Abstract:
The invention concerns a device in linear actuators comprising a carriage ( 1 ) which is guided for movement on or in a rail by means of rotatable threaded spindle ( 3 ) extending in the longitudinal direction of the rail. The spindle runs freely through at least one screw support ( 2, 17, 18, 20, 21, 22, 23 ) which serves as a bearing supporting the spindle ( 3 ) intermediate the ends thereof. The carriage ( 1 ) and the screw support ( 2, 17, 18, 21, 22 ) are provided with interacting locking means ( 4, 5, 6, 7 ) arranged to cause said screw support ( 2, 17, 18, 21, 22 ) to be brought along by said carriage ( 1 ) during part of the movement of the latter along the spindle ( 3 ). In addition. means ( 11, 19, 28, 29 ) are provided for releasing the carriage ( 1 ) and the screw support ( 2, 17, 18, 21, 22 ) from one another as they pass said means while at the same time the secure the screw support ( 2, 17, 18, 21, 22 ) in the position into which it has been moved.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a device in linear actuators of the kind comprising an open rail or a hollow profile rail on or in, as the case may be, a carriage is guided for displacement in the longitudinal direction of the rail with the aid of a rotatable threaded spindle in screw engagement with the carriage. 
     More precisely, the invention concerns a device in linear actuators of the kind in which a screw support is provided at least to one side of the carriage, said screw support arranged to form a bearing supporting the spindle intermediate the points of support at the spindle ends. 
     A screw support of this kind is intended to prevent the threaded spindle, usually a ball bearing screw, from bending or deflecting outwards upon attainment of a so called critical r.p.m. value. Such outwards deflection depends on the length and rotational speed of the spindle. This critical value is attained at an earlier stage when the spindle is of a particularly great length and/or the rotational speed is high than in the case of short spindles or lower rotational speeds. 
     In linear actuators of considerable length, formed with a long spindle that operates at comparatively high r.p.m. values, it is possible to prevent the above-mentioned outwards deflection of the spindle by using one or several support bearings in the form of such screw supports. In order to allow carriage movements from one end of the linear actuator to the other, various technical solutions have been suggested to make the carriage bring along, in its movements, a screw support from a selected point of support positioned along the length of the spindle and then, upon its return movement, release and leave the screw support at the same point of support. Hitherto known locking means for interconnecting carriage and screw supports have, however, suffered from the disadvantage of being unnecessarily complicated, in addition to which they have been subjected to unnecessarily heavy wear during the translatory movements of the screw support by means of the carriage, often resulting in unsatisfactory operational reliability in the linear actuator. Generally, the space requirements of the locking means on one or both sides of the linear actuator are such that there is a risk that the screw support gets wedged on equipment disposed close to the linear actuator, a situation which likewise impairs the operational reliability of the linear actuator and which consequently may lead to breakdowns. 
     The invention provides a device by means of which screw supports may be brought along by the moving carriage and be secured in pre-determined places disposed along the spindle, which device is of simple structure, requires a minimum of space while at the same time it exposes the components of the device to a minimum of wear, in consequence whereof the device is imparted a considerable degree of operational reliability. The features characterizing the device in accordance with the invention appear from the appended claims. 
     BRIEF SUMMARY OF THE INVENTION 
    
    
     The invention will be described in closer detail in the following with reference to the accompanying drawings, wherein: 
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a perspective view of a screw support and a part of a carriage, shown separated from one another and provided with locking means devised in conformity with one embodiment of the invention, 
     FIG. 2 is a similar view of these parts, shown in locked position, 
     FIGS. 3-6 are schematic views illustrating the function of the locking means, 
     FIG. 7 is a broken view from above of the spindle incorporated in the linear actuator, also schematically showing the carriage having one screw support on either side, 
     FIG. 8 is a view similar to FIG. 7 but showing the carriage having one couple of screw supports on either side, 
     FIGS. 9-11 illustrate the carriage and the screw supports in accordance with FIG. 8 in different positions, and 
     FIG. 12 is a view similar to FIG. 1 of the carriage and a screw support but fitted with locking means in accordance with a different embodiment. 
