DE9420108U1 - Parallel gripper with two gripper jaws - Google Patents

Description

Applicant:

Dipl.-Ing. (FH) Bruno Scherr

Weilerweg 2

73235 Weilheim/Teck

3951 002 D-B/mr 15.12.1994

Title: Parallel gripper with two gripper jaws

DESCRIPTION

The invention relates to a parallel gripper with two gripper jaws, at least one of which can be moved towards or away from the other by means of a drive and the movable gripper jaw(s) is/are slidably mounted in a base body. Such grippers are often used in automatic manufacturing processes to bring parts to or from a processing or assembly location. To grip a workpiece or a structural unit, it may be necessary to move the gripper jaws towards or away from each other. If they are moved towards each other, the workpiece or the like is clamped between the jaws.

while in the other case the grippers are inserted into a hole, a depression or a recess and then spread apart so that they rest against opposite walls or wall parts.

Such parallel grippers can grip relatively small elements, but also large and heavy ones. The entire gripper and in particular its gripper jaws must be dimensioned and designed accordingly in terms of strength.

One area of application is, for example, the assembly of electronic components. These are usually gripped by adjusting the jaws against each other.

Because the jaw(s) perform a linear movement when gripping, sliding guides and roller guides are theoretically possible for the gripper jaws or jaw holders. Up to now, it has been common practice to manufacture the corresponding guide elements separately and then attach them to the base body on the one hand and to the jaw holder or gripper jaws on the other. Sliding guides have the disadvantage that a play-free movement, which is required above all when gripping small particles, is practically impossible to achieve. These guides also react very sensitively to moment stress, which occurs with long gripper fingers and high gripping forces due to increased edge pressure.

The result of such excessive stress is increased wear. The maintenance effort is correspondingly high and it reduces the application possibilities of such parallel grippers, e.g. in electronics assembly.

In the latter application area in particular, rolling guides are preferred because they provide a backlash-free, low-maintenance to maintenance-free solution with the highest positioning quality and the lowest friction and thus the smallest drive force.

In automated production, the aim is to make production aids and thus also parallel grippers as small as possible.

The task is therefore to further develop a parallel gripper of the type described above in such a way that a further reduction in its size is possible without having to accept disadvantages with regard to functionality.

To achieve this object, the invention proposes that the parallel gripper according to the preamble of claim 1 is characterized in that the base body and each gripper jaw or a jaw holder receiving it is made of a material suitable for rolling bearings and the rolling bearing raceways

are formed directly on it. Material suitable for rolling bearings is somewhat more expensive than a material of lower quality, but this is at least partially offset by the reduction in size that this makes possible. If the previously usual bearing strips are dispensed with and instead the rolling bearing raceways are attached directly to the parts that can be moved against each other, i.e. in this specific case to the base body on the one hand and to the jaw holder or gripper jaws on the other, this not only reduces the size of the parts in question, but also the weight due to the smaller size. This also at least partially compensates for any weight disadvantage that a material suitable for rolling bearings may have compared to a material that is lighter in comparison.

In addition, the assembly time of this parallel gripper is shortened because the attachment of bearing strips is no longer necessary. Nevertheless, the user is just as free as before with regard to the specific type of rolling bearing. The load-bearing capacity of this parallel gripper is higher than before due to the elimination of joints. This essentially follows from the use of a high-strength material, as is known from the production of rolling bearings.

From the above, it also follows that a part can be gripped by moving a movable jaw towards or away from a fixed one, i.e. both jaws do not necessarily have to be movable. However, if two jaws are moved synchronously, the gripping process can be reduced or halved in a known manner with an identical clamping path.

