US20100327668A1

US20100327668A1 - Robot crash protector

Info

Publication number: US20100327668A1
Application number: US12/882,742
Authority: US
Inventors: William Berrocal; Dana A. Wagner
Original assignee: ATI Industrial Automation Inc
Current assignee: ATI Industrial Automation Inc
Priority date: 2008-01-11
Filing date: 2010-09-15
Publication date: 2010-12-30
Also published as: US20090179504A1; US7964998B2

Abstract

A robotic crash protector device is configured for heavy payload applications. The device includes a housing, a piston and an actuator movably mounted within the housing, a cam member secured within the housing in fixed relation to the housing's base, and a switch. The cam member includes a cam surface with some portions being closer to the housing's base than other portions. The actuator includes bearing members that are configured to, responsive to a rotational force imparted to the actuator, move along the cam surface and thereby collectively displace the piston. The switch detects this displacement and indicates a crash. When moving along the cam surface, the bearing members are each configured to engage the surface along a line of contact, rather than at a single point. With forces imparted to each bearing member and the cam surface distributed across a line, the components better endure heavy payload applications.

Description

This application is a Continuation-In-Part of U.S. patent application Ser. No. 12/351,495, filed Jan. 9, 2009, which claims priority to Provisional U.S. Patent Application 61/020,664 filed Jan. 11, 2008 and entitled, “Linearly Actuated Switch for Robot Crash Protector Device,” both applications of which are incorporated herein by reference in their entireties.

BACKGROUND

Industrial robots have become an indispensable part of modern manufacturing. Whether transferring semiconductor wafers from one process chamber to another in a cleanroom or cutting and welding steel on the floor of an automobile manufacturing plant, robots perform many manufacturing tasks tirelessly, in hostile environments, and with high precision and repeatability.
For safety, and to prevent damage to a robot arm and/or a robotic tool attached to it, crash protector devices are known in the art. A crash protector device is interposed between a robot arm and a robotic tool for detecting and indicating a crash condition, defined as an excessive force or torque applied to the robotic tool, usually as a result of unintended contact. The crash protector device exhibits a predetermined compliance, or allowance of relative movement between the robotic tool and robot arm, prior to indicating a crash condition. The crash condition indication may comprise an electronic signal sent to a robotic controller, which may halt movement of the robotic arm in response, to prevent further damage. The crash protector device mechanically and electrically resets itself when the crash force is removed.
U.S. Pat. No. 6,690,208, commonly owned with the present application and incorporated herein in its entirety, discloses one known crash protector device. The device includes a housing within which are mounted a piston, a cam member, and an actuator. The base of the housing in some embodiments is connected to the robot arm, while the actuator is connected to the robotic tool. Under normal circumstances, the piston is biased away from the base of the housing so as to urge the actuator away from the base of the housing. In this position, each of a plurality of ball members attached to the actuator sit in a different V-shaped groove of the cam member, engaging the surface of the cam member at two points (one on either side of the apex of the groove). When a rotational force is imparted to the robotic tool (and thereby the actuator), the ball members move out of their respective V-shaped grooves and slide along the surface of the cam member, always engaging the cam surface at a single point. This in turn displaces the actuator and the piston back toward the base of the housing. Upon detecting a predetermined degree of displacement, the device indicates a crash.
The crash protector device disclosed in the '208 patent reliably detects a crash even after repeated use of the robotic tool for relatively small payload applications. However, the reliability of the device diminishes considerably when the tool is repeatedly used for heavy payload applications (e.g., heavy material handling). These heavy payload applications place substantial forces on the ball members and the cam surface, forces which quickly wear down the components to an extent that affects the reliability of the crash protector device.

