Fixed or swivel casters equipped with load cells

Abstract

To provide a fixed caster or a universal caster which eases damage of a load cell.SOLUTION: A fixed caster or a universal caster includes at least one wheel and a load cell (3). The wheel is supported by a shaft. The load cell (3) has a force introduction area (8) and an immovable area (5). The force introduction area (8) is connected to the wheel. On at least one vertical longitudinal side surface of the load cell (3), at least one side part thin plate (7) is connected to the immovable area (5) of the load cell (3).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] A fixed or swivel caster having at least one wheel and a load cell, the wheel being supported on an axle, the load cell having a force introduction area and a stationary area, the force introduction area being connected to the wheel. [Background technology]

[0002] Fixed casters are known from the prior art and are used for moving large, heavy objects, such as hospital or nursing beds. For example, EP 0 379 065 A1 and EP 0 356 742 A1 disclose corresponding steerable fixed casters, also called swivel casters.

[0003] Furthermore, WO 9 612 164 A1 shows a weight measurement system assembled on casters, which consists of at least three weight measurement modules attached to the bottom of a bed or container or to any other surface suitable for measuring weight. The weight measurement system consists of casters arranged on the bottom, load cells attached to the casters, strain gauges or other sensors for measuring the load acting on the load cells.

[0004] A drawback of this weighing system is that it can be damaged if a shock load is applied to the caster. Accepting horizontal overloads is not easily achieved with load cells, especially single-point load cells, because the load cell is barely deformed by horizontal or transverse shear forces. In other words, when a horizontal or shear force is applied, the force introduction area deforms only slightly in the horizontal direction. Therefore, the force introduction area cannot be stopped by a stop. In other words, if the maximum "allowable" shear force is exceeded, damage to the load cell is inevitable, and in the worst case, the load cell will break. Summary of the Invention

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a fixed or swivel caster which overcomes or at least alleviates the known disadvantages of the prior art.

[0006] This object is achieved in a fixed or swivel caster as described above by connecting at least one side lamella to the stationary region of the load cell on at least one vertical longitudinal side of the load cell. The at least one side lamella, which represents a kind of guide, is composed, inter alia, of at least one relatively thin plate or lamella extending vertically parallel to the longitudinal side of the load cell. Due to the arrangement of the side lamellas, the side lamella is very stiff in the vertical direction and can thus transmit large forces, such as the weight of the object to be weighed. In contrast, in the horizontal direction transverse to the material thickness of the side lamella, the side lamella is flexible, i.e., it can bend under shear forces. In the context of the present invention, "relatively thin" means that the material thickness of the side lamella is thinner than the width and / or height of the side lamella. In particular, one side lamella is arranged on each of the opposing longitudinal sides of the load cell. Thus, at least two side plates are connected to the load cell.

[0007] In another configuration, a gap exists between the side lamellae and the vertical longitudinal side of the load cell. Based on the maximum allowable shear force for the load cell, the gap width between the inner surface of the side lamellae and the outer surface of the load cell is dimensioned so that when the maximum allowable shear force is exceeded, the inner surface of the side lamellae bends exactly to a width that contacts at least one outer surface of the load cell. Therefore, the bending of the load cell must always remain small based on the shear force acting on the load cell so that the bending of the load cell is entirely within the elastic range of the material. During the measurement operation, a gap exists between the side lamellae and the load cell, and during this measurement operation, the load cell determines, for example, weight, heart rate, and / or breathing frequency.

[0008] In another configuration, the side lamella has a cavity located near the force introduction area and vertically midway along the height of the side lamella. A screw is threaded through the cavity, and a gap exists between the tip of the screw and the outer surface of the load cell. Therefore, when the maximum allowable shear force is exceeded, the tip of the screw contacts at least one outer surface of the load cell. This prevents the side lamella from contacting the load cell before the maximum "allowable" shear force is reached based on the torsional moment acting on the load cell, which could result in measurement errors. In particular, the tip of the screw protrudes beyond the inner surface of the side lamella facing the load cell.

[0009] In another configuration, the side panels are arranged on at least one face of the load cell, which faces in the main direction of movement of the fixed or swivel caster. The narrow face of the load cell is therefore located transversely to the direction of movement. Furthermore, in the highly probable case of a collision with a relatively large force in the direction of movement, the load cell can withstand a larger shear force in the longitudinal direction than in the transverse direction without damage.

