GB2131122A - Torque sensitive couplings - Google Patents

Abstract

A torque sensitive coupling comprises first and second rotary components (27) and (29) having inclined formations (52, 53) arranged such that relative rotation between the two components due to increased torque reaction being transmitted causes relatively axial displacement of the two components against a resilient bias (54). The axial displacement is sensed to control the transmitted torque to a desired preselected maximum level. In a modification, balls are disposed between the inclined formations. <IMAGE>

Description

SPECIFICATION Torque sensitive couplings This invention relates to torque sensitive couplings for mounting in rotary drive arrangements.

In particular, the present invention relates to a torque sensitive coupling adapted to prevent overload.

An object of the present invention is to provide an improved torque sensitive coupling which is reliable, robust and tends to have a long operational life.

According to the present invention a torque sensitive coupling for mounting in association with a rotary drive arrangement having drive motor means and a driven load, comprises a first rotary component drivably connectible to at least a portion of the drive motor means for rotation about an axis, a second rotary component drivably connectible to the driven load and mounted co-axially with the first rotary component, the two rotary components having inclined formations urged axially towards a drive mode by resilient means, the inclined formations being arranged such that in use rotation of one component relatively to the other component due to increased torque reaction being transmitted by the drive arrangement results in relative axial displacement of the two rotary components against the action of the resilient means, and means for sensing when the axial displacement between the two components is. approaching a preselected value.

Preferably, the said means is arranged to activate control activating means arranged to control said portion of the drive motor means.

Preferably, said portion of the drive motor means comprises a hydraulic motor and the control activating means comprises a valve for reducing the pressurised feed to the hydraulic motor when the sensor means senses the axial displacement is approaching the preselected value.

Preferably, stop means are provided for limiting the extent of axial displacement to a preselected value.

Preferably, the two rotary components have engageable dog teeth, the sides of the teeth being inclined.

Alternatively, the inclined formations are constituted by substantially cone shaped recesses, roller elements being mounted in the recesses.

Preferably, the roller means is constituted by a number of spheres.

By way of example only, two embodiments of the present invention will be described with reference to the accompanying drawings, in which: Figure 1 is an incomplete perspective view of a drive arrangement indicating a portion of a hydraulic circuit diagram and including a torque sensitive coupling constructed in accordance with a first embodiment of the present invention.

Figure 2 is a side view of the torque sensitive coupling of Fig. 1, the coupling being drawn on a much enlarged scale; Figure 3 is a longitudinal section of the coupling of Fig. 2; Figure 4 is a longitudinal section of a torque sensitive coupling constructed in accordance with a second embodiment of the present invention; and Figure 5 is a view of the coupling of Fig. 4, a part being removed to expose the inner workings.

Fig. 1 shows a drive arrangement for an underground mine roadway excavating machine having a driven rotary cutting head 1 mounted for rotation about an axis 2 on one end of a pivot arm 3 which is articulatedly mounted at its other end for pivotal movement about an axis 4 on one end of a second pivot arm 5 which in turn is supported at its other end by trunnions (not shown) provided on the machine's body (not shown) for pivotal movement about an axis 6. The pivot arm 3 is pivoted about the axis 4 under the action of a hydraulic drive comprising a hydraulic drive motor 7, a torque sensitive coupling 8, a reduction gearbox 9 and a gearwheel 10 drivably mounted on an output shaft 11. The gearwheel 10 drivably engages a driven gearwheel 1 2 rotatable about the axis 4 and fixedly connected to the pivot arm 3.The pivot arm 5 is pivoted about the axis 6 under the action of a hydraulic drive comprising a hydraulic drive motor 13, reduction gearbox 14 and a gearwheel 1 5 drivably mounted on an output shaft 16. The gear-wheel 1 5 drivably engages a driven gearwheel 1 7 rotatable about the axis 6 and fixedly connected to the pivot arm 5.

The rotary cutting head is rotated by a motor (not shown) mounted on the machine body and having an output shaft along the axis 6. Gearing (not shown) within the arms 3 and 5 drivably connects the motor shaft with the cutting head.

The drive motors 7 and 14 are actuated to pivot the arms 3 and 5 until the rotating cutting head 1 is a desired distance away from the main axis 6. The drive motor 7 then is hydraulically locked in position maintaining a desired fixed relationship between the two pivot arms 3 and 5 while the drive motor 1 3 is actuated to pivot the cutting head 1 around the main axis 6 to form a curved roadway profile suitable for receiving arch type roadway supports (not shown). A brake (not shown) may be provided to maintain the fixed relationship between the two arms.

The supply of pressure fluid required to drive the motor 1 3 is fed via line 18 from a pump 1 9 having an inlet line 20 from tank 21. Exhaust fluid is returned to tank via line 22. Operation of the pump 1 9 is controlled via an activating control 23 arranged to sense a desired operational condition of a relief valve 25 via line 24, the operational condition of this being dependent upon the operational state of the torque sensitive coupling 8 as will be explained later in this specification.

The hydraulic system for feeding the motor 7 is now shown in Fig. 1.

Figs. 2 and -3 show the torque sensitive coupling 8 of Fig. 1 in more detail. A first rotary component 27 is shown to comprise a generally cylindrical, hollow body assembly having one end provided with an internally splined bush 30 drivably and slidably mounted on the output shaft 28 of the motor 7. The inner wall of the generally cylindrical body assembly is provided with a first abutment stop 31 for retaining engagement by one end of a spring 54 constituted by dished washers 32, and a second abutment stop 33 for engagement by an abutment shoulder 34 provided on a second rotary component 29.

