Dual direction clutch brake

Embodiments of the present disclosure provide an improved clutch-brake for a PTO unit. In accordance with a first embodiment of the present disclosure, a dual direction clutch-brake with a clutch cup is disclosed. When moved in one direction, the clutch cup engages a clutch pack resulting in the input shaft being engaged with the output shaft. When the clutch cap is moved in the opposite direction, the clutch cup engages a breaking member, for example a cover or casing of the PTO unit, which applies a force to the output shaft opposite to the direction of rotation and thereby stops the output shaft from rotating.

FIELD

This disclosure relates to power takeoff devices useful for mounting on vehicle transmissions for performing, directly or indirectly, useful work via its selectively rotatable output shaft. More particularly, this disclosure relates to an improved clutch-brake for stopping rotation of the PTO output shaft when the PTO clutch is disengaged.

BACKGROUND

The use of a power takeoff device (herein referred to by its common abbreviation “PTO”) in association with truck or other vehicle (or stationary engine) transmissions is generally known. Generally speaking, such PTO's often include an input gear, an output gear and a mechanism for engaging the input gear with the output gear so as to rotate the output shaft of the PTO to power an auxiliary device to perform useful work when desired. The mechanism also provides a means for disengaging the input gear and the output gear.

In certain conventional designs, the input gear of the PTO is constantly engaged with the appropriate gear in the vehicle's transmission when installed on the vehicle and is, thus, continuously turning whenever that gear in the vehicle's transmission is turning. In order to provide for selective rotation of the output shaft of the PTO (associated with the output gear), a clutch mechanism is frequently provided between this input gear of the PTO and the output gear. When this output shaft is rotated, useful auxiliary work can be performed. For example, the output shaft may be connected to a hydraulic pump that may be used to operate auxiliary equipment, such as garbage compacting bodies, dump bed bodies (a/k/a, “dump trucks”), garbage trucks or trailers, winches, post hole diggers, and the like. Example PTOs are disclosed in U.S. Pat. No. 5,542,306, issued Aug. 6, 1996; U.S. Pat. No. 7,070,036, issued Jul. 4, 2006; and U.S. Pat. No. 7,159,701, issued Jan. 9, 2007.

One type of conventional PTO clutch is operated through an aligned multi-disc stack arrangement located between the shaft of the PTO and the gears of the PTO which engage with the gears of the truck's transmission. When an axial force is applied to the disc stack, the individual discs in the stack are forced together such that the interfacial friction between the discs cause the shaft to be rotationally joined to the rotating gears. Engagement and disengagement of the clutch is frequently effected by an electrically operated solenoid valve arrangement, the switch for which is frequently located (along with an appropriate warning light) in the cab of the truck.

SUMMARY

A problem with many clutch-operated PTO's is that, for one or more reasons, when disengagement of the PTO is attempted or believed to have been accomplished, thereby presumably relieving the inter-disc friction among the discs and stopping shaft rotation, the discs continue to exhibit sufficient frictional connection to create continued, unwanted rotation of the PTO shaft. Such a condition may exist due to, for example, one or more discs being out of tolerance or contamination in the disc stack. Inadvertent shaft rotation, furthermore, may occur not only through continued rotation after the activation of the PTO control from its engaged to its disengaged position, but later, at random times after initial disengagement has been successfully achieved.

Embodiments of the present disclosure provide an improved clutch-brake for a PTO unit. In accordance with a first embodiment of the present disclosure, a dual direction clutch-brake with a clutch cup is disclosed. When moved in one direction, the clutch cup engages a clutch pack resulting in the input shaft being engaged with the output shaft. When the clutch cap is moved in the opposite direction, the clutch cup engages a braking member, for example a cover or casing of the PTO unit, which applies a force to the output shaft opposite to the direction of rotation and thereby stops the output shaft from rotating. Useful characteristics include a clutch-brake with fewer components than other types of PTO output shaft brakes, improved output shaft braking function, simplified manufacturing, lower manufacturing costs, and improved wear characteristics over existing PTO output shaft brakes.

