SELF-LOCKING CUTTING TOOL FOR PLASTIC PIPES
A locking mechanism for a cutting tool for plastic pipes. The tool includes two elongated members pivotally connected to each other in a scissors-like manner. Each elongated member has a handle portion and a jaw portion with one jaw portion including a knife blade and the other an anvil. In the preferred embodiments, the jaws of the cutting tool are spring-biased apart toward an open position. The locking mechanism for the tool includes a bail member on one handle and a C-shaped catch member on the other. In operation, the bail member can be pivoted to an extended position to contact and automatically slide along the opposite handle into a locking position with the catch member as the handles are squeezed together.
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This application is a continuation of U.S. patent application Ser. No. 11/484,077 filed Jul. 12, 2006, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
This invention relates to the field of cutting tools for plastic pipes and more particularly to the field of manually operated cutting tools with locking mechanisms that hold the jaws of the tool safely closed when not in use.
2. Discussion of the Background
Cutting tools for plastic pipes are widely used throughout the world and are an essential piece of equipment for virtually anyone who works with plastic pipes. In a typical design, two elongated members are pivotally connected together in a scissors-like manner. In operation, the handles of the tool can be manually manipulated to separate them and open the jaws of the tool to receive the plastic pipe to be cut. In doing so, the handles can be rubbed along the user's leg to separate them and open the tool's jaws or the user can extend his or her fingers to separate the handles. Once opened with the pipe received between the jaws of the tool, the handles can then be squeezed together to drive the edge of the knife blade on one of the jaws into the pipe. At the same time, the tool is normally swung relative to the pipe as the knife edge continues to be driven into the pipe until the pipe is eventually severed.
In other designs of such cutting tools, a spring or springs are provided to bias the handles apart and the jaws into an open position to receive the pipe. When a number of cuts are to be done, many users find it more efficient to have a spring-biased tool rather than one whose handles must be manually opened for each cut.
In both the manually operated and spring-biased designs, it is desirable to have locking mechanisms to secure the tool in a closed position with the jaws safely together when the tool is not in use. A very popular locking mechanism involves providing a bail on the end of one of the tool handles. In use, the tool can be manually closed to bring the handle ends together and the bail then pivoted over the end of the other handle. To unlock the tool, the bail can be either manually pivoted to release the other handle or rubbed against something to move it away from engagement with the other handle. Although simple and easy to operate, this locking arrangement has the disadvantage that the bail may be inadvertently struck and released as the tool is handled. This can occur because the bail is on the outside of the handle ends exposing it to being contacted and released unintentionally. If the tool is spring-biased toward its open position, the inadvertent release of the locking bail can then cause the tool to open, undesirably exposing the cutting blade of the tool. Other locking designs have the bails mounted on the inside of the handles but are somewhat complicated and expensive to make and can still be inadvertently released
In contrast, the self-locking cutting tool of the present invention is relatively simple to operate and is less prone to being inadvertently released.
SUMMARY OF THE INVENTIONThis invention involves a locking mechanism for a cutting tool for plastic pipes. The tool includes two elongated members pivotally connected to each other in a scissors-like manner. Each elongated member has a handle portion and a jaw portion with one jaw portion including a knife blade and the other an anvil. In the preferred embodiments, the jaws of the cutting tool are spring-biased apart toward an open position.
The locking mechanism for the cutting tool includes a bail member on the handle portion of one of the elongated members and a C-shaped catch member on the handle portion of the other elongated member. The bail member is pivotally mounted to the handle portion and can be manually moved to an out-of-the-way position while the tool is being used to make cuts. Upon completion of the cutting, the bail member can be manually pivoted to extend toward a surface on the opposing handle portion. As the handle portions are then squeezed together, the bail member abuts and slides along the surface of the other handle portion into engagement with the C-shaped catch member to secure the elongated members in a closed position. In the closed position, the knife blade is safely received in the anvil of the opposite jaw.
The operation of the locking mechanism is automatic once the bail member is moved to its extended position and the handle portions squeezed together. In the preferred embodiments, the bail member is pivotally mounted to the handle portion by a frictional fitting. In this regard and once manually moved to its out-of-the-way position or its extending position, the bail member will then stay in place and will resist any free movement of it about its pivotal axis. An additional frictional or interference fit is also provided to aid in holding the bail member in its out-of-the-way or non-locking position when the tool is being used to make cuts.
In
As shown in the perspective view of
In operation, the pipe 2 to be cut (see
In the preferred embodiments, the return spring 15 is a leaf spring. Additionally, in the preferred embodiments, the parts of the cutting tool 1 including the elongated members 3 and 5 and the leaf spring 15 have been specifically designed to be easily and cost effectively manufactured and assembled. In this regard as illustrated in
The leaf spring 15 can be mounted on the elongated member 3 either before the members 3 and 5 are assembled as in
As shown in
Once the cutting operation or operations are done and it is desired to lock the tool 1 safely in its closed position so as not to expose the cutting edge 11′ of the knife blade 11, the sequence of
In doing so as best seen in
In this closed and locked position of
In this manner, inadvertent release of the closed and locked handle portions 3″ and 5″ is virtually eliminated. Further and as described above, the engagement of the bail member 20 and catch member 40 is automatic making it self-locking. That is, all that needs to be done is to move the bail member 20 from its out-of-the-way or non-locking position of
To release the handle portions 3″ and 5″ from the locked position of
In the preferred embodiment, the catch member 40 is fixedly mounted (e.g., integrally molded) to the handle portion 5″ at an end location. The end location as illustrated (e.g.,
As shown in
Further assisting the holding of the bail member 20 in its non-locking position of
Consequently, when the bail member 20 is pivotally moved toward the base portion 58 of the U-shaped cross section in
The above disclosure sets forth a number of embodiments of the present invention described in detail with respect to the accompanying drawings. Those skilled in this art will appreciate that various changes, modifications, other structural arrangements, and other embodiments could be practiced under the teachings of the present invention without departing from the scope of this invention as set forth in the following claims.
