FR2590340A1 - Device for guiding and driving movable mechanical members with linear displacement - Google Patents

Abstract

The carriage made from folded sheet metal 56 is mounted on linear bearings 57 suspended elastically and sliding on slideways 58. It is driven by a nut consisting of a block of plastic 55 bored to the external diameter of the screw 69 and supports two drivers 46, 47 meshed in the pitch and fixed to the metal sheets 62 secured to the block 55 one of which comprises an extension 63 engaged in a slot 64 of the carriage and held elastically against spring leaves 65, 66 secured to the carriage. According to one variant, the screw 69 comprises an added pitch consisting of a spring steel helix fixed at least at one end to the smooth core of the said screw.

Description

Device for guiding and driving mobile mechanical members with linear displacement.

The invention relates to a device for guiding and driving mobile mechanical members with linear displacement.

Various types of guiding and driving devices for mobile mechanical members are already known, and in particular: - the cylindrical slides cooperating with closed or open ball bushings or with smooth rings with low friction coefficient dead in rigid supports, - The bodies moving on these slides are driven by various types of pneumatic, hydraulic, rack and pinion and screw nut means.

These guiding and driving devices are used in machine tools in general, transfer machines, special machines for machining, assembly, packaging, production.

The disadvantages presented by these devices are the following: - they require very high machining precision and in particular parallelism for the cylindrical slides and their support cooperating with a screw-nut drive; - Rigidity of the slides and their support to avoid bending which causes significant friction stresses with premature wear and increased resistant forces requiring an increase in power increasing energy consumption; - significant cost of production which is only justified for special cases of machining or assembly precision; - difficulties in adjusting the end positions of the moving parts on the slides; - difficulties in damping the limit switches when a dispersion occurs in the stop positions, or when the stop of the movable member must be made against a straight stop for a relatively precise positioning in the case of displacement by screw-nut.

Apart from machine tools for removing material or deforming material, the movements of which must be relatively precise and regular, the movements of organs rarely require a regularity of the speed of movement, this is why jacks are often used. which provide great flexibility of movement and make it easier to slow down and dampen the ends of cpurse, which is much more difficult with screw-nut drive.

The device according to the invention solves the problem of linearly guiding and driving movable members with very light means, inexpensive to produce and to assemble, capable of compensating for deviations in parallelism between the guide rails and between the means of 'screw-nut drive and the member to move and absorb the dispersions of end stops even on a straight stop.

These objects are achieved according to the invention by means of linear bearings suspended elastically and by means of two types of screw-nut:
a) with an elastically deformable coupling between the nut and the movable member, the nut comprising two coaches meshing in a screw with a large and wide pitch;
b) with screws, the pitch of which is constituted by a spring steel propeller slid over a cylindrical core and fixed at its ends to said core, the nut being constituted by a folded sheet metal bracket rigidly fixed on the movable member and comprising two coaches meshed in the propeller.

The advantages provided by the device according to the invention are as follows: - very low cost of production and implementation of the movable member and its support which can be of sheet metal cut and folded on machines with digital control; - elimination of the problems of parallelism of the slide and of the "hards" of operation; - elimination of problems due to bending of the carriage or slides or their support; - very low inertia due to the significant reduction in weight of the moving parts compared to traditional carriages; - reduction of static and dynamic resistant forces; - reduction in energy and material consumption; - integrated damping of the limit switches by bending the screw or the nut support which stores the kinetic energy at the end of the stroke and releases it at the start of the next cycle; - absorption of end-of-travel stop dispersions; - great simplification of making screws; - significant reduction in the sliding friction of the nuts on the screws transformed into rolling friction; - simplification and lightening of the slide supports and the screw-nut drive system due to automatic compensation for bending.