SUMMARY

Teachings herein advantageously include a robotic crash protector device configured for heavy payload applications. The device includes a plurality of bearing members that are each configured to engage a cam surface along a line of contact, rather than at a single point, when moving along the cam surface. With forces imparted to each bearing member and the cam surface distributed across a line of contact, the components better endure heavy payload applications and provide for a crash protector device with greater sustained reliability.
More particularly, a robotic crash protector device includes a housing, a piston and an actuator movably mounted within the housing, a cam member secured within the housing in fixed relation to the housing's base, and a switch. The cam member includes a cam surface that is oriented towards the piston, with some portions being closer to the housing's base than other portions. The actuator includes a plurality of bearing members that are configured to, responsive to a rotational force imparted to the actuator, move along the cam surface and thereby collectively displace the piston. The switch detects this displacement and indicates a crash.
When moving along the cam surface, the bearing members are configured to engage the cam surface along a line of contact. In some embodiments, for example, each bearing member includes a half-cylindrical outer surface having a flat side and a curved side, and is configured to slide along the cam surface. When a given bearing member slides along the surface, the length of the member's curved side engages the surface along a line that is transverse to whichever direction the bearing member is currently sliding. In other embodiments, each bearing member includes a substantially cylindrical outer surface and is configured to roll along the cam surface. Each bearing member may comprise, for instance, a spherical bearing. Regardless, when a given bearing member rolls along the surface, the bearing member engages the cam surface along a line that corresponds to the length of the cylindrical outer surface and that is transverse to the direction in which the bearing member is rolling.
Repeated sliding or rolling of the bearing members across the cam surface may inevitably cause the components to wear down, especially when used for heavy payload applications. For example, a groove may begin to form in the cam surface and the portions of the bearing members that slide or roll along the cam surface may begin to flatten. Yet, because any force imparted to the bearing members distributes across a line, this wear occurs at a slower rate than the wear occurring in prior crash protector devices. That is, for a given force imparted over a given time, the wear to the bearing members and the cam surface is less than the wear that would occur to similar components in prior devices (e.g., the groove formed in the cam surface may be less deep, and the bearing members may not flatten as much). This means that the device can be used over a longer period of time before the same level of wear occurs, or can be used for even heavier payload applications.
Of course, the present invention is not limited to the above features and advantages. Indeed, those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a crash protector device according to one embodiment.

FIG. 2 is an exploded view of the crash protector device of FIG. 1.

FIG. 3 is an inverted view of a cap and cam member included in the crash protector device according to one embodiment.

FIGS. 4A-4C illustrate a ball member and a cam surface as used in prior crash protector devices.

FIGS. 5A-5C illustrate a bearing member and a cam surface according to one embodiment of the present invention.

FIGS. 6A-6C illustrate a bearing member and a cam surface according to another embodiment of the present invention.

FIG. 7 is a side view of a cam surface according to one embodiment of the present invention.

FIG. 8 is a top view of a bearing member moving along a cam surface.

FIG. 9 is a side view of an actuator and a bearing member included in the crash protector device according to one embodiment.