     FIG. 1 illustrates a part of a carriage  1  and a screw support  2 . The carriage  1  is in screw engagement with a threaded spindle  3 , which for improved clarity is not illustrated in FIG. 1 but only in FIGS. 7 and 8. The spindle  3  runs freely through the screw support  2 , the latter intended to serve as a bearing to support the spindle  3 . The carriage  1  and the screw support  2  are arranged for movement in a hollow profile rail, which has been deleted from the Figure, likewise for improved clarity. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The carriage  1  and the screw support  2  are provided with interacting locking means. The locking means of the carriage consist, in accordance with one embodiment of the invention, of a connecting rod  4  projecting from the carriage  1  in the longitudinal direction of the spindle  3  and supporting a locking washer  5  at its free end. In accordance with this embodiment, the locking means of the screw support  2  consists of a rocker arm  6  which is located to one side of the screw support  2  and which is pivotally connected to a blocking arm  7 , said latter arm being displaceable in its longitudinal direction transversely of the screw support  2  and formed with a stop portion  8 . By means of a pair of compression springs  9 , each urging a plate  10  into abutment against the rocker arm  6 , the latter tends to assume one of its end positions, i.e. either an open position or a locked position. 
     The function of the locking means will be explained in the following with reference to FIGS. 3-6. FIG. 3 illustrates a position, wherein the screw support  2  is kept fixed with the aid of stationary abutment  11  positioned laterally of the path of movement of the carriage  1 . In this case, the rocker arm  6  and the blocking arm  7  are kept in the open position. The carriage  1  is being displaced in the direction of arrow  12  and thus approaches the screw support  2 . When the carriage  1  reaches the screw support  2 , see FIG. 4, the locking washer  5  passes through a notch  13  formed in the blocking arm  7 , see also FIGS. 1 and 2. When the carriage henceforth carries along the screw support  2  as it continues moving in the same direction, the stationary abutment  11  forces the rocker arm  6  to shift from its open to its locking position. Consequently, the stop portion  8  on the locking arm  7  will assume a position behind the locking washer  5  as seen in the direction of movement. In this manner, the carriage  1  and the screw support  2  become interlocked. 
     When, while assuming an end position on the linear actuator, the carriage  1  reverses and is advanced in the direction of arrow  14 , see FIG. 5, it consequently carries the screw support  2  along in its reverse movement, by means of the connecting rod  4  and the locking washer  5 . As soon as the carriage  1  together with the screw support  2  again passes the abutment  11 , see FIG. 6, their passage forces the rocker arm  6  to rock back to the open position. The locking washer  5  is again able to pass through the notch  13  and the carriage  1  to continue its movement in the direction of arrow  14 , whereas the screw support  2  is held by the abutment  11  and when in its thus fixed position it forms a bearing support on which the spindle  3  is supported until the carriage again reverses its movement and the process just described is repeated. 
     The function of the device in accordance with the invention has been explained above by description of the cooperation of the carriage  1  with one screw support  2  only. FIGS. 7 and 8, on the other hand, illustrate embodiments that are suitable for practical applications. Thus, FIG. 7 shows the spindle  3 , extending between the bearing points  15 ,  16  disposed at the spindle ends, as also the carriage  1 , including two screw supports  17 ,  18 , one on either side. In this case the carriage  1  likewise is formed on either side with a connecting rod  4  supporting a locking washer  5  thereon. One single stationary abutment  19 , preferably centrally located on the spindle  3 , cooperates with both screw supports  17 ,  18 . One of the screw supports, screw support  18  in the position shown in FIG. 7, is always secured to the abutment  19  whereas the other screw support, in the present case screw support  17 , is brought along by the carriage  1 . As the moving carriage comes into contact with the screw support  18 , the latter is released from the abutment  19 , and as soon as the carriage  1  has passed the abutment  19 , the screw support  17  is caught by the abutment, is released from the carriage  1  and fixed whereas the carriage  1  continues its movement, displacing screw support  18  ahead of itself. In each position of the carriage  1  along the spindle  3  the latter thus has a support bearing located centrally thereon, preventing the spindle from deflecting outwards. 
