The present invention relates to a rotary acz ator, pref- erably for adjustable separate mattress supports and beds, said actuator comprising an electric-. otor which, via a transmission, drives a rotatable mourning bracket, preferably shaped as an arm intended to be secured to a movable part, in a structure in which the actuator is incorporated, as well as a fixed arm intended to be secured to a stationary part of the structure.

Rotary actuators of this type may be used performing movements and positional adjustments in articles of fur- niture, including beds and separate mattress supports, care beds, hospital beds, nursing equipment, seats for vehicles, machinery and within the industry. germain Util- ity Model DE 298 02 384 U1 discloses a ma-ress support with incorporated rotary actuators fora'usting the backrest part or the legrest part.

It is unfortunate if something gets jammed between the rotating part and the stationary part of structure, which may cause damage to the structure a--the jammed articlearticleor object if the movement is not stopped, of course it is even more unfortunate if injury oc- curs.

The object of the invention is to provide a rotary actua- tor of the type stated in the opening para----? and pro- vided with a jamming protection arrangement.

This is achieved according to the invention in that the fixed mounting bracket of the actuator co-operates with a profile having a configuration which secures the bracket against rotation in the usual operational state of the actuator, but allows rotation if the movable part is ob- structed in its rotary movement. Thus, if something gets jammed between the movable part and the stationary part of the structure, then the movable part will stand still, while the otherwise fixed mounting bracket will begin to rotate. It will hereby be realized quickly that something has got jammed in the structure so that the rotary move- ment can be stopped and harmful damage be avoided, to the structure as well as to the object which has got jammed.

As will readily be realized, the jamming protection ar- rangement may be configured so that it is easy to mount.

Moreover, it can be configured so that it can be manufac- tured at a reasonable cost.

Special embodiments of the actuator are defined in the dependent claims 2-7 and are explained more fully in con- nection with the example discussed below.

Claim 8 defines a structure, preferably a separate mattress support or bed, comprising a stationary part and at least one part adjustable by means of a rotary actuator according to one of claims 1-7, said actuator being secured to the stationary part with the fixed mounting bracket and to the adjustable part with the rotatable mounting bracket.

In structures in which two actuators must be included, such as mattress supports with adjustable backrest and legrest parts, it is expedier. to arrange these so that the fixed arms may be interconnected with a com. mon pro-

file. The moments in the arms are hereby transferred to the common profile, which is an advantage when the sta- tionary part of the structure is flimsy in general. This is e. g. the case with mattress supports where, for other reasons, the frame is of relatively flimsy wood. Of course, it is advantageous that the arms are disposed on a straight line in that case, so that a rectilinear pro- file may be used, but it is not an absolute necessity.

In the event of a mattress support exclusively with an adjustable backrest part, it may still be advantageous to use a profile which is then secured at the free end to a transverse connection in the bed frame, which may merely be a transverse rod secured in the side members of the frame.

The invention will be explained more fully below with reference to the embodiment illustrated in the accompany- ing drawing. In the drawing: Fig. 1 shows a mattress support intended to be placed or incorporated in a bed, fig. 2 shows a rotary actuator in its entirety, fig. 3 shows a connection between two actuators of the mattress support, seen from the side, fig. 4 shows the connection of fig. 3 seen from above, fig. 5 shows a section along the line V-V in fig. 3, fig. 6 indicates he position of the actuator when some- thing has got ja==-d, and

fig. 7 shows a part of a bed frame in another embodiment of the invention.

The embodiment comprises an adjustable mattress support intended for home beds. The mattress support replaces the slatted bed case, which is otherwise included in a bed.

The mattress support shown in fig. 1 comprises an outer frame 1 which includes a mattress support portion con- sisting of a pivotable backrest part 2, a fixed central part 3, and a legrest part 4 which is articulated. The central part 3 is secured to the sides of the outer frame 1.

The backrest part 2 is pivotable about a shaft 5 likewise secured at the sides of the outer frame 1, and corre- spondingly the legrest part is pivotable about a shaft 6.

