US 3832916 A
A rotary impact wrench transmits its impacts through a torsion unit with variable spring characteristics. The torsion unit comprises a torsion bar that is inserted into a sleeve with a selectively variable part of its length protruding from the sleeve.
Description (OCR text may contain errors)
United States Patent .1 1
Schoeps Sept. 3, 1974 IMPACT WRENCH 2,654,234 10/1953 Christensen 64/6  I entor: Knu Christ an Schoeps, Nac a, Reynolds 81/52.3
- Sw d 2,964,981 12/1960 t 3,129,571 4/1964  Asslgnee' g gzgg Akt'ebolag Nacka 3,306,639 2/1967 Lyon 21/177 A  Filed: Jan. 24, 1973 Primary Examiner-James L. Jones, Jr. 1 pp N011 3261526 Attorney, Agent, or Firm-Flynn & Frishauf  Foreign Application Priority Data Jan. 31, 1972 Sweden 1047/72  ABSTRACT  US. Cl. 81/52.3 A rotary mp re c transmits its impacts through  Int. Cl B251) 19/00 a torsion unit with variable spring chara t ristics. The [5 1 Field Of Search 403/107, 108; 81/52 3, =torsion unit comprises a torsion bar that is inserted 31/177 A; 64/4, 3, 6 into a sleeve with a selectively variable part of its length protruding from the sleeve.  References Cited UNITED STATES PATENTS 13 Claims, 4 Drawing Figures 2,438,633 3/1948 Condor 81/177 A ae-m a s IMPACT WRENCH This invention relates to an impact wrench with an anvil to which a rotating hammer applies intermittent torque that is transmitted to a nut or the like through a torsion unit which comprises a sleeve and a torsion bar conjointly rotating with the sleeve, the effective length and thereby the effective spring characteristics of the torsion bar being variable.
In a prior form of such a wrench, the torsion bar is axially fixedly mounted in the sleeve and protrudes from the sleeve only with a drive square. The torque is transmitted from the sleeve to the bar through a member which is non-rotatable to but in sliding connection with the sleeve as well as with the bar. This design gives relatively large losses in impact energy as compared with a design with a non-adjustable torsion bar.
It is therefore an object of the invention to provide for a nut runner with an adjustable torque transmitting torsion unit which gives small losses. This is provided for by a torsion unit' which includes only one sliding connection, this connection giving a so called slender transmittance of the torque. To this end the invention has been given the characteristics stated in the claims.
The invention will be further described with reference to the accompanying drawings which show two embodiments of the invention.
FIG. 1 is a longitudinal section through the forward portion of a wrench,
FIG. 2 is a cross section at an enlarged scale taken along lines 2-2 in FIG. 1,
FIG. 3 is a longitudinal section through the forward portion of another wrench, and
FIG. 4 is a cross section at an enlarged scale taken along line 4-4 in FIG. 3.
In FIG. 1, the housing of the impact wrench is generally denoted by 11. A drive square 12 protrudes from the housing 11 and it is an integral part of an anvil 13 which has radial anvil surfaces 14. A rotating hammer 15 has impact dogs 16, and it is rotated by a pneumatic sliding vane motor or any other suitable type of motor. The hammer or a part of the hammer has besides its rotating movement also a simultaneous axial movement so that the impact dogs 16 will repeatedly strike (apply intermittent torque to) the anvil surfaces 14 of the anvil at a rate of for instance 2,000 impacts per minute. The drive square 12 is inserted in the rearward end of a sleeve 17 and is axially locked by means of a resiliently mounted pin 18 which protrudes radially from the drive square. The sleeve 17 has through interior axial splines 19 which register with corresponding external splines 20 on the torsion bar 21. The free end of the torsion bar 21 is formed as a drive square 22 on which a nut socket 23 is attached by means of a resiliently mounted pin 24. The bar 21 has a radial hole 25 which canalign with any of four holes 26 in the sleeve 17 since the rodis axially slidable in the sleeve. The bar and the sleeve can be axially interlocked by means of a pin 27 as shown in the figures. The pin 27 is retained by means of a spring plate 28. The pin 27 should have a clearance to the holes 25,26 so that it cannot be subjected to the torque that is transmitted by the spline connection 19,20. With respect to its elastic properties, the torsion unit 17,21 can be divided into three portions, namely: the protruding part of the torsion bar 21, the stiff portion of the spline connection 19,20, and the part of the sleeve 17 which is above the end of the bar 21 and has an elasticity of for instance one tenth of the elasticity of the bar. Thus, by selectively varying the length of the protruding portion of the bar, the operator can vary the total spring characteristics of the torsion unit 17,21 within wide limits.
