Robotic tool changer coupling mechanism with increased torsional stiffness

Abstract

A robotic tool changer includes a main assembly and a tool assembly. When the main assembly and the tool assembly are coupled, rolling members protrude from the main assembly and contact opposing inclined surfaces of a plurality of cutouts formed in a bearing race of the tool assembly. By contacting the opposing inclined surfaces of the plurality of cutouts with the rolling members, torsional play between the main assembly and the tool assembly is eliminated or minimized.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Patent Application No. 17 / 027,931, filed on September 22, 2020, entitled “Robotic ToolChanger Coupling Mechanism with Increased Torsional Stiffness,” the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates generally to robotic tool changers and, in particular, to a robotic tool changer having a coupling mechanism that achieves increased torsional stiffness and reduced freeplay. Background Art

[0004] Industrial robots have become an integral part of modern manufacturing. Whether transferring semiconductor wafers from one processing chamber to another in a cleanroom or cutting and welding steel on the floor of an automotive manufacturing plant, robots perform many manufacturing tasks tirelessly in harsh environments with high precision and repeatability.

[0005] In many robotic manufacturing applications, the considerable cost of an industrial robot is amortized among various tasks by providing different tools or end effectors that can be coupled to a general-purpose robot arm. For example, in an automotive manufacturing application, a robot may be used to cut, grind, or otherwise shape metal parts in one production process and perform various spot welding tasks in another process. Furthermore, even when performing one type of task, a robot may use different tools. For example, different welding tool geometries may be advantageously used with a particular robot to perform welding tasks in different locations or with different orientations.

[0006] In these applications, a robotic tool changer is used to mate different tools to the robot. One half of the tool changer, called the master assembly, is permanently affixed to the robot arm. The other half, called the tool assembly, is affixed to each tool that the robot can use. When the robot controller aligns the master assembly at the end of the robot arm with the tool assembly that assembles to the desired tool, it guides the master assembly to mechanically couple to the tool assembly, thereby assembling the tool to the robot. The robotic tool changer also helps provide utilities to the tools, such as electrical current, air pressure, hydraulic fluid, cooling water, etc., as well as transmitting data from some tools back to the robot controller.

[0007] Ball lock configurations are commonly deployed in robotic tool changers as coupling mechanisms. In one such configuration, a plurality of rolling members (e.g., steel balls) are contained in a bushing of a main assembly that is disposed within a chamber of a tool assembly. The balls are driven radially, such as by advancing a piston, and advance to abut against a bearing race in the tool assembly, thereby mechanically coupling the main assembly and the tool assembly together. To decouple, the piston is retracted, and the balls retreat into the bushing when the main assembly is separated from the tool assembly. Various configurations, drive mechanisms, and operational aspects of such ball lock configurations are described in U.S. Patent Nos. 8,005,570; 8,132,816; 8,209,840; 8,500,132; 8,533,930; 8,601,667; 8,794,418; 9,151,343; 9,724,830; and 10,335,957. All of these patents are assigned to the assignee of the present application, and the disclosures of all of these patents are incorporated herein by reference in their entirety.

[0008] Alignment is required between the master and tool assemblies for proper mechanical coupling of the ball lock mechanism to the tool assembly bearing races and for coupling of the utility transfer modules that are assembled to the master and tool assemblies. This alignment is typically accomplished by one or more alignment pins on the master assembly that engage corresponding alignment sleeves in the tool assembly. In addition, these alignment pins and sleeves also provide torsional stiffness to the coupled tool when the robot is in operation. To prevent sticking, a small amount of radial clearance is required between the alignment pins and their associated alignment sleeves. This minute clearance is the primary source of rotational play in tool changers, which negatively affects position repeatability and torsional stiffness. This effect is magnified in large end-of-arm tools and can cause undesirable variations or position errors in the working point of each end effector. Play can also cause problems with the electrical signal modules assembled to the tool changer because the contact pins on the master and tool sides are allowed to move relative to each other, potentially resulting in intermittent signal loss. It can also cause excessive wear from fore-and-aft displacement, leading to premature failure.

