EP1996501B1

EP1996501B1 - Lifting stand fastening in an industrial truck

Info

Publication number: EP1996501B1
Application number: EP07748343.6A
Authority: EP
Inventors: Per-Erik Cardell; Magnus Alveteg
Original assignee: Toyota Material Handling Europe AB
Current assignee: Toyota Material Handling Europe AB
Priority date: 2006-03-21
Filing date: 2007-03-16
Publication date: 2013-05-15
Anticipated expiration: 2027-03-16
Also published as: SE529788C2; WO2007108767A1; DE07748343T1; EP1996501A4; EP1996501A1; SE0600630L

Description

TECHNICAL FIELD

The present invention relates to an industrial truck comprising a lifting stand having a first and a second journal, in which each journal is provided with a bushing rotatable about the journal, a stand holder, which forms part of the chassis of the industrial truck and comprises a first and a second seat, in which each bushing is rotatably mounted in one of the respective first and second seats such that the stand holder supports the lifting stand.

BACKGROUND ART

The function of a lifting stand of an industrial truck is to form a vertical framework in which a fork is disposed such that it can be raised and lowered for load handling purposes. The lifting stand is fastened in a stand holder which forms part of the chassis of the industrial truck.
A known example of fastening of a lifting stand in a stand holder comprises a first and second seat, which are disposed in the stand holder and are separated in the transverse direction of the industrial truck. Belonging to each seat is a clamp, which can be disposed on top of the respective seat and is connected thereto by means of a screw joint. Both the seat and the clamp are configured with a semi-cylindrical recess, which recesses together form a cylindrical cavity having a horizontal centre axis. The lifting stand, in turn, comprises a first and a second horizontally extended journal, which journals are separated in the transverse direction of the industrial truck with the same spacing as the spacing between the seats. The journals have a circular cross-section with a diameter which substantially conforms to the diameter of the cylindrical cavity. When mounting the lifting stand in the stand holder, the lifting stand is lifted to a level above the seats, for example by means of an overhead crane, after which it is lowered such that the journals are positioned in the respective seat and the weight of the lifting stand is supported by the stand holder. The clamp is subsequently disposed on top of the seats and the screw joint is tightened. The journals are now locked against radial travel in each seat. If the diameter of the journals is made somewhat larger than the diameter of the cavity, the journals can also be locked against axial travel, since the journals will then be firmly clamped in place by the clamp.
An industrial truck according to the preamble of claim 1 is known from US 5 052 881 .
This solution is associated, however, with a number of problems. Since the journals are clamped in place, the torque which is generated in the course of load handling is largely absorbed in the journals. This can give rise to stresses in journals and weld joints, which can lead to fatigue failure. Another problem is that the position of the lifting stand in the stand holder must be finely adjusted after completion of the fastening in order for the lifting stand to acquire the desired orientation. This way of fastening the lifting stand calls for extensive skimming, which is a time-consuming process. Another problem is that the seat and the clamp must be manufactured in pairs (in order for the recesses to fit together) and they cannot afterwards be combined with other seats and clamps, which, because of a more intricate manufacturing and storage process, adds to the cost of the industrial truck. The use of a clamp with associated screw joint also means that the fastening of the lifting stand becomes more complicated and time-consuming.
One solution to the first and second problem is to provide a bushing having an eccentric hole intended for the journal. On the one hand, the bushing will instead be clamped in place by the seat and the clamp, whilst a small clearance nevertheless exists between bushing and journal. The axial locking of the journal can then be released differently. For fine adjustment of the orientation of the lifting stand, the respective eccentric bushing is rotated, which results in a displacement of the position of the journal with respect to the stand holder in a vertical plane lying parallel with the longitudinal direction of the industrial truck. This solution nonetheless requires the use of a clamp for radial locking of the journals in the respective seat.

OBJECT OF THE INVENTION

One object of the invention is therefore to simplify the locking of the journals in the respective seat.
A further object of the present invention is to simplify fastening of the lifting stand in the stand holder.
Yet another object is to make the industrial truck cheaper to produce.