DETAILED DESCRIPTION

FIG. 1 depicts a sectional view, and FIG. 2 a partial exploded view, of a crash protector device 10 according to one embodiment of the present invention. The device 10 includes a housing 12 adapted to be attached to a robot arm (or alternatively to a robotic tool). The housing 12 has a central stem 16 with a bore 18 therethrough, defining a central axis X. A piston 20 having a central through-bore 22 is mounted within the housing 12 with the through-bore 22 slideably engaging the housing stem 16. The piston 20 is thus moveable within the housing 12 in an axial direction (up and down, as depicted in FIGS. 1 and 2). A chamber formed between the housing base 12 a and the lower surface of the piston 20 is filled with, e.g., compressed gas, such as air. Pressure is maintained by an O-ring 26 between the housing stem 16 outer surface and piston 20 inner surface; and an O-ring 28 between the piston 20 outer surface and housing 12 inner surface. The compressed gas biases the piston 20 in a direction away from the housing base 12 a.
An actuator 40 adapted to be attached to a robotic tool (or alternatively to a robot arm) is disposed on the opposite side of the piston 20 from the housing base 12 a. With the piston 20 biased by the compressed gas in a direction away from the housing base 12 a, the actuator is in turn biased by the piston 20 in a direction away from the housing base 12 a. A cap 32 that is rigidly fixed to the housing 12 arrests movement of the actuator 40 and thereby contains the actuator 40 within the housing 12. The actuator 40 is thus biased in a default state to an axially extended position (away from the housing base 12 a).
Any sufficient axial force applied to an attached robotic tool, and hence to the actuator 40, in the direction of the housing base 12 a, forces the actuator 40 out of its default state and toward the housing base 12 a. A contact surface member 21 interposed between the actuator 40 and the piston 20 transfers movement of the actuator 40 into movement of the piston 20 toward the housing base 12 a, against pneumatic pressure. A switch 92 detects this displacement of the piston 20 and indicates a crash responsive thereto.
More particularly, a spring plate 70 is rigidly attached to the housing stem 16 by fasteners 72, and is spaced apart from the upper surface of the housing stem 16 by standoffs 74. An actuation plate 76 spans the central bore of the piston 20, with cut-outs 78 allowing the fasteners 72 and standoffs 74 to pass through the actuation plate 76. A circumferential lip 80 formed in the actuation plate 76 engages with the contact surface member 21 disposed over part of the piston 20, the actuation plate 76 thus spanning the piston bore 22. The actuation plate 76 is free to move in an axial direction between the housing stem 16 and the spring plate 70. An actuation spring 84 biases the actuation plate 76 away from the spring plate 70, and presses the actuation plate circumferential lip 80 against the contact surface member 21.
A linearly actuated switch assembly 90 is disposed within the central bore 18 of the housing stem 16. The switch assembly 90 comprises a linearly actuated switch 92 adjustably disposed within a switch carrier sleeve 94. For example, the switch 92 may include a threaded portion, and at least a portion of the switch carrier sleeve 94 may include corresponding threads. The switch assembly 90 is confined and positioned within the housing stem bore 18 by a spring stop 96 secured to the housing stem, such as by fasteners 98. A carrier spring 100 disposed beneath the spring stop 96 contacts the switch carrier sleeve 94, biasing it towards the housing base 12 a. In addition to adjusting the position of the switch 92 within the switch carrier sleeve 94 by the aforementioned threads, the position of the switch carrier sleeve 94 (and hence the switch assembly 90) within the housing stem bore 18 is adjustable by turning a set screw 102 threadedly disposed in the housing base 12 a.
In its default, extended position, the piston 20 is spaced apart from the housing base 12 a by operation of pneumatic pressure. The contact surface member 21 contacts the actuator 40, urging it to an extended position. In this position, the contact surface member 21 lifts the actuation plate 76 off of the housing stem 16 and away from the end of the switch 92, compressing the actuation spring 84.
Responsive to an axial force applied to the robotic tool, the actuator 40 presses the contact surface member 21, forcing the piston 20 to move axially toward the housing base 12 a. As this occurs, the actuation plate 76 moves toward the housing stem 16. If the movement of the piston 20 is sufficiently large, the actuation plate 76 will contact the end of the linearly actuated switch 92, causing the switch 92 to actuate, or change state (that is, to open the contacts in a normally-closed switch, or to close the contacts in a normally-open switch), and to indicate a crash.