     In the case of long spindles it may be suitable to use one pair of screw supports  20 ,  21  and  22 ,  23 , respectively, on either side of the carriage  1 , as shown in FIG.  8 . Like the carriage  1 , the screw supports  21  and  22  closest to the carriage  1  are then provided with connecting rods  24  and  25 , respectively, and locking washers  26  and  27 , respectively. According to this embodiment abutments  28  and  29 , are provided, one on either side of the spindle  3 . 
     In order to describe the functional process in the simplest possible way with respect to the embodiment of FIG. 8, reference is now made to FIGS. 9-11. The spindle  3  is imagined divided into three thirds, the abutments  28 ,  29  being disposed at a distance from the respective spindle end corresponding to one third of the length of the spindle  3 . 
     In accordance with FIG. 9 the carriage  1  is in a position to the left as seen in that Figure and it is assumed that it moves to the right, in the direction of arrow  30 . In this situation, the carriage  1  brings along the screw support  22  in its movement, said support in turn bringing along screw support  23 . When the carriage  1  reaches the screw support  21 , the latter is released from its engagement with the abutment  29  while at the same time it is interconnected with the carriage  1 , the screw support  22  passes freely past the abutment  29  whereas the screw support  23  is released from screw support  22  and is secured to the abutment  29 . The carriage  1  continues its movement in the manner shown in FIG. 10, i.e. with one screw support  21  ahead and one screw support  22  at the rear. When the carriage  1  reaches the abutment  28  the screw support  20  is released (therefrom) in a corresponding manner while at the same time it is locked to the screw support  21 , this screw support passes freely past the abutment  28  and the screw support  22  is released from the carriage  1  and is secured to the abutment  28 . As apparent from FIG. 11, the carriage  1  then continues its movement, bringing along with it, at its front, screw supports  20 ,  21  while screw supports  22  and  23  are secured to the abutments  28  and  29 , respectively, each support thus forming a bearing supporting the spindle  3  at its respective place. 
     In FIG. 12, the carriage  1  and the screw support  2  are shown with differently configured locking means. In this case, the carriage  1  is formed with a plate  31  having a recess therein forming an edge portion  32  including a rear edge face  33  that is turned away from the screw support  2 . The screw support  2  is provided with a rocker arm  34  which in the same manner as the rocker arm  6  in FIGS. 1 and 2 is spring-biased by spring means  9  urging a plate  10  into abutment against the rocker arm  34 . In contrast to the rocker arm  6  the rocker arm  34  is formed with a hook member  35  which, when actuated by the spring means  9 , snaps behind said rear edge face  33  in order to interconnect the carriage  1  and the screw support  2 . The rocker arm  34  otherwise cooperates with a stationary abutment located laterally of the linear actuator, in the same manner as rocker arm  6 . 
     The invention is not limited to the embodiments described and shown but may be varied in many ways within the scope of the appended claims. For instance, the carriage  1  in accordance with the embodiment of FIG. 12 need not be provided with a plate  31  but instead the wall thereof could be formed with a recess forming a corresponding rear edge face for engagement with the hook member  35 . Instead of a recess, the blocking arm  7  could have a protruding (depressed) portion which is introduced behind the locking washer  5  after the latter has passed above (underneath) the blocking arm  7 . 
     The invention is not either limited to the described embodiments including one, two, or four screw supports, but the device could equally well operate with a larger number of screw supports, such as e.g. six such supports.