The device for guiding and driving mobile mechanical members according to the invention is described in detail in the following text with reference to the appended drawings given by way of nonlimiting examples in which: FIG. 1 shows an example classic guide and carriage drive; - Fig.2 and 3 show, in section and in end view, an example according to the invention of linear guide bearing s # hanged elastically; - figs. 4.5A, 5B, 5C, 5D and 6 show examples of linear bearings suspended elastically with incorporated fixing lugs, - fig.7 shows, in section, a variant of the method of fixing a linear cylindrical bearing; - Fig.8 shows an example of elastic joint of known type transformed into a linear bearing by the addition of a reduced friction ring; - Fig.9 shows an example according to the invention of mounting a carriage with two linear bearings suspended elastically on one side and only one on the other; - fig. 10 shows an example identical to that of FIG. 9, but with two linear bearings on each slide; - Fig.11 shows an example of a carriage mounted on two linear ball bearings on one side and comprising one or two linear bearings with elastic suspension according to the invention on the other anti-roll slide; - Fig.12 and 13 show an example of carriage drive nut according to the invention with a large pitch screw cooperating with coaches; - figs. 14 and 15 show an example of a carriage drive and guide according to the invention with an elastically deformable coupling; - Fig.16 shows a drive variant with elastically deformable coupling; - Fig.17 shows an example of driving distant carriages, in an identical or reverse direction depending on the pitch of the screw, by means of a shaft with compensation for positioning deviation according to the invention; - Figs. 18 to 23 show examples according to the invention, of means for attaching the ends of the spring steel propellers to their core; - Fig. 24 shows an example of a driver nut mounted on a spring steel propeller screw.

Figure l shows a classic example of carriage guidance and drive. It comprises a plate 1 on which three or four ball bearing bushes 2 have been mounted and a traditional screw-nut system 3,4
The assembly of these various organs must be very precise to avoid "hard operation".

Figs. 2 and 3 show, in section and in end view, an example according to the invention of an elastically suspended linear bearing. The ring 5 sliding on the guide rod, has an anti-friction coating to reduce sliding friction in significant proportions.

As all the organs used are made of folded cut sheet metal, it is not possible to obtain significant positioning accuracy, this ring is suspended elastically in its support 6 cooperating with the wall of the carriage 7, by means of two O-rings 8 of elastomer slightly compressed at mounting to ensure sufficient prepositioning on the slide.

The hardness of the rings 8 is a function of the load to be borne and the deviations in precision to be compensated. It is possible to increase the number of these rings as well as that of the rings 5. The ring 5 is retained longitudinally between two folds 9, 10 of the support bracket 6. It absorbs the positioning deviations of the slides G without bringing any notable resistance to displacement of the carriage.

In FIGS. 4,5A, 5B, 5C, 5D and 6, an example according to the invention has been shown of a linear bearing with elastic suspension comprising incorporated fixing lugs. The bearing ring 5 is positioned in a housing 10 of square section by means of an elastomer or similar overmolding 11. The fixing is ensured by two cutout legs 12,13 each comprising a fixing hole 14,15 in which a screw or a rivet 16, 17 to secure it to the carriage 18. The bearing housing can be cut from a tube of square section, or else be cut flat in a sheet of sheet metal and folded with close edges 19 fig.5A or fig. 5C; the fixing lugs can be bent at right angles perpendicular to the longitudinal axis as in fig. 5B for end fixing, or else can be added in the form of a spot welded plate for example as in FIG. 5D.

Fig.7 shows another example of a possible functional form for these linear bearings with elastic suspension. The support housing 20 is tubular in shape with a stepped end 21 allowing the fixing at the end by means of holes 22. The ring 5 is held by an annular overmolding 23 of elastomer or the like as in the previous examples.

In fig.8 we have shown an example of elastic articulation 25 of known type, comprising an outer ring 26 and an inner ring 27 of the same or different length, held together by an overmoulding of elastomer 28. We transformed this articulation in linear bearing by adding a glued fitted ring 5, comprising an anti-friction coating. We could also transform this type of articulation ~ tion into a cylindrical bearing by directly adding the anti-friction coating. But to use it, you have to mount it in a box like the one in fig.7 for example or other previous figures.

This type of suspended bearing can receive all forms of common fasteners integrated into the housing or attached as in fig. 5D.

Figs. 9 and 10 show the mounting methods for these linear bearings on cylindrical slide carriages with three or four or more bearings depending on the load.

In fig.11 there is shown an example of a carriage 30 comprising two ball bearings 31 mounted in a support block 32 fixed on the carriage 30. The anti-roll is ensured by means of a suspended bearing 33 according to the invention fixed on the carriage with a wedge 34 and two bolts 35. The guide rod 36 can be fixed to the frame by a slightly oblong hole in the horizontal direction for Timtter. iù risk of deviation of parallelism of the support.

