Clams and oysters and the like are commonly harvested with a variety of sizes, and automatic machinery which will open clams and oysters is either unavailable or very expensive. Also, seafood items of this type ordinarily retain their taste and freshness better if they are opened at individual restaurants or kitchens immediately prior to consumption rather than being opened sometime before at a central process plant. Clams and oysters are commonly opened at restaurants and clambakes using various hand tools, most commonly special forms of knives. Opening clams rapidly and efficiently with knives and other tools available in the prior art ordinarily requires a person with strong hands and a considerable degree of manual dexterity, and the work is tedious and tiring even to such a person having considerable experience. Unskilled persons also sometimes accidentally cut themselves with clam knives. The difficulty of opening clams and oysters is a primary factor which limits wider consumption of such seafood items.
A variety of attempts have been made to provide tools which will simplify the task, and some prior art attempts are shown in U.S. Pat. Nos. 708,014; 2,017,370; 2,609,565; 2,738,546 and Des. 196,381. While some of the prior art devices may have achieved some substantial usage none of them are believed to have gained widespread acceptance, and all of them suffer from at least one disadvantage which is overcome by the present invention.
While the two half-shells of a clam frequently appear to the casual observer to be tightly sealed together around their entire periphery, it is well known that the two half-shells of a clam are actually held together by a tough, fibrous hinge which is exposed and which extends along only a small portion of the periphery, and held at two other places by powerful muscles which are inside the clam and not exposed.
Prior art clam-opener tools of the plier or lever type have generally included a pair of levers pivotally affixed together, with a knife blade end on one lever pivoting relative to a cup-shaped clam-retaining end on the other lever, so that squeezing the two opposite or handle ends of the levers together advance the knife blade end through the clam toward the cup-shaped clam-retaining end. The distance of the pivot point from the working ends of the two levers determines the mechanical advantage of the tool. If the pivot point is situated too near the handle ends of the tool, the tool will have little mechanical advantage, or even a negative mechanical advantage, frequently making it very difficult or impossible for one to squeeze the tool sufficiently hard to open the clam. While one theoretically can provide any desired mechanical advantage by making the two lever arms long enough, it will be apparent that that offers no solution. The span of the human hand tends to limit the usable lever arm length if the operator is to be capable of holding the tool with one hand while inserting the clam with the other. If, on the other hand, the pivot point is situated quite near to the blade end of the tool, a large mechanical advantage may be obtained, making it easy for one to apply sufficient force with one hand to open the clam. However, the greater the mechanical advantage provided by tool, the lesser will be the distance which the blade will travel for a given distance of travel of the two handle ends toward each other, and the lesser will be the change in distance between the jaws between fully-opened and fully-closed conditions. Thus if the pivot point is situated near the blade end so as to provide sufficient mechanical advantage to open the clam easily, the restricted travel of the blade limits the range of clam sizes on which the tool may be used. Because of that inherent characteristic of a lever, the clam openers of the prior art tend to be incapable of sufficiently cutting a clam by one squeeze of the tool, with the result that the operator then often has had to "open" the tool, rotate the half-severed clam to a different orientation relative to the blade and then to squeeze the tool again. Not only are two (or sometimes more) such operations required, thereby greatly decreasing operator speed, but rotation of the partially-severed clams in the tool has required the operator to use his other hand to accomplish the rotation, rather than allowing him to use it to locate opened clams on a tray or bed of ice and to reach for the next clam. It is a primary object of the present invention to provide an improved plier-like opener tool which overcomes those disadvantages of prior art tools.
The prior art clam knives and plier-like clam tools of the prior art, all are designed to cut the two interior muscles of the clam in order to open the clam, since the two interior muscles are formed by a soft meat-type material which is far easier to sever than the hinge. Prior art clam tools of the plier-type have not attempted to sever the clam hinge, since the great mechenical advantage required would severely restrict the range of clam sizes with which they could be used. Because the two muscles lie wholly inside the clam, the severing blades of prior art tools have been required to separate the shells against the strength of the muscles before the muscles can be cut. The edges of the clam shells are ordinarily much thicker at and adjacent the hinge than around the remainder of the periphery. When prior art blades have been inserted between the thinner edges of a pair of shells in order to cut the muscles, it has been difficult to align such blades so as to avoid breaking the edges of the shells. Also, nature doe not always cause the joint between such edges to be straight, so that forcing a straight blade edge between the shells sometimes chips or breaks the shells. The disadvantages of chipping the shells and mixing shell chips with the clam meat are obvious.
