AU2020460123A1 - Bed frame for a hospital and/or nursing bed - Google Patents

Abstract

The invention relates to a bed frame for a hospital and/or nursing bed, comprising a scissor mechanism (4) for the height adjustment of a bed frame (5) supported by the scissor mechanism (4) and comprising a first and a second undercarriage (1, 2) which is in each case arranged on the scissor mechanism (4), wherein an undercarriage (1, 2) comprises a crosspiece (7) having bearing bushes (8, 9) at the end faces for the respective reception of a wheel unit (10, 11) with a wheel disc (12, 13; 14, 15) that is rotatably mounted about an axis of rotation (16, 17), characterized in that an undercarriage (1, 2) has a connection extension (18, 19) which points downwards starting from the crosspiece (7), is arranged at one end face on the crosspiece (7) and has at the other end face a bearing lug (20, 21) for the rotationally pivotably arrangement on the scissor mechanism (4), wherein the axis of rotation (22, 23) defined by the bearing lug (20, 21) extends in the direction of height (6) of the undercarriage (1, 2) below the axis of rotation (16, 17) of a wheel disc (12, 13; 14, 15).

Description

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Bed Frame for a Hospital and/or Nursing Bed

The invention relates to a bed frame for a hospital and/or nursing bed, comprising a scissor mechanism for height adjustment of a bed frame supported by a scissor mechanism and comprising a first and a second undercarriage which is in each case arranged on the scissor mechanism, wherein an undercarriage comprises a crosspiece having bearing bushes at the end faces for the respective reception of a wheel unit with a wheel disc that is rotatably mounted about an axis of rotation.

Beds in general and bed frames of beds in particular are known per se from prior art so that there is no need for separate printed proof at this point.

In the intended use case of a bed, the bed frame serves to support a mattress frame. The mattress frame in turn serves to receive a mattress base, for example a slatted frame, or is designed as such.

Especially hospital and nursing beds additionally comprise a height adjustment mechanism which supports the mattress frame and serves to move the mattress frame together with the mattress base in height and to adjust it according to the requirements.

A height adjustment mechanism can be configured as hydraulically or pneumatically operated lifting device or as a scissor mechanism.

A lifting device typically comprises two lifting cylinders, one each being arranged for each headboard and provided on the headboard outside of the respective headboard. An advantage of such a lifting device is in particular that the bed can be lowered to a comparatively low entry height. This is possible because the lifting cylinders are not installed below the mattress frame, but are

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mounted on the outside of the bedheads and do thus not impede the lowering movement of the bed. On the other hand, attaching the lifting cylinders to the outside of the bedheads also has a disadvantage. This is because a bed equipped with lifting cylinders builds up accordingly in the longitudinal direction of the bed, which makes it difficult to maneuver in the event that the bed needs to be repositioned and can make it impossible to place it in storage facilities that are standardized in terms of their size dimensions. Particularly in the hospital and/or nursing sector, transport facilities such as elevators, but also doors, corridors and/or the like are standardized in their size dimensions and generally only permit the difficult use of beds equipped with a lifting device, which do not meet this standard.

To avoid the disadvantages described above, the scissor mechanism is used as the height adjustment device. This is arranged below the mattress frame so that a bed equipped with it does not build up in the longitudinal direction, making it easily maneuverable and, in particular, compatible with size dimensions typical in the hospital and/or nursing sector.

Thus, although a bed frame with a scissor mechanism has proven itself in everyday practical use, it is not free of disadvantages. This is because the arrangement of the scissor mechanism below the mattress frame means that the bed can only be lowered to a comparatively high entry height. This disadvantage weighs all the more heavily if the bed is designed to be movable and the bed frame therefore has a corresponding undercarriage, which is also arranged below the mattress frame, namely below the scissor mechanism.

According to a typical and also generic design, one undercarriage is provided for each bedhead. The bed frame thus has a first, head-side undercarriage and a second, foot-side undercarriage, which are arranged on the scissor mechanism and support it in a movable manner. The undercarriages are connected to each other by means of longitudinal struts, which provides the necessary stability when the scissor mechanism is used as intended. Each

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undercarriage has a crosspiece running in the transverse direction of the bed with bearing bushes at the end faces for the respective reception of a wheel unit. Each wheel unit has a wheel disc mounted so that it can rotate about an axis of rotation.