The threshold of force that causes displacement of the piston 20 may be adjusted by adjusting the pneumatic pressure beneath the piston 20. The compliance, or degree of displacement tolerated prior to triggering an interrupt signal, is adjustable—such as by presetting the position of the actuator 40 in the housing (such as via an annular adjustment ring 33), or adjusting the position of the switch 92, or by other means.
Likewise, a non-axial force on the tool (in any radial direction) “cants” the actuator 40 from its axially aligned position. The contact surface member 21 transfers the movement of the actuator 40 into movement of the piston 20 toward the housing base 12 a. Responsive to detecting sufficient displacement of the piston 20, the switch 92 indicates a crash.
In order to account for a rotational force (i.e., torque) applied to the tool, the device 10 includes a cam member 34 and a plurality of bearing members 44. The bearing members 44 and the cam member 34 interact as described below to displace the actuator 40, and thus the piston 20, axially towards the housing base 12 a responsive to a rotational force. The switch 92 detects this displacement and indicates a crash when the piston 20 has been sufficiently displaced.
The cam member 34 is secured within the housing 12, in between the cap 32 and the piston 20, and in fixed relation to the housing base 12 a. Arranged in this way, the cam member 34 includes an annular cam surface 36 that is oriented towards the piston 20 (and thus also the housing base 12 a). Some portions of the cam surface 36 are closer to the housing base 12 a than other portions.
This is best appreciated by inspection of FIG. 3, which depicts a perspective view of the cam surface 36 (i.e., viewed from an inverted position A in FIG. 2 to better display the cam surface 36). As shown in FIG. 3, some portions 37 of the cam surface 36 form crests in the surface 36 and are closest to the housing base 12 a when the cam member 34 is installed in the housing 12. Other portions 38 of the cam surface 36 form troughs, or grooves, in the surface 36 and are furthest from the base 12 a when the cam member 34 is installed in the housing 12. The sectional view of the cam surface 36 in FIG. 1 also depicts this well, by showing one portion 38 of the cam surface 36 (i.e., a trough) as being further from the housing base 12 a than another portion 37 (i.e., a crest).
The plurality of bearing members 44 are radially disposed about the periphery of the base of the actuator 40, with the circumferential distance between bearing members 44 corresponding to that between portions 38 of the cam surface 36. When the actuator 40 is in its default, axially extended state, with no forces imparted to the actuator 40, the bearing members 44 engage the cam surface 36 at or around portions 38. FIG. 1 shows a sectional view of one bearing member 44 actually engaging a portion 38; of course, the bearing member 44 in other embodiments may simply engage the cam surface 36 around the portion 38 so as to in a sense straddle the trough. In any event, this biases the actuator 40 to have a particular rotational orientation in its default state.
Responsive to an applied rotational force, the actuator 40 rotates away from its default rotational orientation. This causes the bearing members 44, which are rigidly secured to the actuator 40, to be displaced from portions 38 and to move along other portions of the cam surface 36. Because these other portions of the cam surface 36 are closer to the housing base 12 a, the displacement of the bearing members 44 collectively causes displacement of the actuator 40 (and thus displacement of the piston 20) in a direction axially towards the housing base 12 a.
When the rotational force on the actuator 40 is removed, the piston 20, under the influence of pressurized air or fluid in the fluid chamber, will urge the actuator 40 in an axial direction away from the housing base 12 a. The bearing members 44 will again move along the cam surface 36, coming to rest at portions 38. In this manner, the crash protector device 10 resets itself following a rotational crash.
A shortcoming of prior art crash protector devices is that the reliability of the devices diminishes considerably when repeatedly used for heavy payload applications (e.g., heavy material handling). Consider FIGS. 4A-4C, which show a ball member 144 and a cam surface 136 as used in prior crash protector devices for responding to a rotational force. In FIG. 4A, the ball member 144 comprises a sphere that slides along the cam surface 136, engaging the cam surface 136 at a single point 145. The force imparted to the ball member 144 during operation of the device focuses entirely at this point 145 and inevitably causes the ball member 144 and the cam member 136 to wear down. For example, over time as the ball member 144 repeatedly slides back and forth along the cam surface 136, the ball member 144 forms a deep groove 146 in the cam surface 136 (FIG. 4B). Also, the bottom tip 144A of the ball member 144 flattens (FIG. 4C). This wear, though inevitable, occurs especially quickly in heavy payload applications, where the force imparted is quite large,
