US3841571A

US3841571A - Safety guard arrangement for shredder-bagger

Info

Publication number: US3841571A
Application number: US00358130A
Authority: US
Inventors: D Dankel; L Herscher
Original assignee: Roper Corp
Current assignee: American Yard Products Inc
Priority date: 1973-05-07
Filing date: 1973-05-07
Publication date: 1974-10-15
Anticipated expiration: 1991-10-15

Abstract

A shredding and bagging machine for yard usage of the type having a cylindrical shredding chamber and superimposed feed housing. A ramp of flaring construction has a throat which registers with a front opening in the feed housing, the ramp being horizontally pivoted in the region of the throat for swinging movement between a lowered ''''ramp'''' position and an upraised ''''hopper'''' position. A horizontally pivoted guard member is provided in the throat with means for swinging the guard member to an out-of-the-way position when the ramp is lowered and for automatically restoring the guard member to throatobstructing position whenever the ramp is raised to prevent ejection of missiles through the receptacle. In the preferred embodiment the guard is pivotally mounted on a lid hinged to the housing and provided with a latching arm cooperating with a stationary keeper so arranged that upward swing of the lid disengages the arm from the keeper for restoration of the guard to its obstructing position. In an alternate embodiment the guard is operated automatically by a linkage in accordance with the swinging movement of the ramp and lid.

Description

United States Patent 1 Dankel et al.

1 SAFETY GUARD ARRANGEMENT FOR SHREDDER-BAGGER [75] Inventors: Douglas D. Dankel; Lee R. Herscher,

both of Kankakee, Ill.

[73] Assignee: Roper Corporation, Kankakee, 111.

[22] Filed: May 7, 1973 [21] Appl. No: 358,130

Primary Examiner--Roy Lake Assistant ExaminerE. F. Desmond Attorney, Agent, or Firm-Wolfe, Hubbard, Leydig, Voit & Osann, Ltd.

[ Get. 15, 1974 [57] ABSTRACT A shredding and bagging machine for yard usage of the type having a cylindrical shredding chamber and superimposed feed housing. A ramp of flaring construction has a throat which registers with a front opening in the feed housing, the ramp being horizontally pivoted in the region of the throat for swinging movement between a lowered ramp position and an upraised hopper position. A horizontally pivoted guard member is provided in the throat with means for swinging the guard member to an out-of-the-way position when the ramp is lowered and for automatically restoring the guard member to throat-obstructing position whenever the ramp is raised to prevent ejection of missiles through the receptacle. 1n the preferred embodiment the guard is pivotally mounted on a lid hinged to the housing and provided with a latching arm cooperating with a stationary keeper so arranged that upward swing of the lid disengages the arm from the keeper for restoration of the guard to its obstructing position. In an alternate embodiment the guard is operated automatically by a linkage in accordance with the swinging movement of the ramp and lid.

11 Claims, 12 Drawing Figures PATENIED 1 5 I974 4 3. 841 .571

W! EM 2 SAFETY GUARD ARRANGEMENT FOR SHREDDER-BAGGER It is an object of the present invention to provide an improved shredding and bagging machine having a ramp which is swingable from a lowered ramp position to an upraised hopper position and in which means are provided for insuring that a guard is interposed in the throat of the ramp when it is in its upraised position to prevent ejection of dangerous missiles from the machine. It is a more specific object to provide a shredding and bagging machine in which garden waste may be swept up the ramp into the machine freely and unobstructed, but which automatically interposes a guard member to prevent ejection of missiles through the receptacle when the ramp is in the hopper mode.

It is a general object of the present invention to provide a shredding and bagging machine for yard usage which may be operated in either the ramp mode or the hopper mode and which is convenient and safe to use in both modes of operation.

It is yet another object of the present invention to provide a machine as characterized above which is simple in construction and operation, which may be safely employed by anyone without special knowledge or instruction, which is economical to manufacture, and which may be operated for long periods of time without any care of maintenance.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reading the attached detailed description and upon reference to the drawings in which:

FIG. I is a perspective view showing a shredding machine with the ramp upraised to form a hopper.

FIG. 2 is a longitudinal section taken through the machine along the axis of the ramp.

FIG. 2a is a horizontal section taken along line 2a-2a of FIG. 2.

FIG. 3 is a view similar to FIG. 1 but showing the ramp in its ground-engaging position.

