Gripping or clamping device comprising a sliding guide and roller guide between jaw guide surfaces and a housing

A gripping or clamping device including a housing body and at least one jaw guide which is provided in the housing body and has two lateral walls, including at least one jaw which can be moved in the jaw guide along a movement direction, guide surfaces being provided on the lateral walls and the jaw having sliding surfaces which interact with the guide surfaces to form a sliding guide, wherein at least one raceway part and rolling elements are provided in the jaw guide, the jaw and the raceway part each having a raceway for abutting against the rolling elements to form a roller guide.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is the United States National Phase application of PCT Application PCT/EP2020/054373 filed Feb. 19, 2020, which relates and claims priority to German Application No. DE 10 2019 104 484.7 filed Feb. 21, 2019, the entirety of each of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a gripping or clamping device comprising a housing body and at least one jaw guide which is provided in the housing body and has two lateral walls, comprising at least one jaw which can be moved in the jaw guide along a movement direction, guide surfaces being provided on the lateral walls and the jaw having sliding surfaces which interact with the guide surfaces to form a sliding guide.

Gripping and clamping devices of this kind are known, for example, from DE 2017 102 652 A1 or DE 10 2015 205 657 A1.

In such gripping or clamping devices, it is necessary to guide the jaws in the jaw guides in a highly precise manner. In addition, a comparatively smooth guidance of the jaws in the jaw guides must be provided. In order to achieve said smooth guidance, the jaws, or the sliding surfaces thereof, and the guide surfaces of the jaw guide are ground. Grinding of this kind is comparatively complex and expensive.

A sliding guide between the jaws and the housing body has the disadvantage that what is referred to as a stick-slip effect occurs. The stick-slip effect causes bodies which are moved against one another to slide in a jerky manner. This effect occurs in particular when the static friction is significantly greater than the sliding friction. Therefore, in order to set the jaw in motion, a higher force is required than is required to maintain the sliding movement.

In order to guide moving components as smoothly as possible, roller guides are known from the prior art that provide rolling elements, such as balls, rollers or needles, which roll between the moving parts. U.S. Pat. No. 4,707,013 A, DE 39 21 055 A1 and DE 20 2011 106 379 U1 thus show gripping and clamping devices comprising roller guides between the jaw and the lateral walls.

The advantage of roller guides is that they do not have a stick-slip effect, as occurs in sliding guides. Roller guides are unsuitable for gripping or clamping devices, however, because they are comparatively sensitive to impact and shock. If, for example, the jaw of a gripping or clamping device that is guided by a roller guide is subject to a shock or impact, the force acting on the jaw is transmitted to the rolling element. This can lead to damage to the rolling surface of the rolling body or to the counter surface thereof comparatively quickly, as a result of which a precise guidance of the jaw is then no longer ensured. In this respect, roller guides are generally not suitable for gripping or clamping devices that are exposed to impacts or shocks.

SUMMARY OF THE INVENTION

The problem addressed by the present invention is that of providing a gripping or clamping device mentioned at the outset that has a sliding guide for guiding the jaws, the stick-slip effect known in sliding guides being as low as possible and in particular being avoided.

This problem is solved by a gripping or clamping device having the features of claim1. Such a gripping or clamping device in particular provides that at least one raceway part and rolling elements are provided in the jaw guide, the jaw and the raceway part each having a raceway for abutment against the rolling elements to form a roller guide. Pretensioning means are also provided for generating a pretensioning force, the pretensioning force acting on the raceway part so that the rolling elements are pressed against the jaw-side raceways. The raceway part in this case preferably extends in the movement direction and is provided laterally next to the jaw, i.e. between the jaw and the lateral walls.

A design of this kind has the advantage that, in addition to the sliding guide, a roller guide is provided, the rolling elements of which are provided between the housing body and the jaw by means of the pretensioning means, i.e. with zero clearance. As a result, a stick-slip effect can be reduced or avoided when starting or moving the jaw, and a gripping or clamping device of this kind can therefore be operated comparatively smoothly. If overloads, impacts or shocks occur, they can be diverted into the housing body via the sliding guide without causing damage to the rolling elements.