The tool of the present invention employs a new technique for opening clams. Rather than inserting a blade into the clam through the thinner edges of the shell in order to cut the interior muscles, the present invention severs through the tough, fibrous exposed hinge, and through one interior muscle, which allows the clam then to be easily opened with one's fingers against the force of the remaining muscle. The severing process begins at the easily-accessible exposed hinge portion of the clam, where the shell is thickest and strongest, so that shell breakage occurs less often, and severing of the hinge occurs without any prior separation of the two shells.
Because the tool of the present invention cuts directly through the tough hinge muscle, considerable mechanical advantage is required, and in order to provide sufficient mechanical advantage one might assume that the range of blade travel, and hence range of clam sizes with which the tool could be used, would be drastically limited. However, in accordance with one important feature of the invention, an automatic variation in the location of the pivot point is provided. A large mechanical advantage is provided during the initial portion of jaw closure as the hinge is severed, but then the pivot point shifts to provide less mechanical advantage and greater blade travel as the blade moves into the clam to sever an internal muscle. Such variation in the tool pivot point allows the jaws of the tool to move sufficiently to accept a wide variety of clam sizes.
A central concept of the present invention involves the use of a plier cutter having a varying pivot point about which the two arms of the tool pivot, to provide large mechanical advantage during an initial portion of a cutting stroke when the hinge is being cut, and thereafter to provide a decreased mechanical advantage and greater knife travel during a remaining portion of a cutting stroke, so that the softer interior muscle will be reached and severed.
A further important feature is that the mechanical advantage of the tool changes in the desired sense automatically as the operator squeezes the tool, without any need for the operator to reset the tool on the clam, or to perform any adjustment to the tool, or to use more than one hand.
Other objects of the invention will in part be obvious and will in part appear hereinafter.
The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts, which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.
For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:
FIG. 1 is a side view of one embodiment of the invention shown with the jaws of the tool fully opened.
FIG. 1a is an opposite-side view of a portion of the tool.
FIG. 2 is side view of the tool of FIG. 1 corresponding to the view of FIG. 1 but with the jaws of the tool shown partially closed.
FIG. 3 is a side view of the tool corresponding to the views of FIGS. 1 and 2 but with the jaws shown fully closed.
FIG. 4 is a plan view of the tool taken at lines 4--4 in FIG. 3.
FIG. 5 is an end section view of the tool taken at lines 5--5 in FIG. 3.
FIG. 6 is a graph useful in understanding the operation of the tool of FIGS. 1-5.
FIG. 7 is an isometric view of some alternative form of the invention.
FIG. 8 a view corresponding to FIG. 1a but showing one optional modification of the tool.
FIG. 9 is a side view of portions of an alternative form of the invention.
FIG. 10 is a side view of portions of a further alternative embodiment of the invention.
Referring now to the FIGURES, and in particular FIGS. 1-5, the tool will be seen to comprise a first rigid arm 11 having a handle end 11a and a knife blade end 11b. A cylindrical pivot pin 12 is fixedly mounted or staked in a hole in arm 11 to extend from a flattened surface portion 11c on arm 11 generally near blade end 11b. Knife blade end 11b, as shown in FIG. 5 preferably is provided with a wedge-shaped cross-section, with its inner side arranged perpendicularly to the axis x--x of pin 12 and its outer side arranged at an acute angle (shown as α) relative to the inner side. The rear portion of flattened inner face 11c of arm 11 terminates at an inwardly-extending or widened portion of arm 11 shaped to provide a rounded cam surface 18 (FIGS. 1 and 4). The tool also includes a second rigid arm 13 having handle 1313a and a widened clam seat end 13b. A flattened surface portion 13c (FIG. 1a) on the inner side of arm 13 includes an arcuate slot 14 through arm 13 within which pin 12 is situated. A flat washer 15 is shown held on pin 12 by means of a screw which threads into pin 12, thereby fastening the two arms pivotally together so that the flattened surfaces 11c, 13c of the two arms slidingly abut each other. If desired, the end of pin 12 may be widened by flattening so that no screw is necessary. Flattened inner face 13c of arm 13 terminates at its forward end by an abrupt widening of arm 13, thereby providing a widened, generally circular, and preferably slightly hollowed or spoon-shaped surface at 13D. Hollowing out surface 13d allows a clam to seat more securely, of course. When the tool is opened, i.e. handle ends 11a, 13a are spread apart, point on arm 11 eventually strikes end 13e of surface 13d, as shown in FIG. 1a, and with pin 12 then located in one end of slot 14, further opening of the tool is prevented.