The splined bush 30 is provided with axially extending dog teeth 35 drivably engageable by dog teeth 36 provided on the second rotary component. Both sets of dog teeth are provided with inclined edges constituting inclined formations 52 and 53, respectively.

In addition, the second rotary component 29 is shown to comprise a flanged bush having an internal spline drivably and fixedly mounted on a drive shaft 61 to the gearbox 9. The flange provides an abutment shoulder for engaging the end of the spring 54 remote from the aforementioned stop 31. A bearing 40 built into the flange facilities relative rotation of the spring 54 and the second rotary component. The flange also carries abutment shoulder 34 engageable by the abutment stop 33 to limit relative axial displacement of the two rotary components. Axially extending dog teeth 36 are provided on the radially outer margin of the flange.

An outwardly extending flange 38 is provided on the first rotary component 27 in order to activate the relief valve 25 discussed earlier with reference to Fig. 1 but not shown in Figs. 2 or 3. In use, upon sufficient relative axial displacement between the two rotary components the flange 38 abuts a control activating element on the relief valve which thereby is urged into the pressure fluid exhausting mode. This is sensed by control 23 via line 24 and the operation of pump 1 9 is suitable adjusted to reduce the flow of pressurised fluid to the motor 1 3 and thereby reduces the driving torque transmitted by the drive motor 13.

In use, the torque sensitive coupling 8 transmits the torque reaction between the drive motor and the driven load, the sets of dog teeth 35, 36 being urged into drivably engagement by the resilient means 54, 32.

Upon the transmitted torque reaction increasing the first rotary component tends to rotate relatively to the second rotary component by an amount proportional to the level of the transmitted torque reaction. The relative rotational movement between the two components is achieved by the inclined edges 52 of the dog teeth 35 sliding up the inclined edges 53 of the dog teeth 36. Although the sets of dog teeth 35, 36 tend to be relatively axially displaced apart as the first component rotates relatively to the second component they are maintained in drivable engagement by the action of the spring 54. Upon the torque reaction increasing such that it approaches a preselected desired maximum valve, the abutment flange 38 is arranged to contact a control activating element of the relief valve 25 to move the valve to its exhausting mode.

Thus, the pressurised fluid feed to the drive motor 1 3 is reduced to maintain the transmitted torque reaction to within a desired maximum level. Upon the transmitted torque reaction falling due to the reduced driving action, the two components tend to be relatively displaced such that the flange 38 breaks contact with the control activating element of the relief valve which thereby moves into its non exhausting mode permitting normal drive conditions.

Figs. 4 and 5 show a second embodiment of torque sensitive coupling in which the dog teeth of the first described embodiment are dispensed with and the inclined formation is constituted by a plurality of generally conical recesses 50 and 51 formed in the splined bush 30 of the first component 27 and in the flange of the second component 29, respectively. A sphere 52 is mounted in each pair of associated recesses 50, 51.

In use of the second embodiment, an increased transmitted torque reaction tends to cause the relative rotation between the two rotary components such that spheres tend to roll up the inclined surfaces of the conical recesses thereby axially displacing the first component relatively to the second component. The further operation of the second embodiment of coupling is similar to that previously described with reference to Figs. 1, 2 and 3. The same reference numerals have been used in Figs. 4 and 5 for similar items to those described with reference to Figs. 1, 2 and 3.

In Fig. 5 the second component 29 has been omitted to expose the spheres 52 and recesses 50.

In both the described embodiments the stop means 33, 34 limit axial displacement of the first component to ensure the two components cannot become totally disengaged.

Claims (8)

1. A torque sensitive coupling for mounting in association with a rotary drive arrangement having drive motor means and a driven load, comprising a first rotary component drivably connectible to at least a portion of the drive motor means for rotation about an axis, a second rotary component drivably connectible to the driven load and mounted co-axially with the first rotary component, the two rotary components having inclined formations urged axially towards a drive mode by resilient means, the inclined formations being arranged such that in use rotation of one component relatively to the other component due to increased torque reaction being transmitted by the drive arrangement results in relative axial displacement of the two rotary components against the action of the resilient means, and means for sensing when the axial displacement between the two components is approaching a preselected value.

2. A coupling as claimed in claim 1, in which the said means is arranged to activate control activating means arranged to control said at least portion of the drive motor means.

3. A coupling as claimed in claim 2, in which said of the drive motor means comprises a hydraulic motor and the control activating means comprises a valve for reducing the pressurised feed to the hydraulic motor when the sensor means senses the axial displacement is approaching the preselected value.

4. A coupling as claimed in claim 1, 2 or 3, in which stop means are provided for limiting the extent of axial displacement to a preselected value.

5. A coupling as claimed in any one of the preceding claims, in which the two rotary components have engageable dog teeth, the side of the teeth being inclined.

6. A coupling as claimed in any one of the preceding claims 1 to 4, in which the inclined formations are constituted by substantially cone shaped recesses, roller elements being mounted in the recesses.

7. A coupling as claimed in claim 6, in which the roller means is constituted by a number of spheres.

8. A torque sensitive coupling substantially as described herein and substantially as shown in Figs. 1, 2 and 3 or Fig. 4 and 5 of the accompanying drawings.