In a particularly preferred embodiment of the invention, each movable gripper jaw or jaw holder can be actuated by means of a working cylinder, the cylinder bore of which is formed directly in the base body. Here, the advantage of the material suitable for rolling bearings is particularly noticeable because it naturally leads to a more compact construction if the cylinder bore is formed directly on the base body instead of a separately manufactured and subsequently assembled cylinder. For weight reasons in particular, a solution with a single common working cylinder is preferred over two separate working cylinders when there are two drivable gripper jaws. Whether the working cylinder acts directly or indirectly on the gripper jaws or jaw holders depends largely on the arrangement of the parallel grippers and the number of working cylinders.

»··" &idigr;&iacgr;

In a further embodiment of the invention, it is proposed that at least one movement deflection means is connected between the piston of the working cylinder and each drivable gripper jaw or jaw holder. If both gripper jaws or jaw holders are driven by a single working cylinder, it is sensible to also provide a common movement deflection means.

A further variant of the invention is given in claim 4. The direction of movement of the piston then runs transversely to that of the drivable jaws. If only one jaw is drivable, it is of course sufficient that the wedge has only one inclined surface in relation to the direction of movement and that this rests or can be brought into contact with the inclined counter surface of the gripper jaw or jaw holder. In addition, with this design, a suitable reset of the gripper jaws or jaw holders must be ensured. Preferably, one or at least one return spring is used for this purpose. In addition, this design is particularly suitable for an internal gripper whose gripper jaws move away from each other during gripping.

Claim 5 describes another preferred embodiment of the invention. If a slot and an element engaging therein, in particular

If a bolt, sliding block, etc. is used, then return springs and similar elements can be dispensed with. Which of the two parts that effect the reversal has the diagonal slot and which has the bolt or similar depends on the criteria that are usually taken into account. These include, for example, the available space and assembly or disassembly.

The direction in which the slots should run diagonally depends, of course, on whether the jaws should move closer together or further away from each other during clamping. In addition, if there is only one movable gripper jaw, a deflection device with diagonal slot and bolt is of course only required there.

The latter also applies analogously to a further embodiment of the invention, which results from claim 6. More precisely, in the case of only one movable jaw, the rack can of course be designed as a normal one-sided rack. A pinion that reverses the movement is then connected between its teeth and those of the other rack on the gripper jaw side. This parallel gripper can also be used as an internal and external gripper. In addition, instead of a double-sided rack, a rack with teeth all around can also be used.

version, but this is usually only advantageous for small gripping forces.

The working cylinder is conveniently double-acting, so that both the outward and inward movement can be achieved using the auxiliary force, preferably compressed air.

Particularly advantageous embodiments in the area of storage are described in claims 8 to 12. Further details can be found in the drawing description.

Since each movable gripper jaw carries out a linear gripping movement, it is obvious and usually also expedient if the drive also delivers a linear movement directly. In a special case, however, it can be advantageous that, according to claim 13, the gripper jaws or jaw holders can be synchronously moved against or away from each other by means of a rotary drive, whereby the rotary element of the rotary drive can be mounted directly in the base body. The rotary element can be, for example, a rotary cylinder that is driven electrically, hydraulically or pneumatically.

In an embodiment with a fixed and a movable gripper jaw, which is expediently

of a working cylinder, at least one return spring is connected between the two gripper jaws, whereby the working direction of the working cylinder is the same as the displacement direction of the gripper jaw. Because there is no movement redirection here, a simple and compact design is obtained. In the case of an external gripper, when the movable jaw is moved against the fixed jaw, the return spring is also tensioned at the same time. As soon as the feed force is removed, the stored force of the return spring can take effect, which leads to the opening of this parallel gripper.

In a particularly preferred manner, the working cylinder is integrated into the movable gripper jaw or its jaw holder and the cylinder is formed directly in it. In this respect, the advantage of the material used can also be exploited in this variant in the manner described at the beginning. The working cylinder is advantageously designed to be double-acting. Otherwise, the return spring or similar that is usual for single-acting working cylinders must be provided.

It is also possible to provide a spindle drive for the movable gripper jaw(s), whereby one can rely on conventional designs. Bearings and similar machined surfaces and places can in turn

be formed directly on the material of the parallel gripper part in question.