The size of the outer diameter of such a wheel disc has a not inconsiderable influence on the entry height that can be achieved when the scissor mechanism is lowered, because the smaller the outer diameter of a wheel disc, the lower the entry height. However, the smaller the outer diameter of a wheel disc, the poorer the running smoothness and running comfort when the bed is moved as intended. In addition, comparatively small wheel discs do not allow the installation of a desirably easy-to-operate parking brake. Consequently, there are conflicting interests with regard to the size of the wheel discs used. And so a bed with a generic bed frame typically has an entry height of, for example, 250 mm.

Based on the described prior art, it is the object of the invention to further develop a bed frame of the type described so that a comparatively low entry height of less than 250 mm is achieved by design, and this while at the same time maintaining or even improving the running comfort during an intended movement of a bed equipped with such a bed frame.

To solve this problem, the invention proposes a bed frame of the type mentioned above, which is characterized by the fact that an undercarriage has a connecting extension which points downwards starting from the corsspiece, is arranged at one end face on the crosspiece and has at the other end a bearing lug for the rotationally pivotably arrangement on the scissor mechanism, the axis of rotation defined by the bearing lug extending in the direction of height of the undercarriage below the axis of rotation of a wheel disc.

In prior art undercarriages, a crosspiece is provided on which both the wheel units and the scissor mechanism are arranged. In contrast, the bed frame

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according to the invention has an undercarriage in which only the wheel units are arranged on the crosspiece. However, a connection extension is provided for coupling the scissor mechanism. According to the invention, the scissor mechanism is not arranged directly on the crosspiece, but indirectly on the crosspiece with the interposition of the connection extension. The connection extension is oriented downward from the crosspiece.

For the rotationally pivotably arrangement of the undercarriage on the scissor mechanism, the connection extension is equipped with a bearing lug. This receives, in the finally mounted state, a corresponding coupling element for the rotationally pivotably arrangement of the scissor mechanism.

Of essential importance to the invention is that the axis of rotation defined by the bearing lug runs below the axis of rotation of a wheel disc in the height direction of the undercarriage. This means that the attachment point of the scissor mechanism is offset downwards compared to prior art, namely below the axis of rotation of a wheel disc of a wheel unit. When the scissor mechanism is lowered, this advantageously results in a much lower entry height than in the prior art, for example 100 mm. At the same time, despite this low entry height, comparatively large wheel discs of, for example, 100 mm outer diameter can be used, which ensures smooth running and good running comfort in the intended use.

With the design of the invention the attachment point of the scissor mechanism at the respective undercarriage is offset downwards in the height direction of the undercarriage. However, this lowering of the scissor mechanism is not bought with smaller wheel discs and the associated disadvantages. Rather, a constructive solution is provided in that a connection extension is used, which is arranged on one end of the crosspiece and which provides a bearing lug on the other end for connecting the scissor mechanism. The connection extension points downwards from the crosspiece in the height direction of the

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undercarriage thus achieving the low positioning of the scissor mechanism in relation to the undercarriage of the prior art.

With the design according to the invention, a bed frame is proposed for the first time, which does not include a lifting device, but instead includes a scissor mechanism for height adjustment of the mattress frame, while it can be lowered to an entry height as low as 100 mm, and this with the simultaneous use of comparatively large wheel discs, which ensures smooth running and good running comfort in the intended use.

According to a further feature of the invention it is provided that an undercarriage has two connection extensions, with the axes of rotation defined by the connection extensions being aligned.

According to this proposal of the invention, not only one connection extension is used to connect the scissor mechanism to an undercarriage, but two connection extensions. This increases the stability of the overall structure. In addition, a possible tilting moment is counteracted, since the scissor mechanism is mounted on two points for each undercarriage.

The rotationally pivotably arrangement of the scissor mechanism on an undercarriage is necessary in order to be able to compensate for length in the direction of the bed when the height adjustment is used as intended. In this case, the scissor mechanism rotates relative to the undercarriage about the respective axes of rotation provided by the bearing lugs. In order for this to be possible without canting, the axes of rotation respectively provided or defined by the bearing lugs are aligned with one another.