According to embodiments of the present invention, each bearing member 44 used in the device 10 is configured to engage the cam surface 36 along a line of contact, rather than at a single point, when moving along the cam surface 36. So configured, the force imparted to a bearing member 44 and the cam surface 36 distributes across a line, instead of focusing at a single point. With the force distributed in this way, the bearing members 44 and the cam surface 36 better endure heavy payload applications and provide for a crash protector device 10 with greater sustained reliability.
FIGS. 5A-5C illustrate embodiments where each bearing member 44 includes a half-cylindrical outer surface having a flat side 44A and a curved side 44B, and is configured to move along the cam surface 36 by sliding along the surface 36. When a given bearing member 44 slides along the surface 36, whether in one direction or another, the length of the member's curved side 44B engages the surface 36 along line 45. This line 45 is transverse to, or substantially perpendicular to, whichever direction the bearing member 44 is currently sliding.
When the robotic tool is used for heavy payload applications, a relatively large force is repeatedly imparted to the bearing member 44 and the cam surface 36. That force inevitably causes the bearing member 144 and the cam member 136 to wear down. The curved side 44B of the bearing member 44, for example, may eventually etch a rectangular groove 46 along the cam surface 36 (FIG. 5B). Also, the bottom 44C of the curved side 44B may flatten (FIG. 5C).
Yet, because any force imparted to the bearing member 44 distributes across line 45, this wear to the bearing member 44 and the cam surface 36 occurs at a slower rate than the wear occurring in prior crash protector devices. Indeed, the amount of force imposed upon any given point along line 45 (e.g., point 45 x) is less than the amount that would have been imposed upon the point had the bearing member 44 engaged the cam surface 36 at only that point (as in prior art devices). With less force being imposed upon any given point along line 45, the bearing member 44 and the cam surface 36 advantageously better endure heavy payload applications. That is, for a given force imparted over a given time, the wear to the bearing member 44 and the cam surface 36 is less than the wear that would occur to similar components in prior devices (e.g., the groove 46 formed in the cam surface 36 may be less deep, and the bearing member 44 may not flatten as much). This means that the device 10 can be used over a longer period of time before the same level of wear occurs, or can be used for even heavier payload applications.
FIGS. 6A-6C illustrate other embodiments where each bearing member 44 includes a substantially cylindrical outer surface, and is configured to move along the cam surface 36 by rolling along the surface 36. With a cylindrical outer surface, the bearing member 44 engages the cam surface 36 along a line 45 that corresponds to the length of the cylindrical outer surface. In much the same way as in FIGS. 5A-5C, this line 45 is transverse to, or substantially perpendicular to, whichever direction the bearing member 44 is currently rolling.
The repeated rolling of the bearing member 44 across the cam surface 36 may, as above, eventually etch a rectangular groove 46 along the cam surface 36 (FIG. 6B). Yet because the bearing member 44 rolls across the cam surface 36 rather than sliding across it, the bearing member 44 wears uniformly around the circumference of its cylindrical outer surface instead of wearing only on one side. As seen in FIG. 6C, for example, the bearing member 44 may eventually wear down to have a cylindrical outer surface 44D with a smaller diameter. Again, though, because any force imparted to the bearing member 44 distributes across line 45, this wear to the bearing member 44 and the cam surface 36 occurs at a slower rate than the wear occurring in prior crash protector devices.