[0009] To reduce torsional play, it is known to machine spherical or cylindrical recesses, referred to herein as "scallops," into the tool bearing races in the tool assembly at corresponding locations on each rolling member. These features reduce play, but do not eliminate it. One disadvantage of known designs is that the scallop features must inherently have a larger radius than their corresponding rolling members to prevent binding. This radial clearance provides minimal freedom for the rolling members to roll back and forth within their respective scallops under reverse torsional loads. For coupling purposes, each rolling member is in 3-point contact, one contact point being the bottom of the hole in the main assembly bushing, a second contact point being the bottom of the scallop in the tool bearing race, and a third point being located on the tapered piston cam. These three contact points are located on the same plane and are spaced approximately 120 degrees apart, although the contact points on the piston or other mechanism that propels the rolling members do not carry significant torsional coupling loads. This 3-point contact scheme, combined with micro-clearance, is sufficient to produce harmful torsional play in the tool changer.

[0010] The background section of this article is provided to place the embodiments of the present invention in a technical and operating context to help those skilled in the art understand their scope and utility. Unless explicitly stated, any statement herein cannot be considered as prior art merely by its inclusion in the background section. Summary of the invention

[0011] A simplified summary of the present disclosure is provided below to provide basic understanding for those skilled in the art. This summary is not a broad overview of the present disclosure and is not intended to identify the key / essential elements of embodiments of the present invention or to describe the scope of the present invention. The sole purpose of this summary is to present some concepts disclosed herein in a simplified form as a preface to a more detailed description provided later.

[0012] The disclosed robotic tool changer is constructed to reduce or minimize torsional play and increase torsional stiffness. As described above, when the main assembly and tool assembly of the robotic tool changer are coupled, the torsional stiffness is generally weak, which results in play around the z-axis of the tool changer. In order to address the torsional stiffness problem, the bearing race of the tool assembly is provided with a plurality of circumferentially spaced shell-shaped cutouts or pockets. Each cutout includes a valley and relative inclined surfaces, i.e., inclined surfaces on both sides of the valley. In one embodiment, the main assembly and the tool assembly are coupled by forcing a plurality of rolling members to contact relative inclined surfaces of the target cutout. That is, some rolling members contact one of the inclined surfaces of the plurality of cutouts, while other rolling members contact relative inclined surfaces of other cutouts. Therefore, the resulting rolling member-inclined surface contact prevents or minimizes relative rotation between the main assembly and the tool assembly.

[0013] In one embodiment, the shell-shaped cutouts are equally spaced around the bearing race. The misalignment between the rolling members and the cutouts is achieved by changing the rolling member-hole pattern in the main assembly. Unlike the cutouts, all holes in the main assembly are not equally spaced. The two pairs of aligned holes are slightly skewed relative to the position of the target cutout. This causes the rolling members of the two pairs of holes to contact the opposite inclined surfaces of the multiple cutouts.

[0014] Other objects and advantages of the present invention will become apparent and obvious from a study of the following description and the accompanying drawings, which are intended to illustrate the present invention only. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be described more fully below with reference to the accompanying drawings, in which embodiments of the present invention are shown. However, the present invention should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make this disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art. The same numbers always refer to the same elements.

[0016] Figure 1 is a perspective view of a robotic tool changer.

[0017] Figure 2 is a cross-sectional view of the robotic tool changer in a coupled state.

[0018] Figure 3A is a perspective view showing an annular collar of the main assembly.

[0019] Figure 3B is a perspective view showing the bearing race of the tool assembly and an enlarged view of one of the conchoidal cutouts found in the bearing race.

[0020] Figure 3C is a perspective view showing an annular collar and a bearing race, and also showing that a rolling member contained in a hole formed in the annular collar contacts an inclined surface of a cutout in the bearing race.

[0021] Figure 4 is a schematic diagram showing a series of rolling element contacting opposing inclined surfaces of various cutouts in a bearing race.

[0022] Figure 5 is a cross-sectional view showing contact points and resultant force vectors between multiple rolling members and the inclined surfaces of various cutouts.

[0023] Figure 5A One rolling member is shown in contact with the right side inclined surface of the cutout.

[0024] Figure 5B One rolling member is shown in contact with the left inclined surface of the cutout.

[0025] Figure 6 is a schematic diagram illustrating the deflection of selected holes in the main assembly to cause misalignment of the selected holes with various cutouts in the bearing race.

