US3827470A

US3827470A - Ratchet screw driver

Info

Publication number: US3827470A
Application number: US00336937A
Authority: US
Inventors: H Douglas; K Graydon
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-03-01
Filing date: 1973-03-01
Publication date: 1974-08-06
Anticipated expiration: 1991-08-06

Abstract

A ratchet screw driver is shown. The screw driver is comprised of a blade carrying shank which is intimately slidable within a sleeve housing provided in the handle. Complementary ratchet teeth are formed on a sloping mating surface of the handle and the shank. The ratchet teeth are normally maintained in a spaced disengaged position from each other by a biassing means in the handle. The ratchet teeth engage with each other when the blade is pressed downwards into the slot of the screw to be operated.

Description

United States Patent [191 Douglas et al.

[ Aug. 6, 1974 1 RATCHET SCREW DRIVER 221 Filed: Mar. 1, 1973 21 Appl. No.: 336,937

[52] U.S. Cl. 145/76, 81/583 [51] Int. Cl B25b 15/04 [58] Field of Search 145/50 R, 76; 81/583 [56] References Cited UNITED STATES PATENTS 20,61) 6/1858 Bond 145/76 1,017,035 2/1912 Benjamin 145/76 1,049,650 1/1913 Benjamin 145/76 1,643,860 9/1927 Shedd l 81/583 2,667,801 2/1954 Eaves 81/583 3,272,246 9/1966 Bohnet 145/76 131,309 4/1951 Swcdcn 145/76 Primary ExaminerAl Lawrence Smith Assistant ExaminerJ. T. Zatarga Attorney, Agent, or Firm-David W. Wong 57] ABSTRACT A ratchet screw driver is shown. The screw driver is comprised of a blade carrying shank which is intimately slidable within a sleeve housing provided in the handle. Complementary ratchet teeth are formed on a sloping mating surface of the handle and the shank. 'lhc ratchet teeth are normally maintained in a spaced disengaged position from each other by a biassing means in the handle. The ratchet teeth engage with each other when the blade is pressed downwards into the slot of the screw to be operated.

6 Claims, 3 Drawing Figures PAIENIEW 3.827. 410

FIG. 3

RATCHET SCREW DRIVER This invention relates to a screw driver and more particularly relates to a ratchet screw driver in which the blade is not fixedly mounted on the handle.

In using a fixed blade screw driver, it is necessary to disengage the screw driver from the screw after each half turn so that the operator can reposition his arm for the next half turn. The operations require the disengaging and re-engaging of the blade of the screw driver with the slot of the screw in each half turn. Ratchet screw drivers are designed to overcome such drawback. Ratchet screw drivers have heretofore been known in which the blade is not fixedly mounted on the handle. In one kind of ratchet screw driver, the blade is mounted to the handle through a coupling section in whicha complicated ratchet arrangement is incorporated. The ratchet arrangement can be operated so that the blade is only engaged to the handle when the handle is turned in one selected direction. This facilitates the tightening or loosening of screws without having to lift the screw driver out of engagement with the screw and thus enhances the efficiency of the operation. However, the ratchet arrangement in this kind of screw driver is complicated in structure and is expensive to fabricate; yet, despite the high cost of making such screw drivers, the ratchet arrangement tends to break down easily even under normal use.

Another kind of ratchet screw driver consists of a blade carrying shank movably mounted to the handle and complementary ratchet teeth are formed on the handle and the shank, which can engage with each other when the screw driver is pressed down by the axial force in use to engage the screw. Many of this kind of ratchet screw drivers are unstable in their construction and are ineffective to operate. The main drawback in this kind of ratchet screw driver is that the mounting means between the handles and the shank tend to fail under the turning stresses.

In US. Pat. No. 572,800 issued to H. F. Henry on Dec. 8, 1896, a ratchet screw driver of the latter type is shown. The screw driver therein includes a blade carrying shank rotatably mounted to the front end of a handle by a mounting cap. The rear end of the shank and the front end of the handle enclosed within the cap have complementary ratchet teeth formed therein. A biassing spring is placed between the handle and the shank so that they are normally disengaged. When the screw driver is pressed down during use, the ratchet teeth on the handle and the shank are engaged together to transmit the turning movement to the screw. In this structure, only a short portion of the shank is enclosed within the retaining cap, which breaks easily due to the bending moment exerted at the joint by the relatively long blade. Furthermore, the ratchet teeth must be small in dimension in order to be formed on rear end of the shank and on the front end of the handle enclosed within the mounting cap. Such fine ratchet teeth are easily worn down due to the extreme shearing stresses thereon during the turning operation of the screw driver.

The principal object of the present invention is to provide a ratchet screw driver which has a ratchet structure that can withstand considerable turning stresses during use.

Another object of the present invention is to provide a ratchet screw driver in which the shank can withstan considerable bending force. i

Still another object of the present invention is to provide a ratchet screw driver in which a simple but strong rigid teeth structure is provided to transmit the turning force from the handle to the blade.

A further object of the present invention is to provide a ratchet screw driver which is easily fabricated or dismounted for replacement or repair.

