WO1993000519A1

WO1993000519A1 - Safety coupling for in-line rotatable shafts

Info

Publication number: WO1993000519A1
Application number: PCT/US1992/005290
Authority: WO
Inventors: Rudolf Richard Castens
Original assignee: Hybo Science, Inc.
Priority date: 1991-06-20
Filing date: 1992-06-22
Publication date: 1993-01-07

Abstract

This invention is a safety coupling of the hyperboloidal type for placement between an input shaft (10) and an output shaft (11) capable of disabling the output shaft (11) at the coupling (18) without impeding the rotation of the input shaft (10). The invention employs two hyperboloidal bearings (16, 24) utilizing a single coupling (18) having the inner race (14) for the first hyperboloidal bearing (16) and the outer race (48) for the second hyperboloidal bearing (24). Engagement of one hyperboloidal bearing is performed by movement of the coupling (18) which in turn disables the other hperboloidal bearing.

Description

SAFETY COUPLING FOR IN-LINE ROTATABLE SHAFTS

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates generally to safety couplings for use with rotatable shafts and in particular to the use of a unidirectional clutch of the hyperboloidal type for coupling first and second segments of a rotatable shaft wherein the first segment of the shaft can be instantaneously and automatically decoupled from the second segment without impeding the rotation of the second segment of the shaft.

2. Description of the Prior Art

The use of a rotating shaft is a common means for transferring torque, speed, or other rotational energy from one machine element to another to perform work. Rotating shafts are found on lathes, electric motors, automobiles, etc. Even simple lawn mowerers utilize an output shaft to provide a direct transfer of power to a blade. As any type of rotating mechanism can cause injury to an untrained or negligent operator, safety devices have been developed to keep the operator from coming into accidental contact with the rotating mechanism. Such devices are termed "shields" if their function is to shield an operator from the rotating mechanism, or "shut off" if their function is to disable the rotating mechanism. In certain situations, however, a shield is not adequate and a shut-off device cannot perform its function quickly enough to prevent injury.

One such example, for ease of description, is the use of a lawn mower. Conventional lawn mowers employ a single engine that rotates a blade by means of direct coupling with the engine crankshaft. This direct coupling has led to serious injuries that need not be detailed. As a direct result of this hazard, laws have been enacted in a number of jurisdictions requiring shields for enshrouding the cutting blade and that the engine be equipped with automatic shut off devices to prevent an unattended lawn mower from causing injury. However, even with devices now available, many situations arise in which the immediate stoppage of the rotating shaft is necessary to prevent injury. However, because the output shaft, and hence engine, is rotating at several hundred, if not thousand, rotations per minute, instantaneous stoppage would create undue stresses in the engine. Instantaneous stoppage of a rotating component drive is a problem that affects rotation mechanisms of any type. While extensive efforts have been made toward resolving these problems, no satisfactory solution has heretofore been provided. My invention is specifically designed to overcome he aforementioned problems and further provide a base for future shaft coupling needs. It is, therefore, to the effective resolution of these problems that the present invention is directed.

SUMMARY OF THE INVENTION The principle object of the present invention is to provide a simple and reliable device or apparatus which overcomes the problems previously mentioned when using an in- line rotating shaft. My invention provides a quick-release shutoff-type safety coupling of the hyperboloidal type capable of disabling a rotating shaft at the coupling without impeding the rotation of the shaft coupled to the other end of the coupling. In a first embodiment, a two-piece vertical output shaft of a typical lawn mower is shown for which the instant invention provides a safety couple. My device employs a dual hyperboloidal unidirectional coupling, which also acts as a bearing for one direction of rotation, utilizing a single coupling member as both the outer race for a first hyperboloidal clutch and an inner race member of the second hyperboloidal bearing. The inner race of the first hyperboloidal bearing is rigidly attached to the engine portion of the crank shaft, now referred to as an input shaft for generalization purposes. The coupling is rigidly attached to the remaining portion of the crankshaft, now referred to as the output shaft, which is directly coupled to the lawn mower cutting blades. The outer race of the second hyperboloidal is rigidly attached to the lawn mower casing or other non rotatable section when used on other devices. Engagement of the first hyperboloidal bearing is by means of positioning the coupling closer to the first hyperboloidal bearing. This upward positioning prevents engagement of the second hyperboloidal bearing while causing the first hyperboloidal to "lock" whereby the direction speed and torque of the input shaft is transferred to the coupling and thus to the output shaft. The result is a unitary connection between the input and output shaft whereby the cutting blades can be used in there ordinary and conventional fashion.