If such a parallel gripper is to be used in a clean room, it must be specially suited for this purpose. Above all, however, it must be maintenance-free. A parallel gripper that is particularly suited for this purpose is explained in claims 18 and 19, shown in the drawing and explained in more detail in the drawing description.

The invention is described in more detail below with reference to the drawing. The drawing shows various embodiments of the invention. These show:

Figure 1 is a side view of a first embodiment of the invention;

Figure 2 shows a section along the line II-II of Figure 1, but with gripper jaws;

Figure 3 is a representation according to Figure 2 of a further variant of the invention;

Figure 4 is a representation according to Figure 2 of a third embodiment of the invention;

Figure 5 shows a fourth embodiment of the invention

in a representation analogous to Figure 2, somewhat schematic;

Figure 6 is a side view of the gripper of Figure 5; Figure 7 is a plan view of the gripper of Figure 5;

Figure 8 is a representation according to Figure 6 of a further variant of the invention.

Two jaw holders 2, 3 are mounted on a base body 1 of the parallel gripper so that they can move in the direction of the double arrow 4. Each jaw holder accommodates a gripper jaw 5 or 6 as shown in Figure 2. In the embodiments of Figures 3 to 8, the gripper jaws are not shown and the gripper jaws of Figure 2 are also only shown schematically. Unless described in more detail, gripper jaws and jaw holders can be designed or attached in a known manner.

All jaw holders 2 can be moved by means of a roller bearing in the direction of the double arrow 4 (Figures 2 to 5) or perpendicularly to the plane of the sheet (Figures 1, 6 and 8). The grippers in Figure 2 are so-called internal grippers, whose fork-like free gripper ends, for example, form part of

·

grip and hold. In this case, the gripper jaws 5 and 6 are moved against each other to hold the part in question.

In the case of an external gripper (not shown), the fork-like gripper ends may point in opposite directions. To hold something, the gripper jaws are moved into a receptacle of a part to be held in the direction of arrow 7 and then moved away from each other. This then brings them into contact with parallel walls or the like.

It is easy to understand that with both an internal and an external gripper, the grip can be held in place even if one of the two gripper jaws is fixed and only the other can be adjusted towards or away from the fixed one. However, the adjustment path must then be overcome by this gripper jaw alone.

In all embodiments, the adjustment drive has a particularly pneumatic working cylinder 8. In a particularly advantageous manner, the cylinder of the working cylinder is integrated into the base body 1. In other words, the cylinder bore 9 of the working cylinder is located in the two-part base body 1 in the embodiment example. The base body consists in accordance with the

13

Invention made of material suitable for rolling bearings, e.g. ball bearing steel. This also makes it possible to form the rolling bearing raceways directly on the material of the base body 1. This will be discussed in more detail below.

A piston 10 is mounted in the cylinder bore 9 in a sealed manner so that it can move in the direction of the double arrow 11. The design of this piston and its piston rod as well as their sealing can be seen in somewhat more detail in Figures 2 to 4 and somewhat schematically in Figure 1. In all embodiments, the direction of movement 11 of the piston 10 with the piston rod runs transversely, in particular perpendicularly to the direction of adjustment 4 of the jaw holder 2. However, this is by no means necessary; the working cylinder can be arranged in any way. The only important thing is that the jaw holders 2, 3 can carry out their adjustment movement in the direction of the double arrow 4. If, for example, only the gripper jaw 5 is an adjustable jaw, its jaw holder can also be driven directly in the direction of the double arrow 13 by the piston of a working cylinder, for example, acting directly on the jaw holder in the direction of the double arrow 13. In this case too, the cylinder bore 9 can be machined directly into the material of the base body 1.