According to the present invention, the screw driver comprises a handle having a hollow cylindrical center which is separated by an abutment means disposed therein into a front sleeve housing and a rear sleeve housing; an opening formed in the abutment means to communicate between the front sleeve housing and the rear sleeve housing; a plurality of ratchet teeth formed around the front end of the front sleeve housing; a blade carrying shank slidably engageable within the front sleeve housing; the shank having a rear portion extensible through the opening in the abutment means into the rear sleeve housing; a plurality of complementary ratchet teeth formed on the shank and dimensionally complementary to the ratchet teeth formed around the front end of the front sleeve housing; and biassing means disposed over the rear portion of the shank within the front sleeve housing and co-acting with the abutment means to maintain the ratchet teeth and the complementary ratchet teeth normally in a spaced disengaged position.

This and other objects of the invention, together with its advantages will be more apparent from the following description and drawings which illustrate a specific embodiment by way of example and in which:

FIG. I is an exploded perspective view showing the components of the ratchet screw driver according to the present invention;

FIG. 2 is a cross-sectional side elevation of the screw driver showing the relationship between the elements in assembly;

FIG. 3 is a fragmentary side elevation showing the relationship between components during use.

Referring now to the drawings in which like reference numerals indicate like parts, the handle 10 has a hollow cylindrical center such as a circular bore 12 having a uniform diameter throughout its length. An abutment means 13 is provided in the bore to divide it into a front sleeve housing 14 and a rear sleeve housing 15. The abutment means 13 may consist of at least two protrusions formed on the wall or a collar having a center opening 17 slightly smaller in diameter than the center bore 12. The front sleeve housing 14 communicates with the rear sleeve housing 15 through the opening 17. The handle 10 may be of a conventional size and configuration which can fit comfortably in the palm of the user, and it may be made of plastics such as polypropylene by molding. A plurality of ratchet teeth 18 are formed in the front edge portion of the front sleeve housing. The front edge portion preferably has a convergently sloping face slanting downwardly and inwardly towards the center axisof the housing as best shown in FIG. 2, so that it appears as a circular depression in the front end of the handle with radial ratchet teeth formed on the slanted side wall of the depression. For example, the handle may have a front edge portion having a 1 inch diameter with a sleeve housing of about /2 inch in diameter. The ratchet teeth have a teeth angle of about 30 to 60 and the sloping surface has about a 1-to-2 slope (i.e., a /8 inch angle fall).

The shank consists of a cylindrical main body portion 21 having a diameter slightly smaller than the diameter of the front sleeve housing but larger than the diameter of the center openings 17 of the collar 13 such that the cylindrical body portion 21 may be intimately slidable within the front sleeve housing with little clearance between them. For the example shown above, the clearance preferably should not be more than 1/16 inch in order to eliminate any undesirable rocking movement of the shank within the front sleeve housing.

A smaller rear portion 23 is formed in the rear of the shank 20. The diameter of the rear portion 23 is slightly smaller than the center opening 17 of the collar 13. When the body portion 21 is fully inserted in the front sleeve housing 14, the rear portion 23 can extend into the rear sleeve housing through the opening 17.

The front portion 25 of the shank is dimensioned and configured complementarily to the front portion of the handle 10. A plurality of ratchet teeth 26 are formed on a bevelled mating surface as best shown in FIG. 1. The mating surface slopes upwardly towards the body portion 21. The slope and the dimension of the ratchet teeth 26 are complementary to that of the ratchet teeth 18 formed on the sloping front edge portion of the front sleeve housing. Thus, the shank may be coupled with the handle as shown in FIG. 3 in which the

ratchet teeth

18 and 26 are fully engaged with each other and the front portion 25 of the shank becomes integral with the front portion of the handle; in this manner, the end portion of the rear portion 23 is extending through the opening 17 of the collar into the rear sleeve housing.

The blade 28 is fixedly mounted in the shank during the molding of the latter in the conventional manner with plastics. Commonly, a portion of the blade molded within the shank is stamped to provide at least two keys 29 so as to transmit the turning moment directly during use from the handle to the blade.

The shank is mounted on the handle by a screw 30 with a washer 31 provided through the rear sleeve housing 15. The screw 30 is fastened to a threaded opening 29 formed at the end of the rear end portion 23 of the shank. The washer is slightly larger than the opening 17, so that once mounted, the shank cannot be retracted from the front sleeve housing.

The total length of the main body portion 21 together with the rear portion 23 of the shank is longer than the length of the front sleeve housing. Thus, when the shank is mounted with the washer 31 abutting the collar 13, the

ratchet teeth

18 and 26 are not engaged with each other. A coil spring 35 is fitted over the rear end portion of the shank to bias the shank such that the

ratchet teeth

18 and 26 are normally disengaged with each other and are disposed in a spaced relation with each other. The coil spring 35 preferably has an inside diameter slightly larger than the rear end portion 23 of the shank and an outside diameter slightly smaller than the diameter of the front sleeve housing in order that it is freely compressible or extensible axially within the front sleeve housing to provide an effective biassing action for the shank.