FIG. 3a is an enlarged fragment showing the ramp hinge construction.

FIG. 4 is a longitudinal section corresponding to FIG. 3.

FIG. 4a is a perspective view showing the guard member.

FIG. 5 is a stop motion diagram showing the latching arm slipping free of the keeper as the ramp is raised.

FIG. 6 is an end view looking along the line 6-6 in FIG. 2 showing the guard member in place with the ramp in upraised position.

FIG. 7 shows a modified form of the present invention using a linkage for operating the guard and shown with the ramp upraised and the guard in place.

FIG. 8 is a view showing the ramp in lowered position, with the guard in its out-of-the-way position.

FIG. 9 is a fragment showing a modified linkage.

While the invention has been described in connection with certain preferred embodiments, it will be understood that I do not intend to be limited to the particular embodiments illustrated but intend, on the contrary, to cover the various alternative and equivalent forms of the invention included within the spirit and scope of the appended claims.

Turning now to the drawings and particularly to FIGS. 1, 2 and 2a, there is disclosed a shredding and bagging machine 10 having a frame 11 supported a short distance above the ground upon a pair of wheels 12 at one end and a bracket 13 at the other. The frame 11 includes a bottom wall 15, a cylindrical side wall 16 and a top plate, or wall 17. Mounted upon the top plate is an engine 20 having a shaft 21 and carrying a rotary blade 22. Cooperating with the tips of the blade 22 are a series of breakers 23 secured inside the side wall 16 and having notches for clearing the tips of the blade. A receptacle 25 is formed in the top plate for admission of leaves, twigs and the like and the side wall is penetrated by a discharge conduit, or chute, 26 through which the shredded material is forcibly ejected into a bag for subsequent disposal.

In accordance with the invention a ramp assembly is provided above the receptacle 25 made up of a housing having a front opening and with. a convergent ramp having a relatively narrow throat registering with the opening, the ramp being pivoted with respect to the opening for up and down swinging movement. A pivotally mounted guard member extends across the throat of the ramp, the guard member being swingable into into an out-of-the-way position when the ramp is in its lowered position but with means for automatically interposing the guard in the throat when the ramp is raised to hopper position to prevent ejection of missiles from the blade through the receptacle. More specifically in accordance with the invention, the guard is provided with manually operated latch for latching the guard in an out-.of-the-way position but with means for automatically triggering the latch incident to upward swinging of the ramp. Still further in accordance with the invention I provide a pivoted coveror lid upon the housing, andforming the top surface thereof, with the lid being'in the path of upward swinging movement of the ramp and with the latch being triggered for release by reason of the upper swinging movement of the lid.

Thus as shown in the drawings, I provide a housing 30, having side walls 31, 32 a wall 33 and a lid 35 defining a front opening 36. The housing is secured to the top plate 17 of the machine by any suitable means and is open-bottomed so as to communicate with the receptacle 25.

For feeding leaves and debris to the housing, a ramp 40 is provided of flaring configuration having

side walls

41, 42 and a flaring bottom 43 having a wide edge 44 at its outer end and a throat 45 at its inner end. For the purpose of hinging the ramp to the housing so that the throat is in register with the front opening 36, a hinge connection is provided which is formed of a bracket 46 of shallow U shape which is welded to the side walls of the housing and which serves to mount a transversely extending pivot rod 47 which is secured to the underside of the ramp by means of spaced brackets 48.

Turning next to the construction of the cover or lid 35, it is hinged to the side walls of the housing at a horizontally extending remote hinge connection 50. The edges of the lid are downwardly turned to

form side flanges

51, 52 as well as a presented flange 53.

In carrying out the invention a guard member is provided pendulously mounted upon the cover 35 and dimensioned to span the throat 45 of the ramp when the guard is in its obstructing position (FIG. 6). As shown in FIG. 4a, the guard preferably includes a body 61 formed of a sheet of rubber or similar material which is vertically slit and which is mounted upon a backing plate 62, being secured thereto by rivets 63 or the like..Extending along the length of the backing plate 62 is a shaft 64, the ends of which are received in registering openings formed in the'side

flanges

51, 52 of the lid,

parts

62, 64 being welded.

For the purpose of raising the guard-60 to an out-ofthe-way position when the edge of the ramp is resting against the ground, alatch arm 70 is provided which may be formed as a continuation of the shaft 64 and which cooperates with a keeper 71 on the side wall 31 of the housing.