Instead, the cylinder bore can of course also be provided directly on the jaw holder, which, as mentioned, is also made of a material suitable for roller bearings. In this case, the piston rod is then held on the base body, which in Figure 2 overlaps the jaw holder 2 on the left. If the intended working pressure is applied to this working cylinder, the cylinder moves relative to the piston and this then results in an adjustment of the jaw holder 2 relative to the base body 1. In this case, one or more compression springs can be connected between the two jaw holders or gripper jaws, which drive the gripper jaws apart again when the working pressure of such an external gripper is removed. It is also easily conceivable for the expert that such a working cylinder can also be single-acting or double-acting.

If the displacement direction of the piston 10 is in the direction of the double arrow 11 and the displacement direction of the gripper jaws 5, 6 is in the direction of the double arrow 4, a movement deflection means 14 is required. Figures 2 to 5 show various possibilities of how the piston movement can be converted into a gripper jaw movement running perpendicular to it.

In Figure 2, at the free end of the piston rod there is a plate-shaped widening 15 with two

Oblique slots 16 and 17. A bolt 18 or 19 or similar sliding element engages in each. In the embodiment, the longitudinal axes of the two oblique slots 16, 17 form an angle of approximately 90°. In addition, their ends facing the piston 10 are closer than the ends far from the piston. This means that during a working stroke of the piston 10 in the direction of the arrow 20, the jaw holders 2, 3, to each of which a bolt 18, 19 is attached, move against each other. The parallel gripper therefore acts as an internal gripper. If the two oblique slots 16, 17 were swapped, the piston working stroke 20 would lead to an increase in the lateral distance between the two gripper jaws 5, i.e. this parallel gripper would be an external gripper.

In the embodiment of Figure 3, there is a double-sided rack 21 at the free end of the piston rod 12, the two rows of teeth of which are in mesh with a pinion 22 or 23. The teeth of each pinion in turn mesh with the teeth of another rack 24 or 25 which extend in the direction of displacement 4 of the jaw holders 2, 3. A downward movement or the working stroke of the piston 10 in the direction of arrow 20 thus causes a rotational movement of the pinions mounted on the base body 1 in the direction of arrow 26 or 27. The rotation of the pinion in the direction of rotation mentioned results in an outward movement of the two gripper jaws of this parallel gripper, i.e. in this case it is also an external gripper. On this occasion

It should also be noted that in all embodiments, internal and external grippers do not result in different clamping forces.

In the embodiment of Figure 4, a movement deflection means 14 is connected between the piston rod and the two jaw holders 2, 3, which corresponds in principle to that of Figure 2. The working stroke 20 of the piston 10 also causes a transverse movement of the two jaw holders or gripper jaws. However, the working stroke 20 takes place against the resistance of a return spring 28. In a single-acting working cylinder, the pressure medium is supplied via channels 29 of the base body 1. Additional channels 30 cause the ventilation in a pneumatic working cylinder.

In contrast, the working cylinder in Figure 2 is a double-acting design with channels 31 and 32 for alternating pressurization and venting. The same also applies to the design in Figure 3.

Figures 5, 6 and 7 show a comparatively simple solution for the movement deflection means 14. The free end of the piston rod 12 is provided with a wedge 33 at its jaw-side end. Each inclined surface of this wedge 33 rests against a counter-slope of the associated jaw holder or 3. This also causes a downward movement 20 there.

of the piston 10 causes an outward movement of the two jaw holders 2, 3 or gripper jaws. If each is moved against a compression spring 34 or 35, which is only indicated schematically, the jaw holders are automatically reset as soon as the downward pressure force on the piston 10 is removed or it is acted upon in the opposite direction by the control means.

In the embodiment of Figures 5 to 7, the jaw holders 2, 3 are mounted perpendicular to the plane of the page according to Figure 6 by means of a four-point bearing 36 or 37. For this purpose, two grooves with flat groove flanks are machined into the base body 1, opposite one another and open towards one another. Each of these grooves is assigned a groove 40 or 41 of the same size and design on each of the two jaw holders 2, 3 in the embodiment. Between them are rows of balls 42 or 43, which are kept at a distance by means of a cage 44 according to Figure 6. According to the invention, the rolling bearing raceways in the case of Figure 6, i.e. the flat surfaces of the grooves 38 to 41, are formed directly on the base body 1 or the jaw holders 2, 3, whereby these parts of the parallel gripper are made of material suitable for rolling bearings, for example ball bearing steel or the like. are manufactured.