[0010] In another configuration, at least one end lamella is arranged on at least one end face of the side lamella. This minimizes the bending of the load cell when a shear force is applied. This is achieved by providing an end lamella, in particular two end lamellas, that form fixed stops for the side lamella on at least one end face, in particular on two end faces of the side lamella. This also means that a single-point load cell mounted in this manner is protected from excessively large shear forces if the bending stiffness of the side lamella and end lamella is designed to accommodate the permissible shear force of the load cell. In this regard, a load cell with two end lamellas and two side lamellas arranged parallel and vertically is optimal from a measurement technology perspective. The provision of the end lamella ensures that the resulting shear force generates a translational movement in the force introduction area, and at the same time, the force is transmitted symmetrically. The distance between the two side lamellae and the immobile areas and / or the force introduction areas of the load cells is precisely selected so that, under the maximum "allowable" shear forces, the side lamellae abut against the immobile areas and / or the force introduction areas of the load cells, so that shear forces are no longer transmitted via the load cells. During the measurement operation, the side lamellae and the load cells do not come into contact. In other words, during the measurement operation, a gap exists between the side lamellae and the load cells, because otherwise frictional and shear forces would affect or corrupt the measurement result and force shunts would occur.

[0011] In another embodiment, the material thickness of the end lamellae is greater than the material thickness of the side lamellae, so that the end lamellae are stiff in the direction of the shear force and undergo translational movements in the force introduction area due to the shear force that occurs.

[0012] In another configuration, a connecting member is disposed above the force introduction area and serves as an overload stop for the load cell and is connected to the object. The distance between the connecting member and the load cell is selected so that the load cell contacts the connecting member as soon as the maximum displacement of the load cell exceeds the rated load. The object is preferably a hospital bed or a nursing bed, but other objects, such as containers, machines, chassis, or scaffolding, are also contemplated. Furthermore, the fixed or swivel caster can be easily replaced with an existing fixed or swivel caster based on the connecting member, or can be inserted into an existing transport system comprising at least one fixed or swivel caster fixed to the object. This allows for easy addition of weight measurement functionality to an existing transport system. Preferably, the connecting member is connected to at least one side panel, and the connecting member is connected to the side panel by a force or material connection.

[0013] In another configuration, the stationary region of the load cell is connected to at least one side plate via a fixed body, whereby the connecting body is connected to the fixed body via the side plate, which is also connected to the stationary region of the load cell, and thus the object is connected to the stationary region via the connecting body.

[0014] In another configuration, the swivel plate is connected to the wheel of the fixed or swivel caster. This makes the fixed or swivel caster maneuverable, since the fixed or swivel caster can move around an additional axis of rotation, in particular an additional vertical axis of rotation, thanks to the swivel plate. In particular, the swivel plate is connected to the force introduction area of the load cell. The connection is located in the extension of the vertical axis of rotation of the swivel plate of the fixed or swivel caster. In particular, the axis or caster rotation axis is arranged offset from the vertical axis of rotation. This ensures good maneuverability of the fixed or swivel caster and optimizes the mechanical properties of the fixed or swivel caster, in particular the tiltability of the fixed or swivel caster.

[0015] In another embodiment, the force introduction area and the connecting body of the load cell are located on the vertical axis of rotation, and the immobile area of the load cell is arranged laterally offset relative to the vertical axis of rotation, so that the mechanical properties of the fixed or swivel caster are not changed. The immobile area is a fixed section of the load cell that is arranged opposite the movable force introduction area.

[0016] Furthermore, a housing can be disposed around the load cell, the housing enclosing at least one side lamella and at least one end lamella. Alternatively, at least one side lamella and at least one end lamella can be part of the housing, in which case the housing would not have a bottom portion. In other words, the housing would be composed of one top portion, two side lamellas, and two end lamellas. The top portion therefore closes the area between the side lamellas and the end lamellas and provides a connection area to the object. In other words, the top portion, side lamellas, and end lamellas connect to the object and the stationary area of the load cell. This protects the load cell and makes cleaning the load cell easier, since all that is required is to remove contaminants from the housing. [Brief explanation of the drawings]