Thus when the device is used with the ramp lowered for sweeping of leaves or the like into the receptacle, the latch arm may be swung upwardly, into the positions shown in FIGS. 3 and 4, and snapped over the keeper 71 which thereby retains the arm, and guard, in the upwardly swung condition.

To provide reinforcement for the backing member and to serve as a stop to limit the outward swinging movement of the guard the backing member 62 preferably has an integral flange 620 which cooperates with the presented downwardly turned flange 53 on the lid to limit the range of movement.

The length of the latching arm 70 is so tailored with respect to the keeper 71 that when the ramp is swung upwardly from the position shown at FIG. 3, accompanied by upward movement of the lid, which is in the path of movement of the ramp, the arm 70 is gradually pulledclear of the keeper, and both the arm and the guard which it controls are then free to swing downwardly into the vertically pendulous position shown in FIG. 2. This clearing of the end of the latching arm, to trigger the latch, is illustrated in FIG. 5. The automatic movement of the guard into its obstructing position incident to raising the ramp insures that the guard will be in place to prevent the ejection of any missiles which might pass fromjthe blade through the receptacle 25. It is to be noted that it is not possible to have the guard in any but an obstructing position when the ramp is upraised, and thus the machine with the present improvemerit can be used by children or adults without necessity for special instructions. Since the guard is preferably of flexible construction, formed of a sheet of rubber or the like with vertical slits, the guard may locally deform to admit a branch or the like to the blade.

For the purpose of temporarily holding the ramp in its upraised position,

notches

81, 82 are formed along the upper edges of the

sides

41, 42 of the ramp structure for hooking engagement with the ends of the shaft 64 in the lid, which thus does double duty. Also, for interfitting the lid and the ramp, the presented flange 53 on the lid may be relieved or notched out at its ends as indicated at 83, 84 for registered reception of the ramp side walls which are preferably roll-formed along the edges for free sliding engagement.

While the interposed guard is important for safety purposes when the ramp is upraised, because of the direct access and line of view of the blade, his not necessary to have the guard in place when the ramp is lowered. Lowering of the ramp is accompanied by lowering of the lid into its horizontal position and this, combined with the shielding effect of the flange 63a on the guard structure, prevents direct access to, or view of, the blade. On the contrary, it is desirable when the ramp is in its lowered position for any artificial obstruction to be out of the way so that leaves, twigs and the like may be swept freely upwardly and into the housing. It is one of the features of the construction, however, that latching is optional when the ramp is lowered; the guard may be either left in place or latched out of the way whichever might be desired.

Notwithstanding the versatility of the above construction it is a feature of the invention, in one of its aspects, to provide means for positively swinging the guard between its obstructing and non-obstructing positions automatically depending upon whether the ramp, and hence the lid 35, are up or down. Such embodiment is illustrated in FIGS. 7 and 8 which show a modified ramp assembly in which corresponding parts have been indicated by corresponding reference numerals with the addition of subscript a. As shown in FIG. 7, the ramp 40a is upraised, raising the lid 35a. According to the invention the arm a, which extends parallel to the side wall of the housing and which is secured to the end of the rod 64a, is coupled, by means ofa link 90, to a fixed pivot pin 91, a pivot pin 92 being interposed between the arm and link. Thus when the ramp 40a is swung downwardly, in the direction of the arrow (FIG. 7), accompanied by downward movement of the lid 35a, the arm 70a and link undergo a relative scissoring movement resulting in upward swing of the arm to the position shown in FIG. 8 accompanied by clockwise rocking of the shaft 64a and swinging of the guard 60a upwardly into its out-of-the-way position.

When this movement is reversed, that is, when the ramp is swung back upwardly to the position shown in FIG. 7, scissoring between the arm and link occurs in the opposite direction, resulting in forcible downward movement of the guard 60a to the illustrated obstructing position. Here again, the device is rendered safe in the hopper mode of operation without necessity for any special instructions to the operator of the machine.