According to a further feature of the invention, it is provided that the connection extensions are each formed off-center in the region of an end section of the crosspiece. The distance between the connection extensions in the longitudinal direction of the crosspiece is thus maximized, which is advantageous for the

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stability of and for applying forces to an undercarriage under load. As a result, a long service life is thus ensured.

According to a further feature of the invention, it is provided that the crosspiece and the connection extensions are made of steel and are welded together. This results in a materially bonded and thus, in particular, robust overall construction. This is also advantageous for a long service life and overall stable overall construction.

According to a further feature of the invention, it is provided that receiving spaces are provided laterally and/or below the mattress frame supported by the scissor mechanism, which serve to receive a respective crosspiece of an undercarriage when the scissor mechanism is in the retracted position.

Since, according to the invention, the scissor mechanism is offset downwards in comparison to a crosspiece of an undercarriage, receiving spaces are provided on the bed frame side to maximize the travel distance, into which the traverses of the undercarriage can dive in each case when the scissor mechanism is lowered. These receiving spaces allow maximum travel, since diving of the crosspieces into these receiving spaces prevents them from colliding with other bed components such as, in particular, the scissor mechanism itself or the mattress frame. In the retracted state of the scissor mechanism, it is folded up to the maximum and lies between the crosspieces of the undercarriages, which in turn dive with their crosspieces into the receiving spaces provided for this purpose. This results in an optimized compact structure, which also contributes to being able to achieve the lowest possible entry height.

According to a further feature of the invention, it is provided that the crosspieces of the two undercarriages are free of a common longitudinal strut.

According to a typical design, the undercarriages used in prior art have a longitudinal strut. By means of this longitudinal strut, the crosspieces of the two

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undercarriages are positively coupled to each other, which serves to ensure a stable design. A disadvantage of this design, however, is that movement of the scissor mechanism downwards is limited, resulting in a comparatively high entry height. This is because the longitudinal strut connecting the crosspieces limits downward movement of the scissor mechanism and/or the mattress frame. The embodiment according to the invention remedies this situation, since the crosspieces are free of a common longitudinal strut. Consequently, there is no downward limitation of the travel in the height direction.

This design according to the invention is advantageous for yet another reason. Since, according to prior art, the crosspieces of the two undercarriages are positively coupled via a longitudinal strut, it is not possible to compensate the distance between the two undercarriages when the scissor mechanism is adjusted in the height direction. According to the state of the art, this makes it necessary to connect the scissor mechanism to the undercarriages by means of a fixed bearing on the one hand and a floating bearing on the other. In the case of vertical travel, length compensation between the undercarriages takes place via the floating bearing. This design is comparatively complex and expensive. With the design according to the invention, such a floating bearing construction can be completely dispensed with, since the undercarriages are not coupled to one another via a common longitudinal strut, so that length compensation between the undercarriages can take place simply by changing the distance between the undercarriages, which is permitted in a simple manner by the fact that each undercarriage is designed to be movable on the basis of its wheel units. According to the design of the invention, the length or distance compensation between the undercarriages required in the case of travel of the scissor mechanism is thus made possible without additional components simply by allowing a relative movement of the two undercarriages in the longitudinal direction of the undercarriage.

According to a further feature of the invention, only two wheel units are provided for each undercarriage. Thus, the first bearing bush accommodates a first wheel

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unit and the second bearing bush accommodates a second wheel unit. Wheel nacelles or double wheel units are therefore not provided. This advantageously simplifies the overall design.

According to a further feature of the invention, two wheel discs mounted rotatably about a common axis of rotation are provided for each wheel unit. A wheel unit thus has two wheel discs which are rotatable about a common axis. The use of two wheel discs per wheel unit improves stability.

In accordance with the invention, the crosspieces of the two undercarriages are free of a common longitudinal strut in order to achieve the lowest possible entry height. In addition, for an overall simplified design, only two wheel units are preferably provided for each undercarriage. The combination of these features results in a certain instability per undercarriage, especially in the event of a load. Since the undercarriages are each arranged to pivot on the scissor mechanism for the purpose of distance compensation, the undercarriages can unintentionally pivot and fold in relation to the scissor mechanism in the event of a load. In prior art, such pivoting is not possible either because the crosspieces are coupled to each other via a longitudinal strut or because double wheel units or nacelle wheels are used. To remedy this, and without complicating the design, the invention according to a further feature proposes that an undercarriage provides a support device arranged on the crosspiece, the support device comprising a support body supporting the crosspiece relative to the ground and arranged at a distance from the crosspiece in the transverse direction of the crosspiece.