[0017] Further advantageous aspects will become apparent from the following description of preferred embodiments which refers to the accompanying drawings. [Figure 1] 1 is a schematic diagram of a fixed or swivel caster with wheels. [Figure 2] FIG. 1 is a schematic diagram of a load cell. [Figure 3] FIG. 2 is a plan view of the load cell. DETAILED DESCRIPTION OF THE INVENTION

[0018] FIG. 1 shows a schematic diagram of a fixed or swivel caster 1 with a wheel 2 and a load cell 3. A connecting element 4 is arranged above the load cell 3 and is connected to an object. The connecting element 4 is connected, on the one hand, to an end plate 6, in particular a first end plate 10, and, on the other hand, to at least one side plate 7, the end plate 6 or the first end plate 10 being arranged on the side of the force introduction area 8 of the load cell 3. In particular, the connecting element 4 has a greater material thickness than the end plate 6 and / or the side plate 7. FIG. 1 shows a cross section of the load cell 3, the connecting element 4, the fixing element 9 and the end plate 6. The fixing element 9 is arranged above the stationary area 5 of the load cell 3. The fixed body 9 is connected on the one hand to the end lamella 6, in particular the second end lamella 11, and on the other hand to at least one side lamella 7, the end lamella 6 or the second end lamella 11 being arranged on the side of the stationary region 8 of the load cell 3. In particular, the fixed body 9 has a greater material thickness than the end lamella 6 and / or the side lamella 7. Furthermore, a first spacer 13 can be arranged between the stationary body 5 and the fixed body 9, which first spacer adjusts for the difference in height between the stationary region 5 and the side lamella 7 as well as the end lamella 6. The first spacer 13 can be part of the load cell 3 or can be provided as an additional component.

[0019] The fixed body 9 is connected to the stationary region 5 of the load cell 3. In particular, the stationary region 5 is connected to the fixed body 9 by a force connection, and at least one screw 12 is inserted into at least one through-hole in the fixed body 9 and screwed into a threaded hole in the stationary region 5. Correspondingly, the first spacer 13 is also provided with at least one through-hole or at least one threaded hole.

[0020] The connecting body 4 is connected via one or more side plates 7 to a fixed body 9, which is in turn connected to the stationary area 5 of the load cell 3. The connecting body 4 is therefore connected to the stationary area 5 of the load cell 3. A fixing pin can be arranged on the connecting body 4, which is connected to the leg 14 of interest.

[0021] The force introduction area 8 of the load cell 3 is connected to the wheel 2. A second spacer 15 can be arranged between the wheel 2 and the force introduction area 8; this second spacer 15 can be part of the load cell 3 or can be provided as an additional component. Furthermore, the second spacer 15 can be part of the fixed caster 1 or the swivel caster 1. There is a gap between the load cell 3 and the connecting body 4, or between the force introduction area 8 and the connecting body 4. The distance between the connecting body 4 and the load cell 3 or the force introduction area 8 is selected so that the load cell 3 comes into contact with the connecting body 4 as soon as the maximum displacement of the load cell 3 is exceeded at rated load. In particular, the material thickness of the first spacer 13, which is arranged in the stationary area 5 of the load cell 3, is selected so that the material thickness of the first spacer corresponds to the maximum "allowable" displacement of the load cell 3 at rated load.

[0022] The force introduction area 8 of the load cell 3, the connecting body 4, and the axis 16 about which the wheel 2 rotates are located on a single vertical axis of rotation 17. The stationary area 5 of the load cell 3 is arranged offset from the vertical axis of rotation 17. The connecting body 4, the force introduction area 8, and the axis 16 are therefore arranged vertically in a line. Alternatively, the wheel 2 can be arranged offset from the vertical axis of rotation 17. In this regard, a rotating plate (not shown) can be arranged between the load cell 3 and the wheel 2. The rotating plate can be an additional component arranged below the second spacer 15, or the rotating plate can be part of the second spacer 15.

[0023] In particular, the side plates 7 and / or the end plates 6, 10, 11 are provided with openings (not shown) for guiding cables, which can supply current to the load cell 3 and transmit the measurement signals of the load cell to the control unit.

[0024] The load cell 3 is preferably a shear beam load cell, or a bending load cell, or a single point load cell, or a collapsible shear beam / bending beam load cell, or a compression load cell.