One difference in the operation of the alternative construction thus far described is the fact that the linkage swings the guard member between its respective positions with positive action, that is, the guard member is positively held, as shown in FIG. 7, in its obstructing position. This is no particular disadvantage as long as the guard is constructed of resilient material and is thus free to yield resiliently as material is fed down the hopper. If it is desired that the guard member in the embodiment of FIGS. 7 and 8 be permitted to swing inwardly with pendulous action, then a linkage of the one way" type should be used (FIG. 9). Such linkage may be formed by providing a slot 93 in the link 90 for the purpose of engaging the pin 91. In operation, when the ramp is upraised, insertion of material into the hopper, for example, a tree branch, will be effective not only to deform the guard material locally but to swing the guard member bodily in the retreating direction with lost motion occurring between the slot 93 and pin 91. Use of the slot has the additional advantage that the lid may be raised an additional amount to provide better access for cleaning or the like.

When the device is used in the ramp mode, the edge 44a simply rests on the ground, establishing contact regardless of ground contour. For convenient transportation from place to place the ramp may be fitted at its corners with

handles

101, 102, and means may be provided for effectively rigidifying the ramp with respect to the housing in a convenient intermediate position. For this purpose an auxiliary set of notches, similar to the

notches

81, 82 may be provided spaced symmetrically inwardly, that is, toward the housing, on the ramp side walls.

It is one of the advantages of the use of linkage as illustrated in FIG. 7 that the lid is limited in its upward swing within a range defined by the full extension of the length, that is, to an extent just slightly greater than that illustrated in the figure. Even with the linkage fully extended the automatically interposed guard will occupy the position shown to perform its safety function. Similarly, in the case of the embodiment illustrated in FIGS. 1 to 6 inclusive, it is contemplated that a stop of simple construction be interposed in the path of upward swinging movement of the lid 35 to limit its upwardly angling to approximately the amount shown in FIG. 2. Such a stop may be made integral with the lid by forming a downwardly extending flange on the lid, similar to the flange 51, but extending transversely adjacent the hinge pin 50. Thus when the lid 35 is raised, the flange will crowd against the wall 33 of the housing to limit the upper swing.

One advantage of both of the embodiments is that when the guard 60 (or 60a) is swung upwardly a flexible material, for example rubber, of which the guard is made tends to droop slightly as illustrated in FIG. 4 so that the material which is swept up the ramp instead of being pocketed in the corners of the housing tends to be guided downwardly by the guard along a curved path and into the receptacle 25. This enables a faster feed while reducing any jamming tendency. The amount of droop depends upon the weight, stiffness and unsupported length of the guard sections 61.

While the lid 35 will normally have sufficient weight and be sufficiently friction free so as to lower itself automatically from its angled position into horizontal position when the ramp is lowered, it is contemplated that the lid may be additionally downwardly biased, if desired, by a suitable spring as, for example, a coil tension spring secured between the flange 51 on the lid and a suitable point on the sidewall 31 of the housing. Use of such a spring is particularly desirable where the lid, instead of being formed of metal, is formed of glassreinforced plastic or similar light material.

It might be assumed that since means are provided for swinging the guard 60 from its obstructing position illustrated in FIG. 2 to a non-obstructing position illustrated in FIG. 4, that FIG. 4 illustrates a less safe condition. Any such assumption is in fact unwarranted, and a little analysis will show that a high degree of safety is achieved even with the guard in its alternate, upraised position. This is true for several reasons. Note that in the illustrated construction the hinge axis of the ramp, indicated at 47, is spaced substantially above the receptacle, with the intervening space filled by the bracket 46. The resulting elevation of the inner edge of the ramp causes the latter to act as a shield, preventing any direct ejection of a missile through the throat 45 at an angle shallow enough to strike the operator. Any missile thrown upwardly through the receptacle at a more vertical, that is, less shallow, angle will either strike the overhanging resilient portion 61 of the guard, the plate 62, or the integral flange, or lip, 62a thereof. Where the missile strikes the resilient strips 61, its energy is immediately dissipated. If, by chance, a missile should exit at a slightly shallower angle striking the plate 62 or the lip 62a, the geometry is such that the missile will rebound downwardly, and safely, with sharply reduced energy content.