The support device provided in accordance with this preferred embodiment serves to keep the undercarriage stable and sturdy even under load. The support device thus ensures that the undercarriage cannot swing unintentionally relative to the scissor mechanism despite the absence of a longitudinal strut and the provision of only two wheel units. This is because the support device counteracts a tilting moment acting on the undercarriage, particularly in the

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event of a load, which provides the necessary stability. In contrast to previously known designs, the design of a support device according to the invention is much less complex and complicated in construction and, moreover, does not conflict with the desired low entry height, which is a disadvantage of previously known designs. In this respect, this design according to the invention proves to be advantageous in two respects. On the one hand, it enables a low entry height and, on the other hand, it ensures a simple and cost-effective overall design.

The support device has a support body. When used as intended, this rests on the ground at the installation site and can thus provide the aforementioned support for the crosspiece relative to the ground. In this case, the support body is arranged at a distance from the crosspiece in the transverse direction of the crosspiece so that any tilting moments to be expected in the intended use can be reliably absorbed.

In combination with the connection extension according to the invention, the synergetic effect of a stable and sturdy construction is achieved while at the same time ensuring a low entry height.

According to a further feature of the invention, it is provided that the support device comprises a support strut which is arranged at one end on the crosspiece and which carries the support body at the other end. The support strut serves to arrange the support body at a distance from the crosspiece. It thus extends in the transverse direction of the crosspiece, being arranged at one end on the crosspiece and carrying the support body at the other end.

According to a further feature of the invention, it is provided that the support body is a wheel rotatable about a vertical axis and having a wheel disc rotatable about an axis of rotation. The design of the support body as a wheel provides the advantage that an intended movement of the bed frame is not impeded. In

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this context, it is also preferred to design the support body as a steerable wheel, so that any bed frame maneuvering is not impeded.

According to a further feature of the invention, it is provided that a support strut is arranged centrally between the two bearing bushes of a crosspiece. This central arrangement is made in particular for improved stability reasons. Tilting moments that may occur under load can be safely absorbed, and this while avoiding undesirable torques about the longitudinal axis of the support strut.

According to a further feature of the invention, it is provided that the end portions of the support struts of the first and second undercarriage carrying the respective support body face each other. The support struts together with the support body therefore do not protrude below the bed frame, but are aligned in the direction of the center of the bed frame. In this way, unnecessary tripping hazards are avoided, a visually appealing impression is created and, in addition, a compact design is given.

According to a further feature of the invention, it is provided that a wheel disc of a wheel unit of an undercarriage has an outer diameter of 100 mm. Despite the low entry height achieved with the design according to the invention, the use of comparatively large wheel discs with an outer diameter of 100 mm is made possible. This results in increased running smoothness and improved running comfort during use. In addition, the design of such large wheel discs allows a centrally actuated braking device to be used for each undercarriage, acting on both wheel units as it were. This also improves ease of operation and also serves to enhance safety.

With the invention, moreover, an undercarriage as such with the aforementioned features is proposed, as is a hospital and/or nursing bed with a bed frame according to the invention.

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Further features and advantages of the invention will be apparent from the following description with reference to the drawing figures.

Fig. 1 shows in a schematic perspective view an undercarriage of the bed frame according to the invention;

Fig. 2 shows in a schematic exploded view the undercarriage according to Fig. 1;

Fig. 3 shows in another schematic perspective view the undercarriage according to Fig. 1;

Fig. 4 shows a schematic front view of the undercarriage according to Fig. 1;

Fig. 5 shows in a schematic top view the undercarriage according to Fig. 1;

Fig. 6 shows in a schematic lateral view the undercarriage according to Fig. 1;

Fig. 7 shows in a schematic perspective view a bed frame according to the invention;

Fig. 8 shows in a top view the bed frame according to Fig. 7;

Fig. 9 shows in a partial sectional side view the bed frame according to Fig. 1;

Fig 10 shows in partial sectional side view a first undercarriage according to detail B of Fig. 9; and

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Fig. 11 shows in partial sectional side view a second undercarriage according to detail C of Fig. 9.

