) are inclined
slightly to the right in relation to the vertical.
[0016] A single deflection unit (10) is illustrated schematically in Figure 1. It comprises
a relatively large central single deflection pulley (13) for deflecting a guide rope
(9) which deflection pulley is rotatably mounted in a support bracket (16) which is
disposed substantially horizontally, the end of the support bracket (16) remote from
the bearing point being attached to the associated ladder diagonal (7) between the
upper and lower beams.
[0017] The deflection unit (10) is also designed for an additional guide rope (8) which
is led round a row of small rollers disposed substantially in a semicircle, these
small rollers having a very small radius (r) compared with the radius of deflection
(R). On account of the multiplicity of small rollers the centre (M₁) of the semicircular
arc or of the radius of deflection (R) can be placed in the vicinity of the centre
(M₂) of the comparatively large central deflection pulley (13), so that a short overall
length is achieved for a double deflection unit for two guide ropes. This short overall
length is directly advantageous when space is very constricted, which is not the case
for the prior art as shown in Figure 6, for example, in which two comparatively large
single pulleys are responsible for the considerable overall length of the deflection
unit, and the long overall length impairs the lateral guidance of a guide rope.
[0018] The rollers (11) for deflecting the guide rope (8) are of substantially identical
construction, and in the embodiment illustrated are disposed on the semicircular arc
at a uniform spacing (d) from each other. Whilst the majority of the rollers (11)
are constructed as illustrated in Figure 3, the first and the last roller (12) of
the semicircular arc, which are placed in the region of the guide rope (9), are of
profiled construction as shown in Figure 4 in order to ensure guidance run-in and
run-out without problems, whilst the remaining rollers (11) inexpensively consist
of standard plain bearings. A large number of rollers (11, 12) is employed, in order
to keep the angle of deflection and thereby the bending stress on the guide rope (8)
low. The deflection unit is of maintenance-free construction in that the rollers consist
of self-lubricating plastics and the bearing pins consist of tubular stainless steel
elements (14) which at the same time function as distance bushes which are braced
between the side checks (16) by fixed bearing bolts (17) as supports.
[0019] The central deflection pulley (13) may optionally also be designed as a row of rollers
of the type employed for the deflection of the guide rope (8). A third row of rollers
for a third guide rope may also be disposed in the same deflection unit (10).
[0020] Even though a "semicircular arc" is mentioned for the invention, the rollers may
be disposed according to the invention on a portion of an ellipse. The length of a
semicircular arc does not have to be exactly half a circle.
1. A turntable assembly (1), particularly a turntable ladder of a fire-fighting vehicle,
having a ladder assembly (2 to 6) and flexible guide ropes (8, 9) disposed substantially
one above another and laid to the top of the ladder, which guide ropes are passed
over deflection units (10) attached to the end faces of ladder diagonals (7), characterised
in that at least one deflection unit (10) is provided with a row of rollers (11) disposed
substantially in a semicircle, via which a guide rope (8) is guided along the semicircular
arc which determines the radius of deflection (R) of the guide rope (8), wherein the
rollers (11) have a radius (r) which is small compared with the radius of deflection
(R).
2. A turntable assembly according to claim 1, characterised in that the rollers (11)
are of substantially identical construction.
3. A turntable assembly according to claim 1 or 2, characterised in that a profiled roller
(12) is provided at each end of the semicircular arc, the radius of which roller corresponds
to the radius (r) of the other rollers (11).
4. A turntable assembly according to claim 2 or 3, characterised in that the rollers
(11, 12) are spaced apart at the same distance (d) from each other.
5. A turntable assembly according to any one of claims 2 to 4, characterised in that
the rollers (11, 12) are situated in close proximity to each other but do not contact
each other.
6. A turntable assembly according to any one of claims 1 to 5, characterised in that
the rollers (11, 12) have axes of rotation which run parallel to each other.
7. A turntable assembly according to any ore of claims 1 to 6, characterised in that
the deflection unit (10) comprises a single central deflection pulley (13), which
is large compared with the rollers (11, 12), for the deflection of another guide rope
(9).
8. A turntable assembly according to claim 7, characterised in that the profiled rollers
(12) are situated in close proximity to the large central deflection pulley (13) or
to the other guide rope (9) but do not contact the latter.
9. A turntable assembly according to any one of claims 1 to 8, characterised in that
the rollers (11) consist of self-lubricating plastic material.
10. A turntable assembly according to any one of claims 1 to 9, characterised in that
the bearing pins of the rollers (11) have tubular stainless steel elements (14).
11. A turntable assembly according to claim 10, characterised in that the stainless steel
elements are distance bushes which are disposed between the side cheek (15) of the
support bracket (16) of the deflection unit (10).
12. A turntable assembly according to claim 10, characterised in that the distance bushes
are screwed to fixed bearing bolts between the side cheeks (15) of the support bracket
(16).
13. A turntable assembly according to any one of claims 1 to 12, characterised in that
the deflection unit (10) has an additional row of rollers for the deflection of a
third (outer) guide rope.