A clam is inserted on rounded surface or seat 13d of end 13b when the jaws are substantially open to approximately the position shown in FIG. 1. Pivot pin 12 is then located at end 14a (FIG. 3) of arcuate slot 14. As the handle ends 11a, 13a are squeezed together, from the position shown in FIG. 1 to that shown in FIG. 2, the knife blade tip 11d rotates around the pin 12 axis at the upper end 14a of slot 14, describing a path shown by dashed line in 17 in FIG. 1. The mechanical advantage of the tool is then determined by, and is proportional to, the ratio of dimension d to dimension a in FIG. 1, assuming that operator force is applied at arrow F in FIG. 1. The clam (not shown) is angularly oriented relative to seat 13d so that path 17 of blade end 11d and the path of blade portions inwardly therefrom will pass through the tough, fibrous hinge of the clam. During this portion of the operation, between the conditions shown in FIG. 1 and FIG. 2, the knife blade severs the clam hinge, and maximum mechanical advantage is provided. The displacement of the knife blade relative to the clam and arm 13 per degree of rotation of the handles about the pivot point is directly proportional to the lever arm distance a, of course, and under such conditions such displacement is minimum. The manner in which the mechanical advantage and rate of travel of the blade vary as the handles are moved from a fully open condition to a fully closed condition is shown graphically in FIG. 6. The abscissa value 2 in FIG. 6 represents the condition shown in FIG. 2, wherein a step decrease in mechanical advantage occurs and a step increase in rate of travel occurs as point f of arm 13 engages point f of cam surface 18 on arm 11.
When the tool arrives at the condition shown in FIG. 2 the hinge will be completely or substantially severed and much less force is required to sever one of the interior muscles. In FIG. 2 point f on arm 13 is shown just striking point f on cam surface 18 of arm 11. As the handles 11a, 13a are squeezed further together, points g and h on arm 13 successively engage points g and h respectively, on cam surface 18 of arm 11, and pin 12 rides upwardly in arcuate slot 14. The edge between points f and h on arm 13 will be seen to act as a cam follower which rolls along cam surface 18 as pin 12 slides in slot 14. When the tool is advanced to the condition shown in FIG. 2 and rotation of arm 11 relative to 13 begins about point f on arm 13, it will be seen that the mechanical advantage of the tool will suddenly be proportional to the ratio of dimension e to dimension b rather than to the ratio of dimension d to dimension a as theretofore. As further closure of the tool causes points g and h on arm 11 to successively engage points g and h on arm 13, so that arm 11 rotates about pivot points which are successively located more rearwardly on arm 13, it will be seen that the mechanical advantage of the tool gradually further decreases, until the tool is fully closed as shown in FIG. 3. At the instant of full closure the mechanical advantage will have become proportional to the ratio of dimension f to dimension c in FIG. 3. As the mechanical advantage decreases, the amount of blade travel through the clam per degree of tool handle closure increases, so that the blade cuts through considerably more of the clam during the last portions of a cutting stroke than if the mechanical advantage had remained unchanged. The manner in which the mechanical advantage and rate of travel vary between the conditions shown in FIGS. 2 and 3 is graphically indicated between abscissa numerals 2 and 3 in FIG. 6. When the tool has fully closed it will have completely severed the hinge and all or most of one of the interior muscles. The clam then may be spread apart very easily with one's fingers against the force of the remaining interior muscle. Provision of a spoon shape on end 13b facilitates removal of clam meat from an opened half-shell.