Figs. 1 to 6 show various views of first undercarriage 1 of a bed frame 3 according to the invention.

The bed frame 3 is especially a bed frame for a hospital and/or nursing bed. As apparent from a combined view of Figs. 7 to 11, the bed frame 3 comprises a height adjustment mechanism in the form of a scissor mechanism 4 for the height adjustment of a mattress frame 5 supported by the scissor mechanism 4. In the illustrated embodiment, the mattress frame 5 is designed as slatted frame and comprises a plurality of slats 36. The slatted frame 35 is subdivided to various segments, namely a head segment 37, a middle segment 38, a leg segment 39 and a foot segment 40. The head segment 37, the leg segment 39 and the foot segment 40 are each of pivotable design allowing an adjustment of the slatted frame 35 for setting different reclining positions.

The bed frame 3 further comprises a first undercarriage 1 and a second undercarriage 2, the first undercarriage 1 being provided on the head side and the second undercarriage 2 being provided on the foot side. The undercarriages 1 and 2 are each arranged on the scissor mechanism 4 and movably support the bed frame 3 when used as intended.

As apparent in particular from a combined view of Figs. 1 to 6 using the example of the head side undercarriage 1, the undercarriage 1 comprises a crosspiece 7 having bearing bushes 8 and 9 at the end faces for the respective reception of a wheel unit 10 or 11. Each wheel unit 10 or 11 for its part comprises wheel discs 12 and 13 or 14 and 15 rotatably mounted about an axis of rotation 16 or 17. Due to their mounting in the bearing bushes 8 and 9, the wheel units 10 and 11 are rotatable about their vertical axis, whereby the undercarriage 1 and the bed frame 3 supported by it are steerable. This is illustrated in the drawings by the different orientation of the wheel units 10 and

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11. The wheel units of the foot side undercarriage 2 not further illustrated are designed as so-called fixed castors, i.e. non-steerable wheel units. Alternatively, these wheel units can also be designed so as to be rotatable about their vertical axis and their rotation can be blocked with a parking brake, which gives quasi fixed castors.

As apparent in particular from Figs. 1 to 6, the undercarriage 1 has two connection extensions 18 and 19 which point downwards starting from the crosspiece 7. These connection extensions 18 and 19 are arranged at one end face on the crosspiece 7 and have at the other end face a bearing lug 20 or 21.

The bearing lugs 20 and 21 serve for the rotationally pivotably arrangement of the undercarriage on the scissor mechanism 4. For this purpose, the scissor mechanism 4 has corresponding receptacles so that in the final assembled state, for example, a bolt is arranged positionally secured on the one hand in a bearing eye and on the other hand in the associated receptacle of the scissor mechanism 4. This results in a rotationally pivotable arrangement of the undercarriage 1 in relation to the scissor mechanism 4, the bearing lugs 20 and 21 defined aligned axes of rotation 22 and 23. A different articulated attachment can also be provided instead of bearing lugs. However, the bearing lug design has the advantage that it is inexpensive to manufacture, easy to assemble or disassemble and also stable.

As shown in the illustration of Fig. 1, the aligned axes of rotation 22 and 23 of the bearing lugs 20 and 21 are arranged in the height direction 6 below the axes of rotation 16 and 17 of the wheel discs 12 and 13 or 14 and 15 of the wheel units 10 or 11.

As apparent in particular from a combined view of Figs. 2 and 3, the undercarriage 1 further comprises a braking device 30. This in turn has a lever 31 arranged pivotably on the crosshead 7, which lever 31 runs parallel to and spaced from the crosshead 7 with the interposition of two bearing levers 34.

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Two end pieces 32 are provided at each end of the lever 31, which are formed of plastic material or are plastic-coated, for example. By means of the lever 31, the braking device 30 is designed to be foot-operated, whereby the braking device 30 acts on both wheel units 10 and 11 in the case of use, which enables central and at the same time safe braking.