DISCLOSURE OF INVENTION

These and other objects of the invention are achieved with a industrial truck as has been defined in the introduction and which is characterized in that the respective bushing and seat have such a mutual geometric configuration that when each bushing assumes a first rotational position in the seat, the bushed journals are radially displaceable in the respective seat such that the lifting stand is disposed detachedly in the stand holder, and when each bushing assumes a second rotational position in the seat, the bushed journals are radially locked in the respective seat such that the lifting stand is fixed in the stand holder. There is therefore no need for any separate clamps to be made and stored, which reduces the cost of the industrial truck Moreover, the mounting of the lifting stand will be simplified, since the bushings can be locked in the radial direction in the respective seat with a simple rotary motion, without the need for any screw joints.
Preferably, each seat has an internally cylindrical shell surface, which extends between a first projection of the seat and a second, corresponding projection and forms a gap having a width which is smaller than the inner diameter of the seat, and each bushing has a first outer diameter which is smaller than the width of the gap and a second outer diameter which is larger than the width of the gap, so that when each bushing assumes the first rotational position, the first outer diameter is positioned with respect to the gap such that the bushing is radially displaceable through the gap, and when each bushing assumes the second rotational position, the second outer diameter is positioned with respect to the gap such that the bushing is radially locked in the seat. A change of lifting stand will also thereby be facilitated, for example should an industrial truck need to be equipped with a stand other than the existing one to allow it to perform a specific lifting function.
Preferably, the gap of each seat is orientated in such a way in the stand holder that the bushing is radially displaceable in the horizontal direction when each bushing assumes the first rotational position. Docking of the lifting stand in the stand holder can thus be realized horizontally, which means that the lifting stand does not need to be raised to enable the journals to be positioned in the respective seat. This eliminates the need for vertical docking, thereby reducing the risk of clamping damage to hoses and electric cables, for example, as the lifting stand is docked in the stand holder, since these can otherwise be crushed under the weight of the lifting stand. Alternatively, the stand holder can be docked in the lifting stand by the industrial truck driving up to an already erected lifting stand and docking it, which is made possible by virtue of the bushings which are radially displaceable in the horizontal direction.
Expediently, each bushing has an external shell surface having at least one cylindrical portion and at least one flat portion, the first outer diameter being defined by a midpoint normal to the flat portion and the second outer diameter being defined by the outer diameter of the cylindrical portion, and preferably each bushing has an external shell surface having two mutually opposing cylindrical portions and two mutually opposing flat portions. A bushing is thus made available which has the desired characteristics in respect of rotation of the bushing between the first and second rotational position.
Expediently, the flat portions are parallel with each other. Docking of the lifting stand in the stand holder is thus made easier still.
Preferably, the angular distance between the first and the second angular position is 90°. The second angular position can thus be easily adjusted after the lifting stand is docked in the stand holder.
Expediently, the flat portion is horizontally orientated when each bushing assumes the first rotational position. A correct first rotational position can thus be easily ensured as the lifting stand is docked in the stand holder.
Preferably, each bushing comprises a, in the axial direction, first cylindrical recess, in which the journal is rotatably disposed, the centre line of the first cylindrical recess being eccentrically situated with respect to the centre line of the bushing.
The position of the journals in the longitudinal direction of the industrial truck and in the vertical direction can thus be adjusted with respect to the stand holder.
Expediently, each bushing comprises an axially threaded first bore, which adjoins the first cylindrical recess, a threaded stop screw being disposed in the threaded hole and penetrating into the first cylindrical recess and axially locking the journal in the first cylindrical recess. The position of the journals, and hence also of the lifting stand, can thus be adjusted in the lateral direction.
Preferably, the threaded stop screw comprises a, in the axial direction, through-recess, and the base of the journal is provided with a threaded second bore, which lies in line with the through-recess, a threaded screw extending through the through-recess and into the threaded second bore. The axial position of the bores will thus be fixed, and hence also the position of the lifting stand in the lateral direction. During operation of the industrial truck, should the industrial truck sway, compressive forces will be generated in the one journal and tensile forces in the other journal. Since the journal is joined to the bushing, by means of the threaded screw, the absorption of force in the stand holder can hence be improved.
Expediently, each seat constitutes an integral part of the stand holder. No separate elements are thus needed to be produced in order to form the seats.
Preferably, each bushing is provided with a control element for rotation of the bushing in the seat. The rotational position of each bushing in the seat is thereby adjustable.
Expediently, each bushing comprises a flange which bears against the stand holder in such a way that the bushing is axially locked in the seat in the direction of the lifting stand. The axial position of the bushing in the direction of the lifting stand will thus be fixed.
Preferably, a clamping ring comprising a, in the axial direction, second cylindrical recess with an internally annular seat is disposed around each bushing in such a way that the flange of the bushing bears against the internally annular seat, the second cylindrical recess having an axial depth down to the internally annular seat which is smaller than the axial thickness of the flange, and the clamping ring comprises a screw joint which is connected to the stand holder and clamps the bushing in place in the stand holder. The rotational position and axial position of each bushing in the seat will thus be fixed.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will now be described with reference to the appended drawings, in which:

Fig. 1 shows a perspective view of a lifting stand of a industrial truck, in which the lifting stand is mounted in a stand holder by means of a fastening mechanism according to the invention,
Fig. 2 shows an exploded perspective view of the integral elements in the fastening mechanism in Fig. 1,
Fig. 3 shows an enlargement of the circled area in Fig. 2,
Fig. 4a-b shows two separate views of the fastening mechanism.

MODE(S) FOR CARRYING OUT THE INVENTION

Fig. 1 shows a perspective view of a lifting stand 1 of an industrial truck. The lifting stand 1 has the function of forming a vertical framework in which a fork (not shown) is disposed such that it can be raised and lowered. The framework comprises two vertical members 3 and upper and lower transverse members 5, which join the vertical members 3. The lifting stand is fastened in a stand holder 7, forming part of the chassis of the industrial truck, by means of a first and second fastening mechanism 9. In this case, the stand holder 7 is constituted by a stand wagon for a sliding stand industrial truck, even though the invention is not limited to sliding stand industrial trucks but can be used in all conceivable industrial trucks comprising lifting stands.
In Fig. 2 it can be seen that each vertical member 3 is equipped with a first and second journal 11, which journals extend perpendicularly in the horizontal direction out from the outer side of the vertical member 3. Each journal 11 is welded in place in the vertical member 3, preferably via a reinforcing element 13. A first and a second bushing 15 are intended to be rotatably disposed on the respective first and second journal 11, as will be described in greater detail below. The stand holder 7 is disposed in a industrial truck chassis (not shown) and comprises first and second side pieces 17, which are joined with a back piece 19. Each side piece 17 comprises a seat 21, in the form of a recess 21 integrated in the side piece, having an internally cylindrical shell surface 23 and a horizontal centre axis. Each bushing 15 is intended to be rotatably disposed in the respective seat 21, as will also later be described in greater detail.
When the lifting stand 1 is fastened in the stand holder 7, the bushed journals 11 will be disposed in the respective seat 21 in such a way that the weight of the lifting stand 1 is supported by the stand holder 7. The fastening mechanism 9 therefore comprises the seat 21, the bushing 15 and the journal 11, the functioning of which will be described in greater detail below. In the lower part of the lifting stand, adjacent to the lower transverse member 5, there is also disposed a lower fastening mechanism 25 in the form of a screw joint 25, so that the lifting stand can also be connected to the stand holder at a lower fastening point.
Fig. 3 shows an enlargement of the circled area in Fig. 2 and illustrates the one side piece 17 of the stand holder, even though the other side piece is configured the same. The journal 11 which is fastened in the vertical member 3 of the lifting stand comprises an inner cylindrical part 27 and an outer cylindrical part 29, in which the outer part adjoins the inner part. The outer part 29 has a smaller diameter than the inner part 27, so that a circular seat 31 is formed in the transition between the inner part 27 and the outer part 29. The inner part 27 has the function of forming a space between the lifting stand 1 and the stand holder 7. The base of the journal is also provided with a threaded hole 33, the function of which will be described later.
From Fig. 3, but also from Fig. 4a-b, it can be seen that the bushing 15 comprises a partially cylindrical body 35 with bevelled surfaces. A cylindrical flange 37 adjoins the partially cylindrical body 35. The body 35 further has a shell surface 40 having two cylindrical portions 39 and two flat portions 41, in which the flat portions 41 are situated directly opposite and parallel to each other. The body 35 comprises in its base 43 a first cylindrical recess 45, into which the outer part 29 of the journal is intended to be introduced. The cylindrical recess 45 has a centre line c₁, which is eccentric in relation to the centre line c₂ of the partially cylindrical body 35, i.e. an eccentricity e₀ is present. The inner diameter of the cylindrical recess 45 is somewhat larger than the diameter of the outer part 29 of the journal, about which the bushing 15 can be rotatably disposed. Furthermore, the depth of the recess 45 is substantially equal in size to the axial length of the outer part 29 of the journal, so that the circular seat 31 in the transition between the inner 27 and outer part 29 of the journal will bear against the base 43 of the bushing. The body 35 of the bushing has two outer diameters, a first outer diameter, which is defined by a midpoint normal to any one of the flat portions 41, and a second outer diameter, which is defined by an outer diameter of the cylindrical portions 39.