In FIGS. 3 and 4, details which correspond to details in FIGS. 1 and 2 have been given the same reference numerals as in the latter figures. The anvil 13 ends in this modification with a hexagonal recess 30, and the bar 21 has a corresponding hexagonal cross section. The bar is inserted in the hexagonal recess with one end and it is axially retained by a ball 31 which register with an annular recess 32 in the bar. The ball 31 is held in place by a spring loaded axially movable retainer sleeve 33. The sleeve 17 has also hexagonal interior cross section which registers with the exterior hexagonal form of the bar, and the bar 21 and the sleeve 17 can be moved axially relative to each other and interlocked by means of a pin 27 in the same way as described with reference to FIGS. 1 and 2. The lower end of the sleeve 17 is formed as a socket 34 for anut, but, of course, it can instead be formed as a drive square for a nut socket of the type shown in FIG. 1.
What I claim is:
1. An impact wrench comprising:
a power rotated hammer adapted to apply rotary impacts to the anvil, and
a torsion unit coupled to said anvil for transmitting from said anvil said rotary impacts as intermittent torque to a nut or the like, said torsion unit comprising:
a torsion bar and a sleeve, said sleeve slidably receiving said torsion bar therein from one end with said torsion bar being non-rotatable relative to said sleeve, said one end forming with said torsion bar a torque transmitting joint, and
means for axially interlocking said torsion bar and said sleeve with a selectively variable part of the length of said bar protruding from said joint, the torque transmission characteristics of said torsion unit being a function of the degree of protrusion of said torsion bar from said joint.
2. A wrench according to claim 1 in which said sleeve is affixed to said anvil, and said torsion bar has a free end protruding from said sleeve.
3. A wrench according to claim 1 in which said torsion bar is affixed to said anvil, and said sleeve has a free end.
4. A wrench according to claim 3 in which the free end of said sleeve is formed as a socket for a nut.
5. A wrench according to claim 1 in which said torsion bar has a generally circular cross section and is provided with a number of axial splines, and said sleeve has a number of axial splines which register with said axial splines in said torsion bar to prevent relative rotation of said torsion bar and sleeve.
6. A wrench according to claim 1 in which said axially interlocking means includes recesses formed in said sleeve and said torsion bar, said recesses being adapted to receive a locking element therein so as to axially interlock said sleeve and said torsion bar.
7. A wrench according to claim 6 in which said recesses are radial holes in said sleeve and said torsion bar, and said locking element comprises a locking pin adapted to be radially inserted in said radial holes in said sleeve and said torsion bar.
8. A wrench according to claim 5 in which said splines of said sleeve are through splines.
9. A wrench according to claim 6 in which said torsion bar has a single recess and said sleeve has a plurality of axially spaced recesses.
10. A wrench according to claim 1 in which said torsion bar has a recess at the end thereof that is disposed inside said sleeve, and said axially interlocking means includes means for engaging with said recess in said torsion bar to axially lock said torsion bar in said sleeve in selectively variable axial positions therebetween.
11. A wrench according to claim 2 wherein said free end of said torsion bar includes means for coupling said rotary impacts to said nut or the like,
12. A wrench according to claim 6 in which a clearance is provided between said locking pin and said radial holes.
13. A wrench according to claim 12 in which said torsion bar has a generally circular cross section and is provided with a number of axial splines, and said sleeve has a number of axial splines which register with said axial splines in said torsion bar to prevent relative rotation of said torsion bar and sleeve. a l