This summary is provided to introduce a selection of the concepts that are described in further detail in the detailed description and drawings contained herein. This summary is not intended to identify any primary or essential features of the claimed subject matter. Some or all of the described features may be present in the corresponding independent or dependent claims, but should not be construed to be a limitation unless expressly recited in a particular claim. Each embodiment described herein is not necessarily intended to address every object described herein, and each embodiment does not necessarily include each feature described. Other forms, embodiments, objects, advantages, benefits, features, and aspects of the present disclosure will become apparent to one of skill in the art from the detailed description and drawings contained herein. Moreover, the various apparatuses and methods described in this summary section, as well as elsewhere in this application, can be expressed as a large number of different combinations and subcombinations. All such useful, novel, and inventive combinations and subcombinations are contemplated herein, it being recognized that the explicit expression of each of these combinations is unnecessary.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to one or more embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended; any alterations and further modifications of the described or illustrated embodiments, and any further applications of the principles of the disclosure as illustrated herein are contemplated as would normally occur to one skilled in the art to which the disclosure relates. At least one embodiment of the disclosure is shown in great detail, although it will be apparent to those skilled in the relevant art that some features or some combinations of features may not be shown for the sake of clarity.

Any reference to “invention” within this document is a reference to an embodiment of a family of inventions, with no single embodiment including features that are necessarily included in all embodiments, unless otherwise stated. Furthermore, although there may be references to “advantages” provided by some embodiments, other embodiments may not include those same advantages, or may include different advantages. Any advantages described herein are not to be construed as limiting to any of the claims.

Specific quantities (spatial dimensions, temperatures, pressures, times, force, resistance, current, voltage, concentrations, wavelengths, frequencies, heat transfer coefficients, dimensionless parameters, etc.) may be used explicitly or implicitly herein, such specific quantities are presented as examples only and are approximate values unless otherwise indicated. Discussions pertaining to specific compositions of matter, if present, are presented as examples only and do not limit the applicability of other compositions of matter, especially other compositions of matter with similar properties, unless otherwise indicated.

Depicted inFIGS. 1 and 2is a power takeoff unit (PTO)50with a clutch-brake100according to one embodiment of the present disclosure. PTO50includes a housing52and a customer/input gear54. Customer/input gear54is coupled to input ratio gear56. In practice, ratio gear56is frequently provided with a specific gear ratio applicable to the needs of the particular vehicle (or stationary apparatus) transmission and the selected torque output desired. Cone bearings58are also provided. PTO50also includes power takeoff output shaft60, which is connectable to some other machinery, such as a hydraulic fluid pump (not shown) operated by rotation of shaft60. Alternatively, shaft60may be directly connected to a hydraulic pump or may be connected to any auxiliary equipment operable by the shaft60.

Associated with the operation of gear56and shaft60, is a connect-disconnect clutch mechanism62. Such a mechanism includes a clutch cup102and a clutch input gear64. Attached to clutch input gear64is a clutch pack66, which includes a plurality of friction discs. Clutch cup102and a clutch hub106are attached to shaft60so as to correspondingly rotate whenever shaft60rotates. Hub106is non-movably attached to shaft60and clutch cup102is slidably attached in the axial direction to shaft60.

Constantly rotating with the rotating gears of the truck's transmission and, thus, not permanently attached or connected to shaft60, are customer/input gear54, input ratio gear56and clutch input gear64. This sub-assembly is allowed to rotate about shaft60on bearings68whenever the PTO is engaged with the rotating gears of the vehicle's transmission, even when the clutch mechanism has successfully achieved its disengage position so that shaft60is not rotating. Clutch input gear64is attached to clutch pack66. Spacer discs in clutch pack66rotate whenever clutch input gear64rotates. The spacer disks in clutch pack66are located so as to be interspersed with the friction disks in clutch patch66. The friction discs in clutch pack66, which are attached to clutch hub106, do not generally rotate when the clutch mechanism is disengaged. As such, rotating spacer discs merely rotate between their respective friction discs until compressed into contact with the friction discs by clutch cup102to cause, via friction in the stack, all of the discs in the clutch pack to rotate together. Selective rotation of shaft60can thereby be achieved.