The cylindrical seat 21 has an inner diameter which is somewhat larger (a few hundredths of a mm) than the second diameter of the bushing 15 to form a slide fit with no significant play. Furthermore, the shell surface 23 of the seat 21 extends between a first projection 49 of the seat 21 and a second, corresponding projection 51 and hence forms a gap 53. The gap 53 is situated in a substantially vertical plane in order to facilitate introduction of the bushing. In the case of the first projection 49, a horizontal guide surface 50 also adjoins the shell surface 23 in order to facilitate introduction of the bushing. The distance between the first 49 and the second 51 projection, hereinafter referred to as the width of the gap, is smaller than the inner diameter of the seat 21. This means that the shell surface of the seat extends more than 180° from the first 49 to the second projection 51. The first outer diameter of the bushing is smaller than the width of the gap 53, whilst the second outer diameter of the bushing is larger than the width of the gap 53. The bushing 15 can hence be introduced into the gap 53, in the radial direction of the seat 21, when the bushing 15 assumes a first rotational position about the journal 11. In this rotational position, the flat portions 41, having the first outer diameter, are positioned with respect to the gap 53 such that the bushings 15 can be displaced horizontally and radially into/out of the respective seat 21. The flange 37 of the bushing will bear in the axial direction against the outer side of the side piece 17 and lock the bushing 15 against axial travel in the direction of the stand. Once in place in the seat, the bushing 15 can be rotated into a second rotational position about the journal 11 such that the bushing 15 is locked in the seat 21 in the radial direction, since the second outer diameter, which is larger, of course, than the width of the gap 53, will prevent a radial displacement of the bushing 15 in the seat 21. The angular distance between the first and the second rotational position is 90°. Rotation of the bushing 15 is achieved by means of a control element 55 in the form of a hexagonal knob 55 disposed in the base of the flange, see Fig. 3.
The flange 37 of the bushing comprises an axially M-40 threaded bore 57, which is concentrically disposed in the hexagonal knob 55 and which concentrically adjoins the first cylindrical recess 45. A threaded stop screw 59, having a through-recess in the form of a socket head handle 61, is disposed in the threaded bore 57 and, via the thread engagement, can be transposed in the axial direction such that it penetrates into the first cylindrical recess 45 in order thereby to bear against the base 32 of the journal. As previously mentioned, the base 32 of the journal is provided with the threaded hole 33, which lies in line with the continuous socket head handle 61. A washered M-16 screw 63 can therefore be introduced through the continuous socket head handle 61 and be screwed into the threaded hole 33 and thus lock the axial position of the stop screw 59 in the threaded bore 57.
Furthermore, the fastening mechanism 9 comprises a clamping ring 65 having a, in the axial direction, second cylindrical recess 67 provided with an internally annular seat 69. The clamping ring 65 is intended to be disposed around the bushing 15 in such a way that the flange 37 of the bushing bears against the seat 69. The second cylindrical recess 67 has an axial depth down to the seat 69 which is smaller than the axial thickness of the flange 37. The clamping ring 65 comprises an annular base 71, which in the circumferential direction is provided with a plurality of through-bores 73, and the side piece 17 of the stand holder, in the circumferential direction around the seat 21, is provided with threaded bores 75 positioned at the same mutual distance apart as the through-bores 73 in the clamping ring 65. When the clamping ring 65 is disposed around the bushing 15 positioned in the seat 21, threaded screws 77 are introduced through the through-bores 73 and screwed in place in the threaded holes 75 in the side piece 17. Since the depth of the second cylindrical recess 67 is somewhat smaller than the axial thickness of the bushing flange 37, the clamping ring 65 will clamp the bushing 15 against the side piece 17 and secure it against movement relative to the side piece 17.