As a result of the provision of the pretensioning means, the roller guide can be zero clearance and does not have to be ground or paired, which reduces manufacturing and assembly costs.

The sliding guide is advantageously designed as a sliding guide with clearance. The sliding guide then has a clearance between the guide surfaces and the sliding surfaces, so that the guide surfaces only act against the sliding surfaces if a force which is counter to the direction of the pretensioning force and counteracts or exceeds the pretensioning force acts on the jaw. If the pretensioning force, by means of which the rolling elements act against the j aw-side raceways, is consequently interrupted due to a force resulting, for example, from an overload, an impact or a shock, the sliding guide comes into effect; forces occurring in the gripping or clamping device can be diverted into the housing body via the sliding guide without damaging the rolling elements.

A gripping or clamping device of this kind consequently has a switchover point at which, in particular depending on the pretensioning force and the sliding guide clearance, the roller guide is relieved and the sliding guide comes into effect. The switchover point can be selected such that it only occurs in the event of an overload, in order to protect the roller guide from overload, impacts or shocks. This results in a roller guide having improved properties, which is protected by a sliding guide in the event of an overload. Since, in this case, the resulting guide clearance is the clearance of the roller guide, the sliding guides can be produced so as to have a comparatively large amount of clearance, and therefore cost-effectively. The greater clearance of the sliding guides only comes into effect after the switchover point at which there is a switch from the roller guide to the sliding guides, and then only occurs when there is an overload.

However, it is also conceivable that the pretensioning force, and thus the switchover point, is selected such that the roller guide comes into effect when the gripping or clamping device is only subject to a low load, and that the sliding guide comes into effect when the gripping or clamping device is operated in nominal operation. In this case, due to the roller guide, only a small driving force is required for starting and moving the jaws. In a process under load or in the gripping state, a large part of the force acting on the gripping device is dissipated via the more robust and resilient sliding guide.

In order to be able to absorb and dissipate forces, which in particular act transversely to the movement direction, it is advantageous if two raceway parts are provided, one raceway part being provided between the jaw and one lateral wall, and the other raceway part being provided between the jaw and the other lateral wall in each case. The raceway parts are preferably arranged symmetrically with respect to one another and/or with respect to a central plane which extends in the movement direction. The central plane extends in the movement direction and is located centrally between the lateral walls.

In this case, the raceway parts can preferably have raceways extending in parallel with one another. Forces can be diverted symmetrically into the housing body as a result.

It is also advantageous if the relevant raceway part has two raceways including an angle and if the relevant jaw has correspondingly extending sliding surfaces. In this case, the raceways can in particular include an angle of between 60° and 120°, preferably in the range of 90°. It is also conceivable that the raceways include an angle of between 300° and 240°, in particular in the range of 270°. The rolling elements can preferably be trapped in a rolling element cage, the rolling element cage being designed such that it holds the rolling elements in accordance with the angle that the raceways include. By providing such an angle, forces acting on the gripping or tensioning device can be reliably deflected and diverted.

In order to provide reliable guidance of the jaw in the jaw guide, it is advantageous if the lateral walls of the jaw guide each have a plurality of guide surfaces, the planes in which adjacent guide surfaces are located including an acute angle. As a result, forces which in particular act on the jaw along the central plane, but not in the movement direction, can be favorably diverted into the housing body.

A further advantageous embodiment is obtained if the jaw has at least two sliding surfaces which interact with a lateral wall, and if at least one jaw-side raceway is arranged between these two sliding surfaces. In particular the raceway and the rolling elements interacting with the raceway can be protected from damage as a result, since the raceway is between the sliding surfaces of the sliding guide.

The pretensioning means can preferably be integral with the raceway part or the housing body. In this case, the pretensioning means can in particular be provided by means of material recesses on the conveyor belt part and/or on the housing body. The material recesses are arranged such that the raceway part or the housing body provides the pretensioning force in an elastically compliant manner.