Clutch cup102moves axially along the output shaft60. Output shaft60and clutch cup102are rotationally coupled by pin121and rotate together. The axial travel of the clutch piston108is restrained by the output bearing110and/or snap ring(s)112.

In other embodiments, alternate means of rotationally coupling the output shaft and the clutch cup are used, such by using splines as depicted inFIG. 3. In still further embodiments, restraining the axial travel of the clutch piston is accomplished using alternate means such as, for example, spacers.

Located between piston108and clutch cup102is piston cavity124. Piston cavity124is in fluidic communication with hydraulic channel122, which is also in fluidic communication with solenoid120.

To assemble clutch-brake100, the clutch piston108and clutch cup102slip on the output shaft60and are sealed with one or more O-rings. Thereafter, the guide pin between output shaft60and clutch cup102presses into the output shaft60. The clutch cup102has a slot in which the guide pin(s) between output shaft60and clutch cup102slides or is received. The output cover118then slides into the housing52and is sealed with one or more O-rings. The friction element(s)116may be splined to the clutch cup102and may be separated with steel plates (not shown).

In use, an operator commands the solenoid120to increase hydraulic fluid pressure within hydraulic channel122. Since hydraulic channel122is in fluidic communication with piston cavity124, the hydraulic pressure within piston cavity124increases. The axial location of clutch piston108along output shaft60does not change since clutch piston108is restrained by the output bearing110and/or spacer(s)112, and the increasing hydraulic pressure within piston cavity124forces clutch cup102away from clutch piston108. For example, as the hydraulic pressure within piston cavity124increases, clutch cup102moves to the right as depicted inFIG. 2and moves against the clutch pack66, thereby engaging the clutch input gear64with the clutch hub106and output shaft60. O-rings119are optionally included to enhance the containment of hydraulic fluid within piston cavity124.

When solenoid120is commanded to decrease and/or remove hydraulic pressure from hydraulic channel122, the clutch deactivation spring114forces the clutch cup102away from the clutch pack66and disengages clutch pack66. For example, as the hydraulic pressure within piston cavity124decreases, clutch cup102moves to the left as the depicted inFIG. 2to disengage clutch pack66. As clutch cup102moves away from the clutch pack66(to the left as depicted inFIG. 2), clutch cup102is pressed into a braking surface, which in the illustrated embodiment is a surface of the output cover118, disengaging the clutch and engaging a braking mechanism. The same member (clutch cup102) that engages the clutch by pressing on the clutch pack66also engages the braking mechanism as it withdraws (or becomes fully withdrawn) from clutch pack66. As such, the disengagement of the clutch and engagement of the clutch brake occur simultaneously and the possibility of having a failure state with the clutch and the clutch brake engaged at the same time is greatly reduced, if not eliminated.

The friction between the output cover118and the clutch cup102creates a braking force that is proportional to the force of the deactivation spring114multiplied by the coefficient of friction, multiplied by the number of active faces, multiplied by the effective contact face radius. The braking torque is transmitted from the clutch cup102to the output shaft60through, for example, a guide pin (not depicted). Optionally, friction element(s)116may be positioned between output cover118and clutch cup102and attached to either cover118and/or clutch cup102to provide additional frictional surfaces for creating the braking force.

Unwanted rotation of shaft60is at least inhibited, if not completely eliminated, by clutch-brake100, which applies braking force to shaft60to prevent rotation of shaft60when the clutch is disengaged.

In at least one embodiment, when the PTO is turned on the hydraulic pressure is present allowing for engagement of the clutch and simultaneous disengagement of the clutch-brake100. When the PTO is turned off, hydraulic pressure is not present and clutch-brake100is engaged by spring114to stop the rotation of the PTO shaft60. This feature facilitates clutch disengagement and brake engagement in response to hydraulic leaks or other malfunctions resulting in loss of hydraulic pressure.

Depicted inFIG. 3is a power takeoff unit (PTO)51with a clutch-brake200according to another embodiment of the present disclosure. PTO51is operably connectable to a transmission and engine, and includes a housing53and a power takeoff output shaft61, which is connectable to other machinery, such as hydraulic fluid pumps or electrical generators (not shown) operated by rotation of shaft61. Alternatively, shaft61may be directly connected to a hydraulic pump or may be connected to any auxiliary equipment operable by the shaft61.