As one example of bearing members 44 configured according to the embodiments illustrated in FIGS. 6A-6C, bearing members 44 may each be spherical bearings. In this case, each bearing member 44 has an outer raceway similar to the outer cylindrical surface depicted in FIG. 6A. The outer raceway rolls along the cam surface 36, engaging the cam surface 36 along line 45. Each bearing member 44 also has an inner raceway that is concentric with the outer raceway, at least in a default state, and one or more anti-friction features disposed between the outer and inner raceways. While the one or more anti-friction features may be of any type, including rolling elements, sliding elements, lubricant, or the like, lubricant in the context of robotic crash protection advantageously accommodates multi-component forces applied to the robotic tool (e.g., a combination of a rotational force and a non-axial force applied to the tool). In any event, regardless of the particular type of anti-friction features included therein, the bearing members 44 reduce rotational friction as the actuator 40 moves along the cam surface 36 in response to a rotational force.
Much of the above discussion has focused on the bearing members 44 and their configuration to engage the cam surface 36 along a line of contact. It should be appreciated, however, that the cam surface 36 and the bearing members 44 may be jointly configured in some embodiments to more fully and/or more consistently engage one another along a line of contact.
More particularly, the cam surface 36 may be configured with crests 37 and troughs 38 as discussed above with respect to FIG. 3, and as further illustrated in FIG. 7. These crests 37 and troughs 38, as flat surfaces, are substantially perpendicular to the central axis X of the housing 12, but are formed at different distances from the housing base 12 a. In some embodiments, the cam surface 36 includes a gradual transition between crests 37 and troughs 38. Portions of the cam surface 36 between a crest 37 and a trough 38 form this gradual transition by transitioning from an approximately convex surface 36A proximal to a trough 38, to an approximately concave surface 36B proximal to a crest 37. The radius of curvature of the surfaces 36A and 36B may be configured in dependence upon the radius of the bearing members 44 and/or the distance between crests 37 and troughs 38.
Furthermore, these portions forming a gradual transition may cant radially inward toward the central axis X of the housing 12, as illustrated in FIG. 3. The angle at which these portions cant radially inward may in turn depend upon the angle at which the bearing members 44 are secured to the actuator 40 and the degree to which those bearing members 44 may deviate from that angle when a force is applied to them. By jointly configuring the cam surface 36 and the bearing members 44 in these ways, the bearing members 44 may remain flush with the cam surface 36 regardless of where on the cam surface 36 the bearing members 44 are located. This means that the bearing members 44 and the cam surface 36 can consistently engage one another along the full length of the intended line of contact.
Of course, even if this is the case, any “play” in the alignment of the bearing members 44 to the cam surface 36 may cause the cam surface 36 to wear inconsistently. Consider, for instance, FIG. 8. In FIG. 8, the cam surface 36 is wider than the outer surface of a bearing member 44. The bearing member 44 first moves along the left side of the cam surface 36, but because of “play” in the alignment of the bearing member 44 to the cam surface 36 shifts to moving along the right side of the cam surface 36. This may cause a groove 46 to form in the cam surface 36 that is inconsistent along the length of the cam surface 36 (as shown), or that is wider than the outer surface of the bearing member 44. In either case, the inconsistent wear degrades the reliability of the device 10.
Some embodiments of the present invention account for this “play” in the alignment of the bearing members 44 to the cam surface 36, so as to prevent or at least mitigate inconsistent wear to the cam surface 36. In FIG. 9, a bearing member 44 includes an outer raceway 44D and an inner raceway 44E, as discussed above, and further includes one or more spring loaded members 44F. These spring loaded members 44F are each secured to the actuator 40 at one end and rest against the outer raceway 44D at the other end. Disposed in this way, the members 44F are configured to maintain the outer raceway 44D in alignment with the cam surface 36. More particularly, the members 44F bias the outer raceway 44D to a particular default alignment (e.g., in the center of the cam surface 36). The tension in springs of the spring loaded members 44F permit some variance from this default alignment upon movement of the actuator 40, but otherwise force the outer raceway 44D back to the default alignment. By preserving a particular alignment of the bearing members 44 to the cam surface 36, these spring loaded members 44F prevent or mitigate inconsistent wear to the cam surface 36.
The present invention may, of course, be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the invention. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

