GB2095782A - A transmission - Google Patents

Abstract

A transmission comprises a driving shaft 3, a driven shaft 7, a gear 9 arranged for rotation with the shaft 7 and for axial displacement along the shaft 7. The gear 9 can be displaced into engagement with a manually operable drive in the form of a worm 17 and a worm wheel 13 which is freely rotatable on the shaft 7. Bores 15 on the gear 9 engage pins on the worm wheel 13. In that condition, the gear 9 can be rotated manually by the worm 17 which can be driven by a crank. In the arrangement described, the gear 9 is a set of gears co-operating with an intermediate shaft 6 to provide more than one transmission ratio when the shaft 7 is being driven by the shaft 3. The shaft 7 can be used for driving a test stand injection pump, the initial position of which can be set manually through the manually operable drive 17, 13, 14 and 15. <IMAGE>

Description

SPECIFICATION A transmission State of the art The invention originates from a transmission according to the preamble to the main claim.

Transmissions are already known which have a driving shaft and a driven shaft. Moreover, the separation between the driving and driven shafts takes place by means of a clutch whereby, after actuating the clutch, a free gear can be selected.

These transmissions have the disadvantage that as regards the clutch linings it is a question of parts that wear out and that the clutches are expensive as regards manufacture and maintenance. If the driving shaft is to be operable manually, then further devices need to be provided which prevents the drive from taking place from both ends.

Advantages of the invention As opposed to this, the transmission in accordance with the invention comprising the characterising features of the main claim has the advantage that the function of driving through the complete drive and driving through the worm shaft are forcibly locked and cannot therefore be performed simultaneously. Thus, without any further safety provisions, a protection is provided for the transmission and for the operating personnel. By using a worm drive it is possible to achieve a large transmission of force so that even machines which are movable with difficulty can be driven.

Advantageous further developments and improvements of the transmission set forth in the main claim are made possible by the measures set forth in the sub-claims. Thus, it is advantageous to provide the driven shaft with grooves, in which the gear wheel engages, in the region of the displaceable gear wheel. By this measure, a more certain and more simple guiding of the gear wheel is possible. However, according to application, even raised portions on the driven shaft, splined shafts or cornered shafts are of advantage. It is also preferable to arrange the worm wheel of the worm drive on the driven shaft by means of a roller bearing. In so doing, a separate shaft for the worm wheel and further bearings therefor is unnecessary. In order to make the transmission ratio variable, it is advantageous to provide an intermediate shaft.The displacement of the gear wheel preferably takes place by means of a shift device. Preferably, the gear wheel has outwardly projecting pins engaging in the bores of the gear wheel in order to guarantee a force-transmitting connection. According to the application, grooves and cams can also be provided on the worm wheel or on the displaceable gear wheel. In order to permit a manual drive, it is favourable to mount a hand crank on the worm shaft.

Drawing An embodiment of the invention is illustrated in the drawing and is described in detail in the following specification.

Description of the embodiment The figure shows a housing 1 in which the transmission is accommodated. A driving shaft 3 which is driven by an electric motor (not shown) is mounted in two bearings 2. A gear wheel 4 mounted on the driving shaft 3 engages in a further gear wheel 5 which is arranged on an intermediate shaft 6. A driven shaft 7 to which is connected the apparatus to be driven, for example the pump of an injection pump test stand, is located above the intermediate shaft 6 between two bearings 8. A movable set of gears 9 which is operatively connected to the gear wheel 5 on the intermediate shaft 6, is located on the driven shaft 7. The set of gears 9 is arranged for movement along a splined shaft 12. A shift device 1 6 serves for moving the set of gears 9.In a first shifting step the larger gear wheel of the movable set of gears 9 engages in a second gear wheel 10 on the intermediate shaft 6. Thus, the transmission ratio of the transmission can be varied by varying the position of the movable set of gears 9. A worm wheel 13 which has pins 1 4 on its periphery, is mounted at the end of the driven shaft 7.

