Patent Application
20140123789
There are many mechanical systems requiring the conversion of linear motion to rotational motion. In one example, a robot forearm may need to rotate using an actuator within an upper arm connected to a shoulder. Helical gears (See. U.S. Pat. No. 5,447,095) are heavy and complex. Some actuators have a limited range of motion. Other actuators occupy too much space. Some suffer from high friction.
Aspects of the invention may provide for an actuator which is lightweight, involves few moving parts, and has a range of motion adaptable for numerous applications. The actuator has a form factor which is long and slender and may include rolling elements with low friction. In some examples, an actuator is provided with a range of motion greater than 360°. The actuator may be back drivable and can be used as a differential. in some aspects, the actuator can be designed with integral internal fluid routing using, for example, slip rings.
Featured are counter-rotating helical cams in the form of inner and outer sleeves, each with at least a pair of helical slots therethrough. A driver includes bearing surfaces received through the helical slots of the inner and outer sleeves.
Featured is an actuator comprising an outer sleeve with at least a pair of helical slots running in a first direction an inner sleeve with at least a pair of helical slots running in a second, opposite direction and a driver including bearings received through the helical slots of the inner sleeve and into the helical slots of the outer sleeve.
The helical slots of the sleeves may wrap partially around or more. The helical slots of the inner and outer sleeve may have a constant but different pitch, or a non-constant and different pitch. There can be at least four helical slots in the outer sleeve and four helical slots in the inner sleeve.
The driver may include a cross-member supporting the bearings thereon and a piston extending from the cross-member. In one design, there are a pair of roller bearings on each end of the cross-member, one inner roller bearing of each pair for a helical slot in the inner sleeve, one outer roller bearing of each pair for a helical slot in the outer sleeve. The bearings can be cylindrical bearings. If the slots are tapered, the bearings can be conical bearings. The driver may be hydraulically driven, electrically driven, or mechanically driven.
The driver may include at least two cross members.
The subject invention, however, in other embodiments, need not achieve all these objectives and the claims hereof should not be limited to structures or methods capable of achieving these objectives.
Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:
Aside from the preferred embodiment or embodiments disclosed below, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. If only one embodiment is described herein, the claims hereof are not to be limited to that embodiment. Moreover, the claims hereof are not to be read restrictively unless there is clear and convincing evidence manifesting a certain exclusion, restriction, or disclaimer.
The helical slots in each sleeve may wrap around their respective sleeves partially, once, or more. They may have a constant pitch as shown. The slots of the inner sleeve may have a different pitch than the slots of the outer sleeve. The helical slots of the outer and inner sleeve may also have a non-constant pitch and again the pitch of the helical slots in the outer sleeve is typically different than the pitch of the helical slots in the inner sleeve creating a non-linear transmission.
By integrating internal fluid routing and slip rings, hydraulic fluid can be provided downstream of the actuator, for example, to one or more components in forearm 16,
The resulting actuator in its various embodiments is lightweight, involves few moving parts, and has an adjustable range of motion suitable for numerous applications. The preferred actuator has a form factor which is long and slender and includes rolling elements with low friction.
Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments.
In addition, any amendment presented during the prosecution of the patent application for this patent is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and/or there are many other reasons the applicant can not be expected to describe certain insubstantial substitutes for any claim element amended.
Other embodiments will occur to those skilled in the art and are within the following claims.