What is claimed is:

1. In a shredding and bagging machine for yard usage, the combination comprising a frame having a bottom wall, circular side wall and top wall defining a shredding chamber, transport means for supporting the frame in horizontal position slightly upraised above the ground, an engine mounted on the top wall and having a drive shaft which extends into the chamber, a blade mounted on the shaft having tip portions extending to the region of the side wall, a plurality of stationary breaker members at spaced positions on the side wall and having notches formed therein for registering with the tip portions of the blade, means including a discharge conduit penetrating the side wall for forcible discharge of the shredded material, the top wall having a receptacle for feeding material into the chamber, a housing arranged above the receptacle and providing a front opening, a ramp of flaring construction having side walls defining a wide outer end and a relatively narrow throat registering with the front opening, the ramp being horizontally hinged in the region of the throat for pivoted swinging movement between a lowered position in which the ramp extends at an angle downwardly into ground engagement and an upraised position in which the ramp is angled upwardly to form a hopper, releaseable means for holding the ramp is upraised position, a pivotally mounted guard member extending across the throat of the ramp, means for swinging the guard member to an out-of-the-way position, clear of the throat, when the ramp is lowered, and means actuated by raising of the ramp for causing the guard member to move into throat-obstructing position to prevent ejection of missiles through the receptacle from the blade. I j

2. In a shredding and bagging machine for yard usage, the combination comprising a frame having a bottom wall, circular side wall and top wall defining a shredding chamber, transport means for supporting the frame in a horizontal position slightly upraised above the ground, an engine mounted on the top wall having a drive shaft which extends into the chamber, a blade mounted on the shaft having tip portions extending to the region of the side wall, a plurality of stationary breaker members at spaced positions on the side wall and having notches formed therein for registering with the tip portions of the blade, means including a discharge conduit penetrating the side wall for forcible discharge of the shredded material, the top wall having a receptacle for feeding material into the chamber, a housing arranged above the receptacle and providing a front opening, a ramp of flaring construction having side walls defining a wide outer end and a relatively narrow throat registering with the front opening, the ramp being hinged in the region of the throat for swinging movement between a lowered position in which the ramp extends at an angle downwardly onto the ground and an upraised position in which the ramp is angled upwardly to form a hopper, releaseable means for holding the ramp in upraised position, a pendulously mounted guard member extending across the throat of the ramp, means for manually latching the guard member into an upwardly swung position clear of the throat when the ramp is in its lowered position, and means coupled to the ramp and actuated incident to swinging the ramp upwardly for releasing the latching means so that the guard member is free to swing pendulously into its throat obstructing position.

3. In a shredding and bagging machine for yard usage, the combination comprising a frame having a bottom wall, circular side wall and top wall defining a shredding chamber, transport means for supporting the frame in a horizontal position slightly upraised above the ground, an engine mounted on the top wall and having a drive shaft which extends into the chamber, a blade mounted on the shaft having tip portions extending to the region of the side wall, a plurality of stationary breaker members at spaced positions on the side wall and having notches formed therein for registering with the tip portions of the blade, means including a discharge conduit penetrating the side wall for forcible discharge of the shredded material, the top wall having a receptacle for feeding material into the chamber, a housing arranged above the receptacle and providing a front opening, a ramp of flaring cross section having side walls defining a wide outer end and a relatively narrow throat registering with the front opening, the ramp being hinged in the region of the throat for swinging movement between a lowered position in which the ramp extends at an angle downwardly into ground engagement and an upraised position in which the ramp is angled upwardly to form a hopper, the housing having a lid, the lid being hinged thereto in the path of movement of the ramp so that the lid occupies a horizontal position when the ramp is in ground engagement but is swung upwardly when the ramp is raised, releaseable means for holding the ramp in its upraised position, a guard member pendulously hinged to the lid and dimensioned to span the throat of the ramp to guard against ejection of missiles from the blade when the ramp is in upraised position, means for latching the guard member into an upwardly swung, out-of-the-way position when the ramp is in its lowered position to permit free passage of material swept up the ramp and into the receptacle, and means responsive to the raising of the lid as the ramp is returned to its upraised position for releasing the latch so that the guard member is automatically restored to its pendulous guarding position.

4. The combination as claimed in claim 3 in which the guard member is supported on a shaft and in which the latch is in the form of an arm secured to one end of the shaft, the arm cooperating with a stationary keeper behind which the arm is manually latched when the ramp and lid are in lowered position, with the arm being dimensioned to slip clear of the keeper to release the latch when the ramp and lid are upraised.