During use, when the blade is pressed downward to engage the slot of the screw, the shank is forced upwards by the axial force until the

ratchet teeth

18 and 26 are fully engaged with each other. As shown in H6. 3, the rear end portion 23 of the shank extends into the rear sleeve housing 15 and the coil spring 35 is being compressed due to the shortening of the rear end portion 23 in the front sleeve housing.

The turning moment of the handle by hand is transmitted to the blade through the fully engaged

ratchet teeth

18 and 26. When it is necessary for the operator to return the hand or arm to a fresh position for the next turning movement, the axial pressure on the handle is relaxed; the biassing coil spring 35 urges the shank 20 downwards until the washer 31 abuts the collar 13 and the

ratchet teeth

18 and 26 become disengaged and are spaced from each other. The biassing coil spring 35 also maintains the blade in engagement with the slot of the screw during the above operation. The handle may then be turned relative to the shank to return the hand or arm of the operator to the initial position. In this manner, the screw can be tightened or loosened effectively without having to lift the blade of the screw driver out of engagement with the slot of the screw after each half turn action.

It can be appreciated that the bevelled surfaces of the

ratchet teeth

18 and 26 enhance the engagement and the transmission of force between the handle and the shank due to the increase in surface contact between the ratchet teeth. The bevelled ratchet teeth 26 also are coupled intimately to the depression formed by the bevelled ratchet teeth 18 and it is very difficult to displace the ratchet teeth 26 from the circular depression. Additionally, due to the complementary dimension between the front sleeve housing and the shank, they are coupled together integrally during use and therefore can withstand extremely high bending stresses.

While illustrative forms of the device in accordance with the invention have been described and shown herein, it will be understood that numeral changes may be made without deparing from the general principles and scope of the invention.

What we claim as new and desire to protect by letters Patent of the United States is:

1. A screw driver comprising a tubular handle having a longitudinal circular center bore of a uniform diameter, a collar formed in said center bore and separating said center bore into a front sleeve housing and a rear sleeve housing, said collar having an opening smaller than the diameter of said centre bore, a depression formed at the front end of said front sleeve housing, said depression having a slanting side wall convergently sloping inwardly towards the axis of said center bore, a plurality of ratchet teeth formed on said slanting side wall, an elongated cylindrical shank having three integral portions therein comprising a main body portion, a smaller rear portion and a larger front portion, the diameter of said rear portion being slightly smaller than said opening of said collar, said main body portion being slidably and intimately receivable in said front sleeve housing until the end portion of said rear portion extends through said collar into said rear sleeve housing, the diameter of said main body portion being slightly less than the diameter of said center bore of said front sleeve housing, the main body portion extending into said front sleeve housing an effective distance to prevent rocking movement between said shank and housing, the diameter of said rear portion being less than that of the main body portion thereby forming a shoulder where the rear portion meets the main body portion, a blade being mounted on said front portion and extending outwardly of the center of the front end therefrom, the back wall of said front portion having a bevelled surface which has a plurality of complementary ratchet teeth formed thereon, said complementary ratchet teeth being operatively engageable with said ratchet teeth formed at the front end of said front sleeve housing, a spiral spring having an outside diameter equal to the diameter of said main body portion and an inside diameter slightly larger than said rear end portion, said spiral spring being slidably disposed about said rear portion and co-acting between said collar and said shoulder entirely within said front sleeve housing to bias said shank such that said complementary ratchet teeth and said ratchet teeth are normally just disengaged and spaced from one another, a mounting means fastened at the end of said rear portion through said rear sleeve housing to prevent said shank from being retrieved from said handle.

2. A screw driver according to claim 1 in which the mounting means comprises a screw fastened to the end of said rear portion through said rear sleeve housing, said screw carrying thereon a washer having a diameter smaller than the diameter of saidcenter bore and larger than the diameter of the opening of said collar so as to prevent said shank from being withdrawn from said front sleeve housing.

3. A screw driver according to claim 2 in which said bevelled surface on said shank and said slanting side wall in said depression have a l-to-2 slope and said ratchet teeth and complementary ratchet teeth have a teeth angle of about 30 to 60.

4. A screw driver according to claim 3 in which the total length of the main body portion and the length of the rear portion of the shank are longer than the length of the front sleeve housing.

5. A screw driver according to claim 4 in which the clearance between the main body portion of the shank and the front sleeve housing is less than 1/16 of an inch.

6. A screw driver according to claim 5 wherein said complementary ratchet teeth formed on said shank are dimensioned and configured complementarily to said ratchet teeth formed in said front end of said front sleeve housing.

Claims

2. A screw driver according to claim 1 in whIch the mounting means comprises a screw fastened to the end of said rear portion through said rear sleeve housing, said screw carrying thereon a washer having a diameter smaller than the diameter of said center bore and larger than the diameter of the opening of said collar so as to prevent said shank from being withdrawn from said front sleeve housing.

3. A screw driver according to claim 2 in which said bevelled surface on said shank and said slanting side wall in said depression have a 1-to-2 slope and said ratchet teeth and complementary ratchet teeth have a teeth angle of about 30* to 60*.