FIELD OF THE INVENTION

The invention relates to manual screwing tools and in particular reversible ratchet wrenches, and more precisely to a ratchet wrench having two handles for combined or alternative operation.

BACKGROUND OF THE INVENTION

Ratchet Wrenches are widespread in mechanical construction and repair shops for safely loosening or tightening nuts and bolts.

However, two drawbacks have been tried to be solved with a multitude of propositions, but still seem hardly overcome:

PROBLEMS TO BE SOLVED

1. Because the ratchet can only stop backward motion at discrete points (i.e., at tooth boundaries), a ratchet needs a defined amount of backward motion to lock in. But sometimes the space for moving the lever is so limited, that the possible angle for turning the bolt or nut therefore is not achieved. Consequently this backlash - which is limited to a maximum distance equal to the spacing between the teeth - must be minimized, and there are quite a few propositions covering this issue.

But, as early inventions propose finer ratchet gears, these inherit the drawback of less applicable torque, even more so with smooth, toothless ratchets with a high friction surface, or even rubber. Here the pawl mostly stays against the surface at an angle so that any backward motion will cause the pawl to jam against the surface and thus prevent any further backward motion. Since the backward travel distance here is primarily a function of the compressibility of the high friction surface, this mechanism can result in significantly reduced backlash— but quite limited torque.

2. At low torque levels, conventional ratchets may not trap, but alternate in both directions without fastening or finally turning out loose screws or bolts. This is a matter of force to overcome the ratcheting mechanism versus torque restraint of the nut or bolt, but of course as well the backlash problem, whereas each one conflicts with the other— and again solutions with friction mechanisms as in US 5.603.393 .result in poor maximum torque.

3. Since the ratchet works with snapped-on intermediate nuts, the applied torque from a single handle necessarily is not in line with the bolt-head or nut, but engages somewhat above it. This can lead to slipping off the screw head or nut, particularly with unskilled or poorly trained staff. PRIOR ART

However, there had quite a few propositions been made to overcome these problems:

US 6.457.389 (B 1), 6.282.992 (B 1) to Hu, as well as US 6.230.591 (B 1) to Ling at al, 6.131.489 to Yang and US 6.230.591 (B l ) Ling try to solve the ratcheting problem with more elaborate pawl constructions to allow finer gauges and finer denticulation of the cogwheel, so to avoid the problem of less applicable torque. But these constructions demand much more precision in manufacturing and therefore are quite more expensive.

Other solutions, e.g. DE 10 2005 020 609 (A l) and US 7.213.491 (B2), where turning the transmitting nut by radially turning the lever around its axis, require an angle gear that must lock at standard action. These systems are known for being prone to defects when applying higher force, as long as the gearbox does not exceed manageable size.

One viable proposition is known from DE 10 2005 033 309 (A l) , where a second handle is locked in at 180° to the first one. But this is hardly applicable for ordinary purposes, since there must be enough space for both levers and enough room to turn it, which rarely is the case.

SUMMARY OF THE INVENTION

The here disclosed invention therefore refers to a ratchet with two handles, that may be operated together or alternatively. Thereby the deviating torque is neutralized and a reversing movement of bolt or nut overcome by holding one and turning the other handle or by counter-rotating one against the other.

Here the second handle works on a secondary gear, mounted above the turning device. So both handles work in the same direction, but can be put on different angles, so to compensate the deviating torque.

Moreover, the invention comprises telescopically extendible levers, so to quickly change torque or angular travel as to given requirement. DETAILED DESCRIPTION OF THE INVENTION

A secondary gearbox is positioned over a standard ratchet device. The action of a secondary lever above the main ratchet lever is thus transmitted from a secondary ratchet gearwheel, that is turned by the secondary lever with an extra pawl and translated to the main gearwheel (the one having the square bar shaft amidst) by another secondary gearwheel. The advantage here is, that the driving direction can be changed by reversing the toggeling pawl's engagement from one denticulation to the opposite section - as usual in the art. GENERAL DESCRIPTION OF THE DRAWING

Fig. 1 demonstrates the here disclosed invention:

it shows a basic embodiment of a bimanual ratchet wrench in a) slanted view, b)top view and c) cut-off side view , where a secondary lever is working through an intermediate Gearbox onto the main axis with the driving bolt.

DETAILED DESCRIPTION OF THE DRAWINGS

Fig. la demonstrates the double gearbox type on a slanted view and Fig lb in top view, where the main ratchet 1 carries another lever 2 for combined action.

Fig. lc explains in a cross-sectional view, how the ratcheting gearbox 3 with the lever for changing direction 4 work on the main ratcheting device 5 via a bolt 6: as the secondary lever 2 turns its cogwheel 7 with an engaged pawl 8 (not seen here) , the torque is transferred to the square 9 through the bolt 6 and the secondary gearwheel 11 fixed on it.