FUNCTIONING

Mounting of the lifting stand 1 in the stand holder 7 of the industrial truck proceeds as follows: the lifting stand 1 is located in the raised position in a rack (not shown) or docking wagon in such a way that the height of the journals 11 above the ground lies in the same horizontal plane as the seats 21 of the stand holder 7. First, the first and the second bushing 15 are disposed on one of the respective first and second journals 11. After this, each bushing 15 is rotated into the first rotational position such that the flat portions 41 end up in the horizontal position. The lifting stand 1 is now ready for docking with the stand holder 7. If the lifting stand 1 is placed in a rack, the industrial truck with the stand holder 7 is driven against the rack for docking with the lifting stand 1, or if the lifting stand 1 is placed in a docking wagon, the latter is driven against the industrial truck with the stand holder 7 for docking. Irrespective of which method is used, the lifting stand 1 is transposed in the horizontal direction relative to the stand holder 7. The bushed journals 11 will hence penetrate horizontally through the gap 53 of the seats 21, which is possible since the first outer diameter of each bushing 15 is smaller than the width of the gap 53 and is positioned with respect to the gap 53 such that the bushing 15 is radially displaceable through the gap 53. In place in the seat 21, each bushing is rotated by 90° into the second rotational position, so that the second outer diameter, which is larger than the width of the gap 53, is positioned with respect to the gap 53 such that the bushing 15 is radially locked in the seat 21.
In this position, the screw joint 25 in the lower fastening mechanism 25 is loosely tightened so that the lifting stand 1 cannot be accidentally rotated with respect to the stand holder 7. The clamping rings 65 are now placed over the respective bushing 15 and the associated screw joint 77 is loosely tightened such that each clamping ring 65 is held in place on the respective side piece 17. The inclination of the lifting stand 1 in the lateral direction is adjusted by rotation of the control element 55 of the bushing 15. Because of the eccentricity of the first cylindrical recess 45, such a rotation will affect the horizontal and vertical position of the journal 11 with respect to the respective seat 21. A matched rotation of the respective bushing 15 hence produces a desired orientation of the lifting stand 1. After this, the inclination of the lifting stand 1 in the longitudinal direction of the industrial truck is adjusted, which is realized by means of skimming, but only on the lower fastening mechanism 25. The screw joint 25 in the lower fastening 25 is then tightened. The screw joint 77 in the clamping ring 65 is subsequently tightened, whereupon the rotational position and the axial position of the bushings 15 in the seats 21 are fixed. After this, each stop screw 59 is tightened such that they bear against the bases 32 of the journals 11 and hence fix the lifting stand 1 in the axial direction. Finally, the threaded screw 63 is tightened such that the axial position of the stop screws 59 is fixed and such that the bushings 15 are connected to the journals 11.

