GB2145359A - Manual screw-driving tool - Google Patents

Abstract

A manual screw driving tool comprises a handle 25 shaped so that the user can rotate and impart an axial thrust to a cage 3 which accommodates in a blind recess 23 the end of a shaft 2 which extends to a chuck 21. The cage 3 can be coupled to the shaft through a first ratchet mechanism 1, 4 or by way of a further ratchet mechanism 5, 42 and planetary gearing 7, 61, 81 when a sleeve 8 which is connected to the reaction member of the gearing is held against rotation. The ratchet mechanisms can be reversed by turning a selecting sleeve 9. <IMAGE>

Description

SPECIFICATION Manual screw-driving tool The invention relates to a manual screw-driving tool of the kind comprising a sun-and-planet gear which transmits the rotary driving movement from a gripping handle to the drive shaft of a screwdriver blade, screwdriver nut or the like and of which the drive output member, for example the sunwheel, is rotationally rigid with the drive shaft whilst its drive input member, for example a planet carrier, is connected to the gripping handle through a ratchet mechanism which can be switched between either direction of rotation, and of which the reaction member for example the housing, is adapted to be manually held against rotation, the drive shaft being adapted to be coupled directly with the gripping handle through a further ratchet mechanism which is also adapted to be switched between either direction of rotation but which is effective in the locking sense only when the housing of the sun-and-planet gear is freely rotating, i.e. idling.

A manual screw-driving tool of ths type is known (US-PS 3299725). In this known tool the two ratchet mechanisms are arranged directly adjacent to each other on that side which is designed for the connection thereto of a screw-driver nut whereas the sun-and-planet gear is arranged on the opposite side. The gripping handle is attached in the form of a lever arm to the cage in which both ratchets are accommodated. The connector socket for the screwdriver nut is mounted on the end face of a locking wheel which is positively connected to the drive shaft. However high axial forces must be able to be applied when driving slotted and cruciform-recessed screws in order to maintain the screwdriver bit in engagement with the screw.

It is the aim of the invention to provide a manual screw driving tool which not only allows high torques to be transmitted to the screwdriver bit at differential transmission ratios but by means of which at the same time axial forces can also be transmitted without applying undue loads to the transmission gear.

According to the invention this problem is solved due to the fact that the gripping handle which is specially constructed for simultaneous transmission of a rotary movement and an axial force, in particular in the form of a pistol grip, is arranged at the end of the tool which is remote from the screwdriver bit and rotationally rigidly secured frontally on a cage accommodating the movable locking parts of the two ratchet mechanisms, and that the through-extending drive shaft has that end thereof which is remote from the screwdriver bit rotatably mounted and axially supported in that end of the said cage which is adjacent the grip.

With the manual screw-driving tool according to the present invention the axial force which is applied to the pistol grip is transmitted direct through the cage to the drive shaft so that the rotatable parts are in no way affected by this force. Due to the force application in the pistol grip it is possible to apply manually, and moreover by one hand, both the axial force and also the driving torque.

This leaves the other hand free for blocking the housing of the planetary gear in order to operate the tool at the gear transmission ratio.

According to a further development of the invention a common connecting bush or sleeve is provided on the cage for both ratche mechanisms.

According to another development of the invention a thrust ring bearing radially and axially on the drive shaft and the ratchet wheels is provided in the cage between a ratchet wheel of the direct drive engaging ratchet mechanism which is rotationally rigid on the drive shaft and a wheel of the other ratchet mechanism which is connected with the drive input part (web) of the sun-and-planet gear.

These two developments provide for easy handling, easy running and also for compact construction without there being any need for the individual components to be very heavy or massive.

In order to enable the screwdriving tool being operated with and without gear transmission in one and the same operatively connected position simply by blocking or releasing the middle part of the sun-and-planet gear a further development of the invention resides in the provision of unlocking or release elements on the drive shaft or on the rear side of the locking pawls for the locking members, here in the form of pawls, of the direct-drive transmitting ratchet mechanism which consists of a locking or ratchet wheel and various locking pawls, which unlocking or release elements release the pawls from their operative blocking position on rotation of the grip with blocked middle part.