PTO51also includes a connect-disconnect clutch mechanism63, which includes a clutch cup202and an input shaft65. Attached to input shaft65is a clutch pack67, which includes a plurality of friction discs. Clutch cup202and a clutch hub206are attached to shaft61so as to correspondingly rotate whenever shaft61rotates. Hub206is non-movably attached to shaft61and clutch cup202is slidably attached in the axial direction to shaft61. Typically rotating with the rotating gears of the engine's transmission and, thus, not permanently attached or connected to shaft61, is input shaft65.

Input shaft65is attached to clutch pack67. Spacer discs in clutch pack67rotate whenever input shaft65rotates. The spacer disks in clutch pack67are located so as to be interspersed with the friction disks in clutch patch67. The friction discs in clutch pack67, which are attached to clutch hub206, are generally intended to not rotate when the clutch mechanism is disengaged. As such, rotating spacer discs are generally intended to merely rotate between their respective friction discs until compressed into contact with the friction discs by clutch cup202to cause, via friction in the stack, all of the discs in the clutch pack to rotate together. Selective rotation of shaft61can thereby be achieved.

Clutch cup202moves axially along the output shaft61. Output shaft61and clutch cup202rotate together, and the axial travel of the clutch piston208is restrained, directly or indirectly, by the output bearing210.

Connected to housing53is at least one friction element230, which is aligned with and adapted to engage with a portion of clutch cup202. An optional mounting member (such as plate231) may be used to connect friction element230to housing53, and clutch cup202may optionally be attached to friction elements that rotate with clutch cup202.

Located between piston208and clutch cup202is piston cavity224. Piston cavity224is in fluidic communication with hydraulic channel222, which is also in fluidic communication with solenoid220.

In use, an operator commands the solenoid220to increase hydraulic fluid pressure within hydraulic channel222. Since hydraulic channel222is in fluidic communication with piston cavity224, the hydraulic pressure within piston cavity224increases. The axial location of clutch piston208along output shaft61does not change since clutch piston208is restrained by the output bearing210, and the increasing hydraulic pressure within piston cavity224forces clutch cup202away from clutch piston208. For example, as the hydraulic pressure within piston cavity224increases, clutch cup202moves to the right as depicted inFIG. 3and moves against the clutch pack67, thereby engaging the input shaft65with the clutch hub206and output shaft61. O-rings219are optionally included to enhance the containment of hydraulic fluid within piston cavity224.

When solenoid220is commanded to decrease and/or remove hydraulic pressure from hydraulic channel222, the clutch deactivation spring214forces the clutch cup202away from the clutch pack67and at least partially disengages clutch pack67. For example, as the hydraulic pressure within piston cavity224decreases, clutch cup202moves to the left as the depicted inFIG. 3to disengage clutch pack67. As clutch cup202moves away from the clutch pack67(to the left as depicted inFIG. 3), clutch cup202is pressed into a braking surface, which in the illustrated embodiment is friction element230, disengaging the clutch and engaging a braking mechanism. The same member (clutch cup202) that engages the clutch by pressing on the clutch pack67also engages the braking mechanism as it withdraws (or becomes fully withdrawn) from clutch pack67. As such, the disengagement of the clutch and engagement of the clutch brake occur simultaneously and the possibility of having a failure state with the clutch and the clutch brake engaged at the same time is greatly reduced, if not eliminated.

Unwanted rotation of shaft61is at least inhibited, if not completely eliminated, by clutch-brake200, which applies braking force to shaft61to prevent rotation of shaft61when the clutch is disengaged.

While illustrated examples, representative embodiments and specific forms of the invention have been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive or limiting. The description of particular features in one embodiment does not imply that those particular features are necessarily limited to that one embodiment. Features of one embodiment may be used in combination with features of other embodiments as would be understood by one of ordinary skill in the art, whether or not explicitly described as such. Dimensions, whether used explicitly or implicitly, are not intended to be limiting and may be altered as would be understood by one of ordinary skill in the art. Exemplary embodiments have been shown and described, and all changes and modifications that come within the spirit of the invention are desired to be protected.