Claims

Industrial truck, comprising
a lifting stand (1) having a first and a second journal (11), in which each journal (11) is provided with a bushing (15) rotatable about the journal (11),
a stand holder (7), which forms part of the chassis of the industrial truck and comprises a first and a second seat (21), in which each bushing (15) is rotatably mounted in one of the respective first and second seats (21) such that the stand holder (7) supports the lifting stand (1), characterized in that
the respective bushing (15) and seat (21) have such a mutual geometric configuration that when each bushing (15) assumes a first rotational position in the seat (21), the bushed journals (11) are radially displaceable in the respective seat (21) such that the lifting stand (1) is disposed detachedly in the stand holder (7), and when each bushing (15) assumes a second rotational position in the seat (21), the bushed journals (11) are radially locked in the respective seat (21) such that the lifting stand (1) is fixed in the stand holder (7).
Industrial truck according to Claim 1, in which each seat (21) has an internally cylindrical shell surface (23) which extends between a first projection (49) of the seat (21) and a second, corresponding projection (51) and forms a gap (53) having a width which is smaller than the inner diameter of the seat (21), and each bushing (15) has a first outer diameter which is smaller than the width of the gap (53) and a second outer diameter which is larger than the width of the gap (53), so that when each bushing (15) assumes the first rotational position, the first outer diameter is positioned with respect to the gap (53) such that the bushing (15) is radially displaceable through the gap (53), and when each bushing (15) assumes the second rotational position, the second outer diameter is positioned with respect to the gap (53) such that the bushing (15) is radially locked in the seat (21).
Industrial truck according to Claim 2, in which the gap (53) of each seat (21) is orientated in such a way in the stand holder (7) that the bushing (15) is radially displaceable in the horizontal direction when each bushing (15) assumes the first rotational position.
Industrial truck according to Claims 1-3, in which each bushing (15) has an external shell surface (40) having at least one cylindrical portion (39) and at least one flat portion (41), the first outer diameter being defined by a midpoint normal to the flat portion (41) and the second outer diameter being defined by the outer diameter of the cylindrical portion (39).
Industrial truck according to Claim 4, in which each bushing (15) has an external shell surface (40) having two mutually opposing cylindrical portions (39) and two mutually opposing flat portions (39).
Industrial truck according to Claim 5, in which the flat portions (39) are parallel with each other.
Industrial truck according to any one of Claims 5-6, in which the angular distance between the first and the second angular position is 90°.
Industrial truck according to any one of Claims 4-7, in which the flat portion (41) is horizontally orientated when each bushing (15) assumes the first rotational position.
Industrial truck according to any one of Claims 1-8, in which each bushing (15) comprises a, in the axial direction, first cylindrical recess (45), in which the journal (11) is rotatably disposed, the centre line of the first cylindrical recess (45) being eccentrically situated with respect to the centre line of the bushing (15).
Industrial truck according to Claim 9, in which each bushing (15) comprises an axially threaded first bore (57), which adjoins the first cylindrical recess (45), a threaded stop screw (59) being disposed in the threaded hole (57) and penetrating into the first cylindrical recess (45) and axially locking the journal (11) in the first cylindrical recess (45).
Industrial truck according to Claim 10, in which the threaded stop screw (59) comprises a, in the axial direction, through-recess (61), and the base (32) of the journal (11) is provided with a threaded second bore (33), which lies in line with the through-recess (61), a threaded screw (63) extending through the through-recess (61) and into the threaded second bore (33).
Industrial truck according to any one of Claims 1-11, wherein each seat (21) constitutes an integral part of the stand holder (7).
Industrial truck according to any one of Claims 1-12, in which each bushing (15) is provided with a control element (55) for rotating the bushing (15) in the seat (21).
Industrial truck according to any one of Claims 1-13, in which each bushing (15) comprises a flange (37) which bears against one side of the stand holder (7) in such a way that the bushing (15) is axially locked in the seat (21) in the direction of the lifting stand (1).
Industrial truck according to Claim 14, wherein a clamping ring (65) comprising a, in the axial direction, second cylindrical recess (67) with an internally annular seat (69) is disposed around each bushing (15) in such a way that the flange (37) of the bushing bears against the internally annular seat (69), the second cylindrical recess (67) having an axial depth down to the internally annular seat (69) which is smaller than the axial thickness of the flange (37), and the clamping ring (65) comprises a screw joint (77) which is connected to the stand holder (7) and clamps the bushing (15) in place in the stand holder (7).