As shown by the exploded view according to Fig. 2, a common rod 33 is provided for a positionally secure reception of the wheel units 10 and 11 in the respective bearing bushes 8 and 9. In the finally assembled state, the rod penetrates through the crosspiece 7 which is designed as a hollow body and secures the corresponding wheel unit 10 or 11 in the associated bearing bush 8 or 9 by its respective end portions. One advantage of this design is in particular easy assembly or disassembly because it allows both wheel units 10 and 11 to be operated simultaneously.

The undercarriage 1 also comprises a support device 24 as also apparent from a combined view of Figs. 1 to 6. For its part, the support device 24 has a support body in the form of a wheel 26, which is arranged with the interposition of a support strut 25 in a transverse direction 43, spaced from the crosspiece 7. The undercarriage 1 thus has a total of three wheels, namely the wheel units 10 and 11 on the one hand and the wheel 26 of the support device 24 serving as a support body on the other. A three-point support for the undercarriage 1 is thus realized.

The support strut 25 is attached to the crosspiece 7 with the interposition of a connecting element 29, so that the scissor mechanism 4 is not restricted by the support strut 25 during a downward travel movement in the height direction 6.

The above-described design according to the invention offers numerous advantages.

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Compared to the prior art, the connection extensions 18 and 19 pointing downward in the height direction 6 ensure that the scissor mechanism 4 is offset further downward in relation to the crosspiece 7 of the undercarriages 1 and 2. This is because the connection extensions 18 and 19 ensure that the axes of rotation 22 and 23 of the bearing lugs 20 and 21 provided for connection to the scissor mechanism 4 lie below the axes of rotation 16 and 17 of the wheel discs 12 and 13 and 14 and 15, respectively, in the vertical direction 6. In contrast to prior art, this allows the scissor mechanism to be lowered with the result that a lowered entry height is achieved.

In contrast to the prior art, there is also no forced coupling of the undercarriages 1 and 2 by means of a longitudinal strut. Although such a longitudinal strut has the advantage of improved stability, it brings with it the disadvantage that a downward movement of the scissor mechanism 4 in the height direction 6 is limited by the longitudinal strut. This limitation is omitted in the embodiment according to the invention, so that the lowering of the scissor mechanism 4 achieved with the connecting extensions can actually be utilized.

Since there is a loss of stability due to the lack of longitudinal strut, the associated support device is provided for each undercarriage. In the event of a load, this ensures that any tipping moments that occur can be absorbed. Despite the lack of longitudinal bracing, this results in a safe and stable stand.

The lack of a longitudinal strut, i.e. forced coupling of the two undercarriages 1 and 2, provides a further advantage. For an intended adjustment of the scissor mechanism 4, it is necessary to support the scissor mechanism 4 variably in the longitudinal direction so that a length compensation can take place. In the design according to the invention, this is achieved in a simple manner by the fact that the two undercarriages 1 and 2 can be moved relative to each other in the absence of forced coupling. For a safe stand, it is sufficient to actuate the braking device 30 of one of the undercarriages in order to fix the respective wheel units. The other undercarriage is then positioned at a variable distance

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from the fixed undercarriage so that, by moving it, the length compensation required during operation of the scissor mechanism 4 can take place.

The support body provided as the third wheel 26 also has the advantage that the undercarriage 1 or 2 gets by with only two wheel units. Neither wheel nacelles nor double wheel units are required on each side of the undercarriage. This is because the three-point support ensures that the respective undercarriage stands securely.

As a result, the design according to the invention provides a reduced entry height of, for example, 150 mm instead of the 250 mm otherwise usual in connection with a scissor mechanism. At the same time, the design according to the invention allows comparatively large wheel discs 12 and 13 or 14 and 15 of, for example, 100 mm to be used, so that in addition to the low entry height, a high level of running smoothness and good running comfort are also ensured during travel.