These unlocking or release elements may be ascending ramps on which, or whereby the pawls run up.

The invention is hereinafter more particularly described with reference to drawings illustrating one embodiment thereof by way of example and in which: Figure 1 is an axial section of a manual screwdriving tool.

Figure 2 is a cross section taken on the line A-B of Figure 1, being a section through a first ratchet mechanism.

Figure 3 is a cross section taken on the line C-D of Figure 1, being a section through a second ratchet mechanism.

Figure 4 is a side view of the first ratchet mechanism, and Figure 5 is a section taken on the line E-F of Figure 1, being a section through a sun-and-planet gear of the tool.

A drive shaft 2 carries at one end thereof a chuck 21 in which screwdriver bits, for example a bit 22 for cruciform recessed screws can be fitted and tightened. The other end of the through-extending drive shaft 2 is rotatably mounted in a blind recess 23 formed in a cage 3 and engages a thrust ball 24.

The end of the cage 3 which receives the end of the through-extending drive shaft 2 is rotationally rigidly secured in a pistol grip 25.

The portion of cage 3 which extends away from the pistol grip 25 is constructed in the form of a sleeve and accommodates two laterally adjacent ratchet mechanisms. A ratchet or locking wheel 1 of the first of these mechanisms is non-rotatably mounted on drive shaft 2. As will be seen from Figures 2 and 4, the locking teeth on the wheel 1 are of different configuration in the two axial halves of the wheel, and more specifically, in each case one flank of each locking tooth has a rising edge 12, 13 which ensures that the locking wheel 1 will be effective in the locking sense in one direction only in each case whilst applying a releasing or unlocking action to a respectively associated locking pawl 4 in the opposite direction of rotation.

The rising edges or ramps 12, 13 are associated with the locking pawls 4 in such a way that for the locking pawl which has a locking effect during right hand rotation they will apply an unlocking action during left hand rotation whilst for a pawl which locks on left hand rotation they have a releasing action during right hand rotation. The locking pawls 4 which are pivotally mounted and retained in recesses 31 respectively of cage 3 are biased by leaf springs 41 urging them in the direction towards the ratchet wheel 1. The locking mechanism 1, 3, 4, 41 is surrounded by a switching sleeve 9 which is provided internally with cut-outs 91 to accommodate the free legs of the locking pawls 4 respectively.

Figure 2 shows the sleeve 9 in a rotational position in which the free leg of the left hand locking pawl 4 has moved into recess 91 so that the beak of the pawl 4 can engage with the teeth of the ratchet wheel 1. The right hand locking pawl on the other hand has its free leg urged into a cut-out or recess 32 of the cage 3 so that its operative beak is kept out of engagement with the teeth of the ratchet wheel 1. When the sleeve 9 occupies this position no relative rotation of cage 3 and ratchet wheel 1 in the anticlockwise direction is possible. In the clockwise direction however such relative rotation can occur because the ramps 12 lift the pawl 4 out of engagement.

The second ratchet mechanism which is axially spaced from the first ratchet mechanism towards the chuck 21 is constructed similarly to the first ratchet mechanism but with the difference that here the rising or ramp edges 43 are arranged at the beaks of the locking pawls 42. Such an arrangement would also be feasible with the first ratchet mechanism. Furthermore, in the second ratchet mechanism, the ratchet wheel 5 is rotatably mounted about said drive shaft 2.

A planet carrier of a sun-and-planet gear is integrally connected with the ratchet wheel 5 and carries planet wheels 61 which are in mesh with a sunwheel 7 which is non-rotatably mounted on a drive shaft 2, and with a reaction member formed by internal annulus gearing 81 of a housing 8. The housing is constructed as a grip-sleeve with longitudinal grooves to facilitate gripping, and is mounted rotatably about the drive shaft 2.

For axial and radial support of the individual parts a spacer disc 10 is rotatably mounted about the shaft 2 within the cage 3 and is located between the ratchet wheel 1 and ratchet wheel 5 and a two-part, or split spacer ring 11 is located between a flange part of the carrier 6 and cage 3 and between a connector portion connecting the ratchet wheel 5 with the carrier 6 and the cage 3.