[0025] FIG. 2 is a schematic diagram of a load cell 3 with two side lamellas 7 and two end lamellas 6, 10, 11. Each side lamella 7 is arranged on a vertical longitudinal side 19 of the load cell 3, which extends from the force introduction area 8 to the stationary area 5 and is arranged perpendicular to the top surface 18 of the load cell 3, which is oriented toward the object connected to the connecting body 4. Furthermore, a gap 20 exists between the load cell 3 and the side lamella 7, or between the side lamella 7 and the vertical longitudinal side 19. The width of the gap between each inner surface of the side lamella 7 and the outer surface of the load cell 3 or the outer surface of the vertical longitudinal side 19 corresponds to the maximum permissible displacement of the load cell 3 when a shear force is applied. If the maximum permissible displacement is exceeded, the load cell 3 may be damaged and therefore become unusable.

[0026] During the measuring operation, the side lamella 7 and the load cell 3 do not come into contact with each other. The end lamellas 6, 10, 11 are arranged on the end faces of the side lamella 7, or the first end lamella 10 is arranged on the side of the force introduction area 8 and the second end lamella 11 is arranged on the side of the stationary area 5. The end lamellas 6, 10, 11 are arranged perpendicular to the side lamella 7 and to the upper surface 18 of the load cell 3. Furthermore, the side lamella 7 has a smaller material thickness than the end lamellas 6, 10, 11. The side lamella 7, the end lamellas 6, 10, 11, the connecting body 4 and the fixing body 9 are connected to each other by material and / or force connections.

[0027] Furthermore, each side plate 7 has at least one cavity 22, which is arranged near the force introduction area 8 and is arranged vertically midway along the height of the side plate 7. A screw 23 is screwed through the cavity 22, and a gap exists between the tip of the screw and the outer surface of the load cell 3.

[0028] 3 shows the load cell of FIG. 2 from below. Threaded holes 21 are arranged in the force introduction area 8, via which the wheel 2 can be fastened to the load cell 3. Due to the relatively thin and long side plates 7, they are very stiff in the vertical direction and can thus transmit large forces. In contrast, horizontal or shear forces F Q In the direction of the shear force F , or in the direction transverse to the material thickness of the side plate 7, the side plate 7 is flexible. Q The end plates 6, 10, 11 connected to the side plate 7 form fixed stops for the side plate 7. This allows the shear force F Q The bending of the load cell 3 when the force F is applied can be limited to a small extent. Q The distance between the two side plates 7 and the immobile area 5 and / or the force introduction area 8 of the load cell 3 is such that the maximum "allowable" shear force F Q When the force F is applied, at least one of the side plates 7 abuts against the immobile area 5 and / or the force introduction area 8 of the load cell 3, and thus the shear force F Q is so precisely chosen that it is no longer transmitted via load cell 3.

[0029] Therefore, excessively high shear force F Q When the shear force F is applied, the side thin plate 7 at least partially contacts the load cell 3, and the side thin plate 7 is subjected to the shear force F Q The end plates 6, 10, 11 are arranged on the side on which the shear force F acts, and the translational movement of the opposing side plates 7 is caused by the end plates 6, 10, 11, so that the gap 20 between the load cell 3 and the opposing side plates 7 or the distance between the load cell 3 and the opposing side plates 7 is Q This results in excessively high shear forces F Qis guided through the side lamellas 7 and the end lamellas 6, 10, 11, and the load cell 3 detects excessively high shear forces F Q be protected from

[0030] Figure 3 shows the shear force F Q The load cell 3 is shown in its normal operating position, where no shear force F acts on the load cell 3. Here, each side lamella 7 has the same gap 20 or distance to the load cell 3. The material thickness of the end lamellas 6, 10, 11 is greater than the material thickness of the side lamella 7. This allows the shear force F Q In the direction of the load cell 3, the end plates 6, 10, 11 are rigid. Furthermore, the clearance between each outer surface of the load cell 3 and the screw 23 or screw tip is such that the maximum "allowable" shear force F Q When this shear force is exceeded, the tip of the screw comes into contact with the outer surfaces of the load cell 3, and thus the shear force F Q is no longer transmitted via the load cell. In particular, the gap 20 between the side lamella 7 and the load cell 3 or each vertical longitudinal side surface 19 is larger than the gap between each outer surface of the load cell 3 and each screw tip, which in particular protrudes from each inner surface of each side lamella 7. [Explanation of symbols]