According to the invention, however, it is also conceivable that the pretensioning means are designed as spring elements provided between the housing body and the raceway part. Pretensioning means of this kind are then provided separately from the raceway part and from the housing body. Said pretensioning means can be designed in particular as coil springs, leaf springs, disc springs or elastomer springs.

It has also proven to be advantageous to provide adjusting means for adjusting the pretensioning force of the pretensioning means. In particular if the pretensioning means are designed as spring elements having an error characteristic which is in particular linear or progressive, it is conceivable to adjust the pretensioning force accordingly by compressing the spring element to different degrees. Possible adjusting means are, for example, screws or bolts which act against the relevant pretensioning means, such that the pretensioning force of the pretensioning means or the spring force of the spring means is adjusted. This allows the position of the switchover point to be changed and adapted to the relevant use.

Another embodiment having two sliding guides would also be conceivable. The first guide would be a guide having a comparatively large amount of clearance and a high load capacity and having a pairing such as steel-steel or steel-aluminum or aluminum-aluminum. The second guide would be, for example, a guide having comparatively little clearance, or a zero-clearance guide, the second guide having a lower load capacity but better sliding properties than the first guide. The second guide can have a pairing of steel-plastic or aluminum-plastic or steel-bronze, for example.

It is also advantageous if the rolling elements are trapped in a cage, the cage being provided between the guide surface and the sliding surface. It is particularly advantageous if the cage has sliding portions which interact with the jaw-side and raceway part-side raceways. The sliding guide can then be formed by the raceways and the sliding portions of the cage that are between said raceways. The raceways therefore act indirectly against each other by means of the interposed cage.

Balls, barrels, rollers or needles are particularly suitable as rolling elements. It has also been found to be particularly advantageous to use hollow rollers, since these can be compliant and resilient, so that a permanent deformation of the rolling elements in the event of shocks or impacts can be avoided.

Further details and advantageous designs of the invention can be found in the following description, on the basis of which embodiments of the invention are described and explained in more detail.

DETAILED DESCRIPTION

The gripping device10shown inFIG. 1comprises a housing body12having a jaw guide14extending through the housing body12in the longitudinal direction. Two displaceably mounted jaws16,18are provided in the jaw guide14, which can be moved towards and away from one another along the movement direction26, which is indicated by a double arrow.

As is also clear from the cross section according toFIG. 2, the jaw guide14has two mutually opposite lateral walls22, on which guide surfaces24are provided. The jaws16,18have sliding surfaces26which interact with the guide surfaces24to form a sliding guide.

In the embodiment according toFIGS. 1 and 2, a total of eight guide surfaces24.1to24.8are provided which interact with eight sliding surfaces26.1to26.8to form a sliding guide. The respectively adjacent guide surfaces24.1and24.2;24.3and24.4;24.5and24.6; and24.7and24.8each include an acute angle α. Correspondingly, the associated jaw-side sliding surfaces26.1to26.8each include a corresponding acute angle α, which is in particular in the range of from 20° to 40°, and further in the range of from 28° to 32° and preferably in the range of 30°.

Overall, the lateral walls22and the portions of the jaws16,18which interact with the lateral walls22are formed symmetrically with respect to a central plane56which extends in the movement direction26and lies between the side walls.

In the jaw guide14, on the lateral walls22, two raceway parts30arranged opposite each other are provided. Rolling elements32, for example in the form of barrels or rollers, are provided between the raceway parts30and the relevant jaw16,18. The arrangement of the rolling elements32can in this case correspond to the arrangement in a crossed roller bearing. The raceway parts30provide raceways34for abutting the rolling elements32. Likewise, the jaws16,18provide jaw-side raceways36for abutting the rolling elements32. The raceways34provided on a raceway part30each include an obtuse angle β which is in the range of 270°. In addition to the sliding guide formed by the guide surfaces24and sliding surfaces26, a roller guide of the jaws16,18is provided due to the provision of the rolling elements32.

Between the housing body12and the raceway parts30, pretensioning means38are provided for generating pretensioning forces F which press the raceway parts30toward the jaw16,18, so that the rolling elements32are pressed against the jaw-side raceways36. Because the pretensioning forces F are of equal magnitude in the idle state, the relevant jaw16,18is held largely centrally in the jaw guide14. InFIG. 2, the pretensioning means38are designed as elastomer spring blocks; helical springs, coil springs or other spring elements can also be used instead of these elastomer spring blocks.