When the switching sleeve 9 occupies the rotational position thereof shown in the drawings the tool is set for left hand rotation. If torque is applied to cage 3 by means of the pistol grip 25 it is transmitted via the locking pawl 4 shown on the left hand side in Figure 2, to ratchet wheel 1 and thus directly to drive shaft 2. For this kind of drive transmission at a transmission ratio of 1:1 the sunand-planet gear is freewheeling, or idling. However, if the grip sleeve 8 is held against rotation the second ratchet mechanism comes into effect.

The rotation movement applied to the pistol grip 25 is then transmitted via cage 3 and pawl 42 to ratchet wheel 5 which drives the planet carrier 6 with the planet wheels 61. These roll around in engagement with the internal gearing 81 of the sleeve 8 which is kept stationary and therefore drive the sunwheel 7 at a given transmission ratio.

The rotational movement thereby applied to drive shaft 2 has a higher angular velocity than the rotational movement which could be transmitted to shaft 2 via the first ratchet mechanism. For this reason ratchet wheel 1 turns anticlockwise relative to cage 3 and therefore also relative to the left hand pawl 4 with the result that this pawl is levered out of engagement with the ramp edges 12.

Simply by holding fast or releasing the sleeve 8 the tool is thus switched over from 1:1 transmission ratio to a higher gear ratio.

Since the component parts of the ratchet mechanism which are functionally involved in the geared torque transmission are completely relieved of the transmission of the axial load, due to the fact that the drive shaft 2 extends continuously from the chuck 21 to the pistol grip 25 the manual screw driver tool has a smooth and easy action. Moreover, because of the absence of an axial loading of those parts which are functionally involved in drive transmission and to the ratchet mechanisms it is possible to dispense with expensive axial support bearings. The whole tool can thus be very simply constructed in compact form. Furthermore, it is easy to operate because axial force as well as rotational movement can be applied through the pistol grip and the other hand of the operator remains freely available for the task of switching the tool over from direct transmission to geared drive transmission merely holding the sleeve fast or releasing the same.

Claims (6)

1. A manual screw driving tool of the kind comprising a sun-and-planet gear which transmits the rotary driving movement from a gripping handle to the drive shaft of a screwdriver bit or the like and of which the drive output member, e.g. sunwheel, is rotationally rigid with the drive shaft whilst the drive input member, e.g. the planet carrier is connected with the gripping handle via a ratchet mechanism which can be switched over in both directions of rotation, and of which the reaction member is adapted to be manually held against rotation, the drive shaft being adapted to be directly drivingly coupled with the gripping handle through a further ratchet mechanism which is also adapted to be switched over to both directions of rotation and which is effective in the locking sense only when the middle part of the planetary gear is freewheeling, characterised in that the gripping handle which is designed for simultaneous transmission of a driving torque and an axial force is arranged at the tool end which is remote from the screwdriver bit and frontally secured in rotationally rigid manner to a cage housing the movable locking elements of the two ratchet mechanisms and in that the end of the through-extending drive shaft which is remote from the screw-driver bit is rotatably mounted and axially supported in that end of the cage which is adjacent the grip.

2. A tool according to Claim 1, characterised by the provision on the cage of a switching sleeve which is common for both ratchet mechanisms.

3. A tool according to Claim 1 or 2 characterised in that a supporting ring giving radial and axial support for the drive shaft and the ratchet wheels is provided in the cage between a ratchet wheel which is rigidly mounted on the drive shaft and is a component part of the direct drive transmitting ratchet mechanism, and a ratchet wheel of the other ratchet mechanism which is connected to a planet carrier of the sun-and-planet gear.

4. A tool according to any one of Claims 1-3 characterised by unlocking elements for the locking elements of the further ratchet mechanism, said locking elements being in the form of pawls and the unlocking elements are disposed on the ratchet wheel of the further ratchet mechanism or on the rear side of the pawls, said unlocking elements releasing the pawls from the locking position when the handle is rotated and the reaction member is held against rotation.

5. A tool according to Claim 4, characterised in that the unlocking elements are defined by inclined ramps.

6. A manual screwdriving tool comprising the conbination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.