Disengagement of the first hyperboloidal bearing is by movement of the coupling closer to the second hyperboloidal bearing. This allows the input shaft to continue rotating, however, the second hyperboloidal is simultaneously engaged by the new positioning causing its bearings to "lock" stopping the output shaft, thus the cutting blades.

Accordingly it is an object of the present invention to provide a coupling that will fit between two rotating shafts and disconnect the rotation of one of the shafts when conditions so warrant the disconnect.

Yet another object of the invention is to provide a coupling that is capable of transmitting 100% of the torque delivered from an input shaft to an output shaft.

Still another object of the invention is to provide unidirection coupling.

Yet still another object of the invention is to provide a coupling of diameter approximating the diameter of the rotating shafts.

Still another object is to provide a safety coupling capable of splicing a rotatable shaft whereby one section of the shaft can be disengaged while the other section of hte shaft remains engaged. Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a fragmentary perspective view showing the double hyperboloidal unidirectional clutch of the present invention engaging an input shaft to an output shaft; Figure 2 is a fragmentary perspective view showing the double hyperboloidal unidirectional clutch of the present invention disengaging the input shaft from the output shaft;

Figure 3 is a cross sectional view taken along line A- A of Figure 1. Figure 4 is a cross sectional view taken along line B-

B of Figure 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As required, detailed embodiments of the present invention are disclosed herein, however, it is to be understood that the disclosed embodiments are merely exemplary of the invention which may be embodied in various forms. Therefore, specific functional and structural details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure.

Figure 1 is a fragmentary perspective view of a lawn mower crankshaft, hereinafter referred to as the input shaft 10, coupled the a cutting blade drive section, hereinafter referred to as the output shaft 12, of a mowing device. The input shaft 10 is coupled to a power source, not shown but visualized as the vertical crankshaft in a typical lawn mower, to the output shaft 12 which drives the actual cutting blades on the lawn mower, also not shown. The coupling of the instant invention utilizes a dual hyperboloidal type bearing in which an inner race 14 of the first hyperboloidal bearing 16 is rigidly attached to the

SUBSTITUTESHEET input shaft 10. A coupling race 18 forms the outer race surface 20 and the inner race 22 of a second hyperboloidal bearing 24. The inner race 14 and lower portion of the coupling race 18 is rigidly attached by use of matching slots/grooves 30 or may be pressed, cast, welded, striated, etc..., the attachment means not deemed to restrict the invention. Note, the upper portion of coupling race 18 is unrestricted either rotationally or vertically between coupling surface 26 and the surface 28 of non-rotatable casing 30. Engagement of the first hyperboloidal bearing 16 is by means of upward positioning of the coupling race 18 by use of positioning rod 32 having an eccentric endpiece 34 insertable into eccentric detente 36 of coupling race 18. Engagement of the first hyperboloidal bearing 16 disengages the second hyperboloidal bearing 24, explained in greater detail later in this disclosure, while disengagement of the first hyperboloidal bearing 16 engages the second hyperboloidal bearing 24 also by means of repositioning of the coupling race 18 as performed by a downward positioning of the coupling race 18 by use of position rod 38.

As shown, first hyperboloidal 16 is rigidly attached having inner race member 14 with race surface 38 of the sub- derivative hyperboloidal type and coupling 18 with race surface 20 of the super derivative hyperboloidal type forming confronting surfaces defining a hollow annular volume therebetween adapted to receive a plurality of thrust transmitting cylindrical rollers 40, all being similarly inclined with respect to radial planes.

Annular shoulder 42 acts to support, either directly or indirectly, rollers 40 axially thereof. By use of annular shoulder 42 located at one end of inner race 14 the hyperboloidal bearing 16 form a unidirectional clutch of the hyperboloidal type which is disclosed in my co-pending U.S. patent application, Serial No. 07/418,795, the disclosure of which is incorporated by reference herein as though fully set forth herein. An annular thrust bearing means, such as annular

SUBSTITUTE H thrust washer 44, may be used to provide support to rollers 40 slidably with respect to annular shoulder 42.