Fig.12 shows an example of a screw-nut according to the invention for driving in linear displacement of the movable members of the carriage type or the like. The movable member 40 is made elastic or not integral with the nut block constituted by a block 41 of plastic material with low coefficient of friction comprising a bore 42 in which is engaged a screw 43 with wide pitch. The block 41 is clamped between support sheet plates 44,45 each receiving a driver 46,47 meshing in the pitch of the screw and offset with respect to each other by a half-step 48. each constituted by a stepped axis 49, a range of which is provided for receiving a needle sleeve 50 meshing in the pitch with the other threaded part of the axis being engaged in a hole in the plate 44,45 and immobilized by a nut 51. of course, a ring made of a material with a low coefficient of friction can be used directly in place of the needle bushing.

Figs. 14 and 15 show an example of a carriage driving and guiding means according to the invention comprising an elastic connection between the nut 55 and the carriage 56 to be moved. This arrangement makes it possible to absorb end-of-travel stop dispersions or dead ends during movement.

The carriage 56 is mounted on four elastic suspension bearings 57 moving on cylindrical slides 58 secured to the chassis 59 by their ends; one of the rods is fixed by means of oblong holes 60 horizontal at its two ends to make up for mounting differences.

The end positions of the carriage are detected for example by two magnetic sensors 61 whose position is adjustable. The nut 60 is supported, with a very slight clearance, on the underside of the carriage 56, one of the plates 62 is extended at 63 through a slot 64 in the carriage, and is trapped between two spring blades 65 , 66 fixed on a block 67 secured to the carriage. When the carriage arrives in frank abutment at the end of the race, for example on washers 68 and the gearmotor (not shown) for driving the screw is not completely stopped, the nut 55 can move further while bending the leaf spring 66 and sliding under the carriage. In the following cycle, the energy stored by the spring is restored and helps overcome the inertia of the movable member. We can provide for detection of the relative displacement between the nut and the carriage when the latter exceeds a threshold to stop the motor, for example in the event that the limit switch is out of order or out of order.

Fig. 16 shows another example of carriage or mobile member drive by means of a screw-nut assembly with elastically suspended coaches. In this example, the nut 70 is not supported under the carriage 71, the anti-reverse of the nut as well as its elastic fixing are ensured by means of two leaf springs 72,73 pierced with a hole for the passage of the screw 74. These springs are fixed by screws under the carriage 71; the free end of these springs is folded back and engaged, by a second fold 75, in a countersunk slot of the nut 70 bearing on the bottom thereof with very slight stress. The screw 74 is mounted, at its two ends, on bearings 76 with friction reduction ring 77. The ends of the screw 74 are supported and supported on the frame 59 by means of needle stops 78. A coupling 79 binds the screw to the motor 80 fixed on the end of the chassis 59.

In fig.17 we have shown an example of synchronous drive of distant carriages 85,86 by means of screws 87,88 of the same direction of pitch, or with reverse pitch, mounted on a light structure in folded cut sheet metal. The connection between the two shafts is made so as to be able to make up for possible mounting differences. The coupling is obtained by means of an intermediate shaft 89 provided at each end with a means 90.91 fitted and pinned at each end and having a bore significantly larger than the diameter of the shaft end 92.93 of the screws .

An elastomer sleeve 94 is introduced into the bottom of the hub bore, cooperating with a washer or a ball also made of elastomer.

the drive between the shafts is obtained by means of a pin 96 also surrounded by an elastomer sleeve 97 at each of its ends, said sleeves 97 being engaged in a corresponding milling of the hub 90. The pins 96.98 are preferably arranged at 900
Figs. 18 to 23 show exemplary embodiments of another type of inexpensive screw-nut capable of absorbing the damping and dispersion of end-of-travel stops in hard abutment. The screw-lock systems used for moving trolleys or moving parts are expensive to machine and generate significant friction and must be carefully fitted. To reduce their cost, rolled screws have been produced which require expensive tools.

The screw presented in these figures is produced by means of a spring steel propeller 100 forming the thread, it can be of round, square or rectangular section, slid over a smooth core 101 and the ends of which alone are secured to the core.

In fig. 18, the end is folded at 102 and engaged in the slot of an open pin 103.

In fig. 19, the ends of the spring screw are immobilized by a hoop 104.

In fig.20, the ends of the spring screw are immobilized in a groove 105 of a ring 106 pinned on the core 101.

In fig. 21, the end 106 of the leaf spring is folded flat on the core 101 on which it is directly pins. A needle stopper 107 has been shown engaged on the end of the core to absorb the axial forces.

 On fig.22 and 23 we showed the end of the spring screw forming an open loop 108 in which is placed a pin 109, fig.22.

and two pins 110,111 on either side of the loop fig.23.