It is desirable that closure of the tool be limited so that blade tip 11d will not be blunted or dulled by striking clam seat 13b. Closure may be limited either by shaping arms 11 and 13 so that handle ends 11a, 13a strike each other slightly before tip 11d can engage seat 13b, or by limiting the length of arcuate slot 14, so that pin 12 seats against end 14c of slot 14 slightly before tip 11d can strike seat 13b, and obviously both such limiting means may be used if desired.
The alternative embodiment of the invention shown in FIG. 7 operates according to the same principles as the previous embodiment. However, cam block 18', which corresponds principle to cam surface 18 of the prior embodiment, is made adjustable in position along arm 11', so that the point of tool closure at which rate of travel is increased can be adjusted. Cam block 18' may be adjusted along slot 20 by loosening screw 21, which holds block 18' on arm 11 with a nut (not shown). The screw 21 passes through block 18' at a distance from the center of block 18', which is shown having the shape of an equilateral triangle. By rotatably adjusting block 18' as well as longitudinally adjusting its position along arm 11, it will be seen that one can vary the magnitude of the step increase in rate of blade travel as well as varying the point at which the increase occurs when closure of the tool causes arm 13 to strike a corner of block 18'. If block 18' is given straight sides as shown, it will be seen that a single step increase of blade travel will occur during closure. One or more sides of block 18' may be curved, if desired, to provide cam surfaces similar to that of cam surface 18 in FIG. 1, so that a gradual increase in blade travel rate will occur after the initial step increase, in the manner of FIGS. 1-6.
Opening of a batch of clams or oysters is made slightly easier if the tool will automatically open to a maximum width that is slightly larger than the largest of the clams or oysters to be opened, rather than opening twice as far as is necessary in order to insert the clam between the jaws, for example. A fixed stop such as 13e in FIG. 1a, if built to allow jaw opening to accommodate large diameter oysters, will allow much more jaw opening than is necessary for small clams, for example. In FIG. 8 the maximum amount which the jaws will open is made adjustable, by means of adjustment screw 13e', which is locked in place by means of nut 22.
It will be apparent that the positions of blade portion 11d and clam portion 13d can be interchanged in any embodiment of the invention with no difference in the operation, i.e., the blade could be fashioned on one end of the arm having the slot and the seat could be provided on the end of the arm carrying the pivot pin and the cam means.
In the device of FIG. 9 a bolt 26 passes through a round hole in arm 11 and through a straight slot 24 in arm 13, and secures the arms together. The head of the bolt and the nut on the end of the bolt are not shown in FIG. 9. A pad 25 formed on arm 13 provides an edge having corners 25a and 25b. When bolt 26 is at the upper end of slot 24 as shown in FIG. 9, corner 25a limits the amount which the tool can be opened. When a clam is placed between the jaws and the handles squeezed, the initial rotation occurs about bolt 26 in the position shown. Eventually corner 25b of pad 25 engages the edge of arm 11 at point j, and the pivot point is thereby suddenly shifted rearwardly to corner 25b. As the handles are squeezed further together, corner 25b then rides along the edge of arm 11 toward point k, while bolt 26 slides downwardly and leftwardly in slot 24. While the pivot point remains at corner 25b, the blade travel rate continues to gradually increase, since movement of bolt 26 in slot 24 moves arm 11 forwardly, thereby increasing the lever arm distance between blade tip 11d and pivot point 25b. Eventually the pivoting about corner 25b causes the force between bolt 26 and slot 24 to act normal to the side of slot 24, preventing further closing of the tool and further forward motion of arm 11 relative to arm 13, so that no further stop means is required to prevent blade tip 11d from blunting on the seat. A stop may be provided instead, either by forming the handle ends so that they meet, or by limiting the length of slot 24 so that bolt 26 reaches the end of slot 24 at the desired limit position.
It should be apparent at this point that the cam surfaces shown are exemplary only, and that a wide variety of equivalent camming arrangements may be substituted without departing from the invention. The cam surfaces need not act on an outside edge of one of the lever members. In FIG. 10, for example, arm 13 carries a pin 13f which extends into a hole 11f through arm 11, to provide equivalent operation to that of surface 18 and the outer edge of arm 13 in FIGS. 1-3.
It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.