Engagement of the first hyperboloidal bearing 16 by upward positioning of rod 32 causes the first hyperboloidal 16 to "lock" in which rollers 40 are placed against thrust washer 44. This placement presents the first hyperboloidal bearing 16 in a unidirectional position whereby rotation is locked resulting in the direction speed and torque of the input shaft 10 being transferred through the rollers to coupling race 18. The coupling race 18, now locked to the input shaft 10 will rotate with the same speed and directional rotational force as presented by input shaft 10. The coupling race 18, rigidly attached to output shaft 12, transfers this direction rotational force presenting a unitary connection between the input shaft 10 and output shaft 12 whereby no loss in torque results and the cutting blades can be used in there ordinary and conventional fashion.

When rod 32 is in the upward position the second hyperboloidal bearing 24 is allowed to freewheel. Inner race 18 is rigidly coupled to output shaft 12 and an outer race 48 rigidly coupled to the non-rotatable casting 30 form within, race surface 22 of a super derivative hyperboloidal type of coupling 18 and race surface 46 of a sub derivative hyperboloidal type of race member 48, confronting surfaces defining a hollow annular volume therebetween adapted to receive a plurality of thrust transmitting cylindrical rollers 50, all being similarly inclined with respect to radial planes. Annular shoulder 52 acts to support, either directly or indirectly, rollers 50 axially thereof. By use of annular shoulder 52 located at one end of coupling member 18 the hyperboloidal bearing 24 forms a unidirectional clutch of the hyperboloidal type which is disclosed in my co-pending U.S. patent application, Serial No. 07/418,795, the disclosure of which is incorporated by reference herein as though fully set forth herein. An annular thrust bearing means, such as annular thrust washer 54, may be used to provide support to rollers 50 slidably with respect to annular shoulder 52. Disengagement of the second Hyperboloidal bearing 24 allows the rollers 50 to freewheel between race surfaces 22 and 46 of the coupling 18 and race member 48 respectfully. The result is a unitary connection between input shaft 10 and output shaft 12 whereby no loss in torque results as rollers 50 are allowed to freewheel, thus the cutting blades are uninhibited and allowed to rotate in there conventional fashion.

Referring to Figure 2 disengagement of the first hyperboloidal bearing 16 is by means of a downward positioning of the coupling race 18 by rotation of position rod 32 thereby engaging the second hyperboloidal bearing 24. Disengagement of the first hyperboloidal bearing 16 separates the rollers 40 from annular thrust shoulder 42 allowing the inner race 14, thus the input shaft 10, to freely rotate without transmitting a rotational force to the coupling race 18. However, disengagement of the first hyperboloidal 16 by downward positioning of rod 32 is designed to prevent continued rotational movement of the cutting blades. Typically, the positioning rod 32 is coupled to a control lever, now required by law in many jurisdictions, whereby the lawn mower operation is possible only by placement of the control lever in a "mower on" position. By placement of the control lever in a "mower off" position the first hyperboloidal 16 is disengaged allowing the input shaft 10 to rotate while hyperboloidal bearing 24 is simultaneously engaged causing bearings 50 of the second hyperboloidal 24 to "lock" whereby the direction speed and torque of the non-rotational casing 28 is transferred to the output shaft 12, which is zero, causing an immediately rotational stoppage of the output shaft 12 and associated cutting blades. This "lock" is a result of bearings 50 placed against thrust washer 54. This placement presents the second hyperboloidal bearing 24 in a unidirectional position whereby rotation is locked resulting in the direction speed and torque of the input shaft 10 being transferred through the rollers to coupling race 18.

Now referring to figure 3, a cross section of the input shaft 10 is shown with first hyperboloidal 16 rigidly attached having inner race member 14 with inwardly facing race surface 38 and outer race member 18 with coupling race surface 20. Inner race surface 38 and coupling race surface 20 define a hollow annular volume therebetween to receive a cylindrical rollers 40. Annular shoulder 42 can include a means for separating rollers 40.

Figure 4, illustrates a cross section of the output shaft 12 is shown with second hyperboloidal 24 rigidly attached having inner race member 18 with outwardly facing race surface 22 and outer race member 48 with race surface 46. Race surface 22 and race surface 46 define a hollow annular volume therebetween adapted to receive a cylindrical rollers 50. Annular shoulder 52 can include a means for separating rollers 50. Outer race bearing 48 is rigidly attached to non-rotatable casing 30 whereby upon engagement of the second hyperboloidal bearing 24 the rollers lock output shaft to the non-rotational casing 28 causing an immediately rotational stoppage of the output shaft 12 and associated cutting blades. Thus the operator is no longer in danger of injury from the rotating shaft which in this case was expounded upon by example. It is believed that a careful consideration of the specification taken in conjunction with the views of the drawing will enable the reader to obtain a clear and comprehensive understanding of the construction, the features and advantages and mode of use. Under the circumstances a more restricted description showing a multitude of examples is deemed to be unnecessary.