[0026] Figure 7 An alternative embodiment is shown and is a schematic diagram illustrating deflection of selected cutouts in a tool assembly to cause misalignment of selected holes and rolling members therein with various cutouts in a bearing race of the tool assembly. DETAILED DESCRIPTION

[0027] For the purpose of simplicity and illustration, the present invention is described mainly by reference to exemplary embodiments of the present invention. In the following description, many specific details are set forth to provide a thorough understanding of the present invention. However, it is easy to understand for those of ordinary skill in the art that the present invention can be practiced without being limited to these specific details. In this description, well-known methods and structures are not described in detail to avoid unnecessary confusion of the present invention.

[0028] Figure 1 A robotic tool changer 10 is shown that employs a ball-lock coupling mechanism. One half of the robotic tool changer 10, referred to as the master assembly 12, is permanently affixed to a robotic arm (not shown). The other half, referred to as the tool assembly 14, is affixed to each tool (not shown) that the robot can use. In any particular application, these mountings may be reversed. Thus, as used herein, the terms "master" and "tool" are reference terms. Figure 1 As seen in FIG. 1 , alignment pins 16 on the main assembly 12 cooperate with alignment sleeves 18 on the tool assembly 14 to ensure that the main assembly 12 and the tool assembly 14 are properly aligned when the assemblies are coupled together.

[0029] The main assembly 12 includes a housing 20 and an annular collar 22 that projects from the housing and extends beyond the plane of the face of the housing 20. The tool assembly 14 includes the housing 24 and a circular chamber 26 formed in the housing 24. A bearing race 38 is disposed in the chamber 26. A series of circumferentially spaced conchoidal cutouts or pockets 40 are formed in the bearing race 38 (see FIG. Figure 3A , 3B ).like Figure 2 As shown, the collar 22 is disposed within the cavity 26 and is spaced inwardly from the bearing race 38 when the main assembly 12 and the tool assembly 14 are coupled.

[0030] A plurality of holes 28 are formed in the collar 22 and extend through the collar 22. The holes 28 are spaced circumferentially around the collar 22. The holes 28 may be tapered, with a slightly larger diameter at the inner surface of the collar 22 than at the outer surface of the collar 22. A rolling member 30, such as a spherical ball, is disposed in each hole 28. Each rolling member 30 is retained within the collar by the tapered hole 28, which has a slightly smaller diameter at the outer surface of the collar 22 than the diameter of the corresponding rolling member 30. Thus, the rolling members 30 move between a retracted position, in which the outermost surface of the rolling members is flush with or inside the outer surface of the collar 22, and an extended position, in which each rolling member 30 extends beyond the outer surface of the collar 22, typically by an amount slightly less than the radius of the rolling member 30.

[0031] In this embodiment, a cam 32 fixed to the end of the pneumatic piston is disposed within the interior space defined by the bushing 22. The cam 32 has at least one tapered surface 34 that contacts the rolling member 30 during coupling of the main assembly and the tool assembly. The tapered surface 34 is aligned so that as the cam advances toward the tool assembly 14, the tapered surface 34 engages the rolling member 30 and displaces the rolling member radially outward through the hole 28 to couple the main assembly 12 and the tool assembly 14. For decoupling, as the cam 32 retracts into the main assembly 12, it creates space that allows the rolling member 30 to retract into the bushing 28. In some embodiments, the rolling member 30 may be advanced and retracted by a mechanism other than a cam mounted to the pneumatic piston, as described in the above-incorporated patents US8,132,816 and US8,209,840.

[0032] Figure 2 is a cross-sectional view of the robotic tool changer 10 showing the coupled main assembly 12 and tool assembly 14. The cam 32 is configured to move between a retracted position and an extended position. As used herein and in the claims, the term "configured to" means "designed to". Figure 2 , cam 32 is in the extended position. Movement of cam 32 is controlled by a robot controller (not shown). As cam 32 moves from the retracted position to the extended position, it engages rolling members 30 and pushes them outward through holes 28. In the fully extended position, cam 32 moves rolling members 30 to contact scalloped cutouts 40 formed in bearing races 38 of tool assembly 14. Details of how rolling members 30 contact portions of cutouts 40 are addressed later herein. In any case, Figure 2 The coupled main assembly 12 and tool assembly 14 are shown. Figure 21 and 2. The Z-axis of the robotic tool changer 10 is shown in FIG. When the robotic tool changer is coupled, the Z-axis extends through the center of the collar 22 and the bearing race 38. As described below, the collar 22, bore 28, rolling member 30, and cutout 40 are configured to prevent or minimize relative rotation about the Z-axis.