Both the backrest part 2 and the legrest part 3 perform their movements with a rotary actuator 7, as shown in fig. 2. The rotary actuator comprises a pipe 10 of quad- rangular cross-section that accommodates an electric mo- tor, which is connected with an arm 11 via a transmission. An arm 12 is secured at each end of the pipe 10. At the backrest part 2, the arm is equipped with a wheel~13 which is guided in a guide rail 14 secured to the backrest part. The pipe 10 is rotatably mounted about its longitudinal axis in a bracket 15 secured at each side of-the outer frame 1. As the other arm 11 of the actuator is'fixed, the pipe 10 and the arms 12 secured on the end thereof will rotate when the actuator is activated. The arms 12 will hereby raise or lower the backrest part, as this will pivot about its shaft 5. The legrest part is raised and lowered in a corresponding

manner, as the ends of the arms 12a on the actuator 7a of the legrest part are rotatably secured to a bracket on the outermost link 4a of the legrest part. Activation of the actuator will cause the legrest part 4 to be raised or lowered, as the arm 12a will cause the innermost link 4b to rotate about the shaft 6 through a raising and rotating movement of the outermost link 4a of the legrest part.

The actuators. 7a, 7b of the backrest part and the legrest part are identical, they are merely rotated 180° relative to each other so that their arms are disposed at the same side of the mattress support. In the plane state of the mattress support portion, the arms 11 are disposed on a straight line and point toward each other. This is read- ily possible in that the arms are symmetrical about their longitudinal axes. Each arm 11, only one is shown in figs. 3-5, is connected with a U-profile 21a via a rivet 20. The arm 11 and the U-profile 21a are mutually ro- tatable about the rivet 20 as a shaft. The U-profile 21a, 21b from each arm is mounted in a U-rail 22. The profile 21a, 21b and the rail 22 are assembled by a pin 23a, 23b which can move in a slot 24a, 24b at both sides of the rail 22. The load on the other arms 12 will try to tilt the arms 21 upwards, but is prevented from domina this in that the-arms hit the bottom of the U-profile 21. The rod connection11,21,22 will relieve the outer-frame of the mattress support, which should preferably be as thin as possible'for other reasons and is typically of wood.

Of course, it is only at the end where the arm 11 is se- cured that the profile 21a needs to have the stated cross-section, otherwise, the remaining length of the profile may have another cross-section.

The two rotary actuators are connected to a power supply, which is in turn connected to the mains, and they are controlled from a manual control or other control panel via a control box.

To raise the backrest part, the rotary actuator is acti- vated via the manual control, whereby the quadrangular pipe/the actuator housing begins to rotate, and the two arms at the ends thereof will raise the backrest part. When the backrest part is lowered, this takes place under usual conditions of operation in the same manner.

If, however, something gets jammed between the backrest part 2 and the outer frame when the backrest part is low- ered, the arm 11 will begin to rotate upwards, since the other arm 12 is obstructed in its downward movement, cf. fig. 6. The arm 11 will partly press the U-profile up- wards and partly push it outwards, thereby causing the pin 23a to slide in the slot 24a. The immediate visible indication to the user that something has got jammed is that the backrest part stands still, so that the user can stop the actuator and remove the jammed object, option- ally by first rotating the backrest part a distance up- wards. The same applies if something has got jammed at the legrest part. The connection between the two actua- tors thus serves as a jamming protection, as a safeguard against damage both to the structure itself and to the object which has got jammed.

In an embodiment of the invention with two actuators, the connection pipe between these is a closed profile, and the bending movement caused by an object which has got

jammed, is absorbed as an elastic bending in the connec- tion pipe.

If the frame of the mattress support alternatively the frame of the bed is sufficiently rigid and strong to be able to transfer the forces, as is the case with hospital beds, the invention may be realized as indicated in fig.

7 by mounting an angular member on the side of the frame.

It will be appreciated that the invention may be realized in other connections than beds or mattress supports, and it will also be appreciated that the invention may be im- plemented in various configurations. For example, it may be mentioned that if a bed or a mattress support just has an adjustable backrest, the end of the U-rail may be se- cured to the bed structure. In this embodiment, the structure is also suitable for a chair. In the foregoing, the structure is configured such that the pipe 10 with arms 12 rotates, but nothing prevents the reverse, viz. that the arms 11 perform the movement, while the pipe 10 with the arms 12 is secured.