5. The combination as claimed in claim 3 in which the latch is in the form of an arm secured to the guard member and extending parallel to one of the side walls of the housing and in which a keeper is provided on such side wall for holding the arm, and hence the guard, upraised when the lid is in its lowered position, the arm being dimensioned to pull clear of the keeper as the lid is upraised thereby to free the guard to move to its pendulous obstructing position.

6. In a shredding and bagging machine for yard usage, the combination comprising a frame having a bottom wall, circular side wall and top wall defining a shredding chamber, transport means for supporting the frame in horizontal position slightly upraised above the ground, an engine mounted on the top wall and having a drive shaft which extends into the chamber, a blade mounted on the shaft having tip portions extending to the region of the side wall, a plurality of stationary breaker members at spaced positions on the side wall and having notches formed therein for registering with the tip portions of the blade, means including a discharge conduit penetrating the side wall for forcible discharge of the shredded material, the top wall having a receptacle for feeding material to the chamber, a housing arranged above the receptacle and having a hinged lid, the forward edge of which defines a front opening, a ramp of flaring construction having side walls defining a wide outer end and a relatively narrow throat registering with the front opening of the housing, the ramp being horizontally hinged in the region of the throat for swinging movement between a lowered position in which the ramp extends at an angle downwardly into ground engagement and an upraised position in which the ramp and lid are angled upwardly to form a hopper, releaseable means for holding the ramp in upraised position, a guard member horizontally hinged to the lid adjacent the front edge thereof and dimensioned to span the throat when the ramp and lid are upraised, means coupled to the guard member for swinging the guard member upwardly into an out-of-the-way position when the ramp and lid are lowered to permit free sweeping of material up the ramp and into the receptacle, and means responsive to relative movement of the lid occurring when the ramp is again swung upwardly into upraised position for restoring the guard to obstructing position.

7. The combination as claimed in claim 3 in which the lid has side flanges and a presented flange overlying the throat of the ramp, the presented flange being notched out at the ends for registered reception of the upper edges of the respective ramp side walls.

8. The combination as claimed in claim 6 in which the means for swinging the guard member includes an arm on the guard and a stationarily pivoted link pinned to the end of the arm for rocking the arm incident to upward and downward swinging of the lid as the ramp is raised and lowered.

9. The combination as claimed in claim 6 in which the guard member is formed of a resilient sheet of rubber-like material vertically slit to permit deflection of individual portions thereof, the material being of such weight and stiffness with respect to the length of the individual portions that the portions droop along a curved path when the guard is in its upraised position thereby to guide material on the ramp along a curved path into the hopper.

10. The combination as claimed in claim 6 in which means are provided for limiting the upward swing of the lid to a shallow angle so that the lid within its range of movement occupies a shielding position above the receptacle to preclude upward ejection of missiles from the housing via the receptacle.

11. The combination as claimed in claim 6 in which the ramp hinge axis is elevated substantially above the receptacle and in which a vertically extending member encloses the space between the hinge axis and the receptacle to block any missiles ejected via the receptacle at a shallow angle when the guard member is upraised, with any missiles ejected at a more vertical angle striking the upraised guard for harmless rebound in the downward direction.

l l l

Claims

1. In a shredding and bagging machine for yard usage, the combination comprising a frame having a bottom wall, circular side wall and top wall defining a shredding chamber, transport means for supporting the frame in horizontal position slightly upraised above the ground, an engine mounted on the top wall and having a drive shaft which extends into the chamber, a blade mounted on the shaft having tip portions extending to the region of the side wall, a plurality of stationary breaker members at spaced positions on the side wall and having notches formed therein for registering with the tip portions of the blade, means including a discharge conduit penetrating the side wall for forcible discharge of the shredded material, the top wall having a receptacle for feeding material into the chamber, a houSing arranged above the receptacle and providing a front opening, a ramp of flaring construction having side walls defining a wide outer end and a relatively narrow throat registering with the front opening, the ramp being horizontally hinged in the region of the throat for pivoted swinging movement between a lowered position in which the ramp extends at an angle downwardly into ground engagement and an upraised position in which the ramp is angled upwardly to form a hopper, releaseable means for holding the ramp is upraised position, a pivotally mounted guard member extending across the throat of the ramp, means for swinging the guard member to an out-of-the-way position, clear of the throat, when the ramp is lowered, and means actuated by raising of the ramp for causing the guard member to move into throat-obstructing position to prevent ejection of missiles through the receptacle from the blade.