[0033] Figure 3A and Figure 3B Portions of the main assembly 12 and the tool assembly 14 are shown. In this embodiment, the collar 22 includes six holes 28 and six rolling members 30. The number of holes and rolling members can vary. The holes 28 are spaced circumferentially around the collar 22 and arranged so that pairs of holes are aligned. Therefore, pairs of rolling members 30 are also aligned. Figure 3B As shown, the scallop cutouts 40 are spaced circumferentially around the bearing race 38 of the tool assembly 14. Pairs of scallop cutouts 40 are also aligned. Thus, when the cam 32 is fully extended, the rolling members 30 protrude outwardly from the bushing 22 and contact portions of the scallop cutouts or pockets 40. As discussed below, at least some of the rolling members 30 are not positioned exactly in the center of the scallop cutouts 40. That is, some of the rolling members 30 are slightly misaligned with the scallop cutouts 40.

[0034] Each shell-shaped cutout 40 includes a valley 40V and opposite inclined surfaces 40S extending from the valley. Figure 3A and Figure 3B . The valley 40V is located at the center of the shell-shaped cutout 40. The inclined surfaces 40S are located on both sides of the valley 40V. Facing one of the cutouts 40 as a reference point, one of the inclined surfaces is referred to as the left inclined surface and the other inclined surface is referred to as the right inclined surface. The term "opposite inclined surfaces" refers to the left and right inclined surfaces of the cutout 40. In the illustrated embodiment, the inclined surfaces 40S are curved. The radius of curvature can vary. It must be sufficient to allow the rolling members 30 to contact one of the inclined surfaces 40S and at the same time be at least slightly offset relative to the center of the cutout. As discussed further below, the robotic tool changer 10 is designed so that when the main assembly 12 and the tool assembly 14 are coupled, at least some of the rolling members 30 engage and contact the inclined surfaces 40S instead of the valley 40V. See. Figure 5A and Figure 5B .

[0035] In one embodiment, two rolling members contact the right inclined surface of the opposing cutouts, while the other two rolling members contact the left inclined surface of the other opposing cutouts. Figure 4 and Figure 5. To provide this contact pattern, some of the holes 28 and their rolling members 30 are misaligned with the target cutout, which is the cutout that is the target of the rolling members 30 during coupling. When placed on one of these inclined surfaces 40S of the cutout 40, the rolling member 30 is slightly offset relative to the valley 40V of the cutout. Since the left and right inclined surfaces of multiple cutouts 40 are contacted by multiple rolling members 30, relative rotation between the main assembly 12 and the tool assembly 14 is prevented or minimized. This contributes to the torsional rigidity of the robotic tool changer 10.

[0036] Figure 4 These principles are schematically illustrated. Among them, four rolling members (30A, 30B, 30C and 30D) are in contact with the inclined surfaces of four cutouts (40A, 40B, 40C and 40D). Note that the center line of the relative rolling member 30 is slightly offset relative to the center or valley 40V of the target cutout. Rolling members 30A and 30B contact the right inclined surface of cutouts 40A and 40B. This prevents or minimizes the cutout and therefore the tool assembly 14 from rotating counterclockwise relative to the main assembly 12. In a similar manner, rolling members 30C and 30D contact the left inclined surface of cutouts 40C and 40D. This prevents or minimizes the cutout and therefore the tool assembly 14 from rotating clockwise relative to the main assembly 12. Therefore, there is only very little (if any) relative rotation between the main assembly 12 and the tool assembly 14, which causes the torsional rigidity of the tool changer 10 to be enhanced.

[0037] Figure 5 is a horizontal cross-sectional view of the tool changer 10. It is similar in some respects to Figure 4 , but in more detail because it shows all rolling members contacting corresponding cutouts. Contact point C and resultant force vectors for rolling members 30A, 30B, 30C and 30D are also shown. In addition to these four rolling members, there are two other rolling members 30E and 30F, which are shown as being disposed in cutouts 40E and 40F. Unlike the other rolling members, rolling members 30E and 30F are disposed exactly in opposite cutouts 40E and 40F. This effectively strengthens the connection between the main assembly 12 and the tool assembly 14. Note the contact point C along reference lines 50, 52. Reference lines 50, 52 extend through contact point C and form an "X". Figure 5 The resultant force vectors resulting from contact of the rolling members with the inclined surfaces 40S of the respective cutouts 40 are shown. On each side of the tool changer 10, the resultant force vectors are generally opposed, which prevents or at least minimizes relative rotation between the main assembly 12 and the tool assembly 14.