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List of reference signs

1 Undercarriage 23 Axis of rotation 2 Undercarriage 24 Support device 3 Bed frame 25 Supporting strut 4 Scissor mechanism 26 Wheel Mattress frame 27 Wheel disc 6 Height direction 28 Wheel disc 7 Crosspiece 29 Connecting element 8 Bearing bush 30 Braking device 9 Bearing bush 31 Lever 10 Wheel unit 32 End piece 11 Wheel unit 33 Rod 12 Wheel disc 34 Bearing lever 13 Wheel disc 35 Slatted frame 14 Wheel disc 36 Slat 15 Wheel disc 37 Head segment 16 Axis of rotation 38 Middle segment 17 Axis of rotation 39 Leg segment 18 Connection extension 40 Foot segment 19 Connection extension 41 Receiving space Bearinglug 42 End profile 21 Bearinglug 43 Transverse direction 22 Axis of rotation

Claims (15)

WO 2022/017624 Patent Claims

1. A bed frame for a hospital and/or nursing bed, comprising a scissor mechanism (4) for the height adjustment of a mattress frame (5) supported by the scissor mechanism (4) and comprising a first and a second undercarriage (1, 2) which is in each case arranged on the scissor mechanism(4), wherein an undercarriage (1, 2) comprises a crosspiece (7) having bearing bushes (8, 9) at the end faces for the respective reception of a wheel unit (10, 11) with a wheel disc (12, 13; 14, 15) that is rotatably mounted about an axis of rotation (16, 17), characterized in that an undercarriage (1, 2) has a connection extension (18, 19) which points downwards starting from the crosspiece (7), is arranged at one end face of the crosspiece (7) and has at the other end face a bearing lug (20, 21) for the rotationally pivotally arrangement on the scissor mechanism (4), wherein the axis of rotation (22, 23) defined by the bearing lug (20, 21) extends in the direction of height (6) of the undercarriage (1, 2) below the axis of rotation (16, 17) of a wheel disc (12, 13; 14, 15).

2. Bed frame according to claim 1, characterized in that an undercarriage (1, 2) has two connection extensions (18, 19), with the axes of rotation (22, 23) defined by the bearing lugs (20, 21) of the connection extensions (18, 19) being aligned with each other.

3. Bed frame according to claim 2, characterized in that the connection extensions (18, 19) are each formed off center in the region of an end section of the crosspiece (7).

4. Bed frame according to any one of the preceding claims, characterized in that the crosspiece (7) and the connection extensions (18, 19) are made of steel and are welded together.

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5. Bed frame according to any one of the preceding claims, characterized in that laterally and/or below the mattress frame (5) supported by the scissor mechanism (4) receiving spaces (41) are provided, each serving for the respective reception of a crosspiece (7) of an undercarriage (1, 2) in a retracted position of the scissor mechanism (4).

6. Bed frame according to any one of the preceding claims, characterized in that the crosspieces (7) of both undercarriages (1, 2) are free of longitudinal struts.

7. Bed frame according to any one of the preceding claims, characterized in that only two wheel units (10, 11) are provided for each undercarriage (1, 2).

8. Bed frame according to any one of the preceding claims, characterized in that two wheel discs (12, 13; 14, 15) which are rotatably mounted about a common axis of rotation (16, 17) are provided for each wheel unit (10, 11).

9. Bed frame according to any one of the preceding claims, characterized in that a wheel disc (12, 13, 14, 15) has an outer diameter of 100 mm.

10. Bed frame according to any one of the preceding claims, characterized in that a braking device (30) is provided which is centrally operated and acts on both wheel units (10, 11) at the same time.

11. Bed frame according to any one of the preceding claims, characterized in that an undercarriage (1, 2) provides a support device (24) arranged on the crosspiece (7), wherein the support device (24) comprises a support body supporting the crosspiece (7) against the ground, which support body is arranged in the transverse direction (43) of and spaced from the crosspiece (7).

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12. Bed frame according to claim 11, characterized in that the support device (24) comprises a supporting strut (25) arranged at one end on the crosspiece (7) and carrying the support body at the other end.

13. Bed frame according to claim 11 or 12, characterized in that the support body is a wheel (26) which is rotatable about a vertical axis and which has a wheel disc (27, 28) rotatable about an axis of rotation.

14. Bed frame according to claim 12 or 13, characterized in that a supporting strut (25) is centrally arranged between the two bearing bushes (8, 9) of a crosspiece (7).

15. Bed frame according to any one of the preceding claims 12 to 14, characterized in that the end sections of the supporting struts (25) of the first and second undercarriage (1, 2) carrying the respective support body are facing each other.