The sliding guide is preferably designed as a sliding guide which has clearance, which guide has clearance between the guide surfaces24and the sliding surfaces26. In this case, the clearance is such that the guide surfaces24act against the sliding surfaces26when a force which acts transversely to the movement direction, counter to the relevant pretensioning force F, and counteracts or exceeds the relevant pretensioning force F acts on the relevant jaw16,18.

An external force of this kind can result in particular from an overload, an impact or a shock. The clearance of the sliding guide is chosen such that when external forces of this kind occur, the sliding guides come into effect before the rolling elements32or the raceways34,36can be damaged. The roller guide is consequently protected from overload by sliding guides which come into use.

Due to the provision of the spring means and the provided pretensioning forces, the roller guide is designed to be zero clearance. This results in the jaws16,18being set into motion in a very low-friction manner, and therefore easily; a slip-stick effect, as occurs in the case of simple sliding guides, is reduced and preferably prevented. If greater loads or forces act on the jaw16,18, the resulting force can be diverted into the housing body12via the sliding guide without causing damage to the roller guide.

In the embodiment shown inFIG. 2, the relevant pretensioning element38and the relevant pretensioning force F resulting therefrom are relatively small. It is thereby achieved that a movement of the jaws16,18takes place via the roller guide without an external force acting on the jaws16,18. Because of the low pretensioning forces, the sliding guide comes into effect as soon as external forces act on the jaws16,18. It is advantageous that no stick-slip effect occurs when the jaws16,18are started.

In the embodiment according toFIG. 3, as in the embodiment according toFIG. 2, a sliding guide and a roller guide are provided. Components corresponding toFIG. 2have corresponding reference signs.

In contrast toFIG. 2, in the embodiment according toFIG. 3the raceways34each include an acute angle γ in the range of preferably 90° on the raceway part30. Providing an angle γ of 90° results in similar conditions in the direction extending transverse to the movement direction, due to the asymmetrical conditions. If the angle γ is less than 90°, this results in better properties in the z-direction, i.e. inFIG. 2in the upward direction. If the angle γ is more than 90°, this results in better properties in the γ-direction, i.e. in the direction of the right-hand or left-hand side inFIG. 2. The rolling elements32are provided between the relevant raceway34and the jaw-side raceway36which corresponds thereto. In total, two rows of rolling elements32interact with each raceway part30. According to the embodiment according toFIG. 2, in the embodiment according toFIG. 3, the jaw-side raceways36are arranged between jaw-side sliding surfaces26.

In the embodiment according toFIG. 3, the sliding surfaces26and the raceways36form a zigzag line in the section plane shown inFIG. 3, which line extends symmetrically with respect to a central longitudinal plane, which is identified inFIG. 3by reference sign40. The sliding surface26.1in this case includes a 90° angle together with the raceway36adjoining said sliding surface. The two raceways36in turn include an angle of 90°, and the lower raceway36likewise includes an angle of 90° together with the sliding surface26.2adjoining said lower raceway, as is clear fromFIG. 3.

In the embodiment according toFIG. 3, the pretensioning means38are designed as spring tongues which are integral with the raceway part30. The spring-tongue-like pretensioning means38have free ends42which, in order to provide the pretensioning forces F, act against the housing body12in an elastically compliant manner.

Also in the embodiment according toFIG. 3, the sliding guide produced by the guide surfaces24and sliding surfaces26is a sliding guide which has clearance and is designed such that the guide surfaces24act against the sliding surfaces26when a force which exceeds the relevant pretensioning force F acts on the jaw16,18.

In the embodiment according toFIG. 3, by comparison with the embodiment according toFIG. 2, significantly greater pretensioning forces F are provided. As a result, the sliding guide forms an overload protection. During normal operation of the gripping device10, the roller guide, which has comparatively large dimensions, comes into effect. The resulting forces are only absorbed by the sliding guide in the event of overload, impacts or shocks, when the external forces acting on the jaw counteract or exceed the relevant pretensioning force F. This has the advantage that the shock-sensitive roller guide is protected in the critical region by the sliding guide.