[0038] There are a number of ways to misalign the holes 28 and rolling members 30 therein with the target cutout 40. One approach is to change the angular spacing of the holes 28 or cutouts 40 so that when the main assembly 12 and tool assembly 14 are coupled, the selected holes are not precisely aligned with the target cutout 40. As a practical consideration, it may be preferable to make such adjustments relative to the holes 28 so that the main assembly 12 properly mates with the tool assembly 14 that is already in the field. Figure 6 1 is a schematic diagram showing an exemplary spacing of holes that causes such misalignment. Reference line 100 (long dashed line) shows an annular liner 22 divided into six equal quadrants, each quadrant being a 60° quadrant. In this example, when the main component 12 and the tool assembly 14 are coupled, the reference line 100 will be aligned with the center of the shell-shaped cutout 40. Reference line 102 shows the center line of the selected hole 28 slightly tilted relative to the reference line 100. Of course, this means that when the main component 12 and the tool assembly 14 are coupled, the rolling members 30 in these four holes are misaligned relative to the target cutout 40. The degree of angular variation between reference lines 100 and 102 can vary. In this example, the difference is about 2°.

[0039] The same effect can be achieved by slightly offsetting the rolling member-hole plane. That is, the rolling member-hole plane is slightly offset so that selected rolling members 30 contact the opposing inclined surfaces 40S of the cutout 40.

[0040] Figure 7 An alternative embodiment is shown in which the selected cutouts 40A, 40B, 40C and 40D are slightly offset relative to the target rolling members 30A, 30B, 30C and 30D, which causes the selected cutouts to be misaligned with the target rolling members. This embodiment is similar to Figure 5 The embodiment shown is different in that Figure 7 In the embodiment of FIG. 4 , the holes and rolling members are equally spaced apart, while the four cutouts 40A, 40B, 40C and 40D are slightly offset relative to the four rolling members 30A, 30B, 30C and 30D. Figure 7 This deflection in is shown by angle β, while angle α represents the equal spacing of the holes and rolling members 30A-30F. Figure 5 and Figure 6 Similar to the illustrated embodiment, this relationship between the respective cutouts and rolling members results in force vectors due to the rolling members contacting the inclined surfaces 40S of the respective cutouts 40. The resultant force vectors are generally opposite, which prevents or at least minimizes relative rotation between the main assembly 12 and the tool assembly 14.

[0041] Embodiments of the present invention present many advantages over the prior art. For example, Figure 5 In the embodiment of FIG. 1 , opposing contact forces are applied to two rolling members on each side of the tool changer 10. Figure 5. Thus, these opposing forces restrict the lateral movement of the corresponding rolling members 30. By having some rolling members 30 contact the left inclined surface of some cutouts 40 and other rolling members contact the right inclined surface of other cutouts, these contact points virtually eliminate torsional play in the robotic tool changer 10.

[0042] Of course, without departing from the essential features of the present invention, the present invention may be implemented in other ways than those specifically described herein. These embodiments are considered in all respects to be illustrative and not restrictive, and all changes within the meaning and equivalent range of the appended claims are intended to be included therein.

Claims

1. A robotic tool changer comprising: A tool kit comprising: Bearing races; a plurality of circumferentially spaced scalloped cutouts formed in the bearing race, each cutout comprising a valley and opposing left and right inclined surfaces on either side of the valley; The main assembly includes: an array of holes, each hole being configured to contain a rolling member; a drive mechanism configured to force the rolling member into the cutout to couple the main assembly and the tool assembly, and to allow the rolling member to retract to decouple the main assembly and the tool assembly; Characterized in that the plurality of holes in the bore and the rolling members therein are not aligned with a target cutout in the cutout; and When the main component and the tool component are coupled, the plurality of holes and the target cut are constructed to reduce the tendency of the tool component to rotate relative to the main component by causing the rolling members in the plurality of holes to assume an offset position in the target cut and contact one of the left and right inclined surfaces of the target cut.

2. The robotic tool changer of claim 1 wherein the valley of the cutout includes a center point, and wherein the rolling members in the plurality of holes do not contact the center point of the valley when the main assembly and tool assembly are coupled.

3. The robotic tool changer of claim 1 , wherein: The plurality of apertures includes a first pair of aligned apertures and a second pair of aligned apertures; wherein each of the rolling members in the first pair of alignment holes contacts a right inclined surface of the target notch; and Each of the rolling members in the second pair of alignment holes contacts a left inclined surface of the target notch.