Claims

1. A robotic crash protector device adapted to be interposed between a robot arm and a robotic tool, and operative to detect a crash, comprising:

a housing having a central axis and a base;

a piston movably mounted within the housing;

a cam member secured within the housing in fixed relation to the base and including a cam surface oriented towards the piston, some portions of the cam surface being closer to the base than other portions of the cam surface;

an actuator movably mounted in the housing and including a plurality of bearing members that are configured to, responsive to a rotational force imparted to the actuator about said central axis, move along the cam surface and thereby collectively displace the piston, each bearing member configured to engage the cam surface along a line of contact when moving along the cam surface; and

a switch configured to detect displacement of the piston and, responsive thereto, to indicate a crash.

2. The robotic crash protector device of claim 1, wherein each bearing member is configured to engage the cam surface along a line of contact that is transverse to a direction in which the bearing member moves along the cam surface.

3. The robotic crash protector device of claim 1, wherein said plurality of bearing members each include a half-cylindrical outer surface having a flat side and a curved side, the length of the curved side engaging the cam surface along a line of contact.

4. The robotic crash protector device of claim 1, wherein said plurality of bearing members are configured to move along the cam surface by sliding along the cam surface.

5. The robotic crash protector device of claim 1, wherein said plurality of bearing members each include a substantially cylindrical outer surface, the length of which engages the cam surface along a line of contact.

6. The robotic crash protector device of claim 1, wherein said plurality of bearing members are configured to move along the cam surface by rolling along the cam surface.

7. The robotic crash protector device of claim 1, wherein said plurality of bearing members comprise a plurality of spherical bearings.

8. The robotic crash protector device of claim 1, wherein said plurality of bearing members each include an outer raceway that engages the cam surface along a line of contact, an inner raceway concentric with the outer raceway, and one or more anti-friction features disposed between the outer raceway and the inner raceway.

9. The robotic crash protector device of claim 1, wherein said plurality of bearing members each include one or more spring loaded members configured to maintain an outer surface of that bearing member in alignment with the cam surface.

10. The robotic crash protector device of claim 1, wherein portions of the cam surface that are closest to the base comprise crests and portions of the cam surface that are furthest from the base comprise troughs, and wherein said troughs and crests comprise flat surfaces that are substantially perpendicular to the central axis of the housing.

11. The robotic crash protector device of claim 10, wherein portions of the cam surface between any given trough and crest form a gradual transition between that trough and crest by transitioning from an approximately convex surface proximal to the trough, to an approximately concave surface proximal to the crest.

12. The robotic crash protector device of claim 10, wherein portions of the cam surface between any given trough and crest cant radially inward toward the central axis of the housing.

13. The robotic crash protector device of claim 1, wherein the piston is biased in a direction away from the base, and the plurality of bearing members engage those portions of the cam surface that are furthest away from the base when no forces are imparted to the actuator.

14. The robotic crash protector device of claim 13, wherein the housing includes a cap rigidly fixed thereto, and wherein the cam member is secured to the cap, the cap and the cam member configured to arrest movement of the actuator in a direction away from the base.

15. The robotic crash protector device of claim 13, wherein the housing contains a cavity, and wherein the piston forms a chamber in the cavity and is biased in a direction away from the base by compressed gas or fluid in the chamber.

16. The robotic crash protector device of claim 13, wherein the plurality of bearing members are configured to, responsive to a rotational force imparted to the actuator about said central axis, move along those portions of the cam surface that are closer to the base and thereby collectively displace the piston in a direction toward the base.

17. The robotic crash protector device of claim 1, further comprising a contact surface member interposed between the piston and the actuator that is configured to transfer movement of the actuator into movement of the piston.

18. A robotic crash protector device adapted to be interposed between a robot arm and a robotic tool, and operative to detect a crash, comprising:

a housing having a central axis and a base;

a piston movably mounted within the housing;

an actuator including bearing means for engaging the cam surface along a line of contact, responsive to a rotational force imparted to said means about said central axis, to thereby displace the piston;

switching means for detecting displacement of the piston and, responsive thereto, indicating a crash.

19. An actuator movably mounted in the housing of a robotic crash protector device that is interposed between a robot arm and a robotic tool, the actuator comprising a plurality of bearing members that are configured to, responsive to a rotational force imparted to the actuator about a central axis of the housing, move along a cam surface of a cam member secured within the housing and thereby collectively displace a piston movably mounted within the housing, each bearing member configured to engage the cam surface along a line of contact when moving along the cam surface.

20. The actuator of claim 19, wherein each bearing member is configured to engage the cam surface along a line of contact that is transverse to a direction in which the bearing member moves along the cam surface.