A development of the embodiment according toFIG. 3is shown inFIG. 4. In the embodiment according toFIG. 4, adjusting means44are additionally provided in the form of threaded bolts which are screwed into the main body12to different degrees. By means of the relevant adjusting means44, the pretensioning force F acting on the relevant raceway part30, which is provided by the relevant pretensioning element38, can be adjusted. For better introduction of force, a pressure plate46is provided between the adjusting means44and the raceway part30. The embodiment according toFIG. 4therefore has the advantage that the pretensioning force F can be actively changed, as a result of which the switchover point between the roller guide and the sliding guide can also be changed and adapted to different uses.

The embodiment shown inFIGS. 5 to 7substantially corresponds to the embodiment according toFIG. 3, a pretensioning means38being provided separately from the raceway part30in this case. As is clear from the isometric view according toFIG. 6, the pretensioning means38is designed as a pretensioned leaf spring38, which acts against the housing body12on one side and against the relevant raceway part30on the other side.

In the embodiment according toFIGS. 8 to 10, the pretensioning means38is designed as a wave spring which is provided between the housing body12and the relevant raceway part30. In the section according toFIG. 10, it is also clear that the individual rolling elements32are trapped in a cage48.

Two further embodiments of a gripping device according to the invention are shown in cross section inFIG. 11, in which components corresponding to components in the previous embodiments have corresponding reference signs. In the embodiment shown in the left-hand half ofFIG. 11, pretensioning means38are provided as material recesses in the housing body12. In the embodiment shown on the right-hand side inFIG. 11, the pretensioning means38are provided as material recesses in the raceway part30. According to the invention, a combination of the embodiment shown inFIG. 11is also conceivable, i.e. material recesses in the housing body12and also in the relevant raceway part30.

A further embodiment is shown inFIGS. 12 and 13, in which components corresponding to the other embodiments are identified with corresponding reference signs. In this embodiment, a pretensioning means38in the form of a spring plate is shown on the face of the raceway parts30that face the housing body12. In the edge region, the spring plate interacts with contact portions50of the relevant raceway part30. In the central region, a raised portion52on the housing body acts against the pretensioning means. The relevant pretensioning force F is provided by elastic deformation of the pretensioning means38.

In the embodiment according toFIGS. 12 and 13, the rolling elements32are arranged in a cage48. The cage48has sliding portions54which extend in parallel with the raceways34,36and are shown inFIG. 13. The sliding portions54, together with the raceways34,36, can be used as a sliding guide when a force, due to which the rolling elements are resiliently compressed in the radial direction, is exceeded. In the embodiment shown inFIG. 13, the rolling elements32can be designed as hollow rollers or hollow needles, as a result of which they are elastically compliant in the radial direction. The compliance can be selected in such a way that the pretensioning means38in the form of the spring plate, as shown inFIG. 12, can be omitted. The compliant hollow rollers or hollow needles then assume the function of the pretensioning means38.

In the embodiment shown inFIGS. 12 and 13, the guide surfaces24and sliding surfaces26, which interact directly with one another, can consequently be omitted and replaced with a sliding guide, which is formed by the cage48or by the sliding portions54of the sliding guide and the raceways34,36. By using the rolling element cage48to form the sliding guide, a very compact gripping or clamping device10can be provided overall.

FIG. 14shows the force F acting on a jaw16,18transversely to the movement direction26by means of the spring travel s of the pretensioning means38. At point P1, the pretensioning force FVacts on the jaw16,18. The pretensioning means38is compressed by the spring travel s1. If the external force F acting on the jaw16,18increases from point P1, the pretensioning means38is compressed further by the clearance of the sliding guide sGFuntil the force FGF, at which the sliding guide comes into effect, is present at point P2. If the force continues to increase at point P2, this further increasing force is absorbed only by the sliding guide, which relieves the roller guide; there is then only minimal deformation due to the resilience of the materials used.