4. The robotic tool changer of claim 3 , wherein a reference line passing through contact points between the rolling members in the first pair of alignment holes and the inclined surfaces of the target cutout and a reference line passing through contact points between the rolling members in the second pair of alignment holes and the inclined surfaces of the target cutout form a substantially “X” shape.

5. The robotic tool changer of claim 4, wherein the center axes of the first pair of alignment holes are substantially aligned with the 10 o'clock and 4 o'clock positions on the tool changer; and wherein the center axes of the second pair of alignment holes are substantially aligned with the 8 o'clock and 2 o'clock positions on the tool changer.

6. A robotic tool changer according to any of the preceding claims, wherein the cutouts are equally spaced around the bearing race; wherein the plurality of holes are formed in an annular collar forming part of the main component; and wherein the plurality of holes are not all equally spaced around the annular collar because some of the holes are skewed relative to the target cutouts in the bearing race, which causes misalignment of the plurality of rolling members with the target cutouts.

7. A method of coupling a master assembly and a tool assembly of a robotic tool changer, comprising: moving a plurality of rolling members disposed in the holes in the main assembly toward a plurality of shell-shaped cutouts formed in the bearing race of the tool assembly so as to seat the plurality of rolling members in the shell-shaped cutouts, each shell-shaped cutout including a valley and opposing left and right inclined surfaces on both sides of the valley; It is characterized in that each of some of the rolling members contacts an inclined surface of its target incision, some of the rolling members include a first pair of aligned rolling members and a second pair of aligned rolling members, and wherein the inclined surface contacted by the first pair of aligned rolling members is opposite to the inclined surface contacted by the second pair of aligned rolling members, thereby generating a reaction force that prevents or minimizes relative rotation between the main component and the tool component, and each of the other rolling members contacts the left and right inclined surfaces on both sides of the valley of its target incision.

8. The method of claim 7, wherein a reference line passing through contact points between the first pair of aligned rolling members and the inclined surface of the target incision forms a substantially "X" configuration with a reference line passing through contact points between the second pair of aligned rolling members and the inclined surface of the target incision.

9. A robotic tool changer comprising: A tool kit comprising: Bearing races; a plurality of target cutouts formed in the bearing race, the target cutouts being spaced circumferentially around the bearing race, each target cutout comprising a valley and opposing inclined surfaces on either side of the valley; The main assembly includes: annular bushing; a row of holes formed in the annular collar, each hole being configured to contain a rolling element; a drive mechanism configured to force the rolling member into the cutout to couple the main assembly and the tool assembly, and to allow the rolling member to retract to decouple the main assembly and the tool assembly; the row of apertures comprising a first pair of generally aligned apertures formed in the annular collar and comprising a first pair of rolling elements, and a second pair of generally aligned apertures formed in the annular collar and comprising a second pair of rolling elements; It is characterized in that when the main component and the tool component are coupled: the first pair of substantially aligned apertures and the second pair of substantially aligned apertures and rolling members therein being misaligned relative to a target cutout; a respective rolling member offset relative to a valley in the target cutout and contacting an inclined surface of the target cutout; wherein the first pair of rolling members generally aligned with the apertures contact inclined surfaces of two of the target cutouts opposite to the inclined surfaces contacted by the second pair of rolling members generally aligned with the apertures; and Wherein the torsional rigidity of the tool changer is enhanced because the respective contact points between the rolling members and the inclined surfaces prevent or minimize rotation of the tool assembly relative to the main assembly.

10. The robotic tool changer of claim 9, wherein the first and second pairs of roughly aligned holes and the rolling members therein are configured such that a reference line passing through contact points between the rolling members in the first pair of roughly aligned holes and the inclined surfaces of the target cutout and a reference line passing through contact points between the rolling members in the second pair of roughly aligned holes and the inclined surfaces of the target cutout in the tool changer present a substantially "X" configuration.

11. The robotic tool changer of claim 10, wherein the first pair of rolling members are configured to contact the inclined surfaces of two of the target cutouts and prevent or minimize rotation of the tool assembly relative to the main assembly in one direction; and wherein the second pair of rolling members are configured to contact the inclined surfaces of two other target cutouts and prevent or minimize rotation of the tool assembly relative to the main assembly in an opposite direction.

Images