It is to be understood that while I have illustrated and described certain forms of the invention, it is not to be limited to the specific forms or arrangement of parts herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification.

Claims

What I Claim Is :

CLAIM 1. A safety device for coupling a rotatable input shaft to a rotatable output shaft comprising: a first inner sub derivative hyperboloidal race and a second inner sub derivative hyperboloidal race, each race having an annular shoulder, said first race rigidly attached to an input shaft, said second race rigidly attached to a non- rotatable base; a coupling having a first outer race surface and a second outer race surface each having a super derivative hyperboloidal surface of revolution, said first outer race confronting said first inner race and second outer race conforming to said second inner race, respectfully, each forming an annular volume therebetween; means for attaching the coupling; means for axial movement of said coupling; and a plurality of thrust transmitting cylindrical rollers disposed in said annular volume's to make thrust transmitting engagement with said inner and outer races with respect to attempted relative rotation of said outer race member with said first inner race member with respect to said inner race member for attempted relative rotation thereof in the opposite direction.

CLAIM 2. The device according to claim 1 wherein said means for axially moving of said coupling comprises a mechanical lever.

CLAIM 3. The device according to claim 1 wherein said means for axially moving of said coupling comprises a electrical actuator.

CLAIM 4. The device according to claim 1 wherein said means for attaching the coupling is the use of groves or slots.

CLAIM 5. The device according to claim 1 wherein said means for attaching the coupling is the use of a friction press fit.

CLAIM 6. The device according to claim 1 wherein said means for attaching the coupling is the use of welding.

CLAIM 7. A safety device for lawn mowers coupling the crankshaft to the cutting blade shaft comprising: a first inner sub derivative hyperboloidal race and a second inner sub derivative hyperboloidal race, each race having an annular shoulder, said first race rigidly attached to the crankshaft, said second race rigidly attached to a non-rotatable section of the lawn mower; a coupling rigidly attached to the cutting blade shaft having a first outer race surface and a second outer race surface each having a super derivative hyperboloidal surface of revolution, said first outer race confronting said first inner race and second outer race conforming to said second inner race, respectfully, each forming an annular volume therebetween; means for axial movement of said coupling; and a plurality of thrust transmitting cylindrical rollers disposed in said annular volumes to make thrust transmitting engagement with said inner and outer races with respect to attempted relative rotation of said outer race member with said first inner race member with respect to said inner race member for attempted relative rotation thereof in the opposite direction.

CLAIM 8. A safety device for coupling a rotatable input shaft to a rotatable output shaft comprising: a first upper inner race having a first and second surface, said first surface being cylindrical and rigidly attached to the input shaft, said second surface having a surface of revolution about the axis of rotation which surface is a sub derivative hyperboloidal, said first upper inner race having an annular shoulder member rigidly connected to one end of said first upper inner race; a coupling having an inner and outer surface and an upper and lower coupling race surface, said upper coupling race surface concentrically disposed on the inner surface having formed therein a super derivative hyperboloidal surface of revolution confronting said first upper inner race and forming an annular volume therebetween, said lower coupling race surface concentrically disposed on the outer surface of said coupling having formed a super derivative hyperboloidal surface of revolution; means for rigidly attaching the inner surface of said coupling to the output shaft; means for axially movement of said coupling; a second inner race having a first and second surface, said first surface being cylindrical and rigidly attached to the other rotatable shaft, said second surface being of cylindrical and conic al having a surface of revolution about the axis of rotation which surface is a sub-derivative hyperboloidal confronting said lower coupling race and forming an annular volume therebetween, said second inner race having an annular shoulder member rigidly connected to one end of said second inner surface; and a plurality of thrust transmitting cylindrical rollers disposed in said annular volumes in line contact with both said first inner and outer race surfaces of the upper and lower portion of said coupling, all said rollers being similarly inclined with respect to radial planes and adapted to make thrust transmitting engagement with said inner and outer races with respect to attempted relative rotation of said outer race member with said first inner race member with respect to said inner race member for attempted relative rotation thereof in the opposite direction.