[0031] 1 Fixed caster / swivel caster 2 wheels 3 load cells 4 Connectors 5 Immovable Realm 6 End thin plate 7 Side Thin Plate 8 Force introduction area 9 Fixed body 10 First end thin plate 11 Second end thin plate 12 screws 13 First spacer 14 Target Legs 15 Second spacer 16 axes 17 Vertical axis of rotation 18 Top load cell 19 Vertical longitudinal side 20 gap 21 screw holes 22 void 23 Screw F Q shear force

Claims

1. A fixed or swivel caster (1) with at least one wheel (2) and a load cell (3), A fixed caster (1) or a swivel caster (1), in which the wheel (2) is supported on an axle (16), the load cell (3) has a force introduction area (8) and a stationary area (5), the force introduction area (8) being connected to the wheel (2), At the vertical longitudinal sides (19) of the load cell (3), side lamellas (7) are connected to the stationary areas (5) of the load cell (3), a gap (20) exists between the side lamella (7) and the vertical longitudinal side (19) of the load cell (3); At least one end plate (6, 10, 11) is arranged on at least one end face of the side plate (7), A fixed or swivel caster (1) characterized in that the material thickness of the end thin plates (6, 10, 11) is greater than the material thickness of the side thin plates (7).

2. 2. A fixed or swivel caster (1) according to claim 1, characterized in that during the measuring operation, the gap (20) exists between the side lamella (7) and the load cell (3).

3. 3. A fixed or swivel caster (1) according to claim 1, characterized in that when a maximum allowable shear force (FQ) is exceeded, the inner surface of the side lamella (7) comes into contact with the outer surface of at least one of the load cells (3).

4. 4. A fixed or swivel caster (1) according to any one of claims 1 to 3, characterized in that the side lamellas (7) have cavities (22).

5. 5. A fixed or swivel caster (1) according to claim 4, characterized in that the cavity (22) is arranged vertically in the middle of the height of the side lamella (7).

6. 6. A fixed or swivel caster (1) according to claim 4 or 5, characterized in that the cavity (22) is arranged in the vicinity of the force introduction area (8).

7. A fixed caster (1) or a swivel caster (1) according to any one of claims 4 to 6, wherein a screw (23) is screwed through the cavity (22) and a gap exists between the tip of the screw and the outer surface of the load cell (3).

8. 8. A fixed or swivel caster (1) according to claim 7, characterized in that when a maximum allowable shear force (FQ) is exceeded, the screw tip comes into contact with at least one outer surface of the load cell (3).

9. A fixed caster (1) or a swivel caster (1) according to any one of claims 1 to 8, characterized in that the side thin plates (7) are arranged on at least one face of the load cell (3) that is located in the main direction of movement of the fixed caster (1).

10. 10. The fixed or swivel caster (1) according to any one of claims 1 to 9, characterized in that a connecting body (4) is arranged above the force introduction area (8), the connecting body (4) being used as an overload stop for the load cell (3) and being connected to an object.

11. 11. A fixed or swivel caster (1) according to claim 10, characterized in that the connecting body (4) is connected to the at least one side lamella (7).

12. 12. A fixed caster (1) or swivel caster (1) according to any one of claims 1 to 11, characterized in that the immobile region (5) of the load cell (3) is connected to the at least one side lamella (7) via a fixing body (9).

13. 13. A fixed or swivel caster (1) according to any one of claims 1 to 12, characterized in that a swivel plate is connected to the wheel (2).

14. 14. Fixed or swivel caster (1) according to claim 13, characterized in that the swivel plate is connected to the force introduction area (8).

15. 15. The fixed caster (1) or swivel caster (1) according to claim 13 or 14, characterized in that the connecting body (4) arranged above the force introduction area (8) is located on an extension of the vertical rotation axis (17) of the rotating plate.

16. 16. The fixed caster (1) or swivel caster (1) according to claim 15, characterized in that the force introduction area (8) of the load cell (3) is located on the vertical axis of rotation (17) and the immobile area (5) of the load cell (3) is arranged offset laterally from the vertical axis of rotation (17).

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