The embodiment of Figure 8 differs from that of Figure 6 in that there is a

Tapered roller bearing 45 is provided. Instead of a left and right row of balls, there are two left and right rows of rolling elements, with the longitudinal axes of the rolling elements each enclosing a preferably approximately right angle with one another. The rolling elements are preferably cylindrical or barrel-shaped. The running surfaces for the rollers, which can also be kept at a distance by cages, were also formed directly on the base body 1 and the two jaw holders 2, 3 in this embodiment. On the base body 1 there are two grooves 46, 47 which are approximately trapezoidal in cross section and open towards one another. The trapezoid flanks are flat and at least partially designed as running surfaces for the rolling elements. Opposite each trapezoidal groove there is a molded-on strip 48 or 49 of the jaw holders 2 and 3 which is approximately triangular in cross section. In Figure 8, an O-shaped arrangement of the four rows of rolling elements is provided. Instead, you can of course also choose an X-shaped arrangement.

In Figures 1 and 3, instead of the tapered roller bearing 45 of Figure 8 with the rolling element rows 50 to 53, a multi-row ball bearing 54 is provided. It consists of two left and two right rows of balls 55, 56 and 57, 58 respectively. Two rows of balls are connected by means of a common groove-shaped cross-section, only

kept at a distance by the schematically illustrated cage 59 or 60, whereby the cages naturally also ensure the mutual distance between adjacent balls. The ball grooves 61 and 62 for each row of balls 55 to 58 are also formed directly on the jaw holder 2 or base body 1 in this variant.

In all embodiments, the working movement is achieved by means of a working cylinder with piston 10. If instead a rotary drive is provided, an element corresponding to the piston rod can carry a rack, which is acted upon by means of a gear wheel rotatably mounted in the base body. As a rule, a single revolution or even just a fraction of a revolution is sufficient for the necessary adjustment movement of the gripper jaws 5, 6. All other known rotary drives are also conceivable.

In a schematic representation, according to Figure 1, two sealing strips 63, 64 with an angled cross-section are provided on the base body, the leg ends of which point towards each other sealingly rest against the associated flank of the jaw holder 2 or 3 or, if necessary, directly on the gripper jaws 5, 6 and thereby ensure a secure sealing of the bearing. This creates a low-maintenance or maintenance-free parallel gripper. A sealing strip can also be provided at the left and right ends (Figure 2).

Suitable sealing must be used, but this must not affect the necessary sliding movements of the jaw holders or gripper jaws. If necessary, sleeve-like elements can be provided, such as those commonly used in machine tool construction.

Claims (19)