Of course, other methods of fixing the spring screw can be used without departing from the invention.

The nut is constituted by a stirrup 115, rigidly fixed on the underside of the carriage 116, on the sides of which are arranged the coaches 117,118 engaged in the pitch of the spring screw. In this case, it is the screw which deforms elastically at the end of travel. It is always longer than necessary to allow useful deformation. Here again, the energy stored at the end of the race, by elastic deformation, is restored to the following cycle.

 This type of guide and carriage drive mounted on light sheet metal supports, makes it possible to produce small special automatic machines, very diverse and inexpensive, very easy to maintain. They are sufficient in a number of cases of production mechanization where it is not necessary to have important details of regularity of speed of movement, a precise positioning being able to be obtained at the end of the race by indexing if necessary.

Claims (7)

CLAIMS: 1 - Device for guiding and driving movable mechanical members with linear displacement comprising at least one slide (G) on which a movable mechanical member moves driven by a motorized screw-lock system, characterized in that -the movable member is a carriage provided with linear bearings with a smooth ring (5) of low coefficient of friction suspended elastically on its support and ensuring compensation for parallelism deviation, and in that said carriage is preferably made of cut and folded sheet metal, and that said carriage is driven by a screw-nut system coupled elastically to absorb the dead ends and dampen the limit switches on free stops. 2 - Device according to claim 1, characterized in that the elastic suspension means of the smooth rings (5) with low coefficient of friction moving on cylindrical slides (G) consists of at least one O-ring (8) made of elastomer or the like disposed captive in a support flange (6) of folded cut sheet metal, removably attached to the carriage (7), and in that the internal wall of said flange (6) cooperates with at least one of the walls of the carriage for define the positioning references of said ring (5). 3 - Device according to claim 1, characterized in that the elastic suspension means of the rings (5) of the linear bearings of the movable members (18) on the cylindrical slides (G) is constituted by a portion of support tube of folded sheet metal or no, of cylindrical or square section (10,20), in which is concentrically disposed a ring of very low coefficient of friction (5) suspended elastically by a molding (11) of elastomer or the like allowing compensations for parallelism of said ring by relative to its support, and in that the tubular portion comprises means for direct fixing on a plane parallel or perpendicular to the axis of the ring (5) 4 - Device according to claims 1, 2 and 3, in which the movable mechanical member moving on linear slides (G) constituted by two cylindrical guide rods (36), characterized in that the first rod (36) receives two rigid plain bearings or ball bearings (31 ), and in that the second rod (36) receives two smooth bearings with elastic suspension (33) ensuring the anti-roll without the need for rigorous positioning. 5 - Device according to claim 1, characterized in that the motorized screw-nut system driving the movable member on the slides comprises a block (41) of plastic material with low coefficient of friction, bored to the outside diameter of the screw (42 ), and in that said screw has a large pitch whose hollow is wide and deep and cooperates with two coaches (46,47) meshed in opposition in the pitch and offset by half a step relative to the other, each fixed on said block (413, and in that said block is made integral with the movable member by means of an elastically deformable fixing capable of absorbing the wattage and ensuring the damping of the limit switches on frank stop, and in that said elastic deformation fixing means also ensures the anti-rotation of said nut block (41), and in that the coaches comprise a smooth sleeve which can be mounted on needle bearing (50). 6 - Device according to claim 1, characterized in that the screw is constituted by a smooth cylindrical steel core (101) on which is attached a spring steel propeller (10G) forming the thread of which the thread is of section round, square or rectangular, and in that said propeller is made integral with the core (101) by at least one of its ends, and in that said screw cooperates with a nut constituted by two coaches (117,118) with bush mounted on bearings with needles meshing in the pitch, and in that the coaches are fixed on a stirrup (115), in cut sheet folded, fixed under the movable member (116), rigidly.  7 - Device according to claims 1.5 and 6, characterized in that the screw comprises several successive segments for simultaneously driving several movable members in synchronism, in the same direction, or in opposite direction according to the direction of the pitch, from the same motorization means. 8 - Device according to claims 1 and 7, characterized in that the segments remote from the screw, are coupled together elastically deformable by means of an intermediate shaft (89) suspended elastically at each end by means of longitudinal rings (94 ) and elastomer or similar washers or balls, mounted on a hub (90) and transmitting the movement by a pin (96) also comprising an elastomer sleeve (97) engaged in a longitudinal milling of the hub.