Moreover, a worm shaft 1 7 engages in the worm wheel 13.

If the movable set of gears 9 is displaced still further by means of the shift device 1 6, then the bores 1 5 which are arranged on the end of the movable set of gears 9 facing the worm wheel 1 3 engage the pins 14 on the worm wheel 13 so that the latter is connected to the movable set of gears 9 for the transmission of force. At the same time however, neither of the gear wheels 5 or 10 on the intermediate shaft can engage in one of the gear wheels of the set of gears 9. The worm wheel 1 3 is likewise mounted on the driven shaft 7 in roller bearings 1 8. Thus, the worm wheel 13 has no force transmissive connection with the driven shaft 7.In this condition, no torque can be transmitted to the driven shaft 7 by the worm shaft 1 7 engaging the worm wheel 1 3. Only on displacement of the set of gears 9 will the worm wheel 1 3 be connected to the driven shaft 7 for the transmission of force by the pins 14 and the bores 1 5 wherein the transmission from the set of gears 9 to the driven shaft 7 takes place through the splined shaft 12. Before the connection between the worm shaft 1 7 and the set of gears 9 becomes force transmissive, the set of gears 9 can no longer transmit force to the gear wheels 5 or 10 on the intermediate shaft 6. Thus, the driven shaft 7 can be rotated by the worm shaft 1 7 without the other drive taking part in this operation.

Transmissions of this kind are particularly suitable for pre-stroke setting operations on pumps which are connected to the driven shaft.

The pre-stroke of such pumps may be set exactly thereby. A further advantageous field of application of this transmission is in connection with machine tools when a particular position of the machine tool is to be set manually or mechanically. The worm shaft 1 7 can be driven either by a hand crank or by an auxiliary motor.

Due to the design of the transmission, a protection is provided without further safety precautions since a simultaneous driving by the drive shaft 3 and by the worm shaft 17 is excluded.

The set of gears 9 may be replaced by a single gear if only one transmission ratio between the drive shaft 3 and the driven shaft 7 is required. In that case, the intermediate shaft 6 could be dispensed with.

The drive between the worm wheel and the gears (or gear) 9 need not necessarily be in the form of a positive drive, such as the illustrated pin and bore arrangement, but could also be in the form of a non-positive or frictional drive. Also, the worm drive could be replaced by some other form of unidirectional drive, for example a drive involving a ratchet and pawl mechanism.

The transmission is particularly useful for setting the position of the driving pump of an injection pump test stand.

Claims (12)

1. A transmission comprising a driving shaft, a driven shaft, a gear arranged for rotation with and axial displacement along the driven shaft and a manually operable drive, the gear being displaceable out of engagement with the driving shaft and into engagement with the manually operable drive for rotation thereby.

2. A transmission according to claim 1, in which the manually operable drive comprises a gear wheel mounted for rotation on the driven shaft.

3. A transmission according to claim 2, in which the gear wheel is the worm wheel of a worm drive.

4. A transmission according to claim 2 or claim 3, in which the gear wheel is mounted on roller bearings.

5. A transmission according to any preceding claim, in which the gear associated with the driven shaft is in the form of a set of gears.

6. A transmission according to claim 5, in which an intermediate shaft is provided between the driving shaft and the driven shaft and cooperates with the set of gears to provide different transmission ratios.

7. A transmission according to any one of claims 2 to 6, in which the gear is provided with bores for engagement with pins provided on the gear wheel.

8. A transmission according to any preceding claim, in which the driven shaft and the gear are splined at least over the range of axial displacement of the gear along the driven shaft.

9. A transmission according to any preceding claim, in which means are provided for applying a hand crank in the manually operable drive.

1 0. A transmission according to any preceding claim, in which a gear shift device is provided for displacing the gear, or set of gears, along the driven shaft.

1 A transmission according to any preceding claim, in which the driving shaft is driven by an electric motor.

12. A transmission substantially as herein described with reference to the accompanying drawing.