PROTECTION CLAIMS 1. Parallel gripper with two gripper jaws (5, 6), at least one of which can be moved towards or away from the other by means of a drive (8) and the movable gripper jaw or jaws (5, 6) is or are displaceably mounted in a base body (1), characterized in that the base body (1) and each gripper jaw (5, 6) or a jaw holder (2, 3) receiving it is made of a material suitable for rolling bearings and the rolling bearing raceways (38 to 41; 46 to 49; 61, 62) are formed directly thereon. 2. Parallel gripper according to claim 1, characterized in that each movable gripper jaw (5, 6) or jaw holder (2, 3) can be actuated by means of a working cylinder (8) and the cylinder bore (9) of which is formed directly in the base body (1). 3. Parallel gripper according to claim 2, characterized in that between the piston (10) of the working cylinder (8) and each drivable gripper jaw (5, 6) or jaw holder (2, 3) at least one movement deflection means (14) is connected. •♦ · · · ♦ 4. Parallel gripper according to claim 3, characterized in that, with two drivable gripper jaws (5, 6), the piston (10) or a piston rod (12) is designed to be wedge-shaped (33) at its or its jaw-side end and each wedge surface is assigned an inclined surface of one of the gripper jaws (5, 6) or jaw holders (2, 3). 5. Parallel gripper according to claim 3, characterized in that with two drivable gripper jaws (5, 6) a movement deflection means (14) consisting of an oblique slot (16, 17) of one part and a bolt (18, 19) or similar element of the other part engaging therein is connected between each gripper jaw (5, 6) or jaw holder (2, 3) and the piston (10) or the piston rod (12). 6. Parallel gripper according to claim 3, characterized in that, with two drivable gripper jaws (5, 6), the piston (10) or the piston rod (12) is provided with a double-sided rack (21), with the teeth of which a pinion (22, 23) mounted on the base body (1) meshes, which is also in meshing engagement with the teeth of a further rack (24, 25) extending in the displacement direction (4) of the gripper jaws (5, 6) and connected to the latter or to a jaw holder (2, 3). 7. Parallel gripper according to at least one of claims 1 to 6, characterized in that the working cylinder (8) is double-acting. 8. Parallel gripper according to at least one of claims 1 to 7, characterized by a four-point bearing (36) between the two parallel longitudinal sides of the gripper jaws (5, 6) or jaw holders (2, 3) and the base body (1), wherein prisms (38 to 41) for the bearing balls (42, 43) are each formed directly on the gripper jaws or jaw holders (2, 3) and the base body (1). 9. Parallel gripper according to at least one of claims 1 to 7, characterized by an inclined roller bearing (45) between the two parallel longitudinal sides of the gripper jaws (5, 6) or jaw holder (2, 3) and the base body (1), wherein the prisms (46 to 49) for the four rolling body groups or rows (50 to 53) are each formed directly on the gripper jaw or jaw holder (2, 3) and base body (1). 10. Parallel gripper according to at least one of claims 1 to 7, characterized by a multi-row ball bearing (45) between the two parallel longitudinal sides of the gripper jaws (5, 6) or jaw holder (2, 3) and the base body (1), wherein the ball grooves (61, 62) for the preferably four ball groups or rows (55 to 58) are each formed directly on the gripper jaws or jaw holder (2, 3) and the base body (1). 11. Parallel gripper according to at least one of claims 8 to 10, characterized in that the rolling elements (42, 43; 50 to 53; 55 to 58) of each row of rolling elements are inserted into a common cage (44, 60) or similar element. 12. Parallel gripper according to claim 9 or 11, characterized in that the running surfaces for the rolling body groups or rows (50 to 53) are each slightly recessed or raised. 13. Parallel gripper according to claim 1, characterized in that the gripper jaws (5, 6) or jaw holders (2, 3) can be synchronously displaced against one another or apart by means of a rotary drive, whereby the rotary member of the rotary drive is mounted directly in the base body (1). 14. Parallel gripper according to claim 1, characterized in that one of the gripper jaws (5, 6) can be driven by means of a working cylinder and is arranged between 25 At least one return spring is connected to both gripper jaws, whereby the working direction of the working cylinder is the same as the displacement direction (4) of the movable gripper jaw (5 or 6). 15. Parallel gripper according to claim 14, characterized in that the working cylinder is integrated into the movable gripper jaws (5 or 6) or its jaw holder (2 or 3) and the cylinder is formed directly therein. 16. Parallel gripper according to claim 15, characterized in that the working cylinder is double-acting. 17. Parallel gripper according to claim 1, characterized by a spindle drive for the movable gripper jaw(s) (5, 6). 18. Parallel gripper according to at least one of claims to 7, characterized by a sealing device (63, 64) between the base body (1) and the gripper jaws (5, 6) or jaw holders (2, 3). 19. Parallel gripper according to claim 18, characterized in that the sealing device (63, 64) is at least partially formed by at least one variable-length or length-elastic member is formed.