Claims
1. A cutting tool (1) primarily intended for cutting plastic pipe (2) said cutting tool including first and second elongated members (3,5) connected to each other for pivotal movement about a first pivotal axis (9) between the respective ends (3′, 3″ and 5′, 5″) of the first and second elongated members,
- said first elongated member (3) having a curved anvil (13) adjacent one end (3′) thereof and a handle portion (3″) adjacent the other end, said second elongated member (5) having a knife blade (11) adjacent one end (5′) thereof and a handle portion (5″) adjacent the other end, said knife blade (11) having a cutting edge (11′) and said curved anvil (13) of said first elongated member (3) having a slot (131) therein for receiving the cutting edge (11′) of said knife blade (11) when said elongated members (3,5) are moved to a closed position by squeezing said handle portions (3″,5″) together,
- said cutting tool (1) further including a spring (15) to bias said handle portions (3″,5″) of said elongated members (3,5) apart toward an open position to separate said knife blade (11) and curved anvil (13) to receive the pipe (2) therebetween, and
- a locking mechanism to selectively lock said first and second elongated members (3,5) in said closed position, said locking mechanism including a substantially U-shaped bail member (20) and a catch member (40) with a substantially C-shape with a center section (43) and a freestanding end portion (41), said U-shaped bail member (20) having two legs (22) and a base portion (24) extending therebetween, said legs being pivotally mounted to the handle portion of one of the elongated members for movement relative thereto about a second pivotal axis (30) with the base portion (24) of the bail member (20) spaced from said second pivotal axis (30), said C-shaped catch member (40) being fixedly mounted to the handle portion of the other elongated member and having a freestanding end portion (41) positioned at a location along said other elongated member spaced farther from the first pivotal axis (9) of the cutting tool (1) than the spacing of said second pivotal axis (30) of the bail member (20) from said first pivotal axis (9) wherein said second pivotal axis (30) of said bail member (20) is spaced closer to said first pivotal axis (9) than said freestanding end portion (41) of said C-shaped catch member (40),
- said handle portion of the other elongated member having a surface (5″′) extending away from the first pivotal axis (9) of the cutting tool (1) toward the C-shaped catch member (40), said bail member (20) being manually positionable about the second pivotal axis (30) with the legs (22) thereof extending toward the handle portion of the other elongated member and with the base portion (24) of the bail member (20) positioned to abut the surface (5″′) of the handle portion of the other elongated member at an acute angle (A) as the handle portions (3″,5″) are moved together toward said closed position, said base portion (24) of the bail member abutting and sliding along said surface (5″′) away from said first pivotal axis (9) as said handle portions (3″,5″) are moved together to engage said bail member (20) with the freestanding end portion (41) of said C-shaped catch member (40) at a location spaced from the center section (43) of the C-shape of the catch member (40) in a locking position to secure said elongated members (3,5) in said closed position.
2. The cutting tool of claim 1 wherein the base portion (24) of the bail member is positionable about said second pivotal axis (30) in a non-locking position extending outwardly beyond the handle portion of the one elongated member relative to the first pivotal axis (9).
3. The cutting tool of claim 1 wherein said handle portion of the one elongated member has a substantially U-shaped inner cross section with two legs (56) and a base portion (58) extending therebetween, said bail member being pivotally mounted to the base portion (58) of the inner cross section.
4. The cutting tool of claim 3 wherein said bail member is pivotally mounted to said handle portion by a frictional fitting (28) wherein said bail member frictionally resists being moved about said second pivotal axis (30).
5. The cutting tool of claim 1 wherein said bail member is pivotally mounted to said handle portion by a frictional fitting (28) wherein said bail member frictionally resists being moved about said second pivotal axis (30).
6. The cutting tool of claim 1 wherein the legs (22) of the bail member extend away from one another in a direction from the second pivotal axis (30) toward the base portion (24) of the bail member.
7. The cutting tool of claim 1 further including pivot members (26) mounted on the legs (22) of the bail member to extend toward one another along the second pivotal axis (30).
8. The cutting tool of claim 7 wherein the pivot members (26) are mounted to the handle portion of the one elongated member by a frictional fitting (28) to resist movement of the bail member relative to the handle portion about the second pivotal axis (30).
9. The cutting tool of claim 1 wherein said C-shaped catch member (40) extends away from the surface (5″′) of the handle portion of the one elongated member in a direction toward the handle portion of the other elongated member.
10. The cutting tool of claim 9 wherein the handle portion of the other elongated member has a substantially U-shaped inner cross section and at least a portion of the C-shaped catch member is received in said cross section when the elongated members are moved together.
11. The cutting tool of claim 1 wherein the handle portion of the other elongated member has a substantially U-shaped inner cross section and at least a portion of the C-shaped catch member is received in said cross section when the elongated members are moved together.
12. The cutting tool of claim 1 wherein said spring with said bail member and C-shaped catch member engaged biases said bail member and C-shaped catch member in said locking position.
13. The cutting tool of claim 12 wherein said spring is a leaf spring.
14. The cutting tool of claim 1 wherein said second elongated member (5) is received in a central aperture (21) through said first elongated member (3).
Type: Application
Filed: Feb 5, 2009
Publication Date: Jun 4, 2009
Applicant: (Golden, CO)
Inventor: Mark A. Mortensen (Wheat Ridge, CO)
Application Number: 12/366,243